JP2015052517A - Infrared sensor manufacturing method and infrared sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an infrared sensor having an excellent in-plane uniformity of a pyroelectric and a high detection sensitivity.SOLUTION: A method for manufacturing an infrared sensor includes: a pyroelectric substance formation step for forming a pyroelectric substance (a pyroelectric body comprising a lower electrode 21, a pyroelectric film 22, and an upper electrode 23; and an infrared absorber 24) on a semiconductor substrate 1; a through hole formation step for forming a plurality of through holes 25 that penetrate the pyroelectric so as to open an upper part of the semiconductor substrate 1; a support part formation step for performing isotropic etching on the semiconductor substrate 1 via the plurality of through holes 25 to partially form cavities 12 at the upper part of the semiconductor substrate 1, thereby forming support parts 13 that are adjacent to the cavities 12 and support the pyroelectric.

Description

  The present invention relates to a method for manufacturing an infrared sensor including a pyroelectric body and an infrared sensor that can be manufactured using the method. In particular, the present invention relates to a method capable of manufacturing an infrared sensor having excellent in-plane uniformity of pyroelectric material and high detection sensitivity, and an infrared sensor that can be manufactured using the same.

  Conventionally, so-called thermal infrared sensors such as a thermopile, a bolometer, and a pyroelectric sensor are known (see, for example, Patent Document 1).

In order to improve the detection sensitivity of the thermal infrared sensor, it is important to design both the heat capacity of the infrared detection unit and the heat loss from the infrared detection unit to be small.
For example, a thermal infrared sensor (semiconductor device) described in Patent Document 1 forms a cavity 5 in a semiconductor substrate (silicon oxide film 1) located below a heat detector 8 having a thin film and a small heat capacity, and is capable of conducting heat. By supporting the heat detection unit 8 with a small support (partition between the cavities 5), both heat capacity and heat loss are reduced (FIG. 2 of Patent Document 1).

However, the manufacturing process of the thermal infrared sensor described in Patent Document 1 is a process of forming the heat detection unit 8 after forming the cavity 5 in the semiconductor substrate 1 (FIG. 1 in Patent Document 1).
In the method of forming the heat detection part after forming the cavity in the semiconductor substrate as described above, the temperature distribution of the semiconductor substrate is not uniform due to the cavity when the heat detection part is formed. For this reason, the in-plane uniformity of the heat detection part formed by vapor deposition etc. on a semiconductor substrate with non-uniform temperature distribution may deteriorate. In particular, when the heat detection unit is composed of a pyroelectric material, the in-plane uniformity greatly affects the detection sensitivity of the heat detection unit.

Japanese Patent No. 3523588

  The present invention has been made in view of such prior art, and is a method for manufacturing an infrared sensor including a pyroelectric body, and an infrared sensor that can be manufactured using the method, and includes in-plane uniformity of the pyroelectric body. It is an object of the present invention to provide a method capable of producing an infrared sensor excellent in detection sensitivity and having high detection sensitivity, and an infrared sensor which can be produced using the method.

  In order to solve the above problems, the present invention provides a pyroelectric body forming step for forming a pyroelectric body on a semiconductor substrate, and a plurality of through holes penetrating the pyroelectric body so that the upper portion of the semiconductor substrate is opened. A through hole forming step of forming a hole, and isotropic etching is performed on the semiconductor substrate through the plurality of through holes to form a cavity partially above the semiconductor substrate, thereby adjacent to the cavity. And a supporting part forming step of forming a supporting part for supporting the pyroelectric body.

According to the present invention, the pyroelectric body is formed on the semiconductor substrate in the pyroelectric body forming step before the cavity is formed in the semiconductor substrate in the support portion forming step. That is, when the pyroelectric material is formed on the semiconductor substrate, since no cavity is formed in the semiconductor substrate, the temperature distribution of the semiconductor substrate can be easily made uniform. For this reason, it can be expected that the in-plane uniformity of the pyroelectric material formed on the semiconductor substrate is excellent, and an infrared sensor with high detection sensitivity can be manufactured.
According to the present invention, a plurality of through holes penetrating the pyroelectric body are formed in the through hole forming step, and isotropic etching is performed on the semiconductor substrate through the plurality of through holes in the support portion forming step. Thus, a cavity is partially formed in the upper part of the semiconductor substrate. A portion adjacent to the cavity that has not been etched in the upper portion of the semiconductor substrate forms a support portion that supports the pyroelectric material. The cavity formed by performing isotropic etching on the semiconductor substrate through the through hole expands in a substantially hemispherical shape centering on the lower end of the through hole (the upper end of the semiconductor substrate) due to the property of isotropic etching. Therefore, the support portion adjacent to the cavity is constricted. That is, the upper part of the support part has a shape with a small horizontal dimension, and the dimension in the horizontal direction increases toward the lower part. Since the upper part of the support part supports the pyroelectric body, heat loss from the pyroelectric body to the support part of the semiconductor substrate can be suppressed, and the size of the lower part of the support part is increased, so that the mechanical strength is kept above a certain level. It is also possible.
Furthermore, according to the present invention, since the pyroelectric body is provided with a plurality of through holes, the pyroelectric body is reduced in weight by that amount, and there is an advantage that the load on the support portion is reduced and the support state is stabilized. .

