Stacked die assembly

Abstract

The present invention discloses a stacked die assembly. A sensor device (1) includes: a lead frame (9); first / second semiconductor dies (2a) having first / second sensor structures (4a, 14a) at first / second sensor positions (L1, L2), and a plurality of first / second bonding pads (7a, 7b) electrically connected to the lead frame (9); the semiconductor die has a square or rectangle with a geometric center (6a); the sensor positions (L1, L2) are offset from the geometric center; the second die (2b) is stacked on top of the first die (2a) and is rotated by a non-zero angle and optionally also offset or displaced (DX, DY) relative to the first die (2a) such that the vertical projections of the first sensor position (L1) and the second sensor position (L2) coincide.

Description

Technical Field

[0001] The present invention relates to the field of sensor devices and, more particularly, to sensor devices used in an automotive environment, the sensor device including two semiconductor dies, one for performing an actual measurement and one for performing a redundant measurement. Background Art

[0002] Sensor devices with high reliability are important in a variety of applications (such as, for example, in automotive applications). In addition, it is generally preferred to include a plurality of substantially identical sensors (e.g., two sensors) in order to provide redundancy (e.g., in applications where ensuring safety is critical).

[0003] Redundant sensor devices are known in the art, where a plurality of substrates each containing at least one sensor are combined in a single package to provide actual sensor measurements and redundant sensor measurements. Devices in which two substrates are placed side by side require a larger coverage area, which is undesirable. To reduce the coverage area, the substrates can be stacked on top of each other (e.g., as Figures 1 - 3 shown), and each solution has its advantages and disadvantages, for example, in terms of package coverage area, package thickness, measurement accuracy, component count, complexity of the production process, etc.

[0004] There is always room for improvement and alternatives. Summary of the Invention

[0005] An object of an embodiment of the present invention is to provide a sensor device including two stacked substrates, each substrate including a sensor structure, in particular a magnetic sensor structure, and a magnetic sensor system including the structure.

[0006] An object of an embodiment of the present invention is to provide such a sensor device and a sensor system for use in an automotive environment to perform actual measurements and redundant measurements (e.g., for improving safety).

[0007] An object of an embodiment of the present invention is to provide such a sensor device in a compact package (e.g., having a relatively small or reduced package coverage area, and / or a relatively small or reduced package height).

[0008] An object of an embodiment of the present invention is to provide such a sensor device in which the measurement results (e.g., the measured signal or the value derived therefrom) better match, and / or are easier or more easily produced or assembled (e.g., are more easily electrically connected to a lead frame, e.g., are more easily wire bonded).

[0009] An object of a specific embodiment of the present invention is to provide such a sensor device in which the two sensor structures are magnetic sensor structures.

[0010] An object of certain embodiments of the present invention is that a sensor device can have two similar or identical substrates, while providing better-matched measurement results and being easy or easier to manufacture or assemble.

[0011] An object of certain embodiments of the present invention is to provide a magnetic sensor device or system that is furthermore highly insensitive to external interference fields.

[0012] These and other objects are achieved by devices and methods according to embodiments of the present invention.

[0013] According to a first aspect, the present invention further provides a sensor device, comprising: a lead frame; a first semiconductor die having a first rectangular shape with a first geometric center (6a), being electrically connected to the lead frame, and comprising a first sensor structure located at a first sensor position; a second semiconductor die having a second rectangular shape equal to the first rectangular shape, having a second geometric center (6b), being electrically connected to the lead frame, and comprising a second sensor structure located at a second sensor position; wherein the first sensor position is offset from the first geometric center; the second sensor position is offset from the second geometric center; the second semiconductor die is stacked on top of the first semiconductor die, and is rotated relative to the first semiconductor die and also optionally shifted, such that the orthogonal projections of the first sensor position and the second sensor position on the lead frame coincide.

[0014] A "sensor structure" comprises one or more "sensitive elements".

[0015] For example, in the case of a "magnetic sensor device", each sensor structure comprises one or more magnetosensitive elements, and may further for example comprise an integrated magnetic concentrator (IMC). For example, the magnetosensitive elements may be selected from the group consisting of: horizontal Hall elements, vertical Hall elements, magnetoresistive elements (such as for example AMR, GMR, TMR elements).

[0016] The "first sensor structure" is located at the "first sensor position", which may be defined as a point that is substantially located "in the middle" of one or more sensitive elements or in the middle between one or more sensitive elements.

[0017] Preferably, the rotation is a rotation about an axis perpendicular to the lead frame.

[0018] Preferably, the first and second semiconductor dies are located on the same side of the lead frame and are oriented such that their active surfaces are oriented in the same direction (e.g., both away from the lead frame).

[0019] Preferably, the relative position L1 of the first sensor position with respect to the first rectangular shape is the same as the relative position of the second sensor position with respect to the second rectangular shape.

[0020] A main advantage of this magnetic sensor device is that electrical connections can be performed in a simple manner on the top side using standard equipment, contrary to Figure 1 the example in Figure 1 where electrical connections 111 (e.g., bonding wires) need to be placed before mounting the second semiconductor die, which complicates the handling.

[0021] An advantage is that the sensor device does not require a spacer or insert to be mounted between the first semiconductor die and the second semiconductor die, although it can be mounted in some embodiments.

[0022] A main advantage is that the first sensor and the second sensor structures are able to measure physical quantities, such as magnetic fields, at substantially the same 3D position. Such sensor devices are ideally suited for automotive applications that require redundancy.

[0023] The first semiconductor die can be mechanically mounted to the lead frame in any suitable manner, such as by means of an insulating tape between the lead frame and the first semiconductor die.

[0024] The present invention also provides a sensor device, which includes: a lead frame; two identical semiconductor dies, including a first semiconductor die and a second semiconductor die, each die having a rectangular shape with a geometric center, and each die including a sensor structure located at a sensor position offset from its geometric center; the second semiconductor die is stacked on top of the first semiconductor die and is rotated by a non-zero angle with respect to the first semiconductor die and is also optionally shifted, such that the orthogonal projections of the first sensor position L1 and the second sensor position L2 are substantially coincident.

[0025] A main advantage lies in using two identical semiconductor dies (at least in terms of hardware), as this simplifies the design, testing, and evaluation of the semiconductor dies.

[0026] In an embodiment, the sensor device includes only two semiconductor dies, namely the first semiconductor die and the second semiconductor die.

[0027] In an embodiment, the first semiconductor die includes a plurality of first bonding pads, and the second semiconductor die includes a plurality of second bonding pads, wherein the plurality of first and second bonding pads of the stacked dies are exposed to allow wire bonding.

[0028] In an embodiment, the first semiconductor die includes a plurality of first bond pads wire-bonded to a lead frame; and wherein the second semiconductor die includes a plurality of second bond pads wire-bonded to the lead frame. In this embodiment, the electrical connection to the lead frame is achieved by means of bond wires or wire bonding. The advantage is that due to the rotation and offset or displacement of the two semiconductor dies, the bond pads are exposed on the top side, making them easily wire-bondable.

[0029] In an embodiment, the relative position of the first sensor location with respect to the first rectangular shape is the same as the relative position of the second sensor location with respect to the second semiconductor die. In this embodiment, the layout can be the same, but this is not absolutely required. It is sufficient that the layouts are similar.

[0030] In an embodiment, the second semiconductor die has the same layout as the layout of the first semiconductor die. Having "the same layout" means that a single mask set can be used. Although not absolutely necessary for the operation of the present invention, the advantage of the embodiment is that the first semiconductor die and the second semiconductor die are the same, as it greatly simplifies design, characterization, qualification testing, logistics, assembly, etc.

[0031] In certain embodiments, the first semiconductor die is obtained from the same silicon wafer as the silicon wafer of the second semiconductor die.

[0032] In other embodiments, the first semiconductor die is obtained from a silicon wafer different from the silicon wafer of the second semiconductor die.

[0033] In an embodiment, the stacked dies overlap at least 60% of the die area, or at least 70% of the die area, or at least 80% of the die area, or at least 90% of the die area.

[0034] In an embodiment, the rectangular shape is a square. (Having a ratio of length / width = 1).

[0035] In an embodiment, the rectangular shape is not a square and has a ratio of length / width > 1.05.

[0036] In an embodiment, the first semiconductor die is implemented in a first semiconductor technology (e.g., CMOS at a specific technology node, e.g., 90 nm), and the second semiconductor die is implemented in a second semiconductor technology different from the first semiconductor technology (e.g., CMOS at a different technology node). For example, the resolution and / or accuracy of the measurement provided by the first semiconductor die can be better than the resolution and / or accuracy of the second semiconductor die, but for safety purposes, the second measurement can still be accurate enough to serve as a redundant measurement.

