JPH06132277A - Heat insulation film for diaphragm structure and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a heat insulation film for a diaphragm structure, which is accompanied by no generation of distortion and destruction and has an excellent heat insulation quality and easy producibility, and to provide a manufacturing method thereof. CONSTITUTION:A heat insulation film 20 for a diaphragm structure and formed in the hollow state of only the periphery thereof supported by a substrate 10, wherein a silicon nitride layer 22 and a plurality of silicon oxide layers 23-25 having different composition ratios of silicon to oxygen are formed in this order from the substrate 10, wherein thereby the residual stresses of the respective layers cancel out to relax the residual stress of the whole of the heat insulation film and to make the prevention of the distortion and destruction thereof possible, and wherein the silicon nitride layer serves effectively as an etching stopper layer when forming the hollow part on the substrate 10 by etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal insulating film for a diaphragm structure and a method of manufacturing the same, and more specifically, in a diaphragm structure used for a thin film sensor or the like, the detecting portion of the sensor is thermally protected from the surroundings. The present invention relates to a heat insulating film mounted in an insulated state and a method for manufacturing such a heat insulating film.

[0002]

2. Description of the Related Art Some thin films have various functions and are widely used as constituent members of various sensors and other fine functional parts. A diaphragm structure may be adopted as the structure of such a functional component. In the diaphragm structure, a thin film is formed in a hollow state in which only a peripheral portion is supported by a substrate and various functional structures are provided on the thin film. In the diaphragm structure, since the functional structure portion is supported only through the thin film, the functional structure portion and the surrounding structure are insulated and isolated, and the influence of the peripheral structure on the functional structure portion can be minimized. it can.

An example of application of the diaphragm structure is a thermal infrared detecting element. The thermal infrared detection element converts the thermal energy or temperature rise due to infrared rays into electrical information such as the temperature change of the thermistor, so that the heat of the infrared detection part such as the thermistor does not escape to the surrounding boards. In addition, it is necessary to thermally insulate and isolate the infrared detector. Therefore, a diaphragm structure using a heat insulating film is adopted, and an infrared detecting section is provided in the hollow portion of the heat insulating film.

As such a heat insulating film, a material having a low heat conductivity is preferable, and a silicon oxide film or the like has been conventionally used. However, in a single layer film of silicon oxide, a large residual stress in the compression direction occurs during the manufacturing process,
Due to this internal stress, the thermal insulation film may be distorted or broken. This is because the thermal insulation film in the diaphragm structure is supported only on the peripheral portion by the substrate, so that when the residual stress or internal stress as described above occurs in the thermal insulation film in the hollow portion, the thin thermal insulation film is It will easily be distorted or destroyed. As a result, such a diaphragm structure has a problem that the production yield is low and the manufacturing cost is high.

Therefore, by using a thermal insulation film having a multi-layer structure in which a thin film and a silicon oxide film, in which a residual stress opposite to that of the silicon oxide film is generated, are alternately laminated, a compressive stress and a tensile stress of both layers can be obtained. It has been considered that the above is canceled and the internal stress of the entire heat insulating film is relaxed. For example, it has been proposed that a low pressure CVD apparatus be used to alternately deposit silicon oxide layers and silicon nitride layers to form a thermal insulation film having a multilayer structure. By appropriately adjusting the film thickness ratio of the silicon oxide layer and the silicon nitride layer, the residual stress of the entire heat insulating film could be suppressed to be small.

[0006]

However, as described above, when the multilayer film of the silicon oxide layer and the silicon nitride layer is used as the thermal insulating film of the diaphragm structure, the effect of reducing the residual stress is achieved to some extent. However, there is a problem that the heat insulating property, which is the original function of the heat insulating film, is deteriorated.

This is because the thermal conductivity of the silicon nitride film is higher than that of the silicon oxide film by about one digit, so that the thermal insulation property of the multilayer film including the silicon nitride layer is deteriorated. Further, conventionally, when a thermal insulating film composed of a multilayer film of silicon nitride and silicon oxide is produced, the substrate is taken out of the thin film forming furnace every time one layer is formed, and the atmosphere in the thin film forming furnace, that is, the introduction. After replacing the gas, the next thin film had to be formed.
Therefore, there are problems that the number of processes increases, the production efficiency decreases, and the cost also increases.

