X-ray exposure apparatus

Abstract: An X-ray exposure method and apparatus wherein exposure chamber (113) coupled with a synchrotron radiation device through a beam line (103) receives synchrotron radiation (101) through a window material (107) provided on the beam line to execute an exposure process; pressure sensor (117) detects pressure in the exposure chamber; cutoff valve (118) is provided in a portion of the beam line between the window material and the synchrotron radiation device; bypass (119) has a communication valve (120) for communicating a portion of the beam line between the window material (107) and the cutoff valve (118) with a portion between the window material (107) and the exposure chamber (113); vacuum evacuating device (123) effects evacuation of a portion of the beam line between the window material and the cutoff valve; pump valve (124) is disposed in a conduit, coupling the beam line with the vacuum evacuating device; and a controller (121) responds to a pressure detected by the pressure sensor (117) so that, when the detected pressure represents a steady state lower than a predetermined pressure, the controller operates to open the cutoff valve (118) and the pump valve (124) and to close the communication valve (120) and, when the detected pressure is higher than the predetermined pressure, the controller operates to close the cutoff valve and the pump valve and thereafter to open the communication valve.

Description: This invention relates to an X-ray exposure apparatus and, more particularly, to an X-ray exposure apparatus for executing exposure by using synchrotron orbital radiation light (hereinafter "SOR light"). In another aspect, the invention is concerned with a semiconductor processing method which uses such an X-ray exposure apparatus. An X-ray exposure apparatus for executing exposure by using SOR light incudes a synchrotron radiation device for producing the SOR light. The synchrotron radiation device is maintained in a ultra high vacuum, and an exposure chamber for accommodating a mask or a wafer is coupled to the synchrotron radiation device by means of a beam line. In an X-ray exposure apparatus of such a structure, there is a possibility that if leakage occurs in the beam line or in the exposure chamber, an atmospheric gas enters the synchrotron radiation device. In an attempt to avoid this, an arrangement such as shown in Figure 5 has been proposed (Japanese Laid-Open Patent Application JP-A-1 061 700). SOR light 501 produced by a synchrotron radiation device (not shown) goes along a beam line 503 and through a window material 507, provided on the beam line 503, and irradiates a mask 512 and a wafer 511 placed in an exposure chamber 503. The beam line is equipped with a shock wave delay tube 504, for retarding advancement of shock waves resulting from vacuum leakage, and a mirror chamber 505 for expanding the SOR light 501, disposed in this order. Provided between the mirror chamber 505 and the window material 507 is a pressure sensor 506, and provided between the synchrotron radiation device and the delay tube 504 is an emergency cutoff valve 502 which is operable in response to the detection by the pressure sensor 506. The mask 515 and the wafer 511 accommodated in the exposure chamber 513 can be replaced by any one of masks 515 accommodated in a mask pre-chamber 516 and any one of wafers 508 accommodated in a wafer pre-chamber 509, respectively, with the cooperation of gate valves 514 and 510, respectively. If the window material 507 is broken as a result of leakage in the beam line 503 or in the exposure chamber 513, the pressure detected by the pressure sensor 506 increases and in response the emergency cutoff valve 502 closes to block entry of atmospheric gas into the synchrotron radiation source device. In the X-ray exposure apparatus of the type described above, the pressure sensor for detecting abnormal pressure is provided at a side (upstream side) of the window material closer to the synchrotron radiation device. If, therefore, the leakage occurs in the exposure chamber, the sensor does not directly detect the leakage but it detects it after the window material breaks. If the window material breaks, the fractions thereof scatter into the exposure chamber and into the beam line. This necessitates complicated operations for recovery as well as a long down time until the exposure operation can start again. JP-A-1061700 discloses an X-ray exposure apparatus wherein the pressure in a beam line disposed between a window and a port to a radiation source detects the pressure and when this rises a valve closes the beam line at a position between the window and the port. No provision is made for avoiding differential pressure across the window due to increased pressure in the exposure chamber. JP-A-63009930 discloses an X-ray exposure arrangement wherein a window is arranged in a beam line and a by-pass structure is arranged to allow the evacuation of either side of the window. JP-A-62291098 discloses an X-ray exposure apparatus wherein a window is arranged in a beam line and a pressure regulator is arranged to regulate the pressure and avoid the window from being broken. EP-A-0358426 discloses an X-ray exposure system in accordance with the preamble of the claims wherein an X-ray exposure chamber is connected to one end of a beam line the other end of the beam line