JPH0286118A - Vertical stepper - Google Patents

Abstract

PURPOSE:To make it possible to expose and transfer reliably a pattern to an extent of submicrons with a shynchrotron radiant light (SOR) which is radiated horizontally by a method wherein with the threedimensional relative position of a mask and a wafer conformed strictly, a step and repeat operation is performed in a vertical plane. CONSTITUTION:A pretreatment wafer 2 is taken out from a wafer stocker 24 by a wafer loader 26 and is sucked using vacuum on a prealignment stage 21. Here, after a rough alignment of the wafer 2 is performed using an image processing technique or a photoelectric conversion element, such as a laser diode and the like, the wafer is transferred up to a wafer stage 18 by a wafer loader 22 and is sucked using vacuum. Then, after the stage 18 is moved to an exposure position to conform strictly the relative position of the wafer and a mask 3, a SOR is irradiated to expose and transfer a pattern on the mask to the wafer 2. Moreover, the whole surface of a the wafer 2 is subjected to exposure by the step and repeat operation of the stage 18. The wafer 2 finished an exposure is again housed in a wafer stocker 25 by the loaders 20 and 22 and an exposure of one sheet of the wafer 2 is finished.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology Problems to be solved by the invention Means for solving the problems Effects of the invention [Summary] Synchrotron radiation (hereinafter referred to as SOR) Regarding the vertical stepper that transfers the circuit pattern on the mask onto the wafer using a light source (abbreviated), in order to reliably expose and transfer the submicron pattern using horizontally emitted SOR, the three-dimensional relative position of the mask and the wafer is The purpose of this project is to provide a vertical stopper that can be precisely aligned and that can perform step-and-repeat operation in the vertical plane.
This vertical stepper is used to expose and transfer a circuit pattern drawn on a mask onto a wafer using a wafer (OR), and includes a coarse wafer movement stage that moves the wafer in steps, and a wafer coarse movement stage that makes fine movements of the wafer. A wafer fine movement stage that precisely aligns the mask with the mask, a mask tilt function that tilts the mask, and a function that adjusts the distance between the mask and the wafer.
Furthermore, there is a mask rotation stage that has the function of rotating the mask within its plane, a mechanism that scans the mask stage that integrates the mask and wafer in a direction perpendicular to the synchrotron radiation (SOR), and a wafer coarse movement mechanism. A mechanism that uses an air cylinder to compensate for the weight of a movable part that has a degree of freedom in the vertical direction, and a synchrotron radiation (S) mechanism for the mask stage.
OR) A mechanism that uses an air cylinder to compensate for the weight of the movable part during scanning, a vibration isolation table that prevents vibrations generated from the stepper installation environment from propagating to the wafer coarse and fine movement stage and the mask stage, and a wafer mounted. A suction mechanism that attaches and integrates the wafer fine movement stage to the mask stage using vacuum suction, a wafer stocker ■ that stocks wafers before exposure and transfer, a wafer stocker ■ that stocks wafers after exposure and transfer, and a wafer stocker ■ that stores wafers before exposure and transfer. A pre-alignment stage that aligns the in-plane position of the wafer based on its orientation flat or V-groove; a wafer rotor that takes out the wafer before exposure and transfer from the wafer stocker and transports it to the pre-alignment stage or vice versa; A wafer loader that transports the wafer on the pre-alignment stage to the wafer fine movement stage and vice versa, a mask magazine that can stock multiple masks, and a mask magazine that extracts the necessary masks from the mask magazine and transports them onto the mask stage or vice versa. and a mask rotor that performs the opposite operation.

[Industrial application field]

The present invention uses synchrotron radiation (hereinafter abbreviated as SOR)
This invention relates to a vertical stepper that uses a light source to transfer a circuit pattern on a mask onto a wafer.

In recent years, S
An X-ray exposure method using OR is attracting attention.

This exposure method is not only suitable for submicron pattern transfer because the exposure light source has a shorter wavelength and better parallelism than conventional ultraviolet exposure methods, but also has high SOR intensity, so high throughput is expected. It has features such as being able to

However, in order to reliably expose and transfer submicron patterns using horizontally emitted SOR, the three-dimensional relative positions of the mask and wafer must be precisely aligned, and step-and-repeat operations in the vertical plane are required. Requires a vertical stepper that is capable of

[Conventional technology]

A horizontal stepper as shown in FIG. 17 is usually used in a conventional exposure apparatus (reduction projection exposure apparatus) for semiconductor manufacturing using ultraviolet rays. FIG. 17 is a diagram illustrating a horizontal stepper, and FIG. 18 is a perspective view of a part of the conventional XY stage for positioning a wafer.

