JP7614883B2 - Exposure apparatus, exposure method, and article manufacturing method - Google Patents

Description

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

In the photolithography process for manufacturing devices such as semiconductor elements, an exposure apparatus is generally used that transfers the pattern of an original (mask or reticle) to the substrate by exposing the substrate through the original. Generally, exposure apparatuses that employ the step-and-repeat method (stepper) and exposure apparatuses that employ the step-and-scan method (scanner) are known as such exposure apparatuses.

Steppers are low-cost devices compared to scanners, and are used in processes that do not require high resolution or high-precision overlay. In a stepper, a substrate stage holding a substrate is driven below the projection optical system (exposure position), and then the substrate's height position (distance from the projection optical system) is measured by a focus sensor, and the substrate stage is driven according to the measurement value to focus the substrate with respect to the projection optical system. Technologies related to measuring such substrate height position have been proposed in the past (see Patent Document 1).

Japanese Patent Application Publication No. 11-87233

However, in a stepper, the measurement value of the focus sensor contains an error caused by vibration of the substrate stage that holds the substrate to be measured. Of these errors, the control deviation of the substrate stage can be corrected by removing it from the measurement value, but unobservable components such as the vibration of the base on which the substrate stage is placed cannot be corrected, leading to defocusing. Because steppers need to be realized as low-cost devices, it is not realistic to provide a sensor to measure the vibration of the base and control it in real time.

Therefore, the present invention has been made in consideration of the problems with the conventional technology, and has as an exemplary object to provide an exposure device that is advantageous in reducing the effects of vibration of the base plate and achieving high-precision exposure.

In order to achieve the above-mentioned object, an exposure apparatus as one aspect of the present invention is an exposure apparatus that exposes a substrate via an original, and includes a stage that holds and moves the substrate, a base plate on which the stage is placed, a projection optical system that projects a pattern of the original onto the substrate, a measurement unit that measures the height position of the substrate held on the stage, and a control unit, wherein the control unit causes the measurement unit to measure the height position of the substrate from the timing at which the vibration amplitude of the base plate that vibrates due to the movement of the stage is maximum or minimum during a measurement period set to 1/2 the vibration period of the base plate that vibrates due to the movement of the stage, and controls the distance between the projection optical system and the stage holding the substrate to be exposed based on the height position of the substrate measured by the measurement unit.

Further objects and other aspects of the present invention will become apparent from the embodiments described below with reference to the accompanying drawings.

The present invention can provide an exposure device that is advantageous for achieving high-precision exposure by, for example, reducing the effects of vibration of the base plate.

1 is a schematic diagram showing a configuration of an exposure apparatus according to one aspect of the present invention. 2 is a flowchart for explaining an exposure process by the exposure apparatus shown in FIG. 1 . 11A and 11B are diagrams illustrating an example of fluctuation in the height position of a substrate. 5A and 5B are diagrams illustrating an example of a measurement error amount included in a measurement value of a measurement unit. 5A and 5B are diagrams illustrating an example of a measurement error amount included in a measurement value of a measurement unit. 11 is a flowchart illustrating a process for setting a measurement period of a measurement unit. FIG. 2 is a diagram showing an example of an exposure layout. 11A and 11B are diagrams illustrating an example of fluctuation in the height position of a substrate. 5A and 5B are diagrams illustrating an example of a measurement error amount included in a measurement value of a measurement unit.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicate explanations are omitted.

Figure 1 is a schematic diagram showing the configuration of an exposure apparatus 1 according to one aspect of the present invention. The exposure apparatus 1 is a lithography apparatus used in the manufacturing process of devices such as semiconductor elements, and forms a pattern on a substrate by exposing the substrate via an original. In this embodiment, the exposure apparatus 1 is a step-and-repeat type exposure apparatus (stepper). Here, the step-and-repeat type is an exposure method in which the substrate is stepped for each full exposure of a shot area of the substrate, and the next shot area is moved to the exposure position (exposure area).

