Proximity sensor device and system

Abstract

Proximity sensor devices and systems are disclosed. A monolithic integrated proximity sensor device, comprising: a semiconductor substrate having an active surface with at least one active or passive component or pad; an interconnect stack comprising a plurality of metal layers in at least two metal layers; at least a first transmitter coil (Tx1) having a first spiral with at least three turns, formed in at least one or at least two metal layers, and defining a first area (ZTx1) having a first inner and outer perimeter; at least a first receiver coil (Rx1) having a second spiral with at least three turns, formed in at least one or at least two metal layers, and defining a second area (ZRx1) having a second inner and outer perimeter; wherein the at least one component or pad is located within the first and / or second inner perimeter. A proximity sensor system. An integrated transformer.

Description

Technical Field

[0001] This invention relates generally to the field of proximity sensors, and more specifically to proximity sensor devices and systems. Background Technology

[0002] Proximity sensor devices and systems are known in the art. They are typically based on sensing a static magnetic field generated by a permanent magnet, or by sensing a dynamic magnetic field generated by a transmitter coil conducting alternating current. The characteristics of the magnetic field change depending on the position of a moving object (e.g., a “metallic target”).

[0003] This invention relates to an inductive proximity sensor, sometimes also called an "inductive proximity switch," because the sensor device typically only needs to distinguish one of two possible locations of the target.

[0004] US8203335 describes an example of a proximity switch.

[0005] There is always room for improvement and alternatives. Summary of the Invention

[0006] The purpose of this invention is to provide a proximity sensor device.

[0007] Another object of the present invention is to provide a proximity sensor system comprising such a device and a target movably arranged relative to the device, such as a conductive target (e.g., a metallic target, or a printed circuit board having a conductive layer or conductive traces) or a magnetic target (e.g., a ferromagnetic target, or a target containing ferromagnetic particles).

[0008] The purpose of this invention is to provide a proximity sensor device that can reliably detect the presence of a conductive or magnetic target at a predetermined distance (air gap). The predetermined distance can be 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, or even 3.0 mm.

[0009] The purpose of this invention is to provide a monolithically integrated proximity sensor device that can reliably detect the presence of a conductive target (e.g., a metallic target) or a magnetic target at a predetermined distance from the device.

[0010] One object of this invention is to provide a monolithically integrated proximity sensor device that can reliably detect the presence of a conductive target (e.g., a metallic target) or a magnetic target at a predetermined distance from the device. The sensor device is manufactured using standard CMOS technology.

[0011] One object of this invention is to provide a monolithically integrated proximity sensor device capable of reliably detecting the presence of a conductive target (e.g., a metallic target) or a magnetic target at a predetermined distance from the device. The device is manufactured using standard CMOS technology and has a single semiconductor substrate with an area less than 6.25 mm². 2 Less than 5.5mm 2 Less than 5.0mm 2 Less than 4.5mm 2 Less than 4.0mm 2 Less than 3.5mm 2 or less than 3.0mm 2 .

[0012] The purpose of this invention is to provide a proximity sensor device that consumes less than 50 milliwatts, or less than 40 milliwatts, or less than 30 milliwatts, or less than 20 milliwatts (e.g., typically consumes about 15 milliwatts).

[0013] These and other objectives are achieved by the proximity sensor device and proximity sensor system according to embodiments of the present invention.

[0014] According to a first aspect, the present invention provides a proximity sensor device comprising a single monolithic integrated semiconductor, including: an active surface including at least one component selected from the group consisting of: an active component, a passive component, and pads; an interconnect stack located on top of the active surface, the interconnect stack including a plurality of metal layers of at least two metal layers separated by an isolation layer; at least a first transmitter coil and a first receiver coil electrically insulated from each other, the first transmitter coil having a first helix having at least three turns formed in a first subset having at least one or at least two metal layers selected from the plurality of metal layers, and wherein the orthogonal projection of the first helix layer on an active substrate has a first inner periphery and a first outer periphery; the first receiver coil having a second helix having at least three turns formed in a second subset having at least one or at least two metal layers selected from the plurality of metal layers, and wherein the orthogonal projection of the second helix on the active substrate has a second inner periphery and a second outer periphery; wherein the at least one component is located within the first inner periphery and within the second inner periphery, or located within the first inner periphery but outside the second outer periphery.

[0015] A “single monolithic integrated semiconductor substrate” may include silicon.

[0016] Proximity sensor devices can be implemented in a packaged chip (also known as an integrated circuit, IC) having multiple pins (or leads) extending from the package. The package can be a ceramic package or a plastic package.

[0017] A key advantage is that at least one component (preferably a relatively large component and / or multiple components) is located within the first inner circumference, and optionally also within the second inner circumference, rather than leaving the space (inside the coil) "empty." This allows for more efficient use of the active surface area and / or allows for more flexible layout, and / or allows for larger transmitter coils and / or larger receiver coils. In other words, it allows for a reduction in "empty space" (i.e., the area of ​​the "active surface" not used for components). Note that the expression "active surface of a semiconductor substrate" has a well-known meaning in the semiconductor field and requires no further explanation here.

[0018] In the field of integrated circuits, positioning at least one component (e.g., an active / passive component, pads, or capacitor array) within an area covered by a transmitter coil and / or receiver coil is not easy, because it is expected that:

[0019] (a) If the transmit power is low, the operation or interconnection of the components will not be interfered with, but the receiver signal (caused by inductive coupling) will be too weak to be reliably detected.

[0020] (b) If the transmit power is high, the receiver signal will be strong enough to be reliably detected, but the operation or interconnection of components will be interfered with.

[0021] In the field of integrated circuits, it was previously unknown which components could be placed in the aforementioned area. Only after designing, manufacturing, and evaluating a large number of test chips did the inventors discover with surprise that it was indeed possible to position certain components in the area while still reliably determining the position of conductive (e.g., metallic) or magnetic targets relative to an integrated proximity sensor device (also referred to herein as an "inductive switch"), and / or reliably detecting the presence of the target near the switch.

[0022] Instead of saying that the orthogonal projection of the first helix onto the active substrate has or defines a first inner periphery and a first outer periphery, it can also be said that the projection of the first helix defines a first region, such as a first strip region having or defining the first inner periphery and the first outer periphery. Similarly, instead of saying that the orthogonal projection of the second helix onto the active substrate has or defines a second inner periphery and a second outer periphery, it can also be said that the projection of the second helix defines a second region, such as a second strip region having or defining the second inner periphery and the second outer periphery.

[0023] The first subset and the second subset may share at least one metal layer, or in other words, they may have at least one common metal layer. However, this is not an absolute necessary condition for the operation of this invention.

[0024] In a preferred embodiment, the orthogonal projection of the outer periphery of at least one receiver coil lies within the orthogonal projection of the inner periphery of at least one transmitter coil. Or, simply put: at least one receiver coil is implemented within the space defined by the transmitter coil.

[0025] Preferably, the projections of the transmitter coil and receiver coil windings do not overlap or intertwine (e.g., as shown in Figures 13(a) and 15(a)). Or in other words, preferably, the first strip region (e.g., ZTx1) and the second strip region (e.g., ZRx1) are non-overlapping regions.

[0026] The advantage is that, for example, compared to existing technologies where the transmitter winding and receiver winding are geometrically related, this allows the transmitter coil and receiver coil to be designed independently of each other.

[0027] Ideally, no components (more specifically: no active components (such as transistors), passive components (such as resistors or capacitors), or pads) are located "below" the transmitter winding or the receiver winding. Alternatively, preferably, no components are located between the first inner and first outer perimeters, and preferably, no components are located between the second inner and second outer perimeters. Or, in other words, preferably, the transmitter and receiver windings do not operate "vertically above" active components such as transistors, and do not operate above passive components such as resistors or capacitors, and do not operate above pads.

[0028] In a preferred embodiment of the invention, preferably, at least 1%, or at least 2%, or at least 5%, or at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70% of the area within the inner periphery of the first receiver coil is occupied by one or more active or passive components, and / or by pads, portions of analog circuitry, and / or portions of digital circuitry, in contrast to existing circuitry in which the area "below the coil" is not used.

[0029] A key advantage is that one or more active or passive components or pads are positioned within the inner periphery of the first receiver coil, because otherwise these components would have to be positioned elsewhere, which would increase the size of the semiconductor substrate, or reduce the area covered by the coil winding, or both. In other words, by positioning one or more of the aforementioned components within the inner periphery, the size of the semiconductor substrate can be reduced and thereby the cost of the semiconductor substrate can be lowered, or the performance of the inductive switch can be improved, or both.

[0030] In one embodiment, the transmitter coil consists of only a single spiral implemented in a single metal layer.

[0031] In one embodiment, the transmitter coil comprises at least two helices, each implemented in a different metal layer. Preferably, the two helices are positioned substantially vertically relative to each other. The two helices may be located in two adjacent metal layers, such as M1 and M2, M2 and M3, or M3 and M4. Alternatively, the two helices may be located in two non-adjacent metal layers, such as M1 and M3, or M2 and M4. The two TX helices may be interconnected via a plurality of vias. These vias may be oriented perpendicular to the semiconductor substrate.

[0032] In one embodiment, the receiver coil comprises a single spiral implemented in a single metal layer.

[0033] In one embodiment, the receiver coil comprises at least two spirals, each implemented in a different metal layer. These two spirals may be connected in series.

[0034] In one embodiment, the receiver coil comprises at least two spirals, each implemented in a different metal layer. These spirals can be connected to be positioned vertically relative to each other and can be interconnected through multiple through-holes.

[0035] In one embodiment, the receiver spiral is implemented in a single metal layer (e.g., M3), and the transmitter coil is implemented in two metal layers, including a metal layer (e.g., M4) above the layer in which the receiver coil is implemented, and a metal layer (e.g., M2) below the metal layer in which the receiver coil is implemented.

[0036] In an embodiment, the interconnect stack has only four metal layers (M1 to M4, M1 being the active surface closest to the semiconductor surface), and at least one helix of at least one transmitter coil Tx1 is implemented in only one or two of these four metal layers, and at least one helix of at least one receiver coil Rx1 is also implemented in only one or two of these four metal layers.

[0037] In one embodiment, the Tx1 spiral is implemented in only three metal layers, while the Rx1 spiral is implemented in only two metal layers.

[0038] In one embodiment, the Tx1 helix is ​​implemented in only two metal layers, while the Rx1 helix is ​​implemented in only three metal layers.

[0039] In the embodiments, the Tx1 spiral is implemented in only three metal layers, and the Rx1 spiral is implemented in only three metal layers.

[0040] The advantage is that at least one metal layer (preferably M1 closest to the substrate) can be used to connect the spirals to the transmitter and receiver circuits. This metal layer can also be used to interconnect different spirals of the receiver coil.

[0041] In an embodiment, at least one transmitter coil is excited at a frequency in the range of 10 to 50 MHz, 15 to 40 MHz, or 15 to 30 MHz.

[0042] In one embodiment, the first transmitter coil includes at least ten windings.

[0043] In one embodiment, the first receiver coil includes at least ten windings.

[0044] In this embodiment, the sensor device is a coreless sensor device, i.e., it does not include an integrated magnetic concentrator (IMC). The advantage is that such sensor devices are easier to manufacture and less expensive.

[0045] In another embodiment, the sensor device also includes an integrated magnetic concentrator (IMC). The advantage of such a sensor device is that it can increase flux concentration.

[0046] In one embodiment, the first transmitter coil is formed in a single metal layer, and the first receiver coil is formed in the same single metal layer as the metal layer in which the first transmitter coil is formed.

[0047] In one embodiment, the first transmitter coil is formed in a single metal layer, and the first receiver coil is formed in a single metal layer that is different from the metal layer in which the first transmitter coil is formed.

[0048] In one embodiment, a first transmitter coil (Tx1) is formed in a first subset of an interconnect stack, the first subset comprising at least two metal layers, and the first subset and the second subset having at least one common metal layer.

[0049] In one embodiment, a first transmitter coil is formed in a first subset of an interconnect stack, the first subset comprising at least two metal layers, and a first receiver coil is formed in a second subset of an interconnect stack, the second subset comprising at least two metal layers; wherein the first subset and the second subset have at least one or at least two common metal layers.

[0050] In an embodiment, the proximity sensor device further includes: a transmitter circuit included in the active surface and connected to a first transmitter coil (e.g., Tx1), configured to transmit an alternating signal; a receiver circuit included in the active surface and connected to a first receiver coil (e.g., Rx1), configured to receive the alternating signal; and an evaluation circuit included in or connected to the receiver circuit, configured to determine the condition and / or position (more specifically, position relative to the proximity sensor device) of a conductive or magnetic target based on the received alternating signal.

[0051] The conductive target can be a metallic target, such as in the form of a metal sheet or metal plate, for example a metal plate with a basic rectangular shape and no opening, or a metal plate with a basic rectangular shape and two openings (e.g., two rectangular openings offset from each other), as shown in Figure 10(a).

[0052] Magnetic targets can be composed of ferromagnetic materials or may include ferromagnetic particles.

