JPH05152276A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a semiconductor device which enables pattern formation by a wet etching method of a ferroelectric thin film or a thin film of a substance having perovskite crystal structure. CONSTITUTION:Solution containing a ferroelectric element is applied by revolution to an Si substrate 11 and thermally treated at 450 deg.C or lower to remove an element excepting ferroelectric composition from the solution and to form a ferroelectric thin film 12. Then, a resist pattern 13 is formed on the ferroelectric thin film 12 by using photolithography and the ferroelectric thin film 12 is etched by weak acid of pH 6.5 or less using the resist pattern 13 as a mask. Lastly, the resist pattern 13 is removed and the ferroelectric thin film 12 is sintered and crystallized by performing heat treatment of 600 deg.C or higher. Thereby, pattern formation of a ferroelectric thin film by wet etching becomes possible.

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 device using a ferroelectric thin film or a thin film of a substance having a perovskite type crystal structure, which is known to have various electrical characteristics.

[0002]

2. Description of the Related Art As a method for forming a pattern of a ferroelectric thin film, it is difficult to selectively etch only the ferroelectric thin film by a wet etching method, and thus an ion milling method has been widely used.

A conventional manufacturing method will be described below.
3A to 3D show a conventional semiconductor device manufacturing method. First, as shown in FIG. 3A, a solution containing a ferroelectric component is spin-coated on a Si substrate 1 by a spinner, and a heat treatment at 450 ° C. or less is performed in the atmosphere for 2 to 3 minutes to remove the ferroelectric from the solution. Components other than the body composition are removed to form a porous and amorphous ferroelectric thin film 2, which is then sintered and crystallized by heat treatment at 600 ° C. or higher. Next in FIG.
As shown in (b), a resist pattern 3 is formed on the ferroelectric thin film 2 by using a lithography method. Next in FIG.
As shown in (c), the ferroelectric thin film 2 is scraped off by causing argon ions accelerated at high speed by an electric field to obliquely enter the surface of the Si substrate 1. Finally, as shown in FIG. 3D, the resist pattern 3 is carbonized and removed by an oxygen plasma asher to form a pattern of the ferroelectric thin film 2.

[0004]

However, in the above conventional structure, since the ions are obliquely incident from the surface of the Si substrate 1, the pattern of the ferroelectric thin film is displaced from the resist pattern. In addition, since this method uses a physical mechanism, it lacks selectivity such that only the ferroelectric thin film is removed. Therefore, in order to remove only the ferroelectric thin film, precise control must be performed in time. Furthermore, since this method uses ions accelerated at high speed by an electric field, the Si substrate 1
There was a problem such as damage to.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device which enables accurate pattern formation of a ferroelectric thin film without damaging the Si substrate. It is a thing.

[0006]

In order to achieve the above object, the present invention provides a step of forming an amorphous ferroelectric thin film on the surface of a supporting substrate and a photolithography method on the ferroelectric thin film. A step of forming a resist pattern using
Using the resist pattern as a mask, the ferroelectric thin film is
It has a structure including a step of etching with a weak acid of H6.5 or less, a step of removing the resist pattern, and a step of crystallizing the ferroelectric thin film.

[0007]

With this structure, the ferroelectric thin film is easily etched by the wet etching method in the amorphous state with a weak acid having a pH of 6.5 or less, so that only the ferroelectric thin film can be etched with a high selective ratio. Therefore, it becomes possible to form a pattern by the wet etching method, which has been difficult in the past.

[0008]

(Embodiment 1) A first embodiment of a method of manufacturing a semiconductor device according to the present invention will be described with reference to FIGS. 1 (a) to 1 (d).

As in the conventional example, as shown in FIG. 1A, a solution containing a ferroelectric component is spin-coated on a Si substrate 11 by a spinner, and a heat treatment at 450.degree. By carrying out for about 3 minutes, components other than the ferroelectric composition are removed from the solution to form a porous and amorphous ferroelectric thin film 12. The steps of spin coating and heat treatment may be repeated several times to obtain a predetermined film thickness. Next, as in the conventional example, as shown in FIG.
A resist pattern 13 is formed on the top by photolithography. Next, as a feature of the present invention, as shown in FIG. 1C, the ferroelectric thin film 12 is etched with hydrofluoric acid diluted with water to about 1/100 to 1/100 using the resist pattern 13 as a mask. Thereafter, as shown in FIG. 1D, the resist pattern 13 is carbonized and removed by an oxygen plasma asher, and the ferroelectric thin film 12 is sintered and crystallized by performing a heat treatment at 600 ° C. or higher to obtain the ferroelectric substance. A pattern of thin film 12 is formed.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. In FIG. 2, the same parts as those in the first embodiment of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. That is, the feature of the second embodiment is that as shown in FIG. 2A, an amorphous ferroelectric thin film is vapor-deposited on a Si substrate 11 by using a sputtering method or a CVD method at a substrate temperature of 300 ° C. or lower. To form an amorphous ferroelectric thin film 21.