is connected to a radiation source. A window is disposed between the exposure chamber and the port. The pressure in the exposure chamber is detected and the differential pressure across the window is controlled in order to avoid breakage of the window. It is accordingly an object of the present invention to provide an X-ray exposure apparatus by which, in an occasion where leakage occurs in an exposure chamber, protection of a synchrotron radiation device can be done without breakage of a window material. In accordance with a first aspect of the present invention, there is provided a X-ray exposure apparatus comprising: an exposure chamber; a beam line communicating said exposure chamber with a port to receive X-ray radiation from a radiation source; a window disposed in said beam line between said exposure chamber and said port to said radiation source; pressure detecting means for detecting a pressure in said exposure chamber; and vacuum control means for controlling a differential pressure across said window; characterised in that: said vacuum control means comprises a cutoff valve disposed between said window and said exposure chamber in the beam line, and control means responsive to said pressure detecting means to close said cutoff valve when a pressure P in said exposure chamber exceeds a predetermined pressure P 0 to thereby suppress an increase in differential pressure across said window In accordance with a second aspect of the present invention, there is provided an X-ray exposure method using an X-ray exposure apparatus comprising an exposure chamber, a beam line communicating said exposure chamber with a port to receive X-ray radiation from a radiation source, a window disposed in said beam line between said exposure chamber and said port to said radiation source, and a cutoff valve disposed in said beam line between said window (107) and said exposure chamber; the method comprising the steps of: detecting a pressure in said exposure chamber; and when the detected pressure exceeds a predetermined pressure, closing said cut off valve to thereby suppress an increase in differential pressure across said window. Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a diagram showing the structure of an exposure apparatus for purposes of illustration only. Figures 2A and 2B are flow charts each showing the operation of a controller 121 in Figure 1. Figures 3 and 4 are diagrams showing the structures of second and third embodiments of the present invention, respectively. Figure 5 is a diagram showing the structure of a known example. Figure 1 shows an exposure apparatus for purposes of illustration only. 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 102, 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 115 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 Figure 5 case, in response, the pressure detected by the pressure sensor 117 increases and the emergency cutoff valve 102 closes to block entry of atmospheric gas into the synchrotron radiation source device. The beam line of this arrangement 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) 124. The pressure sensor 117 is provided between the window material 107 and the exposure chamber 113 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 19995 N/m 2 (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 micrometres thickness). The inside pressure P S (e.g. 19995 N/m 2 (150 Torr) of the exposure chamber 113 is so set as to be lower than the withstand pressure P L of the window material 107 of the aforementioned thickness. Like the Figure 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 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 Figure 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 Figure 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. Figure 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 0 (P S < P 0 < P 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 0 , 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 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 120 is opened before the pressure P reaches the withstand pressure P 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. Figure 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 A (e.g. about 0.133 N/m 2 (10 -3 Torr)) (step S5). If P < P 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. 1.33 x 10 -5 N/m 2 10 -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. Figure 3 shows an embodiment of the present invention. This embodiment corresponds to a simplified form of the Figure 1 arrangement 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 Figure 1 arrangement 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 Figure 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 0 , 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. Figure 4 shows a second embodiment of the present invention. This embodiment corresponds to a combined form of the first embodiment and the arrangement of figure 1, wherein, to the arrangement of figure 1, 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 arrangement of figure 1 and the first embodiment are denoted by the same reference numerals as of Figures 1 and 3, and explanation of them is now omitted. The operation of the present embodiment is essentially the same as that shown in Figures 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 scope of the following claims.