[0053] In the embodiments, the target is made of or contains stainless steel.

[0054] In an embodiment, the conductive target includes a printed circuit board having conductive and non-conductive regions.

[0055] In an embodiment, the proximity sensor device is further configured to output the determined condition, for example, via a digital output port, via a serial interface, via an analog output port, via a "two-wire" interface (e.g., compatible with "two-wire LIN"), via an open-drain switch, etc.

[0056] In an embodiment, the proximity sensor device further includes an integrated capacitor connected in series or in parallel with at least one transmitter coil to form an LC resonator with a resonant frequency within a predefined range, and the transmitter circuit is configured to induce forced oscillation of the LC resonator at a frequency below its resonant frequency.

[0057] Compared to parasitic capacitance, integrated capacitors have better capacitance definition and are insensitive or very insensitive to temperature changes. Therefore, by adding a capacitor C, the resonant frequency can be set and remains essentially unaffected by temperature drift.

[0058] In one embodiment, the proximity sensor device includes a resistor, a capacitor, and a feedback circuit to form an RC oscillator embedded in a semiconductor substrate.

[0059] In an embodiment, the orthogonal projection of at least one of the resistor, capacitor, and feedback circuit lies within the orthogonal projection of the transmitter coil Tx1 and / or the orthogonal projection of the receiver coil.

[0060] In an embodiment, the evaluation circuit is further configured to determine whether the target is in a first predefined position or a second predefined position, and to output a corresponding (analog or digital) signal or value, or to open or close an internal switch between two terminals of the proximity sensor device.

[0061] In one embodiment, the transmitter circuit is configured to modulate a basic signal with a carrier frequency in the range of 12MHz to 30MHz, and the receiver circuit is configured to demodulate the received signal.

[0062] The transmitter circuit may include a BPSK (Binary Phase Shift Keying) modulator.

[0063] The receiver circuit may include a BPSK (Binary Phase Shift Keying) modulator.

[0064] In an embodiment, the receiver circuitry is configured to synchronously demodulate the received signal using the carrier frequency. Demodulation can occur in two consecutive steps, for example, a first down-mixing from the carrier frequency to an intermediate frequency (IF) (e.g., from 24 MHz to 1 MHz), and a second down-mixing from the IF to DC.

[0065] In an embodiment, the orthogonal projection of the outer periphery of at least one receiver coil lies entirely within the orthogonal projection of the inner periphery of the first transmitter coil. Or, in other words, preferably, the second strip region ZRx1 lies entirely within the inner periphery of the first strip region ZTx1.

[0066] In an embodiment, the proximity sensor device further includes at least one metal shield, which takes the form of multiple traces of at least two traces positioned vertically to each other in at least two interconnected stacked layers (e.g., M2 and M3; or M3 and M4; or M2 and M4), the traces being interconnected by multiple through-holes, wherein at least one metal shield is located between the inner periphery of the transmitter coil and the outer periphery of the receiver coil, or between the inner periphery of the transmitter coil and at least one component located within the inner periphery, or between the inner periphery of the receiver coil and at least one component located within the inner periphery.

[0067] In one embodiment, the proximity sensor device includes only two coils, namely the first transmitter coil (e.g., Tx1) and the first receiver coil (e.g., Rx1), and the area between the inner and outer circumferences of the transmitter coil (also referred to herein as the area of ​​the first strip region ZTx1) is equivalent to 36% to 44% of the active area; and the area between the inner and outer circumferences of the receiver coil (also referred herein as the area of ​​the second strip region ZRx1) is equivalent to 15% to 25% of the active area.

[0068] Therefore, in this embodiment, the strip region (i.e., the active surface portion "below" the coil winding, where no components are placed) collectively occupies 41% to 69% of the active area of ​​the semiconductor substrate, which means that only 31% to 59% is left for placing active / passive components or pads.

[0069] In one embodiment, the substrate further includes a second receiver coil (e.g., Rx2) electrically insulated from the first transmitter coil (e.g., Tx1); the second receiver coil has a third helix with at least three turns, formed in a third subset having at least one or at least two metal layers selected from the plurality of metal layers; the orthogonal projection of the third helix onto the active surface lies entirely within the inner circumference of the first transmitter coil.

[0070] This can also be expressed as follows: where the orthogonal projection of the third spiral layer onto the active substrate defines the third strip region ZRx2; where both the second strip region ZRx2 and the third strip region ZRx3 are completely located within the inner periphery of the first strip region ZTx1 of the transmitter coil.

[0071] Preferably, the second strip region (e.g., ZRx2) and the third strip region (e.g., ZRx3) do not overlap, but are different regions.

[0072] The first and third subsets may share at least one metal layer (e.g., M3 or M4), but this is not absolutely necessary.

[0073] The second receiver coil can be connected in series or in parallel with the first receiver coil.

[0074] In one embodiment, the first transmitter coil comprises three parallel helices, each implemented in one of the three metal layers, and having 22 to 32 turns (or windings); the first receiver coil comprises two series-connected helices, each implemented in one of the two metal layers, and having 30 to 40 turns; the second receiver coil comprises two series-connected helices, each implemented in one of the two metal layers, and having 30 to 40 turns.

[0075] In an embodiment, the proximity sensor device includes only three coils: a first transmitter coil (e.g., Tx1), a first receiver coil (Rx1), and a second receiver coil (Rx2); and the area between the inner and outer circumferences of the first transmitter coil (e.g., Tx1) (also referred to herein as the first strip region ZTx1) is equivalent to 36% to 44% of the active area; and the area between the inner and outer circumferences of the first receiver coil (e.g., Rx1) (also referred to herein as the second strip region ZRx1) is equivalent to 12% to 18% of the active area; and the area between the inner and outer circumferences of the second receiver coil (e.g., Rx2) (also referred to herein as the third strip region ZRx2) is equivalent to 12% to 18% of the active area.

[0076] Therefore, in this embodiment, the strip region (i.e., the active surface portion "below" the coil winding, where no components are placed) collectively occupies 60% to 80% of the active area of ​​the semiconductor substrate, which means that only 20% to 40% is left for placing active / passive components or pads.

[0077] In an embodiment, the substrate further includes a second receiver coil (e.g., Rx2) and a second transmitter coil (e.g., Tx2); wherein the second receiver coil is electrically insulated from and from the first transmitter coil, and wherein the second transmitter coil is electrically insulated from both the first and second receiver coils; and the second receiver coil has a third helix formed in the same layer as the first receiver coil, wherein the orthogonal projection of the third helix onto the active substrate defines a third inner periphery and a third outer periphery (also referred to herein as the inner and outer periphery of the third strip region ZRx2); the second transmitter coil has a fourth helix formed in the same layer or multiple layers as the first transmitter coil, wherein the orthogonal projection of the fourth helix onto the active substrate defines a fourth inner periphery and a fourth outer periphery (also referred to herein as the inner and outer periphery of the fourth strip region ZTx2); wherein the outer periphery of the second transmitter coil is completely outside the outer periphery of the first transmitter coil; wherein the outer periphery of the first receiver coil is completely within the inner periphery of the first transmitter coil; and wherein the outer periphery of the second receiver coil is completely within the inner periphery of the second receiver coil.

[0078] Or in other words, the second receiver coil defines a third strip region, and the second transmitter coil defines a fourth strip region, and the second strip region ZTx2 is completely outside the first strip region ZTx1, and the second strip region ZRx1 is completely inside the first strip region ZTx1, and the third strip region ZRx2 is completely inside the fourth strip region ZTx2.

[0079] Or, to put it simply, this embodiment has a first receiver coil disposed "within" a first transmitter coil and a second receiver coil disposed "within" a second transmitter coil.

[0080] The first and second transmitter coils can be arranged at a distance from each other, for example, on opposite sides of the active region, as shown in Figure 15(a). The area between the two transmitter coils can be used to place active / passive components and / or pads. According to the principles of the invention, at least one active or passive component or pad is located within the inner circumference of the first or second transmitter coil and / or the inner circumference of the first or second receiver coil.

[0081] The second transmitter coil may be electrically insulated from the first transmitter coil. Alternatively, the second transmitter coil may be electrically connected in parallel with the first transmitter coil. Alternatively, the second transmitter coil may be electrically connected in series with the first transmitter coil.

[0082] In an embodiment, each of the first and second transmitter coils includes three parallel-connected spirals implemented in three metal layers (e.g., M2, M3, M4) and each having 22 to 32 turns; and each of the first and second receiver coils includes two series-connected spirals implemented in two or three metal layers and each having 30 to 40 turns.

[0083] Experiments show that this combination provides a good working solution for integrated inductive switches.

[0084] In an embodiment, the proximity sensor device includes only four coils (e.g., Tx1, Rx1, Tx2, Rx2), namely first and second transmitter coils and first and second receiver coils, wherein the sum of the area between the inner and outer circumferences of the first transmitter coil (also referred to herein as the first strip region ZTx1) and the area between the inner and outer circumferences of the second transmitter coil (also referred herein as the fourth strip region ZTx2) is equivalent to 35% to 45% of the active area. Furthermore, the sum of the area between the inner and outer circumferences of the first receiver coil (also referred to herein as the second strip region ZRx1) and the area between the inner and outer circumferences of the second receiver coil (also referred to herein as the third strip region ZRx2) is equivalent to 20% to 28% of the active area; and wherein at least 1% of the combined area within the inner circumferences of the first and second receiver coils is occupied by one or more active or passive components or pads, such as portions of analog circuitry (e.g., operational amplifiers, comparators, resistors, voltage generators, analog-to-digital converters, modulators, demodulators, buffers, multiplexers, etc.) and / or portions of digital circuitry (e.g., digital memories, digital processors, counters, shift registers, etc.).

[0085] Therefore, in this embodiment, the strip region (i.e., the active surface portion "directly below" or "below" the coil winding, where no components are placed) collectively occupies 55% to 73% of the active area of ​​the semiconductor substrate. However, it is advantageous to use at least a portion of one or more strip regions for positioning components that would otherwise have to be located "outside the coil".

[0086] In a preferred embodiment, preferably at least 2%, or at least 5%, or at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70% of the area within the inner periphery of the first receiver coil is occupied by one or more active or passive components or pads, for example, by portions of analog circuitry and / or digital circuitry, such as by capacitor arrays.

[0087] In one embodiment, the first transmitter coil includes a stack having at least two helical windings arranged one above the other, with one helix in each layer of the first metal layer subset; wherein adjacent helices are interconnected by a plurality of through-holes spaced apart by less than 100 micrometers, preferably less than 50 micrometers, or less than 20 micrometers, or less than 10 micrometers, or less than 5 micrometers, for example about 4 micrometers, or about 3 micrometers, or about 2 micrometers.

[0088] This is the main advantage of forming the first coil in this way, because, on the one hand, the series resistance of the coil is reduced by connecting the spirals in parallel (e.g., arranged one above the other) in different metal layers; on the other hand, and at least equally important, the parasitic capacitance between the different spirals is significantly reduced by interconnecting them not only at the beginning and end points of the spirals (e.g., at the innermost and outermost positions), but also by interconnecting them through multiple through-holes distributed along their entire path. This is especially true if the spiral windings of the first receiver circuit are implemented in metal layers of different thicknesses.

[0089] The target has a predetermined shape and size.

[0090] In this embodiment, the target includes a ferromagnetic material.

[0091] In this embodiment, the target includes ferromagnetic particles, for example, embedded in a matrix material, such as an electrically insulating matrix material, or in a resin or ceramic. In this embodiment, the magnetic properties of the material are important, rather than its electrical properties.

[0092] In another embodiment, the metallic target does not include ferromagnetic materials. In this embodiment, its electrical properties are more important than its magnetic properties. The target should be conductive on at least a portion of itself to allow eddy currents to flow in the vicinity of an alternating magnetic field.

[0093] In one embodiment, the substrate comprises silicon, and the monolithically integrated inductive switch is manufactured according to a CMOS process, preferably using lithography of 1 μm or smaller, such as 350 nm, 180 nm, 110 nm or 90 nm.

[0094] In one embodiment, each turn of the first transmitter coil has a substantially equal rectangular cross-section, each turn has a predefined height (in the direction perpendicular to the semiconductor substrate) and a predefined width (in the direction parallel to the semiconductor substrate); and the ratio between the sum of the heights (as the numerator) and the average of the widths (as the denominator) is less than 1.

[0095] Alternatively, mathematically, it is best to express N*∑(Hi) / ∑(Wi)<1, where Hi is the height, Wi is the width of the metal track of the metal layer numbered i, and N is the number of metal layers used by the transmitter coil. For example, if the number of metal layers is N, and if all heights are equal to H, and if all widths are equal to W, then it can be written as: (N*H / W) preferably less than 1.0.

[0096] According to a second aspect, the present invention also provides a proximity sensor system, comprising: a proximity sensor device according to a first aspect; and a conductive target movable relative to the proximity sensor device along a predefined trajectory between a first position and a second position.

