Method for controlling BMD of heavily boron-doped substrate and lightly boron-doped epitaxial wafer through RTP

Abstract

The invention relates to a method for controlling BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer through RTP, which belongs to the technical field of silicon wafer processing, and comprises the following operation steps of: 1, drawing a single crystal by adopting a Czochralski method, and doping Bo metal during crystal drawing; and 2, slicing, grinding and thinning, polishing, cleaning and epitaxy processes are carried out. Step 3, dividing the silicon wafers after completion into three groups A, B and C for annealing treatment; and meanwhile, a group of reference silicon wafers without RTP annealing treatment are manufactured. And 4, carrying out low-temperature heat treatment, wherein the low-temperature treatment is used for promoting nucleation of oxygen precipitation. And 5, performing high-temperature heat treatment which is used for promoting the growth of an oxygen precipitation nucleation center in the silicon wafer body so as to form high-density oxygen precipitation and induced defects thereof in the silicon wafer body. The method improves the yield of silicon wafers, greatly shortens the time consumed in the annealing process in the manufacturing of an integrated circuit, meets the actual requirement for low temperature in the manufacturing process of the integrated circuit, reduces the technological process, and saves the cost.

Description

Technical Field

[0001] The invention relates to the technical field of silicon wafer processing, and in particular to a method for controlling a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer BMD through RTP. Background Art

[0002] The raw materials required for CIS chips are lightly boron-doped epitaxy grown on heavily boron-doped substrates. CIS chips are extremely sensitive to impurities in the raw material substrates, requiring the substrate to have a low metal content and a certain metal capture capability.

[0003] Oxygen is one of the main impurities in Cz (direct-pull) Si (silicon) single crystals. It is well known that the supersaturated interstitial oxygen in the Si wafer will precipitate to form oxygen precipitates during the thermal cycle of device manufacturing. The surrounding area is subjected to tensile stress and induces thermal micro defects of a certain density and size in the Si wafer body - bulk micro defects (Bulk Micro Defects: BMD). The internal impurity of direct-pull silicon wafers is to make the oxygen precipitation process only occur in the silicon wafer body through appropriate heat treatment process. The generated oxygen precipitation and its induced defects can remove metal contamination on the surface of the silicon wafer.

[0004] Oxygen exists in silicon in two forms, one is in the form of interstitial oxygen, and the other is in the form of oxygen precipitation. When the device is heat treated under certain conditions, once the interstitial oxygen in silicon is in a supersaturated state, it will aggregate to form oxygen precipitation. Oxygen precipitation is of great significance to the device: on the one hand, oxygen precipitation can pin dislocations and improve the mechanical properties of silicon wafers; on the other hand, oxygen precipitation can be used for the internal impurities such as metals, remove metal contamination in the device, and thus improve the yield of the device. Its main action process is: on the one hand, impurities use oxygen precipitation as the core of precipitation; on the other hand, oxygen precipitation introduces a stress field in the silicon single crystal, thereby adsorbing impurities around the oxygen precipitation.

[0005] Rapid Thermal Process (RTP) can control oxygen precipitation because it can introduce vacancies into silicon wafers and control the depth distribution of their concentration. In recent years, RTP technology has been successfully applied to defect engineering of large-diameter silicon single crystal materials, especially the application of RTP to the internal impurity process of silicon wafers, forming a defect-free clean area in the active area of ​​the device on the surface of the silicon wafer, and forming a reasonable defect-intensive area in the body, the so-called "Magic Clean Zone (MDZ)". Summary of the invention

[0006] The present invention mainly solves the deficiencies in the prior art and provides a method for controlling heavily boron-doped substrates and lightly boron-doped epitaxial wafers BMD through RTP, which improves the yield of silicon wafers, greatly shortens the time consumed by the annealing process in integrated circuit manufacturing, and also meets the actual requirements for low temperature in the integrated circuit manufacturing process, reduces the process and thus saves costs.

[0007] The above technical problems of the present invention are mainly solved by the following technical solutions: A method for controlling the BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer by RTP, comprising the following steps: Step 1: Use the Czochralski method to pull a single crystal, add Bo metal during crystal pulling, and control the resistivity at 10-20mΩ·cm.

[0008] Step 2: After the single crystal is pulled, it is sliced, ground and thinned, polished, cleaned and epitaxially processed.

[0009] Step 3: Divide the finished silicon wafers into three groups, ABC, for annealing; at the same time, make a group of reference silicon wafers without RTP annealing, recorded as condition D.

