JP2011214857A - Infrared sensor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cracking between support legs of an infrared absorbing film on the occasion when the infrared absorbing film of an infrared sensor element having the infrared absorbing film supported by the support legs are made a thin film.SOLUTION: In regard to the infrared absorbing film having at least two or more support legs, a slit is provided between the support legs. Thereby a stress generated between the support legs of the infrared absorbing film in the process of removing a sacrifice layer is relaxed and cracking is suppressed. Therefore, the infrared absorbing film can be made thin and thus the infrared sensor element of higher sensitivity can be provided.

Description

The present invention relates to a thermal infrared sensor element with improved crack resistance of an infrared absorption film.

An infrared sensor is used, for example, to detect weak infrared rays emitted from an object or a person, and is used in various fields such as monitoring or in-vehicle use. There are various infrared detection methods for infrared sensors, and the most commonly used methods are quantum infrared sensors and thermal infrared sensors. The quantum infrared sensor uses the photoelectric effect of a solid material to directly detect absorbed infrared light and convert it into an electrical signal. The thermal infrared sensor converts the received infrared ray into heat once, and detects the temperature change due to the converted heat using a material having a large change in physical properties due to temperature. Such an infrared sensor is currently realized as a semiconductor chip using a semiconductor substrate. An infrared sensor configured using a semiconductor substrate is hereinafter referred to as an “infrared sensor element”.

As a structure of the above-described thermal infrared sensor, a structure in which the infrared absorption film is supported by a support leg having a predetermined bottom area on the heat detection structure as in Patent Document 1, or a part of the infrared absorption film is convex. A structure in which a plurality of support legs formed as described above is formed is disclosed.

Here, there is a response speed as one of the indexes for representing the performance of the thermal infrared sensor. The response speed indicates the concept of time until infrared rays absorbed by the infrared absorption film are transmitted to the heat detection structure. As described above, since the thermal infrared sensor detects the amount of infrared rays converted into heat, in order to increase the reaction speed, the response speed in the heat detection structure may be increased. For this purpose, it is preferable to reduce the heat capacity of the heat detection structure including the infrared absorption film. Patent Document 2 discloses that in a thermal infrared sensor, the thickness of the infrared absorption film is reduced in order to reduce the thermal time constant and increase the reaction rate.
JP 2001-156277 A JP 2006-170937 A

In order to reduce the heat capacity of the infrared absorption film, it is conceivable to reduce the thickness of the infrared absorption film as in Patent Document 2 for the infrared sensor having the structure disclosed in Patent Document 1. When using an infrared sensor element in which a plurality of support legs are formed on an infrared absorption film as in Embodiment 3 of Patent Document 1 and reducing the thickness of the infrared absorption film, the following problems may occur.

FIG. 20 is a plan view of a conventional infrared sensor element in which two support legs are formed on an infrared absorption film. In the infrared sensor element of FIG. 20, support legs 4 are formed at two locations on the infrared absorption portion 3 of the infrared absorption film 2 separated for each pixel, and the outside of the support legs 4 (the outer peripheral region of the infrared absorption film). ) Is provided with an opening 5 for gas injection.

When the sacrificial layer made of resist is removed in the sacrificial layer removing step in Patent Document 1, stress is generated in the infrared absorbing film due to the difference in thermal expansion coefficient between the sacrificial layer and the infrared absorbing film. To do. Since the infrared absorption film is separated for each pixel, the outer peripheral region of the infrared absorption film can be deformed by stress, and the stress generated in the outer peripheral region of the infrared absorption film is relieved by the deformation of the outer peripheral region. . On the other hand, since the expansion and contraction of the infrared absorption film is fixed by the support legs 4 in the area sandwiched between the support legs 4 of the infrared absorption film (hereinafter referred to as the inter-support leg area), the infrared rays are more in comparison with the outer peripheral area of the infrared absorption film. Absorption film is difficult to deform. Therefore, the stress generated in the region between the support legs is not relieved, the stress is concentrated between the support legs, and cracks are generated between the support legs 4 as shown in FIG. When an infrared sensor element is used in a state where cracks are generated, the cracks between the support legs spread to the outer peripheral portion of the infrared absorption film due to vibration due to use, etc., and the infrared absorption film may be divided along the cracks . Therefore, it is difficult to reduce the thickness of the infrared absorption film on which two or more support legs are formed. An infrared sensor element in which the infrared absorption film is thinned to increase the performance and the heat capacity of the infrared absorption film is reduced cannot maintain reliability.

