JP2002029891A - Silicon semiconductor substrate and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To provide a silicon semiconductor substrate having excellent crystal quality, and
Provided is a method for producing the same at a low cost with high productivity. SOLUTION: Czochralski is performed from a melt to which nitrogen is added.
Of silicon single crystal grown by
A semiconductor substrate, wherein the substrate is 2 × 10 ¹⁴atom
s / cm^ThreeMore than 2 × 10¹⁶atoms / cm^ThreeLess nitrogen
Concentration and 7 × 10¹⁷atoms / cm^ThreeLess oxygen concentration
Degree, and the surface defect density of the substrate is FPD ≦ 0.
1 piece / cm^Two, SEPD ≦ 0.1 / cm^Two, And OSF
≤0.1 pieces / cm^TwoAnd the internal defect density of the substrate is L
STD ≦ 1 × 10^FivePieces / cm^ThreeAnd oxidation of the substrate
Film breakdown voltage characteristics are TZDB high C mode pass rate ≧ 90% and T
DDB pass rate ≧ 90% or more
A semiconductor substrate and a method of manufacturing the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon semiconductor substrate having few crystal defects on its surface and good device production yield, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In the manufacture of semiconductor integrated circuits, a substrate made of a silicon single crystal grown by the Czochralski method (CZ method) is mainly used. Various crystal defects described later occur in the silicon single crystal during the crystal growth, and the defects hinder the operation of the elements of the integrated circuit or destroy the circuit itself. In particular, recently, the design rule of an element of an integrated circuit has been miniaturized to 0.15 μm or less, and a fine defect of 0.10 μm or less, which was not a problem in the past, has caused a problem. Therefore, the density of the crystal defects is reduced to eliminate the crystal defects from the device active region, or the defect size is reduced to a size that does not affect the device characteristics, generally to a size less than 1/3 of the design rule. Must be made.

[0003] Crystal growth defects that are particularly problematic in current device fabrication are voids and dislocation loops.
Voids are formed by agglomeration of vacancies taken into the silicon single crystal from the crystal growth interface in supersaturation to form octahedral cavities in the crystal. Self-interstitial atoms incorporated into a single crystal form clusters.

The theory of Voronkov (VVor)
onkov; Journal of Crystal G
rowt, 59 (1982) 625-643)
Whether the vacancies or self-interstitial atoms become supersaturated during crystal pulling depends on the crystal pulling speed V (mm / min).
And the average value G of the temperature gradient in the crystal in the pulling axis direction in the temperature range from the melting point of silicon to 1300 ° C. (C / m
m) and the value of V / G. V /
If G is about 0.16 mm ² / ° C. min or more, the holes become supersaturated, and voids are generated. Conversely, if V / G is less than about 0.14 mm ² / ° C. min, the self-interstitial atoms become supersaturated, and a dislocation loop occurs.
The crystal part grown under the crystal growth condition where voids are generated is called a vacancy type defect region, and the crystal part grown under the crystal growth condition where a dislocation loop is generated is called a self-interstitial type defect region. In addition, a crystal pulled under a growth condition in which V / G is slightly smaller than the vacancy type defect region (about 0.15 mm ² / ° C. min) has an oxidation-induced stacking fault (OSF:
Oxidation induced Stackin
g Fault), which is called an OSF region. Further, a crystal pulled under the condition that the V / G is lower than the OSF region and the V / G is higher than the self-interstitial defect region is: It is called the N region because almost no defects are seen.

According to this finding, if a crystal is formed in the N region, a crystal having almost no defects can be obtained.
Conventionally, it has been difficult to grow an ingot in which the entire region of a silicon single crystal wafer is an N region. As an invention to solve this problem, Japanese Patent Laid-Open Publication No. Hei 8-330316 discloses that when a single crystal is grown by the Czochralski method, the pulling speed is increased by V.
(Mm / min), and assuming that the average value of the temperature gradient in the temperature range from the silicon melting point to 1300 ° C. is G (° C./mm), the V / G value is 30 degrees from the crystal center position and the crystal outer periphery.
0.20 to 0.22 mm ² /
° C min, and 0.20 to 0.22 mm ² / ° Cm between the position from the outer periphery of the crystal to 30 mm and the outer peripheral position of the crystal.
or a method of gradually increasing toward the outer periphery of the crystal. The silicon single crystal wafer thus obtained has infrared scattering defects, O
SF rings and dislocation clusters are not included over the entire surface of the wafer. However, even with this method, V
The allowable range of / G is small, and it is technically difficult to mass-produce industrially. In addition, the pulling speed must be reduced to about 80% of the conventional speed, and there is a problem that productivity is low.

As described above, it is difficult to achieve both crystal quality and productivity by simply improving the crystal growth conditions.
In order to solve this problem, a method of newly adding nitrogen to a silicon single crystal has been used.

