WO2002027778A1

WO2002027778A1 - Method of heat-treating silicon wafer

Info

Publication number: WO2002027778A1
Application number: PCT/JP2001/008327
Authority: WO
Inventors: Norihiro Kobayashi; Masaro Tamatsuka
Original assignee: Shin-Etsu Handotai Co.,Ltd.
Priority date: 2000-09-27
Filing date: 2001-09-26
Publication date: 2002-04-04
Also published as: TW543092B; JP2002110685A

Abstract

A method of heat-treating a silicon wafer, which restricts the slip-dislocation of even a silicon wafer at least 300 mm in diameter by heat-treating it using an RTA device, forms oxygen deposits serving as a sufficient gettering site during a device production process, and does not require an additional process due to the absence of an unnecessary film on the wafer surface after heat treating. A method of heat-treating a silicon wafer produced by a Czochralski method by using a quick heating/quick cooling device, wherein a silicon wafer is heat-treated in an atmosphere of a mixed gas of nitrogen and argon containing 1-50 % by volume of nitrogen at 1150-1350°C for 1-60 seconds.

Description

Description Heat treatment method for silicon A

The present invention relates to a method for heat-treating silicon wafers, and more particularly to a method for heat-treating silicon wafers that can suppress slip dislocation even with silicon wafers having a diameter of 300 mm or more. Background art

Due to the use of a quartz crucible, oxygen is mixed into the silicon crystal produced by the CZ method. It is known that this oxygen becomes a precipitate during the crystal production and during the heat treatment in the device production process after cutting and substrate processing. When oxygen precipitates are present in the device active region, they cause a decrease in device yield.On the other hand, when oxygen precipitates are formed inside the substrate, the effect of improving gettering ability against heavy metal contaminants is reduced. Bring. From these viewpoints, it is extremely important to control the amount of oxygen precipitates in the silicon substrate (control of the oxygen precipitation characteristics).

Conventionally, the control of the oxygen precipitation characteristic has been performed by controlling the oxygen concentration in the crystal during the production of the silicon crystal or by performing a long-time heat treatment on the substrate. However, with regard to the former control, it was necessary to set the crystal production conditions for the required oxygen concentration, and the production work was complicated, and the precision was also inaccurate. Also, even if the oxygen concentration is the same in the growth direction of the silicon crystal, the oxygen precipitation characteristics in the growth axis direction are not uniform due to the influence of the thermal history during crystal production. Long-term heat treatment was required, and productivity was low. Therefore, the technology described in Japanese Patent Application Laid-Open No. 2000-310150 filed by the present applicant has been developed without controlling the oxygen concentration in the silicon wafer manufactured by the CZ method. This is a heat treatment method in which a heat treatment is performed by using a rapid heating / rapid cooling device (Rapid Thermal Annealer: hereinafter sometimes referred to as an RTA device) to obtain silicon atoms having desired oxygen deposition characteristics.

According to this method, although the oxygen concentration is as low as 14 ppm (standard of the Japan Electronic Industry Development Association (JEI DA)), the nuclei that cause oxygen precipitation in the wafer , that the oxygen precipitate density of an internal defect is excellent that Shirikonwe one cog is obtained with levels of oxygen precipitation nuclei that may be required as a 3 X 1 0 ⁹ or ZCM ³ or more gettering site On the other hand, since the gas used for the heat treatment is 100% nitrogen or 100% oxygen or a mixed atmosphere of oxygen and nitrogen, a nitride film, an oxide film, or the like is formed on the surface of the wafer after the heat treatment. There was a need for a process to remove this.

Also, in this method, slip dislocations generated by using an RTA device were not considered at all, and therefore, this method is particularly applicable to large-diameter wafers having a diameter of 300 mm or more where slip dislocations easily enter. In that case there was a problem.

