Automatically adjustable brush assembly for cleaning semiconductor wafers

#The present invention relates in general to a cleaning machine for cleaning the surfaces of semiconductor wafers. More particularly, the present invention relates to an adjustable brush assembly for cleaning semiconductor wafers.

#Semiconductor wafers are typically cleaned in a cleaning machine which includes one or more brush stations each having a pair of rotary brushes for cleaning the upper and lower surfaces of the wafer. When the wafer is positioned between the brushes, the rotary brushes apply pressure across the wafer surfaces to clean the wafer. A pair of stop assemblies engage the forward edge of the wafer to retain the wafer between the brushes and spin the wafer so that the entire surface area may be cleaned by the brushes. One or more liquid agents are sprayed onto the wafer or the brushes to facilitate cleaning of the wafer. After a set period of time, the stop assemblies are pivoted away from the wafer and the wafer is allowed to pass through the brush station into either another brush station or a final spin station where the wafer is rotated at speeds of approximately 2000 rpm to dry the cleaned wafer.

#The cleaning pressure applied to the wafer by the upper and lower brushes is dependent upon the thickness of the wafer and the spacing between the brushes. Preferably, the surfaces of the upper and lower brushes are substantially parallel so that a uniform pressure may be applied to clean the wafer surface. In the brush stations of the available cleaning machines, the lower brush is typically retained in a fixed position. The upper brush is secured to a rigid brush carriage assembly having a transverse bar pivotally mounted to the frame of the machine. The orientation of the brush carriage is manually calibrated so that the upper brush is substantially parallel to the lower brush. Micrometers positioned at opposite sides of the brush carriage are used to manually adjust the height of the brush carriage to obtain the desired spacing between the brushes. This spacing determines the pressure that will be applied to the wafer.

#Additional objects and features of the invention will be more readily apparent from the following detailed description and appended claims when taken in conjunction with the drawings, in which:

#FIG. 1 is a top plan view of an adjustable brush assembly in accordance with the present invention, shown mounted to the frame of a cleaning machine.

#FIG. 2 is a side plan view of the brush assembly of FIG. 1.

#Reference will now be made in detail to the preferred embodiment of the invention, which is illustrated in the accompanying figures. Turning now to the drawings, wherein like components are designated by like reference numerals throughout the various figures, attention is directed to FIGS. 1-5.

#FIGS. 1-5 show a pair of brush stations 6 and 7 of a cleaning machine for cleaning semiconductor wafers 8. An automatically adjustable brush assembly 10 in accordance with the present invention is positioned in each brush station 6 and 7 and mounted to the frame 12 of the cleaning machine for uniformly cleaning semiconductor wafers 8. During operation of the machine, a wafer cassette (not shown) positioned to the right of the first brush station 6 individually feeds the semiconductor wafers 8 into the first brush station. The brush assembly 10 engages the wafer 8 and cleans the wafer surfaces as is described in more detail below. The wafer 8 passes from the first brush station 6 to the second station 7 where it is cleaned by a second brush assembly 10. As is known in the art, liquid agents alone or in combination such as citric acid, deionized water, ammonium hydroxide, hydrogen peroxide, etc. may be sprayed or injected into each brush station by an injection system 9 (shown schematically in FIG. 5) to facilitate cleaning of the wafers 8. From the second brush station 7, the wafer 8 is moved to a spin station (not shown) where the wafer is rotated at high speeds to dry the wafer. The cleaned wafer is ejected from the spin station and deposited in a second cassette (not shown). The construction and operation of the wafer cassettes, spray injectors and spin station is known in the art.

#As shown particularly in FIGS. 1 and 2, the brush assembly 10 includes a lower rotary brush 14 and a brush carriage 16 having an upper rotary brush 18 for cleaning the surfaces of the semiconductor wafer 8. In the illustrated embodiment, the lower brush 14 generally includes a sleeve 20 carried by a lower roller 22. Bearings 24 rotatably mount the roller 22 to the frame 12, securing the lower brush 14 in a fixed position relative to the frame 12. A motor (not shown) carried by the frame and coupled to one end of the lower roller 22 drives the brush 14 in a counter-clockwise direction to polish the lower surface of the wafer 8 and move the wafer forward through the brush station 6.