In general, when nitrogen is added, the value of V / G at the boundary between the vacancy type defect region and the OSF region (0.16 mm ² / ° C. min in the case where nitrogen is not added) increases according to the amount of addition. And the value of V / G at the boundary between the self-interstitial defect region and the N region (0.14 mm ² / ° C. when nitrogen is not added)
Min) is known to decrease (Spring 1999, The 46th Joint Lecture on Applied Physics, Proceedings No. 1, P.471, 29a-ZB-9). Further, it is known that an oxygen precipitate is generated during crystal growth as a defect peculiar to the nitrogen-added crystal (Spring 1999, No. 4).
Proceedings No. 6 1,
P. 468, 29a-ZB-2).

In Japanese Patent Application Laid-Open No. 2000-7486, when growing a silicon single crystal by the Czochralski method,
A method for producing a silicon single crystal in which a single crystal is doped with oxygen having a concentration of less than 6.5 × 10 ¹⁷ atoms / cm ³ and nitrogen having a concentration of more than 5 × 10 ¹³ atoms / cm ³ , and Doping, the pulling speed of the single crystal is V, and the temperature gradient between the single crystal and the melt in the axial direction is G
A method for producing a silicon single crystal, characterized in that the V / G (r) ratio when (r) is at least partially smaller than 1.3 × 10 ³ cm ² min ^-1 K ^-1 is disclosed. ing.

In the former method, vacancy-type defects and self-interstitial-type defects are simultaneously suppressed by adding nitrogen, and the nitrogen concentration is reduced to less than 6.5 × 10 ¹⁷ atoms / cm ^3. Although the formation of OSF generated by the addition can be greatly suppressed, high-density oxygen precipitates of 1 × 10 ⁸ / cm ³ or more are generated in the crystal depending on the pulling conditions. Since this oxygen precipitate does not disappear even by repeated heat treatment in the device process and leads to deterioration of PN leak,
This is a problem during device fabrication. The latter method can suppress Si interstitial defects and at the same time suppress the formation of OSF. However, as in the former method, depending on pulling conditions, a high density of 1 × 10 ⁸ / cm ³ or more can be obtained during crystal growth. Oxygen precipitates are generated and pose a problem during device fabrication. Therefore, the improvement of the crystal quality is insufficient for both methods.

Japanese Patent Application Laid-Open No. 2000-7498 discloses that the crystal pulling speed at which the OSF ring disappears at the center of the single crystal when V is not added is V (mm / mi).
n), when the average temperature gradient between the melting point of silicon and 1400 ° C. is G (K / mm), the crystal pulling speed V
Is in the range of V to V + 0.062 × G, and a method of pulling a crystal while doping with nitrogen is disclosed. According to this method, a crystal without small pits can be grown from the entire surface of the crystal, and an extremely low defect crystal having excellent oxide film breakdown voltage characteristics can be manufactured with high productivity and high yield. However, even with this method, depending on the oxygen concentration of the crystal, high-density oxygen precipitates are also generated, which deteriorates the PN leak and lowers the yield of the device, so that the improvement of the crystal quality is insufficient.

Thus, when nitrogen is not added,
It is difficult to achieve both crystal quality and productivity simply by improving the crystal growth conditions. Therefore, a method of adding nitrogen to a crystal has come to be used.However, in the above-described method conventionally used, it has been considered that the addition of nitrogen prevents generation of oxygen precipitates formed during crystal growth. No improvement in crystal quality was obtained.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a silicon semiconductor substrate to which nitrogen is added is controlled by controlling three of a nitrogen concentration, an oxygen concentration and a crystal growth condition, so that the surface defect-freeness is superior to the conventional method. It is another object of the present invention to provide a silicon semiconductor substrate having excellent oxide film breakdown voltage characteristics and a method of manufacturing the same.

[0013]

Means for Solving the Problems To achieve the above object, we have intensively studied a method of manufacturing a silicon semiconductor substrate to which nitrogen has been added. The inventors have found that a manufacturing method can be provided, and have completed the present invention.

According to the present invention, a chalk is prepared from a melt containing nitrogen.
Made from silicon single crystal grown by Ralsky method
A silicon semiconductor substrate, wherein the substrate is 2 × 10¹⁴
atoms / cm^ThreeMore than 2 × 10¹⁶atoms / cm^ThreeLess than
Lower nitrogen concentration, and 1 × 10 ¹⁷atoms / cm^Threethat's all
7 × 10¹⁷atoms / cm^Three(JEIDA) The following acids
Element density, and the surface defect density of the substrate is FPD ≦ 0.
1 piece / cm^Two, SEPD ≦ 0.1 / cm^Two, And OSF
≤0.1 pieces / cm^TwoAnd the internal defect density of the substrate is L
STD ≦ 1 × 10^FivePieces / cm^ThreeAnd oxidation of the substrate
Film breakdown voltage characteristics are TZDB high C mode pass rate ≧ 90% and T
DDB pass rate ≧ 90% or more
A semiconductor substrate.

