JPH09199379A - High-quality epitaxial wafer and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce at a good yield a more high-performance semiconductor device with little defects having serious influences on the device. SOLUTION: An epitaxial wafer for semiconductor device which meets that the carrier lifetime L (×10<-3> ) in MOSC-t method is not less than T/3N (N is quantity of Ni (×10<12> atoms/cm<2> ) contaminating the surface of the wafer is provided. This high-quality wafer can be produces by heat-treating a Si wafer having an 0 concn. of 1.2×10<18> atoms/cm<3> or more and dopant concn. of 1.0×10<18> atoms/cm<3> in a nonxidative atmosphere over 1000deg. C for specified time to epitaxially grow a Si single crystal film of 0.1-20 microns on the treated wafer surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality epitaxial wafer and a method for manufacturing the same, and more particularly to an epitaxial wafer for semiconductor devices, which has a predetermined MOSC.
The present invention relates to a method for producing a high-quality epitaxial wafer having a carrier lifetime by the -t method, which is obtained by subjecting a silicon substrate to a predetermined high temperature treatment and then epitaxially growing silicon.

[0002]

2. Description of the Related Art In recent years, the degree of integration of semiconductor devices has been remarkably high, and a silicon wafer, which is a substrate thereof, is required to have high performance and to have better crystallinity. Therefore, an epitaxial silicon wafer has been conventionally used as a wafer for a DRAM or MPU substrate. Epitaxial silicon wafers are generally obtained by epitaxially growing a silicon single crystal film with a thickness of several to 10 μm on a silicon substrate surface heavily doped with a carrier source such as boron (B) or phosphorus. Conventionally, a silicon wafer conventionally used as a substrate for this epitaxial wafer is generally subjected to an extremely short time heat treatment of about 1 minute for removing a natural oxide film, or an extremely short time heat treatment. It is directly used for epitaxial growth without performing.

[0003]

However, even if a heavy-doped silicon wafer is kept extremely clean and its surface is mirror-planarized, strictly speaking, there are microstructural defects and growth is formed on the surface. Usually, crystal defects also exist in the surface epitaxial layer. The inventors have paid attention to the influence of these defects on the semiconductor devices formed on the surface layer of the epitaxial wafer, and provide a high-quality epitaxial wafer capable of manufacturing high-performance semiconductor devices with few defects at high yield. We proceeded with the study as the purpose. As a result, the deterioration of the insulating film near the surface of the wafer is greatly affected, and also the deterioration of the lifetime is affected. In this respect, it may have a serious effect on the reliability and stable operation of the device. It was discovered. Specifically, a crystal defect in a silicon crystal causes disorder in the oxide film network of the insulating film, leading to unstable operation on the high breakdown voltage side, and the crystal defect reduces the lifetime. , Has a significant influence on the operation of the transistor. The inventors of the present invention completed the present invention by further diligently studying to eliminate crystal defects of an epitaxial wafer that have a serious influence on these semiconductor devices.

[0004]

According to the present invention, an epitaxial wafer for a semiconductor device, which comprises a MOSC
-T method carrier lifetime L (× 10 ^-3 seconds)
However, the following equation L ≧ T / 3N (where N is the amount of Ni contaminating the epitaxial wafer surface (× 10 ¹² atoms / cm 2)
² ), T is the time (hour) of heat treatment at 1000 ° C after Ni contamination. ) Is provided, a high-quality epitaxial wafer is provided. In the high-quality epitaxial wafer of the present invention, the carrier lifetime L is preferably 0.1-5.

Further, according to the present invention, the oxygen concentration is 1.2.
× is at 10 ¹⁸ atoms / cm ³ or more, and, the silicon wafer is a dopant concentration of 1.0 × 10 ¹⁸ atoms / cm ³ or more, a non-oxidizing gas atmosphere, 1000
High temperature treatment at ℃ or above, 0.1-2 on the surface of the treated wafer
Provided is a method for manufacturing a high-quality epitaxial wafer, which comprises epitaxially growing a 0 μm silicon single crystal film. The silicon wafer manufactured by the manufacturing method of the present invention has a carrier lifetime L (× 10 ⁻³ seconds) according to the MOSC-t method of the following formula L ≧ T / 3N (where N is Ni that contaminates the surface of the epitaxial wafer). Amount (× 10 ¹² a
(Toms / cm ² ), T is the time (hour) of heat treatment at 1000 ° C. after Ni contamination. ) Is high quality.
In the method for producing a high-quality epitaxial wafer according to the present invention, the dopant is preferably boron, phosphorus or antimony, and the non-oxidizing gas is one selected from hydrogen, nitrogen, argon, helium and neon. The above gas or a mixed gas of two or more kinds is preferable.

