JP5222088B2 - Optical system, laser processing apparatus, and scanning apparatus - Google Patents

Description

  The present invention relates to an optical system that guides light to a predetermined location, and more particularly to a technique for adjusting the optical path length to be constant even when there is a movable optical component that moves in an optical path between a light emitting unit and a light receiving unit. The present invention also relates to a laser processing apparatus and a scanning apparatus including such an optical system.

  In the manufacturing process of a semiconductor device, a large number of rectangular chip areas are defined on the surface of a substantially disk-shaped semiconductor wafer by dividing lines arranged in a lattice pattern, and electronic devices such as ICs and LSIs are formed in these chip areas. After forming the circuit, perform necessary processing such as backside grinding on the wafer, then cut the wafer along the planned dividing line and divide it, that is, dicing to obtain each chip area as a semiconductor chip Yes. The semiconductor chip thus obtained is packaged by resin sealing and widely used in various electric / electronic devices such as mobile phones and PCs (personal computers).

  As means for dicing a wafer into semiconductor chips, blade dicing is generally used in which a thin disc-shaped cutting blade rotated at a high speed is cut into the wafer. On the other hand, in recent years, laser dicing has also been attempted in which dicing is performed by irradiating a transmissive laser beam along a planned division line and performing groove processing or cutting processing while melting the wafer. (See Patent Document 1).

JP-A-10-305420

  As a laser processing apparatus that performs laser dicing, a workpiece (for example, the above-described wafer) W is held on a horizontal chuck table that can be moved and rotated in the X and Y directions, and is fixed on the chuck table. A configuration is often employed in which a laser beam oscillated by a laser oscillator is irradiated onto a wafer from a laser beam irradiation unit. Scanning the laser beam along the planned dividing line is performed by moving the chuck table side in the X direction or the Y direction. However, it is possible to improve the processing capability such as increasing the scanning speed and the movement width of each moving mechanism. In order to reduce the size of the apparatus by the reduction, a configuration in which the laser beam irradiation unit side also moves in the X direction or the Y direction has been studied.

  FIG. 11A schematically shows a configuration example in which the irradiation part side of the laser beam is moved. In this case, the laser beam L oscillated in the laser head 61 and irradiated horizontally is reflected by the mirror 62. Reflected downward at an angle of 45 ° and transmitted through the objective lens 63. The laser beam L passing through the objective lens 63 is condensed toward the work W and forms a focal point on the work W. As shown in the figure, when the laser head 61 and the optical system composed of the mirror 62 and the objective lens 63 are moved integrally in the X direction to scan the workpiece W with respect to the workpiece W, the laser beam L The waist position L1 (the position where the diameter of the laser beam is minimized) L1 does not change, and therefore the diameter of the laser beam L reaching the objective lens 63 does not change, so the spot diameter of the laser beam L formed on the workpiece W is constant. Appropriate laser processing is performed. However, this configuration has a problem that it is practically difficult to move the laser head 1 having a large weight or volume.

  Therefore, as shown in FIG. 11B, if the method is such that only the optical system can be moved in the X direction and the objective lens 63 is scanned over the workpiece W, the feasibility increases. However, in this method, the optical path length of the laser beam L between the laser head 61 and the objective lens 63 varies with the movement of the optical system. As a result, the waist position L1 varies, so the diameter of the laser beam L reaching the objective lens 63 is As a result, the spot diameter with respect to the workpiece W is not constant, and there is a disadvantage that stable laser processing cannot be performed.

  The present invention has been made in view of the above circumstances, and in an optical system in which a moving optical component (movable optical component) such as the objective lens is present in the optical path, the entire optical component is moved even if the movable optical component moves. An object of the present invention is to provide a practical optical system in which the optical path length does not fluctuate and is always kept constant, and the configuration is simple.

  The optical system of the present invention is an optical system that guides light emitted from a light emitting unit to an arbitrary light receiving unit through a movable optical component that is movably provided, and is provided so as to move integrally with the movable optical component. A mirror that reflects the light emitted from the light emitting unit to the optical path length adjusting optical path; the optical path length adjusting optical path is changed from the light emitting unit by changing the optical path length of the optical path length adjusting optical path according to the movement amount of the movable optical component; The optical path length to the light receiving unit is adjusted to a certain length, and the optical path is a path until the light reflected by the mirror is reflected again by the mirror.

  According to the optical system of the present invention, the light emitted from the light emitting unit is guided to the optical path length adjusting optical path by the mirror, and reaches the light receiving unit through the optical path length adjusting optical path. Therefore, the optical path length between the light emitting part and the light receiving part is obtained by adding the optical path length adjusting optical path to the distance between the light emitting part and the light receiving part. When the movable optical component moves, the mirror moves integrally, and the optical path length adjustment optical path fluctuates by an amount that cancels the movement amount of the movable optical component. Thereby, the optical path length from the light emitting part including the optical path length adjusting optical path to the light receiving part is kept constant. According to the optical system of the present invention, the optical path can be realized by disposing a mirror that moves integrally with the movable optical component between the light emitting unit and the light receiving unit and providing an appropriate optical path length adjusting optical path. An optical system having a constant length can be provided with a simple configuration.

