JP4539652B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus whose main purpose is drilling a workpiece such as a printed circuit board, and in particular, to improve productivity and processing quality.

Among conventional laser processing apparatuses mainly for drilling a workpiece such as a printed circuit board, a laser processing apparatus capable of performing processing at two locations simultaneously is disclosed in, for example, International Publication No. WO03 / 041904. The publication has a configuration as shown in FIG.
In FIG. 9, 1 is a laser oscillator, 2 is a laser beam, 3 is a mask that cuts out a necessary portion of the laser beam from an incident laser beam to make a processed hole into a desired size and shape, and 4 is a laser beam 2. And a plurality of mirrors that guide the optical path. 24 is a first polarization beam splitter that splits the laser beam 2 into two laser beams, 6 is one laser beam split by the first polarization beam splitter 24, 6p is the polarization direction of the laser beam 6, and 7 is the first polarization beam splitter. The other laser beam split by one polarization beam splitter, 7s is the polarization direction of the laser beam 7, 25 is a first beam for reflecting the laser beam 6 and transmitting the laser beam 7 and guiding it to the second galvano scan mirror 12. Two polarization beam splitters. 10 is a laser beam reflected by the second polarization beam splitter, 11 is a laser beam transmitted by the second polarization beam splitter, and 14 is a mirror for guiding the laser beam 6 to the second polarization beam splitter 25. , 17 is an fθ lens for condensing the laser beams 10 and 11 on the workpiece 20, and 13 is a first one for scanning the laser beam 7 in two directions and guiding it to the second polarization beam splitter 25. A galvano scan mirror 12 is a second galvano scan mirror for scanning the laser beam 10 and the laser beam 11 in two axial directions and guiding them to the workpiece 20. 18 is an XY table for moving the workpiece 20 in the XY direction, 19 is a power sensor for measuring the energy of the laser light emitted from the fθ lens 17, 15 is a first shutter for blocking the laser light 6, and 16 is This is a second shutter that blocks the laser beam 7. The power sensor 19 is fixed to the XY table 18 and can be moved to a position where the laser light strikes the light receiving portion of the power sensor 19 when measuring the energy of the laser light.
As shown in FIG. 9, one laser beam is split into two laser beams by a polarizing beam splitter, and two laser beams are scanned independently, so that two holes can be processed simultaneously. In the laser processing apparatus, the laser beam 2 oscillated by the linearly polarized light from the laser oscillator 1 is guided to the first polarization beam splitter 24 through the mask 3 and the mirror 4.
Then, in the first polarization beam splitter 24, the P wave component of the laser beam 2 is transmitted through the polarization beam splitter 24 to become the laser beam 6, and the S wave component is reflected by the polarization beam splitter 24 and split into the laser beam 7. .
The laser beam 6 that has passed through the first polarization beam splitter 24 is guided to the second polarization beam splitter 25 via the mirror 14.
On the other hand, the laser beam 7 reflected by the first beam splitter 24 is scanned in the biaxial direction by the first galvano scan mirror 13 and then guided to the second polarization beam splitter 25.
The laser beam 6 is always guided to the second polarization beam splitter 25 at the same position, but the laser beam 7 is incident on the second polarization beam splitter 25 by controlling the swing angle of the first galvano scan mirror 13. The position and angle to be adjusted can be adjusted.
Thereafter, the laser beams 10 and 11 are scanned in the biaxial direction by the second galvano scan mirror 12, then guided to the fθ lens 17, and focused on a predetermined position of the workpiece 20.
At this time, the laser beam 11 can be swung within a certain setting range, for example, a 4 mm square range with respect to the optical axis of the laser beam 10 by scanning the first galvanoscan mirror 13. Thereby, for example, it is possible to simultaneously irradiate two different points on the workpiece 20 with laser light via the second galvano scan mirror 12 that swings within a range that can be processed, such as 50 mm square.
FIG. 10 is a schematic diagram for explaining the principle of the polarizing beam splitter 24, with a front view at the center, a side view at the left and right, and a top view at the top.
In FIG. 10, reference numeral 26 denotes a window portion of a polarizing beam splitter, and in the case of a carbon dioxide laser, ZnSe or Ge is used. Reference numeral 27 denotes a mirror for turning the laser beam back to 90 °.
The polarization beam splitter 24 has a structure having a Brewster angle with respect to the incident beam for polarization separation.
Therefore, when the laser beam 28 is incident on the polarization beam splitter 24, the component in the polarization direction 28p (P wave component) is transmitted and the component in the polarization direction 28s (S wave component) is reflected.
Further, if the polarization direction is a circularly polarized light in which all polarization directions exist uniformly, or a polarization direction that forms an angle of 45 ° with the P wave and the S wave, the laser light is equally divided, and the energy of the laser light 29 and the laser light 30 becomes equal. It has the nature of
Therefore, the incident beam 2 to the first polarizing beam splitter 24 is configured to equally separate energy by forming an angle of 45 ° with circularly polarized light or P wave and S wave.
