QDR Cleaning--An Essential Process in Tank Cleaning Equipment
Everyone knows that in the semiconductor manufacturing process, there are various kinds of contamination on the wafer. The physical and chemical properties of these contaminations vary. In order to remove all these stains, various chemicals must be used in the process. In order to ensure the cleaning effect of each chemical solution, after each chemical solution cleaning, it is necessary to add a QDR water wash.
QDR, also known as quick flushing, is mainly used to remove particulate impurities and residual chemical liquid on the wafer surface to make the wafer surface clean. QDR is the most important cleaning process module in wafer wet cleaning. It is mainly composed of spray tank, overflow tank, uniform flow plate, quick exhaust cylinder block, nozzle nozzle, pipeline and pipe fittings, etc. Its principle is shown in the figure below:
The tank body is welded and processed by imported NPP plates, and the fast exhaust cylinder installed at the bottom of the tank body, the DI water injection hole at the bottom and the DI water nozzles on the left and right sides of the top realize the rapid injection and discharge of the tank body, and has the function of nitrogen bubbling . A DIW resistivity detector is installed at the overflow discharge port, which can timely check and control the overflow water quality.
1. Spray pipeline:
There are two upper spraying pipelines, forming mutual cross spraying, but deionized water should not be sprayed directly to rinse the wafer surface. Because the wafer is directly sprayed on the surface of the wafer under the action of water erosion, it is easy to generate particulate sludge and pollute the surface of the wafer. Therefore, during the spraying process of deionized water, it is necessary to adjust the rinse water pressure, water volume, direction and angle Tested to achieve the best results with less particulate contamination. The spray range of a good nozzle covers all wafers and cassettes; while the poor spray rinse shape does not cover all wafers and cassettes, the dead zone that has not been sprayed and rinsed, the residual content of particles, impurities and chemical liquid Still high, but not good cleaning effect.
2. Nitrogen bubbling:
At the same time as the upper spraying, the lower spraying pipe continuously enters water from both sides of the bottom, and then overflows from the upper edge of the inner tank, so that the deionized water in each wafer seam and every corner can be continuously renewed. At the same time, pure nitrogen enters the tank from the lower spray pipeline. Nitrogen bubbling has the following effects: (1) Increase the scouring force of deionized water, which has a good self-cleaning effect on the tank itself; (2) The wafer vibrates in the water flow, and the bubbles cannot adhere to it, The rinse effect is improved; (3) the oxygen content in the deionized water is reduced to avoid oxide formation on the wafer surface.
3. Quick rush and quick row:
QDR spray water filling time and drainage time have a great influence on the quality of wafer cleaning. Because the surface of the wafer is exposed to the air and will contact oxygen molecules or water vapor in the air, a very thin oxide layer (about 0.5~1 nm) will grow at room temperature. The thickness of this layer of natural oxide is related to the exposure The time in the air is related to the length of time. Therefore, the longer the spray is filled with water, the longer the wafer will be exposed to the air, so the thicker the oxide layer will be formed, which is very unfavorable for wafer cleaning. of. The shorter the QDR drainage time, the greater the drainage flow rate, which is beneficial for the deionized water to take away the particulate impurities on the wafer surface. Therefore, in the QDR design, it is necessary to shorten the spraying water filling time and drainage time as much as possible to achieve fast flushing and fast discharge, and the overall efficiency will also be improved.