[0037] In an embodiment, the first rectangular shape has a length defining a length direction (X) and a width defining a width direction (Y) perpendicular to the length direction (X), the length being equal to or greater than the width; and a first sensor position (L1) is offset from the geometric center of the first semiconductor die by a first predefined offset (dx) along the length direction and by a second predefined offset (dy) in the width direction, wherein at least one of the first offset and the second offset is different from zero.

[0038] In an embodiment, one of the first predefined offset and the second predefined offset is equal to zero, while the other of the first predefined offset and the second predefined offset is different from zero.

[0039] In an embodiment, each of the first predefined distance and the second predefined distance is different from zero.

[0040] In an embodiment, the second semiconductor die is rotated 180° relative to the first semiconductor die about an imaginary axis perpendicular to the lead frame; and the second semiconductor die is displaced a first distance in a first direction and a second distance in a second direction, the first distance being equal to twice the first predefined offset and the second distance being equal to twice the second predefined offset.

[0041] In an embodiment, the second semiconductor die is rotated 90° relative to the first semiconductor die about an imaginary axis perpendicular to the lead frame.

[0042] In an embodiment, the first semiconductor die and the second semiconductor die are square and rotated 90° relative to each other (e.g., as Figures 19(a) - 19(b) shown).

[0043] In an embodiment, the first semiconductor die and the second semiconductor die are non-square (i.e., are rectangles with a length greater than the width), and are rotated 90° relative to each other (e.g., as Figures 20(a) - 20(b) , Figures 21(a) - 21(b) or Figures 22(a) - 22(b) shown).

[0044] In an embodiment, the second semiconductor die is rotated relative to the first semiconductor die about an imaginary axis perpendicular to the lead frame by an angle in the range from 10° to 85°, e.g., as Figure 23 and Figure 24 shown.

[0045] In an embodiment, the first and second semiconductor dies are located on the same side of the lead frame, or in other words, the first semiconductor die is located between the lead frame and the second semiconductor die.

[0046] In an embodiment, each of the first and second semiconductor dies has an active side and an inactive side, and wherein the active side of the first semiconductor die is oriented in the same direction as the active side of the second semiconductor die.

[0047] In an embodiment, active sides of both the first and second semiconductor dies are oriented away from the leadframe (ie, facing away from the leadframe).

[0048] In an embodiment, active sides of both the first and second semiconductor dies are oriented in a direction toward the lead frame (ie, facing the lead frame).

[0049] In an embodiment, the second semiconductor die is flipped (ie, turned upside down) relative to the first semiconductor die such that an active side of the first semiconductor die and an active side of the second semiconductor die face each other.

[0050] In an embodiment, the second semiconductor die is flipped (ie, turned upside down) relative to the first semiconductor die such that the active side of the first semiconductor die and the active side of the second semiconductor die face away from each other.

[0051] In an embodiment, each of the first and second semiconductor dies has a thickness of at most 300 μm, or at most 250 μm, or at most 200 μm, or at most 175 μm, or at most 150 μm, or at most 125 μm, or at most 100 μm, or at most 75 μm or at most 50 μm. Such semiconductor dies are referred to as "thinned semiconductor dies". Processes for manufacturing "thinned wafers" (e.g. using etching techniques) are known in the art and therefore do not need to be described in more detail here. Using thinned wafers and / or stacking them directly on top of each other (see further description) provides the advantage that the first and second sensors can be even closer together (compared to a standard wafer with a typical thickness of about 750 microns), so that the difference between the signals measured by the first sensor and the second sensor or the values derived therefrom can be further reduced.

[0052] In an embodiment, the second semiconductor die is stacked on top of the first semiconductor die without utilizing spacers or interposers. An advantage of direct stacking is that no additional components (such as spacers or interposers) are required, thereby saving material. A further advantage is that the sensors are positioned closer together.

[0053] In an embodiment, the second semiconductor die is stacked over the first semiconductor die with a glue layer therebetween.

[0054] In an embodiment, a second semiconductor die is stacked on top of a first semiconductor die using an intermediate isolation layer. The advantage of such an intermediate isolation layer is that current blocking between the two semiconductor dies can be further improved (compared to the passivation layer at the bottom of the second semiconductor die).

[0055] In an embodiment, the first semiconductor die and the second semiconductor die are current-blocking.

[0056] In a preferred embodiment, the two semiconductor dies are current-blocking from each other (at the package level, possibly not at the printed circuit board (PCB) level).

[0057] Preferably, the two semiconductor dies use different pins for ground and for power supply.

[0058] In an embodiment, for example as Figure 15 and Figure 16 shown, the first sensor structure on the first semiconductor die is the same as the second sensor structure on the second semiconductor die. In an embodiment, for example as Figure 18 shown, the first sensor structure on the first semiconductor die is different from the second sensor structure on the second semiconductor die.

[0059] In both cases, the first and second silicon dies are configured to perform the same overall function, such as determining an angular position based on magnetic measurements, but the actual implementation (e.g., the type of sensing element and / or the physical arrangement of the sensing elements) may be different. As an example, the first sensor structure may include horizontal Hall elements, while the second sensor structure includes vertical Hall elements. As another example, the two sensor structures include a plurality of vertical Hall elements arranged on a circle with the same diameter, but the vertical Hall elements of the first silicon die are arranged to measure the circumferential magnetic field component (tangent to the imaginary circle), while the vertical Hall elements of the second silicon die are configured to measure the radial magnetic field component. Such sensor devices are very useful for functional safety, for example, for avoiding "common cause" failure modes.

[0060] In an embodiment, only one of the first predefined distance and the second predefined distance is zero (so the other predefined distance is different from zero).

[0061] In an embodiment, the first and second semiconductor dies are square, and the first predefined offset is non-zero, and the second predefined offset is zero; and the second semiconductor die is shifted by the predefined offset (DX = dx and DY = dx) relative to each of the edges of the first semiconductor die, for example, as illustrated in FIG. 19(b).

[0062] In an embodiment, each of the first predefined distance and the second predefined distance is different from zero.

[0063] In an embodiment, the first semiconductor die and the second semiconductor die have bonding pads positioned adjacent to only one side of a rectangular or square shape (see, for example Figure 15 , Figure 16 , Figures 18 to 20(b) , Figures 22(a) to 24 ).

[0064] In an embodiment, the first semiconductor die and the second semiconductor die have bonding pads positioned adjacent to two edges of a rectangular or square shape (e.g., see Figures 21(a) - 21(b) ).

[0065] In an embodiment, the first sensor structure and the second sensor structure are magnetic sensor structures.

[0066] In an embodiment, the sensor device is a redundant linear position sensor device used in automotive applications.

[0067] In an embodiment, the sensor device is a redundant angular position sensor device used in automotive applications.

[0068] In an embodiment, the first and second sensor structures include one or more magnetosensitive elements and optionally include one or more integrated magnetic concentrators (IMCs). The magnetosensitive elements can be selected, for example, from the group consisting of: horizontal Hall elements, vertical Hall elements, circular Hall elements, magnetoresistive elements (e.g., XMR elements, GMR elements, TMR elements), or combinations thereof. The magnetic sensor structure can be configured to measure at least one magnetic quantity at substantially the same location, such as one magnetic field component (e.g., Bx, By, Bz), or two magnetic field components (e.g., Bx and Bz) at two substantially the same locations, or a magnetic field gradient (e.g., dBx / dx, dBx / dy, dBy / dx, dBy / dx, dBz / dx, dBz / dy).

[0069] In an embodiment, each of the first sensor structure and the second sensor structure includes a single magnetosensitive element (e.g., selected from the group consisting of: horizontal Hall elements, vertical Hall elements, circular Hall elements, magnetoresistive elements, GMR elements, XMR elements, TMR elements).

[0070] In an embodiment, each of the first sensor structure and the second sensor structure includes a plurality of magnetosensitive elements.

[0071] A "sensor structure" can include two sensors spaced apart by a predefined distance, each sensor including, for example, two horizontal Hall elements and including an IMC. Such a "sensor structure" is capable of measuring a field gradient in a plane (e.g., dBx / dx or dBz / dx).

[0072] In an embodiment, the first sensor structure and the second sensor structure each include one or more integrated magnetic concentrators, and the semiconductor die has a thickness of at least 100 microns, or at least 125 microns, or at least 150 microns, or at least 175 microns, or at least 200 microns, but preferably less than 500 microns or less than 350 microns.

