Applications of quartz in semiconductors

I. Outstanding Characteristics of Quartz

Quartz (SiO₂) has become a core material in semiconductor manufacturing equipment, due to its excellent physicochemical properties:

Extremely low thermal expansion coefficient: Quartz exhibits minimal volume change with temperature fluctuations. This characteristic ensures dimensional stability during high-temperature processes in semiconductor manufacturing, preventing precision deviations caused by thermal expansion and contraction.

Ultra-high purity: Semiconductor-grade quartz purity is clearly graded, ranging from the lower-end 3N (99.9%) to the high-end 4N8 (99.998%), meeting the stringent requirements of different processes. High purity ensures that quartz components do not introduce contamination, which is crucial for nanometer-scale semiconductor manufacturing.

Excellent high-temperature performance: Quartz is resistant to deformation or fracture under high temperatures, capable of withstanding the high-temperature environments commonly encountered in semiconductor processes (such as oxidation and diffusion processes, which typically require temperatures exceeding 1000°C).

Chemical inertness: Quartz exhibits excellent stability against most acidic and alkaline chemicals, maintaining its integrity during semiconductor wet cleaning and etching processes without reacting with process chemicals.

Excellent electrical insulation: This characteristic makes quartz an ideal material in plasma processes, effectively isolating electrical field interference.

Good light transmittance and mechanical strength: Quartz exhibits good light transmittance in the ultraviolet to infrared spectral range, while possessing sufficient mechanical strength, making it suitable for manufacturing observation windows and optical components.

II. Quartz Processing Technology

The preparation of semiconductor-grade quartz is a complex process from raw materials to precision components:

Raw material sources: Semiconductor-grade quartz raw materials primarily come from three sources—natural quartz mines, rock crystal, and artificially synthesized quartz. With increasing process requirements, artificially synthesized quartz is increasing in proportion year by year due to its purity and consistency advantages.

Processing flow:

Raw materials undergo selection and purification to obtain high-purity quartz sand.

Quartz sand is processed through melting and molding to produce quartz tubes, quartz rods, or quartz ingots.

Various quartz components are produced through precision processing (cutting, grinding, polishing, etc.).

It is worth noting that the processing of semiconductor-grade quartz must be carried out in a cleanroom environment to avoid contamination, and the processing precision is extremely high, typically reaching the micrometer level or even higher.

III. Key Applications of Quartz in Semiconductor Manufacturing

Quartz components are used throughout the semiconductor manufacturing process. Here are the main application areas:

1. High-temperature process equipment

Quartz furnace tubes: As the core reaction chamber for high-temperature wafer processing (such as oxidation and diffusion), quartz furnace tubes directly determine temperature uniformity and process stability. Their low thermal expansion coefficient ensures dimensional stability during repeated heating and cooling cycles.

Rapid thermal processing (RTP) equipment: Quartz windows and quartz support components play a key role in rapid heating and cooling processes.

2. Wafer transfer and support

Quartz boats: Used to carry and transfer wafers, their design directly affects the airflow distribution and temperature uniformity between wafers.

Quartz baskets: Used for batch loading of wafers in cleaning and wet processes, their chemical stability ensures they are not corroded in strong acid and alkali environments.

Quartz rings: Used to isolate and fix wafer positions, preventing displacement during the process.

3. Thin film deposition equipment

Chemical vapor deposition (CVD): Quartz components serve as reaction chamber liners, preventing metal contamination and maintaining a clean reaction environment.

Physical vapor deposition (PVD): Quartz insulation components are used to control electric field distribution and isolation.

4. Etching and cleaning processes

Quartz components are used as chamber liners in plasma etching (Etch) equipment, withstanding plasma bombardment without generating particulate contamination.

In wet cleaning equipment, quartz baskets and tanks ensure the cleanliness of the cleaning process.

5. Other applications

Quartz crucibles: Used in the single crystal silicon growth process, their high purity and high-temperature resistance ensure the quality of single crystal silicon.

Some optical components in lithography processes also use quartz materials, utilizing their excellent light transmission characteristics.

IV. Technological Development Trends and Challenges

As semiconductor process nodes continue to shrink (towards 3nm and below), higher demands are placed on quartz components:

Purity improvement: The demand for 5N (99.999%) and higher purity quartz is increasing to reduce the impact of trace elements on advanced processes.

Improved processing precision: New memory types such as 3D NAND require quartz components with more complex structures and higher dimensional accuracy.

Development of new quartz materials: Research and development of new materials such as doped quartz and synthetic quartz to meet special process requirements.

Balancing lifespan and cost: How to extend the service life of quartz components while ensuring performance and reducing semiconductor manufacturing costs.

V. Conclusion

Quartz materials, with their unique combination of properties, have become indispensable key materials in semiconductor manufacturing. From crystal growth to chip packaging, almost every manufacturing stage relies on the participation of quartz components. As semiconductor technology advances to more advanced processes, the purity and processing technology of quartz materials will continue to improve, continuing to provide basic material support for the continuation of Moore's Law. In the future, innovative research and development of quartz materials will become one of the important factors driving the progress of semiconductor equipment.