JP2016133751A - Control device of diffraction optical element and control method thereof, as well as drawing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily determine a driving range suitable for a diffraction optical element without actually measuring characteristics of an amount of diffraction light with respect to an input parameter, and to efficiently control the diffraction optical element.SOLUTION: A control device of a diffraction optical element comprises: a light-amount measurement unit that actually measures an amount of light of diffraction light to be reflected by the diffraction optical element as an amount of reflection light when making light incident upon the diffraction optical element; a light-amount calculation unit that calculates the amount of reflection light on the basis of a characteristic of the amount of diffraction light indicative of a change in the amount of reflection light relative to a change in parameters; and a range determination unit that determines a driving range on the basis of a difference between the amount of reflection light actually measured by the light-amount measurement unit under the same condition and the amount of reflection light calculated by the light-amount calculation unit thereunder, and the characteristic of the amount of diffraction light.SELECTED DRAWING: Figure 1

Description

  The present invention is controlled by a control technique for controlling a diffractive optical element that forms a diffraction grating by driving the movable member so that the movable member is displaced with respect to the fixed member in accordance with an input parameter, and is modulated by the diffractive optical element. The present invention relates to a drawing apparatus that draws light by irradiating an object to be drawn.

  For example, as a method for forming a pattern on a substrate such as a semiconductor wafer or a glass substrate, there is a technique of performing drawing by light irradiation. In this technique, a substrate on which a photosensitive layer is formed is used as an object to be drawn, and the photosensitive layer is exposed by irradiating the object to be drawn with light modulated based on drawing data. As a spatial light modulator for performing such light modulation, for example, a diffraction grating type optical element (hereinafter referred to as “diffractive optical element”) such as GLV (Grating Light Valve: registered trademark of Silicon Light Machines, USA). Can be suitably applied.

  In this diffractive optical element, movable members that are movable with respect to the reference surface and fixed members that are fixed with respect to the reference surface are alternately arranged along the reference surface. The light incident on the diffractive optical element is reflected by the movable member and the fixed member. At this time, when the movable member is displaced with respect to the fixed member, a diffraction grating is formed by these members, and diffracted light is emitted from the diffractive optical element. That is, in such a diffractive optical element, it is possible to adjust the amount of diffracted light from the diffractive optical element by controlling the input parameter given to the movable member to displace the movable member to the fixed member.

  For example, in the apparatus described in Patent Document 1, a control voltage is applied to the movable member as an input parameter for controlling the amount of displacement of the movable member with respect to the reference electrode. An electrostatic force is generated by the potential difference between the movable member and the reference electrode due to the voltage application, and the movable member is displaced to the reference electrode side. In addition, the amount of displacement of the movable member differs according to the applied voltage, and the depth of the grating changes. As a result, the amount of 0th-order light emitted from the diffractive optical element (hereinafter referred to as “0th-order diffracted light amount”) changes according to the applied voltage.

JP 2014-106513 A

  The diffractive optical element has, for example, a zero-order diffracted light quantity characteristic (hereinafter referred to as “IV characteristic”) with respect to an applied voltage as shown by a solid line in FIG. In other words, the 0th-order diffracted light quantity changes according to the applied voltage, and is minimized at the voltage Vmin and maximized at the voltage Vmax. Therefore, for example, when the diffractive optical element is used as a spatial light modulator, the exposure adjustment adjustment resolution, that is, the dynamic range is increased by driving the diffractive optical element while changing the applied voltage within the range from the voltage Vmin to the voltage Vmax. can do. In this specification, the range in which the parameter for driving the diffractive optical element is changed is referred to as “driving range” in this specification.

  The diffractive optical element is designed so as to exhibit a desired IV characteristic (for example, an IV characteristic indicated by a solid line in FIG. 1), and is manufactured according to the design data. However, the IV characteristics may vary from product to product due to manufacturing variations. In this case, when the input parameter is changed within the driving range (Vmin to Vmax), the dynamic range is narrowed and the utilization efficiency of the diffractive optical element is lowered even though the IV characteristics are different. . Therefore, in order to increase the utilization efficiency of the diffractive optical element, it is necessary to actually measure the IV characteristic for each product and to newly set a driving range based on the actual measurement. Such a problem is not unique to the 0th-order light, and is exactly the same when other diffracted light components such as the 1st-order diffracted light are used. As described above, in order to control the diffractive optical element with high utilization efficiency, it is necessary to actually measure the diffracted light quantity characteristic with respect to the input parameter, that is, the diffracted light quantity characteristic for each product.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and by easily determining a driving range suitable for driving a diffractive optical element without actually measuring the characteristics of the amount of diffracted light with respect to input parameters, the diffractive optical element is efficiently controlled. It is an object of the present invention to provide a technique that can be performed and a drawing apparatus that can perform drawing with a high dynamic range using the technique.

  According to a first aspect of the present invention, in a diffractive optical element that forms a diffraction grating by driving a movable member so that the movable member is displaced with respect to the fixed member in accordance with an input parameter, the parameter is varied within the driving range. A control device for controlling the formation of the diffraction grating, and a light quantity measuring unit for actually measuring the quantity of diffracted light reflected by the diffractive optical element when the light is incident on the diffractive optical element as a reflected quantity, and for changing the parameter A light amount calculation unit that calculates a reflected light amount based on a diffracted light amount characteristic indicating a change in reflected light amount, a difference between a reflected light amount actually measured by a light amount measurement unit under the same conditions and a reflected light amount calculated by a light amount calculation unit, and And a range determining unit that determines a driving range based on the diffracted light quantity characteristic.

  According to a second aspect of the present invention, in the diffractive optical element that forms the diffraction grating by driving the movable member so that the movable member is displaced with respect to the fixed member in accordance with the input parameter, the parameter is within the driving range. A control method that controls the formation of a diffraction grating by changing the amount of diffracted light reflected by the diffractive optical element when light is incident on the diffractive optical element. A step of measuring the amount of reflected light based on a diffracted light amount characteristic indicating a change in the amount of reflected light with respect to a parameter change in the diffractive optical element, and a step of obtaining a difference between the actually measured amount of reflected light and the calculated amount of reflected light And a step of determining a drive range based on the difference and the diffracted light quantity characteristic.

