Patent Number: 
Section: description

Hereinbelow, an evacuation use sample chamber and a circuit pattern forming apparatus representing one embodiment of the present invention will be explained, while taking an electron beam pattern drawing apparatus as an example, with reference to the drawings. An electron beam pattern drawing apparatus is one in which through generation of electron beam under a super high vacuum environment and scanning therewith LSI patterns are formed on a semiconductor substrate or a glass substrate called as a mask which is used for an exposure apparatus such as a stepper. At first, a first embodiment will be explained with reference to FIGS. 1 through 5. FIG. 1 shows a constitution of an electron beam pattern drawing apparatus representing the first embodiment of the present invention. As shown in FIG. 1, a column 1 is mounted on a sample chamber cover 11, and inside a sample chamber (also called as a work chamber) 10 a sample stage (also called a sample displacement stand or a displacement table device) which is movable in XYZ directions in the drawing, namely an XYZ stage 20 is disposed. The sample chamber cover 11 is designed to be driven by a motor 40 and a friction drive mechanism 41 and is attached with an open and close cover 42 which maintains vacuum inside the column 1. In the XYZ stage 20, Z stage 23 movable in Z direction is mounted on an XY stage 9 movable in XY directions and a top table 21 which holds a sample 8 is coupled to the Z stage 23 by an expandable actuator 22. Further, a bar mirror 13 is attached to the top table 21 and through measurement by laser distance variation to a laser interference meter 12 management of sample position can be performed. The top table 21 will be explained with reference to FIGS. 2 and 3. FIG. 2 shows a perspective view of the top table 21 and FIG. 3 shows a cross sectional view taken along line Axe2x80x94A in FIG. 2. On the top table 21, a sample use recessed portion 21F having depth of about the thickness of the sample 8 and an evacuation use groove portion 21E surrounding the same are formed, and pin Z mechanisms 21A which are used during sample transportation are attached below respective holes. Further, at the time of transportation a pin 21D passes through the hole 21B and acts on the pin Z mechanism to lift up the top table and to facilitate the sample transportation. Further, in order to perform differential evacuation stably, it is necessary to keep flow rate of gas to be evacuated at constant. When it is designed in such a manner that distance AD between the sample use recessed portion 21F and the evacuation use groove portion 21E as illustrated in the drawing is determined more than the radius of an electron beam passage use hole formed in the bottom face of the sample chamber cover 11 and even when the edge of the sample is shifted in XY directions with reference to the center of column the electron beam passage use hole covers inside the evacuation use groove portion, a circuit pattern can be stably drawn over the entire surface of the sample. Now, a series of flow from carrying in the sample into the sample chamber 10 to carrying out the same after completing a circuit pattern drawing will be explained. At a predetermined position of the XYZ stage 20 the sample 8 carried in is held on the top table 21 and the sample 8 is displaced immediately below the column 1. Thereafter, the top table 21 is displaced upward by the Z stage 23 into a detectable range of a Z sensor 19 which can detects position in height direction and inclination of the sample 8. Subsequently, the distance between the upper face of the sample 8 and the bottom face of the sample chamber cover 11 and parallelism of the sample 8 with respect to the bottom face of the sample chamber cover 11 are detected by means of the Z sensor 19 and the actuator 22 is caused to expand or contract so as to assume a distance and parallelism which permit differential evacuation. While keeping a predetermined distance (a few xcexcm-10 and a few xcexcm) and parallelism, vacuum evacuation is performed through the evacuation use tube 21C so as to depressurize a region surrounded by the evacuation use groove portion 21E, the bottom face of the sample chamber cover 11 and the open and close cover 42, and the degree of vacuum in the region is measured by a pressure gauge 50 attached on the sample chamber cover 11. After the region reaches to the degree of vacuum in the column 1, the open and close cover 42 is opened to start a pattern drawing. After completing the pattern drawing, the open and close cover 42 is closed to shield the inside of the column 1, and after terminating the evacuation from the top table 21, the sample 8 is lowered by driving the Z stage 23, then the sample 8 is carried out at the sample transportation position by displacing the XY stage 9. Now, the differential evacuation around a wafer will be explained with reference to FIG. 4. Since the distance between the upper face of the top table 21 and the bottom face of the sample chamber cover 11 is narrow as from a few xcexcm to 10 and few xcexcm, when a flow rate of evacuated gas from the upper face of the top table 21 is sufficiently large with respect to a flow rate flowing into the evacuation use groove portion 21E from inside the sample chamber 10 being in low vacuum, depressurization rapidly advances after the start of evacuation because of small volume of the region surrounded by the evacuation use groove portion 21E, the bottom face of the sample