JPH03196583A - Vertical type silicon thermopile and manufacture thereof - Google Patents

Abstract

PURPOSE:To make it possible to obtain a thermopile of a three-dimensional structure wherein the electromotive force of thermocouples is large and which does not require a large area even when a large number of thermocouples are disposed therein, by fitting an electromagnetic wave absorber on the hot contact side with an insulative layer interlaid. CONSTITUTION:The end faces on one side of P-type layers 21, 22,... and N-type layers 31, 32,..., e.g. the end faces thereof connected by metal layers 52, 53,... constitute the hot contact side, while the end faces connected by metal layers 61, 62,... on the other side constitute the cold contact side. On the hot contact side, an electromagnetic wave absorber 70 is formed with an insulative layer interlaid. In a thermopile thus constructed, the temperature of the electromagnetic wave absorber 70 rises (falls) due to an electromagnetic wave entering the absorber and the temperature of a hot contact of a thermocouple located in the vicinity of the absorber rises higher (falls lower) than that on the cold contact side. Accordingly, a temperature difference occurs between the hot contact and the cold contact of the thermocouple and a thermoelectromotive force is generated by a Seebeck effect. According to this constitution, the thermopile of a three-dimensional structure is obtained and this is effective for a one-dimensional or two-dimensional sensor of high resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermopile using silicon single crystal, which can be used for infrared ray sensors, and a method for manufacturing the thermopile.

[Conventional technology]

As a thermopile using single-crystal silicon, one using a p-type silicon strip and aluminum has been reported (G, D, NIEVELD, Thermopi
lesFabricated using 5il
icon Planar Technology.

5 sensors and actuators, 3.
(1982/83) 179 183).

This thermomobile consists of a p-type silicon strip having a shape of 10 (μm) xl, 5 C+++o+) (mask dimensions) formed in an n-type silicon single crystal, and a silicon oxide film formed on top of the p-type silicon strip.・It has a structure that uses many thermocouples, which are made by connecting a pump and an insulated aluminum strip in series.

The thermoelectromotive force of this thermopile with a silicon strip with a resistivity of 5 x 10-" (Ωcm) is 152
When a pair is connected in series, 76 (mV/K) can be obtained, and the internal resistance value is 250 (kΩ).

In this way, when using a P-type silicon strip and an aluminum strip as a thermopile thermocouple,
Comparing the contribution of both materials to thermoelectromotive force, which is the output of the thermopile, the Seebeck coefficient of p-type single crystal silicon is approximately 450 to 1600 [μV/K], although it also depends on its doping concentration. In contrast, the value of aluminum is about 1.7 [μV/K], and the contribution of aluminum to the output sensitivity of the thermocouple is relatively extremely small. Therefore, to increase the output of the thermopile, it is necessary to replace aluminum with another material with a large Seebeck coefficient.

Furthermore, conventional thermocouples using silicon substrates are of a flat type, in which a large number of thermocouples are arranged on a flat surface and connected in series. In this case, the area occupied by one thermopile cannot be made very small; for example, 4 (m
m) x4 (M). In order to increase the resolution of image elements and the like, it is desired that the elements be further miniaturized.

[Problem to be solved by the invention]

As described above, thermoelectromotive force is not sufficient in thermocouples made of silicon single crystal and aluminum. Furthermore, in a thermopile in which a large number of thermocouples are arranged on a plane, the degree of integration cannot be sufficiently improved.

The present invention improves these points, and the electromotive force of the thermocouple is large.
The purpose is to provide a thermopile with a three-dimensional structure that does not require a large area even if a large number of thermopiles are installed.

[Means to solve the problem]

As shown in FIG. 1, in the present invention, a single crystal silicon substrate 1
A large number of P-type layers 21, 22 . . . . and n-type layers 31, 32 . . . . and an insulation N41 is formed to insulate these from each other. These p-type layer and n-type layer may be made of single crystal silicon, polycrystalline silicon, or amorphous silicon. Further, the insulating layer 41 may be made of silicon dioxide, non-doped polycrystalline silicon, or the like. The front and back surfaces of the substrate IO are also covered with insulating layers 42, 43, and both end surfaces of the p-type layer and n-type layer exposed from this insulating layer are covered with metal layers 51, 52, .・・・・・・
...and 61.62. Connect with... to make the whole into a zigzag series connection. This zigzag series connection body extends in the X direction, and there are multiple sets in the Y direction, all of which are connected in series to constitute one thermopile.