  Furthermore, a third aspect of the present invention is a drawing apparatus that draws a drawing object by irradiating modulated light, and is movable so that the movable member is displaced with respect to the fixed member in accordance with the input parameter. A diffractive optical element that drives a member to form a diffraction grating, an illumination unit that allows light to enter the diffractive optical element, and a parameter that is variable within the driving range and is input to the diffractive optical element and reflected by the diffractive optical element. A modulation unit that modulates light by controlling the amount of diffracted light emitted in a direction toward the drawing object, a light amount measurement unit that measures the amount of diffracted light, and drawing with light modulated by the modulation unit A control unit that adjusts the driving range in advance, and when the amount of diffracted light reflected by the diffractive optical element is reflected when the light is incident on the diffractive optical element, the control unit reflects the change in the parameter. Time to show the change in light intensity Drive based on the light amount calculation unit that calculates the reflected light amount based on the light amount characteristic, the difference between the reflected light amount actually measured by the light amount measurement unit under the same conditions and the reflected light amount calculated by the light amount calculation unit, and the diffracted light amount characteristic And a range determining unit that determines the range.

  According to this invention, as described later, paying attention to the technical matter that the diffracted light quantity characteristic shifts due to manufacturing variations of the diffractive optical element, the drive range is determined without measuring the diffracted light quantity characteristic for each product of the diffractive optical element. doing. Therefore, the diffractive optical element can be easily and efficiently controlled. Further, it is possible to perform drawing with a high dynamic range by controlling the diffractive optical element within the determined driving range.

It is a graph which shows an example of the IV characteristic of a diffraction grating type diffractive optical element. It is a front view which shows typically schematic structure of one Embodiment of the drawing apparatus concerning this invention. It is a figure which shows typically an example of a structure with which a diffractive optical element is provided. It is a figure which shows the non-application state which a diffractive optical element can take. It is a figure which shows the 1st state which a diffractive optical element can take. It is a figure which shows the 2nd state which a diffractive optical element can take. It is a figure which shows typically an example of the detailed structure with which an optical head is provided. It is a figure which shows typically an example of a structure of a spatial light modulator. It is a figure which shows typically an example of the structure for measuring the distance of an optical head and a board | substrate upper surface. FIG. 3 is a block diagram showing a control system of the drawing apparatus of FIG. 2. 3 is a flowchart showing drive range adjustment processing and drawing processing executed by the drawing device of FIG. 2.

A. IV Characteristics FIG. 1 is a graph showing an example of IV characteristics of a diffraction grating type diffractive optical element. When the diffractive optical element is designed to have, for example, the IV characteristic indicated by the solid line in the figure and manufactured according to the design data, the control voltage applied to the diffractive optical element, that is, the applied voltages Vmin0 and Vmax0 are 0. The next diffracted light quantity (relative value) becomes minimum and maximum, respectively. Therefore, as long as it is manufactured according to the design data, a high dynamic range can be obtained by setting the range in which the control voltage is variably applied, that is, the drive range to the range of voltage Vmin0 to voltage Vmax0. In this specification, the drive range (Vmin0 to Vmax0) is referred to as a “reference drive range”.

  However, due to manufacturing variations, for example, the distance between the fixed member (the fixed ribbon 412 in FIG. 3B) and the movable member (the movable ribbon 413 in FIG. 3B) (FIG. 3B in FIG. When the symbol d0) deviates from the design data, the IV characteristic shifts to the low voltage side as shown by the broken line in the figure or to the high voltage side as shown by the one-dot chain line in the figure. . For this reason, the applied voltage at which the 0th-order diffracted light quantity is minimized and the applied voltage at which the 0th-order diffracted light quantity is maximized are shifted, and a drive range suitable for driving the diffractive optical element is designed in advance. ) Will fluctuate. This is one of the causes of narrowing the dynamic range.

  As is well known, the GLV, which is an example of a diffraction grating type diffractive optical element, has a structure in which a fixed ribbon (fixed member) and a movable ribbon (movable member) are alternately arranged while facing a bottom electrode (base member). The diffraction grating is formed by displacing the movable ribbon with respect to the fixed ribbon by applying a control voltage to the movable ribbon. The configuration and operation of the diffractive optical element will be described in detail later with reference to FIGS. 3A to 3D.

Various studies have been conducted on GLV. For example, Jahja I. Trisnadi et al., "Overview and applications of Grating Light Valve TM based optical write engines for high-speed digital imaging", Presented at Photonics West 2004-Micromachining and Microfabrication Symposium, January 26, 2004, San Jose, CA , USA describes an equation showing the relationship between the voltage V applied to the movable ribbon based on the spring-capacitor model and the displacement d (V) of the displacement of the movable ribbon according to the applied voltage (in the same document). (Equation (2.2)). That is, when the distance between the bottom electrode and the movable ribbon is “h”, the dielectric constant between the bottom electrode and the movable ribbon is “Vs”, and the applied voltage is “V”, the displacement amount d accompanying the application of the voltage (V) can be obtained by the following equation. Note that “ω” in Equation 1 is a constant.

  Further, in the above document, an equation indicating the relationship between the distance of the movable ribbon with respect to the fixed ribbon and the amount of diffracted light is described (equation (2.3a) in the document). Here, when the fixed ribbon and the movable ribbon are arranged side by side without a gap, the following relational expression is obtained based on the above relational expression.

ただし、Ｉ0は回折光量、Ｉmaxは最大回折光量、ｄは固定リボンに対する可動リボンの距離、λは回折光学素子に入射される光の波長である。

Where I0 is the amount of diffracted light, Imax is the maximum amount of diffracted light, d is the distance of the movable ribbon to the fixed ribbon, and λ is the wavelength of the light incident on the diffractive optical element.

