JP4543069B2 - Maskless exposure system - Google Patents

Description

  The present invention relates to a maskless exposure apparatus that exposes a pattern on an exposure substrate without using a mask.

Conventionally, in order to form a wiring pattern on a printed circuit board, the pattern is formed in advance on a mask, and the mask pattern is projected and exposed using a mask exposure machine, or the pattern is exposed on the exposed board by contact or proximity exposure. Was. In recent years, a technique for directly exposing an exposure substrate without using a mask has been developed, and industrial utilization has begun (Patent Document 1). With such a maskless exposure apparatus, for example, a printed board having a pattern width of 20 μm could be manufactured.
JP 2004-39871 A

  In order to further improve the mounting density of electronic components and the like, it is desired to reduce the pattern width to 10 μm or less. However, when a pattern of 10 μm or less is exposed, since the depth of focus is narrow, it is difficult to make the pattern width uniform if the exposure substrate is warped or uneven in thickness.

  An object of the present invention is to provide a maskless exposure apparatus capable of solving the above-described problems and exposing a pattern having a uniform width on the surface of a workpiece even when the workpiece has warpage or thickness unevenness.

In order to solve the above problems, the present invention provides an exposure light source that outputs exposure illumination light, a two-dimensional spatial modulator, a first projection lens, a microlens array, a second projection lens, and an exposure. A stage that holds the substrate and moves in a direction perpendicular to the optical axis of the second projection lens, and a first surface in the plate thickness direction is an inclined surface having an angle θ with respect to the other surface in the plate thickness direction. And the second two wedge glasses, and a moving means for moving at least one of the wedge glasses, and the other surface of the first wedge glass with respect to the optical axis of the second projection lens And the second projection lens is combined in such a way that the distance between the one surface of the second wedge glass and the one surface of the first wedge glass becomes a predetermined value. In a maskless exposure apparatus placed on the incident or exit side A plurality of substrate surface height detectors arranged on the front side of the second projection lens in the exposure scanning direction and arranged in a direction orthogonal to the exposure scanning direction; and the plurality of height detectors The focal position of the second projection lens is determined from the plurality of height information detected by the time until the detected position on the substrate reaches the optical axis of the second projection lens by exposure scanning of the substrate. A control circuit that calculates and controls the moving means so that the focal point of the second projection lens coincides with the surface of the substrate at the position when the position on the substrate reaches the optical axis of the second projection lens. And the control circuit stores a detection result detected by the height detection means, and displays a warning after exposure at a position likely to exceed the focal depth of the second projection lens, or the Second projection lens A position that is likely to exceed the focal depth of the image is stored after exposure .

  Even if the workpiece has warpage or uneven thickness, a pattern having a uniform width can be exposed on the surface of the workpiece.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a block diagram of a first maskless exposure apparatus according to the present invention.

  The exposure illumination systems 11 to 17 having seven optical axes have substantially the same structure. In order to avoid the complexity of the drawing, numbers and signal lines (dotted lines) are displayed only in the portions of the seven optical axis systems that are easy to display in the figure, but the same applies to all the optical axes. There are numbers and signal lines. Hereinafter, the exposure illumination system 17 among the exposure illumination systems 11 to 17 will be described.

  The exposure illumination light emitted from the exposure illumination system 17 is applied to the upper two-dimensional spatial modulator 37 by the folding mirror 27. Here, a digital mirror device (hereinafter referred to as “DMD”) 37 is used as a two-dimensional spatial modulator.

  In the DMD 37, a large number of movable micromirrors are arranged in a matrix in the xy plane. When an ON / OFF signal is sent from the control device 9 to each micromirror, the micromirror that receives the ON signal tilts at a certain angle, reflects the incident exposure illumination light, and makes it incident on the first projection lens 47. Further, the exposure illumination light reflected by the micromirror in the OFF state does not enter the first projection lens 47 and does not contribute to the exposure. The exposure illumination light transmitted through the projection lens 47 enters the microlens array 57. Microlenses are arranged at the positions of the microlens array 57 where enlarged images (or reduced images) of the micromirrors of the DMD 37 are formed.

Each microlens disposed on the microlens array 57 is a convex lens of focal length f _M, the exposure illumination light substantially vertically incident on each microlens (exposure illumination light coming from the micro-mirror in the ON state) the micro roughly forming a minute spot on the position of f _M from the lens.

