Radiation sensor with an integrated mechanical optical modulator and related manufacturing processes

Abstract

Embodiments of the present disclosure relate to a radiation sensor having an integrated mechanical optical modulator and related manufacturing processes. A radiation sensor includes a detection assembly and a chopper assembly, the detection assembly and the chopper assembly being mechanically coupled to define a main cavity; and wherein the chopper assembly includes: a suspended movable structure extending in the main cavity; and an actuation structure that is electrically controllable to cause a change in the position of the suspended movable structure. The detection unit includes a detection structure that faces the main cavity and includes a plurality of detection devices. The suspended movable structure includes a first shield made of a conductive material, the first shield shielding the detection devices from radiation, and the shielding of the detection devices varies with the position of the suspended movable structure.

Description

Technical Field

[0001] The present disclosure relates to a radiation sensor with an integrated mechanical optical modulator and a corresponding manufacturing process. Background Art

[0002] As is known, there are currently many radiation (e.g., infrared radiation) sensors available, some of which are characterized by systems of the type Figure 1 shown. Figure 1 The sensor 1 and the characterization system 2 are shown in detail. The characterization system 2 includes: a light source 4 that simulates a black body and emits radiation; a mechanical optical modulator 6 (i.e., a shutter), also referred to as a chopper 6, configured to receive the radiation emitted by the light source 4 and transmit the test radiation; an optical circuit 8 configured to receive the test radiation and direct it to the sensor 1 such that the sensor 1 generates a corresponding electrical signal; and an amplification and control circuit arrangement 10 for receiving and amplifying the electrical signal, generating a corresponding output signal that can be used for characterization and further controlling the chopper 6 to ensure the correct timing of the chopper 6. The amplification and control circuit arrangement 10 typically includes a so-called lock-in amplifier.

[0003] In fact, the mechanical chopper 6 allows the intensity of the test radiation to be modulated in such a way that the electrical signal generated by the sensor 1 lies in a translational frequency band; in this way, the output signal generated by the amplification and control circuit arrangement 10 benefits from greater resilience with respect to, for example, optical noise.

[0004] Unfortunately, the need for a chopper means that the current characterization system 2 is particularly bulky. Summary of the Invention

[0005] Embodiments relate to a radiation sensor, a device including the radiation sensor, and a manufacturing process for forming the radiation sensor. Brief Description of the Drawings

[0006] To better understand the present invention, preferred embodiments of the present invention will now be described only by way of non-limiting example and with reference to the accompanying drawings, in which:

[0007] Figure 1 A block diagram of a known type of characterization system is shown;

[0008] Figure 2 and 4 A cross-section of the radiation sensor in two different operating conditions is schematically shown;

[0009] Figure 3 Is schematically shown Figure 2 A partial top view of the sensor shown;

[0010] Figure 5 、 6and FIGS. 8 schematically show cross-sections of the radiation sensor;

[0011] Figure 7 show the wavelength trend of the radiation irradiating the detection device when the position of the detection device changes along the axis;

[0012] Figure 9 schematically show a cross-section of the package containing the sensor;

[0013] Figures 10 - 16 schematically show a cross-section of the sensor during subsequent steps of the manufacturing process.

[0014] Figure 17 is a cross-section of a radiation sensor according to another embodiment. DETAILED DESCRIPTION

[0015] Figure 2 show the sensor 12, including a first outer body 14, a second outer body 16, and an intermediate body 18.

[0016] The first outer body 14 is formed of a semiconductor material (such as silicon), for example, and is bounded by a top surface S 14t and a bottom surface S 14b at the top and bottom, respectively. The top surface and the bottom surface, as well as other directional terms used herein, are used to refer to the orientation of the outer body 14 (or the sensor and the device) as presented in the drawings. Similarly, the second outer body 16 is formed of a semiconductor material (such as silicon), for example, and is bounded by a corresponding top surface S16t and a corresponding bottom surface S 16b at the top and bottom. In addition, the intermediate body 18 is formed of a semiconductor material (such as silicon), for example, and is bounded by a corresponding top surface S 18t and a corresponding bottom surface S 18b at the top and bottom.

[0017] The sensor 12 further includes a dielectric region 20, which is formed of TEOS (tetraethyl orthosilicate) oxide, for example, and extends under the first outer body 14 and is in direct contact with the bottom surface S 14b The dielectric region 20 laterally defines a cavity 21, which is bounded by the first outer body 14 at the top and is hereinafter referred to as the first actuation half-cavity 21.

[0018] The sensor 12 further includes an intermediate region 22, which is formed of, for example, polysilicon and extends under the dielectric region 20 in direct contact therewith. More specifically, the intermediate region 22 includes: an outer peripheral portion 23 that extends in direct contact with the overlying dielectric region 20; an inner portion that forms a corresponding suspension region 24; and a first intermediate portion 25A and a second intermediate portion 25B that are symmetrically arranged with respect to the suspension region 24 such that each of the first intermediate portion 25A and the second intermediate portion 25B is interposed between a corresponding end of the suspension region 24 and the outer peripheral portion 23.

[0019] In fact, the suspension region 24 extends under the first actuation half cavity 21 and is surrounded by the outer peripheral portion 23 and is fixed to the outer peripheral portion 23 by the first intermediate portion 25A and the second intermediate portion 25B that respectively form a first spring M1 and a second spring M2.

[0020] More specifically, the intermediate region 22 is bounded at the top by a corresponding top surface S that contacts the dielectric region 20 22t and is bounded at the bottom by a corresponding bottom surface S 22b that bounds.

[0021] The sensor 12 further includes an internal metal region 32, which is formed of, for example, aluminum and extends under the intermediate region 22 in direct contact therewith. More specifically, the internal metal region 32 includes: a corresponding outer peripheral portion 33 that extends in direct contact with the overlying outer peripheral portion 23 of the intermediate region 22; a corresponding inner portion that forms a corresponding main shield 34; a corresponding first intermediate portion 35A and a corresponding second intermediate portion 35B that are symmetrically arranged with respect to the main shield 34 such that each of the first intermediate portion 35A and the second intermediate portion 35B is interposed between a corresponding end of the main shield 34 and the outer peripheral portion 33.

[0022] In fact, the main shield 34 extends under the suspension region 24 in direct contact therewith and is laterally fixed to the outer peripheral portion 33 of the internal metal region 32 by the first intermediate portion 35A and the second intermediate portion 35B of the internal metal region 32.

