JP2005317626A - Projection optical system adjustment method and exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust the aberration and focus of a projection optical system partially in the surface of a lens. <P>SOLUTION: A space between neighbored lenses in a lens-barrel is divided into 9 spaces 22a-22i in the surface of the lens by partitioning members consisting of a barrel body 23 and a plate type body 24. Gas is introduced into or withdrawn out of respective spaces 22a-22i independently to change the refractive index of the gas in respective spaces in accordance with the value of adjustment, whereby the aberration and focus are adjusted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for adjusting a projection optical system, and an exposure apparatus configured to be able to implement this method.

In a wafer process for manufacturing semiconductor chips, an exposure process is performed in which a resist film on the wafer is exposed to a pattern of an integrated circuit. This exposure process is usually performed by an exposure apparatus including an exposure light source, a reduction projection optical system, and a wafer stage. This exposure apparatus includes a lens barrel in which a reduction projection lens group is housed as a reduction projection optical system.
An example of a reduced projection exposure apparatus is shown in FIG. This figure is described in Non-Patent Document 1 below. This exposure apparatus includes a mercury lamp 1 as an exposure light source, a reduction projection optical system 2, a reflecting mirror 11 and a condenser lens system 12 for guiding light from the mercury lamp 1 to the reduction projection optical system 2, and a reticle R. It comprises a reticle holding base 15 to be placed and a wafer stage 16 on which the wafer W is placed. The reticle holder 15 is disposed between the condenser lens system 12 and the reduction projection optical system 2. The wafer stage 16 is disposed below the reduction projection optical system 2, and includes an X stage 16a, a Y stage 16b, a Z stage 16c, and a rotation stage 16d.

Conventionally, the aberration and focus of the reduction projection optical system are adjusted by moving several lenses in the lens group in the Z direction (length direction of the lens barrel) or changing the atmospheric pressure in the lens barrel. Yes.
An example of the prior art closest to the present invention is an exposure apparatus described in Patent Document 1 below. This exposure apparatus includes a gas introduction device that independently introduces gas into each space formed by two adjacent lenses housed in a lens barrel and the inner wall of the lens barrel.
Supervised by Tadashi Morisue, “LSI Design and Manufacturing Technology”, Denki Shoin Co., Ltd., September 1987, p. 248 International Publication No. 00/22656 Pamphlet (Figure 3)

  However, in the conventional adjustment method, it is necessary to stop the exposure apparatus when performing the adjustment, so there is room for improvement in terms of production efficiency. In order to shorten the time required for the adjustment, it is preferable that the aberration and the focus can be partially adjusted in the lens surface. However, the conventional method can only adjust the entire lens surface. Note that Patent Document 1 does not describe a method for adjusting the aberration and focus of the projection optical system by introducing gas.

  An object of the present invention is to provide a “projection optical system adjustment method” in which aberrations and focus can be partially adjusted within a lens surface, and adjustment can be performed without stopping the exposure apparatus, and this method is implemented. It is an object of the present invention to provide an exposure apparatus configured to be possible.

  In order to solve the above-mentioned problem, the “projection optical system adjustment method” of the present invention is a method for adjusting the aberration and focus of the projection optical system, in which adjacent lenses in a lens barrel containing a projection lens group are stored. The space is divided into a plurality of spaces in the lens surface so that gas can be taken in and out independently of each space, and the refractive index of the gas in the space is adjusted to an adjustment value by taking gas into and out of the space to be adjusted. The aberration and the focal point are adjusted by changing them accordingly.

According to the method of the present invention, the aberration and focus of the projection optical system can be partially adjusted within the lens surface. Further, the projection optical system can be adjusted without stopping the exposure apparatus.
In the method of the present invention, it is preferable to prepare a mixed gas by mixing a first gas and a second gas having different refractive indexes at a predetermined ratio, and introduce the prepared mixed gas into the space. According to this, it is possible to cope with a large number of adjustment values without preparing a large number of gases having different refractive indexes.

The exposure apparatus of the present invention is an exposure apparatus having a lens barrel in which a lens group for projection is housed, and a partition member that divides between adjacent lenses in the lens barrel into a plurality of spaces in the lens surface, It is characterized by having a gas inlet / outlet device that allows gas to enter / exit independently of the space.
According to the exposure apparatus of the present invention, since the gases having different refractive indexes can be taken in and out of the plurality of spaces independently from the gas taking in and out apparatus, the method of the present invention can be carried out.

In the exposure apparatus of the present invention, the gas inlet / outlet device includes a mixed gas preparation chamber for preparing a mixed gas by mixing a first gas and a second gas having different refractive indexes at a predetermined ratio in the plurality of spaces. It is preferable to provide it independently.
According to this, since the first gas and the second gas having different refractive indexes are mixed at a predetermined ratio, a mixed gas having a predetermined refractive index can be independently introduced into the plurality of spaces. It is possible to cope with a large number of adjustment values without preparing a large number of gases having different refractive indexes. Therefore, the preferred method of the present invention described above can be implemented.