The present invention is configured as described above and has a predetermined carrier lifetime of, for example, 0.1 to 5 × 10 ⁻³ seconds by the MOSC-t method. Since it is a good quality silicon wafer with extremely few fine crystal defects such as stacking faults and impurity contamination, the resulting device is a highly reliable device that can operate stably even on the high breakdown voltage side without disturbance in the insulating film network. Can be obtained. Further, the method for producing a high-quality epitaxial wafer of the present invention is one in which a conventional heavy-doped silicon substrate is subjected to a predetermined high temperature treatment, and then a silicon single crystal is epitaxially grown on the treated surface, which is highly industrial.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The carrier lifetime by the MOSC-t method, which is a characteristic of the high-quality epitaxial wafer of the present invention, has been conventionally known as an electrical evaluation method for crystal defects, and a MOS structure is formed on the wafer to examine the time response of the MOS capacitance. Is used to indirectly measure the crystal state of the surface layer. That is, a voltage is applied to the gate of the MOS diode so as to be in an inverted state, the time until the state returns to the equilibrium state is measured, and the carrier generation in the depletion layer formed on the semiconductor silicon wafer is measured, The central concentration of recombination of carriers in the surface layer of the silicon wafer including the interface of the capacitance was obtained, and it can be seen that the carrier lifetime shows a large value and the crystalline state is good in the electrically active region. The high-quality epitaxial wafer of the present invention has a carrier lifetime L of MOSC-t method.
(× 10 ⁻³ seconds) is expressed by the following formula L ≧ T / 3N (where N is the amount of Ni contaminating the epitaxial wafer surface (× 10 ¹² at
oms / cm ² ), T is the time (hour) of heat treatment at 1000 ° C. after Ni contamination. ) Is satisfied, and if the surface layer satisfying this condition is in a good crystalline state, for example, as will be apparent from the examples described later, it is sufficient even if contamination occurs in the device manufacturing process. The carrier capacity can be retained, and a highly reliable device that guarantees high performance and stable operation can be manufactured.

The high-quality epitaxial wafer of the present invention is
First, the oxygen concentration formed by a conventionally known method is 1.15.
× 10 ¹⁸ in atoms / cm ³ or more, boron, phosphorus, dopant concentration of antimony 1 × 10 ¹⁸ atoms /
A heavy-doped silicon wafer of ³ cm ³ or more is subjected to a predetermined high temperature treatment. The oxygen concentration and the dopant concentration of the silicon wafer used here are the same as those used in the conventional epitaxial wafer, and a normal silicon wafer can be used rather than a special one. The type of dopant may be selected depending on the desired n-type or p-type semiconductor. For example, a silicon wafer obtained by mirror-polishing an ingot pulled up by an ordinary Czochralski method through various steps such as slicing and polishing by a known method is used.

In the present invention, the silicon wafer is treated in a non-reducing gas such as hydrogen gas, an inert gas such as nitrogen, argon, helium, neon, or the like in a gas atmosphere or in a mixed gas atmosphere of two or more gases. High-temperature treatment is performed at 1000 ° C. or higher, preferably 1100 ° C. or higher in an oxidizing gas atmosphere. By this high temperature treatment, various precipitates such as oxygen or dopant existing near the surface of the conventionally used silicon wafer and causing defects in the silicon single crystal layer epitaxially grown on the surface are reduced or eliminated. A silicon substrate having a good surface layer can be formed. As the non-oxidizing gas, it is preferable to use hydrogen gas or a mixed gas of hydrogen gas and one inert gas. The high temperature treatment is performed in a non-oxidizing atmosphere to promote outward diffusion of oxygen or a dopant, and to prevent oxidation of the silicon surface to keep it in a bare state and to oxidize it in a hydrogen gas atmosphere. This is because things can be removed.
This is because if the processing temperature is lower than 1000 ° C., the precipitates and the like on the surface layer of the silicon wafer cannot be sufficiently reduced, and defects occur in the surface layer of the obtained epitaxial wafer. Further, the upper limit of the treatment temperature is 1300 ° C., and it can be appropriately selected depending on the treatment conditions such as the treatment furnace.
Usually, it is carried out at 1000 to 1200 ° C. High temperature treatment time is
Although it varies depending on the treatment temperature, it is generally 1 to 240 minutes at 1200 ° C., and usually a high temperature treatment is performed for 60 minutes.

