Diode Protection against Interlevel Polysilicon Shorts
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
When an N/+/ type polycrystalline silicon layer over a silicon dioxide, which is, in turn, over a P- type silicon capacitor, breaks down, a PN+ junction is formed. This capacitor is now a diode. In the case of double polysilicon wiring, as an example, interlevel silicon dioxide breakdowns are a known cause of polysilicon to polysilicon shorts. Typically, these polysilicon lines are of the same doping type. For diode protection against polysilicon to polysilicon shorts the interlevel lines must be of opposite dopant types; for example, the first polysilicon layer is N+, and the second polysilicon layer is P+. The voltage is then maintained such that when a breakdown occurs, the diode would be in a reverse bias, that is, the N type line more positive than the P type line.