JPH06222040A - Fabrication of solid electrolyte oxygen concentration sensor - Google Patents

Abstract

PURPOSE:To provide a novel method for fabricating a solid electrolyte oxygen concentration sensor. CONSTITUTION:A lower electrode film 2, a solid electrolyte film 3, and an upper electrode film 4 are formed sequentially on a silicon substrate 1. A pinhole 5 is then made through the lower electrode film 2, the solid electrolyte film 3, and the upper electrode film 4. Furthermore, a sacrifice film 7 is formed on the upper electrode film 4 followed by formation of a hollow wall film 8 covering the sacrifice film 7. Etching is then performed from the rear side of the silicon substrate 1 to the pinhole 5 and the sacrifice film 7 above the upper electrode film 4 is removed by etching through the pinhole 5 thus forming a hollow part 12.

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 solid electrolyte oxygen concentration sensor.

[0002]

2. Description of the Related Art A method for manufacturing a solid electrolyte oxygen concentration sensor is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-291144. In this sensor, as shown in FIG. 10, the gas to be measured passes through the pinhole 35 and is introduced into the cavity 36 inside the sensor, and the diffusion of the gas is restricted by the pinhole 35. When a voltage is applied between the electrode films 37 and 38, the oxygen gas in the gas to be measured is ionized at the electrode 37 (cathode), passes through the solid electrolyte 39, reaches the electrode film 38 (anode), and is gasified again. The oxygen concentration is detected by measuring the current between the electrodes 37 and 38.

As a method of manufacturing this sensor, film formation and etching are repeated on the upper surface of the substrate to form a solid electrolyte sandwiched between electrode films on the upper and lower sides, and the lower surface of the substrate is removed to the lower electrode except the peripheral portion. Etching away to form cavities,
After that, a pinhole is formed penetrating the upper surface of the substrate to reach the cavity, and the peripheral portion of the lower surface of the substrate is joined to the pedestal.

[0004]

However, since it is necessary to join the pedestal to form the cavity, a normal IC is used.
There was a problem that it was difficult to incorporate into the manufacturing technology process.

Therefore, an object of the present invention is to provide a method for manufacturing a solid electrolyte oxygen concentration sensor which can manufacture a solid electrolyte oxygen concentration sensor using a novel method.

[0006]

According to a first aspect of the present invention, there is provided a first step of sequentially laminating a lower electrode film, a solid electrolyte thin film and an upper electrode film on a semiconductor substrate, the lower electrode film, the solid electrolyte thin film and an upper layer. Secondly, forming a pinhole penetrating the electrode film
A step, a third step of forming a sacrificial film on the upper electrode film, a fourth step of disposing a cavity wall material covering the sacrificial film, and an etching from the back surface side of the semiconductor substrate to the pinhole. A method of manufacturing a solid electrolyte oxygen concentration sensor, which comprises a fifth step of performing a sacrifice film on the upper electrode film by etching and forming a cavity through the pinhole.

A second aspect of the present invention is to form a sacrificial film on a semiconductor substrate and stack a lower electrode film, a solid electrolyte thin film and an upper electrode film on the sacrificial film in that order, and the lower electrode film and the solid film. The method comprises a second step of forming a pinhole penetrating the electrolyte thin film and the upper electrode film, and a third step of forming a cavity by etching away the sacrificial film below the lower electrode film through the pinhole. The gist of the invention is a method for manufacturing a solid electrolyte oxygen concentration sensor.

[0008]

According to the first invention, the lower electrode film, the solid electrolyte thin film and the upper electrode film are sequentially laminated on the semiconductor substrate by the first step, and the lower electrode film, the solid electrolyte thin film and the upper electrode film are formed by the second step. A pinhole penetrating the sacrificial film is formed, a sacrificial film is formed on the upper electrode film in the third step, a cavity wall material covering the sacrificial film is arranged in the fourth step, and a fifth step is performed from the back surface side of the semiconductor substrate. The etching to reach the pinhole is performed, and the sacrificial film on the upper electrode film is removed by etching through the pinhole to form a cavity.

