JPH1167882A - Substrate suction device/method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold and suck a substrate while the flatness of the substrate is maintained, by providing plural suction parts sucking and holding the substrate in different positions, and controlling the suction operation in accordance with a result obtained by detecting the suction state. SOLUTION: A substrate P is transferred to a substrate holding face PH1 provided with porous areas A, B and C and a vacuum pump 2 is operated. At that time, valves 3B and 3C are set in a wholly closed state. The peripheral part of the substrate P on the porous area A is sucked to the substrate holding face PH1 with the vacuum suction 2. When a pressure sensor 6A detects that the pressure of a piping 1A is reduced to a prescribed value, the valve 3B is opened and the peripheral part of the substrate P on the porous area B is sucked to the substrate holding face PH1. At the same time, the valve 3C is opened by the detection result of the pressure sensor 3B, and the peripheral part of the substrate P on the porous area C in is sucked. Thus, the substrate P is chucked for respective parts at optimum timing, and the substrate can securely be sucked and held.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for adsorbing a substrate, and more particularly to an apparatus and a method for adsorbing and holding a substrate such as a semiconductor or a liquid crystal display element.

[0002]

2. Description of the Related Art In recent years, along with the flow of information visualization, calculators,
As display elements for word processors, personal computers, portable televisions, etc.
Liquid crystal display panels are increasingly used. The liquid crystal display panel is formed by patterning a transparent thin-film electrode into a desired shape on a glass substrate by photolithography. As an apparatus for this lithography, a stepper for exposing an original pattern formed on a mask to a photoresist layer on a glass substrate through a projection exposure system or an exposure apparatus of a mirror projection system is used.
The glass substrate as a substrate to be exposed is becoming larger year by year, and recently, a glass substrate having a size of about 600 mm × 720 mm is prepared.

One problem in exposing an original pattern on a glass substrate is how to keep the position of the photosensitive surface on the glass substrate in the optical axis direction constant. That is, since the glass substrate is a thin plate, it inherently has undulation and warpage. Therefore, if the glass substrate is simply placed on the substrate stage, the position of the photosensitive surface may change due to the undulation or warpage. Incidentally, the depth of focus of the exposure apparatus is several μm or less, and therefore, it is necessary to keep the variation in the position in the optical axis direction on the photosensitive surface of the glass substrate within the range.

Therefore, the exposure apparatus is provided with a suction device in order to accurately hold the glass substrate in the optical axis direction. The suction device forms a perforation on a flat holding surface for holding a glass substrate, and generates a negative pressure in the perforation to suction-hold the glass substrate.

[0005]

Incidentally, when the glass substrate is held by the suction device, there are the following problems. FIG. 9 is a cross-sectional view showing a state where the glass substrate P is sucked on the substrate holding surface PH1 of the suction device PH. FIG.
In, the substrate holding surface PH1 of the suction device PH has holes Pa and Pb as a part of the holes.

As described above, since the glass substrate P is a thin plate, it inherently has undulation and warpage. The glass substrate P thus deformed is placed on the substrate holding surface PH of the suction device PH.
When placed on 1, the part where undulations and the like occurred was a hole Pa,
It may be located between Pb.

Here, when the glass substrate P is sucked by the suction device PH by simultaneously applying a negative pressure to the inside of the holes Pa and Pb, if the swell is small, the distance between the holes Pa and Pb and the hole Pa , Pb, the length between the portions of the substrate P sucked is substantially equal, so that the substrate P is sucked to the holding surface PH1, and the undulation and the like are corrected.

However, if the undulations are relatively large, the length between the portions of the substrate P adsorbed by the holes Pa and Pb becomes larger than the distance between the holes Pa and Pb, and thus the pressure inside the holes is reduced. No matter how much lowers the holding surface PH
1, the glass substrate P is not adsorbed by the suction device P
A so-called air pool S, which partially rises from H, is generated. Due to such an air pool S, the position of the surface of the glass substrate P in the optical axis direction may be shifted out of the depth of focus of the exposure apparatus. In addition, air pool S
Does not always occur at the same position on the substrate,
This can be one of the causes of the displacement during multiple exposure or the like.