Therefore, an object of the present invention is to provide a thermal insulation film for a diaphragm structure as described above, which is free from distortion and breakage, has excellent thermal insulation properties, and is easy to manufacture. It is to provide a heat insulating film and a manufacturing method thereof.

[0009]

A thermal insulation film for a diaphragm structure according to the present invention which solves the above-mentioned problems is a thermal insulation film for a diaphragm structure which is formed in a hollow state in which only the periphery is supported by a substrate. Therefore, a silicon nitride layer and a plurality of silicon oxide layers having different composition ratios of silicon and oxygen are laminated in order from the substrate side.

As the substrate, a substrate material having a normal diaphragm structure such as silicon is used. In order to support the heat insulating film in a hollow state, the substrate is provided with a hollow portion in which a part of the substrate is cut away. The shape and structure of the hollow portion can be freely configured according to the purpose of use of the diaphragm structure.
The silicon nitride layer is provided on the surface adjacent to the substrate in which the hollow portion as described above is formed. This silicon nitride layer is
It is sufficient that the substrate functions as an etching blocking layer when forming the hollow portion in the substrate, and therefore, it is sufficient that the substrate has a necessary minimum thickness capable of performing such a function. In this invention,
Although the silicon nitride layer is not required to have a function of canceling the residual stress of the silicon oxide layer, the residual stress of the silicon nitride layer relaxes the stress of the entire thermal insulating film in addition to the plurality of silicon oxide layers described later. There is also an action.

The plurality of silicon oxide layers are formed by laminating two or more layers having different composition ratios of silicon and oxygen. When the composition ratio of silicon and oxygen in the silicon oxide layer is different, the direction and magnitude of residual stress generated in the manufacturing process change. Therefore, it is preferable to stack a plurality of silicon oxide layers by adjusting the composition ratio of silicon and oxygen so that mutual residual stresses can be canceled well.

As a means for forming a silicon nitride layer and a plurality of silicon oxide layers, a conventional thin film forming means used for forming a heat insulating film or other thin films can be adopted, but an ion cluster beam (ICB) is used. It is preferable to employ a vapor deposition method. That is, in this ICB vapor deposition method, S ₃ N ₄ and SiO are used as evaporation sources, and the oxygen concentration or the nitrogen concentration of the atmospheric gas is changed during the vapor deposition to obtain a silicon nitride layer and a plurality of silicon oxide layers. Can be sequentially laminated. IC
The specific processing conditions of the B vapor deposition method may be the same as the processing conditions of the ICB vapor deposition method for forming various ordinary films.

The structure of the diaphragm structure other than the structure of the heat insulating film described above, for example, the structure of the functional sensor portion formed on the heat insulating film, can adopt the structure of the diaphragm structure in various conventional sensors and the like. Specifically, there is a thermal infrared detecting element in which an infrared detecting portion including a thermistor or the like is formed on a heat insulating film having a diaphragm structure.

[0014]

When a multilayer film in which a plurality of silicon oxide layers having different composition ratios of silicon and oxygen are stacked is used as the heat insulating film, the direction and magnitude of residual stress are different for each silicon oxide layer. The mutual residual stresses cancel each other out, and the internal stress generated in the entire heat insulating film becomes small.

If the composition ratios of silicon and oxygen are different in the same silicon oxide layer, it is possible to change the composition ratio of atmospheric gas while keeping the substrate in one thin film forming furnace. The silicon oxide layer can be continuously formed. However, it is difficult to form a heat insulating film in a hollow state on a substrate with a heat insulating film composed of only a silicon oxide layer. That is, in order to form the heat insulating film in a hollow state on the substrate, after forming the heat insulating film on the substrate,
It is necessary to etch the substrate from the opposite side of the heat insulating film to cut away the back side of the heat insulating film to form a hollow portion. During this etching, only the substrate should be etched, and the thermal insulation film should not be etched. However, there is no practical method for etching only the substrate made of silicon, which is generally used as the substrate of the diaphragm structure, so that the thermal insulating film made of the silicon oxide layer is not etched.