The exposure apparatus 1 has an illumination optical system 102, a projection optical system 104, a stage 105 that holds and moves a substrate S, a measurement unit 106, a structure 107, a platen gap sensor 108, a control unit 109, and a platen 110 on which the stage 105 is placed. In this specification and the accompanying drawings, directions are indicated in an XYZ coordinate system in which a direction parallel to the surface of the substrate S is the XY plane. The directions parallel to the X-axis, Y-axis, and Z-axis in the XYZ coordinate system are the X-direction, Y-direction, and Z-direction, respectively, and the rotations around the X-axis, Y-axis, and Z-axis are θX, θY, and θZ, respectively.

The illumination optical system 102 guides light from the light source 101 to illuminate the original 103. The light source 101 includes, for example, an i-line mercury lamp or an excimer laser. The original 103 has a pattern drawn thereon to be transferred to the substrate S. The projection optical system 104 projects the pattern (pattern image) of the original 103 onto the substrate S.

In the exposure apparatus 1, light passing through the original 103 passes through the projection optical system 104 and forms an image on a substrate held by a stage 105. The pattern image projected onto the substrate S causes a reaction with a photosensitive material such as a resist applied to the substrate S, and a pattern is formed on the substrate by developing the substrate S. Also, as described above, it is possible to expose all of the shot areas of the substrate S by stepping the stage 105 holding the substrate S and sequentially exposing the shot areas of the substrate S (i.e., repeating stepping and exposure).

The position and orientation of the stage 105 are measured by a position measurement device including an interferometer and an encoder, and are managed with high precision under the control of the control unit 109 based on the measurement values. By managing the position and orientation of the stage 105 in this way, it is possible to achieve highly accurate overlay.

The measurement unit 106 measures the height (Z direction) position of the substrate S held on the stage 105 (hereinafter referred to as the "height position of the substrate S"). When exposing the substrate S, it is necessary to align the height position and inclination of the substrate S with respect to the position of the pattern image projected from the projection optical system 104, that is, to focus the substrate S on the imaging plane of the projection optical system 104. Therefore, the measurement unit 106 measures the height position of the substrate S, and based on the measurement value, at least one of the position and attitude of the stage 105 holding the substrate S is controlled under the control of the control unit 109 so that the substrate S is focused on the imaging plane of the projection optical system 104.

In this embodiment, the measurement unit 106 is configured with a focus sensor that performs optical detection, but is not limited to this, and other detection methods using a capacitance sensor, pressure sensor, etc. may be adopted. Furthermore, in order to obtain the tilt of the substrate S in addition to the height of the substrate S, a plurality of measurement points (measurement locations) where the height position is measured by the measurement unit 106 are provided in the exposure area on the substrate.

The projection optical system 104 and the measurement unit 106 are held on a levitated structure 107 via an anti-vibration device so as not to be affected by external vibrations. The platen gap sensor 108 includes, for example, a displacement sensor, and measures the distance between the structure 107 and the platen 110. Here, the position of the projection optical system 104 relative to the structure 107 is guaranteed, and the position of the stage 105 relative to the platen 110 is guaranteed. Therefore, by measuring the distance between the structure 107 and the platen 110 with the platen gap sensor 108, the distance between the projection optical system 104 and the stage 105 can be obtained.

The control unit 109 is composed of a computer including a CPU, memory, etc., and generally controls each part of the exposure apparatus 1 according to, for example, a program stored in the storage unit to operate the exposure apparatus 1. The control unit 109 controls the movement of the stage 105 based on information on the height and tilt of the substrate S obtained by the measurement unit 106 and information on the distance (variation) between the projection optical system 104 and the stage 105 obtained by the platen gap sensor 108. The control unit 109 controls exposure to be performed by a so-called step-and-repeat method, in which the entire area of the substrate S is exposed by repeatedly exposing a shot area on the substrate while moving the stage 105 in steps.

The operation of the exposure apparatus 1, specifically, the exposure process (exposure method) of exposing the substrate S through the original 103 to transfer the pattern of the original 103 to the substrate S, will be described with reference to FIG. 2. The exposure process is performed by the control unit 109 comprehensively controlling each unit of the exposure apparatus 1.

