JP3503882B2 - Thermopile manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a thermopile manufacturing method.
Manufacturing technology. [0002] 2. Description of the Related Art Thermopile comprising a plurality of thermocouple elements
In addition to the contact / non-contact temperature detection field,
Used for outing. As such an example, the inventor
Proposal of thermopile type flow velocity sensor (Japanese Unexamined Patent Publication No. 9-2286)
No. 20). [0003] This thermopile type flow velocity sensor is temperature compensated.
Accurate flow rate without the need for external circuits such as circuits
An excellent flow rate sensor that has the effect of being able to calculate
It is a message. The thermopile of the thermopile type flow rate sensor
Il diffused boron into silicon (“p”)⁺⁺
-Si ") and aluminum
Has a thermocouple. That is, the drawing of this flow sensor is shown in FIG.
It will be described using FIG. The flow rate sensor indicated by reference numeral 1 in FIG.
A silicon substrate (Si substrate) 2 as a support substrate
And a silicon dioxide layer (SiO_TwoLayer) and trisilicon tetranitride
Layer (Si_ThreeN _FourLayer)
Of the diaphragm 3 and the fin formed on the diaphragm 3
Micro heater 4 as a heater and micro heater 4
Downstream side, above the diaphragm 3 except for the cold junction forming part
And a power supply terminal 6A,
6B for supplying a drive current to the micro heater 4
Power supply wiring 6 and output terminals 7A and 7B.
-Output the first temperature detection signal output from the mopile 5
Output wiring 7 and the upstream side of the micro heater 4
Formed on the diaphragm 3 except for the cold junction forming portion
The upstream thermopile 8 and the output terminals 9A and 9B
A second temperature detection output from the upstream thermopile 8
A second output wiring 9 for outputting an output signal.
Has been established. FIG. 2 shows an enlarged top view of the thermopile (FIG. 2).
(A)) and a sectional view (FIG. 2 (b)). In this case
The downstream thermopile 5 and the upstream thermopile
8 has the same configuration, so that the downstream thermopile 5
Will be described. Thermocouple constituting downstream thermopile 5
Is p⁺⁺-Si and aluminum, FIG.
As shown in (b), the cold junction 5 of the downstream thermopile 5
A is a diaphragm of Si substrate 2 (about 400 μm thick)
3 is provided in a portion where no thermopies are formed.
The hot junction 5B of the nozzle 5 is made of SiO_TwoLayer and Si_ThreeN_FourComposed of layers
It is provided on the diaphragm 3 to be formed. According to the downstream thermopile 5, the flow velocity range
Output several tens of mV in a range of 0.01 m / sec to 3 m / sec
Since a large voltage is obtained, large amplification is not required and signal processing is performed.
Management becomes possible. Here, referring to FIG.
The formation process will be described. [0008] First, as shown in FIG.
By oxidizing both surfaces of SiO2, SiO 2_TwoLayer S
It is formed on both sides of the i-substrate 2. Next, as shown in FIG.
In addition, SiO_TwoLayer etched by photolithography
Then, open a window on the upper surface (upper side in the figure) of the Si substrate,
Boron (B), which is a pure substance, is diffused at a high concentration and p
⁺⁺-Forming a Si layer 10; And p⁺⁺-Si layer 10
After the formation of_TwoRemove the layer. [0009] Subsequently, as shown in FIG.
Substrate (p⁺⁺-Si layer 10 is included. 2) Acid on both surfaces
To form SiO 2 again._TwoLayers on both sides of Si substrate 2
Formed. [0010] Then, on both surfaces of the Si substrate 2, Si_ThreeN_FourLayers
Formed by evaporation, Si_ThreeN_FourOxidize the surface to cover the layer
SiO_TwoForm a layer. As a result, the Si-based
SiO 2 on both sides of plate 2_Two/ Si_ThreeN_Four/ SiO_TwoLayer 11 is formed
Will be done. Next, a photoresist film is formed, and the upper surface is
Exposure with a mask corresponding to the contact hole for
As shown in FIG._Two/ Si_ThreeN_Four/ SiO_Two
The layer 11 is removed, and a contact hole 12 is formed. one
The lower surface is exposed with a mask corresponding to the diaphragm.
No, SiO equivalent to the diaphragm_Two/ Si_ThreeN_Four/ Si
O_TwoLayer 11 is removed. Subsequently, as shown in FIG.
Thin film (Al thin film) 13 which is a conductive substance of
Is formed by vacuum evaporation and
Unnecessary Al thin film is etched leaving only the wiring pattern
And sintering. Next, as shown in FIG.
iO_TwoLayer 14 is formed by vapor deposition and photolithography
To open a window at the position corresponding to the bonding pad position.
iO _TwoThe bonding pad 15 is removed by removing the layer.
To form Subsequently, as shown in FIG.
Substrate 2 is made of SiO_Two/ Si_ThreeN_Four/ SiO_TwoLayer 11 with mask
And anisotropically etched to form recesses.
The ear flam 3 is formed. Through the above steps, the downstream side
That the mopile 5 and the upstream thermopile 8 are formed.
