Applied Materials (AMAT, Santa Clara, CA) has entered the wafer cleaning end of semiconductor equipment supply with a 300mm-only, single-wafer, four-chamber wet-clean tool dubbed Oasis.
Tools have already been shipped to logic, foundry, and DRAM customers worldwide. For company executives it's a natural fit, a needed addition to AMAT's broad array of single-wafer cluster tools - the AMAT program to develop Oasis technology was an offshoot of its thermal processing work. Additionally, the wafer cleaning market is big - up to 25% of fab process steps are cleans.
Oasis technology combines several well-understood conventional wet-cleaning chemistries (i.e., RCA SC1 and SC2 cleans). Briefing WaferNews, Satheesh Kuppurao, manager of the wet clean division in AMAT's transistor and capacitor group, says, "A typical process sequence includes a dilute HF clean (30 sec.), a rinse (20 sec.), a one-step SC1 plus SC2 clean using AMAT-proprietary additives and broad-beam megasonics (30 sec.), a rinse (20 sec.), and a spin dry (20sec.). Wafers are cleaned on both sides simultaneously using fresh chemistry for each wafer and dried in ULPA air flow."
Kuppurao would only identify the additives of the AMAT chemistry, which is being supplied by Mitsubishi, as "organic surfactants and chelating agents."
In one specific test, wafers with ~2500 Si3N4 aerosol-deposited particles were given a 40 sec. clean (1:2:80, AM1:H2O2:H2O) at 80 degrees C using ~1.4W/cm2 megasonics, resulting in ~99% average particle removal from both back and front sides of the wafer. Other tests have shown that over 10 days and >5,000 wafer, wafers see fewer than 2<0.12-micron particle "adders."
The market for this new AMAT tool seems enormous, although there are several established wet clean equipment suppliers with single wafer technology. According to Dataquest estimates, the total market for wet cleaning fab equipment was $1.0 billion in 2001 and is projected to grow to $1.9 billion by 2004.
"The portion of that market for 300mm wafer fabs in 2002 is estimated to be $262 million, including both batch and single wafer systems, with single-wafer systems totaling about 20% of the total 300mm cleaning equipment market share," says Kuppurao. Approximately 60% of the market is for FEOL pre-thermal and post-strip cleans, mainly using conventional RCA or HF RCA cleaning prior to thermal processes. "Today, >75% of the market is occupied by wet clean benches. Approximately, 20% of 300mm wet clean market is single-wafer tools, which is forecast to be >50% single-wafer by 2004," he says.-P.B.