JP2002093814A - Substrate single crystal of silicon epitaxial wafer, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the substrate single crystal of an epitaxial wafer, that effectively uses proper gettering effect produced by high-density and stable oxygen deposition (nucleus) where a nitrogen-doped crystal has, and at the same time, prevents the generation of OSF causing an epitaxial defect, and to provide a method for manufacturing the substrate single crystal. SOLUTION: In this substrate single crystal of a silicon epitaxial waver, that can be manufactured by setting pull-up speed to 0.7 mm/min or higher, and/or setting a crystal rotational speed S/R to 1,600/Drpm or lower (D = crystal diameter mm) when the crystal is raised, at least nitrogen concentration is to be within a range of 1×1013 to 1×1015 atoms/cm3; and at the same time, the concentration of oxygen at a distance of 6 mm from an edge is 7 to 10.5 ppma, or the ratio ORG=(Oic-Oie)/Oic of the difference between the concentration of center oxygen Oic and the concentration of oxygen Oie at a distance of 6 mm for the edge to the concentration of center oxygen is set to 15% or higher. In this case, the concentration of oxygen at a distance of 6 mm from the edge is to be 7 to 10.5 ppma, and at the same time, the ORG=(Oic-Oie)/Oic is to be 15% or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a substrate single crystal for a silicon epitaxial wafer excellent in gettering ability manufactured by the Czochralski method (hereinafter referred to as CZ method) and a method for manufacturing the same.

[0002]

2. Description of the Related Art A silicon single crystal used as a substrate material of a semiconductor element is mainly manufactured by a CZ method. The CZ silicon single crystal has excellent features such as high productivity, relatively easy response to a demand for a large diameter, provision of a gettering site for harmful metal impurities due to precipitation of oxygen contained as an impurity. Have. However, with the recent increase in the degree of integration of LSIs, it has become clear that microscopic defects in crystals, which have never been a problem, have a fatal effect on device functions. A typical example is an octahedral microvoid having a diameter of about 0.1 μm. This defect is formed by accumulation of vacancies taken into the crystal as the crystal is pulled up and solidified. It has been reported that voids in the device active region on the surface and immediately below the surface may cause oxide film breakdown voltage failure, element isolation failure, and the like.

An epitaxial (hereinafter, referred to as “epi”) wafer manufactured by forming a silicon crystal on a wafer surface by CVD has been used for a long time, particularly for devices requiring reliability, bipolar devices, and the like. Surface modification by epi is extremely effective for microvoids, and in recent years, epiwafers have been widely used for general-purpose memory devices such as DRAM.

At present, most epi devices for large-diameter wafers having a diameter of 200 mm or more are of a single-wafer type. In the single-wafer epi apparatus, the wafer is formed at a film forming temperature (up to 1150 ° C.)
Until the lamp is rapidly heated. Therefore, most of the oxygen nuclei formed during the crystal pulling process disappear. Although such an epiwafer has extremely excellent surface quality, almost no oxygen precipitation is observed in the substrate wafer in the device process, and it has been an issue to provide gettering characteristics. In particular, in recent years, the use of high-energy ion implantation and rapid thermal process (RTP) in the device process has led to an increasingly large problem of gettering deficiency in epi-wafers due to the low temperature and short time of the thermal process. Under such conditions, little effect was observed in conventional measures such as the use of a high oxygen concentration substrate and the improvement of the heat history of crystal pulling. To form stable precipitation nuclei even with rapid heating, long-time annealing at 800 ° C. or more is effective, but there is a problem that the cost is increased by incorporating this operation.

On the other hand, nitrogen doping has been known as a means for promoting oxygen precipitation (for example, F. Shimura
et al. Appl. Phys. Lett. 48 (3) 224, 1986). According to the reference, the oxygen precipitation nuclei in the nitrogen-doped substrate are stable and
Those that do not decompose even after heat treatment at 250 ° C. are observed. Also, it is known that nitrogen doping has an effect of improving the wafer strength also in CZ crystal, and it has been reported that addition of nitrogen has an effect of suppressing dislocation generation and movement in the epi process (Takao Abe) Others: Silicon crystal and doping 1: 4, 1986 Maruzen).

