JP3182223B2 - Laser processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus for processing a workpiece by condensing a laser beam having passed through a transfer mask.

[0002]

2. Description of the Related Art Conventionally, in order to process holes, cuts, and the like in materials such as plastics, metals, and ceramics,
Laser processing equipment is used.

FIG. 3 is a configuration diagram of a conventional typical laser processing apparatus. In FIG. 3, reference numeral 1 denotes a laser oscillator, which uses a CO ₂ laser, a Nd: YAG laser, an excimer laser, or the like. After passing through the transfer mask 2, the laser light emitted from the laser oscillator 1 is reflected 90 degrees by the reflection mirror 3 and guided to the mask transfer lens 4. When the laser beam passes through the mask transfer lens 4, a mask image is formed on the workpiece 5 at a preset transfer ratio, and the removal processing is performed. After the completion of one processing, the position of the workpiece 5 in the horizontal direction (X-axis direction and Y-axis direction) is changed by the workpiece support device 6, and the next processing is performed.

In the laser processing apparatus having such a configuration, the transfer mask 2, the reflection mirror 3, the mask transfer lens 4,
And the positional relationship of the workpiece 5 satisfies the following equation (1). In the formula, A is the sum of the distance A ₂ from the distance A ₁ between the reflecting mirror 3 to the reflecting mirror 3 to the mask transfer lens 4 from the transfer mask 2, B from the mask imaging lens 4 to the workpiece 5 The distance, f, is the focal length of the mask transfer lens 4.

1 / A + 1 / B = 1 / f (1) And the transfer ratio α is as shown in equation (2).

Α = B / A (2)

[0007]

In the laser processing apparatus having the above structure, when changing the transfer ratio, it is necessary to adjust the distance A and the distance B, as is apparent from the equation (2). That is, at least two components, for example, the transfer mask 2
And work 5 or transfer mask 2 and mask transfer lens 4
Must be moved in a state that satisfies the relationship of equation (1), and the configuration of the apparatus is complicated.

In the case of processing workpieces having different thicknesses without changing the transfer ratio, a method of moving the transfer mask 2 and the mask transfer lens 4 by the same distance, or a method of moving the workpiece 5 of the transfer lens 4 It is necessary to adopt a method of adjusting the position along the optical axis L (Z-axis direction). However, in the former method, two moving mechanisms must be provided, and the device becomes complicated and expensive. On the other hand, in the method of moving the workpiece 5 along the optical axis L, it is necessary to incorporate the Z-axis position adjusting mechanism 6a into the workpiece support device 6. As shown in FIG. 3, when the Z-axis position adjustment mechanism 6a is provided on the XY stage surface of the XY axis position adjustment mechanism 6b, the Z stage surface of the Z-axis position adjustment mechanism 6a, which is a workpiece support surface, is used. Is the X-axis of the XY axis position adjustment mechanism 6b.
Since it is far from the Y stage surface, the deflection of the XY stage surface is enhanced, and the accuracy of focusing is deteriorated. Conversely, when the Z-axis position adjusting mechanism 6a is disposed below the XY-axis position adjusting mechanism 6b, the Z-axis position adjusting mechanism 6a must support the heavy XY-axis position adjusting mechanism 6b. However, there is a problem that the workpiece support device becomes expensive.

Further, when a single lens is used as the mask transfer lens 4, the transfer resolution is poor due to the spherical aberration, so that an expensive combination lens must be used.

Further, as shown in FIG. 4, since the laser beam is incident on the mask transfer lens 4 in parallel, the return light from the second surface of the mask transfer lens 4 is condensed in the lens 4, and Absorption due to alteration increased, which could eventually lead to lens destruction. In particular, a high-power laser such as an excimer laser has a high risk of lens destruction.

Further, in FIG. 4, the laser beam refracted by the mask transfer lens 4 is incident on the workpiece 5 with a considerable spread angle. As a result, there is a problem that a hole is formed obliquely in a peripheral portion in the processing region. Therefore, it is difficult to form a hole having a diameter twice or more the diameter of the image forming hole using a conventional laser processing apparatus.