Further, the present invention is characterized in that in the silicon semiconductor substrate, there is no oxygen precipitate larger than 15 nm in diameter conversion, and the size of the oxygen precipitate does not have a distribution in the substrate depth direction. A silicon semiconductor substrate as described above.

Further, according to the present invention, the pulling speed at which the vacancy type defect region disappears at the center of the crystal diameter is V ₁ (mm / min), and the pulling speed at which the self-interstitial type defect region enters the outer periphery of the crystal is V _2. (Mm / min), silicon grown by a Czochralski method from a nitrogen-added melt under the condition that the single crystal pulling speed V (mm / min) satisfies V ₁ ≧ V ≧ V _2. A silicon semiconductor substrate manufactured from a single crystal, wherein the substrate is 2 × 10 ¹⁴ atoms / c.
a nitrogen concentration of not less than m ^{3 and not} more than 2 × 10 ¹⁶ atoms / cm ³ ,
And 1 × 10 ¹⁷ atoms / cm ³ or more and 7 × 10 ¹⁷ at
A silicon semiconductor substrate containing an oxygen concentration of oms / cm ³ (JEIDA) or less.

The present invention also provides 3 × 10 ¹⁷ atoms / c
A method for producing a silicon semiconductor substrate by processing and polishing a silicon single crystal grown by a Czochralski method from a silicon melt to which nitrogen of m ³ or more and 3 × 10 ¹⁹ atoms / cm ³ or less is added. The pulling speed at which the type defect region disappears at the center of the crystal diameter is V ₁ (mm / min), and the pulling speed at which the self-interstitial type defect region enters the outer periphery of the crystal is V.
₂ (mm / min), the silicon single crystal is grown under the condition that the pulling speed V (mm / min) satisfies V ₁ ≧ V ≧ V ₂ , and the substrate is 1 × 10 ¹⁷ atoms / c.
A method for manufacturing a silicon semiconductor substrate, characterized by containing an oxygen concentration of not less than m ^{3 and not} more than 7 × 10 ¹⁷ atoms / cm ³ (JEIDA).

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

Before giving a specific description of the present invention, the crystal quality evaluation method of the present invention will be described first.

FPD (Flow Pattern De)
Fect) refers to a U-shaped ripple pattern observed when the obtained single crystal wafer is subjected to Secco etching and the surface is observed with a differential interference microscope. The vertex serving as the starting point of the U-shape has a diameter of several μm if it is caused by a void.
If a circular pit having a size of is caused by a dislocation loop, a pit having a jagged edge having a diameter of several to several tens μm is seen, and it can be distinguished whether the FPD is caused by a void or a dislocation loop. When evaluating FPD in the present invention,
As a Secco etching solution, HF (49% by mass): K ₂ Cr ₂ O ₇ (1/6 mol / L) = 2 by volume ratio:
Using a mixture having a mixing ratio of 1, etching was performed at room temperature for 10 minutes. In the surface observation with the differential interference microscope, FPD
The number of vertices serving as the starting point of the U-shaped ripple pattern is counted, and the observation positions are the center position of the wafer, r / 2 position from the wafer center when the wafer radius is r, and 10 mm position from the wafer edge. Points. The average value of these three points was used as the number of FPDs.

SEPD (Secco Etch Pit)
Defect) means that the obtained single crystal wafer has an FPD
These pits are observed when the same Secco etching is performed and the surface is observed with a differential interference microscope. This pit is believed to be due to voids. SEP
When evaluating D, after performing the same Secco etching as the FPD, the number of pits having a size of 5 μm or more was counted as SEPD by surface observation with a differential interference microscope. The observation positions were also set to the same three points as in the case of the FPD, and the average value of the three points was used as the number of SEPDs.

OSF is an oxidation-induced stacking fault observed when a single crystal wafer is subjected to steam oxidation and then lightly etched. When evaluating OSF, steam oxidation was performed at 1100 ° C. for 60 minutes, and light etching was performed. The light etchant is HF (49 wt.
%) 60 ml + HNO ₃ (63 wt%) 300 ml + C
30 ml of rO ₃ (5 mol / l) + CH ₃ COOH 6
The etching time was 90 seconds using a composition of 0 ml + ₂ g of Cu (NO ₃ ) ₂ +60 ml of H ₂ O. afterwards,
The surface of the wafer was observed with a differential interference microscope, and the density of OSF was measured.

LSTD (Laser Scatteri)
ng Tomography Defect) is a method for evaluating crystal defects by infrared scattering, and has a size of 50 nm.
Crystal defects of nm or more can be detected. The measurement was performed using an LSTD scanner (MO6) manufactured by Mitsui Kinzoku Co., Ltd., and the laser wavelength was measured at 700 nm. At this laser wavelength, the number of infrared scatterers existing between the surface layer and a depth of 5 μm can be measured. The entire surface of the wafer was measured at this laser wavelength, and the defect density was determined by dividing the total number of detected defects by the wafer area and the measurement depth.

