JP2007095767A - Exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure apparatus which can appropriately measure the height position of a reflection type mask, even if an exposure area regulating member is placed between the reflection type mask and a projection optical system. <P>SOLUTION: A mask stage 55 wherein a reflection type mask M is placed on, and a substrate stage 56 wherein a sensitive substrate W is mounted, are synchronously moved relatively in the scanning direction to a projection optical system PL. A pattern formed on the reflection type mask M is transferred onto the sensitive substrate W by using an exposing light 32. Such the exposure apparatus includes an exposure area regulating member 1 which is arranged between the reflection type mask M and the projection optical system PL, and has an opening to regulate an exposure area; and a detection means to detect the height of the reflection type mask M, by directing a detection light 3 to the reflection type mask M and receiving the detection light reflected on the reflection type mask M. The exposure area regulating member 1 is formed of a member that does not transmit the exposing light 32 but the detection light 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure apparatus for manufacturing microdevices such as semiconductor elements and liquid crystal display elements in a lithography process.

  In recent years, along with miniaturization of semiconductor integrated circuits, projection lithography technology using EUV (Extreme Ultra Violet) light with a short wavelength (11 to 14 nm) has been developed in order to further improve the resolution. In this wavelength range, a transmission / refraction type optical element such as a conventional lens cannot be used, a reflection type optical element such as a mirror is used, and a reflection type mask is also used.

  In an exposure apparatus using a reflective mask, a field limiting slit having an arc-shaped opening is provided in the vicinity of the reflective mask in order to remove unnecessary light incident on a region other than the exposure region. At the time of exposure, the mask stage on which the mask is placed moves, and the pattern formed on the mask surface is sequentially illuminated. The surface of the mask is not necessarily flat, and when the mask is attached to the mask stage, the position in the height direction may be changed or attached in an inclined state. In such a case, the distance between the mask and the projection optical system fluctuates, and there is a possibility that errors such as image blur, magnification, and transfer position may occur when the wafer is exposed. In order to prevent such errors in magnification and transfer position, it is necessary to measure and control the position in the height direction of the mask.

  The position of the mask in the height direction is measured using an interferometer or the like (see, for example, Patent Document 1). Further, the measurement is performed by irradiating the measurement surface of the mask with light from an oblique direction and measuring the position where the light reflected by the mask surface enters the light receiving surface. That is, when the height of the measurement surface of the mask changes, the incident position of the measured light changes. Therefore, the height of the measurement surface of the mask can be measured by obtaining the amount of variation in the incident position of the light to be measured.

US Pat. No. 6,359,678

  By the way, in the EUV exposure apparatus provided with the above-mentioned field-of-view restriction slit, when measuring the position in the height direction of the exposure surface of the reflective mask during exposure by the above-mentioned optical method, the field-of-view restriction slit blocks the measurement light. Therefore, the position in the height direction of the reflective mask cannot be measured.

  An object of the present invention is to provide an exposure apparatus that can satisfactorily measure the height position of a reflective mask even when an exposure area defining member is installed between the reflective mask and the projection optical system. It is.

  In the exposure apparatus of the present invention, a mask stage (55) on which a reflective mask (M) is placed and a substrate stage (56) on which a sensitive substrate (W) is placed are relative to the projection optical system (PL). In the exposure apparatus for transferring the pattern formed on the reflective mask (M) onto the sensitive substrate (W) by the exposure light (32) by synchronously moving in the scanning direction, the reflective mask (M) And the projection optical system (PL), an exposure region defining member (1) having an opening (S) for defining an exposure region, and detection light (3) with respect to the reflective mask (M). ) And detecting means (4) for detecting the height of the reflective mask by receiving the detection light (3) reflected by the reflective mask (M), and the exposure area defining member (1) does not transmit the exposure light (32); Characterized in that it is formed by members that transmits detection light to (3).

  According to the exposure apparatus of the present invention, since the exposure area defining member is formed of a member that reflects the exposure light and transmits the detection light, the reflection mask is not shielded by the exposure area defining member. Can reach up. Accordingly, the height position of the reflective mask can be satisfactorily measured by the detecting means even during exposure.