On the other hand, Japanese Patent Application Laid-Open No. H11-135554, filed by the present applicant, also discloses an invention aimed at reducing such slip dislocation in a heat treatment using an RTA apparatus. This technology can reduce slip dislocation and COP (Crystal Originated Particle) simultaneously by using a mixed gas of hydrogen and argon with a hydrogen ratio of 10 to 80% by volume as the atmosphere during heat treatment. It is. In addition, since the gases used are argon and hydrogen, they are different from the case of the aforementioned Japanese Patent Application Laid-Open No. 2000-310150. Thus, no unnecessary film is formed on the wafer surface after the heat treatment. However, when such a heat treatment atmosphere is used, the COP on the surface can be reduced, which has the advantage of improving the device characteristics. On the other hand, oxygen precipitation, which is a gettering site in the device manufacturing process, has the advantage. DISCLOSURE OF THE INVENTION, which had the disadvantage of not being formed sufficiently

The present invention has been made in view of such problems, and by performing a heat treatment using an RTA apparatus, slip dislocation is suppressed even in a silicon wafer having a diameter of 300 mm or more. Provides a heat treatment method for silicon wafers that forms oxygen precipitates that will be a sufficient gettering site in the device manufacturing process and that does not require an additional process because unnecessary films are not formed on the surface of the wafer after heat treatment. The purpose is to do. In order to solve the above problems, a first aspect of the heat treatment method for silicon wafers according to the present invention is a method for heat treating a silicon wafer produced by the Czochralski method using a rapid heating / rapid cooling apparatus. In a mixed gas atmosphere of nitrogen and argon in which the proportion of nitrogen is 1 to 50% by volume, heat treatment is performed at a temperature of 1150 to 1350 for 1 to 60 seconds. As described above, by including at least 1% by volume of nitrogen in the heat treatment atmosphere, it is possible to form an oxygen precipitate that is a sufficient gettering site in the device manufacturing process, and to reduce the nitrogen to 50% by volume or less. Thus, the generation of slip dislocations can be suppressed and the formation of a nitride film on the surface can be prevented.

A second aspect of the heat treatment method for silicon wafers according to the present invention is a method for heat treating silicon wafers produced by the Czochralski method using a rapid heating / rapid cooling apparatus, wherein nitrogen is contained at 1% by volume or more. Contains The heat treatment is performed at a temperature of 115 to 135 for 1 to 60 seconds in a mixed gas atmosphere of nitrogen, hydrogen and argon containing 10 to 40% by volume of hydrogen.

As described above, if the atmosphere contains 10% to 40% by volume of hydrogen in addition to 1% by volume or more of nitrogen, sufficient gettering sites can be formed and slip dislocations can be suppressed. Can be removed by migration of silicon atoms, and silicon ゥ eno with excellent quality can be obtained.

Furthermore, there is a case where boron contamination due to the air filter of the clean room adheres to the wafer surface before the heat treatment. However, if the heat treatment is performed in an atmosphere containing hydrogen, such boron contamination can be eliminated. It also has the effect of being removed, and can prevent a change in resistivity near the surface of the wafer after heat treatment.

Also, in any of the heat treatment methods, at a heat treatment temperature as high as more than 135 ° C., problems such as frequent occurrence of slip dislocation and metal contamination occur. Ring site formation and COP removal may be insufficient. In addition, since it is a single-wafer treatment, the heat treatment time is preferably set to 60 seconds or less in consideration of productivity (throughput). Heat treatment for 1 second or more in the range of 0 ° C is required.

If the silicon wafer to be subjected to the heat treatment is a CZ silicon wafer having a diameter of 300 mm, 400 mm or more, the effect of suppressing the slip dislocation in the method of the present invention becomes remarkable.

Hereinafter, the formation of the present invention will be described in more detail.

The present inventors have developed a large-diameter silicon wafer in recent years, and have been strictly demanding for the quality of the wafer (ge-ring ring capability, defect-free). In order to improve the wafer quality by heat-treating the wafers, we thought that an RTA device capable of processing each wafer was the most appropriate, and focused on a heat treatment method using this.

At present, the large-diameter wafer with a diameter of 300 mm or 400 mm, which is expected to become mainstream several years from the mainstream silicon A8 with a diameter of 200 mm, is now heat treated by RTA equipment. In this case, suppression of slip dislocation is a major issue.

In Japanese Patent Application Laid-Open No. 11-135,514, filed earlier, as an atmosphere during the heat treatment, hydrogen having a hydrogen content of 10 to 80% by volume, preferably 40% by volume or less is used. With a mixed gas of argon, slip dislocations could be suppressed while maintaining the COP removal effect of hydrogen. Regarding the reason why slip dislocation can be suppressed by reducing the concentration of hydrogen gas, Japanese Patent Application Laid-Open No. H11-135355 discloses that the activity of hydrogen gas is involved in the generation of slip dislocation. I guess.