[0073] In an embodiment, the first sensor or the first sensor group on the first semiconductor die, and the second sensor or the second sensor group on the second semiconductor die include one or more horizontal Hall elements and one or more integrated magnetic concentrators.

[0074] In an embodiment, the first sensor or the first sensor group on the first semiconductor die, and the second sensor or the second sensor group on the second semiconductor die include one or more horizontal Hall elements without one or more integrated magnetic concentrators.

[0075] In an embodiment, the first sensor or the first sensor group on the first semiconductor die, and the second sensor or the second sensor group on the second semiconductor die include one or more vertical Hall elements; and / or TMR, GMR, AMR.

[0076] In an embodiment, the first sensor or the first sensor group on the first semiconductor die, and the second sensor or the second sensor group on the second semiconductor die include one or more magnetoresistive elements.

[0077] In an embodiment, the first and second sensor structures are MEMS sensor devices, such as accelerometers, gyroscopes, etc.

[0078] In an embodiment, each semiconductor die in the semiconductor dies includes a programmable processor and a non-volatile memory, and these processors are configured to run the same software instructions stored in the non-volatile memory. In this case, external compensation (e.g., via an external ECU) may be required to compensate for a 90° or 180° (or other angle) rotation of the two semiconductor dies.

[0079] In an embodiment, each semiconductor die in the semiconductor dies includes a programmable processor and a non-volatile memory, and the two processors are configured to determine the angular position, but one of the processors is configured to additionally compensate for the rotation of the two semiconductor dies such that the two semiconductor dies provide substantially the same value. In this case, no external compensation (e.g., via an external ECU) is required. This is a major advantage as it provides "true redundancy".

[0080] In an embodiment, each of the first and second semiconductor die is configured to provide a linear or angular position based on a magnetic field gradient. The advantage of using a gradient signal is that the measurement is substantially independent of external interfering fields.

[0081] According to a second aspect, the invention further provides a sensor system comprising: a magnetic sensor device according to certain embodiments of the first aspect; and a magnetic source arranged in the vicinity of the magnetic sensor device.

[0082] In an embodiment, the magnetic source comprises at least one permanent magnet.

[0083] The permanent magnet may be an axially or radially magnetized cylindrical or toroidal or disc-shaped magnet, forming a dipole, quadrupole or higher order magnetic field.

[0084] In an embodiment, the sensor system may be connected to or further comprise an external processor, such as an ECU (engine control unit) in an automotive environment.

[0085] Using the sensor device or sensor system as described above, measurements and redundant measurements are performed in an automotive environment for improved reliability.

[0086] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be combined appropriately with features of the independent claims and with features of other dependent claims, not only as explicitly set forth in the claims.

[0087] These and other aspects of the invention will become apparent and be elucidated with reference to the (multiple) embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figures 1 - 3 Illustrates three prior art methods for integrating two sensors on two die to form a redundant sensor package.

[0089] Figure 1 Illustrates an assembly having two identical die separated by a spacer or interposer.

[0090] Figure 2 Illustrates an assembly having two identical die without a spacer or interposer.

[0091] Figure 3 Illustrates an assembly having two identical die located on opposite sides of a lead frame.

[0092] Figure 4 、 Figure 5 and Figure 6Separate illustrations show the adverse effects of magnetic sensor misalignment that would be obtained in so-called "on-axis" assemblies, "off-axis" assemblies, and "through-axis" assemblies in some prior art systems including a magnet and a sensor device.

[0093] Figures 7 - 9 Illustrates a first exemplary embodiment of the present invention.

[0094] Figure 7 Shows in a top view a first exemplary rectangular semiconductor die having a sensor (or sensor structure) that is offset from the geometric center of the die in the width direction (Y).

[0095] Figure 8 Shows in a top view a stack of two semiconductor dies as can be used in an embodiment of the present invention after shifting and rotating the upper die by 180°. Figure 7 as shown.

[0096] Figure 9 Shows in a side view a stack of wire bonds to a lead frame as can be used in a sensor device according to an embodiment of the present invention. Figure 8 as shown.

[0097] Figures 10 - 11 Illustrates a second exemplary embodiment of the present invention.

[0098] Figure 10 Shows a second exemplary rectangular semiconductor die having a sensor (or sensor structure) that is offset from the geometric center of the die in both the length direction (X) and the width direction (Y).

[0099] Figure 11 Shows a stack of two semiconductor dies as can be used in an embodiment of the present invention after shifting and rotating the upper die by 180° to vertically align the sensor elements. Figure 10 as shown.

[0100] Figure 12 Is a schematic representation of a so-called "on-axis assembly" of a magnet and a sensor device according to an embodiment of the present invention.

[0101] Figure 13 Is a schematic representation of a so-called "off-axis assembly" of a magnet and a sensor device according to an embodiment of the present invention.

[0102] Figure 14 Is a schematic representation of a so-called "through-axis assembly" of a magnet and a sensor device according to an embodiment of the present invention.

[0103] Figure 15 Is a schematic representation showing another exemplary embodiment of the present invention, which can be regarded asFigure 9 A specific example, where a magnetic sensor structure including eight horizontal Hall elements located on a circle is used.

[0104] Figure 16 Is a schematic representation showing another exemplary embodiment of the present invention, which can be regarded as Figure 9 Another specific example, where a magnetic sensor structure including six vertical Hall elements located on a circle and oriented to measure the radial field component is used.

[0105] For illustrative purposes, Figure 17 Part (a) of Figure 17 Parts (f) of show several other exemplary magnetic sensor structures in a top view instead of a perspective view, and these magnetic sensor structures can also be used in the first and second semiconductor dies of an exemplary sensor device according to an embodiment of the present invention. However, the present invention is not limited thereto, and other sensor structures can also be used.

[0106] Figure 18 Shows another "stacked die assembly" according to an embodiment of the present invention, where the first and second semiconductor dies have the same external dimensions but different magnetic sensor structures. The magnetic sensor structures are positioned offset from the geometric centers of the respective dies, and the dies are shifted and rotated relative to each other such that the sensor structures are vertically aligned.

[0107] FIG. 19(a) shows in a top view a square semiconductor die having a sensor structure offset from the geometric center of the die in a direction parallel to one of its edges.

[0108] FIG. 19(b) shows in a top view a stack of two semiconductor dies as shown in FIG. 19(a) after rotating the upper die by 90° and shifting the upper die to align the magnetic centers of the sensor structures.

[0109] FIG. 20(a) shows in a top view a rectangular semiconductor die having a sensor offset from the geometric center of the die in a direction parallel to one of its edges. The die has bonding pads only on one side.

[0110] FIG. 20(b) shows in a top view a stack of two semiconductor dies as shown in FIG. 20(a) after rotating the upper die by 90° and shifting the upper die to vertically align the sensors.

[0111] FIG. 21(a) shows a rectangular semiconductor die in a top view, the rectangular semiconductor die having a sensor offset from the geometric center of the die in a direction parallel to one of its edges. The die has bonding pads on both sides.

[0112] FIG. 21(b) shows in a top view a stack of two semiconductor dies shown in FIG. 21(a) according to an embodiment of the present invention, after rotating the upper die by 90° and shifting the upper die so that the sensors are vertically aligned.

[0113] FIG. 22(a) shows a rectangular semiconductor die in a top view, the rectangular semiconductor die having sensors offset from the geometric center of the die in two directions parallel to each of its edges.

[0114] FIG. 22(b) shows in a top view a stack of two semiconductor dies shown in FIG. 22(a) according to an embodiment of the present invention, after rotating the upper die by 90° and shifting the upper die so that the sensors are vertically aligned.

[0115] Figure 23 A stack of two square semiconductor dies is shown in a top view, each die having a sensor offset from the geometric center of the die and located near a corner. According to an embodiment of the present invention, the dies are stacked after rotating the upper die by about 15° and shifting the upper die so that the sensors are vertically aligned.

[0116] Figure 24 A stack of two square semiconductor dies is shown in a top view, each die having a sensor offset from its geometric center by approximately 25% of the die width. According to an embodiment of the present invention, the dies are stacked after rotating the upper die by about 15° and shifting the upper die to vertically align with the sensors.

[0117] These figures are merely illustrative and not restrictive. In the figures, for illustrative purposes, the dimensions of some of the elements may be enlarged and not drawn to scale. Any reference signs in the claims shall not be construed as limiting the scope. In different figures, the same reference signs indicate the same or similar elements. Detailed Description

[0118] The present invention will be described with respect to specific embodiments and with reference to certain figures, but the present invention is not limited thereto and is only defined by the claims. The described figures are merely illustrative and non - restrictive. In the figures, for illustrative purposes, the dimensions of some of the elements may be enlarged and not drawn to scale. The scale and relative scale do not correspond to an actual reduction in the implementation of the present invention.

