Processing method and apparatus for a resist-coated substrate

Abstract: A processing system includes a processing chamber (1) , a circulating device (6-10) for purifying an inside ambience gas of the processing chamber and for circulating the purified gas back into the processing chamber, a measuring device (11) for measuring the purity of the ambience gas, and an adjusting device (10b) for adjusting the flow rate through the purifying device (10a) in accordance with an output of the measuring device. In another form, a processing system includes a first processing chamber (101) in which a first process is to be performed a second processing chamber (130) in which a second process is to be performed and a device for introducing an ambience gas, having been used in said first processing chamber for the first process, into the second chamber for reuse thereof. The gas subsequently used in the second chamber is introduced back into the first chamber for reuse of the gas. At least a portion of the circulated gas is purified to increase its purity. A purity sensor (110) detects the purity of gas discharged from the second chamber and, in accordance with the detection, the rate of gas purification is adjusted.

Description: FIELD OF THE INVENTION AND RELATED ART This invention relates to a processing system suitable for semiconductor device manufacture, for example. X-rays which are considered effective as exposure light for an exposure apparatus are attenuated considerably by atmosphere, for example, and for this reason, usually X-rays are introduced into an exposure chamber through a beam duct having an ultra high vacuum maintained therewithin. The exposure chamber serves to prevent attenuation of the X-rays and, on the other hand, it is a reduced pressure chamber having an inside reduced pressure ambience filled with a helium gas, for example, for accelerating heat radiation from a wafer or a mask. The pressure or temperature of this reduced pressure ambience or the purity of the helium gas is controlled very precisely so as to prevent any change in intensity of the X-rays at the surface of a wafer to be exposed. Particularly, the purity of helium gas might be decreased by any leakage due to the degree of gas-tightness of the chamber, leakage of a gas into the chamber through an inside wall of the chamber or from air bearing means, for example, used in a mask holding device or a wafer positioning stage device. In order to dilute such impurity gas to keep the helium gas purity within the reduced pressure chamber not lower than 99.9%, for example, it is necessary to continuously supply a high purity helium gas of a purity not lower than 99.9999% into the reduced pressure chamber. Patent Abstracts of Japan, vol. 015, no. 416 (M-1172) & JP-A-03 175224 discloses a filter and by-pass damper for regulating the cleanliness of air circulating in a clean room. Patent Abstracts of Japan, vol. 15, no. 263 (C-0847) & JP-A-03083949 discloses a glove box having a circulating supply of nitrogen gas. The nitrogen gas is circulated through a filter on its way to the glove box. US Patent No. 4,262,091 discloses a glove box for handling cultures of biological material. The glove box is equipped with an air conditioner for removing moisture from the glove box chamber. German Patent Application No. 39 40 405 discloses an apparatus and a method for exposing a semiconductor substrate to X-rays in a helium-filled processing chamber. The helium is used for providing a desired ambience in the chamber and is also used as the operating fluid in a static pressure bearing means. The gas discharged from the chamber may be purified and then circulated to the static pressure bearing means. SUMMARY OF THE INVENTION As described, helium gas of high purity has to be supplied continuously. Also, the helium gas to be supplied is for use in the exposure chamber only. Thus, the efficiency of use of helium gas is quite low. Also, consumption of a large quantity of expensive helium gas directly results in increased running cost. It is accordingly an object of the present invention to provide a method and apparatus for processing a resist-coated substrate in which the efficiency of use of ambience gas is improved and by which the running cost is reduced considerably. In accordance with a first aspect of the present invention, to achieve this object, there is provided a method of processing a resist-coated substrate comprising the steps of: (a) introducing and positioning said resist-coated substrate within a processing chamber; (b) maintaining an ambience of inactive gas in said processing chamber, and (c) exposing said resist-coated substrate to X-rays or ultraviolet radiation emitted from a source; wherein said step of maintaining an ambience of inactive gas in said processing chamber comprises recirculating said inactive gas from outlet port means of said processing chamber to inlet port means of said processing chamber and passing at least a proportion of said recirculating inactive gas through purifying means, thereby controlling the purity of said ambience of said inactive gas in said processing chamber; characterised in that the purity of the inactive gas in said flow is measured and the proportion of recirculating inactive gas passing through the purifying means is adjusted in response to the purity measurement. In accordance with another aspect of the present invention, there is provided apparatus for processing a resist-coated substrate, said apparatus comprising: (a) a processing chamber; (b) means for holding a resist-coated substrate inside said processing chamber; (c) means adapted to connect said processing chamber to a source of inactive gas; and (d) means for maintaining an