JP2001203209A - Method for manufacturing semiconductor wafer having epitaxial layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor wafer which shows an optimized oxygen deposition characteristic in the following heat treatment and is covered with an epitaxial layer in a lamp furnace. SOLUTION: A semiconductor wafer to be mounted entirely to a susceptor is mechnically separated from the susceptor after an epitaxial layer is laminated on the semiconductor wafer, and a heating output is decreased until a cooling speed reaches 20 deg.C/sec or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a semiconductor wafer having an epitaxial layer coated with an epitaxial layer in a lamp furnace exhibiting optimized oxygen deposition properties during a subsequent heat treatment.

A grown single crystal layer on which semiconductor components are mounted, ie a single crystal with a so-called epitaxy or epitaxial growth layer, for example a silicon wafer with a silicon layer, has certain advantages over semiconductor wafers of homogeneous material. Have. For example, epitaxially grown surfaces have a lower defect density than, for example, so-called COPs (crystal originated particles) compared to polished surfaces, which generally leads to higher yields of complete semiconductor components. Furthermore, the epitaxial layer may have no noticeable oxygen content and may be doped with foreign atoms.

During the entire coating or deposition process, the semiconductor wafer is first heated by a heating source, preferably by upper and lower heating sources, such as lamps or lamp banks, and subsequently from a source gas, a carrier gas and optionally a doping gas. Exposed to a gas mixture. Coating and deposition are carried out by means of a lamp furnace in a deposition chamber, for example as described in EP 0 714 998 A2. For coating, the semiconductor wafer is manually or automatically inserted into a susceptor milling section inside the deposition chamber. In this case, the semiconductor wafer is completely mounted on the susceptor, which ensures an even heating of the semiconductor wafer. In addition, the backside of the wafer, where no epitaxial layer is typically deposited, is protected from the source gas. According to the prior art, the deposition chamber is configured for one or more semiconductor wafers. Large amount of heat of susceptor (ther
Due to mische masse), the semiconductor wafer is only cooled slowly after coating, even if the heating power is reduced to zero. The deposition process is between 1070 and 1150
It is carried out in the range of ° C. In this case, the cooling rate is generally less than 15 ° C./sec based on the large amount of heat of the susceptor.
Such a thermal history can be obtained during a subsequent heat treatment, for example at 780
3 hours at a temperature of 1000C and 16 hours at a temperature of 1000C.
It shows very little oxygen precipitation.

[0004] WO 98/38675 describes a semiconductor wafer with ideal oxygen deposition and a method for manufacturing the semiconductor wafer. In this case, ideal oxygen precipitation is understood as the concentration profile of oxygen precipitation having a maximum in a bulk and a minimum within a range close to the surface of the semiconductor wafer.

The production of semiconductor wafers with such oxygen precipitates is, according to WO 98/38675,> 1175 ° C.
The control of the cooling rate, which is carried out at a temperature of and is preferably> 50 ° C./sec. This heat treatment is preferably performed in a lamp furnace (Rapid Thermal Annealer, RTA). Then, for example, at a temperature of 780 ° C. for 3 hours and 10 minutes.
During a subsequent heat treatment at a temperature of 00 ° C. for 16 hours, the precipitation of oxygen with the above-mentioned concentration profile takes place.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a semiconductor wafer having an epitaxial layer deposited in a lamp furnace, which exhibits optimized oxygen deposition properties during a subsequent heat treatment. there were.

[0007]

The object is solved by a method for producing a semiconductor wafer coated with an epitaxial layer in a lamp furnace, which exhibits optimized oxygen deposition properties during a subsequent heat treatment, the method comprising: The semiconductor wafer mounted entirely on the susceptor is mechanically separated from the susceptor after the deposition of the epitaxial layer, and the heating power is subsequently increased to> 25 ° C.
/ Second until the cooling rate is reduced.

