JP2001089293A - Epitaxial wafer and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing an epitaxial wafer, in which a particular device such as a oxidation furnace directly connected to an epitaxially growing reactor is not used and a particular treatment for cleaning or oxidizing the surface after epitaxially growing is not needed, thereby the production process is made simple, and by which an epitaxial wafer good in surface smoothness is produced. SOLUTION: When a wafer is taken out from an epitaxial reactor and taken into a carrying part, an oxide thin film having a thickness of <=1 nm is formed by introducing a small amount of oxygen into the inert gas in a carrying chamber and taking the wafer into the carrying chamber at >=600 deg.C immediately after forming an epitaxial film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an epitaxial wafer for forming an epitaxial thin film of high quality and hardly deteriorated on a semiconductor wafer such as silicon, and performing a special treatment for cleaning and surface oxidation after epitaxial growth. The present invention relates to an epitaxial wafer capable of maintaining surface flatness and cleanliness with a simple process without any processing, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A so-called epitaxial wafer in which a silicon semiconductor wafer is provided with a silicon thin film formed by epitaxial growth, is a surface terminated with hydrogen. Therefore, the surface is negatively charged and has a large contact angle. It is in a state where it easily adheres. (JJAP, Vol.32 (1993), p
(p.L1489 ~ L1491)

[0003] Conventionally, in an epitaxial wafer, the oxidized surface is more stable, and the effect of removing contamination such as adhered particles during transportation is aimed at, after the epitaxial growth, wet cleaning such as RCA cleaning, and the like. Products are shipped after an oxide film is formed by cleaning.

[0004] However, it is known that the surface after epitaxial growth is flat at the molecular level depending on the crystal orientation, but the surface flatness is rather deteriorated by wet cleaning. .

[0005] In addition, there has been a problem that, by performing wet cleaning of the epitaxial layer after the reaction, the epitaxial layer grown in a high-purity epitaxial furnace may be contaminated.

Therefore, a method has been adopted in which after epitaxial growth is performed in an epitaxial furnace, an atmosphere is replaced, an oxide film is formed by thermal oxidation treatment, and then an oxide film is carried out from the reaction furnace (for example, Japanese Patent Laid-Open No. 4-196119). , Patent No. 2540690). Alternatively, there has been proposed a method of forming an oxide film having a thickness of 5 nm or more on an epitaxial surface by performing an ozone oxidation treatment after epitaxial growth.

[0007]

In order to solve the above-mentioned problems, in order to perform the thermal oxidation treatment or the ozone oxidation treatment after the epitaxial growth, an oxidation furnace directly connected to the epitaxial reactor is required, and the processing time is long. Therefore, there is a problem that the process is complicated and the production cost is extremely high.

[0008] According to the present invention, when forming an oxide film for maintaining the flatness and cleanliness of the above-mentioned surface, a special device such as an oxidation furnace directly connected to a reaction furnace is not used, and after the epitaxial growth, An object of the present invention is to provide an epitaxial wafer that does not require special treatment for cleaning or surface oxidation, can simplify the conventional manufacturing process, and has good surface flatness, and a manufacturing method that can provide the same at low cost. And

[0009]

Means for Solving the Problems The inventors of the present invention have conducted various studies on means for keeping the wafer surface shape more flat and preventing deterioration and adhesion of dust, and as a result, an extremely thin oxide film of 1 nm or less was formed on the epitaxial thin film. It has been found that the formation of a contact angle makes the contact angle smaller than that of the surface completely terminated with hydrogen, and reduces the adhesion of dust and the like.

[0010] Further, the inventors have proposed that 1n
As a result of various studies on means for easily providing an extremely thin oxide film of m or less, when taking out from the epitaxial reaction chamber to the transfer section, a slight amount of oxygen was present in the inert gas in the transfer chamber, and immediately after forming the epitaxial film, 600 It was found that a thin oxide film with a thickness of 1 nm or less can be formed on the surface simply by taking the wafer into the transfer chamber at a temperature of at least ° C.

