JPH03178172A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a semiconductor pressure sensor used to measure atmospheric pressure, etc. The present invention relates to a method of forming a recess.

<Prior Art> In this type of semiconductor pressure sensor, it is important to form a diaphragm with a uniform thickness. Therefore, conventionally, the diaphragm region was formed by etching.
Furthermore, by performing the etching twice, a recessed portion of a required depth is formed on the surface of the semiconductor wafer, thereby forming a diaphragm region.

The conventional method for manufacturing a semiconductor pressure sensor is shown below in Figure 3 (a).
) to (c).

First, as shown in FIG. 3(a), a diaphragm etching mask 3 is formed on the back surface of a semiconductor wafer 2. As shown in FIG. The diaphragm etching mask 3 is formed to match the position of the diffused resistor 4 which has already been formed in the shape of a bridge on the surface of the semiconductor wafer 2.

Next, the semiconductor wafers 2 are immersed rod by rod in an etching solution (not shown) and etched to form recesses 5 on the back surface thereof (first etching).

The first etching ends before the thickness of the recess 5 reaches a predetermined value, and the semiconductor wafers 2 are lifted out of the etching solution.

Further, the thickness of each recess 5 of the semiconductor wafer 2 is measured and subtracted from the desired thickness of the diaphragm to calculate the remaining etching amount. Then, each semiconductor wafer 2 is individually precisely etched according to its respective etching amount (second etching). The bottom of the recess 5 thus formed becomes the diaphragm region 6. FIG. 3(b) Thereafter, the diaphragm etching mask 3 is removed by immersing the semiconductor wafer 2 in hydrofluoric acid or the like.

3(c) In the figure, reference numeral 7 is an oxide film formed on the surface of the semiconductor wafer 2, 8 is a metal electrode connected to the diffused resistor 4, and 9 is a glass coat covering the surface of the semiconductor wafer 2.

<Problems to be Solved by the Invention> By the way, in the conventional manufacturing method of semiconductor pressure sensors, in order to control the diaphragm thickness, etching is performed in two steps and the amount of etching is measured between the previous and subsequent etching operations. This requires a lot of work to control the diaphragm thickness, which complicates the control of the diaphragm thickness and makes it difficult to control it precisely.

The present invention has been made in view of these disadvantages, and an object of the present invention is to provide a method for manufacturing a semiconductor pressure sensor that allows the diaphragm thickness to be easily and reliably controlled.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides an oxide film on the surface of one of the semiconductor wafers consisting of a first semiconductor wafer and a second semiconductor wafer. A step of forming a layer and bonding a first semiconductor wafer and a second semiconductor wafer with this oxide film layer as a boundary, and determining the thickness of one of the bonded eleventh and second semiconductor wafers. A method for manufacturing a semiconductor pressure sensor was constructed including the steps of polishing the diaphragm to a predetermined thickness and etching a predetermined position on the surface of the other semiconductor wafer down to the oxide film layer.

<Operation> According to the above method, an oxide film layer is formed inside the bonded semiconductor wafers. Therefore, one semiconductor wafer is polished to a predetermined amount using this oxide film layer as a boundary.
The diaphragm region is formed by etching the other side down to the oxide layer.

At this time, the diaphragm thickness can be controlled by controlling the amount of polishing, and etching can be performed up to the oxide film that serves as an etching stopper.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a sectional view of this embodiment, and FIG. 2(a)
-(d) are cross-sectional views showing the manufacturing process.

The semiconductor wafer 2 of this semiconductor pressure sensor 1 consists of a first semiconductor wafer 2A and a second semiconductor wafer 2B. An oxide film layer 11 is provided inside the semiconductor wafer 2, that is, between the first semiconductor wafer 2A and the second semiconductor wafer 2B.
is formed.

The thickness of the first semiconductor wafer 2A is equal to the thickness t of the diaphragm of the semiconductor pressure sensor 1.

On the surface of the semiconductor wafer 2, a diffused resistor 4, an oxide film 7, and a metal electrode 8 arranged in a bridge shape are formed as in the conventional example, and the surface of the semiconductor wafer 2 is further covered with a glass coat 9. It is being said.

A recess 5 is formed on the back surface of the semiconductor wafer 2 at a position facing the diffused resistor 4 . The bottom of this recess 5 is the first
It reaches the bottom of the semiconductor wafer 2A, and this recess 5
The bottom of the diaphragm region 6 is the diaphragm region 6.

Next, a method of manufacturing this semiconductor pressure sensor will be explained.