Preferably, the pyroelectric body forming step includes a step of forming a pyroelectric body including a pyroelectric film on the semiconductor substrate, and a step of forming an infrared absorber on the pyroelectric body.
The through-hole forming step forms a plurality of through-holes penetrating the infrared absorber and the pyroelectric body so that an upper portion of the semiconductor substrate is opened.

  According to such a preferable configuration, since the infrared absorber is formed separately from the pyroelectric body including the pyroelectric film, it is possible to reliably absorb and detect infrared rays by the pyroelectric body.

  In order to solve the above-mentioned problem, the present invention includes a semiconductor substrate and a pyroelectric body formed on the semiconductor substrate, and the pyroelectric body is opened so that an upper portion of the semiconductor substrate is opened. A plurality of through holes penetrating the pyroelectric body; and the semiconductor substrate supporting a pyroelectric body adjacent to the cavity and a cavity communicating with the plurality of through holes of the pyroelectric body in an upper portion thereof The present invention is also provided as an infrared sensor characterized by comprising an upper constricted support portion.

According to the present invention, the support portion adjacent to the cavity has an upper constricted shape. That is, the upper part of the support part has a shape with a small horizontal dimension, and the dimension in the horizontal direction increases toward the lower part. Since the upper part of the support part supports the pyroelectric body, heat loss from the pyroelectric body to the support part of the semiconductor substrate can be suppressed, and the size of the lower part of the support part becomes large, so that the mechanical strength is kept above a certain level. It is also possible.
Further, according to the present invention, since the pyroelectric body is provided with a plurality of through holes, the pyroelectric body is reduced in weight by that amount, and there is an advantage that the load on the support portion is reduced and the support state is stabilized. .

  Preferably, the pyroelectric body includes a pyroelectric body including a pyroelectric film formed on the semiconductor substrate, and an infrared absorber formed on the pyroelectric body, and the through hole Passes through the infrared absorber and the pyroelectric body so that the top of the semiconductor substrate is open.

  According to such a preferable configuration, since the infrared absorber is provided separately from the pyroelectric body including the pyroelectric film, it is possible to reliably absorb and detect infrared rays by the pyroelectric body.

  According to the present invention, it is possible to obtain an infrared sensor with excellent in-plane uniformity of pyroelectric material and high detection sensitivity.

FIG. 1 is a diagram for explaining a method of manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a method for manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a method for manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 4 is a diagram for explaining a method of manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 5 is a diagram for explaining a method of manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 6 is a diagram for explaining a method of manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 7 is a diagram illustrating a method for manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 8 is a diagram illustrating a method for manufacturing an infrared sensor according to an embodiment of the present invention. FIG. 9 is a diagram illustrating a method for manufacturing an infrared sensor according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings as appropriate.
FIGS. 1-9 is a figure explaining the manufacturing method of the infrared sensor which concerns on one Embodiment of this invention. In each of the drawings, the upper side of (a) and (b) is a plan view, and the lower side is a cross-sectional view taken along line AA of the upper side.
In the manufacturing method of the infrared sensor 100 according to the present embodiment, the pyroelectric body forming step of forming a pyroelectric body (pyroelectric body and infrared absorber 24) on the semiconductor substrate 1 and the upper side of the semiconductor substrate 1 are opened. As described above, a through hole forming step for forming a plurality of through holes 25 penetrating the pyroelectric body, and isotropic etching is performed on the semiconductor substrate 1 through the plurality of through holes 25, A support portion forming step of forming a support portion 13 adjacent to the cavity 12 and supporting the pyroelectric body by partially forming the cavity 12.
Specifically, the pyroelectric body forming step includes forming a pyroelectric body (lower electrode 21, pyroelectric film 22, upper electrode 23) including the pyroelectric film 22 on the semiconductor substrate 1, and Forming an infrared absorber 24 on the pyroelectric body. In the through hole forming step, a plurality of through holes 25 penetrating the infrared absorber 24 and the pyroelectric body are formed so that the upper portion of the semiconductor substrate 1 is opened.

  Hereinafter, the manufacturing method of the infrared sensor 100 according to the present embodiment will be described more specifically in the order of the pyroelectric body forming step, the through hole forming step, and the support portion forming step with reference to FIGS.

