JP2002319666A - Method for manufacturing soi wafer and soi wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce occurrence of faults in high-temperature heat treatment. SOLUTION: A method for manufacturing an SOI wafer comprises the steps of implanting oxygen ions in a silicon substrate 1, and then forming an embedding silicon oxide film 3 in the substrate by heat treating in an atmospheric gas; and in this case, the atmospheric gas is a gas which contains a nitride gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing an SOI wafer having a buried silicon oxide film formed inside a silicon substrate and an SOI wafer.

[0002]

2. Description of the Related Art An SOI (Silicon) in which a silicon (Si) single crystal thin film (called an SOI layer) is formed on a buried silicon oxide film (called a BOX layer) which is an insulating film.
(On Insulator) Wafers have a high dielectric strength because the substrate and the SOI layer, which is the device fabrication layer, are electrically separated, have low parasitic capacitance, have high radiation resistance, and have no substrate bias effect. And so on. Therefore, effects such as high speed, low power consumption, and soft error free are expected, and various developments have been made as substrates for next-generation devices.

A typical SOI wafer fabrication technique is a so-called wafer bonding technique and SIM.
OX (Separation by IMplanted OXygen) technology.
Wafer bonding technology involves forming an oxide film on one or both of the two wafers, and bonding the two wafers between the oxide films. The bonding is performed by mechanically bonding the two wafers. It is performed by heat treatment with
The SOI layer is manufactured by grinding the bonded wafers by grinding and polishing. Since the crystallinity of the SOI film by wafer bonding is the same as that of a bulk silicon wafer, there are few problems such as defects and the characteristics of a device formed on the SOI layer are excellent.

In the SIMOX technology, oxygen is ion-implanted into a silicon substrate, and Ar (argon) / O ₂ (oxygen)
This is a technique in which a region containing oxygen in supersaturation is converted into a silicon oxide film by performing a high-temperature heat treatment in an atmosphere gas of this type, and a silicon single crystal thin film remains on a BOX layer to form SOI. The SIMOX technology does not require a grinding / polishing process unlike the wafer bonding technology, and has an advantage that it can be manufactured by a relatively simple process.

[0005]

However, the above S
The IMOX technology has the following problems.
Conventionally, when forming a buried silicon oxide film inside a silicon substrate by high-temperature heat treatment, many defects have been generated by interstitial silicon. Since these defects have an adverse effect on the characteristics of a device formed on a silicon single crystal thin film on a buried silicon oxide film, a heat treatment with less occurrence of defects is required.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a method for manufacturing an SOI wafer and an SOI wafer that can reduce the occurrence of defects during high-temperature heat treatment.

[0007]

The present invention has the following features to attain the object mentioned above. That is, in the method for manufacturing an SOI wafer of the present invention, after implanting oxygen ions into the inside of the silicon substrate, a buried silicon oxide film is formed inside the silicon substrate by heat treatment in an atmosphere gas.
A method for producing an OI wafer, wherein the atmosphere gas comprises:
It is characterized by containing a nitriding gas.

[0008] In the method for manufacturing the SOI wafer, since the atmospheric gas in the heat treatment comprises nitriding gas, the silicon substrate surface by a gas nitriding Si _x N _y (nitride film) is formed between many Vacancy (grating into the substrate Vacancies are injected, and interstitial silicon is taken into these vacancies, whereby defects can be reduced.

In the method of manufacturing an SOI wafer according to the present invention, it is preferable that the atmosphere gas is a gas containing a nitriding gas only during a temperature increasing process of the heat treatment. That is, in this SOI wafer manufacturing method, the atmosphere gas containing the nitriding gas is used only during the temperature raising step of the heat treatment, so that the atmosphere gas does not contain the nitriding gas during the annealing process held at a high temperature, and the silicon substrate is heated at a high temperature. It is possible to prevent N (nitrogen) from being excessively injected into the inside to adversely affect device characteristics.

In the method for manufacturing an SOI wafer according to the present invention, it is preferable that the atmosphere gas is a gas containing a nitriding gas having a decomposition temperature lower than a temperature at which N ₂ can be decomposed. That is, in this SOI wafer manufacturing method, the atmosphere gas is a nitriding gas having a decomposition temperature lower than the temperature at which N ₂ can be decomposed, such as NH ₃ , NO, N ₂ O, N ₂ O ₂ , hydrazine or dimethylhydrazine. Therefore, the nitriding gas is decomposed even at a lower temperature or for a shorter time than in the case of N ₂ , and the surface of the substrate is nitrided, so that the vacancy can be implanted into the inside, so that excessive implantation of N can be further prevented.