Hereinafter, specific features of the optical system of the present invention will be listed.
The mirror is a first mirror that reflects the light at a reflection angle of 60 °, and the optical system again reflects the light reflected by the first mirror in the optical path length adjusting optical path. The mirror includes a second mirror that guides the mirror so as to reflect at an angle of reflection of 60 °, and the first mirror moves integrally with the movable optical component.

  Alternatively, the mirror is a first mirror that reflects the light at a reflection angle of 30 °, and the optical system re-directs the light reflected by the first mirror in the optical path length adjusting optical path. The first mirror includes a second mirror that guides the mirror so as to reflect at an angle of reflection of 30 °, and the first mirror moves integrally with the movable optical component.

In the configuration in which the mirror includes a first mirror and a second mirror, the second mirror reflects light reflected by the first mirror at an angle of reflection of 0 ° . Alternatively, the second mirror is a pair of mirrors that reflects the light reflected by the first mirror at a reflection angle of 45 °.

  Next, in the laser processing apparatus of the present invention, the light emitting unit in the optical system of the present invention is a laser beam irradiating unit that irradiates a laser beam, and the movable optical component is an optical system that is a condenser, and holds the workpiece. A holding means having a holding surface and having the workpiece held by the holding surface as a light receiving unit, a laser beam oscillation means for oscillating a laser beam, a condenser and a mirror are integrated in a direction parallel to the holding surface. It is characterized by comprising at least a moving means for moving it.

  According to the laser processing apparatus of the present invention, the work is scanned by irradiating the work with a laser beam and performing laser processing. Since the optical path length of the optical system is constant even when the condenser is scanned, there is no fluctuation in the waist position of the laser beam. For this reason, the laser beam spot diameter at the processing point is constant and the laser is stable. Processing can be performed.

  The workpiece that is the object to be processed in the laser processing apparatus of the present invention is not particularly limited. For example, a semiconductor wafer such as a silicon wafer, a DAF (Die Attach Film) provided on the back surface of the wafer for chip mounting, or the like. Adhesives or semiconductor product packages, ceramic, glass, sapphire or silicon substrates, various electronic components, various drivers such as LCD drivers for controlling and driving liquid crystal display devices, and micron-order accuracy is required. Various processing materials are mentioned.

  Next, a scanning apparatus according to the present invention includes the optical system according to the present invention, wherein the light emitting unit is an object to be read, and the light receiving unit is an imaging unit that captures light from the object to be read as an image. It is characterized by being.

  According to the scanning device of the present invention, the light emitted from the reading object that is the light emitting unit enters the imaging unit through the optical system of the present invention, and the imaging unit captures an image of the reading object. The object to be read is scanned with a movable optical component, but the optical path length of the optical system is always constant even when the movable optical component scans the object to be read. It becomes.

  According to the optical system of the present invention, in an optical system in which a movable optical component is present in the optical path, even if the movable optical component moves, the optical path length does not fluctuate and is always kept constant, and the configuration is simple and practical. The effect that the provision of a typical optical system can be achieved is achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1) First Embodiment (1-1) Overview of Laser Processing Apparatus FIG. 1 schematically shows a part of a laser processing apparatus according to the first embodiment. In FIG. Is a chuck table, and W is a workpiece such as a semiconductor wafer.

  The laser head 1 is fixed to a frame or the like (not shown). A laser oscillator 2 that oscillates a laser beam is accommodated in the laser head 1, and the laser beam L oscillated by the laser oscillator 2 is irradiated from the laser head 1 in the horizontal direction (X1 direction in FIG. 1). It has become. The chuck table 5 is a generally known vacuum chuck type, and the horizontal upper surface is a holding surface 5a of the workpiece W. The workpiece W is placed on the holding surface 5a of the chuck table 5, and is sucked and held on the holding surface 5a by the vacuum operation of the chuck table 5.

  The laser beam L irradiated from the laser head 1 is guided to the optical system 11 according to the first embodiment and irradiated onto the workpiece W held on the chuck table 5. The chuck table 5 is provided so as to be movable in the X and Y directions and is rotatable. The workpiece W held on the chuck table 5 rotates as the chuck table 5 rotates, and also moves in the X and Y directions together with the chuck table 5.

Examples of the laser processing on the workpiece W include dicing that divides into a large number of semiconductor chips, such as cutting processing that penetrates the thickness of the workpiece W, groove processing that forms a groove halfway through the thickness, and the like. . The conditions of the laser beam required for laser processing are determined according to the workpiece W and the mode of laser processing for the workpiece W. For example, the conditions are as follows.
-Light source: LD excitation Q switch Nd: YVO4 pulse laser-Wavelength: 355 nm pulse laser-Repetition frequency: 100 kHz
・ Average output: 2W
・ Condensing spot diameter: φ10μm
・ Processing feed rate: 600mm / sec

(1-2) Configuration of Optical System Hereinafter, the optical system 11 according to the first embodiment will be described.
The optical system 11 includes a first mirror 21 that reflects the laser beam L irradiated from the laser head 1 in the X1 direction upward at a reflection angle of 60 °, and the laser beam L reflected by the first mirror 21. A second mirror 22 is provided that reflects at a reflection angle of 0 ° . In the first mirror 21, the laser beam L is an angle of 120 ° (the angle here is an angle formed by an incident angle to the first mirror 21 and a reflection angle, and hereinafter the same meaning). Is reflected toward the second mirror 22. In the second mirror 22, the laser beam L is reflected at an angle of 0 ° , and returns to the first mirror 21 by overlapping the optical path. That is, the laser beam L reciprocates between the first mirror 21 and the second mirror 22 by overlapping the optical path. The first mirror 21 reflects the laser beam L again in the X2 direction at an angle of 120 °.

