JPS62188281A - Manufacture of semiconductor strain gauge - Google Patents

Abstract

PURPOSE:To enable the holding process to be performed without etching an Al electrode by a method wherein hydrazine is used for an etching as a means to make a hole for directly bonding a glass rod on a cantilever type semiconductor strain gauge. CONSTITUTION:In case of making a contact hole 16, an oxide film 13 on a holding part 11 is simultaneously removed because hydrazine etching can not be processed even if there is a bit of residual oxide film 13. Besides, most of the oxide film on the holding part 11 shall be removed before Al evaporation since fluoric acid used for removing the oxide film 13 simultaneously etches an Al interconnection 18 (electrode part). Finally, the Al interconnection 18 is formed by Al evaporation 17, interconnection patterning and etching process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor strain gauge, and more particularly to a method for forming a through hole in a cantilever type semiconductor strain gauge.

[Prior Art] Cantilever type semiconductor strain gauges are widely used in pressure quadrature transducers such as invasive blood pressure transducers for living bodies. This pressure transducer is generally constructed as shown in FIG. In other words, a pressure-sensitive rod 2 is placed at the center of a diaphragm 1 that is displaced in response to pressure.
, one end of the glass rod 3 is glued to the pressure sensitive rod 2, and the other end of the glass rod 3 is attached to the glass rod holder 4.
The gauge 6 is roughly glued to the relay fitting 5 via the relay fitting 5. and diaphragm 1
When the pressure received by the gauge 6 is transmitted to the gauge 6, the gauge 6 is deflected, and the resistance value of a diffusion resistor (not shown) provided near the part where the gauge 6 is fixed to the main body 7 changes. By connecting these resistors in a bridge manner, an output signal proportional to the pressure is outputted.

According to the pressure transducer described above, a pressure sensitive rod 2, a glass rod 3, a glass rod holder 4, and a relay fitting 5 are interposed between the diaphragm 1 and the gauge 6, and each is connected by welding or adhesive. ing. Because of the large number of parts and bonding, there was a problem in that the sensitivity and temperature zero point changed, causing the pressure signal to deviate from the theoretical value and the measured values to vary.

In order to solve this problem, as shown in FIG. The transmission mechanism is simplified and the number of adhesives is reduced, so the sensitivity and temperature zero point changes mentioned above are reduced, and the pressure signal]!!
! It approaches the theoretical value and the variation in measured values decreases. Since the structure is much simpler, the time required for bonding is also reduced, leading to improved yields and productivity.

Conventionally, there have been two methods for drilling holes in such gauges, as described below. The first method is to make holes in the first step of the process, and is carried out by the steps shown in FIG. That is, in (a), an oxide film 10 of 5i02 is formed on both sides of the silicon substrate 9,
In (b), the oxide film 10 is patterned with a hole 11 by a photolithography method (hereinafter simply referred to as patterning) comprising steps such as photoresist application, exposure through a photomask, development, etching, and resist peeling. . Next, in (C), using this oxide film 10 as a mask, etching is performed with an alkaline solution to form holes 12, and in (d), the oxide film 10 is removed. Next, in (e), an oxide film 13 is formed again, in (e), this oxide film 13 is patterned with a diffusion portion 14, and in (g), a diffusion layer 15 is formed.

Contact hole 16 is formed in (h) by similar means.
, perform ^1 steaming 17 in (i), and (j
), the A1 wiring portion is patterned and then etched to form the A1 wiring 18.

In the second method, the diffusion layer 15, contact hole 16 and A1 are formed by steps (e) to (j) in the first method.
This is a method in which holes are formed after each wiring 18 is formed. At this time, the holes were made after the A1 wiring was covered with a film such as a low-temperature oxide film or wax that would not be corroded by an etching solution, and this film was removed after the holes were drilled.

[Problems to be Solved by the Invention] However, in the first method described above, the perforated diffusion layer 15, the contacts 1 to 16 and the A1 wiring 18
A photo-etching process is required to form each photo-etching process, and resist is applied each time, but since holes 12 have already been formed in the substrate 9, the resist cannot be applied smoothly in these areas, resulting in poor accuracy. In the second method, which had the problem of low yield, the etching solution is usually a mixture of ethylenediamine, pyroalcohol, and water mixed with a small amount of pyrazine and heated to about 110 to 120'C. Since low-temperature oxide films, wax, and the like are difficult to withstand etching, there is a problem in that the yield rate decreases. There is also a method of heating a potassium hydroxide solution to about 80 to 90° C., but since alkali ions mix into the gauge 6 and have an adverse effect, no improvement in yield can be expected. This method also forms an etching-resistant film,
There is also the problem that the process is complicated and the cost is high because the process of removing the film again after etching is necessary.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a method for manufacturing a semiconductor strain gauge, which allows holes to be formed in a gauge with a simple process and a high yield.

[Means for Solving the Problems] The present invention uses a wave-making method for semiconductor strain gauges in which the displacement of a diaphragm that is displaced in response to pressure is transmitted via an insulating rod. forming an aluminum electrode part and a diffusion layer through an oxide film, connecting these electrode parts and the diffusion layer through a contact hole formed in the oxide film, and inserting the insulating rod into the substrate. Holes for adhesion are formed by etching with a hydrazine solution.

[Operation] According to the above method, since the hydrazine solution hardly corrodes aluminum, the etching process can be performed with a good yield without forming a special etching-resistant resist film on the aluminum electrode. can.

