Planarization of GaN by photoresist technique using an inductively coupled plasma

Patent metadata

Field	Value
Publication number	US-9230818-B2
Application number	US-201213603130-A
Country	US
Kind code	B2
Filing date	Sep 4, 2012
Priority date	Feb 2, 2006
Publication date	Jan 5, 2016
Grant date	Jan 5, 2016

Abstract

Films of III-nitride for semiconductor device growth are planarized using an etch-back method. The method includes coating a III-nitride surface having surface roughness features in the micron range with a sacrificial planarization material such as an appropriately chosen photoresist. The sacrificial planarization material is then etched together with the III-nitride roughness features using dry etch methods such as inductively coupled plasma reactive ion etching. By closely matching the etch rates of the sacrificial planarization material and the III-nitride material, a planarized III-nitride surface is achieved. The etch-back process together with a high temperature annealing process yields a planarized III-nitride surface with surface roughness features reduced to the nm range. Planarized III-nitride, e.g., GaN, substrates and devices containing them are also provided.

First claim

What is claimed is:

1. A substrate comprising:
a first layer, the first layer having roughness features deviating from a surface plane; and
a sacrificial layer covering the roughness features, the sacrificial layer having an essentially planar surface,
wherein the first layer responds to a first etching method at a first etch rate,
the sacrificial layer responds to the first etching method at a second etch rate, and
the ratio of the second etch rate to the first etch rate is in the range of 0.2 to 1.2.

2. The substrate of claim 1 , wherein a mean thickness of the sacrificial layer is less than 2 times a rms roughness of the surface.

3. The substrate of claim 1 , wherein the first layer is a layer grown on a crystallographic plane.

4. The substrate of claim 1 , wherein the sacrificial layer is a layer which has been applied using spin coating, sputtering, floating, evaporation, melting, stamping, or screen printing.

5. The substrate of claim 1 , wherein a mean thickness of the sacrificial layer is at least 100 Å greater than a maximum height of the roughness features.

6. The substrate of claim 1 , wherein the sacrificial layer comprises material that is a photoresist selected from AZ5214, AZ4330RS, and AZ4620.

7. The substrate of claim 1 , wherein the first etching method comprises inductively coupled plasma reactive ion etching.

8. The substrate of claim 7 , wherein the inductively coupled plasma reactive ion etching uses a plasma comprising a gas selected from the group consisting of: Cl 2 ; BCl 3 ; a mixture of Cl 2 and BCl 3 ; and a mixture of Cl 2 BCl 3 and Ar.

9. The substrate of claim 1 , wherein the first layer comprises a III-nitride material.

10. The substrate of claim 9 , wherein the III-nitride material is GaN and the inductively coupled plasma reactive ion etching uses a plasma comprising Cl 2 , BCl 3 , and Ar.

11. The substrate of claim 7 , wherein the first layer comprises GaN and the inductively coupled plasma reactive ion etching uses a plasma comprising Cl 2 , BCl 3 , and Ar.

Assignees

• Moustakas Theordore D
• Williams Adrian D
• Univ Boston

Inventors

• Moustakas Theordore D
• Williams Adrian D

Classifications

• H10P74/203

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• H10P74/23

  characterised by multiple measurements, corrections, marking or sorting processes · CPC title

• H10P90/126

  by chemical etching · CPC title

• H10P50/246

  of Group III-V materials · CPC title

• H10P50/00

  Etching of wafers, substrates or parts of devices · CPC title