  A polarizing beam splitter 31 is disposed in the optical path of the laser beam L between the laser head 1 and the first mirror 21. Further, the polarizing beam splitter 31 has a 1/1 on the first mirror 21 side. A 4λ wavelength plate 32 is provided. The quarter-wave plate 32 converts the polarization state of the laser beam. For example, the laser beam L irradiated in the X1 direction as linearly polarized light from the laser head 1 is converted into circularly polarized light to become circularly polarized light. The component whose laser beam L is reflected by the first mirror 21 and the second mirror 22 and whose rotation direction is reversed is rotated by 90 ° from the linearly polarized light when the laser head is irradiated. Convert to linear polarization of state. The polarizing beam splitter 31 transmits the laser beam L irradiated from the laser head 1 as it is, but transmits the incident laser beam L through the ¼λ wavelength plate 32 from the first mirror 21 side with a reflection angle 45. Reflect downward (Z direction) at an angle of °. That is, the laser beam L transmitted from the first mirror 21 through the ¼λ wavelength plate 32 and reaching the polarizing beam splitter 31 is reflected downward at an angle of 90 °.

  The optical system 11 includes a third mirror 23 that reflects the laser beam L reflected downward by the polarization beam splitter 31 in the X1 direction at an angle of 45 °, and a laser that is reflected by the third mirror 23. A fourth mirror 24 that reflects the light beam L downward at a reflection angle of 45 °, and the laser beam L reflected by the fourth mirror 24 is collected and applied to the workpiece W held on the chuck table 5. An objective lens 33 that forms an L focal point is provided. The laser beam L traveling downward from the polarization beam splitter 31 is reflected by the third mirror 23 at an angle of 90 ° toward the X2 direction, and then downward by the fourth mirror 24 at an angle of 90 °. Reflected. The distance between the objective lens 33 and the workpiece W is set to the focal length of the objective lens 33.

  The first mirror 21, the fourth mirror 24, and the objective lens 33 are configured to be reciprocally movable in the X direction (X1 and X2 directions) integrally by a moving means such as a motor (not shown). That is, the first mirror 21, the fourth mirror 24, and the objective lens 33 are integrally connected by connecting means (not shown), and are moved synchronously by the same distance in the X direction. Hereinafter, the first mirror 21, the fourth mirror 24, and the objective lens 33, which are the components that move, may be collectively referred to as the moving element 11A. On the other hand, the polarizing beam splitter 31, the quarter-wave plate 32, the second mirror 22, and the third mirror 23 are fixed.

  When the moving element 11A moves in the X direction, the optical path length from the laser head 1 to the first mirror 21 varies by the amount of movement. That is, when the first mirror 21 moves in the X1 direction, the optical path length increases by the amount of movement, and when the first mirror 21 moves in the X2 direction, the optical path length decreases by the amount of movement. Further, when the moving element 11A moves in the X direction, the optical path length between the first mirror 21 and the second mirror 22 varies in proportion to the amount of movement of the first mirror 21. In this case, when the first mirror 21 moves in the X1 direction, the optical path length becomes short, and when the first mirror 21 moves in the X2 direction, the optical path length becomes long.

  When the moving element 11A moves in the X direction, the optical path length from the third mirror 23 to the fourth mirror 24 varies by the amount of movement. That is, when the fourth mirror 24 moves in the X1 direction, the optical path length decreases by the moving amount, and when the fourth mirror 24 moves in the X2 direction, the optical path length increases by the moving amount.

(1-3) Action of Optical System According to the optical system 11, the laser beam L irradiated in the X1 direction from the laser head 1 passes through the polarization beam splitter 31 and then passes through the quarter-wave plate 32. For example, the light is converted from linearly polarized light to circularly polarized light and reaches the first mirror 21. The laser beam L that has reached the first mirror 21 is reflected at an angle of 120 ° toward the second mirror 22, is reflected at an angle of 0 ° by the second mirror 22, and returns to the first mirror 21 again. Come. The laser beam L that has returned to the first mirror 21 is reflected at an angle of 120 ° in the X2 direction and reaches the ¼λ wavelength plate 32, and the λλ plate 32 changes the polarization component from, for example, circularly polarized light to Converted to polarized light.

  The laser beam L transmitted through the ¼λ wavelength plate 32 in the X2 direction is reflected downward by the polarizing beam splitter 31 at an angle of 90 °. Then, after being reflected in the order of the third mirror 23 and the fourth mirror 24, the light is condensed by the objective lens 33, and a focal point is formed on the workpiece W held on the chuck table 5. The workpiece W is moved in the X and Y directions, and the objective lens 33 of the moving element 11A is moved in the X direction to scan the workpiece W, whereby predetermined laser machining (cutting or groove processing) is performed on the workpiece W. Processing).

