SAMCO is presenting a paper at AVS 63rd International Symposium, titled “Deep GaAs Etching with V-shaped Trench Profile Using Inductively Coupled Plasma Technology“.

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Abstract

There is an ongoing demand for device miniaturization, and at the same time, improvement of the die yields per wafer. For die separation with brittle wafer materials such as Gallium Arsenide (GaAs), Indium Phosphide (InP), and Gallium Nitride (GaN), a diamond tipped tool is widely used for the scribe and break process. Using a diamond tipped tool provides deep V-shaped scribe lines with a sharpened point profile on the bottom. However, this scribing method may cause die chipping, and also limits the minimum width of the streets between die. Wet etching can fabricate a V-shaped scribe line with a sharpened point profile on the bottom, but its depth is limited to just a few hundred nanometers [1], and is not deep enough to break substrates that are a few hundred micrometers thick. As an alternative to scribing with the diamond tipped tool or wet etching, plasma scribing technology offers a chipping-free process solution with deep scribe lines and narrow street widths for higher die yields. Additionally, batch processing of multiple wafers by the plasma scribing technology enables higher throughput than other techniques. However, conventional GaAs deep plasma etching processes yield scribe lines with a rounded bottom profile, and the rounded bottom makes the die separation irreproducible. In order to make die separation more precise and reliable for plasma scribing, the trench profile of scribe lines needs to be a V-shape with a sharp bottom profile.

In this research, an Inductively Coupled Plasma (ICP) etching technology suitable for GaAs die separation was developed to achieve a V-shaped trench with sharp bottom profile. Scribing and breaking of GaAs depend on the orientation of the scribe lines on the GaAs surface. The GaAs wafers used for this experiment had a <100> crystal orientation, and were 350 μm thick. A 10 μm wide photoresist mask and chlorine chemistry were used to etch 50 μm deep trenches with a sharp point profile at the bottom. The GaAs etch rate was 9.6 µm/min and the etch selectivity of GaAs over photoresist was approximately 10:1. In the investigation of the relationship between the etch depth and the trench profile, it was found that the bottom flat of the trench shrinks in size from the initial trench width, as the trench depth increases.

The V-shape with the sharp point profile on the trench bottom enables reproducible plasma scribing of GaAs wafers, minimal street widths between die and minimal damage to the die upon die separation.

References

[1] A. Turala, A. Jaouad, D.P. Masson, S. Fafard, R.Arès, and V. Aimez. International Journal of Photoenergy 2013, 583867 (2013)

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Samco is developing a plasma dicing and scribing technologies of silicon and III-V compound semiconductor materials (GaAs, InP and GaN-on-Si).
Our technologies will contribute to advanced packaging for die yields improvement in device production.
For more details of our plasma dicing and scribing technologies, please visit the page below.
Plasma Dicing and Scribing of Silicon & III-V (GaAs, InP and GaN-on-Si)