In recent years, a technique has been proposed in which a nitrogen-doped CZ crystal is applied to an epi-substrate to impart a gettering effect (Japanese Patent Application Laid-Open No. 11-189493). In this technique, the width of the ring-shaped oxidation-induced stacking fault (OSF ring) is increased by nitrogen doping, and an OSF nucleus is uniformly generated on the entire wafer to thereby obtain a gettering effect. However, although the OSF (nucleus) can be expected to have a gettering effect as much as possible, stacking faults may be generated from the nuclei on the surface and may grow together with the formation of the epilayer to form epidefects. In addition, stacking faults generated from nuclei immediately below the surface in the device process may propagate to the epi layer and induce device failure. Therefore, it is safer to obtain getter sites from oxygen precipitation nuclei as proposed in Japanese Patent Laid-Open No. 2000-44389 than from OSF in terms of side effects.

On the other hand, as described above, it is a fact that an OSF ring having an increased width is likely to occur in a nitrogen-doped crystal. In the case where nitrogen is not added, even if a crystal is grown under the condition that no OSF is generated at all, if nitrogen is doped, a region where an OSF nucleus exists around the edge is formed, which causes an epi defect. OSF is the biggest problem of the nitrogen-doped crystal as the epi-substrate, and effective measures have been strongly required.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a main object of the present invention is to provide a high getter provided by high-density and stable oxygen precipitation (nuclei) of a nitrogen-doped crystal. An object of the present invention is to provide a substrate single crystal of an epitaxial wafer which does not generate OSF which causes epi defects while utilizing the ring effect, and a method of manufacturing the same.

[0009]

Means for Solving the Problems In order to solve the problems described above, the present inventors have intensively studied the OSF generation behavior and conditions in nitrogen-doped crystals and the effects on the quality of the epilayer, and have studied the oxygen concentration and the oxygen concentration around the wafer edge. The inventors have found that the distribution of the oxygen concentration in the crystal plane governs the generation of OSF, and have reached the present invention. That is, in the first embodiment of the present invention, the nitrogen concentration is 1 × 10 ¹³ to 1 × 10 ¹⁵ atoms.
/ Cm ^{3 and} the oxygen concentration at a distance of 6 mm from the edge is 7 to 10.5 ppma (ASTM F12
1-83), wherein the substrate is a single crystal silicon epitaxial wafer. If the nitrogen concentration and the oxygen concentration are within these ranges, OSF does not occur near the edge. When the nitrogen concentration or the oxygen concentration is lower than the above lower limit, OSF does not occur, but the oxygen precipitate density becomes 1 × 10 ⁸ / cm ³ or lower, and the gettering performance is lowered. In this specification, the distance from the edge is 6
the oxygen concentration in mm called Oi _e, the Oi _e is, AST at 6mm position from the edge of the silicon wafer
It refers to the oxygen concentration measured by the infrared absorption method based on MF121-83.

In a second aspect of the present invention, a nitrogen concentration
Is 1 × 10¹³~ 1 × 10 ^Fifteenatoms / cm^ThreeIn the range
Yes, at center oxygen concentration and 6 mm from edge
When the ratio of oxygen concentration difference to central oxygen concentration is 15% or more
Silicon epitaxial wafer characterized by the following
Substrate single crystal. Conventional oxygen concentration
In-plane uniformity has been required. In this aspect of the invention
At the center oxygen concentration and at a distance of 6 mm from the edge.
When the ratio of oxygen concentration difference to central oxygen concentration is 15% or more
The reason for this is that nitrogen-doped wafers
On the other hand, by this, the in-plane uniformity of the oxygen precipitate density is
At the same time as improving the edge OSF
Because it is brought. In this specification,
The central oxygen concentration is the central oxygen concentration at the center of the silicon wafer.
Oi refers to oxygen concentration._cNotation. This central acid
Elemental concentration Oi_cAnd oxygen concentration at a distance of 6 mm from the edge
Degree Oi_eThe ratio of the difference to the central oxygen concentration is called ORG.
It shall be. This ORG is represented by the formula (Oi_c-Oi_e) /
Oi_cCan be obtained by

