JP2002076006A - Method of manufacturing epitaxial wafer and epitaxial wafer manufactured by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epitaxial wafer having intrinsic gettering capability of contaminant metals during device manufacturing process. SOLUTION: First, a nitrogen doped silicon single crystal rod is pulled up by Czochralski method, and sliced into silicon wafers. Next, the silicon wafer is held at a specific temperature in the range of 600 to 850 deg.C for 5 to 180 min., and risen to a specific temperature in the range of 1,100 to 1,150 deg.C at a rate of 5 to 20 deg.C/sec. After the temperature rise, hydrogen pretreatment is performed at the specific temperature for the wafer. Thereafter, under the condition that the silicon wafer is held at a specific temperature in the range of 1,050 to 1,150 deg.C, an epitaxial layer is formed on the surface of the silicon wafer. Then, the silicon wafer is fallen to a specific temperature in the range of 600 to 850 deg.C at a rate of 5 to 20 deg.C/second, and held at the specific temperature for 5 to 180 minutes.

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 using a silicon single crystal rod pulled by the Czochralski method (hereinafter referred to as CZ method) and an epitaxial wafer manufactured by this method. It is about.

[0002]

2. Description of the Related Art Usually, a boron concentration is low, that is, a so-called p /
p ^- epitaxial wafer having the structure of, by going through the epitaxial process a relatively high temperature,
Since the oxygen precipitate nuclei in the bulk disappear, almost no oxygen precipitates are generated in the device manufacturing process of the semiconductor device manufacturer. On the other hand, since a small amount of metal contamination generally occurs in the device manufacturing process, it is desirable that the wafer has the gettering ability of the contaminated metal. Therefore,
In order to impart gettering capability to the wafer, a process of forming a film of polysilicon having a metal gettering capability on the back surface of the wafer, or giving damage to the back surface of the wafer by sandblasting, etc., is performed.

[0003]

However, the above-described conventional processes, such as deposition of polysilicon on the back surface of a wafer and application of damage by sandblasting, increase the manufacturing cost of the wafer and reduce the amount of dust generated from the wafer. There was a possibility that the wafer would increase or the wafer would be deformed. Conventionally, in order to eliminate these points, a heat treatment is performed for a long time before passing through the epitaxial process to generate sufficient oxygen precipitation nuclei, and a method in which the oxygen precipitation nuclei do not disappear even in a high temperature process called an epitaxial process. Is being done. However, this method also increases the manufacturing cost, and the wafer may be contaminated by the metal during the heat treatment.

An object of the present invention is to improve the thermal stability of oxygen precipitate nuclei in a silicon wafer before forming an epitaxial layer without performing polysilicon film formation or sandblasting on the back surface of the silicon wafer. An object of the present invention is to provide a method for manufacturing an epitaxial wafer, which can increase the number of atomic vacancies, which are lattice defects that contribute to the generation of the oxygen precipitation nuclei. Another object of the present invention is to provide an epitaxial wafer having intrinsic gettering (hereinafter referred to as IG) capability of a contaminant metal in a device manufacturing process.

[0005]

The invention according to claim 1 is
As shown in FIGS. 1 and 2, a step of pulling up a nitrogen-doped silicon single crystal rod 14 by the Czochralski method, a step of slicing the silicon single crystal rod 14 to produce a silicon wafer, and a step of 600-8
Holding the silicon wafer at a predetermined temperature in the range of 50 ° C. for 5 to 180 minutes, and heating the silicon wafer to a predetermined temperature in the range of 1100 to 1150 ° C. at a rate of 5 to 20 ° C./sec, and then pretreating with hydrogen at the predetermined temperature Performing a step of forming an epitaxial layer on the surface of the silicon wafer while maintaining the silicon wafer at a predetermined temperature in the range of 1050 to 1150 ° C .; Lowering the temperature at a rate of 20 ° C./sec and maintaining the temperature at the predetermined temperature for 5 to 120 minutes.

