JP2025037490A - Method and control device for spatial light modulator, and exposure apparatus - Google Patents

Abstract

To provide a technique for efficiently and accurately adjusting a parameter for driving each channel in a spatial light modulator.SOLUTION: In a state where a channel (1) and a channel (1+x) are turned on, and one or more intermediate channel positioned between the channel (1) and the channel (1+x) are turned off, a first light quantity of light corresponding to the channel (1+x) is measured. In a state where the channel (1+x) is turned on, and the channel (1) and the intermediate channel are turned off, a second light quantity of light corresponding to the channel (1+x) is measured. Then, a reference gap xs being a gap x between the channel (1) and the channel (1+x) when the first light quantity and the second light quantity match under a predetermined reference is determined. A parameter for driving a plurality of channels positioned at the reference gap xs is determined on the basis of a light quantity variation in a case where the plurality of channels are simultaneously turned on while a driving voltage is varied.SELECTED DRAWING: Figure 9

Description

The subject matter disclosed in this specification relates to a method for controlling a spatial light modulator, a control device, and an exposure apparatus.

For example, there is a technique for drawing by light irradiation as a method for forming a pattern on a substrate such as a semiconductor wafer or a glass substrate. In this technique, a substrate on which a photosensitive layer such as a photoresist is formed is treated as a drawing target, and light modulated based on drawing data is irradiated onto the drawing target to expose the photosensitive layer. As a spatial light modulator (SLM) for performing such light modulation, for example, a diffraction grating type optical element (hereinafter referred to as a "diffractive optical element") such as a GLV (Grating Light Valve, a registered trademark of Silicon Light Machines, Inc., USA) or a DMD (Digital Mirror Device) is used. Spatial light modulators are used in direct drawing devices because they are capable of controlling the on/off of an exposure beam of several thousand pixels (for example, Patent Document 1).

Direct imaging devices generally include a light source, an illumination optical system, a spatial light modulator, a projection optical system, and a data generation unit and data transfer unit that display the imaging pattern on the spatial light modulator. The uniformity of the exposure line width on the exposure surface depends mainly on the uniformity of the light amount of the exposure beam and the uniformity of the exposure beam size. The uniformity of the light amount on the exposure surface is distributed mainly according to the reflectance of the illumination optical system and the spatial light modulator.

In a spatial light modulator, the reflectance of each channel is controlled by adjusting the voltage applied to the channel corresponding to each pixel. Therefore, in a spatial light modulator, the light distribution on the exposure surface can be precisely adjusted by adjusting the voltage applied to each channel.

In a direct imaging device, in order to expose a circuit pattern, it is necessary to determine for each channel a drive voltage for the bright side (ON side) that exposes the exposed object to light, and a drive voltage for the dark side (OFF side) that does not expose the exposed object to light. Therefore, in order to determine the two drive voltages, the change in light amount relative to the drive voltage of each channel (hereinafter referred to as the "light amount-voltage characteristic") is obtained. Specifically, the drive voltage applied to all channels is changed in stages, and the light amount distribution on the exposed surface for each drive voltage is measured. Then, the light amount corresponding to each channel is obtained from the light amount distribution of each drive voltage, and the light amount-voltage characteristic of each channel is obtained. Then, based on the obtained light amount-voltage characteristic, the ON side drive voltage and the OFF side drive voltage of each channel are determined.

JP 2016-133751 A

However, in the above method, the light intensity distribution is measured with a drive voltage applied to all channels simultaneously. Therefore, even if the light intensity corresponding to the position of a specific channel is obtained from the light intensity distribution, the obtained light intensity may include not only the light intensity from the specific channel, but also the light intensity from surrounding channels. In such cases, it is difficult to accurately obtain the light intensity of each channel, and therefore difficult to accurately determine the on-side and off-side drive voltages for each channel.

It is possible to obtain the light intensity-voltage characteristics of each channel with high accuracy by driving all channels one by one and measuring the light intensity. However, with this method, it is necessary to repeat the measurement for each channel, so it takes a huge amount of time to determine the drive voltage.

The object of the present invention is to provide a technology that can efficiently and accurately adjust the parameters for driving each channel in a spatial light modulator.

To solve the above problem, the first aspect is a control method for controlling a spatial light modulator capable of spatially modulating light on a channel-by-channel basis according to input parameters, and includes a measurement step of measuring a first amount of light corresponding to the second channel while turning on a first channel and a second channel and turning off one or more intermediate channels located between the first channel and the second channel, and measuring a second amount of light corresponding to the second channel while turning on the second channel and turning off the first channel and the one or more intermediate channels; a reference interval determination step of determining a reference interval that is the interval between the first channel and the second channel when the first amount of light and the second amount of light measured by the measurement step match under a predetermined criterion; and a parameter determination step of determining parameters for driving the multiple channels based on the change in light amount when multiple channels located at the reference interval determined by the reference interval determination step are simultaneously turned on while changing parameters.