[0119] In addition, the terms first, second, etc. in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe an order in terms of time, space, ranking, or any other manner. It should be understood that the terms so used are interchangeable under appropriate circumstances, and the embodiments of the invention described herein are capable of operating in an order other than the order described or illustrated herein.

[0120] Furthermore, terms such as top, bottom, etc. in the specification and claims are used for descriptive purposes and not necessarily to describe relative position. It should be understood that the terms so used are interchangeable under appropriate circumstances, and the embodiments of the invention described herein are capable of operating in an orientation other than the orientation described or illustrated herein.

[0121] It should be noted that the term "comprising" used in the claims should not be construed as being limited to the means listed thereafter; it does not exclude other elements or steps. Thus, the term should be interpreted as specifying the presence of the stated features, integers, steps, or components as mentioned, but not excluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Accordingly, the scope of the expression "an apparatus comprising means A and B" should not be limited to an apparatus consisting only of components A and B. This means that for the present invention, the only relevant components of the apparatus are A and B.

[0122] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" throughout the specification are not necessarily all referring to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, as will be apparent to those of ordinary skill in the art through the present disclosure, the particular features, structures, or characteristics may be combined in any suitable manner.

[0123] Similarly, it should be understood that in the description of the exemplary embodiments of the present invention, for the purpose of streamlining the present disclosure and facilitating the understanding of one or more inventive aspects among the various inventive aspects, the various features of the present invention are sometimes grouped together in a single embodiment, drawing, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. On the contrary, as reflected in the appended claims, the inventive aspects lie in fewer features than all the features of a single foregoing disclosed embodiment. Thus, the appended claims following the detailed description are hereby expressly incorporated into the detailed description, where each claim itself represents a separate embodiment of the invention.

[0124] Furthermore, although some embodiments described herein include some features included in other embodiments but do not include other features included in other embodiments, as will be understood by those skilled in the art, combinations of features from different embodiments are intended to fall within the scope of the present invention and to form different embodiments. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

[0125] In the description provided herein, numerous specific details are set forth. However, it should be understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques are not shown in detail to avoid obscuring an understanding of this description.

[0126] In this document, the term "sensor" or "sensor structure" shall be broadly interpreted to refer to a single sensor component or sensor element or multiple components or structures for measuring physical quantities, such as MEM structures, accelerometers, gyroscopes, "magnetic sensor structures" comprising single or multiple magnetosensitive elements with or without integrated magnetic concentrators.

[0127] In this document, the term "magnetic sensor element" or "magnetic sensor" may refer to a component or a group of components or subcircuits or structures capable of measuring magnetic quantities, such as, for example, a magnetoresistive element, a GMR element, an XMR element, a TMR element, a horizontal Hall plate, a vertical Hall plate, a circular Hall element, a Wheatstone bridge comprising at least one (but preferably four) magnetoresistive elements, etc., or a combination thereof.

[0128] In certain embodiments of the present invention, a “magnetic sensor structure” may include one or more integrated magnetic concentrators (IMCs) and one or more horizontal Hall elements, such as a disk-shaped IMC and two or four horizontal Hall elements arranged near the periphery of the IMC, e.g. Figure 17 As shown in part (b) of Figure 17 As shown in part (e) of FIG.

[0129] The phrase "the geometric center is offset from the sensor position" means the same as "the sensor position is offset from the geometric center", meaning that they do not coincide.

[0130] The present invention relates to the field of sensor devices, and more particularly to sensor devices for use in an automotive environment. The device comprises two semiconductor dies for performing dual measurements, for example one semiconductor die for performing the actual measurement and one semiconductor die for performing a redundant measurement, such as may be used for safety purposes.

[0131] Although the present invention is applicable to several types of sensors (e.g., microelectromechanical systems (MEMs) such as accelerometers or gyroscopes, magnetic sensors, and other sensors), for simplicity of description, the present invention will be mainly described with respect to magnetic sensors, but the present invention is not limited thereto.

[0132] As described in the background section, dual-sensor devices or redundant-sensor devices are known in the art. Such devices typically include two substrates in a single package, one substrate for providing a first sensor measurement (e.g., an actual sensor measurement), and the other substrate for providing a second measurement (e.g., a redundant sensor measurement). Devices in which the two substrates are placed side by side require a relatively large footprint, and thus more board space, which is undesirable. To reduce the footprint, the substrates can be stacked on top of each other, e.g., as Figures 1 - 3 shown, showing three existing solutions for integrating two sensors (one on each die) to form a redundant sensor package.

[0133] Figure 1 An assembly 100 is shown having two identical substrates 102a, 102b that are stacked on top of each other using an intermediate spacer or insert 103. The first substrate 102a has a first sensor 104a. The second substrate 102b has a second sensor 104b. The two substrates are aligned, and the two sensors (in the Z direction) are also aligned. The first substrate 102a is connected to a lead frame 109 via a first bonding wire 112a. The second substrate 102b is connected to the lead frame 109 via a second bonding wire 112b. A disadvantage of this assembly 100 is that it requires a spacer 103 (also referred to as an insert) to allow the first substrate 102a to be wire-bonded to the lead frame 109. The spacer 103 increases the bill of materials, increases the height of the package, increases the distance between the two sensors 104a, 104b (in the height direction), and complicates the assembly process.

[0134] Figure 2 An assembly is shown having two identical substrates 202a, 202b without a spacer or insert. The first substrate 202a has a first sensor 204a. The second substrate 202b has a second sensor 204b. The second substrate 202b is displaced relative to the first substrate 202a (in the X direction) to expose the bonding pads of the first substrate 202a so that these substrates can be wire-bonded to a lead frame 209. The two sensors 204a, 204b are not aligned.

[0135] Figure 3An assembly is shown having two identical substrates 302a, 302b mounted on opposite sides of a lead frame 309. The first substrate 302a has a first sensor 304a. The second substrate 302b has a second sensor 304b. It can be seen that the first substrate 302a is aligned with the second substrate 302b, and the first sensor 304a is aligned with the second sensor 304b. The two sensors are separated by the thickness of the lead frame 309. However, bonding on both the upper and lower sides of the lead frame 309 is not a standard process and considerably complicates the equipment process.

[0136] While sensor misalignment may not be a problem in some applications (such as sensors for measuring the Earth's gravitational field), in some applications (such as, for example, magnetic sensor systems, such as linear position or angular position sensor systems), sensor misalignment is a concern.

[0137] Figures 4 - 6 The figure shows the problem when sensor devices 401, 501, 601 having a sensor configuration as shown are used in angular position sensor systems respectively including permanent magnets 411, 511, 611. Figure 2 as shown. Figure 4 A so-called "on-axis" arrangement is shown. Figure 5 A so-called "off-axis" arrangement is shown. Figure 6 So-called "through-axis" arrangements are shown respectively.

[0138] It should be noted that the sensors are schematically represented by black squares so as not to complicate the figure. Of course, in practice, the sensors can have a more complex (much more complex) structure (see, for example, Figures 15 - 18 ).

[0139] It can be readily understood that the first sensors 404a, 504a, 604a will provide a different value compared to the second sensors 404b, 504b, 604b because it is located at a different (usually at least 1 mm apart, or at least 750 microns apart, or at least 500 microns apart) position. The greater the distance between the sensor positions, the greater the deviation between the sensor signals, which is undesirable. In an ideal dual-sensor device, the first substrate would provide exactly the same signal as the second substrate. This provides the advantage that the threshold for detecting errors or fault conditions can be reduced.

[0140] The inventors of the present invention were asked to provide a sensor device having a better match between measurement results (such as angular position) provided by two semiconductor die, but preferably without the disadvantages of the prior art, in particular without significantly increasing the package thickness, and / or without significantly increasing the material cost, and / or without significantly complicating the assembly process, and preferably all of these.

[0141] In the face of this challenge, after much consideration, the inventors surprisingly proposed to provide a sensor device that includes a lead frame, a first semiconductor die electrically connected to the lead frame, and a second semiconductor die electrically connected to the lead frame. The first semiconductor die includes a first sensor or sensor structure located at a first sensor position, and the second semiconductor die includes a second sensor or sensor structure located at a second sensor position. The first semiconductor die has a first rectangular shape and a first geometric center offset from the first sensor position. The second semiconductor die has a second rectangular shape equal to the first rectangular shape and has a second geometric center offset from the second sensor position. The second semiconductor die is stacked on top of the first semiconductor die and rotated by a non-zero angle and optionally shifted by a non-zero distance relative to the first semiconductor die such that the orthogonal projections of the first sensor position and the second sensor position onto the lead frame coincide.