Of course, if the polarization direction of the laser light incident on the polarization beam splitter 24 is only the P-wave component, all the laser beam is transmitted, and if only the S-wave component is only reflected, the laser beam is reflected.
Therefore, the incident beam to the second polarization beam splitter 25 is such that the laser beam 7 has only the P wave component and the laser beam 6 has only the S wave component, so that the second carbano scan can be performed without energy loss. The configuration leads to the mirror 12.
In the conventional laser processing apparatus as described above, the first polarizing beam splitter 24 and the second polarizing beam splitter 25 both have windows arranged so that the incident angle of the laser light to the window portion 26 becomes the Brewster angle. For example, when a window made of ZnSe is used for carbon dioxide laser spectroscopy, the Brewster angle is 67.5 ° and the incident angle to the window. When the diameter of the laser beam guided to the polarization beam splitter is φ35 mm, the laser beam diameter on the window is 94 mm in the major axis direction. Therefore, the window needs to have an effective diameter of 2.5 times or more of the laser beam diameter, and it is difficult to maintain the manufacturing accuracy.
Further, the laser beam 6 transmitted as the P wave component through the first polarizing beam splitter 24 needs to be reflected as the S wave component by the second polarizing beam splitter 25, and the first polarizing beam splitter 24 is reflected as the S wave component. Since the reflected laser beam 7 needs to be transmitted as a P-wave component in the second polarization beam splitter 25, the first and second polarization beam splitters each have a mirror 27 for turning the laser beam back to 90 °. In addition, the relative positional relationship between the window portion 26 and the mirror 27 greatly affects the accuracy of the optical path after the polarization beam splitter. Because it was also necessary to make a splitter, the polarizing beam splitter would be a more expensive optical component There was also problem point.
In order to obtain more stable processing quality in consideration of the characteristics of the fθ lens 17, it is necessary to shorten the optical path length from the first polarizing beam splitter 24 to the fθ lens 17 as much as possible, and to reduce the effective diameter of the polarizing beam splitter. It was necessary to enlarge. However, since it is difficult to design the effective diameter of the polarizing beam splitter sufficiently large, the effective diameter of the polarizing beam splitter is actually not sufficient, and the diameter of the laser beam guided to the fθ lens 17 is restricted to be smaller than a desired diameter. Then, when the focal length of the fθ lens is constant, the diameter of the laser beam on the workpiece is restricted to be larger than the desired diameter, and an optical path suitable for smaller hole processing cannot be configured, which is required. There was also a problem that it was not possible to obtain the required processing quality.
In addition, individual optical components used in the optical system always have distortion (aberration) in the manufacturing process, and as the flatness is reduced, the required accuracy decreases and the yield increases and the cost increases. Is manufactured with an optical distortion of about 1/10 to 1/20 of the laser wavelength λ. If an optical system is constructed by combining a plurality of optical components without considering any optical components of this level, individual aberrations may accumulate, causing astigmatism, etc., and the required processing quality may not be obtained. There was also a problem.
In addition, since optical parts with flat surface shapes generally have the same manufacturing process for producing the front and back surfaces, both the front and back surface shapes tend to be convex or concave, The transmissive optical component also has a problem of increasing optical distortion (aberration).
The present invention has been made to solve such problems. In a laser processing apparatus that performs processing using laser light that has been dispersed by the polarization separation means, an inexpensive optical component can be used as the polarization separation means. The first object of the present invention is to obtain a laser processing apparatus capable of reducing the diameter of the laser beam on the workpiece.
Another object of the present invention is to obtain a laser processing apparatus capable of reducing the aberration due to the surface shape of the optical component and improving the processing quality.

In order to achieve the above object, the laser processing apparatus according to the first aspect of the present invention has an optical system composed of a plurality of optical components that guide the laser beam emitted from the laser oscillator to the workpiece. Is split into two laser beams by the first polarization separation means, one passes through the mirror, the other scans in the biaxial direction by the first galvano scan mirror, and the two laser lights are second polarization separation means. In the laser processing apparatus that scans with a second galvano scan mirror and processes the workpiece, the first and second polarization separation means are arranged at 45 ° with respect to the optical axis of the laser beam. Is.
In the laser processing apparatus according to the second invention, the first and second polarization separation means are polarization beam splitters having a dielectric multilayer coating formed on the surface.
In the laser processing apparatus according to the third aspect of the present invention, the first and second polarized light separating means have a concave shape on one surface and a convex shape on the back surface.
In the laser processing apparatus according to the fourth aspect of the invention, the first polarized light separating means has a convex surface on the side that reflects the laser light and a concave surface on the back surface, and is reflected by the first polarized light separating means. The laser beam is guided to the first galvano scan mirror having a concave surface, and the second polarization separation means has a concave surface on the side that reflects the laser light and a convex surface on the back surface. is there.
In the laser processing apparatus according to the fifth aspect of the invention, the first polarized light separating means has a concave surface on the side that reflects the laser light and a convex surface on the back surface, and is reflected by the first polarized light separating means. The second laser beam is guided to the first galvano scan mirror having a convex surface, and the second polarization separation means has a convex surface on the side that reflects the laser light and a concave surface on the back surface. is there.