[0011] A third aspect of the present invention is directed to a nitrogen concentration
Is 1 × 10¹³~ 1 × 10 ^Fifteenatoms / cm^ThreeIn the range
Yes, oxygen concentration Oi at a distance of 6 mm from the edge_e
Is 7 to 10.5 ppma and ORG is 15% or more.
Silicon epitaxial wafer characterized by the following
Substrate single crystal. In this crystal, the edge OSF is
In-plane uniformity of oxygen precipitate density while being completely suppressed
The performance is improved.

A fourth aspect of the present invention relates to the above-mentioned method for producing a substrate single crystal having a more reliable high gettering ability, wherein the pulling speed is 0.7 mm / min or more. And a method of manufacturing a substrate single crystal of a silicon epitaxial wafer.

Further, a fifth aspect of the present invention proposes a method for producing a substrate single crystal of a silicon epitaxial wafer having the above-described oxygen concentration distribution, wherein a crystal rotation speed S / R during crystal growth is 1600. / Drpm (where D =
(Crystal diameter mm) or less, a method for producing a substrate single crystal of a silicon epitaxial wafer.

Further, a sixth aspect of the present invention proposes a method for producing a substrate single crystal of a silicon epitaxial wafer with the above-mentioned oxygen concentration distribution while more reliably imparting a high gettering ability. Lifting speed is 0.7
mm / min or more, and the crystal rotation speed S during crystal growth.
/ R is not more than 1600 / Drpm (where D = crystal diameter mm) or less, and a method for manufacturing a substrate single crystal of a silicon epitaxial wafer.

Hereinafter, the present invention will be described in more detail. O
The generation position of the SF ring is called a P band, and is mainly governed by the crystal growth rate. It is already known that the P band is outside the crystal when the growth rate is high, but contracts toward the crystal center as the growth rate becomes low. Inside the P band, there is a region called an H band in which the amount of precipitated oxygen by the heat treatment at 800 to 1000 ° C. is larger than that in the periphery. The conditions (11) usually used in the OSF evaluation heat treatment
(00 ° C., steam oxidation), OSF is generated only in the P band. When the heat treatment temperature is lowered, the OSF generation region may reach the H band.

In a crystal containing 1 × 10 ¹³ atoms / cm ³ or more of nitrogen, the P-band width is increased as described above, and OSF may be generated in the H-band in most cases by ordinary OSF evaluation heat treatment. Do you get it. In a nitrogen-doped crystal, even if the generation of the P band can be suppressed by high-speed pulling,
Bands often remain at the edges. This is the reason why the edge OSF becomes a problem in an epi-wafer using a nitrogen-doped crystal as a substrate. As a result of various studies to solve the edge OSF problem, the present inventors have found that if the amount of oxygen at a distance of 6 mm from the edge is 10.5 ppma or less, OSF does not occur without removing the H band. Was. In this case, if the oxygen amount is 7 ppma or more, oxygen precipitation required for gettering can be secured.

It is effective to make the oxygen concentration at the edge portion lower than that at the center portion in order to obtain uniform oxygen precipitation in the wafer surface. Conventionally, it has been preferred that the ORG be as low as possible. This is because, in a normal crystal containing no nitrogen, uniform oxygen precipitation can be obtained by forming a uniform oxygen concentration distribution in the wafer surface. For this reason, the crystal rotation speed S / R is usually set to 2000 / Drpm (where D = crystal diameter mm) or more.