On the other hand, there is a thought that if the holes 2a and 2b are made to have a negative pressure with a time difference therebetween, it is possible to prevent the formation of an air pocket, but it is not concrete how this is achieved.

Accordingly, an object of the present invention is to provide a suction device and a suction method capable of holding a substrate while maintaining the flatness of the substrate.

[0011]

In order to solve the above-mentioned problems, a substrate suction device (PH) of the present invention includes a first suction portion (1A) for suction-holding a substrate (P) and a first suction portion (1A). A second suction unit (1B) that suction-holds the substrate (P) at a position different from the suction unit (1A), and at least a first suction unit (1);
A) A detecting unit (6) for detecting an adsorption state between the substrate (P) and the substrate (P)
A) and a control unit (CPU) for controlling the suction operation of the second suction unit (1B) according to the detection result of the suction state of the first suction unit (1A). I do.

According to the substrate suction device of the present invention, the control unit (CPU) controls the suction operation of the second suction unit (1B) according to the detection result of the suction state of the first suction unit (1A). Since the control is performed, the substrate (P) can be suctioned for each part at an optimal timing, and the substrate (P) can be reliably formed without forming an air pocket (S) between the substrate (P) and the substrate holding surface (PH1). Can be held by suction.

According to the substrate suction method of the present invention, a first suction portion (1A) for sucking and holding a substrate (P) and a second suction portion for sucking the substrate (P) adjacent to the first suction portion (1A) are provided. A substrate (P) is adsorbed on the substrate (P) by the first adsorbing portion (1B), and the substrate (P) is adsorbed on the first adsorbing portion (1A) by the first adsorbing portion (1A). The substrate (P) is suctioned by the second suction portion (1B) in accordance with the state of suction with the substrate (P).

According to the substrate suction method of the present invention, the substrate (P) is suctioned by the second suction portion (1B) according to the suction state of the first suction portion (1A) and the substrate (P). So
The substrate (P) can be suctioned for each part at an optimal timing, and the suction of the substrate (P) can be surely held without forming an air pocket (S) between the substrate (P) and the substrate holding surface (PH1). It can be carried out.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The projection exposure apparatus as the exposure system shown in FIG. 1 is an example of a liquid crystal manufacturing stepper. As shown in FIG. 1, a stepper is generally installed in a chamber 101. Chamber 1
01, the temperature control is performed with higher accuracy than the normal clean room. For example, the temperature control of the clean room is within a range of ± 2 to 3 ° C., while the temperature control within the chamber 101 is within ± 0.1 ° C. It is kept in.

The illustrated liquid crystal manufacturing stepper is a stepper using a side flow type chamber, and an air outlet is provided on a side surface of the chamber 101 to prevent particles floating in the air from adhering to the apparatus. The airflow whose temperature is controlled moves perpendicularly to the optical axis of the projection exposure system PL from the outlet 102 as shown by an arrow in the figure. In order to prevent foreign matter (dust) floating in the clean room from flowing into the chamber 101, particularly the exposure apparatus main body including the projection optical system, an HEPA (or ULPA) filter is provided with an air inlet or outlet of the chamber 101. It is arranged near the mouth 102.

The projection exposure apparatus shown in FIG. 1 includes a light source such as a mercury lamp and an illumination optical system (not shown), a reticle stage RST for mounting a reticle R, a projection optical system PL, a substrate stage PST for moving a substrate P, and a substrate. It mainly comprises an alignment sensor 100 and the like for positioning. The illumination optical system includes a fly-eye lens, a condenser lens, and the like, and finally illuminates the reticle R via the condenser lens 103. The illumination optical system is a reticle R which is a mask on which a circuit pattern or the like is drawn with illumination light from a light source.
Is illuminated with a substantially uniform illuminance and a predetermined solid angle. These unillustrated light sources and illumination optical systems are generally arranged above the reticle RST in the drawing or on the side of the reticle stage RST when an optical reflection system is used. In particular, the light source is located outside the chamber 101.

