WO2014048213A1

WO2014048213A1 - Method for preparing silicon film

Info

Publication number: WO2014048213A1
Application number: PCT/CN2013/082546
Authority: WO
Inventors: 荆二荣; 周国平; 夏长奉
Original assignee: 无锡华润上华半导体有限公司
Priority date: 2012-09-28
Filing date: 2013-08-29
Publication date: 2014-04-03
Also published as: CN103693612A

Abstract

The present invention relates to a method for preparing a silicon film, which comprises the following steps of: a passivation layer formation step of respectively depositing a passivation layer on the front and back sides of a silicon slice; a seed layer formation step of depositing polycrystalline silicon on the front passivation layer as an epitaxial seed layer; an epitaxial layer formation step of epitaxially growing the polycrystalline silicon on the above-mentioned seed layer to form an epitaxial layer; and a corrosion step of forming a corrosion window on the back passivation layer and starting corroding the back side of the silicon slice through the corrosion window using a corrosive liquid until stopping at the front passivation layer mentioned above. A silicon film with a consistent homogeneity within the slice and an accurately controllable thickness can be prepared by using the present invention.

Description

Method for preparing silicon film

[Technical Field]

The present invention relates to the field of semiconductor fabrication, and more particularly to a method of fabricating a silicon film capable of producing uniformity in on-chip uniformity and precise control of thickness.

【Background technique】

Silicon films have a wide range of applications in the MEMS field, such as sensitive membranes for pressure sensors. The preparation of silicon films has become one of the key technologies for the development and practical application of MEMS devices, and thus various silicon film preparation techniques have been developed.

The simplest technique for preparing a silicon film is to directly perform KOH or TMAH etching on a silicon wafer having a thickness of several hundred micrometers. The thickness of the silicon film can be obtained by subtracting the thickness of the silicon wafer from the thickness of the silicon wafer. When etching to a desired thickness, The silicon wafer can be taken out of the etching solution.

This technique is simple, but has a number of disadvantages, for example, the thickness of the starting silicon wafer is a few micrometers of undulation, which will have a large effect on the uniformity of the resulting silicon film. If there are impurity gradients or defects in the silicon wafer, it will cause different corrosion rates in different regions of the silicon wafer, which will also lead to unevenness of the silicon film. At the same time, there is a large error in the measurement of the thickness and corrosion depth of the silicon wafer, so This technique makes it difficult to obtain a uniform, thickness-accurate silicon film on the chip.

[Summary of the Invention]

In view of the above problems, the present invention has been made in an effort to provide a method for preparing a silicon film which is uniform in sheet and which can be precisely controlled in thickness.

The method of producing a silicon film of the present invention is characterized by comprising the steps of:

a passivation layer forming step of depositing a passivation layer on the front and back sides of the silicon wafer to form a front passivation layer and a back passivation layer;

a seed layer forming step of depositing polysilicon as an epitaxial seed layer on the front passivation layer;

An epitaxial layer forming step of epitaxially growing polysilicon on the seed layer to form an epitaxial layer;

In the etching step, a corrosion window is formed on the back passivation layer and the back side of the silicon wafer is etched through the etching window with an etching solution until the front passivation layer is stopped.

Preferably, the front passivation layer acts as a self-stop layer for etching, and the back passivation layer acts as a masking layer for etching.

Preferably, the material of the front passivation layer and the back passivation layer is SiO ₂ or Si ₃ N ₄ .

Preferably, in the epitaxial layer forming step, polycrystalline silicon is prepared by an epitaxial process.

Preferably, in the epitaxial layer forming step, any one of SiCl ₄ , SiH ₄ , SH ₂ Cl ₂ and SiHCl ₃ is used as the epitaxial gas.

Preferably, in the etching step, the etching solution is a KOH etching solution or a TMAH etching solution.

Preferably, in the seed layer forming step, the deposited thickness of the polysilicon is from 50 nm to 1000 nm.

Preferably, in the epitaxial layer forming step, the thickness of the epitaxially grown polysilicon is set to a desired thickness of the silicon film.

Preferably, in the passivation layer forming step, the front passivation layer and the back passivation layer are deposited to a thickness of 500 to 2000 nm.

Preferably, in the seed layer forming step, polysilicon is deposited by LPCVD.

The silicon film of the present invention is prepared by epitaxially growing polycrystalline silicon to ensure uniformity in the sheet. Further, by using the passivation layer as a self-stopping layer of etching, it is possible to accurately control the etching thickness to obtain a silicon film of a desired thickness. Therefore, with the preparation method of the silicon film of the present invention, it is possible to prepare a silicon film having uniform in-chip uniformity and capable of precisely controlling the thickness.

[Description of the Drawings]

1 to 3 are process flow diagrams showing a method of preparing a silicon film of the present invention.

Fig. 4 is a schematic cross-sectional view showing a silicon film prepared by the method for producing a silicon film of the present invention.

【detailed description】

The following are some of the various embodiments of the invention, which are intended to provide a basic understanding of the invention. It is not intended to identify key or critical elements of the invention or the scope of the invention.

