1. Field of the Invention
The present invention relates to a holding apparatus capable of stably holding an original such as a mask, for example, without employing a magnet or a vacuum chuck in a semiconductor exposure apparatus, and an electron beam(EB) writing apparatus or a pattern dimension measuring apparatus, etc.
2. Related Background Art
An original such as a mask, for example, of a semiconductor exposure apparatus advancing in terms of a hyperfine structure with X-rays serving as exposure light beams, is generally manufactured by steps shown in FIGS. 8A-8F. To be specific, as illustrated in FIG. 8A, an SiC film M is deposited on at least one side of a substrate S composed of silicon. Then, as shown in FIG. 8B, a central portion of the substrate S is removed by back-etching, thereby forming an opening R covered with the SiC film (membrane) M. Thereafter, as depicted in FIG. 8C, an undersurface of the substrate S is bonded to a mask frame H, and, as shown in FIG. 8D, a pattern P of heavy metal is formed on the SiC membrane M at the opening R by a known EB writing method or by plating. Subsequently, as illustrated in FIG. 8E, a magnetic ring G is mounted on the undersurface of the mask frame H. When the thus manufactured mask is fixed to a mask stage T of the semiconductor exposure apparatus, as shown in FIG. 8F, the magnetic ring G on the undersurface of the mask frame H is adsorbed by a permanent magnet or an electromagnet W on the mask stage T.
Incidentally, in a step of forming the pattern P of the mask, or alternatively in a step of measuring a pattern dimension after completely manufacturing the mask, electron beams are used, and hence, a mask chuck involving the use of the permanent magnet and the electromagnet cannot be employed. Instead, the mask is fixed by use of a known vacuum adsorption device, a spring clamp and so forth.
When the mask is thus fixed by employing the vacuum adsorption device and the spring clamp, however, a distortion different from a case of being fixed to the mask stage of the exposure apparatus by the magnet or the electromagnet is caused, enough to produce a large change in the shape of the mask.
Under such circumstances, to obviate this problem, as illustrated in FIGS. 7A and 7B, there was developed a mask holding method based on a so-called kinematic mount system, by which the mask is clamped by three clamp forces Fa-Fc acting perpendicularly on the mask.
This method is that three pieces of balls Ba-Bc are applied onto the backsurface (or the upper surface) of a mask frame 102 of a mask 100; unillustrated clamp members are respectively made to approach the balls Ba-Bc; and the mask frame 102 of the mask 100 is clamped in between the respective balls Ba-Bc and the clamp members. Then, a position of the mask 100 in a perpendicular direction (a Z-axis direction) by the clamping forces Fa-Fc, respectively, and the first ball Bb engages with a conic groove 102a formed in the undersurface of the mask frame 102, thereby fixing only this portion within an X-Y plane perpendicular to the Z-axis. Subsequently, the second ball Ba slidably engages with a V-shaped groove 102b radially extending with respect to the conic groove 102a, thereby fixing a rotating position thereof. Note that the third ball Bc, brought into contact with a flat portion of the undersurface of the mask frame 102, is rollable in arbitrary directions, and is constructed so as not to unnecessarily restrain the mask 100.
More specifically, the construction is such that the mask 100 is positioned in totally hexa-axes directions of X-, Y- and Z-axes, and .omega.X-, .omega.Y- and .omega.Z-axes of the mask 100 by making use of only the clamping forces Fa-Fc acting respectively through the three balls Ba-Bc. This kind of kinematic mask can be stably held without applying an unnecessary restraining force to the mask, and, besides, the exposure apparatus, the EB writing apparatus and the mask holding apparatuses such as a pattern inspecting apparatus can be all constructed the same, thereby making it possible to prevent the change in shape of the transfer pattern. Accordingly, this is suited to the high-accuracy X-ray exposure apparatus and EB exposure apparatus as well.