JP5395643B2 - Orthogonality measuring method, stage mechanism and transfer device - Google Patents

Description

The present invention relates to a method for measuring the degree of orthogonality between two mirrors , a stage mechanism, and a transfer apparatus .

  The scanning exposure apparatus exposes the substrate held by the substrate stage while scanning the stage movable in the XY directions in the XY directions. The position of the stage can be measured using a laser interferometer. The stage is equipped with a mirror to be measured by the laser interferometer (for example, an X mirror for measuring a position in the X direction and a Y mirror for measuring a position in the Y direction). The position of the stage is controlled while measuring the positions of the X mirror and the Y mirror with a laser interferometer. The X mirror and Y mirror must be at right angles to each other. The degree of right angle between two mirrors (X mirror, Y mirror) can be expressed as orthogonality. If the angle formed by the two mirrors is close to a right angle, it is expressed that the degree of orthogonality is high.

  If the angle formed by the X mirror and the Y mirror is deviated by θ with respect to the right angle, for example, when a plurality of shot areas are formed on one substrate, the shot areas are deviated from the normal positions. In the example shown in FIG. 1, the arrangement of shot areas is shifted from the lattice. Such a deviation can cause a problem in a subsequent process in the manufacture of a device such as a liquid crystal panel. However, in reality, since there are processing errors, assembly errors, and the like, it is difficult to make θ completely zero. In addition, the orthogonality between the two mirrors may fluctuate due to an impact caused by acceleration / deceleration of the stage, temperature change, operator error during maintenance, and the like.

  In order to correct the shot area arrangement error due to θ, there is a method of calculating θ through exposure, development, and pattern measurement of the shot area. By calculating the offset amount based on θ and adding the offset amount to the command value at the time of driving the stage, it is possible to reduce the shot area arrangement error. However, the method for calculating θ through exposure, development, and pattern measurement requires a long time for the processing.

  In Patent Document 1, a reflection surface having a known angle is formed with respect to a mirror for an interferometer, and the mirror orthogonality is calculated by driving the stage while measuring the reflection surface with another interferometer. A method is disclosed. In this method, there is a problem that a processing error of a reflection surface having a known angle directly affects a measurement error of the mirror orthogonality. In practice, it is very difficult to form the reflecting surface with high accuracy.

JP-A-9-162113

  The object of the present invention is to provide an advantageous method for measuring the degree of orthogonality between two mirrors quickly and with high accuracy.

  One aspect of the present invention relates to a measuring method for measuring the degree of orthogonality between the reflecting surface of the first mirror and the reflecting surface of the second mirror in an article having a first mirror and a second mirror. Adjusting the optical axis of the laser beam so that the laser beam is incident at a right angle to the reflecting surface of the second mirror, and the article in a direction parallel to the reflecting surface of the first mirror. A detection step of detecting a displacement amount of an optical axis of the laser beam reflected by a corner cube disposed on a reflection surface of the second mirror so that the laser beam is incident when moved by a distance; And a calculation step of calculating an amount by which an angle between the reflection surface of the first mirror and the reflection surface of the second mirror is deviated from a right angle based on the distance and the amount of displacement.

  The present invention provides an advantageous method for measuring the degree of orthogonality between two mirrors quickly and with high accuracy.

It is a figure which illustrates the influence which mirror orthogonality has on the arrangement of a shot field. It is a figure which illustrates the apparatus or article | item to which the measuring method of the measuring method of mirror orthogonality can be applied. It is a figure which illustrates a laser interferometer system. It is a figure explaining 1st Embodiment of this invention. It is a figure explaining 1st Embodiment of this invention. It is a figure explaining 1st Embodiment of this invention. It is a figure explaining 2nd Embodiment of this invention.

  A mirror orthogonality measuring method in the embodiment of the present invention will be described with reference to FIG. FIG. 2 shows an exposure apparatus as an example of an apparatus having a stage provided with two mirrors whose orthogonality is to be measured. Although a specific device will be described here, the present invention can be applied to various devices or articles having two mirrors whose orthogonality is to be measured.