  From these equations (1) and (2), the IV characteristic (solid line in FIG. 1) of the diffractive optical element manufactured according to the design data can be obtained. In addition, when manufacturing variation occurs, the distance between the surface of the fixed ribbon and the surface of the movable ribbon in the non-application state may differ from the design data. As described above, the IV characteristics are high or low. Shift to. Thereby, for example, as shown in FIG. 1, the amount of diffracted light in the non-applied state varies, and the amount of diffracted light also varies in the applied state in which a control voltage is applied to the movable ribbon.

  Here, a detailed study will be made focusing on the case where the IV characteristic is shifted to the high voltage side by ΔV due to manufacturing variations (the one-dot chain line in FIG. 1). In this case, as shown in FIG. 1, the amount of diffracted light in the non-applied state varies by ΔI (= I 1 −I 0), compared to that produced in the design data. A displacement amount d (V) due to manufacturing variation can be obtained from the fluctuation amount ΔI of the diffracted light amount based on the equation (2). Furthermore, the shift amount ΔV of the IV characteristic can be obtained by calculating by substituting the displacement amount d (V) into the equation (1). As described above, by using the above equations (1) and (2), the shift amount ΔV of the IV characteristic due to the manufacturing variation can be obtained without measuring the IV characteristic of the diffractive optical element. The applied voltage at which the amount of diffracted light is minimized and maximized can always be obtained by the diffractive optical element. In the above description, the case where the IV characteristic shifts to the high voltage side is considered, but the same applies to the case where the IV characteristic shifts to the low voltage side (broken line in FIG. 1). It is also possible to determine the shift amount in a state in which an appropriate voltage (a voltage not exceeding the level at which the diffractive optical element does not break) is applied to the movable ribbon instead of the non-application state.

  In this way, the IV characteristic shifts due to the variation in the distance between the fixed ribbon and the movable ribbon in the non-application state due to the manufacturing variation of the diffractive optical element, and the shift amount ΔV is based on the variation amount ΔI of the diffracted light amount. By taking into account the technical matter that can be derived, the following effects can be obtained. That is, the control voltage that minimizes and maximizes the amount of diffracted light can be obtained without measuring the IV characteristics for each product of the diffractive optical element. And those voltage ranges can be made into the drive range suitable for the drive of a movable ribbon. In addition, a high dynamic range can be obtained by driving the diffractive optical element within the driving range. In the present specification, the drive range after the adjustment by the drive range adjustment process is referred to as “adjusted drive range”.

B. Embodiment Next, for each diffractive optical element product, a drive range adjustment process is performed as necessary to obtain an adjusted drive range, and the diffractive optical element is always controlled within the drive range suitable for the diffractive optical element. An embodiment of a drawing apparatus that performs a drawing process by performing modulation will be described.

  FIG. 2 is a front view schematically showing a schematic configuration of an embodiment of a drawing apparatus according to the present invention. The drawing device 100 is a device that draws a pattern by irradiating light onto the upper surface of the substrate W on which a layer of a photosensitive material such as a resist is formed. The substrate W may be any of various substrates such as a semiconductor substrate, a printed substrate, a color filter substrate, a glass substrate for a flat panel display provided in a liquid crystal display device or a plasma display device, and an optical disk substrate. In the illustrated example, the upper layer pattern is drawn so as to overlap the lower layer pattern formed on the upper surface of the circular semiconductor substrate.

  The drawing apparatus 100 includes a main body inside formed by attaching a cover panel (not shown) to the ceiling surface and the peripheral surface of a skeleton composed of the main body frame 101, and a main body outside that is the outer side of the main body frame 101. It has a configuration in which various components are arranged.

  The main body of the drawing apparatus 100 is divided into a processing area 102 and a delivery area 103. Among these areas, the stage 10, the stage moving mechanism 20, the optical unit U, and the alignment unit 60 are mainly arranged in the processing area 102. On the other hand, in the transfer area 103, a transfer device 70 such as a transfer robot for transferring the substrate W to and from the processing area 102 is arranged.

  In addition, an illumination unit 61 that supplies illumination light to the alignment unit 60 is disposed outside the main body of the drawing apparatus 100. Further, the main body is provided with a control unit 90 that is electrically connected to each unit of the drawing apparatus 100 and controls the operation of each unit.

  A cassette placement unit 104 for placing the cassette C is disposed outside the main body of the drawing apparatus 100 at a position adjacent to the transfer area 103. Further, the transfer device 70 corresponding to the cassette placement unit 104 and disposed in the transfer area 103 inside the main body takes out the unprocessed substrate W accommodated in the cassette C placed on the cassette placement unit 104. In addition to loading (loading) into the processing region 102, the processed substrate W is unloaded from the processing region 102 and stored in the cassette C. Delivery of the cassette C to the cassette mounting unit 104 is performed by an external transport device (not shown). The loading process of the unprocessed substrate W and the unloading process of the processed substrate W are performed by operating the transfer device 70 in accordance with an instruction from the control unit 90.

  The stage 10 has a flat outer shape, and is a holding unit that places and holds the substrate W in a horizontal posture on the upper surface thereof. A plurality of suction holes (not shown) are formed on the upper surface of the stage 10, and by applying a negative pressure (suction pressure) to the suction holes, the substrate W placed on the stage 10 is placed on the stage 10. It can be fixedly held on the upper surface of the. Then, the stage 10 is moved by the stage moving mechanism 20.

  The stage moving 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 moving mechanism 20 includes a base plate 24 that supports a support plate 22 that rotatably supports the stage 10, a sub-scanning mechanism 23 that moves the support plate 22 in the sub-scanning direction, and a main plate that moves the base plate 24 in the main scanning direction. And a scanning mechanism 25. The sub scanning mechanism 23 and the main scanning mechanism 25 move the stage 10 in accordance with an instruction from the control unit 90.

  The alignment unit 60 images an alignment mark (not shown) formed on the upper surface of the substrate W. The alignment unit 60 includes an alignment camera 601 having a lens barrel, an objective lens, and a CCD image sensor. The CCD image sensor provided in the alignment camera 601 is constituted by, for example, an area image sensor (two-dimensional image sensor). The alignment unit 60 is supported by a lifting mechanism (not shown) so as to be lifted and lowered within a predetermined range.