Therefore, an object of the present invention is to provide a highly sensitive infrared sensor element having a structure capable of suppressing the occurrence of cracks in an infrared absorption film while keeping the heat capacity of the heat detection structure portion small.

In order to solve the above-described problems, an infrared sensor element of the present invention is connected to a semiconductor substrate having a recess and the semiconductor substrate in the vicinity of the outer edge of the semiconductor substrate, and extends from the vicinity of the outer edge to the upper portion of the recess. A beam portion disposed in a row, a heat detection portion connected to the beam portion and held at the top of the recess, and covering the recess, the beam portion and the heat detection portion, and at least two support legs And an infrared absorber connected to the heat detector via a slit, and a slit is formed in the region between the support legs of the infrared absorber.

According to the structure and the manufacturing method of the infrared sensor element of the present invention, it becomes a structure that suppresses the generation of cracks by providing slits between the support legs of the infrared absorption film, and the reliability of the infrared sensor element can be improved. Moreover, it becomes possible to make an infrared absorption film thin by setting it as the structure where generation | occurrence | production of the crack was suppressed, and the heat capacity of a heat detection structure part can be made small. Therefore, a highly sensitive infrared sensor element with a fast reaction speed can be obtained.

It is sectional drawing of the infrared sensor element which concerns on 1st Example of this invention. It is a top view of the infrared sensor element which concerns on 1st Example of this invention. It is a top view of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is a top view which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is a top view which shows a part of manufacturing process of the infrared sensor element which concerns on 1st Example of this invention. It is a top view which shows the infrared sensor element which concerns on the modification of 1st Example of this invention. It is a top view which shows the infrared sensor element which concerns on the other modification of 1st Example of this invention. It is sectional drawing of the infrared sensor element which concerns on 2nd Example of this invention. It is sectional drawing which shows a part of manufacturing process of the infrared sensor element which concerns on 2nd Example of this invention. It is a top view of the infrared sensor element which concerns on 2nd Example of this invention. It is a top view of the infrared sensor element by a prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The structure of the infrared sensor element of the present invention will be described in detail with reference to FIGS.

FIG. 1 is a sectional view showing the structure of a unit element of an infrared sensor element, that is, an infrared sensor element corresponding to one pixel. In the infrared sensor element, a space surrounded by a silicon substrate 1 having a recess, an etching stopper wall 13 embedded in the silicon substrate 1, and a buried oxide film 14 disposed on the silicon substrate 1 is defined as a gap 12. . A heat detection structure 9 is provided on the buried oxide film 14, and the heat detection structure 9 is composed of a beam portion 8 and a heat detection portion 7. The beam portion 8 is connected to the buried oxide film 14 with wiring 10 and insulation. A film 11 is laminated. An insulating film 11 is formed on the buried oxide film 14 provided around the upper portion of the etching stopper wall 13, and is located below the peripheral circuit wiring 16 provided on the upper surface of the insulating film 11 and the insulating film 11. In order to electrically connect the buried oxide film 14, a buried metal 15 is formed through the insulating film 11. An insulating film 11 is provided on the heat detection unit 7, and the support legs 4 of the infrared absorption film 2 are disposed in contact with the insulating film 11. The infrared absorption film 2 is a single absorption film composed of an infrared absorption portion 3 and a support leg 4, and the plurality of support legs 4 are configured to support the infrared absorption portion 3 by forming a concave shape. The infrared absorbing portion 3 is formed with a gas inflow opening 5 and a slit 6.

FIG. 2 is a plan view of the infrared sensor element as viewed from above, and FIG. 1 is a sectional view taken along line AA ′ in FIG. The infrared absorbing portion 3 is provided with two gas inflow openings 5 and one slit 6. The gas inflow opening 5 is provided in an outer peripheral region that is closer to the end portion of the infrared absorption unit 3 than the position where the support leg 4 is disposed, and an etching gas is formed below the buried oxide film 14 in a manufacturing process described later. It is used as a gas inlet when inflowing. The slit 6 is provided in a region sandwiched between two support legs 4 that are formed in a concave shape to support the infrared absorbing portion 3. The shape of the slit 6 may be rectangular or circular, and may be a layout in which a plurality of such slits are arranged. In addition, the shape of the slit 6 in FIG. 2 shows a rectangular shape (rectangular shape) as an example.