[0023] Similarly as Figure 3 shown, the main shield 34 has a perforated grid shape.

[0024] More specifically, the main shield 34 has a planar shape and includes a plurality of strips 34A which, without loss of generality, extend in the Y direction and are arranged continuously in the X direction perpendicular to the Y direction. In addition, the main shield 34 includes a first elongated portion 34B and a second elongated portion 34C that extend parallel to the X axis, are offset along the Y axis, and are arranged such that each strip 34A has a first end fixed to the first elongated portion 34B and a second end fixed to the second elongated portion 34C.

[0025] The suspension region 24 completely covers the main shield 34 and is pierced by a plurality of holes 37 that face the first actuation half-cavity 21 at the top. In particular, the suspension region 24 includes a first elongated portion 24B and a second elongated portion 24C that extend parallel to the X axis, and a plurality of strip portions 24A. The first elongated portion 24B and the second elongated portion 24C of the suspension region 24 extend respectively above the first elongated portion 34B and the second elongated portion 34C of the main shield 34, while each strip portion 24A of the suspension region 24 extends above the corresponding strip 34A of the main shield 34. Each strip 34A leaves an exposed portion of the partial bottom surface S 22b defined by the overlying strip portion 24A; similarly, the first intermediate portion 35A and the second intermediate portion 35B of the internal metal region 32 leave exposed portions of the partial bottom surface S 22b defined respectively by the first intermediate portion 25A and the second intermediate portion 25B of the intermediate region 22.

[0026] The sensor 12 further includes a passivation region 42 formed, for example, of silicon nitride and including: a corresponding outer peripheral portion 43 that extends in direct contact with the overlying outer peripheral portion 33 of the internal metal region 32; a corresponding internal portion 44 that extends in direct contact with the overlying main shield 34 to cover the main shield 34, and portions of the partial bottom surface S 22b defined by the strip portions 24A are exposed through the underlying strips 34A of the main shield; a corresponding first intermediate portion 45A and a corresponding second intermediate portion 45B are arranged symmetrically with respect to the internal portion 44 such that each of the first intermediate portion 45A and the second intermediate portion 45B is interposed between the corresponding end of the internal portion 44 and the outer peripheral portion 43. The first intermediate portion 45A and the second intermediate portion 45B of the passivation region 42 are respectively arranged below the first intermediate portion 35A and the second intermediate portion 35A, 35B of the internal metal region 32 to additionally cover the partial bottom surface S formed by the first intermediate portion 25A and the second intermediate portion 25B of the intermediate region 22 and exposed through the first intermediate portion 35A and the second intermediate portion 35A, 35B of the internal metal region 32 22bThe first intermediate portion 35A of the internal metal region 32 forms a first spring M1 with the first intermediate portion 25A of the intermediate region 22 and the first intermediate portion 45A of the passivation region 42; the second intermediate portion 35B of the internal metal region 32 forms a second spring M2 with the second intermediate portion 25B of the intermediate region 22 and the second intermediate portion 45B of the passivation region 42.

[0027] In fact, the internal portion 44 of the passivation region 42 and the suspension region 24 encapsulate the main shield 34. In addition, the hole 37 also extends through the internal portion 44 of the passivation region 42.

[0028] The sensor 12 also includes a first bonding region 50, which is formed, for example, of glass frit or an alloy (such as a gold - tin or aluminum - germanium alloy), and extends under the outer peripheral portion 43 of the passivation region 42 and is in direct contact therewith. In addition, the first bonding region 50 laterally defines a cavity 51, hereinafter referred to as a second actuation half - cavity 51; the second actuation half - cavity 51 extends under the internal portion 44 of the passivation region 42 and the first intermediate portion 45A and the second intermediate portion 45B.

[0029] In fact, the suspension region 24, the main shield 34, and the internal portion 44 of the passivation region 42 form a suspension movable structure 55 interposed between the first actuation half - cavity 21 and the second actuation half - cavity 51. These two actuation half - cavities are in fluid communication with each other through the hole 37 facing the second actuation half - cavity 51 at the bottom, such that the first actuation half - cavity and the second actuation half - cavity 51 form a main cavity 61; the suspension movable structure 55 is suspended in the main cavity 61 by the first spring M1 and the second spring M2. In addition, without loss of generality, the suspension movable structure 55 has a periodic shape along the X - axis, that is, each section parallel to the XZ plane and passing through the strip 34A has a periodic shape parallel to the X - axis; in other words, in each of these sections, the main shield 34, the strip portion 24A, and the internal portion 44 of the passivation region 42 all have a periodic shape.

[0030] As Figure 3 shown, the sensor 12 also includes a plurality of movable actuation elements 63 and a plurality of fixed actuation elements 65, which are formed of the same material (such as polysilicon) as the intermediate region 22, are coplanar with the intermediate region 22, have an elongated shape parallel to the Y - axis, and are interdigitated with each other.

[0031] In particular, the fixed actuator element 65 extends cantilever-like from the outer peripheral portion 23 of the intermediate region 22 in the direction of the suspension region 24 and is formed as a single piece therewith. More specifically, the outer peripheral portion 23 of the intermediate region 22 has a hollow shape that surrounds the suspension region 24 and the first intermediate portion 25A and the second intermediate portion 25B of the intermediate region 22. Each fixed actuator element 65 has a respective first end fixed to the outer peripheral portion 23 of the intermediate region 22 and a respective second end that extends toward the suspension region 24 without contacting the suspension region 24. Without loss of generality, the fixed actuator elements 65 are divided into two groups and are arranged symmetrically with respect to the suspension movable structure 55.

[0032] The movable actuator element 63 extends cantilever-like from the suspension region 24 in the direction of the outer peripheral portion 23 of the intermediate region 22 and is formed as a single piece therewith. More specifically, each movable actuator element 63 has a respective first end fixed to the suspension region 24 and a respective second end that extends toward the outer peripheral portion 23 of the intermediate region 22. In particular, the movable actuator elements 63 are divided into two groups and are arranged symmetrically with respect to the suspension movable structure 55; the first group of movable actuator elements 63 is finger-interleaved with the first group of fixed actuator elements 65, and the second group of movable actuator elements 63 is finger-interleaved with the second group of fixed actuator elements 65.

