JP3294723B2 - Silicon wafer manufacturing method and silicon wafer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon wafer for semiconductor devices such as VLSI and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device for an VLSI, a semiconductor in which a trace amount of metal impurities mixed in a wafer and a minute defect existing in a device active region (about 10 μm deep from the wafer surface) of the wafer are manufactured. It may cause deterioration of device characteristics and reliability. Therefore, various measures have conventionally been taken to minimize these metal impurities and minute defects.

As a method of reducing metal impurities, there is a back side damage method (BSD method) in which minute distortion is provided on the back surface of the wafer by sand blasting or the like to capture (getter) the metal impurities. Further, a method of depositing polycrystalline silicon on the back surface of the wafer has also been used.

As a countermeasure for the latter, an epitaxial wafer having a vapor-grown single-crystal silicon layer having no minute defects in a device active region is used.

Further, an intrinsic gettering method (IG method) has been developed in order to perform both measures simultaneously. In the IG method, by subjecting the wafer to high-temperature heat treatment, oxygen on the surface of the wafer is diffused outward to reduce interstitial oxygen serving as nuclei of minute defects, and a denuded zone (DZ layer) having no minute defects in a device active region is formed. Let it form. Further, in a deep region (bulk portion) below the DZ layer, excessive interstitial oxygen contained therein is precipitated by high-temperature heat treatment, and BMD typified by fine SiO ₂ precipitates is generated. These BMDs give strain to the bulk silicon matrix, induce secondary dislocations and stacking faults, and getter metal impurities.

In the IG method, a plurality of stages of heat treatment are performed in order to be unaffected by the thermal history of the pulled single crystal silicon ingot and to use a wafer having a wider oxygen concentration range. . First,
In the pre-heat treatment, heat treatment is performed at a high temperature (up to 1200 ° C.) in an oxygen-containing inert gas atmosphere to diffuse oxygen outward from the wafer surface, thereby reducing BMD nuclei caused by oxygen originally present. Extinguish. Next, BMD nuclei are generated in the bulk portion by performing a middle-stage low-temperature (500 to 900 ° C.) heat treatment in an oxygen atmosphere. Finally, the BMD is subjected to a medium temperature (up to 1000 ° C.) heat treatment in an oxygen atmosphere.
BMD is generated and grown by growing nuclei. Various ideas have been devised for the middle heat treatment, for example, isothermal annealing, multi-stage annealing from a low temperature, and ramping annealing from a low temperature.

In the above-mentioned IG method, actually, the outward diffusion of oxygen by the heat treatment in the preceding stage is not sufficient, and minute oxygen precipitates (such as BMD) may remain in the device active region. Further, since a plurality of heat treatment steps are required, practical use has not progressed much due to workability problems and cost problems.

Recently, instead of such a method requiring a multi-stage heat treatment, 100% reducing gas or 100%
By performing a high-temperature heat treatment in an atmosphere of an inert gas or a mixed gas of a reducing gas and an inert gas, a DZ layer is formed on the wafer surface and a BMD is formed on the bulk portion to provide an intrinsic gettering effect (IG effect). Wafer manufacturing methods have also been implemented. Regarding these production methods, the present applicant has disclosed in Japanese Patent Application Laid-Open Nos.
193458, JP-A-61-193449, JP-A-61-193456, JP-A-62-123098,
We have filed applications such as Japanese Patent Application Laid-Open No. 2-177541.

A typical heat treatment in an inert gas atmosphere in this method is performed by the following temperature process. The temperature raising process for raising the temperature to the heat treatment temperature is about 10 ° C./min from room temperature to 1000 ° C., 3 ° C./min or less from 1000 ° C. to 1200 ° C., and the heat treatment is about 12 ° C.
Over 1 hour at 00 ° C, 1200 ° C cooling process
To 900 ° C. to 3 ° C./min or less. FIG. 1 shows a typical temperature process. In the heat treatment operation of FIG. 1, the temperature rise process is 10 ° C./mi from room temperature to 1000 ° C.
n, 3 ° C./min between 1000 ° C. and 1200 ° C., heat treatment at 1200 ° C. for 1 hour, temperature drop process at 1200 ° C.
3 ° C./min. To 1000 ° C .;
It is performed at 0 ° C./min.