  Note that a pinhole array having an opening diameter substantially equal to the spot diameter may be disposed at the spot forming position. By arranging the pinhole array, extra (unnecessary) light can be shielded.

Spot pattern produced at a position below f _M of the microlens is incident on the second projection lens 67, the exposure illumination light emitted from the second projection lens 67 is wedge glass unit consisting of the wedge glass 717 and the wedge glass 727 Metropolitan A spot pattern array image with a magnification M is formed on the exposure substrate 8 through the GU 7.

  Next, the wedge glass unit GU7 will be described.

  FIG. 2 is a perspective view of the main part of the wedge glass unit GU7, and FIG. 3 is a view taken in the direction of arrow K in FIG.

  In the wedge glass 717, one surface 717b in the plate thickness direction is an inclined surface having an angle θ with respect to the other surface 717a in the plate thickness direction. Further, the wedge glass 727 is an inclined surface in which one surface 727b in the plate thickness direction is at an angle θ with respect to the other surface 727a in the plate thickness direction. The surface 717 a is disposed perpendicular to the optical axis of the second projection lens 67. On the other hand, the wedge glass 727 is arranged in combination so that the surface 727b is a distance (interval) δ with respect to the surface 717b. In this embodiment, the sizes of the wedge glass 727 and the wedge glass 717 are the same in the xy directions, and when they are exactly overlapped as seen from the z direction as shown in FIG. The distance from the surface 717a to the surface 727a of “wedge glass reference position” is t. Hereinafter, the distance t is referred to as “total thickness” of the wedge glass. The total thickness t at the reference position is set to 4 to 7 mm. The distance δ is a constant value between 0.01 and 0.3 mm. The minimum value of the distance δ may be smaller than 0.01 mm, but considering the ease of manufacturing the moving mechanism described later, it is practical to set the minimum value of the distance δ to about 0.05 mm. is there. The reason why the maximum value of the distance δ is 0.3 mm is that the aberration becomes large when the distance δ exceeds 0.3 mm.

  The moving mechanism (not shown) moves the wedge glass 727 (or one of the wedge glasses 717) along the surface 727b (strictly speaking, along the direction of the vector perpendicular to the normal of the slope and parallel to the slope). ) The wedge glass 727 is moved. This moving mechanism is controlled by the control circuit 9.

  Now, if the wedge glass 727 is moved by Δy along the inclined surface in the y direction, the total thickness change Δt of the glass in the direction parallel to the optical axis of the projection lens 2 is given by the following equation (1).

Δt = −Δy · tan θ (Formula 1)
Here, the refractive index of the wedge glasses 717 and 727 is n. Then, when the total thickness changes by Δt, the amount of change Δz of the focal position of the second projection lens 727 is expressed by the following formula 2 (note that the upper part is positive).

Δz = −Δt · (n−1) / n
= Δy · tan θ (n-1) / n (Expression 2)
That is, the wedge glass unit GU7 is a focusing device.

Therefore, when the height h (x, y) of the resist surface on the exposure substrate 8 or the surface on which the resist is placed is measured in advance, the spot image is positioned on the resist surface as follows. Can do. That is, the data of the height h (x, y) is stored in the control circuit 9, the wedge glasses 717 and 727 are arranged at the reference position, and the image plane of the second projection lens 67 is the design of the exposure substrate 8. Make sure it matches the top surface height. Then, an average height h _m of a region where the projection lens is exposed on the basis of the data stored in the control circuit 9, Delta] z in Equation 2 is the height of h _m (Delta] z = h _m) As wedge The glass 72 is moved by Δy and exposed. In this way, exposure with excellent accuracy can be performed.

  By the way, in the conventional maskless exposure apparatus, it is assumed that the surface of the exposure substrate is flat, and the second projection lens 61 to 67 is formed so that the imaging plane of the second projection lenses 61 to 67 coincides with the assumed surface of the exposure substrate. The lenses 61 to 67 were positioned in the z direction.

  However, in the case of a multilayer printed circuit board, for example, not only the plate thickness differs depending on the location, but also there is almost no case where the exposure surface is flat due to warpage or undulation of the substrate surface accompanying the lamination of the substrates. For this reason, for example, it has been difficult to make the width of the pattern uniform.

  Next, a maskless exposure apparatus that can perform exposure with excellent accuracy even when the surface of the exposure substrate is uneven or warps will be described.

