A method for preparing polycrystalline silicon fuse resistors by phosphorus doping

Abstract

This invention belongs to the field of semiconductor manufacturing technology, and specifically relates to a method for preparing polycrystalline silicon fuse resistors by phosphorus doping. The main steps include: a) growing a polycrystalline silicon thin film using LPCVD; b) generating a masking oxide layer using a phosphorus doping furnace tube; c) doping with phosphorus oxychloride as a dopant source; d) forming phosphorus impurities on the polycrystalline silicon surface; e) redistributing the phosphorus impurities to form uniformly doped polycrystalline silicon with controllable resistance. The polycrystalline silicon fuse resistor doping process prepared by this invention has strong process controllability, a simple and easy-to-operate preparation procedure, and is suitable for the manufacture of fuse devices.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and specifically relates to a method for preparing polycrystalline silicon fuse resistors by phosphorus doping. Background Technology

[0002] In semiconductor manufacturing, fuse resistors are commonly used discrete devices. Their main characteristic is that the fuse melts under a certain large current, cutting off the current path. This device is widely used in high-voltage circuits. A top view of a fuse unit is shown below. Figure 1 As shown, in ordinary MOS devices, the thickness of the polycrystalline silicon thin film is usually 300nm to 500nm, mainly used for the gate or upper and lower electrodes of the capacitor. The accuracy requirements for the doped resistor are low, and the accuracy of the doped resistor is generally required to be within ±15%. Therefore, the conventional doping process is relatively easy to implement and control.

[0003] In the fabrication of fuse devices, polycrystalline silicon is the core component of the fuse resistor. Its advantages include controllable thickness and doping resistance, and the ability to be fabricated using general-purpose semiconductor equipment and processes. Because fuse resistors require a large current to flow during operation, the polycrystalline silicon thickness must be much greater than that of ordinary devices, typically exceeding 2000 nm. Furthermore, high precision is required for the doped resistance, generally within ±3%. Such polycrystalline thickness and doped resistance necessitate a specialized phosphorus doping process to meet the specific operating requirements of the fuse. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for preparing polycrystalline silicon fuse resistors by phosphorus doping. The method uses equipment from a general MOS production line to perform high-precision phosphorus doping on thick polycrystalline fuse resistors by furnace tube phosphorus doping. The preparation process is simple and suitable for large-scale production.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a polycrystalline silicon fuse resistor by phosphorus doping, comprising the following steps:

[0006] Step S1: Using LPCVD (low-pressure chemical vapor deposition), silane (SiH4) gas is introduced, and a polycrystalline silicon thin film of a certain thickness is grown on the surface of the silicon wafer at a temperature of 600℃~630℃.

[0007] Step S2: Using a furnace tube device, first introduce a certain proportion of high-purity nitrogen and oxygen for 30 minutes, and grow a thin silicon dioxide masking layer on the surface of the polycrystalline silicon film at a temperature of 950℃.

[0008] Step S3: At 950℃, a certain proportion of high-purity nitrogen, oxygen and phosphorus oxychloride (POCl3) gas carried by nitrogen is introduced for 20 min to 40 min, so that phosphorus pentoxide generated after the reaction of phosphorus oxychloride and oxygen can pass through the silicon dioxide masking layer and enter the polycrystalline silicon thin film.

[0009] Step S4: At 950℃, a certain proportion of high-purity nitrogen and oxygen are introduced for 60 minutes to allow phosphorus pentoxide to react with polycrystalline silicon and generate phosphorus impurities.

[0010] Step S5: At 950℃, high-purity nitrogen gas is introduced for 60 minutes to allow the generated phosphorus impurities to diffuse uniformly into the polycrystalline silicon thin film, thereby forming polycrystalline silicon with controllable doping resistance.

[0011] Preferably, the silicon wafer in step S1 is suitable for silicon wafers with different substrate materials.

[0012] Preferably, the growth thickness of the polycrystalline silicon thin film in step S1 is 2000nm to 2500nm.

[0013] Preferably, the flow rate ratio of high-purity nitrogen to oxygen in step S2 is 80:3.

[0014] Preferably, in step S3, the flow rate ratio of high-purity nitrogen, oxygen, and phosphorus oxychloride gas carried by nitrogen is 60:3:10.

[0015] Preferably, the flow rate ratio of high-purity nitrogen to oxygen in step S4 is 12:1.

[0016] Preferably, the phosphorus doping preparation method can prepare doped polycrystalline silicon with a surface resistivity of 3Ω / □ to 5Ω / □, which is a key material for fuse resistors.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The main steps of the preparation method of this invention include: a) growing a polycrystalline silicon thin film using LPCVD; b) generating a masking oxide layer using a phosphorus-doped furnace tube; c) doping with phosphorus oxychloride as a dopant source; d) forming phosphorus impurities on the polycrystalline silicon surface; and e) redistributing the phosphorus impurities to form a uniformly doped polycrystalline silicon with controllable resistance. The polycrystalline silicon fuse resistor doping process of this invention uses polycrystalline silicon as the fuse resistor layer. By adjusting the process times of the high-purity nitrogen, oxygen, and nitrogen-carried phosphorus oxychloride gas steps, a doped polycrystalline silicon thin film with precisely controlled and continuously adjustable surface resistance can be obtained. The process is highly controllable, simple and easy to operate, fully compatible with MOS process flows, and suitable for the manufacture of fuse devices. Attached Figure Description

[0019] Figure 1This is a top view of the structure of the fuse unit of the present invention.

