JP3212158B2 - Manufacturing method of crystalline thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a crystalline thin film, and more particularly to a method for imparting a predetermined orientation to a crystallized material.

[0002]

2. Description of the Related Art As a method for producing a functional thin film used for an electronic device or the like, a vacuum evaporation method or a sputtering method is generally used. The vacuum evaporation method evaporates the metal in a vacuum,
This is a method of forming a thin metal coating by condensing on a cold work part. On the other hand, the sputtering method
Ar excited by plasma by applying an electric field between the substrate and the material
Strikes the material and strikes out the material particles
This is a method of coating by attaching to a substrate. However,
In these methods, it is often difficult to control the composition of a complex system such as a ferroelectric substance or a piezoelectric substance, and it is often difficult to produce a thin film with good reproducibility.

[0003] For this reason, the sol-gel method has recently attracted attention as a new film forming technique by a chemical technique.
This method obtains a thin film by heating a polymer gel precursor film obtained by coating an alkoxide solution, and comprises three steps of sol preparation, sol application, drying and baking.

Specifically, a mixed alkoxide solution containing a component element is heated to form a composite alkoxide solution, and then water is added to the solution to cause hydrolysis and polycondensation to form a precursor solution. This solution is applied on a substrate to obtain a polymer gel film. As a coating method, a “spin coating method” for obtaining a uniform film by dropping a solution on a substrate and rotating the solution is known. The film thus obtained is dried and fired to obtain a target thin film. The thickness of a single coating is limited to 0.1 μm to 0.2 μm, and can be reduced to several microns by repeating the coating.

A crystalline thin film used for a semiconductor device or the like is required to have a predetermined orientation. If the crystallized material has a preferential orientation, it is possible to orient while maintaining a constant order during crystallization, but if it does not have a preferential orientation, it will have some It is necessary to control the orientation by the above method.

FIG. 3 shows a conventional method for imparting a predetermined orientation to a crystallized material for crystallization. Here, lead zirconic titanate (PZT) will be described as an example of a crystallization material having no preferential orientation. A silicon oxide film 4 is formed on a silicon wafer 2 as an amorphous film. A platinum film 8 is formed on the silicon oxide film 4 by a sputtering method. Since platinum has a preferred orientation, it can be oriented while maintaining a constant order, and a relatively high-quality crystal can be obtained. After the platinum film 8 having a certain orientation is thus obtained, the PZT crystalline thin film 20 is formed on the platinum film 8 by a method such as a vacuum evaporation method, a sputtering method, and a sol-gel method. Since PZT is crystallized under the control of the orientation of the platinum film 8, the PZT crystalline thin film 20 is constructed with a predetermined orientation.

As described above, in the conventional method, first, a crystalline film is formed from a material (platinum or the like) having a preferred orientation and an orientation similar to the orientation to be imparted to the crystalline thin film as the lower layer, and then, By forming a thin film in a manner controlled by the orientation of the lower crystal film, a crystalline thin film having a predetermined orientation (an orientation similar to the orientation of the lower layer) is formed in the upper layer. That is, the orientation of the crystal film growing in the upper layer is controlled by the orientation of the lower crystal film.

[0008]

However, the conventional method for producing a crystalline thin film has the following problems.

During crystallization, the crystallized material starts to grow from the interface with the lower layer in a manner controlled by the orientation of the lower layer. For this reason, the control by the crystallinity of the lower layer is reliable near the boundary surface, and although the obtained crystal is given relatively good orientation, the control by the lower layer becomes uncertain as the distance from the boundary surface increases, and Crystals having an outside orientation and non-crystallized amorphous portions increased, making it difficult to obtain crystals having a desired orientation.

When the lower layer is an amorphous film or a film having a significantly different orientation, these films cannot be used as a base, and a material having a preferred orientation (a platinum Etc.) to form a crystal film and use it as a base. However, an underlayer made of a material having preferential orientation is necessary for controlling the orientation of the crystalline thin film, but may not be necessary after the formation of the crystalline thin film. Because the overall thickness increases,
When used in a semiconductor device, there have been problems such as hindering improvement in the degree of integration of the device.

Further, MFIS (Metal Ferroelectric
It is also necessary to construct a structure in which a ferroelectric crystalline thin film is directly provided on amorphous silicon without including a base layer made of a material having preferential orientation, such as an Insulator Semiconductor structure.

For these reasons, there has been a demand for a structure which imparts good orientation to a crystalline thin film and does not include an underlayer made of a material having a preferred orientation, which is an unnecessary structure. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, to provide a crystalline thin film with better orientation, and to provide a method for forming the entire thin film.

