JPH05299349A - Manufacture of soi substrate - Google Patents

Abstract

PURPOSE:To manufacture an ultra thin film SOI substrate in excellent crystallizability of semiconductor layer and less impurity pollution. CONSTITUTION:A polysilicon layer 8 laminated on the surface of a silicon substrate is implanted with oxygen ions so as to form an SiO2 film 3 and then a silicon layer 4 on the SiO2 film 3 is heat-treated to form an SOI layer 5 thereby manufacturing the title SOI substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an SOI substrate, and more particularly to SIMOX (Separation).
The present invention relates to a method for manufacturing an SOI substrate by the by IM planted OXygen method.

[0002]

2. Description of the Related Art A wafer in which a single crystal silicon thin film is formed on an insulating substrate is an SOI (Silicon On I) wafer.
It is called an abbreviation for “Nusulator”, and MOS (Metal Oxide Semiconductor) is formed on this single crystal silicon thin film.
When a semiconductor element such as a field effect transistor (which is an abbreviation for “onductor”) is formed, the speed of the element can be increased by reducing the parasitic capacitance and increasing the current driving capability.
There is an effect that the short channel effect is reduced. Conventionally,
Many methods have been proposed for forming an SOI structure, in which a high concentration of oxygen ions is implanted into a silicon substrate to form an SO.
The SIMOX method of forming an I structure is one of them. The SIMOX method will be described below.

In the SIMOX method, for example, oxygen ions are implanted into a silicon substrate at an acceleration energy of 200 keV and a dose of 2.0 × 10 ¹⁸ / cm ² , and then 1300.
This is a method of directly forming a buried film (SiO ₂ film) inside a silicon substrate by sufficiently performing heat treatment in a mixed gas of Ar / O ₂ or N ₂ / O ₂ at a high temperature of ℃ or higher. FIGS. 4A to 4C show SOI by SIMOX method.
It is process drawing which shows the manufacturing method of a board | substrate. FIG. 4A is a diagram showing a silicon substrate, and 1 is a silicon substrate. FIG. 4B is a diagram showing a step of implanting oxygen ions into the silicon substrate 1. Silicon substrate 1 500
In a state of being heated to ˜600 ° C., oxygen ions 2 are supplied from the upper surface of the silicon substrate 1 at an acceleration energy of 200 ke, for example.
Implant with V and dose of 2.0 × 10 ¹⁸ / cm ² . By implanting oxygen ions 2, a buried insulating film (hereinafter referred to as a SiO ₂ film) 3 is formed by the reaction between the silicon substrate 1 and the oxygen ions 2. 4 is a silicon layer on the SiO ₂ film 3. FIG. 4C is a diagram showing a step of performing heat treatment after the oxygen ion 2 implantation shown in FIG. For example, by performing heat treatment at a high temperature of 1300 ° C. or higher in an Ar / O ₂ atmosphere for about 5 hours, defects generated by implantation of oxygen ions 2 are eliminated, and the crystallinity is recovered, so that the single crystal silicon layer ( Hereinafter, referred to as an SOI layer) 5 is formed. However, various defects are generated in the silicon substrate 1 because the oxygen ions 2 are implanted at a high implantation amount.
These defects do not disappear even by heat treatment at 00 ° C. or higher. On the contrary, by the high temperature heat treatment, these minute defects grow and become linear defects that reach from the surface of the silicon layer 4 to the boundary surface between the silicon layer 4 and the SiO ₂ film 3.
This is called threading dislocation 6. Furthermore, during heat treatment,
In order to prevent the reaction with the Ar / O ₂ atmosphere, FIG.
As shown in, the protective film 7 (Si
O ₂ ) may be formed in some cases.