In S201, the substrate S is loaded into the exposure apparatus 1. Specifically, the substrate S is loaded into the exposure apparatus 1 via a substrate transport unit (not shown), and the substrate S is held by the stage 105.

In S202, the stage 105 holding the substrate S is moved to the exposure position. For example, the stage 105 holding the substrate S is moved so that the shot area on the substrate (the shot area to be exposed) is positioned at the exposure position below the projection optical system 104.

In S203, the measurement unit 106 measures the height position of the substrate S held by the stage 105 located at the exposure position below the projection optical system 104.

In S204, the substrate S is aligned in the height direction (focused). Specifically, based on the height position of the substrate S measured in S203, at least one of the position and attitude of the stage 105 holding the substrate S is controlled so that the substrate S is focused on the imaging plane of the projection optical system 104. In other words, the stage 105 is moved to control the distance between the projection optical system 104 and the stage 105 so that the substrate S is focused on the imaging plane of the projection optical system 104.

In S205, the substrate S, which was focused in S204, is exposed through the original 103.

In S206, it is determined whether the entire area of the substrate S has been exposed, i.e., whether all shot areas on the substrate have been exposed. If the entire area of the substrate S has not been exposed, the process proceeds to S202 to expose the unexposed shot areas on the substrate. On the other hand, if the entire area of the substrate S has been exposed, the exposure process is terminated.

Here, the influence of vibrations from the floor surface on which the exposure apparatus 1 is installed and the movement of the stage 105 holding the substrate S on such an exposure process will be described. As described above, the stage 105 is placed on the base plate 110. The base plate 110 is influenced by vibrations from the floor surface on which the exposure apparatus 1 is installed and the reaction force of the movement of the stage 105, and mainly vibrates at a frequency based on the characteristic value of the base plate 110. Therefore, in S203, the measurement value (height position of the substrate S) obtained by the measurement unit 106 includes an error caused by the vibration of the stage 105 propagated through the base plate 110. Similarly, even during exposure of the substrate S (S205), it is influenced by the vibration of the stage 105. The stage 105 is controlled by the control unit 109 so that focusing is performed, but since the vibration of the base plate 110 cannot be observed, defocusing occurs due to its influence.

With reference to FIG. 3, the defocus caused by the vibration of the base plate 110 will be specifically described. FIG. 3 is a diagram showing the fluctuation of the height position of the substrate S after the stage 105 is moved to the exposure position. With reference to FIG. 3, it can be seen that the height position of the substrate S (stage 105) fluctuates (vibrates) at the frequency f of the natural frequency of the base plate 110 for a long period of time due to the reaction force generated by the movement of the stage 105 and the vibration from the floor. Mt is a measurement period during which the measurement unit 106 measures the height position of the substrate S. After the stage 105 is moved to the exposure position, the measurement unit 106 measures the height position of the substrate S in a state in which the height position of the substrate S held on the stage 105 fluctuates due to the vibration from the base plate 110. Et is an exposure period during which the substrate S is exposed to light after the substrate S is focused based on the height position of the substrate S measured by the measurement unit 106. During the exposure period Et, as in the measurement period Mt, the substrate S is exposed while the height position of the substrate S held on the stage 105 fluctuates due to vibrations from the base plate 110.

Figure 4 shows the amount of measurement error according to each measurement start timing when the measurement period Mt is set to 0.4 x (1/f) when the height position of the base plate 110, i.e., the substrate S, is vibrating with an amplitude A and a frequency f. The measurement start timing is the start timing of the measurement period Mt at which the measurement unit 106 starts measuring the height position of the substrate S. Referring to Figure 4, when the height position of the substrate S is vibrating with an amplitude A, if the measurement period Mt is set to a period that does not match the vibration period (1/f), which is the reciprocal of the frequency f, the amount of measurement error changes according to the measurement start timing. Therefore, the measurement value obtained by measuring the height position of the substrate S with the measurement unit 106 contains a measurement error as shown in Figure 4, which causes defocusing when focusing the substrate S.