In FIG. 17, reference numeral 1 denotes a wafer positioning stage on which a wafer 2 is placed, and is movable in the X and Y directions. A mask 3 (reticle) located above the wafer 2 and used to expose the wafer 2 through a reduction optical exposure system is held on a mask moving stage 4.

A pattern on a mask held on a mask moving stage 4 is reduced and exposed onto a wafer 2 held on a wafer positioning stage 1 by an exposure light source (mercury lamp) 5. In the case of this exposure, it is necessary to align the mask 3 and the wafer 2.

Conventionally, as an XY stage used for the above-mentioned positioning, there is a horizontal type as shown in FIG. 18, for example.

In FIG. 18, the XY stage consists of an X-axis stage 8 that moves horizontally by a ball screw 6 and a servo motor 7, and a Y-axis stage 11 that moves in a direction perpendicular to the X-axis by a ball screw 9 and a servo motor IO. 12 is a stand, 13 is an X-axis guide mechanism, and 14 is a Y-axis guide mechanism. Further, a laser length measuring device (not shown) is used to detect the position of each stage.

[Problem to be solved by the invention]

Conventionally, a horizontal XY stage as shown in FIG. 18 has been used when reducing and exposing a mask pattern onto a wafer using ultraviolet rays.

However, the X-ray exposure method using SOR is attracting attention as a means of manufacturing VLSIs, and this exposure method has a shorter wavelength and better parallelism of the light source than conventional ultraviolet exposure methods, and is suitable for submicron pattern transfer. Suitable and also SOR
Because of its high strength, high throughput can be expected.

The cross section of the SOR light has a long and narrow shape as shown in Figures 19 and 20, and since the exposed area cannot be covered in one time, it is necessary to perform step-and-repeat operation in addition to vertical scanning during the -times of exposure. It is necessary to move the wafer and expose the entire surface of the wafer.

As shown in FIG. 19, the SOR light is accelerated by an accelerator (not shown) and the electrons incident on the storage ring 15 are
It orbits in the vacuum storage ring 15 while its trajectory is bent by the deflection magnet 16. SOR light is emitted in the tangential direction from the portion where the electron trajectory is bent by the deflection magnet 6. The SOR light necessary for exposure is obtained by cutting off light having wavelengths other than those necessary for exposure using a filter, a Be window, etc. (not shown).

As described above, since SOR emits light in the horizontal direction due to its light emission principle, a stepper for exposing with SOR must necessarily be of a vertical type with a degree of freedom in the vertical direction.

Therefore, the present invention reliably exposes and transfers a submicron pattern using horizontally emitted SOR light, making it possible to precisely match the three-dimensional relative positions of the mask and wafer, and to perform step-and-transfer operations in the vertical plane. The purpose of the present invention is to provide a vertical stepper capable of repeating operations.

[Means to solve the problem]

The present invention will be explained in detail using FIGS. 1 and 2. The operation of each mechanical element will be described below.

In Figure 2, 17 is a vibration isolation table, which has the function of blocking vibrations from the ground.

A wafer stage 18 is a step-and-repeat stage for mounting the wafer 2 and exposing the entire surface of the wafer, and has a degree of freedom in the X-Y axis directions. Note that for the degree of freedom in the vertical plane, a self-weight compensation mechanism is provided to offset the self-weight of the stage so that it does not become a load on the actuator.

19 is a mask stage, on which mask 3 is attached and wafer 2 is placed.
The degree of freedom in the Z-axis direction (Z-axis direction, rotation around the X-axis, rotation around the Y-axis) shown in FIG. In order to irradiate the entire surface of the mask 3 with SOR light that has a degree of freedom to correct rotational displacement (θ-axis rotation direction) and an elongated rod-shaped cross section, it is necessary to move the SOR light up and down or change the relative position of the mask and wafer in some way. It consists of a stage that is fixed and has a beam scanning mechanism in the Y-axis direction that moves up and down. In addition,
The beam scanning mechanism also has a self-weight compensation mechanism.

20 is a wafer rotor, which can be remotely controlled as a wafer stocker ■2
This is a transport machine that can transport unexposed wafers 2 stocked at 4 to a pre-alignment stage 21, which will be described later.

A pre-alignment stage 21 is a stage for automatically roughly aligning the wafer 2 before it is mounted on the wafer stage 18, and has degrees of freedom in the X-Y-θ axis directions.

22 is a wafer loader ■, pre-alignment stage 2
This is an arm-type rotation mechanism that can transport the wafer 2 aligned in step 1 to a wafer stage by remote control.