The second aspect is a method for controlling a spatial light modulator according to the first aspect, in which the channel is a diffraction grating type element in which a movable member is displaced relative to a fixed member in response to input parameters.

The third aspect is a method for controlling a spatial light modulator according to the first or second aspect, in which the parameter determination step includes a step of determining parameters that minimize the amount of light for each of the channels.

A fourth aspect is a method for controlling a spatial light modulator according to the first or second aspect, in which the parameter determination step includes a step of determining parameters that maximize the amount of light for each of the channels.

The fifth aspect is a method for controlling a spatial light modulator according to the first or second aspect, further comprising: a first reference interval determination step for determining a first reference interval, which is the interval when the first light amount and the second light amount match under a predetermined criterion, with the second channel positioned at an interval on one side of the first direction relative to the first channel; and a second reference interval determination step for determining a second reference interval, which is the interval when the first light amount and the second light amount match under a predetermined criterion, with the second channel positioned at an interval on the other side of the first direction relative to the first channel, and the reference interval determination step includes a step of determining the reference interval using the first reference interval and the second reference interval.

The sixth aspect is a control device that controls a spatial light modulator capable of spatially modulating light on a channel-by-channel basis according to input parameters, and includes a light amount acquisition unit that acquires a first amount of light corresponding to the second channel while turning on a first channel and a second channel and turning off one or more intermediate channels located between the first channel and the second channel, and acquires a second amount of light corresponding to the second channel while turning on the second channel and turning off the first channel and the one or more intermediate channels; a reference interval determination unit that determines a reference interval that is the interval between the first channel and the second channel when the first amount of light and the second amount of light acquired by the light amount acquisition unit match under a predetermined criterion; and a parameter determination unit that determines parameters for controlling the multiple channels based on a change in light amount when multiple channels located at the reference interval determined by the reference interval determination unit are simultaneously turned on with parameters changed.

The seventh aspect is an exposure device that includes a light source, a spatial light modulator that spatially modulates light from the light source, an irradiation unit that irradiates an object with the light modulated by the spatial light modulator, and a control device of the sixth aspect that controls the spatial light modulator.

According to the spatial light modulator control method of the first to fifth aspects, a reference interval that can prevent the light amount from affecting each other between channels is specified, and multiple channels located at each reference interval are simultaneously driven. This makes it possible to drive multiple channels simultaneously and obtain the light amount from each channel with high accuracy. Therefore, parameters for each channel can be determined with high accuracy and efficiency.

The second aspect of the spatial light modulator control method allows for efficient determination of parameters for controlling a diffraction grating type channel.

The spatial light modulator control method of the third aspect makes it possible to appropriately determine the parameters that minimize the amount of light for each channel.

The spatial light modulator control method of the fourth aspect makes it possible to appropriately determine the parameters that maximize the amount of light for each channel.

The spatial light modulator control method of the fifth aspect makes it possible to determine an appropriate reference measurement interval even when the interference in the amount of light between channels is directional.

The spatial light modulator control device of the sixth aspect identifies a reference interval that can avoid interference between channels, and simultaneously drives multiple channels located at each reference interval, thereby enabling accurate and efficient determination of parameters for controlling each channel.

1 is a front view that shows a schematic diagram of an exposure apparatus that includes a control device according to an embodiment. FIG. 1 is a cross-sectional view of a diffractive optical element. FIG. 1 is a cross-sectional view of a diffractive optical element. FIG. 2 is a diagram showing the configuration of an observation optical system of the exposure apparatus shown in FIG. 1 . 2 is a block diagram showing a control device of the exposure apparatus shown in FIG. 1 . 1A and 1B are diagrams illustrating a conventional method for determining an appropriate driving range. FIG. 13 is a diagram showing a light amount distribution (simulation) when channels (1) and (6) that are separated by five channels are driven. FIG. 13 is a diagram showing a light amount distribution (simulation) when channels (1) and (18) that are 17 channels apart are driven. FIG. 11 is a diagram showing a process flow for determining a reference interval. 13 is a diagram showing a change in the ratio of a first light amount to a second light amount with respect to the interval between channels. FIG. FIG. 11 is a diagram showing a process flow for determining an appropriate driving range for each channel. FIG. 12 is a diagram showing channels driven in step S21 (light amount-voltage characteristic acquisition process) shown in FIG. 11;

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Note that the components described in this embodiment are merely examples, and are not intended to limit the scope of the present invention to those components alone. In the drawings, the dimensions and numbers of each part may be exaggerated or simplified as necessary for ease of understanding.