[0010] The rapid annealing furnace, i.e., the RTP annealing temperature is 1250° C., the annealing time is 30 seconds, and the annealing atmosphere is oxygen, which is recorded as condition A.

[0011] The rapid annealing furnace, i.e., the RTP annealing temperature is 1250° C., the annealing time is 30 seconds, and the annealing atmosphere is nitrogen, which is recorded as condition B.

[0012] The rapid annealing furnace, i.e., the RTP annealing temperature is 1250° C., the annealing time is 30 seconds, and the annealing atmosphere is argon gas, which is recorded as condition C.

[0013] Step 4: Perform low temperature heat treatment on the three groups of ABC that have completed annealing treatment. The role of low temperature treatment is to promote the nucleation of oxygen precipitation.

[0014] Step 5: Perform high-temperature heat treatment on the three groups of ABC that have completed low-temperature heat treatment. The purpose of high-temperature treatment is to promote the growth of oxygen precipitation nucleation centers in the silicon wafer body, so as to form high-density oxygen precipitation and its induced defects in the silicon wafer body.

[0015] Preferably, a relatively high pulling speed is adopted when pulling the single crystal, and the pulling speed is greater than 0.5 mm / min.

[0016] Preferably, during crystal pulling, the density of oxidation induced defects, namely OISF, is controlled to be 0, and the oxygen content is appropriately increased during crystal pulling, from 10 to 16 ppma, so as to form high-density bulk micro defects, namely BMD.

[0017] As a preferred method, the slice thickness is 875μm±10μm; the thickness of the silicon wafer after polishing and cleaning is 775±10μm; the content of various metals on the surface of the silicon wafer after cleaning is controlled below 1E+8ea / cm3 to avoid the diffusion of surface metal into the body during the annealing process.

[0018] Preferably, the low temperature heat treatment temperature is 600-800°C and the low temperature treatment time is 4 hours.

[0019] Preferably, the high temperature heat treatment temperature is 1100° C. and the high temperature treatment time is 16 hours.

[0020] The present invention can achieve the following effects: The present invention provides a method for controlling heavily boron-doped substrates and lightly boron-doped epitaxial wafers BMD through RTP. Compared with the prior art, the method improves the yield rate of silicon wafers, greatly shortens the time consumed by the annealing process in integrated circuit manufacturing, and also meets the actual requirements for low temperature in the integrated circuit manufacturing process, reduces the process and thus saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0022] The technical solution of the invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0023] Embodiment: A method for controlling the BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer by RTP, comprising the following steps: Step 1: Use the Czochralski method to pull a single crystal, and use a relatively high pulling speed when pulling a single crystal, the pulling speed is greater than 0.5mm / min. Bo metal is added during crystal pulling, and the resistivity is controlled at 10-20mΩ·cm.

[0024] During crystal pulling, the density of oxidation induced defects, namely OISF, is controlled to be 0, and the oxygen content is appropriately increased from 10 to 16 ppma to form high-density bulk micro defects, namely BMD.

[0025] Step 2: After the single crystal is pulled, it is sliced, ground and thinned, polished, cleaned and epitaxially processed.

[0026] The slice thickness is 875μm±10μm; the thickness of the silicon wafer after polishing and cleaning is 775±10μm; the content of various metals on the surface of the silicon wafer after cleaning is controlled below 1E+8ea / cm3.

[0027] Step 3: Divide the finished silicon wafers into three groups, ABC, for annealing; at the same time, make a group of reference silicon wafers without RTP annealing, recorded as condition D.

[0028] The rapid annealing furnace, i.e., the RTP annealing temperature is 1250° C., the annealing time is 30 seconds, and the annealing atmosphere is oxygen, which is recorded as condition A.

[0029] The rapid annealing furnace, i.e., the RTP annealing temperature is 1250° C., the annealing time is 30 seconds, and the annealing atmosphere is nitrogen, which is recorded as condition B.

[0030] The rapid annealing furnace, i.e., the RTP annealing temperature is 1250° C., the annealing time is 30 seconds, and the annealing atmosphere is argon gas, which is recorded as condition C.

[0031] Step 4: Perform low temperature heat treatment on the three groups of ABC after annealing treatment. The low temperature heat treatment temperature is 600-800℃ and the low temperature treatment time is 4 hours.

[0032] Step 5: Perform high temperature heat treatment on the three groups of ABC that have completed low temperature heat treatment. The temperature of high temperature heat treatment is 1100℃ and the high temperature treatment time is 16 hours.