The reticle stage RST includes a projection optical system P
The reticle driving unit (not shown), which is installed on the optical axis AX of L and between the projection optical system PL and the condenser lens 103 and includes a motor or the like, makes X, Y perpendicular to the optical axis AX. And rotation in the θ direction. On reticle stage RST, reticle holder RH is installed, and reticle R is mounted on reticle holder RH.
Installed on top. Reticle R is held by suction on reticle holder RH by a vacuum chuck (not shown). Above the reticle stage RST, a reticle alignment microscope 104 facing the optical axis AX is mounted. With these two sets of microscopes 104, the reticle R
By observing the reference mark formed on the reticle stage, the initial position of the reticle stage RST is determined so that the reticle R is accurately positioned at a predetermined reference position.

Reticle R is illuminated on reticle stage RST in a rectangular illumination area. This illumination area is defined by a field stop (not shown) arranged above or at a surface conjugate with reticle R and above reticle stage RST.

The illumination light passing through the reticle R enters the projection optical system PL, and a circuit pattern image of the reticle R is formed on the substrate P by the projection optical system PL. A plurality of lens elements are housed in the projection optical system PL such that the optical axis AX is a common optical axis. The projection optical system PL includes a flange 124 at an outer peripheral portion thereof and a central portion in an optical axis direction, and the flange portion 124 allows the mount 123 of the exposure apparatus main body.
It is fixed to.

The substrate P is vacuum-adsorbed on a substrate holder PH held on a substrate stage PST. Similar to the reticle stage RST, the substrate stage PST is moved in the X and Y directions in the direction perpendicular to the optical axis AX and moved in the Z direction in the optical axis direction by a substrate stage driving unit (not shown) composed of a motor or the like. And the rotation in the θ direction are possible.
A movable mirror 108 is fixed to an end of the substrate stage PST, and the laser beam from the interferometer 109 is reflected by the movable mirror 108 and the reflected light is detected by the interferometer 109, so that the reflected light is detected within the XY plane of the substrate stage PST. Is constantly monitored. Thereby, the operation of determining the minute position when exposing the pattern image on the reticle R to the predetermined position on the substrate P and the operation of moving to the next exposure area are repeated.

The projection exposure apparatus has a function of accurately exposing a new pattern to a pattern already formed on the substrate P by exposure. In order to execute this function, the projection exposure apparatus has a function (substrate alignment system) for detecting the position of the alignment mark on the substrate P and determining the position for performing the overlay exposure. In this example,
As this substrate alignment system, an optical alignment sensor 100 provided separately from the projection optical system PL is provided. The alignment sensor 100 bends a laser beam emitted from the light source 113 with a mirror or the like to convert the laser beam
Upward, the alignment mark P formed on the substrate P
The difference from M is detected by the detector 114, and the determination unit 115 obtains the amount of misalignment.

FIG. 2 is a perspective view showing the suction device PH according to the embodiment of the present invention and a stage for supporting the same. The suction device PH is disposed on a Z-axis stage ZST that can move in the Z-axis direction (optical axis direction).
ST is arranged on an X-axis stage XST movable in the X-axis direction, and X-axis stage XST is arranged on a Y-axis stage YST movable in the Y-axis direction. That is, the suction device PH can be moved in any three-dimensional direction by driving each stage. The above-described substrate stage PST (FIG. 1) includes a Z-axis stage ZST, X
An axis stage XST and a Y-axis stage YST are included. Adjacent to the suction device PH, Y
An axis moving mirror YM and an X axis moving mirror XM are arranged, and are used to detect the Y axis direction position and the X axis direction position of the suction device PH.

The suction device PH has many holes on the holding surface PH1 of the substrate P. FIG. 3 is a diagram schematically illustrating the substrate holding surface PH1 of the suction device PH. In FIG.
The hatched portion is a region in which porosity is formed, and such a region is divided into a rectangular central region A and elongated rectangular regions B and C adjacent to the region A. Although hatching is not applied between the regions, this is performed to clearly show the boundaries of the regions. If one type of substrate P is not actually used vertically and horizontally, it is not necessary to provide a gap between the regions.

Below the porous areas A, B and C, closed spaces are respectively formed inside the adsorption device PH, and these spaces are respectively connected to the negative pressure station 5 by polyurethane tubes (not shown). ing. The negative pressure station 5 is connected to a vacuum pump (not shown).