  The exposure apparatus EX shown in FIG. 2 can be used to transfer a mask (original plate) pattern onto a substrate such as a glass substrate for manufacturing a display panel such as a liquid crystal panel. The exposure apparatus EX is configured as a scanning exposure apparatus. A mask stage mechanism 20 is disposed on the object plane side of the projection optical system 10, and a substrate stage mechanism 30 is disposed on the image plane side of the projection optical system 10.

  The substrate stage mechanism 30 includes a base 31, a Y stage 32 disposed on the base 31, and an X stage 33 disposed on the Y stage 32. Here, directions are expressed in accordance with an XYZ coordinate system in which a plane parallel to the plane of the substrate 36 is an XY plane, and a direction orthogonal to the XY plane is a Z direction. The Y stage 32 is a stage driven in the Y direction, and the X stage 33 is a stage driven in the X direction. The substrate stage mechanism 30 further includes a θZ stage 34 disposed on the X stage 33 and a table 35 disposed on the θZ stage 34. The table 35 has a chuck that holds the substrate 36. With the above configuration, the substrate 36 held by the table 35 can move in the X, Y, and Z directions, and can rotate in the XY plane (that is, can rotate around the Z axis).

  The mask stage mechanism 20 includes a base 21 and an XYθ stage 22 disposed on the base 21. The XYθ stage 22 has a chuck that holds the mask 23. With this configuration, the mask 23 held by the XYθ stage 22 can move in the X and Y directions and can rotate in the XY plane (that is, can rotate around the Z axis). Above the mask stage 20 mechanism, an observation optical system 40 for observing the mask 23 and the substrate 36 and an illumination optical system 41 for illuminating the mask 23 are arranged. The positions of the table 35 of the substrate stage mechanism 30 and the XYθ stage 22 of the mask stage mechanism 20 are measured by the laser interferometer system 50.

  The laser interferometer system 50 includes a laser head 51, laser interferometers 52 and 53, a mirror 54 attached to the table 35, and a mirror 55 attached to the XYθ stage 21. The position of the laser beam incident on the mirror 52 in the Z direction can coincide with the position of the image plane of the projection optical system 10 in the Z direction. The position of the laser light incident on the mirror 55 in the Z direction can coincide with the position of the object plane of the projection optical system 10 in the Z direction.

  Next, the laser interferometer system for the substrate stage mechanism 30 will be described in more detail with reference to FIG. A substrate 36 is held by the table 35. The table 35 is provided with an X mirror 541 for measuring the position of the table 35 in the X direction and a Y mirror 540 for measuring the position of the table 35 in the Y direction. Laser interferometer 52 includes an interferometer 521 that measures the position of table 35 in the X direction, and an interferometer 520 that measures the position of table 35 in the Y direction. Here, the table 35 or the substrate stage mechanism 30 can be considered as an article having a first mirror and a second mirror. The first mirror is, for example, an X mirror 541, and the second mirror is, for example, a Y mirror 540.

  A mirror orthogonality measuring method according to the first embodiment of the present invention will be described with reference to FIGS. This measurement method may include an adjustment step, an arrangement step, a detection step, and a calculation step. Here, it is assumed that the reflection surface of the Y mirror 540 has an angle of (90 + θ) degrees with respect to the reflection surface of the X mirror 541. Here, when θ is 0, the reflection surface of the Y mirror 540 is completely orthogonal to the reflection surface of the X mirror 541. Here, it is assumed that the attitude of the θZ stage 34 around the Z axis is maintained constant. This can be done, for example, by controlling the θZ stage 34 so as to keep θZ constant while monitoring the rotation amount θZ around the Z axis of the θZ stage 34 with a measurement system (not shown).