  According to the optical system 11 of the first embodiment, the optical path length from the laser head 1 to the objective lens 33 is kept constant even when laser processing is performed by moving the objective lens 33 in the X direction. It is supposed to be. The principle will be described below.

  As shown in FIG. 1, it is assumed that the moving element 11A has moved one unit in the X1 direction from the state where the focal position of the laser beam L transmitted through the objective lens 33 is 0 in the X direction, and the movement amount is “+1”. To do. Then, when the total optical path length from the laser head 1 to the objective lens 33 is viewed, the optical path length increases or decreases with respect to the optical path extending in the X direction. In this case, first, the fourth mirror 24 approaches the third mirror 23, and the optical path length between the mirrors 23 and 24 is shortened by one unit. Therefore, the total optical path length before the movement is “−1”. Become.

FIG. 2 geometrically shows the relationship between the reflection point of the first mirror 21 and the second mirror 22 that reflects the laser beam L and the amount of movement of the first mirror 21. In this figure, M ₁ 0: reflection point of the first mirror 21 before the movement, M ₂ 0: reflection point of the second mirror 22 before the movement, M ₁ 1: reflection of the first mirror 21 after the movement. Point, M ₂ 1: Reflection point of the second mirror 22 after the movement, and the movement amount is a distance a between M ₁ 0 and M ₁ 1 (this is “+1”).

Here, when a line F passing through M ₁ 1 perpendicular to the optical path M ₁ 0 → M ₂ 0 is drawn, the optical path length between the intersection F1 of the line F and the optical path M ₁ 0 → M ₂ 0 and M ₂ 0 is It is equal to the optical path length between the optical paths M _{1 1 to} M ₂ 1. Further, the angle formed by the optical path M ₁ 0 → M ₁ 1 and the optical path M ₁ 0 → M ₂ 0 is 60 °, and the angle formed by the line F and the optical path M ₁ 0 → M ₂ 0 is 90 °. Due to the relationship of the trigonometric function, the optical path length of M ₁ 0 → F ₁ is ½ of the distance a. As a result, the optical path length of the optical path M ₁ 0 → M ₁ 1 → M ₂ 1 → M ₁ 1 → M ₁ 0 after the movement becomes the optical path length of the optical path M ₁ 0 → M ₂ 0 → M ₁₀ before the movement. “+1”.

  Accordingly, since the optical path length from the third mirror 23 to the fourth mirror 24 fluctuates by “−1” as described above, the increase / decrease in the optical path length is offset to zero. As a result, the total optical path length from the laser head 1 to the objective lens 33 remains unchanged.

In this embodiment, in the state before the first mirror 21 is moved, reciprocally optical path optical path length adjustment between the reflection point M _{2 0} from the reflection point M _{1 0} of the first mirror 21 and the second mirror 22 is the optical path, in a state after providing the first mirror 21 is moved, the optical path length adjusting optical path round-trip optical path between the reflection point M _{2 1} of the second mirror 22 from the reflection point M _{1 1} of the first mirror 21 Is done.

  The principle of canceling the optical path length between the first mirror 21 and the second mirror 22 described above is applied regardless of the moving amount or moving direction of the moving element 11A. When the moving direction of the moving element 11A is the X2 direction opposite to the X1 direction, the moving amount + and-are only reversed, and the X from the third mirror 23 to the fourth mirror 24 is reversed. The fluctuation amount of the optical path length in the direction is always canceled out to zero by the fluctuation amount of the optical path length adjustment optical path.

  By providing the optical system 11, in the laser processing apparatus shown in FIG. 1, the optical path length of the optical system 11 is always kept constant even when the objective lens 33 is scanned in the X direction. There is no fluctuation in the waist position. As a result, the spot diameter of the laser beam L at the laser processing point on the workpiece W becomes constant, and as a result, stable laser processing can be performed.

(2) Second Embodiment Next, a second embodiment of the present invention will be described. FIG. 3 schematically shows a part of the laser processing apparatus according to the second embodiment. In the figure, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

(2-1) Optical System As shown in FIG. 3, in the optical system 12 of the second embodiment, the polarizing beam splitter 31 and the ¼λ wavelength plate 32 are removed from the constituent elements. Further, the third mirror 23 and the fourth mirror 24 are also omitted. A mirror 29 is provided as a substitute for the polarizing beam splitter 31, and a pair of second mirrors 22A and 22B arranged opposite to each other with a predetermined distance in the Y direction are provided as a substitute for the second mirror 22. . Thus, the second mirror may be composed of a plurality of mirrors. The moving element 12 </ b> A that moves in the X direction in the second embodiment is the first mirror 21, the objective lens 33, and the mirror 29.

  In the second embodiment, a laser beam L is emitted from the laser head 1 in the X2 direction, and the laser beam L directly reaches the first mirror 21 and is reflected at an angle of 120 ° to be one second mirror 22A. To reach. The laser beam that has reached one second mirror 22A is reflected at an angle of 90 °, travels in the Y direction, and reaches the other second mirror 22B. Thereafter, the laser beam is reflected downward at an angle of 90 ° by the second mirror 22B and guided to the first mirror 21. Thereafter, the laser beam L is reflected again at an angle of 120 ° by the first mirror 21 and travels in the X1 direction.