However, in the case of a nitrogen-doped crystal, if the oxygen concentration is made uniform, oxygen precipitation at the edge becomes excessive. 15%
In the above ORG, the effect of lowering the oxygen concentration at the edge can be more effective to make oxygen precipitation uniform. A high ORG is also effective in suppressing the occurrence of the edge OSF. ORG ≧ 15%
As shown in FIG. 2, the crystal rotation speed S
It is effective to make / R not more than 1600 / Drpm (where D = crystal diameter mm). Decreasing S / R is a matter of crystal-
The edge OSF is prevented by the flattening of the melt (solid-liquid) interface shape and the synergistic effect of the effect of reducing the edge oxygen concentration and the effect of expanding the H band diameter.

Furthermore, the oxygen concentration Oi _e at a distance 6mm from edges in 7～10.5Ppma, simultaneously OR
When G is 15% or more, the generation of the edge OSF is completely suppressed, and at the same time, uniform oxygen precipitation in the wafer surface is obtained. When the crystal pulling speed is set to 0.7 mm / min or more, the B required for gettering at a low nitrogen / oxygen concentration is reduced.
Simultaneously with the MD density (for example, ≧ 1 × 10 ⁸ / cm ³ ), the microvoid size in the crystal is reduced. These are both effective for obtaining good epi quality.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a cross section of a CZ crystal growth furnace related to the present invention.
Usually, it is provided with a diameter control camera 8, an isolation 22, and the like. In the glow chamber 1, a quartz crucible 2 containing the raw material polycrystalline silicon and its melt, a carbon susceptor 3 holding the quartz crucible, a heater 4 for heating and melting the raw material, and a heater for stably maintaining a high temperature environment in the furnace. A heat insulating shield 5 and the like surrounding the periphery are arranged. The crucible support shaft 6 supports the susceptor and the crucible and has a rotary elevating mechanism. The amount of oxygen in the crystal is mainly controlled by the number of rotations of the crucible. The single crystal 10 is firstly immersed in the melt 7 with the seed crystal 12 held in the seed crystal holder 11 and then pulled up while narrowing the diameter to make it dislocation-free, and then enlarge the diameter of the dislocation-free crystal, After reaching the predetermined diameter, the outer diameter is controlled to a substantially constant value and pulled up. The crystal is pulled up at a predetermined speed by winding up a tungsten wire 21 hanging from the pull head 30 and engaging with the seed crystal holder 11. Further, the pull head 30 has a mechanism for rotating the crystal. The direction of crystal rotation is opposite to that of the crucible rotation, and the higher the number of rotations, the more uniform the distribution in the crystal diameter direction of the concentration of impurities such as dopant and oxygen.

[0021]

EXAMPLES Hereinafter, the effects of the present invention will be specifically described with reference to examples.

Example 1 A p-type (100) crystal having a diameter of 200 mm was pulled up using the crystal growth furnace shown in FIG. 2
140 kg of polycrystalline weight in a 4 inch crucible, 320 mg
Of silicon nitride and boron dopant. The pulling speed S / L is 1.0 mm / min, and the crystal rotation S / R is 6r.
pm. The crucible rotation speed was adjusted so that the crystal center oxygen concentration was 13 ppma.

The target of oxygen concentration and nitrogen concentration of this crystal was as follows. Oxygen concentration center: 13 ± 0.5 ppma Edge: 6 mm; 10.4 to 9.3 ppma ORG: 20 to 40% Nitrogen concentration Straight body head: 6 × 10 ¹³ atoms / cm ³ Straight body bottom: 22 × 10 ¹³ atoms / Cm ³

The crystal was sliced and polished, and a wafer was used as a substrate.
Was manufactured. This was oxidized in a steam atmosphere at 1100 ° C. for 80 minutes, and after steam oxidation, was selectively corroded with a Wright solution to evaluate OSF generation behavior. No ring-shaped swirl pattern was observed by visual inspection under a condensing lamp. Also, the results of scanning observation in the diameter direction from the wafer edge to the opposite edge with a microscope show that the OSF
The density was a maximum of 2.5 pieces / cm ² , and the average was less than 0.5 pieces / cm ² , which was a level that was no problem at all. Another epiwafer was oxidized in two steps at 800 ° C. × 4 hours + 1000 ° C. × 16 hours in a nitrogen atmosphere, and the oxygen precipitation behavior was investigated. Table 1 shows the results.

