JPH01149482A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To enable the improvement of a poor yield due to a defective mask by a method wherein tantalum nitride is sputtered to form a tantalum film at a low temperature after processing of a semiconductor for the formation of a gauge is completed, the tantalum film is oxidized to form a tantalum pentoxide film, and a diaphragm is etched using the tantalum pentoxide film as a mask to form a distortion generating section. CONSTITUTION:A gauge 14n is formed on a face of a silicon wafer 19, and then wires to be joined to the gauge 14n are performed thereon as the face of the wafer 19 on which the gauge is formed is protected with a nitride film 20, and a tantalum nitride 24 is sputtered onto the rear of the wafer 19 at a low temperature with aluminum wirings 22n and 23n being joined with the gauge 14n. Then the tantalum nitride film 24 is patterned to provide two or more openings 25n. Moreover, the face of the tantalum nitride thin 24 is oxidized in an oxygen atmosphere for the formation of a tantalum pentoxide film 26. The wafer 19 is subjected to an anisotropic etching using the tantalum pentoxide film 26 as a mask so as to provide two or more recessed parts 27n to the wafer 19 for the formation of a distortion generating section 28n. By these processes, a poor yield due to a detective mask which is used for the formation of the distortion generating section can be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method of manufacturing a semiconductor pressure sensor that detects measured pressure as a change in electrical resistance corresponding to the measured pressure with a gauge formed on a silicon diaphragm. In particular, the present invention relates to a method for manufacturing a semiconductor pressure sensor, which is an improved method for manufacturing a diaphragm.

<Prior Art> FIG. 2 is a vertical cross-sectional view showing an outline of the structure of a conventional semiconductor pressure sensor, which is the basis for improving the manufacturing method of the present invention.

10 is a diaphragm made of n-type silicon single crystal and has a recess 11;
The strain-generating part 12 has a thin single crystal due to the formation of the strain-generating part 12, and a fixing part 13 around the strain-generating part 12 is formed.

A gauge 14 is installed near the boundary between the strain generating part 12 and the fixed part 13.
However, due to the diffusion of impurities, the conduction type is p-type. The upper surface of the diaphragm 10 is covered with a protective film 15 such as an oxide film (SLO2) and a nitride film to protect the gauge 14.

The fixing part 13 is fixed to a substrate 17 made of, for example, Pyrex glass, which has a through hole 16 for introducing the measurement pressure P, by anodic bonding or the like, and the substrate 17 is further bonded to a metal casing 18.

When the measurement pressure P is applied to the diaphragm 10, a strain is generated in the strain-generating portion 12, and this strain is applied to the gauge 14.
The resistance of the gauge 14 changes in response to the measured pressure P. Therefore, the measured pressure can be determined from the change in resistance of the gauge 14.

FIG. 3 is a process diagram showing an outline of the manufacturing process for manufacturing such a semiconductor pressure sensor.

In FIG. 3(A), a wafer 19 whose both sides are polished is prepared. Alternatively, the back side of a wafer that has been polished on one side is polished.

After this, as shown in FIG. 3(b), a plurality of gauges 14 n (n = 1
+2, . . . ), and cover this with an oxide film 15.

Next, as shown in FIG. 3C, nitride films 20 and 21 are formed on the upper surface of the oxide film 15 and the lower surface of the wafer 19, and
Protect 4n.

FIG. 3(d) shows the aluminum wiring process. Nitride film 20 and oxide film 15 corresponding to both ends of gauge 14 n
Patterning is performed on the substrate to form openings, and aluminum wirings 22n and 23n are formed in these portions.

Thereafter, as shown in FIG. 3(E), after patterning a strain-generating part pattern on the nitride film 21 on the side opposite to the gauge forming side so as to finally become the strain-generating part 12, potassium hydroxide ( Etch the wafer 19 with a KOH) solution to form the recesses 11.
n, thereby forming the strain-generating portion 12n.

FIG. 3(f) shows the dicing process.

Since a large number of gauges 14n are formed on the wafer 19 by the steps shown in FIGS. 3(A) to 3(E), the wafer 19 is divided into each gauge and, for example, the diaphragm 10 having the gauges 14 is cut out.

The diaphragm 10 made as described above is shown in Figure 3 (
As shown in g), it is bonded to the substrate 17 by a bonding method such as anodic bonding.

Next, the diaphragm 10 insulated by the substrate 17 is fixed to a metal housing 18.

<Problems to be Solved by the Invention> However, such a conventional method for manufacturing a semiconductor pressure sensor has the following problems.

