JP6970772B2 - Infrared detection element - Google Patents

Description

The present invention relates to an infrared detection element having an infrared absorption film.

The conventional infrared detection element is formed on a membrane supported by a heat insulating structure on a semiconductor substrate such as silicon, but an infrared absorbing film is formed on the membrane in order to increase the endothermic efficiency. The infrared detection element absorbs infrared rays emitted from an object to be measured, the element is warmed by the thermal effect of the infrared rays, and changes in electrical properties caused by an increase in temperature are detected. As this infrared absorbing film, there is metal black in which a metal material is formed into a porous shape by vacuum deposition or electrodeposition. Since this metallic black absorbs the incident infrared rays while diffusely reflecting them, the infrared rays can be efficiently converted into heat energy. When gold is used as the metal black, it is a gold black film, and when platinum is used, it is a platinum black film. These are known to have a high absorption rate for infrared rays. Patent Document 1 describes an infrared detecting element using a metal black film as an infrared absorbing film.

Patent Document 1 discloses an infrared sensor capable of increasing the adhesion of metal black to a membrane without deteriorating the characteristics. The heat detection element constituting the infrared sensor is formed by forming a thermal resistance element portion on a membrane and further forming an infrared absorption film made of a platinum black absorption film on the thermal resistance element portion. Here, the platinum black absorbent film has a small cluster size on the membrane side, a large one in the middle, and a small one on the surface side. This makes it possible to increase the adhesion to the platinum-black membrane and prevent the large cluster size from increasing the weight of the membrane and deteriorating the characteristics of the heat detection element.

Japanese Unexamined Patent Publication No. 2001-74549

In the conventional infrared detection element described in, for example, Patent Document 1, in the structure of the metal black film, the cluster size in the portion away from the membrane and closer to the light receiving side than the cluster size directly above the membrane (memblem side). Is larger. By reducing the cluster size on the membrane side, the adhesion to the platinum-black membrane can be increased, and by increasing the cluster size in the middle part, the weight of the membrane increases and the characteristics of the heat detection element deteriorate. It is to prevent that. In Patent Document 1, platinum black is used to expect a high absorption rate, and the electrodeposition method is used to solve the vulnerability (see paragraph 0030). In this case, the film thickness of platinum black is preferably 1 to 15 μm in order to secure the absorption rate of infrared rays, and the absorption rate can be increased by setting the film thickness to 3 to 5 μm in particular.
The present invention was made by such circumstances, to provide an infrared sensing element in which the infrared absorptivity was improved compared with the conventional infrared absorption film.

One aspect of the infrared detection element of the present invention is a first gold-black film including a semiconductor substrate, a membrane formed in a light receiving region on the diaphragm structure of the semiconductor substrate, and clusters formed in columns on the membrane. When, made form on the first gold black film, larger than the cluster size of the cluster size of the first gold black film, than the planar density of the cluster planar density of the first gold black film It is characterized by being small and having a second gold-black film having a planar density of 1.6 pieces / 100 μm ^{2 or more.}
Further, in one aspect of the infrared detection element of the present invention, the first gold black film and the second gold black film are films in which gold fine particles are deposited and deposited.
Further, in one aspect of the infrared detection element of the present invention, the cross-sectional area of the first gold black film in a plan view is larger than the cross-sectional area of the second gold black film in a plan view.

Further, one aspect of the method for manufacturing an infrared detection element of the present invention includes a step of forming an infrared absorbing film in a light receiving region on a semiconductor substrate, and the step of forming the infrared absorbing film deposits fine-grained gold. In the first film forming step of forming the first gold black film of the lower layer by depositing with, and by further depositing fine particle gold on the first gold black film of the lower layer by vapor deposition, the first of the upper layer. Before the second film forming step of forming the gold black film of 2 and the second film forming step are performed, the semiconductor substrate after the completion of the first film forming step is subjected to the first and first films. The film forming step of 2 includes a thinning film forming preparation step of exposing to air having a different temperature or humidity, and the second gold black film of the upper layer has a cluster size of the lower layer by the thinning film forming preparation step. It is characterized in that it is larger than the first gold black film and the planar density of the clusters on the surface portion on the light receiving side is 1.6 / 100 μm ^{2 or more.} It is also possible to further have a step of enhancing the mutual adhesion of the gold fine particles by temporarily adding water to the infrared absorbing film formed through the first and second film forming steps. ..