In the laser processing apparatus according to the sixth invention, the concave or convex shapes on the surfaces of the first and second polarization separation means are formed with an accuracy of λ / 20 or less when the wavelength of the laser beam is λ. It is what has been.
In a laser processing apparatus according to a seventh aspect of the present invention, in the optical system, a pair of optical components having substantially the same surface shape is used, and a beam incident surface of one optical component is perpendicular to a beam incident surface of the other optical component. And the beam incident angle on one optical component is the same as the beam incident angle on the other optical component.
In the laser processing apparatus according to the eighth aspect of the present invention, a mask is provided in the laser beam path from the laser beam emitted from the laser oscillator to the first polarization separation unit, and the mask and the workpiece are The set of optical components is arranged between them.
In the laser processing apparatus according to the ninth aspect of the present invention, when the holder has a holder for individually fixing the set of optical components, and the holder has directionality, the axis indicating the directionality is set to each optical component. They are arranged in the same direction with respect to the incident surface.
In the laser processing apparatus according to the tenth invention, the surface shape of the one set of optical components is formed with an accuracy of λ / 10 to λ / 20, where λ is the wavelength of the laser beam. is there.
In the laser processing apparatus according to the eleventh aspect of the invention, the first and second polarization separation means are provided with a mechanism capable of adjusting the angle in two axial directions perpendicular to the traveling direction of the laser light and perpendicular to each other. It is.
In a laser processing apparatus according to a twelfth aspect of the present invention, a damper is provided to absorb laser light leaking as energy loss from the second polarization separation means.
According to the present invention, by using the polarization beam splitter having an incident angle of 45 ° as the polarization separating means, a laser beam having a larger diameter can be made incident on the fθ lens, and the diameter of the laser beam on the workpiece can be reduced. It can be made smaller and finer processing can be performed. Further, the polarization separating means is inexpensive and the cost can be reduced.

FIG. 1 is a block diagram of a laser machining apparatus showing Embodiment 1 of the present invention.
