JPH06104454A - Manufacture of semiconductor sensor - Google Patents

Abstract

PURPOSE:To enable diaphragms for every chip to be formed uniformly to a desired thickness. CONSTITUTION:This manufacture comprises the following: the step to form an epitaxial crystal growth layer 10 over the whole face of a silicon substrate 1; the step to form two passivation films 2, 6 over both faces of the substrate 1; the step to form predetermined patterns to both passivation films 2, 6, to form an external extraction electrode 11 to a wafer edge on a crystal growth layer 10 and a conductor 16 made of a metal or a low resistance semiconductor to the periphery of a chip top face, and to connect the external extraction electrode 11 and the conductor 16; the step to form a diaphragm 5 for every chip by dipping the substrate 1 into an etchant, by etching with DC voltage impressed using the electrode 11 and the conductor 16 as the anode and an etching electrode as the cathode, and by stopping the progress of etching at the boundary face between the substrate 1 and the crystal growth layer 10; and the step to form a gage resistor 3 by diffusing impurities into the crystal growth layer 10.

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 semiconductor force sensor such as a pressure sensor, an acceleration sensor, a flow rate sensor and a humidity sensor, which forms a diaphragm by an electrochemical etching stop method.

[0002]

2. Description of the Related Art A conventional semiconductor force sensor, for example, a semiconductor pressure sensor will be described with reference to FIGS. First, in FIG. 5 showing the semiconductor pressure sensor, 1
Is a silicon substrate (hereinafter referred to as Si substrate), 2 is a SiO ₂ film formed on the Si substrate 1 and protecting the Si substrate 1, 3
Is a gauge resistance portion formed by diffusing impurities on the Si substrate 1 and 4 is an Al bonding pad formed on the Si substrate 1. Wire bonding is performed with an external terminal to take out an output. Reference numeral 5 is a diaphragm formed under the Si substrate 1 by etching.

When pressure is applied to this semiconductor pressure sensor, the diaphragm 5 is bent and distorted, and the stress generated by the distortion changes the resistance of the gauge resistor 3 due to the piezo effect, and the pressure can be taken out as an electric signal. The amount of change in resistance of the gauge resistor 3 is proportional to the amount of stress that is generated, the amount of stress is proportional to the area of the diaphragm 5, and is inversely proportional to the square of the thickness of the diaphragm 5. Therefore, it is important to reduce the thickness of the diaphragm 5 in order to increase the sensitivity to pressure.

Next, a manufacturing method will be described with reference to FIG. First, as shown in FIG. 6A, a SiO ₂ film 2 having a required thickness is formed on both surfaces of an n-type Si substrate 1, and then, as shown in FIG.
As shown in FIG. 6B, a SiN film 6 serving as an etching mask is formed on the SiO ₂ film 2 by a CVD method, and the SiN film 6 is formed by a photolithography technique as shown in FIG. 6C.
Are formed into a predetermined pattern.

Next, anisotropic etching is performed using a potassium hydroxide (KOH) aqueous solution to form the diaphragm 5 shown in FIG. 6D. After that, as shown in FIG. 6E, unnecessary S
The iN film 6 is removed.

Here, the anisotropic etching will be described in detail. 7 is a hot water washing machine kept at 80 ° C., 8 is a Teflon beaker put in the hot water washing machine 7, 9 is 2 of the Teflon beakers 8.
It is a 0% KOH aqueous solution.

When the patterned wafer is put into the Teflon beaker 8, the Si substrate 1 is etched at an etching rate of about 1 μm / min. A thick diaphragm structure is completed.

However, in this method, a thickness variation of ± 3 μm is always caused, and this variation causes variations in the characteristics of the semiconductor pressure sensor. Therefore, it is not possible to manufacture a thin diaphragm 5 by this method. Not practical.

Therefore, a manufacturing method by the electrochemical etching stop method is performed, and this manufacturing method will be described with reference to FIGS. 8 and 9. In these drawings, the same reference numerals as those in FIGS. 5 to 7 indicate the same or corresponding ones.

Reference numeral 10 is an n-type Si epitaxial crystal growth layer formed on one surface of the Si substrate 1, and 11 is a crystal growth layer 10.
It is an external extraction electrode formed at the edge of the upper wafer.

Then, as shown in FIG. 8A, an n-type Si epitaxial crystal growth layer 10 having a target thickness is formed on one surface of the p-type Si substrate 1, and an S-type epitaxial layer is formed on both surfaces of the Si substrate 1.
The iO ₂ film 2 is formed. Next, as shown in FIG. 8B, a SiN film 6 serving as an etching mask is deposited by a CVD method, and as shown in FIG. 8C, the SiN film 6 is formed into a predetermined pattern by a photolithography technique. Next, as shown in FIG. 8D, 1% Sb-containing Au is vapor-deposited, and the external extraction electrode 11 used for the electrochemical etching stop method is formed around the wafer by photolithography. Then, as shown in FIG. 8E, anisotropic etching is performed by an electrochemical etching stop method in a KOH aqueous solution,
The diaphragm 5 is formed. After that, as shown in FIG. 8F, the unnecessary SiN film 6 is removed.