[0097] In an embodiment, the target may move in a predetermined direction parallel to the semiconductor substrate; and the amount of overlap between the projection of the target and the inner periphery of at least one receiver coil differs when the target is in its first position or its second position; the evaluation circuit is configured to determine whether the target is in its first position or its second position based on the amount of overlap.

[0098] In the case where the inductive switch has only a single receiver coil, the evaluation circuit can be configured to compare the received signal or the signal derived from it (e.g., after demodulation) with one or more threshold levels to determine the location of the target.

[0099] In the case of an inductive switch having two receiving coils, the evaluation circuit can be configured to compare the received signals or signals derived therefrom (e.g., after demodulation) with each other and determine the location of the target based on the result of the comparison.

[0100] In the case of an inductive switch having two receiving coils, the evaluation circuit can be configured to combine the two received signals and compare the combined signal or the signal derived therefrom (e.g., after demodulation) with one or more threshold levels to determine the location of a target (e.g., a metallic or magnetic target).

[0101] In one embodiment, the proximity sensor system includes at least two monolithically integrated proximity sensor devices according to the first aspect, and a target movable relative to the at least two proximity sensor devices. The system may also include a controller connected to the at least two proximity sensor devices and configured to determine the position of the target relative to the proximity sensor devices based on signals provided by the devices.

[0102] In an embodiment, the proximity sensor device is configured to determine and optionally output whether a target (e.g., a metallic or magnetic target) is in its first position or its second position.

[0103] In one embodiment, the proximity sensor device includes a semiconductor substrate, and a predefined trajectory is substantially parallel to the semiconductor substrate and located at a predefined distance (g) from the semiconductor substrate.

[0104] In a preferred embodiment, the ratio of the total area (in square millimeters) of the semiconductor substrate including the first transmitter coil and the first receiver coil to the predefined distance (in millimeters) is less than 2.75, or less than 2.5, or less than 2.25, or less than 2.0, or less than 1.75, or less than 1.50, or less than 1.25, for example, approximately equal to 1.

[0105] This is a key advantage of embodiments of the invention, where the area of ​​the semiconductor substrate is only 1.0 to 5.0 times larger than the distance between the target and the semiconductor substrate, resulting in a more compact and cost-effective sensor device. This is a major difference from the prior art, where the ratio between the sensor size and the air gap is typically 3 to 6.

[0106] According to a third aspect, the present invention also provides a seatbelt buckle that includes a monolithically integrated proximity sensor device according to the first aspect.

[0107] According to a fourth aspect, the present invention also provides an integrated circuit comprising: a semiconductor substrate; an interconnect stack including a plurality of metal layers located on top of the semiconductor substrate; and a coil arrangement including a transmitter coil (e.g., TX) and a receiver coil (e.g., RX), both implemented in one or more layers of the interconnect stack, each of the transmitter coil and the receiver coil including at least one helix, each helix including at least three windings; wherein the orthogonal projection of the receiver coil lies entirely within the orthogonal projection of the transmitter coil; wherein the orthogonal projection of the transmitter coil has an axis of symmetry and has one or more cross nodes located on the axis of symmetry.

[0108] Figure 19 An example of such a transmitter coil is shown in the figure.

[0109] In an embodiment, the orthogonal projection of the receiver coil has an axis of symmetry and has one or more cross nodes located on the axis of symmetry.

[0110] In an embodiment, the start point (e.g., c1) and end point (e.g., c2) of the transmitter coil are located at the outer periphery of the transmitter coil; and the start point (e.g., c3) and end point (e.g., c4) of the receiver coil are located at the inner periphery of the receiver coil.

[0111] Figure 19 Examples of such transmitter and receiver coils are shown in the figure.

[0112] According to a fifth aspect, the present invention also provides an integrated transformer comprising the integrated circuit according to the fourth aspect.

[0113] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not merely as expressly set forth in the claims.

[0114] These and other aspects of the invention will be apparent from the embodiments described herein, and are illustrated with reference to these embodiments. Attached Figure Description

[0115] Figure 1(a) shows a perspective view, and Figure 1(b) shows a side view schematically representing an exemplary proximity sensor system from viewpoint a. The proximity sensor system includes a proximity sensor according to embodiments of the present invention, a proximity sensor device, such as in the form of a packaged semiconductor device (also referred to as an integrated circuit or "chip"), and includes a conductive target movable relative to said device.

[0116] Figure 2(a) shows an exemplary block diagram of a proximity sensor device according to an embodiment of the present invention, including at least one transmitter circuit and transmitter coil, at least one receiver circuit and receiver coil, and a switch that opens or closes according to the detected location of a conductive target.

[0117] Figure 2(b) shows another exemplary block diagram of a proximity sensor device according to an embodiment of the present invention, including at least one transmitter circuit and transmitter coil, at least one receiver circuit and receiver coil, and an interface circuit for outputting a value indicating the location of a detected conductive target.

[0118] Figures 3(a) to 7(c) Several examples of proximity sensor device arrangements according to embodiments of the present invention are shown, including one or more transmitter coils and one or more receiver coils integrated in a monolithic device, and including conductive targets in first and second positions relative to the coils. In the examples of Figures 3(a) and 3(b), the device has only a single transmitter coil and a single receiver coil. Figures 4(a) to 6(b) In the example, the device has a single transmitter coil and two receiver coils. Figures 7(a) to 7(c) In the example, the device has two transmitter coils and two receiver coils.

[0119] Figures 8(a) to 8(d) The illustration schematically shows how at least one transmitter coil can be implemented in some embodiments of the invention.

[0120] Figures 9(a) to 9(d)The illustration schematically shows how at least one receiver coil can be implemented in some embodiments of the invention.

[0121] Figure 10(a) shows another arrangement of a proximity sensor system according to an embodiment of the present invention, wherein the proximity sensor device includes a transmitter coil and two receiver coils, and a target (e.g., a metallic target or a magnetic target) having two openings and being movable in a direction parallel to the sensor device in a direction laterally to the receiver coils.

[0122] Figure 10(b) shows the measurement results of the proximity sensor system of Figure 10(a) and illustrates how the sensor device uses a single threshold voltage to determine the position of the target.

[0123] Figure 10(c) shows the measurement results of the proximity sensor system of Figure 10(a) and illustrates how the sensor device uses two or more threshold voltages to determine the position of a target and / or detect mechanical problems.

[0124] Figure 10(d) shows the measurement results of another proximity sensor system when the target moves parallel to the semiconductor device.

[0125] Figure 10(e) is another representation of the data in Figure 10(d), showing which signal will be measured when the target moves in a direction perpendicular to the sensor device.

[0126] Figure 11(a) shows a schematic block diagram of an exemplary transmitter circuit, and

[0127] Figure 11(b) shows a schematic block diagram of an exemplary receiving circuit that can be used in embodiments of the present invention.

[0128] Figure 12(a) shows a schematic block diagram of another exemplary transmitter circuit, and

[0129] Figure 12(b) shows a schematic block diagram of an exemplary receiver circuit that can be used in embodiments of the present invention.

[0130] Figures 13(a) to 13(c) An example of a possible layout, as may be used in embodiments of the invention, is shown, wherein the device includes a single transmitter coil and two receiver coils.

[0131] Figure 13(a) shows a rough impression of how much silicon area would be required if all active and passive components and pads were located outside the area defined by the emitter and receiver coils(s). Figure 13(b) shows an impression of how much silicon area would be required if the circuit were moved to the area defined by the emitter coils but outside the area defined by the receiver coils. Figure 13(c) shows an impression of how much silicon area would be required if a portion of the circuit were moved to the area defined by the receiver coils, and how much silicon area would be available for other circuitry.

[0132] Figures 14(a) to 14(c) It corresponds to Figures 13(a) to 13(c) A schematic representation of the layout is provided to give an impression of the geometric dimensions of each region. Figure 14(c) is shown in a more compact manner than Figure 13(c).

[0133] Figure 15(a) shows an example of a possible layout that can be used in an embodiment of the invention, wherein the sensor device includes two transmitter coils and two receiver coils. Figure 15(b) gives a rough impression of how much area would be required if all active and passive components and pads were located outside the area defined by the transmitter and receiver coils. Figure 15(c) gives an impression of the case where some circuitry is moved to the area defined by the receiver coils.

[0134] Figure 16 An example of a metal shield that may be arranged, for example, between the windings of a transmitter coil(s) and the windings of a receiver coil(s).

[0135] Figures 17(a) to 17(d) This schematically illustrates how a single transmitter coil can be implemented in a single metal layer, as can be achieved in embodiments of the invention.

[0136] Figures 18(a) to 18(d) This schematically illustrates how a single receiver coil can be implemented in a single metal layer, as can be achieved in embodiments of the invention.

[0137] Figure 19 An integrated circuit is shown, which includes a transmitter coil having an axis of symmetry and having one or more cross nodes located on the axis of symmetry.

[0138] The accompanying drawings are illustrative only and not restrictive. In the drawings, some elements may be enlarged and not drawn to scale for illustrative purposes. No reference numerals in the claims should be construed as limiting. In different drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0139] The invention will be described with reference to specific embodiments and particular drawings, but the invention is not limited thereto but is defined only by the claims. The described drawings are merely illustrative and not restrictive. In the drawings, for illustrative purposes, the dimensions of some elements may be enlarged and not drawn to scale. Scale and relative scale do not correspond to an actual reduction in the implementation of the invention.

[0140] Furthermore, the terms first, second, etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe an order in time, space, rank, or any other way. It should be understood that the terms thus used are interchangeable where appropriate, and the embodiments of the invention described herein can be operated in a different order than that described or illustrated herein.

[0141] Furthermore, the terms "top," "below," etc., used in the specification and claims are for descriptive purposes and are not necessarily used to describe relative positions. It should be understood that such terms are interchangeable where appropriate, and that embodiments of the invention described herein can operate in orientations different from those described or illustrated herein.

[0142] It should be noted that the term "comprising" as used in the claims should not be construed as limiting oneself to the means listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the features, integers, steps, or components stated as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the scope of the expression "device comprising means A and B" should not be limited to a device consisting solely of components A and B. It means that for the purposes of this invention, the only relevant components of the device are A and B.

[0143] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrase "in one embodiment" or "in an embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, as will be obvious to those skilled in the art from this disclosure, particular features, structures, or characteristics can be combined in any suitable manner.

[0144] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description for the purpose of streamlining the disclosure and aiding in understanding one or more of the inventive aspects. However, this method of disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the appended claims, inventive aspects exist in fewer features than all the features of a single foregoing disclosed embodiment. Therefore, the claims appended following the detailed description are thus explicitly incorporated into this detailed description, wherein each claim itself represents a separate embodiment of the invention.

[0145] Furthermore, while some embodiments described herein include features that are included in other embodiments but not others, it will be understood by those skilled in the art that combinations of features from different embodiments are intended to fall within the scope of the invention and form different embodiments. For example, any embodiment of the claimed embodiments in the appended claims can be used in any combination.

[0146] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0147] In this document, the term "monochip circuit" refers to an integrated circuit that uses a single semiconductor die.

[0148] "The inner circumference of a 2D helix" refers to the circumference of the largest possible concave polygon that fits inside the helix.

[0149] "The inner perimeter of a 3D spiral" refers to the circumference of the largest possible concave polygon that fits the orthogonal projection of the spiral onto a semiconductor substrate.

[0150] "The periphery of a 2D helix" refers to the periphery of the smallest possible concave polygon that fits around the helix.

[0151] The “periphery of a 3D spiral” refers to the periphery of the smallest possible concave polygon that fits the orthogonal projection of the spiral onto the semiconductor substrate.

[0152] In this document, the terms "transmitting circuit," "transmitter circuit," and "excitation circuit" have the same meaning.

[0153] In this document, the terms “transmitting coil” and “transmitter coil” as well as “excitation coil” and “TX coil” have the same meaning.

[0154] In this document, the terms "receiver circuit" and "receiver circuit" have the same meaning.

[0155] In this document, the terms "receiver coil," "receiver coil," and "RX coil" have the same meaning.

[0156] In this document, the terms “week” or “circumference” have the same meaning.

[0157] In this document, the statement “the receiver coil is located within the transmitter coil” means that the orthogonal projection of the receiver coil is located within the orthogonal projection of the transmitter coil, unless the context clearly indicates otherwise.

[0158] This invention relates to a "proximity sensor device" for detecting whether a conductive target (e.g., a metallic object or a printed circuit board with a conductive layer or a printed circuit board with a conductive path, etc.) – further referred to as a "metallic target" or a "magnetic target" (e.g., a target composed of or containing ferromagnetic particles), both referred to as "target" for ease of description – is located near the sensor device; or, when used in a proximity sensor system (where the target is movable on a predefined trajectory between a first position and a second position), for determining whether the target is at its first predefined position or its second predefined position; and optionally also for detecting that the time period during which the target is neither at its first position nor its second position is longer than a predefined time period, for example, for detecting mechanical failure.

[0159] In a preferred embodiment of the invention, the proximity sensor device is capable of reliably detecting the presence of a target (e.g., a metallic or magnetic target) at a predetermined distance (or air gap) from which the proximity sensor device is located. This predetermined distance can be 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, or 3.0 mm. In known systems, this requires the coil diameter to be at least three times the distance, therefore the coil diameter is at least 9 mm. In the prior art, such coils are therefore typically implemented on a printed circuit board (PCB).

