Showerhead Reactor Conclusions

Daniel M. Dobkin
ShowerheadConclusions

Temperature control
Good heat transfer to wafer by conduction and radiation, but losses primarily through radiation, not uniform across wafer. Zone heating required for good uniformity.

Radid temperature changes may be implemented thought control is complex.

Radial film uniformity

Adjustable by changes in temperature and showerhead design.

Flexibility

Configuration lends itself to capacitive discharge plasmas for PECVD and chamber cleaning.

Productivity advantages

Batch configuration with manual load. Single-wafer configuration with fully automated load is relatively easy; reactor is then small and easily clustered with other functions. Easy in situ clean with plasma. Every wafer sees an identical environment.

Productivity disadvantages

Single-wafer configuration or mini-batch [e.g. several showerheads in a single chamber] require high deposition rates for good throughput, which tends to degrade film quality.

If lower platen is heated and ceiling cold, wafers tend to "potato chip" if loaded without preheat, can slide on platen.

Process advantages

Rapid change in gas conditions for multiple-layer films possible.

Process disadvantages

Plasma discharges tend to sputter contamination from reactor walls onto wafers, enhanced at electrode edges.

Small showerhead dispense holes can clog or erode, degrading uniformity.

Showerhead reactors are widely used for "back end" processes: deposition of intermetal dielectric layers, metals (e.g. CVD tungsten), and final passivation. Small manually-loaded showerhead reactors are very popular in R&D environments due to their versatility.

Reactors: Table of Contents

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Temperature control	Good heat transfer to wafer by conduction and radiation, but losses primarily through radiation, not uniform across wafer. Zone heating required for good uniformity. Radid temperature changes may be implemented thought control is complex.

Radial film uniformity	Adjustable by changes in temperature and showerhead design.

Flexibility	Configuration lends itself to capacitive discharge plasmas for PECVD and chamber cleaning.

Productivity advantages	Batch configuration with manual load. Single-wafer configuration with fully automated load is relatively easy; reactor is then small and easily clustered with other functions. Easy in situ clean with plasma. Every wafer sees an identical environment.

Productivity disadvantages	Single-wafer configuration or mini-batch [e.g. several showerheads in a single chamber] require high deposition rates for good throughput, which tends to degrade film quality. If lower platen is heated and ceiling cold, wafers tend to "potato chip" if loaded without preheat, can slide on platen.

Process advantages	Rapid change in gas conditions for multiple-layer films possible.

Process disadvantages	Plasma discharges tend to sputter contamination from reactor walls onto wafers, enhanced at electrode edges. Small showerhead dispense holes can clog or erode, degrading uniformity.