JP3900816B2 - Silicon wafer manufacturing method - Google Patents

Description

【００２２】
表１から明らかなように、アニール温度が低くかつアニール時間が短い比較例１〜９のウェーハでは総パーティクル数が多かったのに対し、アニール温度が高くアニール時間が長い実施例１〜３のウェーハでは総パーティクル数は極めて少なかった。これはシリコン単結晶棒に窒素をドープしかつこのシリコン単結晶棒を所定の条件で引上げることにより、シリコン単結晶棒内に発生したボイド状欠陥（原子空孔の凝集体）のサイズを小さくすることができ、このシリコン単結晶棒をスライスして作製されたシリコンウェーハを比較的高い温度で比較的長い時間だけ水素アニール処理することにより、ウェーハ表層部のボイド状欠陥を消滅させることができたためであると考えられる。
【００２３】
【発明の効果】
以上述べたように、本発明によれば、窒素をドープしたシリコン単結晶棒をＶ／Ｇが０．２９０〜０．３４０ｍｍ²／分・℃となるような引上げ速度Ｖで引上げ、この引上げに伴う１１３０℃から１０５０℃までの冷却時間が１０〜３０分間であり、更にこのシリコン単結晶棒をスライスして作製されたシリコンウェーハを水素アニール処理したので、シリコン単結晶棒の引上げ時間を短縮でき、またシリコン単結晶棒内のボイド状欠陥のサイズを小さくでき、更にシリコンウェーハのウェーハ表層部のボイド状欠陥を消滅させて、ウェーハ表層部をボイド状欠陥のない無欠陥領域とすることができる。この結果、半導体素子の製造歩留りの向上を図ることができる。
【図面の簡単な説明】
【図１】本発明実施形態のシリコンウェーハを作製するためのシリコン単結晶棒を引上げる引上げ機の縦断面図。
【図２】そのシリコンウェーハを水素アニール処理するときの温度の時間に対する変化を示す図。
【符号の説明】
１３ シリコン融液
１４ シリコン単結晶棒[0001]
BACKGROUND OF THE INVENTION
The present invention Czochralski method is relates to the way of manufacturing a silicon wafer using a pulled silicon single crystal rod at (hereinafter, referred to CZ method.).
[0002]
[Prior art]
Conventionally, as a method of manufacturing this type of silicon wafer, a silicon single crystal rod doped with nitrogen is pulled up by the CZ method, the single crystal rod is sliced and processed into a silicon single crystal wafer, and then the wafer is heated rapidly and rapidly. A method for producing a silicon single crystal wafer that has been heat-treated by a cooling device is disclosed (Japanese Patent Laid-Open No. 11-322490). In this method of manufacturing a silicon single crystal wafer, nitrogen of 1 × 10 ^{10 to} 5 × 10 ¹⁵ cm ⁻³ is doped into a silicon single crystal rod. In addition, the heat treatment by the rapid heating / cooling device for the wafer is performed for 1 to 60 seconds at a temperature of 1100 ° C. to a silicon melting point or lower in an atmosphere of oxygen, hydrogen, argon, or a mixture thereof. The reason why the heat treatment is limited to 1 to 60 seconds is that when it exceeds 60 seconds, new crystal defects and oxygen precipitation occur during the temperature rise.
In the method for producing a silicon single crystal wafer configured as described above, the growth of crystal defects in the silicon single crystal produced by the CZ method can be suppressed and the crystal defects in the surface layer of the wafer can be eliminated. As a result, an extremely low defect silicon single crystal wafer can be produced efficiently.
[0003]
[Problems to be solved by the invention]
However, in the conventional method for producing a silicon single crystal wafer disclosed in Japanese Patent Application Laid-Open No. 11-322490, the heat treatment of the wafer at a temperature of 1100 ° C. to a silicon melting point or less is as short as 1 to 60 seconds. There was a problem that oxygen and nitrogen did not diffuse sufficiently outward, and crystal defects on the surface layer of the wafer were not completely eliminated.
In order to solve this problem, if the heat treatment time is extended, there is a problem that oxygen precipitation nuclei increase.
An object of the present invention is to reduce the size of void-like defects (aggregates of atomic vacancies) by nitrogen doping into a silicon single crystal rod, and to perform a hydrogen annealing treatment on a silicon wafer cut out from the silicon single crystal rod. makes it possible to eliminate the void-like defects is to provide a manufacturing how the silicon wafer.
Another object of the present invention is to provide a method for producing a silicon wafer, which can shorten the pulling time while maintaining good quality of a silicon single crystal rod for producing a silicon wafer.