[0033] Again without loss of generality, for each movable actuator element 63, the sensor 12 further includes a corresponding movable conductive region 67, the movable conductive region 67 having an elongated shape parallel to the Y axis, arranged below the movable actuator element 63 and formed as a single piece with the main shield 34. Similarly, for each fixed actuator element 65, the sensor 12 further includes a corresponding fixed conductive region 69, the fixed conductive region 69 having an elongated shape parallel to the Y axis and arranged below the fixed actuator element 65. The movable conductive region 67 and the fixed conductive region 69 can be formed, for example, of the same material as the material forming the internal metal region 32. In addition, although not shown, the movable conductive region 67 and the fixed conductive region 69 can be covered at the bottom by corresponding protection regions, the protection regions being formed of the same material as the material forming the passivation region 42.

[0034] Although not shown, the sensor 12 further includes terminals that allow biasing the movable conductive region 67 and the fixed conductive region 69 with a variable voltage, serving as opposing plates of a variable capacitor, to apply an electrostatic force that moves the suspension movable structure 55 parallel to the X axis; this movement is allowed because the first spring M1 and the second spring M2 bend along the X axis. The movement of the suspension movable structure 55 causes the main shield 34 to move parallel to the X axis.

[0035] More specifically, for example, the movable conductive region 67 and the fixed conductive region 69 can be biased by including a so-called through-silicon via (TSV) and a conductive path that traverses the first outer body 14, the dielectric region 20, and the intermediate region 22. Additionally, the movable conductive region 67 and the fixed conductive region 69 are electrically separated; to this end, although not shown, at least a portion of the outer peripheral portion 23 of the intermediate region 22 can have reduced doping (e.g., can be intrinsic type); additionally or alternatively, a dielectric separation region (not shown) can extend through the outer peripheral portion 23 of the intermediate region 22, and the dielectric separation region is arranged to electrically separate the fixed conductive region 69 from the outer peripheral portion 33 of the internal metal region 32, and the outer peripheral portion 33 is in electrical contact with the movable conductive region 67.

[0036] The sensor 12 further includes a second bonding region 64, which is formed, for example, of glass powder or an alloy (such as a gold-tin or aluminum-germanium alloy), and is interposed between the bottom surface S of the intermediate body 18 18b and the top surface S of the second outer body 16 16t and is in direct contact with both surfaces.

[0037] Another cavity 71 (hereinafter referred to as the detection cavity 71) passes through the intermediate body 18 and the second bonding region 64. In particular, the detection cavity 71 extends between the top surface S of the intermediate body 18 18t and the top surface S of the second outer body 16 16t and extends therebetween.

[0038] The sensor 12 further includes a detection structure 80, which is interposed between the second actuation half-cavity 51 and the detection cavity 71.

[0039] Without loss of generality, in the Figure 2 illustrated embodiment, the detection structure 80 includes a support structure 90 that is suspended above the detection cavity 71 and thus extends between the detection cavity 71 below the suspended movable structure 55 and the second actuation half-cavity 51. Additionally, the sensor 12 includes an outer peripheral structure 92 that is interposed between the intermediate body 18 and the first bonding region 50; in particular, the outer peripheral structure 92 surrounds the support structure 90.

[0040] More specifically, the support structure 90 is laterally constrained (e.g., fixed) to the outer peripheral structure 92. As a first approximation, the support structure 90 and the outer peripheral structure 92 are coplanar.

[0041] Without loss of generality, each of the carrier structure 90 and the outer peripheral structure 92 can be formed, for example, of one or more dielectric layers that can also have conductive regions or semi-conductive regions (not shown) extending therein.

[0042] Additionally, the sensor 12 includes a plurality of detection devices 94 integrated in the carrier structure 90 (inFigure 2 (qualitatively shown in). For example, and without loss of generality, sensor 12 may include an array of detection devices 94. Thus, the detection devices 94 have a planar arrangement and are photodetectors capable of changing the corresponding electric quantity according to the irradiated radiation.

[0043] Always by way of example, each detection device 94 is formed, for example, by a device selected from the following: a corresponding thermocouple; a corresponding thermopile (i.e., a plurality of thermocouples connected in series or in parallel); a corresponding TMOS sensor, i.e., a CMOS - SOI type sensor; a corresponding bolometer. Thus, each detection device 94 includes a corresponding active region sensitive to the irradiated radiation.

[0044] The arrangement of the detection devices 94 relative to the axis bearing structure 90 causes the following to occur.

[0045] As Figure 2 shown, when the sensor 12 operates in the first operating mode, the detection devices 94 are laterally offset relative to the main shield 34, i.e., arranged as a first approximation such that the corresponding active regions are vertically aligned with the corresponding holes 37. In fact, in the first operating mode, the active regions of the detection devices 94 are laterally offset relative to the strips 34A of the main shield 34; in other words, the projection along the Z - axis (perpendicular to the X - axis and the Y - axis) of the strip 34A does not intersect the active regions of the detection devices 94.

[0046] For example, the first operating mode of the sensor 12 may correspond to the case where the movable conductive region 67 and the fixed conductive region 69 are not biased and the suspended movable structure 55 is in the rest position.

[0047] The movable conductive region 67 and the fixed conductive region 69 may also be biased such that the sensor 12 operates in the second operating state, as Figure 4 shown, in which, relative to the rest position, the suspended movable structure 55 is translated along the X - axis such that, as a first approximation, the active regions of the detection devices 94 are vertically aligned with the corresponding strips 34A of the main shield 34 used as an electromagnetic shield. In particular, and without loss of generality, assuming that radiation vertically (i.e., parallel to the Z - axis) irradiates the sensor 12, the strips 34A of the main shield 34 may completely shield the corresponding detection devices 94; in other words, the projection along the Z - axis of each strip 34A completely covers the active regions of the corresponding detection devices 94.

[0048] In use, the possibility of switching between the first operating mode and the second operating mode enables the sensor 12 to implement a chopper function; this chopper is represented by the suspended movable structure 55 and is thus integrally formed with the detection devices 94, thereby allowing the avoidance of having to rely on an external chopper during the characterization procedure of the sensor 12.

