JPS61276378A - Manufacture of diaphragm-type semiconductor sensor - Google Patents

Abstract

PURPOSE:To enable a diffused resistance to be formed independently from the thickness of a semiconductor substrate, by forming a through hole in a part of the substrate so that the size of a region from which the etching is started is determined based on the size of the through hole. CONSTITUTION:Diffused resistances 3 are provided at predetermined positions on the surafce of a single crystal Si substrate 1. Thin films resistive to etching 11 are formed on both the faces of the substrate 1. An aperture 13 for forming a through hole 15 is formed on the surface of the substrate 1 by photo etching the same so as to have a dimension of (A) and to be correctly positioned with respect to the resistances 3. The aperture 13 is then etched to form the through hole 15 reaching the film 11 on the rear face of the substrate. The aperture angle of the hole 15 is 54.7 degrees when the crystal face of the substrate 1 is (100). The dimension (a) of a side of the the rear-face opening 17 of the hole 15 is varied according to the thickness (D) of the substrate 1 when the dimension (A) is constant. Therefore, the size of an opening 9 for forming a recess on the rear face of the substrate 1 is determined based on the dimension (a) and then the substrate 1 is etched from the opening 9 to form the recess. According to this method, stable characteristics can be obtained independently from the thickness (D) of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a diaphragm semiconductor sensor that can measure pressure, acceleration, etc. with high reliability.

[Technical background of the invention and its problems]

With the recent development of semiconductor technology, semiconductors, especially silicon, have become extremely important as circuit elements, but their importance has also increased as a material for various sensors. By forming a circuit, there is an advantage that miniaturization can be achieved.

FIG. 3 is a sectional view showing the structure of a silicon diaphragm pressure sensor. In the figure, 101 is a silicon single crystal (hereinafter referred to as the "substrate"), and by forming a recessed part 107 in a part of this substrate 101, the film is thinned so that it is sensitive to unevenness due to the pressure difference between the upper and lower sides. Daicephram 105
is formed. Four diffused resistors 103 are formed in this diaphragm portion 105, and these four diffused resistors 103 are connected to form a Wheatstone bridge circuit.

In such a configuration, when pressure is applied to the diaphragm portion 105, the diaphragm portion 105 undergoes uneven deformation, so the diffused resistor 103 expands and contracts, and the resistance value of the diffused resistor 103 increases to the value of the diaphragm portion 1 due to the so-called piezoresistance effect.
It changes depending on the pressure applied to 05. Then, the pressure applied to the diaphragm portion 105 due to this resistance change is measured.

Next, an outline of the manufacturing process of a conventional silicon diaphragm pressure sensor will be explained using FIG. 4, which is a partial cross-sectional view of FIG. 3.

First, a substrate 101 with a thickness D1 whose crystal plane is the (100) plane.
A required diffused resistor 103 is formed on the surface. Next, an etching-resistant thin film 111 that can withstand an alkaline etching solution is formed on the entire back surface of the substrate 101, and the etching-resistant thin film 111 in the region where the recessed part 107 is to be formed is removed to open an opening with a predetermined size. A portion 109 is formed. Then, by etching the recess-forming opening 109 with an alkaline etching solution, a recess 107 is formed, thereby forming a diaphragm portion 105 thinned to a thickness of, for example, about 20 to 30 μm. Note that since the crystal plane of the substrate 101 is the (100) plane, the opening angle of the recessed portion 107 is 54.7°.

By the way, the degree of distortion of the diffused resistor 103 differs depending on the position where the diffused resistor 103 is formed, and the rate of change in resistance of the diffused resistor 103 changes. Therefore, in order to stably and accurately measure the pressure applied to the diaphragm portion 105, The position where the diffused resistor 103 is formed in the diaphragm portion 105 is an important factor.

However, in such conventional manufacturing processes,
Since openings for forming recesses with preset dimensions are provided on the back side of the substrate regardless of the thickness of the substrate, and a process of etching is used to form the recesses, variations in the thickness of the substrate are avoided. In some cases, the dimensions of the recessed portion vary depending on the thickness of the substrate, making it difficult to form a diffused resistor at a predetermined position in the diaphragm portion.

