Method of manufacturing LPCVD in-situ doped polysilicon thin film
By adjusting the pressure and temperature of the LPCVD furnace tube and using silane and phosphine gases to deposit polycrystalline silicon films, the problem of defects in polycrystalline silicon films on crystal boats with small tank spacing was solved, and the quality of polycrystalline silicon films was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUA HONG SEMICON WUXI LTD
- Filing Date
- 2024-01-17
- Publication Date
- 2026-06-02
AI Technical Summary
When using a crystal boat with more slots and smaller slot spacing, LPCVD in-situ doped polycrystalline silicon furnace tubes exhibit severe bulging or buried layer granular defects.
By adjusting the pressure and temperature of the furnace tube cavity, silane and phosphine gases are used to deposit doped polycrystalline silicon films under different pressures to form first and second polycrystalline silicon films of appropriate thickness to reduce defects.
This effectively reduces process defects in crystal boats with many slots and small slot spacing, and improves the quality of polycrystalline silicon thin films.
Smart Images
Figure CN117947402B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films. Background Technology
[0002] Vertical furnace tube machines are one of the important process equipment in the front-end processes of semiconductor production lines. They are used for diffusion, oxidation, annealing and alloying processes in industries such as large-scale integrated circuits, discrete devices, power electronics, optoelectronic devices and optical fibers.
[0003] Due to the limited height of cleanrooms and the limited height of vertical furnaces, in order to more effectively improve the utilization efficiency of the equipment, a crystal boat with more slots and smaller slot spacing can be used to load a larger number of wafers. This also means that the spacing between wafers on the crystal boat is smaller, but this will bring various process problems.
[0004] Please see Figure 2 When using a crystal boat with more slots and smaller slot spacing in an LPCVD in-situ doped polycrystalline silicon furnace tube (in the example, the crystal boat height was the same, but the slot spacing was reduced from 6.5mm to 5.32mm, and the number of slots was reduced from 143 to 170), more serious defects will occur. Please refer to [link to relevant documentation]. Figure 2 The defects are specifically manifested as bulging or buried granular defects, with sizes ranging from approximately 0.2 to 2.0 μm.
[0005] To address the aforementioned issues, a novel method for manufacturing in-situ doped polycrystalline silicon thin films using LPCVD is required. Summary of the Invention
[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films, which solves the problem that serious defects occur when using a crystal boat with more slots and smaller slot spacing in the LPCVD in-situ doped polycrystalline silicon furnace tube.
[0007] To achieve the above and other related objectives, the present invention provides a method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films, comprising:
[0008] Step 1: Provide a furnace tube for in-situ doping of polycrystalline silicon by LPCVD. The cavity of the furnace tube is provided with multiple crystal boats with a slot spacing less than or equal to the target distance. A substrate is provided on the crystal boat.
[0009] Step 2: Adjust the pressure in the cavity to 0.6 to 0.8 Torr and the temperature to 560℃-580℃, then introduce silane and phosphine into the cavity to form a doped first polycrystalline silicon film on the substrate.
[0010] Step 3: Adjust the pressure in the cavity to 0.2 to 0.4 Torr and the temperature to 560℃-580℃. Then, introduce silane and phosphine into the cavity to form a doped second polycrystalline silicon film on the first polycrystalline silicon film, so that the number of defects on the first and second polycrystalline silicon films is lower than the target number.
[0011] Preferably, the substrate in step one comprises a bulk semiconductor substrate or a silicon-on-insulator (SOI) substrate.
[0012] Preferably, step two further includes the step of forming an undoped film layer on the substrate before forming the first polycrystalline silicon film layer.
[0013] Preferably, the undoped film layer can be diffused into by phosphorus atoms in the doped polycrystalline silicon film layer.
[0014] Preferably, the effect of the undoped film on resistivity testing is within a preset range.
[0015] Preferably, the cavity is provided with a plurality of crystal boats with a slot spacing of less than or equal to 8.5 mm.
[0016] Preferably, in step two, the gas flow rate of the silane introduced is 1.0-1.4 slm, the gas flow rate of the phosphine introduced is 80-150 sccm, and the deposition time is 5-12 min.
