Cerium oxide polishing solution and polishing condition for STI (Shallow Trench Isolation) technology

Abstract

The invention discloses a cerium oxide polishing solution for an STI (Shallow Trench Isolation) technology. The cerium oxide polishing solution is prepared from the following raw materials in percentage by mass: 0.1 to 1 weight percent of CeO2 abrasive, 0.01 to 1 weight percent of piperazine, imidazole and / or pyridine hydrochloride, 0.01 to 1 weight percent of polyacrylic acid and the balance of deionized water, and the pH regulator is used for regulating the pH to 3-6. The invention further discloses a polishing condition of the cerium oxide polishing solution for the STI technology. Under the condition that the high selection ratio of TEOS / Si3N4 is guaranteed, the removal rate of N3Si4 is further reduced so as to achieve a better polishing effect.

Description

Technical Field

[0001] The invention relates to the field of semiconductor chemical mechanical planarization, and in particular to a cerium oxide polishing liquid and polishing conditions used in STI technology. Background Art

[0002] CMP (chemical mechanical planarization) is one of the most important semiconductor processes and is essential for achieving performance improvements in microprocessors and memory chips. In the 0.2μm technology node, STI (shallow trench isolation technology) replaced the traditional LOCOS (silicon local oxidation technology) to provide a better device isolation environment. Therefore, the oxide on the top of the nitride must be completely removed, otherwise it will affect the change in the surface morphology of the wafer and the subsequent wet etching process. Products on the market, led by silicon oxide polishing liquid, can no longer meet the requirements of high oxide removal and low nitride removal.

[0003] There are also many reports in the industry about cerium oxide polishing with high selectivity and high removal rate of TEOS / Si3N4. In patent CN117304813 A, under the condition of pH=2-6, by adding amino acids and polyols, a cerium oxide polishing liquid with high selectivity and long-term stability within a certain range was obtained. However, the nitride removal rate obtained by this patent is still relatively high, which may affect the Si3N4 stop layer.

[0004] The current patents mainly focus on high TEOS / Si3N4 selectivity, lower oxide loss, and shallower dishing defects. There are few reports on polishing solutions with lower Si3N4 removal rates and high selectivity. Summary of the invention

[0005] The object of the present invention is to provide a cerium oxide polishing liquid for STI technology.

[0006] The invention also provides polishing conditions of a cerium oxide polishing liquid used in the STI technology.

[0007] The innovation of the present invention is that the present invention further reduces the removal rate of N3Si4 to achieve a better polishing effect while ensuring a high TEOS / Si3N4 selectivity.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0009] A cerium oxide polishing liquid for STI technology is characterized in that it includes the following raw materials in mass fraction: CeO2 abrasive: 0.1-1wt%, piperazine, imidazole and / or pyridine hydrochloride: 0.01-1wt%, polyacrylic acid: 0.01-1wt%, and the balance is deionized water; a pH regulator adjusts the pH to 3-6.

[0010] Furthermore, the molecular weight of the polyacrylic acid is 2000-5000.

[0011] Furthermore, the structural formula of the piperazine is

[0012] Furthermore, the structural formula of the imidazole is

[0013] Furthermore, the structural formula of the pyridine hydrochloride is

[0014] Furthermore, the particle size of the CeO2 abrasive is 30 to 400 nm.

[0015] The invention discloses polishing conditions of a cerium oxide polishing liquid used in STI technology, wherein the rotating speed of a turntable / swing arm of a polishing machine is 80-100 / 50-75 rpm, the polishing pressure is 1.5-4 psi, and the flow rate is 100-300 mL / min.

[0016] The beneficial effects of the present invention are:

[0017] 1. In the present invention, pyridine hydrochloric acid can be adsorbed on silicon nitride to inhibit the oxidation of nitride to oxide. The cerium oxide polishing liquid of the present invention satisfies both high oxide removal rate and low nitride removal rate.

[0018] 2. The cyclic amines (piperazine, imidazole and / or pyridine hydrochloride) in the present invention have little side effects on the removal of TEOS, will not inhibit the removal rate of TEOS, and will inhibit the removal rate of Si3N4; the cyclic amines will adhere to TEOS and Si3N4 at the same time, but the adhesion effect on TEOS is not obvious, and will not have a great impact on the removal of TEOS, but will adhere to Si3N4 in large quantities and form a substance similar to a protective layer to prevent the removal of Si3N4, but the adhesion of cyclic amine substances will have a saturation degree and will not increase with a substantial increase in the amount added.

[0019] 3. In the present invention, the optimal removal effect is achieved by controlling the rotation speed, pressure and flow rate of the polishing conditions.

[0020] 4. In the present invention, when the pH is between 3 and 6, piperazine, imidazole and / or pyridine hydrochloride can stably exert their effects. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0022] Example 1: A cerium oxide polishing liquid for STI technology, comprising the following raw materials by mass fraction: CeO2 abrasive: 0.1wt%, piperazine: 0.01wt%, polyacrylic acid: 0.01wt%, deionized water 99.88%; pH regulator adjusts the pH to 3. The particle size of CeO2 abrasive is 30-400nm, the molecular weight of polyacrylic acid is 2000-5000, and the structural formula of piperazine is

[0023] A method for preparing a cerium oxide polishing liquid for STI technology comprises the following steps: taking raw materials according to 0.1wt% CeO2 abrasive, 0.01wt% piperazine, 0.01wt% polyacrylic acid and 99.88% deionized water, mixing the CeO2 abrasive, piperazine and polyacrylic acid, adding deionized water, and ultrasonicating at 40MHZ for 1 hour, adjusting the pH to 3 with a pH regulator, and then continuing ultrasonicating for 0.5 hour to obtain the cerium oxide polishing liquid.