3A omits the infrared absorption film 2, the insulating film 11, the buried metal 15 and the peripheral circuit wiring 16 in FIG. 1, and the arrangement of the thermal detection section 7, the wiring 10 of the beam section 8, and the etching stopper wall 13 is omitted. FIG. 1 is a cross-sectional view taken along line BB ′ in FIG.

In FIG. 3A, the wiring 10 is formed in a crank shape that is bent and connected to the heat detection unit 7 in the region surrounded by the etching stopper wall 13. At the end of the wiring 10 on the etching stopper wall side, there is a buried metal forming region 26, which is connected to the upper buried metal 15 (see FIG. 1). The buried metal 15 is filled in a through-hole formed in the insulating film 11 and connected to a peripheral circuit wiring 16 for connection with a peripheral circuit provided on the insulating film 11. By connecting the external circuit to the peripheral circuit wiring 16, the peripheral circuit and the heat detection unit 7 are electrically connected via the embedded metal 15 and the wiring 10.

Further, FIG. 3A shows the heat detection unit 7 connected to the wiring 10 in detail. The heat detector 7 includes a diode 23 and a connection electrode 24, and the diode 23 includes a high concentration P-type region 20, a low concentration N-type region 21, and a high concentration N-type region 22. In this embodiment, the two diodes 23 are connected in series via the connection electrode 24, and the rectangular heat detection unit 7 is configured by the two diodes 23 and the connection electrode 24. Further, the heat detection unit 7 is not limited to the structure including the two diodes 23 and the connection electrodes 24 as described above, and may be configured by one diode as shown in FIG. As shown in FIG. 3, it may be composed of three or more diodes.

Next, the operation of the infrared sensor element and the function of each part will be described.

Infrared rays incident from the outside are absorbed from the upper surface of the infrared absorbing portion 3. Infrared rays absorbed by the infrared absorbing portion 3 are converted into heat inside the infrared absorbing film 2. The converted heat is transmitted to the support leg 4 and is transmitted to the heat detection unit 7 for detecting the temperature via the first silicon oxide film 11. The electrical signal detected by the heat detection unit 7 is transmitted to the peripheral circuit wiring 16 via the wiring 10 and the embedded metal 15 of the beam unit 8 and can be transmitted to an external circuit.

The infrared absorbing film 2 includes an infrared absorbing portion 3 and a support leg 4. The infrared absorbing portion 3 has a large surface area in order to absorb more infrared rays incident from the outside, and the support leg 4 formed of a film having the same configuration has a structure that supports the infrared absorbing portion 3. ing. Note that two or more support legs 4 can more stably support the infrared absorbing portion 3 than one. In order to efficiently transmit the heat converted from the infrared rays inside the infrared absorption film 2 to the heat detection unit 7, it is preferable that the length of the support leg 4 is short. The infrared absorbing film 2 has a laminated structure composed of an insulating film and a metal film formed on the insulating film.

The heat detection unit 7 detects heat transmitted from the support leg 4 through the first silicon oxide film 11 and includes a diode 23 and a connection electrode 24. In order to improve the performance of the heat detector 7, it is only necessary to increase the number of diodes, and it is particularly preferable to connect them in series.

The beam portion 8 is a path for transmitting the temperature of heat detected by the heat detection portion 7 to an external circuit as an electric signal, and has a configuration in which the wiring 10 is formed on the buried oxide film 14. In order to increase the sensitivity of the infrared sensor element, it is necessary to prevent the heat converted by the infrared absorption unit 3 from escaping to the silicon substrate 1 via the support leg 4, the heat detection unit 7 and the beam unit 8. For this purpose, the heat insulating property of the beam portion 8 may be increased. In order to enhance this heat insulation characteristic, the cross-sectional area of the beam portion 8 may be reduced, and the distance from the heat detection portion 7 to the contact point with the silicon substrate may be increased. The beam portion 8 of the present invention has a narrow crank shape. It has a long structure.

