| PATENT ASSIGNEE'S COUNTRY | Japan |
| UPDATE | 06.99 |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT CLAIMS |
Substrate is processed using a PO4H3 processing soln, the IMPROVEMENT comprising using as said processing soln a purified PO4H3 which is prepd by - Heating PO4H3 - Dipping a semiconductor base which is different from subs trate into heated PO4H3 so as to deposit impurities therein on base - Removing semiconductor base therefrom & has an impurity content < 0.001 Bq/mL as defined by the concn of a contained radioactive element selected from Pb & applying a protective film of Si3N4 or SiO2 for preventing adsorption of impurities to an unprocessed back surface area of substrate, said purified PO4H3 being used to process other areas of said substrate |
| PATENT PHOTOCOPY | Available on request |
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