FIG. 4 shows an adsorption device P according to this embodiment.
FIG. 2 is a configuration diagram schematically showing H. The substrate P is placed on the substrate holding surface PH1 of the suction device PH. The porous areas A, B, and C of the substrate holding surface PH1 correspond to those in FIG. 3, but are shown in a different arrangement from the actual ones in order to simplify the piping in FIG.

The porous area A is connected to a vacuum pump 2 via a first pipe 1A. The porous region B is the first region.
It is connected to the vacuum pump 2 via a second pipe 1B branched from the pipe 1A. The porous region C is connected to the vacuum pump 2 via a third pipe 1C branched from the second pipe 1B. Each pipe is distributed to each area via the negative pressure station 5.

A first valve 3B is arranged at a branch point of the second pipe 1B from the first pipe 1A. First
The valve 3B is a disc-shaped butterfly valve, which is driven and rotated by the first actuator 4B, thereby opening or closing the second pipe 1B.

On the other hand, in the third pipe 1C, the second pipe 1
A second valve 3C is disposed at a branch point from B. The second valve 3C is also a disc-shaped butterfly valve, and is driven and rotated by the second actuator 4C, so that the third pipe 1C can be opened or closed.

The first pipe 1A is provided with a first air pressure sensor 6A as a detecting unit, which measures the air pressure in the first pipe 1A and outputs it as an electric signal. On the other hand, the second pressure sensor 6 is also provided as a detection unit in the second pipe 1B.
B is provided to measure the air pressure in the second pipe 1B and output it as an electric signal.

Vacuum pump 2, actuator 4
B, 4C and the atmospheric pressure sensors 6A, 6B are electrically connected to a CPU 7 as a control unit.

Next, the operation of this embodiment will be described below. Substrate P delivered from a transport system (not shown)
When suction is to be performed on the substrate holding surface PH1 of the suction device PH, the vacuum pump 2 is operated by the CPU 7 in a state where the substrate P is delivered to the substrate holding surface PH1 of the suction device PH. Here, the first valve 3B and the second valve 3C are fully closed.

FIG. 5 is a graph showing the degree of decrease in the atmospheric pressure in the pipe with respect to time when the vacuum pump 2 operates. Due to the force of the air sucked into the vacuum pump 2, the periphery of the porous region A of the substrate P becomes
, The pressure in the first pipe 1A gradually decreases according to the graph shown in FIG.

When the first pressure sensor 6A detects that the pressure in the first pipe 1A has decreased to a predetermined value Vac1, the CPU 7 drives the first actuator 4B to
The first valve 3B is opened. FIG. 4 shows such a state. Therefore, the vacuum pump 2 is connected to the second pipe 1
The air in B is sucked, whereby the periphery of the porous region B of the substrate P is adsorbed on the substrate holding surface PH1, and the pressure in the second pipe 1B decreases.

Further, the second pressure sensor 6B is connected to the second pipe 1
When detecting that the atmospheric pressure of B has decreased to the predetermined value Vac1, the CPU 7 drives the second actuator 4C to open the second valve 3C. Thereby, the vacuum pump 2 sucks the air in the third pipe 1C, so that the periphery of the porous region C of the substrate P is adsorbed on the substrate holding surface PH1, and
The air pressure in the second pipe 1B decreases. In this way, the substrate P can be automatically sucked and held on the substrate holding surface PH1 without forming an air pocket.

The pressure sensor detects the pressure in the pipe by Vac
The CPU 7 may open the valve by detecting that it has decreased to Vac2 or Vac3 lower than 1. Thereby, the holding of the substrate becomes more reliable. Also,
A specific valve (for example, the second valve 3
It is also possible to give an instruction not to release C), whereby the size of the substrate P is small with respect to the substrate holding surface PH1, so that the substrate P does not exist on a specific area (for example, the area C). In this case, it is possible to prevent air from being unnecessarily sucked from the specific area.

In the above embodiment, since the valve is opened using the barometric pressure sensor and the actuator, the configuration is relatively complicated and the manufacturing cost is increased.
Therefore, a simpler configuration may be required.

FIG. 6 is a schematic view of an adsorption apparatus PH according to a second embodiment of the present invention which meets such a request. In contrast to the above-described first embodiment, the second embodiment is the same for each piping configuration from the substrate holding surface PH1 to the vacuum pump 2. However, as shown in FIG. 6, instead of providing a barometric pressure sensor and an actuator, springs 8B and 8C are provided.

