JPH027412A - Reduction projection aligner - Google Patents

Abstract

PURPOSE:To enhance a throughput by a method wherein an apparatus structure has a spring characteristic as a whole so as to behave in a horizontal-direction translation advance and vibration, the apparatus structure is supported by a stand used to minimize the vibrating time, and a stepwise external force pattern in a horizontal direction is made an optimally controlled pattern in order to optimize the residual vibrating behavior time. CONSTITUTION:A laminated mount 11 (formed by laminating natural rubber sheets and sheet-like steel plates alternately by using an adhesive or the like) is applied in such a way that a horizontal-dirdection translation advance and vibration mode remains with reference to a stepwise feed external force of an X-Y stage 6 during the actually operating time. As a result, a relative displacement amount can be made minimum. When a stepwise feed rate pattern of The X-Y stage 6 is changed as shown by 8, 9, a stepwise feed pattern of the X-Y stage 6 can be made optimum in such a way that a horizontal-direction vibration displacement 10 of a main base 1 can be adjusted in a short time; accordingly, the vibration displacement of the main base 1 can be adjusted at each exposure operation even during a continuous exposure operation. Thereby, a circuit pattern can be exposed with high accuracy and a throughput can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reduction projection exposure apparatus, and particularly to a reduction projection exposure apparatus, which is particularly useful for realizing low vibration of an apparatus structure subjected to horizontal direction drive and shortening of residual vibration settling time. The present invention relates to a suitable reduction projection exposure apparatus.

[Conventional technology]

An example of an air spring type vibration isolator currently in practical use will be outlined using FIG. 1 is a main base, and a column body 2 is integrally connected to the main base 1. 3 is an illumination system, 4 is a reticle, the wafer 5 is held on an XY stage 6 connected to the main base 1, and the reticle 4 is fixed on the column body 2.

In the actual exposure sequence, first, the XY stage 6 is moved in steps and positioned at a predetermined position, and then the reticle image is reduced and transferred onto the wafer 5 through a reduction lens.

In order to guarantee the accuracy of transfer reproduction to a predetermined position on the wafer 5, the illumination system 3. Ideally, the reference points of the reticle 4 and the wafer 5 always align on the same exposure optical axis 7. However, air spring type mount 1
As for the spring characteristics of No. 2, since the vertical spring stiffness is smaller than the horizontal spring stiffness, when an external force accompanying step feeding of the XY stage 6 acts, a rigid body rocking vibration behavior as shown by the two-dot chain line in Fig. 1 occurs. Therefore, the illumination system 3 and the main base 1 receive forced forces having opposite phases to each other, which is disadvantageous compared to the above-mentioned ideal conditions.

In addition, when the air spring type mount 12 exceeds the initial set horizontal level value, the level adjustment mechanism operates, but due to the limits of the insensitive body of the adjustment mechanism and the limits of the air transmission characteristics,
There is also a limit to reducing the continuous step feed cycle time.

Figure 2 (a) shows an outline of the residual vibration situation when the xY stage 6 is fed step by step. In Figure 0, 8 indicates the stage position signal, 9 indicates the XY stage speed signal, and For example, the horizontal vibration displacement of the main base 1 is 10 when the main base 1 is positioned at a predetermined position by deceleration.

At the time when the residual vibration displacement becomes zero, the reticle 4
Since this satisfies the ideal condition that the reference point of the wafer 5 and the reference point of the wafer 5 are on the same exposure optical axis 7, exposure can be performed during this time period, but there is a restriction on throughput (the number of wafers processed per unit time). In reality, exposure is performed within a certain allowable residual vibration displacement time range, and conventional methods have limitations in improving throughput and positioning accuracy.

[Problems that conventional methods try to solve]

The above conventional technology uses an air spring type vibration isolation table with lower spring stiffness in the vertical direction than in the horizontal direction.
In other words, the upper and lower parts of the entire device structure receive inertial forces that are in opposite phases to each other, resulting in forced changes.
This has the disadvantage that the relative deviation from the same exposure optical axis becomes large. In addition, there is an unavoidable dead zone in the air transmission delay and level adjustment mechanism, and there is a limit to how narrow the dead zone can be.Therefore, there is a limit to how much throughput can be improved.

The purpose of the present invention is to maintain a translation mode in which the upper and lower parts of the entire system are in the same phase with respect to the external force of XY stage step feed, and to minimize the amount of relative deviation from the same exposure optical axis. To provide a reduction projection exposure apparatus capable of improving positioning accuracy, minimizing residual vibration settling time of the entire system by optimizing the step feed pattern of an XY stage, and improving throughput.

[Means to solve the problem]

The above purpose is to minimize the amount of relative displacement due to forced vibration displacement of each component part related to the exposure optical axis, so that the entire system of the apparatus structure takes horizontal translational vibration behavior in response to the action of an external step force in the horizontal direction. supporting the device structure with a frame that has elastic properties and minimizes the vibration behavior time;
The above-mentioned horizontal step external force pattern is made into an optimal control pattern to achieve a configuration that aims to shorten the residual vibration time.

