High Aspect Ratio (HAR) Micro-plated Structure Using KMPR®

Electroplating using high aspect ratio (HAR) photo lithography-defined microstructures is an important tool for the fabrication of micro metal structures. Electroplating molds with HAR features requires that the photoresist will survive harsh Ni, Cu, and Au electroplating bath environments and still be removed (plasma: O2/CF4) after the metal has been deposited. KMPR®, a thick (4 – 110µm) negative photo epoxy that uses standard aqueous alkaline developers, meets these requirements.

KMPR®: Benefits/Attributes

  • High aspect ratio imaging with vertical sidewalls
  • Up to 100+ µm in a single spin coat
  • Compatible with standard aqueous developers
  • No cracking
  • Strippable with standard wet or dry chemistry
  • Excellent metal adhesion
  • Excellent plating bath stability

Process Flow

1. KMPR® is coated onto seed layer.

2. KMPR® is exposed.

3. KMPR® is post-exposure baked.

4. KMPR® is developed.

5. KMPR® is electroplated.

Removal of KMPR®

6. Immersed in NMP (MCC’s Remover PG), KMPR® swells.

7. Further immersed in heated NMP, KMPR® continues to swell and then to lift.

8. Depending on resist thickness, plasma (O2/CF4) may be required. KMPR® is removed. Rinse.

9. Result: High aspect ratio (HAR) plated structures.

50 μm tall Cu post grid array, KMPR® removed
Source: Kayaku Advanced Materials, Inc.
Resist thickness: 800 nm Lines and spaces: 250 nm