FIG. 2 is a schematic view of a holder portion for fixing the polarization beam splitter according to the first embodiment of the present invention.
FIG. 3 is a block diagram of a laser processing apparatus showing Embodiment 2 of the present invention.
FIG. 4 is a schematic diagram for explaining the relationship between the optical component surface shape and refractive power of the laser processing apparatus according to Embodiment 2 of the present invention.
FIG. 5 is a schematic diagram for explaining the arrangement of optical components of the laser machining apparatus according to Embodiment 2 of the present invention.
FIG. 6 is a schematic diagram for explaining the relationship between the refractive power and the arrangement of optical component holders having directionality of the laser processing apparatus according to the second embodiment of the present invention.
FIG. 7 is a block diagram of a laser processing apparatus showing Embodiment 3 of the present invention.
FIG. 8 is a schematic diagram for explaining the relationship between the optical component surface shape and refractive power of the laser processing apparatus according to Embodiment 3 of the present invention.
FIG. 9 is a block diagram of a laser processing apparatus showing the prior art according to the present invention.
FIG. 10 is a schematic diagram for explaining a polarization beam splitter of a laser processing apparatus showing the prior art according to the present invention.

（１）式は、焦点距離ｆのｆθレンズにより、ワーク上で集光されるビームスポット径ｄは、ｆθレンズに入射するレーザ光のビーム径Ｄに反比例することを示している。
よって、同じ径のウィンドウで偏光ビームスプリッタを構成することを考えた場合、上記のように入射角が４５°の偏光ビームスプリッタはより有効にレーザ光の有効径を確保でき、同じｆθレンズを使う場合、ｆθレンズに入射するビーム径Ｄを大きくすることができるため、さらにビームスポット径の小さい加工を実施することを可能にしている。
また、光路を９０°に折り返すミラーは不要となるため、偏光ビームスプリッタがより安価となり加工装置のコスト削減が可能となる。
尚、この発明の実施形態では、レーザ光を９０°に折り返す光路を構成しているため、入射角が４５°の偏光ビームスプリッタを適用している。この構成にすることによりＸＹテーブル１８上で２軸のガルバノスキャンミラーのスキャン方向が直行するので、第１図のように、この直行する方向をＸＹ方向に合わせることで、Ｘ方向、Ｙ方向をそれぞれガルバノスキャンミラーに１対１に対応させることができ、加工に際するガルバノスキャンミラーの制御が分かりやすくシンプルな構成とすることができる。
偏光ビームスプリッタでの、レーザ光の折り返し角度を９０°より鋭角にした場合、偏光ビームスプリッタの有効径を大きくし、さらにビームスポット径の小さい加工を実施することが可能となる。ただし、この場合はＸＹテーブル上で２軸のガルバノスキャンミラーのスキャン方向が直行しないので、例えば一方のガルバノスキャンミラーのスキャン方向をＸ方向に合わせても、Ｙ方向は他方のガルバノスキャンミラーとＸ方向のガルバノスキャンミラーとの合成でしかスキャンできないため、加工に際するガルバノスキャンミラーの制御が上記レーザ光を９０°に折り返す光路に比べて複雑になる。
実施の形態２．
分光した２つのレーザ光は共に第二の偏光ビームスプリッタを経た後、第１図のＸ方向の軸に平行でかつ、第二のガルバノスキャンミラー１２の中心に導かれる必要があるため、分光されたレーザ光６、７は独立して光軸の調整を実施する必要がある。
レーザ光１０、１１を精度よく第二のガルバノスキャンミラー１２に導くためには、第一の偏光ビームスプリッタ５の直前に設けられたミラー４ｚ以降の光路中において、光路の進行方向に対して垂直で、互いに直交する２軸方向に角度調整が可能なミラーがそれぞれ最低２枚必要であるが、本実施の形態では、レーザ光１０は第一の偏光ビームスプリッタ５直前のミラー４ｚと第二の偏光ビームスプリッタ８により光軸を調整可能とし、一方レーザ光１１は第一の偏光ビームスプリッタ５と第一のガルバノスキャンミラー１３により光軸を調整可能としている。ここで、第一のガルバノスキャンミラー１３は互いにねじれの方向に角度調整可能なミラーを２枚有し、互いに直交する２軸方向に角度調整可能な１枚のミラーと同じ機能を持つとみなせる。