[0049] The sensor 12 further includes another shield 99, hereinafter referred to as the secondary shield 99. However, in Figure 2 the illustrated embodiment, the secondary shield 99 is generally optional. Figure 17 A sensor 12a is shown that is structurally and functionally identical to the Figure 2 sensor 12, except that the Figure 17 sensor 12a does not include the secondary shield 99. Specifically, the secondary shield 99 is formed of a metallic material (such as aluminum or gold or platinum) and extends above the top surface S of the first outer body 14. 14t In addition, the secondary shield 99 is formed in one piece and is perforated, i.e., includes a plurality of openings A 99 through which radiation can pass; although not shown, the secondary shield 99 can have, for example, a grating shape.

[0050] Without loss of generality, in the Figure 2 illustrated embodiment, the secondary shield 99 is laterally offset relative to the detection device 94, i.e., the projection of the Z axis of the secondary shield 99 falls outside the active region of the detection device 94; correspondingly, the projection of the Z axis along the opening A 99 falls on the corresponding detection device 94. In addition, when the sensor 12 is operating in the first operating mode, the secondary shield 99 is superimposed on the main shield 34 at a certain distance; in particular, without loss of generality, the projection along the Z axis of the secondary shield 99 falls on the main shield 34.

[0051] In fact, relative to what has been described above, the presence of the secondary shield 99 does not change the behavior of the sensor 12 with respect to radiation with normal incidence. However, the shape and arrangement of the secondary shield 99 can be selected according to different irradiation angles of the radiation, for example, in order to optimize the shielding of the active region of the detection device 94 during the second operating mode, i.e., to integrate the shielding provided by the main shield 34.

[0052] Generally, the movable conductive region 67 and the fixed conductive region 69 can also be biased such that the sensor 12 operates in an intermediate operating mode between the first operating mode and the second operating mode, i.e., such that the suspended movable structure 55 is in an intermediate position between the rest position and the position where the sensor 12 operates in the second operating mode; in this case, the active region of the detection device 94 can be partially shielded from the projection of the strip 34A of the main shield 34 along the Z axis. In fact, the shielding degree of the active region of the detection device 94 by the main shield 34 can be adjusted in a progressive manner.

[0053] There can also be various variations, in which the shapes and / or arrangements of the detection device 94, the main shield 34, and the secondary shield 99 are different from those already described. For example, in the case where the reference radiation has normal incidence, the main shield 34 can also shield a part of the detection device 94 in the first operating mode, that is, the projection of the main shield 34 along the Z axis can partially fall into the active area of the detection device 94. Referring again to the case of normal incidence, in the second operating mode, it is also possible that the main shield 34 only partially shields the detection device 94.

[0054] Always by way of example, an embodiment in which the projection of the secondary shield 99 along the Z axis partially falls into the active area of the detection device 94 is also possible. More generally, even for radiation with normal incidence, it is possible that the shielding of the detection device 94 depends on the embodiment of the mutual positioning between the suspended movable structure 55 and the secondary shield 99; in this case, for a certain position between the positions taken by the suspended movable structure 55 in the first operating condition and the second operating condition, maximum shielding can be obtained.

[0055] For practical purposes, by appropriately selecting the shapes and arrangements of the main shield 34 and the secondary shield 99, the desired degree of shielding of the detection device 94 can be obtained for radiation from a given irradiation angle and different positions taken by the suspended movable structure 55.

[0056] To facilitate the placement of electrical contacts (not shown) to provide the electrical signal generated by the detection device 94 to the outside world, a part of the outer peripheral structure 92 that is laterally offset with respect to the main cavity 61 and the lower detection cavity 71 is exposed, that is, not covered by the first bonding region 50. In fact, the set formed by the first external body 14, the dielectric region 20, the intermediate region 22, the internal metal region 32, and the passivation region 42 is represented as the chopper assembly 101, and the following occurs.

[0057] The chopper assembly 101 has an extension along the X axis, which is smaller than the extensions of the second external body 16 and the intermediate body 18, and these extensions together with the second bonding region 64, the detection structure 80, and the outer peripheral structure 92 form the detection assembly 102. In addition, as a first approximation (i.e., ignoring the possible movement along the X axis), the suspended movable structure 55 is vertically aligned with the lower detection structure 80. More precisely, the suspended movable structure 55 can take at least one position in which the projection of at least a part of the main shield 34 on the Z axis falls into the active area of the detection device 94, thereby shielding it from radiation with normal incidence.

[0058] As Figure 5As shown, an embodiment without the detection cavity 71 is also possible. In this case, the support structure (denoted herein as 190) of the detection structure (denoted herein as 180) is arranged on the intermediate body 18 and integrally formed therewith. Although not shown in detail, in this case, the detection device denoted herein as 194 can be a CMOS-type device; thus, the detection structure 180 can form, for example, a charge-coupled device (CCD). Generally, what has been described above with reference to the movement of the suspended movable structure 55, the optional presence of the secondary shield 99, and the shielding of the detection device 194 in the first and second operating modes also applies to Figure 5 the embodiment shown in

[0059] Still referring to Figure 2 and Figure 5 the embodiment shown, generally, the second external body 16 can be absent; in addition, the detection cavity 71 may not be completely enclosed by the detection structure at the top. Therefore, the detection structure can have an opening (not shown) such that the detection cavity 71 communicates with the second actuation semi-cavity 51. However, in the presence of these openings, the second external body 16 may be present, thereby allowing the detection cavity 71 to be enclosed at the bottom such that the cavity formed integrally by the detection cavity 71 and the main cavity 61 is hermetically enclosed, which has an advantage in terms of detection sensitivity. In this regard, the fact that at least the main cavity 61 in which the suspended movable structure 55 moves is hermetically enclosed and in a vacuum means that the movement of the suspended movable structure 55 is not hindered by friction with air.

[0060] Figure 6 FIG. shows another embodiment, and now the differences thereof with respect to Figure 2 will be described; unless otherwise specified, the reference numerals already used in Figure 2 will continue to be used.

[0061] As described above, the sensor denoted herein as 212 still includes the chopper assembly 101 and the detection assembly (denoted herein as 202) as well as the secondary shield 99. In addition, as will be explained in more detail below, the suspended movable structure 55 serves as a diffraction grating.

[0062] The detection unit 202 also includes an intermediate body, denoted herein as 218. The top surface S of the intermediate body 218t is bonded to the first bonding region 50. In addition, the peripheral structure (denoted as 292) and the detection structure (denoted as 280) extend below the bottom surface S of the intermediate body 218 218b

[0063] ​The detection structure 280 extends below the detection cavity, here indicated by 271. In particular, the detection cavity 271 still extends through the intermediate body 218 and is open at the top to communicate with the overlying second actuation half-cavity 51. In fact, in addition to the first actuation half-cavity 21 and the second actuation half-cavity 51, the main cavity, here indicated by 261, also includes a lower detection cavity 271 and is closed at the bottom by the detection structure 280.

