JP2020109531A - Exposure device, exposure method and method for producing article - Google Patents

Abstract

To provide an exposure device advantageous for improving a focus accuracy.SOLUTION: An exposure device exposes a substrate, and includes: a stage configured to hold and move the substrate; a projection optical system configured to project a mask pattern to the substrate held by the stage; and a control part configured to operate a step movement of the stage and a control of a position of the stage in a first direction along an optical axis of the projection optical system, and to control an exposure of the substrate according to a step-and-repeat method. The control part is configured to obtain a step size of the step movement, and to determine a correction value for correcting the position of the stage in the first direction according to the obtained step size.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exposure apparatus, an exposure method, and an article manufacturing method.

An exposure apparatus that transfers a mask pattern onto a substrate is one of the apparatuses used in the manufacturing process (lithography process) of semiconductor devices and the like. In such an exposure apparatus, it is required to accurately arrange the surface of the substrate on the image forming surface (focus surface) of the projection optical system in order to superimpose the mask pattern on the shot area on the substrate with high accuracy.

Patent Document 1 discloses a method of correcting a positional deviation of the surface of a substrate caused by a manufacturing error of a control system, a measurement error of a measuring instrument, a control error of a control system, etc. in a scanning exposure apparatus that performs exposure while scanning a substrate. Proposed. In Patent Document 2, in a step-and-repeat type exposure apparatus, in a direction (Z direction) parallel to an optical axis generated by driving a substrate stage in a direction (XY direction) perpendicular to the optical axis of the projection optical system. A method of correcting the positional deviation of the surface of the substrate has been proposed. Patent Document 3 proposes a method of accurately performing focus measurement before reaching an exposure area in a step-and-repeat type exposure apparatus.

JP, 2013-130407, A JP, 2004-111995, A JP-A-2000-208391

In the exposure apparatus, focusing for placing the substrate surface on the focus surface is generally performed by feedback control for higher accuracy. On the other hand, speeding up focusing is an important requirement for improving throughput. In order to improve the throughput, it is possible to increase the acceleration of the movement of the substrate stage, relax the settling tolerance of the substrate stage and move the focus measurement ahead of time. However, in that case, the focus measurement is performed in the state where the deviation from the target position of the substrate stage remains, so that the measurement error may increase. Therefore, more effective correction is required.

An object of the present invention is to provide, for example, an exposure apparatus that is advantageous for improving focus accuracy.

According to one aspect of the present invention, an exposure apparatus for exposing a substrate, the stage holding and moving the substrate, a projection optical system for projecting a pattern of a mask on the substrate held by the stage, A control unit that performs step movement of the stage and control of the position of the stage in a first direction along the optical axis of the projection optical system, and controls exposure of the substrate according to a step-and-repeat method. The exposure unit is characterized in that the control unit acquires a step size of the step movement and determines a correction value for correcting the position of the stage in the first direction according to the acquired step size. A device is provided .

According to the present invention, for example, it is possible to provide an exposure apparatus that is advantageous for improving focus accuracy.

The figure which shows the structure of the exposure apparatus in embodiment. The figure which shows the example of the measurement point arrange|positioned at the to-be-exposed area|region. 6 is a flowchart of a process of calculating a focus correction formula in the embodiment. The flowchart of the process which determines an exposure angle of view. The figure which shows the example of the shot layout by a different angle of view. The flowchart which shows the calculation process of a correction formula. The flowchart which shows exposure processing. 9 is a flowchart showing a correction formula calculation process in the exposure process. The figure which shows the example of a display of the result of the correction formula for every angle of view. The figure explaining the effect of embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following embodiments are merely examples of the practice of the present invention, and the present invention is not limited to the following embodiments. In addition, not all combinations of features described in the following embodiments are essential for solving the problems of the present invention.

FIG. 1 is a view showing the arrangement of a step-and-repeat type reduction projection exposure apparatus according to this embodiment. The projection optical system 1 reduces and projects a circuit pattern of a reticle (not shown) to form a circuit pattern image on its focal plane. Further, the optical axis AX of the projection optical system 1 is in a relationship parallel to the Z axis direction in the drawing. The substrate 2, the photosensitive material has been applied to the surface, the same pattern with each other are formed in the previous exposure step, a plurality of exposure area (shot area) are arranged. The substrate stage 3 that holds the substrate 2 is an X stage that moves in the X axis direction that is orthogonal to the Z axis, a Y stage that moves in the Y axis direction that is orthogonal to the Z axis and the X axis, and a Z stage that moves in the Z axis direction. , Y, Z axes, and a Z stage that rotates about axes parallel to the respective directions. Therefore, by driving the substrate stage 3, the position of the surface of the substrate 2 can be adjusted in the optical axis AX direction of the projection optical system 1 and the direction along the plane orthogonal to the optical axis AX, and further the focal plane, that is, the circuit pattern image. The inclination with respect to can also be adjusted.