One end surface of the p-type layer and the n-type layer, for example, the metal layer 51.52
．． The end surface connected by . . . is the hot junction side, and the other end surface is the metal layer 61, 62 . The end face connected with ...... becomes the cold junction side. An electromagnetic wave absorber 70 is formed on this hot junction side via an insulating layer (not shown).

This thermopile is made by bonding a p-type silicon substrate and an n-type silicon substrate, making a hole in the p-type substrate and growing or depositing an n-type silicon layer, and then forming a hole in the n-type substrate to grow or deposit a p-type silicon layer.
type silicon layers are grown or deposited, holes are drilled around these silicon growths or deposited layers, and an insulating layer is grown or deposited in the holes, thus forming a p-type layer 121. through the p,n silicon substrate. 22. -...- and n-type layers 31, 32°... are formed, and metal layers 51, 52°...61, 62... are formed on these end faces.・・・・・・
and an electromagnetic wave absorber 7 on the hot junction side via an insulating layer.
It can be created by attaching 0.

[Effect]

In this thermopile, the electromagnetic wave incident on the electromagnetic wave absorber 70 causes the temperature of the absorber to rise (fall), and the temperature of the hot junction of the thermocouple in the vicinity rises (falls) more than the cold junction side. This creates a temperature difference between the hot and cold junctions of the thermocouple, and a thermoelectromotive force is generated due to the Seebeck effect. The electromagnetic wave is, for example, infrared rays, and the electromagnetic wave absorber 19
Anything that can be absorbed by the body and turn into heat can be used, and it can be of any wavelength band type. n-type layers 21, 22. . . ., n-type layers 31, 32, . Since a thermomobile is constructed by connecting a plurality of such thermocouples in series, its apparent electromotive force is the sum of the thermoelectromotive force generated by each thermocouple.

This thermopile also has thermocouple elements 21, 31, 22, 32. ... extend in the thickness direction of the substrate 10, and these elements are buried below the hot junction group. Therefore, the degree of integration is high,
Since there is no non-photosensitive area around the hot junction, it is possible to easily configure an image sensor having a structure in which a large number of minute pixels are arranged one-dimensionally or two-dimensionally.

In this thermopile, metal layers 51, 52 .・・・・・・61.6
2. Connect via... Since the temperature on the hot junction side can be considered to be the same everywhere, the law of intermediate metals is applied, and the metal layer 51. ...does not affect the electromotive force of the thermocouple.

This thermopile can be manufactured by applying a transistor manufacturing process and is easy to manufacture.

〔Example〕

To give a specific example of this thermopile, the n-type layers 21, 22
．． The size of ... is 25 [μm] in the X direction, 25 [μm] in the X direction, 500 [μm] in the Z direction, and n
Mold layers 31, 32. The size of ... is 25 in the X direction
[μm], 25 [μm] in the X direction, 500 [μm] in the Z direction
m]. The number of thermocouples consisting of one n-type layer and one n-type layer is 50, and when both the P-type layer and the n-type layer are polycrystalline silicon, a temperature difference of 1 generates 25 mV of heat. Generates an electromotive force. The overall size of this thermomobile is 4 in the X direction.
75 [μm], 475 (μm) in the X direction, and approximately 500 [μm] in the Z direction.

Figure 2 shows the manufacturing process of this thermopile.

First, as shown in (+), a p-type wheel crystal silicon substrate 11 and an n-type single crystal silicon substrate 12 are prepared, and silicon dioxide films 13 and 14 are formed on their surfaces by thermal oxidation.

Next, as shown in (2), these substrates 11 and 12 are bonded together. This bonding can be carried out by wetting the oxide films 13 and 14 with pure water, overlapping them, baking them at 200°C, and then heat-treating them at a temperature of 800 to 1000''C for 30 to 60 minutes.

