Why Semiconductors Use Nitrogen

Nitrogen is widely used in the semiconductor manufacturing process, mainly based on its unique physical and chemical properties and irreplaceable role in many key process links, the specific reasons are as follows:

1. Chemical inertness: core barrier to isolate contamination

nitrogen molecules by two nitrogen atoms through the triple bond, the structure is stable, almost no reaction with any substance at room temperature. This property makes it an ideal shielding gas in semiconductor manufacturing:

• prevent oxidation in high temperature processes (such as annealing and film growth), nitrogen can isolate oxygen in the air, avoid the formation of oxide layer on the surface of silicon wafers and other materials, and ensure stable electrical performance. For example, in rapid thermal annealing (RTP), nitrogen serves as a thermal medium to achieve a rapid ramp in temperature while maintaining an oxygen-free environment.
• Inhibition of impurity introduction in chemical vapor deposition (CVD), physical vapor deposition (PVD) and other thin film preparation processes, nitrogen is used as a carrier gas or reaction gas to prevent impurities from mixing into the thin film and improve device reliability. For example, when nitrogen mixed with fluoride is used to etch silicon wafers, the micro-nano structure morphology can be precisely controlled.

2. High purity and easy access: to meet the needs of harsh process

through air separation technologies such as cryogenic distillation, nitrogen with a purity of 99.999 percent or more can be produced on a large scale to meet the requirements of semiconductor manufacturing for extremely low impurity content:

• equipment purging and purging: Nitrogen is used to purge pipes and equipment to remove residual moisture, oxygen and particles and ensure the system reaches a clean level (e. g. ISO Class 1 standard) prior to pilot production on the production line.
• reaction atmosphere control in metal organic chemical vapor deposition (MOCVD), nitrogen is used as a carrier gas to uniformly transport metal organic compounds (such as trimethylgallium) to the reaction chamber to ensure the composition uniformity of compound semiconductor materials (such as gallium nitride).

3. Mobility and permeability: efficient removal of residues

nitrogen molecules are small and have excellent fluidity in gas delivery pipes and reaction chambers, which can quickly fill the internal space of the equipment and penetrate into tiny gaps:

• cleaning and purging after manufacturing steps such as acid-base treatment, nitrogen is used to clean residual impurities on the wafer surface; during process conversion, nitrogen purging can avoid cross-contamination and ensure batch quality consistency.
• Inhibition of particle deposition nitrogen maintains a positive pressure environment in the optical cavity, forming an invisible barrier to prevent the intrusion of external particles, especially suitable for core equipment such as lithography machines that are sensitive to particle contamination.

4. Temperature control and stability: guarantee process accuracy

nitrogen has a low thermal conductivity (thermal conductivity of about 0.02447W/(m · K)), which can help to achieve uniform temperature distribution during heat treatment:

• rapid thermal annealing: Nitrogen is used as a heat medium to help the silicon wafer quickly heat up and cool evenly at high temperatures, optimizing material properties.
• Optical Equipment Protection in lithography machines and other equipment, nitrogen stabilizes the humidity (dew point below -60 ℃) and temperature (fluctuation controlled at ± 0.1 ℃) in the cavity through Purge mechanism to avoid optical path distortion and component corrosion.

5. Reliability assurance of packaging and testing

• welding protection in nitrogen-filled reflow soldering and wave soldering, nitrogen can inhibit solder oxidation, improve wettability, reduce solder balls and bridging defects, and ensure solder joint quality.
• Simulate the actual environment in the semiconductor test link, the nitrogen environment can simulate the actual use conditions of the device and accurately evaluate the performance.

6. Cost-effectiveness and supply stability

• large scale preparation: Nitrogen accounts for 78% of the atmospheric volume and is rich in sources. It can be produced on a large scale at low cost through the cryogenic air separation method.
• On-site gas-making mode large semiconductor plants usually use on-site nitrogen production equipment to reduce repeated investment and transportation risks through large-scale production to meet stable gas demand.