[0064] The peripheral structure 292 surrounding the detection structure 280 is joined to the second joining area 64 below, and below that is the second outer body 16. The second joining area 64 laterally delimits an additional cavity 275, which is closed at the top by the detection structure 280 and at the bottom by the second outer body 16. In practice, the detection structure 280 is interposed between the main cavity 261 and the additional cavity 275. Although not shown, the detection structure 280 may include an opening so that the main cavity 261 and the additional cavity 275 are in fluid communication with each other.

[0065] In more detail, the detection structure 280 is laterally offset relative to the overlying suspended movable structure 55. For example, without loss of generality, Figure 6 , the detection structure 280 is to the left relative to the suspended movable structure 55 (reference Figure 6 In addition, hz indicates the distance between the suspended movable structure 55 and the detection structure 280 measured along the Z axis (in particular, the distance between planes parallel to the XY plane, where Figure 6 The center of gravity B of the suspended movable structure 55 is qualitatively shown in 55 , and the detection device 94 is respectively located in the XY plane), relative to Figure 2 As is the case in the illustrated embodiment, this distance is increased for the same sensor size because the detection structure 280 extends below the intermediate body 218. The advantages associated with this feature will be explained below.

[0066] In detail, Figure 6 In the embodiment shown, the suspended movable structure 55 spatially performs chromatic scattering of the radiation impinging thereon. Furthermore, the primary shield 34 continues to act as a chopper. In this way, the sensor 212 has the following optical behavior.

[0067] In detail, the sensor 212 may be dimensioned to act as a spectrometer. In practice, wx denotes the center of gravity B of the universal detection device 94 relative to the suspended movable structure 55 measured along the X axis. 55 and assuming that the radiation impinges on the suspended movable structure 55 at a given angle, the size of this offset wx is designed so that the detection device 94 receives radiation having a wavelength falling within the corresponding wavelength range.

[0068] More specifically, the following can be observed for dimension design: using A, θ i and θ m to represent the spatial periodicity of the suspension movable structure 55 along X, the angle of the radiation incident on the first outer body 14 (and the secondary shield 99) and then on the suspension movable structure 55, and the exit angle of the radiation from the suspension movable structure 55 respectively, then:

[0069] A * [sin(θ m ) - sin(θ i )] = m * λ;

[0070] wx = hz * tg(θ m )

[0071] where λ represents the radiation wavelength, and m = 0, 1, 2... represents the so-called diffraction order. Therefore, once the distance hz and the spatial periodicity A have been fixed, and considering for example the diffraction order m = 1, the radiation wavelength λ for irradiating the detection device 94 changes with the change of the distance wx. For example Figure 7 as shown, where, assuming for example A = 14 μm, hz = 300 μm, θ i = 0°. Therefore, assuming that the general detection device 94 extends within the range [wx0 - wx1], it will receive radiation with wavelengths included in the range [λ0 - λ1], that is, radiation with wavelengths falling within the corresponding bandwidth. In this regard, in Figure 6 the three different wavelength ranges related to the radiation incident on three different detection devices 94 are represented as Δλ′, Δλ″′, Δλ″.

[0072] These detection devices 94 can be of the same type as the device described with reference to Figure 2 the description.

[0073] Without prejudice to what has been previously described regarding the color scattering operated by the suspended movable structure 55, the radiation intensity irradiating the detection device 94 can be modulated by a controlled movement of the suspended movable structure 55 and the resulting change in the position of the main shield 34 relative to the secondary shield 99, as a first approximation without changing the corresponding wavelength bandwidth. In other words, the wavelength bandwidth associated with each detection device 94 does not vary with the change in position along the X axis of the suspended movable structure 55. In fact, as a first approximation, the variable alignment between the main shield 34 and the secondary shield 99 allows modulating the radiation intensity exiting the suspended movable structure 55 (and thus the transmittance of the assembly formed by the main shield 34 and the secondary shield 99), and thus affecting the radiation intensity of the irradiation detection device 94, but not the wavelength. In other words again, the variable alignment between the main shield 34 and the secondary shield 99 affects the degree of shielding (attenuation) suffered by the radiation irradiating the secondary shield 99, which means that the radiation irradiating the secondary shield 99 is reduced in intensity compared to the total radiation propagating downstream of the suspended movable structure 55.

[0074] In general, the applicant also notes that, in Figure 2 the embodiment shown, the suspended movable structure 55 can also act like a diffraction grating, but the proximity position of the detection device 94 relative to this suspended movable structure 55 means that there is not enough space for the radiation to be chromatically separated before irradiating the detection device 94.

[0075] As Figure 8 shown, an embodiment is also possible in which the detection structure (designated 380) and the peripheral structure (designated 392) are integrated on the second external body 16. In this case, there is no additional cavity 275, and the support structure (designated 390) and the peripheral structure 392 extend to contact the second external body 16 below. In addition, the second bonding zone 64 is interposed between the intermediate body (here designated 318) and the peripheral structure 392. The detection device, designated 194 here, can be of the same type as the Figure 5 detection device shown. In this case, the detection structure 380 can also be used as a spectrometer.

[0076] As Figure 9 shown, the sensor of the present invention can be encapsulated in a package 500, the package 500 including a packaging structure 502 defining a receiving cavity 504, the sensor (for example, without loss of generality, Figure 9 with reference to Figure 2The illustrated sensor 12) is disposed in the receiving cavity 504. The encapsulation structure 502 is opaque to radiation (i.e., does not allow radiation to enter the receiving cavity 504) and is formed of, for example, FR4 or an organic material or steel. The sensor 12 is joined to the encapsulation structure 502 by a joining layer 505 which is interposed between the second external body 16 and the encapsulation structure 502.

[0077] The encapsulation structure 502 defines an opening 507 which is closed by a lens 510 that is stacked at a distance from the secondary shield 99 (optional) of the sensor 12. The lens 510 is transparent to radiation and is used to direct the radiation onto the sensor 12, in particular onto the detection structure 80, after the radiation from the outside has passed through the main shield 34 which serves as a chopper. The presence of the lens 510 allows an increase in the numerical aperture of the sensor 12. For example, the lens 510 is a biconcave lens. The lens 510 also performs the function of focusing the light beam onto the suspended movable structure 55.

