JPS61193458A - Treatment of silicon wafer - Google Patents

Abstract

PURPOSE:To realize appropriate crystal characteristics by a method wherein a silicon wafer is heated to a temperature not lower than 800 deg.C in an atmosphere of hydrogen or inert gas containing some hydrogen for the effective elimination in a short period of time of oxygen precipitates from the silicon wafer surface containing inter-lattice oxygen. CONSTITUTION:An Si wafer 11 equipped with a resistivity of 5-20OMEGA/cm is subjected to heat treatment in an argon atmosphere including 10% of hydrogen for the elimination of oxygen precipitates in the vicinity 11a of the surface of the Si wafer 11. In this process, oxygen in the vicinity 11a of the surface of the Si wafer 11 is diffused outward from the surface of r the formation of a defect-free layer in the vicinity 11a of the wafer surface. Simultaneously, a layer containing few lattices is formed in the inside 11b of the wafer. A process follow wherein the wafer 11 is subjected to oxidation in a dry atmosphere at a temperature not lower than 800 deg.C, preferably at 1,000 deg.C, for the formation of an oxide film 12, whereon a polycrystalline silicon film 13 is subsequently formed containing phosphorus.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method of processing a silicon wafer for eliminating oxygen precipitates near the surface of the silicon wafer containing interstitial oxygen.

[Technical background of the invention and its problems]

Conventionally, in the manufacture of semiconductor integrated circuits, a semiconductor ingot was cut into wafer shapes, the wafers were surface polished and then fed as they were into an integrated circuit manufacturing system. Furthermore, in the integrated circuit manufacturing process, a process with an upper limit of 1000 [°C] has generally been adopted.

In recent years, the degree of integration of semiconductor integrated circuits has increased significantly.
4. □□Ib i: m'v 6yu□4o71.

There's something. For this reason, lowering the process temperature is being considered. However, in processes at temperatures below 1000[deg.] C., breakdown voltage failures of the thermal oxide film occur due to the crystal characteristics of the 3i wafer as described below. The cause of the outbreak is expected to be elucidated through subsequent investigation, but there are currently no speculations.
The process of occurrence of breakdown voltage failure is as follows. That is, interstitial oxygen atoms contained in the Si wafer are captured by oxygen precipitates in the 3i crystal, and become even larger precipitates. During the heat treatment process of integrated circuit manufacturing, impurities such as heavy metals are captured in the region of the strong strain field generated around these large precipitates. If these heavy metal-containing precipitates are incorporated into the thermal oxide film, they will cause oxide film defects, resulting in poor breakdown voltage and shortening the lifetime of minority carrier generation.

Therefore, the intrinsic gettering method has recently been attracting attention as a method for removing these minute oxygen precipitates. That is, the S1 wafer is heated at high temperature (for example, 1150°C)
Heat treatment is carried out for 100 hours, and the supersaturated interstitial oxygen carried out during crystal growth is diffused outward to form a region with low oxygen concentration ranging from several to several tens [μTrL] from the surface of the 3t wafer. This step also has the effect of dissolving minute precipitates that have entered the crystal during crystal growth. Furthermore, low temperature (80
After several hours of heat treatment at 0°C) to stabilize the precipitates, the product was put into the normal integrated circuit manufacturing process.
Precipitates grow inside the wafer during the manufacturing process at 00°C. When this intrinsic gettering method is adopted in the integrated circuit manufacturing process, the minute precipitates generated within the wafer getter metal impurities attached to the wafer surface during the process, keeping the surface layer free of impurities. Therefore,
A thermal oxide film created by such a process is expected to have fewer defects.

However, this type of method has the following problems. That is, in order to reliably eliminate oxygen precipitates on the surface of a silicon wafer, it is necessary to perform high-temperature heat treatment for a long time, which is impractical.

In addition, even if it is thought that high-temperature heat treatment is performed for a long time to sufficiently lower the oxygen concentration near the surface and dissolve oxygen precipitates, the current situation is that the breakdown voltage failure of the thermal oxide film does not decrease as much as expected. It is believed that more complex phenomena than those described above occur in the actual manufacturing process of semiconductor integrated circuits.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to effectively eliminate oxygen precipitates on the surface of a silicon wafer containing interstitial oxygen in a short period of time. An object of the present invention is to provide a highly practical silicon wafer processing method that can improve crystal properties.

[Summary of the invention]

The gist of the present invention is to utilize a hydrogen atmosphere to promote outward diffusion of oxygen from the silicon surface during intrinsic gettering.

