Phosphorus doping preparation method of polycrystalline silicon fuse resistor

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and particularly relates to a phosphorus doping preparation method of a polycrystalline silicon fuse resistor. The method mainly comprises the following steps: a) growing a polycrystalline silicon film by using LPCVD; b) generating a masking oxide layer by using a phosphorus-doped furnace tube; c) using phosphorus oxychloride as a doping source for doping; d) forming phosphorus impurities on the surface of the polycrystalline silicon; e) redistributing the phosphorus impurities to form the uniformly-doped resistance-controllable polycrystalline silicon. The polycrystalline silicon fuse resistance doping process is high in process controllability, the preparation process is simple and easy to operate, and the polycrystalline silicon fuse resistance doping process is suitable for manufacturing fuse devices.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a phosphorus-doped preparation method for a polysilicon fuse resistor. Background Art

[0002] In semiconductor manufacturing, fuse resistors are a commonly used discrete device. Its main feature is that the fuse melts under a certain high current, cutting off the current path. This device is widely used in high-voltage circuits. The top view of the fuse unit structure is as follows: Figure 1 As shown, for ordinary MOS devices, the thickness of the polysilicon film is usually 300nm~500nm, which is mainly used for the gate or the upper and lower poles of the capacitor. The precision requirement for the doping resistor is low, and the precision of the doping resistor is generally required to be within ±15%. Therefore, the conventional doping process is easier to implement and control.

[0003] In the manufacturing process of fuse devices, polysilicon is the core part of the fuse resistor, which is characterized by controllable thickness and doping resistance, and the advantage is that it can be manufactured using general semiconductor equipment and processes. Since the fuse resistor needs to pass a large current when working, the thickness of polysilicon is much greater than the polycrystalline thickness of ordinary devices, usually above 2000nm, and the precision of doping resistance is high, generally required to be within ±3%. For such polycrystalline thickness and doping resistance, a special phosphorus doping process is required to complete it in order to meet the special working mode of the fuse. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a method for preparing polysilicon fuse resistors by phosphorus doping. The method adopts the equipment of 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] In order to solve the above technical problems, the present invention provides a method for preparing a polysilicon fuse resistor by phosphorus doping, comprising the following steps:

[0006] Step S1: using the LPCVD (low pressure chemical vapor deposition) method, introducing silane (SiH4) gas, and growing a polysilicon film of a certain thickness on the surface of the silicon wafer at a temperature of 600° C. to 630° C.;

[0007] Step S2: using a furnace tube device, first introducing a certain ratio of high-purity nitrogen and oxygen for 30 minutes at a temperature of 950° C. to grow a thin silicon dioxide masking layer on the surface of the polysilicon film;

[0008] Step S3: at a temperature of 950° C., introducing a certain proportion of high-purity nitrogen, oxygen and phosphorus oxychloride (POCl3) gas carried by nitrogen for 20 to 40 minutes, so that phosphorus pentoxide generated by the reaction of phosphorus oxychloride and oxygen can pass through the silicon dioxide masking layer and enter the polysilicon film;

[0009] Step S4: at a temperature of 950° C., introducing a certain proportion of high-purity nitrogen and oxygen for 60 minutes to react phosphorus pentoxide with polysilicon to generate phosphorus impurities;

[0010] Step S5: At a temperature of 950° C., high-purity nitrogen is introduced for 60 minutes to allow the generated phosphorus impurities to diffuse evenly into the polysilicon film to form polysilicon with controllable doping resistance.

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

[0012] Preferably, the growth thickness of the polysilicon thin film in step S1 is 2000nm-2500nm.

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

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

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

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

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

[0018] The main steps of the preparation method of the present invention include: a) growing a polysilicon film by LPCVD; b) generating a masking oxide layer by using a phosphorus doping furnace tube; c) doping by using phosphorus oxychloride as a doping source; d) forming phosphorus impurities on the surface of polysilicon; e) redistributing the phosphorus impurities to form uniformly doped polysilicon with controllable resistance. The polysilicon fuse resistor doping process prepared by the present invention uses polysilicon as the fuse resistor layer, and by adjusting the process time of high-purity nitrogen, oxygen and phosphorus oxychloride gas carried by nitrogen, a doped polysilicon film with accurately controlled and continuously adjustable surface resistance can be obtained. The process has strong controllability, the preparation process is simple and easy to operate, and it is completely compatible with the MOS process flow, and is suitable for the manufacture of fuse devices. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Figure 2 The present invention is a flow chart of a method for preparing a polysilicon fuse resistor by phosphorus doping. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0022] Example 1

[0023] An embodiment of the present invention provides a method for preparing a polysilicon fuse resistor by phosphorus doping, comprising the following steps:

[0024] a. Using LPCVD, at a temperature of 600-630°C, introduce reactive gas silane to grow a 2000nm polycrystalline silicon film;

[0025] b. Doping by furnace tube;

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

[0027] d. At a temperature of 950°C, high-purity nitrogen, oxygen and phosphorus oxychloride gas carried by nitrogen were introduced for 20 minutes in a ratio of 60:3:10;

[0028] e. At a temperature of 950°C, introduce high-purity nitrogen and oxygen for 60 minutes in a ratio of 12:1;

[0029] f. At a temperature of 950°C, introduce high-purity nitrogen for 60 minutes;

[0030] By using the above method, a doped polysilicon film with a surface resistance of 4.5Ω / □ can be obtained.

