1. Field of the Invention
The present invention relates to a cleaning apparatus for cleaning semiconductor wafers, glass for photomasks and the like (hereinafter referred to as substrates) and, more specifically, to a cleaning apparatus provided with a contact buffer apparatus.
2. Description of Related Art
A cleaning apparatus of interest to the present invention is disclosed in, for example, Japanese Patent Laying-Open Gazette No. 90941/1982. FIG. 1 is a side view of the cleaning apparatus shown in the gazette. The cleaning apparatus shown therein is called a swing type cleaning apparatus, since an arm provided with a cleaning brush is swingable.
Referring to FIG. 1 of the prior disclosure, the conventional cleaning apparatus comprises a cleaning portion 121 for cleaning a substrate 141, and a supporting portion 122 for supporting the cleaning portion 121. The cleaning portion 121 comprises: a rotary cleaning brush 102 for cleaning the substrate 141; a swing arm 101 for supporting the rotary cleaning brush 102 swingable in a horizontal direction; a driving motor 103 for rotating the cleaning brush, which rotatably drives the cleaning brush 102; and a transmission belt 104 for transmitting the drive of the driving motor 103 to the rotary cleaning brush 102. The support portion 122 comprises: an arm support 105 for supporting the cleaning portion 121 enabling rotation and elevation of the cleaning portion 121; a rotary driving apparatus 111 for rotating the arm support 105; an elevating apparatus 117 for elevating the arm support 105; a rotating position detecting sensor 115 for detecting the rotating position of the cleaning brush 102; and a stop 107 for adjustably setting the position to which the swing arm 101 is lowered. The rotary driving apparatus 111, the elevating apparatus 117, the rotating position detecting sensor 115 and the stop 107 are mounted on a base 140 by means of brackets and the like. The rotary driving apparatus 111 comprises a rotary driving motor 112 for rotating the arm support 105 through the transmission belt 114, and the elevating apparatus 117 comprises an output rod 119 being in contact with a lower end portion of the arm support 105 for elevating/lowering the arm support 105. When the rotary cleaning brush 102 is located in the position illustrated in FIG. 1, a spin chuck 142 for holding the substrate 141 is provided therebelow. A rotating position detecting apparatus 115 comprises three rotating position detecting sensors 115A, 115B and 115C which detect that the rotary cleaning brush 102 is at a standby position A, a central position B of the substrate 141 and the peripheral position C of the substrate 141 shown in FIG. 1, respectively.
The operation of the swing type cleaning apparatus will be described in the following. When the substrate 141 is to be cleaned, first, the arm support 105 is raised by the elevating apparatus 115 at the standby position A shown in FIG. 1, so that the swing arm 101 is raised. Thereafter, the rotary driving motor 112 is rotated, the swing arm 101 is swung through the arm support 105, and the cleaning brush 102 is moved to a position above the central position B of the substrate 141. The cleaning brush 102 is rotated about its axis at the position B and the swing arm 101 is lowered under control of the stop 107 through the arm support 105. After the rotary cleaning brush 102 is brought into contact with the surface of the substrate 141, the rotary cleaning brush 102 is swung about the arm support 105 from the central position B to the peripheral position C of the substrate 141, so that the substrate 141 is cleaned by means of the rotary cleaning brush 102.
Usually, very fine circuit patterns are formed on the surface of the substrate 141 before or after the step of cleaning. Therefore, the substrate must be handled delicately in cleaning so as to prevent any minute damage on the surface of the substrate. As the degree of integration of the IC circuits has been increased, it has become necessary to more delicately treat the substrate to prevent any damage on the substrate, to remove dust more completely, etc.
In the above described conventional cleaning apparatus, when the cleaning brush 102 is brought into contact with the substrate 141, the brush is lowered at the operational velocity of the output rod 119 of the elevating apparatus 117. Consequently, the edge of the cleaning brush 102 strikes the surface of the substrate 141 with relatively large energy. Especially, when the brush has a smaller contact area, the shock at the time of contact becomes larger. Consequently, the surface of the substrate is damaged and the above described strict conditions of cleaning are not satisfied.