[0025]

[Table 1]

As described above, the epi-wafer made of the crystal of the present embodiment is a wafer which is free from OSF on the entire surface of the wafer, has an oxygen precipitate density of 10 ⁸ / cm ³ or more, and has excellent surface properties and gettering characteristics. It indicates that there is. In particular, it is noted that the precipitate density is substantially uniform in the plane despite the low initial oxygen concentration at the edge.

(Comparative Example) A p-type (100) crystal having a diameter of 200 mm was pulled up using the same crystal growth furnace as in Example 1.
140 kg polycrystal weight in a 24 inch diameter crucible, 16
Filled with 0 mg silicon nitride and boron dopant.
Pulling speed S / L is 1.0mm / min, crystal rotation S / R
Was set to 12 rpm. The crucible rotation speed was adjusted such that the crystal center oxygen concentration was 14 ppma.

The targets of oxygen concentration and nitrogen concentration of this crystal were as follows. Oxygen concentration center: 14 ± 0.5 ppma Edge: 6 mm; 14.5 to 12.9 ppma ORG: ≦ 5% Nitrogen concentration Straight body head: 3 × 10 ¹³ atoms / cm ³ Straight body bottom: 11 × 10 ¹³ atoms / cm cm ³

From this crystal, 3 μm was obtained in the same process as in Example 1.
m epiwafers were produced. This is 80 at 1100 ° C.
After oxidation in a water vapor atmosphere, selective corrosion was performed with a Wright solution to evaluate the OSF generation behavior. In a visual inspection under a condensing lamp, a ring-shaped swirl pattern was observed at the edge. As a result of microscopic inspection of the swirl part, the OSF density was over 130 / cm ² and was rejected. Another epiwafer was oxidized in two steps at 800 ° C. × 4 hours + 1000 ° C. × 16 hours in a nitrogen atmosphere, and the oxygen precipitation behavior was investigated. Table 2 shows the results.
Shown in

[0030]

[Table 2]

The oxygen precipitate density at the edge portion is high and H-
This shows the characteristics of band precipitation. It is clear that the epi-wafer obtained in this example is not suitable as an LSI manufacturing wafer because of the high OSF density at the edge.

Example 2 A 300 mm diameter p-type (100) crystal was pulled up using a 300 mm diameter crystal growth furnace. 250 kg polycrystalline weight in a 32 inch crucible, 60
Filled with 0 mg silicon nitride and boron dopant.
Pulling speed S / L is 0.7mm / min, crystal rotation S / R
Was set to 4 rpm. The crucible rotation speed was adjusted such that the crystal center oxygen concentration was 12.5 ppma.

The target of oxygen concentration and nitrogen concentration of this crystal was as follows. Oxygen concentration center: 12.5 ± 0.5 ppma Edge: 6 mm; 9.0-7.5 ppma ORG: 20-40% Nitrogen concentration Straight body head: 6 × 10 ¹³ atoms / cm ³ Straight body bottom: 15 × 10 ¹³ atoms / cm ³

An epi-wafer having a thickness of 2.5 μm was manufactured from the crystal in the same process as in Example 1. This is 110
After oxidation in a steam atmosphere at 0 ° C. × 80 minutes, selective corrosion was performed with a Wright solution to evaluate the OSF generation behavior. No ring-shaped swirl pattern was observed by visual inspection under a condensing lamp. Also, the results of scanning observation in the diameter direction from the wafer edge to the opposite edge with a microscope show that the OSF
The density was a maximum of 1.5 pieces / cm ² , and the average was less than 0.5 pieces / cm ² , which was a level that was no problem. Another epiwafer was oxidized in two steps at 800 ° C. × 4 hours + 1000 ° C. × 16 hours in a nitrogen atmosphere, and the oxygen precipitation behavior was investigated. Table 3 shows the results.

