JP2004363198A - Method of producing strained silicon soi substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a strained Si-SOI (silicon-on-insulator) substrate having a flat and flawless surface and containing only Si. <P>SOLUTION: The production method is characterised in that, after an amorphous SiGe layer containing Ge at a set concentration and an amorphous silicon thin film are formed sequentially on an SOI substrate, hydrogen ions are injected into the interface between the Box oxide film and an Si layer on the SOI substrate and then heat treatment is performed at least once at a specified temperature in an oxidizing atmosphere, and subsequently, the amorphous SiGe layer and the amorphous silicon layer are melted by heat treatment and the oxide film is removed before a strained silicon film is deposited. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a substrate for a semiconductor device, in particular, a strained silicon SOI substrate.
[0002]
[Prior art]
Silicon MOS devices have achieved both high speed and low power consumption by reducing the size and operating voltage in accordance with the scaling rule.
However, when the gate length is in the region of 100 nm or less, it is becoming difficult to achieve both of the above. For this reason, the introduction of an SOI substrate and strained silicon has been studied. In particular, a substrate in which strained silicon has been introduced on an SOI substrate is considered to be the ultimate substrate, and research is proceeding.
[0003]
As a first method, a combination of an SOI substrate and a SiGe epi technology is provided (for example, see Patent Document 1). The method disclosed in Patent Document 1 is a method in which a SiGe epilayer is formed on an existing SOI substrate to cause strain relaxation, and a Si film is formed on the strain-relaxed SiGe film to obtain strained Si.
As a second method, a method of forming a strain-relaxed SiGe layer on a buried oxide film by an oxygen ion implantation separation method (SIMOX) is disclosed (for example, see Patent Document 2).
[0004]
As a third method, a method is disclosed in which a SiGe film is formed on an SOI substrate, and then strain is relaxed while diffusing Ge by heat treatment in an oxidizing atmosphere (for example, see Patent Document 3).
As a fourth method, a method is disclosed in which a SiGe film is formed on an SOI substrate, the SiGe layer is melted by heat treatment, and then the SiGe layer is solidified while diffusing Ge, thereby relaxing strain (for example, disclosed). And Patent Document 4.).
[0005]
[Patent Document 1]
JP-A-7-169926 [Patent Document 2]
JP-A-9-321307 [Patent Document 3]
JP 2000-243946 A [Patent Document 4]
JP-A-2003-31495 [0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for manufacturing a strained Si-SOI substrate that has a flat surface, few defects, and contains only Si.
[0007]
[Means for Solving the Problems]
According to the present invention, after an Amorphous SiGe layer containing a set concentration of Ge and an Amorphous silicon thin film are sequentially formed on an SOI substrate, hydrogen is ion-implanted into an interface between the Box oxide film and the Si layer of the SOI substrate to form an oxidizing atmosphere. A heat treatment at a predetermined temperature and for a predetermined time under heat, a heat treatment for melting the amorphous SiGe layer and the amorphous silicon layer, and removing an oxide film to form a strained silicon SOI. This is a method for manufacturing a substrate.
In the method for manufacturing a strained silicon SOI substrate according to the present invention, the hydrogen atom implantation condition is such that the acceleration voltage is selected by the total thickness of the film formed by epitaxial growth of Si, SiGe or the like on the Box oxide film, and the implantation amount is 1 × 10 ¹⁴ to 1 × 10 ¹⁶ atoms / cc.
[0008]
Elements to be implanted are helium, carbon, and oxygen in addition to hydrogen. The maximum temperature of the heat treatment is lower than the solidus depending on the Ge concentration in the final SiGe film. After removing the oxide film, a flattening process is performed.
The heat treatment after the implantation of the hydrogen atoms is performed at a temperature lower than the solidus depending on the Ge concentration in the final SiGe film.
[0009]
Since hydrogen is easily ion-implanted at the interface between the Box oxide film and the Si layer of the SOI substrate, the atomic bond therebetween is easily broken, and the subsequent melted and single-crystallized SiGe layer is sufficiently relaxed and the formed strain is reduced. The silicon layer can have a sufficient amount of strain according to the Ge concentration of the SiGe layer. Further, if the element to be implanted is large, the crystallinity of the silicon layer of the SOI substrate may be disturbed. For the same reason, it is better that the injection amount is small.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
First, as shown in FIG. 1, an amorphous SiGe layer 4 having a Ge concentration of 42% is 125 nm and an amorphous silicon layer 5 having a thickness of 30 nm is formed on an SOI substrate having a BOX oxide film 2 and a silicon thin film 3 having a thickness of 55 nm on a silicon 1. They are formed sequentially by a CVD apparatus. In this case, a CVD apparatus was used as a film forming apparatus, but the method is not particularly limited. Thereafter, 5 × 10 ¹⁵ atoms / cc of hydrogen atoms are implanted into the interface between the BOX oxide film 4 and the silicon thin film 5 of the SOI substrate. The hydrogen injection amount at this time is preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁶ atoms / cc. When the implantation amount is 1 × 10 ¹⁴ or less, the Raman peak shift is small and the SiGe layer is not sufficiently relaxed. Therefore, the implantation amount of 1 × 10 ¹⁴ or more is necessary. In order to disturb the crystallinity of the silicon thin film 3, the injection amount is preferably as small as possible, and is preferably 1 × 10 ¹⁶ or less. Hydrogen is the best element to be implanted, but helium, carbon, and oxygen also provide the same effect.
[0011]
Next, an insulator 6 is formed on the surface as shown in FIG. This is to prevent the Ge component from evaporating from the surface in the subsequent melting process. The insulator may be formed by oxidizing the amorphous silicon 5 on the surface. Next, heat treatment is performed at 1210 ° C. for 2 hours in order to melt the SiGe and further single-crystallize it. In order to perform single crystallization after melting, it is necessary to set the temperature to be lower than the solidus temperature according to the Ge concentration after the heat treatment according to the SiGe-based phase diagram shown in FIG. The horizontal axis in FIG. 3 represents the Si content (%) of SiGe, and the vertical axis represents the temperature (° C.). Of the two curves in the figure, the upper curve is called a liquidus line, and on a higher temperature side, it completely melts and is in a liquid state. The lower curve is called the solidus line, and it is in a solid state at lower temperatures. The region surrounded by the two curves is in a partially melted state. As described above, the amorphous SiGe layer 4 and the amorphous silicon layer 5 become a single crystal silicon thin film 3 and a SiGe single crystal 7 having a Ge concentration of 25% at 210 nm using the silicon thin film 3 as a seed crystal. FIG. 4 shows a schematic sectional view of the wafer after the heat treatment. After that, the insulating film on the surface was removed. Here, FIG. 5 shows the relationship between the amount of implantation and the amount of Raman peak shift after the insulating film is removed by heat treatment. This indicates how much the SiGe layer is relaxed, but the Raman shift amount is not sufficient for those without hydrogen implantation and the SiGe layer is not sufficiently relaxed, but the hydrogen implantation amount is approximately 1 × 10 ¹⁵ From the above, it can be seen that for the case where the heat treatment was performed for 110 minutes or more, a sufficient Raman shift with respect to the Ge concentration was obtained, and the SiGe layer was sufficiently relaxed. Thereafter, SiGe 8 having a Ge concentration of 25% and 50 nm and a strained silicon layer 9 having a thickness of 20 nm are successively formed by CVD to obtain a strained silicon wafer having an insulating film as a lower layer as shown in FIG. The surface roughness of the wafer manufactured according to the present embodiment after the heat treatment is very flat, approximately 0.5 nm in RMS. Further, the surface roughness could be reduced to 0.3 nm by performing a CMP treatment before CVD and continuously forming SiGe 8 having a Ge concentration of 25%, 50 nm, and a strained silicon layer 9 having a thickness of 20 nm by CVD.
[0012]
【The invention's effect】
According to the manufacturing method of the present invention, a strained silicon wafer having a sufficient amount of strain according to the concentration of the SiGe layer on the oxide film can be manufactured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram when an Amorphous SiGe layer containing Ge at a set concentration and an Amorphous silicon thin film are sequentially formed on an SOI substrate.
FIG. 2 is a cross-sectional configuration diagram when an insulator is formed on the laminate of FIG.
FIG. 3 is a state diagram of a SiGe system.
FIG. 4 is a schematic cross-sectional view of a wafer after heat treatment.
FIG. 5 is a diagram showing a relationship between an implantation amount and a Raman peak shift amount after a heat treatment is performed to remove an insulating film.
FIG. 6 is a sectional configuration diagram of a strained silicon wafer having an insulating film as a lower layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Silicon substrate 2 ... BOX oxide film 3 ... Silicon thin film 4 ... Amorphous SiGe layer 5 ... Amorphous silicon layer 6 ... Insulating film layer 7 ... Single crystal SiGe layer 8 after heat treatment 8 ... Single crystal SiGe layer 9 reformed by CVD ... Strained silicon layer

