Abstract: A second purifying apparatus 2 for furthermore purifying working solution purified by a first purifying apparatus 1 is disposed downstream of the first purifying apparatus 1. A working-solution introducing pipe 42 which is capable of diffusing and discharging the working solution from the lower end thereof is disposed in substantially the central portion of the working-solution accumulating tank 40 in which the working solution is accumulated. A filter 44 for vertically sectioning the working-solution accumulating tank 40 at an intermediate position is provided. A weir 45 is formed at an upper end of the working-solution accumulating tank 40. Moreover, a separating wall is formed along the inner wall of the weir 45. A solution gathering groove 47 is provided for the outer surface of the weir 45.

Abstract: Transfer data indicating a measurement status of a characteristics test of a semiconductor memory device is written into the semiconductor memory device itself in any one of a series of measurement steps. In the immediately following measurement step, the transfer data is read out, before performance of a characteristics test of this step, to judge the measurement status of the preceding measurement step. For example, the transfer data is data indicating that the characteristics test has been performed in the preceding step. Alternatively, it is classification data indicating a rank of the semiconductor memory device.

Abstract: Test data is written into respective semiconductor memory devices, e.g., EEPROMs formed on a wafer. Then, the semiconductor memory devices, still located on the wafer, are baked in a high-temperature atmosphere for a predetermined time. Examples of the baking temperature and time are 200.degree. C. and 8 hours. The test data is read from the respective semiconductor devices to check whether the test data is held by the respective memory devices in a correct manner.