JP4366853B2 - Membrane manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a membrane.
[0002]
[Prior art]
Conventionally, as a method of manufacturing a membrane (thin film structure), a thin film made of an oxide film or the like is formed on a silicon substrate, and the silicon substrate is used using an alkaline solution such as KOH (potassium hydroxide) or TMAH (tetramerthiammonium hydroxide). There is a technique of manufacturing a membrane on the surface of a silicon substrate by removing the silicon substrate under the thin film by performing etching.
[0003]
In the above prior art, it is necessary to form an aluminum pad and aluminum wiring for electrical connection on the silicon substrate and an aluminum wiring protective film for protecting the aluminum wiring. In addition, an aluminum wiring protective film on the aluminum pad must be opened.
[0004]
However, if the silicon substrate is etched after the aluminum wiring protective film is opened, the etching selectivity of aluminum to silicon is not about 1 at all, so that the aluminum pad in the aluminum wiring protective film opening region is eroded by the etching. .
[0005]
For this reason, in Japanese Patent Laid-Open No. 10-312987, when etching a silicon substrate, the entire surface including the aluminum pad opening region is protected with an etching protective film, and after etching of silicon, the etching protective film only on the aluminum pad opening region is protected. To be removed.
[0006]
[Problems to be solved by the invention]
However, it is important to control the membrane stress in the membrane part. Therefore, when the etching protective film only on the aluminum pad opening region is removed after the etching of the silicon substrate, the membrane stress balance of the membrane is lost and the seat There is a problem that it may bend.
[0007]
Therefore, an object of the present invention is to form an etching protective film on an aluminum pad, and to form a film structure that does not buckle while maintaining the balance of film stress of the membrane.
[0008]
[Means for Solving the Problems]
The method for manufacturing a membrane according to claim 1 is characterized in that after the substrate under the first film is etched to form the membrane portion, the third film on the second film and the electrode terminal opening region is entirely removed. It is said.
[0009]
By such a membrane manufacturing method, the third film is removed not only on the electrode terminal opening region but also on the entire surface, so that the membrane stress balance of the membrane can be maintained and a film structure without buckling can be formed.
[0010]
The method for manufacturing a membrane according to claim 2 is characterized in that a fourth film is provided between the first film and the second film.
[0011]
With such a membrane manufacturing method, the film has a four-layer / second-film structure. Therefore, when the third film is removed, even if there is a pinhole in the second film, the first film Etching can be prevented.
[0012]
The membrane manufacturing method according to claim 3 is characterized in that the film thickness of the fourth film is defined so that the total film stress is pulled.
[0013]
Since the film stress is proportional to the film thickness, by forming the fourth film with the minimum necessary film thickness that does not compress the film stress, the film stress balance of the membrane is maintained and a film structure without buckling is formed. be able to.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings.
[0018]
<First Embodiment>
FIG. 1 shows a cross-sectional view of the infrared detection device of the present embodiment. 2 and 3 show the manufacturing process of the infrared detecting device of this embodiment.
[0019]
In this embodiment, as shown in FIG. 1, the cavity 2 is formed by etching from the surface of the silicon substrate 1. Further, on the silicon substrate 1, an interlayer insulating film 3a, polysilicon 4 for measuring a change in electromotive force caused by a change in temperature, an interlayer insulating film 3b, an aluminum wiring 5a, and an aluminum pad 5b are formed. A silicon nitride film 6 for protecting the aluminum wiring 5a is formed on the aluminum wiring 5a.
[0020]
On the aluminum pad 5b, a silicon nitride film 6 is opened and an aluminum pad opening region 8 is formed for electrical connection with the outside by wire bonding or the like.
[0021]
Hereinafter, the manufacturing process of this embodiment will be described.
[0022]
First, as shown in FIG. 2A, an interlayer insulating film 3a made of an oxide film is deposited on a silicon substrate 1 to form polysilicon 4 in a desired pattern. Then, an interlayer insulating film 3b made of an oxide film is deposited to form a contact hole, and then an aluminum wiring 5a and an aluminum pad 5b are formed.
[0023]
Next, as shown in FIG. 2B, a silicon nitride film 6 for protecting the aluminum wiring 5a is deposited on the interlayer insulating film 3b, the aluminum wiring 5a, and the aluminum pad 5b, and is electrically connected to the outside. For this purpose, the silicon nitride film 6 on the aluminum pad 5b is removed, and an aluminum pad opening region 8 is formed.
[0024]
Next, as shown in FIG. 3A, a silicon oxide film 7 having a selection ratio different from that of the silicon nitride film 6 is deposited on the silicon nitride film 6 and the aluminum pad 5b.
[0025]
Next, as shown in FIG. 3B, an opening is provided at a desired position in the film structure including the interlayer insulating films 3a and 3b, the silicon nitride film 6, and the silicon oxide film 7.
[0026]
Thereafter, when silicon oxide film 7 is used as a protective film for aluminum pad opening region 8 and anisotropic etching is performed from the surface of silicon substrate 1 using an alkaline solution such as KOH, cavity 2 is opened in silicon substrate 1. And the membrane 10 is formed.
