Method for manufacturing semiconductor memory

A method for manufacturing a semiconductor read-only memory on which data has been written, comprising the steps of:

• forming on a semiconductor substrate a plurality of memory cells for storing data, each including an insulated gate transistor having a gate electrode;
• forming on said semiconductor substrate by chemical vapor deposition a dielectric film to bury therein said insulated gate transistors formed on said semiconductor substrate;
• performing thermal processing on said substrate to reduce the water content of said dielectric film;
• and
• writing data by implanting ions into said memory cells selected to bias a threshold voltage of said transistors of said memory cells selected corresponding to data to be written,
• wherein metal wiring is formed for said memory cells on said dielectric film, and after said metal wiring is formed, said thermal processing is conducted on said substrate at a temperature lower than the melting point of said metal wiring.

A method for storing semiconductor wafers for manufacture of read-only memories in which data has been written, comprising of the steps of:

• forming a plurality of memory cells for storing data on a semiconductor substrate made of a semiconductor wafer;
• forming a dielectric film on said semiconductor substrate to cover said memory cells;
• performing thermal processing on said substrate to reduce the water content of said dielectric film for long-term storage;
• and
• storing said semiconductor substrate after receiving said thermal processing until data is written in said memory cells.

A method for storing semiconductor wafers for manufacture of read-only memories in which data has been written, comprising the step of:

• forming a plurality of memory cells for storing data on a semiconductor substrate made of a semiconductor wafer;
• forming a dielectric film on said semiconductor substrate to cover said memory cells;
• performing thermal processing on said substrate to reduce the water content of said dielectric film;
• and
• storing said semiconductor substrate after receiving said thermal processing until data is written in said memory cells, said semiconductor substrate being stored under the condition that a water-proofing film to prevent entry of moisture into said dielectric film is formed on the surface of said heat-treated dielectric film,
• wherein said water-proofing film is formed by a barrier metal.