CN1269186C - Carbon doped silicon sheet with internal impurity absorbing function and production thereof - Google Patents

Abstract

The carbon-doped silicon wafer with internal gettering function of the present invention has an oxygen concentration of 5-15×10 ¹⁷ cm ^-3 and a carbon concentration of 5-30×10 ¹⁶ cm ^-3 . The preparation steps are as follows: 1) The Czochralski method is used to grow the crystal, and the carbon-doped carbon with the oxygen concentration of 5-15×10 ¹⁷ cm ^-3 and the carbon concentration of 5-30×10 ¹⁶ cm ^-3 is obtained by controlling the process parameters in the crystal growth process. Silicon wafers; 2) Put carbon-doped silicon wafers with an oxygen concentration of 5 to 15×10 ¹⁷ cm ^-3 and a carbon concentration of 5 to 30×10 ¹⁶ cm ^-3 in a heat treatment furnace, under the protection of argon or nitrogen, First keep warm at 1100-1250°C for 1-3 hours, then keep warm at 600-900°C for 4-50 hours, and then keep warm at 1000-1200°C for 4-30 hours. The Czochralski silicon chip invented has a high internal gettering ability and has a good gettering effect on harmful metals. The silicon chip is applied to integrated circuits and can increase the yield of integrated circuits.

Description

A method for preparing a carbon-doped silicon wafer with internal gettering function

technical field

The invention relates to a method for preparing a carbon-doped silicon wafer with an internal gettering function, belonging to the field of semiconductors.

Background technique

In the early stages of silicon crystal research and production, researchers found that high concentrations of carbon in crystals would seriously damage the performance of diodes, transistors and other devices. Carbon can not only affect the precipitation of oxygen in silicon wafers or even precipitate SiC, reducing the quality of silicon wafers, but also It will cause the breakdown voltage of the device to be greatly reduced and the leakage current to increase, which will have a negative impact on the quality of the device. Therefore, many researchers believe that the introduction of carbon impurities should be avoided as much as possible during the crystal growth process. After years of hard work, in the current high-purity zone fused silicon single crystals and Czochralski silicon single crystals for integrated circuits, the carbon concentration is generally controlled below 2.5-5×10 ¹⁵ cm ^-3 , which is detected by infrared spectrometers. Below the limit. Therefore, high-carbon silicon single crystals and silicon wafers have not been used as silicon materials for integrated circuits.

With the continuous development of semiconductor device technology, integrated circuit technology no longer imitates the use of the overall high-purity and defect-free silicon single crystal required by early device technology, but only requires the formation of a 2-5 μm high-purity and defect-free region near the surface of the silicon wafer. , called clean area or clean area. To achieve such a purpose, external gettering or internal gettering techniques are usually used.

At present, crystals grown by the Czochralski method (Czochralski method) are generally controlled by controlling the pulling speed of the crystal ingot, the rotation speed of the crystal ingot, the rotation speed of the crucible, the gas pressure and gas composition in the growth furnace, etc. Process parameters to achieve precise control of oxygen content and carbon content in silicon wafers. The fundamental reason why integrated circuits are almost always made of Czochralski silicon wafers is that Czochralski silicon wafers contain oxygen impurities on the order of 10 ¹⁸ cm ^-3 , which can enhance the mechanical strength of Czochralski silicon wafers and reduce the The warpage caused by the thermal cycle does not affect the overlay accuracy of the photolithography process; on the other hand, through proper heat treatment, oxygen impurities will precipitate in the silicon wafer and form secondary defects (BMD), while near the surface of the silicon wafer The region forms a defect-free region due to the out-diffusion of oxygen, which is the so-called internal gettering process.