In the oxide film breakdown voltage evaluation, TZDB (Time
Zero Dielectric Breakdown
n) and TDDB (Time Dependent Di)
(Electric Breakdown) characteristics were examined. The measurement conditions for the high C mode pass rate in TZDB are:
Oxide film thickness 25 nm, electrode area 20 mm ² , judgment current 10
0 mA / cm ² . The percentage of cells that break down above 11 MV / cm is defined as the high C mode pass rate. Also,
Apart from the high C mode pass rate, the C mode pass rate was also examined.
The measurement conditions for the C mode pass rate are an oxide film thickness of 25 nm, an electrode area of 20 mm ² , and a determination current of 1 μA / cm ² . 8MV
The ratio of cells that cause dielectric breakdown at / cm or more is defined as the C-mode pass rate. The measurement of the TDDB characteristic was such that the oxide film thickness was 7 nm, the electrode area was 20 mm ² , and a stress current of 5 mA / cm ² was continuously applied. The breakdown was determined when the electric field strength exceeded 10 MV / cm, and the yield when the total amount of electrification Q _bd = 2 C / cm ² passed through the oxide film until the oxide film was broken down was defined as the TDDB pass rate.

The size of the oxygen precipitate is measured from an arbitrary position of the prepared sample by a transmission electron microscope (TEM).
The largest diagonal length of the observed oxygen precipitate was defined as a diameter-converted value of the oxygen precipitate size.

In the present invention, the oxygen concentration is measured by an infrared absorption method using a converted value of JEIDA (source from the Japan Electronics Industry Association), and the nitrogen concentration is measured using a secondary ion mass spectrometer (SIMS). The measured value is converted based on a reference obtained by ion implantation of nitrogen.

Hereinafter, the present invention will be described specifically.

The present inventors do not independently control the oxygen concentration, the nitrogen concentration, and the crystal growth conditions as in the conventional method. Instead, the oxygen concentration and the nitrogen concentration are set to specific ranges, respectively. By growing crystals under suitable pulling conditions, the effect of suppressing the generation of defects by adding nitrogen was fully utilized, and at the same time, the formation of oxygen precipitates by adding nitrogen was successfully suppressed. The present invention was completed by finding a method that can reduce the density of all crystal defects, which was difficult in the past, to such an extent that the device yield is not affected, and reduce the size of all crystal defects. Things.

The condition of the defect density that does not affect the device yield is that the surface defect density of the substrate is FPD
≦ 0.1 defects / cm ² , SEPD ≦ 0.1 defects / cm ² , and OSF ≦ 0.1 defects / cm ² , and the internal defect density of the substrate is LSTD ≦ 1 × 10 ⁵ defects / cm ³ . And the withstand voltage characteristic of the oxide film of the substrate is TZDB high C mode pass rate ≧ 90%
And TDDB pass rate ≧ 90% or more.

Voids and dislocation loops, which are the identity of FPDs, almost certainly destroy the structure of the device.
If the device density is larger than 0.1 / cm ^2, for example, if the size of the device is 1 cm ² , the yield drop due to this defect reaches about 10%, which is a serious problem. In addition, the identity of SEPD is also void, and almost certainly destroys the structure of the device.
When the size is larger than cm ² , the yield drop when the size of the device is 1 cm ² reaches about 10%, which is a serious problem.

The OSF is a large defect having a diameter as large as 10 μm and surely destroys the structure of the device. Therefore,
For the same reason as described above, it must be 0.1 / cm ² or less.

LSTD is partially identified by FPD and SEPD
As well as oxygen precipitates. Oxygen precipitates exacerbate the PN leak and cause the yield to drop. LSTD density of 1 × 10 ⁵ / cm ³
If the size of the device is 1 cm ² , more than 10 LSs can be obtained from the wafer surface to a depth of 1 μm.
Although the TD is a calculation, the existence of the LSTD does not necessarily destroy the structure of the device, and the magnitude of the effect on the device differs depending on where the LSTD exists in the device element. However, when the depth of the device active layer is 5 μm, the LSTD existing in the active layer is
If the total number exceeds 50, that is, if the LSTD density is larger than 1 × 10 ⁵ / cm ³ , a serious problem occurs.

The pass rate of the TZDB high C mode and TDDB indicates the soundness of the gate oxide film formed on the surface of the single crystal wafer. In the evaluation of the conventional oxide film breakdown voltage, Japanese Patent Application Laid-Open
As described in JP-A-135511 and JP-A-11-324991, it was common to use TZDB.
However, with the recent increase in demand for flash memories, wafers having excellent long-term reliability, that is, TDDB characteristics, as well as TZDB characteristics under a high electric field, are required. Therefore, at present, it is required that the TZDB characteristics in a high electric field have a high C mode pass rate ≧ 90% and the long term reliability that the TDDB pass rate ≧ 90% or more.