[0004]
[Means for Solving the Problems]
In the invention according to claim 1, as shown in FIG. 1, the pulling speed of the silicon single crystal rod 14 doped with nitrogen is V (mm / min), and the solid-liquid interface between the silicon single crystal rod 14 and the silicon melt 13 is used. V / G is 0.290 to 0.340 mm ² / min · ° C., where G (° C./mm) is the average value of the temperature gradient in the pulling direction in the silicon single crystal rod 14 up to 10 mm above this interface. A step of pulling up at a pulling speed V (mm / min) such that: a step of cooling the silicon single crystal rod 14 as it is pulled up; and slicing the silicon single crystal rod 14 to produce a silicon wafer; First, hold in a hydrogen gas atmosphere at a predetermined temperature in the range of 550 to 850 ° C. for 10 to 100 minutes, and then at a rate of 2 to 10 ° C./minute to a predetermined annealing temperature in the range of 1100 to 1250 ° C. Was raised, the time further silicon wafer and a step of hydrogen annealing process to hold 30 to 240 minutes at a predetermined annealing temperature in the range of above 1100 to 1250 ° C., cooling the silicon single crystal rod 14 to 1050 ° C. from 1130 ° C. Is a method for producing a silicon wafer, wherein 10 to 30 minutes.
[0005]
In this silicon wafer manufacturing method, the silicon single crystal rod 14 is pulled up at a relatively high pulling speed as described above, and the silicon single crystal rod 14 is being pulled up from 1130 ° C. to 1050 ° C. When the cooling time is 10 to 30 minutes, the pulling time can be shortened while maintaining good quality of the silicon single crystal rod 14. Further, by doping the silicon single crystal rod 14 with nitrogen, the size of void defects (aggregates of atomic vacancies) can be reduced. Furthermore, the silicon wafer produced by slicing the silicon single crystal rod 14 is subjected to hydrogen annealing treatment, thereby eliminating the void-like defects in the wafer surface layer portion, which is the semiconductor element forming region of the silicon wafer, and forming the void in the wafer surface layer portion. A defect-free region without defects can be obtained. Since the quality of the silicon wafer is good as described above, oxygen precipitation nuclei are not newly generated in the wafer when the temperature is raised or lowered in the hydrogen annealing process.
[0006]
The concentration of nitrogen doped in the silicon single crystal rod 14 is preferably 5 × 10 ^{12 to} 5 × 10 ¹⁴ cm ⁻³ .
Further comprising the claims 1 or 2 silicon-way Ha produced by the method described in denuded zone free of void-like defects in the wafer surface layer portion is a semiconductor element forming region, i.e. DZ (Denuded Zone) layer.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the silicon wafer of the present invention was pulled up from the silicon melt 13 in the quartz crucible 12 of the puller 11 under the first and second pulling conditions described later by the CZ method. Thereafter, the silicon single crystal rod 14 is sliced. The 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 cm ⁻³ , preferably 3 × 10 ^{13 to} 3 × 10 ¹⁴ cm ⁻³ . The reason for limiting the nitrogen concentration to the range of 5 × 10 ^{12 to} 5 × 10 ¹⁴ cm ⁻³ is that the solid solubility in the silicon single crystal rod 14 of atomic vacancies does not increase if it is less than 5 × 10 ¹² cm ^−3. This is because void defects are likely to occur due to the subsequent thermal history of the silicon single crystal rod 14, and if it exceeds 5 × 10 ¹⁴ cm ⁻³ , the amount of donors related to nitrogen increases and the resistivity of the single crystal is reduced. It is because it changes greatly. As a method for doping nitrogen into the silicon single crystal rod 14, polycrystalline silicon mixed with nitride or polycrystalline silicon formed with a nitride film is put into a quartz crucible 12 and a silicon melt 13 containing nitrogen is added. The silicon single crystal rod 14 is pulled up from the substrate, or the silicon single crystal rod 14 is pulled up in an inert gas atmosphere containing nitrogen gas.
[0008]
A cylindrical casing 25 is connected to the upper end of the chamber 24 of the puller 11, and a pulling means 26 is provided in the casing 25. 1 is a wire cable that hangs down toward the center of rotation of the quartz crucible 12, and a seed crystal for pulling up the silicon single crystal rod 14 by dipping in the silicon melt 13 at the lower end of the wire cable 26a. 26b is attached. The outer surface of the quartz crucible 12 is covered with a graphite susceptor 27, the lower surface of the graphite susceptor 27 is fixed to the upper end of the support shaft 28, and the lower portion of the support shaft 28 is connected to the crucible driving means 29.