Reference numerals 4 to 11 are elements of a detection optical system provided for detecting the surface position and the inclination of the substrate 2. Reference numeral 4 is a light source for illumination with high brightness such as a light emitting diode and a semiconductor laser, and 5 is an illumination lens. The light emitted from the illumination light source 4 becomes a parallel light flux by the illumination lens 5, becomes a plurality of light fluxes via the mask 6, enters the folding mirror 8 via the imaging lens 7, and is directed by the folding mirror 8. , And is incident on the surface of the substrate 2. That is, the imaging lens 7 and the folding mirror 8 form a plurality of pinhole images of the mask 6 on the substrate 2. As shown in FIG. 2, the light flux that has passed through the plurality of pinholes has five measurement points 71, 72, 73 including the central portion (the position corresponding to the optical axis AX) of the exposed region 100 of the substrate 2. , 74, 75, and are reflected at each location. In the example of FIG. 2, the measurement point 71 is located at the center of the exposed area 100 that intersects the optical axis Ax, and the other measurement points 72, 73, 74, and 75 are located at regular intervals around the measurement point 71. It is in. The light beams reflected at the five measurement points 71, 72, 73, 74, and 75 in the exposed region 100 are changed in direction by the bending mirror 9, and then the elements are two-dimensionally passed through the detection lens 10. It is incident on the position detection element 11 arranged at. In this way, the image of the pinhole of the mask 6 is formed on the position detection element 11 by the imaging lens 7, the bending mirror 8, the substrate 2, the bending mirror 9, and the detection lens 10. Therefore, the mask 6, the substrate 2, and the position detection element 11 are at positions optically conjugate with each other.

Although the position detection element 11 is schematically shown in FIG. 1, a plurality of position detection elements 11 may be arranged corresponding to each pinhole when optical arrangement is difficult. For example, the position detecting element 11 is composed of a two-dimensional CCD or the like, and it is possible to independently detect the incident positions of a plurality of light fluxes through a plurality of pinholes on the light receiving surface of the position detecting element 11. Has become. The position change of the substrate 2 in the optical axis AX direction with respect to the projection optical system 1 can be detected as a deviation of the incident positions of a plurality of light beams on the position detection element 11. Information on the position of the surface of the substrate 2 in the optical axis AX direction at the five measurement points 71 to 75 in the exposed region 100 of the substrate 2 is output as a signal from the position detection element 11 via the surface position detection device 14. It is input to the control device 13 (control unit).

The displacements of the substrate stage 3 in the X-axis and Y-axis directions can be measured by a known method using the reference mirror 15 and the laser interferometer 17 provided on the substrate stage 3. A signal indicating the displacement amount of the substrate stage 3 is input from the laser interferometer 17 to the control device 13 via a signal line. The movement of the substrate stage 3 is controlled by the stage driving device 12. The stage drive device 12 receives a command signal from the control device 13 via a signal line, and servo-drives the substrate stage 3 in response to this signal. The stage driving device 12 includes a first driving unit and a second driving unit, and adjusts the positions x and y and the rotation θ in the plane orthogonal to the optical axis AX of the substrate 2 by the first driving unit to perform the second driving. The section adjusts the position z and the inclinations α and β of the substrate 2 in the optical axis AX direction (Z direction). The surface position detection device 14 detects the surface position of the substrate 2 based on the output signal (surface position data) from the position detection element 11, and transfers the detection result to the control device 13. Based on the detection result by the surface position detection device 14, the control device 13 operates the second drive unit of the stage drive device 12 by a predetermined command signal to adjust the position and the inclination of the substrate 2 in the optical axis AX direction. The storage device 18 can store data necessary for driving the stage. The storage device 18 may be a memory configured inside the control device 13. The user interface 19 can include a console unit for a user to perform an operation related to parameter setting, a display unit for displaying a parameter related to stage drive, and the like.