Therefore, the surface defect density of the substrate is FPD ≦
0.1 pieces / cm ² , SEPD ≦ 0.1 pieces / cm ² , and O
SF ≦ 0.1 defects / cm ² , the internal defect density of the substrate is LSTD ≦ 1 × 10 ⁵ defects / cm ³ , and the oxide film breakdown voltage characteristic of the substrate is TZDB high C mode pass rate ≧ 90% If the TDDB pass rate ≧ 90% or more is satisfied, it can be said that the silicon semiconductor substrate is a high-quality silicon semiconductor substrate that does not affect the device yield.

In order to achieve the above-mentioned defect density and to make it difficult for the device to be destroyed by the void defect by utilizing the effect of transforming the void defect by nitrogen, the nitrogen concentration is set to 2 × 10 ¹⁴ atoms / cm ³ or more. × 10 ¹⁶ atom
s / cm ³ or less and the oxygen concentration is 1 × 10 ¹⁷ atom
ms / cm ³ or more 7 × 10 ¹⁷ atoms / cm ³ (JEI
DA) It is necessary to do the following.

First, the nitrogen concentration for exerting the effect of suppressing the defect of nitrogen is 2 × 10 ¹⁴ atoms / cm ³ or more.
× 10 ¹⁶ atoms / cm ³ or less.
If the nitrogen concentration is lower than 2 × 10 ¹⁴ atoms / cm ^{3, the} effect of suppressing the voids and dislocation loops due to the addition of nitrogen sharply decreases, and the nitrogen concentration becomes 1 × 10 ¹³ atoms / cm ^3.
When reduced to cm ³ , the size and density of the voids or dislocation loops is no longer the same as without nitrogen addition. On the other hand, when the nitrogen concentration is 2 × 10 ¹⁶ atoms /
If it is higher than cm ³ , the silicon crystal is dislocated, and a single crystal cannot be grown. Therefore, the nitrogen concentration is set to 2 × 10 ¹⁴ atoms / cm ³ or more and 2 × 10 ¹⁶ at.
When the content is within the range of oms / cm ³ or less, the effect of suppressing the voids and dislocation loops due to the addition of nitrogen is sufficiently obtained, and a silicon single crystal without dislocations can be grown.

Further, when the oxygen concentration is 7 × 10 ¹⁷ atoms /
If it is larger than ³ cm ³ (JEIDA), the size of oxygen precipitates generated by adding nitrogen becomes 30 nm or more, and the density of oxygen precipitates measured by LSTD becomes 1 × 10 ⁸ / cm ³ or more. On the contrary, the addition lowers the yield of the device. However, when the oxygen concentration is lower than 1 × 10 ¹⁷ atoms / cm ³ (JEIDA), it is difficult to grow a single crystal by the Czochralski method, and the mechanical strength of the semiconductor substrate is reduced. Become.

Further, when the oxygen concentration is 7 × 10 ¹⁷ atoms
/ Cm ³ (JEIDA) or less, oxygen precipitates are generated by repeated heat treatment in the device process, and the precipitates may destroy the device. In order to prevent such a situation, the size of the oxygen precipitate is preferably set to 15 nm or less. If the size of the oxygen precipitate is 15 nm or less, the oxygen precipitate on the wafer surface does not grow even by the heat treatment of the device, but rather disappears, so that the yield does not deteriorate. Further, by using the method of the present invention, it is possible to obtain a silicon semiconductor substrate in which the size of the oxygen precipitate does not have a distribution in the substrate depth direction, and it is possible to improve various characteristics of the device.

As a method for manufacturing such a semiconductor substrate, for example, the following method can be used. That is, the nitrogen concentration is 2 × 10 ¹⁴ atoms / cm ³ or more and 2 × 1
0 ¹⁶ atoms / cm ³ or less, oxygen concentration 1 × 10 ¹⁷ at
oms / cm ³ or more 7 × 10 ¹⁷ atoms / cm ³ (JE
IDA) This is a method in which crystals in the following range are formed under the OSF region pulling conditions. For this purpose, in growing the crystal, the crystal having the nitrogen concentration and the oxygen concentration in the range is pulled up at a high speed (for example, 1.5 mm / min or more).
From a low speed (for example, 0.2 mm / min or less). When the crystal is grown in this way, a defect region distribution as shown in FIG. 1 appears in one ingot. At this time, when the pulling speed was reduced,
The speed V _{1 at} which the vacancy type defect region disappears at the center of the crystal diameter,
Further obtaining the pulling rate V ₂ which interstitial type defect region appears in the outer peripheral portion of the crystal. As a criterion for determining a defect area, a void-type defect area is determined by FPD or SEPD caused by voids.
May be a region where the density of FPDs is larger than 0.1 / cm ² , and the self-interstitial defect region may be a region where the density of FPD due to dislocation loops is larger than 0.1 / cm ² . By growing the ingot between the pulling speeds V ₁ and V ₂ , that is, at a pulling speed V satisfying V ₁ ≧ V ≧ V ₂ , the crystal in the OSF region is pulled up, the density of crystal defects is low, and the defect size is small. Small crystals can be obtained.