1. Embodiment
1 is a front view showing a schematic diagram of an exposure apparatus 100 including a control apparatus 90 according to an embodiment. The exposure apparatus 100 is an apparatus that draws a pattern by irradiating light onto an upper surface of a substrate W on which a layer of a photosensitive material such as a resist has been formed. The substrate W is, for example, a semiconductor substrate, a printed circuit board, a substrate for a color filter, a glass substrate for a flat panel display used in a weather display device or a plasma display device, or a substrate for an optical disk.

The exposure apparatus 100 includes a main body frame 101. Inside the main body frame 101, the exposure apparatus 100 includes a processing area 102 and a transfer area 103. The processing area 102 includes a stage 10, a stage movement mechanism 20, and an optical unit U, and the transfer area 103 includes a transport device 70 that loads and unloads the substrate W.

The exposure apparatus 100 includes a control device 90. The control device 90 is electrically connected to each part of the exposure apparatus 100 and controls the operation of each part. The control device 90 is configured, for example, by a computer including a processor such as a CPU and a storage unit 99 such as a RAM that is electrically connected to the processor. The processor executes various processes by running programs stored in the storage unit 99.

A cassette placement section 104 for placing a cassette C is disposed adjacent to the transfer area 103. The transport device 70 removes unprocessed substrates W contained in the cassette C and transports them into the processing area 102, and also transports processed substrates W from the processing area 102 and stores them in the cassette C. The cassette C is transferred to and from the cassette placement section 104 by an external transport device (not shown). The transport device 70 transports substrates W in and out under the control of the control device 90.

The stage 10 has a rectangular shape when viewed from above. The stage 10 has an upper surface that holds the substrate W. The substrate W is placed in a horizontal position on the upper surface of the stage 10. A number of suction holes are formed in the upper surface of the stage 10. The stage 10 is capable of fixing the substrate W to the upper surface of the stage 10 by applying negative pressure (suction pressure) to the suction holes.

The stage movement mechanism 20 is a mechanism that moves the stage 10 in the main scanning direction (Y-axis direction), the sub-scanning direction (X-axis direction), and the rotation direction (rotation direction around the Z axis (θ-axis direction)). The stage movement mechanism 20 has a support plate 22, a sub-scanning mechanism 23, a base plate 24, and a main scanning mechanism 25.

The support plate 22 rotatably supports the stage 10. The base plate 24 supports the support plate 22 and the sub-scanning mechanism 23. The sub-scanning mechanism 23 moves the support plate 22 in the sub-scanning direction. The main scanning mechanism 25 moves the base plate 24 in the main scanning direction. The operations of the sub-scanning mechanism 23 and the main scanning mechanism 25 are controlled by a control device 90. The sub-scanning mechanism 23 and the main scanning mechanism 25 include a ball screw mechanism equipped with a rotary motor and a ball screw, or a linear motor, etc.

The optical unit U has one or more optical heads 4. The optical heads 4 are capable of modulating laser light based on strip data corresponding to the drawing pattern. In this example, two optical heads 4 are arranged along the X-axis direction.

The optical unit U has one or more light irradiation units 5. Each light irradiation unit 5 irradiates a corresponding optical head 4 with laser light. In detail, the light irradiation unit 5 has a laser driving unit 51, a laser oscillator 52, and an illumination optical system 53. When the laser driving unit 51 is operated, the laser oscillator 52 emits laser light to the illumination optical system 53. The illumination optical system 53 changes the magnification of the incident laser light and homogenizes the light amount distribution. The laser light emitted from the illumination optical system 53 is irradiated to the optical head 4.

The optical head 4 has a spatial light modulator. The spatial light modulator spatially modulates the laser light irradiated from the light irradiation unit 5 on a channel-by-channel basis. The optical head 4 reflects the modulated laser light onto the substrate W moving directly below the optical head 4. In this way, the drawing pattern is exposed onto the unprocessed substrate W. The optical head 4 is an example of an "irradiation unit."

The spatial modulator modulates the laser light using a diffractive optical element 410 such as a GLV. Figure 2 is a cross-sectional view of the diffractive optical element 410. Figure 3 is a cross-sectional view of the diffractive optical element 410.