[0142] Put simply, such a sensor device can be referred to as a "stacked die assembly" that includes two semiconductor dies, where the two sensor structures are "aligned" and can be easily bonded in a standard manner (from the top). In the case where wire bonding is used to complete the electrical connection, such an assembly is also referred to as a "wire-bonded stacked die assembly". Preferably, the stacked die assembly is encapsulated by molding with a plastic compound to form a "(wire-bonded) stacked die package" (not shown).

[0143] The first sensor or sensor structure includes one or more sensor elements, such as magnetosensitive elements, and optionally includes other elements (such as an integrated magnetic concentrator). Similarly, the second sensor or sensor structure includes one or more sensor elements, such as magnetosensitive elements, and optionally includes other elements (such as an integrated magnetic concentrator). Where the "sensor position" (e.g., Figure 15 L1 in) refers to the (real or imaginary) central position defined by one or more magnetosensitive elements, which is, for example, at the middle between the sensitive elements. For example, in the case of a single sensitive element, the "sensor position" is defined as the position of the single sensitive element. In the case where the sensor structure has a plurality of sensitive elements arranged on a virtual circle, the "sensor position" is defined as the center of the virtual circle. In the case where the sensor structure has two spaced-apart sensing elements, the "sensor position" is defined as the intermediate position between the two sensing elements, etc.

[0144] The inventors surprisingly discovered a unique and highly advantageous combination of technical features, namely: (1) two semiconductor dies, (2) stacked on top of each other, (3) both dies having a sensor position offset from the geometric center of the die (not in the middle), (4+5) the upper die being rotated (4) and shifted (5) relative to the lower die such that the vertical projections of the sensors coincide.

[0145] The advantage provided by this unique combination is that the two sensor positions are "vertically aligned", such that the first sensor and the second sensor can measure essentially the same one or more physical (e.g., magnetic) quantities, as opposed to Figure 2 the stack shown in, where the first sensor position and the second sensor position are offset in at least one direction parallel to the lead frame.

[0146] Preferably, each die in the die further includes bonding pads located on its active surface, which are preferably exposed at their top sides when the dies are stacked. This facilitates wire bonding from the top easily.

[0147] The main advantage of this magnetic sensor device is that, as opposed to Figure 1 electrical connections can be performed in a simple manner on the top side using standard equipment, such as wire bonding, where in Figure 1 bonding wires 111 need to be placed before mounting the second semiconductor die, which complicates the handling.

[0148] The advantage is that the stacked arrangement proposed by the present invention does not require the installation of spacers or inserts between the first semiconductor die and the second semiconductor die, although spacers or inserts can be installed in some embodiments.

[0149] The main advantage is that the first sensor and the second sensor are capable of measuring physical quantities, such as magnetic fields, at substantially the same 2D or even 3D positions. Such sensor devices are ideally suited for automotive applications where redundancy is required for safety reasons.

[0150] It should be noted in this regard that "redundancy" does not require the use of exactly the same circuits on the first and second semiconductor dies, and / or does not require that exactly the same physical quantity / quantities be measured at exactly the same (multiple) physical positions (see, for example, Figure 16 , where the individual sensor elements are misaligned, but the sensors as a whole are aligned), and / or does not require that the measurement results or values derived therefrom need to be exactly the same (e.g., the angle measured by the first semiconductor die of Figure 9 can be phase-shifted by 180° relative to the angle measured by the second semiconductor die), but the measurement results or values obtained from the first semiconductor die are consistent with the measurement results or values obtained from the second semiconductor die.

[0151] Although not absolutely necessary (see, for example, Figure 18), but in a preferred embodiment, the first semiconductor die and the second semiconductor die are identical (meaning: manufactured using all the same masks). If both are obtained from the same wafer, this can further improve the matching of the results provided by the first and second semiconductor dies. If obtained from different wafers, this can reduce the risk of common cause failure modes associated with wafer processing.

[0152] In a preferred embodiment, the semiconductor dies are directly stacked on top of each other (without intermediate components or layers), and are preferably thinned to a thickness of less than 350 μm (e.g., less than 300 μm, e.g., less than 250 μm, e.g., equal to approximately 200 μm, or even less than 200 μm). This has the effect of further reducing the distance between the sensor structures of the first semiconductor die and the second semiconductor die and further improving the matching of the results. No prior art solution known to the inventors provides this effect. In fact, in order to obtain this effect, only the upper die needs to be thinned. In some embodiments, the lower die has its normal thickness, which can improve mechanical stiffness or mechanical robustness.

[0153] In a preferred embodiment, the two semiconductor dies are electrically isolated from each other, including power lines and ground lines, which means (in particular) that the two semiconductor dies are wire-bonded to different pins of the package to achieve true redundancy.

[0154] These are the main basic ideas of the present invention, which will be described in further detail.

[0155] As described above Figures 1 - 6 .

[0156] Figures 7 - 9 The figure shows a first exemplary sensor device 900 and the semiconductor die used therein.

[0157] Figure 7 A rectangular semiconductor die 702 having a length L (in the X direction) and a width W (in the Y direction) is shown in a top view. The length L is equal to or greater than the width W. The rectangle has a geometric center 706, which is schematically represented by a star, and the geometric center 706 is located at the intersection of the two diagonals ( Figure 7 not shown in, but see Fig. 20(a)), which is the same as the intersection of two lines parallel to the length direction and the width direction and at half of the length and width (as Figure 7 shown).

[0158] The semiconductor die 702 includes a sensor or sensor structure 704 having a "sensor position" L1 (e.g., referred to as the "magnetic center" in the case of a magnetic sensor structure), which is schematically represented by a square for simplicity of the figure. In this example, the "sensor position" L1 is offset from the geometric center 706 by a predefined distance "dy" in the Y direction. Examples of "sensor positions" will be provided further (e.g., see Figures 15 - 18 "L1" and "L2" therein), but briefly, the sensor position is a point that is substantially "in the middle" of one or more sensitive elements or in the middle between one or more sensitive elements.

[0159] The semiconductor die 702 preferably further includes a region 708 that includes a plurality of bonding pads 707. This region is located on the side of a rectangle (only on one side in the example) and has a width that is at most twice the offset "dy", so the width of region 708 ≤ 2*dy. Or in other words, for a given width of the pad region 708, the offset "dy" between the sensor position and the geometric center must be at least 50% of said width. In a preferred embodiment, the width has a value in the range from 110 to 250 μm, or from about 150 to about 210 μm, to allow for example electrical connection to a lead frame via wire bonding, but the invention will also work for larger regions (e.g., regions having a width of up to 250 μm, or up to 300 μm, or up to 400 μm, or up to 450 μm).

[0160] Figure 8 Shown is a stack 800 of two semiconductor dies 802a, 802b having Figure 7 the geometry (i.e., the size, shape, and relative position of the sensor structure and the bonding pads) after rotating the upper die 802b 180° about an axis perpendicular to the semiconductor die and optionally shifting the upper die 802b such that the long edges of the upper and lower dies are parallel but spaced apart by a distance DY equal to twice the offset dy (so DY = 2*dy). (For completeness, it should be noted that if the upper die is rotated about an axis passing through the sensor position L1, no translation is required).

[0161] It can be seen that by doing so, a stack is created in which the 2D projections of the geometric centers 806a, 806b are spaced apart by 2*dy but the 2D projections of the sensor positions L1, L2 coincide. Thus, the sensor structures 804a and 804b are "aligned", which means they will measure substantially the same physical quantity. It should be noted that as will become further clear (see for example Figure 16) The respective quantities measured by the sensing elements of the first sensor structure 804a and the second sensor structure 804b may be different, but the measurement results (e.g., angular position) derived therefrom are substantially the same for the two semiconductor dies.

[0162] In addition, it should be noted that the sensor positions L1, L2 do not exactly coincide, but in reality, they are separated in the height direction by the thickness of the upper die 802b. However, for practical purposes, these two positions can be considered substantially "the same", especially if the upper semiconductor die 802b is "thinned", e.g., thinned to a thickness below 350 μm, or below 250 μm, e.g., thinned to about 200 μm. In addition, in a preferred embodiment of the present invention, the results measured by the sensor device, which is part of the angular position sensor system, are in any case highly insensitive to the axial distance between the sensor device and the magnet.

[0163] Figure 9 A side view shows the Figure 8 stack mounted on the lead frame 9. As can be appreciated, the bonding pads 907a of the first (lower) semiconductor die 902a can be electrically connected (e.g., by wire bonding with the first bonding wire 912a) to the lead frame 909, and the bonding pads 907b of the second (upper) semiconductor die 902b can be electrically connected (e.g., by wire bonding with the second bonding wire 912b) to the lead frame 909 without problems.

