Method for improving resolution in microelectronic circuits using photoresist overlayer by using thermally processed polyimide underlayer formed from positive photoresist and polyamic acid

Claim 1

In a process for manufacturing integrated circuits, said circuits having a first layer of conductors supported on a substrate, a process for reducing scattered light from a polyimide/photoresist interface during the exposure of a photoresist layer with light in a process for defining a second layer of conductors comprising: depositing a layer of polyamic acid on said first layer of conductors, said polyamic acid layer including a quantity of a positive photoresist; said positive photoresist including a diazo-oxo napthalene photoactive compound selected from the group consisting of 2-diazo-1 oxo napthalene, 1-diazo-2 oxo-napthalene and acids or an ester thereof, the quantity of the photoresist selected to provide the polyimide layer with an index of refraction approaching that of the photoresist layer; converting the polyamic acid to polyimide by successively heating to a first cure temperature in the range 90-110 degrees C., a second cure temperature in the range 150-250 degrees C., and a third cure temperature in the range 270-350 degrees C.; applying a layer of photoresist containing a dizao-oxo napthalene photoactive compound selected from the group consisting of 2-diazo-1 oxo napthalene, 1-diazo-2 oxo napthalene and acids or an ester thereof, on said polyimide layer; lithographically defining a pattern in said photoresist layer by exposure to light and subsequent development; and depositing the second layer of conductors through the pattern in the photoresist layer on said polyimide layer; whereby the polyimide layer with photoresist will reduce the undesired scattered and reflected light due to its light absorptive properties and index of refraction approaching that of the photoresist layer.