Cover Story
Above: Fig. 4. Patterned Sapphire Substrate wafer etched
using an Oxford Instruments Plasmalab System133 ICP380
Left: Figure 2: 12 x 2” Sapphire Wafers ready for etching
Figure 2 shows a fully loaded carrier with twelve 2”
wafers in-situ. The plate is designed to deliver helium to the
rear of each substrate, and to clamp the wafers in a sandwich.
There is clearly space to accommodate larger batch sizes, and
18
designs exist for up to 18 x 2” wafers.
The efficiency of the cooling is shown in Figure 3. This is
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the temperature of one of the batch of 2” sapphires carried
.eur on the sandwich plate. The wafer temperature is kept well
Templates for Blue
oasiasemiconductor
below 90°C even after one hour of etching, sufficient to
and UV LEDs
ensure the integrity of the photoresist.
A prime example of using this technique is Patterned
GaN, AlN, AlGaN, InN, InGaN
Sapphire Substrate (PSS) etching for high quality GaN growth.
Figure 4 shows a typical feature etched onto a wafer, this
pattern is repeated across the batch of twelve wafers.
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Etching large numbers of wafers with a photoresist mask
requires good temperature control of each wafer, and this
requires an understanding of how to transfer the heat from
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Issue II 2009
the plasma away from the samples to the cooled electrode.
Helium backside cooling is the key, and understanding how to
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enable this for every wafer ensures success.
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Contact us now! Technologies & Devices International
Tel: +1 301 572 7834
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®
www.oxford-instruments.com/tdi3
Figure 3: Wafer temperature during etch
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