JP7207204B2 - Method for producing carbon-doped silicon single crystal wafer - Google Patents

Description

The present invention relates to a carbon-doped silicon single crystal wafer and its manufacturing method.

Silicon single crystal wafers are widely used as substrates for manufacturing semiconductor devices. In addition, it is well known to impart gettering ability to silicon single crystal wafers in order to getter metal impurities mixed in during the manufacturing process of semiconductor devices. By the way, in recent years, the manufacturing conditions for state-of-the-art devices have been decreasing in temperature. Since it acts as a gettering site for metal impurities in the manufacturing process, carbon-doped silicon single crystal wafers, which easily form BMDs (Bulk Micro Defects) due to oxygen precipitation even in low-temperature processes, have come to be used. is coming.

Further, it is well known that silicon single crystal wafers are improved in wafer strength by doping nitrogen or carbon. However, since nitrogen has a high diffusion rate in a silicon single crystal, in a nitrogen-doped silicon single crystal wafer, nitrogen diffuses outward during heat treatment for device fabrication, making it difficult to obtain high surface layer strength. On the other hand, since carbon has a small diffusion coefficient, it is possible to improve surface layer strength in a carbon-doped silicon single crystal wafer.

In addition, it is known that a carbon-doped silicon single crystal wafer for a solid-state imaging device achieves small dark current and excellent photosensitivity because carbon suppresses injection of carriers from the electrode (Non-Patent Document 1).

It is also well known that carbon in a silicon single crystal wafer has the effect of suppressing the formation of oxygen donors generated during heat treatment (see Patent Document 1).

JP 2011-54656 A JP 2018-190903 A

"Structural Elements of Ultrashallow Thermal Donors Formed in Silicon Crystals"A. Hara, T. Awano, Y.; Ohno and I. Yonenaga: Jpn. J. Appl. Phys. 49 (2010) 050203.

As techniques for improving the wafer strength of a silicon single crystal wafer, carbon doping or nitrogen doping of the silicon single crystal wafer, making the wafer into a high oxygen concentration crystal, and precipitating oxygen in the wafer are known. However, if the crystal is doped with carbon or nitrogen at the stage of growing a silicon single crystal (silicon single crystal ingot) by the Czochralski method, the segregation phenomenon causes the impurity concentration to change depending on the position of the single-crystallized crystal. , a difference in the amount of precipitated oxygen occurs due to a difference in the crystal position.

In addition, there is a limit to controlling the amount of precipitated oxygen in a silicon single crystal wafer only by oxygen concentration, and it is difficult to control the amount of precipitated oxygen to a high density without doping with carbon or nitrogen.

Furthermore, due to the recent progress in the low-temperature process of the device process described above, it is becoming more and more difficult for oxygen to precipitate in silicon single crystal wafers. was desired.

On the other hand, it has been proposed to control the BMD to a high density by heat-treating a silicon single crystal wafer in a carbon-containing gas atmosphere (see Patent Document 2). However, in Patent Document 2, since the heat treatment is performed by resistance heating, carbon diffuses outward during the temperature drop, and the carbon concentration on the wafer surface cannot be sufficiently increased, which is undesirable in terms of wafer strength. was enough.

The present invention has been made in view of the above problems, and the carbon concentration that can improve the wafer strength by increasing the carbon concentration in the surface layer of a silicon single crystal wafer and making the carbon concentration distribution on the surface uniform. An object of the present invention is to provide a doped silicon single crystal wafer and a method for manufacturing the same.

In order to achieve the above object, the present invention provides a step of preparing a silicon single crystal wafer not doped with carbon, and performing a first RTA on the silicon single crystal wafer in an atmosphere containing a carbon atom-containing compound gas. and performing a second RTA treatment that follows the first RTA treatment at a temperature higher than that of the first RTA treatment, wherein the first and second RTA treatments by implanting vacancies and doping carbon into the silicon single crystal wafer, and increasing the carbon concentration to 1×10 ¹⁷ atoms/cm ³ within a depth range of 0.1 μm from the surface of the silicon single crystal wafer. A method for producing a carbon-doped silicon single crystal wafer characterized by the above is provided.