Next, the ion implantation conditions adopted to manufacture the SOI substrate will be described below. Figure 5
FIG. 4 is a diagram showing the oxygen concentration in the silicon substrate 1 with respect to the implantation amount of oxygen ions 2. Here, the acceleration energy is 2
It is set to 00 keV. In the figure, when the implantation amount of oxygen ions 2 is small, oxygen has a Gaussian distribution in the silicon substrate 1, and the SiO ₂ film 3 is not formed in the silicon substrate 1.
However, the critical injection amount necessary for implantation of oxygen ions 2, SiO ₂ film 3 is formed in the silicon substrate 1 (1.
Becomes a 35 × 10 ¹⁸ / cm ²⁾ or more, the oxygen concentration in the vicinity of the injection peak, the number of oxygen atoms per 1 cm ³ contained in SiO _2, i.e., the SiO ₂ stoichiometric concentrations (4.
4 × 10 ²² / cm ³ ). Therefore, excess oxygen diffuses toward the bottom of the distribution, and the silicon substrate 1
Reacting with to form a SiO _2, it is possible to obtain the SiO ₂ film 3 of sharp interface in the silicon substrate 1. The reaction at this time is expressed as follows. xSi + 2Oi → SiO ₂ + (x-1) Sii …………………… (1) (Oi: interstitial oxygen, Sii: interstitial silicon) Here, interstitial oxygen is something other than interstitial oxygen. Is an oxygen atom that is not bonded to the atom, and interstitial silicon is a silicon atom that is not bonded to other atoms interrupted between the lattices. By implanting oxygen ions 2 in an amount equal to or greater than the critical implant amount, SiO ₂ is produced, but interstitial silicon is released to mitigate the simultaneous volume increase. The interstitial silicon is absorbed by the surface of the silicon substrate 1 serving as a sink. However, as the implantation amount of oxygen ions 2 increases, the number of interstitial silicon generated increases,
Over time, the excess interstitial silicon coalesces with each other and remains as defects in the layer of silicon layer 4. This defect is stabilized as threading dislocations 6 fixed between the surface of the silicon substrate 1 and the SiO ₂ film 3 in the subsequent heat treatment step, and causes the crystal quality of the silicon substrate 1 to deteriorate.

The density of threading dislocations 6 depends on the ion implantation conditions. FIG. 6 is a diagram showing the dependency of dislocation density in the SOI layer on the oxygen ion implantation amount and the acceleration voltage. As shown in FIG. 6, the dislocation density tends to increase as the implantation amount of oxygen ions increases and as the acceleration voltage decreases. Therefore, high-quality SiO ₂ without causing threading dislocations 6
In order to form the film 3, there is a multi-ion implantation (multi-stage implantation) method that utilizes the correlation between the implantation amount and the defect density. In this method, in order to reduce the dislocation density, oxygen ions are implanted with a lower implantation amount (0.5 to 1.0 × 10 ¹⁸ / cm ² ) as compared with the conventional method, and then a heat treatment is performed to obtain crystalline After recovery and precipitation of SiO _2, the method of repeating this implantation / heat treatment is repeated several times in order to obtain a prescribed implantation amount. With this method, an SOI substrate having an extremely high quality SiO ₂ film having a very steep Si / SiO ₂ interface and a dislocation density in the SOI layer of 10 ³ / cm ² or less can be realized. However, this method is not suitable for commercial mass production because the process becomes complicated.

Further, in order for the SOI substrate to be used as a substrate for forming a thin film SOI / MOS field effect transistor, it is required that the film thickness of the SOI layer is 1000 Å or less. FIG. 7 is a diagram showing the oxygen ion implantation amount and the acceleration voltage dependency of the film thickness of the SOI layer. As shown in FIG. 7, the film thickness of the SOI layer can be made thinner as the oxygen ion implantation amount increases and the acceleration voltage becomes lower.
However, since all of these conditions increase the dislocation density, a method for satisfying both the thickness of the SOI layer and the dislocation density has not been developed yet. Further, in the process of ion implantation and heat treatment in the SIMOX method, there remains a problem that the silicon substrate 1 is contaminated with impurities from the device.

[0007]

As described above, in the SOI substrate manufactured by the conventional manufacturing method, threading dislocations remain or are contaminated with impurities, so that the crystal quality is inferior and the MOS substrate on the SOI substrate is deteriorated. -Type field-effect transistor causes the breakdown voltage due to defects and impurities being taken into the gate oxide film during the formation of the gate oxide film and the increase in power consumption due to the current generated by the defects existing in the depletion layer. However, there is a problem that the characteristics of (3) are deteriorated. Further, since a thin film SOI layer having a film thickness of 1000 Å or less cannot be obtained without leaving threading dislocations, there is a problem that it is not suitable for a substrate for forming a thin film SOI / MOS field effect transistor.

The present invention has been made to solve the above problems, and can improve the crystallinity and impurity contamination of the SOI layer, and can form the SOI layer to a thickness of 1000 Å or less. It is an object to provide a method for manufacturing an SOI substrate.

[0009]

A method of manufacturing a silicon substrate according to the present invention comprises a step of laminating a polycrystalline silicon layer on a first surface of a silicon substrate, and an ion implantation from the first surface of the silicon substrate. And a step of forming a silicon oxide film in the silicon substrate, and a step of heat-treating the silicon layer between the polycrystalline silicon layer and the silicon oxide film.

Further, instead of the polycrystalline silicon layer,
It is a stack of amorphous silicon layers.