  The reflection point of the laser beam L to the second mirror 22A in the first mirror 21 and the incident point of the laser beam L from the second mirror 22B in the mirror 29 are the optical path length between the second mirrors 22A and 22B. Is shifted in the Y direction by a distance of. The laser beam L reflected by the first mirror 21 in the X1 direction is then reflected downward by a mirror 29 at an angle of 90 °, collected by the objective lens 33 and irradiated onto the workpiece W.

  Here, the first mirror 21 is composed of two mirrors divided in the Y direction, the reflection point of the laser beam L to the second mirror 22A in the first mirror 21, and the second mirror in the mirror 29. The incident point of the laser beam L from 22B may be provided on each of the divided first mirrors. Thus, the first mirror may be composed of a plurality of mirrors.

  In the second embodiment, when the mirror 29 moves in the X direction, the optical path length in the X direction varies by the amount of movement. This amount of variation is comparable to the amount of movement of the fourth mirror 24 in the first embodiment. That is, for example, if the unit moves in the X2 direction, “−1” is obtained. In the second embodiment, similarly to the first embodiment, when the objective lens 33 moves in the X direction, the optical path length is increased or decreased by the same amount as the movement amount by the optical path length adjustment optical path between the first mirrors 21. Occurs. For this reason, the optical path length from the laser head 1 to the objective lens 33 is kept constant.

  In the second embodiment, a pair of second mirrors 22A and 22B is used to shift the optical path in the Y direction so that the optical paths from the first mirror 21 to the mirror 29 do not overlap. For this reason, unlike the first embodiment, the polarizing beam splitter 31 and the ¼λ wavelength plate 32 for separating the optical paths are not required, and the configuration can be simplified.

(2-2) Specific Example of Laser Processing Apparatus FIGS. 4 to 7 show a specific example of a laser processing apparatus including the optical system 12 shown in the schematic diagram of FIG. In these drawings, reference numeral 41 denotes a base, and a support board 42 is fixed to the base 41 in a vertical direction, and a guide rail 43 extending in the horizontal direction (X direction) is provided on the lower front surface of the support board 42. Is fixed. A slider 44 is slidably attached to the guide rail 43. The slider 44 is moved in the X direction along the guide rail 43 by a moving means (not shown) made of a motor or the like.

  As shown in FIG. 7, the mirror 29, the first mirror 21, and the objective lens 33 are fixed to the slider 44. The mirror 29 is fixed to a bracket 45 fixed to the slider 44. The objective lens 33 is fixed to a bracket 46 disposed below the mirror 29 and fixed to the slider 44. In FIG. 7, the first mirror 21 that reflects the laser beam L irradiated in the X2 direction upward at a reflection angle of 60 ° is fixed to the left of the objective lens 33 in the bracket 46.

  A vacuum chuck type chuck table 5 is disposed below the objective lens 33. The chuck table 5 is moved in the X and Y directions by a drive means (not shown) and is rotated by a rotation drive means (not shown). The workpiece W is placed on the holding surface 5a which is the horizontal upper surface of the chuck table 5, and is sucked and held on the holding surface 5a by the vacuum operation of the chuck table 5.

  Above the guide rail 43, a square-shaped bracket 47 extending at an angle of 30 ° with respect to the guide rail 43 is disposed and fixed to the support board 42. A pair of second mirrors 22 </ b> A and 22 </ b> B are fixed to the lower surface of the bracket 47. The laser beam L reflected by the first mirror 21 reaches one of the second mirrors 22A, and then the laser beam L is directed at an angle of 90 ° toward the second mirror 22B by the second mirror 22A. Reflects in the Y direction. The laser beam L reaching the second mirror 22B is reflected toward the first mirror 21 at an angle of 90 °.

  On the base 41 on the back side of the support board 42, a laser head 1 for irradiating a laser beam in the X1 direction is disposed. The laser beam emitted from the laser head 1 travels in the X2 direction through a reflection mirror group (mirrors 48a, 48b, 48c, etc.) and directly reaches the first mirror 21. Next, the laser beam L is reflected by the first mirror 21 at an angle of 120 ° to the upper second mirror 22A, and further reflected by the second mirror 22A at an angle of 90 ° in the Y direction. To the mirror 22B.

  In the second mirrors 22A and 22B, the laser beam L is reflected from the second mirror 22A to the second mirror 22B, whereby the optical path of the laser beam L is shifted in the Y direction. Then, the laser beam L reflected on the second mirror 22A by the second mirror 22B is reflected at an angle of 90 ° toward the first mirror 21, and the angle of 120 ° again by the first mirror 21. Is reflected by the mirror 29. Thereafter, the laser beam is reflected downward by the mirror 29 at an angle of 90 ° toward the objective lens 33, and the laser beam L is focused by the objective lens 33 toward the workpiece W held on the chuck table 5. Thus, a focus is formed on the workpiece W.