In the method of manufacturing an epitaxial wafer according to the present invention, the heat treatment is performed on the silicon wafer before and after the formation of the epitaxial layer, whereby the oxygen precipitation nuclei in the silicon wafer before the formation of the epitaxial layer are formed. The thermal stability can be improved, and the number of atomic vacancies, which are lattice defects that contribute to the generation of the oxygen precipitation nuclei, can be increased. The concentration of nitrogen doped in the silicon single crystal rod 14 is preferably 5 × 10 ^{12 to} 5 × 10 ¹⁴ cm ⁻³ . A third aspect of the present invention is an epitaxial wafer manufactured by the method according to the first or second aspect. The epitaxial wafer according to the third aspect has an IG capability of a contaminant metal even in a device manufacturing process.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG. 2, the silicon wafer for forming the epitaxial layer of the present invention is CZ
A silicon single crystal rod 14 from a silicon melt 13 in a quartz crucible 12 of a pulling machine 11 by a method described below.
After the silicon single crystal rod 14
Is made by slicing. The above silicon single crystal rod 14
Is doped with nitrogen. The concentration of nitrogen doped in the silicon single crystal rod 14 is 5 × 10 ^{12 to} 5 × 10 ¹⁴ c
m ⁻³ , preferably 3 × 10 ^{13 to} 3 × 10 ¹⁴ cm ⁻³ . The nitrogen concentration was limited to the range of 5 × 10 ^{12 to} 5 × 10 ¹⁴ cm ^{-3 because} the solid solubility of atomic vacancies in the silicon single crystal rod 14 did not increase below 5 × 10 ¹² cm ^-3. Atomic vacancies tend to disappear due to the subsequent thermal history of the silicon single crystal rod 14, and if it exceeds 5 × 10 ¹⁴ cm ^-3 , the generation amount of nitrogen-related donors increases and the resistivity of the single crystal decreases. This is because it greatly changes. As a method of doping nitrogen into the silicon single crystal rod 14, polycrystalline silicon mixed with nitride or polycrystalline silicon formed with a nitride film is charged into the quartz crucible 12, and a silicon melt 13 containing nitrogen is added. This is performed by pulling the silicon single crystal rod 14 from the substrate or pulling the silicon single crystal rod 14 in an inert gas atmosphere containing nitrogen gas. The silicon single crystal rod 14 has a size of 5 × 10 ^{14 to} 5 × 10 ¹⁵ atoms /
Boron is also doped to obtain an epitaxial wafer having a p / p ⁻ structure, albeit with a low concentration of cm ³ .

[0008] A cylindrical casing 25 is connected to the upper end of the chamber 24 of the pulling machine 11.
5 is provided with a pulling means 26. Reference numeral 26a in FIG.
Is a wire cable hanging down toward the rotation center of the quartz crucible 12, and a seed crystal 26b for immersing in the silicon melt 13 and pulling up the silicon single crystal rod 14 is attached to a lower end of the wire cable 26a. The outer surface of the quartz crucible 12 is covered with a graphite susceptor 27, and the lower surface of the graphite susceptor 27 is fixed to an upper end of a support shaft 28, and a lower portion of the support shaft 28 is connected to a crucible driving unit 29.

Further, a gas supply / discharge means 33 for supplying an inert gas to the silicon single crystal rod side of the chamber 24 and discharging the inert gas from the inner peripheral surface side of the crucible of the chamber 24 is connected to the chamber 24. . One end of the gas supply / discharge means 33 is connected to the peripheral wall of the casing 25 and the other end is connected to a supply pipe 34 connected to a tank (not shown) for storing the inert gas. And a discharge pipe 3 having the other end connected to a vacuum pump (not shown).
And 5. The supply pipe 34 and the discharge pipe 35 are respectively provided with first and second flow control valves 31 and 32 for controlling the flow rate of the inert gas flowing through these pipes.

On the other hand, the first pulling condition is as follows: the pulling speed of the silicon single crystal rod 14 is V (mm / min), from the solid-liquid interface of the silicon single crystal rod 14 and the silicon melt 13 to 10 mm above this interface. Silicon single crystal rod 14
When the average value of the temperature gradient in the pulling direction is G (° C./mm), V / G is 0.290 to 0.340 mm ² / min · ° C., preferably 0.300 to 0.330 mm ² / min.・
In this case, the pulling speed V (mm / min) is set so that the temperature becomes ° C. The reason why V / G is limited to the range of 0.290 to 0.340 mm ² / min · ° C. is to form a region where atomic vacancies are predominant in the silicon single crystal rod 14.

