Method of prefilling of keyhole at the top metal level with photoresist to prevent passivation damage even for a severe top metal rule

A method of planarizing a surface of a photoresist layer formed above a layer formed over a gap in a blanket silicon nitride passivation layer which in turn is formed above a keyhole in metallization with a thin glass layer therebetween on the surface of a semiconductor device, comprising the steps as follows:

• form said thin glass layer only in said keyhole located only well below the top of the metallization,
• form said blanket silicon nitride passivation layer covering said metallization and said keyhole, said blanket silicon nitride passivation layer having a deep narrow hole formed therein with a narrow neck and a wide gap formed deep in said blanket silicon nitride passivation layer above said keyhole,
• form a blanket, first photoresist layer above said blanket silicon nitride passivation layer with a relatively sharp depression therein above said keyhole caused by said gap,
• partially strip said first photoresist layer in a wet and dry etching process leaving a residual portion of said first photoresist layer in said gap, and
• form a blanket, second photoresist layer above said blanket silicon nitride passivation layer and perform a soft bake, an exposure, a developing step, and a hard bake of the second photoresist layer, thereby providing a planarized surface on said second photoresist layer.

A method of planarizing a surface of a photoresist layer formed above a layer formed over a gap in a blanket silicon nitride passivation layer which in turn is formed above a keyhole in metallization, the metallization having a top, with a SOG (Spin on Glass) film therebetween on the surface of a semiconductor device, comprising the steps as follows:

• form said thin SOG film only at the bottom of said keyhole, well below the top of the metallization,
• form said blanket silicon nitride passivation layer covering said metallization and of the semiconductor device and said SOG in said keyhole, said blanket silicon nitride passivation layer having a deep narrow hole formed therein with a narrow neck and a wide gap formed deep in said blanket silicon nitride passivation layer above said keyhole,
• form a blanket, first photoresist layer above said blanket silicon nitride passivation layer with a relatively sharp depression therein above said keyhole caused by said gap,
• partially strip said first photoresist layer in a wet and dry etching process leaving a residual portion of said first photoresist layer in said gap, and
• form a blanket, second photoresist layer above said blanket slicon nitride passivation layer and perform a soft bake, an exposure, a developing step, and a hard bake of the second photoresist layer, thereby providing a planarized surface on said passivation layer provided by said first and said second photoresist layers.