第２図は、この発明の実施の形態２に係り、偏光ビームスプリッタをレーザ光の進行方向に対して垂直で、互いに直交する２軸方向に角度調整が可能な機構を示した図である。第２図において、偏光ビームスプリッタ５または８は固定ホルダー３１により支持されており、固定ホルダー３１はホルダー支え３２に第一の回転軸３５ａを介して回転自在に支持されている。また、ホルダー支え３２は光学系を支持する光学基台３６に第一の回転軸３５ａに直交した第二の回転軸３５ｂを介して回転自在に支持されている。これにより、偏光ビームスプリッタは光路の進行方向に対して垂直で、互いに直交する２軸方向に角度調整が可能となっている。また、ホルダー支え３２の固定ホルダー３１との接合部には固定ホルダー３１の回転方向に長い第一の調整穴３４ａが設けられ、第一の固定ねじ３３ａが貫通し固定ホルダー３１にねじ込まれており、回転調整後、第一の固定ねじ３３ａを締め付けることで固定ホルダー３１をホルダー支え３２に固定できる構造となっている。ホルダー支え３２と光学基台３６との接合部も同様に、第二の調整穴３４ｂと第二の固定ねじ３３ｂにより回転調整後固定可能な構造となっている。
一方、偏光ビームスプリッタの角度調整による偏光ビームスプリッタを透過するレーザ光の光軸の変化量は反射するレーザ光に比べ極度に小さく、無視できる程度であるので、第一の偏光ビームスプリッタ５により反射するレーザ光７、１１の光軸を調整しても透過するレーザ光６、１０の光軸にはほとんど影響を与えず、第二の偏光ビームスプリッタ８により反射するレーザ光６、１０の光軸を調整しても透過するレーザ光７、１１の光軸にはほとんど影響を与えないので、それぞれ独立して調整することができる。
また、ミラー４ｚや第一および第二の偏光ビームスプリッタ５，８の角度を調整した場合、偏光ビームスプリッタへの入射角が４５°からずれる場合もあり、このときレーザ光のエネルギーロスが増加するが、通常角度調整は微小でありエネルギーロスも微小である。また、レーザ発振器の出力による補正も可能なので、光軸調整による加工精度の向上を優先する事が望ましい。
次に、上記調整機構を備えた偏光ビームスプリッタ等による光軸の調整について説明する。
第一の偏光ビームスプリッタ５直前のミラー４ｚの角度調整を実施すると、レーザ光１０、１１は第二のガルバノスキャンミラー１３上で同じ方向に移動する。そのため、光軸調整方向の順序としては、まず２つのレーザ光に作用するミラー４ｚを用いたレーザ光１０の光軸の調整完了後、レーザ光１１の光軸調整を実施する必要がある。また、一度光軸の調整が完了していれば、第一の偏光ビームスプリッタ５直前のミラー４ｚの角度調整を実施することにより、第二のガルバノスキャンミラー１２上での２つレーザ光の相対位置関係を保ったままレーザ光１０、１１の光軸調整を実施することができ、精度よく第二のガルバノスキャンミラー１２の中心に２つのレーザ光を導くための光軸調整を容易にしている。
実施の形態３．
第３図はこの発明の実施の形態３に係り、１つのレーザ光を２つのレーザ光に分光し、２つのレーザ光を独立に走査することにより、２箇所同時に加工を実施することができる穴あけ用レーザ加工装置において、マスク転写を行う光学系を有し、特にマスク後に配置する略同一表面形状を有した１組の光学部品であるミラー４ａ、４ｂもしくは１４ａ、１４ｂを、一方のミラーのビーム入射面が他方のミラーのビーム入射面に対し垂直で、かつ一方のミラーへのビーム入射角が他方のミラーへのビーム入射角と同一（例えば４５°）となるように配置（例えば、一方のミラーでＸ方向から入射したレーザ光をＺ方向に反射し、その後他方のミラーでＹ方向に反射するように配置）した構成を示す構成図である。
第３図において、４ａ、４ｂはレーザ光２をマスク３から第一の偏光ビームスプリッタ５へ導くための略同一表面形状であるミラー、１４ａ、１４ｂは第一の偏光ビームスプリッタ５から第二の偏光ビームスプリッタ８へ導くための略同一表面形状であるミラーである。
本実施の形態３は、実施の形態１と偏光ビームスプリッタに関しては同一であるが、ミラー４，１４の配置もしくは表面形状が異なるので、この発明の特徴である光学部品の配置について第４図を用いて説明する。
第４図において、Ｐｒｕ（α）、Ｐｒｖ（α）はビーム入射角αで入射された入射ビームがミラーにより反射された反射ビームに係るｕ方向、ｖ方向の屈折力であり、Ｐｔｕ（α）、Ｐｔｖ（α）はビーム入射角αで入射された入射ビームがミラーを透過する透過ビームに係るｕ方向、ｖ方向の屈折力である。ここで、ｕ方向は各ビームの進行方向に垂直でかつビーム入射面（入射ビームと反射ビームにより形成される面）に平行な方向であり、ｖ方向は各ビームの進行方向に垂直でかつビーム入射面に垂直な方向である。
ここで、屈折力（Ｐｏｗｅｒ）は光学部品の屈折させる性能を表すパラメータの一つであり、屈折面の状態を示し、一般的に表面曲率半径Ｒに反比例、屈折率ｎに比例する。第４図において、表面曲率半径Ｒが同心円状に均一であり、かつ光学系に対し十分に大きく（光学部品の表面形状を略平面であるとしたとき）、屈折率をｎとすると、屈折力Ｐｒｕ（α）、Ｐｒｖ（α）は次式で与えられる。

一般的に光学部品は表面形状を平面として製作しても、製作工程の中で僅かに歪みを持ち、λ／１０〜λ／２０程度が一般的な加工精度であり、λ／２０より高精度で表面形状を仕上げるためには莫大な時間とコストを必要とする。したがって、一般的な光学部品はλ／１０〜λ／２０程度の表面曲率半径Ｒを持つといえる。例えばＺｎＳｅ（ｎ＝２．４１）に誘電体多層膜コーティングを施したビーム入射角４５°の偏光ビームスプリッタの場合、（２）（３）式より、それぞれ次式が得られる。

（４）（５）式より明らかなように、ビーム入射角４５°では、反射時にｕ方向のほうがｖ方向の屈折力よりも大きくなる。このｕ方向とｖ方向の屈折力の差が加工点にまで伝播すると、非点収差となるので、安定した加工品質を得ることが困難となる可能性がある。