[0013]

According to a first aspect of the present invention, there is provided a method of manufacturing a crystalline thin film of a second substance, comprising the steps of: forming a thin film of a crystallized material of a first substance on a substrate; On the thin film, an intermediate portion control film forming step of forming an intermediate portion control film having preferential orientation, the first thin film is heat treated and crystallized as a control film for controlling the orientation of the intermediate portion control film, A first thin film crystallization step of forming a crystalline thin film of one substance, an intermediate control film removing step of removing an intermediate control film, and a film made of a crystallized material of a second substance on the crystallized first thin film Forming a second thin film, forming an upper control film having a preferred orientation on the second thin film, controlling the orientation of the crystallized first thin film and the upper control film. Heat treatment of the second thin film as a control film for Was crystallized, it is characterized by comprising a second thin film crystallization step, forming a crystalline thin film of a second material.

[0014]

In the manufacturing method of the first aspect, in the step of forming an intermediate portion control film, an intermediate portion control film having preferential orientation is formed on the first thin film. Thereby, a film having a predetermined orientation is formed on the first thin film.

Next, in the first thin film crystallization step,
The first thin film is crystallized by heat treatment to form a crystalline thin film of the first substance. Here, the crystallized material of the first substance grows from the upper boundary surface based on the orientation of the control film formed on the upper part. Therefore, it is possible to impart a predetermined orientation to the crystalline thin film of the first substance.

Thereafter, the intermediate portion control film is removed in the intermediate portion control film removing step. As a result, the intermediate part control film which has become an unnecessary structure by giving the crystalline thin film a predetermined orientation is removed.

Further, in the second thin film forming step,
A second thin film made of a crystallized material of the second substance is formed on the crystalline thin film of the first substance, and in the upper control film forming step, an upper control film having preferential orientation is formed on the second thin film. As a result, a film having a predetermined orientation is formed on the upper and lower portions of the second thin film.

Next, in the second thin film crystallization step,
The second thin film is crystallized by a heat treatment to form a crystalline thin film of the second substance. Here, the crystallized material of the second substance grows from the upper and lower boundaries based on the orientation of the films formed on both the upper and lower sides. Therefore, it is possible to more reliably control the orientation as compared with the case where the control is performed based on the orientation of the film formed on one side, and it is possible to impart better orientation to the crystalline thin film of the second substance.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a crystalline thin film according to an embodiment of the present invention will be described with reference to the drawings.

[0020] H a silicon wafer 2 of 950 ° C. in FIG. 1A ₂
Place in an O atmosphere and thermally oxidize the surface. As a result, FIG.
As shown in FIG. 2B, a silicon oxide film 4 is formed on the silicon wafer 2 as an amorphous film. Next, as shown in FIG. 1C, on the upper surface of the silicon oxide film 4,
A strontium titanate thin film 6 is formed by sputtering strontium titanate, which is a first substance, by a magnetron sputtering method. Since the strontium titanate thin film 6 is controlled by the amorphous silicon oxide film 4, it has no orientation and becomes amorphous.

Further, a platinum film 8 as an intermediate control film is formed on the amorphous strontium titanate thin film 6 by magnetron sputtering. Since the platinum film 8 has a preferred orientation, it is less than <111 without being affected by the amorphous strontium titanate thin film 6 serving as a base.
> Formed with orientation. As a result, as shown in FIG. 1D, the platinum film 8 having a <111> orientation is formed on the amorphous strontium titanate thin film 6 to be crystallized.
Is formed.

Next, this structure is referred to as RTA (Rapid Therma
l Annealing) heat treatment at 700 ° C. for several seconds to 2 minutes. The heat-treated amorphous strontium titanate thin film 6 is crystallized to form the strontium titanate crystalline thin film 16, which is the first thin film in FIG. 1E. At this time, the platinum film 8 on the amorphous strontium titanate thin film 6 functions as a base having excellent orientation when the strontium titanate crystal elongates. That is, the strontium titanate crystallizes under the control of the platinum film 8, so that the formed strontium titanate crystalline thin film 16 is given the <100> orientation.

After forming the strontium titanate crystalline thin film 16, the platinum film 8 is removed by etching (FIG. 1).
F). Further, on the upper surface of the strontium titanate crystalline thin film 16 which has appeared by etching, a second substance, PZ
An amorphous PZT thin film 10, which is a second thin film, is formed using T (FIG. 2G). This amorphous PZT thin film 10 is formed by applying a PZT precursor solution prepared according to a sol-gel method on a strontium titanate crystalline thin film 16 by spin coating to form a polymer gel-like coating film, and then drying. It is a gel dried film.