  The illumination unit 61 is connected to the lens barrel via the fiber 611 and supplies illumination light to the alignment unit 60. The light guided by the fiber 611 extending from the illumination unit 61 is guided to the upper surface of the substrate W through the lens barrel of the alignment camera 601, and the reflected light is received by the CCD image sensor through the objective lens. As a result, the upper surface of the substrate W is imaged and image data is acquired. The alignment camera 601 is electrically connected to the image processing unit of the control unit 90, acquires imaging data in accordance with an instruction from the control unit 90, and transmits the acquired imaging data to the control unit 90.

  Based on the imaging data provided from the alignment camera 601, the control unit 90 performs an alignment process of detecting a reference mark provided at the reference position of the substrate W and positioning the relative position between the optical unit U and the substrate W. Then, pattern drawing is performed by irradiating a predetermined position of the substrate W with laser light modulated according to the drawing pattern from the optical unit U.

  The optical unit U has a schematic configuration in which two optical heads 4 that modulate laser light based on strip data corresponding to a drawing pattern are arranged along the X-axis direction. The number of optical heads 4 is not limited to this. Since these optical heads 4 have the same configuration, the configuration related to one optical head 4 will be described below.

  The optical unit U is provided with a light irradiation unit 5 that irradiates the optical head 4 with laser light. The light irradiation unit 5 includes a laser driving unit 51, a laser oscillator 52, and an illumination optical system 53. Then, the laser beam emitted from the laser oscillator 52 by the operation of the laser driving unit 51 is irradiated to the optical head 4 through the illumination optical system 53. The optical head 4 modulates the laser light emitted from the light irradiation unit 5 with a spatial light modulator, and is incident on the substrate W that moves immediately below the optical head 4. Thus, the upper layer pattern (drawing pattern) is overlaid and exposed on the lower layer pattern formed on the unprocessed substrate W.

  The spatial light modulator of the optical head 4 uses, for example, the diffractive optical element 410 (FIG. 3A) having the same configuration as the above-described Patent Document 1 (GLV described in JP 2014-106513 A). It modulates laser light.

  3A to 3D are diagrams schematically illustrating an example of the configuration of the diffractive optical element. More specifically, FIG. 3A is a diagram schematically showing a schematic configuration of the diffractive optical element 410. 3B shows a non-application state that the diffractive optical element 410 can take, FIG. 3C shows a first state that the diffractive optical element 410 can take, and FIG. 3D shows a second state that the diffractive optical element 410 can take. .

  As shown in FIG. 3A, the diffractive optical element 410 has a schematic configuration in which the fixed ribbon 412 and the movable ribbon 413 are opposed to the surface of the flat bottom electrode 411 and alternately arranged in a direction parallel to the surface. The fixed ribbon 412 and the movable ribbon 413 have reflection surfaces 412s and 413s that are finished into a flat surface and reflect light. The fixed ribbon 412 is fixed to the bottom electrode 411 at a predetermined interval.

The movable ribbon 413 is provided so as to be displaceable with respect to the bottom electrode 411 and is displaced in the approaching / separating direction with respect to the bottom electrode 411 according to the applied control voltage. The displacement amount of the movable ribbon 413 depends on the magnitude of the potential difference generated between the movable ribbon 413 and the bottom electrode 411 due to the control voltage. In the diffractive optical element 410 of this embodiment, no control voltage is applied to the movable ribbon 413, that is, no voltage is applied, and the height difference d0 between the surface 412s of the fixed ribbon 412 and the surface 413s of the movable ribbon 413 is the wavelength of incident light. For λ:
2d0 <(2n + 1) · λ / 2
The diffractive optical element 410 is manufactured so as to satisfy (n is an integer of 0 or more). On the other hand, the diffractive optical element 410 takes a first state shown in FIG. 3C and a second state shown in FIG. 3D depending on the magnitude of the control voltage applied to the movable ribbon 413.

In the first state shown in FIG. 3C, the height difference d1 between the surface 412s of the fixed ribbon 412 and the surface 413s of the movable ribbon 413 is expressed by the following equation with respect to the wavelength λ of the incident light:
2d1 = (2n + 1) · λ / 2
It is represented by That is, twice the height difference d1 is an odd multiple of a half wavelength. The left side (2d1) of the above equation is movable when the light Li incident perpendicularly to the surface of the diffractive optical element 410, that is, from the normal direction of the reflecting surfaces 412s and 413s, is reflected by the surface 412s of the fixed ribbon 412. This corresponds to a difference in optical path length from the case of being reflected by the surface 413 s of the ribbon 413. Since the optical path length difference is an odd multiple of the half wavelength, the light reflected by the surface 412s of the fixed ribbon 412 and the light reflected by the surface 413s of the movable ribbon 413 cancel each other out of phase. For this reason, the reflected light (regular reflected light) in the vertical direction is not emitted, and the emitted light in the oblique direction having a different optical path length, that is, the first-order or higher order diffracted light Lg is emitted.

In contrast, in the second state shown in FIG. 3D, the height difference d2 between the surface 412s of the fixed ribbon 412 and the surface 413s of the movable ribbon 413 is expressed by the following equation with respect to the wavelength λ of the incident light:
2d2 = 2n · λ / 2 = n · λ
(N is an integer of 0 or more). That is, the height difference d2 is an even multiple of a half wavelength and an integral multiple of a wavelength. In this case, since the light reflected by the surface 412s of the fixed ribbon 412 and the light reflected by the surface 413s of the movable ribbon 413 have the same phase, these lights are diffracted as regular reflection light (0th order diffracted light) Lo. The light is emitted from the element 410.