[0011] Further, the inventors have set that the temperature is desirably 600 to 900 ° C as conditions for forming the thin oxide film having a thickness of 1 nm or less, and that N ₂ having a purity of 99.99 to 99.999% is used as an oxygen-containing atmosphere.
Gas or Ar gas, or by oxygen intended N ₂ gas or Ar gas partial comprises 5 to 1000 ppm, without providing a special oxidation process after epitaxial growth, 1n the surface
The inventors have found that a thin oxide film having a thickness of m or less can be formed, and have completed the present invention.

[0012] Further, the inventors have found that an epitaxial wafer according to the present invention can be used for RCA immediately before device process introduction.
It has been found that an oxide film can be easily removed by cleaning with at least one cleaning solution of the cleaning method or a cleaning solution containing HF.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when taking out from an epitaxial reaction chamber to a transfer section, for example, a small amount of oxygen in an inert gas in the transfer chamber is used or slightly present to complete the epitaxial reaction. It is characterized in that a thin oxide film of 1 nm or less is formed on the surface by simply taking out the wafer to a transfer chamber at 600 ° C. or higher.

That is, the wafer taken out of the epitaxial reaction chamber has a desorption temperature of 450 ° C. of hydrogen existing on the surface.
Higher than the temperature at which the whole wafer is oxidized,
The oxide film is formed on the surface by taking out from the reaction chamber into an inert atmosphere containing some oxygen. At this time, when taken out at a temperature of 500 ° C. or less, the surface is terminated with hydrogen. If the temperature is higher than 500 ° C. and lower than 600 ° C., the resulting film is not uniform and is not practical.

In the present invention, the measurement of the thickness of the oxide film is as follows. Oxide film thickness d _ox is an ESCA (Electron Spectrosopy for Chemical Analy
sis). Si chemically shifted by oxidation
A photoelectron number N _ox of _2p spectrum, the ratio of the number of photoelectrons N _Si of Si _2p spectrum of the substrate _{Si, d ox = λ ox ·} cosθ · In [k · N
_ox / N _Si ) +1]. Here, λ _ox is the escape depth of Si _2p photoelectrons in the oxide film, which is 2.5 nm. k is a constant which is 2.086.

In the present invention, the oxygen concentration in the atmosphere for forming the oxide film is required to be at least 5 ppm, but is preferably 1000 ppm or less from the viewpoint of safety. If the epitaxial film is taken out to the transfer chamber at a temperature exceeding 900 ° C., the quality of the epitaxial film is deteriorated.

In addition, industrially, the atmosphere should be 99.99-9 purity.
By setting it in 9.999% N ₂ gas or Ar gas, it is possible to obtain the same operation and effect as in the above-mentioned trace oxygen-containing atmosphere.

By forming a thin oxide film on the surface immediately after the epitaxy reaction, there is an advantage that dust adhesion and the like are reduced as compared with the surface terminated with hydrogen. In addition, as an operation, an oxide film can be formed only by setting the temperature of taking out from the reaction furnace to 600 ° C. or higher and containing 5 to 1000 ppm of oxygen in the atmosphere, so that a wafer can be easily manufactured without increasing the number of steps. Further, there is an advantage that the subsequent cleaning step becomes unnecessary, and labor can be saved in the step.

In the present invention, an oxide film having a thickness of 1 nm or less can be easily removed by the most standard chemical cleaning method called a so-called RCA method. For example, to hydrogen peroxide (H ₂ O ₂₎ to the base, a high pH alkaline mixture is used in two stages washed with an acid mixture of low pH, generally H ₂ called SC-1 O -H ₂ O ₂ -NH ₄ OH or SC-2 composition cleaning solution can be appropriately selected and used. HF such as HF and HF / O ₃
Containing cleaning liquids can also be used.

