showerhead

A showerhead is the gas distribution component in a CVD chamber that disperses process gases uniformly across the wafer surface. **Design**: Flat plate with hundreds to thousands of small holes (0.5-2mm diameter) arranged in a pattern optimized for uniform gas distribution. **Position**: Located above the wafer, parallel to the surface. Serves as one electrode in parallel-plate PECVD reactors. **Material**: Typically anodized aluminum or ceramic-coated aluminum. Must withstand plasma, heat, and corrosive gases. **Function**: Creates uniform gas flow field across wafer diameter. Converts bulk gas flow into distributed shower pattern. **Hole pattern**: Optimized hole spacing and diameter for target uniformity. May vary from center to edge to compensate for flow effects. **Dual-zone**: Some designs have separate inner and outer gas zones for tuning center-to-edge uniformity. **Plasma role**: In PECVD, showerhead is often powered electrode (RF applied). Wafer chuck is ground or secondary RF. **Cleaning**: Accumulates deposited film over many wafers. Cleaned periodically with NF3 plasma or replaced. **Gap**: Distance between showerhead and wafer (gap) affects uniformity, deposition rate, and plasma characteristics. **Consumable**: Showerheads are consumable parts replaced during scheduled maintenance.