Method and system for controlled isotropic etching on a plurality of etch systems
A method for forming identical isotropic etch patterns in an etch system is disclosed. The method comprises providing a wafer paddle, a wafer, a plurality of identical etch systems, utilizing identical etch recipes within each of the plurality of etch systems, providing a fixed temperature stability time FTST for each system so that the heat transfer from the paddle to the wafer is constant, wherein the FTST is the same on each of the plurality of etch systems; and utilizing the plurality of identical etch systems to produce identical etches on each of the wafers based upon the FTST, wherein a five-second preheat step in the etch process is not utilized.
1. A method of forming identical isotropic etch patterns in a plurality of systems, wherein each etch system is identical and includes a plurality of wafer paddles and a plurality of wafers, the method comprising:
utilizing identical etch recipes within each of the plurality of etch systems;
providing a fixed temperature stability time (FTST) for each etch system so that the heat transfer from the wafer paddle to the wafer is constant, wherein the FTST is the same on each of the plurality of etch systems; and
utilizing the plurality of identical etch systems to produce identical etches on each of the wafers based upon the FTST.
2. The method of claim 1 , including determining the etch time of each of the wafers based upon the FTST.
3. The method of claim 2 wherein the determining step further comprises:
providing a plurality of wafers in each of the etch systems;
providing a different etch time for each wafer;
obtaining an isotropy undercut percentage of each etched wafer by measuring the critical dimensions of each wafer with a scanning electron microscope,
correlating the isotropy undercut percentage of each wafer with its particular different etch time,
selecting a desired etch time based on the correlated isotropy undercut percentage,
utilizing the desired etch time on each of the plurality of etch systems.
4. The method of claim 1 wherein the FTST varies according to the wafer material.
5. The method of claim 1 wherein the FTST is 30 seconds for silicon.
6. The method of claim 1 wherein the etch time is 12-28 seconds.
7. The method of claim 2 wherein the correlated isotropy undercut percentage is 33-50%.