First embodiment

1 to 3 are process flow charts showing a method of producing a silicon film of the present invention. Fig. 4 is a schematic cross-sectional view showing a silicon film prepared by the method for producing a silicon film of the present invention.

Hereinafter, a method of preparing a silicon film according to a first embodiment of the present invention will be specifically described with reference to FIGS. 1 to 4.

As shown in FIG. 1, SiO _{2 is} deposited on the front and back sides of the silicon wafer 100 to form

passivation layers

201 and 202. The deposition thickness of SiO ₂ of the

passivation layers

201 and 202 is 500 to 2000 nm, respectively. The passivation layer 201 on the front side of the silicon wafer 100 is referred to as a front passivation layer, and the passivation layer 202 on the back side of the silicon wafer 100 is referred to as a back passivation layer. The front passivation layer 201 will act as a self-stop layer for etching in a subsequent step, and the back passivation layer 202 will serve as a mask layer for etching in subsequent steps.

Next, as shown in FIG. 2, a thin polycrystalline silicon is deposited on the front passivation layer 201 to a thickness of 50 nm to 1000 nm to form a seed layer 300 as an epitaxial growth.

Here, the deposited polysilicon may be LPCVD. LPCVD (Low Pressure Chemical Vapor Deposition , low pressure vapor deposition) is a chemical vapor deposition performed at a reaction pressure of 27 to 270 Pa. Its characteristics are: good quality and uniformity of the film, high output, low cost and easy automation.

Then, as shown in FIG. 3, polysilicon is epitaxially grown by using the seed layer 300 of polycrystalline silicon as an epitaxial seed. Generally, the method of epitaxially growing polycrystalline silicon can be classified into two types of vapor deposition and vacuum deposition. For example, in the case of a chemical vapor deposition method, a carrier gas (such as hydrogen) is used to carry a vapor containing a compound, and the reaction is carried out at a high temperature to reduce the silicon oxide and deposit it on the substrate to form an epitaxial layer. . As the epitaxial gas, any one of SiCl ₄ , SiH ₄ , SH ₂ Cl ₂ , and SiHCl ₃ is used, and the reaction temperature in the epitaxial process is 900 to 1200 ° C. For example, when SiCl4 is used as the epitaxial gas, the mixed gas interacts at a high temperature to perform the following reaction:

CO ₂ +H ₂ ⇔ H ₂ O+CO

SiCl ₄ +2H ₂ O SiO SiO ₂ +4HCl

Thus, the epitaxial layer 400 is formed by epitaxially growing polysilicon over the seed layer 300 by using an epitaxial process. Since the epitaxial layer 400 is formed by an epitaxial process, uniformity within the silicon film can be ensured.

Next, a corrosion window is formed on the back passivation layer 202, and the back surface of the silicon wafer is etched by the KOH etching solution. The KOH etching solution etches the silicon wafer through the etching window, as shown in FIG. 4, and finally the etching stops at the front passivation layer 201. . During the etching process, the back passivation layer 202 functions as a mask layer for etching, and the front passivation layer 201 functions as a self-stop layer for etching. Thus, the thickness of the etching can be precisely controlled by the front passivation layer 201, and thus the thickness of the silicon film can be precisely controlled. In the present invention, the thickness of the epitaxial layer 400 can be determined according to the required thickness of the silicon film, that is, how many thicknesses of the silicon film are required, and the thickness of the epitaxial layer 400 can be set to the thickness. According to the present invention, a silicon film having a precisely controlled thickness can be obtained.

Second embodiment

The method for preparing a silicon film according to the second embodiment of the present invention is different from the method for preparing a silicon film according to the first embodiment described above in that SiN4 is deposited on the front and back sides of the silicon wafer 100 to form a front passivation layer 201, Back passivation layer 202.

Specifically, first, as shown in FIG. 1, SiN4 is deposited on the front and back sides of the silicon wafer 100 to form a front passivation layer 201 and a back passivation layer 202, which will serve as a self-stop of corrosion in a subsequent step. The layer, back passivation layer 202 will act as a masking layer for the etch in subsequent steps.

Next, as shown in FIG. 2, a thin polycrystalline silicon is deposited on the front passivation layer 201 to a thickness of 50 nm to 1000 nm to form a seed layer 300 as an epitaxial growth. Here, the method of depositing polysilicon may employ LPCVD.

Then, as shown in FIG. 3, polysilicon is epitaxially grown by using the seed layer 300 of polycrystalline silicon as an epitaxial seed. As the epitaxial gas, any one of SiCl ₄ , SiH ₄ , SH ₂ Cl ₂ , and SiHCl ₃ is used, and the reaction temperature of the epitaxial process can be controlled at 900 to 1200 degrees Celsius. Thus, the epitaxial layer 400 is formed by epitaxially growing polysilicon over the seed layer 300 by using an epitaxial process. Since the epitaxial layer 400 is formed by an epitaxial process, uniformity within the silicon film can be ensured.