  According to this laser processing apparatus, the X of the objective lens 33 in a state where the optical path length from the laser head 1 to the objective lens 33 is fixed by a simple optical system that guides the laser beam only by a combination of mirrors and one moving means. Directional movement is realized. Therefore, it is possible to improve the processing capability such as increasing the scanning speed and to reduce the apparatus size by reducing the moving width of each moving mechanism.

  Further, when the mirror 29, the first mirror 21 and the objective lens 33 are moved by a plurality of moving means, there may be a problem that a movement error occurs. However, according to this laser processing apparatus, the mirror 29, the first mirror 21 and the objective lens 33 are integrally moved by one moving means in a state where the mirror 29 and the first mirror 21 are integrally fixed. In addition, it is possible to reliably obtain an action of fixing the optical path length from the laser head 1 to the objective lens 33 constant.

(3) Third Embodiment Next, an optical system according to a third embodiment of the present invention will be described.
(3-1) Optical System As shown in FIG. 8, the optical system 13 of the third embodiment emits a laser beam L emitted horizontally from the laser head 1 in the same manner as the optical system 11 of the first embodiment. The first mirror 21, the second mirror 22, and the first mirror 21 are reflected to the polarizing beam splitter 31 in this order, and then reflected downward at an angle of 90 ° by the polarizing beam splitter 31. It is the structure which leads to.

  The third embodiment is different from the first embodiment in that the combination of the horizontal reflecting mirror and the lower reflecting mirror disposed between the polarizing beam splitter 31 and the objective lens 33 is three-stage in the vertical direction (first embodiment). In the embodiment, it is provided with a first stage comprising a third mirror 23 for horizontal reflection and a fourth mirror 24 for downward reflection. That is, the laser beam L reflected downward from the polarization beam splitter 31 is reflected by the third mirror 23 in the X2 direction, and then the fourth mirror 24, the fifth mirror 25, and the sixth mirror 26. The light is reflected by the seventh mirror 27 and the eighth mirror 28 and proceeds downward in a zigzag manner to reach the objective lens 33.

  In the third embodiment, among the third to eighth mirrors 23 to 28, the fourth mirror 24, the fifth mirror 25, and the eighth mirror 28 arranged in the vertical direction on the left side in FIG. Together with the mirror 21 and the objective lens 33, the moving element 13A is reciprocally moved integrally in the X direction. On the other hand, among the third to eighth mirrors 23 to 28, the third mirror 23, the sixth mirror 26, the seventh mirror 27, and the second mirror arranged in the vertical direction on the right side in FIG. Reference numeral 22 denotes a fixed state. Further, the polarization beam splitter 31 and the 1 / 4λ wavelength plate 32 are also fixed.

The first mirror 21 reflects the laser beam L irradiated from the laser head 1 in the X1 direction and transmitted through the polarizing beam splitter 31 and the ¼λ wavelength plate 32 upward at a reflection angle of 30 °. 2 to the mirror 22. That is, the laser beam L is reflected at an angle of 60 ° by the first mirror 21 and reaches the second mirror 22. In the second mirror 22, the laser beam L is reflected at an angle of 0 ° , and returns to the first mirror 21 by overlapping the optical path. Then, the laser beam L is again reflected in the X2 direction at an angle of 60 ° by the first mirror 21.

  A polarizing beam splitter 31 and a quarter-wave plate 32 disposed in the optical path between the laser head 1 and the first mirror 21 are the same as those in the first embodiment. That is, the ¼λ wavelength plate 32 converts the polarization state of the laser beam. For example, when the laser beam L irradiated from the laser head 1 in the X1 direction is received, the linearly polarized light is converted into circularly polarized light. When the polarized laser beam L is received from the first mirror 21 side, the circularly polarized component is converted into linearly polarized light. The polarization beam splitter 31 transmits the laser beam L irradiated from the laser head 1 as it is, but transmits the laser beam incident through the ¼λ wavelength plate 32 from the first mirror 21 side to the lower third beam. The light is reflected toward the mirror 23 at an angle of 90 °.

(3-2) Action of Optical System In the optical system 13, the laser beam L irradiated in the X1 direction from the laser head 1 passes through the polarization beam splitter 31 and the quarter-wave plate 32 as in the first embodiment. The light is transmitted, reciprocates between the first mirror 21 and the second mirror 22, and is reflected by the first mirror 21 in the X2 direction. Then, the light passes through the ¼λ wavelength plate 32 and is reflected by the polarizing beam splitter 31 toward the third mirror below. Thereafter, the laser beam L is reflected in the X2 direction by the third mirror 23, then is reflected by the fourth to eighth mirrors 24 to 28, reaches the objective lens 33, and is set downward by the objective lens 33. The light is condensed on an object (for example, the workpiece W) to form a focal point.

  Now, in the optical path between the third mirror 23 to the eighth mirror 28 of the optical system 13 of the third embodiment, the optical path extending in the X direction is between the third mirror 23 to the fourth mirror 24 and the fifth. There are three positions between the mirror 25 to the sixth mirror 26 and between the seventh mirror 27 to the eighth mirror 28. Therefore, when the moving element 13A moves by 1 unit in the X direction, the moving element 13A moves by a total of 3 units in the optical path between the third mirror 23 and the eighth mirror 28.