  An exposure apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an exposure apparatus according to the embodiment. In the following description, the orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W as the sensitive substrate, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z axis is set to the vertical direction. In this embodiment, the direction (scanning direction) in which the wafer W is moved is set to the X direction.

  The EUV light (exposure light) 32 emitted from the EUV light source 31 constitutes an illumination optical system 33, becomes a substantially parallel light beam via a concave reflecting mirror 34 that acts as a collimator mirror, and consists of a pair of fly-eye mirrors 35a and 35b. The light enters the optical integrator 35. As the pair of fly-eye mirrors 35a and 35b, for example, a fly-eye mirror disclosed in US Pat. No. 6,452,661 can be used.

  A substantial surface light source having a predetermined shape is formed in the vicinity of the reflecting surface of the second fly-eye mirror 35b, that is, in the vicinity of the exit surface of the optical integrator 35. The light from the substantial surface light source is deflected by the plane reflecting mirror 36, passes through the elongated arc-shaped field-of-view restriction slit S (see FIG. 2) of the exposure area defining member 1, and is on the mask (reflection mask) M An elongated arc-shaped illumination area is formed.

  FIG. 2 is a view showing the configuration of the exposure area defining member 1. The exposure area defining member 1 is disposed between the mask M and the projection optical system PL, and has an arc-shaped field limiting slit (opening) S that defines the exposure area on the wafer W. As the EUV light passes through the arc-shaped field-of-view restriction slit S, the illumination area in the mask M becomes arc-shaped. This is due to the fact that paraxial rays cannot be used due to the arrangement of the reflecting mirrors M1 to M6 of the projection optical system PL, which will be described later, and that it is desired to reduce aberrations while ensuring the widest possible exposure area. This is to make the aberration determined by the distance from the optical axis such as a curve almost constant and to easily correct these aberrations. Since the exposure area by the EUV light guided onto the wafer W only needs to be defined in a predetermined shape, the EUV light is limited by the field limiting slit S before the EUV light is reflected by the mask M. May be. Further, the EUV light may be limited by the field limiting slit S after the EUV light is reflected by the mask M. In addition, although the exposure area | region concerning this embodiment is prescribed | regulated in circular arc shape based on the above-mentioned advantage, you may make it have another shape.

  Further, the exposure area defining member 1 reflects EUV light (exposure light) 32 or does not transmit it by absorption or the like, but transmits a detection light for detecting a position in the height direction of a mask M described later, For example, it is made of a material such as optical glass or synthetic quartz. Further, as shown in FIG. 2, the exposure region defining member 1 is constituted by combining a plurality (two in this embodiment) of members 1a and 1b. That is, as shown in FIG. 3, the member 1a and the member 1b are processed and manufactured, and as shown in FIG. 2, the processed members 1a and 1b are combined.

  The edge portion of the field limiting slit S of the exposure area defining member 1 needs to be processed with high accuracy because it affects the exposure amount error. However, the field limiting slit S is made high on a member such as one optical glass or synthetic quartz. It takes time and cost to form holes with precision and polishing, and the field-of-view restriction slit S cannot be easily manufactured. However, by dividing the exposure region defining member 1 into the members 1a and 1b, the visual field limiting slit S can be easily manufactured.

  Moreover, the width | variety in the scanning direction (X direction) of the visual field restriction | limiting slit S can be changed by changing the combination position of the members 1a and 1b which comprise the exposure area | region definition member 1. FIG. FIG. 4 is a diagram showing an example in which the combination position of the members 1a and 1b is changed, and FIG. 5 is a graph showing the positions of the edges E1 and E2 shown in FIG. The vertical axis of the graph shown in FIG. 5 indicates the position coordinates of the edges E1 and E2 in the X direction (scanning direction), and the horizontal axis indicates the position coordinates of the edges E1 and E2 in the Y direction (non-scanning direction). As shown in FIGS. 4 and 5, when the member 1a is moved by a predetermined amount in the + Y direction, the width W2 can be made larger than the width W1 in the scanning direction of the field limiting slit S.