これに対しこの発明では、光学系を構築するにあたり複数枚の光学部品のうち略同一表面形状である１組の光学部品を、一方の光学部品のビーム入射面が他方の光学部品のビーム入射面に対し垂直で、かつ一方の光学部品へのビーム入射角が他方の光学部品へのビーム入射角と同一となるように配置する。
ここで、ミラー１４ａ、１４ｂを用いて構成を説明する。第５図において、ミラー１４ａはＸ方向から入射したレーザ光を２方向に反射し、ミラー１４ｂはミラー１４ａに反射されたレーザ光をＹ方向に反射するように配置されている。また、ミラー１４ａのミラー表面曲率半径をＲａとし、ミラー１４ｂのミラー表面曲率半径をＲｂとする。ミラー１４ａのｕ方向の屈折力をＰａｒｕ（４５°）、ｖ方向の屈折力をＰａｒｖ（４５°）とし、ミラー１４ｂのｕ方向の屈折力をＰｂｒｕ（４５°）、ｖ方向の屈折力をＰｂｒｖ（４５°）とすると、ミラー１４ｂによって反射されたレーザ光のミラー１４ａおよびミラー１４ｂの合成されたｕ方向の屈折力Ｐｒｕ、ｖ方向の屈折力Ｐｒｖは以下のとおりとなる。

ここで、ミラー１４ａとミラー１４ｂは略同一表面形状であるので、Ｒａ≒Ｒｂとなり上記ＰｒｕとＰｒｖは略等しくなり、これによりｕ方向とｖ方向の屈折力の差をキャンセルし、結果として加工点での非点収差を低減でき、安定した加工品質を得ることができる。ミラー４ａ、ミラー４ｂについても同様な構成となっているので、同様な効果が得られる。
上記はα＝４５°で検討したが一般的な角度では以下のようになる。

Ｒａ≒Ｒｂの場合、（８）（９）式より明らかなように、ＰｒｕとＰｒｖは略等しくなり、これによりｕ方向とｖ方向の屈折力の差をキャンセルし、α＝４５°の時と同様に、加工点での非点収差を低減でき、安定した加工品質を得ることができる。
ところで、光学部品を固定するホルダー部材が方向性を持つ構造となっており、このホルダーに支持されたミラーの表面曲率半径がその方向性に沿って変化してしまい非点収差が発生する場合、１組の前記ホルダーに支持されたミラーを、ホルダーの方向性を各入射面に対して同じ方向に合わせるとともに、一方の光学部品のビーム入射面が他方の光学部品のビーム入射面に対し垂直で、かつ一方の光学部品へのビーム入射角が他方の光学部品へのビーム入射角と同一となるように配置する。
第６図に一例を示す。第６図において第一の光学部品３７ａと第二の光学部品３７ｂは同一表面形状の光学部品、第一のホルダー部材３８ａと第二のホルダー部材３８ｂは同一形状の光学部品固定部材である。Ａ、Ｂはそれぞれホルダー部材の持つ方向軸を示し、このホルダーにミラー等の光学部品を取り付けると、ミラー表面の曲率半径が、Ａ方向にはＲＡとなり、Ｂ方向にはＲＢとなる。
第６図のように、第一の光学部品３７ａと第二の光学部品３７ｂとを、第一の光学部品３７ａのビーム入射面が第二の光学部品３７ｂのビーム入射面に対し垂直で、かつ第一の光学部品３７ａへのビーム入射角が第二の光学部品３７ｂへのビーム入射角と同一（例えば４５°）となるように配置し、ホルダー部材の方向性を合わせるためにＡ方向を入射面に平行にした場合、第二の光学部品３７ｂの反射時のｕ方向、ｖ方向の屈折力Ｐｒｕ、Ｐｒｖは以下のようになる。

（１０）（１１）式より明らかなようにＰｒｕとＰｒｖは等しくなり、方向性を持ったホルダーによる非点収差をキャンセルすることができる。これにより、加工点における非点収差を低減することができ、安定した加工品質を得ることができる。入射角が４５°以外のときも非点収差をキャンセルできることは上述したように明らかである。
また、方向性を持った安価なホルダー部材を使用することができ、加工装置のコスト低減になるという効果がある。
なお、本実施の形態ではマスク転写を行う光学系において、マスク後に配置される複数枚の光学部品について説明を行った。これは、マスク転写においては、主にマスク後の光学部品の収差が加工点でのビーム品質に影響を与えるという理由からである。更に、マスク前の複数枚の光学部品についても同様の考え方で配置を行うとより効果が得られることは言うまでもない。
また、マスク転写を行う光学系だけでなくても、同様の考え方で光学部品の配置を行うことにより光学的な収差を低減する効果がある。
実施の形態４．
第７図は、この発明の実施の形態４に係り、第一の偏光分離手段として表面が凸形状、裏面が凹形状である偏光ビームスプリッタと、第二の偏光分離手段として、表面が凹形状、裏面が凸形状である偏光ビームスプリッタを用い、１つのレーザ光を２つのレーザ光に分光し、２つのレーザ光を独立に走査することにより、２箇所同時に加工を実施することができる穴あけ用レーザ加工装置を示す構成図である。
第７図において、２２は表面が凸形状、裏面が凹形状である偏光ビームスプリッタ（第８図（ａ）参照）、２３は表面が凹形状、裏面が凸形状である偏光ビームスプリッタ（第８図（ｂ）参照）である。ここで、それぞれの表面形状は製作機械である研磨機の形状等によって決められるので、制作方法を制御することによって、所望の加工精度の平面度で凹形状か凸形状のどちらかを選択し、製作することができる。
本実施の形態４は、実施の形態１と偏光ビームスプリッタの表面形状の構成が異なっており、この発明の特徴である偏光ビームスプリッタの形状について説明する。
第４図において、Ｐｔｕ（α）、Ｐｔｖ（α）はビーム入射角αで入射された入射ビームが光学部品を透過する透過ビームに係るｕ方向、ｖ方向の屈折力であり、表面曲率半径Ｒが同心円状に均一であり、かつ光学系に対し十分に大きく（光学部品の表面形状を略平面であるとしたとき）、屈折率をｎとすると、屈折力Ｐｔｕ（α）、Ｐｔｖ（α）は次式で与えられる。

例えばＺｎＳｅ（ｎ＝２．４１）に誘電体多層膜コーティングを施したビーム入射角４５°の偏光ビームスプリッタの場合、（１２）（１３）式より、それぞれ次式が得られる。

（４）（５）（１４）（１５）式より明らかなように、ビーム入射角４５°では、反射時だけではなく透過時もｕ方向のほうがｖ方向の屈折力よりも大きくなる。このｕ方向とｖ方向の屈折力の差が加工点にまで伝播すると、非点収差となるので、安定した加工品質を得ることが困難となる可能性がある。