As described above, the control device 13 performs the feedback control via the stage drive device 12 so as to arrange the substrate surface on the focus surface when driving the substrate stage 3 in the Z direction. Here, in order to improve the throughput, it is considered that the acceleration of the movement of the substrate stage 3 is increased, the settling tolerance of the substrate stage 3 is relaxed, and the focus measurement is advanced. However, in that case, since the focus measurement is performed in a state where the deviation of the substrate stage 3 from the target position remains, the measurement error may increase. Therefore, the control device 13 needs to correct and output the command value to the stage drive device 12. Here, the deviation of the measured value of the remaining substrate stage from the target value is referred to as "focus residual". According to the study by the inventors, it was found that this focus residual changes depending on the exposure field angle (step size). It was also found that the focus residual changes depending on the step direction and the position of the shot area to be exposed on the substrate. Therefore, in the present embodiment, the control device 13 obtains a correction formula according to the angle of view, the step direction, and the position of the target shot area on the substrate. Therefore, the control device 13 executes a process of calculating the focus correction formula.

FIG. 3 is a flowchart of the process of calculating the focus correction formula executed by the control device 13. Although this process is performed before the exposure process, it need not be performed immediately before the exposure process, and the control device 13 may store information regarding the calculated correction formula in the storage device 18.

In S101, the control device 13 determines an angle of view that is a condition for calculating the correction formula. FIG. 4 is a flowchart of a process of determining a plurality of view angle candidates. The control device 13 determines the minimum value and the maximum value of the candidate view angles in S201, and determines the pitch of the view angle between the determined minimum and maximum view angles in S202. These values may be set by the user. In S203, the control device 13 determines the shot layout for each of the plurality of view angles acquired according to the minimum value, the maximum value, and the pitch of the view angle determined in S201 and S202. The determined plurality of view angles and/or shot layouts are stored in the storage device 18. FIG. 5 shows an example of a shot layout with an angle of view A and an example of a shot layout with an angle of view B narrower than the angle of view A. An example of the correction formula calculation layout calculated in FIG. 4 is described. Since the view angle B is narrower than the view angle A, the number of shot areas formed by the view angle B is larger than the number of shot areas formed by the view angle A.

The description returns to FIG. In step S102, the substrate 2 is loaded into the apparatus and mounted on the substrate stage 3. In S103, the control device 13 changes the exposure layout in S103 according to the angle of view determined in S101. In S104, the control device 13 performs alignment measurement, and in S105, drives the substrate stage 3 so that the target shot area is located at the focus measurement position (drives the substrate stage in the horizontal direction with respect to the image plane), and S106. Then, focus measurement is performed. In S107, the control device 13 carries out focus driving according to the focus measurement value and the focus target value measured in S106 (driving the substrate stage in the direction perpendicular to the image plane). In S108, the control device 13 calculates the difference between the focus measurement value and the focus target value as the focus residual. In S109, the control device 13 stores the identification number of the target shot area and the focus residual calculated in S108 in the storage device 18 in association with each other. The position of the shot area on the substrate can be specified by the identification number of the shot area. In S110, the control device 13 determines whether the measurement has been completed for all shot areas. If not finished yet, the processing of S105 to S109 is repeated for the next shot area. When the measurement is completed for all the shot areas, the control device 13 determines in S111 whether the measurement is completed for all the layouts determined in S101. If it has not been completed yet, the process returns to S103 and is repeated in order to measure the next layout. When the measurement is completed for all the layouts, the control device 13 calculates a correction formula in S112.

FIG. 6 is a flowchart showing the correction formula calculation process in S112. In S301, the control device 13 acquires the plurality of field angles determined in S101. In S302, the control device 13 determines the view angle to be processed from the acquired view angles. In S303 to S306 below, processing is performed with respect to the angle of view determined in S302. In S<b>303, the control device 13 acquires the focus residual information for each shot area stored in the storage device 18. Next, in S304, the controller 13 classifies the acquired focus residual information for each shot area in the step direction (plus direction/minus direction) of the substrate stage 3. In step S<b>305, the control device 13 performs a polynomial approximation on the relationship with the focus residual for each shot area classified for each step direction and stores the relationship in the storage device 18. In S307, the control device 13 determines whether the processing has been completed for all the angle of view. If the processing has not been completed for all angle of view, the process returns to S303 and the process is repeated for the next angle of view. In this way, the correction formula is calculated for each angle of view.