Next, the electrochemical etching stop method will be described in detail. Reference numeral 12 is a sealing jig for fixing the patterned wafer, 13 and 14 are Pt electrodes serving as a silver chloride reference electrode and an etching electrode, which are charged in a 30% KOH aqueous solution in a Teflon beaker 8, and 15 is a potentiostat. Is a voltage regulator called the both electrodes 13, 1
4 is connected.

Then, the temperature is kept at 65 ° C. by the hot water washing machine 7,
When the wafer fixed to the sealing jig 12 is put into the Teflon beaker 8 and a DC voltage is applied with the external extraction electrode 11 as an anode and the Pt electrode 14 as a cathode, the Si substrate 1 is etched at an etching rate of about 1 μm / min. Is etched and reaches the pn junction surface, a current rapidly flows from the external extraction electrode 11 toward the surface to be etched, and an anodic oxide film is formed on the etching surface of the diaphragm 5, that is, the pn junction surface. Will stop the etching. in this case,
The variation in the thickness of the diaphragm is ± 1 μm.

Further, as another conventional example, Japanese Patent Publication No. 3-40
In the manufacturing method described in Japanese Patent Publication No. 959 (H01L 29/84), a low impurity concentration layer is formed on one surface of a high impurity concentration silicon substrate, a gauge resistance is formed on this low impurity concentration layer, and the other surface of the substrate is formed. A SiO ₂ film and a gold alloy film containing chromium are formed, and a diaphragm is formed by an electrochemical etching stop method.

[0015]

In the conventional manufacturing method by the electrochemical etching stop method shown in FIG.
When a diaphragm having a thickness of m or less is formed, as the distance from the external extraction electrode 11 at the wafer edge to the diaphragm 5 of each element increases, the epitaxial crystal growth layer 10
There is a problem that the device itself becomes a resistor, a voltage drop occurs, a current required for anodic oxidation cannot flow, etching does not stop, and a diaphragm 5 having a desired thickness cannot be obtained.

Further, according to the manufacturing method by the electrochemical etching stop method of Japanese Patent Publication No. 3-40959, the Si substrate
Since the voltage is applied only to the locations, no voltage is applied to each element, and a voltage drop occurs as the distance from the location to which the voltage is applied increases in the Si substrate, and the diaphragm of each element There is a problem that the thickness cannot be formed uniformly. An object of the present invention is to provide a method for manufacturing a semiconductor force sensor in which the diaphragm of each chip can be uniformly formed to a desired thickness in view of the above points.

[0017]

In order to solve the above problems, a method of manufacturing a semiconductor force sensor according to the present invention comprises a step of forming an epitaxial crystal growth layer on one surface of a silicon substrate and two layers on both surfaces of the substrate. Step 2 of forming a protective film
A predetermined pattern is formed on the protective film of the layer, an external extraction electrode is formed on the edge of the wafer on the crystal growth layer, and a conductor made of metal or a low resistance semiconductor is formed around the upper surface of the chip to connect the external extraction electrode and the conductor. The step of connecting, the substrate is immersed in an etching solution, the electrodes and conductors are used as the anode, and the etching electrode is used as the cathode to apply a DC voltage for etching, and the progress of etching is stopped at the interface between the substrate and the crystal growth layer. And forming a diaphragm for each chip, and a step of diffusing impurities in the crystal growth layer to form a gauge resistance. Further, the surface of the external extraction electrode and the conductor made of metal is made of gold.

[0018]

According to the method of manufacturing a semiconductor force sensor of the present invention having the above-described structure, the epitaxial crystal growth layer is formed on one surface of the silicon substrate, and the external extraction electrode and the chip upper surface are formed on the edge of the wafer on the crystal growth layer. Since a conductor made of metal or low-resistance semiconductor is formed around the periphery to connect the conductor to the external extraction electrode, the distance to the diaphragm is not from the periphery of the wafer but from the periphery of the chip, and the distance is extremely small. The current required for anodic oxidation is supplied from the conductor, the voltage drop due to the resistor in the crystal growth layer itself can be ignored, etching can be stopped at the bonding surface between the substrate and the crystal growth layer, and the diaphragm has the desired thickness. Can be uniformly formed, the variation in sensor characteristics can be reduced, and the yield can be improved.

Further, the conductor serves as a mark for separating the chips, and the workability at the time of separating the chips is improved.