The silicon substrate 1 is disposed below the heat detection unit 7 and the beam unit 8 via the buried oxide film 14. A space surrounded by the silicon substrate 1, the etching stopper wall 13, and the buried oxide film 14 is defined as a gap 12, and the gap 12 expands according to the shape of the recess that is the upper surface of the silicon substrate 1. 5 is deepest near the infrared sensor element and becomes shallower toward the periphery of the infrared sensor element, and is shallowest in the vicinity of the etching stopper wall 13 serving as the inner wall of the recess. The etching stopper wall 13 is formed in the outer peripheral region of the silicon substrate 1 so as to surround the unit element of the infrared sensor element.

Next, a method for manufacturing an infrared sensor as an embodiment of the present invention will be described in detail with reference to FIGS. In this embodiment, a method for manufacturing a structure of an infrared sensor element corresponding to a unit element of an infrared sensor element, that is, one pixel is shown.

FIG. 4 shows an SOI substrate on which an etching stopper wall is formed. As a semiconductor substrate, an SOI substrate in which a buried oxide film 14 and an SOI layer 31 are sequentially stacked on a silicon substrate 1 is prepared. For example, the SOI substrate may be bonded or SIMOX (Silicon Implanted
Oxide) method or the like. Next, in order to provide the etching stopper wall 13 in the outer peripheral region of the unit element structure, a resist is applied on the prepared SOI substrate, and the resist is patterned by photolithography. Further, etching is performed using the patterned resist as a mask to form a trench for an etching stopper wall (also referred to as an opening groove) on the SOI substrate so as to surround one pixel of the infrared sensor element. After the resist is removed, the opening groove is filled with silicon oxide by, for example, a CVD method. At this time, since silicon oxide is deposited in areas other than the opening grooves, the silicon oxide deposited in areas other than the opening grooves is removed by dry etching or CMP (Chemical Mechanical Polishing), thereby forming the etching stopper wall 13 in the SOI substrate. Note that the silicon oxide embedded in the trench may have a stacked structure of silicon oxide and a polycrystalline silicon film.

Subsequently, in FIG. 5, the heat detector 7 and the wiring 10 are formed on the buried oxide film 14. Each region to be used as the heat detection unit 7 and the wiring 10 is etched on the SOI layer 31, boron and phosphorus are ion-implanted in the heat detection unit 7 to form a diode, and titanium or cobalt is formed in the wiring unit 10. Deposit metal such as.

6 corresponds to a plan view of the structure after the process shown in FIG. 5 is completed, and a cross-sectional view taken along the line CC 'in FIG. 6 is FIG. The SOI layer 31 whose central portion has been etched into a rectangular shape is formed by ion-implanting boron and phosphorus into the rectangular silicon portion so that the high-concentration P-type region 20, the low-concentration N-type region 21, and the high-concentration N-type region. 22 is formed. The high concentration P-type region 20, the low concentration N-type region 21 and the high concentration N-type region 22 constitute a diode 23. Further, a metal such as titanium or cobalt is deposited on the rectangular shape portion that is connected from the high-concentration P-type region 20 side or the high-concentration N-type region 22 side of the heat detection unit 7 to the etching stopper wall 13 and subjected to heat treatment. Thus, the wiring 10 for taking out an electrical signal from the heat detection unit 7 is formed. Similarly, a metal such as titanium or cobalt is deposited and subjected to heat treatment to form a connection electrode 24 for connecting the two diodes 23 between the diodes 23. Thus, the diode 23 and the connection electrode 24 constitute the heat detection unit 7 that detects heat according to incident infrared rays.

Subsequently, in FIG. 7, an insulating film 11 is deposited so as to cover the heat detector 7 and the wiring 10. For example, a silicon oxide film is deposited by a CVD method. The insulating film 11 to be formed may have a two-layer structure including a first silicon oxide film / silicon nitride film, and further, a three-layer structure including a first silicon oxide film / silicon nitride film / second silicon oxide film. It is good also as a laminated structure. With a two-layer or three-layer structure, the film thickness can be easily controlled in etching for thinning the insulating film 11 performed in a later step.