Further, in the method for manufacturing a silicon substrate according to the present invention, a step of performing ion implantation from the first surface of the silicon substrate to form a first silicon oxide film in the silicon substrate, and the first silicon. Forming a second silicon oxide film outside the element formation region on the surface of the silicon layer on the oxide film; and stacking a polycrystalline silicon layer on the surface of the silicon layer and the surface of the second silicon oxide film. A step of performing a heat treatment on the silicon layer after laminating the polycrystalline silicon layer, a step of polishing and removing the polycrystalline silicon layer using the silicon oxide film as a stopper film after the heat treatment step, After the removing step, the polycrystalline silicon layer remaining on the surface of the silicon layer is removed by selective etching.

[0012]

In the manufacturing method of the present invention, the first silicon substrate is used.
After depositing a polycrystalline layer on the surface of the silicon substrate, ion implantation for forming a silicon oxide film in the silicon substrate is performed, and heat treatment is performed after the ion implantation, so that the silicon on the silicon oxide film is formed along with the formation of SiO _2. It is possible to prevent a large amount of interstitial silicon generated in the layer from being absorbed by the crystal grain boundaries in the polycrystalline layer and causing threading dislocations in the silicon layer. Further, the thin film SOI layer can be formed by making the implantation depth of oxygen ions shallow by the film thickness of the polycrystalline layer.

Further, after the ion implantation, a second silicon oxide film is formed on the surface of the silicon layer on the first silicon oxide film outside the element formation region, and a large amount is formed on the surface of the silicon layer and the surface of the silicon oxide film. Since the heat treatment is performed on the silicon layer after the crystal layers are stacked, it is possible to prevent threading dislocation from occurring in the silicon layer below the element formation region as described above. Further, the polycrystalline layer is polished and removed using the second silicon oxide film as a stopper film, and the polycrystalline layer remaining on the surface of the silicon layer is removed by selective etching. The second silicon oxide film serves as a stopper layer due to the difference in polishing rate from the silicon oxide film, and the thickness of the polycrystalline layer can be made as thin as the thickness of the second silicon oxide film. The etching time can be shortened, and the silicon layer can be prevented from being over-etched due to the etching of the polycrystalline layer. Therefore, the film thickness of the silicon layer can be made uniform.

[0014]

EXAMPLES Example 1. FIG. 1 is a process drawing showing a method for manufacturing an SOI substrate showing an embodiment of the present invention. In the figure, 1 to 5 indicate parts that are the same as or correspond to those of the conventional technique. Reference numeral 8 is a polysilicon layer. Next, the manufacturing process will be described. Since the basic manufacturing process is almost the same as that described in the prior art, only the differences from the prior art will be described. As shown in FIG. 1A, a polysilicon layer is laminated on the surface of the silicon substrate 1 before oxygen ion implantation. Figure 1
As shown in (b), the SiO ₂ film 3 is formed by implanting oxygen ions 2. 4 is a silicon layer on the SiO ₂ film 3. Next, as shown in FIG.
When the heat treatment is performed at about 300 ° C., the crystallinity of the silicon layer 4 is improved and the SOI layer 5 is obtained. Figure 1 after heat treatment
As shown in (d), by removing the polysilicon layer 8 on the surface by selective etching, a good-quality SOI substrate with improved crystallinity can be obtained.

The polysilicon layer 8 has many crystal grain boundaries that can serve as sinks for interstitial silicon. It is possible to absorb a large amount of interstitial silicon that accompanies the formation of SiO ₂ during ion implantation and heat treatment, and it is possible to significantly suppress the generation and growth of defects. For example, the acceleration energy of oxygen ions is 200 keV, and the dose is 2.0 × 1.
The dislocation density of the SOI layer 5 formed under the implantation conditions of 0 ¹⁸ / cm ² is 1.0 × 10 ⁸ / cm ² to 1.0 × 10 ^{8 of the} conventional one.
^It can be significantly reduced to about ³ / cm ² and the crystallinity is remarkably improved.

Next, the thinning of the SOI layer 5 will be described. As shown in FIG. 1B, since oxygen ions 2 are implanted through the polysilicon layer 8, the oxygen ions 2
The penetration depth of is smaller than that without the polysilicon layer 8 by the film thickness of the polysilicon layer 8. For example, the acceleration energy of oxygen ions is 200 keV, and the dose is 2.0 × 1.
When injected under the condition of 0 ¹⁸ / cm ² , from FIG.
Although the SOI layer 5 of 0 Å is formed, in the present invention, the thickness of the polysilicon layer 8 is set to the desired value.
The thickness of the SOI layer can be easily formed into a thin film having a thickness of 1000 Å or less by setting such that For example, by setting the film thickness of the polysilicon layer 8 to 1500Å, it is possible to obtain the thin film SOI layer 5 having a film thickness of 500Å.