For example, if the standard thickness of the substrate 101 is D, and the distance from the end of the diaphragm section 105 to the center position of the diffused resistor 103 closest to the end of the diaphragm section 105 is L, then the thickness becomes, for example, D-. A substrate 1 having a thickness D
When a diaphragm part 105 is formed with the same thickness (20 to 30 μl) as that formed in 01, the shape of the recessed part 107 changes as shown by the dotted line in FIG. The distance to the center of the resistor 103 is L-, and the position of the diffused resistor 103 formed on a substrate with a thickness D- is from the end of the diaphragm part 105 to (
It will move away by L−−L).

Therefore, the characteristics of the diaphragm turgor pressure sensor vary depending on the thickness of the substrate, resulting in a problem that stable and accurate measurements cannot be made.

(Object of the Invention) This invention has been made in view of the above, and its object is to provide a diaphragm that can obtain stable characteristics without depending on the thickness of the substrate and has high reliability. An object of the present invention is to provide a method for manufacturing a shaped semiconductor sensor.

(Summary of the Invention) In order to achieve the above object, a diffused resistor is formed on the surface of a substrate, and a concave portion is formed in the substrate so that a part of the substrate including the diffused resistor becomes a diaphragm portion having a predetermined thickness. In the method of manufacturing a diaphragm type semiconductor sensor, which includes a step of forming a diaphragm semiconductor sensor by etching from the back surface of the substrate, the present invention provides a method for manufacturing a diaphragm semiconductor sensor, which includes forming a through hole through the substrate by etching from the front surface of the substrate before the step of forming the recessed portion. The gist is to form the concave portion by forming a hole, determining the size of a region where etching is to be started based on the size of the through hole, and then etching from the region.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial sectional view showing the structure of a diaphragm type semiconductor sensor manufactured by a manufacturing method according to an embodiment of the present invention, and is applied to a pressure sensor. In the figure, 1 is a silicon single crystal substrate (hereinafter referred to as "substrate"). ), and when the thickness of the substrate 1 is D, there is a recess forming opening (
Hereinafter, this will be referred to as the "opening". ) 9 is formed, and when the thickness of the substrate is D', an opening 9 whose side dimension is W- is formed, and the opening 9 is formed according to the respective thickness of the substrate 1. A diaphragm portion 5 is formed to have a predetermined thickness so that a concave portion 7 is formed in the portion 9 and the diaphragm portion 5 is sensitively deformed into irregularities due to the pressure difference between the upper and lower portions. and,
Four diffusion resistors 3 are formed on the surface of this diaphragm portion 5, and these four diffusion papers M3 are connected to form a Wheatstone bridge circuit.

In such a configuration, when pressure is applied to the diaphragm portion 5, the diaphragm portion 5 is sensitively deformed into irregularities due to the pressure difference between the upper and lower sides, and the diffused resistor 3 formed on the diaphragm portion 5 expands and contracts. Due to this expansion and contraction of the diffused resistor 3, the interatomic distance of the silicon crystal changes, and the resistance value of the diffused resistor 3 changes. Therefore, the pressure applied to the diaphragm portion 5 is measured using the change in the resistance value of the diffused resistor 3 due to the so-called piezoresistance effect described above.

Next, the manufacturing process of this diaphragm turgor pressure sensor is carried out in the seventh step.
This will be explained with reference to the drawings and FIGS. 2(A) to 2(C).

■ Boron with a concentration of about 1 x 10180 II l-3 is placed at a predetermined position on the surface of the silicon single crystal substrate 1, which is N type with a specific resistance of about 5 Ω cm and whose crystal plane is the (100) plane and has a thickness D. is selectively diffused to form a diffused resistor 3 (FIG. 2(A)).