In accordance with the present invention, a semiconductor wafer having a> 115
After heating to 0 ° C., it must be mechanically separated from the susceptor to ensure a cooling rate of> 25 ° C./s, which results in semiconductor wafers exhibiting optimized oxygen deposition properties during subsequent heat treatments . Epitaxial layer deposition <1
If carried out at a temperature of 150 ° C., additional heating of the semiconductor wafer to> 1150 ° C. is performed before or after mechanical separation from the susceptor. In this case, the semiconductor wafer is <11
Heating to a temperature of 50 ° C. is preferably for 1 to 60 seconds, particularly preferably 5 to 25 seconds.

Accordingly, the object of the present invention is also solved in a method for producing a semiconductor wafer coated with an epitaxial layer in a lamp furnace, which exhibits optimized oxygen deposition properties during a subsequent heat treatment, the method comprising: The semiconductor wafer mounted entirely on the susceptor is mechanically separated from the susceptor after the deposition of the epitaxial layer and heated to a temperature of> 1150 ° C., and the heating power is subsequently reduced until a cooling rate of> 25 ° C./sec occurs. It is characterized by the following.

The object of the invention is also solved by a method for producing a semiconductor wafer coated with an epitaxial layer in a lamp furnace, which exhibits optimized oxygen deposition properties during a subsequent heat treatment, the method comprising the steps of: Heating the semiconductor wafer mounted on the susceptor to a temperature of> 1150 ° C. after deposition of the epitaxial layer and mechanically separating it from the susceptor, and subsequently reducing the heating power until a cooling rate of> 25 ° C./sec occurs. Features.

According to the present invention, mechanical separation of the semiconductor wafer from the susceptor ensures rapid heating and rapid cooling of the wafer.

The source gases, doping and cleaning gases used, and the deposition protocol, ie, processing times, sequence of process steps, and temperature relationships during epitaxial layer growth and deposition rates are not the subject of this invention and will be understood by those skilled in the art. Include, for example, “Epitaxial Technology, Ed. Jaya
nt, Academic Press Inc. Orlando, Florida; 1986 ".

Prior to performing the epitaxial coating, the semiconductor wafer is placed in a lamp furnace in a reducing gas atmosphere at 1150 mm.
Heat treatment can be performed at a temperature of 1300 ° C. for 1 to 60 seconds. The gaseous atmosphere preferably comprises argon and hydrogen having preferably 10 to 80% by volume of hydrogen. The heat treatment lowers the COP density on the surface of the semiconductor wafer, thereby suppressing the occurrence of crystal defects.

After the epitaxial coating has been carried out, the semiconductor wafer has a hydrophobic surface and can be treated in this way with the method according to the invention. However, while not required within the scope of the present invention, making the wafer surface hydrophilic,
That is, it is possible to cover with a thin oxide layer, for example, by treating with an oxidizing gas, for example, ozone.

After the deposition and / or oxidation treatment of the epitaxial layer, the lamp furnace, in particular the deposition chamber, is cleaned with an inert cleaning gas, for example nitrogen, in order to drive off any source gas, carrier gas or oxidizing gas still present. . Next, the deposition chamber is placed under an inert gas atmosphere. The gas atmosphere is preferably selected from the group of gases including hydrogen, argon, nitrogen and any mixtures of these gases. Particularly preferably, the gas atmosphere comprises 10 to 70% by volume of argon and hydrogen. Cleaning of the deposition chamber occurs before or after mechanical separation from the susceptor.

The mechanical separation of the semiconductor wafer from the susceptor (before or after heating to a temperature of> 1150 ° C.) is performed by lowering the susceptor or raising the susceptor. If a stationary susceptor is used, the wafer is separated by lifting the susceptor. This is performed, for example, by a pin support (Pin-Auflage) guided in the through hole of the susceptor toward the back side of the semiconductor wafer. In the case of a movable susceptor, the wafer is separated from the susceptor by lowering the susceptor, while the wafer itself rests on the pin support. The pin support is made of a heat-resistant material that does not contaminate the wafer, such as quartz glass, aluminum oxide, nitrogen carbide or silicon, and preferably has a small support surface and a small amount of heat.