And In the above process, SiO_Two/ Si_ThreeN_Four/ SiO_Twolayer
When etching the Si substrate 2 using 11 as a mask
Is p⁺⁺-Si etching rate causes boron diffusion.
1/1 compared to the etching rate of unformed silicon
The fact that it is about 00 is used. But
Ra p⁺⁺-Si does not dissolve in etchant at all
Instead, after the high concentration diffusion of boron,
P with an iodine film formed⁺⁺-Si surface relatively etching speed
High degree of dissolution due to prolonged etching
Extremely high electrical resistance or continuity at the contacts
Problems such as being cut off occurred. To solve such a problem, the present inventors have
Using Reactive Ion Etching Equipment (RIE)
The silicon is etched vertically and SiO_TwoLayers
For Si etchant used for etching
By forming a highly selective film, p⁺⁺-Prevents dissolution of Si
The technology was proposed in the past. This technique will be described with reference to FIG.
FIG. 4A is a view showing a thermopile, and FIG.
FIGS. 4B to 4C show the process of forming a cross section along the line AA in FIG.
4 (h). As shown in FIG. 4B, a p-type
The impurity boron is diffused by ion implantation or the like, and p
⁺⁺-Forming a Si layer 10; Then photolithography
By law⁺⁺Resist having opening on Si layer 10
A layer was formed (see FIG. 4C). Then p⁺⁺-Si
The portion of layer 10 corresponding to this opening is
Etching is performed by an etching method. After removing the resist layer, heat treatment or the like is performed.
Si0 on both sides_TwoForming a layer,_TwoCVD method on the layer
By Si_ThreeN_FourForming a layer (hereinafter, these two layers are combined)
Si_ThreeN_Four/ Si0_TwoLayer 11). Thereafter, a resist layer is formed, and Si_ThreeN_Four
/ Si0_TwoMask and expose the part of the layer other than the part to be removed
I do. As a result, as shown in FIG._ThreeN_Four/
Si0_TwoUnwanted portions of the layer are removed. Then, as shown in FIG.
Aluminum (or platinum) thin film 1 which is a conductive substance
3 is formed by vacuum deposition or the like,
By etching, only the wiring part is left, and unnecessary
Remove the minium thin film. Finally, the lower side of 2 of the Si substrate
To form recesses by performing anisotropic etching
To form the diaphragm 3. However, in such a manufacturing method,
In active ion etching, etchant in wafer surface
There is a variation in the switching speed, resulting in wiring resistance and sensor
Causes a variation in the heat capacity of the wafer. [0023] SUMMARY OF THE INVENTION The present invention relates to the above-described configuration.
To improve the problem of the future, ie etch silicon
P when doing⁺⁺-Prevents dissolution of Si
The purpose is to provide an easy thermopile manufacturing method.
You. [0024] According to the present invention, there is provided a thermopile comprising:
In order to solve the above problem, a manufacturing method according to claim 1
As shown in FIG.
The thermopa made of impurity-diffused Si and conductive material
In the method for producing a thermopile for forming
SiO on recon substrate_TwoAfter layer formation, impurity diffusionI do
Partial SiO_TwoRemove layer and expand impurities in oxygen atmosphere
Scattered impurity diffusion Si layer in a desired pattern
SiO containing impurities on the entire plate surface_TwoForming a layer and
Then, the SiO containing the impurity_TwoSi on the layer_ThreeN_FourLayers
After forming the contact, the contact forming part of the thermopile and the die
SiO containing impurities in the portion where flam holes are formed_TwoLayer and S
i_ThreeN_FourAfter removing the layers, a conductive material layer is
A pile is formed and then silicon etching is performed.
A method for manufacturing a thermopile forming an ear flam portion.
You. [0025] DETAILED DESCRIPTION OF THE INVENTION A method for manufacturing a thermopile according to the present invention.
In the silicon substrate prior to the impurity diffusion
The parts that do not require impurity diffusion are oxidized in advance_TwoTo be
It is necessary. Such SiO_TwoTrout consisting of
Diffusion of impurities to necessary parts
Becomes easier. The impurity diffusion is performed in an atmosphere containing oxygen (oxygen atmosphere).
Qi). Due to the oxygen in this atmosphere
In the area where impurities are diffused, SiO_TwoLayer
It is formed. Boron is an example of an impurity to diffuse.
I can do it. In the prior art, boron is diffused to a high concentration
Made of silicon⁺⁺-Si on the Si layer_TwoShape layers
Had been done. At this time, p⁺⁺-Boron concentration on the surface of the Si layer
The degree decreases, and this part is etched during silicon etching,
It was etched at the same time. However, in the present invention, p
⁺⁺At the time of forming the Si layer;_TwoLayer formed
Boron SiO_TwoLayer formed
Being p⁺⁺-A decrease in the boron concentration of the Si layer is prevented,
As a result, p during etching of the Si layer⁺⁺-Shadow on Si layer
The sound is prevented. Hereinafter, the method for producing the thermopile of the present invention will be described.