Next, contact holes 25 for forming the buried metal 15 are formed in the outer peripheral region of the insulating film 11. Since the embedded metal 15 formed using the contact hole 25 is connected to the end of the wiring 10, the contact hole 25 is formed so as to reach the wiring 10. A detailed position for forming the contact hole 25 is an upper portion of the buried metal forming region 26 which is an end portion of the wiring 10 in contact with the etching stopper wall 13 shown in FIG.

Subsequently, in FIG. 8, a peripheral circuit wiring 16 for connection with the embedded metal 15 and the peripheral circuit is formed. A laminated film of titanium / titanium nitride / tungsten is deposited by sputtering, for example, in the contact hole 25 and on the insulating film 11. Thereafter, the titanium / titanium nitride / tungsten laminated film deposited on the insulating film 11 at a portion other than the contact hole 25 is removed by dry etching or CMP, and the titanium / titanium nitride / tungsten laminated film is formed in the contact hole 25. As a result, the buried metal 15 is formed in the contact hole 25. Next, on the insulating film 11 and the buried metal 15, a metal film to be used as the peripheral circuit wiring 16 for connection to the peripheral circuit is deposited by, for example, sputtering. Thereafter, a resist is applied onto the metal film, and the resist is patterned by photolithography into a shape that leaves the metal film on the buried metal 15. Etching is performed using the patterned resist as a mask to leave a metal film on and around the buried metal 15, thereby forming peripheral circuit wiring 16 connected to the buried metal 15.

Subsequently, in FIG. 9, the insulating film 11 is thinned in order to reduce the heat capacities of the heat detector 7 and the wiring 10. A resist is applied on the insulating film 11 and the peripheral circuit wiring 16, and etching is performed using the resist as a mask, so that the regions corresponding to the heat detecting portion 7 and the wiring 10 of the insulating film 11 are thinned to a desired thickness. Here, when the insulating film 11 has a three-layer structure of first silicon oxide film / silicon nitride film / second silicon oxide film, the silicon nitride film can function as an etching stopper, so Only the second silicon oxide film positioned can be etched, and control when the film is thinned is facilitated. Further, the insulating film 11 having a laminated structure can flatten the thinned insulating film 11.

Subsequently, in FIG. 10, the beam portion 8 is formed in the heat detection portion 7 and the wiring portion 10 which are regions where the insulating film 11 is thinned. In order to form the beam portion 8, a resist is applied on the thin insulating film 11, and the resist is patterned by photolithography. Etching is performed using the patterned resist as a mask, and an opening penetrating the insulating film 11, the wiring 10, and the buried oxide film 14 is formed by etching. By forming such an opening, a crank-shaped beam portion 8 having a thin and long structure as shown in FIG. 3A is formed. FIG. 3A is a diagram showing a structure obtained by removing the insulating film 11, the buried metal 15 and the peripheral circuit wiring 16 above the etching stopper wall 13 from the structure shown in FIG. In this way, the heat detection structure portion 9 is configured by the heat detection portion 7 and the beam portion 8 including the wiring 10.

Subsequently, in FIG. 11, a sacrificial layer 17 having an opening 18 is formed on the insulating film 11. A resist is applied as a sacrificial layer 17 on the entire upper surface of the insulating film 11, and support leg openings 18 for infrared absorbing films are formed in the sacrificial layer 17 at two locations by photolithography. The sacrificial layer 17 may be polyimide or the like, for example. The support leg opening 18 opens to a region reaching the insulating film 11 on the upper layer of the heat detection unit 7.

Subsequently, in FIG. 12, the infrared absorption film 2 is formed on the sacrificial layer 17. For example, an insulating film is deposited on the surface of the sacrificial layer 17 and inside the support leg opening 18 by a CVD method, and further a metal film is deposited on the insulating film deposited by a sputtering method. The infrared absorption film 2 is constituted by a deposited layer made of these insulating film and metal film. For example, the insulating film is made of silicon oxide or silicon nitride. The metal film is made of titanium, chromium, or vanadium, or nitride, oxide, or carbide of titanium, chromium, or vanadium. The infrared absorption film 2 may have a three-layer structure of insulating film / metal film / insulating film by further depositing an insulating film on the metal film. The infrared absorption film 2 formed here is composed of an infrared absorption part 3 formed on the upper part of the sacrificial film 17 and a support leg 4 formed inside the support leg opening 18.

