MicroTech Systems, Inc. Engineering Wet Process Solutions

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Quick Dump Rinsing

General Purpose of Quick Dump rinsing

After chemical treatment of semiconductor wafers for cleaning, etching or stripping applications the process media shall be completely removed from the surface in order to stop the chemical reaction and take away chemical residues. When taken out of a chemical bath (or stopping the direct dispense in spray type equipment) typically 50 – 200 ml of medium is carried over with each 25 wafer batch. Chemistry is still covering the wafer surface, in particular within recess structures of the topology (moats, trenches) resulting in continuation of the chemical process outside the bath. This is in particular critical for etch applications, since local over etching might occur which destroys the pattern and therefore causes significant yield loss. Simultaneous the wafer will partly dry off leaving crystallized residues or contaminants which have attached during the transfer of the air liquid interface on the wafer. This typical ionic contamination can interact with the chemical of the subsequent step or create time dependent defect (caused by continuous growth of crystal by taking up airborne moisture. Therefore an immediate replacement of the active chemical is needed, as well as an effective method to remove loosely attached particles. This is achieved by high efficiency rinsing.
The primary objectives of effective rinsing processes after all chemical steps therefore are:

  1. To quickly and effectively stop the chemical reaction on the surface after the wafers have been removed from the bath. Typically this is achieved by diluting the surface concentration to less than 1 % of the chemistry previously used in the chemical treatment.
  2. To fully remove chemical and contaminant residues from the wafer, which are carried over from the chemical bath without ANY impact on the wafer surface. Typically a three orders of magnitude reduction is sufficient not leave residues on the wafer.
  3. To take off particulates from the wafer before the next chemical step or drying.

Independent of the type of wet processing equipment like immersion or spray tools this is achieved by rinsing the substrates with Ultra Pure Water (UPW). Basically three types of rinsing are used in Semiconductor manufacturing, depending on the tool type and application:

  • Overflow rinsing: immersion of wafers into a rinse bath with continuous introduction of water from the bottom of the tank and overflowing at the top rim.
  • Spray rinsing: Dispense of ultra pure water through spray nozzles directly onto the wafer at variable flow, pressure or temperature in a single pass mode (standard process of single wafer equipment)
  • Quick dump rinsing: a combination of the above for wet benches consisting of placing the wafer into a overf

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