  As shown in FIG. 8, when the moving element 13A moves 1 unit in the X1 direction from the state where the focal position of the laser beam L transmitted through the objective lens 33 is 0 in the X direction, the movement amount is set to “+1”. To do. Then, each optical path length between the third mirror 23 to the fourth mirror 24, between the fifth mirror 25 to the sixth mirror 26, and between the seventh mirror 27 to the eighth mirror 28 is 1 unit. Shorter. That is, the total is shortened by 3 units, and the total optical path length is “−3” in this portion.

  On the other hand, when the first mirror 21 of the moving element 13A moves in the X direction, the optical path length between the first mirror 21 and the second mirror 22 varies according to the amount of movement. That is, when the first mirror 21 moves in the X1 direction, the optical path length between the first mirror 21 and the second mirror 22 increases, and conversely decreases when the first mirror 21 moves in the X2 direction.

FIG. 9 geometrically shows the relationship between the reflection point that reflects the laser beam L in the first mirror 21 and the second mirror 22 and the amount of movement of the first mirror 21. In this figure, M ₁ 0: reflection point of the first mirror 21 before the movement, M ₂ 0: reflection point of the second mirror 22 before the movement, M ₁ 1: reflection of the first mirror 21 after the movement. Point, M ₂ 1: Reflection point of the second mirror 22 after the movement, and the movement amount is a distance a between M ₁ 0 and M ₁ 1 (this is “+1”).

Here, when a line F passing through M ₁ 0 perpendicular to the optical path M ₁ 1 → M ₂ 1 is drawn, the optical path length between the intersection F1 of the line F and the optical path M ₁ 1 → M ₂ 1 and M ₂ 1 is , Equal to the optical path length between the optical paths M _{10 to} M ₂₀ . Further, the angle formed by the optical path M ₁ 0 → M ₁ 1 and the optical path M ₁ 1 → M ₂ 1 is 60 °, and the angle formed by the line F and the optical path M ₁ 1 → M ₂ 1 is 90 °. Due to the relationship of the trigonometric function, the optical path length of M ₁ 1 → F 1 is ½ of the distance a. Thereby, the optical path length of M ₁ 0 → M ₁ 1 → M ₂ 1 → M ₁ 1 → M ₁ 0 after the movement is “+3” to the optical path length of M ₁ 0 → M ₂ 0 → M ₁ 0 before the movement. "

Thus, the difference in the optical path length between the reflection points of the second mirror 22 before and after the movement when the reflection point M ₁₀ before the movement of the first mirror 21 is the base point is “+3”. The optical path length is increased by 3 units. However, since the optical path length between the third mirror 23 and the eighth mirror 28 fluctuated by “−3” as described above, the increase / decrease in the optical path length is offset to zero. Therefore, the total optical path length from the laser head 1 to the objective lens 33 is kept constant without change.

In the third embodiment, in the state before the first mirror 21 is moved, reciprocally optical path optical path length adjustment between the reflection point M _{2 0} from the reflection point M _{1 0} of the first mirror 21 and the second mirror 22 is the optical path, in a state after providing the first mirror 21 is moved, the optical path length adjusting optical path round-trip optical path between the reflection point M _{2 1} of the second mirror 22 from the reflection point M _{1 1} of the first mirror 21 Is done.

  The above optical path length canceling principle is applied regardless of the moving amount and moving direction of the moving element 13A. When the moving direction of the moving element 13A is the X2 direction opposite to the X1 direction, the movement amounts + and-are only reversed, and the X from the third mirror 23 to the eighth mirror 28 is reversed. The fluctuation amount of the optical path length in the direction is always canceled out to zero by the fluctuation amount of the optical path length adjustment optical path.

(4) Fourth Embodiment Next, a scanning apparatus according to a fourth embodiment using the optical system 11 of the first embodiment shown in FIG. 1 will be described with reference to FIG.

  FIG. 10 is a schematic diagram of the scanning apparatus. The components common to the first embodiment in the optical system 14 of the fourth embodiment applied to the scanning apparatus are the first mirror 21 to the fourth mirror 24. A polarizing beam splitter 31 and a quarter-wave plate 32. The first mirror 21 and the fourth mirror 24 are moving elements 14A that move in the X direction in this case. Below the fourth mirror 24, a reading object P is disposed horizontally, and this reading object P is illuminated by illumination means 51 such as a fluorescent lamp. The light L illuminating the object P to be read by the illuminating means 51 travels in the X1 direction through the fourth mirror 24, the third mirror 23, and the polarization beam splitter 31, and passes through the ¼λ wavelength plate 32. It reaches the first mirror 21.

The light L that has reached the first mirror 21 is reflected by the first mirror 21 toward the second mirror 22 at an angle of 120 °, and is reflected by the second mirror 22 at an angle of 0 ° . The first mirror 21 is reflected again in the X2 direction. Thereafter, the light passes through the ¼λ wavelength plate 32 and the polarizing beam splitter 31 and reaches the objective lens 35. By passing through the objective lens 35, the light is condensed on the image pickup means 52 having a CCD element, and an image of the reading object P is formed.

  According to this scanning device, by moving the fourth mirror 24 in the X direction, the image of the reading object P is scanned and imaged by the imaging means 52, and the image is read as imaging data. During scanning, the optical path length between the fourth mirror 24 and the third mirror 23 varies, and the amount of variation varies from the first mirror 21 to the second mirror 22 as described in the first embodiment. It is offset by the optical path length adjusting optical path generated between the two. Therefore, the optical path length from the reading object P to the objective lens 35 is always kept constant, and the imaging by the imaging means 52 is always in focus.

  As described above, the specific configuration of the present invention has been described in the first to fourth embodiments. However, the present invention is a mirror that guides light to the optical path length adjusting optical path (in the above embodiment, two mirrors: the first mirror and the second mirror). The configuration and number of mirrors) and the configuration of the optical path are not limited to the above embodiment. The present invention guides light to an optical path length adjustment optical path by a mirror that moves integrally with the movable optical component, and adjusts the optical path length according to the movement amount of the movable optical component regardless of the X, Y, and Z directions. Any configuration that can be adjusted in the optical path and the total optical path length can be adjusted to a certain length includes all the configurations.

It is a schematic diagram of the laser processing apparatus to which the optical system which concerns on 1st Embodiment of this invention was applied. It is a figure which shows the optical path length adjustment optical path set to the optical system which concerns on 1st Embodiment, Comprising: Between the reflective point which reflects the laser beam in a 1st mirror and a 2nd mirror, and the moving amount of a 1st mirror It is a figure which shows a relationship geometrically. It is a schematic diagram of the laser processing apparatus to which the optical system which concerns on 2nd Embodiment of this invention was applied. It is a front view which shows the specific example of the laser processing apparatus provided with the optical system which concerns on 2nd Embodiment. It is a partial perspective view of the laser processing apparatus. It is a partial perspective view of the laser processing apparatus. It is a partial perspective view of the laser processing apparatus. It is a schematic diagram of the optical system which concerns on 3rd Embodiment of this invention. It is a figure which shows the optical path length adjustment optical path set to the optical system which concerns on 3rd Embodiment, Comprising: The reflection point which reflects the laser beam in a 1st mirror and a 2nd mirror, and the movement amount of a 1st mirror It is a figure which shows a relationship geometrically. It is a schematic diagram of the scanning apparatus to which the optical system which concerns on 4th Embodiment of this invention was applied. It is a side view which shows the conventional optical system.

Explanation of symbols

1 ... Laser head (light emitting part, laser beam irradiation part)
2 ... Laser oscillator (laser beam oscillation means)
5 ... Chuck table (holding means)
5a ... Holding surface 11-14 ... Optical system 11A-14A ... Moving element 21 ... 1st mirror 22 ... 2nd mirror 24 ... 4th mirror (movable optical component: 4th Embodiment)
33 ... Objective lens (movable optical component, condenser: first to third embodiments)
52 ... Imaging means (light emitting part)
L: Laser beam M ₁ 0 → M ₂ 0 → M ₁ 0 ... Optical path length adjusting optical path M ₁ 0 → M ₁ 1 → M ₂ 1 → M ₁ 1 → M ₁ 0 ... Optical path length adjusting optical path P ... Reading object ( (Light emitting part)
W: Workpiece (light receiving part)

Claims (7)

An optical system that guides light emitted from the light emitting unit to an arbitrary light receiving unit via a movable optical component provided movably,
The optical path length adjustment optical path is provided to move integrally with the movable optical component and reflects light emitted from the light emitting unit to an optical path length adjustment optical path, and the optical path length adjustment optical path is in accordance with a movement amount of the movable optical component. By adjusting the optical path length of the optical path length adjusting optical path, the optical path length from the light emitting unit to the light receiving unit is adjusted to a certain length. The optical path until the light reflected by the mirror is reflected by the mirror again. An optical system characterized by that. The mirror is a first mirror that reflects the light at a reflection angle of 60 °;
The optical system includes, in the optical path length adjusting optical path, a second mirror that guides the light reflected by the first mirror so that the first mirror reflects again at an angle of reflection of 60 °. ,
The optical system according to claim 1, wherein the first mirror moves integrally with the movable optical component. The mirror is a first mirror that reflects the light at a reflection angle of 30 °;
The optical system includes, in the optical path length adjusting optical path, a second mirror that guides the light reflected by the first mirror so that the first mirror reflects again at an angle of 30 °. ,
The optical system according to claim 1, wherein the first mirror moves integrally with the movable optical component. 4. The optical system according to claim 2, wherein the second mirror reflects the light reflected by the first mirror at a reflection angle of 0 ° . 5.   4. The optical system according to claim 2, wherein the second mirror is a pair of mirrors that reflect the light reflected by the first mirror at a reflection angle of 45 °. 5. The optical system according to any one of claims 1 to 5 , wherein the light emitting unit is a laser beam irradiation unit that irradiates a laser beam, and the movable optical component is a condenser.
Holding means having a holding surface for holding a workpiece, and using the workpiece held on the holding surface as the light receiving unit;
Laser beam oscillation means for oscillating the laser beam;
Moving means for integrally moving the condenser and the mirror in a direction parallel to the holding surface;
A laser processing apparatus comprising at least: The light emitting portion is a read object, said light receiving portion and having an optical system according to any one of claims 1 to 5 which is an imaging means for imaging light from said read object as an image Scanning device.

Images