According to a second aspect of the present invention, a sacrificial film is formed on the semiconductor substrate by the first step, and a lower electrode film, a solid electrolyte thin film and an upper electrode film are sequentially laminated on the sacrificial film,
A pinhole penetrating the lower electrode film, the solid electrolyte thin film, and the upper electrode film is formed by the step, and the sacrificial film below the lower electrode film is removed by etching through the pinhole to form a cavity.

[0010]

【Example】

(First Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

1 to 5 show the manufacturing process of the solid electrolyte oxygen concentration sensor of this embodiment. As shown in FIG. 1, a single crystal silicon substrate 1 having a flat surface is prepared, and a lower electrode film 2, a solid electrolyte thin film 3 and an insulating film 40 are formed on the surface of the silicon substrate 1 by a sputtering method, a CVD method, a vapor deposition method or the like. The films are sequentially formed using the vacuum film forming method. Here, platinum is used as the lower electrode film 2, YSZ (yttria-stabilized zirconia) is used as the solid electrolyte thin film 3, and plasma SiN _x or SiO ₂ is used as the insulating film 40.

Then, the insulating film 40 is etched to form a base for the portion which will become the heater 6 in a later step. next,
The upper electrode film 4 is formed using a vacuum film forming method such as a sputtering method, a CVD method, or a vapor deposition method.

Then, the upper electrode film 4, the solid electrolyte thin film 3, and the lower electrode film 2 are sequentially etched to form a pinhole 5. At the same time, the electrode is processed into a predetermined shape. Further, a part of the upper electrode film 4 is separated from the upper electrode film 4, formed into a strip shape, and formed into a meandering shape, thereby processing a part of the upper electrode film 4 into the heater 6. Further, unnecessary parts are removed. The heater 6 is for heating the solid electrolyte thin film 3.

Then, as shown in FIG.
The sacrificial layer 7 is formed on the upper electrode film 4 including the inside by a vacuum film forming method such as a sputtering method, a CVD method, a vapor deposition method, and an etching method. Here, as the sacrificial layer 7, polysilicon, amorphous silicon, alkali metal, or alkaline earth metal is used.

Further, as shown in FIG. 3, a cavity wall film 8 is formed on the silicon substrate 1 so as to cover the sacrifice layer 7 by a vacuum film forming method such as a sputtering method, a CVD method or a vapor deposition method. As the cavity wall film 8, a plasma SiNx film or S
An iO ₂ film is used. Then, a contact hole 10 to the electrode 9 is formed in the cavity wall film 8 by etching.

Subsequently, as shown in FIG. 4, a silicon nitride film 11 is formed in a predetermined region on the back surface of the silicon substrate 1, and the silicon nitride film 11 is formed by using KOH, NaOH or an organic alkaline aqueous solution as an etching solution. Using the as a mask, the silicon substrate 1 is wet-etched from the back surface side. Then, the lower electrode film 2 and the pinhole 5 are exposed by this wet etching, and the sacrifice layer 7 is selectively removed by etching through the pinhole 5.
As a result, the hollow portion 9 is formed.

A plurality of such sensor elements are formed in a silicon wafer (silicon substrate 1) and are diced from the state shown in FIG. 4 to be cut into chips.

The sensor chip thus manufactured is packaged as shown in FIG. That is, the pedestal 14 is bonded onto the stem 13, and the back surface side of the silicon substrate 1 is bonded onto the pedestal 14. The stem 13 is covered with a shell 15 so as to cover the silicon substrate 1 and the like. A gas introducing pipe 16 is fixed to the stem 13 in a penetrating state, and the gas introducing pipe 16 communicates with the pinhole 5 through a through hole 17 of the pedestal 14. Further, a plurality of lead terminals 18 are fixed to the stem 13 in a penetrating state, and the electrodes 9 and the lead terminals 1 are
8 is connected by a wire 19.