The internal defect area formed by the gettering process in the silicon wafer can absorb the inevitable metal contamination in the device manufacturing process, and the clean area near the surface of the silicon wafer can be used as the active area of the integrated circuit. The improvement of film rate is of great significance. The internal gettering phenomenon of Czochralski silicon wafer was first reported in 1976 (Rozgonyi, G.A., et al., J.Electrochem.Soc.123, 1910 (1976)), and the internal gettering concept was proposed in 1977 (Tan , T.Y., et al., Appl. Phys. Lett. 30, 175 (1977)). After several years of research, the so-called "high-low-high" three-step annealing standard internal gettering process (Nagasawa, et al., Appl. Phys. Lett. 37, 622 (1980); Peibt, H. , et al., Phys.Stat.Sol., A 68, 253(1981); Peibt, H., et al., Phys.Stat.Sol., A 68, 253(1981)). That is: the first step is annealing at a temperature higher than 1100°C, so that the oxygen impurities in the near-surface area of the silicon wafer are diffused to form a clean area. This step is usually carried out under an inert atmosphere; the second step is at a low temperature of 600-750°C. Annealing to form the core of oxygen precipitation in the silicon wafer; the third step is annealing at a medium and high temperature of 1000-1100 ° C to make the oxygen precipitation core formed in the second step annealing grow and form secondary defects. Thus, a defect-free clean area is formed near the surface of the silicon wafer, and micro-defects (oxygen precipitation and secondary defects) with high density are formed in the body. The strength of the internal gettering ability can be expressed by the width of the clean area and the density of oxygen precipitation.

The density of micro-defects in the existing Czochralski silicon wafer is low, and the gettering effect on harmful metals needs to be further improved.

Contents of the invention

The purpose of the present invention is to propose a new concept of using high-carbon silicon single crystal to provide a method for preparing carbon-doped silicon wafers with higher internal gettering function.

The preparation method of the carbon-doped silicon chip with internal gettering function of the present invention, its steps are as follows:

1) The Czochralski method is used to grow the crystal, and the carbon-doped silicon wafer with the oxygen concentration of 5-15×10 ¹⁷ cm ^-3 and the carbon concentration of 5-30×10 ¹⁶ cm ^-3 is obtained by controlling the process parameters during the crystal growth process;

2) Put a carbon-doped silicon wafer with an oxygen concentration of 5 to 15×10 ¹⁷ cm ^-3 and a carbon concentration of 5 to 30×10 ¹⁶ cm ^-3 in a heat treatment furnace. Heat preservation at ~1250°C for 1-3 hours, then heat preservation at 600-900°C for 4-50 hours, and then heat preservation at 1000-1200°C for 4-30 hours.

The invented Czochralski silicon wafer contains a relatively high carbon concentration, because carbon can promote oxygen precipitation, after the internal gettering process, a clean area with a certain width and no defects is formed near the surface of the silicon wafer, and the microscopic particles in the body The density of defects (oxygen precipitation and secondary defects) is significantly improved. Therefore, it has a higher internal gettering ability and has a better gettering effect on harmful metals. The silicon wafer is used in integrated circuits, which can improve the yield of integrated circuits .

Description of drawings

Figure 1 is a photomicrograph of the distribution of defects on the cleavage plane of a common CZ-Si wafer (CZ-Si) and a carbon-doped Czochralski silicon wafer (HCCZ-Si) after three-step internal gettering heat treatment, where Figure (a) is The photomicrograph of CZ-Si magnified 200 times, picture (b) is the photomicrograph of HCCZ-Si magnified 200 times, picture (c) is the photomicrograph of CZ-Si magnified 1000 times, picture (d) is the micrograph of HCCZ-Si Micrograph of Si at 1000X magnification.

Detailed ways

Example 1

A 3-inch carbon-doped Czochralski silicon wafer (HCCZ-Si) grown under the protection of argon gas is selected, the carbon concentration is 1×10 ¹⁷ cm ^-3 , the oxygen concentration is 8×10 ¹⁷ cm ^-3 , and the resistivity is 10 ohm.cm. In order to form a clean area and a bulk defect area in the silicon wafer, the silicon wafer is kept in a heat treatment furnace at 1200°C for 2 hours, then at 750°C for 16 hours, and after the treatment is completed at 1050°C for 16 hours. All heat treatments were performed under an argon atmosphere. After heat treatment, the silicon wafer was cleaved and etched in Sirtl preferential etching solution for 5 minutes, and then the distribution of defects on the cleavage plane was observed and photographed with an OLYMPUS MX50 microscope.