[0035]

[Table 3]

As described above, even with a 300 mm crystal, the epiwafer according to the present invention has an extremely low OSF density over the entire surface of the wafer and an oxygen precipitate density of 10 ⁸ / cm ³ or more, and has excellent surface properties and gettering characteristics. This shows that a wafer can be obtained. In particular, it is the same as in Example 1 that the precipitate density is almost uniform in the plane despite the low initial oxygen concentration at the edge portion.

In the above embodiment, the magnetic field application (MC
Although no particular mention was made of Z), the effects of the present invention do not change at all in a silicon epitaxial substrate manufactured by applying MCZ. Further, in the fourth to sixth aspects relating to the crystal production method according to the present invention,
The present inventors have confirmed that the effect is not negatively affected by applying the MCZ.
Therefore, it should be understood that the CZ method in the present invention also includes the MCZ method.

[0038]

As described above, the epitaxial wafer using the substrate of the present invention can effectively utilize the oxygen precipitation nuclei that are stable even at a high temperature obtained by nitrogen doping, and can almost completely generate OSF, which is a weak point of nitrogen-doped crystals. Is suppressed.
As a result, the present invention provides an epi-wafer having both excellent surface integrity and excellent gettering characteristics due to high-density oxygen precipitation nuclei inside.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a CZ crystal growth furnace to which a single crystal manufacturing method of the present invention is applied.

FIG. 2 is a graph showing a relationship between a crystal rotation speed and ORG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glow chamber, 2 ... Quartz crucible, 3 ... Carbon susceptor, 4 ... Heater, 5 ... Heat insulation shield, 6 ... Crucible support shaft, 7 ... Raw material melt, 8 ... Camera for diameter control, 10 ... Single crystal silicon, 11 ... seed crystal holder, 12 ... seed crystal, 20 ...
Receiving chamber, 21 ... Tungsten wire, 2
2 ... Isolation, 30 ... Pull head.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Morsen Banan United States 63376 Missouri, St. Peter's, Pearl Drive No. 501 FMC Electronic Materia Reals Inc. F-term (reference) 4G077 AA02 BA04 CF10 EB10 EH08 EH09 HA12 5F053 AA13 DD01 GG01 JJ01 KK03 RR03 RR20

Claims (6)

[Claims] A nitrogen concentration of 1 × 10 ¹³ to 1 × 10 ¹⁵ at.
oms / cm ³ , 6 mm from edge
The oxygen concentration Oi _e in the 7~10.5ppma (AS
(TMF121-83). 2. A nitrogen concentration of 1 × 10 ¹³ to 1 × 10 ¹⁵ at.
oms / cm in the range of ^3, the central oxygen concentration Oi _c and the ratio of the central oxygen concentration difference between the oxygen concentration Oi _e at a distance 6mm from edges _{ORG = (Oi c -Oi e)} / Oi c
Is not less than 15%. 3. A nitrogen concentration of 1 × 10 ¹³ to 1 × 10 ¹⁵ at.
oms / cm ³ , 6 mm from edge
The oxygen concentration Oi _e is in 7～10.5Ppma, further substrate monocrystalline silicon epitaxial wafer, wherein the ORG is 15% or more in. 4. The method for producing a substrate single crystal of a silicon epitaxial wafer according to claim 1, wherein the pulling speed is 0.7 mm / min or more. 5. The crystal rotation speed S / R during crystal growth is 16
The method for producing a substrate single crystal of a silicon epitaxial wafer according to any one of claims 1 to 3, wherein the ratio is not more than 00 / Drpm (where D = crystal diameter mm). 6. When the lifting speed is 0.7 mm / min or more,
Further, the crystal rotation speed S / R during crystal growth is 1600 / Dr
The method for producing a substrate single crystal of a silicon epitaxial wafer according to any one of claims 1 to 3, which is not more than pm.