As shown in FIG. 2, the diffractive optical element 410 has a bottom electrode 411, a plurality of fixed ribbons 412, and a plurality of movable ribbons 413. The bottom electrode 411 is flat. The fixed ribbons 412 and the movable ribbons 413 are arranged alternately in one direction on the bottom electrode 411. Each fixed ribbon 412 and each movable ribbon 413 faces the bottom electrode 411. The fixed ribbons 412 and the movable ribbons 413 each have a fixed reflecting surface 412S and a movable reflecting surface 413S, which are finished to a flat surface and reflect light.

The fixed ribbon 412 is arranged to be a predetermined distance away from the bottom electrode 411. The movable ribbon 413 is arranged to be movable in a direction toward and away from the bottom electrode 411 depending on the applied voltage (driving voltage).

The amount of displacement of the movable ribbon 413 depends on the magnitude of the potential difference generated between the movable ribbon 413 and the bottom electrode 411 by the driving voltage. As shown in FIG. 3, the diffractive optical element 410 is designed so that when no driving voltage is applied to the movable ribbon 413, that is, when no voltage is applied, the height difference d between the fixed reflecting surface 412S and the movable reflecting surface 413S is approximately zero. When the height difference d is zero, the light reflected by the fixed reflecting surface 412S and the light reflected by the movable reflecting surface 413S are in phase, and these lights are emitted from the diffractive optical element 410 as regular reflection light (zeroth-order diffracted light) L0.

When the wavelength of the incident light _IL is λ, if the optical path difference (=2d) between the light reflected by the movable reflecting surface 413S and the light reflected by the fixed reflecting surface 412S is an integer multiple of the wavelength λ (=n×λ (n is an integer equal to or greater than 0)), the light reflected by the fixed reflecting surface 412S and the light reflected by the movable reflecting surface 413S will be in phase. Therefore, in this case as well, these lights are emitted from the diffractive optical element 410 as specularly reflected light L0.

Also, as shown in FIG. 3, when the optical path difference (= 2d) between the light reflected by the movable reflecting surface 413S and the light reflected by the fixed reflecting surface 412S is an odd multiple (= (2n + 1) · λ/2) of half the wavelength (= λ/2), the light reflected by the fixed reflecting surface 412S and the light reflected by the movable reflecting surface 413S are in opposite phase to each other and cancel each other out. Therefore, the reflected light in the vertical direction is not emitted, and light with a different optical path length difference is emitted in an oblique direction, that is, first-order or higher diffracted light Lg is emitted.

The exposure apparatus 100 performs drawing by irradiating the substrate W with the zero-order diffracted light emitted from the diffractive optical element 410. Therefore, in terms of the exposure beam emitted toward the substrate W, when the diffractive optical element 410 is in the state shown in FIG. 2 (total reflection state), for example, the exposure beam is emitted, and when the diffractive optical element 410 is in the state shown in FIG. 3, the exposure beam is not emitted. In the following description, in order to make it easier to understand the state of light emission, the state shown in FIG. 2 will be referred to as the "on state" and the state shown in FIG. 3 as the "off state". The on state is a state in which light is irradiated from the diffractive optical element 410 toward the substrate W, and the off state is a state in which the light is not irradiated. These are distinguished by the magnitude of the drive voltage applied to the movable ribbon 413.

The driving voltage can be set individually for each movable ribbon 413. Therefore, it is possible to produce an on state and an off state for each ribbon pair consisting of one movable ribbon 413 and an adjacent fixed ribbon 412. In the following explanation, the smallest unit for controlling on/off consisting of a pair is called a "channel". In the drawings, "channel" may be abbreviated to "ch". In addition, when distinguishing between multiple channels, numbers starting from 1 that are assigned sequentially from one side of the arrangement to the other are written in parentheses, such as "ch(1)".

In the optical head 4, the diffractive optical element 410 is arranged so that the normal of its reflecting surface is inclined with respect to the optical axis OA, and the light emitted from the illumination optical system 53 is irradiated onto the diffractive optical element 410. The state of each channel of the diffractive optical element 410 is then switched by the control device 90 according to the drawing data, thereby modulating the laser light incident on the diffractive optical element 410. One pixel represented by the drawing data corresponds to one or more channels. By appropriately tuning the driving voltage according to the angle of incidence of the light on the diffractive optical element 410 to adjust the amount of displacement of the movable ribbons 413, it is possible to realize an ON state in which the zeroth-order diffracted light is emitted and an OFF state in which it is not emitted.