[0024] Example 2: A cerium oxide polishing liquid for STI technology, comprising the following raw materials by mass fraction: CeO2 abrasive: 0.5wt%, imidazole: 0.05wt%, polyacrylic acid: 0.05wt%, deionized water 99.4%; pH regulator adjusts the pH to 5. The particle size of CeO2 abrasive is 30-400nm, the molecular weight of polyacrylic acid is 2000-5000, and the structural formula of imidazole is

[0025] Example 3: A cerium oxide polishing liquid for STI technology, comprising the following raw materials by mass fraction: CeO2 abrasive: 1wt%, pyridine hydrochloride: 1wt%, polyacrylic acid: 1wt%, deionized water 97%; pH regulator adjusts the pH to 6. The particle size of CeO2 abrasive is 30-400nm, the molecular weight of polyacrylic acid is 2000-5000, and the structural formula of pyridine hydrochloride is

[0026] Example 4: Polishing conditions of a cerium oxide polishing liquid for STI technology. The polishing liquid of Example 1 is used to polish a silicon oxide membrane (TEOS) with a diameter of 100 mm and a thickness of 400 nm prepared by CVD and an N3Si4 with a diameter of 100 mm and a thickness of 100 nm prepared by plasma enhanced chemical vapor deposition. The turntable / swing arm speed of the polishing machine is 80 / 50 rpm, the polishing pressure is 1.5 psi, and the flow rate is 100 mL / min.

[0027] Example 5: Polishing conditions of a cerium oxide polishing liquid for STI technology. The polishing liquid of Example 2 is used to polish a silicon oxide membrane (TEOS) with a diameter of 100 mm and a thickness of 400 nm prepared by CVD and an N3Si4 with a diameter of 100 mm and a thickness of 100 nm prepared by plasma enhanced chemical vapor deposition. The turntable / swing arm speed of the polishing machine is 90 / 60 rpm, the polishing pressure is 2.5 psi, and the flow rate is 200 mL / min.

[0028] Example 6: Polishing conditions of a cerium oxide polishing liquid for STI technology. The polishing liquid of Example 3 is used to polish a silicon oxide membrane (TEOS) with a diameter of 100 mm and a thickness of 400 nm prepared by CVD and an N3Si4 with a diameter of 100 mm and a thickness of 100 nm prepared by plasma enhanced chemical vapor deposition. The turntable / swing arm speed of the polishing machine is 100 / 75 rpm, the polishing pressure is 4 psi, and the flow rate is 300 mL / min.

[0029] Comparative Example 1: Referring to Example 4, CeO2 abrasive: 0.11wt%, polyacrylic acid: 0.01wt%, deionized water 99.88%; pH regulator adjusts pH to 3. The particle size of CeO2 abrasive is 30-400nm, the molecular weight of polyacrylic acid is 2000-5000, and the structural formula of piperazine is The polishing conditions remain unchanged.

[0030] The data are given according to the above-mentioned Examples 4 to 6 and Comparative Example 1.

[0031] Use the Filmetrics-F20 film thickness measurement system to measure 9 points symmetrically distributed on the wafer surface and take the average value (at the center, edge points in four directions, and points between the four edge points and the center)

[0032]

[0033] (TEOS is a type of silicon oxide). The selection ratio is the ratio of TEOS polishing rate to silicon nitride polishing rate. The larger the ratio, the better the polishing effect. The better the protection of silicon nitride, the more conducive to the subsequent process.

[0034] The described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A cerium oxide polishing liquid for STI technology, characterized in that: The invention comprises the following raw materials in mass fraction: 0.1-1wt% of CeO2 abrasive, 0.01-1wt% of piperazine, imidazole and / or pyridine hydrochloride, 0.01-1wt% of polyacrylic acid, and the balance of deionized water; and a pH regulator is used to adjust the pH to 3-6.

2. The cerium oxide polishing liquid for STI technology according to claim 1, characterized in that: The molecular weight of the polyacrylic acid is 2000-5000.

3. The cerium oxide polishing liquid for STI technology according to claim 1, characterized in that: The structural formula of the piperazine is 4. The cerium oxide polishing liquid for STI technology according to claim 1, characterized in that: The structural formula of the imidazole is 5. The cerium oxide polishing liquid for STI technology according to claim 1, characterized in that: The structural formula of the pyridine hydrochloride is 6. The cerium oxide polishing liquid for STI technology according to claim 1, characterized in that: The particle size of the CeO2 abrasive is 30-400 nm.

7. A polishing condition of the cerium oxide polishing liquid for STI technology as claimed in claims 1 to 6, characterized in that: The turntable / swing arm speed of the polishing machine is: 80~100 / 50~75rpm, polishing pressure: 1.5~4psi, flow rate: 100~300mL / min.

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