Subsequently, in FIG. 13, a groove portion 19, a gas inflow opening 5, and a slit 6 for separating pixels of the infrared absorption portion 3 are formed. After applying a resist on the infrared absorbing portion 3 and patterning the resist by photolithography, the infrared absorbing portion 3 is etched using the patterned resist as a mask. By such etching, a groove portion 19 for separating the infrared absorbing film 2 between adjacent pixels and gas injection openings 5 are formed at two locations on the outside of the support leg 4 (outer peripheral region of the infrared absorbing film 2). A slit 6 having a predetermined shape is formed in a region sandwiched between the support legs 4 of the infrared absorbing portion 3. The two openings 5 for gas inflow are through holes penetrating to the silicon substrate of the SOI substrate, and XeF2 gas flows in through the through holes. The silicon substrate 1 is etched by flowing XeF2 gas, and the lower layer of the buried oxide film 14 becomes a gap 12 as shown in FIG. Since such etching has the property of proceeding isotropically with respect to the silicon substrate 1, if the through-hole that is the gas inflow opening 5 is near the center of the pixel, the etching proceeds so that the center is deepest. . Examples of gases that realize isotropic etching with respect to silicon include XeF4, XeF6, KrF4, KrF6, ClF3, BrF3, BrF5, and IF5.

FIG. 14 is a diagram showing the infrared absorption film 3 of FIG. 13 from the top. By forming the groove portion 19, the pixels are separated from each other, and the infrared absorption film 2 of the infrared sensor element having a multi-pixel structure is divided into a single pixel structure. In addition, the slit 6 is formed in a rectangular shape so as to be parallel to each support leg 5 in a region sandwiched between the support legs 4 of the infrared absorbing portion 3.

15 and 16 are diagrams showing the infrared absorption film 3 of FIG. 13 from the top, and illustrate the shape of the slit 6. The slit is formed in a process before the sacrificial layer removing process because it is provided to relieve stress generated in a region sandwiched between the support legs 5 when the sacrificial layer is removed in the sacrificial layer removing process which is a later process. It is essential to form in a region sandwiched between the supporting legs 5. In addition, the shape of the slit 6 may be a rectangle or a circle, and a plurality of each shape may be provided. For example, FIG. 15 shows a case where two rows of rectangular slits are formed, and FIG. 16 shows a case where two rows of divided rectangular slits are formed. In order to relieve the stress between the support legs 5 more efficiently, the slit preferably has a continuous shape extending over the entire long side direction in the region between the support legs 5. Further, even when there are a plurality of support legs of three or more, as in the case of two support legs, a slit may be provided in a region sandwiched between the plurality of support legs on the infrared absorbing portion 3. .

Finally, oxygen plasma treatment is performed through the gas inflow opening 5, the slit 6 and the groove portion 19 to remove the sacrificial layer 17. By such removal, the infrared absorption film 2 becomes a hollow structure in which the infrared absorption portion 3 is supported by the support legs 4, and the infrared sensor element as shown in FIG. 1 is completed.

When the sacrificial layer removing step is performed without providing a slit as in the prior art, stress is concentrated between the support legs 5 to form a crack, and the crack spreads starting from the crack. On the other hand, in the present invention, since the sacrificial film removing step is performed by providing the slit, the stress concentrated between the support legs 5 is relieved by the slit, so that no crack is generated from the slit. That is, in the infrared sensor element according to the present invention, the slit 6 is provided between the support legs 4 of the infrared absorption film 2 to suppress cracks in the infrared absorption film 2 that may occur when the sacrificial layer 17 is removed. it can. As a result, a highly reliable infrared sensor element can be obtained. Furthermore, in the infrared absorbing film 2 in which cracks can be suppressed, the infrared absorbing portion 3 can be made thinner, and the heat capacity of the heat detecting portion 7 including the infrared absorbing film 2 can be reduced. As a result, a high reaction speed can be maintained, and a highly sensitive infrared sensor element can be obtained.

The structure of the infrared sensor element in the present embodiment will be described in detail with reference to FIG.

