JP2632416B2 - Exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus in which the positioning mechanism of a wafer stage is improved to facilitate replacement of a mask or a wafer.

2. Description of the Related Art As a conventional exposure apparatus, as described in, for example, JP-A-62-108523, a step-and-repeat type exposure apparatus that projects a circuit pattern on a mask onto a wafer through a reduction optical system is mainly used. Met. Since such an exposure apparatus has a high degree of freedom in setting the position interval between the mask and the wafer, the spatial clearance required when loading the replacement mask or the wafer, particularly in the direction perpendicular to the mask and the wafer surface. Providing clearance was a technically overcome task.

However, in recent years, as circuit patterns have been miniaturized, the ultraviolet region light conventionally used as exposure light has been forced to transition to a shorter wavelength region from the limit of resolution viewed from the wavelength side. This is the situation. Therefore, recently, one of the new light sources for circuit pattern transfer
One example is soft X-ray light from a synchrotron, but the technology for obtaining an arbitrary light beam using light in this band using an optical system such as a mirror or a lens is still far from practical use. Therefore, a proximity exposure method in which a mask and a wafer are brought close to each other to obtain an exposure pattern of the same magnification has become mainstream at present.

[Problems to be Solved by the Invention] However, in this method, there is a problem in attaching / detaching a wafer before and after exposure and in attaching / detaching a mask when exchanging a mask. That is, since the clearance between the mask and the wafer is poor, it is difficult to perform these operations at a position where exposure can be actually performed. Therefore, as a method for overcoming this, the present inventors have proposed a method in which the mask and the wafer are released from the position where the wafer stage is exposed for exposure in a direction parallel to the wafer surface until the mask and the wafer no longer face each other. We are studying a method for desorption. However, in this method, when the position of the entire stroke of the wafer stage is to be measured by a laser interferometer, a large mirror for reflecting the laser optical axis mounted on the wafer stage is required, so that it is difficult to process the mirror. Problem.

Means for Solving the Problems To achieve the above object, according to the present invention, a wafer stage for holding a wafer, a stage position measuring means for measuring the position of the wafer stage using a laser interferometer, and a stage position measuring means Stage drive control means for controlling the drive of the wafer stage based on the output of the mask, and alignment measuring means for optically detecting the positional shift between the mask and the wafer. In an exposure apparatus for aligning a wafer with respect to a mask by control means and exposing and transferring the pattern of the mask onto the wafer, a light source whose relative positional relationship changes in response to movement of the wafer stage, and light emitted by the light source The light receiving means capable of detecting the axis position and the stage position measuring means Means for detecting the position of the wafer stage by the light source and the light receiving means when the measurement is started and when the measurement is returned.

The light source is fixed on the same rigid body as the housing of the apparatus, and the light receiving means has a light receiving element fixed on the same rigid body as a reflecting mirror for reflecting laser light of a laser interferometer provided on the wafer stage. .

The light receiving means is also included in the alignment measuring means, and also receives light emitted by the alignment measuring means.