  In this way, by changing the width of the field limiting slit S in the scanning direction, an inclination component can be given to the exposure amount by the exposure light passing through the field limiting slit S. FIG. 6 is a graph showing the exposure amount distribution when the width of the field limiting slit S in the scanning direction is changed as shown in FIGS. The vertical axis of the graph shown in FIG. 6 indicates the exposure amount, and the horizontal axis indicates the position in the Y direction (non-scanning direction). As shown in FIG. 6, since an inclination component can be given to the exposure amount by the exposure light passing through the field limiting slit S, when an exposure amount distribution (illumination unevenness) occurs during exposure, the field limiting slit S By appropriately changing the width in the scanning direction, the exposure amount distribution can be corrected.

  The EUV light that has passed through the field limiting slit S of the exposure area defining member 1 illuminates the pattern formed on the mask M. The mask M is mounted on the mask stage 55, and the mask stage 55 is configured to be movable in the X, Y, and Z axial directions and the rotational directions around the respective axes. The EUV light reflected by the mask M is an image of the pattern of the mask M on the wafer W via the projection optical system PL composed of a plurality of reflecting mirrors (six exemplary reflecting mirrors M1 to M6 in FIG. 1). Form. The wafer W is mounted on the wafer stage 56, and the wafer stage 56 is configured to be movable in the X, Y, and Z axial directions and the rotational directions around the respective axes.

  The positions of the mask stage 55 and the wafer stage 56 in the XY directions are measured by interferometers (not shown). The measurement result by the interferometer is output to the control device 51, and the control device 51 outputs drive signals 57 and 58 to the mask stage 55 and the wafer stage 56. The mask stage 55 and the wafer stage 56 are moved by an actuator (not shown) such as a linear motor or an air actuator.

  In this embodiment, a mask position detection device (detection means) for detecting the position of the mask M in the height direction (Z direction) is provided. Since the mask position fluctuation and the wafer position fluctuation are relative problems, the conventional exposure apparatus using a transmissive mask measures the height of the mask side and the wafer side, and either the mask side or the wafer side is measured. The position in the height direction was corrected. However, in the case of the reflective mask according to this embodiment, it is difficult to make the mask M side a telecentric optical system. That is, the positional deviation in the height direction on the mask M side may cause a magnification variation error. Therefore, it is preferable that the correction of the position in the height direction on the mask side and the wafer side is performed independently.

  FIG. 7 is a diagram for explaining the configuration of the mask position detection apparatus. As shown in FIG. 7, the detection light 3 emitted from the projector 2 including a halogen lamp and a laser light source constituting the mask position detection device is a portion other than the field limiting slit S and the field limiting slit S of the exposure region defining member 1 ( Hereinafter, the light passes through one of the light shielding portions and enters the mask M. That is, the detection light 3 is configured not to hit the edge portion of the visual field limiting slit S. The detection light 3 has a wavelength different from the wavelength of EUV light as exposure light. The detection light 3 reflected by the mask M passes through one of the field limiting slit S and the light shielding portion of the exposure region defining member 1 and is measured by the light receiver 4 including a CCD or the like. The positional deviation in the height direction (Z direction) of the mask M surface can be measured as the deviation of the incident position of the light beam on the incident surface of the detection light of the light receiver 4, and the height of the mask M is determined based on the position of the light beam. Can be detected. In FIG. 7, illustration of the detection light passing through the visual field restriction slit S is omitted, and only the detection light passing through the light shielding portion is illustrated.

  In FIG. 7, only one detection light 3 is shown, but actually, a slit substrate having a plurality of slits is arranged between the projector 2 and the exposure region defining member 1, and the slit substrate The light transmission optical system is arranged so that the image is formed on the mask M, and the imaging optical system is arranged so that the slit image is formed on the light receiver 4. Therefore, the position in the height direction of a plurality of points of the mask M can be simultaneously measured from the position of each slit image on the light receiver 4. The inclination of the mask M can also be detected by simultaneously measuring the positions in the height direction of a plurality of points. For example, even when the height distribution is generated in the Y direction due to the deflection of the mask M, the scanning direction (X Each position of (direction) can be obtained accurately. This measurement result is output to the control device 51.