ここで、偏光ビームスプリッタの透過時の屈折力に着目する。透過時の屈折力は偏光ビームスプリッタ表面での屈折力に加え、裏面での屈折力が加算される。すなわち、（１４）、（１５）式より透過時のｕ方向、ｖ方向の屈折力Ｐｔｕａ（４５°）、Ｐｔｖａ（４５°）は、表面、裏面をそれぞれ１、２の添字で示すと以下のようになる。

したがって、第８図（ａ）に示すように表面が凸形状（Ｒ１＞０）、裏面が凹形状（Ｒ２＜０）であると、表面と裏面の屈折力が打ち消すため、透過時の屈折力は小さくなる。結果として、ｕ方向とｖ方向の屈折力の差が小さくなるので、非点収差を低減する効果がある。
また、第８図（ｂ）に示すような表面が凹形状（Ｒ１＜０）、裏面が凸形状（Ｒ２＞０）であるときも同様に表面と裏面の屈折力が打ち消すため、透過時の屈折力は小さくなり、結果として、ｕ方向とｖ方向の屈折力の差が小さくなるので、非点収差を低減する効果がある。
この発明における偏光ビームスプリッタの表面形状は、表面と裏面との曲率半径の絶対値を同等にする必要があるので、加工精度を通常よりも良くすることが望ましく、λ／２０以下が望ましい。
次に光学系全体における第一の偏光ビームスプリッタ、並びに第二の偏光ビームスプリッタの最適形状について説明する。
先までの屈折力の議論と同様、光学系全体においても個々の光学部品の屈折力が加算され、結果として収差が大きいか小さいかが決定される。そこで、第７図の光学系において使用している第一の偏光ビームスプリッタ２２から第二の偏光ビームスプリッタ２３の間の光学部品について、第一の偏光ビームスプリッタを透過するレーザ光６の光路Ａと反射するレーザ光７の光路Ｂとに分けて説明する。
光路Ａでは、第一の偏光ビームスプリッタ２２を透過したレーザ光６がミラー１４ａと１４ｂにより第二の偏光ビームスプリッタ２３に導かれる。ミラー１４ａと１４ｂは、比較的製作が容易であるため、仕上げられる平面度の精度はλ／１０〜λ／２０程度のものが得られる。ただし、以下に示すようにガルバノスキャンミラーの平面度が比較的悪くなる傾向があるので、λ／１５〜λ／２０程度の精度で仕上げることが望ましい。
これに対し、光路Ｂでは、第一の偏光ビームスプリッタ２２を反射したレーザ光７が第一のガルバノスキャンミラー１３ａと１３ｂにより位置決めされ、第二の偏光ビームスプリッタ２３に導かれる。第一のガルバノスキャンミラー１３ａと１３ｂは、高速に動かすために非常に軽い必要があり、また、（１）式で説明したように加工品質を劣化させないようにするためには面積を大きくする必要があるため、薄くて広い形状となり製作が非常に困難であり、仕上げられる平面度は上記ミラーと比較して悪いものになる傾向が強く、λ／１０〜λ／１５程度である。また、表面形状としては、より強く製作機械に依存してしまい、例えば強い凹形状となる。
光路Ａと光路Ｂで個々の平面度が異なると加算される屈折力に差が発生する可能性がある。この屈折力の差は、光路Ａと光路Ｂによる焦点差となる可能性がある。
この発明では、第一のガルバノスキャンミラー１３ａと１３ｂの表面形状が強い凹形状の場合、第一の偏光ビームスプリッタ２２の表面形状を凸形状、裏面形状を凹形状とし、第二の偏光ビームスプリッタ２３の表面形状を凹形状、裏面形状を凸形状としている。
このような構成にすることで、光路Ａでは、第一の偏光ビームスプリッタ２２の透過時にはほとんど屈折力を発生することがなく、ミラー１４ａ、１４ｂでは表面形状の僅かな凹形状から僅かに収束方向の屈折力を持ち、第二の偏光ビームスプリッタ２３に導かれ、第二の偏光ビームスプリッタ２３の反射時に表面形状の僅かな凹形状から僅かに収束方向の屈折力が加算される。結果として僅かに収束方向の屈折力を持つレーザ光となる。
これに対し、光路Ｂでは、第一の偏光ビームスプリッタ２２の反射時に表面の凸形状から僅かに発散方向の屈折力を持って、第一のガルバノスキャンミラー１３ａ、１３ｂに導かれる。第一のガルバノスキャンミラー１３ａ、１３ｂは強い凹形状であるため、強い収束方向の屈折力が加算され、結果として僅かに収束方向の屈折力を持つレーザ光７が第二の偏光ビームスプリッタ２３をほぼ同じ屈折力のまま透過する。
上記では、ミラー１４ａ、１４ｂの表面形状を僅かな凹形状としたが、僅かな凸形状の場合でも、第一のガルバノスキャンミラー１３ａと１３ｂの表面形状を強い凹形状のときに、第一の偏光ビームスプリッタ２２の表面形状を凸形状、裏面形状を凹形状とし、第二の偏光ビームスプリッタ２３の表面形状を凹形状、裏面形状を凸形状とすることで、光路Ａと光路Ｂの屈折力の差を低減することができる。しかし、ミラー１４ａ、１４ｂの表面形状を僅かな凹形状とした方が低減する効果が高いので、凹形状が望ましい。
以上のように、この発明によれば、個々の光学部品が持つ収差成分を光学系の中でキャンセルし、結果として、非点収差や焦点差などの光学的な収差の少ない光学系を得るという効果がある。
また、本実施の形態では、第一の偏光分離手段として表面が凸形状、裏面が凹形状である偏光ビームスプリッタと、第二の偏光分離手段として、表面が凹形状、裏面が凸形状である偏光ビームスプリッタとしたが、第一のガルバノスキャンミラー１３ａ、１３ｂが強い凸形状の場合は、第一の偏光分離手段として表面が凹形状、裏面が凸形状である偏光ビームスプリッタと、第二の偏光分離手段として、表面が凸形状、裏面が凹形状である偏光ビームスプリッタとした上記と逆の配置とすれば、個々の光学部品が持つ収差成分を光学系の中でキャンセルすることができる。
上記説明からも明らかなように、光学系、或いは光学系に使用する光学部品によっては、形状、並びに平面度の最適値が異なることは言うまでもない。
また、本実施の形態では、第一、第二の偏光分離手段の形状に着目したが、上記説明からも明らかなように他の光学部品においても同様の考え方により最適値があることは言うまでもない。
また、実施の形態を１、２、３と分けて説明したが、これらを組み合わせることが可能であることは言うまでもない。Embodiment 1 FIG.