In this embodiment, the vibration period and frequency of the base plate 110 on which the stage 105 is placed are acquired in advance, and the measurement period Mt is set according to the vibration period and frequency of the base plate 110, thereby reducing the effect of the measurement error contained in the measurement value of the measurement unit 106. In other words, the measurement errors contained in the measurement value of the measurement unit 106 are averaged (cancelled out by each other), and the substrate S is focused based on this, thereby reducing the effect of the vibration of the base plate 110, which cannot be observed.

Figure 5 is a diagram showing the amount of measurement error according to each measurement start timing when the measurement period Mt is set to t1 (not coincident with the vibration period (1/f)), t2 (not coincident with the vibration period (1/f)), and t3 (coincident with the vibration period (1/f)). Referring to Figure 5, it can be seen that by setting the measurement period Mt to an integer multiple of the vibration period 1/f of the base plate 110, the amount of measurement error is averaged and becomes small (to zero) regardless of the measurement start timing. Therefore, in this embodiment, the measurement period Mt is set to an integer multiple (t3) of the vibration period 1/f of the base plate 110.

Also, when exposing the substrate S (S205), the exposure period Et is set to an integer multiple of the vibration period 1/f of the surface plate 110, so that the effect of fluctuations in the height position of the substrate S caused by the vibration of the surface plate 110 is averaged (reduced), and further improvement in accuracy can be achieved. In this case, it is advisable to control the intensity of the light exposing the substrate S in accordance with the exposure period Et set to an integer multiple of the vibration period 1/f of the surface plate 110, so that the exposure amount on the substrate S becomes the target exposure amount.

Next, referring to FIG. 6, an example of a process for acquiring the vibration period of the base plate 110 and setting the measurement period Mt during which the measurement unit 106 measures the height position of the substrate S will be described. Such a process is performed, for example, during a preparation period before the actual exposure period during which the exposure process shown in FIG. 2 is performed (before the substrate S is exposed). Since the base plate 110 is a large structure, the frequency of its vibration is generally 100 Hz or less. On the other hand, in this embodiment, the focus sensor configured as the measurement unit 106 has a measurement band of, for example, 2 kHz or more, and therefore can perform measurements at a speed sufficiently faster than twice the maximum frequency of vibration that can occur in the base plate 110.

In S601, similar to S201, the substrate S is loaded into the exposure apparatus 1. In S602, similar to S202, the stage 105 holding the substrate S is moved to the exposure position.

In S603, the fluctuation in the height position of the substrate S caused by the vibration of the base plate 110 is acquired. Specifically, while the stage 105 is being moved so that the substrate S is positioned under the projection optical system 104, or after the stage 105 has been moved, the measurement unit 106 continuously measures the height position of the substrate S held on the stage 105 at high speed for a predetermined period of time. This makes it possible to acquire the fluctuation in the height position of the substrate S caused by the vibration of the base plate 110 influenced by vibrations from the floor surface on which the exposure apparatus 1 is installed, reaction forces from the movement of the stage 105, and the like.

In S604, the vibration period 1/f of the base plate 110 (or the vibration frequency f of the base plate 110) is calculated from the fluctuation in the height position of the substrate S obtained in S603.

In S605, the measurement period Mt during which the measurement unit 106 measures the height position of the substrate S is set to an integer multiple ((1/f) x n (n = 1, 2, 3, ...)) of the vibration period of the surface plate 110 determined in S604. From the viewpoint of throughput, it is clearly advantageous to set the measurement period Mt to one period (1x) of the vibration period of the surface plate 110. However, depending on the response characteristics of the focus sensor configured as the measurement unit 106, it is also possible that the measurement speed is slower than the vibration period of the surface plate 110. In such a case, the measurement period Mt should be set to an integer multiple of the vibration period of the surface plate 110 so as to satisfy the measurement speed and to minimize the measurement period Mt.