[0027]
Here, if the aluminum pad opening region 8 is formed after the etching process, the resist solution used when forming the aluminum pad opening region 8 enters the cavity 2 formed by the etching process. It is necessary to form the aluminum pad opening region 8 on the surface.
[0028]
Next, as shown in FIG. 1, after the membrane 10 is formed, the entire surface of the silicon oxide film 7 is removed with a silicon oxide film etchant composed of ammonium fluoride, hydrofluoric acid, and acetic acid.
[0029]
As a result, the film of the membrane 10 is removed by removing the entire surface of the silicon nitride film 6 and the silicon oxide film 7 on the aluminum pad opening region 8 as compared with the case of removing the protective film on the aluminum pad opening region 8. It is possible to maintain a stress balance and form a film structure without buckling.
[0030]
<Second Embodiment>
Since the second embodiment has substantially the same configuration as the first embodiment, the same reference numerals are given to the same configuration as the first embodiment, and only different parts will be described.
[0031]
In FIG. 4, the manufacturing process of the infrared rays detection apparatus of this embodiment is shown.
[0032]
This embodiment is characterized in that a silicon oxide film 9 is formed between the interlayer insulating film 3b and the silicon nitride film 6 as shown in FIG.
[0033]
In the first embodiment, when the silicon nitride film 6 has many pinholes, when the silicon oxide film 7 is removed, the silicon oxide film etchant permeates from the pinholes, so that the interlayer insulation under the silicon nitride film 6 There is a problem that even the film 3b is etched.
[0034]
Therefore, as shown in FIG. 4A, a silicon nitride film 6 is deposited after depositing a silicon oxide film 9 having a minimum necessary thickness that does not compress the film stress.
[0035]
Then, as shown in FIG. 4B, after the membrane 10 is formed, the entire surface of the silicon oxide film 7 is removed with a silicon oxide film etchant.
[0036]
At this time, since the silicon oxide film 9 exists, even if the silicon nitride film 6 has a pinhole, the interlayer insulating film 3b under the silicon nitride film 6 is not immediately etched.
[0037]
Thus, the interlayer insulating film 3b has a margin for the etching of the silicon oxide film 7 by using the two-layer structure of the silicon oxide film 9 / silicon nitride film 6 as the protective film.
[0038]
In addition, since the outermost silicon oxide film 7 is completely removed after the membrane 10 is formed, the balance of film stress of the membrane 10 can be maintained and a film structure without buckling can be formed.
[0039]
< Reference example >
For Example, to explain about the parts different from the first embodiment.
[0040]
FIG. 5 shows a cross-sectional view of an infrared detection device of a reference example .
[0041]
In the first and second embodiments, the membrane 10 is formed from the front surface of the silicon substrate 1, but in this reference example , the membrane 10 is formed from the back surface.
[0042]
When the membrane 10 is formed from the back surface, if the aluminum pad opening region 8 is formed after the etching step, the membrane 10 formed by the etching step is destroyed by the resist formed when the aluminum pad opening region 8 is formed. Therefore, it is necessary to form the aluminum pad opening region 8 before the etching process.
[0043]
Therefore, even when the membrane 10 is formed from the back surface as in this reference example , it is effective to apply the present invention.
[0045]
In addition, this invention is not restricted to the said embodiment, It can apply to various aspects.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an infrared detection device according to a first embodiment.
FIGS. 2A and 2B are diagrams illustrating manufacturing steps of the infrared detection device according to the first embodiment. FIGS.
FIGS. 3A and 3B are diagrams illustrating manufacturing steps of the infrared detection device according to the first embodiment; FIGS.
FIGS. 4A and 4B are diagrams illustrating manufacturing steps of the infrared detection device according to the second embodiment. FIGS.
FIG. 5 is a cross-sectional view of an infrared detection device according to a reference example .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Cavity, 3a, 3b ... Interlayer insulation film, 4 ... Polysilicon, 5a ... Aluminum wiring, 5b ... Aluminum pad, 6 ... Silicon nitride film, 7 ... Silicon oxide film, 8 ... Aluminum pad opening area , 9 ... Silicon oxide film, 10 ... Membrane

Claims (3)

A first step of forming a first film on the substrate;
A second step of forming a wiring portion and an electrode terminal on the first film;
A third step of forming a second film formed on the first film and covering the wiring portion and having an opening region on the electrode terminal;
A fourth step of forming a third film on the opening region and the second film;
After forming an opening at a desired position of the film structure composed of the first film , the second film, and the third film, the substrate is anisotropically etched with an etching treatment liquid through the opening, A fifth step of forming a membrane portion having the first film and the second film as constituent elements corresponding to the cavity by forming a cavity in the substrate ;
And a sixth step of removing the entire surface of the third film after the fifth step.   The method for manufacturing a membrane according to claim 1, wherein a fourth film is provided between the first film and the second film.   3. The membrane manufacturing method according to claim 2, wherein a film thickness of the fourth film is regulated so that a total film stress of the first film, the second film, and the fourth film is pulled. Method.

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