Next, as shown in (3), an n-type layer 31.
32. A hole corresponding to the cross section of . . . (hereinafter referred to as 30) is drilled. This hole is made of oxidized W413 from the bonding part.
, I4 and open until the n-substrate 12 is exposed. Thereafter, an n-type silicon layer is grown or deposited by CVD or the like, and the hole is filled with the silicon layer. 12a shows an n-type silicon layer grown or deposited in this hole, which may be single crystal, polycrystalline or amorphous. Since the thermoelectromotive force of a thermocouple is higher in a single crystal, it is better to manage the process so that single crystal silicon grows. N-type silicon also grows or deposits on the p-substrate around the hole, but this is removed by etching or the like (the same goes for others).

Next, as shown in (4), the n-type layer 21°22 is placed on the n-substrate 12.
, ... (hereinafter referred to as 20) is made, and p-type silicon Ila is grown or deposited in this hole. It can also be single crystal, polycrystalline, or amorphous, but it is preferred to grow a single crystal. In this way, as shown in (5), the bonded p-type substrate 11 and n
N-type layers 20 and n-type layers 3 pass through the type substrate 12 and are arranged alternately.
0 is completed.

Next, a groove is created around the n-type layer of the p-type substrate 11, and an insulating layer (silicon dioxide, etc.) 41 is formed in this groove using a CVD method or the like.
grow or deposit a. As shown in (7), a groove is also formed around the n-type layer on the n-type substrate 12 side, and an insulating layer (such as silicon dioxide) 41b is grown or deposited in this groove.

Next, as shown in (8), a metal such as aluminum is deposited and patterned to form metal layers 50° and 60. This completes the thermomobile shown in Figure 1.

Note that an insulating film on the surface is formed and removed as appropriate.

Next, as shown in (9), the electromagnetic wave absorber 70 is attached to the hot junction side, which can be done by forming an insulating layer 71, depositing metal (gold Au in this case), and patterning it.

. The thickness of the p-type substrate 11 and the n-type substrate 12 is 200 to 300 [
μm], and the combined length of the p-type layer 20 and n-type layer 30 is 500 to 600 (μm).p/n
The cross section of the mold layer is approximately 100 (μm) x 100 [μm], which makes it possible to make a thermomobile that fits within ICIIIm'').

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to provide a thermomobile with a three-dimensional structure, and it is effective in providing a one-dimensional or two-dimensional sensor with high resolution.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the thermomobile of the present invention, and FIG. 2 is an explanatory diagram showing the manufacturing process of the thermomobile of the present invention. In FIG. 1, 21, 22 are p-type layers, 31, 32 .・・・・・・
- is an n-type layer, 51, 52. ......,61,62.
. . . is a metal layer, and 70 is an electromagnetic wave absorber. Applicant Nippon Steel Corporation

Claims (1)

[Claims] 1. A plurality of P in the thickness direction of a single crystal silicon substrate.
A type layer, an n-type layer, and an insulating layer that insulates them are formed, and the end faces of these p-type and n-type layers are connected by metal layers deposited on the front and back surfaces of the substrate, and the whole is connected in series in a zigzag shape. A vertical silicon thermopile characterized by having an electromagnetic wave absorber layer coated on the side that serves as a hot junction via an insulating layer. 2. The step of bonding a p-type single crystal silicon substrate and an n-type single crystal silicon substrate with an insulating film on their surfaces, and drilling a hole in the bonded p-type substrate that reaches the n-type substrate, and filling the hole with n-type silicon. growing or depositing layers and drilling holes in the bonded n-type substrate to reach the p-type substrate;
growing or depositing a p-type silicon layer in the hole; forming a hole around the n-type silicon layer grown or deposited in the hole of the p-type substrate and growing or depositing an insulating layer in the hole;
There is also a step of making a hole around the p-type silicon layer grown or deposited in the hole of the n-type substrate and growing or depositing an insulating layer in the hole, and bonding the p-type substrate and n-type substrate that are bonded together in this way. A step in which the end faces of the p-type layer and n-type layer, which are insulated from each other by an insulating layer, are connected by a metal layer to form a zigzag series connection, and the end face on the hot junction side is connected via an insulating film. 1. A method for manufacturing a vertical silicon thermopile, comprising the step of depositing an electromagnetic wave absorber.