  As will be described later, in this embodiment, drawing is performed by irradiating the substrate W with 0th-order diffracted light emitted from the diffractive optical element 410. Therefore, as far as the exposure beam emitted toward the substrate W is concerned, the exposure beam is not emitted when the state of the diffractive optical element 410 is the first state shown in FIG. 3C, and the second state shown in FIG. 3D. An exposure beam is emitted when it is in a state. Therefore, in the following description, in order to facilitate understanding of the light emission state, the first state shown in FIG. 3C is referred to as an “exposure off state”, and the second state shown in FIG. 3D is referred to as an “exposure on state”. . The exposure on state is a state in which light is irradiated from the diffractive optical element 410 toward the substrate W, and the exposure off state is a state in which the light is not irradiated. These are distinguished by the magnitude of the control voltage applied to the movable ribbon 413.

  The control voltage can be individually set for each movable ribbon 413. Therefore, an exposure on state and an exposure off state are caused to appear for each ribbon pair including one movable ribbon 413 and a fixed ribbon 412 adjacent thereto. be able to. The minimum unit of exposure on / off configured by one ribbon pair is hereinafter referred to as a “channel”. In this embodiment, description will be made assuming that a diffractive optical element having a total of 8001 channels with channel numbers 0 to 8000 is used, but the number of channels is arbitrary.

  4A and 4B are diagrams schematically illustrating an example of a detailed configuration of the optical head. As shown in FIG. 4A, the optical head 4 is provided with a spatial light modulator 41 having a diffractive optical element 410. Specifically, the spatial light modulator 41 attached to the upper portion of the support column 400 extending in the vertical direction (Z direction) on the optical head 4 has the reflection surface of the diffractive optical element 410 facing downward. 40.

  As shown in FIG. 4B, the spatial light modulator 41 supports the diffractive optical element 410, the linear motion stage 414 that supports the diffractive optical element 410 and moves in a uniaxial direction, and supports the linear motion stage 414 while diffracting itself. A rotation stage 415 that rotates around an axis orthogonal to the reflection surface of the optical element 410 and a base portion 416 that supports the rotation stage 415 are provided, and the base portion 416 is fixed to the column 400.

  For later explanation, as shown in FIG. 4B, an RST orthogonal coordinate system is set on the linear motion stage 414. The R direction is an arrangement direction of the fixed and movable ribbons 412 and 413 in the diffractive optical element 410. The S direction is the longitudinal direction of each of the fixed and movable ribbons 412 and 413. The T direction is a direction orthogonal to the surface of the diffractive optical element 410. Further, the rotation direction around the T axis is defined as the α direction. Among these axial directions, the R direction and the S direction change along with the rotation of the rotation stage 415.

  Further, an R′S′T ′ orthogonal coordinate system is set on the base portion 416. The S ′ direction is the moving direction of the linear motion stage 414, and the T ′ direction is a direction orthogonal to the surface of the diffractive optical element 410 as in the T direction. The S ′ direction is a direction orthogonal to these. The rotation direction around the T ′ axis is defined as the α ′ direction.

  When the linear motion stage 414 and the rotation stage 415 are at the initial positions, the relationship between both coordinate systems is set to be the following relationship. The R axis and the R ′ axis are parallel, and the S axis and the S ′ axis are parallel. The T axis and the T ′ axis are always parallel. In addition, the origin in the RS plane and the origin in the R ′S ′ plane differ only in the T-axis direction (or T′-axis direction). That is, when viewed from the T-axis direction (T′-axis direction), the RS plane and the R ′S ′ plane have the same origin and coordinate axis direction.

  Referring back to FIG. 4A, in the optical head 4, the diffractive optical element 410 is disposed such that the normal line of the reflecting surface thereof is inclined with respect to the optical axis OA, and the light emitted from the illumination optical system 53 is a strut. The light enters the mirror 43 through the opening 400, is reflected by the mirror 43, and then irradiates the diffractive optical element 410. The state of each channel of the diffractive optical element 410 is switched by the control unit 90 according to the drawing data, and the laser light incident on the diffractive optical element 410 is modulated. One pixel represented by the drawing data corresponds to one or a plurality of channels. Although the incident direction of light to the diffractive optical element 410 is oblique with respect to the normal of the reflecting surface and the optical path length of the reflected light is different from that in FIGS. 3C and 3D, the control voltage is appropriately tuned according to the incident angle. By adjusting the amount of displacement of the movable ribbon 413, it is possible to realize an exposure-on state in which zero-order diffracted light is emitted and an exposure-off state in which no zero-order diffracted light is emitted.

  At this time, the diffractive optical element 410 is irradiated with the laser light made uniform by the illumination optical system 53. That is, the light emitted from the laser oscillator 52 is shaped into a linear line beam light (light having a linear beam cross section) with a uniform intensity distribution by the illumination optical system 53, and enters the effective region of the diffractive optical element 410. Irradiated. Here, the effective region is a region where the diffractive optical element 410 can perform modulation on incident light. Further, the major axis direction of the line beam light is targeted to the R direction which is the ribbon arrangement direction in the diffractive optical element 410.

  In the optical head 4, the laser light reflected as the 0th-order diffracted light from the diffractive optical element 410 enters the lens of the projection optical system 43, while the laser light reflected from the diffractive optical element 410 as the first-order or higher-order diffracted light. Does not enter the lens of the projection optical system 43. That is, basically, only the 0th-order diffracted light reflected by the diffractive optical element 410 is incident on the projection optical system 43.

  The light that has passed through the lens of the projection optical system 43 is guided onto the substrate W through the focusing lens 441 at a predetermined magnification. This focusing lens 441 is attached to a focus drive mechanism 442. Then, the focus drive mechanism 442 moves the focusing lens 441 up and down along the vertical direction (Z-axis direction) in accordance with a control command from the control unit 90, so that the convergence position of the laser light emitted from the focusing lens 442 is the substrate. It is adjusted to the upper surface Ws of W.