In the method for manufacturing an SOI wafer according to the present invention, the nitriding gas preferably contains NH ₃ (ammonia). That is, in the manufacturing method of the SOI wafer, by using a nitriding gas containing NH _3, NH ₃
Since H (hydrogen) generated by the decomposition has a cleaning effect of removing a natural oxide film or the like on the surface of the silicon wafer, nitriding of the surface and implantation of vacancy are further promoted.

In the method for manufacturing an SOI wafer according to the present invention, it is preferable that the nitriding gas is turned into plasma. That is, in this SOI wafer manufacturing method, since the nitriding gas is turned into plasma, the nitriding gas becomes an activated nitriding gas, and further, nitriding of the surface and Vacan is performed.
The injection of cy is promoted.

The SOI wafer of the present invention is an SOI wafer in which an embedded silicon oxide film is formed in a silicon substrate by heat treatment in an atmosphere gas after oxygen ions are implanted in the silicon substrate.
The heat treatment is performed by a method of manufacturing an I wafer.

In this SOI wafer, the S
Since the heat treatment is performed by the method of manufacturing an OI wafer, internal defects are significantly reduced, and a high-quality wafer excellent in characteristics of a device to be manufactured is obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a method for manufacturing an SOI wafer and an SOI wafer according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing the SOI wafer of the present invention in the order of the manufacturing steps, and FIG.

[Oxygen Ion Implantation Step] In order to manufacture the SOI wafer of the present invention, first, oxygen is ion-implanted from the front surface side of the silicon substrate 1 as shown in FIG.
At this time, an oxygen implantation region 2 in which oxygen is excessively present at a certain depth inside the silicon substrate 1 is formed. Note that the depth and oxygen concentration of the oxygen implantation region 2 are determined by the acceleration energy and dose (implantation amount) of oxygen ions.

[Annealing Step] After oxygen ion implantation, the silicon substrate 1 is placed in a heat treatment furnace, and a high-temperature heat treatment is performed for a predetermined time in a predetermined atmosphere gas as shown in FIG. The oxygen in the oxygen implantation region 2 is reacted with silicon to form SiO ₂ , forming a buried silicon oxide film 3 and, on the buried silicon oxide film 3, a silicon single crystal thin film 4 as a device fabrication region.

As shown in FIG. 2, the temperature profile of the heat treatment is as follows: the temperature is raised at a rate of, for example, 5 ° C./min, and at a constant high temperature of 1300 ° C. to 1400 ° C. for several hours, for example, 1350 ° C.
High-temperature annealing is performed at 4 ° C. for 4 hours, and thereafter, the temperature is lowered at a constant cooling rate. At this time, the atmosphere gas was N ₂ / O containing N ₂ as a nitriding gas only during the temperature raising process.
And ₂ mixed gas, the subsequent high temperature annealing held at a constant temperature, is supplied by switching to mixed gas of Ar / O _2.

[0019] Thus, in the present embodiment, because it contains N ₂ atmosphere gas in the Atsushi Nobori process, the silicon substrate 1 surface Si _x N _y is formed a silicon substrate 1 inside many by N ₂ Are implanted, and interstitial silicon is taken into these vacancies, whereby defects can be reduced. Further, by using an atmosphere gas containing N ₂ only in the temperature raising step of the heat treatment, the atmosphere gas does not contain N ₂ in the annealing step kept at a constant high temperature, and excessive N ₂ is contained inside the silicon substrate 1 at a high temperature. Is implanted to prevent adverse effects on device characteristics. If N is excessively implanted, a silicon oxynitride film may be formed inside the silicon substrate 1 and adversely affect device characteristics. Furthermore, N
_In the case of an atmosphere gas containing ₂ , the roughness of the surface of the silicon substrate 1 is also improved.

Next, a second embodiment of the method for manufacturing an SOI wafer and the SOI wafer according to the present invention will be described.

