Method for improving rapid heat treatment slip line

Abstract

The invention relates to a method for improving a rapid heat treatment slip line, which belongs to the technical field of silicon wafer processing, and comprises the following operation steps of: 1, cleaning a silicon wafer, and then drying the silicon wafer in a rotary spin-drying or infrared drying mode; step 2, entering a rapid heat treatment furnace, and during annealing of rapid heat treatment, mixing one or more of H2, Ar and O2 at the annealing temperature of 1100-1300 DEG C; and 3, the shape of the PIN of the rapid heat treatment equipment adopts a round head, and the contact area of the round head PIN and the silicon wafer is large, so that the influence of shear stress is reduced, and the generation of a slip line is reduced or avoided. And 4, after the silicon wafer is subjected to rapid heat treatment, single-sided or double-sided polishing is carried out to completely eliminate surface slip lines. And 5, cleaning the silicon wafer, and finally drying the silicon wafer in a rotary spin-drying or infrared drying mode. After the BMD and DZ depths are adjusted, the slip line of the silicon wafer is reduced or even avoided, and the GOI integration characteristic of the back-end process is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon wafer processing, and particularly relates to a method for improving slip lines in rapid thermal processing. Background Art

[0002] Heat treatment of large-diameter silicon wafers in an Ar or H2 atmosphere at temperatures up to 1300°C is becoming increasingly important. Rapid thermal processing can break through the limitation of the original oxygen content in single crystals and is a mature method developed by MEMC that can significantly improve the bulk microdefects (BMD) and the width of the denuded zone (DZ) in single-crystalline silicon wafers. Usually during high-temperature heating, thermal or gravitational forces during processing can generate shear stress in the wafer. In critical cases, the maximum resolvable shear stress caused by temperature-related loads may exceed the yield stress of the silicon crystal, resulting in dislocations and ultimately plastic deformation. Slip-free high-temperature processing is a key issue.

[0003] The traditional method for supporting silicon wafers in a rapid thermal processing chamber is 3-point or 4-point pin (PIN) support to reduce thermal non-uniformity and achieve a good temperature distribution within the silicon wafer. However, during the use of the pins, although the heating of the PIN pins can be achieved by laser to reduce the influence of the PINs on the temperature field, it is actually unavoidable. Especially for large-size silicon wafers, the PIN imprints are more obvious, and the slip lines after silicon wafer heat treatment are severe, deteriorating the characteristics such as the GOI of the device. Therefore, how to reduce the slip lines caused by the PIN pins is particularly important. Summary of the Invention

[0004] The present invention mainly addresses the deficiencies existing in the prior art and provides a method for improving slip lines in rapid thermal processing. After improving the shape of the PIN pins and performing polishing treatment, while adjusting the BMD and the depth of the DZ, the slip lines of the silicon wafer are reduced or even avoided, and the GOI integration characteristics of the backend process are improved.

[0005] The above technical problems of the present invention are mainly solved by the following technical solutions: A method for improving slip lines in rapid thermal processing includes the following operating steps: First step: Wash the silicon wafer, and then dry the silicon wafer by means of spin drying or infrared drying.

[0006] Second step: Enter a rapid thermal processing furnace. During the annealing of the rapid thermal processing, a gas mixture of one or more of H2, Ar, or O2 is used, and the annealing temperature is 1100 - 1300°C.

[0007] Third step: The morphology of the PIN pins inside the rapid thermal processing equipment is a round head. The round-head PIN pins have a large contact area with the silicon wafer, significantly improving the slip lines, reducing the influence of shear stress, and thus reducing or avoiding the generation of slip lines.

[0008] Step 4: After rapid thermal processing of the silicon wafer, perform single-sided or double-sided polishing to completely eliminate surface slip lines.

[0009] Step 5: Wash the silicon wafer again, and finally dry the silicon wafer by spin drying or infrared drying.

[0010] Preferably, the silicon wafer is washed by tank wet cleaning, single-wafer wet O3-HF cyclic cleaning or RCA cleaning to remove organic substances, particles and metal residues on the surface of the silicon wafer, reaching a level of 1E10 atoms / cm2.

[0011] Preferably, the RCA cleaning mainly includes four cleaning solutions, namely SPM solution, DHF solution, APM solution and HPM solution; the SPM solution uses a mixture of sulfuric acid and hydrogen peroxide, which has strong oxidation ability at high temperature and can remove heavy organic contamination and part of metals; the DHF solution is also called diluted hydrofluoric acid, which is used to remove the natural oxide film on the surface of the silicon wafer and dissolve the metal ions attached to the oxide film at the same time; the APM solution is the SC-1 solution, a mixture of ammonia water and hydrogen peroxide, which is mainly used to remove particles, metals and organic substances; the HPM solution is the SC-2 solution, a mixture of hydrochloric acid and hydrogen peroxide, which is mainly used to remove metal impurities.