Reference numeral 23 is a mask rotor, which selects one mask from among the masks stocked in a mask magazine (not shown) by remote control, passes through hole a as indicated by the dotted line arrow, and ascends to the uppermost position for mask replacement. This is a transport machine that transports the mask to the mask stage 19.

A wafer stocker 24 stores unprocessed wafers. A wafer stocker 25 stores exposed wafers.

The above problems can be solved by the vertical stepper of the present invention having the above functions.

[Effect]

Next, the procedure for exposing the wafer 2 in the vertical stepper of the present invention will be described.

First, the unprocessed wafer 2 is taken out from the wafer stocker 24 by the wafer rotor 20 and vacuum-adsorbed onto the pre-alignment stage 21. After roughly aligning the wafer 2 using an image processing method or a photoelectric conversion element such as a laser diode, the wafer loader 22
The wafer is transported to the wafer stage for 1 day, and vacuum suction is carried out. (The mask stage 19 is retracted upward.) Next, the wafer stage 18 is moved to the exposure position and the relative position with the mask 3 is precisely adjusted, (the mask stage 19 is lowered from above and the wafer stage 18 is moved to the exposure position). 18) irradiates the pattern on the mask 3 onto the wafer 2.
Transfer to exposure to light.

Further, the entire surface of the wafer 2 is exposed by a so-called step-and-repeat operation in which the wafer stage 18 is moved step by step to repeat the exposure. After exposure, the wafer 2 is stored in the wafer stocker 25 again by the wafer loader 20 and the wafer loader 22, and one wafer 2
Finish the exposure.

Next, a procedure for mounting the mask 3 on the mask stage 19 will be described.

First, the mask rotor 23 extracts a necessary mask from a mask magazine (not shown), transports it to the mask stage 19 (the mask stage 19 is located above, and passes through the hole a as indicated by the dotted line arrow), and the mask stage 19 descends. After positioning, the mask 3 is fixed on the mask stage 19 by vacuum suction.

Next, after the wafers 2 are loaded and the necessary number of wafers are exposed according to the procedure described above, the masks 3 are stored in the mask magazine by the mask rotor 23 again.

〔Example〕

A specific example that realizes each function required for a vertical stepper for SOR will be described. Note that the same reference numerals represent the same objects throughout the figures.

(1) Because SOR is emitted horizontally due to its generation principle, the mask and wafer must not be held vertically. Therefore, since the stage has a degree of freedom in the vertical direction, Requires a self-weight compensation mechanism to compensate.

That is, for the degree of freedom in the vertical direction, a self-weight compensation mechanism using an air cylinder 28 as shown in FIG. 3 is used.

The stage 29, which has a degree of freedom in the vertical direction, has a guide mechanism 3.
0, actuator (in this example, a rotary DC servo motor 26 and a ball screw 27) and an air cylinder 28
By constantly supplying gas at a constant pressure to the air cylinder 28, the movable part (stage 29)
The stage's own weight can be offset regardless of its position. In this embodiment, as shown in FIG. 4, four air cylinders 28 (A, B, C, D
) The air pressure is set so that the differential pressure (PI = P2) is equal to the dead weight, and even if the air pressure changes, the differential pressure does not fluctuate, and stable dead weight compensation can always be performed.

In addition, the air cylinder 28 has the feature that it stabilizes the servo system of the wafer stage by the damper effect of the gas itself, and does not double the mass of the moving parts, which is a disadvantage of self-weight compensation using a counterweight. .

29a is a coarse movement X-axis movable part, and 30a is a coarse movement X-axis guide mechanism.

(2) As a wafer stage, a fine movement XY stage 31 shown by a dotted line is placed on a coarse movement
Adopts a two-stage stage configuration equipped with. That is, the coarse movement XY stage includes a metal roller guide bearing (not shown), an actuator that combines a rotary DC servo motor 26 and a ball screw 27, and a position detector (not shown) of a rotary rotary encoder directly connected to the DC servo motor 26. By using feedback control, positioning on the micron order is possible. In addition to this, a multipolar linear DC motor may be used as the actuator of the coarse movement XY stage, and a linear scale or laser interferometer may be used as the position detector. Further, the fine movement XY stage 31 includes a parallel plate spring guide 32 and a piezoelectric element 3 as shown in FIG.
It has a configuration of fine X-axis and Y-axis rotation parts 42 and 41 as shown in Figure 6, in which a single-axis stage combining 3 is stacked in two stages, and is used for high-resolution devices such as laser interferometers and differential transformers. A position detector (not shown) detects the displacement ΔX of the fine X-axis movable part,
By detecting ΔY and performing feedback control, submicron positioning is possible. In addition to this, the seventh
An XY-axis integrated guide mechanism shown in FIGS. (a) and (b) may also be used.