Further, when the polysilicon layer 8 is laminated on the silicon substrate 1, it has a function of gettering impurities in silicon. Therefore, this laminated polysilicon layer 8
Can getter the impurities mixed in during the ion implantation and the heat treatment, and can significantly reduce the impurities in the SOI layer 5.

This embodiment is a manufacturing method excellent in mass productivity because the process is not complicated unlike the multi-ion implantation method shown in the prior art. Further, when the MOS field effect transistor is formed on the SOI substrate 5, the withstand voltage defect of the gate oxide film is improved, and the generated current generated by the dislocation, which is one of the causes of the leakage current, is reduced.
The junction leakage current between the source and drain is reduced, and power consumption can be reduced.

Example 2. In the first embodiment, the same polysilicon layer was used from the oxygen ion implantation to the heat treatment step. However, as shown in FIG. 2A, if the polysilicon layer 8 is further stacked after the oxygen ion implantation, , FIG. 2 (b)-
As shown in (c), after the oxygen ion implantation, the polysilicon layer 8 may be removed and a new polysilicon layer 8 may be laminated, and the same effect as that of the above-described first embodiment can be obtained.

Example 3. Further, considering only the effect of reducing dislocation density and impurity contamination, the above effect can be obtained even if the polysilicon layer 8 is stacked and processed only in one of the steps of oxygen ion implantation or heat treatment. Is.

Example 4. In the first embodiment, the case where the interstitial silicon sink and the polysilicon layer 8 are stacked to control the oxygen ion penetration depth has been described. However, if the surface layer serves as the interstitial silicon sink, many other materials are used. A crystal layer or an amorphous layer (including an amorphous silicon layer) and a silicon surface may be subjected to damage treatment, and the same effect as that of the above-described first embodiment is obtained.

Embodiment 5. In addition, although the silicon semiconductor substrate and oxygen are used as the ion-implanted atoms in the first embodiment, any semiconductor substrate and ion can be used as long as an insulator can be formed in the semiconductor substrate by the ion-implantation method. Needless to say, the same effect can be obtained by using atoms.

Example 6. 3A to 3D are process drawings showing a method of manufacturing an SOI substrate showing another embodiment of the present invention. In the figure, 1 to 5 indicate parts that are the same as or correspond to those of the conventional technique. Reference numeral 8 is a polysilicon layer, 9 is a SiO ₂ thin film, and 10 is an element forming region. Next, the manufacturing process will be described. Since the basic manufacturing process is almost the same as that described in the prior art, only the differences from the prior art will be described.
First, as shown in FIG. 3A, the oxygen ions 2 are accelerated with an acceleration energy of 150 keV and a dose of 2.0 × 10 ^18.
/ Cm ² , and the SiO ₂ film 3 is formed. 4 is S
It is a silicon layer on the iO ₂ film 3. Next, as shown in FIGS. 3B and 3C, a SiO ₂ thin film 9 having a film thickness of 300 Å is formed outside the element formation region by using a normal patterning technique.
Are formed to expose the element formation region 10. Furthermore, FIG.
As shown in (d), a film thickness of 5 is formed on the entire surface of the silicon substrate 1.
A 000Å polysilicon layer 8 is deposited, and then, as shown in FIG.
As shown in (e), with respect to the silicon layer 4, Ar + 1%
Heat treatment is performed at 1300 ° C. for 6 hours in an O ₂ atmosphere.
The heat treatment improves the crystallinity of the silicon layer 4,
The SOI layer 5 having a film thickness of 1000Å is obtained. Next, FIG.
As shown in (f), the polysilicon layer 8 is polished and removed using the SiO ₂ thin film 9 as a stopper layer. Next, FIG.
As shown in (g), the SiO ₂ thin film 9 is removed by selective etching to leave the polysilicon layer 8 having a film thickness of 300 Å. Further, as shown in FIG. 3H, the polysilicon layer 8 is removed by selective etching to form a good-quality SOI substrate with improved crystallinity.

In the manufacturing method of the present embodiment, the function of the polysilicon layer 8 laminated on the silicon layer 4 is achieved even if the enzyme ion implantation conditions are adopted so that the SOI layer 5 is formed to have a film thickness of 1000Å. With the detailed description in Example 1, it is possible to suppress the occurrence of threading dislocations in the SOI layer 5, and to obtain the SOI layer 5 with improved crystallinity. Further, the thickness of the polysilicon layer 8 can be reduced to 300 Å due to the effect of the stopper layer of the SiO ₂ thin film 9, and thus the etching time of the polysilicon layer 8 can be shortened. It is possible to prevent the SOI layer from being over-etched due to the etching. Therefore, the SOI is more than the first embodiment.
It is possible to obtain an SOI substrate in which the film thickness uniformity of the layer 5 is good.