The steps of FIGS. 2B and 2C are as shown in FIG.
Similar to (c), the resist pattern 13 is carbonized and removed by an oxygen plasma asher in the step of FIG. 2D, and then the ferroelectric thin film 2 is heat-treated at 600 ° C. or higher.
The pattern of the ferroelectric thin film 21 is formed by crystallizing the ferroelectric thin film 1.

Further, instead of the ferroelectric thin film, a thin film of a substance having a perovskite type crystal structure can be used.

That is, a solution containing a component having a perovskite type crystal structure is spin-coated on the surface of the supporting substrate, and 45
By performing heat treatment at 0 ° C. or lower, components other than the composition constituting the perovskite type crystal structure are removed from the solution to form a thin film. Next, a resist pattern is formed on the thin film by photolithography, and the thin film is etched with a weak acid having a pH of 6.5 or less using the resist pattern as a mask. After that, the resist pattern was removed, and heat treatment was performed at 600 ° C. or higher to sinter and crystallize the thin film to form a thin film having a perovskite type crystal structure.

The invention is likewise applicable to vapor deposition processes. That is, the surface of the supporting substrate is sputtered or CV
Using method D, an amorphous thin film having a composition that constitutes a perovskite type crystal structure is deposited under the condition that the temperature of the supporting substrate is 300 ° C. or lower. Next, a resist pattern is formed on the amorphous thin film by a photolithography method, and the amorphous thin film is adjusted to pH 6.5 using the resist pattern as a mask.
Etching is performed with the following weak acid. After that, the resist pattern was removed, and heat treatment was performed at 600 ° C. or higher to crystallize the amorphous thin film to form a thin film having a perovskite type crystal structure.

In the above two embodiments, the support substrate is made of S.
Although the i substrate is used, other supporting substrates such as a GaAs substrate, a quartz substrate, and a glass substrate may be used, or a supporting substrate having elements such as transistors formed on the surface may be used, or A metal thin film may be formed at least partially, and a ferroelectric thin film, a thin film having a perovskite type crystal structure, etc. may be formed on the metal thin film. Further, although hydrofluoric acid diluted with water was used as the etching solution in the above two examples, the pH of hydrochloric acid, nitric acid, etc. diluted with acetic acid or water was adjusted to pH 6.
A weak acid of 5 or less may be used.

[0016]

As described above, since the method for manufacturing a semiconductor device of the present invention has a structure in which a pattern is formed by a wet etching method with a weak acid having a pH of 6.5 or less, only the ferroelectric thin film has a good selection ratio and is highly accurate. A method for manufacturing a semiconductor device that can be formed in a pattern can be provided.

[Brief description of drawings]

FIG. 1 is a process sectional view of a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a process sectional view of a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a process sectional view of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 11 Si substrate (supporting substrate) 12 Ferroelectric thin film 13 Resist pattern

Claims (5)

[Claims] 1. A step of spin-coating a solution containing a ferroelectric component on the surface of a supporting substrate and performing a heat treatment at 450 ° C. or lower to form a ferroelectric thin film, and a photolithography method on the ferroelectric thin film. A step of forming a resist pattern using the resist pattern, a step of etching the ferroelectric thin film with a weak acid having a pH of 6.5 or less using the resist pattern as a mask, a step of removing the resist pattern,
And a step of subjecting the ferroelectric thin film to a heat treatment at a temperature of not less than 0 ° C. to sinter and crystallize the ferroelectric thin film. 2. A sputtering method or a CVD method on the surface of a supporting substrate.
Forming an amorphous ferroelectric thin film under the condition that the temperature of the supporting substrate is 300 ° C. or less by using a photolithography method, and forming a resist pattern on the ferroelectric thin film by using a photolithography method. A step of etching the ferroelectric thin film with a weak acid having a pH of 6.5 or less using the resist pattern as a mask; a step of removing the resist pattern; and a heat treatment at 600 ° C. or more to crystallize the ferroelectric thin film. A method of manufacturing a semiconductor device, comprising: 3. A solution containing a component having a perovskite type crystal structure is spin-coated on the surface of a supporting substrate, and a heat treatment at 450 ° C. or lower is performed to remove components other than the composition constituting the perovskite type crystal structure from the solution. A step of removing and forming a thin film, a step of forming a resist pattern on the thin film by using a photolithography method, and a pH of the thin film of 6.5 using the resist pattern as a mask.
The method has the following steps of etching with a weak acid, removing the resist pattern, and performing heat treatment at 600 ° C. or higher to sinter and crystallize the thin film to form a thin film having a perovskite crystal structure. A method of manufacturing a semiconductor device, comprising: 4. A sputtering method or a CVD method on the surface of a supporting substrate.
Using the method to deposit an amorphous thin film having a composition forming a perovskite type crystal structure under the condition that the temperature of the supporting substrate is 300 ° C. or lower, and a resist pattern on the amorphous thin film using a photolithography method. , A step of etching the amorphous thin film with a weak acid having a pH of 6.5 or less using the resist pattern as a mask, a step of removing the resist pattern, and 600 ° C.
And a step of crystallizing the amorphous thin film by the above heat treatment to form a thin film having a perovskite type crystal structure. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the support substrate is a support substrate having a metal thin film formed in advance on a predetermined portion of the surface thereof.