In the crystal obtained by pulling the crystal at a pulling speed higher than V _1, the size of the void is apparently reduced by the addition of nitrogen, but actually 1 × 10 ⁷ fine voids having a diameter of 0.1 μm or less are obtained. / Cm ³ or higher. Therefore, when pulled at a greater pulling speed than V ₁ was voids in the crystal destroying the device,
This causes a decrease in device yield.

In the crystal pulled at a pulling speed smaller than V ₂ , the size of the dislocation loop is reduced due to the addition of nitrogen, but actually 1 × 10 ⁵ fine dislocation loops / c.
It exists at a high density of m ³ or more. Therefore, when pulled at a voltage V smaller than V ₂ , the dislocation loop destroys the device and causes a reduction in yield.

As a specific method for adding nitrogen to the melt, the following known method may be used. More specifically, Japanese Patent Application Laid-Open No.
No. 1190, Japanese Unexamined Patent Publication No.
A method of dissolving a polycrystalline raw material in a nitrogen gas atmosphere disclosed in Japanese Patent No. 94780, or a method of mixing FZ silicon with nitrogen added to the polycrystalline raw material or a wafer having a silicon nitride film formed on the surface is used. good. In order to obtain a silicon semiconductor substrate having a nitrogen concentration of 2 × 10 ¹⁴ atoms / cm ³ or more and 2 × 10 ¹⁶ atoms / cm ³ or less, which is a necessary condition of the present invention, 3 × 10 ¹⁷ atoms / cm ³ or more and 3 × 10 ³ or more. ^A crystal may be grown by a Czochralski method from a silicon melt to which nitrogen of ¹⁹ atoms / cm ³ or less is added.

The size of the oxygen precipitate can be reduced by increasing the rate at which the crystal is cooled to room temperature. In particular, 1200 ° C. or less, more preferably 1150 ° C.
Increase cooling rate from below ℃ to 800 ℃, 1150 ℃
The diffusion distance (Dt) ^1/2 of oxygen from the temperature to room temperature may be set to 3 μm or less. Here, D is a diffusion coefficient of oxygen, and D (T) = 0.13 exp (−2.53 / k)
T) cm ² / sec, k is Boltzmann's constant, T is the temperature of the crystal, and the function T (t) of the cooling time t
It is expressed as Therefore, the (Dt) ^1/2, the crystal of the time (Dt) ^1/2 to room 1150 ° C. is throughout the time of cooling is determined by integrating.

[0044]

EXAMPLES The following 1) to 6) were carried out by the Czochralski method.
Crystal was pulled up. All crystals were grown using the same pulling furnace. About 40 kg of a silicon raw material was dissolved to prepare an about 30 kg ingot having a diameter of 155 mm, and a p-type (100) Si single crystal of 10 Ωcm was obtained.

The addition of nitrogen was performed by forming a nitride film on a non-doped silicon wafer by a CVD method and dissolving the raw materials at the same time. The oxygen concentration in the crystal is
It was measured by an infrared absorption method using a converted value of JEIDA. The nitrogen concentration in the crystal was measured using a secondary ion mass spectrometer (S
IMS), and the measured value was converted based on a reference into which nitrogen was ion-implanted. In the following, the crystal of the nitrogen concentration to when the Secco etching, the pulling speed region void due the FPD or SEPD is seen more than 0.1 pieces / cm ² is extinguished at the wafer center V ₁ (mm / min), and the speed at which the region where the FPD due to the dislocation loop is observed more than 0.1 / cm ² enters the wafer edge is V.
₂ (mm / min).

1) A single crystal was grown by the Czochralski method without adding nitrogen. The oxygen concentration is 6.6-7.0 × 1
0 ¹⁷ atoms / cm ³ and 2.0-2.5 × 10 ¹⁷
atoms / cm ³ , and the crystal pulling speed V
Was set to 1.00 mm / min. At this time, V ₁ is set to 0.
30 mm / min, V ₂ is 0.35 mm / min, V to be V ₁ or less V ₂ or more ranges were not present.

2) Nitrogen was added to the raw material melt at 1.4 × 10 ¹⁷
Atoms / cm ^{3 were} added to grow a single crystal. When the nitrogen concentration of the crystal was measured by SIMS, the nitrogen concentration in the crystal was 1 × 10 ¹⁴ atoms / cm ³ . The oxygen concentration was set to 6.6 to 7.0 × 10 ¹⁷ atoms / cm ³ and 2.0 to 2.5 × 10 ¹⁷ atoms / cm ³ , and the crystal pulling speed V was set to 0.60 mm / min. . V ₁ at the nitrogen concentration is 1.05 mm / min, V ₂
Was 0.23 mm / min.

