Purification Grades
MOS, VLSI, ULSI and SLSI Quality
MOS
metal oxide semiconductor
Impurity metal ion concentration (per element) approx. 100 ppb, particle concentration < 1000/ml
VLSI
very large scale integration
Impurity metal ion concentration (per element) approx. 10-50 ppb, particle concentration < 250/ml
ULSI
ultra large scale integration
Impurity metal ion concentration (per element) approx. 10 ppb, particle concentration < 30 ... 100/ml
SLSI
super large scale integration
Impurity metal ion concentration (per element) approx. 1 ppb, particle concentration < 30 ... 100/ml
PPM, PPB and PPT
1 ppm (parts per million, 10-6) corresponds approximately to one drop (approx. 30 µl) in a rather large bucket.
1 ppb (parts per billion, 10-9) corresponds to one drop in a comparably small swimming-pool.
1 ppt (parts per trillion, 10-12) would be one drop in a small lake, or a 5 µm particle dissolved in a cup of coffee, or approx. 100,000 atoms in a drop!
How ‘Clean’ is Reasonable?
The reasonable purity degree of process chemicals depends – among many other parameters – on the minimum feature size to be realized, the required yield, the cleanroom class and subsequent process steps.It is almost impossible to definitely correlate suboptimum process results with a purity degree of the chemicals applied being too low. Therefore, one cannot make a definitive statement on the required purity grade.With VLSI and ULSI qualities, we fulfil almost all requirements in research and development as well as in production. In our booklet “Our Products” (available on request!), we introduce our resists, solvents and etchants with their available purity degree(s). Please contact us for any further questions!