When the cluster of the infrared absorbing film has a columnar structure, the infrared absorption rate is improved to some extent, but if the density is too low, the background reflection increases, and if the density is too dense, the incident infrared rays are reflected more and the absorption rate decreases. Therefore, the cluster size directly above the membrane is reduced, and the cluster size at the portion distant from the membrane on the light receiving side (the surface portion on the light receiving side) is made larger than that. This is realized by a gold black film formed by thin film deposition, and further, by setting the planar density of the clusters on the surface portion on the light receiving side to 1.6 / 100 μm ² or more, the infrared absorption rate can be improved.
Regarding the step of forming an infrared absorbing film in the method for manufacturing an infrared detection element of the present invention, the manufacturing process of forming a gold black film by vapor deposition is a generally known technique, but in the present invention, it is further a conventional step. By adding a thinning film formation preparation step that is not available in, the planar density of the cluster can be further reduced compared to the case where the film is formed without this step, and the infrared absorption rate. Can be improved.

FIG. 3 is a cross-sectional view of the infrared detection element according to the first embodiment. FIG. 3 is a schematic cross-sectional view of an infrared absorbing film constituting the infrared detecting element of FIG. 1. The schematic plan view of the infrared absorption film formed on the semiconductor substrate shown in FIG. 1.

Hereinafter, embodiments of the invention will be described with reference to examples.

The first embodiment will be described with reference to FIGS. 1 to 3.
As shown in FIG. 1, the infrared detection element 1 of this embodiment is formed on a semiconductor substrate 2 such as silicon. The infrared detection element 1 has a semiconductor substrate 2, a membrane 4 made of a silicon nitride film formed on the semiconductor substrate via a cavity 3, and an amorphous silicon layer 5 formed on the membrane 4. ing. The amorphous silicon layer 5 is used as a base film when the infrared absorbing film 6 formed on the amorphous silicon layer 5 is vapor-deposited and deposited. A thermoelectric member 7 such as a plurality of thermocouples is formed on the membrane 4 so that one end thereof is connected to the infrared absorbing film 6. The input heat-converted as the temperature change of the infrared absorbing film 6 is detected via the thermoelectric member 7.

The infrared absorbing film 6 is a film in which gold fine particles are vapor-deposited and deposited, and is composed of a first gold black film 8 and a second gold black film 9 laminated on the first gold black film 8. It is configured. These gold black films heat and evaporate the material in a vacuum and attach it to the undercoat film which is the amorphous silicon layer 5 on the membrane 4 formed on the semiconductor substrate 2 to form a thin film.
In the infrared absorbing film 6, the cluster size of the second gold black film 9 is larger than that of the first gold black film 8 formed in the lower layer, and the planar density of the cluster is 1.6 / 100 μm ² or more. be. The gold black film formed by vacuum vapor deposition becomes a film on which gold fine particles are deposited, but depending on the vapor deposition conditions, the vapor-deposited fine particles may be deposited in a disjointed state, or some fine particles may stick together to form a slightly larger lump. It becomes (lump). Here, this mass is called a cluster, and its size is called a cluster size.

FIG. 2 shows an infrared absorbing film 6 formed on the base film 5 on the membrane 4, and the infrared absorbing film 6 is a first gold black film 8 and a first gold black film 9 on the base film 5. It is composed of. These gold black films 8 and 9 have a columnar structure of clusters, which contributes to the improvement of the infrared absorption rate. FIG. 3 is a plan view showing the infrared absorbing film 6 formed on the semiconductor substrate 2, and shows the surface state of the second gold-black film 9 constituting the infrared absorbing film 6. FIG. 2 is a cross-sectional view of an arbitrary position of the region A displayed on the surface thereof.

When the cluster has a columnar structure, the infrared absorption rate is improved to some extent, but if the density is too low, the background reflection increases, and if the cluster is too dense, the incident infrared ray reflection increases and the absorption rate decreases. Therefore, the cluster size immediately above the membrane 4 is reduced, and the cluster size at the portion distant from the membrane 4 on the light receiving side (the surface portion on the light receiving side) is made larger than that. The infrared absorbing film 6 can be realized by the gold black films 8 and 9 formed by vapor deposition, and the planar density of the clusters on the surface portion on the light receiving side can be set to about ^{1.6 / 100 μm 2 or more.} It was found to be good for improving the absorption rate.

