JPH0567794A - Manufacture of pressure sensor - Google Patents

Abstract

PURPOSE:To provide a method which can manufacture a pressure sensor readily at a low cost by using an ordinary thin film forming equipment without requiring special and expensive equipment such as a both-sided mask aligner. CONSTITUTION:At least two through-holes 5 for mask alignment are provided to a silicon wafer 1 before a diaphragm 9 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a pressure sensor.

[0002]

2. Description of the Related Art As a pressure sensor, for example, a pressure detecting element such as a diffusion resistance element or an electrostatic capacitance element is provided on one side of a silicon wafer, and a diaphragm is provided from the other side of the silicon wafer so as to correspond to the pressure detecting element. Is formed by etching.

When manufacturing a pressure sensor of this type, since the pressure detecting element is produced on one flat surface of the silicon wafer, the diaphragm must be produced from the other side. Therefore, it is necessary to match the patterns on both sides of the silicon wafer with each other, but since the mask aligner used in general thin film technology and semiconductor processes cannot be used, conventionally, a double-sided mask aligner is used to I was doing pattern matching.

[0004]

However, the above-mentioned double-sided mask aligner is a very special mask aligner, which is used only for manufacturing a pressure sensor, and is extremely expensive. Therefore, the conventional pressure sensor must be manufactured by using a special mask aligner, which inevitably increases the cost.

The present invention has been made in consideration of the above matters, and the purpose thereof is not to use special and expensive equipment such as a double-sided mask aligner, and to use ordinary thin film forming equipment. It is an object of the present invention to provide a method that can be used and can manufacture a pressure sensor simply and inexpensively.

[0006]

In order to achieve the above object, in the present invention, a pressure detecting element is provided on one side of a silicon wafer, and the pressure detecting element is provided from the other side of the silicon wafer so as to correspond to the pressure detecting element. In the method of manufacturing a pressure sensor in which the diaphragm is formed by etching, at least two through holes for mask alignment are provided in the silicon wafer before forming the diaphragm.

[0007]

In the method of the present invention, the through holes formed in the silicon wafer can be used as a mask alignment pattern, so that the patterns on both sides of the silicon wafer can be easily aligned.

[0008]

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

1 and 2 show an example of a method of manufacturing a pressure sensor according to the present invention. As shown in FIG. 1A, etching masks 2 and 3 such as a silicon nitride film (SiN) are formed on both upper and lower surfaces of a silicon wafer (hereinafter referred to as a wafer) 1.

Next, phosphoric acid, hydrofluoric acid, or the like is used as an etchant to dissolve predetermined portions of the etching mask 3 on the lower side of the wafer 1 to form through-hole etching patterns (for example, squares) 4 at two locations. Formed (see FIG. 1B).

Then, the wafer 1 is anisotropically etched using an alkaline aqueous solution such as KOH as an etchant to form a square through hole 5 of a predetermined size for mask alignment (see FIG. 1C). ). In this case, if the surface of the wafer 1 is the (100) surface, the angle α in FIG. 1C is 55 °, and the inclined through hole 5 is formed,
If the surface of the wafer 1 is the (111) plane, the angle α is 90 °, and the etching is performed vertically.

When the through hole 5 is a square as in this embodiment, its sides are along the orientation of the silicon crystal, which is convenient, as shown in FIG. Then, in the following steps, the through hole 5 is used as an alignment pattern. In FIG. 3, 6 is a sensor chip and 7 is an orientation flat.

After the through holes 5 are formed in the wafer 1 as described above, first, phosphoric acid is used to dissolve a predetermined portion of the etching mask 3 on the lower side of the wafer 1 to form the diaphragm etching pattern 8. Are formed (see FIG. 2A). In this case, the lower opening 5d of the through hole 5 is used as an alignment pattern.

Then, the wafer 1 is anisotropically etched using KOH to form the diaphragm 9 on the lower portion of the wafer 1 (see FIG. 2B).

Next, the etching masks 2 and 3 on both surfaces of the wafer 1 are removed using phosphoric acid (see FIG. 2C).

The pressure detecting element 10 is provided on the upper side of the wafer 1.
To form a diffusion resistance. In this case, the opening 5u above the through hole 5 is used as an alignment pattern. Then, the bonding pad is formed on the upper surface of the wafer 1 and the electrode 11 is formed (see FIG. 2D). The diaphragm 9 is preferably dipped in an alkaline aqueous solution such as KOH for finishing.

Further, the glass substrate 12 is bonded to the lower surface of the wafer 1 to perform anodic bonding to form a sealed chamber 13 surrounded by the silicon wafer 1, the diaphragm 9 and the glass substrate 12, and at the same time dicing and wire By performing the bonding, the pressure sensor 14 as shown in FIG. 2 (E) is obtained.

As can be understood from the above description of the manufacturing flow, in the method for manufacturing a pressure sensor according to the present invention, the through holes 5 formed in the wafer 1 are used as a mask alignment pattern, and therefore the wafer is The patterns on both sides of 1 can be easily matched. Therefore, unlike the conventional case, the pressure sensor 14 can be easily manufactured without using special and expensive equipment such as a double-sided mask aligner.

Although anisotropic etching is performed twice in the above manufacturing flow, when a high-concentration boron diffusion layer or an epitaxial layer is used as the etch stop layer for the diaphragm 9, the diaphragm 9 is formed and the through hole is formed. 5 can be formed at the same time, which is simpler than the above manufacturing flow.

The method of manufacturing the pressure sensor according to the present invention is not limited to the above embodiment, and the etching masks 2 and 3 may be formed of an oxide film, for example. In this case, it is preferable to use hydrofluoric acid as the etchant. Then, instead of the diffusion resistance 10, an electrostatic capacitance measuring electrode may be formed. In addition, two through holes 5 for mask alignment are formed.
You may provide more than one. Further, the shape of the through hole 5 may be a square such as a rectangle, in addition to the above square.

The pressure sensor 14 shown in FIG.
The structure of was for absolute pressure measurement, as shown by the phantom line in this figure, the hole 15 is provided in the glass substrate 12,
It is also possible to adopt a structure for gauge pressure measurement in which both sides of the diaphragm 9 are measured.

[0022]

As described above, according to the present invention,
Unlike the conventional case, it is not necessary to use special and expensive equipment such as a double-sided mask aligner, and the pressure sensor can be easily and inexpensively manufactured by using ordinary thin film forming equipment.

[Brief description of drawings]

1A to 1C show an example of a method of manufacturing a pressure sensor according to the present invention, and particularly, a through hole for mask alignment is formed from a step of forming an etching mask on a silicon wafer. It is a figure which shows the process until it does.

2A to 2E show a continuation of the method for manufacturing the pressure sensor, in which the diaphragm and the pressure detection element are formed from the step of forming the diaphragm etching pattern on the silicon wafer to obtain the pressure sensor. It is a figure which shows the process to.

FIG. 3 is a plan view showing a state in which a through hole is formed in a silicon wafer.

[Explanation of symbols]

1 ... Silicon wafer, 5 ... Through hole, 9 ... Diaphragm,
10 ... Pressure detection element, 14 ... Pressure sensor.

Claims (1)

[Claims] 1. A method of manufacturing a pressure sensor, wherein a pressure detecting element is provided on one side of a silicon wafer, and a diaphragm is formed by etching from the other side of the silicon wafer so as to correspond to the pressure detecting element. A method of manufacturing a pressure sensor, characterized in that at least two through holes for mask alignment are provided in a silicon wafer before forming a diaphragm.