Thereafter, as shown in FIG. 2H, a platinum film 12 as an upper control film is formed on the upper surface of the amorphous PZT thin film 10 by magnetron sputtering. Since the platinum film 12 has preferential orientation, amorphous PZT
It is formed in the <111> orientation without being affected by the thin film 10. Thereby, the amorphous P to be crystallized is
The ZT thin film 10 is used as an intermediate layer,
1> Oriented strontium titanate crystalline thin film 16
Then, a structure on which the platinum film 12 is formed is constructed.

Next, this structure was converted to a 70
Heat treatment is performed at 0 ° C. for several seconds to 2 minutes. The heat-treated amorphous PZT thin film 10 is sintered and crystallized, and the PZT thin film 10 shown in FIG.
A ZT crystalline thin film 20 is formed. At this time, the platinum film 12 above the amorphous PZT thin film 10 and the strontium titanate crystalline thin film 16 below the amorphous PZT thin film 10 function as a base having excellent orientation when the PZT crystal elongates. That is, PZT is crystallized from the boundary surface under the control of the upper platinum film 12 and the lower strontium titanate crystalline thin film 16, so that the formed PZT crystalline thin film 20 is given a <100> orientation. . In addition, since the control is performed from the upper and lower surfaces, the control is performed more reliably than the control from the lower one surface, and the formed PZT crystalline thin film 20 is formed.
In, the crystal part provided with the desired orientation increases,
The proportion of crystals having an orientation other than the predetermined one and the proportion of amorphous portions are reduced. In addition, since crystal growth is sufficient, a large crystallite can be obtained.

As described above, the PZT crystalline thin film 20 is provided with good orientation, and a film structure that does not include the unnecessary platinum film 8 is obtained.

Although the strontium titanate crystalline thin film 16 and the PZT crystalline thin film 20 are formed as crystalline thin films in this embodiment, other crystalline thin films may be used. Instead, films made of the same type of substance may be used. Further, although the platinum film 8 is formed as a crystalline thin film and removed by etching, the platinum film 8 may be formed as a crystalline bulk and removed by physical treatment (physical peeling), thereby making the production of the crystalline thin film easier. Become. Further, when the platinum film 12 has finished its function due to imparting a predetermined orientation to the PZT crystalline thin film 20 and becomes an unnecessary structure, it may be removed by etching.

When the strontium titanate crystalline thin film 16 and the PZT crystalline thin film 20, which are crystalline thin films, are formed, the platinum films 8 and 12 are used as films for controlling the orientation. It may be a crystalline thin film having an orientation. Further, the PZT crystalline thin film 20 is obtained by crystallizing the amorphous PZT thin film 10 formed according to the sol-gel method, but may be obtained by crystallizing a PZT thin film formed according to magnetron sputtering or the like.

The term "crystalline thin film" refers to a polycrystalline thin film or a single crystal thin film having crystal plane orientation. In addition, the crystalline bulk refers to a polycrystalline bulk or a single crystal bulk having crystal plane orientation.

[0030]

According to the manufacturing method of the first aspect, the first thin film is crystal-grown based on the orientation of the control film formed on the upper portion, and the crystalline thin film of the first substance having the predetermined orientation is formed. After that, the control film is removed.

Thereafter, a second thin film and a control film are sequentially formed on the crystalline thin film of the first material, and the second thin film is crystal-grown based on the orientations of the upper and lower films to form a second thin film. I have a thin film.

Therefore, it is possible to impart better orientation to the crystalline thin film of the second substance and to form the entire thin film.

[Brief description of the drawings]

FIG. 1 is a view illustrating a method of manufacturing a crystalline thin film according to one embodiment of the present invention.

FIG. 2 is another diagram showing a method of manufacturing a crystalline thin film according to one embodiment of the present invention.

FIG. 3 is a diagram showing a method for producing a crystalline thin film by a conventional method.

[Explanation of symbols]

 6 ... Amorphous strontium titanate thin film 8,12 ... Platinum film 10 ... Amorphous PZT thin film 16 ... Strontium titanate crystalline thin film 20 ... PZT crystalline thin film

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Claims (1)

(57) [Claims] 1. A first thin film forming step of forming a thin film made of a crystallization material of a first substance on a substrate, an intermediate portion control film forming an intermediate portion control film having preferential orientation on the first thin film. A film forming step, a first thin film crystallization step of heat treating and crystallizing the first thin film as a control film for controlling the orientation of the intermediate portion control film to form a crystalline thin film of the first material, an intermediate portion control film An intermediate portion control film removing step of removing a second thin film forming step of forming a film made of a crystallized material of a second substance on the crystallized first thin film; and forming a preferential orientation on the second thin film. An upper control film forming step of forming an upper control film having a second material crystallized by heat-treating the second thin film as a control film for controlling the orientation of the crystallized first thin film and the upper control film; Crystallization of second thin film to form conductive thin film -Up method for producing a crystalline thin film of a second material, characterized in that it comprises a.