FIG. 17 is a cross-sectional view showing an infrared sensor element according to Embodiment 2 of the present invention. In each figure, components having the same number indicate the same thing. A feature of the structure of this embodiment is that an opening 27 penetrating to the gap 12 is formed between the support legs 4. The opening 27 is an opening that also serves as the slit 6 and the gas inflow opening 5 provided in the infrared absorption film 2 in Example 1 (FIG. 1). In the first embodiment, the gas inflow opening is formed on the outside of the support leg 4 (outer peripheral region of the infrared absorption film 2), and the slit is formed in a different position on the region sandwiched between the support legs 4 of the infrared absorption unit 3. Was. However, by forming the slit between the support legs 4 as a through hole reaching the silicon substrate 1, the slit provided in the infrared absorption film 2 can be used as the XeF2 gas inflow opening.

Next, the manufacturing method of the infrared sensor in a present Example is demonstrated in detail, referring FIG. 18 thru | or FIG. In this embodiment, a method for manufacturing a structure of an infrared sensor element corresponding to a unit element of an infrared sensor element, that is, one pixel is shown. Further, the steps from the preparation of the SOI substrate corresponding to FIGS. 4 to 12 to the step of forming the infrared absorption film 2 are the same steps, and therefore will be omitted.

FIG. 18 is a step subsequent to FIG. 12, in which a groove 19 and an opening 27 are formed for separating pixels of the infrared absorption unit 3. After applying a resist on the infrared absorbing portion 3 and patterning the resist by photolithography, the infrared absorbing portion 3 is etched using the patterned resist as a mask. By this etching, an opening 27 is formed in a region sandwiched between the groove portion 19 for separating the infrared absorption film 2 between adjacent pixels and the support leg 4 of the infrared absorption portion 3. The opening 27 is a through hole penetrating to the silicon substrate of the SOI substrate, and XeF 2 gas flows in through the through hole. The silicon substrate 1 is etched by flowing XeF2 gas, and the lower layer of the buried oxide film 14 becomes a void 12 as shown in FIG. Since such etching has the property of proceeding isotropically with respect to the silicon substrate 1, if the through hole, which is the opening 27, is near the center of the pixel, the etching proceeds so that the center is deepest. Examples of gases that realize isotropic etching with respect to silicon include XeF4, XeF6, KrF4, KrF6, ClF3, BrF3, BrF5, and IF5.

The shape of the opening 27 may be a rectangle or a circle, and a plurality of each shape may be provided. Further, even when there are a plurality of support legs of three or more, as in the case of two support legs, if the openings 27 are provided in the regions sandwiched between the plurality of support legs on the infrared absorbing portion 3, respectively. Good.

Here, a top view when the opening 27 is formed will be described with reference to FIG. FIG. 19 omits the infrared absorption film 2, the insulating film 11, the buried metal 15, and the peripheral circuit wiring 16 in FIG. 17, and shows the arrangement of the heat detection unit 7, the wiring 10 of the beam unit 8, and the etching stopper wall 13. FIG. 19 is a plan view, and a sectional view taken along line DD ′ in FIG. 19 corresponds to FIG. In providing a through hole that reaches the opening 27 to the silicon substrate 1, it is also necessary to penetrate the heat detection unit 7 as shown in FIG. In that case, what is necessary is just to enable it to provide a through-hole in the middle of arrangement | positioning of the diode 23 of the heat detection part 7, and the connection electrode 24. For example, when the diodes are arranged in two rows as shown in FIG.

Finally, oxygen plasma treatment is performed through the opening 27 and the groove 19 to remove the sacrificial layer 17. By such removal, the infrared absorption film 2 becomes a hollow structure in which the infrared absorption portion 3 is supported by the support legs 4, and an infrared sensor element as shown in FIG. 17 is completed.

As is apparent from the above description, in the infrared sensor element according to the present invention, the infrared absorbing film 2 that can be generated when the sacrificial layer 17 is removed by providing the opening 27 between the support legs 4 of the infrared absorbing film 2. Cracks can be suppressed. As a result, a highly reliable infrared sensor element can be obtained. Furthermore, in the infrared absorption film 2 in which cracks can be suppressed, the film thickness of the infrared absorption section 3 can be reduced, and the heat capacity of the heat detection section 7 including the infrared absorption film 2 can be kept small. As a result, a high reaction speed can be maintained, and a highly sensitive infrared sensor element can be obtained.

