JP3729425B2 - Stage device, substrate delivery method, and semiconductor manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate delivery technique in a stage apparatus used in a semiconductor manufacturing apparatus such as an exposure apparatus .
[0002]
[Prior art]
In lithography processes in the manufacture of semiconductor integrated circuits, step-and-repeat (including step-and-scan) reduction projection exposure apparatuses, so-called steppers, play a central role. In this stepper, it is necessary to improve the performance of the wafer stage year by year in response to the reduced line width of the circuit formed in about a submicron, and the demand for satisfying both high speed and high accuracy is increasing. A simple structure and a weight as small as possible are important for high-speed and high-accuracy positioning. For example, according to Japanese Patent Laid-Open No. 7-111238, it is possible to realize a lightweight wafer stage having a long stroke in the Z (vertical) direction.
[0003]
In a so-called alignment process for aligning the pattern formed on the wafer, the wafer that is roughly aligned in the θ direction (rotating direction about the Z axis) based on the outer shape is transferred to the wafer chuck, After the θ position deviation is measured by the alignment microscope and the θ sub-alignment is performed, further precise position measurement is performed. At this time, since it is difficult to provide a notch in the wafer chuck that holds the back surface of the wafer uniformly, in order to transfer the wafer to the wafer chuck, the wafer is once placed on the temporary support portion and then placed on the wafer chuck. Methods are starting to be used. For the temporary support portion, for example, three pins having a negative pressure suction hole provided on the temporary support surface on which the wafer is placed are used.
[0004]
Further, in order to perform θ sub-position alignment, the temporary support portion has a θ drive mechanism. Actually, the measurement of the θ positional deviation and the θ sub-alignment are as follows. When measuring the θ position deviation of the wafer, since it is necessary to move the wafer surface up and down within the depth of focus of the alignment microscope, the θ position deviation is measured with the wafer placed on the chuck. Next, with the wafer placed on the temporary support portion, θ sub-alignment is performed based on the θ position deviation measurement result. This eliminates the need for a mechanism in the vertical direction of the temporary support portion, thereby simplifying and reducing the weight of the mechanism.
[0005]
[Problems to be solved by the invention]
At this time, a problem is a positional deviation that occurs during delivery. In order to minimize the displacement, it is desirable to overlap the negative pressure adsorption of the temporary support portion and the negative pressure adsorption of the wafer chuck at the time of delivery. At that time, in order to reduce the stress applied to the wafer, a method of paying attention to the operation amount when the chuck is driven up and down has already been devised (Japanese Patent Application No. 7-51118). As a result, the positional deviation of the wafer is reduced when the temporary support surface of the temporary support portion and the chucking surface of the chuck are at the same height.
[0006]
However, when the chuck is lowered at a high speed from the same height, a large stress is applied to the wafer. This is because when the chuck is pulled away from the wafer at high speed, air does not sufficiently flow in from the negative pressure suction holes formed around the chuck and on the suction surface. Because it becomes pressure. This negative pressure causes stress on the wafer, causing unpredictable deformation such as distortion and warping. If this stress is larger than the allowable amount, the wafer will be displaced even though it is supported by the temporary support portion.
[0007]
The present invention has been made in consideration of the above points, and an object of the present invention is to provide a highly accurate substrate delivery technique that enables delivery with less stress to a substrate such as a wafer.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a stage apparatus of the present invention includes a temporary support portion having a temporary support surface for temporarily supporting a substrate,
A chuck having a suction surface for sucking and holding the substrate;
A stage that supports the chuck movably in a direction intersecting the temporary support surface;
Driving means for moving the stage along the moving direction;
First control means for stopping the chucking and holding operation of the substrate by the chuck, on condition that the drive current value of the drive means exceeds a predetermined value;
A second control unit for controlling the driving unit, wherein the first control unit stops the chucking and holding of the substrate by the chuck, and reduces the moving speed of the stage by the driving unit; And a second control means for controlling the driving means.
Furthermore, the substrate delivery method of the present invention includes a temporary support portion having a temporary support surface for temporarily supporting a substrate, a chuck having a suction surface for sucking and holding the substrate, and the chuck in a direction intersecting the temporary support surface. In a stage apparatus having a stage that is movably supported and a driving unit that moves the stage along the movement direction, the substrate delivery method for delivering the substrate from the chuck to the temporary support unit,
A first stage of stopping the chucking and holding operation of the substrate by the chuck, on condition that the driving current value of the driving means exceeds a predetermined value;
A second stage of controlling the driving means so that the moving speed of the stage by the driving means is reduced after the chucking and holding of the substrate by the chuck is stopped by the first stage. To do.
