Manufacturing method of polycrystalline silicon resistor with U-shaped resistivity temperature characteristic
By using LPCVD process and RTA rapid thermal annealing and other technical means in polysilicon resistor devices, P-type polysilicon resistors and low-concentration P-polysilicon parallel structures are formed, which solves the problem of large resistivity changes in existing polysilicon resistor devices within the common temperature range, and achieves the effect of resistivity temperature coefficient close to 0ppm/℃.
Patent Information
- Application Number
- CN202411486802.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2025-02-28
AI Technical Summary
The resistivity of existing polysilicon resistor devices varies greatly within the temperature range of -55℃~+125℃, making it difficult to meet the performance requirements of electronic products.
The polycrystalline silicon thin film was deposited by the LPCVD process, and the TEOS dielectric layer was deposited thereon for RTA rapid thermal annealing and high-temperature annealing of the furnace tube, forming a P-type polycrystalline silicon resistance and low-concentration P-polysilicon parallel structure, and a protective layer and a stress matching layer were formed through photolithography and etching.
Within the temperature range of -55℃~+125℃, the resistivity of polycrystalline silicon exhibits a U-shaped characteristic with temperature change, the turning temperature is about room temperature, and the resistivity temperature coefficient is close to 0ppm/℃, meeting the temperature stability requirements of electronic products.
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Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor integrated circuit technology, in particular to a method for manufacturing a polysilicon resistor with U-shaped resistivity-temperature characteristics. Background Art
[0002] Semiconductor resistor devices are one of the most widely used devices in semiconductor chip products. The temperature characteristics of resistors are very important in product applications. The fluctuation of resistivity with temperature changes often directly affects product performance and product application range. Polycrystalline silicon thin film resistors are commonly used materials for preparing resistor devices because they have no PN junction isolation, stable performance, and low cost. They are widely used in microelectronic devices, semiconductor integrated circuits, MEMS pressure sensors, thermistors and other fields. The commonly used temperature range of the above-mentioned electronic products is -55℃~+125℃, and the resistivity needs to change very little in the entire temperature range. How to reduce the change of polysilicon resistivity in the full temperature range is a technical problem that technicians in this field need to solve urgently.
[0003] After searching existing patents and literature, the Chinese document "Resistivity Temperature Characteristics of Polysilicon Films Doped with Boron on AIN Substrates" shows that when polysilicon films of different thicknesses are deposited at different deposition temperatures and heavily doped with boron, the resistivity changes with temperature in the temperature range from room temperature to 450°C, showing a U-shaped characteristic, with a transition temperature of about 250°C. The temperature range of this U-shaped characteristic is too high, and the transition temperature is also very high, both of which are far higher than the commonly used temperature range of electronic products. From the temperature range of -55°C to +125°C, the resistivity changes are still large. Summary of the invention
[0004] The purpose of the present invention is to solve the defect of large change in low temperature resistivity in the prior art and to provide a method for manufacturing a polysilicon resistor with U-shaped resistivity-temperature characteristics.
[0005] The technical solution adopted by the present invention is as follows: A method for manufacturing a polysilicon resistor with U-shaped resistivity-temperature characteristics, characterized by comprising the following steps: 1) On the silicon substrate and its silicon oxide layer, a 4000A polysilicon film is deposited using the LPCVD process. 2) Using LPCVD process, a 300A~500A thick tetraethoxysilane TEOS dielectric layer is deposited on the polysilicon film, followed by RTA rapid thermal annealing. The annealing conditions are 1080℃, oxygen is introduced, the oxygen flow rate is 1L / min, and the RTA rapid thermal annealing densifies the TEOS dielectric layer; high temperature annealing by furnace tube process is used to recrystallize the polysilicon. The annealing process conditions are 1150℃, 90 minutes, and N2 is introduced at a flow rate of 14L / min. 3) Apply a photoresist layer on the tetraethoxysilane dielectric layer, and then perform photolithography to implant windows. Inject boron impurities through the implant windows. The implantation dose is 2.0E15 / cm2 and the energy is 80 KeV. Doping the polysilicon forms a P-type polysilicon resistor. 4) Then, the P-type polysilicon resistor pattern is photolithographically etched to the silicon oxide layer, and a certain width of intrinsic polysilicon around the P-type polysilicon resistor is retained; 5) A 6000A PSG dielectric layer is deposited on the silicon oxide layer and the P-type polysilicon resistor as a protective layer for the polysilicon resistor. At the same time, the stress is matched, and nitrogen is introduced for low-temperature annealing. The annealing conditions are 800°C, 30 minutes, and the nitrogen flow rate is 10L / min. This allows the central P-type area to diffuse to the surroundings to form a low-concentration P-polysilicon, which is connected in parallel with the P-type polysilicon resistor.
