Why Are Semiconductor Chips Baked?

In semiconductor manufacturing, chips are highly susceptible to moisture absorption from the environment during production, transportation, and storage. Additionally, they may contain volatile impurities. These factors can negatively impact chip performance and reliability. For instance, moisture can vaporize rapidly during subsequent high - temperature processes, generating internal pressure that damages the chip's internal structure, causing cracks or delamination. This affects electrical performance and may even scrap the chip. Volatile impurities can be released during chip usage, potentially causing short - circuits and corrosion. Chip baking effectively eliminates these issues, prevents oxidation, stabilizes metal particles, enhances test accuracy, and improves reliability, soldering quality, performance, and stability.

Reasons for Chip Baking

1. Moisture Removal: Chips absorb moisture during manufacturing, transport, and storage. In subsequent high - temperature processes like reflow soldering, this moisture vaporizes quickly, creating internal pressure. This can damage the chip's internal structure, causing cracks or delamination, which affects electrical performance and may lead to chip rejection.
2. Removal of Volatile Substances: Chips may contain volatile organic compounds and other impurities. Baking allows these substances to escape, preventing their release during subsequent packaging and usage. This avoids negative impacts on chip performance and reliability, such as short - circuits and corrosion.
3. Oxidation Prevention: In high - temperature environments, metal leads and pads on chips are prone to oxidation. Oxides can affect solderability and reduce electrical conductivity. Baking in an inert gas atmosphere prevents chip surface oxidation.
4. Metal Particle Stabilization:Baking redistributes and stabilizes metal particles within and on the wafer through heat treatment. This reduces electromigration and lowers the risk of voids in metal interconnects, enhancing the integrated circuit's lifespan and reliability.
5. Improved Test Accuracy:In the wafer - level testing (CP) process, baking removes moisture and impurities from the wafer's surface and interior. This prevents changes in electrical conductivity due to moisture and contaminants, ensuring accurate test results and reliable data.

Functions of Chip Baking

1. Enhanced Chip Reliability: Removing moisture and volatile substances reduces the risk of chip failure caused by internal stress and cracks during operation, extending its lifespan.
2. Improved Soldering Quality:Baked chips allow solder paste activators to activate more easily, improving solder wetting and resulting in higher - quality and more reliable solder joints.
3. Optimized Chip Performance:Eliminating impurities and contaminants reduces interference with electrical performance, improving conductivity and signal transmission stability.
4. Increased Chip Stability:Baking relieves internal stress, reduces micro - cracks and defects, and ensures greater stability during subsequent packaging, testing, and usage.

Types of Ovens for Chip Baking

1. Nitrogen - Filled Ovens:By introducing nitrogen to reduce oxygen levels, these ovens minimize oxidation and are suitable for oxidation - sensitive chips, effectively protecting chip surfaces.
2. High - Temperature Ovens: Used for short - duration baking at high temperatures, they feature rapid heating and cooling functions. The temperature and time can be set based on the chip's moisture - sensitivity level and material properties.
3. Clean, Oxygen - Free Ovens:Creating a high - temperature, low - oxygen, and clean baking environment by introducing inert gases, these ovens are ideal for chips with stringent baking requirements, such as precision electronic components and semiconductor chips. They prevent contamination and oxidation during baking.
4. Vacuum ovens:Baking in a vacuum lowers the boiling points of water vapor and volatile substances, facilitating their removal from the chip. This accelerates evaporation and organic decomposition, improving baking effectiveness while preventing chip oxidation and contamination. They are suitable for chips requiring high - quality baking or those needing to eliminate internal gaps and deeply - embedded moisture.

Chip baking is indispensable in semiconductor manufacturing. It removes moisture and volatile substances, prevents oxidation, stabilizes metal particles, and enhances test accuracy. Its functions include boosting chip reliability, improving soldering quality, optimizing performance, and increasing stability.