In such a method for producing a carbon-doped silicon single crystal wafer, single crystallization is achieved by injecting carbon and vacancies together in the RTA (Rapid Thermal Annealing) treatment stage by rapid heating and rapid cooling. The diffusion coefficient of carbon can be increased by the action of vacancies without being affected by the crystal position. As a result, carbon can be uniformly diffused from the surface, and the carbon concentration in the range of 0.1 μm depth from the surface of the silicon single crystal wafer can be increased to 1×10 ¹⁷ atoms/cm ³ or more. , high wafer strength can be obtained.

In the method for producing a carbon-doped silicon single crystal wafer of the present invention, the carbon concentration is set to 1×10 ¹⁵ atoms/cm ³ or more in a region deeper than 0.1 μm from the surface of the carbon-doped silicon single crystal wafer to be produced. is preferred.

By setting the carbon concentration in the bulk portion of the wafer to be manufactured in this way, it is possible to control the wafer strength to a higher level and the desired amount of precipitated oxygen.

Moreover, it is preferable that the silicon single crystal wafer to be prepared has an oxygen concentration of 11 ppma or more.

Thus, by setting the oxygen concentration of the wafer to be prepared to 11 ppma, oxygen precipitation in the carbon-doped silicon single crystal wafer becomes easier. Incidentally, in the explanation of the present invention, the oxygen concentration is indicated according to the JEITA standard.

Moreover, it is preferable to include, after the step of performing the second RTA treatment, a step of removing an amorphous carbide film formed on the surface of the carbon-doped silicon single crystal wafer by the first and second RTA treatments. .

By removing the amorphous carbonized film formed on the surface in this way, it is not necessary to remove the amorphous carbonized film again when fabricating the device.

Moreover, it is preferable that the silicon single crystal wafer to be prepared is a silicon single crystal wafer comprising any one of the Nv region, the Ni region and the V region.

Since carbon is present in the silicon single crystal wafer produced by the method for producing a carbon-doped silicon single crystal wafer of the present invention, oxygen precipitates can be formed in any defect region. Oxygen precipitation is more likely to occur by using a wafer having such a defective region as a wafer to be subjected to oxygen deposition.

Further, it is preferable that the atmosphere in the first and second RTA processes be a mixed atmosphere containing hydrocarbon gas and containing Ar or _NH3 or both Ar and _NH3 .

By heat-treating in such an atmosphere, vacancies can be more effectively injected together with carbon.

Further, the first RTA treatment is performed at a temperature of 600° C. or more and 850° C. or less for a time of 5 seconds or more and 60 seconds or less, and the second RTA treatment is performed at a temperature of 1100° C. or more and the melting point of silicon or less. It is preferable to hold for 10 seconds or more and 150 seconds or less.

Voids can be more effectively injected together with carbon under such RTA processing conditions.

The present invention also provides a silicon single crystal wafer doped with carbon and having vacancies, wherein the carbon concentration is 1×10 ¹⁷ atoms/m in a depth range of 0.1 μm from the surface of the silicon single crystal wafer. A carbon-doped silicon single crystal wafer characterized by having a surface area of 1 cm ³ or more is provided.

Such a carbon-doped silicon single crystal wafer has a surface carbon concentration as high as 1×10 ¹⁷ atoms/cm ³ or more, so that high wafer strength can be obtained.

Further, in a region deeper than 0.1 μm from the surface of the carbon-doped silicon single crystal wafer, the carbon concentration is preferably 1×10 ¹⁵ atoms/cm ³ or more.

By setting the carbon concentration in the bulk portion in this way, it is possible to control the wafer strength to a higher level and the desired amount of precipitated oxygen.

Moreover, it is preferable that the carbon-doped silicon single crystal wafer has an oxygen concentration of 11 ppma or more.

With such an oxygen concentration, oxygen precipitation in the carbon-doped silicon single crystal wafer becomes easier.