[0012] Preferably, the DHF+O3 combination is used to remove surface metals. O3 oxidizes the silicon on the surface of the silicon wafer, and the DHF solution corrodes the surface SiO2, and at the same time removes part of the metals and particle contamination adsorbed by SiO2. The equation is 4HF + SiO2 = SiF4 + 2H2O. Then, after cleaning with O3 and ultrapure water, the surface of the silicon wafer becomes hydrophilic. Finally, the silicon wafer is dried. The O3 concentration during O3+HF cleaning is 15-25 mg / L, the HF concentration is 1%±0.2, the process temperature is 25±3°C, the flow rate is 1.2±0.1 L / min, the process time is 20±10 S, repeated 10 times, and finally rinsed with ultrapure water for 20 s.

[0013] Preferably, the gas flow rate during rapid thermal processing is 5-40 slm, and the heat treatment time is 2S-60S. slm is a unit used to represent liters per minute under standard conditions (0°C, 1 atm).

[0014] Preferably, the polishing depth of CMP single-sided is 1-10 μm, and the polishing depth of CMP double-sided is controlled at 2-20 μm; CMP polishing, also known as chemical mechanical polishing, combines chemical corrosion and mechanical polishing to remove uneven materials on the surface of the silicon wafer and achieve atomic-level flatness.

[0015] Preferably, the rapid thermal processing is infrared lamp heating with a heating rate of 10°C / s to 80°C / s. In the rapid thermal processing equipment, the silicon wafer is supported by three thumbtacks. After the top shape of the thumbtack is changed from a pointed head to a round head, the contact area increases from small to large, reducing the shear stress and avoiding the generation of slip.

[0016] The present invention can achieve the following effects: The present invention provides a method for improving slip lines in rapid thermal processing. Compared with the prior art, after improving the shape of the PIN thumbtack and performing polishing treatment, after adjusting the BMD and DZ depths, the slip lines of the silicon wafer are reduced or even avoided, and the GOI integration characteristics of the back-end process are improved. Specific embodiments

[0017] The technical solution of the invention will be further specifically described below through embodiments.

[0018] Embodiment: A method for improving slip lines in rapid thermal processing includes the following operating steps: First step: The silicon wafer is washed and then dried by spin drying or infrared drying.

[0019] Second step: Enter the rapid thermal processing furnace. During the annealing of the rapid thermal processing, a gas mixture of one or more of H2, Ar, or O2 is used, and the annealing temperature is 1100 - 1300°C. The gas flow rate during rapid thermal processing is 5 - 40 slm, and the heat treatment time is 2S - 60S.

[0020] Third step: The morphology of the PIN pins inside the rapid thermal processing equipment uses round heads. The round-headed PIN pins have a large contact area with the silicon wafer, reducing the influence of shear stress, thereby reducing or avoiding the generation of slip lines. The rapid thermal processing is infrared lamp heating with a heating rate of 10°C / s to 80°C / s. In the rapid thermal processing equipment, the silicon wafer is supported by three thumbtacks. After the top shape of the thumbtack is changed from a pointed head to a round head, the contact area increases from small to large, reducing the shear stress and avoiding the generation of slip.

[0021] Fourth step: After rapid thermal processing of the silicon wafer, single-sided or double-sided polishing is performed to completely eliminate surface slip lines.

[0022] The polishing depth for CMP single-sided is 1 - 10 μm, and the polishing depth for CMP double-sided is controlled at 2 - 20 μm; CMP polishing is also called chemical mechanical polishing, which combines chemical corrosion and mechanical polishing to remove uneven materials on the surface of the silicon wafer and achieve atomic-level flatness.

[0023] Fifth step: The silicon wafer is washed again and finally dried by spin drying or infrared drying.

[0024] The cleaning of silicon wafers adopts tank wet cleaning, single-wafer wet O3-HF cyclic cleaning or RCA cleaning to remove organic substances, particles and metal residues on the surface of the silicon wafers, reaching a level of 1E10 atoms / cm2. RCA cleaning mainly includes four cleaning solutions, namely SPM solution, DHF solution, APM solution and HPM solution; the SPM solution uses a mixture of sulfuric acid and hydrogen peroxide, which has strong oxidizing ability at high temperature and can remove heavy organic contamination and some metals; the DHF solution is also called diluted hydrofluoric acid, which is used to remove the natural oxide film on the surface of the silicon wafer and dissolve the metal ions attached to the oxide film at the same time; the APM solution is the SC-1 solution, a mixture of ammonia water and hydrogen peroxide, which is mainly used to remove particles, metals and organic substances; the HPM solution is the SC-2 solution, a mixture of hydrochloric acid and hydrogen peroxide, which is mainly used to remove metal impurities.