  Further, the detection light 3 may be reflected by the exposure region defining member 1 depending on the angle at which the detection light 3 enters the exposure region defining member 1 and the refractive index of the exposure region defining member 1. In this case, the incident angle adjusting members 1c to 1f may be provided to adjust the effective incident angle with respect to the exposure region defining member 1. The incident angle adjusting members 1c to 1f are preferably made of the same material as that of the exposure region defining member 1, but may be made of other materials.

  FIG. 8 is a view showing a state in which detection light that has passed through a plurality of slits on a slit substrate (not shown) disposed between the projector 2 and the exposure area defining member 1 has reached the exposure area defining member 1. In this embodiment, 17 slits are formed on the slit substrate disposed between the projector 2 and the exposure area defining member 1. As shown in FIG. 8, the detection lights 3 a to 3 g that have passed through the predetermined seven slits pass through the light shielding portion of the exposure region defining member 1 and reach the detection point on the mask M. The detection lights 3h to 3j that have passed through the predetermined three slits pass through the field-of-view restriction slit S of the exposure area defining member 1 and reach the detection point on the mask M. Further, the detection lights 3k to 3q that have passed through the predetermined seven slits pass through the light shielding portion of the exposure area defining member 1 and reach the detection point on the mask M.

  As shown in FIG. 8, it is prescribed | regulated that the detection lights 3a-3q pass either one of the visual field restriction | limiting slit S and the light-shielding part of the exposure area | region definition member 1. As shown in FIG. This is to prevent occurrence of a detection error due to vibration of the exposure region defining member 1 or the like. 9 is a diagram showing the positional relationship between the mask M, the mask stage 55 and the exposure region defining member 1 at the start of exposure, and FIG. 10 is a diagram showing the positional relationship between the mask M, the mask stage 55 and the exposure region defining member 1 during the exposure. It is. From the position at the start of exposure shown in FIG. 9, the mask stage 55 (mask M) is scanned and moved in the X direction as shown in FIG. 10, thereby performing scanning exposure and simultaneously measuring the position of the mask M in the height direction. To do. That is, the position in the height direction on the entire surface of the mask M can be measured. The measurement result is output to the control device 51. The control device 51 corrects the height position of the mask stage and the rotation about the X axis and the Y axis based on the measurement result. Specifically, the control device 51 outputs a drive signal 57 to the mask stage 57 and moves the mask stage 55 to correct the height position of the mask M surface.

  When measuring the position of the pattern region where the pattern on the mask M surface is formed, a measurement error may occur due to the unevenness of the surface of the mask M due to the pattern. In the case of a reflective mask used in an exposure apparatus for EUV light according to this embodiment, an absorber pattern layer is formed on the multilayer film, or a pattern to be transferred is obtained by partially removing the multilayer film. Since it is formed, irregularities occur. Therefore, it is desirable to simultaneously measure the position in the height direction of the peripheral region on the mask M on which no pattern is formed.

  In the vicinity of the wafer stage 56, a wafer position detection device for detecting the position in the height direction (Z direction) of the wafer W, which is the same as the mask position detection device, is disposed. As shown in FIG. 1, the detection light emitted from the projector 52 is reflected by the wafer W and enters the light receiver 54. The measurement result of the detection light incident on the light receiver 54 is output to the control device 51. The control device 51 detects the position of the wafer W in the height direction based on the measurement result by the light receiver 54.

  According to the exposure apparatus of this embodiment, since the exposure region defining member is formed of a member that reflects EUV light and transmits detection light, the detection light is not blocked by the exposure region defining member. Can reach on the mask. Therefore, the height position of the mask can be satisfactorily measured by the mask position detection device even during exposure.

  In the exposure apparatus according to this embodiment, the position of the mask M in the height direction is detected by the mask position detection device. For example, a half mirror (reflection area) 10 as shown in FIG. By providing on the lower surface of the defining member 1, the position in the height direction of the mask M and the distance between the mask M and the exposure region defining member 1 can be detected. As shown in FIG. 11, a half mirror 10 is installed on the lower surface of the exposure region defining member 1 on which the detection light 3 emitted from the projector 2 enters. A part of the exposure area defining member 1 may be processed to be a half mirror. The detection light 3 emitted from the projector 2 enters the half mirror 10. The detection light 3 that has passed through the half mirror 10 passes through the exposure region defining member 1, is reflected by the mask M, passes through the exposure region defining member 1, and is received by the light receiver 4. On the other hand, the detection light 3 reflected by the half mirror 10 is received by the light receiver 5. The measurement result of the detection light received by the light receiver 4 and the light receiver 5 is output to the control device 51. The control device 51 detects the interval between the mask M and the exposure area defining member 1 based on the optical path difference between the detection light received by the light receiver 4 and the detection light received by the light receiver 5.