ambience of said inactive gas in said processing chamber by causing a flow of said inactive gas through said processing chamber from inlet port means to outlet port means; wherein said means for maintaining said ambience of inactive gas in said processing chamber comprises means for recirculating said inactive gas from said outlet port means to said inlet port means and purifying means through which at least a proportion of said recirculating gas is passed; characterised by a sensor for measuring the purity of said inactive gas and adjusting means for adjusting the proportion of recirculating inactive gas passing through said purifying means in response to the purity measurement. These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of a processing system according to a first embodiment of the present invention. Figure 2 is a schematic view of a modified form of the processing system of the Figure 1 embodiment. Figure 3 is a flow chart of semiconductor device manufacturing processes. Figure 4 is a flow chart of a wafer process of the processes of Figure 3. DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] Figure 1 shows an exposure process system which is a processing system according to a first embodiment of the present invention. Reduced pressure chamber 1 accommodates therein a wafer positioning stage (substrate holding means) 21 and a mask holding device 22. The reduced pressure chamber 1 is provided with a beam duct 2 for introducing, into the reduced pressure chamber 1, X-rays produced by a light source S such as a synchrotron radiation X-ray source, for example, while maintaining an ultra high vacuum state. The reduced pressure chamber 1 is further provided with a beryllium window 3 for intercepting the reduced pressure inside ambience of the reduced pressure chamber 1 from the ultra high vacuum ambience within the beam duct 2. The X-rays advancing along the beam duct 2 and introduced through the beryllium window 3 into the reduced pressure chamber 1, impinge on a mask 23 held by the mask holding device 22, and subsequently on a wafer (substrate) 24 held by the wafer positioning stage 21, whereby exposure of the wafer is performed. For controlling the reduced pressure inside ambience of the reduced pressure chamber 1, the processing system is provided with a first evacuation line 4 for evacuating the reduced pressure chamber 1 to a predetermined vacuum degree (e.g., 0.13 Pa (1x10 -3 Torr)) after the wafer or the mask is introduced into the reduced pressure chamber. The processing system is further provided with a second evacuation line (evacuation means) 6 for adjusting, after the predetermined vacuum degree is reached in the reduced pressure chamber 1, the vacuum degree within the reduced pressure chamber 1 on the basis of an output of a pressure sensor 5. The processing system is further provided with a helium gas supply line 7, which serves as ambience gas supplying means and also as evacuation and circulating means, for supplying a helium gas (ambience gas) into the reduced pressure chamber 1. The first evacuation line 4 has a first vacuum pump 4a and an openable/closable valve 4b. The second evacuation line 6 has a second vacuum pump 6a, a flow rate controlling valve 6b and a controller 6c therefor. The controller 6c serves to control the flow rate controlling valve 6b on the basis of an output of the pressure sensor 5, to thereby adjust the degree of vacuum inside the reduced pressure chamber 1. The helium gas supply line 7 has a compressor 7a for collecting a discharged gas from the second evacuation line 6, and a reservoir 7b connected thereto. The helium gas stored in the reservoir 7b is temperature adjusted by means of a constant-temperature vessel 7c to a predetermined temperature, and the thus temperature adjusted helium gas is introduced into the reduced pressure chamber 1 through a first helium gas introducing line 8 having an openable/closable valve 8a or a second helium gas introducing line 9 having a flow rate controlling valve 9a. In operation, the reduced pressure chamber 1 is evacuated by the first evacuation line 4 to a predetermined vacuum level. Then, the valve 8a of the first helium gas introducing line 8 is opened, and a relatively large quantity of helium gas is supplied into the reduced pressure chamber 1 until the inside ambience gas of the chamber 1 reaches a predetermined ambience pressure, for example, 20000 Pa (150 Torr). Thereafter, the valve 8a of the first helium gas introducing line 8 is closed. Then, the flow rate control valve 9a of the second helium gas introducing line 9 is opened, and, while adding a predetermined flow rate of helium gas, the vacuum degree of the reduced pressure chamber 1 is adjusted by means of the second evacuation line 6 so as to maintain the predetermined ambience pressure mentioned above. Under the control of the reduced pressure inside ambience of the reduced pressure chamber 1 in the manner described above, the exposure process of a wafer 24 starts. During the exposure process of the wafer 24, the purity of the helium gas inside the reduced pressure chamber 1 may reduce due to any impurity gas leaked from the air bearing means of the wafer positioning stage 21, for example. In consideration of this possibility, adjustment of vacuum level through the second evacuation line 6 and replenishment of helium gas through the second helium gas introducing line 9 continue. Here, the helium gas (exhaust gas) discharged from the reduced pressure chamber 1 through the second evacuation line 6, is collected by the compressor 7a into the reservoir 7b. The collected helium gas is circulated back into the reduced pressure chamber 1, together with the helium gas having been reserved