  First, an adjustment step is executed. In the adjustment step, the optical axis of the laser beam LB1 is adjusted so that the laser beam LB1 is incident at a right angle to the reflecting surface of the Y mirror 540 in a state where the rotation amount θZ of the θZ stage 34 is controlled to be constant. In this example, the laser beam LB1 is applied to the reflection surface of the Y mirror 540 via the half mirror M1. Laser light LB1 may be prepared by distributing laser light for laser interferometers used elsewhere, or a dedicated laser light source may be prepared. The irradiated laser beam LB1 is reflected by the Y mirror 540, then passes through the half mirror M1, is reflected by the mirror M2, and enters the optical position detection element PS1. As the optical position detection element PS1, for example, a sensor such as a CCD, CMOS, PSD (abbreviation of Position-Sensitive-Detector), QPD (abbreviation of Quadrant-Photodiode), that is, a position where light is incident is detected. Various sensors that can be used can be used. If the angle between the Y mirror 540 and the laser beam LB1 deviates from a right angle, an error occurs in the measurement result of the orthogonality between the X mirror 541 and the Y mirror 540. For this reason, the optical axis (direction) of the laser beam LB1 is adjusted so that the angle between the reflection surface of the Y mirror 540 and the laser beam LB1 becomes a right angle.

  With reference to FIG. 5, the procedure of an adjustment step for adjusting the optical axis (direction) of the laser beam LB1 so that the angle between the reflection surface of the Y mirror 540 and the laser beam LB1 is a right angle will be described. First, the mirrors M1 and M2 and the light detection element PS1 are arranged so that the laser beam LB1 reflected by the Y mirror 540 is detected by the light position detection element PS1.

  Next, the table 35 is moved in the Y direction by driving the Y stage 32 in the Y direction while keeping the rotation amount θZ of the θZ stage 34 constant. At this time, when the angle between the reflecting surface of the Y mirror 540 and the laser beam LB1 is deviated from a right angle, the position of the laser beam LB1 incident on the position detection element PS1 changes as the table 35 moves. . Therefore, the position adjustment of the mirror M1 and the laser beam LB1 is repeated until the position of the laser beam LB1 incident on the position detection element PS1 does not change as the table 35 moves. Adjusting the positions of the mirror M1 and the laser beam LB1 means adjusting the optical axis of the laser beam LB1. The adjustment accuracy at this time can be determined by the position detection resolution of the optical position detection element PS1 and the stroke length of the Y stage 32 in the Y direction.

  After the above adjustment step, the control system of the substrate stage mechanism 30 is stopped for safety. In the arranging step, as illustrated in FIG. 6, the corner cube CC1 is installed at the position where the laser beam LB1 on the reflecting surface of the Y mirror 540 is incident. The accuracy of installation of the corner cube CC1 does not affect the measurement accuracy of the mirror orthogonality.

  Thereafter, the following detection steps are performed. The control system of the substrate stage mechanism 30 is set to the operating state, and the rotation amount θZ of the θZ stage 34 is controlled to be constant. Then, the table 35 is moved to a position where the laser beam LB1 is reflected by the corner cube CC1 and the laser beam LB3 reflected by the corner cube CC1 enters the optical position detection element PS1. At this time, the incident position of the laser beam LB1 on the optical position detecting element PS1 (hereinafter referred to as a first incident position) is stored.

  Thereafter, the table 35 is moved by a known distance L in the Y direction (direction parallel to the reflection surface of the X mirror 541). At this time, when the angle of the reflecting surface of the Y mirror 540 with respect to the reflecting surface of the X mirror 541 is deviated from a right angle (when the Y axis and the laser beam LB1 are not parallel), the laser beam LB1 is incident on the corner cube CC1. The position is displaced. Thereby, the incident position of the reflected light LB3 with respect to the optical position detecting element PS1 is displaced (shifted) from the first incident position to the second incident position. The displacement amount ΔS at this time is geometrically expressed by equation (1). Here, detecting the amount of displacement of the incident position of the reflected light LB3 with respect to the light position detecting element PS1 means detecting the amount of displacement of the optical axis of the reflected light LB3.

ΔS = 2L × tan θ (1)
That is, θ is given by equation (2).

θ = tan ⁻¹ (ΔS / 2L) (2)
Following the detection step, a calculation step is performed. In the calculation step, θ, which is the amount by which the angle between the reflection surface of the X mirror 541 and the reflection surface of the Y mirror 542 deviates from a right angle, is calculated according to equation (2). At the time of device manufacture, that is, when the substrate 36 is exposed, an offset amount is calculated based on θ, and the offset is a command value related to the Y direction when the substrate stage mechanism 30 is operated (target position of the Y stage 32). Add to. Specifically, assuming that the positions in the X direction between the shot areas are X ₁ , X ₂ ,..., The offset amounts in the Y direction in the exposure of each shot area are X ₁ tan θ, X ₂ tan θ,.