In the figure, ■, ■, ■, ■ are attachment parts to the coarse movement XY stage, and 32a is a parallel plate spring guide composed of four leaf springs, which are located at four locations and support the fine movement XY stage movable part 31. do. FIG. 8 shows its operating principle. That is, when the FlO force is applied by the piezoelectric element, the members ■■■ are displaced by ΔY due to the bending deformation of the parallel leaf spring guide 32a that supports them. The same applies to displacement in the X-axis direction. 9th
The figure shows an example of simultaneous displacement in two directions of the X and Y axes. These fine movement stages have a structure that allows them to be separated from the coarse movement stage so that they can be vacuum-adsorbed to the mask stage during SOR scanning, which will be described later.

By having such a structure in which the coarse movement XY stage and the fine movement stage are stacked, it is possible to achieve both high-speed step-and-repeat operation and precise positioning operation.

Further, the mask stage side is provided with degrees of freedom in the 21 to 23 axis directions in FIG. 1 and degrees of freedom in the θ axis direction to facilitate three-dimensional relative positioning of the mask and the wafer at the exposure position. Specifically, the degrees of freedom in the 21st to 23rd axis directions are:
As shown in the perspective view of FIG. 10 and the sectional view of FIG.
The movable part is guided by a doughnut-shaped diaphragm-shaped leaf spring 34, and is moved as shown in FIG. It is possible to correct the spacing and relative tilt of the mask and wafer. Note that for position detection, it is appropriate to use a differential transformer or a linear scale (not shown). 35 is a mask chuck, and 45 is a part fixed to the mask stage.

If the movable range of the piezoelectric element is too small, the movable range may be expanded by combining three piezoelectric elements to perform the main movement as shown in FIG. 13. Furthermore, the degree of freedom in the θ direction is - For example, as shown in FIG. This can be realized by driving with 33. If the movable range is too small, the inchworm movement may be performed by combining three piezoelectric elements 33, as in the case of the Zl-23 axis. 48' is a position detector.

(3) For the SOR scanning mechanism, a scanning mechanism as shown in FIG. 15 is adopted. That is, the rotary servo motor 37 and the screw 38 are moved while strictly maintaining the relative positions of the mask stage 19 and the wafer guided by the linear guide mechanism.
By scanning in the vertical direction, the entire exposure area can be irradiated with SOR. In this case, the position of the mask stage 19 is detected by a rotary encoder (not shown) directly connected to the rotary servo motor 37. 46 is a linear guide, 47 is a base portion, and 4th is a rail for a metal roller guide bearing.

(4) Regarding the vibration isolation mechanism (see Figure 2), the positioning accuracy of the mask stage 1 is reduced due to vibrations from the environment.
9. Place the wafer stage 18 on the vibration isolation table 17 to block vibrations from the ground. Further, as shown in FIGS. 16(a) and 16(b), during SOR scanning, the fine movement stage part 39 of the wafer 2 is separated from the coarse movement stage part 40 and vacuum-adsorbed to the mask stage 19 side, and the mask 3 and wafer 2 are integrated to reduce relative vibration. In this case, the fine movement stage 39 of the wafer 2 may be completely detached from the coarse movement stage 40 for scanning, or may be partially connected to the coarse movement stage 40 of the wafer 2 in the vertical direction. It is also possible to scan while being dragged by the mask stage 19 with the degree of freedom released. 49 is an absorber for vacuum adsorption.

(5) Since SOR is harmful to the human body, it is not possible to enter the thermal chamber where a vertical stepper is installed during exposure. Therefore, the transportation, attachment and detachment of the wafer 2, the transportation and attachment and detachment of the mask, and the pre-alignment of the wafer are all automated and remotely controlled by commands from a controller installed outside the chamber.

By providing the above mechanism in a vertical stepper, it is possible to precisely align the three-dimensional relative positions of the mask and wafer, and step-and-repeat operations can be performed in the vertical plane. Submicron patterns can be reliably exposed and transferred.