In particular, the deposition of the epitaxial layer is reduced to <115
If carried out at 0 ° C., the wafer is heated to a temperature of> 1150 ° C. for at least 1 second with a lamp, preferably with an upper and lower lamp or lamp bank, in the above-mentioned inert gas atmosphere. In this case, the wafer rests on the susceptor or is already mechanically separated from the susceptor and rests, for example, on a pin carrier.

After depositing the epitaxial layer at a temperature of> 1150 ° C. or after heating the semiconductor wafer to a temperature of> 1150 ° C., the heating power is rapidly reduced by the semiconductor wafer to preferably 950 ° C., particularly preferably 850 ° C. Lower until cool to temperature. The cooling rate after the deposition of the epitaxial layer or the heating of the semiconductor wafer is preferably in the temperature range up to 950 ° C., preferably up to 850 ° C., preferably from 10 ° C./sec to 200 ° C./sec, particularly preferably from 20 ° C./sec to 150 ° C. ° C
/ Sec and especially 30 ° C / sec to 100 ° C / sec.

A speed of 30 ° C./sec to 100 ° C./sec is achieved by shutting off the lamp or lamp bank, ie reducing the heating power to zero. Increasing the cooling rate to> 100 ° C./sec is achieved by flushing the lamp furnace with an inert gas such as nitrogen, argon, helium or a mixture of these gases.

Mechanical separation of the semiconductor wafer from the movable susceptor allows spatial separation from the front and back of the semiconductor wafer, so that the back can be cleaned with a different gas than the front (see FIG. 1). It is shown). Preferably, the back side of the semiconductor wafer is cleaned in order to increase the changes in the deposition, in particular the deposition density.

After the semiconductor wafer has been cooled to a temperature of at least 800 ° C., the semiconductor wafer is automatically or manually removed from the lamp furnace. The semiconductor wafer coated with this epitaxial layer shows optimized oxygen deposition properties during the subsequent heat treatment. The subsequent heat treatment is carried out in a vertical or horizontal furnace according to the prior art, for example at a temperature of 780 ° C. for 3 hours and at a temperature of 1000 ° C. for 16 hours.

[0022]

1a, 1b, 2a and 2b show two preferred embodiments of an apparatus for mechanically separating a semiconductor wafer from a susceptor which is fully mounted during the epitaxial coating of the semiconductor wafer. Have been. Furthermore, the structure of a lamp furnace having an upper chamber and a lower chamber which is suitable for carrying out the method according to the invention is shown schematically.

While performing the epitaxial coating shown in FIGS. 1a and 2a, the deposition chamber 1 of the lamp furnace
Is heated by the heating elements 2 and 3. In this case, the semiconductor wafer 4 is entirely mounted on the susceptor 5. The inflow of the source gas, the carrier gas and / or the doping gas takes place via gas supply conduits 7 and 8, and the gas discharge takes place via gas discharge conduits 9, 10. The pin support 11 is inserted into a through hole in the susceptor. These are wafer 4
Do not touch. After performing the epitaxial coating, preferably both chambers are cleaned and placed under an inert gas atmosphere.

The wafer is separated from the susceptor by lowering the movable susceptor, while the wafer rests on a stationary pin support (shown in FIG. 1b).

FIG. 2b shows the mechanical separation of a semiconductor wafer from a stationary susceptor by lifting the wafer. This separation is performed by, for example, a pin support that is guided in the hole passing through the susceptor toward the rear surface of the semiconductor wafer.

If the deposition of the epitaxial layer is carried out at a temperature of <1150 ° C., the heating of the semiconductor wafer to a temperature of> 1150 ° C. takes place before or after the mechanical separation from the susceptor.

After heating by the heating elements 2 and 3 to a temperature of> 1150 ° C. for at least 1 second, the heating power is reduced until the semiconductor wafer is rapidly cooled to a temperature of at least 950 ° C. During cooling, the semiconductor wafer is preferably resting on a pin support, i.e. the semiconductor wafer is separated from the large heat of the susceptor.