In addition, the surface of the carbon-doped silicon single crystal wafer may not have an amorphous carbonized film.

Thus, if the carbon-doped silicon single crystal wafer does not have an amorphous carbide film on the surface, it is not necessary to remove the amorphous carbide film again when fabricating devices.

Moreover, it is preferable that the silicon single crystal wafer consists of any one of Nv region, Ni region and V region.

Oxygen precipitation is more likely to occur by using a wafer having such defect regions.

According to the method for producing a carbon-doped silicon single crystal wafer of the present invention, by implanting carbon and vacancies together in the RTA treatment stage, carbon is injected by the action of vacancies without being affected by the single-crystallized crystal position. can increase the diffusion coefficient of As a result, carbon can be uniformly diffused from the surface, and the carbon concentration in the range of 0.1 μm depth from the surface of the silicon single crystal wafer can be increased to 1×10 ¹⁷ atoms/cm ³ or more. , high wafer strength can be obtained. In addition, since the carbon-doped silicon single crystal wafer of the present invention has a high carbon concentration of 1×10 ¹⁷ atoms/cm ³ or more in a range of depth of 0.1 μm from the surface, high wafer strength can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows an example of the manufacturing method of the carbon doped silicon single crystal wafer of this invention. 1 is a graph showing an outline of the temperature profile of RTA treatment in the method for producing a carbon-doped silicon single crystal wafer of the present invention. FIG. 2 is a schematic cross-sectional view showing adhesion of hydrocarbon gas during the process of the method for producing a carbon-doped silicon single crystal wafer of the present invention; 4 is a graph showing the results of SIMS measurement of the carbon concentration distribution of carbon-doped silicon single crystal wafers in Examples. FIG. 10 is a graph showing the results of SIMS measurement of the carbon concentration distribution of a carbon-doped silicon single crystal wafer in a comparative example. FIG.

As described above, due to the recent progress in low temperature processes in device processes, oxygen precipitation in silicon single crystal wafers is becoming more and more difficult. technology was desired. In order to improve the wafer strength, the present inventors doped the silicon single crystal wafer with carbon, and set the carbon concentration in the range of 0.1 μm depth from the wafer surface to 1×10 ¹⁷ atoms/cm ³ . I found that I needed to do more. In addition, the present inventors further discovered that by implanting carbon and vacancies together in the heat treatment step, the diffusion coefficient of carbon can be increased by the action of the vacancies without being affected by the single-crystallized crystal position. The inventors have found that oxygen precipitation can be uniformly grown at an accelerated rate, and have completed the present invention.

The present invention relates to a method for producing a carbon-doped silicon single crystal wafer, comprising the steps of preparing a silicon single crystal wafer that is not doped with carbon; , a step of performing a first RTA treatment, and a step of performing a second RTA treatment following the first RTA treatment at a temperature higher than that of the first RTA treatment, wherein the first and By the second RTA treatment, vacancies are injected into the silicon single crystal wafer and carbon is doped, and the carbon concentration is reduced to 1×10 within a depth range of 0.1 μm from the surface of the silicon single crystal wafer. It is characterized by being ¹⁷ atoms/cm ³ or more.

First, as shown in FIG. 1(a), a silicon single crystal wafer not doped with carbon is prepared (step a). The silicon single crystal wafer prepared here is preferably a silicon single crystal wafer produced from a silicon single crystal ingot pulled by the Czochralski method. In addition, in the present invention, "not doped with carbon" means that carbon is not intentionally added to the silicon single crystal wafer, and the silicon single crystal wafer containing carbon as an unintentional and unavoidable impurity is It is included in "silicon single crystal wafer not doped with carbon".

A silicon single crystal wafer not doped with carbon to be prepared here can be prepared, for example, as follows. First, a silicon single crystal ingot is pulled up by the Czochralski method (CZ method). Here, it is preferable to pull the silicon single crystal ingot at a pulling speed at which a silicon single crystal ingot free of Grown-in defects can be pulled. Next, the silicon single crystal ingot is processed into a silicon single crystal wafer by a known method such as slicing, grinding, polishing, etching (CW processing).

