| 摘要 |
PURPOSE:To obtain an interlayer insulating film wherein the leak current is little and the dielectric breakdown strength is large, by forming a floating gate composed of polycrystal silicon in which impurity element is diffused in the state of a specified heating temperature and processing time, and forming an interlayer insulating film composed of an oxide silicon film by thermal oxidation. CONSTITUTION:As for a forming method for the interlayer insulating film of an EPROM, after a field insulating film 2 is formed on a p-type silicon substrate 1 by LOCOS method, a gate insulating film 3 is formed, and then a polycrystal silicon film 14 containing no impurity is stuck by CVD method. The substrate is heated at 900 deg.C, and subjected to a doping treatment in a reduced pressure atmospher for 15 mininutes, by applying phosphorus oxychloride to a diffusion source. In order that impurity element may not exist excessively in crystal grain boundary, the heating temperature and the processing time are predetermined. Further it is preferable that a test piece is made and its sheet resistance is measured and managed by 4-probe method. By thermal oxidation, an interlayer insulating film 15 is formed. A control gate film 6, the interlayer insulating film 15, a floating gate film 4 and the gate insulating film 3 are subjected to patterning, and an n<+> type source region 7 and a drain region 8 are settled to complete a device. |