[0160] The inventors of this invention have taken a completely different approach and successfully implemented a proximity sensor on a single monolithic integrated semiconductor substrate using a medium-sized standard CMOS process. Many biases, challenges, and uncertainties had to be overcome, such as:

[0161] - In order to reduce the size of the substrate, they decided to implement (multiple) transmitter coils and (multiple) receiver coils in the interconnect layer (sometimes called "interconnect stack" or "metal layer"). Assuming that four metal layers are available, as is the case in some CMOS processes, they decided to implement the receiver coil "inside" the transmitter coil.

[0162] - In order to create (multiple) transmitter / receiver coils with relatively high inductance values ​​(L) (e.g., in the range of 1 to 10 nH), multi-turn (or winding) helices are implemented;

[0163] - In order to create a transmitter coil with relatively low series resistance, the transmitter coil may include at least two helices, each implemented in a corresponding metal layer, and these helices may be connected in parallel;

[0164] - To increase the inductance (L) of the receiver coil(s), the receiver coil(s)(s) may include at least two helices, each implemented in a corresponding metal layer. These helices may be connected in series (increasing the number of windings, thus increasing inductance, but also increasing resistance) or in parallel (creating a larger cross-section, thus reducing resistance without increasing the number of windings);

[0165] - Preferably, the integrated capacitor is connected in series or in parallel with the transmitter coil to create a resonant circuit (referred to as an "LC resonant circuit" or "LC resonator"), which has a well-defined and relatively stable resonant frequency that does not change significantly with temperature (unlike parasitic capacitors).

[0166] The inventors also decided to reduce the risk of instability by using forced oscillation of the LC resonant circuit by applying an excitation voltage or current at a frequency lower than the resonant frequency of the LC resonator.

[0167] The overall performance of such transmitter and receiver circuits cannot be predicted, especially in terms of capacitive coupling (e.g., capacitive coupling between winding portions of a given coil, or capacitive coupling between the RX coil and the TX coil).

[0168] However, the inventors did not know if the circuit would work, let alone how well it would work. But the inventors went a step further and conducted several experiments to further reduce the size of the substrate by building a test chip and moving certain components (active components such as transistors and / or passive components such as resistors, capacitors or capacitor arrays) and / or pads into the central region below the transmitter coil and / or receiver coil, without knowing whether the alternating magnetic field would significantly / obviously interfere with the function of the analog and / or digital circuits, and vice versa.

[0169] Through these experiments, they also found that simply connecting the helices of the transmitter coil in parallel (e.g., at their start and end points) was feasible, but not ideal. More specifically, they found that performance could be further improved by additionally interconnecting the traces of the helices, which were positioned vertically to each other, using multiple through-holes. Although the exact reason for this improvement is not fully understood, and although the inventors do not wish to be bound by any theory, it is believed that this improvement may be related to the fact that the through-holes "short-circuit" the parasitic capacitance between the metal trace portions located above each other, which theoretically (if the width and thickness of each metal trace portion were exactly the same) should have exactly the same voltage, but in practice obviously do not have the same voltage, possibly due to manufacturing tolerances. Through-holes are particularly beneficial in embodiments in which the helical winding of the transmitter coil is implemented in metal layers of different thicknesses, because the sheet resistance of these different metal layers is actually different (not just because of manufacturing tolerances). For example, although not shown to scale, the fourth metal layer M4 shown in Figure 8(c) or Figure 9(c) is typically thicker than any of the other three metal layers M1 to M3.

[0170] The inventors also experimented by adding one or more “metallic shields” between the transmitter and receiver coils by stacking traces arranged vertically on top of each other in at least two of these metal layers (preferably three upper metal layers (M2, M3, M4)) and vertically interconnecting these lines via vias. The vertical projection of these traces onto the active surface must not form a closed loop to avoid eddy currents.

[0171] The cross-section of the vias can range from about 1 μm × 1 μm to about 1 μm × 10 μm, and these vias can be spaced apart by less than 5 μm (e.g., spaced apart by 4 μm, 3 μm, or 2 μm) to form a “metallic mesh” in the interconnect stack. The “metallic shield” can optionally be grounded, or connected to a relatively constant voltage (e.g., VDD), or left floating.

[0172] (Multiple) metal shields may also include traces implemented in the lowest metal layer M1 (separated from some of the pathways for connecting the transmitter coil), and may even include traces implemented in the active surface (e.g., a diffusion layer or polysilicon) that are also connected via vias.

[0173] One or more metal shields may also be added in a similar manner between the receiver coils and the space "inside and under the RX winding" to shield the electronic devices from the influence of one or more active or passive components or pads located there.

[0174] One or more metal shields can also be added in a similar manner between the transmitter coil and the space "inside and below the TX winding" to shield the electronic devices from the influence of one or more active or passive components or pads located there.

[0175] Figure 16 An example of one or more “metallic shields” that can be arranged between the transmitter coil and the receiver coil(s) is shown. In this example, the metallic shield consists of four wall sections. If present, this shield reduces capacitive coupling between the transmitter coil winding and the receiver coil winding.

[0176] The inventors also experimented with various modulation and demodulation schemes, as will be discussed in conjunction with Figures 11 and 12.

[0177] The inventors also experimented with different targets. In some embodiments, the target is made of a conductive metal (e.g., aluminum or copper). The alternating magnetic field generated by the (multiple) transmitter coils causes eddy currents to flow within the target. They also experimented with targets composed of or including ferromagnetic materials or ferromagnetic particles. Ferromagnetic targets can be electrically isolated. The material can be ferrite. Ferromagnetic targets can include magnetic particles. They surprisingly found that such targets induce magnetic gain. While the inventors do not wish to be bound by any theory, such targets appear to concentrate magnetic field lines such that an Rx coil (or coil portion) covered or overlapped by the magnetic target will see a higher magnetic flux density or a stronger magnetic field than an Rx coil (or coil portion) not covered or overlapped by the target.

[0178] As a result of all these experiments, the inventors successfully fabricated several proximity sensor devices comprising a monolithic integrated semiconductor substrate using various combinations of one or more of the aforementioned features, all of which have a size ranging from approximately 3 mm. 2 up to about 4mm 2 The sensor device can reliably detect the presence or location of targets (such as metallic or magnetic targets) with air gaps as large as 2 mm or even 3 mm.

[0179] Now refer to the attached figures.

[0180] Figure 1(a) shows a perspective view of a schematic representation of an exemplary proximity sensor system 100, and Figure 1(b) shows a side view of a schematic representation of the proximity sensor system 100 from viewpoint a, the system 100 including a proximity sensor device 101 (or simply "sensor device") and a target 102. The target may be a conductive target (also further referred to as a "metallic target") or a magnetic target.

[0181] Target 102 is movable relative to sensor device 101 in a virtual plane parallel to the semiconductor substrate of sensor device 101. In the example of FIG1(a), the direction of movement of target 102 is parallel to the virtual line X (shown as a dashed line) passing through the centers of the two receiver coils, but this is not always necessary. For example, see FIG3, which has only one receiver coil, or FIG10(a), where the direction of movement of target 1002 is perpendicular to the virtual line X passing through the centers of the two receiver coils.

[0182] The target 102 can be mounted via a bracket 103 or other guiding device, and the mounting device for the target may also include springs, etc., but these aspects are not the focus of the present invention, and any mounting arrangement can be used. To understand the principle of the present invention, it is only necessary to know that the conductive target 102 can move between a first predefined position and a second predefined position. The sensor device 101 according to the present invention only needs to be able to distinguish between these two predefined positions, and is therefore named an "inductive switch".

[0183] Figure 1(b) shows that the target 102 can be moved in a virtual plane α at a distance “g” (also referred to herein as the “air gap”) from the distance sensor device 101. In embodiments of the invention, this distance “g” can be selected as a value ranging from about 0.1 mm to about 3.0 mm, or from 0.1 mm to 2.5 mm, or from 0.1 mm to 2.0 mm, or from 0.1 mm to 1.5 mm, or from 0.1 mm to 1.0 mm. In practice, the target is preferably mounted at a distance of at least 0.5 mm to reduce the risk of mechanical contact, thereby reducing mechanical wear.

[0184] In other embodiments (not shown), the target 102 may move toward and away from the proximity sensor device 101 in a direction perpendicular to the substrate 104 of the sensor device 101, or at any other angle between 0° (parallel) and 90° (perpendicular), but the same principle applies.

[0185] Figure 2(a) shows an exemplary block diagram of a proximity sensor system 200 including a proximity sensor device 201 and a target 202 (e.g., a metallic or magnetic target) movable relative to the proximity sensor device 201. The sensor device 201 includes at least one transmitter circuit 210 connected to at least one transmitter coil Tx1. Optionally, the sensor device 201 may also include a second transmitter coil Tx2, which may also be connected to the transmitter circuit 210, or may be connected to a second transmitter circuit (not shown). The sensor device 201 includes at least one receiver circuit 220 connected to at least one receiver coil Rx1. Optionally, the sensor device 201 may also include a second receiver coil Rx2, which may also be connected to the receiver circuit 220, or may be connected to a second receiver circuit (not shown). The sensor device 201 also includes an evaluation circuit 230 configured to interpret signals(s) received from at least one receiver coil Rx1, Rx2, and more specifically, to determine whether the target 202 is in a first position or a second position relative to the sensor device.

[0186] In the embodiment of FIG. 2(a), the sensor device 201 further includes a switch 240 (e.g., a "normally closed switch" or a "normally open switch") controlled by the evaluation circuit 230. In one embodiment, the switch 240 will close when the target 202 is relatively close to the sensor device 201, and will open when the target is relatively far away from the sensor device. In another embodiment, the switch 240 will open if the target 202 is relatively close to the sensor device 201, and will close if the target is relatively far away from the sensor device.

[0187] These are the most important blocks of the proximity sensor device 201, which will be described in more detail. However, in actual implementations, there may be other blocks and / or components (not explicitly shown), such as, for example: oscillator circuit, clock divider, phase-locked loop (PLL), (multiple) amplifiers, (multiple) comparators, modulator, demodulator, analog-to-digital converter (ADC), (multiple) resistors, (multiple) capacitors, (multiple) diodes, voltage regulator, digital processor, shift register, timer, non-volatile memory, serial interface, pads. All of these blocks and / or components are known in the art and therefore do not require further explanation here.

[0188] In this application, blocks and components including those in the transmitting circuit 210, receiving circuit 220 and evaluation circuit 230 will be subdivided into four categories: coils, active components (e.g., transistors), passive components (e.g., resistors, capacitors) and pads, for reasons that will be further clarified.

[0189] Figure 2(b) shows another exemplary block diagram of a proximity sensor system 250, which includes another proximity sensor device 251 and a target 202, which may be the same as or different from the metallic or magnetic target in Figure 2A.

[0190] The proximity sensor device 251 can be considered a variant of the proximity sensor device 201 of FIG2(a), which does not include switch 240, but provides a value or signal of the evaluation circuit or derived therefrom to an output (e.g., a node or pin of sensor device 251). All other things described above for sensor device 201 of FIG2(a) also apply to sensor device 251 of FIG2(b). In fact, sensor device 251 of FIG2(b) is often referred to as an “inductive switch” even though it does not have an “internal switch” that provides a low-resistance or high-resistance path between two pins as shown in FIG2(a), but outputs a value or signal (e.g., a binary value or signal) indicating the detected target position to a general purpose input / output pin (GPIO).

[0191] Those skilled in the art will understand that Figure 2(b) shows only one specific example of how the detection signal can be output, but the invention is certainly not limited to this specific example, and other methods are also envisioned, such as using a two-wire interface, where power is supplied from the outside, the sensor device requires only two pins, and data is transmitted back with either low or high current consumption, in which case the GPIO pins can be omitted; or, for example, via a serial interface (e.g., I...). 2 The interface can be either a C-type interface, a two-wire LIN interface, or a TWI interface, or via a parallel interface, or via any other suitable interface, such as by outputting an analog voltage signal with, for example, three possible levels. This allows it to output not only the detected target position but also the error status, as can be used, for example, in Figure 10(c).

[0192] Figures 3(a) to 7(b) Several examples of proximity sensor systems, including a proximity sensor device and a target, are shown. The proximity sensor device includes one or more transmitter coils Tx1, Tx2 and one or more receiver coils Rx1, Rx2, as well as corresponding electronics (not shown) fully integrated into a monolithic device. The target (e.g., a metallic or magnetic target) can move between a first predefined position and a second predefined position relative to the proximity sensor device (and more specifically, relative to the coils).

[0193] As will be explained in Figure 8(b), the transmitter coil Tx1 has a helix implemented in at least one or at least two metal layers of an interconnect stack located on top of the so-called “active surface” of the semiconductor substrate. The orthogonal projection of this helix onto the active substrate of the semiconductor substrate defines a first (e.g., strip-shaped) region ZTx1 having a first inner perimeter Pi1 and a first outer perimeter Po1. These can also be considered as the inner and outer perimeters of the helix itself.

