CN1440052A

CN1440052A - Preparation for silicon material on thick film insulative layers

Info

Publication number: CN1440052A
Application number: CN 03115827
Authority: CN
Inventors: 张峰; 程新利; 林志浪; 王永进
Original assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Current assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Priority date: 2003-03-14
Filing date: 2003-03-14
Publication date: 2003-09-03
Anticipated expiration: 2023-03-14
Also published as: CN100342492C

Abstract

A method to prepare thick film SOI (silicon on insulator) material uses thin SOI material prepared by SIMOX technique as the substrate and then to utilize vapor phase epitaxy method to make epitaxy for growing single crystal silicon layer. The SOI material prepared with this method can be used as the light waveguide material and the epitaxial layer thickness can be controlled as per the requirements. SiCl4, SiHCl3, SiH2Cl2 or SiH4 can be selected as the silicon source at the time of epitaxial growth and doping type of epitaxy can be selected according to the requirements as well as the backing should be baked with H2 high temperature to improve the surface situation of it. The silicon layer thickness of eptaxial layer will be 5-10 mu and the speed rate of deposition will be 0.3-0.8 mu/min.

Description

Preparation method of silicon material on thick film insulating layer

Technical Field

The invention relates to a Silicon On Insulator (SOI) material used as a thick film insulating layer of an optical communication waveguide material, provides a preparation method of the material, describes key technology therein, and belongs to the technical field of new materials.

Background

The wavelengths of light used for current optical communication are 1.30 mu and 1.55 mu, which are almost transparent to Si; the SOI material is characterized by a top layer of silicon and a buried layer of silicon oxide (SiO)₂) The refractive index difference is large, and the top layer silicon can be used for optical communicationThe light wave conducting layer has buried silica as the cladding, so that SOI material is one excellent optical waveguide material and the top silicon surface is oxidized to form the cladding during the manufacture of waveguide device. In view of the demand of the conventional optical communication devices, the thickness of the top layer silicon as the SOI material for optical communication is required to be generally 5 μ or more. There are several methods for producing SOI materials, and more mature SIMOX (separation by implantation of oxygen) with bonding thinning technique and oxygen implantation isolation. The bonding thinning method can be used for preparing SOI material with very thick top silicon, the thickness of the top silicon can be controlled as required, but the uniformity of the thickness of the top silicon is difficult to control during thinning, so the smoothness of the interface on the top silicon cannot be ensured, and the optical transmission loss can be increased, which is unfavorable for manufacturing waveguide devices [ Lijinhua, Linchengdu, G.T.Reed, and the like, silicon-bonded SOI planar waveguide exploration, optical science and report, Vol, 14, No.2, 1994p 169-172]. The SIMOX technology is to implant high-energy oxygen ions into the surface layer of a silicon wafer and then to fully combine the implanted oxygen with silicon through high-temperature annealing to form an insulated buried oxide layer. In the initial manufacturing process, due to the limitation of annealing conditions, the interface between the buried oxide layer and the Si layer in the prepared SOI material is poor, and the defect density of the top silicon layer is as high as 10⁷/cm²The order of magnitude [ Sadao Nakashima, Katsutoshi Izumi, Analysis of buried oxide layer formation and mechanism of reproduction of the substoichiometric oxygen gene region, J.Mater.Res., Vol.8, No.3, Mar1993, p 523-534]. After long-time research on injection and annealing processes, SOI wafers with good performance can be prepared at present. However, because of the energy limitation in the implantation process, the thickness of the top silicon layer of the SOI wafer prepared by the SIMOX process is too thin, generally less than 0.5 μ, and it is difficult to fabricate an optical waveguide device directly coupled with an optical fiber device. The invention aims to solve the problem that the top layer silicon of the SOI material is too thin.

Disclosure of Invention

The invention provides a method for preparing a thick-film SOI material, which overcomes the difficulties in the prior art. The method is characterized in that an SOI material prepared by SIMOX technology is used as a substrate, a monocrystalline silicon layer is grown on top silicon in a vapor phase epitaxial mode, a thick-film SOI material with good quality can be obtained, the upper interface and the lower interface (namely the interface with a buried oxide layer) of the top silicon are smooth, and the thickness of the top silicon can be controlled according to needs, as shown in figure 1.

