JPH04115511A - Manufacture of soi substrate - Google Patents

Abstract

PURPOSE:To manufacture a SOI substrate that allows the density of impurity on the surface thereof to be accurately grasped and that generates no leakage current by removing a defective area from the surface of singlecrystal silicon. CONSTITUTION:Silicon substrate 10 is thermally treated after injecting oxygen ion to prepare silicon oxide layer 12 embedded inside the bottom of singlecrystal silicon layer 14 prepared on the surface of the substrate, the surface of singlecrystal silicon layer 14 is oxidized to prepare a surface silicon oxide layer 16. Next, a bearing silicon substrate 20 is bonded to the surface silicon oxide layer 16 and the silicon substrate 10 and embedded silicon oxide layer 12 are removed by etching. Further, a transition region 18 is oxidized and the prepared silicon oxide layer 18' is selectively removed by etching. With this, the transition region 18 that has much surface defect is removed, the SOI(Silicon On Insulatior) substrate having good characteristic that no leakage current is generated can be made, and further the impurity density of singlecrystal silicon layer 14 which is the same as that of silicon substrate 10 can be accurately grasped in advance.

Description

[Detailed Description of the Invention] [Summary] SOI (S
An object of the present invention is to provide a method for manufacturing an SOI substrate in which the impurity concentration on the surface can be accurately determined and an SOI substrate with good characteristics without leakage current can be manufactured. A step of implanting oxygen ions into a silicon substrate and then performing heat treatment to form a buried silicon oxide layer buried inside the single crystal silicon layer on the surface of the silicon substrate; a step of oxidizing to form a surface silicon oxide layer; a step of bonding the silicon substrate to a support substrate so that the surface silicon oxide layer is adhered; and a step of burying a substrate portion of the silicon substrate so that the silicon oxide layer is exposed. etching away the buried silicon oxide layer from the bottom surface of the substrate until the single crystal silicon layer is exposed; and oxidizing the exposed surface of the single crystal silicon layer to remove the silicon oxide layer. and removing defective regions on the exposed surface of the single crystal silicon layer by etching.

[Industrial Application Fields] The present invention is directed to S in which a single crystal silicon layer is formed on an insulating layer.
OI (Silicon On In5ulator)
The present invention relates to a method for manufacturing a substrate.

SOI technology, which forms semiconductor elements on SOI substrates, is
■CMO that allows complete isolation between elements using insulators
There is no latch-up in 3, and high density is possible.
■It is attracting attention as a technology that can be expected to achieve high-speed operation because it can reduce parasitic capacitance. The basic methods for forming an SOI substrate include: ■ forming a single crystal silicon layer on an insulating substrate; ■ forming a single crystal of amorphous silicon on a silicon oxide layer; and ■ forming a single crystal silicon layer on a silicon oxide layer. There are two methods: (1) forming a buried silicon oxide layer while leaving a single crystal layer; and (2) bonding a support substrate and a silicon substrate together, removing the silicon substrate from the bottom and forming a single crystal silicon layer on the support substrate.

[Prior Art] As a method of manufacturing an SOI substrate in which a buried silicon oxide layer is formed while leaving a single crystal layer on the surface of a silicon substrate, oxygen ions of high concentration are implanted into the silicon substrate with high energy to form a buried silicon oxide layer inside the silicon substrate. SIM OX (Separation by I) forming a buried silicon oxide layer
(planted Oxygen) technology is known.

However, in the case of SIMOX technology, the buried silicon oxide layer formed inside the silicon substrate is formed by ion implantation, so defects occur in the transition region at the boundary between the buried silicon oxide layer and the single crystal silicon layer, resulting in leakage current. There was a problem that occurred.

A method of bonding a supporting substrate and a silicon substrate together and removing the silicon substrate from the bottom to form a single crystal silicon layer on the supporting substrate. A technique that uses the difference in etching rate depending on impurity concentration to act as an etching stopper for the silicon substrate. There is. An impurity is added to the silicon substrate to form a layer with a high impurity concentration, and the silicon substrate laminated to the support substrate is etched from the bottom using an etching solution whose etching rate differs depending on the impurity concentration. Stop the etching with a new layer.

However, with this method, etching stops at the transition region from the high concentration impurity layer to the low concentration impurity layer.
For this reason, there is a problem in that the impurity concentration on the surface of the SOI substrate that is not exposed by etching is not determined.

[The problem that the invention seeks to solve! ] Conventionally, in the case of the SIMOX technology, there has been a problem in that defects occur in the transition region at the boundary between the buried silicon oxide layer and the single crystal silicon, resulting in leakage current. Further, in the case of the bonding technique, there is a problem that the impurity concentration on the surface of the SOI substrate is not determined.