[0009]
In order to achieve the above object, a semiconductor manufacturing apparatus according to the present invention includes the stage apparatus .
[0010]
[Action]
According to the present invention, when the chuck for sucking the substrate and the stage on which the chuck is mounted descends from a state where the temporary support surface of the temporary support portion and the suction surface of the chuck are at the same height, The operation amount for lowering the stage is limited so as not to exceed a predetermined value, so that air sufficiently flows from the negative pressure suction holes formed around the chuck and the suction surface. For this reason, the negative pressure exceeding the allowable amount is instantaneously generated between the back surface of the substrate and the chucking surface of the chuck, thereby preventing the substrate from being subjected to stress exceeding the allowable amount. Therefore, the alignment accuracy can be improved.
[0011]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a substrate transfer device portion of a semiconductor manufacturing apparatus (stepper) according to an embodiment of the present invention. In this figure, W is a substrate such as a semiconductor wafer to be aligned (hereinafter referred to as a wafer), WC is a wafer chuck having a suction surface WCS for holding the wafer W in a flat state, and WH is a wafer W. Is temporarily aligned with the outer shape and then placed on the temporary support portion TC. The temporary support portion TC has a temporary support surface TCS. By temporarily supporting the wafer W, the distance between the wafer chuck WC and the wafer W can be increased. At least the thickness of the wafer hand WH is secured.
[0012]
WF is a wafer feeder that drives the wafer hand WH to position the outer shape of the wafer W at a desired position, OA is a microscope that observes alignment marks on the wafer W and measures the positional deviation, and XY is a horizontal (XY) direction. An XY stage that performs two-dimensional movement, Z fixes the wafer chuck WC, and a top plate that becomes a Z stage movable in the vertical (Z) direction with respect to the XY stage XY, ZM is on the XY stage XY The linear motor ZS is installed on the XY stage XY and serves as a measuring unit for measuring the vertical displacement of the top plate Z. The linear motor ZS is a driving unit for moving the top plate Z in the vertical (Z) direction. It is a displacement sensor.
[0013]
MD is connected to the motor ZM and a motor driver (driving device) for controlling the driving current (i) to the motor ZM, DF is a target value (c) output from the control device C and a current value output from the displacement sensor ZS The difference unit MC for obtaining the deviation (e) of the value (y) is connected to the motor driver MD, and is a phase compensation device that converts the deviation (e) calculated by the difference unit DF into the manipulated variable (I). This constitutes the position servo means. The motor driver MD drives the motor ZM based on this operation amount (I).
[0014]
M is a mirror that is installed on the top plate Z and serves as a measurement reference for the displacement of the XY stage XY in the XY direction. This mirror M includes a laser interference measuring machine (not shown) in the XY direction of the XY stage XY. Laser light is irradiated to measure the displacement. QM is a θ motor that is installed on the XY stage XY and rotates the temporary support portion TC in the θ direction on the XY stage XY.
[0015]
PST is connected to the temporary support portion TC via a pipe and a temporary support portion pressure sensor for measuring the suction pressure at the temporary support portion TC. PSC is connected to the wafer chuck WC via a pipe to measure the suction pressure at the wafer chuck WC. A wafer chuck pressure sensor, SVT, is arranged in a pipe connecting the temporary support part TC and the negative pressure source VS, and a switching valve SVC for switching the pressure of the temporary support part TC between atmospheric pressure and negative pressure (suction pressure) The switching valve is arranged in a pipe connecting the wafer chuck WC and the negative pressure source VS, and switches the pressure of the wafer chuck WC between atmospheric pressure and negative pressure (suction pressure).
[0016]
The control device C described above generates the suction pressure of the temporary support portion TC (output of the temporary support portion pressure sensor PST), the suction pressure of the wafer chuck WC (output of the wafer chuck pressure sensor PSC), and the motor drive current (i). At the same time, it receives the displacement sensor target value (c) and the command output to the temporary support section switching valve SVT and the wafer chuck switching valve SVC.
[0017]
A deviation (e) is obtained from the measured value (y) from the displacement sensor ZS and the target value (c) generated by the control device C by the differentiator DF. The phase compensator MC converts the deviation (e) into an operation amount (I) to the motor ZM that gives the driving device MD. With these configurations, the top plate Z is servoed to a desired position in the vertical (Z) direction.