The second pulling condition is that when pulling the silicon single crystal rod 14, the temperature range from 1130 ° C. to 1050 ° C. is 10 to 30 minutes, preferably 15 to 25 minutes.
Minutes, and the third pulling condition is the pulling of the silicon single crystal rod 14, which is performed at 850 ° C. to 650 ° C.
C. for a temperature range of 120 to 200 minutes, preferably 1
Cooling for 30 to 180 minutes. The reason why the temperature range from 1130 ° C. to 1050 ° C. is limited to 10 to 30 minutes is to suppress the disappearance of atomic vacancies, which are lattice defects in the silicon single crystal rod 14. Also from 850 ° C to 6
The reason why the temperature range up to 50 ° C. is limited to 120 to 200 minutes is to generate oxygen precipitation nuclei in the silicon single crystal rod 14 using the above-mentioned atomic vacancies.

In order to satisfy the first to third pulling conditions, the heat shielding member 16 in which the cylindrical heat insulating material 17c and the conical heat insulating material 18c are filled in the walls of the cylindrical portion 17 and the conical portion 18, respectively. Preferably, it is used. The heat shielding member 16 is provided between the outer peripheral surface of the silicon single crystal rod 14 and the quartz crucible 12.
A cylindrical portion 17 which is provided between the inner peripheral surface of the cylindrical portion and blocks radiant heat from the heater 21; a conical portion 18 which is provided at a lower end of the cylindrical portion 17 and has a diameter gradually reduced as it goes downward; A flange portion 19 for supporting the cylindrical portion 17 at its upper edge. The cylindrical portion 17 includes an outer tube 17a and an inner tube 17a at a predetermined distance from the outer tube 17a.
a It has an inner tube 17b provided concentrically, and a cylindrical heat insulating material 17c filled between the outer tube 17a and the inner tube 17b. The conical portion 18 has an outer cone 18a, an inner cone 18b having a smaller taper angle than the outer cone 18a and provided inside and concentric with the outer cone 18a, an outer cone 18a and an inner cone. 18b, and a conical heat insulating material 18c filled therebetween. The heat shielding member 16 is provided by mounting the flange portion 19 on the heat retaining cylinder 22 via the ring plate 23,
The conical portion 18 is fixed in the chamber 24 so that the lower edge of the conical portion 18 is located a predetermined distance above the surface of the silicon melt 13.

After the silicon single crystal rod 14 pulled as described above is sliced to produce a silicon wafer, an epitaxial layer is formed on the surface of the silicon wafer to obtain an epitaxial wafer. The epitaxial layer is preferably formed by a CVD method from the viewpoints of its crystallinity, mass productivity, simplicity of equipment, ease of forming various device structures, and the like. CV
In the epitaxial growth of silicon by the D method, for example, S
A source gas containing silicon, such as iCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , SiH ₄ , is introduced into a reaction furnace together with H ₂ gas, and is generated on the surface of the silicon wafer by thermal decomposition or reduction of the source gas. This is performed by depositing the silicon.

Specifically, as shown in FIG. 1, a polished silicon wafer is first heated at a predetermined temperature in the range of 600 to 850 ° C., preferably 750 to 800 ° C. for 5 to 180 minutes.
It is preferably held for 10 to 60 minutes, and the silicon wafer is kept at 1100 to 1150 ° C., preferably 1130 to 1110.
After the temperature is raised to a predetermined temperature in the range of 50 ° C. at a rate of 5 to 20 ° C./sec, preferably 8 to 18 ° C./sec, hydrogen pretreatment is performed at the predetermined temperature. 600-850 silicon wafers
The temperature was kept at a predetermined temperature in the range of 5 ° C. for 5 to 180 minutes because the silicon single crystal rod 14 was sliced to grow the oxygen precipitation nuclei existing in the initial state of producing the silicon wafer,
This is because oxygen precipitate nuclei that disappear when a high-temperature epitaxial layer is formed are reduced as much as possible, and the size of the oxygen precipitate nuclei increases after the epitaxial layer is formed, so that thermally stable oxygen precipitate nuclei are generated. In addition, the silicon wafer is cooled to a predetermined temperature in the range of 1100 to 1150 ° C. for 5 to 2 hours.
The reason why the temperature was raised at a rate of 0 ° C./sec is to gain a little throughput (a quantity that can be processed per unit time).