The high-quality epitaxial wafer of the present invention is
A silicon single crystal film having a thickness of 0.1 to 20 μm can be epitaxially grown on the silicon substrate that has been subjected to the high temperature treatment. The epitaxial treatment of the present invention is
It can be carried out by a conventionally known method and is not particularly limited. For example, silicon chlorides (SiCl ₄ , SiCl _4
2 ), silanes (SiH ₄ , SiHCl ₃ , SiHCl
₂ ) Si-containing reaction gas such as about 850 to 1200 ℃
Then, it can be performed by circulating it on the silicon substrate that has been subjected to the high temperature treatment. If the thickness of the epitaxial film is less than 0.1 μm, it cannot be used as a device active layer. 20μ
If it exceeds m, the latch-up characteristic, which is an advantage of using an epitaxial wafer, is deteriorated, which is not preferable. Usually, it is grown to a thickness of 1 to 10 μm.

The high-quality epitaxial wafer of the present invention is
By subjecting the silicon wafer to a high temperature treatment in a predetermined non-oxidizing atmosphere in the above manufacturing process, minute defects existing in its surface layer are reduced as described above, and a silicon single crystal is formed on a good surface of the silicon substrate. By epitaxial growth, an epitaxial film having good crystallinity is formed, and a more complete silicon single crystal surface layer is provided. Therefore, the failure due to wear of the oxide film formed on the highly crystalline surface layer is postponed, and the lifetime of the formed semiconductor device is also postponed. In addition, although there are no defects in the surface crystal layer, high-density precipitation defects remain in the bulk of the substrate, so that the getter ability is high, the resistance to contamination is high, and a high-performance semiconductor device is provided. Obtainable.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments. However, the present invention is not limited by the following examples. Examples and Comparative Examples Twenty silicon wafers with a boron concentration of 1.07 × 10 ¹⁹ atoms / cm ³ and an oxygen concentration of 1.6 × 10 ¹⁸ atoms / cm ³ were prepared. High temperature treatment was carried out at 1200 ° C. for 1 hour in the furnace. The remaining 10 sheets were not processed at all. Then, all of the above 10 high temperature processed and 10 unprocessed silicon wafers were treated with SiCl ₂ H ₂ gas as a raw material.
It is processed under conditions of epitaxial growth at 050 ° C. for 5 minutes to form a silicon epitaxial growth film on each silicon wafer to a thickness of 5 μm, and 10 high temperature pretreated epitaxial wafers (A sample) and untreated epitaxial wafers (B sample) are formed. 10 sheets were obtained respectively.

For each of the 10 epitaxial wafers of the A and B samples obtained above, Ni contamination was performed in the following procedure in order to inspect the gettering ability. That is,
Standard solution for atomic absorption analysis (Ni concentration 0.1010 mg /
SC- in which a nickel nitric acid solution (20 ° C.)) was added dropwise.
1 (NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 1: 6) solution, the above A and B samples were immersed for 1 hour, and 5 to 6 × 10 ¹² Ni was applied to the surface of each epitaxial wafer. atom
Contamination occurred at a density of s / cm ² . Next, each of the 10 Ni-contaminated A and B samples obtained was subjected to the following four heat treatments. Heat treatment is performed at 780 ° C. in 100% oxygen atmosphere for each of A and B samples.
After processing for 3 hours, the temperature is further raised to 1000
The two-step heat treatment was performed by holding at 16 ° C. for 16 hours. In addition, the heat treatment ~, for each three A and B samples,
Similarly, in an atmosphere of 100% oxygen, at 1000 ° C. for 1 hour (heat treatment), 3 hours (heat treatment) and 9 hours (heat treatment).
Hold and process.

An etching solution of HF (49 wt% concentration): HNO ₃ (60 wt% concentration): H ₂ O = 1: 15: 4 (volume ratio) was prepared from each of the A and B samples treated by the above heat treatment. Etching treatment was performed. Each of the etched epitaxial wafers was cut and an optical micrograph was taken of the cross-sectional structure. The obtained optical micrograph is shown in FIG.
A sample is shown in (A), and B sample is shown in FIG. 1 (B). In Fig. 1, sample A is 1 from the surface.
No defects are found in the region up to 5 μm and a good layer is formed, whereas in the B sample, some defects such as stacking faults are observed in the same region. From these, it is clear that the epitaxial wafer in which the silicon single crystal is epitaxially grown after the high temperature treatment at 1200 ° C. in the hydrogen atmosphere has a good crystal structure with no defects in the surface layer. Further, the cross section of each of the etched epitaxial wafers was observed by an infrared tomography method. The infrared tomograph thus obtained is shown in FIG.
B samples are shown in (B). In FIG.
It is observed that the sample A has less defects in a region of 10 μm from the surface, and that it has excellent gettering ability of contaminants, while in the sample B, a defect-free layer is formed in a region of about 5 μm from the surface of the epitaxial film. It turns out that it is only confirmed.