In this embodiment, the vibration period (frequency of vibration (dominant frequency)) of the base plate 110 is obtained using the measurement unit 106, but this is not limited to the above. For example, the vibration period of the base plate 110 may be obtained by separating the dominant frequency component specific to the base plate 110 from the vibration propagating through the connection parts that connect the various parts of the exposure apparatus 1 based on the vibration frequency of the stage 105 and the base plate sensor 108. Also, the vibration period of the base plate 110 may be obtained by estimating the vibration of the base plate 110 based on the design value of the stage 105 and the design value of the base plate 110.

In addition, in this embodiment, the case where the vibration period of the surface plate 110 is obtained during the preparation period for the actual exposure period has been described, but the timing for obtaining the vibration period of the surface plate 110 is not limited. For example, the vibration period of the surface plate 110 may be obtained during the period before the first substrate of multiple substrates included in a lot is exposed (e.g., the period between S202 and S203) after the first substrate is loaded into the exposure apparatus 1. In this case, the period before the first substrate is exposed (e.g., the period during which steps S201 and S202 are performed) is considered to be the preparation period, and the period for actually exposing the first substrate (e.g., the period during which steps S203 to S205 are performed) is considered to be the actual exposure period.

In addition, if it is estimated from the measurement value of the measurement unit 106 that the vibration period of the base plate 110 determined in advance is changing over time, it is advisable to adjust the measurement period Mt in accordance with the change over time.

In this way, according to the exposure apparatus 1 of this embodiment, by setting the measurement period Mt and the exposure period Et to an integer multiple of the vibration period of the base plate 110, it is possible to reduce the effects of the vibration of the base plate 110 and achieve highly accurate exposure.

Note that since the vibration of the base plate 110 is caused by the reaction force of the movement of the stage 105, the frequency of the vibration of the base plate 110 after the stage 105 is moved to the exposure position is uniquely determined by the layout (exposure layout) of the shot area of the substrate S. As shown in FIG. 7, consider moving the stage 105 so that the shot area located at the exposure position changes from shot area Sa to shot area Sb. FIG. 8 is a diagram showing the change in the height position of the substrate S after moving the stage 105 so that the shot area located at the exposure position changes from shot area Sa to shot area Sb. The movement time T0 of the stage 105 required to change the shot area located at the exposure position from shot area Sa to shot area Sb is determined by the exposure layout from the size of the shot area (movement distance of the stage 105) and the movement speed of the stage 105. The vibration of the base plate 110 is generated by the reaction force of the movement of the stage 105, so by calculating the vibration of the base plate 110 for each shot area, the vibration phase of the base plate 110 after the stage 105 is moved can also be calculated.

As described above, it is possible to obtain the vibration phase of the base plate 110 from the fluctuation of the height position of the substrate S, and the movement distance and movement speed of the stage 105. By obtaining the vibration phase of the base plate 110, the time T1 from when the stage 105 moves to the exposure position to when the measurement of the height position of the substrate S is started can be set to the timing (phase angle 90 degrees or 270 degrees) at which the amplitude of the vibration of the base plate 110 becomes maximum or minimum. This makes it possible to set the measurement period Mt during which the measurement unit 106 measures the height position of the substrate S to 1/2 the vibration period (1/f) of the base plate 110, thereby shortening the measurement period Mt. FIG. 9 is a diagram showing the amount of measurement error corresponding to each measurement start timing when the measurement period Mt is set to 1/2f for the vibration (amplitude A, frequency f) of the base plate 110. In FIG. 9, 901, 902, 903, 904, 905, and 906 indicate the timing at which the amplitude of the vibration of the base plate 110 becomes maximum or minimum. By setting the start timing of the measurement period Mt, at which the measurement unit 106 starts measuring the height position of the substrate S, to timing 901, 902, 903, 904, 905, or 906, the measurement error contained in the measurement value of the measurement unit 106 can be averaged and reduced.