The oxygen concentration of the silicon single crystal wafer prepared here is preferably 11 ppma or more. This oxygen concentration can be achieved by adjusting the conditions during pulling. Moreover, the silicon single crystal wafer prepared here is preferably a silicon single crystal wafer composed of any one of the Nv region, the Ni region and the V region. A silicon single crystal wafer having these defect regions can be obtained by adjusting the pulling conditions, particularly the pulling speed. A wafer entirely composed of the Nv region, a wafer entirely composed of the Ni region, or a wafer entirely composed of the V region may be used, or a wafer in which these are mixed. In the silicon single crystal pulled by the Czochralski method, point defects (vacancies, interstitial silicon) are introduced in the crystal manufacturing process, and these aggregate to form Grown-in defects (V region , I region), and a perfectly crystalline region (N region) in which point defects are not aggregated. Also, in the N region, there are an Nv region in which vacancies are predominant and an Ni region in which interstitial silicon is predominant, although point defects are not aggregated.

Next, as shown in FIG. 1(b), the silicon single crystal wafer which is not doped with carbon and is prepared as described above is subjected to a first RTA treatment in an atmosphere containing a carbon atom-containing compound gas. (Step b).

Next, as shown in FIG. 1(c), a second RTA treatment, which follows the first RTA treatment, is performed at a temperature higher than that of the first RTA treatment (step c).

The atmosphere in the first and second RTA processes is preferably a mixed atmosphere containing hydrocarbon gas and containing Ar or NH ₃ or both Ar and NH ₃ . By heat-treating in such an atmosphere, vacancies can be more effectively injected together with carbon.

FIG. 2 shows an outline of the temperature profile of the RTA treatment for the first RTA treatment and the second RTA treatment. The first RTA treatment is preferably carried out at a temperature of 600° C. or higher and 850° C. or lower for a period of 5 seconds or longer and 60 seconds or shorter so that the hydrocarbon gas adheres to the entire surface of the silicon single crystal wafer so as not to carbonize. In addition, it is preferable to hold the second RTA treatment at a temperature of 1100° C. or more and the melting point of silicon or less for 10 seconds or more and 150 seconds or less, thereby inwardly diffusing carbon adhering to the surface of the silicon single crystal wafer. Voids can be more effectively injected together with carbon under such RTA processing conditions.

By the first RTA treatment (step b) and the second RTA treatment (step c), vacancies can be injected into the silicon single crystal wafer and carbon can be doped. In addition, according to the present invention, by implanting carbon and vacancies together in the RTA process, it is possible to increase the diffusion coefficient of carbon by the action of vacancies without being affected by the position of single-crystallized crystals. As a result, carbon can be uniformly diffused from the surface, and the carbon concentration in the range of 0.1 μm depth from the surface of the silicon single crystal wafer can be increased to 1×10 ¹⁷ atoms/cm ³ or more. , high wafer strength can be obtained.

Further, in the method for producing a carbon-doped silicon single crystal wafer of the present invention, the carbon concentration is set to 1×10 ¹⁵ atoms/cm ³ or more in a region deeper than 0.1 μm from the surface of the carbon-doped silicon single crystal wafer to be produced. can do.

The reason why such a carbon concentration distribution in the wafer thickness direction can be controlled is that the diamond structure of a silicon single crystal has many gaps and is a structure in which impurities are easily diffused. In particular, in a state where vacancies are dominant, the action of vacancies makes it extremely easy for carbon to diffuse. Therefore, first, as shown in FIG. 3, carbon is uniformly deposited on the surface of the silicon single crystal wafer W by the first RTA. In the subsequent second RTA, the carbon concentration in the range of 0.1 μm depth from the surface of the silicon single crystal wafer can be made 1×10 ¹⁷ atoms/cm ³ or more, and preferably the carbon concentration in the bulk region. can be controlled to 1×10 ¹⁵ atoms/cm ³ or more, and a high wafer strength and a desired amount of precipitated oxygen can be obtained.