[0078] Regardless of the embodiment, the chopper assembly 101 can be manufactured in the following manner.

[0079] First, as Figure 10 shown, an oxide layer 620 is formed above the semiconductor wafer 614. The oxide layer 620 and the semiconductor wafer 614 are respectively used to form the dielectric region 20 and the first external body 14.

[0080] Subsequently, as Figure 11 shown, a polysilicon layer 622 for forming the intermediate region 22 is formed above the oxide layer 620; in addition, a first conductive layer 632 is formed above the polysilicon layer 622.

[0081] Then, as Figure 12 shown, an etching is performed to selectively remove a part of the first conductive layer 632 and expose a first part of the polysilicon layer 622. The remaining part of the first conductive layer 632 forms the internal metal region 32, in particular forms the outer peripheral part 33, the first intermediate part 35A and the second intermediate part 35B of the internal metal region 32, and the main shield 34. In addition, a passivation layer 642 for forming the passivation region 42 is formed on the internal metal region 32 and on the first exposed part of the polysilicon layer 622.

[0082] Subsequently, as Figure 13 shown, the part of the passivation layer 642 which is arranged to be in contact with the underlying polysilicon layer 622 is selectively removed, thereby exposing a second part of the polysilicon layer 622. The remaining part of the passivation layer 642 forms the passivation region 42.

[0083] Then, as Figure 14As shown, etching is performed using the passivation region 42 as a mask to selectively remove the second portion of the polysilicon layer 622 described above, exposing the underlying portion of the oxide layer 620. In fact, a hole 37 is formed whose bottom is temporarily blocked by the underlying oxide layer 620; in addition, the remaining portion of the polysilicon layer 622 forms the intermediate region 22. In this way, the suspended movable structure 55 is formed.

[0084] Subsequently, as Figure 15 shown, a portion of the oxide layer 620 disposed below the first intermediate portion 25A and the second intermediate portion 25B of the intermediate region 22, and below the suspended region 24, is selectively removed to form the first actuation semi-cavity 21 and release the suspended movable structure 55 and the first spring M1 and the second spring M2. The remaining portion of the oxide layer 620 forms the dielectric region 20. In this way, in addition to the secondary shield 99 (optional), the chopper assembly 101 is also formed.

[0085] More specifically, etching is performed through hydrogen fluoride (HF) from the exposed portion of the oxide layer 620 in order to release the suspended movable structure 55.

[0086] Then, as Figure 16 shown, the chopper assembly 101 is flipped and joined to the detection assembly 102, which has been pre-formed in a manner known per se and thus is not shown. After this operation, the chopper assembly 101 completely covers the peripheral structure 92. In order to facilitate the formation of electrical contacts (not shown) for providing the electrical signal generated by the detection device 94 to the outside world, a cutting operation (not shown) of a portion of the chopper assembly 101 that is laterally offset with respect to the main cavity 61 is then performed, and the portion laterally offset with respect to the main cavity 61 exposes the peripheral structure 92; the remaining portion of the semiconductor wafer 614 forms the first external body 14. Although not shown, the secondary shield 99 (if any) can be formed before performing the above-described cutting operation of the portion of the chopper assembly 101 that is laterally offset with respect to the main cavity 61.

[0087] It is clear from the above description the benefits that the sensor of the present invention allows to obtain. In particular, the sensor of the present invention allows the chopper to be integrated in the optoelectronic device. Some embodiments also allow the diffraction grating and the chopper to be integrated in the same optoelectronic device to form, for example, a spectrometer with an integrated chopper.

[0088] Finally, it is obvious that, as previously mentioned, modifications and variations can be made to what has been described and shown herein without departing from the scope of protection of the present disclosure.

[0089] For example, the main shield 34 can have a shape different from the one described.

[0090] The secondary shield 99 can be replaced by a plurality of physically separated shield portions (not shown) such that the set of these shield portions has an optical behavior of partially transmitting the radiation incident thereon under any circumstances.

[0091] The internal metal region 32 can be formed of a multi-layer structure such as titanium and titanium nitride, for example.

[0092] The first external body, the second external body, and the intermediate body can be formed of materials different from those already described. For example, an embodiment in which the first external body 14 is formed of a material (such as glass) transparent to so-called near-infrared radiation is possible depending on the wavelength used.

[0093] A radiation sensor can generally be summarized as including:

[0094] A detection assembly (102; 202) and a chopper assembly (101), the detection assembly (102; 202) and the chopper assembly (101) being mechanically coupled to define a main cavity (61; 216); and wherein, the chopper assembly (101) includes: a suspended movable structure (55) extending in the main cavity (61; 261); and an actuation structure (63, 65), the actuation structure (63, 65) being electrically controllable to cause a change in the position of the suspended movable structure (55); and wherein, the detection assembly (102; 202) includes a detection structure (80; 180; 280; 380), the detection structure (80; 180; 280; 380) facing the main cavity (61; 261) and including a plurality of detection devices (94; 194); and wherein, the suspended movable structure (55) includes a first shield (34) of a conductive material, the first shield (34) being configured to shield the detection devices (94) from radiation, and the shielding of the detection devices (94) varying according to the position of the suspended movable structure (55).

[0095] The chopper assembly (101) can include a corresponding fixed body (14) and deformable structures (M1, M2), and the suspended movable structure (55) is coupled to the fixed body (14) of the chopper assembly (101) by the insertion of the deformable structures (M1, M2); and the actuation structure (63, 65) can be electrically controllable to cause the movement of the suspended movable structure (55) relative to the fixed body (14) of the chopper assembly (101) and the deformation generated by the deformable structures (M1, M2).

[0096] The detection devices (94) can have a planar arrangement; and the actuation structure (63, 65) can be configured to move the suspended movable structure (55) parallel to the planar arrangement.

[0097] The detection assembly (102) may include a main semiconductor body (18) that laterally defines an additional cavity (71), and an external body (16) that may be fixed to the main semiconductor body (18); and a detection structure (80) may be fixed to the main semiconductor body (18) and suspended over the additional cavity (71), the additional cavity (71) being closed at the bottom by the external body (16).

[0098] The detection assembly (102) may include a main semiconductor body (18); and a detection structure (180) may be integrated on the main semiconductor body (18).

