JPS63168054A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To improve sensitivity and to contrive to reduce a cost by mass production by a method wherein a thick Si substrate is bonded to an Si sensor substrate, the sensor substrate is polished to a prescribed thickness and after a base plate having penetrating holes is bonded to the sensor substrate is removed and pressure gauges are formed at prescribed positions. CONSTITUTION:An oxide film 22 is formed on an Si sensor substrate 21 and a thick supporting substrate 23 is bonded to the substrate 21 through the film 22. The substrate 21 is polished to shave its thickness (t) to 50-300mum. Then, penetrating holes 25 and 26 are made in an Si base plate 24 and with a shattered layer at the time of processing of the holes removed by chemical etching, square parts are each formed at the upper parts 25a and 26a of the holes 25 and 26. The substrate 21 and the plate 24 are bonded together by heating through an oxide film 27. The oxide film 22 is removed, gauges 28 and 29, whose pressures are changed by applying measuring pressure, are formed by an ion-implantation method and so on and the whole surface is covered with a protective oxide film 30. This structure is split into plural pieces to use as pressure sensors 31 and 32.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a method for manufacturing a semiconductor pressure sensor in which measured pressure is detected 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 sectional view showing the structure of a conventional semiconductor pressure sensor.

10 is a diaphragm made of n-type silicon single crystal and has four parts 11;
Due to the formation of part 1, the thickness of the part 11 becomes thinner
and a fixed part 13 around it.

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 n-type. The upper surface of the diaphragm 10 is covered with an oxide layer (S(02>15) to protect the gauge 14.

The fixing part 13 is fixed to a silicon substrate 17 having an opening 1G through which the measurement pressure P is introduced, for example, by anodic bonding via a glass mold, and the substrate 17 is further bonded to a metal casing 18. There is.

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 process for manufacturing such a semiconductor pressure sensor.

FIG. 3(a) shows a step of forming a gauge 14 that senses the measured pressure by diffusing, for example, a p-type impurity in a predetermined position of an n-type silicon substrate 19, and covering the gauge 14 with an oxide film 15. ing.

Thereafter, as shown in FIG. 3(b), four parts 11 are formed by grinding or etching on the opposite side of the silicon substrate 19 from the side on which the gauge is formed, thereby forming the strain-generating part 12.

The diaphragm 10 made as described above is shown in Figure 3 (
As shown in c), 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 connected to the substrate 1
It is fixed to a metal casing 18 via 7 (FIG. 3(d)).

The semiconductor pressure sensor shown in FIG. 2 is manufactured through the steps outlined above.

<Problems to be Solved by the Invention> However, such conventional methods of manufacturing semiconductor pressure pins have the following problems.

(a) When forming the recess 11 by grinding, especially when the pressure range is low, the silicon substrate 19 with a thickness of 300 to 500 μm should be formed with a thickness of 50 μm! Therefore, it is difficult to accurately control the thickness of the strain-generating portion 12.

Further, in the case of grinding, as shown in FIG. 5, protrusions 20 tend to remain at the bottom of the strain-generating portion, making it difficult to process it flat.

Furthermore, since it is not possible to form a large number of dies 11 and flamms 10 by forming a plurality of holes on the silicon substrate 19 with a wide bottom surface, it is difficult to reduce costs through ceiling-mounted production. Historically, it has become necessary to protect the forming surface of the gauge 14 from vibrations during processing.

(b) When forming the recess 11 by etching, it is not possible to form a circular hole when using anisotropic etching, and it is not possible to form a deep hole when using isotropic etching.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention provides a sensor by bonding a thick silicon support substrate to a silicon sensor substrate. After polishing the substrate to a predetermined thickness, a silicon base plate with a through hole for introducing measurement pressure is bonded to the sensor substrate, the support substrate is removed, and the measurement pressure is applied to a predetermined position on the sensor substrate. A semiconductor pressure sensor is manufactured by forming a gauge whose resistance value changes according to the method.

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

FIG. 1 is a process diagram showing a manufacturing process according to an embodiment of the present invention.

As shown in FIG. 1(A), an oxide film <St 02 > with a thickness of about 1 μm is formed on the sensor substrate 21 made of silicon.
22 is formed by, for example, a thermal oxidation method. Next, a thick supporting substrate 23 made of silicon is bonded via the oxidized pIQ 22 (FIG. 1(c)).

