Patent Number: 051704188
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention. SOR light 101 produced by a synchrotron radiation device (not shown) goes along a beam line 103 and through a window material 107, provided on the beam line 103, and irradiates a mask 112 and a semiconductor wafer 111 accommodated in an exposure chamber 113. This irradiation contributes to processing the wafer 111 surface in accordance with a pattern of the mask 112. The beam line 103 is equipped with a shock wave delay tube 104, for retarding advancement of shock waves resulting from vacuum leakage, and a mirror chamber 105 for expanding the SOR light 101, disposed in this order. Provided between the mirror chamber 105 and the window material 107 is a pressure sensor 106, and provided between the synchrotron radiation device and the delay tube 104 is an emergency cutoff valve 102 which is operable in response to the detection by the pressure sensor 106. The mask 112 and the wafer 111 accommodated in the exposure chamber 113 can be replaced by any one of masks 115 accommodated in a mask pre-chamber 116 and any one of wafers 108 accommodated in a wafer pre-chamber 109, respectively, with the cooperation of gate valves 114 and 110, respectively. If the window material 107 is broken as a result of leakage in the beam line 103 or in the exposure chamber 113, like the FIG. 5 case, in response, the pressure detected by the pressure sensor 106 increases and the emergency cutoff valve 102 closes to block entry of atmospheric gas into the synchrotron radiation source device. The beam line of the present embodiment is further equipped with a pressure sensor (pressure detecting means) 117 for detecting the pressure in the exposure chamber 113; a cutoff valve 118 effective to intercept the mirror chamber 105 and the window 107 from each other; a bypass 119 for defining a bypass, communicating through a communication valve 120 the exposure chamber with a portion between the cutoff valve 118 and the window material 107; and a vacuum pump (vacuum evacuating means) 123 for vacuum evacuating a portion between the window 107 and the cutoff valve 118. The vacuum pump 123 is communicated with the aforementioned portion of the beam line by means of a conduit having a pump valve (switch valve) 122. The pressure sensor 117 is provided between the window material 107 and the exposure chamber 118, while the pressure sensor 122 is provided between the window material 107 and the cutoff valve 118. The exposure chamber 113 is equipped with a vacuum pump 125 for vacuum evacuation of the chamber interior through a pump valve 126. Outside the beam line 103 and the exposure chamber 113 of the structure described above, there is provided a controller 121 for controlling the operations of the cutoff valve 118 and the communication valve 120 as well as the operations of the pump valves 124 and 126, in response to the pressure as detected by the pressure sensor 117 or 122. The wafer 111 placed in the exposure chamber 113 is exposed with the SOR light 101, having passed through the beam line 103 and the window material 107 and having been partially blocked by the mask 112. During this exposure process, heat is generated in the mask due to irradiation with the SOR light 101. In consideration thereof, the exposure chamber 113 is filled with a reduced-pressure gas ambience (e.g. He gas of 150 Torr), reduced to an order assuring necessary heat conduction. The window material 107 should have good transmissivity to the SOR light 101, and it may be a thin beryllium material (10-20 micron thickness). The inside pressure P.sub.S (e.g. 150 Torr) of the exposure chamber 113 is so set as to be lower than the withstand pressure P.sub.L of the window material 107 of the aforementioned thickness. Like the FIG. 5 example, for replacement of the mask 112 or the wafer 111 by any one of masks 115 accommodated in a mask pre-chamber 116 or any one of wafers 108 accommodated in a wafer pre-chamber 109, the wafer pre-chamber 109 or the mask pre-chamber 116 is maintained in a state (load-locked state) filled with an ambience similar to that in the exposure chamber 113. While not shown in the drawing, each of the exposure chamber 113, the wafer pre-chamber 109 and the mask pre-chamber 106 is equipped with vacuum evacuating means and gas supplying means for accomplishing the above-described inside ambience, with pressure control. Only illustrated in FIG. 1 is the vacuum pump (vacuum evacuating means) 125 communicated with the exposure chamber 113 by way of a conduit having the pump valve (switch valve) 126. In normal exposure operation, the emergency cutoff valve 102 and the cutoff valve 118 as well as the pump valve 122 are all maintained open, while the communication valve 120 is kept closed. Thus, also the vacuum pump 123 serves to maintain the vacuum in the beam line 103. If leakage occurs in the beam line during the exposure operation, the leakage is detected by the pressure sensor 106 as in the FIG. 