Claims: An X-ray exposure apparatus comprising: an exposure chamber (113); a beam line (103) communicating said exposure chamber (113) with a port to receive X-ray radiation from a radiation source; a window (107) disposed in said beam line (103) between said exposure chamber (113) and said port to said radiation source; pressure detecting means (122) for detecting a pressure in said exposure chamber (113); and vacuum control means (121;301;120) for controlling a differential pressure across said window; characterised in that: said vacuum control means (121;301;120) comprises a cutoff valve (301) disposed between said window (107) and said exposure chamber (113) in the beam line (103), and control means (121) responsive to said pressure detecting means (122) to close said cutoff valve (301) when a pressure P in said exposure chamber (113) exceeds a predetermined pressure P 0 to thereby suppress an increase in differential pressure across said window (107). An X-ray exposure apparatus according to claim 1 including a second cutoff valve (118) disposed in said beam line (103) between said window (107) and said port to said vacuum source; a bypass having a communication valve (120) for communicating a portion of said beam line (103) between said window (107) and said cutoff valve (301) with a portion of said beam line (103) between said window (107) and said second cutoff valve (118); vacuum evacuating means (123) for vacuum evacuating a portion of said beam line 103) between said window (107) and said second cutoff valve (118); and a pump valve (124) provided in a conduit coupling said beam line (103) with said vacuum evacuating means (123); wherein said control means (112) is responsive to said pressure detecting means (122) to close said second cutoff valve (118) and said pump valve (124) and thereafter to open said communication valve (120). An X-ray exposure apparatus according to claim 1 or claim 2 including a second pressure detecting means (106) provided in a portion of said beam line (103) between said window (107) and said port to said radiation source, and a third cutoff valve (102) disposed in a portion of said beam line (103) between said window (107) and said port to said radiation source, a third cutoff valve (102) disposed in a portion of said beam line (103) between said second pressure detecting means (106) and said port to said radiation source, and means to close said third cut off valve (102) in response to a rise in pressure above a threshold detected by said second pressure detecting means (106). An X-ray exposure method using an X-ray exposure apparatus comprising an exposure chamber (113), a beam line (103) communicating said exposure chamber (113) with a port to receive X-ray radiation from a radiation source, a window (107) disposed in said beam line (103) between said exposure chamber (113) and said port to said radiation source, and a cutoff valve (301) disposed in said beam line (103) between said window (107) and said exposure chamber (113); the method comprising the steps of: detecting a pressure in said exposure chamber (113); and when the detected pressure exceeds a predetermined pressure, closing said cut off valve (301) to thereby suppress an increase in differential pressure across said window (107). An X-ray exposure method according to claim 4 using said X-ray apparatus including a second cut off valve (118) between said window (107) and said port to said radiation source, a bypass having a communication valve (120) for communicating a portion of said beam line (103) between said window (107) and said cut off valve (301) with a portion of said beam line (103) between said window (107) and said second cut off valve (118), and a pump valve (124) provided in a conduit coupling said beam line (103) with said vacuum evacuating means (123); the method including the step of closing said second cut off valve (118) and said pump valve (124) and thereafter opening said communication valve (120) when the detected pressure in said exposure chamber (113) exceeds a predetermined pressure. An X-ray exposure method according to claim 4 or claim 5 using said X-ray apparatus including a third cut off valve (102) disposed in said beam line (103) between said window (107) and said port to said radiation source, the method including the steps of detecting pressure in a portion of said beam line (103) between said window (107) and said their cut off valve (102), and closing said cut off valve (102) if the detected pressure exceeds a second predetermined pressure. An X-ray exposure method according to claim 4 or claim 5 including the step of exposing a semiconductor substrate to X-rays from said radiation source when the pressure detected in said exposure chamber is below the predetermined pressure. An X-ray exposure method according to claim 6 including the step of exposing a semiconductor substrate to X-rays from said radiation source when the pressure detected in said exposure chamber is below the predetermined pressure and the pressure detected in the portion of the beam line (103) between said window (107) and said third cut off valve (102) is below the second predetermined pressure.

Inventors: EBINUMA RYUICHI, EBINUMA, RYUICHI, EBINUMA, RYUICHI, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1991
Main classification: G03F7
IPC codes: G03F7, H05G2, H01L21