[Effect]

A laminated rubber mount is made by laminating, for example, sheet-like natural rubber and sheet-like steel plates alternately by adhesion, etc., and the spring stiffness in the horizontal and vertical directions depends on the sheet-like natural rubber and steel plates that make up the mount. It is possible to design a relatively wide area depending on the thickness of the plate or the combination of the number of layers, and in the case of a reduction projection exposure system, the resonance point in the horizontal direction must be at least 4 Hz or higher, judging from practical throughput specifications. However, conventional pneumatic springs have their limitations, so we made it possible to achieve the above throughput by using a laminated rubber mount.

In addition, in order to shorten the residual vibration settling time of the entire device structure, it is necessary to suppress the external force of XY stage step feed to a minimum, and in order to achieve this, for example,
A predetermined throughput can be achieved by providing a step pattern that minimizes horizontal changes in the device structure and minimizes residual vibration displacement settling time.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2.

FIG. 1 is a schematic diagram showing an embodiment of a reduction projection exposure apparatus of the present invention. In FIG. 1, a column body 2 is coupled to a main base 1, a separately supported illumination system 3 is arranged at the top, and a reticle 4 and a main base 1 are disposed along its exposure optical axis 7. There is an XY stage 6 fixed above for mounting a wafer 5. The entire system of these devices is supported by a laminated rubber mount 11. During actual exposure, first, the XY stage 6 is moved by a predetermined distance by step feed (not shown) to position the wafer 5 at a predetermined position, and the relative position of the reticle 4 with the reference point is performed by a separate means. Next, after confirming that this positioning amount is within an allowable value, actual exposure is performed by an exposure operation. In this way, the XY stage 6 is continuously moved in steps in the X and Y directions, and exposure is sequentially and repeatedly carried out. In order to expose and transfer the circuit pattern to a predetermined position on the wafer 5 with high precision, it is important to make the relative deviation between the reticle 4 fixedly arranged along the exposure optical axis 7 and the wafer 5 as close to zero as possible. It is. For this purpose, it is ideal that the vibration displacement be zero at the timing of detecting the amount of relative positional deviation between the two and during the actual exposure time.

This ideal state is after the step feed of XY stage 6.

Although this can be achieved by providing a waiting time until the vibration settles, the practical throughput required by the user cannot be satisfied.

In this embodiment, the laminated mount 11 (made by laminating sheet-like natural rubber and sheet-like steel plates alternately by adhesion, etc.) is applied so that it can move horizontally in translation against the step feed external force of the XY stage 6 during actual operation. The vibration mode is made to remain, and as a result, the above-mentioned relative positional deviation amount can be minimized.

Next, when the XY stage 6 is fed in steps according to the conventional constant speed pattern, as illustrated in FIG. 2(a), for example, the settling time of the horizontal vibration 10 of the main base is It becomes larger than the stage speed signal 9 as shown in the figure. The vibration displacement during continuous exposure operation that satisfies the throughput is shown by 10 on the right side of Figure 2 (a), but since the vibration is not necessarily stabilized, it exhibits an irregular vibration state and a stable relative displacement cannot be reproduced. ,Also,
The amount of relative deviation also increases.

In this embodiment, for example, as shown in FIG. 2(b),
By changing the step feed rate pattern of stage 6 to 8 and 9, the step feed pattern of XY stage 6 is optimized so that the horizontal vibration displacement 10 of main base 1 can be stabilized in a short time. So,
Even in continuous exposure operations, the vibration displacement of the main base 1 is stabilized for each exposure operation, as shown at 10 on the right side of FIG. 2(b). This makes it possible to improve the drawbacks of conventional constant speed pattern step feeding, realize highly accurate circuit pattern exposure, and improve throughput. Note that the optimal step feeding pattern can be determined through experiments and a vibration simulator.

Note that the laminated rubber mount 11 may be provided with a parallel link mechanism that allows movement in the horizontal direction.

The same effect can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the entire system of the apparatus can be set to the horizontal translational residual vibration mode, so the amount of forced deviation of each part from the exposure optical axis can be minimized, and the residual mode By giving horizontal spring stiffness to the laminated rubber mount so that the resonance point of the can be minimized, and is effective in shortening the settling time.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the reduction projection exposure apparatus of the present invention, and FIG. 2 shows a conventional air spring type vibration isolation system and a laminated rubber mount type vibration isolation system according to the present invention on an xY stage. FIG. 3 is a diagram showing a residual vibration state when a step feed external force is applied. FIG. 3 is a schematic diagram of a conventional example. 1... Main base, 2... Column body, 3...
Illumination system, 4... Reticle, 5... Wafer, 6... XY stage, 7... Exposure optical axis, 11... Laminated rubber mount.

Claims (1)

[Claims] 1. To minimize the amount of relative displacement due to forced vibration displacement of each component part related to the exposure optical axis in an apparatus structure that receives an external force from a step in the horizontal direction of a reduction projection exposure apparatus for semiconductor manufacturing. The device structure is mounted on a frame that has spring characteristics such that the entire system of the device structure takes horizontal translational vibration behavior in response to the action of the horizontal step external force, and minimizes the vibration behavior time. A reduction projection exposure apparatus characterized in that the reduction projection exposure apparatus is configured to shorten residual vibration settling time by converting the step external force pattern in the horizontal direction into an optimal control pattern. 2. The reduction projection exposure apparatus according to claim 1, wherein the pedestal is provided with a parallel link mechanism movable in the horizontal direction. 3. The pedestal is comprised of a laminated rubber mount having higher spring rigidity in the vertical direction than in the horizontal direction.
Reduction projection exposure apparatus as described in .