[0194] Similarly, as will be explained in Figure 9(b), the receiver coil Rx1 also has a helix implemented in at least one or at least two metal layers of an interconnect stack located on top of the active surface of the semiconductor substrate. The orthogonal projection of this helix onto the active substrate of the semiconductor substrate defines a second (e.g., strip-shaped) region ZRx1 having a second inner perimeter Pi2 and a second outer perimeter Po2.

[0195] Referring back to Figure 3(a), it can be seen that the outer periphery Po2 of the second (strip) region ZRx1 corresponds to the projection of the receiver winding onto the active surface. This outer periphery Po2 is completely located within the inner periphery Pi1 of the first (strip) region ZTx1, which corresponds to the projection of the transmitter winding onto the active surface. For ease of description, the implementation can be abstracted in the height direction of the semiconductor device, and the relative positions of the coil and the metal plate 302 in Figure 3(a) can be represented as follows: the receiver coil Rx1 is "located" "inside" the transmitter coil Tx1, and the target 302 does not "overlap" with either of these coils. This means that, in fact, the orthogonal projection of the metal plate 302 onto the active surface of the semiconductor substrate of the sensor device 301 does not overlap with either the (e.g., strip) region ZTx1 corresponding to the winding of the transmitter coil Tx1 or the (strip) region ZRx1 corresponding to the winding of the receiver coil Rx1. This is the first position of the target 302.

[0196] In Figure 3(b), the target is in its second position, and it can be seen that the projection of the target completely overlaps with the projection of the Tx1 coil and the projection of the Rx1 coil.

[0197] A simple detection mechanism can work as follows:

[0198] Assuming target 302 is not near the coil as shown in Figure 3(a), when an alternating current is applied to the transmitter coil Tx1, an alternating magnetic field is generated by the alternating current flowing through the windings of the transmitter coil Tx1. Due to inductive coupling, the receiver coil Rx1 will experience alternating magnetic flux, which will generate an alternating voltage between the start and end nodes of the receiver coil.

[0199] When the target 302 is placed near the coil as shown in Figure 3(b), when the same alternating current is applied to the transmitter coil Tx1, the transmitter coil Tx1 will generate the same alternating magnetic field. However, eddy currents will now flow in the target 302, which will reduce the alternating magnetic flux received by the receiver coil Rx1, thereby causing a decrease in the voltage between the start node and the end node of the receiver coil Rx1.

[0200] Therefore, by measuring the voltage between the start and end nodes of the receiver coil Rx1 and comparing this value with a predetermined threshold voltage, the proximity sensor device can determine whether a target is near the coil.

[0201] Of course, more complex detection schemes can be used, some of which will be described in more detail in Figures 11 and 12.

[0202] Figure 4(a) illustrates a proximity sensor system 400 including a target 402, which is movably arranged relative to a proximity sensor device 401 having a single transmitter coil Tx1 and two receiver coils Rx1, Rx2. The proximity sensor systems 400 of Figures 4(a) and 4(b) can be considered variations of the proximity sensor system 300 of Figures 3(a) and 3(b), the main difference being that the sensor device 401 has two receiver coils instead of just one. Again, for ease of description, only a strip-shaped area is shown, and the height dimension is abstracted. It can be seen that the two receiver coils Rx1, Rx2 are adjacent to each other and both are located within the transmitter coil Tx1.

[0203] In fact, Figures 4(a) to 4(c) Two different embodiments of the proximity sensor system are shown:

[0204] i) Proximity sensor system 400, wherein target 402 is movable between a first position (as shown in FIG4(a), in which the target does not “overlap” with any receiver coil) and a second position (as shown in FIG4(b), in which the target “overlaps” with only one receiver coil);

[0205] ii) Proximity sensor system 450, wherein target 402 is movable between a first position (as shown in FIG. 4(b), in which the target “overlaps” with only one receiver coil) and a second position (in which the target overlaps with two receiver coils).

[0206] In an embodiment, Figures 4(a) to 4(c)The proximity sensor devices 401 and 451 may include a single transmitter circuit and a single receiver circuit, and the two receiver coils Rx1 and Rx2 may be connected in series or in parallel, and the evaluation circuit may be configured to test whether the combined received signal is higher or lower than a predefined threshold.

[0207] In another embodiment, Figures 4(a) to 4(c) The proximity sensor devices 401, 451 may include a single transmitter circuit for stimulating a transmitter coil and two receiver circuits, one for each receiver coil, and an evaluation circuit may be configured to compare signals obtained from the two receiver circuits, or to subtract the signals obtained from the two receiver circuits and to compare the difference with a predefined threshold.

[0208] Figures 5(a) and 5(b) illustrate a proximity sensor system 500 comprising a target 502 (e.g., a metallic or magnetic target) movably arranged relative to a proximity sensor device 501 having one transmitter coil Tx1 and two receiver coils Rx1, Rx2. The proximity sensor systems of Figures 5 and 5(b) can be considered variations of the proximity sensor systems 300 of Figures 3(a) and 3(b) having two receiver coils instead of just one, or variations of the proximity sensor systems 400 of Figures 4(a) and 4(b) with different targets. More specifically, the target 502 of Figures 5(a) and 5(b) is configured to move between a first position (in which only one receiver coil (e.g., only Rx2 in Figure 5(a)) overlaps) and a second position (in which only the other receiver coil (e.g., only Rx1 in Figure 5(b)) overlaps).

[0209] In the examples shown in Figures 5(a) and 5(b), target 502 is relatively small and movable in the direction X parallel to the virtual line passing through the center of the first and second receiver coils, but other arrangements are possible, such as targets having two through holes, an example of which will be described in Figure 10(a).

[0210] Figures 6(a) and 6(b) show a proximity sensor system 600 similar to the proximity sensor systems of Figures 5(a) and 5(b), but in which the target 602 is configured to overlap with only one receiver coil Rx2 when in its first position (shown in Figure 6(a)) or not overlap with any receiver coil when in its second position (shown in Figure 6(b)). This arrangement is equivalent to the system 400 of Figures 4(a) and 4(b), but uses a smaller target 602.

[0211] Figures 7(a) and 7(b) show a proximity sensor system 700 similar to the proximity sensor systems of Figures 4(a) and 4(b), but in which the proximity sensor device 701 includes two transmitter coils Tx1 and Tx2 instead of just one. It can be seen that the first transmitter coil Tx1 and the second transmitter coil Tx2 are adjacent to each other, the first receiver coil Rx1 is located within the first transmitter coil Tx1, and the second receiver coil Rx2 is located within the second transmitter coil Tx2. Sensor device 701 may have a single transmitter circuit configured to simultaneously excite two transmitter coils Tx1 and Tx2 with the same polarity (e.g., when the current in Tx1 flows clockwise, the current in Tx2 also flows clockwise, such that the magnetic field generated by Tx1 at the center of Rx1 points in the same direction as the magnetic field generated by Tx2 at the center of Rx2); or to simultaneously excite the two transmitter coils Tx1 and Tx2 with opposite polarities (e.g., when the current in Tx1 flows clockwise, the current in Tx2 flows counterclockwise, such that the magnetic field generated by Tx1 at the center of Rx1 points in the opposite direction to the magnetic field generated by Tx2 at the center of Rx2). The latter may consume less power. Evaluation circuitry is configured to determine whether the target is in the position shown in Figure 7(a), where neither receiver coil is overlapped by the target, or in the position shown in Figure 7(b), where only one receiver coil is overlapped by the target. The sensor device 700 may have a single receiver circuit and two receiver coils may be connected in series, or the single receiver circuit may be selectively coupled to one of the receiver coils, for example, depending on which transmitter coil is being activated, or the sensor device may have two separate receiver circuits, each connected to a receiver coil.

[0212] Figure 7(b) is used in two different embodiments, but only one picture is shown.

[0213] Figures 7(b) and 7(c) show a proximity sensor system 750 similar to the proximity sensor systems of Figures 4(b) and 4(c), which is a variant of the proximity sensor system 700 described above. In this variant, the evaluation circuit is configured to determine whether the target 702 is in the position shown in Figure 7(b) where only one receiver coil Rx2 is overlapped by the target, or in the position shown in Figure 7(c) where both receiver coils Rx1 and Rx2 are overlapped by the target 702.

[0214] Figures 3(a) to 7(c) The proximity sensor system shown is only an exemplary arrangement of the proximity sensor device and the target, but the invention is not limited to these specific examples and other arrangements, such as the arrangement in FIG10(a), may also be used.

[0215] Figures 8(a) to 8(d)This illustrates how a first transmitter coil Tx1 and (if present) a second transmitter coil Tx2 are implemented in certain embodiments of the invention. Figures 8(a) to 8(d) In the example shown, the transmitter coil comprises three spirals implemented in metal layers M2, M3, and M4, but the invention is not limited thereto, and the transmitter coil can also be implemented in a single metal layer, for example, as shown in... Figures 17(a) to 17(d) As shown.

[0216] Figure 8(a) shows an oversimplified top view of the Tx1 coil, which has only two windings, to keep the figure simple. Figure 8(b) shows a simplified perspective view, where the ends are slightly moved relative to Figure 8(a) for illustrative purposes. Figure 8(c) shows a cross-sectional view in plane α, perpendicular to the semiconductor surface, which passes through the start and end points of Figure 8(a). Figure 8(d) shows a cross-sectional view in plane β, which does not include the start or end points. These figures are not drawn to scale but are intended only to illustrate the principles used.

[0217] According to the principles of the present invention, the proximity sensor device is implemented as a monolithic integrated circuit having a single semiconductor substrate (or "single chip"), preferably implemented in a CMOS process. The semiconductor substrate may be a silicon substrate.

[0218] The semiconductor substrate may have an active surface AS, and may further include at least a transmitter circuit 210, a receiver circuit 220, and an evaluation circuit 230, as well as at least one pad. The semiconductor substrate includes at least one component selected from the group consisting of: active components (such as transistors), passive components (such as resistors or capacitors), and pads.

[0219] The semiconductor substrate may also include an interconnect stack located above or on top of the active surface. The interconnect stack includes multiple metal layers in at least two metal layers, such as four metal layers M1, M2, M3, and M4 separated by an isolation layer (e.g., silicon dioxide).

[0220] According to the principles of the invention, the first transmitter coil Tx1 has a first helix having at least three turns (or windings) formed in a first subset S1 having at least one or at least two metal layers selected from the plurality of metal layers (e.g., M2 and M3, or M2 and M4, or M3 and M4, or M2 and M3 and M4).

[0221] In some embodiments of the invention, the transmitter coil Tx1 is formed in three metal layers M2 to M4, and each of these layers includes about 25 to about 30 turns, for example, 27 or 28 turns. In fact, the number of turns does not have to be an integer; for example, the transmitter coil Tx1 may also contain 27.2 or 27.5 turns.

[0222] The helical trace may have a rectangular cross-section with a width of about 6 μm to about 8.5 μm and a height of about 3 μm to about 5 μm. The spacing between adjacent trace portions may range from about 1 μm to about 5 μm.

[0223] The first metal layer M1 can be used, for example, via connections 861 and 862 implemented in the metal layer M1 to connect the start and end points of the spiral of the metal layer M2 to the transmitter circuit.

[0224] The helix of the first transmitter coil Tx1, when orthogonally projected onto the active surface of the substrate, defines a first region (e.g., a strip region) ZTx1 having a first inner periphery Pi1 and a first outer periphery Po1. Preferably, no active or passive components or pads are implemented in the active surface "AS" between the first inner periphery Pi1 and the first outer periphery Po1 (although they may be implemented) to reduce or minimize capacitive coupling of the Tx1 coil.

[0225] In a preferred embodiment of the invention, the helixes of the transmitter coil Tx1 are connected in parallel at their starting and ending points. Preferably, the helixes of the transmitter coil Tx1 are interconnected not only at their starting and ending points, but also through "additional interconnections" at multiple locations between the starting and ending points, such as at least once per turn, or at least four times per turn, or at least once every 50 μm along the helix, or at least once every 5 μm along the helix. As an example, one such "additional hole vx" is shown in Figure 8(b).

[0226] Alternatively, the helices of the transmitter coil Tx1 can be connected in series.

[0227] Figures 9(a) to 9(d) The figure illustrates how at least one receiver coil Rx1 is implemented in some embodiments of the invention. Figures 9(a) to 9(d) In the example shown, the receiver coil comprises two spirals implemented in metal layers M2 and M3, but the invention is not limited thereto, and the receiver coil may also be implemented in only one metal layer, for example, as shown in... Figures 18(a) to 18(d) As shown in the diagram.

[0228] Figure 9(a) shows an oversimplified top view of the Rx1 coil, which has only two windings (or "turns"), to keep the figures simple. Figure 9(b) shows a simplified perspective view, where the endpoint is slightly shifted relative to Figure 9(a) for illustrative purposes. Figure 9(c) shows a combined view of three cross-sectional views in three planes perpendicular to the semiconductor surface, one through the starting point (including trace 871), one through the interconnect (including trace 873), and one through the endpoint (including trace 872). Figure 9(d) shows a cross-section in plane β, excluding the starting point or endpoint or intermediate interconnect. These figures are not drawn to scale but are intended only to illustrate the principles used.