In this regard, the present inventors have further examined this point. As a result, not only is the activity of hydrogen gas involved, but also by mixing argon gas having a specific heat that is at least one order of magnitude smaller than that of hydrogen gas. However, it was clarified that the specific heat of the entire atmosphere was reduced, the temperature unevenness on the surface of the wafer was reduced, and the in-plane uniformity of thermal expansion of the wafer was improved.

Therefore, it was conceived that if nitrogen having a small specific heat is used in place of hydrogen as in the case of argon, slip dislocations can be suppressed and oxygen precipitation can be promoted by heat treatment in a nitrogen atmosphere. In this case, if all the hydrogen is replaced with nitrogen, it becomes difficult to obtain the effect of reducing the COP on the silicon surface by hydrogen, but in this case, the silicon wafer originally manufactured from the silicon single crystal manufactured under the condition that the COP is small is used. C may be used. Also, add hydrogen It was conceived that the effects of suppressing slip dislocation, accelerating oxygen precipitation, and reducing C〇P could be simultaneously achieved if the atmosphere contained a certain amount of the atmosphere. It is. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the relationship between the N ₂ concentration in the Ar / N ₂ mixed gas and the internal defect density in Experimental Example 1.

FIG. 2 is a graph showing the relationship between the H ₂ concentration in the H ₂ ZN ₂ ZA ₂ mixed gas and the slip length in Experimental Example 2.

FIG. 3 is a graph showing the relationship between the H ₂ concentration in the H ₂ ZN ₂ ZA ₂ mixed gas and the C〇P number in Experimental Example 2.

FIG. 4 is a schematic explanatory view showing an example of a rapid heating / rapid cooling device (RTA device). BEST MODE FOR CARRYING OUT THE INVENTION

In the method of the present invention, as a typical example of a device capable of rapidly heating and rapidly cooling a silicon wafer, a lamp heating device using heat radiation can be cited. However, rapid heating and rapid heating of a silicon wafer suitably used in the present invention can be mentioned. An example of a cooling device (RTA device) is described with reference to FIG. FIG. 4 is a schematic explanatory diagram showing an example of the RTA device.

In FIG. 4, reference numeral 10 denotes a heat treatment apparatus, in other words, an RTA apparatus. The heat treatment apparatus 10 has a chamber 11 made of quartz, and heats the wafer 18 in the chamber 11. Heating is performed by a heating lamp 12 arranged so as to surround the chamber 11 from above, below, left and right. The heating lamps 12 can control the power supplied independently. A gas inlet 19 is provided on the gas introduction side of the champer 11 and an auto shirt 13 is installed on the gas exhaust side to block the outside air. The auto shutter 13 is provided with a wafer insertion port (not shown) that can be opened and closed by a gate valve. In addition, a gas exhaust port 20 is provided in the auto-shut 13 so that the atmosphere in the furnace can be adjusted.

Then, the wafer 18 is placed on a three-point support 15 formed on the quartz tray 14. A quartz buffer 16 is provided on the gas inlet side of the quartz tray 14 to prevent the gas introduced from the gas inlet 19 from directly hitting the wafer 18. it can.

Also, a special window for temperature measurement (not shown) is provided in the chamber 11 and the temperature of the chamber 18 is controlled through the special window by a pyrometer 17 installed outside the chamber 11. Can be measured.

The process of rapidly heating and rapidly cooling the wafer 18 by the heat treatment apparatus 10 as described above is performed as follows.

First, the wafer 18 is put into the chamber 11 from the inlet of the wafer (not shown) by a wafer handling apparatus (not shown) arranged adjacent to the heat treatment apparatus 10 and placed on the quartz tray 14. Close the auto shutter. Then, electric power is supplied to the heating lamp 12 to raise the temperature of the wafer 18 to a predetermined temperature of, for example, 115 ° C. to 135 ° C. At this time, the time required to reach the target temperature is, for example, about 20 seconds.