A MOS structure was formed using each of the three A and B samples obtained in the above heat treatments, and the generation lifetime was measured. The results are shown in FIG. 3 as a relationship diagram between the heat treatment time at 1000 ° C. in an oxygen atmosphere and the lifetime. ○ in the figure is sample A
The symbol ⋄ indicates sample B. From these results, after the Ni contamination, in the heat treatment at 1000 ° C. for 1 hour in the oxygen atmosphere, the samples A and B both have the same lifetime, and the epitaxial wafer surface has the lifetime killer (irrespective of the presence or absence of the pretreatment). It can be seen that there is a high concentration of contaminated Ni atoms). However, when the heat treatment times of the heat treatment for 3 hours and the heat treatment for 9 hours were increased, the lifetime of the pretreated sample A was recovered and was 1.5 to 10 times that of the B sample. It can be seen that it has a lifetime and the final value reached is high. That is,
It can be seen that the epitaxial wafer, which has been subjected to a predetermined high temperature treatment before the formation of the epitaxial growth film, has an excellent gettering ability to reduce contaminants by oxidation heat treatment and has a high resistance to contamination during the device manufacturing process.

As is clear from the above Examples and Comparative Examples, the epitaxial wafer having an epitaxial film grown on a silicon substrate after being subjected to a high temperature treatment in a non-oxidizing gas atmosphere such as hydrogen gas according to the present invention has a defect in the surface layer. It can be seen that there is no crystallinity and the crystallinity is excellent. Further, it can be seen that the contamination resistance is higher than the untreated one, and the carrier lifetime according to the predetermined MOSC-t method is present and the contamination resistance is excellent.

[0017]

The high-quality epitaxial wafer of the present invention has a surface layer of a good silicon single crystal,
An epitaxial wafer for semiconductors having no crystal defects such as precipitation defects and stacking faults in a region up to 5 μm,
It is possible to manufacture a high-performance semiconductor device having high performance in an electrically active region, excellent gettering ability for contaminants, and ensuring stable operation. In addition, a silicon wafer can be simply and easily formed by subjecting it to a predetermined high temperature pretreatment, which is industrially highly practical.

[Brief description of drawings]

FIG. 1 is an optical microscope photograph after selective etching of the cross-sectional structures of the epitaxial wafers obtained in Example (A) and Comparative Example (B) of the present invention.

FIG. 2 is an infrared tomographic photograph of the cross-sectional structure of the epitaxial wafer obtained in Example (A) and Comparative Example (B) of the present invention.

FIG. 3 is a diagram showing the relationship between the heat treatment time after contamination and the lifetime of the epitaxial wafers obtained in Examples and Comparative Examples of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Goto 30 Soya, Hadano City, Kanagawa Prefecture Toshiba Ceramics Co., Ltd.

Claims (6)

[Claims] 1. A high-quality epitaxial wafer for a semiconductor device, characterized in that a carrier lifetime L (× 10 ⁻³ seconds) according to the MOSC-t method satisfies the following formula. L ≧ T / 3N where N is the amount of Ni contaminating the epitaxial wafer surface (× 10 ¹² atoms / cm ² ), and T is 10 after Ni contamination.
This is the time (hour) of heat treatment at 00 ° C. 2. The carrier lifetime L is 0.1.
The high-quality epitaxial wafer according to claim 1, wherein 3. The oxygen concentration is 1.2 × 10 ¹⁸ atoms /
cm ³ or more and the dopant concentration is 1.0 × 1
A silicon wafer having a density of 0 ¹⁸ atoms / cm ³ or more,
In a non-oxidizing gas atmosphere, high temperature treatment at 1000 ° C or higher,
A method for producing a high-quality epitaxial wafer, which comprises epitaxially growing a silicon single crystal film of 0.1 to 20 μm on the surface of the wafer after the treatment. 4. The oxygen concentration is 1.2 × 10 ¹⁸ atoms /
cm ³ or more and the dopant concentration is 1.0 × 1
A silicon wafer having a density of 0 ¹⁸ atoms / cm ³ or more,
In a non-oxidizing gas atmosphere, high temperature treatment at 1000 ° C or higher,
A silicon single crystal film having a thickness of 0.1 to 20 μm is epitaxially grown on the processed wafer surface, and the carrier lifetime L (× 10 ⁻³ seconds) by the MOSC-t method is L ≧ T / 3.
N (however, N is N that contaminates the surface of the epitaxial wafer)
i amount (× 10 ¹² atoms / cm ² ), T is the time (hour) of heat treatment at 1000 ° C. after Ni contamination. ) Is satisfied, the manufacturing method of the high-quality epitaxial wafer characterized by satisfying. 5. The method for producing a high-quality epitaxial wafer according to claim 3, wherein the dopant is boron, phosphorus or antimony. 6. The high-quality epitaxial wafer according to claim 3, 4 or 5, wherein the non-oxidizing gas is one gas selected from hydrogen, nitrogen, argon, helium and neon or a mixed gas of two or more gases. Manufacturing method.