[0099] The chopper assembly (101) may further include a partially transmissive second shield (99), the second shield (99) being fixed to the fixed body (14) of the chopper assembly (101) and having a shape such that the shielding of the detection device (94) depends on the position of the suspended movable structure (55) relative to the detection structure (80; 180; 280; 380) and on the position of the suspended movable structure (55) relative to the second shield (99).

[0100] The suspended movable structure (55) may extend below the fixed body (14) of the chopper assembly (101); and the chopper assembly (101) may further include a second shield (99) disposed on top of the fixed body (14) of the chopper assembly (101) and being partially transmissive; and wherein the detection structure (280; 380) may be laterally offset relative to the suspended movable structure (55), the suspended movable structure (55) being configured to receive radiation after the radiation has impinged on the second shield (99) and has passed through the second shield (99) and the fixed body (14) of the chopper assembly (101); the suspended movable structure (55) is further configured to chromatically scatter the received radiation to direct radiation whose wavelength depends on the lateral offset of the detection device (94) relative to the suspended movable structure (55) towards the respective detection devices (94); and wherein the first and second shields (34, 99) may be configured to attenuate the radiation impinging on the second shield (99) according to the position of the suspended movable structure (55) relative to the second shield (99).

[0101] The detection assembly (202) may include a main semiconductor body (218) that laterally defines a portion of a main cavity (261); and the main cavity (261) may be closed at the bottom by a detection structure (280), the detection structure (280) being joined under the main semiconductor body (218).

[0102] The detection component (202) may include a main semiconductor body (16) and a spacer (318); and wherein, the spacer (318) may be interposed between the fixed body (14) of the chopper component (101) and the main semiconductor body (16) of the detection component (202), and may laterally define a part of the main cavity (261), the main cavity (261) may be closed at the bottom by a detection structure (380), and the detection structure (380) may be integrated on the main semiconductor body (16) of the detection component (202).

[0103] An apparatus may generally include: a sensor (12; 212) according to any one of the preceding claims; and a package (500) including a packaging structure (502) that is optically opaque and defines a receiving cavity (504) covered by an opening (507); and a lens (510) that closes the opening (507); wherein, the sensor (12; 212) is disposed within the receiving cavity (504) and below the lens (510), and the lens (510) is configured to focus radiation onto the sensor (12; 212).

[0104] A manufacturing process of a radiation sensor (12; 212) may generally include the following steps: forming a detection component (102; 202) and a chopper component (101); and mechanically coupling the detection component (102; 202) and the chopper component (101) such that the detection component (102; 202) and the chopper component (101) define a main cavity (61; 216); wherein, the step of forming the chopper component (101) includes:

[0105] forming a suspended movable structure (55) extending in the main cavity (61; 261); and forming an actuation structure (63, 65) that is electrically controllable to cause a change in the position of the suspended movable structure (55); wherein, the step of forming the detection component (102; 202) includes forming a detection structure (80; 180; 280; 380) including a plurality of detection devices (94) to face the main cavity (61; 261); and wherein, the step of forming the suspended movable structure (55) includes forming a first shield (34) of a conductive material, and the first shield (34) is configured to shield the detection devices (94) from radiation, and the shielding of the detection devices (94) varies with the position of the suspended movable structure (55).

[0106] The step of forming the chopper component (101) may include: forming a fixed body (14) and a deformable structure (M1, M2); and the step of forming the suspended movable structure (55) may be such that the suspended movable structure (55) may be coupled to the fixed body (14) of the chopper component (101) by the insertion of the deformable structure (M1, M2).

[0107] The steps of forming the chopper assembly (101) may include: forming a dielectric layer (620) on a wafer (614); forming an intermediate layer (622) of a different material from the dielectric layer (620) on the dielectric layer (620); forming a conductive layer (632) on the intermediate layer (622), and then selectively removing a portion of the conductive layer (632) to expose a first portion of the intermediate layer (622), and leaving the remaining portion of the conductive layer (632) to form a first shield (34); coating the first shield (34) and the first exposed portion of the intermediate layer (622) with a passivation layer (642); selectively removing a portion of the passivation layer (642) disposed on the intermediate layer (622) to expose a second portion of the intermediate layer (622); selectively removing the second portion of the intermediate layer (622) to expose a portion below the dielectric layer (620); and starting from the exposed portion of the dielectric layer (620), selectively removing a portion of the dielectric layer (620) disposed below the first shield (34) to release the suspended movable structure (55).

[0108] The dielectric layer (620) may be formed of an oxide; the intermediate layer (622) is formed of polysilicon.

[0109] The various embodiments described above herein can be combined to provide further embodiments.

[0110] In light of the teachings detailed above, these and other modifications may be made to the embodiments. In general, the terms used in the following claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include the entire scope of all possible embodiments and equivalents of the claims. Accordingly, the claims are not limited by the present disclosure.

Claims

1. A radiation sensor, comprising: A first body; A second body; A main cavity between the first body and the second body; A detection cavity between the main cavity and the second body; A detection assembly and a chopper assembly between the first body and the second body, the detection assembly and the chopper assembly being mechanically coupled to define the main cavity, wherein the chopper assembly comprises: A suspended movable structure in the main cavity; and An actuation structure including a first component embedded in the suspended movable structure, and the actuation structure being configured to be electrically controllable to cause a change in the position of the suspended movable structure, Wherein the detection assembly comprises: A member extending between the detection cavity and the main cavity across the detection cavity and facing the main cavity, and A plurality of detection devices embedded in the member; and Wherein the suspended movable structure includes a first shield of conductive material, the first shield being configured to shield the plurality of detection devices from the radiation, and the shielding of the plurality of detection devices varies according to the position of the suspended movable structure.

2. The radiation sensor according to claim 1, wherein the chopper assembly comprises a fixed body and a deformable structure, the suspended movable structure being coupled to the fixed body of the chopper assembly by the interposition of the deformable structure, wherein the actuation structure is electrically controllable to cause movement of the suspended movable structure relative to the fixed body of the chopper assembly and the resulting deformation of the deformable structure.

3. The radiation sensor according to claim 2, wherein the plurality of detection devices have a planar arrangement; and wherein the actuation structure is configured to move the suspended movable structure parallel to the planar arrangement.