The purpose of the present invention is to be able to accurately determine the impurity concentration on the surface;
An object of the present invention is to provide a method for manufacturing an SOI substrate that can manufacture an SOI substrate with good characteristics that does not generate leakage current.

[Means for Solving the Problem] The above object is to implant oxygen ions into a silicon substrate and then perform heat treatment to form a buried silicon oxide layer buried inside a single crystal silicon layer on the surface of the silicon substrate. a step of oxidizing the surface of the single crystal silicon layer to form a surface silicon oxide layer; a step of bonding the silicon substrate to a support substrate so that the surface silicon oxide layer is bonded; etching away the substrate portion from the bottom surface of the substrate until the buried silicon oxide layer is exposed; etching and removing the buried silicon oxide layer until the single crystal silicon layer is exposed; and exposing the single crystal silicon layer. This is achieved by a method for manufacturing an SOI substrate, which comprises the steps of: removing defective regions on the exposed surface of the single crystal silicon layer by oxidizing the surface and etching away the silicon oxide layer.

[Operation] According to the present invention, the impurity concentration on the surface can be accurately determined,
It is possible to manufacture an SOI substrate with good characteristics that does not cause leakage current.

[Example] A method for manufacturing an SOI substrate according to an example of the present invention will be described with reference to FIG.

First, oxygen ions are implanted into the silicon substrate 10 at an acceleration energy of about 200 keV and a dose of 1018 cm-2, and then high-temperature heat treatment at about 1200° C. is performed. Then, a buried silicon oxide layer 12 is formed inside the silicon substrate 10 while maintaining the single crystal on the surface thereof. However, a transition region 18 with many defects exists between the single crystal silicon layer 14 and the buried silicon oxide layer 12 on the surface of the silicon substrate 10. Subsequently, the surface of the single crystal silicon layer 14 is oxidized to form a silicon oxide layer 16 with a thickness of approximately 1100 nm (FIG. 1(a)).

Next, a silicon substrate 20 for support is prepared, and the silicon substrate 1 is placed so that the silicon oxide layer 16 is adhered to the surface thereof.
Turn 0 over and paste it together. Next, the substrate portion of the silicon substrate 10 is etched from the bottom using an etching solution mainly composed of hydrofluoric acid (HF) and nitric acid (HNO).
Figure 1(b)). The buried silicon oxide layer 12 serves as an etching stopper, and etching progresses until the buried silicon oxide layer 1112 is exposed.

Next, the buried silicon oxide layer 12 is etched away using an etching solution containing hydrofluoric acid (HF) as a main component (FIG. 1(C)). The single-crystal silicon layer 14 serves as an etching stopper, and etching progresses until the single-crystal silicon layer 14 is exposed, and the transition region 18 of the single-crystal silicon layer 14, which has many defects, is exposed at the surface.

Next, wet oxidation is performed for a predetermined time so that the transition region 18 with many defects is completely oxidized to form a silicon oxide layer 18' (FIG. 1(d)). Subsequently, the silicon oxide layer 18' is selectively etched away using an etching solution containing hydrofluoric acid (HF) as a main component (FIG. 1(e)), and the single crystal silicon layer 14 exposed in this way is removed. In this case, the transition region 18 with many defects on the surface is removed, and a good single crystal silicon layer 14 is formed on the silicon oxide layer 16, resulting in an SOI substrate. Further, since the impurity concentration of the single crystal silicon layer 14 is the same as the impurity concentration of the silicon substrate 10, it can be accurately determined in advance.

The present invention is not limited to the above embodiments, and various modifications are possible.

For example, any type of substrate may be used as the support substrate as long as it can support a silicon substrate.

[Effects of the Invention] As described above, according to the present invention, the impurity concentration on the surface can be accurately determined, and an SOI substrate with good characteristics without leakage current can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a process sectional view of a method for manufacturing an SOI substrate according to an embodiment of the present invention. In the figure, 10...Silicon substrate 12...Buried silicon oxide layer 14...Single crystal silicon layer 16...Silicon oxide layer 18...Transition region 18'...Silicon oxide layer 20... silicon substrate

Claims (1)

[Claims] 1. A step of implanting oxygen ions into the silicon substrate and then performing heat treatment to form a buried silicon oxide layer buried inside the single crystal silicon layer on the surface of the silicon substrate; oxidizing the surface of the crystalline silicon layer to form a surface silicon oxide layer; bonding the silicon substrate to a support substrate so that the surface silicon oxide layer is adhered; and embedding the substrate portion of the silicon substrate. etching away the silicon oxide layer from the bottom surface of the substrate until the silicon oxide layer is exposed; etching away the buried silicon oxide layer until the single crystal silicon layer is exposed; oxidizing the exposed surface of the single crystal silicon layer; A method for manufacturing an SOI substrate, comprising the step of removing a defective region on an exposed surface of the single crystal silicon layer by etching away the silicon oxide layer.