XPL-300 Cluster System for Wafer Backside Etching and thinning without Frontside Protection
XPL-300 was developed by Secon based on chemical downstream etching with a high yield radical generator base on the SEMWAVE technology without additional frontside protection on the wafer.
The substrate is transported and placed in the etch chamber in the normal mode (frontside up). The radical generator is mounted at the bottom of the chamber. According to normal CDE, the radicals diffuse to the substrate and react there. The etch products are pumped off via a ring shaped slit above the wafer edge.
The frontside of the wafer is protected non invasively by a neutral gas. The neutral gas flow, which is suppresses the diffusion of the reactive radicals to the frontside, is maintained by a special design of the chamber head. Due to this design, it is possible to etch in different modes. Often it is beneficial to remove layers not only from the wafer backside. Etching the rim of the wafer and a small but sharply defined region on the wafer edge on the frontside (edge exclusion) can avoid cracking or popping on these areas (better contamination control).
The edge exclusion can be realized by use of a special sealing mechanism. After the wafer is placed to movable chuck (the spider), the chuck moves towards the upper sealing. The spider is stopped by an indirect stop outside the area reserved for the wafer. With a correct adjustment of the stop, the distance between sealing and wafer frontside is £ 0.2 ± 0.01mm.
Applying a slight overpressure of the neutral gas within the sealing, a constant gas flow towards the sealing can be maintained. This gas flow prevents a penetration of the reactive radicals but is not strong enough to influence the process on the wafer backside and the defined wafer edge areas. The pressure difference between the etch and the neutral (protection) gas influences strongly the transition region between etched and unetched regions under the sealing. It is, therefore, an important parameter to adjust a sharp transition between these regions. With an optimized setup, a transition length smaller than 0.2 mm can be obtained which means that the transition looks optically very sharp. Using an optimized six pin spider, the regions under the pin can be etched residue-free.
XPL-300 Etching Chamber for single wafer processing (top view)
XPL-300 Cluster System
Surface Roughness Improvement After the Dry Etching for Damage removal
Mechanical Grind 15s Dry Etching 4min Dry Etching
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