In the solid electrolyte oxygen concentration sensor manufactured as described above, the gas to be measured passes through the pinhole 5 and is introduced into the cavity 12, and the diffusion of the gas is restricted by the pinhole 5. Further, a voltage is applied between the lower and upper electrode films 2 and 4 so that the oxygen gas in the gas to be measured is changed to the upper electrode film 4.
It is ionized at the (cathode), passes through the solid electrolyte membrane 3, reaches the lower electrode membrane 2 (anode), and is vaporized again. The oxygen concentration is detected by measuring the current between the lower and upper electrode films 2 and 4 here.

The lower electrode film 2, the solid electrolyte thin film 3, the upper electrode film 4, the sacrifice layer 7, and the cavity wall film 8 are formed by vacuum film forming and are formed by etching. -A film may be formed / processed by a method such as a pressure CVD method, an atmospheric pressure / pressure oxidation method, a sol-gel method, or formed into a predetermined shape from the beginning by a lift-off method, a metal mask method, or the like. Good.

In the solid electrolyte oxygen concentration sensor manufactured as shown in FIG. 5, since the pinhole 5 and the contact hole 10 are completely separated above and below the sensor element, for example, the element is a small chip. If you do
If the sensor element is airtightly mounted on the pedestal 14 as described above, a sensor structure in which the electrical wiring portion does not come into contact with the gas to be measured can be easily realized. This structure is effective when the sensor is placed in a relatively harsh gas environment such as a combustion control sensor.

Further, in FIG. 4, when the heater 6 is heated to a high temperature, heat is transferred to the silicon substrate 1 only through the thin film (insulating film 40, lower electrode film 2, solid electrolyte thin film 3), and the silicon substrate 1 is Since it can be kept at a low temperature, no ingenuity such as using a heat-resistant packaging material is required. In other words, for example, when the sensor element is a small chip, it can be easily mounted on the pedestal or substrate of the sensor package by means of bonding, eutectic, brazing, soldering, welding, etc. The sensor characteristics are not affected by the morphology.

Further, the same structure has a pinhole 5,
By using means such as adjusting the area and volume of the cavity 12 and providing the electrodes (lower electrode film 2 and upper electrode film 4) by dividing them into a plurality of parts, the so-called limiting current method can be used without impairing the above advantages. It is possible to use a plurality of types of sensor elements such as the oxygen sensor described above, or an oxygen sensor using a sensor cell / pump cell.

As described above, in this embodiment, the silicon substrate 1
A lower electrode film 2, a solid electrolyte thin film 3, and an upper electrode film 4 are sequentially stacked on a (semiconductor substrate) (first step), and a pin penetrating the lower electrode film 2, the solid electrolyte thin film 3, and the upper electrode film 4 is formed. A hole 5 is formed (second step), a sacrificial film 7 is formed on the upper electrode film 4 (third step), and a cavity wall film 8 (cavity wall material) that covers the sacrifice film 7 is formed (fourth step). Process), silicon substrate 1
Etching is performed from the back surface side to the pinhole 5 and the sacrificial film 7 on the upper electrode film 4 is removed by etching through the pinhole 5 to form a cavity 12 (fifth portion).
Process). Therefore, it is possible to manufacture the solid electrolyte oxygen concentration sensor by using a normal IC manufacturing technique and a new method.

As an application example of this embodiment, the cavity wall film 8 is not formed on the silicon substrate 1 and the sacrificial layer 7, but, for example, glass, ceramics, metal, etc. which are processed into a predetermined structure in advance. The cap may be formed on the silicon substrate 1 / sacrificial layer 7 by a method such as adhesion, eutectic, brazing, soldering, and welding. (Second Embodiment) Next, the second embodiment will be described focusing on the differences from the first embodiment.