Next, the wafer 18 can be subjected to a high-temperature heat treatment by maintaining it at that temperature for a predetermined time. When a predetermined time has elapsed and the high-temperature heat treatment has been completed, the output of the heating lamp 12 is lowered, and the temperature of the heater 18 is lowered. This cooling can be performed in about 20 seconds, for example. Finally, the heat treatment is completed by removing the wafer with an e-handling device. I do.

Example

Hereinafter, the present invention will be described more specifically with reference to experimental examples.

(Experimental example 1)

A silicon wafer with a crystal orientation <100>, a diameter of 300 mm, and an interstitial oxygen concentration of 16 ppma (JEI DA) pulled up by the CZ method was fabricated. Using a TA device, heat treatment was performed at 1200 ° C for 30 seconds in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ), and the nitrogen gas concentration (volume%) in the atmosphere was measured as shown in Fig. 1. The change was performed as shown on the axis.

After heat treatment with RTA equipment, these wafers were subjected to heat treatment at 800 ° CZ for 4 hours + 100 ° C ° CZ for 16 hours using a normal diffusion furnace to remove oxygen precipitates inside the wafer. After growing to a detectable size, the internal defect density was measured by the OPP (Optical Precipitate Profiler) method. The results are shown in FIG.

As shown in Fig. 1, it can be seen that a high internal defect density can be obtained if nitrogen is present at 1% or more in the atmosphere of the heat treatment using the RTA apparatus. Also, it was confirmed that when the nitrogen gas concentration was 50% or less, almost no nitride film was formed on the surface of the wafer. Slip dislocations hardly occurred regardless of the nitrogen gas concentration.

(Experimental example 2)

A silicon wafer with the same specifications as in Experimental Example 1 was subjected to heat treatment at 1200 ° C for 30 seconds in a mixed gas atmosphere of argon, nitrogen, and hydrogen (H ₂ ) using the same RTA apparatus. The argon gas concentration was fixed at 50% by volume, and the nitrogen gas and hydrogen gas concentrations (% by volume) were varied as shown in FIGS. Observe the slip dislocation in the wafer after heat treatment by X-ray topograph, measure the total length, and refer to the length when the hydrogen gas concentration is 50% (nitrogen gas concentration 0%). Normalized and shown in Figure 2. In addition, the number of COPs before and after the heat treatment (the entire surface of the wafer) was observed with a particle counter, and the number of COPs after the heat treatment was normalized based on the number of COP before the heat treatment as shown in Fig. 3.

According to FIG. 2, it can be seen that no slip dislocation is observed at a hydrogen gas concentration of 40% or less. On the other hand, according to FIG. 3, it was found that the COP reduction effect was high when the hydrogen gas concentration was about 10% or more.

Furthermore, when the internal defect density of these wafers was measured by the same method as in Experimental Example 1, the internal defect density was high if the atmosphere contained about 1% or more of nitrogen gas. It was found that increasing the gas concentration did not increase much. Industrial applicability

As described above, according to the method of the present invention, by performing the heat treatment using the RTA apparatus, even if the silicon wafer has a diameter of 300 mm or more, the slip dislocation is suppressed, and the silicon dislocation is sufficiently sufficient in the device manufacturing process. Oxygen precipitates serving as gettering sites are formed, and an unnecessary film is not formed on the wafer surface after the heat treatment.

Claims

0 Scope of request

1. Rapid thermal apparatus in a method of heat-treating the silicon © er c produced by Chiyokurarusuki method using, ~ 1 the ratio of nitrogen 5 0 volume ^_0/0 nitrogen and argon mixed gas atmosphere of Below, temperature 1 1 5 0 ~

A heat treatment method for silicon wafers, wherein the silicon wafer is heat-treated at 135 ° C. for 1 to 60 seconds.

2. Rapid heating · A method for heat-treating silicon wafers manufactured by the Czochralski method using a rapid cooling device, containing 1% by volume or more of nitrogen and 10 to 40% by volume of hydrogen. Temperature of 150 to 135 in a mixed gas atmosphere of nitrogen, hydrogen and argon. A heat treatment of the silicon wafer for 1 to 60 seconds.

3. The silicon wafer heat treatment method according to claim 1, wherein the diameter of the silicon wafer is 300 mm or more.