  An irradiating unit 451 and a light receiving unit 452 functioning as an autofocus unit are provided below the housing of the optical head 4. The irradiation unit 451 irradiates light emitted from a light source configured by a laser diode (LD) obliquely to the upper surface Ws of the substrate W. The light receiving unit 452 includes a solid-state imaging device such as a complementary metal oxide semiconductor (CMOS) sensor or a charge coupled device (CCD) sensor, and detects reflected light from the upper surface Ws of the substrate W. Then, the control unit 90 detects the distance between the optical head 4 and the substrate upper surface Ws from the detection result of the light receiving unit 452.

  That is, when the substrate upper surface Ws moves away from the optical head 4 as shown by the solid arrow in FIG. 4A or when the substrate upper surface Ws approaches the optical head 4 as shown by the broken arrow, the reflected light from the substrate upper surface Ws The optical paths change in the directions indicated by solid line arrows and broken line arrows, respectively, and the amount of light received at each light receiving position of the light receiving unit 452 also varies. Therefore, the peak position of the received light amount in the light receiving unit 452 changes as indicated by the solid line arrow and the broken line arrow, respectively. The control unit 90 uses this to detect the distance between the optical head 4 and the substrate upper surface Ws. Then, the control unit 90 operates the focus driving mechanism 442 according to the detection distance to move the focusing lens 441 up and down so that the focus of the focusing lens 441 is aligned with the substrate upper surface Ws, and the laser beam convergence position is set to the substrate. Adjust accurately to the top surface Ws (autofocus).

  In order to make such autofocus function effectively, it is necessary to know in advance the distance between the optical head 4 and the substrate upper surface Ws when the focusing lens 441 is focused on the substrate upper surface Ws. This distance does not change much in the short term, but changes as the device is used for a long time. Therefore, the drawing apparatus 100 is provided with a configuration for measuring the distance between the optical head 4 and the substrate upper surface Ws.

  FIG. 5 is a diagram schematically showing an example of a configuration for measuring the distance between the optical head and the upper surface of the substrate. As shown in the figure, an observation optical system 80 for receiving the laser beam emitted from the optical head 4 and observing the image of the laser beam is disposed on the side of the stage 10. In the observation optical system 80, for example, a light-transmitting dummy substrate 801 formed in a flat plate shape by quartz glass is provided horizontally.

  An observation camera 803 is disposed below the dummy substrate 801, that is, on the opposite side of the optical head 4 with the dummy substrate 801 interposed therebetween, via a beam splitter 806. For example, the observation camera 803 converges the laser light incident from the dummy substrate 801 via the beam splitter 806 on the solid-state imaging device by the optical system. The dummy substrate 801 and the observation camera 803 are respectively attached to and integrated with the case 804, and the focal position of the optical system of the observation camera 803 is adjusted to match the upper surface 801 s of the dummy substrate 801. The case 804 is supported by a support frame 805 erected on the support plate 22 so that the case 804 can be moved up and down, and the position of the case 804 in the vertical direction (Z-axis direction) can be adjusted by the control unit 90. Thus, the observation optical system 80 and the dummy substrate 801 move integrally with the stage 10 in the horizontal direction (XY direction), and can move independently of the stage 10 in the vertical direction (Z-axis direction). Yes.

  In measuring the distance between the optical head 4 and the substrate upper surface Ws, the observation optical system 80 is positioned immediately below the optical head 4, and the upper surface 801 s of the dummy substrate 801 is the upper surface of the substrate W placed on the stage 10. Positioned at the same height as Ws. Then, the control unit 90 changes the position of the focusing lens 431 in the vertical direction (Z-axis direction) while taking an optical image of the laser light emitted from the optical head 4 onto the dummy substrate upper surface 801s with the observation camera 803. Thus, the position of the focusing lens 441 is set so that the optical image is minimized (the contrast of the optical image is maximized). As a result, the focusing lens 441 is focused on the upper surface 801s of the dummy substrate. Then, the control unit 90 obtains the distance between the optical head 4 and the dummy substrate upper surface 801s at this time. In the subsequent drawing operation, the autofocus can be appropriately executed by adjusting the position of the focusing lens 441 based on the distance thus obtained.

  A part of the laser light incident on the observation optical system 80 through the dummy substrate 801 is changed in course by the beam splitter 806 and is incident on the light amount detector 807 provided in the case 804. Although not shown, a condensing optical system is provided between the beam splitter 806 and the light amount detector 807 so that all the light divided by the beam splitter 806 is received by the light amount detector 807. It has become. The light amount detector 807 outputs an electrical signal corresponding to the amount of light incident on the light receiving surface, and does not require resolution with respect to the light incident position. Thus, for example, a photodiode can be used. The output of the light amount detector 807 is used for measurement of the diffracted light amount in the non-application state described later.

  FIG. 6 is a block diagram showing a control system of the drawing apparatus shown in FIG. In the control unit 90, the following functional blocks 91 to 95 are realized by a CPU (Central Processing Unit) (not shown) executing a control program stored in the storage unit 99 in advance or by dedicated hardware. The illumination control unit 91 controls the light irradiation unit 5 of the optical unit U to emit line beam light.

  The focus control unit 94 manages the autofocus operation. The stage controller 93 controls the stage moving mechanism 20 to move the stage 10 relative to the optical head 4. The alignment control unit 92 performs alignment processing based on image data output from the alignment camera 601 of the alignment unit 60.

  The drawing control unit 95 controls the driver 951 based on the drawing recipe stored in the storage unit 99 and applies a control voltage from the driver 951 to each movable ribbon 413 of the diffractive optical element 410 so as to correspond to the pattern to be drawn. To modulate the line beam light. Further, the drawing control unit 95 obtains an appropriate drive range of the control voltage and executes a drive range adjustment process for adjusting as necessary.

  The technical significance of executing this drive range adjustment processing is that the drive range is appropriate in accordance with the shift variation of the IV characteristic of the diffractive optical element 410 as described in the section “A.IV characteristic”. It is in the point which aims at. As a result, a driving range suitable for the diffractive optical element 410 can be obtained without actually measuring the IV characteristic of the diffractive optical element 410, and a dynamic voltage can be obtained by applying a control voltage to the movable ribbon 413 within this driving range. The range (the exposure resolution adjustment resolution) can be increased. Hereinafter, the drive range adjustment process will be described in detail with reference to FIG.

