JP3112578B2 - 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 piece. On the other hand, the sputtering method
A method in which a metal with a high melting point is discharged and melted as an electrode, and the molten particles are sprayed onto the material to be plated at high speed to cover the material.
Also called thermal spraying. However, in these methods, composition control is difficult in 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 component elements 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 independently maintain a certain order during crystallization, but if it does not have a preferential orientation, it is necessary to perform some sort of crystallization. It is necessary to control the orientation by the above method.

FIG. 2 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 12 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 12 having a certain orientation is thus obtained, the PZT crystalline thin film 20 is formed on the platinum film 12 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 12, 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 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.

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 preferential orientation (such as platinum) is formed on the upper layer. Therefore, it was necessary to form a crystal film and use this as a base. However, even though these underlayers are necessary for controlling the orientation of the crystalline thin film, they may not be necessary after the formation of the crystalline thin film. By leaving the underlayer, the thickness of the entire film increases. For this reason, when used in a semiconductor device, problems such as hindering improvement in the degree of integration of the device have occurred.

Further, MFS-FET (Metal Ferroelect)
It is necessary to construct a structure in which a crystalline thin film of PZT is directly provided on amorphous silicon, such as a ric semiconductor field effect transistor).

Furthermore, since the underlayer for controlling the orientation of the crystalline thin film is incorporated as a structural body, it is necessary to reduce the thickness of the underlayer as much as possible. could not.

The present invention solves the above-mentioned problems, and imparts a predetermined orientation to a crystalline thin film by controlling a crystal film provided on an upper layer of a crystallizing material to be imparted with an orientation. It is an object of the present invention to provide a method for forming a thin film as a whole.

[0013]

According to a first aspect of the present invention, there is provided a method for producing a crystalline thin film, comprising the steps of: applying a sol-gel precursor of a crystallization material onto a substrate to form a precursor layer; Upper control film forming step of forming an upper control film having a preferred orientation on the body layer, crystallization by heat treatment of the precursor layer, and crystallization step of forming a crystalline thin film,
An upper control film removing step of removing the upper control film.

According to a second aspect of the present invention, the upper control film is a crystalline thin film or a crystalline bulk.

[0015]

According to the first and second manufacturing methods, in the upper control film forming step, an upper control film having preferential orientation is formed above the sol-gel precursor of the crystallized material. As a result, a film having a predetermined orientation is formed on the sol-gel precursor of the crystallized material.

Next, in a crystallization step, the sol-gel precursor layer of the crystallized material is crystallized by heat treatment to form a crystalline thin film. Here, the crystallized material is crystallized based on the orientation of the film formed on the upper portion. That is, the orientation of the crystalline thin film formed by crystallization of the crystallized material can be controlled by the orientation of the film formed on the top. Therefore, it becomes possible to impart a predetermined orientation to the crystalline thin film.

Finally, in the upper control film removing step, the upper control film which has become an unnecessary structure is removed by imparting a predetermined orientation to the crystalline thin film. Therefore, the thickness of the entire film can be reduced.

Further, since the upper control film is removed and is not incorporated as a structure, not only a thin crystalline film but also a thick crystalline bulk can be used as the upper control film. Thus, the upper control film can be removed by physical peeling.

[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.

In this embodiment, a crystalline thin film (PZT) having a predetermined orientation is crystallized by controlling the orientation of a crystallization material (PZT precursor) under the platinum film as an upper layer while controlling the orientation.
T thin film). The PZT film and the platinum film are both formed as crystalline thin films, but the object to which the orientation is imparted is the PZT film.

[0021] 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, P
A ZT precursor layer 10 is formed. The PZT precursor layer 10 is formed by applying a PZT precursor solution prepared according to a sol-gel method on the silicon oxide film 4 by a spin coating method to form a polymer gel-like coating film, and then drying the gel. It is a film.

Further, a platinum film 12 as an upper control film is formed on the PZT precursor layer 10 by a magnetron sputtering method. Since the platinum film 12 has a preferred orientation, it is less than <111 without being affected by the underlying PZT precursor layer 10.
> Formed with orientation. As a result, as shown in FIG. 1D, <1 is formed on the PZT precursor layer 10 to be crystallized.
11> A structure on which a platinum film 12 having an orientation is formed is constructed.

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 PZT precursor layer 10 is sintered and crystallized to form a PZT crystalline thin film 20 of FIG. 1E.
At this time, the platinum film 12 on the PZT precursor layer 10 functions as a base having excellent orientation when the PZT crystal elongates. That is, the PZT crystallizes under the control of the platinum film 12, so that the formed PZT crystalline thin film 20 is given a <100> orientation.

The platinum film 12 on the PZT crystalline thin film 20 is made of PZT.
When the T crystalline thin film 20 is given a predetermined orientation, the function ends and an unnecessary structure is formed. The platinum film 12 is removed by etching to obtain the structure shown in FIG. 1F.

In this embodiment, the PZT crystalline thin film 20 is used as the crystalline thin film, but other crystalline thin films may be used. Although the platinum film 12 is formed as a crystalline thin film and removed by etching, the platinum film 12 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. Furthermore, P
When the ZT precursor layer 10 is crystallized to form a PZT crystalline thin film 20, a platinum film 12 as an upper layer which affects the orientation is formed.
However, a crystalline thin film having another preferred orientation may be used.

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

[0027]

According to the first and second aspects of the present invention, in the upper control film forming step, a film having a predetermined orientation is formed on the sol-gel precursor of the crystallized material, and the crystal is formed. In the crystallization step, the crystallized material is crystallized by controlling the film having the orientation formed on the upper part, and finally, the upper control film is removed in the upper control film removing step. Accordingly, it is possible to impart a predetermined orientation to the crystalline thin film without being controlled by the crystalline properties of the film constituting the lower portion, and to form the entire thin film. In addition, since it can be removed by physical peeling after control using the crystalline bulk, removal of the upper control film becomes easy.

[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 a diagram showing a method for producing a crystalline thin film by a conventional method.

[Explanation of symbols]

 10 PZT precursor layer 12 Platinum film 20 PZT crystalline thin film

Claims (2)

(57) [Claims] 1. A precursor layer forming step of applying a sol-gel precursor of a crystallizing material on a substrate to form a precursor layer, and forming an upper control film having preferential orientation on the precursor layer. An upper control film forming step; a crystallization step of crystallizing the precursor layer by heat treatment to form a crystalline thin film; and an upper control film removing step of removing the upper control film. Manufacturing method. 2. The method according to claim 1, wherein the upper control film is a crystalline thin film or a crystalline bulk.