Next, a corrosion window is formed on the back passivation layer 202, and the back surface of the silicon wafer is etched by the KOH etching solution. The KOH etching solution etches the silicon wafer through the etching window, as shown in FIG. 4, and finally the etching stops at the front passivation layer 201. . During the etching process, the back passivation layer 202 functions as a mask layer for etching, and the front passivation layer 201 functions as a self-stop layer for etching. Thus, the thickness of the etching can be precisely controlled by the front passivation layer 201, and thus the thickness of the silicon film can be precisely controlled. Further, in the present invention, the thickness of the epitaxial layer 400 can be determined in accordance with the required thickness of the silicon film, that is, how many thicknesses of the silicon film are required, and the thickness of the epitaxial layer 400 can be set to the thickness. Therefore, according to the present invention, a silicon film having a precisely controlled thickness can be obtained.

Third embodiment

The method for producing a silicon film according to the third embodiment of the present invention is different from the method for producing a silicon film according to the first embodiment described above in that the back surface of the silicon wafer is etched using TMAH as an etching solution.

Specifically, first, as shown in FIG. 1, SiO ₂ is deposited on the silicon wafer 100 to form a front passivation layer 201 and a back passivation layer 202, which serves as a self-stop layer for etching in a subsequent step. The back passivation layer 202 acts as a masking layer for the etch in subsequent steps.

Next, as shown in FIG. 2, a thin polycrystalline silicon is deposited on the front passivation layer 201 to a thickness of 50 nm to 1000 nm to form a seed layer 300 as an epitaxy. Here, the method of depositing polysilicon may employ LPCVD.

Then, as shown in FIG. 3, polysilicon is epitaxially grown by using the seed layer 300 of polycrystalline silicon as an epitaxial seed. As the epitaxial gas, any one of SiCl ₄ , SiH ₄ , SH ₂ Cl ₂ , and SiHCl ₃ can be used, and the reaction temperature of the epitaxial process can be controlled at 900 to 1200 ° C. Thus, the epitaxial layer 400 is formed by epitaxially growing polysilicon over the seed layer 300 by using an epitaxial process. Since the epitaxial layer 400 is formed by an epitaxial process, uniformity within the silicon film can be ensured.

Next, a corrosion window is formed on the back passivation layer 202, and the back side of the silicon wafer is etched by the TMAH etching solution. The TMAH etching solution etches the silicon wafer through the etching window, as shown in FIG. 4, and finally the etching stops at the front passivation layer 201. . During the etching process, the back passivation layer 202 functions as a mask layer for etching, and the front passivation layer 201 functions as a self-stop layer for etching. Thus, the thickness of the etching can be precisely controlled by the front passivation layer 201, and thus the thickness of the silicon film can be precisely controlled. Further, in the present invention, the thickness of the epitaxial layer 400 can be determined in accordance with the required thickness of the silicon film, that is, how many thicknesses of the silicon film are required, and the thickness of the epitaxial layer 400 can be set to the thickness. Therefore, according to the present invention, a silicon film having a precisely controlled thickness can be obtained.

The above examples mainly illustrate the preparation method of the silicon film of the present invention. Although only a few of the specific embodiments of the present invention have been described, it is understood that the invention may be embodied in many other forms without departing from the spirit and scope of the invention. Accordingly, the present invention is to be construed as illustrative and not restrictive, and the invention may cover various modifications without departing from the spirit and scope of the invention as defined by the appended claims With replacement.

Claims

A method of preparing a silicon film, comprising the steps of:

a passivation layer forming step of depositing a passivation layer on the front and back sides of the silicon wafer to form a front passivation layer and a back passivation layer;

a seed layer forming step of depositing polysilicon on the front passivation layer as a seed layer for epitaxial growth;

An epitaxial layer forming step of epitaxially growing polysilicon on the seed layer to form an epitaxial layer;

In the etching step, a corrosion window is formed on the back passivation layer and etching is performed on the back side of the silicon wafer through the etching window with an etching solution until the front passivation layer is stopped.
The method of preparing a silicon film according to claim 1, wherein the front passivation layer serves as a self-stop layer for etching, and the back passivation layer serves as a mask layer for etching.
The method of preparing a silicon film according to claim 2, wherein the material of the front passivation layer and the back passivation layer is SiO 2 or Si 3 N 4 .
The method of producing a silicon film according to claim 1, wherein in the epitaxial layer forming step, any one of SiCl 4 , SiH 4 , SH 2 Cl 2 and SiHCl 3 is used as the epitaxial gas.
The method of producing a silicon film according to claim 2, wherein in the etching step, the etching solution is a KOH etching solution or a TMAH etching solution.
The method of producing a silicon film according to claim 1, wherein in the seed layer forming step, the polycrystalline silicon is deposited to a thickness of 50 nm to 1000 nm.
A method of producing a silicon film according to claim 1, wherein in said epitaxial layer forming step, the thickness of the epitaxially grown polycrystalline silicon is set to a thickness of a desired silicon film.
The method of producing a silicon film according to claim 2, wherein in the step of forming the passivation layer, the front passivation layer and the back passivation layer are deposited to a thickness of 500 to 2000 nm.
A method of producing a silicon film according to claim 1, wherein in said seed layer forming step, polycrystalline silicon is deposited by LPCVD.