[0018]
The control device C serving as the control means first sets the target value (c) so that the suction surface WCS of the wafer chuck WC is sufficiently below the temporary support surface TCS of the temporary support portion TC. Next, the wafer W roughly positioned according to the outer shape by the wafer feeder WF is placed on the wafer hand WH and moved onto the temporary support portion TC. The control device C opens the temporary support section switching valve SVT to the negative pressure side and waits for the wafer W to be placed on the temporary support section TC. The wafer hand WH descends in the Z direction at a sufficiently low speed so as not to cause a positional shift. Eventually, the back surface of the wafer W reaches a height equal to the temporary support surface TCS of the temporary support portion TC, and the wafer W is supported by the temporary support portion TC. After the front surface of the wafer hand WH is lowered to a position away from the back surface of the wafer W, the wafer hand WH is returned along the XY plane to a position where it does not interfere with the wafer chuck WC. At the same time, the control device C moves the XY stage XY along the XY plane to a position where the wafer chuck WC and the wafer hand WH do not interfere with each other.
[0019]
Next, the control device C slowly raises the target value (c) corresponding to the measurement value (y) of the displacement sensor ZS, thereby bringing the suction surface WCS of the wafer chuck WC closer to the back surface of the wafer W. Then, the wafer chuck switching valve SVC is switched to the negative pressure side. The top plate Z rises in the Z direction until the suction surface WCS of the wafer chuck WC is above the back surface of the wafer W supported by the temporary support portion TC, and the measured value of the wafer chuck pressure sensor PSC reaches the desired pressure. After reaching, the control device C opens the temporary support portion switching valve SVT to the atmospheric pressure side.
[0020]
As a result, the wafer W is peeled off from the temporary support portion TC by the wafer chuck WC and transferred to the wafer chuck WC. During this time, the wafer W is always sucked and held by either the wafer chuck WC or the temporary support portion TC, so that there is little deviation occurring when the wafer is changed.
[0021]
The control device C sets a target value (c) corresponding to the measured value (y) of the displacement sensor ZS so that the surface of the wafer W attracted by negative pressure on the wafer chuck WC is within the depth of focus of the microscope OA. Then, after the surface of the wafer W is within the depth of focus of the microscope OA, the control device C measures the positional deviation of the two alignment marks on the wafer W through the microscope OA, and the positional deviation of the wafer W in the XYθ direction. Ask for.
[0022]
Next, the control device C monitors the current value (i), and if the change exceeds a certain range, the control device C immediately waits to open the wafer chuck switching valve SVC to the atmospheric pressure side. Note that the current value (i) from the motor driver MD to the motor ZM is almost constant if the change of the target value (c) corresponding to the measured value of the displacement sensor ZS is sufficiently slow.
[0023]
Thereafter, the control device C opens the temporary support portion switching valve SVT to the negative pressure side, and slowly lowers the target value (c) of the displacement sensor ZS. When the back surface of the wafer W comes into contact with the temporary support surface TCS of the temporary support portion TC, a weak force acts upward on the back surface of the wafer W from the temporary support portion TC. Then, the deviation (e) between the measured value (y) of the displacement sensor ZS and the target value (c) becomes large, the operation amount (I) of the phase compensation device MC, and the motor current value (i) from the motor driver MD. Changes in a direction to reduce the deviation (e). At this time, the temporary support surface TCS of the temporary support portion TC and the suction surface WCS of the wafer chuck WC are at the same height. In this state, the negative pressure suction of the temporary support portion and the negative pressure suction of the wafer chuck overlap. Then, the control device C opens the wafer chuck switching valve SVC to the atmospheric pressure side. In the above, the positional deviation of the wafer W when the temporary support surface TCS of the temporary support portion TC and the suction surface WCS of the wafer chuck WC are the same height is small.
[0024]
Next, after confirming that the suction surface WCS of the wafer chuck WC has become sufficiently atmospheric pressure, the target value (c) of the displacement sensor ZS is further slowly lowered. At this time, if the descending speed is high, air does not sufficiently flow in from the negative pressure suction holes formed around the wafer chuck WC and the suction surface WCS, so there is a moment between the wafer W back surface and the wafer chuck WC suction surface WCS. Negative pressure (hereinafter referred to as dynamic negative pressure). The dynamic negative pressure causes stress on the wafer W, causing unpredictable deformation such as distortion and warpage. As described above, when the stress is larger than the allowable amount, the wafer W is displaced even though the wafer W is sucked and supported by the temporary support portion TC.
[0025]
Further, the dynamic negative pressure works upward with respect to the top plate Z which is going to descend at a constant speed, and becomes a load on the motor ZM. Therefore, the magnitude of the dynamic negative pressure is observed by the operation amount (I) and the motor current value (i). Therefore, the top plate is lowered so that the operation amount does not exceed a predetermined value. As a result, the stress on the wafer W due to the dynamic negative pressure is suppressed to an allowable amount or less, and the positional deviation when the wafer chuck WC is lowered is reduced.