  An actual Y mirror may have a local surface shape waviness component. Θ measured by this swell component may include an error. Therefore, measurement may be performed for a plurality of points on the Y mirror, and the results may be averaged to obtain θ.

  The above method is an example in the case where the reflecting surface of the Y mirror is not parallel to the X axis. However, even in the case where the reflecting surface of the X mirror is not parallel to the Y axis, θ is changed in the same manner except that the axis is switched. It can be measured.

  The mirror orthogonality measuring method according to the second embodiment of the present invention will be described below with reference to FIG. Matters not specifically mentioned here can follow the first embodiment. In the first embodiment, the corner cube is attached and detached when measuring θ, which is the amount by which the angle between the reflection surface of the X mirror and the reflection surface of the Y mirror is deviated from a right angle. In the second embodiment, a method of measuring θ without attaching / detaching the corner cube will be described.

  As illustrated in FIG. 7, the laser beam LB4 is incident on the half mirror M3. The laser beam LB4 is incident on the corner cube CC2 after being reflected by the half mirror M3. The corner cube CC2 has a polarization characteristic that transmits the first polarization component of the laser light and reflects the second polarization component. Of the laser beam LB4, the laser beam LB5, which is the first polarization component that can pass through the corner cube CC2, is reflected by the reflecting surface of the Y mirror 540. The laser beam LB5 reflected by the reflecting surface of the Y mirror 540 passes through the half mirror M3 and also passes through the polarization beam splitter M4. The laser beam LB5 that has passed through the polarization beam splitter M4 is reflected by the mirror M5 and enters the optical position detection element PS3. The optical position detection element PS3 detects the position where the laser beam LB5 is incident.

  On the other hand, the laser beam LB6, which is the second polarization component reflected by the corner cube CC2 in the laser beam LB4, passes through the half mirror M3, is reflected by the polarization beam splitter M4, and enters the optical position detection element PS2. The optical position detection element PS2 detects the position where the laser beam LB6 is incident. Note that the polarization direction of the laser beam LB4 is adjusted so that the laser beams LB6 and LB5 having a sufficient amount of light are incident on the optical position detection elements PS2 and PS3, respectively. In FIG. 7, the laser beam LB4 is deviated from the apex of the corner cube CC2, but it is not actually necessary to do this.

  In the adjustment step, in order to adjust the angle between the reflection surface of the Y mirror 540 and the laser beam LB6 to a right angle, a method similar to that of the first embodiment may be executed using the optical position detection element PS3. That is, the position adjustment of the mirror M3 and the laser beam LB4, that is, the optical axis adjustment of the laser beam LB4, is repeated until the position of the laser beam LB5 incident on the position detection element PS3 does not change as the table 35 moves in the Y direction. That's fine.

  After the angle between the reflecting surface of the Y mirror 540 and the LB 4 is adjusted to a right angle by the above adjustment step, the detection step and the calculation step are performed. In the detection step, the table 35 is moved by a distance L in the Y direction while measuring the laser beam LB6 reflected by the corner cube CC2 by the optical position detection element PS2, and the displacement amount ΔS is detected by the optical position detection element PS2. Then, in the calculation step, as in the first embodiment, based on the displacement amount ΔS, θ, which is the amount by which the angle between the reflection surface of the X mirror 541 and the reflection surface of the Y mirror 542 deviates from a right angle, is detected. can do.

  According to the second embodiment, once the corner cube is installed on the Y mirror, it is not necessary to attach or detach the corner cube thereafter.

  As described above, according to the first and second embodiments, since it is not necessary to perform exposure, development, and pattern measurement, the orthogonality can be evaluated quickly. Further, according to the first and second embodiments, a reflective surface (a reflective surface that directly affects the measurement error of the orthogonality) as in Patent Document 1 is not used. The corner cube installation accuracy in the first and second embodiments is advantageous for high-precision measurement because it does not affect the orthogonality measurement accuracy.