[0009]
Further, 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 crucible inner peripheral surface side of the chamber 24 is connected to the chamber 24. The gas supply / discharge means 33 has one end connected to the peripheral wall of the casing 25 and the other end connected to a tank (not shown) for storing the inert gas, and one end connected to the lower wall of the chamber 24. And a discharge pipe 35 having the other end connected to a vacuum pump (not shown). The supply pipe 34 and the discharge pipe 35 are respectively provided with first and second flow rate adjusting valves 31 and 32 for adjusting the flow rate of the inert gas flowing through these pipes.
[0010]
On the other hand, the first pulling condition is that the pulling speed of the silicon single crystal rod 14 is V (mm / min), the silicon single crystal rod 14 and the silicon melt 13 from the solid-liquid interface up to 10 mm above this interface. When the average value of the temperature gradient in the pulling direction of the crystal rod 14 is G (° C./mm), V / G is 0.290 to 0.340 mm ² / min · ° C., preferably 0.300 to 0.330 mm. ^The pulling speed V (mm / min) is set to ² / min · ° C. The reason why V / G is limited to the range of 0.290 to 0.340 mm ² / min · ° C. is to create a dominant region of atomic vacancies in the silicon single crystal rod 14. The second pulling condition is that the time for cooling the silicon single crystal rod 14 from 1130 ° C. to 1050 ° C. is 10 to 30 minutes, preferably 15 to 25 minutes. The reason why the temperature range from 1130 ° C. to 1050 ° C. is limited to 10 to 30 minutes is to suppress the generation of void defects which are crystal defects in the silicon single crystal rod 14.
[0011]
In order to satisfy the first and second pulling conditions, the heat shielding member 16 is preferably used in the pulling machine 11. The heat shielding member 16 is provided between the outer peripheral surface of the silicon single crystal rod 14 and the inner peripheral surface of the quartz crucible 12, and has a cylindrical cylindrical portion 17 that blocks radiant heat from the heater 21, and a lower end of the cylindrical portion 17. A conical portion 18 that is continuously provided and gradually decreases in diameter as it goes downward, and a flange portion 19 that supports the cylindrical portion 17 at its upper edge. The cylindrical portion 17 is filled between an outer tube 17a, an inner tube 17b provided at a predetermined interval from the outer tube 17a and concentrically with the outer tube 17a, and between the outer tube 17a and the inner tube 17b. And a cylindrical heat insulating material 17c. The cone portion 18 includes an outer cone 18a, an inner cone 18b having a smaller taper angle than the outer cone 18a, provided inside the outer cone 18a and concentrically with the outer cone 18a, and the outer cone 18a and the inner cone. 18b and a conical heat insulating material 18c filled between them. The heat shielding member 16 is configured such that the lower edge of the conical portion 18 is positioned above the surface of the silicon melt 13 by a predetermined distance by placing the flange portion 19 on the heat retaining cylinder 22 via the ring plate 23. Fixed in the chamber 24.
[0012]
The silicon single crystal rod 14 pulled up as described above is sliced to produce a silicon wafer, and this silicon wafer is placed in a heat treatment furnace and subjected to hydrogen annealing treatment (FIG. 2). In this hydrogen annealing treatment, the polished silicon wafer is first placed in a heat treatment furnace, and the silicon wafer is placed in a hydrogen gas atmosphere at a predetermined temperature in the range of 550 to 850 ° C., preferably 650 to 750 ° C., preferably 10 to 100 minutes, Hold for 20-40 minutes. Then, after the silicon wafer is heated to a predetermined annealing temperature in the range of 1100 to 1250 ° C., preferably 1150 to 1230 ° C. at a rate of 2 to 10 ° C./min, preferably 3 to 5 ° C./min, Hold at a predetermined annealing temperature in the range of 1100-1250 ° C. for 30-240 minutes. Here, the silicon wafer was held at a predetermined temperature in the range of 550 to 850 ° C. for 20 to 40 minutes in order to equalize the furnace temperature and the temperature of the wafer charged into the furnace, and to inert gas in the furnace. This is to replace the atmosphere with a hydrogen gas atmosphere. The reason why the temperature of the silicon wafer is raised to a predetermined annealing temperature in the range of 1100 to 1250 ° C. at a rate of 2 to 10 ° C./min is to prevent the occurrence of slip. Further, the reason why the silicon wafer was held at a predetermined annealing temperature in the range of 1100 to 1250 ° C. for 30 to 240 minutes was to eliminate COP (Crystal Originated Particles) in the wafer (particularly in the surface layer 10 μm from the surface).
