Recognizing the importance of impurity content of gases in the manufacture of semiconductors, suppliers responded by introducing products with improved analytical characterization, notably for trace impurities. Products which meet all of the requirements may be described as "meeting SEMI specifications." Where an analytical procedure different from that provided is substituted by a supplier or user, the burden of proof is on said supplier or user to confirm the equivalency. It should be noted that the following list of criteria was considered when determining the specified analytical method: Reliability; Ease of Use; Maintenance; Precision; Accuracy; Sensitivity; Versatility; and Availability of Equipment.

This specification is specific to Helium (He) in Cylinders 99.9995% Quality - used in the manufacture and processing of semiconductors and advanced electronic devices and circuits. A gas conforming to the specifications will commonly contain more of the major component than the minimum permissible limit or contain less of an impurity (or several impurities) than the SEMI C3 maximum permissible limit. In neither case shall the gas be considered as of higher quality than that defined by the specification.

The intent of these specifications and the associated procedures is, on one hand, to assure that a gas is suitable for the common uses to which it may be put in the manufacture and processing of semiconductor devices and, on the other hand, to be consistent with contemporary manufacturing processes for that gas.

Referenced SEMI Standards
None.

Revision History
SEMI C3.20-92 (Reapproved 0999)
SEMI C3.20-92 (technical revision)
SEMI C3.20-82 (first published)