The second embodiment will be described more specifically. A first valve 13B is disposed at a branch point of the second pipe 1B from the first pipe 1A. First
The valve 13B is a disk-shaped valve that is movable in the axial direction, and is pushed by the first spring 8B in a direction to close the second pipe 1B.

On the other hand, in the third pipe 1C, the second pipe 1
A second valve 13C is arranged at a branch point from B. The second valve 13C is also a disc-shaped valve that is movable in the axial direction, and is pushed by the second spring 8C in a direction to close the third pipe 1C.

In the second embodiment, the first spring 8B
The elastic force of the second pipe 1 is sucked in the first pipe 1A.
When a pressure difference (for example, Vac1) occurs between B and B,
The value is set such that the first valve 13B moves in the axial direction to open the second pipe 1B.

On the other hand, when the inside of the second pipe 1B is sucked and a pressure difference (for example, Vac1) is generated between the second pipe 8B and the third pipe 1C, the valve 13C moves in the axial direction. It is set to a value that moves to open the third pipe 1C. With such a setting, the same operation as in the second embodiment can be achieved without using an electrical configuration.
Thereby, the configuration can be simplified.

FIG. 7 shows a substrate holding surface PH2 of the suction device PH according to the third embodiment. The arrangement of the porous region is different from the embodiment of FIG.
More specifically, a rectangular area A1 is arranged in the center of the substrate holding surface PH2, a frame-shaped area B1 is arranged around the area A1, and the frame-shaped areas C1, D1, and E1 are similarly arranged. I have. The two regions F1 on the elongated rectangle are arranged so as to sandwich the region E1. Each area is connected to the vacuum pump 2 (FIG. 4) by a separate pipe.

In the same manner as in the first embodiment, the air pressure in each pipe is sequentially reduced, and areas A1, B1, C1, D1,
The substrates are attracted radially from the center in the order of E1 and F1. Therefore, similarly to the first embodiment,
The substrate can be suction-held on the substrate holding surface without forming an air pocket.

FIG. 8 shows a substrate holding surface PH3 of the suction device PH according to the fourth embodiment. The arrangement of the porous region is different from the embodiment of FIG.
More specifically, a rectangular area A2 is disposed at the center of the substrate holding surface PH3, a pair of U-shaped areas B2 are disposed around the area A2, and a U-shaped area C2 is further disposed therearound. The pair is arranged facing each other.

As in the first embodiment, the air pressure in each pipe is sequentially reduced, and the substrates are adsorbed radially from the center in the order of the areas A2, B2 and C2. Therefore, as in the first embodiment, the substrate can be suction-held on the substrate holding surface without forming an air pocket.

In the embodiment, the suction unit is used as a detection unit for detecting the suction state between the substrate (the glass substrate P in the embodiment) and the suction unit (the substrate holding surface PH1 provided in the suction device in the embodiment). Although the air pressure sensor for directly detecting the air pressure in the pipe for supplying the negative pressure is employed, the present invention is not limited to this. For example, the following sensors may be employed. (1) A displacement sensor that detects a change in the distance between the substrate and the suction unit. For example, an optical sensor that irradiates a substrate with obliquely incident light flux and detects the position of reflected light on the substrate to detect displacement of the substrate can be used. In this case, a single optical sensor (for example, a one-dimensional or two-dimensional CCD or the like) detects a change in the position of the suction surface at a plurality of points in the area of the suction surface of the substrate on which the substrate is sucked by the suction unit. An adsorption state between the substrate and the adsorption section is detected based on the detection result. or,
It is also possible to provide a plurality of optical sensors (for example, SPD or the like), measure the position of the surface to be sucked at a plurality of points, and detect a change in the position of the surface to be sucked at each point. Note that this displacement sensor is provided on the gantry 12 of the exposure apparatus main body in this embodiment.
3 or a rigid body fixed to the frame 123. (2) A pressure-sensitive sensor that detects the degree of contact between the substrate and the suction section. For example, a pressure-sensitive sensor that detects the degree of contact is provided on the substrate holding surface PH1, and the area, pressure, and the like of each suction portion of the substrate holding surface PH1 that are in contact with the substrate are detected, and based on the detection result, The state of suction between the substrate and the suction section is detected. In addition, this pressure-sensitive sensor can be configured such that even if a single pressure-sensitive sensor having a two-dimensional spread is separately provided in the first suction portion and the second suction portion, the first suction portion and the second suction portion can be provided separately. A single pressure-sensitive sensor having a two-dimensional spread may be provided over both of the suction unit. Further, a plurality of pressure-sensitive sensors discretely arranged in each of the first suction unit and the second suction unit may be provided for detection.