  FIG. 7 is a flowchart showing drive range adjustment processing and drawing processing executed by the drawing apparatus of FIG. In the drawing apparatus 100, the drive range adjustment process is executed after the diffractive optical element 410 is assembled or replaced. This drive range adjustment process is executed by the control unit 90 controlling each part of the apparatus as follows in accordance with the control program stored in the storage unit 99.

  In the drive range adjustment process, the control unit 90 reads design data of the diffractive optical element 410 (step S1). This data reading may be performed via an operation panel (not shown) of the drawing apparatus 100 or may be performed by network communication. The design data includes a height difference d0 between the surface 412s of the fixed ribbon 412 and the surface 413s of the movable ribbon 413 in the non-application state. Then, the control unit 90 that has read the design data derives the IV characteristic of the diffractive optical element 410 based on the design data (step S2). Here, the description of the drive range adjustment process is continued on the assumption that the IV characteristic indicated by the solid line in FIG. 1 is obtained in step S2.

  In the next step S3, the control unit 90 obtains an applied voltage Vmin0 at which the 0th-order diffracted light amount is minimized and an applied voltage Vmax0 at which the 0th-order diffracted light is minimized based on the IV characteristics, and uses this voltage range (Vmin0 to Vmax0) as a reference drive range. Remember as. In this way, the driving range when the diffractive optical element 410 mounted on the apparatus 100 is manufactured according to the design data is derived. Further, the control unit 90 calculates the 0th-order diffracted light quantity I0 in the non-application state based on the IV characteristic (step S4).

  Further, in parallel with the execution of steps S3 and S4, the control unit 90 causes the line beam light to enter the diffractive optical element 410 in the non-application state (step S5), and the zero next time in the non-application state by the light amount detector 807. The folding light quantity I1 is measured (step S6). Here, if the height difference d0 between the fixed ribbon 412 and the movable ribbon 413 varies due to manufacturing variations of the diffractive optical element 410, the calculated value I0 of the 0th-order diffracted light quantity does not match the measured value I1 as shown in FIG. It becomes. On the other hand, when the diffractive optical element 410 is manufactured according to the design data, the calculated value I0 and the actually measured value I1 match or substantially match.

  Therefore, in the present embodiment, the control unit 90 calculates the difference ΔI (= I1−I0) between the calculated value I0 of the 0th-order diffracted light quantity and the actually measured value I1 (step S7), and whether the difference ΔI is zero. It is determined whether or not (step S8). If “YES” is determined in this step S8, that is, if the diffractive optical element 410 is manufactured according to the design data, the drive range adjustment processing is terminated at this stage, and the control voltage is varied within the reference drive range. Then, the drawing process is executed (step S9).

On the other hand, when it is determined as “NO” in step S8, that is, when it is determined that the diffractive optical element 410 is not manufactured according to the design data and the shift variation of the IV characteristic occurs, the control unit 90 performs the IV process. A characteristic shift amount ΔV is calculated based on the difference ΔI (step S10). The calculation of the shift amount ΔV is the same as the calculation described in the section “A.I-V characteristics”. Then, the control unit 90 shifts the reference drive range by the shift amount ΔV. In other words, the following formula: Vmin1 = Vmin0 + ΔV
Vmin1 = Vmin0 + ΔV
Accordingly, the applied voltage Vmin1 at which the 0th-order diffracted light amount is minimized and the applied voltage Vmax1 at which it is maximized are calculated, and the driving range (Vmin1 to Vmax1) suitable for the diffractive optical element 410 provided in the apparatus 100 is varied in manufacturing. The adjusted adjusted driving range is stored in the storage unit 99 (step S11). After completing the drive range adjustment process in this way, the control unit 90 executes the drawing process while varying the control voltage within the adjusted drive range (step S12).

  As described above, the distance d between the fixed ribbon 412 and the movable ribbon 413 in the non-application state due to manufacturing variations of the diffractive optical element 410 may deviate from the design data. Side or low applied voltage side. Therefore, in this embodiment, when the shift of the IV characteristic occurs, the shift amount ΔV is calculated, the reference drive range is shifted by the shift amount ΔV, and the adjusted drive range for each product of the diffractive optical element 410 is adjusted. Seeking. Therefore, it is not necessary to measure the diffracted light quantity characteristic for each product of the diffractive optical element 410, and a driving range suitable for driving the diffractive optical element 410 can be easily determined, and the diffractive optical element 410 is efficiently controlled. It is possible. Moreover, the drawing apparatus 100 equipped with the above-described control technology for the diffractive optical element 410 can perform drawing with a high dynamic range by controlling the diffractive optical element 410 within a driving range suitable for driving.

  Further, in the above-described embodiment, the calculated value I0 and the actually measured value I1 of the 0th-order diffracted light quantity are obtained under the same condition of no application state. Of course, the calculated value I0 and the actually measured value I1 may be obtained under the same condition that a control voltage other than 0 [V] is applied. However, when a control voltage is applied to a plurality of movable ribbons 413, the voltage sensitivity characteristics of each movable ribbon 413 may vary, and in order to avoid this, the 0th-order diffracted light quantity is measured without application. desirable.