The diffractive optical element 410 is irradiated with laser light that has been homogenized by the illumination optical system 53. In other words, the light emitted from the laser oscillator 52 is shaped by the illumination optical system 53 into a linear line beam light (light with a linear beam cross section) with a uniform intensity distribution, and is irradiated onto the effective area of the diffractive optical element 410. Here, the effective area is the area in which the diffractive optical element 410 can perform modulation on the incident light. The long axis direction of the line beam light is set to the R direction, which is the ribbon arrangement direction in the diffractive optical element 410.

Figure 4 is a diagram showing the configuration of the observation optical system 80 of the exposure device 100 shown in Figure 1. As shown in Figure 5, the observation optical system 80 is disposed on the side of the stage 10. The observation optical system 80 is a device for receiving the laser light emitted from the optical head 4 and observing the light of the laser light.

The observation optical system 80 includes a dummy substrate 801, an observation camera 803, a case 804, a support frame 805, a beam splitter 806, and a light amount detector 807. The dummy substrate 801 is a light-transmitting substrate formed into a flat plate shape, for example, from quartz glass. The dummy substrate 801 is placed on top of the case 804.

An observation camera 803 is disposed below the dummy substrate 801 via a beam splitter 806. The observation camera 803 captures, for example, laser light incident from the dummy substrate 801 via the beam splitter 806. The dummy substrate 801 and the observation camera 803 are each attached to a case 804 and integrated together. The focal position of the optical system of the observation camera 803 is adjusted to the upper surface 801S of the dummy substrate 801.

The case 804 is supported by a support frame 805 erected on the support plate 22 so that it can be raised and lowered freely. The movement of the case 804 in the vertical direction can be controlled by the control device 90. In this way, the observation optical system 80 and the dummy substrate 801 move integrally with the stage 10 in the horizontal direction (X direction and Y direction), but can move independently of the stage 10 in the vertical direction (Z direction).

A portion of the laser light that passes through the dummy substrate 801 and enters the observation optical system 80 is redirected by the beam splitter 806 and enters the light amount detector 807 provided in the case 804. A focusing optical system (not shown) is provided between the beam splitter 806 and the light amount detector 807. The focusing optical system focuses the light split by the beam splitter 806 and makes it enter the light amount detector 807.

The light amount detector 807 outputs an electrical signal according to the amount of light incident on the light receiving surface. The light amount detector 807 has, for example, a photodiode. The light amount detector 807 is used for light amount measurement, which will be described later. When the light amount detector 807 is configured as a line sensor, the line beam light is scanned by the light amount detector 807 by moving the stage 10 in a direction along the line beam light. This makes it possible to measure the light amount distribution in the line beam light.

Figure 5 is a block diagram showing the control device 90 of the exposure apparatus 100 shown in Figure 1. The control device 90 has a processor such as a CPU, and a storage unit 99 composed of a memory such as a RAM electrically connected to the processor and a storage device such as a hard disk. The processor functions as an illumination control unit 91, a stage control unit 93, a drawing control unit 95, and a driver 951 by executing a control program stored in the storage unit 99. Note that at least some of the functions of the control device 90 may be realized in hardware by a dedicated circuit.

The illumination control unit 91 controls the light irradiation unit 5 of the optical unit U to cause the light irradiation unit 5 to emit a line beam of light. The stage control unit 93 controls the stage movement mechanism 20 to move the stage 10 relative to the optical head 4. The drawing control unit 95 controls the driver 951 based on the drawing recipe stored in the memory unit 99 to apply a driving voltage from the driver 951 to each movable ribbon 413 of the diffractive optical element 410. As a result, the control device 90 causes the diffractive optical element 410 to modulate the line beam of light so as to correspond to the drawing pattern. In addition, the drawing control unit 95 determines an appropriate range of the driving voltage (hereinafter referred to as the "appropriate driving range") as described below.

<Light intensity-voltage characteristics of diffractive optical elements>
6A and 6B are diagrams for explaining a conventional method for determining an appropriate driving range.
6A is a diagram showing the light quantity distribution for a plurality of applied voltages V1 to V5. In Fig. 6A, the horizontal axis indicates the pixel position (corresponding to the position of each channel) on the exposure surface, and the vertical axis indicates the light quantity (light intensity). Fig. 6B is a diagram showing the change in light quantity with respect to the drive voltage (hereinafter referred to as "light quantity-voltage characteristic") for the channel corresponding to the specific position X shown in Fig. 6A.

As shown in FIG. 6(A), in order to obtain the light intensity voltage characteristics of each channel, driving voltages V1 to V5 are applied in stages to all channels of the diffractive optical element 410, and the light intensity distribution for each driving voltage is measured. Then, from the obtained light intensity distribution, the voltage Va when the light intensity is maximum (on state) and the voltage Vb when the light intensity is minimum (off state) are determined for each channel, as shown in FIG. 6(B).

