| 摘要 |
PURPOSE:To prevent the magnification error owing to a fluctuation in temp. and atm. pressure and the generation of a fluctuation in focus by maintaining the temp. and pressure of the gas in a housing vessel which houses airtightly a projecting optical system and a photosensitive body at prescribed values and flowing the gas between the plural optical elements. CONSTITUTION:A pressure regulator 26 maintains the pressure in a chamber 20 at a specified value and a temp. regulator 18 discharges a gas having a specified temp. via a filter 23 toward the 2nd condenser lens 6, a reticle R and a projecting lens 7. The gas circulates in a chamber 20, passes the circumference of a wafer W and a stage 8 and flows again to a fan 21 of the regulator 18. The reticle R, the lens 7 and the wafer W are installed in the gas maintained always at the specified temp. and specified pressure in the above-mentioned way and further the lens elements L1-L4 in the lens 7 are also exposed to the flow of said gas and therefore the imaging state of the projected image is maintained always in an optimum state without fluctuating the optical characteristic by the light energy incident to the lens 7 through the reticle R. |