(Effects of the Invention) As explained above, according to the present invention, it is possible to configure a practical exposure system using horizontally emitted SOR as a light source, and it is possible to construct a practical exposure system using a horizontally emitted SOR as a light source, and it is possible to construct a DRAM of 16M biftles or more, for which explosive demand is expected in the future. The effect of being able to provide a means of manufacturing VLSIs as typified by the following is significant.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the distribution of the degrees of freedom of the present invention, Fig. 2 is a block diagram of the vertical stepper of the present invention, Fig. 3 is a block diagram of the two-tiered stage of the present invention, and Fig. 4 is a diagram of the third 5 is a diagram of a uniaxial stage combining a temporary spring and a piezoelectric element according to the present invention, FIG. 6 is a perspective view of a two-stage stacked stage according to the present invention, and FIG.
(a) and (b) are diagrams of the guide mechanism of the integrated XY axis type of the present invention, Figure 8 is a diagram of the operating principle of Figure 7, Figure 9 is a diagram of Figure 7 with simultaneous displacement in the x and y axis directions, and Figure 10. The figure is a perspective view of the mask side stage of the present invention, No. 11.
The figure is a sectional view of Fig. 10, Fig. 12 is an operating state diagram of Fig. 11, Fig. 13 is a diagram of the operating principle of the length straight type moving mechanism of the present invention, and Fig. 14 is a rotary type bearing of the present invention. Fig. 15 is a diagram of the beam scanning mechanism of the present invention, Fig. 16 is a diagram illustrating the adsorption of the fine movement XY stage of the present invention, and Fig. 17 is a diagram illustrating a conventional horizontal stepper. Figure, 1st
FIG. 8 is a perspective view of a conventional XY stage, FIG. 19 is a diagram showing the shape of synchrotron radiation (SOR), and FIG. 20 is a diagram showing the relationship between the exposure area and the SOR light. In the figure, 2 is a wafer, 3 is a mask, 17 is a vibration isolation table, 18 is a wafer stage, 19 is a mask stage, 20 is a wafer loader, 21 is a pre-alignment stage, 23 is a mask rotor, 24 is a wafer stocker, 25 is a Wafer stocker ■, 26 is a rotary DC servo motor, 27 is a ball screw, 28 is an air cylinder, 29 is a stage, 30 is a guide mechanism, 31 is a fine movement X-Y stage, 32.32a is a parallel plate spring guide, 33 is a piezoelectric element, 34 is a diaphragm leaf spring, 35 is a mask chuck, 36 is a rotary bearing, 40 is a coarse movement xy stage, 41 is a fine movement Y-axis movable part, 42 is a fine movement X-axis movable part, 43 is a stage movable part 45 is a stage fixed part, 46 is a movable part, 47 is a protrusion, 48' is a position detector, 36th automatic V leisure time 1-9 diagram, kei + 2 32 + fi, suction rack, a main leg g Paper agreement between the old Q version and the original Q version
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Claims (1)

[Scope of Claims] A vertical stepper that uses synchrotron radiation (SOR) as a light source to expose and transfer a circuit pattern drawn on a mask (3) onto a wafer (2), comprising: A wafer coarse movement stage (2) that moves the wafer (2) in steps, a wafer fine movement stage (18) that makes fine movements of the wafer (2) and precisely aligns it with the mask (3), and a mask (3). A function to tilt the mask, a function to adjust the distance between the mask (3) and the wafer (2), and a function to adjust the distance between the mask (3) and the wafer (2).
) within its plane, and a mechanism that scans the mask stage (19) on which the mask (3) and wafer (2) are fixed in a direction perpendicular to the synchrotron radiation (SOR). A mechanism that uses an air cylinder to compensate for the weight of the movable part that has a degree of freedom in the vertical direction in the wafer coarse movement mechanism, and a mechanism that compensates for the weight of the movable part during synchrotron radiation (SOR) scanning of the mask stage (19). A compensation mechanism using an air cylinder, a vibration isolation table (17) that prevents vibrations generated from the installation environment of the stepper from propagating to the wafer coarse/fine movement stage (18) and the mask stage (19), and the wafer (2). A suction mechanism that suctions and integrates the mounted wafer fine movement stage onto the mask stage (19) using vacuum suction, a wafer stocker (1) (24) that stocks wafers (2) before exposure and transfer, and wafer stockers (1) and (24) that store wafers (2) before exposure and transfer. A wafer stocker (2) (25) for stocking wafers (2), a pre-alignment stage (21) for aligning the in-plane position of the wafer (2) before exposure transfer based on its orientation flat or V-groove, and an exposure A wafer rotor (1) (20) that takes out the wafer (2) before transfer from the wafer stocker (1) (24) and transports it to the pre-alignment stage (21) or vice versa, and a pre-alignment stage (21). A wafer rotor 2 (22) that transports the upper wafer to the wafer fine movement stage and vice versa, a mask magazine that can stock a plurality of masks (3), and a mask magazine that extracts the necessary mask (3) from the mask magazine and stores the mask. A vertical stepper characterized by having a mask rotor (23) that carries the mask up to the stage (19) or vice versa.