Patent Number: 
Section: description

The electron beam exposure apparatus in the embodiment of the present invention has almost the same configuration as the conventional ones as shown in FIG. 1. FIG. 4 illustrates the block mask 21, the first through the fourth mask deflectors 16, 18, 23, and 25, and related drive circuits of the electron beam exposure apparatus. The CPU 41 reads out the drawing data stored in the magnetic tape 42 and the magnetic disc 43 via the bus 44, and sends out the data relating to the selection of a block mask, which is generated from the drawing data, to the exposure control portion 45. The CPU 41 also generates deflection data for the main deflector 31 and sub-deflector 32 and focus data for the focus coil 29, and sends them to each drive circuit, though an explanation is not provided here. The deflection position data relating to the block mask selection sent from the CPU 41 via the bus 44 is provided to the exposure control portion 45 via the interface 46. The lookup table 47 stores the signal values (output values) to be applied to the drive circuits of each mask deflector 16, 18, 23, and 25, and the deflector 17 according to the deflection position data. The exposure control portion 45 reads out the output value corresponding to the specified aperture pattern and sends it to the drive circuit 48 consisting of a D/A converter (DAC) and amplifier (AMP). The DAC/AMP circuit 48 generates an analog signal corresponding to the output value and applies it to the first through the fourth mask deflectors 16, 18, 23, and 25, and the deflector 17. A block mask is thus selected in the manner described above. In the present embodiment, the following measurement and adjustment are carried out after the abovementioned settings are completed. First of all, a block mask 21 in which all aperture patterns 61 include the adjusting aperture patterns as shown in FIGS. 5A through 5C is provided. Each adjusting aperture pattern has independent apertures of the same shape arranged along the opposite sides of the maximum aperture area 63. In FIG. 5A, for example, there are four rectangular apertures 71 to 74 arranged along each side of the maximum aperture area 63. The rectangular apertures 71 and 72 arranged along the opposite sides have the same shape and so do the apertures 73 and 74. In this case, the shapes of apertures 71 and 72 coincide with those of the apertures 73 and 74, respectively, after a rotation of 90 degrees. In FIG. 5B, there are four square apertures 75 to 78 in each corner of the maximum aperture area 63, and in FIG. 5C, there are five more square apertures 79 to 83 of the same shape, four at the middle of each side, and one in the center of the maximum aperture area 63, in addition to the apertures in FIG. 5B. The pattern shown in FIG. 5A is used here for explanation, though any pattern is possible. FIG. 6A illustrates the fine line 90 provided on the specimen (wafer) 1 to be used for measurement. A shifted (embossed or etched) pattern, in which the fine line 90 is made higher or lower than another part, is placed on the specimen 1. The fine line 90 has the line 90A that extends in the Y direction and the line 90B that extends in the X direction. When the specimen 1 that has a shifted pattern 90 as shown in FIG. 6A is scanned by the electron beam 10, the amount of the reflected electron while the electron beam traverses the pattern 90 increases and the increment can be detected by the reflected electron detector 33 shown in FIG. 1. An electron beam shaped into the adjusting aperture pattern in FIG. 5A is radiated onto the specimen after each line of the fine line 90 is adjusted to extend in the X and Y directions, respectively, as shown in FIG. 6B. At this time, the sides of the rectangular electron beam patterns 71xe2x80x2 to 74xe2x80x2 corresponding to the apertures 71 to 74 are adjusted so that they are parallel to the line 90A and line 90B, respectively. Then, the sub-deflector 32 is used to scan in the X and Y directions and the output of the reflected electron detector 33 is observed. FIGS. 7A and 7B illustrate examples of the variations in the detected signal when scanned in the X direction. FIG. 7A shows two high peaks corresponding to the patterns 71xe2x80x2 and 72xe2x80x2, and a low and wide peak corresponding to the patterns 73xe2x80x2 and 74xe2x80x2. The difference in height between the two peaks on both ends indicates the difference in intensity and it can be concluded that the position of the selected adjusting aperture pattern is different from that of the beam deflected by the mask deflector. Therefore, it is necessary to conduct the observation similarly with another adjusting value in the lookup table 47 in FIG. 4 until the two peaks have the same height as shown in FIG. 7B. At the same time, the value should be selected so that the height of the peaks is as high as possible. Similarly, the same adjustment is applied in the Y direction. The abovementioned adjustment will optimize the positions of the selected adjusting aperture pattern and the deflected beam. The optimum deflection for each aperture pattern can be obtained by applying the abovementioned adjustment to other adjusting aperture patterns of the block mask. In the manufacturing process of the electron beam exposure apparatus, a block mask 21 consisting only of adjusting aperture patterns is used to adjust the deflection position for each aperture pattern. Since the adjusted deflection amount may change with time, periodical checks and modifications are required. In this case, however, it is not necessary to check all the aperture patterns, instead, just taking measurement of only several central and peripheral aperture patterns and correcting the deviation using interpolation will do. The block mask 21 consisting only of adjusting aperture patterns can also be used for the abovementioned periodical checks and modifications. It is, however, necessary to change the block mask each time, making the work more troublesome. Therefore, it is advisable to use a block mask shown in FIG. 8. This block mask 21 has adjusting aperture patterns only at the aperture patterns 65 diagonally hatched and other aperture patterns are the normal ones that can be used with a normal optical exposure. If a block mask 21 like this is used, checks and adjustments can be conducted without replacement of the block mask 21. As explained above, the present invention can provide a precise amount of deflection of the mask deflector according to each aperture pattern because the difference in position between the beam deflected by the mask deflector and each aperture pattern is measured precisely. This not only realizes an exposure with high accuracy and without exposure variation, but also increases the efficiency by increasing the number of the aperture patterns formed on the block mask.