[0164] Compared with Figure 1 the semiconductor dies 902a, 902b of Figure 9 are rotated 180° and their edges are offset from each other, and no insert is required. Compared with Figure 2 the sensor structures of Figure 9 are aligned. Compared with Figure 3 the two semiconductor dies in Figure 9 are both located on the same side of the lead frame, and their active surfaces are oriented in the same direction (upward), and bonding only needs to be performed on one side of the lead frame. In other words, the solution provided by the present invention has all the benefits of the prior art solutions.

[0165] Although not explicitly shown, Figure 9 the stack of the sensor device 900 of

[0166] Preferably (as in Figure 9As shown, two semiconductor dies 902a and 902b are directly stacked on top of each other without an intermediate component (e.g., spacer or insert). And preferably, at least the upper die 902b is thinned (not shown). This further reduces the distance between the two sensor structures 904a and 904b.

[0167] Although not explicitly shown in Figure 9 , the first and second semiconductor dies are preferably current-blocked, including separate connections to a ground pin and a power pin. To provide sufficient isolation, the back side of the semiconductor die may be provided with a passivation layer, such as an oxide layer or a nitride layer or a combination thereof. Alternatively or additionally, electrical isolation may also be provided by an electrically insulating layer between the semiconductor dies, such as an insulating tape, which is made of, for example, polyimide and has a thickness of, for example, about 50 to 100 μm.

[0168] In another variant (not shown), the sensor or sensor structure 704 is offset from the geometric center in the X direction (the long direction of the rectangle) instead of the Y direction (the wide direction of the rectangle), and the region 708 having the bonding pads 707 will be located near the short edge.

[0169] In another variant, the rectangle is a square and the two dies are rotated 180°.

[0170] Figure 10 and Figure 11 FIG. shows a second example of a semiconductor die 1002 (e.g., a silicon die) suitable for stacking and a stacked die arrangement 1100 using two such semiconductor dies 1102a and 1102b (e.g., silicon dies), and the die arrangement 1100 can be regarded as Figures 7 - 9 a variant of the stacked die arrangement of the sensor device 900 of

[0171] Figure 10A second exemplary semiconductor die 1002 is shown in a top view. The semiconductor die has a rectangular shape, and its geometric center 1006 is indicated by a star. The semiconductor die has a sensor structure 1004 (schematically represented by a square for illustrative purposes), which is offset from the geometric center 1006 by a predefined distance "dx" in the length direction (X) and by a predefined distance "dy" in the width direction (Y). The semiconductor die has a plurality of bonding pads 1007, which are located in a rectangular region 1008 having a width of at most 2*dy along an edge extending in the X direction of the semiconductor die 1002, and / or in a region 1018 having a width of at most 2*dx along an edge extending in the Y direction of the semiconductor die, and the rectangular region 1008 and the rectangular region 1018 together form an L shape. Alternatively, for given dimensions of the regions 1008 and 1018 (if any), the minimum offsets dx and dy can be determined.

[0172] Figure 11 Shown after rotating the upper die by 180° and optionally shifting the upper die 1102b so that the dies are offset by a distance DX = 2dx in the X direction and a distance DY = 2dy in the Y direction, Figure 10 the stack 1100 of the two semiconductor dies 1102a, 1102b as shown. (As mentioned above, if the rotation is performed about an axis passing through L1, L2, only rotation is required and no translation is needed). It can be seen that this aligns the sensor positions L1, L2, so that the sensor structures 1104a, 1104b will measure substantially the same physical quantity, despite the 180° rotation.

[0173] Similar to Figures 7 - 9 as described in, the two semiconductor dies 1102a, 1102b can be thinned (e.g., thinned to a thickness of about 100 to 350 microns, e.g., equal to about 200 microns), can be stacked directly on top of each other, or with an intermediate insulating layer or insulating tape, and the two semiconductor dies 1102a, 1102b are preferably current-blocking, including providing separate ground and power lines, and the stacked assembly can be overmolded.

[0174] Figures 7 - 11 Two exemplary embodiments of an encapsulated stacked die arrangement including two sensor structures are described, the two sensor structures being aligned such that the projections of the sensors in a direction perpendicular to the lead frame coincide.

[0175] In fact, the semiconductor die may further include a bias circuit for biasing the sensor structure, a readout circuit, an amplification circuit, a digitization circuit, a processing circuit, etc. However, since such circuits are not the main focus of the present invention and are well known in the art, they do not need to be described in further detail herein. It can be said that as long as the alignment is accurate enough, and the thickness of the semiconductor die is at least 100 microns, or at least 150 microns, or at least 200 microns, the principle of the present invention can be used in combination with any magnetic sensor structure, even a sensor structure including an integrated magnetic concentrator (IMC).

[0176] The fact that the second semiconductor die is rotated 180° relative to the first semiconductor die and can provide a measurement value (such as a rotation angle) different from the measurement value provided by the first semiconductor die can be easily solved by a post-processing step, which can be executed by the circuit of one of the sensor devices itself. For example, the circuit can be programmed to rotate the result by 180°, or executed by an external processor (such as an ECU). Mathematically, the post-processing step can be as simple as adding 180° or subtracting 180° to the angle provided by the second semiconductor die, so that the value is within the range of 0° to 360°.

[0177] Figures 12 - 14 Illustrates how the sensor devices 1201, 1301, 1401 can improve the matching between the results provided by the two semiconductor dies included therein.

[0178] Figure 12 Illustrates an exemplary sensor system 1200, more specifically an angular position sensor system, including a disc-shaped permanent magnet 1211 and a sensor device 1201 arranged in a so-called "on-axis arrangement". For example, the sensor device 1201 can have a stacked die arrangement as shown in Figure 8 、 Figure 9 or Figure 11 . For illustrative purposes, the two sensor structures 1204a, 1204b are schematically indicated by two black squares, which are substantially coincident in 3D space because the distance between them (in the direction perpendicular to the semiconductor die) is typically only about 100 to 350 microns, such as about 200 microns, while the distance "g" between the magnet 1211 and the sensor device 1201 is typically of a much larger order of magnitude (such as about 2.0 to 5.0 mm).

[0179] It should be appreciated that, compared with Figure 4 , the two sensor structures 1204a, 1204b of the sensor device 1201 are aligned with the rotation axis of the magnet 1211. In Figure 4In both sensor structures, they are offset from the rotation axis. Additionally, it can be appreciated that the two sensor structures 1204a, 1204b of the device 1201 will sense substantially the same magnetic field. Thus, not only can the individual results (related to the unwanted offset from the rotation axis) be improved, but in particular (of course, after considering a 180° rotation), the results provided by the first semiconductor die and the second semiconductor die will match better. This makes the sensor device 1201 ideally suitable for security applications.

[0180] Figure 12 The example of uses a disc-shaped magnet, but the present invention is not limited thereto, and other magnets such as bar magnets or ring magnets can also be used. Additionally, although Figure 12 the magnet 1211 of is a two-pole magnet (radially magnetized or axially magnetized for example), higher-order magnets such as quadrupole magnets or hexapole magnets can also be used. Of course, the sensor structures and / or algorithms used within the sensor device 1201 must correspond to the specific magnet used and to the position of the sensor device relative to the magnet (the on-axis position in the Figure 12 example), as is the case with existing solutions. The interested reader can find suitable sensors in, for example, WO2014029885A1, the entire content of which is incorporated herein by reference. The present invention is not limited thereto.

[0181] Figure 13 Another exemplary sensor system 1300 is shown, more specifically an angular position sensor system, including a disc-shaped permanent magnet 1311 and a sensor device 1301 arranged in a so-called "off-axis arrangement". The same or similar comments as those Figure 12 given apply here as well.

[0182] Figure 13 and Figure 5 The comparison with shows that the sensor device 1301 does not suffer from the Figure 5 same angular offset problem because the two sensor structures (indicated by the black squares) substantially coincide.

[0183] Many variants of the system have been conceived, such as having quadrupole magnets and / or toroidal magnets and / or bar magnets and / or specific sensor topologies for measuring one or more magnetic field components and / or circuits for determining one or more magnetic field gradients, and / or using specific circuits or formulas or algorithms to determine a linear position or an angular position based on one or more of these values. As described above, the main concern of the present invention is not to describe such algorithms or such sensor topologies, and therefore, the details thereof are omitted in the present disclosure. Interested readers can find suitable sensors, for example, in the patent application EP19193068.4 filed by the same applicant on August 22, 2019, which was re-filed as patent application EP20191167.4 on August 14, 2020, both of which are incorporated herein by reference in their entirety, especially the Figure 5 , Figure 12 and Figure 13 and the associated text. The present invention is not limited thereto.