  Thus, in the above embodiment, the control voltage (applied voltage) applied to the movable ribbon 413 corresponds to an example of the “parameter” of the present invention. Further, the bottom electrode 411, the fixed ribbon 412 and the movable ribbon 413 correspond to examples of the “base member”, “fixed member” and “movable member” of the present invention, respectively. Further, the direction in which the movable ribbon 413 approaches the bottom electrode 411 according to the applied control voltage corresponds to the “displacement direction” of the present invention. The 0th-order diffracted light quantity corresponds to an example of the “reflected light quantity” of the present invention. Moreover, the light irradiation part 5 is equivalent to an example of the “illumination part” of the present invention. Further, the drawing control unit 95 and the driver 921 function as a “modulation unit” of the present invention. Furthermore, while the light amount detector 807 functions as the “light amount measurement unit” of the present invention, the drawing control unit 95 of the control unit 90 functions as the “light amount calculation unit” and the “range determination unit” of the present invention, These constitute the “diffractive optical element control device” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, only the 0th-order diffracted light amount of the light reflected by the diffractive optical element 410 is set as the “reflected light amount” of the present invention, and a driving range suitable for the diffractive optical element 410 is obtained. The amount of the diffracted light may be used as the “reflected light amount” in the present invention. For example, when the light amount of the first-order diffracted light is used as the reflected light amount, a light amount detector is disposed on the diffractive optical element side of a slit plate (not shown) for extracting only the 0th-order light in the projection optical system 43, and the slit plate The first-order diffracted light shielded by the light can be received, and the amount of the first-order diffracted light can be measured as the “reflected light amount” of the present invention.

  In the present embodiment, the present invention is applied to a drawing apparatus that performs drawing processing using zero-order light. However, a drawing apparatus that uses other diffracted light components other than zero-order light, for example, first-order diffracted light. The present invention can be applied to.

  In the above embodiment, the control voltage applied to the movable ribbon 413 is used as the “parameter” of the present invention. However, the “parameter” is not limited to this, and for example, the bottom electrode 411, the movable ribbon 413, May be used as a “parameter” of the present invention.

  Further, although the diffractive optical element 410 of the above embodiment is a GLV element, the diffractive optical element to which the present invention can be applied is not limited to the GLV, and the diffraction grating is formed by bending the movable member by the control voltage. Any type of optical element may be used.

  Furthermore, the application target of the present invention is not limited to an apparatus that draws a semiconductor substrate W such as a wafer by irradiating the substrate with light as a “drawing object” of the present invention. Various objects such as a glass substrate can be used as the drawing object.

  The present invention relates to a technique for controlling a diffractive optical element that forms a diffraction grating by driving a movable member so that the movable member is displaced with respect to a fixed member in accordance with an input parameter, and drawing using the technique The present invention can be suitably applied to all devices.

DESCRIPTION OF SYMBOLS 5 ... Light irradiation part 41 ... Spatial light modulator 90 ... Control part 95 ... Drawing control part 100 ... Drawing apparatus 410 ... Diffraction optical element 411 ... Bottom electrode 412 ... Fixed ribbon 413 ... Movable ribbon 807 ... Light quantity detector 921 ... Driver W …substrate

Claims (8)

In the diffractive optical element that forms the diffraction grating by driving the movable member so that the movable member is displaced relative to the fixed member in accordance with the input parameter, the diffraction grating is formed by varying the parameter within the driving range. A control device for controlling
A light amount measurement unit that measures the amount of diffracted light reflected by the diffractive optical element when light is incident on the diffractive optical element as a reflected light amount; and
A light amount calculation unit that calculates a reflected light amount based on a diffracted light amount characteristic indicating a change in the reflected light amount with respect to a change in the parameter;
A range determining unit that determines the drive range based on the difference between the reflected light amount actually measured by the light amount measuring unit and the reflected light amount calculated by the light amount calculating unit under the same conditions, and the diffracted light amount characteristic; A control apparatus for a diffractive optical element. A control device for a diffractive optical element according to claim 1,
The amount of reflected light is the amount of zero-order light among the reflected light reflected by the diffractive optical element.
Control device for diffractive optical element. A control device for a diffractive optical element according to claim 1 or 2,
In the diffractive optical element, a base member is disposed in a displacement direction in which the movable member is displaced,
The parameter is a potential difference between the movable member and the base member.
Control device for diffractive optical element. A control apparatus for a diffractive optical element according to claim 3,
The parameter is a voltage applied to the movable member.
Control device for diffractive optical element. A control device for a diffractive optical element according to claim 4,
The light quantity measurement unit measures the reflected light quantity without applying voltage to the movable member,
The light amount calculation unit calculates the reflected light amount in the non-application state,
Control device for diffractive optical element. A control apparatus for a diffractive optical element according to claim 4 or 5,
The range determining unit sets a range shifted by a voltage corresponding to the difference from a driving range determined based only on the diffracted light quantity characteristic as a driving range for driving the diffractive optical element.
Control device for diffractive optical element. In the diffractive optical element that forms the diffraction grating by driving the movable member so that the movable member is displaced relative to the fixed member in accordance with the input parameter, the diffraction grating is formed by varying the parameter within the driving range. A control method for controlling
When the amount of diffracted light reflected by the diffractive optical element when light is incident on the diffractive optical element is taken as a reflected light amount,
Calculating the reflected light amount based on a diffracted light amount characteristic indicating the change in the reflected light amount with respect to a change in the parameter in the diffractive optical element under actual measurement of the reflected light amount;
Obtaining a difference between the actually measured reflected light amount and the calculated reflected light amount;
And a step of determining the drive range based on the difference and the diffracted light quantity characteristic. A drawing apparatus that draws light by irradiating a drawing object with modulated light,
A diffractive optical element that drives the movable member to form a diffraction grating so that the movable member is displaced relative to the fixed member in accordance with an input parameter;
An illuminating unit for making light incident on the diffractive optical element;
The parameter is varied within the driving range and input to the diffractive optical element, and light modulation is performed by controlling the amount of diffracted light reflected by the diffractive optical element and emitted in the direction toward the drawing object. A modulation unit;
A light quantity measuring unit for measuring the quantity of the diffracted light;
A controller that adjusts the driving range before performing drawing with light modulated by the modulator;
When the amount of diffracted light reflected by the diffractive optical element when light is incident on the diffractive optical element is taken as a reflected light amount,
The controller is
A light amount calculation unit that calculates a reflected light amount based on a diffracted light amount characteristic indicating a change in the reflected light amount with respect to a change in the parameter;
A range determining unit that determines the driving range based on the difference between the reflected light amount actually measured by the light amount measuring unit and the reflected light amount calculated by the light amount calculating unit under the same conditions, and the diffracted light amount characteristic; A drawing apparatus characterized by.

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