In the etching step shown in FIG. 3 (e), the nitride film formed in step (c) is patterned and the wafer is etched with an aqueous solution of potassium hydroxide using the remaining nitride film as a mask, but the nitride film is not formed. Nitriding 1 in the manufacturing process after
21 may be damaged and pinholes may be formed, as shown in FIG. 3 (e), resulting in an insufficient mask during the process. If a nitride film is formed immediately before this etching step, this problem will not occur, but since the nitride film is formed at a temperature of about 100°F, aluminum wiring with a melting point of 660°C is not exposed to the nitride film. A new problem arises in that it cannot be done before formation.

Means for Solving the Problems> In order to solve the above problems, the present invention forms a gauge on one side of a silicon wafer and then protects the gauge forming surface of the wafer with a nitride film. Wiring to connect to the gauge is applied from above the lever, and then tantalum nitride is sputtered on the other side of the wafer at a low temperature, and the tantalum nitride film is patterned to form a predetermined pattern of strain-generating parts. Then, the remaining surface is oxidized to form a tantalum pentoxide film, which is used as a mask to etch the other surface to form a thin strain-generating portion that is distorted by the measurement pressure.

After the semiconductor process for forming the gauge is completed, tantalum nitride is sputtered at low temperature to form a tantalum film, which is then oxidized to form a tantalum pentoxide film, which is used as a mask for etching to create a diaphragm. Create a distorted part. By taking such a step, yield defects due to mask defects can be eliminated.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a manufacturing process diagram showing one embodiment of the present invention.

The steps from FIG. 1 (a) to (c) are the same as the steps from FIG. 3 (a) to (c).

In the step of FIG. 1(d), the nitride film 21 formed on the lower surface of the wafer 19 in the step of FIG. 1(c) is removed.

Next, in the aluminum wiring step shown in FIG. 1(e), aluminum wirings 22n and 23n are formed at both ends of the gauge 14n with the nitride film 21 removed.

Furthermore, as shown in FIG. 1(f), tantalum nitride 24 is sputtered at a low temperature onto the lower surface of the wafer 19 with the aluminum wires 22n and 23n bonded to the gauge 14n.

After this, in the patterning step shown in FIG. 1(g), the tantalum nitride 24 film is patterned by plasma etching using CF4, and a plurality of openings 25n are formed to have the shape of the strain-generating portion to be finally formed. will be established.

Furthermore, in the oxidation step shown in Figure 1 (h),
The surface is oxidized in an oxygen atmosphere at 00''C to form tantalum pentoxide JIi26, which is resistant to strong alkalis.

Next, in the etching process shown in FIG. 1, using the tantalum pentoxide 26 as a mask, anisotropic etching is performed using a solution of potassium hydroxide (KOH) to create a plurality of recesses 27n in the wafer 19 and to form strain-generating portions. 28n is formed.

After this, the wafer 19 is diced and divided into a plurality of diaphragms 29n (FIG. 1(N)), and one of them, for example, the diaphragm 29, is bonded to the substrate 17 by anodic bonding or the like as shown in FIG. 1(R). Join.

In the manner described above, semiconductor pressure sensors can be manufactured in large quantities and easily.

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, after the semiconductor process for forming the gauge is completed, tantalum nitride is sputtered at a low temperature to form a tantalum film, and then the tantalum film is oxidized. A film of tantalum pentoxide that can withstand strong alkalinity is formed, and this film is used as a mask and etched to create a strain-generating portion in the diaphragm. Therefore, yield defects due to mask defects that form strain-generating portions can be eliminated.

[Brief explanation of the drawing]

Fig. 1 is a manufacturing process diagram showing one embodiment of the present invention, Fig. 2 is a vertical cross-sectional view showing the configuration of a conventional semiconductor pressure sensor, and Fig. 3 is a manufacturing process for manufacturing the semiconductor pressure sensor shown in Fig. 2. It is a diagram. 10...Diaphragm, 11.27n...Recess, 1
2.12n, 28n... strain generating part, 14.14n...
Gauge, 19... Wafer, 20.21... Nitride film,
22n, 23n... electrode, 24... tantalum nitride film, 25n... opening, 26... tantalum pentoxide film,
28n...Strain-generating portion, 29...Diaphragm. Figure 1 Figure 1 2q ]b Figure 2 - 1511 Salary Figure 3 Figure 3

Claims (1)

[Claims] After forming the gauge on one side of the silicon wafer,
The gauge forming surface of this wafer is protected with a nitride film, and wiring to connect to the gauge is applied from above, and then tantalum nitride is sputtered at a low temperature on the other surface of the wafer, and then a predetermined strain-generating part pattern is formed. This tantalum nitride film is patterned so that the remaining surface is oxidized to form a tantalum pentoxide film, and the other surface is etched using this as a mask to form a thin wall that is distorted by the measurement pressure. Method for manufacturing a semiconductor pressure sensor characterized by forming a strain-generating portion