[0006] The present invention deposits a polysilicon film on a silicon dioxide layer, firstly deposits a thin TEOS dielectric layer by using an LPCVD process, and then performs RTA rapid thermal annealing. Then, a furnace tube high temperature annealing process is used to recrystallize the polysilicon to change the grain size and grain boundaries of the polysilicon. Subsequently, photolithography and implantation of boron impurities are used to form a P-type polysilicon resistor, and then photolithography and etching of the polysilicon pattern are performed. Finally, a thick PSG dielectric layer is deposited, and nitrogen is used for low temperature densification.
[0007] The present invention deposits TEOS on the polysilicon layer and performs RTA annealing to prevent the impurity ions on the surface and edge of the polysilicon from diffusing outward and losing, thereby improving the consistency of the polysilicon resistance. The key is that after the polysilicon layer is deposited and grown and before the impurity ion doping, it first undergoes a furnace tube high-temperature annealing process, so that the polysilicon grains become larger and the grain boundaries become smaller, thereby reducing the impurity ion implantation dose of the P-type low temperature coefficient polysilicon resistor and adjusting its temperature characteristics. A thick PSG dielectric layer is deposited and nitrogen is densified to protect and stress-match the polycrystalline resistor. More importantly, the P-type resistor is photolithographically implanted and has a positive temperature coefficient. Finally, the nitrogen low-temperature densification process is performed to diffuse the central P-type region to the surroundings to form a low-concentration P-region with a negative temperature coefficient. The diffused P-region (negative TCR) with a certain width is retained by photolithography and etching to connect the central P-type (positive TCR) polysilicon resistor in parallel. Therefore, in the temperature range of -55℃~+125℃, the resistivity of polysilicon shows a U-shaped characteristic with temperature change, the turning temperature is about room temperature, and the resistivity temperature coefficient in the temperature range from -55℃ to +125℃ is close to 0ppm / ℃. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 is a schematic diagram of step 1 of the preparation method of the present invention; Figure 2 It is a schematic diagram of step 2 of the preparation method of the present invention; Figure 3It is a schematic diagram of step 3 of the preparation method of the present invention; Figure 4 is a schematic diagram of step 4 of the preparation method of the present invention; Figure 5 is a schematic diagram of step 5 of the preparation method of the present invention; Figure 6 Resistivity-temperature characteristic test curve. DETAILED DESCRIPTION
[0009] The present invention provides a method for manufacturing a polysilicon resistor with a U-shaped resistivity-temperature characteristic, comprising the following steps: On the silicon substrate 1 and its silicon oxide layer 2, a 4000A polysilicon film 3 is deposited by LPCVD process, as shown in FIG. Figure 1 shown.
[0010] A TEOS (tetraethoxysilane) dielectric layer 4 with a thickness of 300A~500A is deposited on the polysilicon film 3 by using the LPCVD process, and then RTA rapid thermal annealing is performed. The annealing conditions are 1080°C, oxygen is introduced, the oxygen flow rate is 1L / min, and the RTA rapid thermal annealing densifies the TEOS dielectric layer; a furnace tube process high temperature annealing is used to recrystallize the polysilicon. The annealing process conditions are 1150°C, 90 minutes, N2 is introduced, and the flow rate is 14L / min. Figure 2 shown.
[0011] A photoresist layer 5 is coated on the TEOS (tetraethoxysilane) dielectric layer 4, and then a photolithography implantation window is performed, and boron impurities are implanted through the implantation window. The implantation impurity dose is 2.0E15 / cm2 and the energy is 80 KeV, and the polysilicon is doped to form a P-type polysilicon resistor 3-1, as shown in FIG. Figure 3 shown.