First, as shown in FIG. 2(a), an oxide film layer 11 is formed on the surface of one semiconductor wafer (second semiconductor wafer 2B in this embodiment). Then, the semiconductor wafers 2A and 2B are bonded together with this oxide film layer 11 as a boundary to form the semiconductor wafer 2.

This bonding is performed, for example, as follows. That is, the first semiconductor wafer 2A and the second semiconductor wafer 2B are stacked with the oxide film layer 11 as a boundary. ±1 on the boundary surface between the eleventh second semiconductor wafers 2A and 2B.
Apply a pulse voltage of 00 to 500V. After this, 1
Heat to a maximum of 800°C while reducing the pressure to about 0-'Pa. Then, the eleventh and second semiconductor wafers 2A and 2B are bonded together. Then, in order to further strengthen the bonding, the semiconductor wafer 2 is heat-treated at about 1100° C. in an electric furnace under a nitrogen atmosphere.

As shown in FIG. 2(b), the surface of the bonded semiconductor wafers 2, that is, the surface of the first semiconductor wafer 2A, is polished to a desired thickness t of the diaphragm.

This polishing is performed by rotating the semiconductor wafer 2 on a rotating table and polishing its surface with a grinding stone or the like.

The amount of polishing can be controlled simply and reliably by controlling the polishing time, the rotation speed of the rotary table, etc. Thereafter, both the front and back surfaces of the semiconductor wafer 2 are polished to a mirror surface for pattern formation.

As shown in FIG. 2(C), on the surface of the semiconductor wafer 2, that is, on the surface of the first semiconductor wafer 2A, an oxide film 7, a diffused resistor 4 assembled in a bridge, and a metal electrode 8 are formed.
After that, the surface of the semiconductor wafer 2 is covered with a glass coat 9. Further, a diaphragm etching mask 3 is formed on the back surface of the semiconductor wafer 2, that is, on the surface of the second semiconductor wafer 2B, in alignment with the diffused resistor 4.

After forming the diaphragm etching mask 3, the second
As shown in Figure (d), a recess 5 is formed by diaphragm etching on the back side of the semiconductor wafer 2. Since the thickness of the first semiconductor wafer 2A has already been polished to the desired diaphragm thickness t, it is sufficient to perform this etching up to the oxide film layer 11. By the way, when etching reaches the oxide film layer 11, the etching rate becomes extremely slow. Therefore, the oxide film layer 11 plays the role of an etching stopper, and the amount of etching can be easily controlled.

After etching the diaphragm so that the bottom of the recess 5, that is, the entire surface of the diaphragm region 6 is etched down to the oxide film layer 11, the semiconductor wafer 2 is immersed in hydrochloric acid or the like to remove the diaphragm etching mask 3 and the recess 5. By removing the oxide film layer 11 located at the bottom of the semiconductor pressure sensor, a semiconductor pressure sensor as shown in FIG. 1 is completed.

In the above embodiment, the first semiconductor wafer 2A side was polished and the second semiconductor wafer side was etched, but conversely, the first semiconductor wafer 2A side was etched and the second semiconductor wafer side was etched. The semiconductor wafer 2B side may also be polished.

<Effects of the Invention> As described above, according to the present invention, one of the bonded first and second semiconductor wafers is polished to have the same thickness as the desired diaphragm thickness, and the other is coated with an oxide film layer. The diaphragm was formed by etching up to

Therefore, it is not necessary to control the diaphragm thickness by controlling the amount of etching as in the past, but by controlling the amount of polishing, which is simpler.
Diaphragm thickness control is now easy and reliable.

Furthermore, the amount of etching at this time can be easily controlled because the oxide film layer acts as an etching stopper.

[Brief explanation of drawings]

1 to 2 (a) to (d) relate to the present invention, FIG. 1 is a cross-sectional view thereof, and FIG. 2 (a) to (d) are cross-sectional views showing the manufacturing process thereof. . FIGS. 3(a) to 3(C) are cross-sectional views showing the manufacturing process of a conventional example. ■ l... Semiconductor pressure sensor 2... Semiconductor wafer A... First semiconductor wafer B... Second semiconductor wafer... Oxide film layer t... Thickness of diaphragm

Claims (1)

[Claims] (1) Among semiconductor wafers consisting of a first semiconductor wafer and a second semiconductor wafer, an oxide film layer is formed on the surface of one semiconductor wafer, and the first semiconductor wafer and the second semiconductor wafer are separated by forming an oxide film layer on the surface of one semiconductor wafer. a step of polishing the thickness of one of the bonded first and second semiconductor wafers to a predetermined diaphragm thickness; and a step of polishing the surface of the other semiconductor wafer. etching a predetermined position of the semiconductor pressure sensor up to the oxide film layer.