<Pyroelectric forming process>
In this step, first, as shown in FIG. 1A, a Si wafer as a semiconductor substrate 1 is prepared. As the Si wafer, for example, one having a thickness of about 625 μm and 5 inches can be exemplified. Then, as shown in FIG. 1B, the semiconductor substrate 1 is subjected to a thermal oxidation process to form an oxide film 11 on the surface. The thickness of the oxide film 11 is about 100 nm, for example. In the following drawings, the display of the oxide film 11 is omitted for convenience.

  Next, as shown in FIG. 2A, a lower electrode 21 is formed on the semiconductor substrate 1. For example, sputtering is used as the film forming method. Examples of the lower electrode 21 include a Pt and Ti laminated electrode having a Pt thickness of about 100 nm and a Ti thickness of about 20 nm.

  Next, as shown in FIG. 2B, a pyroelectric film 22 is formed on the lower electrode 21. For example, sputtering is used as the film forming method. As the pyroelectric film 22, for example, PZT is used, and the thickness thereof is about 3 μm.

  Next, as shown in FIG. 3A, a resist R is applied on the pyroelectric film 22, and the resist R is formed into a predetermined pattern by photolithography. Next, as shown in FIG. 3B, the pyroelectric film 22 is etched through a resist R formed in a predetermined pattern. As an etching method, for example, wet etching is used.

  Next, after removing the resist R as shown in FIG. 4A, an upper electrode 23 is formed on the pyroelectric film 22 or the lower electrode 21 as shown in FIG. 4B. For example, sputtering is used as the film forming method. As the upper electrode 23, for example, a stacked electrode of Au and Ti, with a thickness of Au of about 300 nm and a thickness of Ti of about 20 nm can be exemplified.

  Next, as shown in FIG. 5A, a resist R is applied on the upper electrode 23, and the resist R is formed into a predetermined pattern by photolithography. Next, as shown in FIG. 5B, the upper electrode 23 and a part of the pyroelectric film 22 are etched through a resist R formed in a predetermined pattern. As an etching method, for example, ion beam etching is used.

  Next, as shown in FIG. 6A, after removing the resist R, as shown in FIG. 6B, the resist R is formed on the upper electrode 23, the pyroelectric film 22 or the lower electrode 21. The resist R is applied to form a predetermined pattern by photolithography. The pattern of the resist R is a pattern corresponding to a through hole 25 described later. Although the resist R shown in FIG. 6B is shown on a rectangular cross section, actually, the resist is a lift-off resist in which the upper dimension is larger than the lower dimension.

  Next, as shown in FIG. 7A, an infrared absorber 24 is formed on the resist R or the upper electrode 23. For example, vacuum deposition is used as the film forming method. As the infrared absorber 24, for example, a metal film containing Au or Al as a main component, which can improve the infrared absorption rate by roughening the surface or making the film itself porous can be exemplified. Next, as shown in FIG. 7B, the resist R is removed together with the infrared absorber 24 formed thereon.

  As described above, the pyroelectric body forming step of forming the pyroelectric body (the pyroelectric body including the lower electrode 21, the pyroelectric film 22, the upper electrode 23, and the infrared absorber 24) on the semiconductor substrate 1 is performed. Executed.

<Through hole formation process>
In this step, as shown in FIG. 8A, a resist R is applied on the infrared absorber 24, the upper electrode 23, the pyroelectric film 22 or the lower electrode 21, and the resist R is predetermined by photolithography. To form a pattern. Specifically, the pattern is formed so that the resist R is laminated on a portion excluding a portion corresponding to a through hole 25 described later. Next, as shown in FIG. 8B, the upper electrode 23, the pyroelectric film 22 and the lower electrode 21 are etched through a resist R formed in a predetermined pattern. As an etching method, for example, ion beam etching is used.

  As described above, the plurality of through holes 25 penetrating the pyroelectric body (the lower electrode 21, the pyroelectric film 22, the upper electrode 23, and the infrared absorber 24) so that the upper side of the semiconductor substrate 1 is opened. The through-hole formation process to form is performed.