Next, this silicon wafer was loaded with
An epitaxial layer is formed on the surface of the silicon wafer while being maintained at a predetermined temperature of 150 ° C., preferably 1100 to 1140 ° C., and the epitaxial wafer is heated at a predetermined temperature of 600 to 850 ° C., preferably 750 to 800 ° C. Up to 5-20 ° C / sec, preferably 8-18 ° C
/ Second at a predetermined temperature for 5 to 120 minutes,
Preferably, it is maintained for 10 to 60 minutes. Further, the epitaxial wafer is taken out of the heat treatment furnace and naturally cooled to room temperature. The reason why the silicon wafer was held at a predetermined temperature in the range of 1050 to 1150 ° C. when forming the epitaxial layer was to form an epitaxial layer with few defects. After the epitaxial layer is formed,
The reason why the temperature is lowered at a rate of 5 to 20 ° C./sec to a predetermined temperature in the range of 00 to 850 ° C. is to increase the throughput as much as possible. Further, holding the wafer at a predetermined temperature in the range of 600 to 850 ° C. for 5 to 120 minutes further increases the oxygen precipitation nuclei that have not disappeared during the formation of the epitaxial layer, and generates thermally stable oxygen precipitation nuclei. That's why.

In the epitaxial wafer manufactured in this manner, the silicon single crystal rod 14 is pulled at a relatively high pulling speed, thereby increasing the concentration of atomic vacancies and shortening the pulling time of the silicon single crystal rod 14. be able to. Further, by doping nitrogen into the silicon single crystal rod 14, the solid solubility of the atomic vacancies generated in the silicon single crystal rod 14 is increased to suppress the disappearance of the atomic vacancies and to utilize the atomic vacancies. And silicon single crystal rod 1
4 can generate many oxygen precipitation nuclei. Further, by performing the heat treatment before and after forming the epitaxial layer on the surface of the silicon wafer prepared by slicing the silicon single crystal rod 14, the thermal stability of oxygen precipitation nuclei in the silicon wafer can be improved. Atomic vacancies, which are lattice defects that contribute to the generation of the oxygen precipitation nuclei, can be increased. As a result, the epitaxial wafer does not need to be subjected to polysilicon film formation or sandblasting on the back surface of the silicon wafer as in the related art.
It has the IG capability of contaminant metals in the device fabrication process.

[0017]

As described above, according to the present invention, a silicon single crystal rod doped with nitrogen is pulled up by the Czochralski method, and the silicon single crystal rod is sliced to produce a silicon wafer. Since a predetermined heat treatment was performed before and after the formation of the epitaxial layer on the front surface of the silicon wafer, the oxygen in the silicon wafer before the formation of the epitaxial layer was formed without forming the polysilicon film or sandblasting on the back surface of the silicon wafer. The thermal stability of the precipitation nucleus can be improved, and the number of atomic vacancies, which are lattice defects that contribute to the generation of the oxygen precipitation nucleus, can be increased. As a result, the epitaxial wafer manufactured by the above method has IG capability of a contaminant metal in a device manufacturing process.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in a heat treatment temperature with time before and after an epitaxial layer is formed on an epitaxial wafer according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a pulling machine for producing a silicon single crystal rod for producing an epitaxial wafer.

[Explanation of symbols]

 13 Silicon melt 14 Silicon single crystal rod

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiro Harada 1-5-1, Otemachi, Chiyoda-ku, Tokyo Mitsui Material Silicon Co., Ltd. (72) Hiroyoshi Kaihara 1-5, Otemachi, Chiyoda-ku, Tokyo No. 1 Mitsubishi Materials Silicon Corporation

Claims (3)

[Claims] A silicon single crystal rod doped with nitrogen (14)
Pulling the silicon wafer by the Czochralski method; slicing the silicon single crystal rod (14) to produce a silicon wafer; holding the silicon wafer at a predetermined temperature in the range of 600 to 850 ° C. for 5 to 180 minutes. Performing a hydrogen pretreatment at the predetermined temperature after raising the silicon wafer to a predetermined temperature in the range of 1100 to 1150 ° C. at a rate of 5 to 20 ° C./sec. Forming an epitaxial layer on the surface of the silicon wafer while maintaining the silicon wafer at a predetermined temperature in a range of 600C, and cooling the silicon wafer to a predetermined temperature in a range of 600 to 850C at a rate of 5 to 20C / sec. And holding at a predetermined temperature for 5 to 120 minutes. 2. The method for producing an epitaxial wafer according to claim 1, wherein the concentration of nitrogen doped in the silicon single crystal rod is 5 × 10 ^{12 to} 5 × 10 ¹⁴ cm ^-3 . 3. An epitaxial wafer manufactured by the method according to claim 1.