Impact of Polycrystalline Silicon Processing on Properties of MOS Memory Devices

In EEPROMs mèmory devices, tunnel oxides with high fluence, and interpoly oxides with low conductivity and high breakdown field are needed. Tunnel oxide fluence is degraded by high temperature annealing after the polysilicon deposition, while interpoly oxide is degraded by low temperature oxidation, particularly on rough films. As a consequence, a process optimization, giving a good compromise between these two quantities is required. In this work we shown that if a flat polysilicon is used, an interpoly oxide of good quality can be obtained at low temperature, maintaining a high value for the tunnel oxide fluence.