Returning to FIG. 3, in S113, the substrate is unloaded, and the process ends. Summarizing the above points of the correction formula calculation process performed in advance of the exposure process, the correction formula calculation process includes the following actual measurement steps. (A) Focus measurement is performed to obtain a measurement value for focus drive of the substrate stage (S106). (B) Focus drive is performed according to the obtained measured value (S107). (C) Focus measurement is performed after the end of the focus drive, and the residual of the measured value obtained by the focus measurement with respect to the target value is calculated. In the actual measurement step, the above steps (a) to (c) are repeated for each shot area for each of the plurality of field angles. Further, in the correction formula calculation process, a plurality of correction formulas are calculated based on the residuals for each shot area obtained for each of the plurality of field angles by the above-described actual measurement process (S112).

Next, the exposure process in this embodiment will be described with reference to the flowchart in FIG. First, in step S401, the control device 13 calculates a correction formula that matches the exposure layout. FIG. 8 shows a flowchart of the correction formula calculation process in S401. In step S501, the control device 13 acquires information on the angle of view (that is, the layout) at the time of exposure in the target exposure recipe. In S502, the control device 13 determines whether the acquired layout can be corrected. For example, it is determined whether the driving direction that is the main body of the substrate stage is the same in the layout and the exposure condition when the correction formula is obtained. When it is determined that the correction is impossible, the coefficient of the correction formula is set to 0. When it is determined that the correction is possible, in S503, the control device 13 confirms whether the angle of view at the time of exposure acquired in S501 is outside the range between the minimum value and the maximum value of the plurality of angle of view determined in S101. To do. If the view angle acquired in S501 is out of the range, in S504, the correction formula for the view angle closest to the exposure view angle is acquired among the plurality of view angles determined in S101. That is, when the angle of view at the time of exposure is smaller than the minimum angle of view of the plurality of angles of view, the correction formula for the minimum angle of view is determined as the correction formula for the angle of view at the time of exposure. When the angle of view at the time of exposure is larger than the maximum angle of view of the plurality of angles of view, the correction formula for the maximum angle of view is determined as the correction formula for the angle of view at the time of exposure.

On the other hand, if the view angle acquired in S501 is within the range, in S505, the correction formulas for the two view angles before and after the exposure view angle are acquired. For example, when the plurality of field angles determined in S101 are acquired at a pitch of 1.0 [mm] and the exposure field angle acquired in S501 is 22.5 [mm], 22.5[ The correction formulas of two view angles of 23.0 [mm] and 22.0 [mm] before and after [mm] are acquired. In S506, the control device 13 determines a correction formula according to the angle of view at the time of exposure by interpolating the parameters from the two angle-of-view correction formulas acquired in S505.

In the following example, for the sake of simplicity, the order of the correction formula is first order, and when calculating the correction formula, linear approximation is performed with two field angles before and after the acquired exposure field angle. When obtaining the correction formula for the exposure field angle 22.5 [mm], it is set to 23.0 [mm] (Z=5.0X+10.0) and 22.0 [mm] (Z=10.0X+20.0). The interpolation correction formula is calculated from the correction formula of ). However, here, X is the position of the shot area in the X direction of the substrate, and Z is the correction value in the Z direction. The coefficients of both correction equations are linearly interpolated and the intercepts are linearly interpolated. Accordingly, the correction formula for 22.5 [mm] is Z=7.5X+15.

Returning to FIG. 7, the substrate is loaded in S402, and alignment measurement is performed in S403. In S404, the control device 13 calculates a correction value in the Z direction in each shot area from the correction formula that matches the exposure angle of view calculated in S401. The controller 13 performs focus measurement in S405, reflects the correction value obtained in S404 on the command value of the substrate stage as an offset, and then performs focus follow-up drive in S407. After the focus follow-up drive is completed, the control device 13 performs exposure in S408. The control device 13 performs focus measurement during exposure in S409, and stores (learns) the focus residual in S410.

In step S411, the control device 13 determines whether all shot areas to be exposed have been exposed. If the exposure of all shot areas has not been completed, the process returns to S404 and the processing is repeated for the next unexposed shot area. When exposure has been completed for all shot areas, the substrate is unloaded in S412, and at the same time, a newly used correction formula for the exposure field angle is calculated. The newly calculated correction formula is stored in the same manner as the correction formula obtained and stored in FIG. As a result, the accuracy of interpolation correction formula calculation can be improved.

FIG. 9 shows a display example of the result of the correction formula for each angle of view calculated in S112 by the user interface 19. Item 91 indicates the angle of view. Items 92 and 93 indicate the step direction of the substrate stage. Item 94 indicates the calculated correction coefficient. Each coefficient of the correction formula that is approximated by the function is represented as "Coefficient" and the intercept as "intercept".