[0229] According to the principles of the invention, the first receiver coil Rx1 has a second helix having at least three turns (or windings) formed in a second subset S2 having at least one or at least two metal layers selected from the plurality of metal layers (e.g., M2 and M3, or M2 and M4, or M3 and M4, or M2 and M3 and M4). The helices of the Rx1 coils of different layers can be connected in series to obtain a large inductance.

[0230] Both the first subset S1 and the second subset S2 use at least one of the same metal layers. Figures 8(a)-8(d) and Figures 9(a)-9(d) In the example, both the Tx1 coil and the Rx1 coil use metal layers M2 and M3.

[0231] In embodiments of the invention, the receiver coil Rx1 may be formed in only two metal layers (e.g., M2 and M3, or M2 and M4, or M3 and M4), and may include approximately 30 to 40 windings in each layer, for example, a total of 35 × 2 = 70 windings. In other embodiments of the invention, the receiver coil Rx1 may be formed in three metal layers (e.g., M2, M3, and M4), and may include approximately 30 to 40 turns in each layer, for example, a total of 34 × 3 = 102 turns. The helical trace may have a rectangular cross-section with a width of approximately 5 μm, a height of approximately 3 μm, and a spacing of approximately 0.5 or 0.6 μm.

[0232] The first metal layer M1 can be used to connect the start point of the first spiral and the end point of the last spiral, but it can also be used to interconnect spirals (e.g., see interconnection 873 in Figure 9(b)).

[0233] The orthogonal projection of the helix of the first receiving coil Rx1 onto the active surface AS of the substrate defines a second region (e.g., a strip region) ZRx1 having a second inner periphery Pi2 and a second outer periphery Po2. Preferably, no active or passive components or pads are implemented in the active surface AS between the second inner periphery Pi2 and the second outer periphery Po2 to reduce or minimize the capacitive coupling of the Rx1 coil.

[0234] Figure 10(a) shows another proximity sensor system 1000, which can be considered a variant of the proximity sensor system 500 of Figures 5(a)-(b). It can be seen that the proximity sensor device of Figure 10(a) also includes a transmitter coil Tx1 and two receiver coils Rx1, Rx2, but the target 1002 has a first rectangular opening 1091 and a second rectangular opening 1092, which are offset in the X and Y directions. The target 1002 can move parallel to the sensor device in a direction perpendicular to a virtual line X passing through the center of the receiver coils Rx1, Rx2.

[0235] When the target 1002 is in its second position, as shown in FIG10(a), the metal or conductive portion of the target overlaps with the first receiver coil Rx1, while the second opening 1092 overlaps with the second receiver coil Rx2. When the target 1002 is in its first position (not shown), the metal portion of the target overlaps with the second receiver coil Rx2, while the first opening 1091 overlaps with the first receiver coil Rx1, or vice versa.

[0236] Figure 10(b) illustrates an example of a measurement performed by the proximity sensor system 1000 of Figure 10(a), showing the difference (in arbitrary units) between the signal strength received by the first receiver coil Rx1 and the signal strength received by the second receiver coil Rx2 as a function of the position Y of the target 1002 along the Y-axis. Receiver coils Rx1 and Rx2 can be connected in series and the combined difference signal can be evaluated, for example, by active subtraction of an amplifier; or receiver coils Rx1 and Rx2 can be connected in parallel, and the signals received by Rx1 and Rx2 can be passively subtracted, with the result applied as a single-ended input signal to an amplifier and referenced relative to a reference voltage.

[0237] In applications where a proximity sensor system is used to detect whether a target 1002 is in its first or second position, it is sufficient to compare the measured difference signal with a single threshold voltage Vth. Specifically, if the difference signal is greater than the threshold voltage Vth, the target is in its first position, and if the difference signal is less than the threshold voltage, the target is in its second position. In these applications, the transition region between the first and second positions is not considered.

[0238] In practical implementations, a Schmitt trigger can be used instead of a simple comparator because the Schmitt trigger has a certain hysteresis to avoid unnecessary switching during the transition from the first position to the second position.

[0239] Note that the two openings 1091 and 1092 of the specific target shown in Figure 10(a) are both rectangular in shape, but this is not necessary for the operation of this invention, and other shapes, such as triangles or trapezoids, or even circles or ellipses, can be used. Furthermore, in actual implementations, the relative positions of the two openings 1091 and 1092 may differ from those shown in Figure 10(a). For example, the two openings may be spaced apart by a distance 1093 in the X direction, which may be greater than or equal to zero, and / or the two openings may be spaced apart by a distance 1094 in the Y direction, which may be greater than or equal to zero. These distances 1093 and 1094 may be equal, or they may be different. The size of the openings, the shape of the openings, and the offset between the openings can be optimized to obtain the maximum signal amplitude. They can also be optimized to obtain the desired signal shape as a function of mechanical movement. However, these aspects are not within the scope of this invention.

[0240] Figure 10(c) shows a variant of Figure 10(b) where the measured signal is compared to two threshold levels. Such a system also allows detection of the target 1002 in its first position when the difference signal is greater than a first threshold Vth1, and detection of the target 1002 in its second position when the difference signal is less than a second threshold Vth2. However, it also allows for the detection of problems, such as detecting mechanical defects if the difference signal remains between the first and second thresholds for a period exceeding a predetermined time. This provides additional functionality that can be used for purposes such as functional safety.

[0241] Figure 10(d) shows the measurement results of another proximity sensor system when the target moves parallel to the semiconductor device. In fact, three curves are shown: the first curve (indicated by a black square) for an arrangement where the target moves parallel to the sensor device at a distance g equal to 1.0 mm; the second curve (indicated by a black circle) for an arrangement where the target moves parallel to the sensor device at a distance g equal to 1.5 mm; and the third curve (indicated by a black triangle) for an arrangement where the target moves parallel to the sensor device at a distance g equal to 2.0 mm. It can be seen that the smaller the value of the air gap “g”, the stronger the signal. More specifically, the signal strength at distances of 1.5 mm and 2.0 mm is approximately 40% and 15% of the signal strength at 1.0 mm, respectively.

[0242] Figure 10(e) is a graph derived from the measurements in Figure 10(d), which can be used by another proximity sensor system in which the target moves in a direction perpendicular to the sensor device. By comparing the measured signal with a threshold level Vth3, the sensor device can determine whether the target is closer to or farther than 1.0 mm from the sensor device. Similarly, by comparing the measured signal with a threshold level Vth4, the sensor device can determine whether the target is closer to or farther than 1.5 mm. By comparing the measured signal with a threshold level Vth5, the sensor device can determine whether the target is closer to or farther than 2.0 mm, and so on. From the measurement results in Figure 10(d), it can be understood that if the signal-to-noise ratio is high enough, targets reaching approximately 2.5 mm or approximately 3.0 mm can also be detected.

[0243] Figure 11(a) shows a schematic block diagram of an exemplary transmitter circuit 1110, and Figure 11(b) shows a schematic block diagram of an exemplary receiver circuit 1120, followed by an exemplary evaluation circuit 1130 (as may be used in embodiments of the present invention).

[0244] Transmitter circuitry, receiver circuitry, and evaluation circuitry are known in the art and are not the primary focus of this invention. The following explanations are for illustrative purposes only and are therefore brief. For the same reason, this invention is not limited to... Figures 11(a) to 12(b) The specific circuit disclosed herein can also be used.

[0245] The transmitter circuit 1110 of Figure 11(a) includes a bridge circuit having: a first branch in which a first transistor T1 and a second transistor T2 are connected in series between a power supply voltage Vdd and a ground voltage Vss; and a second branch in which a third transistor T3 and a fourth transistor T4 are connected in series between Vdd and Vss. The gate nodes of the transistors are driven by complementary signals RCO and RCO′, which are obtained from an oscillator circuit (not shown), configured, for example, as an RC oscillator oscillating in a frequency range of about 20 MHz to about 30 MHz (e.g., about 24 MHz). The source nodes of the transistors are connected to the power supply or ground voltage, and the drain nodes of the transistors are connected to an LC resonator (or LC resonant circuit) formed by the transmitter coil Tx1 and capacitor C1.

[0246] In a preferred embodiment of the invention, the inductance of the transmitter coil is preferably relatively high, and the series resistance of the transmitter coil is preferably relatively low. Capacitor C1 is intentionally added to avoid the effective capacitance of the LC oscillator being primarily determined by parasitic capacitance, which also depends on temperature.

[0247] In a preferred embodiment of the invention, the LC circuit formed by the transmitter coil Tx1 and capacitor C1 is not excited at its resonant frequency, but is preferably driven at a frequency intentionally chosen slightly lower than the resonant frequency of the LC oscillator. This frequency can be generated by an RC oscillator circuit, optionally followed by a PSK (phase shift keying) modulator. In one embodiment, the R and C of the RC oscillator are embedded in a semiconductor substrate, and may even be located inside the transmitter coil Tx1 and / or (multiple) receiver coils.

[0248] As described above, the main purpose of the transmitting circuit 1110 is to pass an alternating current through the transmitter coil Tx1 to generate an alternating magnetic field that can be sensed by the receiver coil.

[0249] Figure 11(b) shows a circuit in which two receiver coils, Rx1 and Rx2, are connected in series to generate a differential voltage signal induced by the alternating magnetic flux received by the receiver coils, due to their inductive coupling with the transmitter coil Tx1. The differential signal is amplified by a differential amplifier and then mixed, demodulated, or down-converted using a reference signal “Ref” (e.g., a sinusoidal signal with a predetermined frequency, for example, obtained from an RCO oscillator (optionally followed by a PSK modulator)). The demodulated signal can then be rectified (not shown) and / or low-pass filtered (LPF) to generate a signal indicating the amount of magnetic flux received by the receiver coils, an example of which is shown below. Figures 10(b) to 10(d) As shown.

[0250] The advantage of using two receiver coils (instead of just one) is that they allow for easier debalancing of the differential amplifier, thereby improving contrast. Another advantage is that, for example, if the combined signals obtained from the two receiver coils have opposite polarities, they may be less sensitive to external interference fields.

[0251] The signal can then be further processed, for example, compared with at least one threshold voltage Vth in the evaluation circuit 1130. The comparator output can be used to operate the switch shown in Figure 2(a), or can be output as an analog signal, or can be digitized and output as a digital signal indicating the target position, for example via a general purpose input / output pin (GPIO), or via a serial communication bus (not shown), or via a two-wire interface, etc.

[0252] Figure 12(a) shows a schematic block diagram of another exemplary transmitting circuit 1210, and Figure 12(b) shows a schematic block diagram of another exemplary receiver circuit 1220, which can be used in embodiments of the present invention and can be regarded as a variant of the circuits of Figures 11(a) and 11(b).

[0253] The main difference between transmitter circuit 1210 in Figure 12(a) and transmitter circuit 1110 in Figure 11(a) is that the gate is not driven by a complementary signal of the RC oscillator itself, but by a signal fmod, fmod′ derived from it by modulation (e.g., by phase shift keying (PSK)), more specifically, by BPSK modulation (binary phase shift keying) at about 500 kHz to about 2 MHz (e.g., about 1 MHz).

[0254] The main difference between receiver circuit 1220 in Figure 12(b) and receiver circuit 1120 in Figure 11(b) is that the mixer or modulator or demodulator is not driven by the oscillator signal itself, but by a modulated (e.g., BPSK modulated) version.

[0255] The main advantage of using a modulator in the transmitter circuit and a corresponding demodulator in the receiver circuit is that the resulting signal "out" is less affected by amplifier offset, thus allowing for a more accurate comparison with the threshold voltage.

[0256] Preferably, a synchronous demodulator is used, although this is not always necessary.

[0257] Figures 11(a) and (b) and Figures 12(a) and (b) illustrate two single-stage transmitter and receiver circuits that can be used in proximity sensor devices, but the invention is certainly not limited to these specific circuits, and other transmitter and receiver circuits can also be used. In a preferred embodiment, the receiver circuit has at least two or at least three down-conversion stages, each with an amplifier and a demodulator. In this way, the received signal can be amplified, and the amplifier offset can be reduced. Such circuits are well known in the art and therefore do not need to be described in detail here.

[0258] Figures 13(a) to 13(c) An example of a possible layout that can be used in embodiments of the invention is shown, wherein the proximity sensor device includes a single transmitter coil Tx1 and two receiver coils Rx1, Rx2. As described above, the inventors designed, implemented, and evaluated several test chips to verify:

[0259] (i) Whether it is possible to implement the transmitter coil and receiver coil, as well as the electronics (particularly including the transmitter circuit, receiver circuit, and evaluation circuit), on a single chip, i.e., as a monolithic integrated semiconductor substrate; and

[0260] (ii) Whether the received signal is large enough to be distinguished from noise (or in other words, whether it has a sufficiently high signal-to-noise ratio (SNR); and

[0261] (iii) For a target in the first position, is the received signal sufficiently different from that of a target in the second position, especially considering a distance (air gap) of 2.0 mm, or even 2.5 mm, or even 3.0 mm;

[0262] (iv) Last but not least, it is important to determine whether the circuit can still function reliably if one or more active components (e.g., transistors, amplifiers, etc.) and / or passive components (e.g., resistors, capacitors, etc.) and / or pads are implemented within the inner circumferential region of any coil.