Hereinafter, embodiments of the present invention will be described.
As shown in FIGS. 1 to 3, the exposure apparatus of this embodiment is characterized by a lens barrel 20 in which a lens group for projection is housed, and other parts are the same as those of the conventional exposure apparatus (FIG. 4) described above. The same. Further, FIG. 1 is a diagram in which five convex lenses 21a to 21e are housed in the lens barrel 20 of the reduction projection optical system 2 for simplification, but actually, for example, as shown in FIG. Contains a large number of lenses of various shapes. For example, at the position of the pupil plane of the reduction projection optical system 2, adjacent lenses in the lens barrel 20 are divided into a plurality of spaces in the lens plane.

Here, between the convex lenses 21b and 21c in the lens barrel 20, as shown in FIG. ing. The end face of the partition member is fixed to the surfaces of both lenses 21b and 21c with an adhesive.
These spaces are composed of a central portion 22a and eight peripheral portions 22b to 22i. The center portion 22a is a space inside the cylindrical body 23 disposed between the convex lenses 21b and 21c. The cylindrical body 23 is disposed so as to be concentric with a circle forming a planar view of the lens surface. The peripheral portions 22b to 22i are formed by equally dividing a ring-shaped space formed by the cylindrical body 23 and the inner peripheral surface of the lens barrel 20 into eight by a radially extending plate-like body 24.

FIG. 3 is a partial perspective view showing a partition member composed of a cylindrical body 23 and a plate-like body 24. The partition member and the lens barrel will be described in detail with reference to this drawing.
In this partition member, the end face on the cylindrical body 23 side of the plate-like body 24 is aligned with the inner peripheral surface 23 a of the cylindrical body 23. The end surface of the plate-like body 24 on the lens barrel 20 side is aligned with the inner peripheral surface 20 a of the lens barrel 20. A large number of through holes 24 a are formed in the plate-like body 24. Each through-hole 24a extends straight from the end surface on the cylindrical body 23 side to the end surface on the lens barrel 20 side.

  A groove 25 along the axial direction is formed in a portion of the inner peripheral surface 20a of the lens barrel 20 where each plate-like body 24 is disposed. Further, a through-hole 26 that penetrates the lens barrel 20 in the radial direction communicates with all the grooves 25. And the piping 31 is connected to each through-hole 26 using the connection hardware 33 which can maintain airtightness. Through these through-holes 26, grooves 25, and through-holes 24a, gas is taken in and out from the pipe 31 to the central portion 22a.

In addition, two through-holes 27 penetrating the lens barrel 20 in the radial direction are formed at positions corresponding to the peripheral portions 22 b to 22 i of the lens barrel 20. And as shown in FIG. 1, piping 32a, 32b is connected to these through-holes 27 using the connection metal fitting 33 which can maintain airtightness.
Here, the partition member formed of the cylindrical body 23 and the plate-like body 24 is preferably manufactured using the same material as the lens (for example, quartz). When quartz is used, it can be manufactured by the following procedure.

In addition, as an adhesive for fixing the partition member to the lens, an adhesive (for example, an ultraviolet curable adhesive) that has high heat resistance and hardly deteriorates by exposure is used.
Further, an antireflection film corresponding to the exposure light source is formed on the surface of the partition member so that the exposure performance (pattern resolution performance or the like) is not reduced by the reflected light from the partition member. Further, in order to reduce the illuminance unevenness that occurs in the exposure region due to the provision of the partition member, it is preferable to provide a filter for adjusting the illuminance unevenness at the bottom of the condenser lens system 12. An example of this filter is a “hole lens” in which a number of fine fly-shaped holes are formed in the filter surface. This filter disperses light and controls the path of light so that unevenness in illuminance is reduced.

The configuration of the gas inlet / outlet apparatus in this embodiment will be described with reference to FIG.
As shown in FIG. 2, the pipes 31 communicating with the through holes 24a of the plate-like body 24 extend from eight places in the circumferential direction of the lens barrel 20, and four of them are gas introduction pipes for the central portion 22a. 31a and the remaining four are gas outlet pipes 31b from the central portion 22a. The mixed gas preparation chamber 4 is connected to the tip of the gas introduction pipe 31a. Of the two pipes connected to the peripheral portions 22b to 22i, the pipe 32a is a gas introduction pipe, and the pipe 32b is a gas introduction pipe. The mixed gas preparation chamber 4 is connected to the tip of the gas introduction pipe 32a.

Two gas introduction pipes 41 and 42 are connected to each mixed gas preparation chamber 4. One gas introduction pipe 41 is connected to the nitrogen cylinder 51 via a header 51a. The other gas introduction pipe 42 is connected to the oxygen cylinder 52 through a header 52a.
Each piping 31a, 31b, 32a, 32b, 41, 42 is provided with electromagnetic on-off valves V1 to V6 and a flow meter (not shown). Moreover, the pressure gauge P1 which measures the pressure of center part 22a, and the pressure gauges P2-P9 which measure the pressure of each peripheral part 22b-22i are provided. Moreover, the measured value by the flow meter installed in each piping and the measured value by the pressure gauges P1-P9 are input into the controller which is not shown in figure. The controller is configured to control the opening / closing of the electromagnetic on-off valves V1 to V6 of the respective pipes based on signals indicating these measured values and a command signal accompanying the space to be adjusted and the adjustment value.