Therefore, according to the present invention, among the thermal insulation films,
A silicon nitride layer is formed on the side adjacent to the substrate, and a multilayer film of the silicon oxide layer as described above is formed thereon. Since the silicon nitride layer is not etched by the etching liquid for the substrate for the diaphragm structure such as silicon, it is possible to reliably prevent the silicon oxide layer thereon from being etched. As described above, the silicon nitride layer only needs to function as an etching stop layer, and thus may have a small thickness, and various functions may be provided on the multilayer film of the silicon oxide layer formed thereon. Since the structure is formed, the transfer of heat from these functional structures to the substrate is surely blocked by the multilayer film of the silicon oxide layer, and the thermal conductivity of the entire heat insulating film is sufficiently small,
Good heat insulation can be exhibited.

When the ion cluster beam method is adopted as a method for producing the thermal insulating film composed of the silicon nitride layer and the plurality of silicon oxide layers as described above, the evaporation source arranged in the thin film forming furnace is switched or the atmosphere is changed. By changing the composition ratio of the gas, the silicon nitride layer, and
All of the plurality of silicon oxide layers having different composition ratios of silicon and oxygen can be continuously formed in the same thin film forming furnace.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of a thermal type infrared detecting element adopting a diaphragm structure. A substantially square hollow portion 12 is formed in the center of the substrate 10 made of silicon. Hollow part 1 of substrate 10
A heat insulating film 20 is formed so as to cover 2. The heat insulating film 20 is integrally bonded to the substrate 10 in the peripheral portion of the hollow portion 12. The thermal insulation film 20 includes a silicon nitride layer 22 and a plurality of silicon oxide layers 23 to 2 from the substrate 10 side.
It is composed of 5. The silicon oxide layers 23 to 25 have different composition ratios of silicon and oxygen.
25 is represented by SiOx (x = 0.6~1.0), the silicon oxide layer 24 is represented by Si0 _2.

A thermistor 40 made of amorphous silicon or the like is provided in the center of the hollow portion 12 on the heat insulating film 20.
The thermistor 40 is provided with electrodes 30, 30 made of chromium or the like on the upper and lower surfaces thereof. The electrodes 30, 30 extend to the outside of the hollow portion 12, and the pads 32 are provided at the ends thereof. The upper surface of the thermistor 40 is covered with an infrared absorption film 50 made of silicon oxide or the like.

In this way, the thermistor 40 is connected to the upper and lower electrodes.
If sandwiched between 30, 30,
Increase the volume of the thermistor 40 sandwiched between the poles 30, 30.
Therefore, there is an advantage that noise can be reduced. As above
A method of manufacturing an infrared detecting element having a structure will be described. Well
First, a heat insulating film is formed on the silicon substrate. ICB steaming
By deposition, 500 Å of silicon nitride (Si₃N_Four) Layers, 1
500Å SiOx layer, 2000Å SiOx ₂Layer, 15
Thermal insulation film consisting of a total of four layers of 00x SiOx layer
Was formed.

Specifically, as an ICB vapor deposition furnace,
Place the evaporation source and select the evaporation source to use from the operation panel.
Using a device that can be replaced, as an evaporation source,
Si ₃N_FourAnd SiO was arranged. And
Without Si as an evaporation source₃N_FourIn a nitrogen atmosphere
Si₃N_FourThe layers were deposited. Next, the evaporation source is SiO
And changing the oxygen concentration in the atmosphere during deposition.
The SiOx layer, SiO₂Layer, 3 layers of SiOx layer
Were successively formed by vapor deposition. These silicon oxide layers
The film forming conditions are as follows.
Plate head 200 ℃, acceleration voltage 1.0kV, SiO₂layer
When forming a film, the oxidation concentration is 1.0 × 10^-FourExcept for Torr
Was the same as when the SiOx layer was formed.