6 to 9 show the manufacturing process of the solid electrolyte oxygen concentration sensor of this embodiment. As shown in FIG. 6, a single crystal silicon substrate 20 having a flat surface is prepared, and a sacrifice layer 21 and a cavity sidewall layer 22 are formed on the substrate 20 by a vacuum film forming method such as a sputtering method, a CVD method, a vapor deposition method, and etching. Mold in place using the method. The sacrifice layer 21 and the cavity side wall layer 22 are obtained by disposing the cavity side wall layer 22 in the peripheral portion of the sacrifice layer 21. Here, the sacrificial layer 21 is made of polysilicon, amorphous silicon, alkali metal or alkaline earth metal, and the cavity side wall layer 22 is made of plasma SiNx film or SiO ₂ film.

Then, as shown in FIG. 7, a lower electrode film 23, a fixed electrolyte thin film 24, and an insulating layer 25 are formed on the sacrificial layer 21 and the cavity side wall layer 22 by a sputtering method and a CVD method.
And the insulating layer 25 are etched by a vacuum film forming method such as a vapor deposition method and a vapor deposition method. Here, platinum is used as the lower electrode film 23, and Y is used as the fixed electrolyte thin film 24.
SZ (yttria-stabilized zirconia) is used, and as the insulating layer 25, a plasma SiNx film or a SiO ₂ film is used.

After that, an upper electrode film 26 is formed on the fixed electrolyte thin film 24 and the insulating layer 25. Upper electrode film 2
Platinum is used as 6. Further, as shown in FIG. 8, the upper electrode film 26, the fixed electrolyte thin film 24, and the lower electrode film 23 are sequentially etched to form a heater 27, a wiring film 28, and a pinhole 29. The pinhole 29 is
Upper electrode film 26, fixed electrolyte thin film 24, and lower electrode film 23
Penetrates through.

Subsequently, as shown in FIG. 9, KOH and N
The sacrificial layer 21 is selectively removed by etching through the pinhole 29 by using aOH or an organic alkaline aqueous solution as an etching solution to form the cavity 30.

The sacrificial layer 21, the cavity side wall layer 22, the lower electrode film 23, the fixed electrolyte thin film 24, the insulating layer 25, and the upper electrode film 26 are formed by a vacuum film forming method and processed by etching. However, film formation / processing using atmospheric pressure / pressurization CVD method, atmospheric pressure / pressurization oxidation method, sol-gel method, etc., or a predetermined method from the beginning by lift-off method, metal mask method, etc. It may be formed in a shape. The sacrificial layer 21 and the cavity side wall layer 22 are not formed on the silicon substrate 20, but are formed on the surface of the silicon substrate 20 by, for example, impurity diffusion or particle beam irradiation such as electron beam irradiation or ion beam irradiation. To modify the sacrificial layer 2
1 and the etching rate ratio of the silicon substrate 20 and the cavity side wall layer 22 may be made sufficiently large.

Further, the state shown in FIG. 9 is packaged in the same manner as in FIG. 5 in the first embodiment. In the solid electrolyte oxygen concentration sensor manufactured in this way, heat is transferred to the silicon substrate 20 only through the thin films (lower electrode film 23, fixed electrolyte thin film 24, wiring film 28) even when the heater 27 is heated to a high temperature. Therefore, since the silicon substrate 20 is kept at a low temperature and there is no functional portion or wiring under the sensor element, for example, when the sensor element is a small chip, adhesion, eutectic, brazing, soldering, welding It can be easily mounted on the pedestal or the substrate of the sensor package by such means, and the sensor characteristics are not affected by the method and form. In addition, the same structure has pinholes 29,
The area and volume of the cavity 30 can be adjusted, the lower electrode film 23,
By using a means such as providing the upper electrode film 26 by dividing it into a plurality of parts, a plurality of types such as a so-called limiting current type oxygen sensor or an oxygen sensor using a sensor cell / pump cell can be used without impairing the above advantages. It can be a sensor element.