In this way, it is possible to set the measurement period Mt to 1/2 the vibration period of the base plate 110, and set the start timing of the measurement period Mt to the timing when the vibration amplitude of the base plate 110 is maximum or minimum. In this case, while shortening the measurement period Mt, it is possible to average out the measurement error contained in the measurement value of the measuring unit 106 and reduce the influence of the vibration of the base plate 110, which is unobservable.

The method for manufacturing an article according to an embodiment of the present invention is suitable for manufacturing articles such as flat panel displays, liquid crystal display elements, semiconductor elements, and MEMS. The manufacturing method includes a step of exposing a substrate coated with a photosensitive agent using the exposure apparatus 1 described above, and a step of developing the exposed photosensitive agent. In addition, an etching step, an ion implantation step, and the like are performed on the substrate using the developed photosensitive agent pattern as a mask, to form a circuit pattern on the substrate. These steps of exposure, development, etching, and the like are repeated to form a circuit pattern consisting of multiple layers on the substrate. In a post-process, dicing (processing) is performed on the substrate on which the circuit pattern is formed, and chip mounting, bonding, and inspection steps are performed. The manufacturing method may also include other well-known steps (oxidation, film formation, deposition, doping, planarization, resist stripping, and the like). The method for manufacturing an article according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article compared to the conventional method.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

1: Exposure device 103: Original 104: Projection optical system 105: Stage 106: Measurement unit 109: Control unit 110: Base plate S: Substrate

Claims (7)

An exposure apparatus that exposes a substrate through an original, comprising:
a stage for holding and moving the substrate;
A base on which the stage is placed;
a projection optical system that projects a pattern of the original onto the substrate;
a measuring unit that measures a position in a height direction of the substrate held on the stage;
A control unit,
The control unit is
measuring a position of the substrate in a height direction from a timing when a vibration amplitude of the base plate vibrating due to the movement of the stage becomes maximum or minimum during a measurement period set to 1/2 of a vibration period of the base plate vibrating due to the movement of the stage, by the measurement unit;
an exposure apparatus that controls a distance between the projection optical system and the stage that holds the substrate to be exposed, based on the position of the substrate in the height direction measured by the measurement unit; 2. The exposure apparatus according to claim 1, wherein the control unit sets the measurement period to an integer multiple of a vibration period of the base before exposing the substrate, and sets the timing at which the measurement unit starts measuring the height direction position of the substrate to the timing at which the vibration amplitude of the base is maximum or minimum. 3. The exposure apparatus according to claim 2, wherein the control unit determines the vibration period from a fluctuation in the height position of the substrate during a predetermined period, which is obtained by having the measurement unit measure the height position of the substrate held on the stage for the predetermined period while the stage is being moved so that the substrate is positioned under the projection optical system or after the stage has been moved, and determines the vibration phase of the base from the fluctuation, and the moving distance and moving speed of the stage. 4. The exposure apparatus according to claim 3 , wherein the control unit sets a timing at which the measurement unit starts measuring the position of the substrate in the height direction, based on a vibration phase of the surface plate. 5. The exposure apparatus according to claim 1 , wherein the exposure apparatus is a step-and-repeat type exposure apparatus. 1. An exposure method for exposing a substrate using an exposure apparatus having a stage that holds and moves a substrate, a base on which the stage is placed, a projection optical system that projects a pattern of an original onto the substrate, and a measurement unit that measures a position in a height direction of the substrate held by the stage, comprising:
measuring a position of the substrate in a height direction from a timing when a vibration amplitude of the base plate vibrating due to the movement of the stage becomes maximum or minimum during a measurement period set to 1/2 of a vibration period of the base plate vibrating due to the movement of the stage, by the measurement unit;
an exposure method, comprising: controlling a distance between the projection optical system and the stage holding the substrate to be exposed, based on the position in the height direction of the substrate measured by the measurement unit; exposing a substrate using the exposure apparatus according to any one of claims 1 to 5 ;
developing the exposed substrate;
producing an article from the developed substrate;
A method for producing an article, comprising the steps of:

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