The present invention has been made in view of the above circumstances, and has as its object to provide a laser processing apparatus capable of solving the various problems described above.

[0013]

According to a first aspect of the present invention, a transfer mask is irradiated with a parallel laser beam emitted from a laser oscillator, and a mask image of the transfer mask is formed. In a laser processing apparatus for processing a workpiece by projecting the workpiece on a workpiece, a first mask transfer lens disposed between the transfer mask and the workpiece;
A second mask transfer lens disposed between the first mask transfer lens and the second mask transfer lens, and a first mask disposed between the first mask transfer lens and the second mask transfer lens. A beam splitter that reflects laser light transmitted through the transfer lens and guides the laser light to the second mask transfer lens, and transmits visible light emitted from the workpiece and transmitted through the second mask transfer lens; and the beam splitter. Means for observing the processed surface of the workpiece with visible light transmitted through the lens. The distance (C) between the transfer mask and the first mask transfer lens is determined by the focal length of the first mask transfer lens. (F ₁ ), the distance (D) between the second mask transfer lens and the workpiece is the focal length (f ₂ ) of the _second mask transfer lens, and Said Distance between the second mask transfer lens _{(E = E 1 + E 2} ) longer than the focal length (f ₁₎ of the first mask transfer lens, the first mask transfer lens and said beam splitter (E ₁ ) is shorter than the focal length (f ₁ ) of the first mask transfer lens.

Further, the laser processing apparatus is characterized in that it has means for adjusting the distance between the transfer mask and the first mask transfer lens. Further, it is preferable to provide a means for adjusting the distance between the second mask transfer lens and the workpiece.

The distance (E = E ₁ + E ₂ ) between the first mask transfer lens and the second mask transfer lens is preferably
The size is equal to the sum of the focal length of the first mask transfer lens and the focal length of the second mask transfer lens (f ₁ + f ₂ ).

Further, the means for receiving the visible light transmitted through the beam splitter and observing the processing surface of the workpiece includes a CCD camera, a visible light relay lens for forming an image of the visible light on the imaging surface of the CCD camera, and a CCD. The one provided with a monitor television connected to the camera is preferable.

[0017]

The distance between the transfer mask and the first mask transfer lens is defined as the focal length of the first mask transfer lens, and the distance between the second mask transfer lens and the workpiece is defined as the second mask transfer lens. If the focal length of the mask image, the transfer ratio of the mask image is the ratio of the focal lengths of the first and second lenses, and
The mask image is always focused on the processed surface of the workpiece. Further, in such an arrangement, the spread angle of the laser light from the second mask transfer lens with respect to the workpiece is reduced.

By providing a means for adjusting the distance between the transfer mask and the first mask transfer lens, if the focal length of the first mask transfer lens is changed to change the transfer ratio, And the distance between the mask and the lens can be easily matched. As this adjusting means, a means for moving the transfer mask is preferable.

Also, by changing the focal length of the second mask transfer lens, the transfer ratio of the mask image can be changed, and therefore, the distance between the second mask transfer lens and the workpiece can be adjusted. It is preferable to provide a means for moving the second mask transfer lens, particularly a means for moving the second mask transfer lens. By allowing the distance between the second lens and the workpiece to be adjusted, fine adjustment can be performed when the thickness of the workpiece varies, and it can be used for focusing.

