Special glass components used in semiconductor etching

Semiconductor etching imposes strict requirements on the corrosion resistance, thermal stability, and optical purity of materials in plasma environments. Special glass components have become key consumables due to their characteristics of "low impurities, corrosion resistance, and high transparency". Their applications can be divided into equipment modules:

1、 Etching cavity observation and optical components

1. High purity quartz glass observation window

Using synthetic quartz glass with hydroxyl content<50ppm (SiO ₂ purity>99.99%), its resistance to HF corrosion rate<0.05 μ m/h is achieved in a 13.56MHz RF plasma environment. For example, the SEMI-5500 etching machine applied to Tokyo Electronics (TEL) has a quartz observation window coated with a 50nm thick Al ₂ O3 protective film by magnetron sputtering, which increases the transmittance of ultraviolet light (172nm) to 95% while avoiding surface etching caused by plasma bombardment.

2. Borosilicate glass spectral monitoring window

Using 7740 borosilicate glass (B ₂ O3 content 14%), its thermal expansion coefficient (3.3 × 10 ⁻⁶/℃) is close to that of quartz, and it will not crack due to thermal mismatch at an etching temperature of 300 ℃. In Lam Research's Kiyo equipment, borosilicate glass windows combined with Fourier transform infrared spectroscopy (FTIR) monitoring can analyze the decomposition products of CF ₄ plasma in real time with an error rate of less than 2%.

2、 Gas delivery and distribution system

1. Quartz glass gas spray pipe

Quartz glass prepared by gas refining method (with a bubble content of<1/cm ³) has an inner wall roughness Ra<0.1 μ m, which can reduce flow fluctuations caused by NF ∝ gas adsorption. In the Prismo A7 etching machine of Zhongwei Company, the quartz spray tube achieves gas flow uniformity error<1% through laser drilling technology (aperture 50-100 μ m), ensuring etching rate deviation of ≤± 0.3nm/min.

2. Aluminum silicate glass gas mixing chamber

Aluminum silicate glass containing 12% Al ₂ O ∝, with a corrosion resistance level of 1 to NaOH solution, can be used for gas mixture components in wet etching. For example, in the BOE (Buffer Oxide Etching) process of an 8-inch wafer, the mixed cavity made of glass is designed with microchannels (width 500 μ m) to achieve precise ratio of HF and NH ₄ F, with etching selectivity controlled at SiO ₂/SiN=30:1.

3、 Wafer support and electrostatic shielding components

1. English glass electrostatic shielding ring

The quartz glass shielding ring polished with hydrofluoric acid has a surface flatness of<50nm and can form a uniform electric field at a static voltage of 150V, suppressing plasma etching deviation at the edge of the wafer. In the etching equipment of TSMC's 5nm process, the shielding ring is designed with magnetic shielding to control the edge etching depth difference within ± 5nm.

2. Microcrystalline glass wafer positioning block

The positioning block made of Schott ZERODUR microcrystalline glass (thermal expansion coefficient ± 0.03 × 10 ⁻⁶/℃) is processed into a V-shaped groove with an accuracy of ± 10 μ m by ion beam etching. It can achieve a positioning accuracy of ± 20 μ m when loading 12 inch wafers, avoiding wafer displacement caused by mechanical stress.