In this heat treatment operation, in the temperature raising process in the region of 1000 ° C. or higher, if the temperature raising rate is higher than about 3 ° C./min, there is a possibility that the wafer being processed may slip. In addition, the heat treatment furnace that is usually used has not been heated at a high speed because of heat insulation and restrictions on heating elements.

The mechanism of the formation of the wafer structure by the above heat treatment process can be estimated as follows. Since the heating rate is slow during the heating process, BMD
At the same time as oxygen grows, outward diffusion of oxygen occurs in the surface layer, and the oxygen concentration in the surface layer decreases. After reaching the heat treatment temperature, oxygen in the surface layer is further diffused outward, so that interstitial oxygen serving as BMD nuclei in the surface layer decreases, and the BMD in the surface layer decreases.
Disappearance is accelerated. In the bulk portion, oxygen diffuses in the wafer due to the high-temperature heat treatment, and the BMD shrinks. However, BMD does not disappear due to a small amount of oxygen reduction. During the temperature lowering process, the rate of temperature rise is slow, so that theoretically BMD growth occurs even in the surface layer portion of the wafer, but since oxygen in the surface layer portion is reduced by outward diffusion, BMD is not formed and BMD is not formed.
It becomes a Z layer. On the other hand, BMD grows and precipitates again in the bulk portion.

FIG. 2 shows that the wafer is 100% argon gas.
The relationship between the initial oxygen concentration of the wafer and the BMD density of the bulk portion of the wafer after the heat treatment when the heat treatment as shown in FIG. FIG. 2 shows that B in the bulk portion after heat treatment
It is understood that the MD density depends on the initial oxygen concentration of the wafer, and the BMD density of the bulk portion increases as the initial oxygen concentration increases.

In recent years, in order to improve the characteristics of memory devices and the like, which are becoming highly integrated, it is better to make the device active layer on the surface of the silicon wafer as a starting material defect-free to improve the characteristics thereof. It is more necessary and important than gettering impurities.

Further, the initial oxygen concentration is high (1.6 × 10
¹⁸ atoms / cm ³ or more) As shown in FIG. 2, 10 ⁹ wafers / wafer were obtained by the conventional high-temperature heat treatment in a reducing or inert gas.
A BMD of cm ³ or more is formed. Although a wafer on which such a BMD is formed is excellent in terms of a gettering effect of metal impurities, when an excessive BMD is formed, not only the mechanical strength of the wafer is reduced, but also the device active layer or the vicinity thereof is formed. However, since BMD is formed, device characteristics may be deteriorated.

[0015] Under these circumstances, wafers with more perfect defect-free layers have recently been required, and therefore have lower oxygen concentrations (1.4 × 10 ¹⁸ atoms / c).
While those of m ³⁾ are beginning to be required, such wafer fabrication is difficult productivity by the conventional manufacturing methods and conditions, there are many terms of cost issues.

The present invention has been made in order to solve the above-mentioned problems. Even if the wafer has a relatively high oxygen concentration range, the device active layer is more defect-free and the BMD of the bulk portion is not damaged. It is an object of the present invention to provide a low-density silicon wafer manufacturing method and such a silicon wafer.