[Operation] In this configuration, the size of the mirror fixed on the wafer stage for reflecting light from the laser interferometer in the stage position measuring means usually has only a stroke used for wafer exposure, When the wafer stage is retracted from the position facing the mask (mask position) for the attachment / detachment of the mask, the stage position measurement by the laser interferometer is interrupted, but the stage is returned to the mask position after the attachment / detachment of the wafer or the mask is completed. Later, a light-emitting device (hereinafter, referred to as LD (Laser Diod
e)) by receiving light beams emitted from a light source such as a PSD (Photo Sensitive Device) to obtain data to be used to reproduce the previous state of the wafer stage. The reproduction of the previous state is performed. Therefore, even after the wafer or mask has been detached, exposure is performed under the same wafer stage position control as before or after holding the wafer stage position before the detachment.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial view of an exposure apparatus according to one embodiment of the present invention. In the drawing, reference numerals 1 and 2 denote a mask and a wafer held in parallel with a gap of 10 to 50 μm, 3 denotes a wafer stage, 5 denotes a mirror fixed to the wafer stage 3, 10
8 is a wafer chuck mounted on the mirror 5, and 6 is a PSD mounted on the mirror 5. The wafer stage 3 moves the position of the wafer chuck 108 along six axes (X, Y, Z, ω _x , ω _y , ω _z ).
It has the function of controlling in the direction. 106 and 107 are electric cylinders for coarse Y-axis and coarse X-axis, respectively (not shown)
Is a guide. As will be described later with reference to FIG. 2, a fine movement stage by a piezo actuator is mounted on the coarse movement X, Y axis stage guided by this. 4
Reference numeral denotes a measurement optical axis at the time of position measurement by a laser interferometer (not shown). The mirror 5 reflects the measurement optical axis of the laser interferometer, and its mirror surface 5a corresponds to a mirror for measuring the X axis and the ω _y axis. On the other hand, the mirror surface 5b that reflects the parallel measuring optical axis 4 in the Y-axis has a purpose to measure the Y-axis and omega _x-axis and omega _z-axis. Reference numeral 7 denotes an LD which emits a light beam in a direction perpendicular to the mask plane. For the wafer stage 3, before starting the position measurement by the interferometer, the PSD 6 is positioned at the position facing the LD 7 to perform the origin search correction. 105 is a mask chuck and mask omega _z direction rotation stage. 101
Is a pre-alignment measurement unit, and when loading the wafer 2, the wafer stage 3 holds the wafer chuck.
108 is positioned at a position facing the pre-alignment measurement unit 101. 102a and 102b are fine alignment measuring optical systems (pickups) mounted on the pickup stages 104a and 104b, respectively, and can be arbitrarily moved in the XY plane by the actuators 103a and 103b. The position of the optical axis dropped from the measurement optical systems 102a and 102b can be detected by the PSD 6, and a correction value of the control position of the pickup stage viewed from the stage 3 can be obtained based on this position. Reference numeral 8 denotes a Y-axis coarse movement stage guide 106, LD7, mask chuck
105, the pickup stages 104a and 104b, and the pre-alignment unit 101 are all installed on this housing. Reference numeral 9 denotes a linear scale, and X
When the stage 3 is located at a position where measurement in the axial direction cannot be performed, for example, at the pre-alignment position (pre-AA position in the figure), the wafer stage 3 returns to the position facing the mask 1 (mask position) and measures the position by the laser interferometer. The coarse position is measured until is returned. Reference numeral 10 denotes a reference mark fixed on the mirror 5 of the wafer stage 3 and used when performing mask alignment.

With the configuration described above, the coordinates of the wafer stage 3 and the coordinates of the pickup stages 104a and 104b can be managed under a single coordinate system having the PSD 6 as a medium and the LD 7 on the housing 8 as a fixed point. .

FIG. 2 is a conceptual diagram of the wafer stage 3. In the figure, reference numeral 201 denotes a ω _z coarse movement stage, which is driven by an inch worm piezo actuator and used to rotate the wafer in the ω _z direction during pre-alignment, and in other cases, the piezos at both ends of the inch worm are clamped to the guide. It does not move. Reference numeral 202 denotes a tilt stage, which has a structure supported by three piezos, and moves a minute displacement in the Z, ω _x , and ω _y directions. Numerals 203 to 205 denote minute displacement stages using piezo actuators in the ω _z , X and Y directions, respectively.
206 and 207 are X-direction and Y-direction coarse movement stages driven by the above-described electric cylinder.

Next, an electrical hardware configuration for controlling the operation of this device will be described below.

As shown in FIG. 3, all functions of the exposure apparatus of this embodiment are managed under the main processor unit 301 located at the top. Main processor unit 30
1 is connected to each hardware unit via a communication path 302 and a communication I / F 303. In FIG. 3, hardware units including an alignment function, a stage control function, and a pickup stage control function are extracted therefrom. Is shown. Here, these hardware units are referred to as main body control blocks.