As described above, in this embodiment, the silicon substrate 2 is used.
While forming the sacrificial film 21 on 0 (semiconductor substrate),
The lower electrode film 23, the solid electrolyte thin film 24, and the upper electrode film 26 are sequentially stacked on top of this (first step).
Then, a pinhole 29 penetrating the solid electrolyte thin film 24 and the upper electrode film 26 is formed (second step), and the sacrificial film 21 under the lower electrode film 23 is removed by etching through the pinhole 29 to form a cavity 30. (Third step). Therefore,
The solid electrolyte oxygen concentration sensor can be manufactured by a new method using a normal IC manufacturing technique.

[0033]

As described above in detail, according to the present invention,
The excellent effect that a solid electrolyte oxygen concentration sensor can be manufactured using a novel method is exhibited.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a solid electrolyte oxygen concentration sensor of a first embodiment.

FIG. 2 is a cross-sectional view showing a manufacturing process of the solid electrolyte oxygen concentration sensor of the first embodiment.

FIG. 3 is a cross-sectional view showing a manufacturing process of the solid electrolyte oxygen concentration sensor of the first embodiment.

FIG. 4 is a cross-sectional view showing a manufacturing process of the solid electrolyte oxygen concentration sensor of the first embodiment.

FIG. 5 is a cross-sectional view showing a manufacturing process of the solid electrolyte oxygen concentration sensor of the first embodiment.

FIG. 6 is a cross-sectional view showing the manufacturing process of the solid electrolyte oxygen concentration sensor of the second embodiment.

FIG. 7 is a cross-sectional view showing the manufacturing process of the solid electrolyte oxygen concentration sensor of the second embodiment.

FIG. 8 is a cross-sectional view showing the manufacturing process of the solid electrolyte oxygen concentration sensor of the second embodiment.

FIG. 9 is a cross-sectional view showing the manufacturing process of the solid electrolyte oxygen concentration sensor of the second embodiment.

FIG. 10 is a cross-sectional view showing the operation of the solid electrolyte oxygen concentration sensor.

[Explanation of symbols]

 1 Silicon Substrate as Semiconductor Substrate 2 Lower Electrode Film 3 Solid Electrolyte Thin Film 4 Upper Electrode Film 5 Pinhole 7 Sacrificial Film 8 Cavity Wall Film as Cavity Wall Material 12 Cavity 20 Silicon Substrate as Semiconductor Substrate 21 Sacrificial Film 23 Lower Electrode Membrane 24 Solid electrolyte thin film 26 Upper electrode membrane 29 Pinhole 30 Cavity

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masataka Naito 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute (72) Inventor Yasunari Sugito 1-1, Showa-cho, Kariya city, Aichi Japan Denso Co., Ltd.

Claims (2)

[Claims] 1. A first step of sequentially stacking a lower electrode film, a solid electrolyte thin film and an upper electrode film on a semiconductor substrate, and forming a pinhole penetrating the lower electrode film, the solid electrolyte thin film and the upper electrode film. A second step, a third step of forming a sacrificial film on the upper electrode film, a fourth step of disposing a cavity wall material covering the sacrificial film, and a rear surface side of the semiconductor substrate to the pinhole. And a fifth step of etching away the sacrificial film above the upper electrode film through the pinhole to form a cavity, and a method for manufacturing a solid electrolyte oxygen concentration sensor. 2. A first step of forming a sacrificial film on a semiconductor substrate and sequentially laminating a lower electrode film, a solid electrolyte thin film and an upper electrode film on the sacrificial film, and the lower electrode film, the solid electrolyte thin film and the upper part. A second step of forming a pinhole penetrating the electrode film, and a third step of forming a cavity by etching away the sacrificial film below the lower electrode film through the pinhole. Method for manufacturing solid electrolyte oxygen concentration sensor.