Claims (8)

A measurement method for measuring an orthogonality between a reflection surface of the first mirror and a reflection surface of the second mirror in an article having a first mirror and a second mirror,
An adjustment step of adjusting the optical axis of the laser beam so that the laser beam is incident at a right angle to the reflecting surface of the second mirror;
When the article is moved by a known distance in a direction parallel to the reflection surface of the first mirror, the laser beam is reflected by a corner cube disposed on the reflection surface of the second mirror so as to enter. A detection step of detecting a displacement amount of the optical axis of the laser beam;
A calculation step of calculating an amount by which an angle between the reflection surface of the first mirror and the reflection surface of the second mirror is deviated from a right angle based on the distance and the displacement amount;
A measurement method comprising: Before the detection step, the method further includes an arrangement step of arranging the corner cube at a position where the laser beam is incident on the reflection surface of the second mirror.
The measurement method according to claim 1, wherein: Performing the adjusting step, the detecting step and the calculating step with respect to a plurality of positions of a reflecting surface of the second mirror;
The measurement method further includes averaging the results obtained in the calculation step for each of the plurality of positions.
The measuring method according to claim 1, wherein Measurement for measuring the orthogonality between the reflective surface of the first mirror and the reflective surface of the second mirror in an article having a first mirror and a second mirror, and a corner cube disposed on the reflective surface of the second mirror A method,
The corner cube is configured to transmit the first polarization component of the laser light and reflect the second polarization component;
The measurement method is:
Using the first polarization component transmitted through the corner cube and reflected by the reflection surface of the second mirror so that the optical axis of the laser beam is perpendicular to the reflection surface of the second mirror, An adjustment step for adjusting the optical axis of the laser beam;
A detection step of detecting a displacement amount of the optical axis of the second polarization component reflected by the corner cube when the article is moved by a known distance in a direction parallel to a reflection surface of the first mirror;
A calculation step of calculating an amount by which an angle between the reflection surface of the first mirror and the reflection surface of the second mirror is deviated from a right angle based on the distance and the displacement amount;
A measurement method comprising: When the distance is L, the displacement amount is ΔS, and the amount that the angle between the reflection surface of the first mirror and the reflection surface of the second mirror is deviated from a right angle is θ,
In the calculating step,
θ = tan ⁻¹ (ΔS / 2L)
Θ is calculated based on
The measurement method according to any one of claims 1 to 4, wherein:   A stage mechanism comprising: a table having a first mirror and a second mirror; and a measuring means for measuring a degree of orthogonality between the reflecting surface of the first mirror and the reflecting surface of the second mirror,
  The measuring means includes
  Means for adjusting the optical axis of the laser beam so that the laser beam is incident at a right angle to the reflecting surface of the second mirror;
  When the table is moved by a known distance in a direction parallel to the reflection surface of the first mirror, the laser beam is reflected by a corner cube disposed on the reflection surface of the second mirror so as to enter. Means for detecting the amount of displacement of the optical axis of the laser beam;
  Means for calculating an amount by which an angle between the reflection surface of the first mirror and the reflection surface of the second mirror deviates from a right angle based on the distance and the displacement amount;
  A stage mechanism characterized by that.   A table having a first mirror and a second mirror, a corner cube disposed on the reflection surface of the second mirror, and a measurement for measuring the orthogonality between the reflection surface of the first mirror and the reflection surface of the second mirror A stage mechanism comprising means,
  The corner cube is configured to transmit the first polarization component of the laser light and reflect the second polarization component;
  The measuring means includes
  Using the first polarization component transmitted through the corner cube and reflected by the reflection surface of the second mirror so that the optical axis of the laser beam is perpendicular to the reflection surface of the second mirror, Means for adjusting the optical axis of the laser beam;
  When the table is moved by a known distance in a direction parallel to the reflection surface of the first mirror, the laser beam is reflected by a corner cube disposed on the reflection surface of the second mirror so as to enter. Means for detecting the amount of displacement of the optical axis of the laser beam;
  Means for calculating an amount by which an angle between the reflection surface of the first mirror and the reflection surface of the second mirror deviates from a right angle based on the distance and the displacement amount;
  A stage mechanism characterized by that.   A transfer device for transferring a pattern to a substrate,
  The stage mechanism according to claim 6 or 7 configured to hold and move the substrate,
  A transfer device characterized by that.

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