[0031] Example 2

[0032] An embodiment of the present invention provides a method for preparing a polysilicon fuse resistor by phosphorus doping, comprising the following steps:

[0033] a. Using LPCVD, at a temperature of 600-630°C, introduce reactive gas silane to grow a 2200nm polycrystalline silicon film;

[0034] b. Doping by furnace tube;

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

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

[0037] e. At a temperature of 950°C, introduce high-purity nitrogen and oxygen for 60 minutes in a ratio of 12:1;

[0038] f. At a temperature of 950°C, introduce high-purity nitrogen for 60 minutes;

[0039] By using the above method, a doped polysilicon film with a surface resistance of 4Ω / □ can be obtained;

[0040] Example 3

[0041] An embodiment of the present invention provides a method for preparing a polysilicon fuse resistor by phosphorus doping, comprising the following steps:

[0042] a. Using LPCVD, at a temperature of 600-630°C, introduce reactive gas silane to grow a 2500nm polycrystalline silicon film;

[0043] b. Doping by furnace tube;

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

[0045] d. At a temperature of 950°C, high-purity nitrogen, oxygen and phosphorus oxychloride gas carried by nitrogen were introduced for 30 minutes in a ratio of 60:3:10;

[0046] e. At a temperature of 950°C, introduce high-purity nitrogen and oxygen for 60 minutes in a ratio of 12:1;

[0047] f. At a temperature of 950°C, introduce high-purity nitrogen for 60 minutes;

[0048] By using the above method, a doped polysilicon film with a surface resistance of 3.5Ω / □ can be obtained.

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

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

Claims

1. A method for preparing a polysilicon fuse resistor by phosphorus doping, characterized in that: The steps include: Step S1: using the LPCVD method, introducing silane gas, and growing a polysilicon film of a certain thickness on the surface of the silicon wafer at a temperature of 600° C. to 630° C.; Step S2: using a furnace tube device, first introducing a certain ratio of high-purity nitrogen and oxygen for 30 minutes at a temperature of 950° C. to grow a thin silicon dioxide masking layer on the surface of the polysilicon film; Step S3: at a temperature of 950° C., introducing a certain proportion of high-purity nitrogen, oxygen and phosphorus oxychloride gas carried by nitrogen for 20 to 40 minutes, so that phosphorus pentoxide generated by the reaction of phosphorus oxychloride and oxygen can pass through the silicon dioxide masking layer and enter the polysilicon film; Step S4: at a temperature of 950° C., introducing a certain proportion of high-purity nitrogen and oxygen for 60 minutes to react phosphorus pentoxide with polysilicon to generate phosphorus impurities; Step S5: At a temperature of 950° C., high-purity nitrogen is introduced for 60 minutes to allow the generated phosphorus impurities to diffuse evenly into the polysilicon film to form polysilicon with controllable doping resistance.

2. The phosphorus doping method for preparing a polysilicon fuse resistor according to claim 1, characterized in that: The silicon wafer in step S1 is suitable for silicon wafers made of different substrate materials.

3. The phosphorus doping method for preparing a polysilicon fuse resistor according to claim 1, characterized in that: The growth thickness of the polysilicon film in step S1 is 2000nm-2500nm.

4. The phosphorus doping method for preparing a polysilicon fuse resistor according to claim 1, characterized in that: The flow ratio of high-purity nitrogen and oxygen introduced in step S2 is 80:

3.

5. The phosphorus doping method for preparing a polysilicon fuse resistor according to claim 1, characterized in that: In step S3, the flow ratio of high-purity nitrogen, oxygen and phosphorus oxychloride gas carried by nitrogen is 60:3:

10.

6. The phosphorus doping method for preparing a polysilicon fuse resistor according to claim 1, characterized in that: The flow ratio of high-purity nitrogen and oxygen introduced in step S4 is 12:

1.

7. The method for preparing a polysilicon fuse resistor by phosphorus doping according to any one of claims 1 to 6, characterized in that: By using the phosphorus doping preparation method, doped polysilicon with a surface resistance of 3Ω / □ to 5Ω / □ can be prepared.

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