[0013]
Next, the silicon wafer is cooled to a predetermined temperature in the range of 550 to 850 ° C., preferably 600 to 700 ° C. at a rate of 3 to 5 ° C./min, and held at the predetermined temperature for 10 to 50 minutes, preferably 20 to 40 minutes. To do. Further, the silicon wafer is taken out from the heat treatment furnace and naturally cooled to room temperature. The reason why the temperature of the silicon wafer was lowered to a predetermined temperature in the range of 550 to 850 ° C. at a rate of 3 to 5 ° C./min is to prevent the occurrence of slip, and the silicon wafer was cooled to a predetermined temperature in the range of 550 to 850 ° C. The reason for holding for 10 to 50 minutes is to replace the inside of the furnace from a hydrogen gas atmosphere to another inert gas atmosphere.
[0014]
In the silicon wafer thus manufactured, even if the silicon single crystal rod 14 is pulled at a relatively high pulling speed such that V / G is 0.290 to 0.340 mm ² / min · ° C., the heat shielding member 16 The time for cooling from 1130 ° C. to 1050 ° C. during the pulling of the silicon single crystal rod 14 is 10 to 30 minutes, so that the quality of the silicon single crystal rod 14 is kept good and the silicon single crystal rod 14 is pulled up. Time can be shortened. Further, by doping the silicon single crystal rod 14 with nitrogen, the size of void defects (aggregates of atomic vacancies) generated in the silicon single crystal rod 14 can be reduced. Further, the silicon wafer produced by slicing the silicon single crystal rod 14 is subjected to hydrogen annealing treatment, thereby eliminating the void-like defects in the wafer surface layer portion, which is a semiconductor element forming region of the silicon wafer, so that the wafer surface layer portion is voided. It is possible to make a defect-free region free from defects. Since the quality of the silicon wafer is good as described above, oxygen precipitation nuclei are not newly generated in the wafer when the temperature is raised or lowered in the hydrogen annealing process.
[0015]
【Example】
Next, examples of the present invention will be described in detail together with comparative examples.
<Examples 1-3>
The silicon single crystal rod 14 was pulled up using the pulling machine 11 shown in FIG. The first pulling condition at that time is that the pulling speed of the silicon single crystal rod 14 is V (mm / min), the silicon single crystal rod 14 and the silicon melt 13 from the solid-liquid interface up to 10 mm above this interface. When the average value of the temperature gradient in the pulling direction of the crystal rod 14 is G (° C./mm), the pulling speed V (mm / min) is set so that V / G is 0.300 mm ² / min · ° C. did. The second pulling condition was that the time for cooling the silicon single crystal rod 14 from 1130 ° C. to 1050 ° C. was 25 minutes. The oxygen concentration in the silicon single crystal rod 14 was 1.39 × 10 ^{18 to} 1.33 × 10 ¹⁸ atoms / cm ³ .
[0016]
Three silicon wafers were prepared by slicing the silicon single crystal rod 14 pulled up as described above, and these silicon wafers were put into a heat treatment furnace and subjected to hydrogen annealing treatment (FIG. 2). In this hydrogen annealing treatment, the polished silicon wafer was first placed in a heat treatment furnace, and the silicon wafer was kept in a hydrogen gas atmosphere at 700 ° C. for 30 minutes. Next, after the silicon wafer was heated up to an annealing temperature of 1200 ° C. at a rate of 5 ° C./min, the silicon wafer was held at the annealing temperature of 1200 ° C. for 3600 seconds (60 minutes). Furthermore, the temperature of the silicon wafer was lowered to 700 ° C. at a rate of 3 ° C./min and held at that temperature for 20 minutes, then taken out from the heat treatment furnace and naturally cooled to room temperature. These silicon wafers were referred to as Examples 1 to 3.
[0017]
<Comparative Example 1>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at an annealing temperature of 1190 ° C. in a hydrogen atmosphere for 60 seconds (1 minute). This silicon wafer was referred to as Comparative Example 1.
<Comparative example 2>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at an annealing temperature of 1190 ° C. for 30 seconds in a hydrogen atmosphere. This silicon wafer was referred to as Comparative Example 2.
<Comparative Example 3>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at an annealing temperature of 1190 ° C. for 5 seconds in a hydrogen atmosphere. This silicon wafer was designated as Comparative Example 3.
[0018]
<Comparative example 4>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at an annealing temperature of 1100 ° C. for 60 seconds (1 minute) in a hydrogen atmosphere. This silicon wafer was referred to as Comparative Example 4.
<Comparative Example 5>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at an annealing temperature of 1100 ° C. for 30 seconds in a hydrogen atmosphere. This silicon wafer was designated as Comparative Example 5.