[0020] Figure 2 This is a flowchart of a method for preparing a polycrystalline silicon fuse resistor by phosphorus doping according to the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0022] Example 1

[0023] This invention provides a method for preparing a phosphorus-doped polycrystalline silicon fuse resistor, comprising the following steps:

[0024] a. Using LPCVD, a 2000 nm polycrystalline silicon thin film is grown by introducing the reactive gas silane at a temperature of 600–630 °C.

[0025] b. Using furnace tube doping method;

[0026] c. At a temperature of 950℃, first introduce high-purity nitrogen and oxygen in a ratio of 80:3 for 30 minutes;

[0027] d. At a temperature of 950℃, high-purity nitrogen, oxygen and phosphorus oxychloride carried by nitrogen are introduced for another 20 minutes in a ratio of 60:3:10.

[0028] e. At a temperature of 950℃, high-purity nitrogen and oxygen are introduced for 60 minutes in a ratio of 12:1.

[0029] f. At a temperature of 950℃, high-purity nitrogen gas is introduced for 60 minutes;

[0030] Using the above method, a doped polycrystalline silicon thin film with a surface resistivity of 4.5 Ω / □ can be obtained.

[0031] Example 2

[0032] This invention provides a method for preparing a phosphorus-doped polycrystalline silicon fuse resistor, comprising the following steps:

[0033] a. Using LPCVD, a 2200 nm polycrystalline silicon thin film is grown by introducing the reactive gas silane at a temperature of 600–630 °C.

[0034] b. Using furnace tube doping method;

[0035] c. At a temperature of 950℃, first introduce high-purity nitrogen and oxygen in a ratio of 80:3 for 30 minutes;

[0036] d. At a temperature of 950℃, high-purity nitrogen, oxygen and phosphorus oxychloride carried by nitrogen are introduced for 22 minutes in a ratio of 60:3:10.

[0037] e. At a temperature of 950℃, high-purity nitrogen and oxygen are introduced for 60 minutes in a ratio of 12:1.

[0038] f. At a temperature of 950℃, high-purity nitrogen gas is introduced for 60 minutes;

[0039] Using the above method, a doped polycrystalline silicon thin film with a surface resistivity of 4Ω / □ can be obtained;

[0040] Example 3

[0041] This invention provides a method for preparing a phosphorus-doped polycrystalline silicon fuse resistor, comprising the following steps:

[0042] a. Using LPCVD, a 2500 nm polycrystalline silicon thin film is grown by introducing the reactive gas silane at a temperature of 600–630 °C.

[0043] b. Using furnace tube doping method;

[0044] c. At a temperature of 950℃, first introduce high-purity nitrogen and oxygen in a ratio of 80:3 for 30 minutes;

[0045] d. At a temperature of 950℃, high-purity nitrogen, oxygen and phosphorus oxychloride carried by nitrogen are introduced for another 30 minutes in a ratio of 60:3:10.

[0046] e. At a temperature of 950℃, high-purity nitrogen and oxygen are introduced for 60 minutes in a ratio of 12:1.

[0047] f. At a temperature of 950℃, high-purity nitrogen gas is introduced for 60 minutes;

[0048] Using the above method, a doped polycrystalline silicon thin film with a surface resistivity of 3.5 Ω / □ can be obtained.

[0049] The above doping process can use silicon wafers with various substrate materials, and can obtain doped polycrystalline silicon with a surface resistivity of 3 to 5 Ω / □ for polycrystalline silicon films with a thickness of 2000 to 2500 nm, which is a key material for fuse resistors.

[0050] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for preparing a polycrystalline silicon fuse resistor by phosphorus doping, characterized in that, Includes the following steps: Step S1: Using the LPCVD method, silane gas is introduced, and a polycrystalline silicon thin film of a certain thickness is grown on the surface of the silicon wafer at a temperature of 600℃~630℃. Step S2: Using a furnace tube device, first introduce a certain proportion of high-purity nitrogen and oxygen for 30 minutes, and grow a thin silicon dioxide masking layer on the surface of the polycrystalline silicon film at a temperature of 950℃. Step S3: At 950℃, a certain proportion of high-purity nitrogen, oxygen and phosphorus oxychloride gas carried by nitrogen is introduced for 20min~40min so that phosphorus pentoxide generated after the reaction of phosphorus oxychloride and oxygen can pass through the silicon dioxide masking layer and enter the polycrystalline silicon thin film. Step S4: At 950℃, a certain proportion of high-purity nitrogen and oxygen are introduced for 60 minutes to allow phosphorus pentoxide to react with polycrystalline silicon and generate phosphorus impurities. Step S5: At 950℃, high-purity nitrogen gas is introduced for 60 minutes to allow the generated phosphorus impurities to diffuse uniformly into the polycrystalline silicon thin film, thereby forming polycrystalline silicon with controllable doping resistance. The growth thickness of the polycrystalline silicon thin film in step S1 is 2000nm~2500nm; In step S2, the flow rate ratio of high-purity nitrogen to oxygen is 80:

3. In step S3, the flow rate ratio of high-purity nitrogen, oxygen, and phosphorus oxychloride gas carried by nitrogen is 60:3:

10. In step S4, the flow rate ratio of high-purity nitrogen to oxygen is 12:

1. Phosphorus doping can be used to prepare doped polycrystalline silicon with a surface resistivity of 3Ω / □~5Ω / □.

2. The method for preparing a polycrystalline silicon fuse resistor by phosphorus doping as described in claim 1, characterized in that, The silicon wafers used in step S1 are suitable for silicon wafers with different substrate materials.

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