Claims (6)

After an Amorphous SiGe layer containing Ge at a set concentration and an Amorphous silicon thin film are sequentially formed on an SOI substrate, hydrogen is ion-implanted into an interface between the Box oxide film and the Si layer of the SOI substrate, and a predetermined amount is formed under an oxidizing atmosphere. A heat treatment for melting the amorphous SiGe layer and the amorphous silicon layer at least once at a temperature and for a time, and then forming a strained silicon film after removing an oxide film. Method. The hydrogen atom implantation conditions are such that the acceleration voltage is selected based on the total thickness of the film formed by epitaxial growth of Si, SiGe, or the like on the Box oxide film, and the implantation amount is 1 × 10 ¹⁴ to 1 × 10 ¹⁶ atoms / cc. A method for manufacturing a strained silicon SOI substrate according to claim 1. 3. The method according to claim 1, wherein the element to be implanted is helium, carbon, or oxygen in addition to hydrogen. 2. The method according to claim 1, wherein the maximum temperature of the heat treatment is lower than the solidus temperature according to the Ge concentration in the final SiGe film. 2. The method according to claim 1, wherein a flattening process is performed after removing the oxide film. 2. The method according to claim 1, wherein the heat treatment after the implantation of the hydrogen atoms is performed at a temperature lower than the solidus depending on the Ge concentration in the final SiGe film.

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