[0017]

According to a first aspect of the present invention, an interstitial oxygen concentration [Oi] manufactured from a single crystal silicon ingot manufactured by a Czochralski method is 1.5 to 1.8. A silicon wafer of × 10 ¹⁸ atoms / cm ³ was heated in an inert gas atmosphere at a heat treatment temperature of 11
00 ° C to 1300 ° C, heat treatment time 1 minute to 48 hours,
The heating rate in the temperature range from 1000 ° C. the Atsushi Nobori process up to the heat treatment temperature was 15 to 100 ° C. / min
Heat treatment under the conditions described above, the size is 20n at least over a depth of 10 μm or more from the wafer surface.
m has a defect-free layer having a BMD of 10 ³ / cm ³ or less, and has an oxygen precipitate density [BM
D] is [BMD] ≧ 1 × 10 ³ / cm ³ and [B
MD] ≦ exp ｛9.210 × 10 ⁻¹⁸ × [Oi] +
A gist of the present invention is a method for manufacturing a silicon wafer, which is characterized by manufacturing a wafer having a size of 3.224 ° / cm ³ . Further, in the second invention of the present application, the interstitial oxygen concentration [Oi] manufactured from a single crystal silicon ingot manufactured by the Czochralski method is 1.5 to 1.8 × 10 ¹⁸ a.
The silicon wafer toms / cm ^3, in an inert gas atmosphere, 1100 ° C. to 1300 ° C. The heat treatment temperature, 48 hours 1 minute annealing time, from 1000 ° C. heating process
BMD having a size of 20 nm or more over at least a depth of 10 μm or more from the wafer surface manufactured by performing a heat treatment under a condition in which a heating rate within a temperature range up to a heat treatment temperature is 15 to 100 ° C./min.
Has a defect-free layer of 10 ³ / cm ³ or less, and the oxygen precipitate density [BMD] of the bulk portion inside the wafer is [BM]
D] ≧ 1 × 10 ³ pieces / cm ³ and [BMD] ≦ exp
{9.210 × 10 ⁻¹⁸ × [Oi] +3.224} pieces /
The gist of the present invention is a silicon wafer characterized by a cm ³ .

In this specification, all oxygen concentrations are Ol
d Value based on a conversion coefficient according to ASTM.

Generally, BMD when heat-treating a wafer
The behavior of will be described.

According to the classical nucleation theory, BMD grows and contracts by attaching and detaching supersaturated oxygen with oxygen clusters as uniform nuclei.

Whether the BMD existing at a certain time grows or shrinks / disappears depends on the critical nuclear radius determined by the size of the BMD at that time and the temperature (and oxygen concentration) at that time. The critical nuclear radius depends on the temperature,
As the temperature increases, the critical nuclear radius increases. When the wafer is held at a certain temperature, the BMD that has already grown larger than the critical nucleus radius at that temperature continues to grow, and the BMD with a diameter smaller than the critical nucleus radius shrinks or disappears.

Based on the above findings, the present inventors can control the BMD by applying the present invention to a wafer manufacturing method, know that a wafer suitable for manufacturing a highly integrated device can be manufactured, and can accomplish the present invention. It is a thing.

The present invention is a region having a relatively high oxygen concentration, which can be generally obtained in a silicon wafer manufactured from a silicon ingot manufactured by a general Czochralski method, from 1.5 to 1.8. × 10 ¹⁸ atoms /
Apply to heat treatment of cm ³ wafer. As described above, the BMD density of a wafer having a lower oxygen concentration can be reduced without performing the heat treatment of the present invention.

The heat treatment of the present invention is performed in a 100% inert gas atmosphere. Performing in an atmosphere of 100% inert gas is preferable in the same manner as in an atmosphere of 100% hydrogen gas, from the viewpoints of formation of a defect-free layer, easiness of outward diffusion of oxygen, and difficulty in roughening during heat treatment. .

The heat treatment of the present invention is performed at 1100 ° C. to 1300 ° C.
Done in At 1100 ° C. or lower, the effect of the present invention cannot be obtained. At 1300 ° C. or higher, the outward diffusion effect of oxygen is excellent, but there is a problem in the safety and reliability of the device.

The heat treatment time of the present invention is 1 minute to 48 hours. If the time is less than 1 minute, the effect of the present invention cannot be obtained, and even if the heat treatment is performed for more than 48 hours, the effect cannot be expected to be improved.