[0263] The inventors faced numerous biases, challenges, and uncertainties. For example, how to fabricate a coil with relatively high inductance and relatively low series resistance on a relatively small chip (e.g., approximately 1.0 mm × 2.0 mm), allowing only a very limited number of coil turns, while considering the need for very small traces and sufficient spacing between traces, meant that the transmitter's "quality factor" would be quite poor (e.g., in the range of approximately 1.3 to approximately 3.5), resulting in a very weak received signal. It was uncertain whether the receiver signal would be sufficiently strong relative to noise. Furthermore, it was impossible to predict the effects of placing active or passive components (especially those with metal parts, such as capacitors or pads) within the receiver coil, particularly how a weak receiver signal would affect the circuit, and vice versa.

[0264] For the sake of completeness, it should be noted that the test chip may not have undergone sufficient space optimization to reduce design and placement workload, but the layout of various modules should still be kept as similar as possible. Therefore, the chip area indices presented should not be regarded as absolute or optimal values, but they are good indicators that are achievable.

[0265] Figure 13(a) gives a rough impression of how much area would be required if all active and passive components, as well as pad 1350, were located outside the area defined by the transmit and receive coils (or more specifically, outside the perimeter Po1 of the transmit coil). Similarly, while the size of this layout could be further reduced by moving the receiver coil closer and decreasing the size of the transmitter coil, this was not achieved because the inventors wanted to compare the performance of various test chips while the coils remained unchanged, but certain components were moved into the strip area.

[0266] Figure 13(b) shows one of the layouts of the test chip, illustrating how much area would be required with all active and passive components and pad 1350 located within the inner periphery Pi1 of the transmit coil Tx1 but outside the outer peripheries Po2a and Po2b of the receiver coils Rx1 and Rx2.

[0267] Figure 13(c) shows another layout of one of the test chips, wherein a first portion 1350a (in a specific example: two pads) of active and / or passive components and / or pads is located within the inner periphery of the first receiver coil Rx1, a second portion 1350b of active and / or passive components and / or pads (in a specific example: two pads) is located within the inner periphery of the second receiver coil Rx2, and the remaining active and passive components and pads 1350c are located within the inner periphery of the transmitter coil Tx1 but outside the outer periphery of the receiver coils Rx1 and Rx2. Preferably, the layout of the two receiver coils and their components is symmetrical (e.g., mirrored). For completeness, it should be noted that all test chips are coreless, i.e., they do not have integrated magnetic concentrators or flux conduits.

[0268] The test chip was evaluated, and the experimental results are summarized as follows: the chip size is approximately 3 to 4 mm. 2 (e.g., 2.0mm × 2.0mm or 1.4mm × 2.15mm), the typical distance to the target is: 0.2mm to 1mm, or 0.2mm to 2mm, or 0.2mm to 3mm, the power supply voltage used is about 3 volts DC, the power consumption of the entire chip is about 15 to 20mW, and the power consumption of the transmitting circuit and transmitting coil is about 6 to 10mW. The frequency of the RC oscillator is about 24MHz. Divide this frequency by a factor of (10) to generate a 2.4MHz digital clock, and then divide by a factor of two to obtain a 1.2MHz BPSK frequency. The amplitude of the current flowing in the transmitter coil Tx1 is about 0.5 to 10mA, and the amplitude of the difference signal detected by the receiver coil is about 10μV to 10mV (depending on the air gap and temperature), and it has been found that the output signal (after amplification and demodulation) has a sufficiently high signal-to-noise ratio (above 20dB, as from Figures 10(b) to 10(d) (This is understandable) to allow reliable detection of whether the target is in its first or second position. This paragraph is for illustrative purposes only, but of course, the invention is not limited to these specific values, and other values ​​may be used, for example, a power supply voltage of 5V or 12V may also be used.

[0269] Surprisingly, virtually no interference was found between the RF signal and the digital circuitry. One might assume that an uncorrelated clock must be used to avoid or reduce interference, but this is not the case. While the digital clock frequency in the test chip was generated by dividing the RF frequency by a factor of 10, other division factors in the range of 2 to 20 could also be used, such as 4, 5, 6, 8, 12, or 16.

[0270] The inventors were astonished to discover that, optionally by using higher supply voltages and / or higher transmit power, the test chip's detection operates reliably in air gaps up to 2.0 mm, and the signal-to-noise ratio (SNR) indicates that the detection can even operate in air gaps up to 2.5 mm or even 3.0 mm. This is far superior to known prior art systems, where the coil diameter needs to be at least six times the maximum air gap, i.e., at least 18 mm.

[0271] In some test chips, the pads are located on the inner periphery of the receiver coil strip area and can also function.

[0272] In some test chips, the capacitor array is located within the inner periphery of the receiver coil strip region, and it can still work, which is quite surprising because capacitors contain a lot of metal.

[0273] In some test chips, both analog and digital circuitry are located within the inner periphery of the receiver coil's strip region, and this works, which is quite surprising, especially considering the very small signal received by the receiver coil. One would expect that analog and digital circuitry would interfere with the receiver signal, and vice versa.

[0274] Those skilled in the art who benefit from this disclosure—once this invention is published—will certainly be able to place more electronic components and / or all pads within the inner periphery of the receiver coil and further optimize the design by applying the teachings of this invention.

[0275] Figures 14(a) to 14(c) yes Figures 13(a) to 13(c) The abstract representation, originally drawn in color to calculate the area of ​​different regions, is presented in shade in this patent application because a patent application cannot be filed in color at the time of filing this application.

[0276] A comparison of Figures 14(a) and 14(b) shows that moving circuit 1450 into the Tx1 coil can result in a saving of approximately 15%.

[0277] A comparison of Figures 14(b) and 14(c) shows that further moving a portion of the circuitry within the Rx1 and Rx2 coils could save an additional 3.25%, but there is still room for further reduction. In fact, the portions occupied by the various areas of the layout in Figure 14(b) are listed in the table below:

[0278] (Strip) area ZRx1 + (Strip) area ZRx2 of receiver coil Approximately 29% Electronic components + pads Approximately 13% Available space within the inner circumference of the receiver coil Approximately 11%

[0279] The table shows that if the space within the inner circumference of the receiver coil is completely filled with electronic components, the receiver coil is moved closer together, and the size of the transmitter coil is reduced, and assuming that the performance remains roughly the same, the chip area in Figure 14(b) will be reduced by 11%, which is huge, but perhaps a bit too optimistic.

[0280] As another example of estimating the area that can be saved (which may be considered an underestimation of what can be achieved), the electronic component region 1450 of Figure 14(b) is artificially divided into eight equal parts, and one of these eight parts 1450a is moved into the inner circumference of the first receiving coil Rx1, a second part 1450b is moved into the inner circumference of the second receiving coil, and the remaining six parts 1450c have smaller areas, the distance between the receiving coils is reduced, and the size of the transmitting coil is reduced. In this example, 2 / 8 = 1 / 4 of the area can be saved, which is approximately 3.25% of the chip area of ​​Figure 14(b). This is still a significant saving due to the principles and discoveries of the present invention.

[0281] Overall, the area of ​​the sensor device in Figure 14(a) can therefore be reduced by approximately 18.25% (i.e., 15% + 3.25%) to a value in the range of approximately 26% (i.e., 15% + 11%), which is substantial.

[0282] Figure 15(a) illustrates another example of a possible layout that can be used in embodiments of the present invention. In this example, the proximity sensor device has two transmitter coils Tx1, Tx2 and two receiver coils Rx1, Rx2 in the region between the two transmitter coils, electronic component 1550, two pads located within the inner periphery of the strip region of the first receiver coil Rx1, and two pads located within the inner periphery of the strip region of the second receiver coil Rx2. As mentioned above, this is not a fully optimized design.

[0283] The two transmitter coils can be driven by the same excitation signal or excitation signals with opposite polarities, and the receiver coils can be connected in series again (so that the signals are subtracted), and the terminals can be connected to the differential amplifier again.

[0284] Figure 15(b) provides a rough impression of the area required when all active and passive components and pads are located outside the area defined by the transmit and receive coils. The table below lists the portion of the area occupied by each region in the layout of Figure 15(b):

[0285] The (band-shaped) region of Rx1+Rx2 Approximately 23% Electronic components + pads Approximately 21% Available space within Rx1+Rx2 (receiver coil) Approximately 15%

[0286] Therefore, theoretically, if the space inside the receiver coil can be completely filled, the required chip area will be reduced by 15%. This can be considered an upper limit.

[0287] Figure 15(c) provides an impression of how much area can be saved by “moving” a portion of the circuitry into the inner periphery of the strip region of the receiver coil. In Figure 15(b), region 1550 is divided into 16 equal parts, with two parts 1550a moved into coil Rx1 and two other parts 1550b moved into coil Rx2, resulting in a chip area reduction of approximately 5%. This is a significant saving, made possible by the principles and discoveries of this invention, demonstrating that a monolithic proximity sensor device can be constructed using electronic components (e.g., active and / or passive components), and / or pads can be placed within the inner periphery of the transmitter coil and / or receiver coil.

[0288] Figure 16 An example of a shield 1600 (e.g., a metallic shield) that can be arranged, for example, between a winding of a transmitter coil and windings of one or more receiver coils is shown. This reduces capacitive coupling between the transmitter coil and the receiver coil. Such a shield can also be arranged between the transmitter coil and an electronic component or pad located within the inner periphery of the transmitter coil to reduce capacitive coupling between the transmitter coil and the component or pad. Similarly, such a shield can be arranged between the receiver coil(s) and an electronic component or pad located within the inner periphery of the receiver coil(s) to reduce capacitive coupling between the receiver coil(s) and the component or pad.

[0289] In the specific example shown, the shielding consists of four essentially planar walls, but this is not always necessary. Figure 16 In the example shown, these walls are not interconnected, but considering that the orthogonal projection of the walls will not form loops that generate eddy currents, they can be interconnected, for example, between three of the four corners. The walls can remain suspended or be connected to ground or a power supply voltage. In the example shown, channels for providing two signals in metal layer M1 can be provided, but of course, more or fewer channels can be provided.

[0290] Figures 17(a) to 17(d) yes Figures 8(a) to 8(d) This is a variant of the present invention, and schematically illustrates how a transmitter coil with only one helix (at least three turns) can be implemented in a single metal layer, as implemented in an embodiment of the present invention. In the example shown, the helix is ​​implemented in metal layer M2, and metal layer M1 is used to connect the start and end points of the helix to the transmitter circuit (not shown), but the invention is not limited thereto, and other metal layers may also be used.

[0291] Figures 18(a) to 18(d) yes Figures 9(a) to 9(d)This is a variant of the present invention, and schematically illustrates how a receiver coil with only one spiral can be implemented in a single metal layer, as implemented in an embodiment of the invention. In the example shown, the spiral is implemented in metal layer M3, and metal layer M1 is used to connect the start and end points of the spiral to the transmitter circuit (not shown), but the invention is not limited thereto, and other metal layers may also be used.

[0292] Figure 19 Another method for reducing capacitive coupling between the transmitter coil Tx and the receiver coil Rx is shown. The helical traces of the transmitter and receiver coils can be implemented primarily in a single metal layer of the interconnect stack (except for cross nodes 1997a, 1997b, 1998, which can be achieved by using two vias at each cross node to form a U-shape or bridge), or in multiple metal layers of the interconnect stack, in which case the "crossing" occurs in different layers, thus eliminating the need for vias.

[0293] It can be seen that, Figure 19 The projection of the transmitter coil is essentially symmetrical about the Y-axis, except at the crossover points 1997a and 1997b. This causes the voltage swing at each point on the transmitter coil to decrease from the outer periphery to the inner periphery. This holds true regardless of the layout of the RX coil. Figure 19 In the example, the orthogonal projection of the RX coil also has an axis of symmetry, but this is not absolutely necessary.

[0294] In the example shown, both the TX and RX coils have only three turns to avoid overloading the image, but the invention is certainly not limited to this.

[0295] exist Figure 19 In the example, both the TX and RX coils have orthogonal projections that are substantially symmetrical about the Y-axis (except for the crossover node). The start point c1 and end point c2 of the transmitter coil Tx are located on the outer periphery of the transmitter coil Tx. Transmitter circuit ( Figure 19 (Not shown) is configured to apply an AC voltage ΔV1 between these points. Therefore, the voltage swing ΔV1 generated between the starting point c1 and the ending point c2 of the transmitter coil Tx is larger than the voltage swing ΔV2 further inward. Typically, when using this configuration, the voltage swing decreases from the outer periphery of the TX coil towards the inner periphery.