Of the layers thus formed, S
The i ₃ N ₄ layer and the SiOx layer with x = 0.6 to 1.0 exhibit tensile residual stress, and the SiO ₂ layer exhibits compressive residual stress. The insulating film as a whole exhibits only a small residual stress. Next, the substrate temperature of 20 is applied on the heat insulating film by electron beam evaporation.
A chromium film having a thickness of 500 Å was formed at 0 ° C. and patterned in a photolithography process to form a lower electrode. The shape of the electrode is a square of 1.9 × 1.9 mm at the center, and a thin extension is provided on the outer circumference. By adding an appropriate impurity to chromium, the thermal conductivity can be reduced and the detection sensitivity of the element can be improved. Further, nickel chrome having a small thermal conductivity can be used instead of chrome.

A thickness of 1 is formed on the electrode by glow discharge decomposition method.
A p-type a-SiC film with a thickness of μm is formed, and the photolithography process
A thermistor was formed by patterning a square of 2 mm. The film forming conditions at this time are 900 mol% of methane,
Using hydrogen-diluted monosilane to which 0.25 mol% of diborane was added, the substrate temperature was 180 ° C., the pressure was 0.9 Torr, the frequency was 13.56 MHz, and the discharge power was 20 W.

On the thermistor, a chromium film having a thickness of 500 Å was formed at a substrate temperature of 200 ° C. by an electron beam evaporation method and patterned into a predetermined shape by a photolithography process to form an upper electrode. Its shape is the same as that of the lower electrode, but the extension to the outer periphery extends in a direction different from that of the lower electrode. A silicon oxide layer having a thickness of 1 μm was formed on the upper electrode by a glow discharge decomposition method, and a 2 × 2 mm square pattern was formed by a photolithography process to obtain an infrared absorbing film. The film forming conditions at this time were 700 mol% of dinitrogen monoxide gas, the substrate temperature was 250 ° C., and the pressure was 1 To.
rr, frequency 13.56 MHz, and discharge power 30 W.

Aluminum was deposited on the infrared absorbing film by electron beam evaporation and patterned to form pads at the ends of the upper and lower electrodes. In this way, after the thermal insulation film and the infrared detecting section are formed on the substrate, the substrate is anisotropically etched with potassium hydroxide from the side opposite to the side where the infrared detecting section is formed to form the hollow section. Formed. The etching with potassium hydroxide did not etch the Si ₃ N ₄ layer of the thermal insulation film. As a result, the heat insulating film in the hollow portion became a 2.5 × 2.5 mm square.

The infrared detecting element manufactured as described above showed high sensitivity during use without distorting or breaking the heat insulating film portion, and exhibited good use performance.

[0027]

As described above, the thermal insulating film for the diaphragm structure according to the present invention is a silicon nitride layer, and
By combining multiple silicon oxide layers with different composition ratios of silicon and oxygen, residual stress can be reduced, and it is possible to satisfactorily prevent the thermal insulation film from being distorted or broken, and to improve the thermal conductivity. It is possible to exhibit excellent thermal insulation without lowering the temperature.

As a result, the manufacturing yield of the diaphragm structure can be improved, the productivity can be improved and the production cost can be reduced, and a high-performance diaphragm structure excellent in thermal insulation performance can be provided. If the ion cluster beam method as described above is adopted as the method for manufacturing the heat insulating film, the silicon nitride layer and the silicon oxide layer having different composition ratios can be formed by simply changing the evaporation source or the atmospheric gas during the continuous film forming process. Since it is possible to form the structure, it is possible to reduce the manufacturing labor, improve the production efficiency, and reduce the production cost. In particular, when forming a multi-layered film of silicon oxide layers, the composition ratio of silicon and oxygen can be easily adjusted, so that the residual stress of the entire thermal insulating film can be minimized in each silicon oxide layer. The magnitude and direction of the generated residual stress can be accurately controlled, and it is also very effective in preventing distortion and destruction of the thermal insulating film.

[Brief description of drawings]

FIG. 1 is a sectional view of an infrared detection element adopting a diaphragm structure according to an embodiment of the present invention.