chamber cover 11 and the open and close cover 42. Further, the smaller the distance G1 between the upper face of the top table 21 and the bottom face of the sample chamber cover 11, the less is the flow rate from the region in low vacuum. Accordingly, when it is designed to evacuate the environment around the sample 8 into high vacuum in the shortest time, it is sufficient as illustrated in FIG. 5 to provide a step in the top table 21 and to determine the distance G1 between the upper face of the top table 21 at the outer portion from the evacuation use groove portion 21E and the bottom face of the sample chamber cover 11 smaller than the distance G2 between the upper face of the top table 21 and the bottom face of the sample chamber cover 11. Now, a second embodiment will be explained with reference to FIGS. 6 through 11. FIG. 6 shows a constitution of an electron beam pattern drawing apparatus representing the second embodiment of the present invention. As illustrated in FIG. 6, the XYZ stage 20 is guided by an air bearing and is movable in XYZ direction like the first embodiment, and in place of the sample chamber which maintains vacuum, the sample chamber cover 11, on which the column 1 is mounted, is supported by a framework 31 provided with a variation eliminating mechanism 32. A region surrounded by the framework 31, a base disk 33 and the sample chamber cover 11 (which corresponds to the inside of the sample chamber in the first embodiment) is in the atmospheric state, therefore, such preliminary evacuation installation as the load chamber is unneeded for the sample transportation. Further, because of the use of the air bearing no lubricants such as lubricant oil are needed, therefore, possible contamination such as inside the column and parts around the sample can be greatly reduced. The structure of the top table 21 and the differential evacuation of the second embodiment will be explained with reference to FIGS. 7 through 9. FIG. 7 shows a perspective view of the top table 21 of the second embodiment, FIG. 8 shows a cross sectional view taken along line Bxe2x80x94B in FIG. 7, and FIG. 9 is a diagram showing the differential evacuation action. The top table 21 is provided with, in addition to the mechanism as explained in connection with the first embodiment, an air pad 21I of a porous material such as ceramics which permits passing of gas and a gas supply use tube 21J which permits supply of compressed gas. In the present embodiment, through blowing out gas fed from the gas supply use tube 21J from the upper face of the air pad 21I, the top table 21 can be supported through the air bearing with respect to the bottom face of the sample chamber cover 11. In the structure of the top table 21 as explained in connection with the first embodiment, when the environment around the top table 21 is in atmospheric pressure and the environment around the sample 8 is in high vacuum, a high pressure caused by the pressure difference will act onto the bottom face of the top table 21, thereby, the top table 21 possibly contacts to the bottom face of the sample chamber cover 11. According to the second embodiment through the gas supply pressure from the air pad 21I the distance G3 between the top table 21 and the bottom face of the sample chamber cover 11 is kept constant and the above possible contact can be avoided. Further, through managing the profile irregularity of the bottom face of the sample chamber cover 11, the top table 21 moves following the bottom face of the sample chamber cover 11, thereby, variation amount in the height direction of the top table 21 can be reduced. Further, FIG. 10 is an example where a step xcex94Z is provided between the upper face of the air pad 21I and the upper face of the top table 21 at the outer circumferential side in order to reduce air flow rate flown in into the evacuation use groove portion 21E from the air pad 21I. In the present structure, since the distance G3 between the bottom face of the sample chamber cover 11 and the air pad 21I is selected larger than the distance G1 between the bottom face of the sample chamber cover 11 and the upper face of the top table 21, the air fed from the air pad 21I can be easily flown out from the top table 21, thereby, the environment around the sample can be kept in further higher vacuum. Further, as shown in FIG. 11 through provision of the evacuation use groove portion in two or more steps, it is possible to evacuate around the sample more rapidly into a high degree of vacuum. Hereinabove, the circuit pattern forming apparatuses have been explained by taking the electron beam pattern drawing apparatuses as examples, the circuit pattern forming apparatus of the present invention can be used as a circuit pattern inspection apparatus for inspecting circuit patterns for samples on which circuit patterns are already formed. According to the present invention, through the stable gas evacuation the environment around the sample can be kept in high degree of vacuum constantly, thereby, an evacuation use sample chamber which can realize always stable vacuum is provided. Further, through use of the evacuation use sample chamber a circuit pattern forming apparatus can be provided which permits a pattern drawing (exposure, inspection) over the entire face of a sample under environment condition of the sample chamber in low degree of vacuum or in atmospheric pressure while keeping the electron beam passage in high vacuum and without deteriorating the attitude accuracy of the top table.