  When the control device 51 determines that the interval between the mask M and the exposure area defining member 1 needs to be corrected, the control device 51 drives the mask stage 55 to move the mask M in the Z direction. The distance from the exposure area defining member 1 is corrected. Further, for example, an actuator 60 or the like is provided on the exposure area defining member 1 so that the exposure area defining member 1 can be moved in the Z direction. By moving the exposure area defining member 1 in the Z direction, The interval may be corrected. As described above, since the distance between the mask M and the exposure region defining member 1 can be controlled, it is possible to prevent the variation in exposure amount caused by the variation in the distance between the mask M and the exposure region defining member 1.

  In addition, the exposure apparatus according to this embodiment includes an exposure region defining member configured by two members, but includes an exposure region defining member configured by three or more members. Also good.

It is a figure which shows the structure of the exposure apparatus concerning embodiment. It is a figure which shows the structure of the exposure area prescription | regulation member concerning Embodiment. It is a figure which shows the structure of the member which comprises the exposure area prescription | regulation member concerning embodiment. It is a figure which shows the state which changed the combination position of the member which comprises the exposure area prescription | regulation member concerning embodiment. It is a graph which shows the position of the edge part of each member which comprises the exposure area prescription | regulation member concerning Embodiment. It is a graph which shows the exposure amount distribution of EUV light which passes the visual field restriction | limiting slit of the exposure area | region prescription | regulation member concerning embodiment. It is a figure for demonstrating the structure of the mask position detection apparatus concerning embodiment. It is a figure which shows the position of the detection light which reaches | attains the exposure area prescription | regulation member concerning embodiment. It is a figure which shows the positional relationship of the exposure area prescription | regulation member at the time of an exposure start, and a mask (mask stage). It is a figure which shows the positional relationship of the exposure area prescription | regulation member and mask (mask stage) at the time of scanning exposure. It is a figure which shows the structure of another mask position detection apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Exposure area | region definition member, 1c-1f ... Incident angle adjustment member, 2,52 ... Light projector, 3 ... Detection light, 4,54 ... Light receiver, 31 ... Light source, 33 ... Illumination optical system, 51 ... Control apparatus, 55 ... mask stage, 56 ... wafer stage, 60 ... actuator, M ... mask, PL ... projection optical system, W ... wafer.

Claims (5)

A mask stage on which a reflective mask is placed and a substrate stage on which a sensitive substrate is placed are synchronously moved in the scanning direction relative to the projection optical system, and the reflective mask is placed on the sensitive substrate by exposure light. In the exposure apparatus for transferring the pattern formed in
An exposure area defining member disposed between the reflective mask and the projection optical system and having an opening that defines an exposure area;
Detecting means for detecting the height of the reflective mask by irradiating the reflective mask with detection light and receiving the detection light reflected by the reflective mask;
With
The exposure apparatus according to claim 1, wherein the exposure region defining member is formed of a member that does not transmit the exposure light but transmits the detection light.   The exposure apparatus according to claim 1, wherein the detection unit is disposed at a position where the detection light passes through one of the opening and a portion other than the opening. The exposure area defining member is configured by combining a plurality of members,
3. The exposure apparatus according to claim 1, wherein the width of the opening in the scanning direction is changed by changing a combination position of the plurality of members.   The exposure apparatus according to any one of claims 1 to 3, wherein the exposure light and the detection light have different wavelengths. The exposure area defining member includes a reflection area where the detection light is reflected,
The distance between the mask and the exposure area defining member is measured based on the detection light reflected by the mask and the detection light reflected by the reflection area. 5. The exposure apparatus according to any one of items 4.

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