JPH0374883A - Manufacture of diaphragm of pressure sensor - Google Patents

Abstract

PURPOSE:To enable easy formation of a projection in a diaphragm part by etching a substrate with anisotropic etchant using a mask pattern of specified configuration. CONSTITUTION:A silicon substrate 1 is etched with anisotropic etchant by using rim formation mask 2 and a mask having concentraic patterns 4, 5 which are separated properly; then a diaphragm part having a projection is formed readily. The diaphragm moves easily at a peripheral part and becomes a diaphragm of a pressure sensor to detect a pressure at high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a diaphragm of a pressure sensor suitable for detecting minute pressures such as blood pressure or wind pressure inside a vacuum cleaner.

[Conventional technology]

A method for manufacturing a diaphragm for this type of semiconductor pressure sensor is described in, for example, the Institute of Electronics, Information and Communication Engineers technical report HD86-16
(1986). FIG. 4 is an enlarged plan view of a silicon substrate for carrying out the manufacturing method, and FIG. 5 is an enlarged sectional view of the diaphragm of the manufactured semiconductor pressure sensor. When manufacturing a diaphragm for a semiconductor pressure sensor using this manufacturing method, a photomask 2 made of 5iO1 is formed with an appropriate width along the periphery of the silicon substrate 1 on the surface to be etched of a square thin silicon substrate 1. do.

After that, when etching was performed using an alkaline solution such as hydrazine, as shown in FIG. A thin diaphragm portion DF with a flat surface is formed to complete the diaphragm of the semiconductor pressure sensor.

Apart from this, Japanese Patent Publication No. 63-13357 discloses a semiconductor pressure transducer element in which a protrusion is formed in the center of a diaphragm to make it thicker. The diaphragm of this semiconductor pressure transducer element has a protrusion formed in its center, thereby improving the nonlinearity between pressure and strain characteristics without sacrificing sensitivity.

[Problem to be solved by the invention]

By the way, in order to manufacture the diaphragm of the semiconductor pressure sensor mentioned above, in order to change the thickness of the diaphragm part,
Conventionally, the composition of the etching solution and the amount of rotation of the silicon substrate in the etching solution have been adjusted. Therefore, there is a problem that the etching operation becomes complicated and it takes time to manufacture the diaphragm.

SUMMARY OF THE INVENTION In view of this problem, it is an object of the present invention to provide a method for manufacturing a diaphragm for a pressure sensor, in which a protrusion can be easily formed on a diaphragm formed by etching.

[Means to solve the problem]

The method for manufacturing a diaphragm of a pressure sensor according to the present invention includes:
In a method for manufacturing a diaphragm for a pressure sensor in which a protrusion is formed on a surface of a substrate by etching the substrate using an etching solution, a mask is formed concentrically at appropriate intervals on the surface of the substrate to be etched. The method is characterized in that the pattern is used to etch the substrate with an anisotropic etching solution.

[Effect]

A concentric mask pattern is used on the etched surface of the substrate. The substrate is immersed in an anisotropic etching solution to erode the inner peripheral side of each mask pattern to form a diaphragm portion. A protrusion is formed on the diaphragm portion of the substrate, and the peripheral edge side becomes thinner.

This allows the diaphragm to move easily around its periphery, allowing pressure to be detected with high sensitivity.

〔Example] The present invention will be described in detail below with reference to drawings showing embodiments thereof.

FIG. 1 is an enlarged plan view of a silicon substrate used to manufacture a diaphragm of a pressure sensor.

On one side 3 of the square silicon substrate to be etched, a wide rim forming mask 2 is formed along the periphery of the silicon substrate 1 using 5i02. Inside this mask 2, there is a square-shaped frame with a width that is extremely narrower than the width of the mask 2, and is spaced apart from the inner peripheral edge of the mask 2 by a distance approximately equal to the width of the mask 2. A first mask 4 for forming a diaphragm portion is formed concentrically with the mask 2.

Further, inside the first mask 4, a square shaped piece having the same width as the mask 40 is located at a distance slightly longer than the width of the mask 4 from the inner peripheral edge of the mask 4. a second mask 5 for forming a frame-shaped diaphragm portion;
is formed concentrically with the mask 4. These masks 4 and 5 are formed using the aforementioned 5i02. Such masks 2, 4.5 are formed by applying photolithography technology.

Now, when manufacturing a pressure sensor, first, as described above, a mask 2 for forming a rim portion is placed on one surface 3 of a silicon substrate.
A mask 4.5 for forming a diaphragm portion is formed, and the other and side surfaces of the base film are entirely masked with SiO□.

After such mask processing, an anisotropic etching solution heated to 80'C, such as kawalum hydroxide solution (I
The silicon substrate 1 is immersed in N-KOH for about 2 hours. Then, the surface of the silicon substrate on which the masks 2, 4 and 5 are not formed is corroded by the etching solution in the thickness direction of the silicon substrate 1.