3) Nitrogen is added to the raw material melt at 3 × 10 ¹⁷ at.
oms / cm ^{3 was} added to grow a single crystal. When the nitrogen concentration of the crystals was measured by SIMS, the nitrogen concentration was 2 × 10 ¹⁴ atoms / cm ³ in the crystal. The oxygen concentration is 6.6 to 7.0 × 10 ¹⁷ atoms / cm ³ and 2.
0 to 2.5 × 10 ¹⁷ atoms / cm ³ ,
The crystal pulling speed V is 1.45, 1.40, 0.80,
Five patterns of 0.21 and 0.20 mm / min were set. At the nitrogen concentration, V ₁ is 1.40 mm / min, and V ₂ is 0.
It was 21 mm / min.

4) Nitrogen was added to the raw material melt at 1.4 × 10 ¹⁸
Atoms / cm ^{3 were} added to grow a single crystal. When the nitrogen concentration of the crystal was measured by SIMS, the nitrogen concentration was 1 × 10 ¹⁵ atoms / cm ³ in the crystal. The oxygen concentration was set to 6.6 to 7.0 × 10 ¹⁷ atoms / cm ³ and 2.0 to 2.5 × 10 ¹⁷ atoms / cm ³ , and the crystal pulling speed V was set to 1.50 and 0.80. , 0.0
7 and 0.05 mm / min. Further, a crystal having an oxygen concentration of 7.1 to 7.5 × 10 ¹⁷ atoms / cm ³ and a crystal pulling speed V of 1.00 mm / min was also grown. V ₁ at the nitrogen concentration is 1.50 mm / m
in more than, V ₂ was 0.07mm / min.

5) Nitrogen is added to the raw material melt at 3 × 10 ¹⁹ at.
oms / cm ^{3 was} added to grow a single crystal. When the nitrogen concentration of the crystal was measured by SIMS, the nitrogen concentration was 2 × 10 ¹⁶ atoms / cm ^{3 in the} crystal. The oxygen concentration is 6.6 to 7.0 × 10 ¹⁷ atoms / cm ³ and 2.
0 to 2.5 × 10 ¹⁷ atoms / cm ³ ,
The crystal pulling speed V is 1.50, 0.80 and 0.10
mm / min. V ₁ at the nitrogen concentration is more than 1.50 mm / min, and V ₂ is 0.05 mm / min.
It was smaller.

6) 3.0 × 10 ¹⁹ nitrogen was added to the raw material melt.
An attempt was made to grow crystals by adding atoms / cm ³ , but the oxygen concentration was increased to 7.1 to 7.5 × 10 ¹⁷ atoms / c.
In each of m ³ , 6.6 to 7.0 × 10 ¹⁷ atoms / cm ³ and 2.0 to 2.5 × 10 ¹⁷ atoms / cm ³ , dislocation occurs during the growth and the single crystal is pulled. Could not. When the concentration of nitrogen at the time of dislocation was calculated from the equilibrium segregation coefficient, 2.1 × 10 ¹⁶ atoms were found in the crystal.
s / cm ³ .

A single crystal was grown with the combination of the oxygen concentration, the nitrogen concentration and the pulling rate as described above, and was processed from a single crystal rod into a mirror wafer through a normal processing step.

FPD density and SEP for each of the above wafers
Each evaluation of D density, OSF density, LSTD, precipitate size, and oxide film breakdown voltage was all performed by the method described in the embodiment of the invention.

Table 1 shows the above evaluation results.

[0055]

[Table 1]

No. 1 in Table 1. 1 means that the oxygen concentration is 7.5 × 1
Except for 0 ¹⁷ atoms / cm ³ , the nitrogen concentration and the pulling rate satisfy the conditions of the present invention. However, in the oxide film breakdown voltage evaluation, both the TZDB high C mode and the TDDB are lower than 90%, and the crystal quality is not sufficiently improved.

No. 1 in Table 1. 2-No. When the oxygen concentration is reduced to 7 × 10 ¹⁷ atoms / cm ³ or less as in 15, both the high C mode pass rate and the TDDB pass rate of the oxide film breakdown voltage are as high as 90% or more within the range of the embodiment. Indicates a value. This is due to the lower oxygen concentration
This is because the formation of oxygen precipitates is suppressed, and the oxygen precipitates are miniaturized to a size of 15 nm or less in diameter, and the breakdown voltage of the oxide film is not deteriorated. Nitrogen concentration is 2 × 10 ¹⁴ atoms
If it is lower than / cm ³ , voids or dislocation loops cannot be sufficiently suppressed, and the remaining voids or dislocation loops deteriorate oxide film breakdown voltage characteristics and leak characteristics, causing a reduction in device yield. When the nitrogen concentration is 2 × 10
^{Even at 14} atoms / cm ³ or more, V
In the case of the one having a large V, voids are present, and in the case of a V smaller than that of the embodiment, dislocation loops remain in the crystal, which deteriorates the oxide breakdown voltage characteristics and leak characteristics, and causes a reduction in device yield. For this reason, the pass rate of the TZDB high C mode and the pass rate of the TDDB in the oxide film breakdown voltage evaluation are both lower than 90% in both cases where V is larger or smaller than that of the embodiment.

