maintain the relative humidity in the tank 12 to 80 and more a preferred embodiment of an apparatus for preparing and or supplying a slurry for a cmp apparatus according to the present invention has been described the present invention however is not limited to the illustrative embodiment described above and various aspects may be implemented for example although the term u201c humidifying air u201d that comprises pure water and air is used an arrangement that uses water that has generally a similar effect including pure water and ultra pure water and nitrogen gas are within equivalents of the present invention and may also be implemented the slurry preparation apparatus etc 10 in a configuration as shown in fig1 was used to carry out cmp for verifying the effect of the present invention the capacity of the tank 12 was 15 liter and a colloidal silica slurry from cabot type ss 25 was used as a stock slurry solution ic1000 from rodel inc was used as a polishing pad a silicon wafer with an oxide film deposited was used for a working substrate humidity in the tank 12 during operation of the slurry preparation apparatus etc 10 was set to 92 and cmp was continuously run for 8 hours the slurry as it was after the run was used to polish working substrates for the test and microscratches were counted for polished 5 working substrates the number of microscratches in plane.