in the reservoir 7b. Provided between the reservoir 7b and the constant temperature vessel 7c of the helium gas supply line 7 is a helium gas purifying branched line 10 which serves as purity adjusting means, for purifying a portion of the helium gas supplied from the reservoir 7b to a high purity, and for flowing the purified gas, together with the remaining helium gas, into the constant temperature vessel 7c. This helium gas purifying line 10 has a helium gas purifier 10a and a flow rate control valve 10b. The purifier 10a may have a filter, for example, for trapping gas molecules of active gas and for passing only inactive gas, to thereby purify the helium gas (inactive gas). The second evacuation line 6 is provided with a purity sensor (purity detecting means) 11 for measuring the purity of helium gas discharged from the reduced pressure chamber 1. The flow rate control valve 10b of the helium gas purifying line 10 is provided with a controller 10c which is controlled in response to an output of the purity sensor 11, to change the flow rate of helium gas to be branched into the purifier 10a. Namely, since the helium gas to be supplied to the reduced pressure chamber 1 from the reservoir 7b of the helium gas supply line 7 contains helium gas as collected from the second evacuation line 6, at least a portion thereof is directed to the purifier 10a for purification thereby to improve the purity of the gas. The thus purity improved gas is then introduced into the reduced pressure chamber 1. The purity of the helium gas within the reduced pressure chamber 1 may be measured by means of the purity sensor 11, provided in a portion of the second evacuation line 6, and the proportion of the helium gas to be purified by the purifier 10a may be changed in accordance with an output of the purity sensor 11 to adjust the purity of the helium gas just going to be replenished into the reduced pressure chamber 1. This allows extremely precise and quick control of the purity of the helium gas within the reduced pressure chamber 1. The purity sensor 11 may comprise, for example, a sensor for directly detecting the gas purity or a sensor for measuring the temperature and sound speed in a gas to thereby indirectly detect the purity thereof. Any type of sensor may be used. The helium gas purifying branched line 10 may be provided in any portion of the line for collecting the helium gas from the second evacuation line 6 and for circulating it back to the helium gas supply line 7. For example, as shown in Figure 2, a helium gas purifying branched line 20, which has a purifier 20a and a flow rate control valve 20b, similarly to the helium gas purifying branched line 10 of this embodiment, may be provided between the second vacuum pump 6a and the compressor 7a. In accordance with this embodiment of the present invention, as described hereinbefore, the helium gas discharged from the reduced pressure chamber is collected and reused. This effectively reduces the quantity of helium consumption as well as the running cost. Additionally, the purity of helium gas discharged from the reduced pressure chamber may be directly measured so that any change in purity of the helium gas within the reduced pressure chamber can be detected. On the basis of this detection, the purity of helium gas to be replenished into the reduced pressure chamber may be changed. Thus, in that occasion, it is assured to control the purity of helium gas within the reduced pressure chamber extraordinarily precisely. This is effective to accomplish stable X-ray intensity and thus high precision X-ray lithography. [Embodiment 2] Now, an embodiment of a device manufacturing method which comprises manufacturing processes, including a process to be performed through a processing system described with reference to the foregoing embodiment , will be explained. Figure 3 is a flow chart of the sequence of processes for manufacturing microdevices such as a semiconductor chip (e.g. IC or LSI), a liquid crystal panel, a CCD, a thin film magnetic head, or a micromachine, for example. Step 1 is a design process for designing the circuit of a semiconductor device. Step 2 is a process for manufacturing a mask on the basis of the circuit pattern design. Step 3 is a process for manufacturing a wafer by using a material such as silicon. Step 4 is a wafer process which is called a pre-process wherein, by using the so prepared mask and wafer, circuits are practically formed on the wafer through lithography. Step 5 subsequent to this is an assembling step which is called a post-process wherein the wafer processed by step 4 is formed into semiconductor chips. This step includes assembling (dicing and bonding) and packaging (chip sealing). Step 6 is an inspection step wherein operability check, durability check and so on of the semiconductor devices produced by step 5 are carried out. With these processes, semiconductor devices are finished and they are shipped (step 7). Figure 4 is a flow chart showing details of the wafer process. Step 11 is an oxidation process for oxidizing the surface of a wafer. Step 12 is a CVD process for forming an insulating film on the wafer surface. Step 13 is an electrode forming process for forming electrodes on the wafer by vapor deposition. Step 14 is an ion implanting process for implanting ions to the wafer. Step 15 is a resist process for applying a resist (photosensitive material) to the wafer. Step 16 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step 17 is a developing process for developing the exposed wafer. Step 18 is an etching process for removing portions other than the developed resist image. Step 19 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer. The device manufacturing method of this embodiment enables manufacture of microdevices such as semiconductor devices of high density, with lowered cost. 