[0025] The DHF+O3 combination is used to remove surface metals. O3 oxidizes the silicon on the surface of the silicon wafer, and the DHF solution corrodes the surface SiO2, and at the same time removes some metals and particle contamination adsorbed by SiO2. The chemical equation is 4HF+SiO2=SiF4+2H2O. Then, after cleaning with O3 and ultrapure water, the surface of the silicon wafer becomes hydrophilic. Finally, the silicon wafer is dried. When performing O3+HF cleaning, the O3 concentration is 15-25 mg / L, the HF concentration is 1%±0.2, the process temperature is 25±3°C, the flow rate is 1.2±0.1 L / min, the process time is 20±10 s, repeated 10 times, and finally rinsed with ultrapure water for 20 s.

[0026] In summary, for the method of improving the rapid thermal processing slip lines, after improving the shape of the PIN thimble and performing polishing treatment, and for the purpose of adjusting the BMD and DZ depths, the slip lines of the silicon wafers are reduced or even avoided, and the GOI integration characteristics of the backend process are improved.

[0027] The above are only specific embodiments of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A method for improving slip lines in rapid thermal processing, characterized in that It includes the following operation steps: Step 1: Wash the silicon wafer, and then dry the silicon wafer by spin drying or infrared drying; Step 2: Enter the rapid thermal processing furnace. When annealing by rapid thermal processing, one or more gases among H2, Ar or O2 are used for mixing, and the annealing temperature is 1100 - 1300 °C; Step 3: The morphology of the PIN pins inside the rapid thermal processing equipment adopts round heads. The round - head PIN pins have a large contact area with the silicon wafer, reducing the influence of shear stress, thereby reducing or avoiding the generation of slip lines; Step 4: After rapid thermal processing of the silicon wafer, perform single - side or double - side polishing to completely eliminate surface slip lines; Step 5: Wash the silicon wafer again, and finally dry the silicon wafer by spin drying or infrared drying.

2. The method for improving the slip lines of rapid thermal processing according to claim 1, wherein: The silicon wafer is washed by tank - type wet cleaning, single - wafer wet O3 - HF cyclic cleaning or RCA cleaning to remove organic substances, particles and metal residues on the surface of the silicon wafer, reaching a level of 1E10 atoms / cm2.

3. The method for improving the slip lines in rapid thermal processing according to claim 2, wherein: RCA cleaning mainly includes four cleaning solutions, namely SPM solution, DHF solution, APM solution and HPM solution; The SPM solution uses a mixture of sulfuric acid and hydrogen peroxide, which has strong oxidation ability at high temperature to remove heavy organic contamination and some metals; The DHF solution is also called diluted hydrofluoric acid, which is used to remove the native oxide film on the surface of the silicon wafer and dissolve the metal ions attached to the oxide film at the same time; The APM solution is the SC - 1 solution, a mixture of ammonia water and hydrogen peroxide, which is mainly used to remove particles, metals and organic substances; The HPM solution is the SC - 2 solution, a mixture of hydrochloric acid and hydrogen peroxide, which is mainly used to remove metal impurities.

4. The method for improving slip lines in rapid thermal processing according to claim 2, wherein: Use the DHF + O3 combination to remove surface metals. O3 oxidizes the silicon on the surface of the silicon wafer, and the DHF solution corrodes the surface SiO2, and at the same time removes some metals and particle contamination adsorbed by SiO2. The chemical equation is 4HF+SiO2 = SiF4 + 2H2O. Then, after cleaning with O3 and ultrapure water, the surface of the silicon wafer becomes hydrophilic. Finally, the silicon wafer is dried. When performing O3 + HF cleaning, the O3 concentration is 15 - 25 mg / L, the HF concentration is 1% ± 0.2, the process temperature is 25 ± 3 °C, the flow rate is 1.2 ± 0.1 L / min, the process time is 20 ± 10 s, repeated 10 times, and finally rinsed with ultrapure water for 20 s.

5. The method for improving slip lines in rapid thermal processing according to claim 1, wherein: The gas flow rate during rapid thermal processing is 5 - 40 slm, and the heat treatment time is 2 s - 60 s.

6. The method for improving slip lines in rapid thermal processing according to claim 1, wherein: The polishing depth of CMP single - side is 1 - 10 μm, and the polishing depth of CMP double - side is controlled at 2 - 20 μm; CMP polishing is also called chemical mechanical polishing, which combines two methods of chemical corrosion and mechanical grinding to achieve the purpose of removing uneven materials on the surface of the silicon wafer and achieving atomic - level flatness.

7. The method for improving slip lines in rapid thermal processing according to claim 1, wherein: Rapid thermal processing is infrared lamp heating, and the heating speed is 10 °C / s - 80 °C / s. In the rapid thermal processing equipment, the silicon wafer is supported by three thimbles. After the top shape of the thimbles is changed from pointed to round, the contact area increases from small to large, reducing the shear stress and avoiding the generation of less slip.