PROBLEM:
The integrated circuit (IC) industries’ current photoresist stripping processes are quickly becoming inadequate as the size of device geometries continually decrease. The rising costs, environmental hazards and waste treatment of the toxic chemicals used in the ashers and wet benches to remove photoresist are rapidly increasing the demand for an all-dry photoresist removal process.

SOLUTION:
The XLC-100 removes hard baked photoresist from silicon wafers in a single process step without the use of wet chemicals or excessive handling. The XLC-100 process uses a patent pending technique which involves an excited zone of near-visible/visible energy and reactive gas with no waste-treatable by products. The cost is low and throughput is comparable to current asher and wet bench processes. A typical cycle time is approx. 3 minutes.

Additional benefits/advantages of this process are:
€ All-dry process
€ Carbon free and damage free
€ Small volumes of green gases
€ Small footprint
€ Minimal facility needs
€ Total elimination of water & chemical waste
€ Zero emissions

RESULTS:
Hard baked wafer samples were processed in the XLC-100 using wafers coated with Shipley 1818 photoresist baked at 120°C for 60 seconds with various thickness. These samples were then sent for XPS and AFM analysis showing carbon levels below the limit of detectability (approx. 3Å) and no surface roughening of the wafer.

XPS ANALYSIS OF WAFER SAMPLES: <table>
Substrate / Description Carbon Thickness (Å)
Si / Control 2.32
Si / XLC-100 Cleaned 2.43

PROCESS:
The cleaning process uses a patent pending technique involving an excited zone of energy and reactive gases with no waste-treatable by products. The processing parameters for this application include an oxygen, ozone and water vapor gas recipe combined with near-visible/visible radiation under vacuum. The typical process time to completely remove hard baked photoresist is approx. 186 seconds per wafer.

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BEFORE:
AFM of Silicon wafer before XLC-100 photoresist removal showing an RMS deviation equal to 1.54Å.

AFTER:
AFM of Silicon wafer after XLC-100 photoresist removal showing an RMS deviation equal to 2.43Å.