[0017] Preferably, in step three, the gas flow rate of the silane introduced is 1.0-1.4 slm, the gas flow rate of the phosphine introduced is 80-150 sccm, and the deposition time is 150-200 min.
[0018] Preferably, the thickness of the first polycrystalline silicon film layer in step three is less than 10% of the total thickness of the first and second polycrystalline silicon film layers.
[0019] Preferably, the defect in step three is a bulge or buried granular defect.
[0020] As described above, the method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films of the present invention has the following beneficial effects:
[0021] This invention can reduce the process defects that occur when using a crystal boat with many slots and small slot spacing in LPCVD in-situ doped polycrystalline silicon furnace tubes. Attached Figure Description
[0022] Figure 1 The diagram shown is a schematic representation of a crystal boat using existing technology. Figure 2 This diagram illustrates the formation of defects in existing technologies. Figure 3 The diagram shown illustrates the principle of defect reduction in this invention. Figure 4 The diagram shown is a schematic representation of the process flow of the present invention. Figure 5 This diagram shows a comparison of the number of defects in the present invention and the prior art. Detailed Implementation
[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0024] Please see Figure 1 This invention provides a method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films, comprising:
[0025] Step 1: Provide a furnace tube for in-situ doping of polycrystalline silicon by LPCVD. The cavity in the furnace tube is equipped with multiple crystal boats with a slot spacing less than or equal to the target distance. A substrate is placed on the crystal boat.
[0026] In some embodiments, the substrate in step one comprises a bulk semiconductor substrate or a silicon-on-insulator (SOI) substrate. The SOI substrate includes an insulating layer beneath a thin semiconductor layer serving as the active layer. The semiconductor in the active layer and the bulk semiconductor typically comprise the crystalline semiconductor material silicon, but may also include one or more other semiconductor materials, such as germanium, silicon-germanium alloys, compound semiconductors (e.g., GaAs, AlAs, InAs, GaN, AlN, etc.) or alloys thereof (e.g., GaxAl1-xAs, GaxAl1-xN, InxGa1-xAs, etc.), oxide semiconductors (e.g., ZnO, SnO2, TiO2, Ga2O3, etc.), or combinations thereof. The semiconductor material may be doped or undoped. Other substrates that may be used include multilayer substrates, gradient substrates, or mixed-orientation substrates.
[0027] In some embodiments, step two further includes forming an undoped film layer on the substrate before forming the first polysilicon film layer. For example, the undoped film layer may be a gate oxide layer.
[0028] In some embodiments, undoped films can be diffused into by phosphorus atoms in doped polycrystalline silicon films.
[0029] In some embodiments, the effect of undoped films on resistivity testing is within a preset range.
[0030] In some embodiments, the cavity in step one is provided with multiple crystal boats with a slot spacing of less than or equal to 8.5 mm.
[0031] For example, the crystal boat is made of silicon carbide, with a length of 988mm, 170 slots, and a slot pitch of 5.32mm.
[0032] Step 2: Adjust the pressure in the cavity to 0.6 to 0.8 Torr (the cavity pressure in the prior art is about 0.2 Torr), for example, 0.6 Torr, 0.65 Torr, 0.7 Torr, 0.75 Torr or 0.8 Torr, and the temperature to 560℃-580℃, for example, 560℃, 565℃, 570℃, 575℃ or 580℃. Then, introduce silane and phosphine into the cavity to form a doped first polycrystalline silicon film layer on the substrate.
[0033] In some embodiments, the flow rate of silane introduced in step two is 1.0-1.4 slm, for example 1.0 slm, 1.1 slm, 1.2 slm, 1.3 slm or 1.4 slm, the flow rate of phosphine introduced is 80-150 sccm, for example 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm or 150 sccm, and the deposition time is 5-12 min, for example 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min or 12 min.
[0034] Please see Figure 3 The theoretical basis for reducing defects is as follows: 1. High-pressure gas has a higher density and a shorter mean free path; 2. With higher gas density, phosphorus atoms are more likely to meet and form aggregates; 3. A longer mean free path facilitates further nucleation and growth.
