Semiconductor Wafer Particle Extractor

The invention relates to semiconductor device processing apparatus, and more particularly to an apparatus and method for removing silicon particles from semiconductor wafers during wafer flat alignment.

During semiconductor wafer processing, it is necessary to locate and align the flat edges of the wafers in the wafer cassette to enable automated equipment to process the wafers and provide the proper wafer alignment during processing. A flat finder apparatus is used to align as many as twenty-five semiconductor wafers in a cassette or wafer boat. Flat finders are needed in almost every step in the manufacturing process, which can be a many as 170 different steps.

Wafer flats are located by placing a number of wafers in a flat locator and rotating the wafers until all the flats are aligned. During the rolling and alignment process, particles of silicon or other material resulting from surface and edge polishing, and other processing steps adhere to the surface and edges of the wafers. These particles lead to device defects if they are not removed.

The invention is to an apparatus for removing particles from semiconductor wafers which is used in conjunction with and forming part of a flat alignment apparatus. The apparatus is a roller used on a flat alignment apparatus. The roller, which is used to turn the semiconductor wafers during flat aligning, is cylindrical in shape and has perforations around its outer surface through which a vacuum is pulled to pull loose particles, and particles from the surface and edges of the wafers into the cylinder for disposal.

As the wafers are aligned, the roller turns on bearings and the vacuum is pulled through a rotating joint that connects the roller to the vacuum source. Roller may be turned by hand, or connected to a motor used with automatic wafer aligners.

The technical advance represented by the invention as well as the objects thereof will become apparent from the following description of a preferred embodiment of the invention when considered in conjunction with the accompanying drawings, and the novel features set forth in the appended claims.

FIG. 1 illustrates a typical wafer aligner with a vacuum roller;

FIG. 2 is a side view, in part, showing the wafers on the vacuum port roller;

FIG. 3 is an end view, in part, showing the air and particle flow into the vacuum roller.

FIG. 1 illustrates a flat alignment apparatus 10 positioned under a semiconductor wafer cassette 11. Aligner 10 includes a frame having ends 16 and 17 connected by side rails 21 and 22. Wafer cassette 11 is positioned on aligner 10 and positions wafers 12 on roller 13. Knob 15 turns roller 13 which in turn rotates wafers 12 during alignment. Roller 13 is shown with openings 14 around the surface of the roller which extend through the roller wall into the center opening in the roller. A vacuum is drawn in roller 13 through openings 14.

A sensor switch 26 on frame 21 is for applying or starting the vacuum when a cassette of wafers is mounted on the aligner frame.

FIG. 2 is a side view of aligner 10, showing the location of the wafers on roller 13. The wafer cassette is not shown. Roller 13 is mounted on hollow shaft 18 which extends through end plates 16 and 17, mounting roller 13, and permitting roller 13 to freely rotate on shaft 18. Attached to shaft 18 a rotating seal-joint 19, attaching shaft 18 to vacuum line 20. As roller 13 rotates, wafers 12 also rotate for aligning the wafer flats. A vacuum is drawn through line 20 and shaft 18 drawing air into openings 14 in roller 13. As wafers 12 rotate, silicon particles and other contaminants fall from wafers 12 and are drawn into roller 13, removing the particle contaminants from the vicinity of the wafers. The drawn vacuum also helps to draw or "suck" contaminant particles from the wafers.

FIG. 3 is a cross-sectional view, in part, showing wafers 12 held between the walls 11a and 11b of cassette 11. Cassette 11 is positioned in the side rails 21 and 22 of aligner 10. Roller 13 is in rolling contact with wafers 12. Arrows 29, 27 and 28 show air flow into roller 13 through openings 14. Contaminant particles from wafers 12 are drawn into roller 13 through openings 14, removing the contaminant particles from the area around the wafers.

In operation, semiconductor wafers are loaded into wafer cassette 11. The cassette is placed on aligner 10 and roller 13 is turned until the flats of the wafers are over roller 13 and stop turning.

During the rotation of wafers 12, a vacuum is applied to shaft 18 which is connected (not shown) into the interior cavity of hollow roller 13. Air is drawn into roller 13, pulling contaminant particles into roller 13, removing the particles from the vicinity of the wafers.

The roller has been illustrated with a particular hole pattern placing a row of holes around the circumference of the roller at positions between the wafers. However, the hole pattern is not critical as long as air is drawn into the roller on each side of a wafer.