The main body control block includes a pickup stage control unit 305 that controls the positioning of the four pickups 102a, 102b, etc. in two axial directions (α axis, β axis) with respect to the alignment system, and displaces and parallelizes the wafer 2 and the mask 1 on a plane. AA.AF control units 309a to 309d for performing wafer X and Y
Coarse movement stages 206 and 207 and wafer fine movement stages 203 to 20
A stage control unit 313 for performing positioning control of 5 is connected. The main body control unit 304 is a control section that stores a program for performing a predetermined sequence, and operates each of the control units according to the sequence. As described above, the main body control unit 304 communicates with the upper main processor unit 301 and the communication path 30.
2. It is connected via the communication I / F 303 and exchanges data with them.

Furthermore, among the above control units, the fine AA.AF control unit 3
09a to 309d and the stage control unit 313 are communication I / Fs 306 and 308, respectively.
And exchanges data with the main unit control unit 304 through the communication paths 307 and 311 via the communication paths 310 and 312.

The main unit control unit 304
Each control unit connected to is equipped with a CPU inside, and all signal processing in hardware is completed in this. According to this configuration, each control unit can be operated independently and hierarchized.

FIG. 4 is a detailed block diagram of the stage control unit 313 shown in FIG. This unit is, as described above, a communication I / F 310, 312 and a communication path 311 with the main body control unit 304.
Exchange of information via. The wafer stage control unit 401 has a CPU (not shown) inside,
The drive amount of each actuator mounted inside the wafer stage is calculated with respect to the target position of the stage sent from the main body control unit 304. In addition, a PSD length measurement system control unit 409 that receives a signal output from the light receiving sensor (PSD) 6 on the wafer stage.
It also has a processing function to convert the data sent from the E-mail into appropriate position data. In FIG. 4, reference numeral 402 denotes a laser interference measurement length unit, which performs position measurement on five axes excluding the axis in the normal direction to the wafer surface, that is, the Z axis. Reference numeral 403 denotes a micro-displacement sensor control unit which measures the Z-axis displacement of the wafer stage by driving a micro-displacement sensor of the tilt stage mounted on the coarse movement stage and performing signal processing.

Reference numeral 404 denotes an X, Y coarse movement controller, which is X coarse movement (X _c ) Y
The electric cylinder for coarse movement (Y _c ) is controlled. 405 is a θ coarse controller, θ Sodojiku (ω _z coarse stage)
Is mounted on the X, Y drive axes (stages 204 to 207), the Z, ω _x , ω _y drive axes (stage 202) and the θ fine movement axis (stage 203), and moves the θ coarse movement axis. Is not reflected in the movement of the mirror 5 for reflecting the optical axis 4 from the interferometer. Therefore, in the present embodiment, the use of the inchworm actuator as the actuator for the θ coarse movement axis eliminates position fluctuation after the θ axis coarse adjustment. Reference numeral 406 denotes a tilt stage controller that controls the position of the tilt stage 202 mounted on the X and Y drive axes and the θ fine movement axis in accordance with a command from the wafer stage control unit 401. Reference numeral 407 denotes a fine movement stage controller that controls a small displacement actuator for the X and Y drive axes. Reference numeral 408 denotes a mask θ controller, which controls a mask θ fine movement stage (mask ω _z- direction rotation stage) 105 mounted on the mask stage.

FIG. 5 shows an operation sequence at the time of wafer replacement in this embodiment. Referring to FIG. 5, when the wafer exchange operation is started, first, in step 501, coarse movement X, the voltage applied to the electrodes of the piezo actuators responsible for the movement of the fine movement stages 204, 205 mounted on the Y axis is a predetermined constant. The movement of the fine movement stages 204 and 205 is fixed at a fixed value.
Next, in step 502, the wafer stage 3 is lowered to the pre-AA position (see FIG. 1). The Y can be measured by a laser interferometer in this position, the position of the omega _x and omega _z-axis direction, the position of the X-axis direction is performed by the linear scale 9 is a rough position measuring device. Regarding the Z and ω _y axes, the same value is maintained because the associated piezo actuator is fixed. Next, in step 503, the exposed wafer is collected, and in step 504, the unexposed wafer is sucked onto the wafer chuck. In step 505, the pre-alignment of the attracted wafer is performed by using the pre-alignment measurement optical system 101 and driving the coarse movement X, Y, and θ axes. Then, in step 506, the wafer stage 3 is raised to a position facing the mask 1, and in step 507, the PSD 6 on the wafer stage 3 is positioned at the light projection spot of the LD7. At this time, since the position measurement on the X-axis side of the laser interferometer of the wafer stage 3 has not yet returned, the coarse X-axis feed is performed using the linear scale 9. In step 508, the coordinate values held so far are corrected so that the projected beam spot of the LD 7 becomes exactly the origin of the X axis and the ω _y axis. From this point, the X axis and the ω _y axis of the laser interferometer are corrected. Return position measurement. In step 509, the piezo actuator of the fine movement stage is driven, and the exposure process is started.