Thus, an amorphous carbon film is formed on the surface by the two-step heat treatment of RTA. At the same time, vacancies are generated, which facilitates the inward diffusion of carbon, and the carbon concentration on the pole surface becomes extremely high. Also, the carbon concentration in the bulk portion can be diffused to the solid solubility of carbon at the temperature of the second RTA having a higher heat treatment temperature.

Further, in the method for producing a carbon-doped silicon single crystal wafer of the present invention, after the second RTA treatment (step c), as shown in FIG. (step d) of removing the amorphous carbonized film formed on the surface of the carbon-doped silicon single crystal wafer by the RTA treatment.

Since an amorphous carbonized film of about 15 nm is formed by the first RTA treatment and the second RTA treatment as described above, it is preferable to remove it. Although this step is an optional step, removing the amorphous carbonized film formed on the surface eliminates the need to remove the amorphous carbonized film again when fabricating the device. Further, if the carbon concentration in the range of 0.1 μm depth from the surface of the carbon-doped silicon single crystal wafer can be made 1×10 ¹⁷ atoms/cm ³ or more, the step of polishing the surface deeper than the amorphous carbide film is performed. I don't mind.

The carbon-doped silicon single crystal wafer manufactured by the method for manufacturing a carbon-doped silicon single crystal wafer of the present invention is a silicon single crystal wafer doped with carbon and having vacancies. A carbon-doped silicon single crystal wafer having a carbon concentration of 1×10 ¹⁷ atoms/cm ³ or more in a depth range of 0.1 μm. Moreover, in a region deeper than 0.1 μm from the surface of the carbon-doped silicon single crystal wafer, the carbon concentration is preferably 1×10 ¹⁵ atoms/cm ³ or more.

Further, the carbon-doped silicon single crystal wafer preferably has an oxygen concentration of 11 ppma or more, and is preferably composed of any one of Nv region, Ni region and V region.

Further, by performing the above step (d), it is possible to obtain a carbon-doped silicon single crystal wafer having no amorphous carbide film on its surface.

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but these Examples are not intended to limit the present invention.

(Example)
First, by pulling up a silicon single crystal ingot by the Czochralski method and processing it into a wafer, a silicon single crystal wafer not doped with carbon has a diameter of 200 mm, a crystal plane (100), a P-type, normal resistance, A silicon single crystal wafer having an oxygen concentration of 12 ppma (JEITA), a carbon concentration of less than 2.5×10 ¹⁵ atoms/cm ³ and a crystal region of Nv region was prepared (step a).

Next, the first and second RTA treatments were performed as follows.

After the silicon single crystal wafer was placed in the RTA processing apparatus, the temperature was raised from room temperature to less than 800° C., and then held at 800° C. for 20 seconds (step b, first RTA). At this time, the atmosphere was CH ₄ +NH ₃ /Ar with a carbon concentration of 2%.

Next, the temperature was raised to 1200° C. and held at 1200° C. for 10 seconds (step c, second RTA). At this time, the atmosphere was CH ₄ +NH ₃ /Ar continuously from the first RTA, and the carbon concentration was 2%. After that, the temperature was lowered.

Next, the amorphous carbonized film adhering to the surface of the silicon single crystal wafer was removed (step d). At this time, polishing processing was performed with a removal allowance of 0.1 μm.

Finally, SIMS (secondary ion mass spectrometry) was used to measure the depth distribution of the carbon concentration of the produced carbon-doped silicon single crystal wafer. The results are shown in FIG. The carbon concentration in the range of 0.1 μm depth from the surface of the carbon-doped silicon single crystal wafer was 1×10 ²¹ atoms/cm ³ . Also, the carbon concentration in the region deeper than 0.1 μm from the surface is 3×10 ¹⁶ atoms/cm ³ or more, which is close to the solid solubility of carbon at 1200°C. The lower detection limit of carbon concentration by SIMS is about 7×10 ¹⁵ atoms/cm ³ .