The pin carrier advantageously has as small a support surface as possible, so that no energy is transferred from the carrier to the wafer during the cooling period. Finally, the wafer can be removed from the lamp furnace and subjected to a subsequent heat treatment.

FIGS. 3a and 3b show the oxygen precipitation density as a function of cooling rate (FIG. 3a) and temperature (FIG. 3b).

In particular, FIG. 3a shows that the epitaxial layer was coated for a cooling rate after heating in a lamp furnace to a temperature of 1200 ° C. for 10 seconds, followed by a heat treatment at a temperature of 780 ° C. for 3 hours and at a temperature of 1000 ° C. for 16 hours. 3 shows the dependence of the density of oxygen precipitation on a semiconductor wafer. In particular, FIG.
Heating in a lamp furnace and at a cooling rate of 80 ° C./second for 10 seconds, followed by a heat treatment at a temperature of 780 ° C. for 3 hours and a temperature of 1000 ° C. for 16 hours, the oxygen of the semiconductor wafer coated with the epitaxial layer with respect to the temperature. 4 shows the dependency of the density of precipitation.

[Brief description of the drawings]

FIG. 1A is a view showing an epitaxial coating step in a first embodiment of an apparatus for performing a method according to the present invention, and FIG. 1B is a view showing a heat treatment step in the embodiment.

FIG. 2A is a view showing an epitaxial coating step in a second embodiment of the apparatus for performing the method according to the present invention, and FIG. 2B is a view showing a heat treatment step in the embodiment.

FIG. 3A is a graph showing the dependency of the oxygen precipitation density on the cooling rate, and FIG. 3B is a graph showing the dependency of the oxygen precipitation density on the temperature.

[Explanation of symbols]

1 deposition chamber, 2 heating element, 3 heating element,
Reference Signs List 4 semiconductor wafer, 5 susceptor, 7 gas supply conduit, 8 gas supply conduit, 9 gas discharge conduit, 10
Gas supply device, 11 pin support

Continued on the front page (72) Inventor Reinhold Warich, Germany Tit Morning Blumenstrasse 10 (72) Inventor Alfred Buchner, Austria Pischelsdorf Nummer 66

Claims (5)

[Claims] 1. A method for producing a semiconductor wafer coated with an epitaxial layer in a lamp furnace, which exhibits an oxygen deposition characteristic optimized during a subsequent heat treatment. Mechanically separated from the susceptor after deposition, and subsequently heating output,
A method for producing a semiconductor wafer having an epitaxial layer, wherein the cooling rate is reduced until a cooling rate of> 25 ° C./sec occurs. 2. A method for producing a semiconductor wafer coated with an epitaxial layer in a lamp furnace, wherein the semiconductor wafer has an oxygen deposition characteristic optimized during a subsequent heat treatment. A semiconductor wafer having an epitaxial layer, characterized in that it is mechanically separated from the susceptor after deposition, heated to a temperature of> 1150 ° C. and subsequently reduces the heating power until a cooling rate of> 25 ° C./s occurs. Production method. 3. A method for producing a semiconductor wafer coated with an epitaxial layer in a lamp furnace, wherein the semiconductor wafer has an oxygen deposition characteristic optimized during a subsequent heat treatment. Heating the semiconductor wafer after deposition to a temperature of> 1150 ° C., mechanically separating it from the susceptor, and subsequently reducing the heating power until a cooling rate of> 25 ° C./s occurs; Production method. 4. The method according to claim 1, wherein the semiconductor wafer is subjected to 115.degree.
The method according to any one of claims 1 to 3, wherein the heat treatment is performed at a temperature of 0 to 1300 ° C for 1 to 60 seconds. 5. The method according to claim 1, wherein the mechanical separation of the semiconductor wafer is performed by lifting the wafer from a stationary susceptor and lowering the susceptor from a movable susceptor.