FIG. 6 shows an operation sequence at the time of mask replacement. As shown in the figure, when the mask exchanging operation is started, first, in step 601, the piezo actuator of the fine movement stage of the wafer stage 3 is fixed at a constant value. Next, step 60
In step 2, the wafer stage 3 is retracted to the pre-AA position. In step 603, the old mask is collected, and in step 604, the new mask is set on the mask chuck 105. Then, in step 605, the wafer stage 3 is returned to the mask position,
In step 606, the wafer stage 3 is sent so that the PSD 6 is located below the light projection spot of the LD 7, and the origin is corrected in step 607. Further, in step 608, the piezo actuator of the fine movement stage is unlocked, and in step 608, the mask is aligned by aligning the alignment mark on the mask with the reference mark 10 on the stage. Align with the optical axis 4 of the interferometer and enter the exposure process.

[Effects of the Invention] As described above, according to the present invention, the absolute position of the wafer stage can be detected at the start of measurement of the wafer stage position by the laser interferometer and at the time of measurement return. In this case, the procedure for exchanging the wafer and the mask at the position where the wafer stage is retracted from the exposure position can be established, and the exchange of the wafer and the mask can be easily performed.

[Brief description of the drawings]

FIG. 1 is a partial view of an exposure apparatus according to an embodiment of the present invention, FIG. 2 is a conceptual view of a wafer stage used in the apparatus of FIG. 1, and FIG. 3 controls the apparatus of FIG. FIG. 4 is a detailed block diagram of a wafer stage control unit in FIG. 3, FIG. 5 is a flowchart showing a wafer exchange sequence in the apparatus of FIG. 1, and FIG. 3 is a flowchart showing a mask exchange sequence in the apparatus shown in FIG. 1: Mask, 2: Wafer, 3: Wafer stage, 4: Laser interferometer measurement optical axis, 5: Laser interferometer measurement optical axis reflection mirror, 6: PSD, 7: LD, 8: Housing, 9 : Linear scale.

Continued on the front page (72) Inventor Shunichi Uzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Nobutoshi Mizusawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Takuo Kariya 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-1-166522 (JP, A) JP-A-58-28748 (JP, A) JP-A-62-108523 (JP, A) JP-A-63-90702 (JP, A)

Claims (3)

(57) [Claims] 1. A wafer stage for holding a wafer, a stage position measuring means for measuring the position of the wafer stage using a laser interferometer, and a stage drive control means for driving and controlling the wafer stage based on an output of the stage position measuring means. And an alignment measuring means for optically detecting a positional shift between the mask and the wafer, wherein the mask is aligned with the mask by the stage position measuring means and the stage drive control means based on the output of the alignment measuring means. An exposure apparatus for exposing and transferring the pattern onto a wafer, a light source whose relative positional relationship changes in accordance with the movement of the wafer stage, a light receiving means capable of detecting an optical axis position of light emitted by the light source, and a stage position The light source and the light receiving means at the time of measurement start and measurement return by the measuring means Therefore the exposure apparatus characterized by comprising a means for detecting the position of the wafer stage. 2. The light source is fixed on the same rigid body as the housing of the apparatus, and the light receiving means is fixed on the same rigid body as a reflecting mirror for reflecting laser light of a laser interferometer provided on the wafer stage. The exposure apparatus according to claim 1, further comprising a light receiving element. 3. An exposure apparatus according to claim 1, wherein said light receiving means is also included in the alignment measuring means, and also receives light emitted from the alignment measuring means.