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Gallium Phosphide Etchant
For Light Emitting Diodes

Controlled chemical etching of gallium phosphide for light emitting diodes, (LED), and matrix arrays with dielectric isolation.

FEATURES
  • Produces polished, unpitted surface
  • Does not attack silica or titanium masks or beam lead metallizations
  • Removes surface damage
  • Etches <100> and <111> crystal orientations
  • Etch rate 5 mils/hour at 80 °C
GALLIUM PHOSPHIDE ETCHANT
DESCRIPTION:

Transene Gallium Phosphide Etchant is an effective etchant designed for the fabrication of light emitting diodes and diode matrix arrays. It offers controlled chemical etching of gallium phosphide to produce mesa structures required for efficient LED and for the separation of LED to generate matrix arrays of alpha numeric displays. During the separation the LED can be shaped into domed structures also essential for efficient electroluminescent devices. The etchant is, furthermore, compatible with lead beam technology.

Transene Gallium Phosphide Etchant exhibits a high etch rate for all crystal orientations. All crystal faces of the <100> orientation of GaP are etched uniformly, producing a polished, unpitted surface. The faces of the <111> orientation etch differently; the <111> (Ga plane A face) develops a smooth orange-peel surface, whereas the <111> (P plane B face) becomes smooth, polished and unpitted. N- and P-type GaP have equivalent etch rates.

GaP Etchant is a stable, consistent formulation based on potassium hexacyanoferrate and easily applied to the manufacture of state-of-the-art gallium phosphide LED and beam lead electroluminescent devices. The etchant does not attack Pd, Au or Pt lead beam metallizations. Ti and SiO2 masks show minimal attack. GaP Etch is also effective for gallium nitride etching applications.

PROPERTIES OF GALLIUM PHOSPHIDE ETCHANT

Appearance

Amber liquid

Boiling point

> 100 °C

pH

13 - 14

Solvent Rinse

H2O

Etch Rates at 80 °C in Microns/hour

  

P-Type <100>

210

N-Type <100>

210

P-Type <111>

  

A Face (Gallium)

115

B Face (Phosphorus)

210

Compatible Dielectric Material

Sputtered or Silane SiO2

Compatible Masking Material

SiO2, Ti, Au, KMER

Compatible Beam Lead Materials

Ti, Pd, Au, Pt

Recommended Oper. Temp.

70-80 °C

Etch Capacity

12 grams/liter


APPLICATION:

Transene Gallium Phosphide Etchant is employed in several manufacturing operations for the production of light emitting diodes. The etchant may be used first to remove surface damage of mechanically polished p-type and n-type gallium phosphide. The following procedures are generally followed for device fabrication:
  1. Formation of mesa configuration with GaP etchant and SiO2 as a mask.
  2. Beam lead metallization and contact metallizations using photoresist techniques.
  3. Separation of GaP wafer into individual dies, by partial cutting with abrasive dicing machines followed by chemical etching with Transene GaP Etchant.