No. in the table. 16-No. As shown in FIG. 29, the oxygen concentration was further reduced to 2.0 to 2.5 × 10
^{At 17} atoms / cm ³ , oxygen precipitates are no longer observed, the crystal quality is further improved, and the withstand voltage of the oxide film is 1 in both the TZDB high C mode pass rate and the TDDB pass rate.
00%.

From the above, only those having a level within the scope of the claims according to the present invention exhibited good crystal quality in all evaluations.

[0060]

As described above, according to the present invention,
By processing the grown silicon single crystal into a wafer by controlling the oxygen concentration and pulling conditions by the Czochralski method from the nitrogen-added melt, the surface layer has excellent defect-free properties and has excellent oxide film breakdown voltage characteristics. Also, an excellent silicon semiconductor substrate can be obtained. Further, according to the present invention, it is possible to produce a silicon semiconductor substrate having a crystal quality corresponding to future miniaturization of design rules without significantly increasing the production cost even in comparison with the conventional production cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a defect distribution on a plane including a crystal axis when a silicon single crystal is grown from a nitrogen-added silicon melt by sequentially changing a pulling speed from a high speed to a low speed.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Wataru Ohashi 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Masahiro Tanaka 20-1 Shintomi, Futtsu-shi, Chiba Made in New Japan Inside the Technology Development Division of the Iron & Steel Company (72) Katsuhiko Nakai 20-1 Shintomi, Futtsu-shi, Chiba Prefecture Inside the Technology Development Division of Nippon Steel Corporation (72) Hiroyuki Deai 20-1 Shintomi, Futtsu-shi, Chiba New Japan-made Within the Technology Development Division, Steel Corporation (72) Inventor Yasumitsu Ota 20-1 Shintomi, Futtsu-shi, Chiba F-term (Reference) within the Technology Development Division, Nippon Steel Corporation GG01 HH04 KK10 RR03

Claims (4)

[Claims] Czochralski from a melt to which nitrogen has been added.
Of silicon single crystal grown by
A semiconductor substrate, wherein the substrate is 2 × 10 ¹⁴atom
s / cm^ThreeMore than 2 × 10¹⁶atoms / cm^ThreeLess nitrogen
Concentration, and 1 × 10¹⁷atoms / cm^ThreeMore than 7 × 10
¹⁷atoms / cm^ThreeThe substrate containing the following oxygen concentration:
Has a surface defect density of FPD ≦ 0.1 / cm^Two, SEP
D ≦ 0.1 / cm^Two, And OSF ≦ 0.1 / cm^Twoso
Yes, the internal defect density of the substrate is LSTD ≦ 1 × 10^FivePieces
/ Cm^ThreeAnd the withstand voltage characteristic of the oxide film of the substrate is TZ.
DB high C mode pass rate ≧ 90% and TDDB pass rate ≧
A silicon semiconductor substrate characterized by being 90% or more
Board. 2. The method according to claim 1, wherein the silicon semiconductor substrate has no oxygen precipitate larger than 15 nm in diameter conversion, and the size of the oxygen precipitate has no distribution in the substrate depth direction. The silicon semiconductor substrate as described in the above. 3. The vacancy type defect region disappears at the center of the crystal diameter.
V₁(Mm / min), self-interstitials
The pulling speed at which the recessed region enters the outer periphery of the crystal is V _Two(Mm /
min), the single crystal pulling speed V (mm /
min) is V₁≧ V ≧ V_TwoAdd nitrogen under conditions that satisfy
Grown from the melt by the Czochralski method
A silicon semiconductor substrate fabricated from single crystal
And the substrate is 2 × 10¹⁴atoms / cm^ThreeMore than 2 ×
10¹⁶atoms / cm^ThreeThe following nitrogen concentration, and 1 × 1
0¹⁷atoms / cm^ThreeMore than 7 × 10¹⁷atoms / c
m^ThreeSilico characterized by containing the following oxygen concentration
Semiconductor substrate. 4. 3 × 10 ¹⁷ atoms / cm ³ or more and 3 ×
A method for manufacturing a silicon semiconductor substrate by processing and polishing a silicon single crystal grown by a Czochralski method from a silicon melt to which nitrogen of 10 ¹⁹ atoms / cm ³ or less has been added, wherein the vacancy-type defect region is a crystal. The pulling speed at which the vanishes at the center of the diameter is V ₁ (mm / min), and the pulling speed at which the self-interstitial defect region enters the outer periphery of the crystal is V ₂ (mm / min).
min), the silicon single crystal is grown under the condition that the pulling speed V (mm / min) satisfies V ₁ ≧ V ≧ V ₂ , and the substrate is 1 × 10 ¹⁷ atoms / cm ³ or more.
A method for manufacturing a silicon semiconductor substrate, characterized by containing an oxygen concentration of × 10 ¹⁷ atoms / cm ³ or less.