[0035] Step 3: Adjust the pressure in the cavity to 0.2 to 0.4 Torr, for example, 0.2 Torr, 0.3 Torr, or 0.4 Torr, and the temperature to 560℃-580℃, for example, 560℃, 565℃, 570℃, 575℃, or 580℃. Then, introduce silane and phosphine into the cavity to form a doped second polycrystalline silicon film on the first polycrystalline silicon film, so that the number of defects on the first and second polycrystalline silicon films is lower than the target number.
[0036] In some embodiments, the flow rate of silane introduced in step three is 1.0-1.4 slm, for example 1.0 slm, 1.1 slm, 1.2 slm, 1.3 slm or 1.4 slm, the flow rate of phosphine introduced is 80-150 sccm, for example 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm or 150 sccm, and the deposition time is 150-200 min, for example 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min or 150 min.
[0037] In some embodiments, the thickness of the first polycrystalline silicon film layer in step three is less than 10% of the total thickness of the first and second polycrystalline silicon film layers.
[0038] In some embodiments, please refer to Figure 2 The defects in step three are bulging or buried particulate defects. After the groove spacing is reduced, the gas flow is affected. Phosphine containing lone pairs of electrons has a stronger adsorption capacity and preferentially nucleates silane on the substrate surface, resulting in abnormal film formation and defects.
[0039] Please see Figure 5 The diagram shows a comparison of the number of defects between the embodiments of the present invention and the prior art. The method of the present invention can reduce the process defects that occur when using a crystal boat with a large number of slots and a small slot spacing in LPCVD in-situ doped polycrystalline silicon furnace tube.
[0040] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0041] In summary, this invention can reduce the process defects that occur when using a crystal boat with many slots and small slot spacing in LPCVD in-situ doping of polycrystalline silicon. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.
[0042] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for manufacturing an in-situ doped polycrystalline silicon thin film using LPCVD, characterized in that, At least including: Step 1: Provide a furnace tube for in-situ doping of polycrystalline silicon by LPCVD. The cavity of the furnace tube is provided with multiple crystal boats with a slot spacing less than or equal to the target distance. A substrate is provided on the crystal boat. Step 2: Adjust the pressure in the cavity to 0.6 to 0.8 Torr and the temperature to 560℃-580℃, then introduce silane and phosphine into the cavity to form a doped first polycrystalline silicon film on the substrate. Step 3: Adjust the pressure in the cavity to 0.2 to 0.4 Torr and the temperature to 560℃-580℃. Then, introduce silane and phosphine into the cavity to form a doped second polycrystalline silicon film on the first polycrystalline silicon film, so that the number of defects on the first and second polycrystalline silicon films is lower than the target number.
2. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 1, characterized in that: The substrate in step one includes a bulk semiconductor substrate or a silicon-on-insulator (SOI) substrate.
3. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 1, characterized in that: Step two further includes the step of forming an undoped film layer on the substrate before forming the first polycrystalline silicon film layer.
4. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 3, characterized in that: The undoped film can be diffused into by phosphorus atoms in the doped polycrystalline silicon film.
5. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 3, characterized in that: The effect of the undoped film on resistivity testing is within a preset range.
6. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 1, characterized in that: The cavity in step one is provided with multiple crystal boats with a slot spacing of less than or equal to 8.5 mm.
7. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 1, characterized in that: In step two, the gas flow rate of the silane introduced is 1.0-1.4 slm, the gas flow rate of the phosphine introduced is 80-150 sccm, and the deposition time is 5-12 min.
8. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 1, characterized in that: In step three, the gas flow rate of the silane introduced is 1.0-1.4 slm, the gas flow rate of the phosphine introduced is 80-150 sccm, and the deposition time is 150-200 min.
9. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 1, characterized in that: In step three, the thickness of the first polycrystalline silicon film layer is less than 10% of the total thickness of the first and second polycrystalline silicon film layers.
10. The method for manufacturing LPCVD in-situ doped polycrystalline silicon thin films according to claim 1, characterized in that: The defect mentioned in step three is a bulging or buried granular defect.