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: A method of processing a resist-coated substrate (24) comprising the steps of: (a) introducing and positioning said resist-coated substrate (24) within a processing chamber (1); (b) maintaining an ambience of inactive gas in said processing chamber (1), and (c) exposing said resist-coated substrate (24) to X-rays or ultraviolet radiation emitted from a source (S); wherein said step of maintaining an ambience of inactive gas in said processing chamber (1) comprises recirculating said inactive gas from outlet port means of said processing chamber (1) to inlet port means of said processing chamber (1) and passing at least a proportion of said recirculating inactive gas through purifying means (10a, 20a), thereby controlling the purity of said ambience of said inactive gas in said processing chamber (1); characterised in that the purity of the inactive gas in said flow is measured and the proportion of recirculating inactive gas passing through the purifying means (10a, 20a) is adjusted in response to the purity measurement. A method as claimed in claim 1, further comprising passing said recirculating inactive gas through a filter prior to passing it through said purifying means (10a, 20a). A method as claimed in claim 1 or claim 2, further comprising passing said recirculating inactive gas through temperature adjusting means (7c) prior to returning it to the processing chamber (1). A method as claimed in any preceding claim, further comprising passing said recirculating inactive gas through a compressor (7a) and storing it in a reservoir (7b) prior to returning it to the processing chamber (1). A method as claimed in any preceding claim wherein substrate coating, substrate exposure and developing of the exposed substrate are carried out in the processing chamber (1). A method as claimed in any preceding claim, wherein the pressure of the inactive gas ambience in the processing chamber (1) is reduced to a predetermined value. A method for manufacturing an integrated circuit device comprising the steps of: (a) providing a substrate (24) having a resist-coating; (b) providing a mask (23) corresponding to a circuit pattern design; (c) introducing and positioning said mask (23) within a processing chamber (1); (d) introducing and positioning said resist-coated substrate (24) in said processing chamber (1), creating an ambience of inert gas in said processing chamber (1) and exposing said resist-coated substrate (24) to radiation in accordance with the method defined in any one of claims 1 to 6; and (e) developing the substrate (24) exposed in step (d). A method of manufacturing an integrated circuit comprising the steps (a) to (e) as set forth in claim 7, followed by the steps of: (f) removing the unwanted resist coating from said substrate (24); and (g) completing manufacture of the integrated circuit device. A method as claimed in claim 8, wherein step (g) includes steps of dicing the substrate, bonding and packaging. Apparatus for processing a resist-coated substrate (24), said apparatus comprising: (a) a processing chamber (1); (b) means (21) for holding a resist-coated substrate (24) inside said processing chamber (1); (c) means adapted to connect said processing chamber (1) to a source of inactive gas; and (d) means for maintaining an ambience of said inactive gas in said processing chamber (1) by causing a flow of said inactive gas through said processing chamber (1) from inlet port means to outlet port means; wherein said means for maintaining said ambience of inactive gas in said processing chamber (1) comprises means (7) for recirculating said inactive gas from said outlet port means to said inlet port means and purifying means (10a, 20a) through which at least a proportion of said recirculating gas is passed; characterised by a sensor (11) for measuring the purity of said inactive gas and adjusting means (10c, 10b, 20b) for adjusting the proportion of recirculating inactive gas passing through said purifying means (10a, 20a) in response to the purity measurement. Apparatus as claimed in claim 10, wherein the processing chamber (1) further comprises means for coating a substrate; means (S, 2) for exposing a substrate and means for developing the exposed substrate. Apparatus as claimed in claim 10 or claim 11, wherein the processing chamber (1) further comprises means (4a, 4b, 6a, 6b) for reducing the pressure of the inactive gas ambience in said processing chamber (1). Apparatus as claimed in any one of claims 10 to 12, further comprising a compressor (7a) for compressing the recirculating inactive gas before it is returned to the processing chamber (1). Apparatus as claimed in claim 13, wherein the compressor (7a) is arranged to compress the recirculating inactive gas downstream of the purifying means (10a, 20a). Apparatus as claimed in any one of claims 10 to 14, wherein the adjusting means comprises a controller (10c) and a valve (10b, 20b) connecting the purifying means (10a, 20a) in parallel with the recirculating inactive gas path of the recirculating means (7), the controller (10c) being responsive to a signal supplied by the sensor (11) to control the valve (10b, 20b) so as to control the proportion of recirculating inactive gas that is supplied to the purifying means (10a, 20a) in accordance with a signal from the sensor (11).

Inventors: FUJIOKA HIDEHIKO, HASEGAWA TAKAYUKI, YONEYAMA YOSHITO, FUJIOKA, HIDEHIKO, HASEGAWA, TAKAYUKI, YONEYAMA, YOSHITO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1995
Main classification: G03F7
IPC codes: G03F7, H01L21