[0184] Figure 14 FIG. shows another exemplary sensor system 1400, more specifically an angular position sensor system, including a disc-shaped permanent magnet 1411 and a sensor device 1401 arranged in a so-called "coaxial" arrangement. The same or similar comments as those given in Figure 12 and Figure 13 are also applicable here. Suitable sensor structures are described, for example, in patent applications EP19193068.4 and / or EP20191167.4, especially in the Figure 15 and the associated text. The present invention is not limited thereto.

[0185] Figure 14 and Figure 6 show that the sensor device 1401 does not suffer from the same angular offset problem as Figure 6 because the two sensor structures of the two semiconductor dies of the present invention basically coincide, as described above. Many variants of the sensor system 1400 have been conceived, similar to those described in Figure 13 .

[0186] Figure 15 is a schematic representation of an exemplary sensor device 1500 having a lead frame 1509 that is electrically connected (e.g., wire bonded) to two identical semiconductor dies 1502a, 1502b stacked, rotated, and offset or shifted in the manner shown in Figure 9 .

[0187] Figure 15The main purpose is to show a specific example of a sensor device according to the present invention, which has a slightly more complex sensor structure 1504, in this case, consisting of eight horizontal Hall elements located on a circle and angularly spaced 45° apart (described in detail in WO2014029885A1). When used in combination with a quadrupole magnet in an axial position (as in Figure 12 of the present application), the circuit on the first semiconductor die 1502a can determine the angular position α1, and the circuit on the second semiconductor die 1502b can determine the angular position α2, which should be substantially equal to α1 within a certain tolerance margin, since the measurement range of these sensor structures is limited to from 0° to 180°.

[0188] Interestingly, it should be noted that in the Figure 15 example, the individual sensor elements (here: horizontal Hall elements) of the first sensor structure 1504a of the lower semiconductor die 1502a are located at substantially the same positions as the individual sensor elements (here: horizontal Hall elements) of the second sensor structure 1504b of the upper semiconductor die 1502b, but this is not absolutely necessary, as will be further described (see, for example, Figure 16 ). However, it is important that the magnetic center L1 of the first sensor structure 1504a (here: the center of the circle on which the horizontal Hall elements are located) is aligned with the magnetic center L2 of the second sensor structure 1504b. This example also illustrates that the magnetic center L1 does not need to be located on the magnetosensitive elements, but can be located between them.

[0189] In a variant of this system (not shown), the sensor structure of the second semiconductor die 1502b contains eight horizontal Hall elements located on a circle and spaced 45° apart, but the radius of this circle is different from the radius of the circle of the sensor structure of the first semiconductor die 1502a (for example, at least 10% larger or 10% smaller). In this case, the first and second semiconductor dies have the same external dimensions, and the relative positions of the magnetic sensor structures are the same, but preferably, at least 50% of the other circuits of the two semiconductor devices are the same, which simplifies the design, testing, and evaluation of the semiconductor dies.

[0190] Figure 16 is a schematic representation of another exemplary sensor device 1600 having a lead frame 1609 that is electrically connected (e.g., wire bonded) to two identical semiconductor dies 1602a, 1602b stacked, rotated, and offset or shifted in the manner shown in Figure 9 .

[0191] Figure 16The main purpose is to show another specific example of a sensor device according to the present invention, which has another sensor structure 1604 that is slightly more complex. In this case, it consists of six vertical Hall elements located on a circle, angularly spaced in a specific manner and oriented for measuring the radial magnetic field component (as described in detail in WO2014029885A1). When used in combination with a six-pole magnet at an axial position (as in Figure 12 of the present application), the circuit (not shown) on the first semiconductor die 1602a can determine the angular position α1 (in the range from 0° to 120°), and the circuit on the second semiconductor die 1602b can determine the angular position α2 (in the range from 0° to 120°), which is substantially equal to (α1 + 60° + k * 120°) within a certain tolerance margin, where k is an integer value.

[0192] Interestingly, it should be noted that in the Figure 16 example, the individual sensor elements (here: vertical Hall elements) of the first sensor structure 1604a of the lower semiconductor die 1602a are not located at substantially the same positions as the individual sensor elements of the second sensor structure 1604b of the upper semiconductor die 1602b, but are between them. But this is acceptable as long as the magnetic center L1 of the first sensor structure 1604a (here: the center of the circle where the vertical Hall elements are located) is aligned with the magnetic center L2 of the second sensor structure 1604b.

[0193] As mentioned above, the present invention works with various sensor structures. Some examples of these sensor structures and the points indicating the positions of their "magnetic centers" are shown in Figure 17 part (a) to Figure 17 part (f) of Figure 15 and Figure 16 . For illustrative purposes, these sensor structures are shown in a top view, but are shown adjacent to each other rather than in a perspective view.

[0194] In Figure 17 part (a), each sensor structure 4a, 4b has four vertical Hall elements. For example, such sensor structures can be used to determine the angular position when used in combination with a dipole ring or disk magnet and when installed at an off-axis position or in a through-axis position. (For example, as described in more detail in patent applications EP19193068.4 and / or EP20191167.4).

[0195] In Figure 17In part (b), each sensor structure 4a, 4b has two sets of four horizontal Hall elements arranged at the periphery of the disc-shaped IMC. For example, such sensor structures can be used to determine the angular position when combined with a dipole ring-shaped or disc-shaped magnet, and when mounted in an off-axis position or in an on-axis position (e.g., as described in more detail in patent applications EP19193068.4 and / or EP20191167.4).

[0196] In Figure 17 part (c), each sensor structure 4a, 4b has two vertical Hall elements and two horizontal Hall elements. For example, such sensor structures can be used to determine the angular position when combined with a dipole ring-shaped or disc-shaped magnet, and when mounted in an off-axis position or in an on-axis position (e.g., as described in patent applications EP19193068.4 and / or EP20191167.4).

[0197] Figure 17 Part (d) shows Figure 17 a variant of part (a), which can be combined with a bipolar ring-shaped or disc-shaped magnet when mounted in an off-axis position or an on-axis position.

[0198] Figure 17 Part (e) shows Figure 17 a variant of part (b), which can be combined with a bipolar ring-shaped or disc-shaped magnet when mounted in an off-axis position or an on-axis position.

[0199] Figure 17 Part (f) shows Figure 17 a variant of part (c), which can be combined with a bipolar ring-shaped or disc-shaped magnet when mounted in an off-axis position or an on-axis position.

[0200] It is explicitly stated that the present invention is not limited to these specific sensor structures. They are selected only to illustrate that the sensor elements of the first and second semiconductor dies do not need to be precisely located on top of each other, and if the upper semiconductor substrate has a thickness of at least 100 microns, or at least 150 microns, or at least 200 microns, it can even include an integrated magnetic concentrator (IMC). Based on the above, it should be clear to those skilled in the art that other sensor structures can also be used, such as sensor structures with magnetoresistive elements (not shown).

[0201] Figure 15 、 Figure 16 and Figure 17An embodiment is shown in which the first sensor structure 4a of the first semiconductor substrate and the second sensor structure 4b of the second semiconductor substrate are the same. However, this is not necessary for the operation of the present invention. It is sufficient that the two semiconductor dies have the same size and shape, and that the two sensor structures have the same offsets dx, dy from the geometric center so that the magnetic centers L1, L2 coincide when they are stacked, rotated, and offset (e.g., shifted), as Figures 7 - 11 described. As an example, Figure 18 A stacked die arrangement is shown having two semiconductor dies 1802a, 1802b with different magnetic sensor structures 1804a, 1804b configured to measure the angular position of the respective semiconductor dies.

[0202] So far, the present invention has been explained for non-square rectangular semiconductor dies that are rotated 180° relative to each other and offset (e.g., shifted) relative to each other. However, the present invention is not limited thereto and will also apply to two semiconductor dies having a square or rectangular shape and having sensor structures offset from their geometric centers, which are stacked and rotated by another angle (e.g., 90°, or even an angle less than 90°), and optionally offset or shifted.

[0203] FIG. 19(a) shows in a top view a square semiconductor die 1902 having a sensor structure 1904 (schematically indicated by a square) that is offset by a distance “dx” in the X direction from the geometric center 1906 of the semiconductor die 1902. In this example, the semiconductor die has bonding pads adjacent to only one edge, and the shift “dx” is in a direction parallel to the edge adjacent to the bonding pad 1907.