[0026]
The control device C executes the θ sub-positioning by rotating the θ motor QM for the positional deviation of the wafer W in the θ direction measured by the microscope OA. Next, the temporary support portion TC is switched to the wafer chuck WC. Finally, projection optics for projecting and exposing a pattern for manufacturing a semiconductor integrated circuit on a reticle on the reticle with the XY stage XY while adjusting the XY direction displacement of the wafer W measured with the microscope OA by moving the XY stage XY. The system is moved to a pattern projection position of a system (not shown), and pattern exposure onto the wafer W is executed in a step-and-repeat manner.
[0027]
As described above, the stepper having a simple θ alignment mechanism is realized that has a high-accuracy wafer W transfer function without giving stress to the wafer W.
[0028]
In the above embodiment, in order to prevent the dynamic negative pressure from exceeding the allowable amount, the wafer chuck WC is lowered so that the operation amount does not exceed the predetermined value, but the lowering speed is set to the predetermined value. The following may be set.
[0029]
In addition, a servo valve may be disposed in a pipe connected to a negative pressure suction hole formed on the suction surface WCS of the wafer chuck WC, and a pressure sensor may be provided on the suction surface WCS to control the pressure of the dynamic negative pressure. By realizing high-speed and high-precision pressure control, the wafer chuck can be lowered at high speed.
[0030]
Further, the phase compensator MC and the difference unit DF do not need to be realized by hardware, and may be realized by software such as a numerical arithmetic processor (DSP) including the control device C.
[0031]
【The invention's effect】
As described above, according to the present invention allows for less stress transfer to the board, it is possible to provide a high accuracy of the substrate transfer technology.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a substrate transfer apparatus according to the present invention.
[Explanation of symbols]
W: Wafer, WC: Wafer chuck, WCS: Adsorption surface, TC: Temporary support portion, TCS: Temporary support surface, WF: Wafer feeder, OA: Microscope, XY: XY stage, Z: Top plate, ZM: Motor, ZS : Displacement sensor, MD: Motor driver, DF: Differencer, MC: Phase compensator, M: Mirror, QM: θ motor, PST: Temporary support part pressure sensor, PSC: Wafer chuck pressure sensor, SVT: Temporary support part switching Valve, SVC: Wafer chuck switching valve, C: Control device.

Claims (9)

A temporary support portion having a temporary support surface for temporarily supporting the substrate;
A chuck having a suction surface for sucking and holding the substrate;
A stage that supports the chuck so as to be movable in a direction intersecting the temporary support surface;
Driving means for moving the stage along the moving direction;
First control means for stopping the chucking and holding operation of the substrate by the chuck, on condition that the driving current value of the driving means exceeds a predetermined value;
A second control unit for controlling the driving unit, wherein the first control unit stops the chucking and holding of the substrate by the chuck, and reduces the moving speed of the stage by the driving unit; And a second control means for controlling the drive means. The second control unit controls the operation amount related to the driving unit to be less than a predetermined value after the first control unit stops the suction and holding of the substrate by the chuck. Item 2. The stage device according to Item 1. 2. The control unit according to claim 1 , wherein the second control unit controls the moving speed to be a predetermined value or less after the first control unit stops the chucking and holding of the substrate by the chuck. The stage apparatus as described. 2. The apparatus according to claim 1 , further comprising third control means for controlling an air pressure between the suction surface and the substrate after the suction control of the substrate by the chuck is stopped by the first control means. 4. The stage apparatus according to any one of 3.   A semiconductor manufacturing apparatus comprising the stage apparatus according to claim 1. A temporary support portion having a temporary support surface for temporarily supporting a substrate; a chuck having a suction surface for sucking and holding the substrate; a stage for supporting the chuck movably in a direction intersecting the temporary support surface; and the stage In a stage apparatus having a driving means for moving the substrate along the moving direction, the substrate transferring method for transferring the substrate from the chuck to the temporary support portion,
A first stage of stopping the chucking and holding operation of the substrate by the chuck, on condition that the driving current value of the driving means exceeds a predetermined value;
And a second step of controlling the driving unit so that the moving speed of the stage by the driving unit is reduced after the chucking and holding of the substrate by the chuck is stopped by the first step. Substrate delivery method. 8. In the second step, after the suction holding of the substrate by the chuck is stopped in the first step , control is performed so that an operation amount related to the driving unit becomes less than a predetermined value. The board delivery method described in 1. 8. The control according to claim 7, wherein, in the second stage, after the suction holding of the substrate by the chuck is stopped in the first stage , the moving speed is controlled to be a predetermined value or less. Board delivery method. After suction holding of the substrate by the chuck is stopped by the first stage, according to claim 7-8, characterized in that it comprises a third step of controlling the pressure between the substrate and the suction surface The substrate delivery method according to any one of the above.

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