Since a beam splitter is arranged between the first and second mask transfer lenses so that an image of a workpiece can be taken out, the processed surface can be observed. Since the image of the workpiece is obtained through the second mask transfer lens, when the image of the workpiece is in focus, it can be determined that the workpiece is properly positioned at the focal point of the second mask transfer lens. Further, since the beam splitter is located out of focus of the first mask transfer lens,
Irradiation of the focused laser light to the beam splitter is prevented.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the configuration of a laser processing apparatus according to one embodiment of the present invention. Reference numeral 10 denotes a laser oscillator, preferably an excimer laser oscillator. The laser light emitted from the excimer laser oscillator 10 passes through the transfer mask 11 and then irradiates the first mask transfer lens 12. When a printed board on which an IC is to be mounted is prepared, a transfer mask 11 in which holes having a diameter of 60 μm are formed in a stainless steel plate having a thickness of 30 μm in an IC pattern, for example, is used. After passing through the first mask transfer lens 12, the laser light is reflected at a 90 ° angle by a beam splitter 13 such as a dichroic mirror and guided to the second mask transfer lens 14. The beam splitter 13 reflects the laser light but has a wavelength of 350 to 700
It has a property of transmitting visible light of about nm. The laser beam reflected by the beam splitter 13 is applied to a workpiece 16 fixed on a stage surface of a workpiece support device 15 via a second mask transfer lens 14. In the case of an excimer laser, a glass epoxy resin plate or the like is used for the workpiece 16.

The transfer mask 11 is set on a mask mount 17, and the mask mount 17 is mounted on a mount moving mechanism 18.
Thereby, it can be moved along the optical axis L. Although various types of the mount moving mechanism 18 are conceivable, in the illustrated embodiment, the screw 20 is rotated by a stepping motor 19 and the screw hole 21 of the mask mount 17 to which the screw 20 is screwed. It is configured.

The first mask transfer lens 12 is fixed at a predetermined position by a fixed lens mount 22.

The second mask transfer lens 14 is mounted on a movable lens mount 23. A focus adjustment mechanism 24 is provided on the movable lens mount 23 so that the position of the second mask transfer lens 14 can be finely adjusted along the optical axis L. Focus adjustment mechanism 24 in the illustrated embodiment
Consists of a screw body 26 connected to the rotation shaft of the stepping motor 25 and a screw hole 27 of the lens mount 23 to which the screw body 26 is screwed, but is not limited to this.

The position of the stage surface of the workpiece support device 15 can be adjusted only in the horizontal direction (XY axis direction), and is fixed in the optical axis direction (Z axis direction). Therefore, a Z-axis position adjusting mechanism is not required.

Further, in the laser processing apparatus of this embodiment, a visible light relay lens 28 and a CCD camera 29 are coaxial with the optical axis of the second mask transfer lens 14 at a position above the beam splitter 13 in FIG. Are located in
A monitor television 30 is connected to the CCD camera 29.

In such a configuration, the transfer mask 11
The distance C between the first mask transfer lens 12 and the first
The focal length f ₁ of the mask transfer lens 12 of FIG. The distance D between the processing surface of the workpiece 16 and the second mask transfer lens 14 is equal to the second mask transfer lens 14.
It is the focal length f ₂ of the. The distance E between the first and second mask transfer lenses 12 and 14 (that is, the distance E from the first mask transfer lens 12 to the beam splitter 13)
_1, although the sum of the distances E ₂ from the beam splitter 13 to the second mask imaging lens 14) is arbitrary, it is preferable that a distance greater than the focal length f ₁ of the first mask imaging lens 12 . In particular, the interval E is the standard first
The focal length f ₁ of the mask imaging lens 12 to be best to the sum of the focal length f ₂ of the second mask imaging lens 14. For example, the focal length f of the first mask transfer lens 12
_{When 1} is 300 mm and the focal length f _{2 of} the second mask transfer lens 14 is 100 mm, the interval C is 300 mm,
The interval D is 100 mm, and the interval E is 400 mm.

The distance between the first mask transfer lens 12 and the beam splitter 13 is preferably shorter than the focal length f ₁ . This is because the first mask transfer lens 12
If the beam splitter 13 is arranged at a position where the laser beam is narrowed in the above, the multilayer coating may be destroyed.

Next, the operation of the laser processing apparatus according to the present invention in such a configuration will be described.