An example will be described using a model diagram. FIG. 5 (a)
Is a thermopile produced according to the present invention.
FIG. 5 schematically illustrates the manufacturing process for the cross section in FIG.
(B) to FIG. 5 (g). First, a Si substrate (silicon substrate) 2
Heating in an oxidizing atmosphere,_Two(Silicon dioxide) layer
(See FIG. 4B), after which impurity diffusion is unnecessary
Part of SiO_TwoRemove the layer. Next, in an oxygen atmosphere, the Si substrate is
Diffuses boron in the desired pattern by diffusing boron
Si layer, that is, silicon with a high concentration of boron
P⁺⁺Providing a -Si layer; At this time, made above
SiO_TwoBoron diffuses into the layer and boron SiO_Twolayer
Becomes On the other hand, p⁺⁺-Atmosphere on the surface of the Si layer
Oxidized by oxygen in the_TwoOnce the layer is formed
In addition, this SiO_TwoBoron diffuses into the layer and boron SiO_Two
Layer and contains boron as an impurity on the entire substrate surface.
SiO_TwoLayer (boron SiO_TwoLayer) is formed (FIG. 5).
(C)). Next, the boron SiO_TwoSi on the layer_ThreeN_Four
The layers and the like are formed by a CVD method or the like (see FIG. 5D).
See). After that, a photoresist film (not shown) is formed.
And the upper surface is only the part corresponding to the wiring contact hole
Exposure is performed using a mask.
Exposure is performed using only the mask corresponding to the
These contact hole 12 and diaphragm forming portion
Si_ThreeN_Four/ SiO_TwoLayer 11 is removed. Further, metals such as aluminum and platinum;
Or, conductive materials that are made of various alloys and are thin film wiring
By providing a material layer, p⁺⁺-Consists of Si layer and conductive material
Form a thermopile with multiple thermocouples and then heat
Drazine, tetramethylammonium hydride (T
MAH), potassium hydroxide, etc.
To remove the Si layer on the back of the thermopile.
A diaphragm is formed. During this etching, p⁺⁺
-There was no portion where the boron concentration was reduced in the -Si layer
Therefore, the influence of etching is extremely small. According to the method for producing a thermopile described above,
And p⁺⁺-Elimination of excessive etching of the Si layer
Therefore, the thermopile can be formed with high accuracy. Improvement of manufacturing yield and suppression of variation in resistance value
Becomes possible. Silicon etching does not proceed excessively
It is easy to manage the processing time of
Very reliable. Fewer processes, shorter production time and reduced cost
Becomes Since reactive ion etching is not required,
It is easy to reduce capital expenses and reactive
It is not necessary to determine the conditions for ion etching. And the like. [0036] According to the method for producing a thermopile of the present invention, p
⁺⁺-Accuracy without excessive etching of Si layer
Good reliability, high reliability
Cost savings and many other benefits.
This is a method for producing a thermopile.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a flow sensor using a thermopile. FIG. 2A is an enlarged top view of a thermopile. (B) It is a figure showing the sectional view of a thermopile. FIG. 3 is a model diagram showing a method for manufacturing a thermopile according to the related art. (A)-(g) It is a model figure which shows each process of manufacture. FIG. 4 is a model diagram showing a method for manufacturing a thermopile according to the related art. (A) It is an enlarged top view which shows a thermopile. (B)-(h) It is a model figure which shows the manufacturing process of the cross section in AA of (a). FIG. 5 is a model diagram showing a method for manufacturing a thermopile according to the present invention. (A) It is an enlarged top view which shows a thermopile. It is a model figure showing a manufacturing process of a section in AA of (b)-(g) (a). [Description of Signs] 1 Flow velocity sensor 2 Si substrate 3 Diaphragm 4 Micro heater 5 Downstream thermopile 5A Cold junction 5B Hot junction 6 Power supply wiring 7 First output wiring 8 Upstream thermopile 9 Second output wiring 10 p ++-Si layer 11 ( SiO ₂ /) Si ₃ N ₄ / SiO ₂ layer 12 Contact hole 13 Conductive substance such as Al 14 SiO ₂ layer 15 Bonding pad 16 Resist

Claims (1)

(1) A method of manufacturing a thermopile comprising: forming a diaphragm portion on a silicon substrate; and a thermopile made of impurity-diffused Si and a conductive material on the diaphragm portion. after forming the SiO ₂ layer, to remove the SiO ₂ layer part for the impurity diffusion, and the impurity diffusion Si layer in a desired pattern by diffusing impurities in an oxygen atmosphere,
Further, an SiO ₂ layer containing impurities is formed on the entire surface of the substrate, and then a Si ₃ N ₄ layer or the like is formed on the SiO ₂ layer containing the impurities, and then a contact forming portion and a diaphragm hole forming portion of a thermopile are formed. SiO ₂ layer containing impurities of
A method for manufacturing a thermopile, comprising: forming a thermopile by providing a conductive material layer after removing an i ₃ N ₄ layer and the like; and performing silicon etching to form a diaphragm portion.