The difference between the second embodiment and the first embodiment is that a mixed gas of N ₂ / O ₂ is used as an atmosphere gas in the temperature increasing process in the annealing step of the first embodiment.
In the temperature raising process in the annealing step of the second embodiment, an atmosphere gas containing a nitriding gas having a decomposition temperature lower than the temperature at which N ₂ can be decomposed is employed. That is, the atmosphere gas is a nitriding gas having a decomposition temperature lower than the temperature at which N ₂ can be decomposed, for example, NH ₃ , NO, N
₂ O, N ₂ O ₂ , hydrazine, dimethyl hydrazine and the like, or a mixed gas thereof, or mainly a mixture of Ar, N ₂ , O ₂ ,
It is a mixed gas with H ₂ (hydrogen) or the like. In the case of these atmospheric gases, the nitriding gas is decomposed even at a lower temperature or for a shorter time than in the case of N _{2, and} the surface of the silicon substrate 1 is nitrided, so that vacancy can be implanted into the interior, thereby preventing excessive implantation of N. be able to.

In this embodiment, it is desirable to use an atmosphere gas mainly composed of NH ₃ . That is, by using a nitriding gas containing NH ₃ as an atmospheric gas, H (hydrogen) generated by decomposition of NH ₃ has a cleaning effect of removing a natural oxide film or the like on the surface of the silicon substrate 1. , And surface nitridation and vacancy
Injection is promoted.

The technical scope of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. For example, in the above embodiment, the atmosphere gas containing the nitriding gas is used only in the temperature raising process, but the defect reduction effect can be obtained even if the atmosphere gas containing the nitriding gas is used in the entire range of the annealing step. However, as described above, in order to prevent excessive injection of N, it is necessary to use an atmosphere gas containing a nitriding gas only during the temperature raising process, and to switch to an atmosphere gas containing no nitriding gas during high-temperature annealing. preferable.

Further, the above-mentioned plasma-formed nitriding gas may be used as an atmospheric gas. In this case, since the nitriding gas is activated by being turned into plasma, nitriding of the surface and injection of vacancy are further promoted.

The pressure of the atmosphere gas may be any of reduced pressure, normal pressure and pressurized state. Further, the nitride film formed on the surface of the silicon substrate according to the above embodiment may be an oxynitride film (silicon oxynitride film), and the nitride film may contain hydrogen.

[0026]

According to the present invention, the following effects can be obtained.
According to the method for manufacturing an SOI wafer and the SOI wafer of the present invention, since the atmosphere gas in the heat treatment contains a nitriding gas, defects can be reduced by incorporating interstitial silicon into the vacancy injected into the substrate. Thus, a high quality SOI wafer can be obtained.

[Brief description of the drawings]

FIG. 1 is an essential part cross-sectional view showing an SOI wafer manufacturing method and a SOI wafer according to a first embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a graph showing a temperature profile of an annealing step in the SOI wafer manufacturing method and the SOI wafer according to the first embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 oxygen implantation region 3 buried silicon oxide film 4 silicon single crystal thin film

Continuing from the front page (72) Inventor Tetsuya Nakai Inside Mitsubishi Materials Silicon Co., Ltd. 1-1-1, Otemachi, Chiyoda-ku, Tokyo

Claims (6)

[Claims] 1. A method for manufacturing an SOI wafer in which oxygen ions are implanted into a silicon substrate and then a buried silicon oxide film is formed inside the silicon substrate by heat treatment in an atmosphere gas, wherein the atmosphere gas is a nitriding gas. S characterized by including
A method for manufacturing an OI wafer. 2. The method for manufacturing an SOI wafer according to claim 1, wherein the atmosphere gas is a gas containing a nitriding gas only during a temperature increasing process of the heat treatment. 3. The method for manufacturing an SOI wafer according to claim 1, wherein the atmosphere gas includes a nitriding gas having a decomposition temperature lower than a temperature at which N ₂ can be decomposed. Production method. 4. The SOI wafer manufacturing method according to claim 3, wherein the nitriding gas contains NH _3.
Wafer manufacturing method. 5. The SO according to claim 1, wherein:
In the method for manufacturing an I wafer, the nitriding gas is converted into plasma. 6. An SOI wafer in which a buried silicon oxide film is formed in a silicon substrate by heat treatment in an atmosphere gas after oxygen ions are implanted in the silicon substrate, and wherein the silicon oxide film is formed in the SOI wafer. Wherein the heat treatment is performed by a method for manufacturing an SOI wafer.