Convex point production method capable of preventing blue film

Abstract

The invention provides a convex point fabrication method which can avoid blue membrane appearance. The existing convex point fabrication method uses low-temperature sulfuric acid solution for carrying out the etching, so as to remove a metal layer below the convex point; the metal layer below the convex can be removed, but the blue membrane is easy to be generated. In the convex point fabrication method of the invention which can avoid the blue membrane appearance, a metal layer below the convex point is firstly deposited on the existing wafers with a metal pad and a passivation layer fabricated, a light resistance layer is plated on the metal layer and the convex point images are transferred on the light resistance layer by lithography and development; the convex point is then fabricated and the light resistance is removed then; the sulfuric acid solution is then used for carrying out the etching, so as to remove the metal layer below the convex point which is covered by non-convex point; the convex point is finally refluxed; wherein, in the step that the metal layer below the convex point under the coverage of non-convex point is removed by carrying out the etching with the sulfuric acid solution, the etching temperature is not lower than 35 DEG C and the etching time is not less than 310 seconds. Blue membranes can be avoided by adopting the method of the invention when the convex point is fabricated.

Description

technical field

[0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for making bumps that can avoid blue films. Background technique

[0002] In order to meet the requirements of short, small, light and thin components for portable electronic products, bumps are made on the metal pad of the wafer chip as the lead-out end, and then directly flip-chip soldered. In order to save costs, the commonly used bumps are lead-tin bumps.

[0003] The production of bumps usually includes the following steps: first deposit an under-bump metal layer on the wafer with metal pads and passivation layer, then apply a photoresist layer and transfer the bump pattern by photolithography and development onto the photoresist, then make bumps, then remove the photoresist, and then etch with a sulfuric acid solution to remove the UBM layer not covered by the bumps, and finally reflow the bumps. In the above step of etching with sulfuric acid solution ...

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