While the dislocation density of the SOI substrate according to the conventional manufacturing method is 1.0 × 10 ⁸ / cm ² , the dislocation density of the SOI substrate prepared by adopting this embodiment is 1.0 ×. It is 10 ³ / cm ² . That is, the dislocation density of the SOI substrate is greatly reduced and the crystallinity is significantly improved as compared with the conventional case. Further, regarding the film thickness uniformity, by adopting this embodiment, the film thickness uniformity of 0.1 ± 0.01 μm, which is about the same as the film thickness uniformity of the SOI substrate by the conventional manufacturing method that does not use the polysilicon layer 8. And can be good.

Example 7. In Embodiment 6, after removing by selective etching the SiO ₂ film 9 has been removed by selective etching of the polysilicon layer 8, the polysilicon layer 8 after selective etching, selecting etching the SiO ₂ film 9 Similar to Example 6, a good-quality SOI substrate with improved crystallinity can be formed.

[0027]

As described above, according to the method of manufacturing an SOI substrate of the present invention, the polycrystalline silicon layer is laminated on the surface of the silicon substrate and then the heat treatment is performed, so that the interstitial silicon which is the source of the defect is generated. Can be supplied, and since the polycrystalline silicon layer has a gettering effect of impurities, an SOI substrate having an SOI layer having a film thickness of 1000 Å or less and excellent in crystallinity with less impurity contamination can be obtained.

In addition, after forming a SiO ₂ thin film as a stopper film outside the element formation region on the surface of the silicon substrate, a polycrystalline silicon layer is laminated, the polycrystalline silicon layer is polished and removed, and is left on the silicon substrate. By selectively etching the polycrystalline silicon layer, the time for selective etching of the polycrystalline silicon layer can be shortened, so that over-etching of the SOI layer due to selective etching of the polycrystalline silicon layer can be prevented and the film thickness can be made uniform. An SOI substrate having excellent properties can be obtained.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of an SOI substrate showing a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of an SOI substrate showing a second embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of an SOI substrate showing a sixth embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of a conventional SOI substrate by a SIMOX method.

FIG. 5 is a diagram showing an oxygen concentration in a silicon substrate with respect to an oxygen ion implantation amount.

FIG. 6 is a diagram showing the dependence of dislocation density in an SOI layer on oxygen ion implantation amount and accelerating voltage.

FIG. 7 is a diagram showing oxygen ion implantation amount and acceleration voltage dependency of the film thickness of the SOI layer.

[Explanation of symbols]

1 Silicon Substrate 2 Oxygen Ion 3 Embedded Insulating Film (SiO ₂ Film) 4 Silicon Layer 5 Single Crystal Silicon Layer (SOI Layer) 6 Threading Dislocation 8 Polysilicon Layer 9 SiO ₂ Thin Film 10 Device Forming Area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Nishimura 4-1-1 Mizuhara, Itami City Mitsubishi Electric Corp. LSI Research Laboratory

Claims (3)

[Claims] 1. A step of laminating a polycrystalline silicon layer on a first surface of a silicon substrate, and ion implantation from the first surface of the silicon substrate,
A method of manufacturing an SOI substrate, comprising: a step of forming a silicon oxide film in a silicon substrate; and a step of heat-treating a silicon layer between the polycrystalline silicon layer and the silicon oxide film. 2. The method for manufacturing an SOI substrate according to claim 1, wherein an amorphous silicon layer is laminated instead of the polycrystalline silicon layer. 3. A step of performing ion implantation from a first surface of a silicon substrate to form a first silicon oxide film in the silicon substrate, and forming an element on the surface of the silicon layer on the first silicon oxide film. Forming a second silicon oxide film outside the region; laminating a polycrystalline silicon layer on the surface of the silicon layer and the surface of the second silicon oxide film; and after laminating the polycrystalline silicon layer. A step of performing a heat treatment on the silicon layer; and a step of polishing and removing the polycrystalline silicon layer up to the surface of the second silicon oxide film using the second silicon oxide film as a stopper film after the heat treatment step. After the step of polishing and removing, a step of removing the polycrystalline silicon layer left on the surface of the silicon layer on the first silicon oxide film by selective etching SOI substrate manufacturing method characterized by comprising and.