4. The radiation sensor according to claim 2, wherein the detection assembly comprises a main semiconductor body that laterally defines the detection cavity and an external body fixed to the main semiconductor body, wherein the detection structure is fixed to the main semiconductor body and is suspended at the detection cavity, the detection cavity being closed at the bottom by the external body.

5. The radiation sensor according to claim 2, wherein the detection assembly comprises a main semiconductor body, and wherein the detection structure is integrated on the main semiconductor body.

6. The radiation sensor according to claim 4, wherein the chopper assembly further comprises a partially transmissive second shield fixed to the fixed body of the chopper assembly and having a shape such that the shielding of the plurality of detection devices depends on the position of the suspended movable structure relative to the detection structure and on the position of the suspended movable structure relative to the second shield.

7. The radiation sensor according to claim 2, wherein the suspended movable structure extends below the fixed body of the chopper assembly, wherein the chopper assembly includes a second shield disposed on top of the fixed body of the chopper assembly and being partially transmissive, wherein the detection structure is laterally offset relative to the suspended movable structure, the suspended movable structure being configured to receive radiation after the radiation has impinged on the second shield and has passed through the second shield and the fixed body of the chopper assembly, the suspended movable structure being configured to chromatically scatter the received radiation to direct radiation having a wavelength depending on the lateral offset of the detection device relative to the suspended movable structure towards respective detection devices; and wherein the first shield and the second shield are configured to attenuate the radiation impinging on the second shield according to the position of the suspended movable structure relative to the second shield.

8. The radiation sensor according to claim 7, wherein the detection assembly includes a main semiconductor body that laterally defines a portion of the main cavity, wherein the main cavity is closed at the bottom by the detection structure that is joined beneath the main semiconductor body.

9. The radiation sensor according to claim 7, wherein the detection assembly includes a main semiconductor body and a spacer, and wherein the spacer is interposed between the fixed body of the chopper assembly and the main semiconductor body of the detection assembly and laterally defines a portion of the main cavity, the main cavity being closed at the bottom by the detection structure that is integrated on the main semiconductor body of the detection assembly.

10. An apparatus, comprising: a radiation sensor, the radiation sensor including: a first body; a second body; a main cavity between the first body and the second body; a detection cavity between the main cavity and the second body; a detection assembly between the first body and the second body, coupled to a chopper assembly, the detection assembly and the chopper assembly defining the main cavity, wherein the chopper assembly includes: a suspended movable structure in the main cavity; and an actuation structure including a first component embedded in the suspended movable structure and being configured to be electrically controllable to cause a change in position of the suspended movable structure, wherein the detection assembly includes a member and a plurality of detection devices, the member extending across the detection cavity between the detection cavity and the main cavity and facing the main cavity, and the plurality of detection devices being embedded in the member, and wherein the suspended movable structure includes a first shield of conductive material configured to shield the plurality of detection devices from the radiation, the shielding of the plurality of detection devices varying according to the position of the suspended movable structure, a package including a packaging structure that is optically opaque and defines a receiving cavity covered by an opening; and a lens covering the opening Wherein, the radiation sensor is disposed in the accommodation cavity, and the lens is positioned and configured to focus the radiation onto the radiation sensor.

11. The apparatus according to claim 10, wherein the chopper assembly includes a fixed body and a deformable structure, and the suspended movable structure is coupled to the fixed body of the chopper assembly by interposition of the deformable structure.

12. The apparatus according to claim 11, wherein the actuation structure is electrically controllable to cause movement of the suspended movable structure relative to the fixed body of the chopper assembly and resulting deformation of the deformable structure.

13. The apparatus according to claim 12, wherein the chopper assembly further includes a partially transmissive second shield, the partially transmissive second shield being fixed to the fixed body of the chopper assembly, and the partially transmissive second shield having a shape such that shielding of the plurality of detection devices depends on the position of the suspended movable structure relative to the detection structure and on the position of the suspended movable structure relative to the second shield.

14. The apparatus according to claim 10, wherein the detection assembly includes a main semiconductor body that laterally defines a portion of the main cavity, wherein the main cavity is closed at the bottom by the detection structure that is joined beneath the main semiconductor body.

15. A process for manufacturing a radiation sensor, comprising: forming a first body and a second body; forming a main cavity between the first body and the second body; forming a detection cavity between the main cavity and the second body; forming a detection assembly and a chopper assembly between the first body and the second body; and mechanically coupling the detection assembly and the chopper assembly such that the detection assembly and the chopper assembly define the main cavity, wherein forming the chopper assembly includes: forming a suspended movable structure in the main cavity; and forming an actuation structure that includes a first component embedded in the suspended movable structure and that is electrically controllable to cause a change in position of the suspended movable structure, wherein forming the detection assembly includes forming a member that extends across the detection cavity between the detection cavity and the main cavity and that includes a plurality of detection devices facing the main cavity and embedded in the member, and wherein forming the suspended movable structure includes forming a first shield of conductive material configured to shield the plurality of detection devices from the radiation, the shielding of the plurality of detection devices varying according to the position of the suspended movable structure.

16. The process according to claim 15, wherein forming the chopper assembly includes: forming a fixed body and a deformable structure, wherein the suspended movable structure is formed such that the suspended movable structure is coupled to the fixed body of the chopper assembly by interposition of the deformable structure.

17. The process according to claim 16, wherein forming the chopper assembly includes: Form a dielectric layer on the wafer; Form an intermediate layer of a material different from that of the dielectric layer on the dielectric layer; Form a conductive layer on the intermediate layer and selectively remove part of the conductive layer to expose a first part of the intermediate layer, wherein the remaining part of the conductive layer forms the first shield; Coat the first shield and the exposed first part of the intermediate layer with a passivation layer; Selectively remove the part of the passivation layer disposed on the intermediate layer and expose a second part of the intermediate layer; Selectively remove the second part of the intermediate layer and expose the underlying part of the dielectric layer; And Starting from the exposed part of the dielectric layer, selectively remove the part of the dielectric layer disposed under the first shield and release the suspended movable structure.

18. The process according to claim 17, wherein the dielectric layer is formed of an oxide and wherein the intermediate layer is polysilicon.

19. The process according to claim 15, wherein the detection component is formed on the main semiconductor body.

20. The process according to claim 19, wherein the main semiconductor body laterally defines a part of the main cavity, wherein the main cavity is closed at the bottom by the detection structure, and the detection structure is joined under the main semiconductor body.

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