The role of purified nitrogen in semiconductor processes

In semiconductor processes, purified nitrogen plays a vital role, and its application runs through multiple key links in the entire production process. The specific functions are as follows:

1. Protective gas

Purified nitrogen serves as a protective gas and can effectively isolate oxygen, water vapor and other components in the air that may adversely affect semiconductor materials during the semiconductor manufacturing process. This protective effect is mainly reflected in the following aspects:

1. Prevent material oxidation: Semiconductor materials easily react with oxygen at high temperatures, causing oxidation. Purified nitrogen, as an inert gas, can form a barrier that effectively isolates the external environment and prevents semiconductor materials from coming into contact with oxygen during processing, thereby avoiding oxidation reactions and protecting the performance and stability of semiconductor materials.
2. Maintain material purity: In the storage, transportation and processing of silicon wafers in various manufacturing equipment, the presence of purified nitrogen can ensure that the cleanliness and original state of the silicon wafer surface are maintained and prevent pollution.

2. Equipment purging and purification

Equipment purging is a key operation during daily maintenance and process conversion of semiconductor manufacturing equipment. Purified nitrogen can remove residual unreacted gases, reaction by-products and possible impurities inside the equipment, avoid cross-contamination to the next process, thereby ensuring the quality consistency of each batch of products.

3. Reaction atmosphere control

Many semiconductor manufacturing processes need to be carried out in specific atmospheric environments, and purified nitrogen is often used as a key gas to control the reaction atmosphere. For example:

1. high temperature annealing process: In the high-temperature annealing process, purified nitrogen can reduce the oxygen concentration in the furnace to extremely low levels, creating an oxygen-free or low-oxygen reaction environment, ensuring that only the expected internal structural adjustments occur during the annealing process, and are not oxidized.
2. Metal Organic Chemical Vapor Deposition (MOCVD) Process: Purified nitrogen as a carrier gas can uniformly transport metal-organic compounds (such as trimethylgallium, etc.) into the reaction chamber, ensuring uniform distribution of the concentration of the source material in the reaction area, thereby ensuring that the grown compound semiconductor material has uniform composition, good crystal structure and excellent electrical properties.

4. Chemical vapor deposition (CVD) and physical vapor deposition (PVD)

1. CVD process: During chemical vapor deposition, purified nitrogen is used as a carrier gas or reactive gas to help form high-quality thin films, such as silicon nitride (Si3N4). These films have excellent insulation and chemical stability, which are crucial to improving the performance and reliability of semiconductor devices.
2. PVD process: During physical vapor deposition, purified nitrogen is used to create a reactive atmosphere that facilitates the deposition of thin films of metals or other materials. By controlling the flow rate of purified nitrogen and the reaction environment, films with specific characteristics, such as hardness or electrical conductivity, can be obtained.

5. Cleaning and purging

In all aspects of the semiconductor production line, purified nitrogen is often used to clean and purge equipment to remove residual impurities and pollutants and ensure the cleanliness of the production environment. This cleaning and purging effect is of great significance for improving the yield and reliability of semiconductor products.

6. Packaging and testing

1. encapsulation process: During the semiconductor packaging process, purified nitrogen can protect semiconductor devices from the external environment, such as preventing the intrusion of oxygen and water vapor, reducing oxidation risks, and protecting packaging materials and chips. For example, during lead-free soldering, purified nitrogen is used to reduce oxidation and ensure the quality and reliability of solder joints.
2. test session: Purified nitrogen helps simulate the actual use environment and accurately evaluate the performance of semiconductors.

7. Prevent oxidation and pollution

Purified nitrogen is also used to prevent oxidation and contamination in semiconductor processes. In key processes such as lithography and etching, purified nitrogen can effectively inhibit the chemical reaction between photoresist and oxygen, avoid changes in photoresist performance, and ensure pattern fidelity. At the same time, it can also prevent materials from being oxidized or contaminated during the etching process and maintain the purity and flatness of the silicon wafer surface.

8. Rapid thermal annealing

During rapid thermal annealing, purified nitrogen serves as a carrier gas to help achieve rapid temperature rise and fall. By accurately controlling the flow and temperature of purified nitrogen, the electrical properties of semiconductors can be optimized and product quality and stability can be improved.