Furthermore, since the surface of the external extraction electrode and the conductor made of metal is made of gold, it is resistant to acids and alkalis and is not immersed in the KOH aqueous solution.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment will be described with reference to FIGS. In these drawings, the same reference numerals as those in FIGS. 5 to 9 designate the same or corresponding parts, and FIGS.
2 is that a conductor 16 made of metal is formed around the upper surface of the chip, and a manufacturing method will be described next.

The manufacturing steps of FIGS.
As shown in FIG. 1D, Cr 100 nm and Au 300 nm are vapor-deposited on the crystal growth layer 10, and the external extraction electrode 11 and the chip are formed on the edge of the wafer on the crystal growth layer 10 by photolithography as shown in FIG. 1D. A conductor 16 is formed around the upper surface, and then, as shown in FIG. 1E, a diaphragm 5 is formed by an electrochemical etching stop method as in the conventional example, and thereafter, an unnecessary SiN film is formed as shown in FIG. 1F. Remove 6.

Next, another embodiment will be described with reference to FIG. In the figure, the same reference numerals as those in FIGS. 1 and 2 denote the same or corresponding parts, and the difference from FIG. 1 is that the conductor 16 made of a metal is a conductor made of a low resistance semiconductor. Is a process similar to that of FIG. 1, and as shown in FIG. 4D, ion implantation is performed on the crystal growth layer 10 to form the conductor 17 of the n ⁺ layer. Then, as shown in FIG. 4E, the SiO ₂ film 2 and the SiN film 6 on the crystal growth layer 10 are removed, and thereafter, as shown in FIG.
_{2 The} film 2 is laminated on the conductor 17, and the diaphragm 5 is formed by the electrochemical etching stop method.
The film 6 is removed.

[0024]

Since the present invention is constructed as described above, it has the following effects. According to the method for manufacturing a semiconductor force sensor of the present invention, the epitaxial crystal growth layer 10 is formed on one surface of the silicon substrate 1, and the crystal growth layer 10 is formed.
The outer extraction electrode 11 is formed at the end of the upper wafer, and the conductors 16 and 17 made of a metal or a low resistance semiconductor are formed around the upper surface of the chip so that the outer extraction electrode 11 and the conductors 16 and 17 are connected to each other. The distance to 5 is from the periphery of the chip as compared to the conventional periphery of the wafer,
The distance is extremely small, a current required for anodic oxidation can be supplied from the conductors 16 and 17, the voltage drop due to the resistor of the crystal growth layer 10 itself can be ignored, and the substrate 1 and the crystal growth layer can be grown. Etching can be stopped at the bonding surface with the layer 10, the diaphragm 5 can be uniformly formed to a desired thickness, the characteristic variation of the sensor can be reduced, and the yield can be improved.

Further, the conductors 16 and 17 serve as marks when the chips are separated, and the workability when separating the chips can be improved.

Furthermore, since the surfaces of the external extraction electrode 11 and the conductor 16 made of metal are made of gold, they are resistant to acids and alkalis and are not attacked by the KOH aqueous solution.

[Brief description of drawings]

1A to 1F are process diagrams of one embodiment of the present invention.

FIG. 2 is a plan view of a completed state of one embodiment of the present invention.

FIG. 3 is a cut front view of one process of one embodiment of the present invention.

4A to 4F are process diagrams of another embodiment of the present invention.

FIG. 5 is a partially cutaway perspective view of a conventional force sensor.

6A to 6E are process diagrams of a conventional example.

FIG. 7 is a cut front view of one step of a conventional example.

8A to 8F are process diagrams of another conventional example.

FIG. 9 is a cut front view of a step of another conventional example.

[Explanation of symbols]

1 Silicon Substrate 2 SiO ₂ Film 3 Gauge Resistor 5 Diaphragm 6 SiN Film 10 Crystal Growth Layer 11 External Extraction Electrode 16 Conductor 17 Conductor

Claims (2)

[Claims] 1. A step of forming an epitaxial crystal growth layer on one surface of a silicon substrate, a step of forming two layers of protective films on both sides of the substrate, and a step of forming a predetermined pattern on both of the two layers of protective films. An external extraction electrode is formed on the edge of the wafer on the crystal growth layer, and a conductor made of a metal or a low resistance semiconductor is formed around the upper surface of the chip.
A step of connecting the external extraction electrode and the conductor; and immersing the substrate in an etching solution, etching by applying a DC voltage with the electrode and the conductor as an anode and the etching electrode as a cathode, And a step of forming a diaphragm for each chip by stopping the progress of etching at the interface between the crystal growth layer and a step of forming a gauge resistance by diffusing impurities in the crystal growth layer. Production method. 2. The method for manufacturing a semiconductor force sensor according to claim 1, wherein the surface of the external extraction electrode and the conductor made of metal is gold.