However, with this method, the light intensity is measured with a drive voltage applied to all channels, so that light interference occurs between nearby channels, causing the light intensity to affect each other. For this reason, it is difficult to accurately obtain the light intensity of each channel from the light intensity distribution in Figure 6 (A). Therefore, even if the light intensity-voltage characteristic of a specific channel is obtained, as shown in Figure 6 (B), it is possible that it may deviate from the actual light intensity-voltage characteristic.

Figure 7 shows the light intensity distribution (simulation) when channels (1) and (6), which are five channels apart, are driven. In Figure 7, curve C11 shows the light intensity distribution when channels (1) and (6) are turned on and the others are turned off. Curve C12 shows the light intensity distribution when channel (1) is turned off and only channel (6) is turned on.

As shown in FIG. 7, as is clear from curves C11 and C12, when channel (6) is turned on and channel (1) is switched from on to off, the light intensity of channel (6) fluctuates (here, decreases). This shows that it is difficult to accurately measure the light intensity of each channel when they are driven simultaneously because the light intensity of channels that are five channels apart affects each other.

Figure 8 shows the light intensity distribution (simulation) when channels (1) and (18), which are 17 channels apart, are driven. In Figure 8, curve C21 shows the light intensity distribution when channels (1) and (18) are turned on and the other channels are turned off. Curve C22 shows the light intensity distribution when channel (1) is turned off and only channel (18) is turned on.

As shown in Figure 8, when channel (18) is turned on and channel (1) is switched from on to off, the amount of light in channel (18) hardly changes. This shows that the amount of light in two channels that are 17 channels apart hardly affects each other, so that the amount of light in each channel can be measured with high accuracy even when they are driven simultaneously.

As described above, by driving multiple channels at appropriate intervals, the amount of light for each channel can be measured with high accuracy. Therefore, the drawing control unit 95 first determines the interval between channels (hereinafter referred to as the "reference interval") at which the light amounts of the channels do not affect each other even when driven simultaneously.

Figure 9 is a diagram showing a process flow for determining the reference interval. First, the drawing control unit 95 turns off all channels (step S11). Specifically, in step S11, the drawing control unit 95 darkens the light from all channels by, for example, applying the maximum voltage that can be applied to all channels. From this state, the drawing control unit 95 turns on only channel (1) and channel (1+x) that is separated from channel (1) by an interval x (step S12). Note that "x" is an integer of 2 or more. The drawing control unit 95 performs light intensity measurement with only channel (1) and channel (1+x) turned on. As a result, the drawing control unit 95 obtains the first light intensity (peak value) at the position corresponding to channel (1+x) from the obtained light intensity distribution (step S13).

Then, the drawing control unit 95 turns off channel (1) and turns on only channel (1+x) (step S14). Then, the drawing control unit 95 performs light intensity measurement and obtains the second light intensity (peak value) at the position corresponding to channel (1+x) from the obtained light intensity distribution (step S15).

Furthermore, the drawing control unit 95 determines whether the first light amount and the second light amount acquired in steps S13 and S15 match under a predetermined criterion (step S16). As the predetermined criterion, a threshold value indicating the maximum difference or error allowed to satisfy the match criterion is set in advance. In addition, the drawing control unit 95 may calculate a ratio R of the first light amount to the second light amount (=first light amount/second light amount) as an index for the determination. In this case, if the ratio R satisfies 1-α<R<1+α (α is a threshold), it is determined that there is a match, and if it does not, it is determined that there is a mismatch. Alternatively, the drawing control unit 95 may calculate a difference between the first light amount and the second light amount as an index for the determination. In this case, if the difference is equal to or less than a predetermined threshold, it is determined that there is a match, and otherwise it is determined that there is a mismatch.

If the first light amount and the second light amount do not match (No in step S16), the drawing control unit 95 increases the interval x by 1 (step S17) and executes steps S11 to S15 again. On the other hand, if the first light amount and the second light amount match (Yes in step S16), the drawing control unit 95 stores the interval x at that point in time in the memory unit 99 as the reference interval xs (step S17). In this way, by increasing the interval x by 1 and searching for the interval x at which the first light amount and the second light amount match, the smallest reference interval xs can be determined.

In the process flow shown in FIG. 9, channel (1) corresponds to the "first channel", channel (1+x) corresponds to the "second channel", and the channel between channel (1) and channel (1+x) corresponds to the "intermediate channel". Steps S12 to S15 correspond to a "measurement process" for measuring the first light amount and the second light amount. Step S16 corresponds to a "reference interval determination process" for determining the reference interval. The drawing control unit 95 corresponds to a "light amount acquisition unit" and a "reference interval determination unit".