During the heat treatment process of the present invention, the heating rate is set to 1 within the temperature range from 1000 ° C. or higher to the heat treatment temperature.
It is necessary to raise the temperature at 5 to 100 ° C./min.

By setting the heating rate to 15 ° C./min in the region of 1000 ° C. or more, the rate of increase of the critical nucleus radius can be made higher than the growth rate of the existing BMD at that temperature. it can. As a result, the critical nuclear radius becomes larger than the diameter of the existing BMD,
BMD does not grow but heads for reduction. However, in fact, there is almost no thing that completely disappears during the heating process because the time of the heating process is short. Preferably, the heating rate is 20 ° C./min or more, more preferably 30 ° C./min.
At the heat treatment temperature described above, since the outward diffusion of oxygen proceeds in the surface region, the oxygen concentration around the BMD near the surface decreases, and the oxygen further disappears to form a DZ layer. Even in the bulk portion, the BMD advances in the direction of reduction and may disappear. However, in the bulk portion, the effect of the decrease in the oxygen concentration due to the outward diffusion of oxygen is small, and the concentration of the dissolved oxygen melted around the BMD due to the reduction of the BMD increases, so that it takes time to completely disappear. It takes.

During the cooling process, the size and density of the BMD and the oxygen concentration in the surface layer are already low, so that it is considered that the BMD does not grow so much even if the cooling rate is changed. However, the temperature lowering rate is 2 to 300 ° C./min from the viewpoints of productivity, wafer quality (prevention of slip and surface roughening), and structural problems of the furnace used.
It is desirable that

By performing such a heat treatment, the initial oxygen concentration becomes 1.5 to 1.8 × 10 ¹⁸ atoms / cm.
³ silicon wafers, 1 from the wafer surface
B having a size of 20 nm or more over a depth of 0 μm or more
It has a DZ layer having an MD of 10 ³ / cm ³ or less, and has a BMD density [BM] of a bulk portion in a region deeper than the DZ layer.
D] ≧ 1 × 10 ³ / cm ³ or more and [BMD] ≦ ex
it is possible to produce a wafer is ^{p {9.210 × 10 -1 8 ×} [Oi] +3.224}.

Such a wafer is shown by the area A + B + C in the graph of FIG.

A wafer having the above-described initial oxygen concentration, which has a good DZ layer in the surface layer portion, and has a BMD density in the bulk portion within the above-mentioned range has not existed conventionally, and the present invention has It is provided for the first time.

A more preferable range of the BMD density is as follows:
1 × 10 ³ ≦ [BMD] ≦ 1 × 10 ⁸ and [BMD]
≦ exp ｛9.210 × 10 ⁻¹⁸ × [Oi] +3.22
4｝ / cm ³ (region B + C in FIG. 2), more preferably [BMD] ≦ expｅｘ5.757 × 10 ⁻¹⁸
× [Oi] + 3.224 ° / cm ³ (region C in FIG. 2).

A wafer having a BMD density in such a range has a gettering function, and the surface device active layer becomes a good defect-free DZ layer and does not lower the mechanical strength.

The BMD in the surface layer DZ layer is preferably substantially zero. The reason for defining the BMD in the DZ layer as described above is that the detection limit of the size of the BMD of the current device is 20 nm, and when the BMD density exceeds 10 ³ / cm ³ , it is no longer defect-free. However, this is because the characteristics of the manufactured device are adversely affected.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described. All used wafers were cut from a silicon ingot pulled up by the Czochralski method, manufactured by a usual method, and used a mirror-finished silicon wafer. These wafers have N-type, plane orientation (100), specific resistance of 1 to 1000 Ω / cm, and initial interstitial oxygen concentration [Oi] of 1.45 to 1.74 × 10 ¹⁸ at.
oms / cm ³ .

Further, the furnace used has improved heat insulation and increased the amount of heat generated by the heating source. For example, an infrared heating type furnace was used.