The laser light emitted from the laser oscillator 10 travels in parallel with the optical axis L and passes through the transfer mask 11. Next, the laser beam passes through the first mask transfer laser 12,
The beam is bent by 90 degrees by the beam splitter 13 and irradiates the processing surface of the workpiece 16 via the second mask transfer lens 14. When the components of the laser processing apparatus are in the above-described positional relationship, the image of the point on the optical axis L of the transfer mask 11 travels along the optical path indicated by the dotted line, and at the intersection with the optical axis L on the processing surface of the workpiece 16. Focused. Therefore, in the above positional relationship, the mask image is transferred to the processing surface of the workpiece 16 in a focused state. The transfer ratio β at this time is as shown in the following equation (3).

Β = D / C = f ₂ / f ₁ (3) In the above positional relationship, the laser beam emitted from the second mask transfer lens 14 to the workpiece 16 is substantially as shown in FIG. Since the light beams are parallel to each other, the processing state in the vicinity of the optical axis and the processing state in the periphery of the processing area are substantially equal. Further, since the light incident on the second mask transfer lens 14 is not parallel, the light returned by the second surface of the second mask transfer lens 14 is not collected in the lens 14.
Therefore, there is no risk of lens breakage due to return light as in the related art, and this is particularly effective when a high-power laser such as an excimer laser is used.

The state of the processing surface of the workpiece 16 is determined by the CCD through the beam splitter 13 and the visible light relay lens 28.
The image is received by the camera 29, and the image is displayed on the monitor television 30. Here, when the thickness of the workpiece 16 is different from the predetermined thickness and the mask image and the workpiece image are out of focus, the stepping motor 25 of the focus adjusting mechanism 24 is driven to drive the second It is necessary to move the mask transfer lens 14 so that the distance D matches the focal length f ₂ of the second mask transfer lens 14. At this time, if the amount of change in the thickness of the workpiece 16 with respect to the predetermined thickness is known, the second mask transfer lens 14 may be moved by that amount. On the other hand, when the amount of change is unknown, the position of the second mask transfer lens 14 is adjusted so as to be in focus while watching the monitor television 30.

As long as the conditions of the interval C = the focal length f _{1 of} the first mask transfer lens and the interval D = the focal length f ₂ of the second mask transfer lens are satisfied, the processing surface of the workpiece 16 is the same as the above. A mask image is formed at the transfer ratio of Expression (3). Therefore, when changing the transfer ratio, the first mask transfer lens 12 is detached from the lens mount 22 and another mask transfer lens having a different focal length is mounted on the lens mount 22.
Attach to Then, by driving the mount moving mechanism 18 to move the mask mount 17 so that the focal length f ₁ ′ of the new first mask transfer lens and the distance C between the transfer mask and the lens coincide with each other. , The transfer ratio is f
A mask image of ₂ / f ₁ 'is obtained. Since the transfer mask 11 and the mask mount 17 are relatively lightweight, the load applied to the mount moving mechanism 18 is small, and high-precision adjustment is possible.

In the above embodiment, the first mask transfer lens 12 is replaced with another one having a different focal length, and the distance C between the transfer mask 11 and the first mask transfer lens 12 is adjusted. In this case, the transfer ratio is changed in the focused state. In particular, the adjustment of the interval C is performed by moving the transfer mask 11. However, the means for changing the transfer ratio is not limited to the above means. For example, the transfer mask 11 may be fixed, and the mounting position of the first mask transfer lens 12 may be changed. Further, the second mask transfer lens 14 may be replaced with another one having a different focal length, and the distance D between the workpiece 16 and the second mask transfer lens 14 may be adjusted. In this case, the adjustment of the interval D does not move the workpiece 16,
It is desirable to move the mask transfer lens 14 of FIG.

Further, although the first mask transfer lens 12 and the second mask transfer lens 14 are shown as single lenses in FIG. 1, they may be composed of a plurality of lenses. In particular,
The first mask transfer lens 12 is preferably a zoom lens capable of continuously changing the focal length. in this case,
The mount moving mechanism 18 can be automatically driven in response to a change in the focal length of the zoom lens.