For comparison, an ordinary Czochralski silicon single crystal (CZ-Si) with the same oxygen concentration and resistivity, and a carbon concentration below the infrared detection limit, was also subjected to the same treatment. Fig. 1 has provided the photos of the defect distribution of the cleavage plane of ordinary Czochralski silicon wafer (CZ-Si) and carbon-doped Czochralski silicon wafer (HCCZ-Si) after the heat treatment as mentioned above, wherein graph (a) and (b) is a micrograph at 200X magnification, and panels (c) and (d) are micrographs at 1000X magnification. From Figure 1(a) and (b), it can be seen that after three-step gettering heat treatment process, clean (DZ) zone and bulk microdefect (BMD) zone are formed in both CZ-Si and HCCZ-Si , and the width of the clean area is basically similar, all of which can reach more than 20 μm, indicating that the carbon-doped silicon wafer proposed by the present invention can meet the requirements of large-scale integrated circuits for forming a high-purity and defect-free thin layer near the surface of the silicon wafer.

It can be seen from Figure 1(c) and (d) that after the three-step internal gettering process, HCCZ-Si forms denser oxygen precipitates than CZ-Si, and in the bulk microdefect (BMD) region The formation of higher-density micro-defects will facilitate internal gettering and improve the gettering effect of silicon wafers on harmful metals in the device manufacturing process.

Example 2

A 3-inch carbon-doped Czochralski silicon wafer grown under the protection of argon gas was selected, the carbon concentration was 5×10 ¹⁶ cm ^-3 , the oxygen concentration was 15×10 ¹⁷ cm ^-3 , and the resistivity was 1 ohm.cm. Put the silicon wafer into the heat treatment furnace at 1150°C and keep it warm for 2 hours, then keep it at 650°C for 50 hours, and keep it at 1100°C for 6 hours after the treatment. All heat treatments were performed under an argon atmosphere. A silicon wafer with internal gettering ability can be obtained, with a certain width of defect-free clean area near the surface and a certain density of micro-defects (oxygen precipitation and secondary defects) in the body.

Example 3

A 4-inch carbon-doped Czochralski silicon wafer grown under the protection of argon gas was selected, the carbon concentration was 3×10 ¹⁷ cm ^-3 , the oxygen concentration was 6×10 ¹⁷ cm ^-3 , and the resistivity was 20 ohm.cm. Put the silicon wafer into the heat treatment furnace at 1250°C and keep it warm for 0.5 hours, then keep it at 850°C for 10 hours, and keep it at 1200°C for 20 hours after the treatment. All heat treatments were performed under an argon atmosphere. It is also possible to obtain a silicon wafer with internal gettering ability, a clean area with a certain width and no defects near the surface, and a certain density of micro-defects (oxygen precipitation and secondary defects) in the body.

Claims (1)

1. preparation method with carbon doped silicon sheet of internal impurity absorbing function is characterized in that step is as follows:

1) adopt the Grown by CZ Method crystal, obtaining oxygen concentration by technological parameter in the control crystal growing process is 5～15 * 10 ¹⁷Cm ^-3, concentration of carbon is 5～30 * 10 ¹⁶Cm ^-3Carbon doped silicon sheet;

2) be 5～15 * 10 with oxygen concentration ¹⁷Cm ^-3, concentration of carbon is 5～30 * 10 ¹⁶Cm ^-3Carbon doped silicon sheet, under argon gas or protection of nitrogen gas, in heat-treatment furnace earlier 1100～1250 ℃ of insulations 1～3 hour, then 600～900 ℃ of insulations 4～50 hours, again 1000～1200 ℃ of insulations 4～30 hours.

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