FIG. 10 is a diagram showing the effect of the correction according to this embodiment. In FIG. 10, the horizontal axis represents the angle of view at which the focus residual is acquired, and the vertical axis represents the focus residual 3σ in the substrate plane. As shown in FIG. 10, according to the present embodiment, the focus residual can be corrected at all exposure field angles, so that the focus accuracy can be improved at each field angle.
<Embodiment of article manufacturing method>
The article manufacturing method according to the embodiment of the present invention is suitable for manufacturing an article such as a microdevice such as a semiconductor device or an element having a fine structure. In the method for manufacturing an article according to the present embodiment, a step of forming a latent image pattern on a photosensitive agent applied to a substrate using the above-described exposure apparatus (step of exposing the substrate), and the latent image pattern is formed in this step. Developing the substrate. Further, the manufacturing method includes other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method of the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.
<Other Embodiments>
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. It can also be realized by the processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

1: Projection optical system, 2: Substrate, 3: Substrate stage, 12: Stage drive device, 13: Control device, 14: Surface position detection device

Claims (11)

An exposure apparatus for exposing a substrate,
A stage for holding and moving the substrate,
A projection optical system that projects a mask pattern onto the substrate held by the stage;
A controller that performs step movement of the stage and control of the position of the stage in a first direction along the optical axis of the projection optical system, and controls exposure of the substrate according to a step-and-repeat method ;
Have
The exposure apparatus, wherein the control unit acquires a step size of the step movement and determines a correction value for correcting the position of the stage in the first direction according to the acquired step size. .. Wherein, based on a plurality of correction formulas according to each of the plurality of step sizes and determining the correction equation for the step size of the step movement, determining said correction value by using the determined correction formula The exposure apparatus according to claim 1, wherein: The exposure apparatus according to claim 2, wherein the plurality of correction formulas include a correction formula representing a relationship among a step size of the step movement, a position of an exposure area , and a correction value. The exposure apparatus according to claim 2 , wherein the plurality of correction expressions are correction expressions that represent a relationship among a step size of the step movement, a step direction of the step movement, and a correction value . The control unit determines a correction formula for the step size of the step movement by interpolating parameters of a correction formula for two step sizes before and after the step size of the step movement among the plurality of correction formulas. The exposure apparatus according to any one of claims 2 to 4. The control unit is
If the step size of the step movement is minimum step size is smaller than one of said plurality of step sizes, determine a correction formula for said minimum step size as the correction equation for the step size of the step movement,
Claim step size of the step movement larger than the maximum step size of the plurality of step sizes, which is characterized by determining a correction formula for said maximum step size as the correction equation for the step size of the step movement The exposure apparatus according to item 5. An exposure method of exposing a substrate with light from a projection optical system of an exposure apparatus by a step-and-repeat method ,
A measurement step of measuring the position of the stage, which holds and moves the substrate, in the first direction along the optical axis of the projection optical system after the step movement of the stage;
To correct the difference between the target position of the stage in the first direction and the position of the stage controlled to move to the target position based on the position of the stage in the first step measured in the measuring step. A control step of controlling the movement of the stage in the first direction according to the correction value of
An exposure step of performing exposure of an exposure area on the substrate after the control step,
Have
The exposure method, wherein the correction value is determined according to a step size in the step movement . The method further includes the step of previously determining a correction formula for the step size in the exposure based on a plurality of correction formulas corresponding to a plurality of step sizes , and determining the correction value using the determined correction formula. The exposure method according to claim 7, wherein: 9. The exposure method according to claim 8, wherein the correction formula is a formula representing a correction value according to the position of the exposure region on the substrate. The step of determining the correction value includes
For each of the plurality of step sizes , for each exposure area,
(A) measuring the position of the stage in the first direction after step movement of the stage,
(B) controlling the drive of the stage in the first direction so that the position of the stage approaches the target position based on the result of the measurement,
(C) Repeatedly performing the measurement of the position of the stage in the first direction after controlling the drive of the stage, and calculating the residual difference which is the difference between the measured position and the target position. The actual measurement process,
A calculation step of calculating the plurality of correction formulas based on the residual difference for each exposure area obtained for each of the plurality of step sizes by the actual measurement step;
The exposure method according to claim 9, further comprising: Exposing a substrate using the exposure apparatus according to any one of claims 1 to 6;
Developing the exposed substrate in the step,
Including
An article manufacturing method, comprising manufacturing an article from the developed substrate.

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