[0204] FIG. 19(b) shows in a top view the stacking of the two semiconductor dies shown in FIG. 19(a) after rotating the upper die 1902b 90° relative to the lower die 1902a and shifting the upper die by DX equal to dx in the X direction and by DY equal to dx in the Y direction so as to align the sensor structures 1904a, 1904b (schematically indicated by squares). It can be seen that the bonding pads of the two semiconductor dies are all exposed for easy electrical connection (e.g., by wire bonding) to a lead frame (not shown).

[0205] In a Figures 19(a) - 19(b) variant, the semiconductor die has bonding pads along two of its edges (e.g., similar to Figures 21(a) - 21(b) in).

[0206] FIG. 20(a) shows in a top view a rectangular semiconductor die 2002 having a sensor structure 2004 (schematically indicated by a square), the sensor structure 2004 being offset by a distance “dx” from the geometric center 2006 of the die 2002 in the X direction. In this example, the semiconductor die has bonding pads adjacent to only one edge, and the shift “dx” is in a direction parallel to the edge adjacent to the bonding pads.

[0207] FIG. 20(b) shows in a top view a stack of the two semiconductor dies shown in FIG. 20(a) after rotating the upper die 2002b by 90° relative to the lower die 2002a and shifting the upper die by DX in the X direction and by DY in the Y direction so as to align their sensor structures 2004 (schematically indicated by squares). It can be seen that the bonding pads of the two semiconductor dies are all exposed for easy electrical connection (e.g., by wire bonding) to a lead frame (not shown).

[0208] FIG. 21(a) shows a semiconductor die 2102, which is a variant of the semiconductor die 2002 shown in FIG. 20(a), wherein the semiconductor die 2102 has pads along two of its edges.

[0209] FIG. 21(b) shows a stacked die assembly, which is a variant of the stacked die assembly of FIG. 20(b). It can be seen that the bonding pads are exposed on the top side of the semiconductor die and can be easily electrically connected (e.g., using wire bonding) to a lead frame.

[0210] FIG. 22(a) shows in a top view a rectangular semiconductor die 2202 having a sensor structure 2204 (schematically indicated by a square), the sensor structure 2204 being offset by a distance “dx” from the geometric center 2206 of the semiconductor die 2202 in the length direction X and by a distance “dy” from the geometric center 2206 of the semiconductor die 2202 in the width direction Y. This is a variant of FIG. 20(a), where the sensor structure 2204 is shifted in two directions. In this example, the semiconductor die has pads near only one edge.

[0211] FIG. 22(b) shows in a top view a stack of the two semiconductor dies shown in FIG. 22(a) after rotating the upper die 2202b by 90° relative to the lower die 2202a and optionally shifting the upper die by DX in the X direction and by DY in the Y direction so as to align their sensor structures 2004 (schematically indicated by squares). It can be seen that the bonding pads of the two semiconductor dies are all exposed for easy electrical connection (e.g., by wire bonding) to a lead frame (not shown).

[0212] In variants (not shown) of FIGS. 22(a) and 22(b), the semiconductor die has bonding pads positioned adjacent to two of its edges, similar to those shown in FIGS. 21(a) and 22(b).

[0213] Figure 23 A stack of two square semiconductor dies 2302a, 2302b is shown in a top view, each die having a sensor structure 2304 located near one of the corners of the semiconductor die. In the example, the dies are stacked after rotating about an axis perpendicular to the semiconductor die by about 15° and passing through the magnetic center, but other angles can also be used, such as angles in the range from about 10° to about 85°, or from 15° to 80°, or from 15° to 40°. It can be seen that multiple bonding pads of the two semiconductor dies are exposed for easy electrical connection (e.g., by wire bonding) to a lead frame (not shown). Those skilled in the art benefiting from this disclosure can easily find a suitable angle, for example, by trial and error.

[0214] Figure 24 A stack of two square semiconductor dies 2402a, 2402b is shown in a top view, each die having corresponding sensor structures 2404a, 2404b offset from their geometric centers 2406a, 2406b by approximately 25% of the width W of the die. After rotating the upper die about an axis perpendicular to the semiconductor die by about 15° and passing through the magnetic center, the dies are stacked. It can be seen that multiple bonding pads of the two semiconductor dies are exposed for easy electrical connection (e.g., by wire bonding) to a lead frame (not shown). Those skilled in the art benefiting from this disclosure can easily find a suitable angle, for example, by trial and error.

[0215] For completeness, it should be noted that the sensor structure cannot be displaced in any direction. The following table provides a list of effective displacements:

[0216]

[0217] Table 1: List of displacements

[0218] where ZZ is the width of the region containing the bonding pads.

[0219] Reference Signs:

[0220] -01 Sensor device

[0221] -02a / -02b First / Second semiconductor die

[0222] -03 Spacer, insert

[0223] -04a / 04b First / Second Magnetic Sensor

[0224] -06a / / 6b Geometric Center of the First / Second Semiconductor Die -08 / -18 Edge Region of the First / Second Semiconductor Die Containing Bonding Pads -09 Lead Frame

[0225] -11 Magnet

[0226] -12 Electrical Connection, Such as Bonding Wire

[0227] L1 / L2 First / Second Sensor Position

Claims

1. A sensor device, the sensor device comprising: A lead frame; A first semiconductor die having a first rectangular shape with a first geometric center, electrically connected to the lead frame, and including a first sensor structure located at a first sensor position; A second semiconductor die having a second rectangular shape equal to the first rectangular shape, having a second geometric center, electrically connected to the lead frame, and including a second sensor structure located at a second sensor position; Wherein: The first rectangular shape has a length defining a length direction and a width defining a width direction perpendicular to the length direction, the length being equal to or greater than the width; The first sensor position is offset from the first geometric center; The second sensor position is offset from the second geometric center by a first predetermined offset along the length direction and by a second predetermined offset in the width direction; At least one of the first predetermined offset and the second predetermined offset is different from zero; The second semiconductor die is stacked on top of the first semiconductor die and rotated 180° relative to the first semiconductor die about an imaginary axis perpendicular to the lead frame; and The second semiconductor die is displaced a first distance in the length direction and a second distance in the width direction, the first distance being equal to twice the first predetermined offset and the second distance being equal to twice the second predetermined offset.

2. The sensor device according to claim 1, It is characterized in that The first semiconductor die includes a plurality of first bonding pads wire-bonded to the lead frame; and Wherein the second semiconductor die includes a plurality of second bonding pads wire-bonded to the lead frame, Wherein a first wire bond and a second wire bond are located on the same side of the lead frame.

3. The sensor device according to claim 1, It is characterized in that The relative position of the first sensor position with respect to the first rectangular shape is the same as the relative position of the second sensor position with respect to the second semiconductor die.

4. The sensor device according to claim 1, It is characterized in that The second semiconductor die has the same layout as the layout of the first semiconductor die.

5. The sensor device according to claim 1, Among them, The first semiconductor die is located between the second semiconductor die and the lead frame.

6. The sensor device according to claim 1, Among them, One of the first predetermined offset and the second predetermined offset is equal to zero, while the other of the first predetermined offset and the second predetermined offset is different from zero.

7. The sensor device according to claim 1, Among them, Each of the first predetermined offset and the second predetermined offset is different from zero.

8. The sensor device according to claim 1, Among them, The sensor device includes only two semiconductor dies, namely the first semiconductor die and the second semiconductor die.

9. The sensor device according to claim 1, Among them, The first semiconductor die overlaps the second semiconductor die by at least 60%.

10. The sensor device according to claim 1, Among them, each of the first semiconductor die and the second semiconductor die has an active side and a passive side, and wherein the active side of the first semiconductor die is oriented in the same direction as the active side of the second semiconductor die.

11. The sensor device according to claim 1, Among them, the second semiconductor die is stacked on top of the first semiconductor die without using a spacer or an insert.

12. The sensor device according to claim 1, Among them, the first sensor structure on the first semiconductor die is the same as the second sensor structure on the second semiconductor die.

13. The sensor device according to claim 1, Among them, the first sensor structure on the first semiconductor die is different from the second sensor structure on the second semiconductor die.

14. The sensor device according to claim 1, Among them, the first sensor structure and the second sensor structure are magnetic sensor structures.

15. The sensor device according to claim 14, Among them, each of the first semiconductor die and the second semiconductor die is configured to provide a linear position or an angular position based on a magnetic field gradient.

16. A sensor system, the sensor system comprising: a magnetic sensor device according to claim 14; and a magnetic source arranged in the vicinity of the magnetic sensor device.

17. The sensor system according to claim 16, wherein the magnetic source includes at least one permanent magnet.

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