  That is, in the exposure apparatus of this embodiment, the gas inlet / outlet device includes the plate-like body 24 in which the through holes 24a are formed, the grooves 25 provided in the lens barrel 20, the through holes 26, the through holes 27, and the gas introduction. Pipes 31a, 32a, 41, 42, gas outlet pipes 31b, 32b, connection hardware 33, mixed gas preparation chamber 4, nitrogen cylinder 51, headers 51a, 52a, oxygen cylinder 52, and electromagnetic on-off valve V1 ~ V6, pressure gauges P1 to P9, a flow meter, and a controller.

  Next, an example of a method for adjusting the projection optical system in this embodiment will be described. At the start of operation of the exposure apparatus, nitrogen and oxygen are mixed so that the ratios are the same in all the mixed gas preparation chambers 4, and this mixed gas is applied to the central portion 22a and all the peripheral portions 22b to 22i at the same pressure. Introduce until. And when adjusting an aberration and a focus, the gas is taken in and out with respect to the space (at least one of the center part 22a and the peripheral parts 22b-22i) to be adjusted.

Specifically, first, the gas in the space to be adjusted is discharged. Next, in the mixed gas preparation chamber 4 connected to this space, nitrogen and oxygen are mixed so that the refractive index of the mixed gas becomes a value corresponding to the adjustment value. Next, this mixed gas is introduced into the space to be adjusted. The mixed gas is introduced until the same pressure as that of the other space is reached.
In order to perform this control, the controller includes the refractive index data of each gas mixture having a different ratio of nitrogen and oxygen, the refractive index of the space to be divided, the lens aberration, and the focus prepared for each type of projection optical system. A characteristic curve indicating the relationship between the two and a calculation processing program for performing the control are stored.

  According to the method of this embodiment, the aberration and focus of the microprojection optical system 2 can be adjusted separately in nine spaces including the central portion 22a and the peripheral portions 22b to 22i. Further, the aberration and focus of the microprojection optical system 2 can be adjusted without stopping the exposure apparatus. In addition, nitrogen and oxygen are mixed at a predetermined ratio in the mixed gas preparation chamber 4 to prepare a mixed gas, and the prepared mixed gas is independently introduced into the central portion 22a and the peripheral portions 22b to 22i. A large number of adjustment values can be handled without preparing a large number of different gases.

  In this embodiment, the exposure apparatus provided with the microprojection optical system 2 is described. However, the present invention can also be applied to an exposure apparatus provided with an equal magnification projection optical system.

FIG. 3 is a cross-sectional view showing a reduced projection optical system of the embodiment in a simplified manner. The schematic block diagram which shows the partition member and gas in / out apparatus of embodiment. The fragmentary perspective view which shows the partition member of embodiment. The block diagram which shows the conventional reduction projection exposure apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mercury lamp (exposure light source), 2 ... Reduction projection optical system, 11 ... Reflection mirror, 12 ... Condensing lens system, R ... Reticle, 15 ... Reticle holding stand, W ... Wafer, 16 ... Wafer stage, 20 ... Mirror Cylinder, 20a ... inner peripheral surface of lens barrel, 21a-21e ... lens, 22a-22i ... space divided in lens surface, 23 ... cylindrical body (partition member), 24 ... plate-like body (partition member), 24a ... through holes, 25 ... grooves, 26 ... through holes, 27 ... through holes, 31a, 32a ... gas introduction pipes, 31b, 32b ... gas outlet pipes, 33 ... connection hardware, 4 ... mixed gas preparation chambers, 41,42 ... Gas introduction pipe, 51 ... Nitrogen cylinder, 51a, 52a ... Header, 52 ... Oxygen cylinder, V1-V6 ... Electromagnetic on-off valve, P1-P9 ... Pressure gauge.

Claims (4)

In a method for adjusting the aberration and focus of a projection optical system,
The adjacent lenses in the lens barrel in which the lens group for projection is housed are divided into a plurality of spaces in the lens surface so that gas can be taken in and out independently of each space, and the space to be adjusted is adjusted. A method for adjusting a projection optical system, wherein the aberration and focus are adjusted by changing the refractive index of the gas in the space in accordance with an adjustment value by taking in and out the gas.   2. The projection optical system according to claim 1, wherein a mixed gas is prepared by mixing a first gas and a second gas having different refractive indexes at a predetermined ratio, and the prepared mixed gas is introduced into the space. System adjustment method. In an exposure apparatus provided with a lens barrel containing a lens group for projection,
An exposure apparatus comprising: a partition member that divides adjacent lenses in the lens barrel into a plurality of spaces within a lens surface; and a gas inlet / outlet device that allows gas to be taken in / out independently of each space.   The said gas taking-out apparatus is equipped with the mixed gas preparation chamber which mixes the 1st gas and 2nd gas from which refractive index differs by a predetermined | prescribed ratio, and prepares mixed gas independently in these several space. The exposure apparatus described.

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