(Comparative example)
First, as in the example, a silicon single crystal wafer not doped with carbon had a diameter of 200 mm, a crystal face (100), P-type, normal resistance, an oxygen concentration of 12 ppma (JEITA), and a carbon concentration of 2.5×10 ¹⁵ . A silicon single crystal wafer having a crystal region of less than atoms/cm ³ and a Nv region was prepared.

Next, carbon doping heat treatment was performed using a vertical heat treatment furnace. First, it was placed in a vertical heat treatment furnace at 750° C. and then heated up to 1000° C. at a rate of 10° C./min. Thereafter, the temperature was raised from 1000° C. to 1200° C. at a rate of 3° C./min, held at 1200° C. for 60 minutes, and then cooled at a rate of −3° C./min. After that, it was taken out from the vertical heat treatment furnace at 700°C. The gas atmosphere in the entire heat treatment process was CO ₂ +Ar with a carbon concentration of 1%.

Finally, the surface oxide film of the heat-treated wafer was removed to evaluate the SIMS carbon profile. The results are shown in FIG. The carbon concentration in the range of 0.1 μm depth from the surface of the wafer is 2×10 ¹⁶ atoms/cm ³ , and the carbon concentration near the depth of 2 μm is 3×10 ¹⁶ atoms/cm ³ , which is close to the solid solubility. It was confirmed that the carbon concentration decreased in the bulk direction.

It can be seen that the method of the present invention can increase the carbon concentration to 1×10 ¹⁷ atoms/cm ³ or more in a depth range of 0.1 μm from the surface of the silicon single crystal wafer.

It should be noted that the present invention is not limited to the above embodiments. The above embodiment is an example, and any device that has substantially the same configuration as the technical idea described in the claims of the present invention and produces similar effects is the present invention. It is included in the technical scope of the invention.

W: Silicon single crystal wafer.

Claims (7)

preparing a silicon single crystal wafer not doped with carbon;
a step of subjecting the silicon single crystal wafer to a first RTA treatment in an atmosphere containing a carbon atom-containing compound gas;
performing a second RTA treatment subsequent to the first RTA treatment at a higher temperature than the first RTA treatment;
has
By the first and second RTA treatments, vacancies are injected into the silicon single crystal wafer and carbon is doped into the silicon single crystal wafer, and the carbon concentration is reduced in a range of depth of 0.1 μm from the surface of the silicon single crystal wafer. is 1×10 ¹⁷ atoms/cm ³ or more, a method for producing a carbon-doped silicon single crystal wafer. 2. The carbon-doped silicon single crystal according to claim 1, wherein a carbon concentration is set to 1×10 ¹⁵ atoms/cm ³ or more in a region deeper than 0.1 μm from the surface of the carbon -doped silicon single crystal wafer. Wafer manufacturing method. 3. The method for producing a carbon-doped silicon single crystal wafer according to claim 1, wherein the silicon single crystal wafer to be prepared has an oxygen concentration of 11 ppma or more. A step of removing an amorphous carbide film formed on the surface of the carbon-doped silicon single crystal wafer by the first and second RTA treatments after the step of performing the second RTA treatment. The method for producing a carbon-doped silicon single crystal wafer according to any one of claims 1 to 3. 5. The carbon-doped silicon according to any one of claims 1 to 4, wherein the silicon single crystal wafer to be prepared is a silicon single crystal wafer comprising any one of Nv region, Ni region and V region. A method for manufacturing a single crystal wafer. The atmosphere in the first and second RTA processes is a mixed atmosphere containing hydrocarbon gas and containing Ar or _NH3 or both Ar and _NH3 . A method for producing a carbon-doped silicon single crystal wafer according to any one of claims 1 to 3. The first RTA treatment is performed at a temperature of 600° C. or more and 850° C. or less for a time of 5 seconds or more and 60 seconds or less,
7. The method according to any one of claims 1 to 6, wherein the second RTA treatment is performed at a temperature of 1100[deg.] C. or more and below the melting point of silicon for a time of 10 seconds or more and 150 seconds or less. A method for producing a carbon-doped silicon single crystal wafer of

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