Example 1 [Oi] of the wafer was 1.72 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The temperature rise rate in the range of 000 ° C to 1200 ° C is 30 ° C / m
in, and the temperature decreasing rate was 300 ° C./min.

Example 2 A heat treatment was performed under the same conditions as in Example 1 except that a wafer having [Oi] of 1.61 × 10 ¹⁸ atoms / cm ³ was used.

Example 3 A heat treatment was performed under the same conditions as in Example 1 except that a wafer with [Oi] of 1.55 × 10 ¹⁸ atoms / cm ³ was used.

Comparative Example 1 [Oi] of the wafer was 1.50 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The heating rate in the range from 000 ° C to 1200 ° C is 6.3 ° C /
min, and the cooling rate was 10 ° C./min.

Comparative Example 2 [Oi] was 1.61 × 10 ¹⁸ at among the wafers.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The heating rate in the range from 000 ° C to 1200 ° C is 6.3 ° C /
min, and the cooling rate was 10 ° C./min.

Comparative Example 3 Among the wafers, [Oi] was 1.70 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The rate of temperature rise in the range from 000 ° C to 1200 ° C is 3.8 ° C /
min, and the temperature drop rate was 3.8 ° C./min.

Comparative Example 4 Of the wafer, [Oi] was 1.45 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The heating rate in the range from 000 ° C to 1200 ° C is 8.5 ° C /
min, and the temperature drop rate was 3.8 ° C./min.

Comparative Example 5 Among the wafers, [Oi] was 1.50 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The heating rate in the range of 000 ° C to 1200 ° C is
min, and the temperature drop rate was 2-3 ° C./min.

Comparative Example 6 Of the wafers, [Oi] was 1.56 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The heating rate in the range of 000 ° C to 1200 ° C is
min, and the temperature drop rate was 2-3 ° C./min.

Comparative Example 7 Among the wafers, [Oi] was 1.60 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The heating rate in the range of 000 ° C to 1200 ° C is
min, and the temperature drop rate was 2-3 ° C./min.

Comparative Example 8 Among the wafers, [Oi] was 1.74 × 10 ¹⁸ at.
The oms / cm ³ wafer was heat-treated at 1200 ° C. for 1 hour in a 100% argon gas atmosphere. However, 1
The heating rate in the range of 000 ° C to 1200 ° C is
min, and the temperature drop rate was 2-3 ° C./min.

From the cross-sections ((110) plane) of the wafers subjected to the heat treatments of these Examples and Comparative Examples, the density of BMDs generated by infrared tomography was measured. The minimum detectable BMD size in the infrared tomography method used is 20 nm. This method depends on the measurement area.
The detection limit of MD density is different. In this measurement, the measurement was performed on a rectangular parallelepiped region of 4 × 200 μm and a depth of 185 μm on the wafer surface. In this case, the measurement limit of the BMD density is 6.8 × 10 ⁶ / cm ³ . Under such conditions, the BMD having a size of 20 nm or more defined by the present invention is 10
The thickness of ³ / cm ³ or less DZ layer first BMD typical field of view corresponds to the depth from the surface to be detected.

Tables 1 and 2 show the measurement results together with the heat treatment conditions.
Shown in FIG. 2 shows the initial oxygen concentration of the wafer and the BMD.
A graph showing the relationship between the densities is shown.

[0051]

[Table 1]

[Table 2] As is clear from Tables 1 and 2, and FIG. 2, the wafer subjected to the heat treatment of the present invention has a good DZ layer formed even if the initial oxygen concentration [Oi] is high, and is further formed in the bulk portion. BMD can be reduced in density. That is, a BMD having a size of 20 nm or more and a BMD having a size of 20 nm or more from the surface at least 10 μm or more has a defect-free layer of 10 ³ / cm ³ or less, and the oxygen precipitate density [BMD] of the bulk portion inside the wafer is [BMD]. ] ≧ 1 × 10 ³ pieces / cm
³ and [BMD] ≦ exp ｛9.210 × 10 ⁻¹⁸ ×
[Oi] + 3.224 ° wafers / cm ³ can be manufactured.