(2) Next, an etching-resistant thin film 11 made of, for example, SiO2 or nitride m, which can withstand an alkaline etching solution, is formed on both sides of the substrate 1. Then, the opening 13 for forming the through hole 15, for example, whose side dimension is A, is accurately aligned with the diffused resistor 3 in the region where the recess 7 is not formed, and then the photoetching method is performed. This through-hole forming opening 13 is etched using an alkaline etching solution such as a mixture of ethylenediamine, pyrocatechol, and water to remove the surface on which the diffusion resistor 3 is not formed (hereinafter referred to as "back surface J"). A through hole 15 is formed that reaches the etching-resistant thin film 11 formed on the substrate 1. The opening angle of the through hole 15 is such that the crystal plane of the substrate 1 is (100).
Since it is a plane, the angle is 54.7°, and the thickness of the substrate 1 is D.
Then, the dimension a of one side of the back opening 17 of the through hole 15 is
l, tA - (20/lan 54.7"). Therefore, when the dimension A of one side of the back opening 17 is constant, the dimension A of one side of the through hole forming opening 13 is constant. For example, in a substrate with a thickness of D, the dimension a of one side of the back opening 17 is A-(2D'/jan 54.7°). When changes from D to D', the amount of change Δa in the dimension of one side of the back opening 17 is expressed by the following equation ((8) in FIG. 2).

Δa = 2 (D-D=)/lan 54.7°・<1
>■ Apply a positive resist on the etching-resistant thin film 11 on the back surface of the substrate 1. And the dimension of the − side is (W+a)/
Using a mask in which two patterns 21 and 23 are formed that allow light to pass through, first, the two sides 21a and 21b of the pattern 21 match the two sides and corner (bottom left of the drawing) of the back opening 17. Then, similarly, using the opening 17 as a guide, align the mask pattern 21 in the order of F → G-41-1, and expose sequentially at each position. Let's do it. At this time, the concave portion 7
As the mask moves, the pattern 23 positioned in the area where the pattern 23 is formed is also sequentially exposed in the same manner as described above, and an exposed area with the - side dimension W is formed on the back surface of the semiconductor substrate 1.

Next, a resist pattern 19 is formed by developing the exposed area, and the area where this resist pattern 19 is formed is etched to form an opening 9 having a side dimension of W. Then, etching is performed from the opening 9 using an alkaline etching solution to form the concave portion 7, thereby forming the diaphragm portion 5 of a predetermined thickness, thereby forming the diaphragm turgor pressure coil (second Figure (C)).

By the way, when the thickness of the substrate is D-, the diaphragm part 5 and the diffused resistor 3 closest to this diaphragm part 5
In order to make the distance from
It is necessary to make W-Δa. Therefore, if the dimension of one side of the through-hole forming opening 13 of the substrate with the thickness D- is A, then
By etching the through hole forming opening 13 to form the through hole 15, the back opening 17 whose side dimension a' is a+Δa is formed as described above. Therefore, by aligning the mask using the back opening 17 as a guide and performing exposure, development and etching in the same manner as described above, an opening 9 with a -side dimension of W-Δa is formed. Therefore, an opening having a size corresponding to the thickness of the substrate 1 can be easily formed.

Thereby, it is possible to form a diaphragm type semiconductor sensor in which the distance from the end of the diaphragm portion 5 to the center position of the diffused resistor 3 closest to the end of the diaphragm portion 5 is constant regardless of the thickness of the substrate 1.

〔Effect of the invention〕

As explained above, according to the present invention, a through hole penetrating the semiconductor substrate is formed in a part of the semiconductor substrate, and the size of the area where etching is to be started is determined based on the size of the through hole. After that, a concave portion is formed by etching the region, so that a diffused resistor can be formed at a predetermined position without depending on the thickness of the semiconductor substrate.

As a result, it is possible to provide a method for manufacturing a diaphragm type semiconductor sensor that can obtain stable characteristics regardless of the thickness of the semiconductor substrate and has high reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a diaphragm semiconductor sensor according to an embodiment of the present invention, and FIGS. 3 is a sectional view showing the structure of a conventional example of a diaphragm type semiconductor sensor, and FIG. 4 is a partial sectional view of FIG. 3. Patent applicant Nissan Motor Co., Ltd. Figure 3 Figure 4

Claims (1)

[Claims] A diaphragm shape comprising the step of forming a diffused resistor on the surface of a substrate, and forming a concave portion by etching from the back surface of the substrate so that a portion of the substrate containing the diffused resistor becomes a diaphragm portion with a predetermined thickness. In the method for manufacturing a semiconductor sensor, a through hole is formed through the substrate by etching from the surface of the substrate before the step of forming the recessed part, and a region where etching is started from the size of the through hole is formed. A method for manufacturing a diaphragm type semiconductor sensor, characterized in that the recessed portion is formed by etching the region after determining its size.