  The wedge glass unit GU7 may be disposed on the entrance side of the second projection lens 67 (that is, between the microlens array 57 and the second projection lens 67).

  FIG. 4 is a block diagram of a maskless exposure apparatus according to the present invention. The same components as those in FIG. FIG. 5 is a block diagram of the height detector.

  A number of height detectors 600 are provided on one side in the y direction (the front side in the figure) of the second projection lens group (second projection lenses 61 to 67) disposed above the stage 80. A multi-height detector 600U arranged side by side in the x direction is provided. Each height detector 600 detects the surface height of the resist surface of the exposure substrate 8 or the exposure substrate itself under the resist.

  Next, the structure of the height detector 600 will be described.

  As shown in FIG. 5, the height detector 600 includes a light emitter 601, a lens 602, a lens 603, and a position sensor 604. The light emitter 601 is a light emitting diode (LED) or a semiconductor laser (LD) that outputs red light that does not expose a resist. The lens 602 collects the light emitted from the light emitter 601 on the surface of the exposure substrate 8. The lens 603 collects the light reflected by the substrate surface and forms an image on the position sensor 604 as a reflection part of the substrate.

  With the above configuration, the height of the exposure substrate 8 is the height set in the processing program (the average height or the design height obtained by actually measuring the heights of a plurality of locations on the exposure substrate 8. If it is different from the “set height”, the imaging position on the position sensor changes according to the amount of deviation from the set height. Therefore, the actual height of the exposure substrate 8 can be detected by reading the amount of change.

  Next, the operation of this embodiment will be described.

  The stage 80 on which the exposure substrate 8 is mounted is moved in the y direction at a constant speed v corresponding to the sensitivity of the photosensitive material from the near side to the heel side in FIG. Each height detector 600 detects the surface height of the exposure substrate 8 at regular time intervals. The detected surface height is stored in the storage unit of the control circuit 9 together with the position information of the exposure substrate 8 (the xy coordinate value of the measured location). The position where the height is detected reaches the exposure position 87 (a rectangle similar to the DMD 37) when the time determined by the speed v elapses. The control circuit 9 calls the surface height of the exposure substrate 8 that has reached the exposure position 87 from the storage unit, moves the wedge glass 727 in the y direction based on this information, and moves the image plane of the second projection lens 67 to the second projection lens 67. It is made to correspond to the surface of the exposure substrate 8.

  FIG. 6 is a cross-sectional view of the exposure substrate 8, schematically showing the vicinity of the surface when the exposure substrate 8 is cross-sectioned in the x direction.

  In the figure, the surface of the exposure substrate 8 is indicated by a solid line. Further, the surface 700 (Σex0) is a set height. As shown in the figure, the height in the exposure position 87 varies depending on the location. Here, since the detectors 600 are arranged at both ends of each exposure position, the imaging plane of the second projection lens indicated by the dotted line is positioned at the average value of the heights at both ends of each exposure position. Note that by narrowing the arrangement interval of the detectors 600, variation in the difference between the actual surface of the exposure substrate 8 and the imaging surface of the projection lens can be reduced.

  Further, although the cross section in the x direction has been described here, the same applies to the y direction. Therefore, for example, assuming that the exposure position 87 has a length in the y direction of y1 and a length in the x direction of x1, the height of the imaging plane of the second projection lens is measured in the region y1 × x1. It is practical to match the average height. The same applies to the other exposure positions 81 to 86.

  As described above, in this embodiment, the measurement of the surface height of the exposure substrate and the position adjustment in the height direction of the imaging surface are performed in parallel during the exposure, so that the imaging surface is substantially covered over the entire surface of the exposure substrate. It can be matched to the surface of the exposure substrate. As a result, the pattern width becomes uniform.

  Next, a method for further improving the height detection accuracy of the exposed substrate surface by the detector 600 will be described.

The measurement light output from the light emitter 607 described in FIG 5 is P-polarized light, is incident as a Brewster angle theta _B determined by the refractive index of the incident angle of the principal ray B11 disposed on the surface of the exposed substrate 8 photosensitive layer . In this way, as shown in FIG. 7, all incident light passes through the photosensitive layer 81 (that is, is not reflected on the surface of the photosensitive layer) and reaches the underlying substrate surface. Further, the light that is reflected by the underlying substrate surface and returns upward remains almost P-polarized light and is not reflected by the surface of the photosensitive layer, and returns to the upper position as it is, and is emitted from the photosensitive layer as detection light D11 to the position sensor 604. Incident. That is, the noise light D11n indicated by the dotted line in the figure reflected on the surface of the photosensitive layer that becomes noise during detection becomes zero. Moreover, the incident light incident on the position sensor 604 is hardly attenuated. Therefore, detection (measurement) with excellent accuracy can be performed.