Figure 10 is a diagram showing the change in the ratio R of the first light amount to the second light amount with respect to the distance x between channels. In Figure 10, the horizontal axis represents the distance x, and the vertical axis represents the ratio R. In the example shown in Figure 10, the distance x is increased by 1 from the initial value of 5, and the ratio R for each distance x is found. In this example, when the distance x is 17, the ratio R is approximately 1. For this reason, the reference distance is set to 17.

When the first light amount and the second light amount are equal, it means that the light from channel (1) does not affect the light amount of channel (1+x). Therefore, even if multiple channels separated by a reference interval xs are driven simultaneously, the light amount of each channel can be measured with high accuracy.

Figure 11 is a diagram showing a process flow for determining the appropriate driving range of each channel. As shown in Figure 11, the drawing control unit 95 acquires the light intensity voltage characteristics of each of multiple channels (channel (m), channel (m + xs), channel (m + 2 xs) ... (m is an integer between 1 and xs. The initial value of m is 1)) located at a predetermined reference interval xs (step S21). That is, the drawing control unit 95 changes the driving voltage in steps from the minimum voltage (e.g., 0 V) to the maximum voltage and measures the light intensity distribution under each driving voltage. Then, the drawing control unit 95 acquires the light intensity of the multiple channels at the reference interval from the light intensity distribution of each driving voltage. This acquires the light intensity voltage characteristics of the multiple channels at the reference interval.

Next, the drawing control unit 95 judges whether the light amount-voltage characteristics for all channels have been acquired (step S22). If the light amount-voltage characteristics for all channels have not been acquired (No in step S22), the drawing control unit 95 increments m by 1 (step S23) and executes step S21 again. This allows the light amount-voltage characteristics of the adjacent channels to be acquired from the channels whose light amount-voltage characteristics have been acquired earlier. If the light amount-voltage characteristics for all channels have been acquired (Yes in step S22), the drawing control unit 95 determines the appropriate driving range for each channel (step S23). That is, the off-side driving voltage and the on-side driving voltage for each channel are determined. Step S24 corresponds to a "parameter determination step" for determining parameters for controlling each channel. The drawing control unit 95 corresponds to a "parameter determination unit".

12 is a diagram showing the channels driven in step S21 (light quantity voltage characteristic acquisition process) shown in FIG. 11. FIG. 12(A) shows the channels driven in step S21 executed the first time, and FIG. 12(B) shows the channels driven in step S21 executed the second time. When the reference interval xs is 17, as shown in FIG. 12(A), in the first step S21, channel (1) is driven in order, followed by channel (18), channel (35), etc., to acquire their voltage light quantity characteristics. Also, as shown in FIG. 12(B), in the second step S21, channel (19), channel (36), etc. are driven in order, followed by channel (2). In other words, the multiple channels driven the second time are adjacent to each channel driven the first time.

As described above, in this embodiment, multiple channels separated by a reference interval xs are driven simultaneously to obtain the light intensity voltage characteristics (change in light intensity with respect to drive voltage) of multiple channels. This makes it possible to avoid the influence of light intensity between channels, and therefore the light intensity voltage characteristics of each channel can be obtained with high accuracy. Therefore, the appropriate drive range of each channel can be appropriately determined. In addition, in this case, the light intensity voltage characteristics of all channels can be obtained by repeating the measurement of the light intensity distribution the same number of times as the reference interval xs. Therefore, the number of measurements can be significantly reduced compared to the case where the light intensity voltage characteristics are obtained by driving each channel. For example, when there are 8000 channels, 8000 measurements are required to drive each channel, but according to this embodiment, when the reference interval xs is 17, only 17 measurements are required. Therefore, the appropriate drive range of each channel can be efficiently determined.

2. Modified Examples
Although the embodiment has been described above, the present invention is not limited to the above, and various modifications are possible.

For example, in the process flow shown in FIG. 9, when determining the reference interval xs, one channel is fixed to channel (1), but it may be a channel other than channel (1).

In the process flow shown in FIG. 9, the reference interval xs is determined by assuming that the second channel is channel (1+x) located at a distance x on one side of the arrangement direction (first direction) from the first channel, channel (1). However, the reference interval xs may also be determined by assuming that the second channel is located at a distance x on the other side of the arrangement direction from the first channel. For example, the first channel may be channel (8000) and the second channel may be channel (8000-x).