On the other hand, as can be understood from the comparative example, it is understood that the higher the initial oxygen concentration, the more BMDs are formed in the wafer that has been subjected to the heat treatment under the conditions outside the range of the present invention. In Comparative Examples 2 to 3 and 7 and 8, although a defect-free layer was formed, a large amount of BMD was formed in the bulk portion inside the wafer, and many BMs were also formed near the defect-free layer on the surface.
D is formed. As a result, BMD is present in a portion of the wafer surface close to the device active layer, which adversely affects the characteristics of the manufactured device. Also,
The mechanical strength of the wafer also decreases.

Further, since the wafer of the present invention is configured as described above, the device active layer has no defect, and the BMD near the active layer is small, so that devices having good characteristics can be manufactured with good yield. it can.

[0054]

According to the present invention, since the BMD density formed even on a wafer having a high initial oxygen concentration can be lowered, a highly integrated device having good characteristics can be manufactured with high yield. Further, such a wafer can be provided. In addition, since a wafer having a high oxygen concentration can be used as a wafer suitable for manufacturing a highly integrated device, the yield of the wafer can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a temperature process of a conventional heat treatment.

FIG. 2 is a diagram showing a relationship between an initial oxygen concentration of a wafer and a BMD density after a heat treatment.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuka Kashima 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. (72) Yoshio Kirino 30 Soya, Hadano-shi, Kanagawa Toshiba Ceramics Co., Ltd. Within the development laboratory (56) References JP-A-6-295912 (JP, A) JP-A-6-252154 (JP, A) JP-A-5-74782 (JP, A) JP-A-4-69937 (JP, A) A) JP-A-61-193458 (JP, A) JP-A-59-202640 (JP, A) JP-A-58-56343 (JP, A) JP-A-57-167637 (JP, A) JP-A-8 -97221 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/322 H01L 21/02 H01L 21/324

Claims (2)

(57) [Claims] 1. An interstitial oxygen concentration [Oi] manufactured from a single crystal silicon ingot manufactured by the Czochralski method is 1.5 to 1.8 × 10 ¹⁸ atoms / cm ^3.
Heat treatment temperature of 1100 ° C. to 1300 ° C. and heat treatment time of 1 minute
48 hours, the temperature rises from 1000 ° C to the heat treatment temperature
Up to 15 to 100 ° C /
By performing the heat treatment under the conditions of min , the BMD having a size of 20 nm or more and a BMD having a size of 20 nm or more at a depth of at least 10 μm from the wafer surface has a defect-free layer of 10 ³ pieces / cm ³ or less. When the precipitate density [BMD] is [BMD] ≧ 1 × 10 ³ / c
m ³ and [BMD] ≦ exp ｛9.210 × 10 ⁻¹⁸
× [Oi] + 3.224 ° wafers / cm ³ , wherein the wafer is manufactured. 2. The interstitial oxygen concentration [Oi] manufactured from a single crystal silicon ingot manufactured by the Czochralski method is 1.5 to 1.8 × 10 ¹⁸ atoms / cm ^3.
Heat treatment temperature of 1100 ° C. to 1300 ° C. and heat treatment time of 1 minute
48 hours, the temperature rises from 1000 ° C to the heat treatment temperature
Up to 15 to 100 ° C /
BMDs having a size of 20 nm or more over a depth of at least 10 μm from the wafer surface manufactured by performing a heat treatment under the conditions of 10 ³ / cm ^3
3 or less, and the oxygen precipitate density [BMD] of the bulk portion inside the wafer is [BMD] ≧ 1 × 10 ³
Pieces / cm ³ , and [BMD] ≦ exp２１０9.210 × 1
0 ^-18 × [Oi] +3.224} pieces / silicon wafer, comprising cm ^3.