That is, the present invention provides a method for processing a silicon wafer in which oxygen near the surface of the silicon wafer containing interstitial oxygen is extinguished, in which the silicon wafer is preferably heated to 800[° C.] or higher in an atmosphere of hydrogen or an inert gas containing hydrogen. is 10
This method involves heating to 00[°C] or higher.

〔Effect of the invention〕

According to the present invention, outward diffusion of oxygen near the surface of the silicon wafer can be promoted by heat treatment in a hydrogen atmosphere, thereby effectively eliminating oxygen precipitates near the surface in a short time. I can do it.

For this reason, the practicality of in-1 linthic gettering is improved, and the characteristics of elements formed subsequently can be improved. In particular, it is possible to improve the reliability of an MO8 type integrated circuit having a gate oxide film as thin as 1000 [people] or less.

[Embodiments of the invention]

First, before explaining embodiments, the basic principle of the present invention will be explained.

The disappearance process of oxygen precipitates in silicon in intrinsic gettering can be considered as follows. That is, when a silicon wafer is heat-treated at a high temperature, interstitial oxygen diffuses outward from the silicon surface, and the interstitial oxygen concentration around oxygen precipitates near the surface decreases. Eventually, when the temperature drops below the solid solubility limit, oxygen flows out from the oxygen precipitates and begins to dissolve again.

At this time, the flow of oxygen is limited by a solid solution reaction at the interface between the oxygen precipitate and the silicon, and a process in which oxygen dissolved in solid solution at the interface of the precipitate diffuses to the surrounding area. At the initial stage of solid solution re-dissolution, the radius of the precipitate is large, so the outflow of oxygen due to the solid solution reaction is sufficiently fast, and diffusion controls the overall solid solution rate. However, as the solid solution progresses and the precipitate radius becomes smaller, the solid solution reaction at the interface is slower than the diffusion rate and becomes reaction rate-limiting. When this reaction becomes rate-limiting, the rate of solid solution decreases and the extinction time increases.

Conventionally, high-temperature heat treatment to eliminate oxygen precipitates near the silicon surface has been carried out in an oxidizing atmosphere or an inert gas atmosphere, and the re-solid solution of the precipitates is caused by the sulfur in the oxide.
It is necessary to cut the r -o-s + network structure using only thermal energy, and even if intrinsic gettering is performed, high-temperature heat treatment is required to eliminate the defect density of the oxide film formed on the surface. It needed to be done for a long time.

Therefore, the present inventors have considered performing high-temperature heat treatment in a hydrogen atmosphere as a method to solve this problem. In this case, the solid solubility limit of hydrogen in silicon is large, and the diffusion coefficient is also 10.
Since the temperature is as large as approximately 4×10 7 μm 2 /hl at 0.00° C., when the above-mentioned high-temperature heat treatment is performed, hydrogen reaches the oxygen precipitates in S1.

As a result, the outward diffusion of oxygen from the 81 surface caused the annihilation process to occur, and at the interface of the microprecipitates, which entered the interfacial reaction rate-determining stage, a reduction reaction mediated by hydrogen proceeded, promoting the interfacial reaction. Extinction speed increases. Therefore, it is possible to completely eliminate oxygen precipitates in an S1 wafer that has been heat-treated in a hydrogen-containing atmosphere in a shorter time than in a 3i wafer that has been heat-treated at a high temperature in an oxidizing atmosphere near the surface. Become.

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIGS. 1(a) and 1(b) show M related to an embodiment of the method of the present invention.
3 is a cross-sectional view showing the manufacturing process of an OS capacitor, and is an example applied to a 3i wafer manufactured by the Czochralski method (CZ method).

First, as shown in FIG.
By performing heat treatment at a temperature of 1190 [° C.] for 10 minutes in argon gas containing hydrogen, oxygen precipitates near the surface of 81 are eliminated and crystal properties are improved. As a result, oxygen in the vicinity of the wafer surface diffuses outward, and the surface of the Si wafer 11 has a defect-free layer in the vicinity of the surface 11a, as shown in FIG. is formed. At the same time, a minute defect layer is formed inside the wafer 11b.