[0033] The BMD results of each group are as follows Figure 1 As shown, Group A uses oxygen as the atmosphere for RTP, oxidizes the surface of the silicon wafer, drives silicon atoms to diffuse into the body of the silicon wafer in the form of self-interstitial, and the self-interstitial silicon atoms will hinder the formation of oxygen precipitation, controlling the low BMD density. Group B uses nitrogen as the atmosphere for RTP, nitrides the surface of the silicon wafer, and increases the vacancy density in the body of the silicon wafer, which is conducive to the formation of BMD and controls the formation of high BMD density. Group C uses argon as the atmosphere for RTP, which can simultaneously stimulate the density of holes and interstitial silicon atoms in the body, but the diffusion rate of self-interstitial silicon atoms is relatively faster, so the improvement of BMD is not as good as that of nitrogen atmosphere. Group D is a comparison group without RTP. Control the increase or decrease of BMD of heavily boron-doped substrates and lightly boron-doped epitaxial wafers to obtain the target BMD.

[0034] Since the formation of oxygen precipitation includes two steps: nucleation and growth. There are two ways of nucleation of oxygen precipitation: homogeneous nucleation and heterogeneous nucleation. Among them, the supersaturation of oxygen is the driving force for homogeneous nucleation. At a lower temperature, the interstitial oxygen is in a supersaturated state and is easy to aggregate to form oxygen precipitation. The oxygen precipitation in heterogeneous nucleation uses the defects in silicon as the nucleation center of oxygen precipitation, providing a place for the aggregation of interstitial oxygen, thereby promoting the nuclear growth of oxygen precipitation. The growth of oxygen precipitation refers to the fact that the oxygen precipitation core larger than the critical size at a certain temperature will further aggregate interstitial oxygen atoms and grow, and the oxygen precipitation smaller than the critical size will gradually dissolve and disappear.

[0035] In summary, the method of controlling the BMD of heavily boron-doped substrates and lightly boron-doped epitaxial wafers through RTP improves the yield of silicon wafers, greatly shortens the time consumed by the annealing process in integrated circuit manufacturing, and also meets the actual requirements for low temperature in the integrated circuit manufacturing process, reduces the process and thus saves costs.

[0036] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are included in the patent scope of the present invention.

Claims

1. A method for controlling the BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer by RTP, characterized in that The steps are as follows: Step 1: Use the Czochralski method to pull a single crystal, add Bo metal during crystal pulling, and control the resistivity to 10-20 mΩ·cm; Step 2: After the single crystal is pulled, it is sliced, ground, thinned, polished, cleaned and epitaxially processed; Step 3: Divide the finished silicon wafers into three groups, ABC, for annealing. At the same time, make a group of reference silicon wafers without RTP annealing, which is recorded as condition D. The rapid annealing furnace, i.e., the RTP annealing temperature is 1250°C, the annealing time is 30 seconds, and the annealing atmosphere is oxygen, which is recorded as condition A; The rapid annealing furnace, i.e., the RTP annealing temperature is 1250°C, the annealing time is 30 seconds, and the annealing atmosphere is nitrogen, which is recorded as condition B; The rapid annealing furnace, i.e., the RTP annealing temperature is 1250°C, the annealing time is 30 seconds, and the annealing atmosphere is argon, which is recorded as condition C; Step 4: Perform low temperature heat treatment on the three groups of ABC that have completed annealing treatment; Step 5: Perform high temperature heat treatment on the three groups of ABC that have completed low temperature heat treatment.

2. The method for controlling the BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer by RTP according to claim 1, characterized in that: A relatively high pulling speed is used when pulling a single crystal, and the pulling speed is greater than 0.5 mm / min.

3. The method for controlling the BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer by RTP according to claim 1, characterized in that: During crystal pulling, the density of oxidation induced defects, namely OISF, is controlled to be 0, and the oxygen content is appropriately increased from 10 to 16 ppma to form high-density bulk micro defects, namely BMD.

4. The method for controlling the heavily boron-doped substrate and the lightly boron-doped epitaxial wafer BMD by RTP according to claim 1, characterized in that: The slice thickness is 875μm±10μm; the thickness of the silicon wafer after polishing and cleaning is 775±10μm; the content of various metals on the surface of the silicon wafer after cleaning is controlled below 1E+8ea / cm3.

5. The method for controlling the BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer by RTP according to claim 1, characterized in that: The low temperature heat treatment temperature is selected to be 600-800°C, and the low temperature treatment time is 4 hours.

6. The method for controlling the BMD of a heavily boron-doped substrate and a lightly boron-doped epitaxial wafer by RTP according to claim 1, characterized in that: The high temperature heat treatment temperature is 1100°C and the high temperature treatment time is 16 hours.

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