Thereafter, as shown in FIG. 1), the sensor substrate 21 is polished to a thickness t of 50 to 300 μm, which is the appropriate thickness of dixiphram.

Next, as shown in FIG. 1(E), through holes 25 and 26 for introducing the measurement pressure P are formed in the base plate 24 made of thick single crystal silicon.

The through holes 25 and 26 can be formed easily and in a short time by using a one-shot blast or a grinding machine. After this, the crushed layer on the circumferential surface of the through-holes 25 and 26, which was created when drilling the through-holes 25 and 26, is removed by chemical etching, and as shown in FIG.
In order to clarify the fulcrum of the strain-generating part, the through hole 2
5. Perform patterning on the -E parts 25a and 268 of 26 to step the corners.

The sensor substrate 21 and the base plate 1-24, which have been polished to a thickness t in the bonding step shown in FIG.

Next, the thick support substrate 23 is removed by, for example, chemical etching that takes advantage of the difference in etching rate (FIG. 1(d)).

Thereafter, the oxide film 22 is removed, and gauges 28 and 29 whose resistance value changes upon application of measurement pressure P are formed at predetermined positions on the sensor substrate 21 with a predetermined thickness by, for example, ion implantation. The gauges 28 and 29 are covered with an oxide film 30 to protect them (see FIG. 1).

After this, in the dicing process shown in Figure 1 (N)? It is divided into several Q pieces, each serving as a pressure sensor 31 and 32.

Although the oxide films 22 and 27 are bonded in the bonding process shown in FIGS. They may also be bonded by a wafer bonding method in which they are directly bonded. For this joining, each joint surface is polished to a mirror finish, and each of these polished surfaces is soaked in a mixture of sulfuric acid and hydrogen peroxide to make it hydrophilic. These bonding surfaces are directly brought into close contact and heated to bond each other under conditions that do not mix.

In the explanation so far, only a gauge is formed on the parking plate 21, but this is not limited to this.For example, in addition to the gauge, it is also possible to drive the gauge, amplify its output, and perform signal processing. The processing circuits may be formed in the same f-tube L.

・,: Effects of the Invention> As specifically explained above with the examples, the manufacturing method of the present invention has various effects as described below.

(a) Since the support substrate has sufficient thickness, it is possible to grind the entire surface of the sensor substrate uniformly and to a thin layer. Therefore, the diaphragm can be made thinner to a degree (for example, about 2 μm) that is slightly thicker than the junction depth of the diffused resistor forming and covering the gauge.

Therefore, the sensitivity can be increased, making it possible to realize a low-pressure nor-range sensor, and the diameter of the diaphragm can also be made smaller, so the chip area can be reduced.

(b) All processes can be performed in units of eight wafers, so production can be done by one person, and economies of scale can be easily achieved by increasing the size of the wafers. Therefore, cost reduction is easy.

(c) According to the present invention, since the base plate can be made thicker, it is possible to reduce the temperature pillow point error caused by the difference in coefficient of thermal expansion even when the sensor substrate is bonded to the base plate.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a vJ manufacturing method according to an embodiment of the present invention;
Fig. 2 is a vertical cross-sectional view showing the structure of a conventional semiconductor pressure sensor, Fig. 3 is a process diagram showing the process of manufacturing the semiconductor pressure sensor shown in Fig. 2, and Fig. 4 is a semiconductor pressure sensor based on Fig. 2. There is an explanatory diagram r explaining the problem. 10,...diaphragm, 11...recess, 12...
・Strain part, 14.28.29... Gauge, 17...
Substrate, 18,... Housing, 21... Sensor board, 23
...Support board, 24...Base plate, 25.2
G... Mouth hole, 28.29... Gauge, 31.32
...Pressure Kasenza.

Claims (1)

[Claims] A thick silicon support substrate is bonded to a sensor substrate made of silicon, and after polishing the sensor substrate to a specified thickness, a silicon base with a through hole for introducing measurement pressure is formed. Manufacture of a semiconductor pressure sensor, characterized in that after bonding a boot to the sensor substrate and removing the support substrate, a gauge whose resistance value changes upon application of the measurement pressure is formed at a predetermined position on the sensor substrate. Method.