  Moreover, since the result measured by the detector 600U is stored in the control circuit 9, for example, even when there is a warp exceeding the focal depth of the second projection optical system, it is possible to easily identify the position where the warp is present. it can. Therefore, it is possible to display such a position on the substrate in advance, to display a warning that there is a high risk that this part will be defective after exposure, or to store it as data.

It is a block diagram of the maskless exposure apparatus which concerns on Example 1 of this invention. It is a principal part perspective view of the wedge glass unit which concerns on this invention. FIG. 3 is a view taken in the direction of arrow K in FIG. 2. It is a block diagram of the maskless exposure apparatus which concerns on Example 2 of this invention. It is a block diagram of a height detector. It is sectional drawing of an exposure board | substrate. It is explanatory drawing of the measurement light which concerns on this invention.

Explanation of symbols

8 Exposure substrate 67 Second projection lens 717 First wedge glass 727 Second wedge glass 717u First wedge glass surface 727u Second wedge glass surface θ Angle of inclined surfaces of wedge glasses 717 and 727 δ surface Distance between 717u and surface 727u

Claims (2)

An exposure light source that outputs exposure illumination light, a two-dimensional spatial modulator, a first projection lens, a microlens array, a second projection lens, and an optical axis of the second projection lens holding an exposure substrate A stage that moves in a direction orthogonal to the first, second wedge glass in which one surface in the thickness direction is inclined with respect to the other surface in the thickness direction, and the wedge glass Moving means for moving at least one of the first wedge glass, the other surface of the first wedge glass being arranged perpendicular to the optical axis of the second projection lens, and the second wedge glass A maskless exposure apparatus in which the one surface of the second projection lens is combined so that the distance from the one surface of the first wedge glass becomes a predetermined value and is arranged on the incident side or the emission side of the second projection lens In
A plurality of substrate surface height detection means arranged on the front side of the second scanning lens in the exposure scanning direction and arranged in a direction perpendicular to the exposure scanning direction;
From the plurality of height information detected by the plurality of height detection means, the second position during which the detected position on the substrate reaches the optical axis of the second projection lens by exposure scanning of the substrate. The focal position of the projection lens is calculated, and when the position on the substrate reaches the optical axis of the second projection lens, the focal point of the second projection lens coincides with the surface of the substrate at the position. A control circuit for controlling the moving means;
Equipped with a,
The control circuit stores a detection result detected by the height detection unit and displays a warning after exposure at a position likely to exceed the focal depth of the second projection lens. apparatus. An exposure light source that outputs exposure illumination light, a two-dimensional spatial modulator, a first projection lens, a microlens array, a second projection lens, and an optical axis of the second projection lens holding an exposure substrate A stage that moves in a direction orthogonal to the first, second wedge glass in which one surface in the thickness direction is inclined with respect to the other surface in the thickness direction, and the wedge glass Moving means for moving at least one of the first wedge glass, the other surface of the first wedge glass being arranged perpendicular to the optical axis of the second projection lens, and the second wedge glass A maskless exposure apparatus in which the one surface of the second projection lens is combined so that the distance from the one surface of the first wedge glass becomes a predetermined value and is arranged on the incident side or the emission side of the second projection lens In
A plurality of substrate surface height detection means arranged on the front side of the second scanning lens in the exposure scanning direction and arranged in a direction perpendicular to the exposure scanning direction;
From the plurality of height information detected by the plurality of height detection means, the second position during which the detected position on the substrate reaches the optical axis of the second projection lens by exposure scanning of the substrate. The focal position of the projection lens is calculated, and when the position on the substrate reaches the optical axis of the second projection lens, the focal point of the second projection lens coincides with the surface of the substrate at the position. A control circuit for controlling the moving means;
With
Together with the control circuit stores the result of detection by said height detecting means, the second possible features and to luma Sukuresu exposure to saving the likely position beyond the depth of focus of the projection lens after exposure apparatus.

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