The drawing control unit 95 may also determine a reference interval xs1 (first reference interval) by assuming that the second channel is located on one side of the arrangement direction relative to the first channel, and may further determine a reference interval xs2 (second reference interval) by assuming that the second channel is located on the other side of the arrangement direction relative to the first channel. The drawing control unit 95 may then use the reference intervals xs1 and xs2 to determine the final reference interval xs. For example, the drawing control unit 95 may set the average of the reference intervals xs1 and xs2 as the final reference interval xs.

In addition, in the above embodiment, a drive voltage for turning on and off the zeroth-order diffracted light is determined for each channel, but a drive voltage for turning on and off other than the zeroth-order diffracted light may be determined. For example, a drive voltage for turning on and off the first-order diffracted light may be determined.

In addition, in the above embodiment, the spatial light modulator is described as using a diffractive optical element such as a GLV, but it may also be using other MEMS (Micro Electro Mechanical Systems) such as a DMD.

Although this invention has been described in detail, the above description is merely illustrative in all respects and does not limit the invention. It is understood that countless variations not illustrated can be envisioned without departing from the scope of this invention. The configurations described in the above embodiments and variations can be combined or omitted as appropriate as long as they are not mutually contradictory.

4 Optical head (illumination unit)
90 Control device 95 Drawing control unit 100 Exposure device 410 Diffractive optical element 412 Fixed ribbon 413 Movable ribbon

Claims (7)

A method for controlling a spatial light modulator capable of spatially modulating light on a channel-by-channel basis in accordance with input parameters, comprising:
a measuring step of measuring a first amount of light corresponding to the second channel while turning on a first channel and a second channel and turning off one or more intermediate channels located between the first channel and the second channel, and measuring a second amount of light corresponding to the second channel while turning on the second channel and turning off the first channel and the one or more intermediate channels;
a reference interval determination step of determining a reference interval between the first channel and the second channel when the first light amount and the second light amount measured in the measurement step match under a predetermined criterion;
a parameter determination step of determining parameters for driving the plurality of channels based on a change in light amount when the plurality of channels positioned at the reference interval determined by the reference interval determination step are simultaneously turned on while changing parameters;
A method for controlling a spatial light modulator, comprising: 2. A method for controlling a spatial light modulator according to claim 1, comprising the steps of:
A method for controlling a spatial light modulator, wherein the channel is a grating type element in which a movable member is displaced relative to a fixed member in response to input parameters. A method for controlling a spatial light modulator according to claim 1 or 2, comprising the steps of:
A method for controlling a spatial light modulator, wherein the parameter determination step includes a step of determining, for each of the channels, a parameter that minimizes the amount of light. A method for controlling a spatial light modulator according to claim 1 or 2, comprising the steps of:
A method for controlling a spatial light modulator, wherein the parameter determination step includes a step of determining, for each of the channels, a parameter that maximizes the amount of light. A method for controlling a spatial light modulator according to claim 1 or 2, comprising the steps of:
a first reference interval determination step of determining a first reference interval, which is the interval when the first light amount and the second light amount are equal under a predetermined criterion, with the second channel being positioned at an interval on one side in a first direction with respect to the first channel;
a second reference interval determination step of determining a second reference interval, which is the interval when the first light amount and the second light amount are equal under a predetermined criterion, with the second channel being positioned at an interval on the other side in the first direction with respect to the first channel;
Further comprising:
A method for controlling a spatial light modulator, wherein the reference interval determination step includes a step of determining the reference interval using the first reference interval and the second reference interval. A control device for controlling a spatial light modulator capable of spatially modulating light on a channel-by-channel basis in accordance with input parameters,
a light amount acquiring unit that acquires a first amount of light corresponding to the second channel while turning on a first channel and a second channel and while turning off one or more intermediate channels located between the first channel and the second channel, and acquires a second amount of light corresponding to the second channel while turning on the second channel and while turning off the first channel and the one or more intermediate channels;
a reference interval determination unit that determines a reference interval between the first channel and the second channel when the first light amount and the second light amount acquired by the light amount acquisition unit match under a predetermined criterion;
a parameter determination unit that determines parameters for controlling the plurality of channels based on a change in light amount when the plurality of channels positioned at the reference interval determined by the reference interval determination unit are simultaneously turned on while changing parameters;
A control device comprising: An exposure apparatus comprising:
A light source;
a spatial light modulator that spatially modulates light from a light source;
an illumination unit that illuminates an object with the light modulated by the spatial light modulator;
A control device according to claim 6 for controlling the spatial light modulator;
An exposure apparatus comprising:

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