[0020]

EXAMPLE A thin film was formed on a silicon wafer by epitaxial growth using a general vertical vapor phase epitaxy apparatus. Immediately after the completion of the epitaxial reaction, the wafer was taken out of the reaction chamber by an adjacent robot transfer to a transfer chamber. The atmosphere in the transfer chamber is a N ₂ gas atmosphere at a temperature of 800 ° C. and containing 100 ppm of oxygen.

When taking out a wafer, 300 ° C, 500 ° C, 600 ° C, 7
It was taken out at various temperatures of 00 ° C., 750 ° C., 800 ° C., and 900 ° C., and was in a transfer room atmosphere while being stored in a transfer cassette by a robot transfer from the transfer room.

After the above operation, each epitaxial wafer taken out
Measure the surface condition of wafer by ATR infrared absorption spectrum
did. Figure 1 shows the infrared absorption of the samples taken at 300 ° C and 700 ° C.
The spectrum is shown. Wafer at 700 ° C
An oxide film was found on the entire surface. Acid at 300 ° C
No converted film was found. In addition, 1250-1000cm of FIG. ^-1of
The peak is the absorption of the oxide film due to the absorption of Si-O.
You.

FIG. 2 shows the relationship between each of the above-mentioned removal temperatures and the thickness of the oxide film. When the removal temperature was 600 ° C. or higher, an oxide film was obtained on the entire surface of the wafer. Also, oxygen in the N ₂ gas atmosphere
In the case of 5 ppm or less, no oxide film was obtained on the epi surface regardless of the temperature taken out.

[0024]

According to the wafer of the present invention, the surface immediately after the epitaxial reaction, that is, the Si surface layer actually used for the device can be protected by a thin oxide film of 1 nm or less. It is protected from the attachment and contamination of greetings and can maintain stable quality for a long time.

In the epitaxial wafer according to the present invention, the oxide film can be easily washed and removed before the device is subjected to a device process, and is not affected by contamination in the oxide film and on the oxide film. , Available.

According to the present invention, in a general epitaxial reactor, the temperature required for taking out from the reaction chamber to the transfer chamber is set to a specific temperature, and the required thickness can be reduced by a simple operation of only containing a small amount of oxygen in the atmosphere. The oxide film can be easily formed without any additional step in the epitaxial formation step. Further, according to the present invention, it is possible to omit the cleaning step after the epitaxial film formation, which is conventionally required, and to simplify the steps.

[Brief description of the drawings]

FIG. 1 is a graph showing an infrared absorption spectrum of an epitaxial wafer surface.

FIG. 2 is a graph showing a relationship between an extraction temperature from an epitaxial reaction chamber and an oxide film thickness.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G077 AA02 BB03 FE04 5F043 AA02 AA32 BB22 DD12 GG10 5F058 BA05 BC02 BE01 BF55 BF62 BH11 BJ01

Claims (7)

[Claims] 1. An epitaxial wafer having an oxide film having a thickness of 1 nm or less on an epitaxially grown film. 2. A method for manufacturing an epitaxial wafer, comprising a step of forming an oxide film having a thickness of 1 nm or less on an epitaxial growth film. 3. After the epitaxial growth, a wafer kept at a high temperature is taken out of the reaction chamber into an oxygen-containing atmosphere,
A method for manufacturing an epitaxial wafer in which an oxide film having a thickness of 1 nm or less is formed on an epitaxially grown film in the same atmosphere. 4. The high temperature holding temperature is 600 to 900 ° C.
3. The method for producing an epitaxial wafer according to item 1. 5. The method for producing an epitaxial wafer according to claim 3, wherein the oxygen-containing atmosphere is in an N ₂ gas or an Ar gas containing 5 to 1000 ppm of oxygen. 6. The oxygen-containing atmosphere has a purity of 99.99 to 99.999%.
4. The method for producing an epitaxial wafer according to claim 3, wherein the method is in an N ₂ gas or an Ar gas. 7. A method for manufacturing an epitaxial wafer, comprising a step of cleaning an epitaxial wafer having an oxide film having a thickness of 1 nm or less on an epitaxial growth film with at least one cleaning liquid of RCA cleaning method or a cleaning liquid containing HF.