The technical scheme of the invention is as follows:

cleaning an SOI substrate by using a semiconductor standard cleaning process before the SOI substrate is put into an epitaxial furnace;

2. etching the substrate by using HCl gas at 1200-1220 ℃ for 0.5-1 minute to remove the oxide layer on the surface of the substrate;

3. h is used at high temperature (deposition temperature) of SOI substrate before epitaxial deposition₂Baking for 0.5-1.5 hours to improve the surface condition of the substrate and remove the surface oxide layer remained in the step 2. The SOI substrate manufactured by the SIMOX process has larger surface roughness and a plurality of pits, and a plurality of defects are caused after the epitaxy on the substrate and pass through H₂After high-temperature baking, the oxide layer on the surface can be mixed with H₂After the reaction, the reaction product is removed, the surface condition can be obviously improved, the original pits disappear, and the surface becomes very flat.

4. SiCl may be used in epitaxial growth₄，SiHCl₃，SiH₂Cl₂Or SiH₄Performing epitaxial growth as silicon source, selecting appropriate doping source to prepare n or p type epitaxial layer and intrinsic epitaxial layer according to requirement, and introducing diluted PH when performing n type epitaxy₃If p-type epitaxy is also prepared, diluted B is introduced₂H₆. The reaction principle can comprise the following four reaction processes at high temperature:

(temperature 1150-1200 ℃ C.)

(temperature 1100-1150 deg.C)

(temperature 1050 ~ 1150 ℃ C.)

(temperature 1000-1100 ℃ C.)

5. The epitaxial growth time is controlled according to the deposition rate to obtain the required SOI top layer silicon thickness, the deposition quality is better within the range of 0.3-0.8 mu/min, and the thickness is more suitable for manufacturing the optical waveguide when the silicon is 5-10 mu. The temperature and time of epitaxial growth are determined according to the selected silicon source, the temperature is within the range of 1000-1200 ℃, and the time of epitaxial growth is about 6-15 minutes.

The invention is characterized in that the SOI material prepared by the SIMOX technology is used as a substrate to prepare the thick-film SOI material, the thickness of the top silicon of the material can be controlled according to the requirements of devices, the problem of insufficient thickness of the top silicon of the SOI material prepared by the SIMOX technology can be solved, and the surface flatness of the top silicon is superior to that of the SOI material prepared by the bonding thinning method. The invention is to epitaxially grow a monocrystalline silicon layer on an SOI substrate, which is different from epitaxial growth by using a common silicon wafer as a substrate, wherein the SOI substrate is influenced by the SIMOX process, the surface condition of the SOI substrate has more defects, metal contamination and the like compared with the common silicon wafer, the surface flatness of the SOI substrate is poorer than that of the bulk silicon, the defects and the metal contamination and the like have important influence on the growth of an external delay monocrystalline silicon layer, and the quality of the grown monocrystalline layer is not as good as that of the monocrystalline silicon layer epitaxially grown on the common silicon wafer under the same condition. The SOI substrate is thus treated before epitaxyto improve the surface condition to obtain a high-quality epitaxial single crystal silicon layer. In the present invention, H is used at high temperature₂Baking to improve the surface condition, wherein the surface of the substrate is planarized, FIG. 2 shows that the SOI substrate surface prepared by SIMOX technique is treated with H₂The change condition before and after baking and the flatness improvement of the substrate surface can reduce the generation of defects in the epitaxial growth process, and can obtain a single crystal epitaxial layer with good quality. Compared with the SOI wafer prepared by bonding and thinning method, the method has the advantages that the surface smoothness of the silicon single crystal layer on the insulating layer is good, and the method is very beneficial to reducing the interface loss when light propagates in the silicon layerIn (1). The method for preparing the thick-film SOI material utilizes a mature silicon epitaxial process except substrate treatment, and is easy to realize.