In addition, since the opening 27 also serves as the gas inflow opening 5 and the slit 6 of the first embodiment, the infrared absorption film removal area is reduced as compared with the first embodiment. For this reason, the substantial surface area of the infrared ray absorbing film can be enlarged, and infrared rays can be efficiently absorbed. That is, by increasing the area of the infrared absorption film and reducing the film thickness of the infrared absorption film, an infrared sensor element with higher reliability and higher sensitivity can be obtained.

Furthermore, since the gas inflow opening approaches the vicinity of the center of the pixel, if isotropic etching is performed, etching becomes shallow in the vicinity of the etching stopper wall, and it is not necessary to form a deep etching stopper wall. It becomes possible to make the trench shallow when forming. That is, high aspect ratio etching and deep trench embedding can be avoided, and the etching time required for trench formation can be reduced.

1 Silicon substrate, 2 Infrared absorbing film, 3 Infrared absorbing part, 4 Support legs,
5 Gas inflow opening, 6 Slit, 7 Heat detection part, 8 Beam part, 9 Heat detection structure part,
10 wiring, 11 insulating film, 12 gap, 13 etching stopper wall,
14 buried oxide film, 15 buried metal, 16 peripheral circuit wiring, 17 sacrificial layer,
18 support leg openings, 19 grooves, 20 high-concentration P-type region, 21 low-concentration N-type region,
22 high-concentration N-type region, 23 diode, 24 connection electrode, 25 contact hole, 27 opening, 31 SOI layer

Claims (9)

A semiconductor substrate having a recess;
A beam portion connected to the semiconductor substrate in the vicinity of the outer edge of the semiconductor substrate and arranged to extend above the recess from the vicinity of the outer edge;
A heat detector connected to the beam and held on top of the recess;
An infrared absorber that covers the recess, the beam and the heat detector, and is connected to the heat detector via at least two support legs;
An infrared sensor element, wherein a slit is formed in the region between the support legs of the infrared absorbing portion. The infrared sensor element according to claim 1, further comprising the infrared absorbing portion having an opening formed in an outer peripheral region of the support leg. 3. The infrared sensor element according to claim 1, wherein the slit has a rectangular shape and has one infrared absorbing portion. 4. The infrared sensor element according to claim 1, wherein the infrared absorbing element has two or more slits, and each of the slits has a rectangular or circular shape. 5. The infrared sensor element according to claim 1, wherein the infrared sensor element has three or more support legs, and the slits are provided between the support legs of the infrared absorbing portion. A heat detection structure forming step of forming a beam part having a heat detection part and a wiring electrically connected to the heat detection part on a semiconductor substrate;
An insulating layer forming step of forming an insulating layer covering the heat detecting portion and the beam portion;
A sacrificial layer forming step of forming a sacrificial layer on the insulating layer;
Infrared absorbing film formation for forming an infrared absorbing film comprising at least two or more supporting legs on the sacrificial layer, and an infrared absorbing part having a slit in the region between the supporting legs and an opening in the outer peripheral region of the supporting leg. Process,
A through hole forming step of forming a through hole reaching the semiconductor substrate below the opening;
A gap forming step of forming a gap in the semiconductor substrate by performing etching through the through hole;
And a sacrificial layer removing step of removing the sacrificial layer through the through hole after the gap forming step. The method for manufacturing an infrared sensor element according to claim 6, wherein the insulating layer forming step forms a plurality of insulating film layers including at least a silicon oxide film. A heat detection structure forming step of forming a beam part having a heat detection part and a wiring electrically connected to the heat detection part on a semiconductor substrate;
An insulating layer forming step of forming an insulating layer covering the heat detecting portion and the beam portion;
A sacrificial layer forming step of forming a sacrificial layer on the insulating layer;
An infrared absorption film forming step of forming an infrared absorption film comprising: at least two support legs on the sacrificial layer; and an infrared absorption part having an opening in the region between the support legs;
A through hole forming step of forming a through hole reaching the semiconductor substrate below the opening;
A gap forming step of forming a gap in the semiconductor substrate by performing etching through the through hole;
And a sacrificial layer removing step of removing the sacrificial layer through the through hole after the gap forming step. 9. The method of manufacturing an infrared sensor element according to claim 8, wherein the insulating layer forming step forms a plurality of insulating film layers including at least a silicon oxide film.