[Example] Hereinafter, an example of the tea method for a semiconductor strain gauge according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In this figure, the sixth
Parts not shown in the figures that are the same as those of the conventional example are designated by the same reference numerals.
The explanation will be omitted. The step (a) of forming the oxide film 13 on the substrate 9, the step (b) of patterning the diffusion portion 14, and the step (C) of forming the diffusion layer 15 are respectively the steps (e) of the conventional example shown in FIG. This is the same as (f) and ((+). At the time of forming the contact hole 16 in step (d), the oxide film 13 on the hole (hole 11) is removed at the same time. This is due to the hydrazine etching described later. Sometimes, if even a small amount of the oxide film 13 remains, it will not be etched.
This is because it is necessary to completely remove the Furthermore, hydrofluoric acid is used to remove this oxide film 13, but since this hydrofluoric acid will etch the oxide film 18, in order to prevent this, the oxide film of the portion 11 should be removed to a large extent before the AI evaporation. Part of it needs to be removed. Next, in steps (e) and (f), A1 vapor deposition 17, wiring patterning, and etching are performed, respectively, to form A1 wiring 18. The wafer at this stage is placed in air or in an oxygen mixture (for example, 02:N2=
1:4) at about 200'C for about 2 hours to slightly oxidize the hemisurface. This is to increase the etching resistance against drazine and to increase the wettability of the resist during the resist coating process. Next, resist is applied to both sides of this wafer.

The resist used at this time is one with high viscosity, such as 0MR83,100CPS manufactured by Tokyo Ohka. This is because the thickness of the vapor-deposited layer is about 1.5 μm, and if a low-viscosity resist 1 is used, there is a possibility that a step breakage will occur.

After applying the resist, the perforated portions 11 are patterned by conventional means, and then the resist is peeled off. As the resist stripping agent used at this time, it is desirable to use a lolobenzene-based resist stripper, such as Resist Stripper #502 manufactured by Tokyo Ohka Co., Ltd., heated to about 110°C. Then, within about 30 minutes after the resist is removed, the next step ((1), hydrazine etching) is performed.

The time between resist stripping and hydrazine etching is made as short as possible in order to prevent formation of an oxide film on the perforated portion 11.

For hydrazine etching, the ratio of hydrazine to water is approximately 1:1.
The solution was run in a reflux mold heated to 100°C to 120'C while bubbling N2 at 31/min. N2 bubbling is performed to increase the uniformity of etching and to prevent explosion of explosive hydrazine. For example, Tokyo Ohkaso OAP is applied to the surface after etching.
Apply hexamethyldisilaryne such as Nato,
dry.

This treatment roughens the surface of the oxide film 13 and prevents water from easily adhering to it, forming silanol groups, and increasing leakage current.

According to this embodiment, A
After forming the group I electrodes, I used a hydrazine solution as an etching solution, which does not easily dissolve A1, in order to open the hole 8 for inserting the glass rod 3 of the pressure transducer. Drilling can be performed relatively easily without forming a resist film with good etching resistance. Furthermore, since the A1 wiring is not etched, the production yield of the gauge can be improved.

In the above-mentioned embodiment, the case where the diffusion layer 15 is provided only directly under the contact 1 to the hole 16 as shown in FIG. 2 has been described, but as shown in FIG. 15 may be formed, and in this case, the effect of preventing leakage current deterioration is greater. The reason for this is that in the case of the structure shown in FIG. 2, although the oxide film 13 exists under the A1 wiring 18 drawn out from the diffusion layer 15, the diffusion layer 15 exists and the contact hole 16 is It is assumed that a pinhole 19 is generated in the oxide film 13 during formation. At this time, if this pinhole 19 overlaps with the pinhole 20 generated in the A1 wiring 18, the etching may proceed to the substrate 9 through the pinhole 19, 20 due to hydrazine etching. At this time, the Au lead wire 21 mounted on the A1 wiring directly connects to the substrate 9.
leakage current will deteriorate. Even in such a case, if the diffusion layer 15 is formed on the entire lower part of the A1 wiring 18 as shown in FIG. 3, the Au lead wire 21 will directly contact the substrate 9 even if the pinhole 19. This prevents deterioration of leakage current.

[Effects of the Invention] As described above, according to the present invention, hydrazine is used as an etching solution as a means for forming a hole for directly bonding a glass rod to a gauge of a cantilever type semiconductor strain gauge. Holes can be formed relatively easily without etching the electrodes, improving product precision and yield.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing steps according to an embodiment of the method for manufacturing a semiconductor strain gauge according to the present invention, Figures 2 and 3 are cross-sectional views illustrating another embodiment of the present invention, and Figures 4 and FIG. 5 is a cross-sectional view showing a semiconductor strain gauge, and FIG. 6 is a cross-sectional view showing steps in a conventional method for manufacturing a semiconductor strain gauge.

Claims (2)

[Claims] (1) In a method for manufacturing a semiconductor strain gauge in which the displacement of a diaphragm that is displaced in response to pressure is transmitted via an insulating rod, an aluminum electrode portion and a diffusion layer are formed on the substrate of the strain gauge via an oxide film. These electrode parts and the diffusion layer were connected through a contact hole formed in the oxide film, and a hole for inserting and mounting the insulating rod into the substrate was formed by etching with a hydrazine solution. A method for manufacturing a semiconductor strain gauge, characterized by: (2) The method of manufacturing a semiconductor strain gauge according to claim 1, wherein the diffusion diagram is formed at a position aligned with the lower part of the entire surface of the electrode portion on the substrate.