Drawings

FIG. 1(a) schematic view of epitaxial growth of single crystal silicon on SOI substrate

(b) And epitaxially growing the thick-film SOI material.

FIG. 2(a) AFM photograph of SOI substrate surface prepared by SIMOX technique

(b) The SOI substrate surface prepared by SIMOX technology is subjected to high temperature H₂AFM photograph after baking.

FIG. 3 is a cross-sectional electron micrograph of a thick film SOI material epitaxially grown on an SOI substrate.

In the figure:

1-Bulk silicon, 2-buried oxide, 3-substrate top silicon (epitaxial substrate), 4-silicon (or doped) atoms to be deposited, 5-epitaxially grown single crystal silicon layer, Bulk-Si being Bulk silicon, Epi-Si being epitaxial silicon layer.

Detailed Description

Example 1

And (3) taking the full-dose SOI material prepared by the SIMOX process as a substrate to epitaxially grow a thick-film SOI material. The SOI substrate parameter is P type (100), the resistivity is 10-20 omega cm, the thickness of the buried oxide layer is about 400nm, and the thickness of the top silicon layer is about 200 nm; in a barrel type epitaxial furnace, SiCl is adopted₄As a silicon source, the epitaxial growth temperature was 1180 ℃ using H₂And (3) starting epitaxial growth after baking for 1 hour, wherein the deposition rate in the epitaxial process is 0.7-0.8 mu/min, the time is 10 minutes, no doping is carried out in the epitaxial process, and the prepared intrinsic SOI epitaxial wafer is. FIG. 3 is a transmission electron micrograph of the cross section of the thick film SOI material prepared. The epitaxial layer is about 8 mu thick.

Example 2

And (3) taking the full-dose SOI material prepared by the SIMOX process as a substrate to epitaxially grow a thick-film SOI material. In this example, an N-type epitaxial wafer was prepared by introducing PH during epitaxy₃As a doping source, the other conditions were the same as in example 1The same is true. The epitaxial layer is about 8 mu thick.

Example 3

And (3) taking the full-dose SOI material prepared by the SIMOX process as a substrate to epitaxially grow a thick-film SOI material. In this example, a P-type epitaxial wafer was prepared by introducing B during epitaxy₂H₆As a doping source, SiHCl is selected₃The epitaxial growth temperature as a silicon source was 1100 deg.c, and the thickness of the epitaxial layer was about 7.4 μ under the same conditions as in example 1.

Claims

1. A preparation method of silicon material on a thick film insulating layer comprises the use of SIMOX preparation technology, and is characterized by comprising the following specific steps:

(1) the SOI material prepared by the SIMOX technology is used as a substrate, the substrate is etched for 0.5-1 minute at 1200-1220 ℃ by HCl gas after being cleaned, and an oxide layer on the surface of the substrate is removed;

(2) the SOI substrate is treated with H at deposition temperature before epitaxial deposition₂Baking for 0.5-1 hour;

(3) epitaxial growth using SiCl₄，SiHCl₃，SiH₂Cl₂Or SiH₄And performing epitaxial growth as a silicon source, wherein the deposition rate is 0.3-0.8 mu/min, and the epitaxial growth temperature is 1000-1200 ℃.

2. The method of forming a thick film silicon-on-insulator material as claimed in claim 1 wherein said cleaning of said SOI substrate is a semiconductor standard cleaning process.

3. A method of forming a thick film silicon-on-insulator material as claimed in claim 1 wherein the epitaxial growth is by selection of a suitable dopant source to form an n-type or p-type epitaxial layer.

4. A process for the preparation of a thick film silicon-on-insulator material as claimed in claim 3 wherein the diluted pH is introduced during the preparation of the n-type epitaxial layer₃(ii) a Introducing diluted B when preparing p-type epitaxial layer₂H₆A doping source.

5. The method for preparing a silicon material on a thick film insulating layer according to claim 1, wherein the thickness of the epitaxial silicon layer is 5 to 10 μ, and the deposition time is 6 to 15 minutes.