<Comparative Example 6>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at an annealing temperature of 1100 ° C. for 5 seconds in a hydrogen atmosphere. This silicon wafer was designated as Comparative Example 6.
[0019]
<Comparative Example 7>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at an annealing temperature of 1000 ° C. for 60 seconds (1 minute) in a hydrogen atmosphere. This silicon wafer was referred to as Comparative Example 7.
<Comparative Example 8>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was kept at an annealing temperature of 1000 ° C. for 30 seconds in a hydrogen atmosphere. This silicon wafer was designated as Comparative Example 8.
<Comparative Example 9>
A silicon wafer was produced in the same manner as in Example 1 except that the silicon wafer was held at 1000 ° C. annealing temperature in a hydrogen atmosphere for 5 seconds. This silicon wafer was designated as Comparative Example 9.
[0020]
<Comparison test and evaluation>
After the silicon wafers of Examples 1 to 3 and Comparative Examples 1 to 9 were SC1 cleaned for a predetermined time (0 minutes, 40 minutes, 80 minutes, 120 minutes, 160 minutes and 200 minutes), the diameter was measured using a particle counter. The total number of particles of 0.13 μm or more was measured. The results are shown in Table 1 together with the hydrogen annealing conditions.
[0021]
[Table 1]

[0022]
As is clear from Table 1, the wafers of Examples 1 to 9 having a low annealing temperature and a short annealing time had a large annealing temperature and a long annealing time, whereas the wafers of Comparative Examples 1 to 9 had a large total number of particles. So the total number of particles was very small. This is because the silicon single crystal rod is doped with nitrogen and the silicon single crystal rod is pulled up under predetermined conditions, thereby reducing the size of void defects (aggregates of atomic vacancies) generated in the silicon single crystal rod. Void defects on the surface layer of the wafer can be eliminated by subjecting a silicon wafer produced by slicing this silicon single crystal rod to hydrogen annealing treatment at a relatively high temperature for a relatively long time. This is probably because
[0023]
【The invention's effect】
As described above, according to the present invention, a nitrogen-doped silicon single crystal rod is pulled at a pulling speed V such that V / G is 0.290 to 0.340 mm ² / min · ° C. The cooling time from 1130 ° C. to 1050 ° C. is 10 to 30 minutes, and the silicon wafer produced by slicing this silicon single crystal rod is subjected to hydrogen annealing treatment, so that the pulling time of the silicon single crystal rod can be shortened. In addition, the size of the void defect in the silicon single crystal rod can be reduced, and the void defect on the wafer surface layer portion of the silicon wafer can be eliminated to make the wafer surface layer a defect-free region free of void defects. . As a result, it is possible to improve the manufacturing yield of the semiconductor element.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a pulling machine that pulls up a silicon single crystal rod for producing a silicon wafer according to an embodiment of the present invention.
FIG. 2 is a diagram showing a change in temperature with respect to time when the silicon wafer is subjected to a hydrogen annealing treatment;
[Explanation of symbols]
13 Silicon melt 14 Silicon single crystal rod

Claims (2)

The pulling rate of the nitrogen-doped silicon single crystal rod (14) is V (mm / min), and the solid-liquid interface between the silicon single crystal rod (14) and the silicon melt (13) is 10 mm above this interface. When the average value of the temperature gradient in the pulling direction in the silicon single crystal rod (14) is G (° C./mm), the pulling is such that V / G is 0.290 to 0.340 mm ² / min · ° C. A step of pulling up at a speed V (mm / min);
Cooling the silicon single crystal rod (14) as it is pulled;
After slicing the silicon single crystal rod (14) to prepare a silicon wafer, the silicon wafer is first held in a hydrogen gas atmosphere at a predetermined temperature in the range of 550 to 850 ° C. for 10 to 100 minutes, and then 1100 to 1100. Hydrogen annealing treatment in which the temperature is increased to a predetermined annealing temperature in the range of 1250 ° C. at a rate of 2 to 10 ° C./min, and the silicon wafer is maintained at the predetermined annealing temperature in the range of 1100 to 1250 ° C. for 30 to 240 minutes. Including the steps of
A method for producing a silicon wafer, wherein the time for cooling the silicon single crystal rod (14) from 1130 ° C. to 1050 ° C. is 10 to 30 minutes. The method for producing a silicon wafer according to claim 1, wherein the concentration of nitrogen doped in the silicon single crystal rod (14) is 5 x 10 ^{12 to} 5 x 10 ¹⁴ cm ^-3 .

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