[0296] exist Figure 19 In the example, the start point c3 and end point c4 of the receiver coil Rx are located at the inner circumference of the receiver coil Rx. Therefore, the voltage swing at the outer circumference of the RX coil is relatively low and increases towards the inner circumference and towards the start point c3 and end point c4.

[0297] It is important to note that the voltage swing V1 applied by the transmitter circuit is relatively large, while the voltage swing U1 caused by the AC magnetic field is relatively low. This is why the symmetrical arrangement of the TX coil significantly reduces the capacitive coupling between the TX and RX coils. A symmetrical arrangement of the RX coil can further reduce this capacitive coupling, but as mentioned above, it is not an absolutely necessary factor for the effectiveness of this invention.

[0298] To the best of the inventor's knowledge, such as Figure 19 The coil arrangement shown is unknown in the art: it includes a transmitter coil TX and a receiver coil RX, each implemented in one or more metal layers of an interconnect stack of semiconductor devices, wherein the orthogonal projection of the receiver coil RX lies entirely within the orthogonal projection of the transmitter coil TX, and the orthogonal projection of the TX coil has an axis of symmetry Y (except for the cross node). Furthermore, to the inventor's knowledge, the technical effect of reducing capacitive coupling between the coil TX and the RX coil located therein is also unknown in the art.

[0299] This structure can be used in proximity sensor devices as described above, but it can also be used in other applications, such as in integrated transformers.

[0300] While the invention has been primarily described with respect to targets in the form of metal plates with openings, it is not limited thereto and is also applicable to other conductive targets, such as printed circuit boards having one or more conductive areas / regions and electronically non-conductive areas / regions. The latter can be a physical opening in the printed circuit board or simply an area without a metal plane or metal trace.

Claims

1. A proximity sensor device comprising a single monolithic integrated semiconductor substrate, the proximity sensor device comprising: An active surface, the active surface comprising at least one component selected from the group consisting of: an active component, a passive component, and a pad; An interconnect stack, the interconnect stack being on top of the active surface, the interconnect stack comprising multiple metal layers (M1, M2, M3, M4) of at least two metal layers separated by an isolation layer. At least a first transmitter coil (Tx1) and a first receiver coil (Rx1) are electrically insulated from each other. The first transmitter coil (Tx1) has a first helix with at least three turns, formed in a first subset (S1) having at least one metal layer (M2, M3, M4; M2, M3, M4) selected from the plurality of metal layers, and wherein the orthogonal projection of the first helix on the active surface has a first inner periphery (Pi1) and a first outer periphery (Po1). The first receiver coil (Rx1) has a second helix with at least three turns, formed in a second subset (S2) having at least one metal layer (M3, M4; M2, M3, M4) selected from the plurality of metal layers, and wherein the orthogonal projection of the second helix on the active surface has a second inner periphery (Pi2) and a second outer periphery (Po2). The at least one component is located within the first inner periphery (Pi1) and within the second inner periphery (Pi2), or is located within the first inner periphery (Pi1) but outside the second outer periphery (Po2).

2. The proximity sensor device as described in claim 1, in, The first transmitter coil (TX1) is formed in a single metal layer, and the first receiver coil (RX1) is formed in the same single metal layer as the transmitter coil. Alternatively, the first transmitter coil (TX1) is formed in only one metal layer, and the first receiver coil (RX1) is formed in only one metal layer that is different from the metal layer in which the transmitter coil is formed; Alternatively, the first transmitter coil (Tx1) is formed in a first subset (S1) of the interconnect stack, the first subset comprising at least two metal layers; and wherein the first subset (S1) and the second subset (S2) have at least one common metal layer (M3). Alternatively, the first transmitter coil (Tx1) is formed in a first subset (S1) of the interconnect stack, the first subset comprising at least two metal layers; and the first receiver coil (Rx1) is formed in a second subset (S2) of the interconnect stack, the second subset comprising at least two metal layers; and the first subset (S1) and the second subset (S2) have at least one or at least two common metal layers.

3. The proximity sensor device as claimed in claim 1, further comprising: A transmitter circuit is included in the active surface and connected to the first transmitter coil (Tx1), and is configured to transmit an alternating signal; A receiver circuit is included in the active surface and connected to the first receiver coil (Rx1), and is configured to receive the alternating signal; An evaluation circuit, which is included in or connected to the receiver circuit, is configured to determine the condition of a conductive or magnetic target based on a received alternating signal.

4. The proximity sensor device as described in claim 3, in, The evaluation circuit is further configured to determine whether the conductive target or the magnetic target is in a first predefined position or a second predefined position, and to output a corresponding signal or value, or to open or close an internal switch between two terminals of the proximity sensor device.

5. The proximity sensor device as described in claim 1, in, The orthogonal projection of the second outer periphery (Po2) of the first receiver coil (Rx1) lies entirely within the orthogonal projection of the first inner periphery (Pi1) of the first transmitter coil (Tx1).

6. The proximity sensor device as described in claim 1, The device further includes at least one metal shield (1600), which takes the form of a plurality of traces of at least two traces positioned vertically to each other in at least two layers of the interconnect stack, the traces being interconnected through a plurality of vias; The metal shield is located between the first inner periphery of the first transmitter coil (Tx1) and the second outer periphery of the first receiver coil (Rx1).

7. The proximity sensor device as described in claim 1, It includes only two coils, namely the first transmitter coil (Tx1) and the first receiver coil (Rx1). And among them, The area between the first inner circumference and the first outer circumference of the first transmitter coil (Tx1) is equivalent to 36% to 44% of the active surface; Furthermore, the area between the second inner circumference and the second outer circumference of the first receiver coil (Rx1) is equivalent to 15% to 25% of the active surface.

8. The proximity sensor device as described in claim 1, in, The substrate further includes a second receiver coil (Rx2), which is electrically insulated from the first transmitter coil (Tx1); The second receiver coil (Rx2) has a third helix with at least three turns, formed in a third subset (S3) having at least one or at least two metal layers selected from the plurality of metal layers; The first subset (S1) and the third subset (S3) share at least one metal layer (M3, M4). Furthermore, the orthogonal projection of the third helix onto the active surface lies entirely within the first inner circumference (Pi1) of the first transmitter coil (Tx1).

9. The proximity sensor device as described in claim 8, It includes only three coils: the first transmitter coil (Tx1), the first receiver coil (Rx1), and the second receiver coil (Rx2). And among them, The area between the inner and outer circumferences of the first transmitter coil (Tx1) is equivalent to 36% to 44% of the active surface; Furthermore, the area between the inner and outer circumferences of the first receiver coil (Rx1) is equivalent to 12% to 18% of the active surface; Furthermore, the area between the inner and outer circumferences of the second receiver coil (Rx2) is equivalent to 12% to 18% of the active surface.

10. The proximity sensor device as claimed in claim 1, in, The substrate further includes a second receiver coil (Rx2) and a second transmitter coil (Tx2); Wherein, the second receiver coil (Rx2) is electrically insulated from the first transmitter coil (Tx1) and from the second transmitter coil (Tx2), and wherein the second transmitter coil (Tx2) is electrically insulated from both the first receiver coil (Rx1) and the second receiver coil (Rx2); The second receiver coil (Rx2) has a third helix formed in at least one layer in the same place as the first receiver coil (Rx1), wherein the orthogonal projection of the third helix onto the active surface defines a third inner periphery and a third outer periphery; The second transmitter coil (Tx2) has a fourth helix formed in at least one layer in the same place as the first transmitter coil (Tx1), wherein the orthogonal projection of the fourth helix onto the active surface defines a fourth inner periphery and a fourth outer periphery; Wherein, the outer periphery of the second transmitter coil (Tx2) is completely outside the outer periphery of the first transmitter coil (Tx1); Furthermore, the outer periphery of the first receiver coil (Rx1) is completely located within the inner periphery of the first transmitter coil (Tx1); Furthermore, the outer periphery of the second receiver coil (Rx2) is completely located within the inner periphery of the second receiver coil (Rx2).

11. The proximity sensor device as claimed in claim 10, in, Each of the first transmitter coil (Tx1) and the second transmitter coil (Tx2) includes three spirals connected in parallel, the spirals being implemented in three metal layers (M2, M3, M4) and each having 22 to 32 turns; Furthermore, each of the first receiver coil (Rx1) and the second receiver coil (Rx2) includes two spirals connected in series, the spirals being implemented in two metal layers (M3, M4) or in three metal layers (M2, M3, M4) and each having 30 to 40 turns.

12. The proximity sensor device as claimed in claim 10, Includes only four coils (Tx1, Rx1, Tx2, Rx2); And among them, The sum of the area between the inner and outer circumferences of the first transmitter coil (Tx1) and the area between the inner and outer circumferences of the second transmitter coil (Tx2) is equivalent to 35% to 45% of the active surface. Furthermore, the sum of the area between the inner and outer circumferences of the first receiver coil (Rx1) and the area between the inner and outer circumferences of the second receiver coil (Rx2) is equivalent to 20% to 28% of the active surface; and Wherein, at least 1% of the combined area within the second inner periphery (Pi2) of the first receiver coil (Rx1) and the third inner periphery (Pi3) of the second receiver coil (Rx2) is occupied by one or more active or passive components or pads.

13. The proximity sensor device as claimed in claim 1, in, The first transmitter coil (Tx1) comprises a stack having at least two helical windings arranged one above the other, with each layer in the first subset (S1) of the metal layers having one helix; Adjacent spirals are interconnected by multiple through-holes, which are spaced apart by less than 100 micrometers.

14. The proximity sensor device as described in claim 13, in, The multiple through holes are spaced apart by less than 50 micrometers.

15. The proximity sensor device as claimed in claim 13, in, The multiple through holes are spaced apart by less than 20 micrometers.

16. The proximity sensor device as claimed in claim 13, in, The multiple through holes are spaced apart by less than 10 micrometers.

17. The proximity sensor device as claimed in claim 13, in, The multiple through holes are spaced apart by less than 5 micrometers.

18. The proximity sensor device as claimed in claim 1, in, Each turn of the first transmitter coil (Tx1) has a substantially equal rectangular cross-section, and each turn of the first transmitter coil (Tx1) has a predefined height in a direction perpendicular to the semiconductor substrate and a predefined width in a direction parallel to the semiconductor substrate; and Wherein, the ratio of the sum of the heights to the average of the widths is less than 1.

19. A proximity sensor system (100; 200; 250), comprising: The proximity sensor device (101) as described in claim 1; 201; 251）； And a conductive or magnetic target (102; 202; 252) that can move relative to the proximity sensor device along a predefined trajectory between a first position and a second position.

20. The proximity sensor system as described in claim 19, in, The conductive target or the magnetic target can move in a predefined direction parallel to the semiconductor substrate; Furthermore, the amount of overlap between the projection of the conductive target or the magnetic target and the inner circumference of the at least one receiver coil (Rx1, Rx2) is different when the target is in a first position or a second position of the conductive target or the magnetic target; Furthermore, the proximity sensor device further includes an evaluation circuit configured to determine, based on the overlap amount, whether the conductive target or the magnetic target is at a first position or a second position of the target.

21. The proximity sensor system of claim 19, comprising: At least two monolithically integrated proximity sensor devices as described in claim 1; A metallic target that is movable relative to the at least two proximity sensor devices.

22. The proximity sensor system as described in claim 19, in, The proximity sensor device includes a semiconductor substrate; Furthermore, the predefined trajectory is substantially parallel to the semiconductor substrate and located at a predefined distance (g) from the semiconductor substrate.

23. The proximity sensor system as described in claim 22, in, When in mm 2 The ratio of the total area of ​​the semiconductor substrate, including the first transmitter coil (TX1) and the first receiver coil (RX1), to the predefined distance when expressed in mm is less than 2.

75.

24. The proximity sensor system as described in claim 23, in, When in mm 2 The ratio of the total area of ​​the semiconductor substrate, including the first transmitter coil (TX1) and the first receiver coil (RX1), to the predefined distance when expressed in mm is less than 2.

0.

25. The proximity sensor system as described in claim 23, in, When in mm 2 The ratio of the total area of ​​the semiconductor substrate, including the first transmitter coil (TX1) and the first receiver coil (RX1), to the predefined distance when expressed in mm is less than 1.

25.

26. A seatbelt buckle, comprising the proximity sensor device as described in claim 1.

27. An integrated circuit, comprising: Semiconductor substrate; Interconnect stack, including multiple metal layers located on top of the semiconductor substrate; The coil arrangement includes a transmitter coil (TX) and a receiver coil (RX), both of which are implemented in one or more layers of the interconnect stack. Each of the transmitter coil and the receiver coil includes at least one helix, and each helix includes at least three windings. Wherein, the orthogonal projection of the receiver coil (RX) lies entirely within the orthogonal projection of the transmitter coil (TX); and The orthogonal projection of the transmitter coil (TX) has an axis of symmetry (Y) and has one or more cross nodes (1997a, 1997b) located on the axis of symmetry.

28. An integrated transformer comprising the integrated circuit as claimed in claim 27.

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