JPS6327066A - Manufacture of diaphragm type pressure sensor - Google Patents

Abstract

PURPOSE:To easily recognize the etching of a diaphragm in a predetermined thickness by using a first groove formed on one side surface of a substrate and a second groove etched simultaneously upon forming of the diaphragm oppositely to the first groove. CONSTITUTION:After a piezo resistance element 2 is formed on the surface of a substrate 1, silicon oxide films 3, 4 are formed on the front and rear surfaces of the substrate. After windows 5 7 for forming grooves are then formed on the films 3, 4, the substrate 1 is etched by the windows. The etching through the windows 5 is stopped when the depth arrives at the thickness lof a diaphragm 11 to form a first groove 8. The etching of a window 6 for forming a diaphragm and a window 7 is continued until a second groove 10 by the window 7 arrives at the groove 8. When the groove 10 arrives at the groove 8, the substrate 1 is split to finish the etching. At this time, it can recognize that the diaphragm 11 of the thickness l is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION A] Industrial Application Field The present invention relates to a method for manufacturing a diaphragm pressure sensor.

(C1) Conventional technology Generally, a diaphragm pressure sensor has a thickness of 400 μm.
A diaphragm portion with a thickness of approximately 20 to 30 μm is formed by etching one side of a silicon substrate of approximately
This diaphragm portion is provided with a plurality of diffused piezoresistive elements (see, for example, Japanese Patent Publication No. 59-2192).

(c) Problems to be Solved by the Invention Incidentally, when forming the diaphragm portion as described above, it is necessary to etch the silicon substrate at a depth of 37 degrees from 0 to 380 μm. This type of etching requires a very long time, and it is difficult to maintain the temperature and concentration of the etching solution during this time. Therefore, the etching speed changes and the diaphragm part cannot be precisely formed to a predetermined thickness. It becomes difficult to form the diaphragm, and the thickness of the diaphragm portion must be repeatedly measured during etching.

Therefore, an object of the present invention is to ensure that the thickness of the diaphragm portion is a predetermined thickness K.

B) Means for Solving the Problems The method for manufacturing a diaphragm pressure sensor of the present invention includes forming a first groove portion having the same depth as the thickness of the diaphragm portion on one or the other surface of the substrate; Alternatively, a second groove is formed on one surface facing the first groove by etching at the same time as the diaphragm is formed, and the etching of the diaphragm is finished when the second groove reaches the first groove. It is characterized by

According to the present invention, the substrate is separated by the first groove portion having the same depth as the thickness of the diaphragm portion and the second groove portion formed simultaneously with the formation of the diaphragm portion. The etching formation on the diaphragm part can be easily recognized.

(F) Embodiment FIGS. 1A to 1A are side sectional views showing an embodiment of the present invention in the order of steps.

In FIG. 1, a plurality of piezoresistive elements (2) are formed by boron diffusion from the surface of a substrate (1) made of silicon with a thickness of 400 μm and having a (100) plane, and further on the front and back surfaces of the substrate (1). An acid arsenic silicon film +3++41 with a thickness of about 5 μm is formed on the surface.

In the same figure [bl, u is in the silicon oxide film (3), w in the middle
is 42.4 μm and crosses the substrate 1).
) are formed along the (1)0) axial direction, and the silicon oxide film (4) has a 2000 μm square diaphragm part forming window (6) and a width W' of 523 μm or more crossing the base #fl+. Window (7) Calyx 1) is formed along the 0> axial direction. At this time, the first grooved window (5) and the second grooved window (7
1 are grooved so that their respective longitudinal groove centers face each other, and 61 is a piezoresistive element (
2).

In FIG. 1et, the first groove-shaped window (5), the window (6), and the second groove-shaped window f7+ or the substrate fi+ that outputs bits are at a liquid temperature of 7.
Anisotropically etched with an aqueous potassium hydroxide solution at 2°C and 2096°C. By such etching, the substrate (1
) is etched into a trapezoidal shape, and the maximum depth g that can be etched is expressed as /=w/p. Therefore, when the depth e of the first groove (8) formed by the first groove window (5) reaches 30 μm, it becomes V-shaped and is not etched any further. On the other hand, the rectangular recess (9) and the second groove aα formed by the window (6) and the second groove window (71) are further etched.

In the same figure (di, the depth e' of the second groove part αα is 370
When the depth reaches 370 μm, this groove 001 is connected to the first groove 81, and the substrate (1) is separated into two parts.
A diaphragm portion (1)) is formed. Therefore,
At what point does the etching process end?

In FIG. 1et, although not shown in the figure, the electrode arrangement layer connected to the piezoresistive element (2) is a silicon oxide film (3).
A silicon nitride film Gz is laminated thereon. Furthermore, the silicon oxide film (4) is removed. In this way, a diaphragm type pressure sensor 03 is formed.

In the above embodiment, the first n part (8) and the second groove opening (2) are completely formed without any relation to the pressure sensor 0, but generally a plurality of pressure sensors [1] are formed on a wafer-shaped silicon plate at the same time. After that, they are individually diced, so the first groove part (8) and the second groove part (
By forming the film, a dicing process can be made unnecessary.

Note that the thickness of the diaphragm portion (13J) is arbitrary.

Therefore, the depth of the first groove part (8) is made equal to the thickness of the diaphragm part 1) 1 by adjusting the width W of the first groove window (5). Moreover, the formation positions of the first groove part (8) and the second groove part (1(lI) may be reversed.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figure 1 1al to 1 (el is a side sectional view showing an embodiment of the present invention step by step. (1) One substrate, (8)...first groove part, (10)・
...Second groove part, (1))...Diaphragm part.

Claims (1)

[Claims] (1) A method for manufacturing a diaphragm pressure sensor in which a diaphragm portion is formed by etching from one surface of a substrate, the method comprising etching a diaphragm portion on one or the other surface of the substrate to a depth equal to the thickness of the diaphragm portion. a second structural part is formed on the other or one surface of the substrate facing the first groove part by etching at the same time as the formation of the diaphragm part, and the second groove part reaches the first groove part. A method for manufacturing a diaphragm type pressure sensor, characterized in that etching of the diaphragm portion is completed at the time when the diaphragm portion is etched.