5 example, and the emergency cutoff valve 102 is closed for protection of the synchrotron radiation device. The leakage detection in regard to the exposure chamber 113 as well as the protection of the window material 107 are made under the control of the controller 121. FIG. 2A is a flow chart showing the operation of the controller 121 during the exposure operation. In the exposure operation, the controller 121 continuously monitors (step S1) whether the pressure P in the exposure chamber 113 as detected by the pressure sensor 117 is higher than a predetermined pressure P.sub.O (P.sub.S &lt;P.sub.O &lt;P.sub.L). If a failure in load-locking occurs in the mask pre-chamber 106 or in the wafer pre-chamber 109 or a failure in pressure adjustment occurs in the exposure chamber 113 and, as a result, the pressure P becomes higher than the predetermined pressure P.sub.O, then the cutoff valve 118 as well as the pump valves 124 and 126 are closed (step S2) and, subsequently, the communication valve 120 is opened (step S3). Since the cutoff valve 118 is closed before the pressure P reaches the withstand pressure P.sub.L of the window material 107, at least the scattering of fractions of the window material 107 at an upstream portion of the beam line can be prevented. Also, since the communication valve 122 is opened before the pressure P reaches the withstand pressure P.sub.L of the window material 107, it is possible to effectively prevent application of pressure to the window material and, thus, to avoid breakage of the window material 107. FIG. 2B is a flow chart showing the operation of the controller 121 after the leakage in the exposure chamber is fixed so that the exposure operation is going to be re-started. At the re-start, the controller 121 opens the pump valve 126 (step S4) and causes the vacuum pump 125 to effect the vacuum evacuation of the exposure chamber 113. This operation continues until the pressure P detectable by the pressure sensor 117 becomes lower than a predetermined pressure P.sub.A (e.g. about 10.sup.-3 Torr) (step S5). If P&lt;P.sub.A is satisfied, the communication valve 120 is closed (step S6). Then, the pump valve 124 is opened to start the introduction of He gas into the exposure chamber 113 (step S7). After this, whether the pressure P as detected by the pressure sensor 122 is lower than a vacuum level (e.g. 10.sup.-7 Torr) required in the beam line 103 for the exposure process, is checked (step S8). Further, whether the inside pressure of the exposure chamber 113 is at the predetermined level for the exposure process so that it allows the exposure process, is checked (step S9). After this, the cutoff valve 118 is opened (step S10). With the above-described operations, it is possible to prevent entry of He gas into the beam line 103 and, thus, to re-start the exposure process smoothly. FIG. 3 shows a second embodiment of the present invention. This embodiment corresponds to a simplified form of the FIG. 1 embodiment and an additional cutoff valve 301 is provided. Corresponding elements are denoted by the same reference numerals, and explanation of them is now omitted. In the present embodiment, the cutoff valve 118, the bypass 119, the communication valve 120, the pump valve 122 and the vacuum pump 123 of the FIG. 1 embodiment are omitted. At a position in the exposure chamber 113 and adjacent to the window material 107 and at such position interposing the pressure sensor 117 between it and the window material 107, the cutoff valve 301 is provided (the operation of the cutoff valve 301 is controlled by the controller 121). In FIG. 3, the vacuum pump 125 and the pump valve 126 provided in the exposure chamber 113 are not illustrated. When the pressure P detected by the pressure sensor 117 becomes higher than a predetermined pressure P.sub.O, the controller 121 closes the cutoff valve 301. This prevents application of additional pressure to the window material 107 and, thus, avoids breakage of the window material 107. FIG. 4 shows a third embodiment of the present invention. This embodiment corresponds to a combined form of the first and second embodiments, wherein, to the first embodiment, a cutoff valve 301 is added which valve is provided between the exposure chamber 113 and the portion of the bypass 119 communicating with the exposure chamber 113. Thus, similar elements as of the first and second embodiments are denoted by the same reference numerals as of FIGS. 1 and 3, and explanation of them is now omitted. The operation of the present embodiment is essentially the same as that shown in FIGS. 2A and 2B, and the opening/closing motion of the cutoff valve 118 and the opening/closing motion of the cutoff valve 301 are operationally associated with each other. This assures that, after the cutoff valves 118 and 301 are closed, no stress is applied to the window material as a result of the leakage. Thus, the level of safety is enhanced significantly. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.