FIG. 2 is a schematic enlarged sectional view showing changes in the corrosion state when a silicon substrate is etched with a potassium hydroxide solution. The masks 2, 4.5 are formed on the surface 3 of the silicon substrate 1 as described above, and before being immersed in an etching solution, the state is as shown in FIG. 2(a). When such a silicon substrate 1 is immersed in an etching solution,
Due to the etching solution, the portion of the surface 3 of the substrate 1 that is not masked by the Sin is corroded in the thickness direction of the substrate 1, and as shown in FIG. 2(b), the area between the masks 2 and 4.

The space between the masks 4 and 5 and the inside of the mask 5 are gradually recessed over time. If this condition continues further, the erosion of the lower surface of the mask 4.5 will progress and the silicon substrate 1
The width of the mask 4.5 gradually becomes narrower, and both the masks 4.5 and 5 separate from the silicon substrate 1, resulting in the state shown in FIG. 2(C). As a result, the silicon substrate 1 on which the mask 4°5 was formed
The portion 4.5 is further eroded in the same way as the portion where the mask 4.5 is not formed, resulting in the state shown in FIG. 2(d). In other words, since the portion that formed the mask 4.5 does not erode until the mask 4.5 is removed, a diaphragm portion DF with a semicylindrical cross section is formed in the portion corresponding to the mask 4.5. . The silicon substrate 1 thus etched is taken out from the etching solution and the attached etching solution is removed to complete the production of the pressure sensor.

The peripheral edge portion DFI of this diaphragm portion DF is thinner than the center portion. As a result, the diaphragm portion DF moves easily at its peripheral portion DF, which means that the amount of change in stress becomes large.

Although a potassium hydroxide solution was used as the anisotropic etching solution, a similar etching state can be obtained by using a mixed solution of ethylenediamine, pyrocatechol, and water.

By the way, a semiconductor strain gauge using, for example, piezoresistance was placed on the edge side of the silicon substrate 1 of the diaphragm of the pressure sensor manufactured as described above, and the stress change in the silicon substrate was measured, as shown in Fig. 3. The stress characteristics shown in the figure were obtained.

In FIG. 3, the horizontal axis is the position in the width direction of the diaphragm portion, and the vertical axis is the stress. The solid line shows the characteristics of the diaphragm manufactured by the present invention, and the broken line shows the characteristics of the diaphragm manufactured by the conventional manufacturing method. There is. When a constant pressure is applied, as is clear from FIG. 3, the stress is negative (-) and changes little from the center side position DF of the diaphragm leaf to just before reaching the edge side position OF. but,
As the position approaches the edge side position DFI, the stress turns to the positive (+) side, and a large stress is generated.

Then, by the conventional manufacturing method, the diaphragm part DF
Compared to the stress characteristics of a conventional diaphragm in which a protrusion is formed in the diaphragm, the stress in the diaphragm manufactured by the manufacturing method of the present invention is significantly increased at the peripheral edge position DFI of the diaphragm portion OF.

As a result, it was confirmed that the diaphragm manufactured by the manufacturing method of the present invention can detect pressure with high sensitivity, and can obtain a pressure detection sensitivity approximately 1.4 times that of a conventional semiconductor pressure sensor. did it.

Furthermore, since it is sufficient to simply immerse the silicon substrate in the etching solution for a predetermined period of time, the etching operation is less labor intensive and the diaphragm of the pressure sensor can be manufactured easily.

In this embodiment, the mask for forming the diaphragm portion has a square shape, but it may have a circular or triangular shape.

Alternatively, the mask may be formed by forming a resist on a silicon substrate and removing it with a resist removal liquid.

Furthermore, the silicon substrate to be etched is merely an example, and is not limited to silicon substrates.

〔Effect of the invention〕

As detailed above, according to the method for manufacturing a diaphragm for a pressure sensor according to the present invention, it is sufficient to simply immerse the substrate in an anisotropic etching solution for a predetermined period of time. can be manufactured easily and inexpensively. In addition, the diaphragm portion can be moved more sensitively to the received pressure, resulting in excellent effects such as being able to manufacture a pressure sensor that detects minute pressures with high sensitivity.

[Brief explanation of drawings]

FIG. 1 is an enlarged plan view of a silicon substrate on which a mask is formed to carry out the method for manufacturing a diaphragm for a pressure sensor according to the present invention, FIG. 2 is an enlarged cross-sectional view of the silicon substrate showing changes in the etching state, and FIG. 3 is a characteristic curve diagram showing the stress change in the widthwise position of the diaphragm, FIG. 4 is an enlarged plan view of a silicon substrate on which a mask is formed to apply the conventional diaphragm manufacturing method for a semiconductor pressure sensor, and FIG. 5 is a diagram showing the diaphragm manufacturing method. FIG. 3 is an enlarged cross-sectional view of the subsequent silicon substrate. 1... Silicon substrate 2... Rim part forming mask 4
．． 5...Diaphragm part forming mask DF...Diaphragm part 1 Fig. JP-A-3-74883 (5)

Claims (1)

[Claims] 1. A pressure sensor diaphragm manufacturing method in which a protrusion is formed on the surface of the substrate by etching the substrate using an etching solution, wherein the surface of the substrate to be etched is spaced at appropriate intervals. Using a mask pattern made concentrically,
A method for manufacturing a diaphragm for a pressure sensor, the method comprising etching a substrate with an anisotropic etching solution.