[0037]

As described above, according to the present invention, when the transfer ratio of the mask image is changed, the focal length of the mask transfer lens is changed, and only one of the components of the laser processing apparatus is moved. And the driving mechanism for that purpose is relatively simple. Therefore, the manufacturing cost of the laser processing device is low. Further, since the driving mechanism is simple, it is possible to form a mask image with high accuracy.

The distance between the first and second mask transfer lenses can be arbitrarily determined as long as the positional relationship described in claim 1 is satisfied. Can be passed. As a result, even if a single lens having a large peripheral spherical aberration is used as the second mask transfer lens, the processing resolution does not decrease.

Further, since the laser beam from the second mask transfer lens to the workpiece is a parallel beam or a beam having a very small divergence angle, the processing state of the central portion and the peripheral portion of the processing region is almost the same. As a result, even when a hole that is twice as large as the imaging hole diameter is formed, uniform processing performance can be obtained over the entire processing region.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a laser processing apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an optical path of a laser beam passing through a second mask transfer lens in the laser processing apparatus of FIG.

FIG. 3 is a schematic view showing a conventional laser processing apparatus.

FIG. 4 is an explanatory diagram showing an optical path of a laser beam passing through a mask transfer lens in the laser processing apparatus of FIG. 3;

[Explanation of symbols]

Reference Signs List 10 laser oscillator, 11 transfer mask, 12 first mask transfer lens, 13 beam splitter, 14 second mask transfer lens, 15 work support device, 16
Workpiece, 17: Mask mount, 18: Mount moving mechanism, 24: Focus adjusting mechanism, 28: Visible light relay lens, 29: CCD camera, 30: Monitor television.

Claims (7)

(57) [Claims] 1. A laser processing apparatus that irradiates a transfer mask with parallel laser light emitted from a laser oscillator, projects a mask image of the transfer mask onto a workpiece, and processes the workpiece. A first mask transfer lens disposed between the workpiece, a second mask transfer lens disposed between the first mask transfer lens and the workpiece, and a first mask transfer The laser light is disposed between a lens and the second mask transfer lens, reflects the laser light transmitted through the first mask transfer lens, guides the laser light to the second mask transfer lens, and is emitted from the workpiece and emitted from the workpiece. A beam splitter that transmits visible light that has passed through the second mask transfer lens; and a unit that observes a processed surface of the workpiece with the visible light that has passed through the beam splitter; Click the focal length of the first first mask transfer lens spacing (C) between the mask imaging lens (f
₁ ), and the distance (D) between the second mask transfer lens and the workpiece is the focal length (f ₂ ) of the _second mask transfer lens.
The distance (E = E ₁ + E ₂ ) between the first mask transfer lens and the second mask transfer lens is made longer than the focal length (f ₁ ) of the first mask transfer lens, A laser processing apparatus, wherein an interval (E ₁ ) between the first mask transfer lens and the beam splitter is shorter than a focal length (f ₁ ) of the first mask transfer lens. 2. The laser processing apparatus according to claim 1, further comprising means for adjusting a distance between the transfer mask and the first mask transfer lens. 3. The laser processing apparatus according to claim 2, wherein the means for adjusting the distance between the transfer mask and the first mask transfer lens is means for moving the transfer mask. 4. The laser processing apparatus according to claim 1, further comprising means for adjusting a distance between the second mask transfer lens and the workpiece. 5. The apparatus according to claim 4, wherein said means for adjusting the distance between said second mask transfer lens and said workpiece is means for moving said second mask transfer lens. Laser processing equipment. 6. A means for receiving visible light transmitted through the beam splitter and observing a processed surface of the workpiece, comprising:
6. The camera according to claim 1, further comprising a D camera, a visible light relay lens that forms the visible light on an imaging surface of the CCD camera, and a monitor television connected to the CCD camera. The laser processing apparatus according to the above section. 7. The first mask transfer lens and the second mask transfer lens.
(E = E ₁ + E ₂ ) was set equal to the sum of the focal length of the first mask transfer lens and the focal length of the second mask transfer lens (f ₁ + f ₂ ). The laser processing apparatus according to claim 1, wherein: