JPS6045016A - Formation of functional element - Google Patents

Abstract

PURPOSE:To control the transfer of a boundary between the high impurity concentration region and the low impurity concentration region of a functional element according to high temperature treatment by a method wherein an Si substrate containing arsenic and antimony as to make at least one side of them to have the specified resistivity is used, and a film having the specified resistivity is used as a single crystal Si film. CONSTITUTION:A single crystal silicon film 5 is grown epitaxially on a silicon single crystal substrate 4, then a functional element is formed in the silicon film 5 thereof, and at least a part of the silicon substrate 4 is removed. A substrate containing as to make impurities of at least one side of arsenic or antimony to have resistivity of 0.015OMEGA.cm or more is used as the silicon substrate 4 at formation of the functional element containing such a peocess, and moreover, a film having resistivity of 0.068OMEGA.cm or more is used as the single crystal silicon film 5. Because the diffusion coefficients of arsenic and antimony are small, when a substrate grown with a silicon epitaxial layer introduced with arbitrary impurities on the low resistance silicon substrate containing only arsenic, only antimony or only arsenic and antimony is used, the silicon single crystal film having arbitrary impurity concentration can be obtained.

Description

[Detailed description of the invention] The present invention relates to a method for forming a functional element.

One of the methods for manufacturing functional devices in a silicon single crystal film is to grow a silicon epitaxial layer on a single crystal silicon substrate, form devices on this epitaxial layer, and then etch the silicon substrate from the back side to form a silicon epitaxial layer. There is a way to leave it behind.

Elements include electronic devices, LSIs, and sensors.

When this method is applied to LSI manufacturing, the silicon epitaxial layer on which elements such as transistors are formed is transferred onto an insulator, which has the advantage of reducing parasitic capacitance, and also eliminates the need to stack multiple layers. You can also do it. Further, this method is applied to the manufacture of sensors when it is desired to form a silicon thin film in a pressure sensor or the like with good control.

2f! also applies to the method of forming functional elements as described above! ! There are many kinds. One method, as shown in FIG. 1, is to use a substrate in which a silicon layer 2 into which t is introduced at a high concentration is formed on the surface of a silicon substrate 10, and a silicon epitaxial layer 3 is grown thereon. be. Compared to a mixture of hydrofluoric acid and nitric acid that is normally used for silicon etching, the etching rate of the silicon layer 2 containing boron at a high concentration is very low, so the silicon substrate is etched from the back side. In this case, it is possible to stop the etching with the silicon layer 2 into which boron is introduced at a high concentration. Taking advantage of this fact, it is possible to form a functional device consisting of a silicon layer 2 into which #1 borium is introduced at a high concentration and a silicon epitaxial layer 3 on which the device is formed by etching the substrate from the back side. can.

However, there is a drawback that it is difficult to grow a high-quality silicon epitaxial layer on a silicon layer into which boron is introduced at a high concentration. In addition, since the diffusion coefficient of boron is large, when depositing the silicon epitaxial layer 3, the diffusion of boron from the silicon 1 2 into which boron is introduced at a high concentration is significant, resulting in a high resistance P-type silicon epitaxial layer or a thin silicon epitaxial layer. There are drawbacks such as difficulty in growing an n-type silicon epitaxial layer.

On the other hand, another method is to etch the silicon substrate from the back side, leaving only the silicon epitaxial layer.
・Use a low resistance substrate 4 with a resistivity of 006 or less on it.
A substrate on which a silicon epitaxial layer 5 of 8Ω·- or more is grown is used. The Electrochemical
Society, Expedited Abstracts ('
l'he Electro-chemical 5oc
As detailed in ``Iity Extended Abstracts'' Vol. 12-1, page 74, the etching rate of a low-resistance silicon substrate is higher than that of a high-resistance silicon epitaxial layer.
Hydrofluoric acid, nitric acid, and acetic acid have a 1:3:8 ratio.
There is a silicon etchant with a composition ratio of . By etching the substrate 4 having a resistivity of 0.015 Ω·m or more from the back side, it is possible to selectively expose the silicon epitaxial layer 5 having a resistivity p of 068 Ω·α or more. Functional elements can be formed in the silicon epitaxial layer 5 by utilizing this small size.

However, even if this second method is used, if a normal low resistance substrate is used, the boundary between the high impurity concentration region (substrate) 4 and the low impurity concentration region (epitaxial layer) 5 will easily move due to high temperature treatment. Indeed, the transition region between the high impurity concentration region 4 and the low impurity concentration region 5 is easily expanded by high temperature treatment.

Therefore, it is difficult to keep the concentration of the silicon epitaxial layer 5 uniformly low throughout, and the characteristics of functional elements formed thereon or subsequently formed will deteriorate.

An object of the present invention is to provide a method for forming a functional element that eliminates such drawbacks.

According to the present invention, a method for forming a functional element includes the steps of epitaxially growing a single crystal silicon film on a silicon single crystal substrate, then forming a functional element on the silicon film, and then removing at least a portion of the silicon substrate. , the silicon substrate contains at least one impurity selected from arsenic and antimony, and has a resistivity of 00.
A substrate with a resistivity of 15Ω・α or less is used, and the single crystal silicon film has a resistivity of 0.068Ω・
A method for forming a functional element characterized by using a film having a thickness of α or more can be obtained.

In the second method described above, it is possible in principle to use impurities of the low resistance substrate used (1, J) and [7] such as boron, aluminum, phosphorus, arsenic, and antimony.

However, boronate, aluminum, and phosphorus have large diffusion coefficients. Arsenic and antimony have small diffusion coefficients.

Therefore, if a silicon epitaxial layer containing any impurity is grown on a low-resistance silicon substrate containing only arsenic, only antimony, or only arsenic and antimony, the second method described above can be used. , it becomes possible to obtain a silicon single crystal film having an arbitrary impurity concentration.

According to the present invention, movement of the boundary between the high impurity concentration region and the low impurity concentration region due to high temperature treatment can be suppressed. Furthermore, expansion of the transition region between the high impurity concentration region and the low impurity concentration region due to high temperature treatment can also be suppressed. Therefore,
A silicon single crystal film consisting of a thin silicon epitaxial layer with arbitrary impurities and impurity concentrations can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a substrate used in manufacturing a silicon 1r crystal film by a first conventional method.
-1 is a silicon substrate, 2 is a silicon layer containing boron at a high concentration, and 3 is a silicon epitaxial layer. FIG. 2 is a schematic cross-sectional view showing the structure of a substrate used in manufacturing a silicon single crystal film by a second conventional method;
4 is a low-resistance silicon substrate with a resistivity of 0015Ω and a bottom edge.
5 is a silicon epitaxial layer having a resistivity of 0.068° or more. Agent BL511 Uchihara Y7 Figure 1 Figures 63-72

Claims (1)

[Claims] A method for forming a functional element comprising the steps of epitaxially growing a single crystal silicon film on a silicon single crystal substrate, then forming a functional element on this silicon film, and then removing at least a portion of the silicon substrate. and at least one impurity selected from arsenic or antimony has a resistivity Ofl 15Q-cm
A method for forming a functional element, characterized in that a substrate having the following properties is used, and a film having a resistivity of 0D68Ω and 100 or more is used as the single crystal silicon film.