<Supporting part forming step>
In this step, as shown in FIG. 9A, isotropic etching is performed on the semiconductor substrate 1 through the plurality of through holes 25, and the cavity 12 is partially formed in the upper portion of the semiconductor substrate 1, A support portion 13 is formed adjacent to the cavity 12 and supporting the pyroelectric body (lower electrode 21, pyroelectric film 22, upper electrode 23, and infrared absorber 24). As the isotropic etching, for example, dry etching using xenon difluoride (XeF ₂ ) gas is used. By appropriately controlling the etching time, the pitch of the through holes 25, the pressure of the xenon difluoride gas, and the like, the desired shape of the cavity 12, and thus the desired shape of the support portion 13 can be obtained. The depth of the cavity 12 is, for example, about 50 to 100 μm. Finally, as shown in FIG. 9B, the infrared sensor 100 is obtained by removing the resist R. In the infrared sensor 100 shown in FIG. 9 (b), infrared rays are absorbed by the infrared absorber 24 to generate heat, and the heat is conducted to the pyroelectric film 22 to generate charges, so that the upper electrode 23A (lower electrode 21) is generated. And the upper electrode 23B, it is possible to detect infrared rays.

  According to the manufacturing method of the infrared sensor 100 according to the present embodiment described above, the pyroelectric material is formed on the semiconductor substrate 1 in the pyroelectric body forming step before the cavity 12 is formed in the semiconductor substrate 1 in the support portion forming step. Will be formed. That is, when the pyroelectric material is formed on the semiconductor substrate 1, since the cavity 12 is not formed in the semiconductor substrate 1, it is easy to make the temperature distribution of the semiconductor substrate 1 uniform. For this reason, it can be expected that the pyroelectric material formed on the semiconductor substrate 1 is excellent in in-plane uniformity, and the infrared sensor 100 having high detection sensitivity can be manufactured.

  Moreover, according to the manufacturing method of the infrared sensor 100 according to the present embodiment, the plurality of through holes 25 penetrating the pyroelectric body are formed in the through hole forming step, and the plurality of through holes 25 are interposed in the support portion forming step. By subjecting the semiconductor substrate 1 to isotropic etching, a cavity 12 is partially formed above the semiconductor substrate 1. A portion adjacent to the cavity 25 that has not been etched in the upper portion of the semiconductor substrate 1 forms a support portion 13 that supports the pyroelectric material. The cavity 12 formed by performing isotropic etching on the semiconductor substrate 1 through the through hole 25 is substantially hemispherical with the lower end of the through hole 25 (the upper end of the semiconductor substrate 1) as the center due to the nature of isotropic etching. Expands into a planar shape. Therefore, as shown in FIG. 9, the support portion 13 adjacent to the cavity 25 is in a constricted shape. That is, the upper portion of the support portion 13 has a shape with a small size in the horizontal direction and a shape in which the size in the horizontal direction becomes larger toward the lower portion. Since the upper portion of the support portion 13 supports the pyroelectric body, heat loss from the pyroelectric body to the support portion 13 of the semiconductor substrate 1 can be suppressed, and the size of the lower portion of the support portion 13 is increased. It is also possible to keep it above a certain level.

  Furthermore, according to the manufacturing method of the infrared sensor 100 according to the present embodiment, since the pyroelectric body is provided with the plurality of through holes 25, the pyroelectric body is reduced in weight, and the load on the support portion 13 is reduced. There is also an advantage that the supporting state is stabilized.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 12 ... Cavity 13 ... Support part 21 ... Lower electrode 22 ... Pyroelectric film 23 ... Upper electrode 24 ... Infrared absorber 100 ... Infrared sensor R ... resist

Claims (4)

A pyroelectric material forming step of forming a pyroelectric material on a semiconductor substrate;
A through hole forming step of forming a plurality of through holes penetrating the pyroelectric body so that an upper portion of the semiconductor substrate is opened;
A support portion that is adjacent to the cavity and supports the pyroelectric body is formed by performing isotropic etching on the semiconductor substrate through the plurality of through holes and partially forming a cavity in the upper portion of the semiconductor substrate. And a support portion forming step for forming the infrared sensor. The pyroelectric body forming step includes a step of forming a pyroelectric body including a pyroelectric film on the semiconductor substrate, and a step of forming an infrared absorber on the pyroelectric body.
The said through-hole formation process forms the several through-hole which penetrates the said infrared rays absorber and the said pyroelectric body so that the upper part of the said semiconductor substrate may be open | released, The Claim 1 characterized by the above-mentioned. Infrared sensor manufacturing method. A semiconductor substrate;
Comprising a pyroelectric body formed on the semiconductor substrate,
The pyroelectric body includes a plurality of through holes penetrating the pyroelectric body so that an upper portion of the semiconductor substrate is opened;
The semiconductor substrate includes a cavity communicating with the plurality of through holes of the pyroelectric body and an upper constricted support portion adjacent to the cavity and supporting the pyroelectric body. Infrared sensor. The pyroelectric body comprises a pyroelectric body including a pyroelectric film formed on the semiconductor substrate, and an infrared absorber formed on the pyroelectric body.
The infrared sensor according to claim 3, wherein the through hole penetrates the infrared absorber and the pyroelectric body so that an upper portion of the semiconductor substrate is opened.

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