[0048]

As described above, according to the substrate suction apparatus of the present invention, the control unit controls the suction operation of the second suction unit according to the detection result of the suction state of the first suction unit. Therefore, the substrate can be suctioned for each part at an optimal timing, and the substrate can be surely suction-held without forming an air pocket between the substrate and the substrate holding surface.

According to the substrate sucking method of the present invention, the substrate is sucked by the second sucking section in accordance with the sucking state between the first sucking section and the substrate. The suction can be performed, and the suction and holding of the substrate can be reliably performed without forming an air pocket between the substrate and the substrate holding surface.

[Brief description of the drawings]

FIG. 1 is a schematic view of a liquid crystal manufacturing stepper according to the present invention.

FIG. 2 is a perspective view showing the suction device PH according to the embodiment of the present invention and a stage supporting the same.

FIG. 3 is a diagram schematically illustrating a substrate holding surface of the suction device PH.

FIG. 4 is a configuration diagram schematically showing an adsorption device PH according to the present embodiment.

FIG. 5 is a graph showing the degree of decrease in the atmospheric pressure in the pipe with respect to time when the vacuum pump 2 operates.

FIG. 6 is a configuration diagram schematically showing an adsorption device PH according to a second embodiment.

FIG. 7 shows a substrate holding surface of a suction device PH according to a third embodiment.

FIG. 8 shows a substrate holding surface of a suction device PH according to a fourth embodiment.

FIG. 9 is a cross-sectional view showing a state where the glass substrate P is sucked on the substrate holding surface of the suction device PH.

[Explanation of symbols]

 1A, 1B, 1C Piping 2 Vacuum pump 3A, 3B, 13A, 13B Valve 4B, 4C Actuator 5 Negative pressure station 6A, 6B Pressure sensor 7 … CPU 8B, 8C… Spring P… Substrate PH… Suction device

Claims (6)

[Claims] A first suction unit that suctions and holds the substrate; a second suction unit that suctions and holds the substrate at a position different from the first suction unit; and at least the first suction unit and the second suction unit. A detection unit that detects a suction state with the substrate; and a control unit that controls a suction operation of the second suction unit according to a detection result of the suction state of the first suction unit. Substrate suction device. 2. The apparatus according to claim 1, wherein the first suction unit has a first vacuum path for vacuum-sucking the substrate, the second suction unit has a second vacuum path for vacuum-sucking the substrate, 2. A vacuum control unit for controlling said first vacuum path and said second vacuum path when sucking a substrate and at least sucking said substrate in said first vacuum path. The substrate suction device according to any one of the preceding claims. 3. The detecting section is disposed in the first vacuum path so as to measure an air pressure in the first vacuum path, and the first suction is performed based on the air pressure in the first vacuum path. 3. The substrate suction device according to claim 2, wherein a suction state between the unit and the substrate is detected. 4. The device according to claim 1, wherein the first suction unit sucks a substantially central portion of the substrate, and the second suction unit suctions a peripheral portion of the first suction unit. 4. The substrate suction device according to 2 or 3. 5. A substrate suction method in which a substrate is sucked by a first suction unit that sucks and holds a substrate, and a second suction unit that is adjacent to the first suction unit and sucks the substrate. A substrate suction method, wherein the substrate is sucked by the first suction unit, and the substrate is sucked by the second suction unit according to a suction state between the first suction unit and the substrate. . 6. The device according to claim 1, wherein the first suction unit sucks a central portion of the substrate, and the second suction unit suctions a peripheral portion of the substrate sucked by the first suction unit. The substrate suction method according to claim 5, wherein