As described above, as shown in the examples, the cluster size immediately above the membrane is reduced, the cluster size at the portion away from the membrane on the light receiving side (the surface portion on the light receiving side) is made larger than that, and this is formed by vapor deposition. It is realized by the gold-black film, and the infrared absorption rate can be improved by setting the planar density of the clusters on the surface portion on the light receiving side to 1.6 / 100 μm ^{2 or more.}

Next, a second embodiment relating to a method for manufacturing an infrared detection element will be described with reference to FIGS. 1 and 2. In forming an infrared detection element on a semiconductor substrate such as silicon, a membrane 4 supported by a heat insulating structure is formed on the semiconductor substrate 2, and an infrared absorbing film 6 is provided via a base film 5 in order to increase the heat absorption efficiency of the membrane 4. Form (see FIG. 1).

The step of forming the infrared absorbing film 6 in the light receiving region on the semiconductor substrate 2 is performed by the following steps. First, the first film forming step of forming the first gold black film 8 of the lower layer is performed by depositing about 2 μm of fine-grained gold by vapor deposition. In the thin-film deposition method performed here, gold is heated and evaporated in a low vacuum, and the gold is deposited on the undercoat film 5 formed on the membrane 4. Then, similarly, gold is heated and evaporated in a low vacuum, and fine-grained gold is further deposited on the first gold black film 8 by vapor deposition to form a second gold black film 9 in the upper layer. Perform the film formation process. Through these first and second film forming steps, a gold black film having a thickness of about 8 μm as a whole is formed.
Convection is generated in the vacuum vessel (chamber) on which the thin-film-deposited thin film is formed due to the temperature difference generated inside, and the thin-film-deposited thin film is composed of clusters having a columnar structure. Then, before the second film forming step is performed, the semiconductor substrate after the completion of the first film forming step is exposed to air having a temperature or humidity different from that of the first and second film forming steps. A thinning film formation preparation process is carried out.

By this thinning film formation preparation step, the cluster size of the second gold black film 9 is larger than that of the first gold black film 8, and the planar density of the clusters on the surface portion on the light receiving side is 1.6 /. It is formed to be 100 μm ^{2 or more.}
Further, if necessary, water is temporarily added to the infrared absorbing film 6 formed through the first and second film forming steps. This makes it possible to enhance the mutual adhesion of the gold fine particles constituting the gold black films 8 and 9.
A manufacturing process of forming a gold-black film by vapor deposition in forming an infrared absorbing film 6 is conventionally known, but in this embodiment, a thinning film formation preparation step is performed, and when this is performed, it is continuous. The plane density of the cluster can be further reduced as compared with the case where the film is formed, and as a result, the infrared absorption rate can be further improved.

According to the method of the present invention, the gold black film formed by vapor deposition has a smaller cluster size immediately above the membrane, and a larger cluster size at a portion distant from the membrane on the light receiving side (surface portion on the light receiving side). Become. It is considered that the growth of the cluster of gold particles deposited in the first time is partially suppressed in the second deposition by performing the thinning preparation step.

1 ... Infrared detection element 2 ... Semiconductor substrate 3 ... Cavity 4 ... Membrane 5 ... Amorphous silicon layer (base film)
6 ... Infrared absorption film 7 ... Thermoelectric member 8 ... First gold black film 9 ... Second gold black film

Claims (3)

With a semiconductor substrate,
A membrane formed in the light receiving region on the diaphragm structure of the semiconductor substrate, and
A first gold black film containing clusters formed in columns on the membrane, and
The made form the first gold black film, larger than the cluster size is the cluster size of the first gold black film, the plane density of the cluster is smaller than the planar density of the first gold black film, An infrared detection element including a second gold-black film having a cluster planar density of 1.6 / 100 μm ^{2 or more.} The infrared detection element according to claim 1, wherein the first gold black film and the second gold black film are films in which gold fine particles are vapor-deposited and deposited. The infrared detection element according to claim 1 or 2, wherein the cross-sectional area of the first gold black film in a plan view is larger than the cross-sectional area of the second gold black film in a plan view.

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