[Explanation of symbols]

10 substrate 12 hollow portion 20 thermal insulation layer 22 of silicon nitride layer 23 SiOx (x = 0.6~1.0) layer 24 SiO ₂ layer 25 SiOx (x = 0.6~1.0) layer 30 electrode 40 thermistor 50 Infrared absorption film

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[Procedure amendment]

[Submission date] January 11, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

As such a heat insulating film, a material having a low heat conductivity is preferable, and a silicon oxide film or the like has been conventionally used. However, the single layer film of silicon oxide, in the production process, that a large residual stress in the compression direction is generated
In many cases , this internal stress may cause distortion or breakage in the thermal insulating film. This is because the thermal insulation film in the diaphragm structure is supported only on the peripheral portion by the substrate, so that when the residual stress or internal stress as described above occurs in the thermal insulation film in the hollow portion, the thin thermal insulation film is It will easily be distorted or destroyed. As a result, such a diaphragm structure has a problem that the production yield is low and the manufacturing cost is high.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

As a means for forming a silicon nitride layer and a plurality of silicon oxide layers, a conventional thin film forming means used for forming a heat insulating film or other thin films can be adopted, but an ion cluster beam (ICB) is used. It is preferable to employ a vapor deposition method. That is, in the ICB deposition method, a vapor source, using the S i ₃ N ₄ and SiO, during deposition, by varying the oxygen concentration or nitrogen concentration in the atmosphere gas, a silicon nitride layer, and a plurality of silicon oxide The layers can be sequentially laminated. I
The specific processing conditions of the CB vapor deposition method may be the same as the processing conditions of the ICB vapor deposition method for forming various ordinary films.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Therefore, according to the present invention, among the thermal insulation films,
A silicon nitride layer is formed on the side adjacent to the substrate, and a multilayer film of the silicon oxide layer as described above is formed thereon. Silicon nitride layer is to be etched in the etching solution for a substrate for diaphragm construction such as silicon
Since the plow (the etching rate is very small) , it is possible to reliably prevent the silicon oxide layer thereon from being etched. As described above, the silicon nitride layer only needs to function as an etching stop layer, and thus may have a small thickness, and various functions may be provided on the multilayer film of the silicon oxide layer formed thereon. Since the structure is formed, the transfer of heat from these functional structures to the substrate is surely blocked by the multilayer film of the silicon oxide layer, the thermal conductivity of the entire thermal insulating film is sufficiently small, and the good thermal insulating property is obtained. Can be demonstrated.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

Specifically, as an ICB vapor deposition furnace, a device in which a plurality of vapor deposition sources are arranged and the vapor deposition sources to be used can be selectively switched from the operation panel is used.
Si ₃ N ₄ and SiO were arranged. Then, first, Si ₃ N ₄ was selected as an evaporation source, and a Si ₃ N ₄ layer was formed by vapor deposition in a nitrogen atmosphere. Next, the evaporation source is SiO
By changing the oxygen concentration in the atmosphere during vapor deposition, the three layers of the SiOx layer, the SiO ₂ layer, and the SiOx layer were successively vapor deposited and formed. Film formation conditions of the silicon oxide layer, during the formation of SiOx layer, the oxygen concentration of 0, substrate Ondo 200 ° C., and an acceleration voltage 1.0 kV, SiO ₂
During the formation of the layers, except that the oxygen concentration in the 1.0 × ¹⁰ -4 Torr was the same as during deposition of SiOx layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayoshi Awai 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Keiji Kakite 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works Co., Ltd. Within

Claims (2)

[Claims] 1. A thermal insulating film for a diaphragm structure, which is formed in a hollow state in which only the periphery is supported by a substrate, and comprises a silicon nitride layer and a plurality of silicon / oxygen composition ratios different from the substrate side. 2. A heat insulating film for a diaphragm structure, characterized in that the silicon oxide layers are laminated. 2. The method for producing a heat insulating film according to claim 1, wherein the ion cluster beam method is used as an evaporation source
₃ N ₄ and SiO are used, and a silicon nitride layer and a plurality of silicon oxide layers are sequentially laminated by changing the oxygen concentration or the nitrogen concentration of the atmosphere gas during vapor deposition. Method for manufacturing heat insulating film.