Next, the wafer 11 is heated at 1000° C. in a dry atmosphere.
It is oxidized by treatment at a temperature of [°C] for 35 minutes, and the result is shown in Fig.
As shown in b), an oxide film 12 with a thickness of 400 mm was formed. Subsequently, a phosphorus-doped polycrystalline silicon film 13 was formed on the oxide film 12 to a thickness of 4,000 mm using the LPCVD method. Thereafter, the polycrystalline silicon film 13 was patterned by photolithography to form a gate electrode.

When the breakdown voltage defect rate of the sample formed above was measured, the results shown in FIG. 3 were obtained. Here, 1. In the figure, A shows the case where no heat treatment was performed, B shows the case where the heat treatment was performed in an oxidizing atmosphere, and C shows the case where the method of this embodiment was used. Note that the gate area is 10 [#lIl+2] in both cases.
When the oxide film electric field was 7 [MV], those whose current was 1 [μA] or more were determined to be defective.

As is clear from FIG. 3, there is some improvement in case B compared to case A, but it is not sufficient. On the other hand, in the case of C (in this example), a remarkable improvement is seen compared to the case of B.

In this way, according to the method of this embodiment, the intrinsic
By performing gettering in a hydrogen atmosphere, oxygen precipitates near the surface of the Si wafer can be effectively eliminated. Therefore, the defect density of the thermal oxide film 12 can be significantly reduced. Therefore, the ripple effect on semiconductor integrated circuits is enormous. For example, it is possible to easily reduce the thickness of the gate oxide film in an MO8 integrated circuit, increase the operating speed, widen the operating margin, and improve the reliability of the operation. - Note that the present invention is not limited to the above-described method. For example, the heat treatment temperature when performing the above-mentioned intrinsic gettering is not limited to 1190 [°C], but is 800°C. It is sufficient if the temperature is [°C] or higher. However, for the purpose of shortening the processing time, it is preferable to set the temperature to 1000 [°C] or higher.

Furthermore, the proportion of hydrogen in the atmosphere during heat treatment is 10
It is not limited to [%] and can be changed as appropriate. Hydrogen 1001%] is also effective, but in this case there is a risk of explosion during high-temperature heat treatment, and it is necessary to take sufficient explosion-proof measures for the heat treatment equipment.

When high-temperature heat treatment is performed in nitrogen gas containing 10% hydrogen, a degraded layer appears to be formed on the wafer surface, and it is necessary to chemically remove more than 0.1 μTrL of the wafer surface after the heat treatment. there were. A considerable number of high-temperature heat treatments were performed in argon gas containing 20% hydrogen in a conventional airtight high-temperature heat treatment apparatus, but no accidents such as explosions occurred. Further, in addition to the above conditions such as the heat treatment temperature and the proportion of hydrogen, conditions such as the heat treatment time can also be changed as appropriate depending on the specifications. Here, the higher the temperature and the longer the time, the more completely the oxygen precipitates in the silicon disappear from the surface to the deeper region. That is, the thicker the oxide film, the higher the heat treatment temperature and the longer the heat treatment time.

In addition, although the above embodiment was applied to the manufacture of MOS capacitors, it can of course be applied to the manufacture of MOSFETs and other MO8 integrated circuits.
It can be applied to wafer processing of various semiconductor devices having other thermal oxide films. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) show M related to an embodiment of the method of the present invention.
2 is a cross-sectional view showing the manufacturing process of an OS capacitor, FIG. 2 is a schematic diagram showing an enlarged view of the part surrounded by the broken line P in FIG. It is a characteristic diagram showing the breakdown voltage failure rate of Goo 1 to oxide film. 11... 3i wafer, 11a... Wafer surface vicinity region, '11b... Wafer internal region, 12... Thermal oxide film (gate oxide film), 13... Phosphorus-doped polycrystalline silicon film . Applicant's agent Patent attorney Takehiko Suzuta Figure 1 Figure 2 ~\~ Figure 3

Claims (4)

[Claims] (1) In the silicon wafer processing method for eliminating oxygen near the surface of the silicon wafer containing interstitial oxygen, the silicon wafer is heated to 800 [°C] or more in an atmosphere of hydrogen or an inert gas containing hydrogen. Characteristic silicon wafer processing method. (2) The processing temperature of the silicon wafer is 1000 [℃]
A method for processing a silicon wafer according to claim 1, characterized in that the above settings are made. (3) The atmosphere during the heat treatment contains 20% hydrogen.
3. The method of processing a silicon wafer according to claim 1, wherein the atmosphere is an inert gas atmosphere containing: (4) The silicon wafer processing method according to claim 3, wherein argon is used as the inert gas.