The basic chemical reaction used for epitaxial growth in integrated circuit (IC) fabrication is the reduction of a gas containing silicon to deposit a thin layer of silicon onto a substrate.
The most common reaction for epitaxial growth involves the use of silane (SiH₄) as a precursor, typically in a chemical vapor deposition (CVD) process. The chemical reaction is as follows:
SiH4 (g)→Si (solid)+2H2 (gas)\text{SiH}_4 \, (\text{g}) \rightarrow \text{Si} \, (\text{solid}) + 2\text{H}_2 \, (\text{gas})SiH4(g)→Si(solid)+2H2(gas)
In this reaction:
- SiH₄ (silane) is the precursor gas.
- Si (silicon) is deposited on the substrate.
- H₂ (hydrogen) is released as a byproduct.
Process Overview:
- Silane gas (SiH₄) is introduced into a reaction chamber, typically under a controlled temperature and pressure.
- The gas undergoes a decomposition reaction due to the heat from the substrate (which is typically heated to around 1000°C).
- The silicon atoms from the decomposed silane are deposited on the wafer, growing a high-quality silicon layer on the surface in an epitaxial manner, where the crystalline structure of the deposited layer is aligned with the underlying substrate.
This process is crucial for growing a high-quality silicon layer on a silicon wafer, especially in the fabrication of bipolar and CMOS integrated circuits, where it is important to maintain the crystal structure of the substrate.