[0012] Photolithography and etching of the P-type polysilicon resistor pattern to the silicon oxide layer, retaining a certain width (about 0.6um) of intrinsic polysilicon 3 around the P-type polysilicon resistor 3-1, such as Figure 4 shown.
[0013] A 6000A PSG dielectric layer 7 is deposited on the silicon oxide layer and the P-type polysilicon resistor to serve as a protective layer for the polysilicon resistor. At the same time, the stress is matched, and then nitrogen is introduced for low-temperature annealing. The annealing conditions are 800°C, 30 minutes, and the nitrogen flow rate is 10L / min. This low-temperature annealing process can not only increase the density of the PSG dielectric layer, but more importantly, make the central P-type region diffuse to the surroundings to form a low-concentration P-polysilicon 3-2, which is connected in parallel with the P-type polysilicon resistor 3-1. Figure 5 shown.
[0014] In the figure, 1 is the silicon substrate; 2 is the oxide layer; 3 is the polysilicon layer; 4 is the TEOS (tetraethoxysilane) dielectric layer; 5 is the photoresist; 3 is the polysilicon layer; 3-1 is the P-type polysilicon resistor; 3-2 is the P-polysilicon resistor; and 7 is the PSG phosphorus silicon glass dielectric layer. Implementation Effect
[0015] After processing, testing and verification, a U-shaped polysilicon resistor with temperature characteristics of resistivity manufactured by the method of the present invention was tested for resistivity and temperature coefficient within the temperature range of -55°C to +125°C. The specific data are shown in the following table. The calculation formula of the temperature coefficient of resistance is: TCR=(R2-R1) / (T2-T1) / R1*1E6.
[0016] Table 1 Test data table
[0017] Resistivity and temperature characteristic curve reference Figure 6 .
[0018] From the above table and Figure 6 It can be seen that the polysilicon resistor realized by this method has a U-shaped characteristic of resistivity changing with temperature in the temperature range of -55℃~+125℃, and the turning temperature is about 25℃ from room temperature. The resistivity temperature coefficient in the temperature range from -55℃ to +125℃ is 3.18 ppm / ℃, which is close to 0ppm / ℃.
Claims
1. A method for manufacturing a polysilicon resistor with U-shaped resistivity-temperature characteristics, characterized in that The following steps are involved: 1) depositing a polysilicon film (3) with a thickness of 4000A on a silicon oxide layer (2) on a silicon substrate (1) by using an LPCVD process; 2) Using LPCVD process, a tetraethoxysilane dielectric layer (4) with a thickness of 300A to 500A is deposited on the polysilicon film (3), followed by RTA rapid thermal annealing, the annealing conditions are 1080°C, oxygen is introduced, the oxygen flow rate is 1L / min, and the RTA rapid thermal annealing densifies the TEOS dielectric layer; using furnace tube process high temperature annealing to recrystallize the polysilicon, the annealing process conditions are 1150°C, 90 minutes, N2 is introduced, and the flow rate is 14L / min; 3) Coating a photoresist layer (5) on the tetraethoxysilane dielectric layer (4), then photolithography an injection window, injecting boron impurities through the injection window, with an impurity dose of 2.0E15 / cm2 and an energy of 80 KeV, to dope the polysilicon to form a P-type polysilicon resistor (3-1). 4) Then, the P-type polysilicon resistor pattern is photolithographically etched to the silicon oxide layer, and a certain width of intrinsic polysilicon (3) is retained around the P-type polysilicon resistor (3-1); 5) A PSG dielectric layer (7) with a thickness of 6000A is deposited on the silicon oxide layer and the P-type polysilicon resistor to serve as a protective layer for the polysilicon resistor and to match the stress. Nitrogen is then introduced for low-temperature annealing at 800°C for 30 minutes with a nitrogen flow rate of 10L / min, so that the central P-type region diffuses to the surroundings to form a low-concentration P-polysilicon (3-2) which is connected in parallel with the P-type polysilicon resistor (3-1).