FIG. 1 relates to the first embodiment of the present invention, using a polarization beam splitter having an incident angle of 45 ° as polarization separation means, splitting one laser beam into two laser beams, and scanning the two laser beams independently. It is a block diagram which shows the laser processing apparatus for drilling which can implement 2 places simultaneously by doing. The same components as those in FIG. 9 of the prior art are designated by the same reference numerals, and detailed description thereof is omitted.
In FIG. 1, 5 is a first polarization beam splitter, 6 is a laser beam transmitted through the first polarization beam splitter 5, 6p is a polarization direction that becomes a P-wave component for the first polarization beam splitter of the laser 6, and 6s. Is a polarization direction that is an S wave component for the first polarization beam splitter of the laser beam 6, 7 is a laser beam reflected from the first polarization beam splitter 5, and 7s is an S wave for the first polarization beam splitter of the laser beam 7. The polarization direction which becomes a component, 7p is the polarization direction which becomes a P-wave component for the first polarization beam splitter of the laser beam 7, 8 is the second polarization beam splitter, 9 is a damper which receives the laser beam generated as an energy loss, 10 Is the laser beam reflected by the second polarization beam splitter 8 of the laser beam 6, and 11 is the second polarization beam splitter of the laser beam 7. A laser light transmitted in.
When the laser beam is polarized and separated in the prior art, a window having an incident angle as the Brewster angle is used, and the laser beam including the P wave component and the S wave component is polarized and separated, so that the transmitted P wave component and the reflection are reflected. The S wave component is equally distributed, and the energy of the laser beam is equally divided.
However, in the present embodiment, by using a polarizing beam splitter having a reflective surface coated with, for example, a dielectric multilayer film, the incident angle is set to 45 ° with respect to the optical axis instead of the Brewster angle. The P wave is transmitted with accuracy and the S wave is reflected with a certain accuracy to divide the energy of the laser light equally.
As an example, a case where a polarizing beam splitter coated so as to transmit 95% of the P wave and 5% of the S wave and reflect 95% of the S wave and 5% of the P wave will be described. Assuming that the energy of the laser light incident on the first polarizing beam splitter 5 is 100%, the laser light 6 transmitted through the first polarizing beam splitter 5 has a P-wave component of 47.5% and an S-wave component of 2.5. % Will be included. Thereafter, laser light including 47.5% S-wave component and 2.5% P-wave component is incident on the second polarizing beam splitter 8, and the laser light reflected by the second polarizing beam splitter 8 is The energy of the laser beam 10 including 45.125% S-wave component and 0.125% P-wave component and guided to the second galvano scan mirror 12 is finally 45.25%. The laser beam that causes energy loss that passes through the second polarization beam splitter 8 includes 2.375% of S wave component and 2.375% of P wave component.
On the other hand, the laser beam 7 reflected from the first polarization beam splitter 5 goes through the same process, and 45.25% of the energy is guided to the second galvano scan mirror 12 and 4.75% of the energy is lost. Become.
Therefore, a total of 9.5% is not led to the second galvano scan mirror 12 as an energy loss, but when the optical path according to the present embodiment is configured, the loss of the laser light 6 is the second polarization beam splitter. Since the loss of the laser beam 7 is reflected, all the laser beam that causes this energy loss can be collected in the portion of the damper 9 to prevent damage to the optical components and the like due to the laser beam of the loss. Can do.
The polarizing beam splitter transmits 95% of the P wave and 5% of the S wave and reflects 95% of the S wave and 5% of the P wave at an incident angle of 45 °, but the incident angle deviates from 45 °. In this case, the ratio of the transmitted P wave and the reflected S wave is decreased, and the energy loss is increased.
In the above description, it was explained that the energy loss of the polarizing beam splitter that transmits 95% of the P wave and 5% of the S wave and reflects 95% of the S wave and 5% of the P wave is 9.5%. It is clear that the energy loss becomes smaller than 9.5% if the transmittance of P wave and the reflectance of S wave are made higher than 95%.
In addition, since the polarization beam splitter according to the present embodiment is arranged with the incident angle of the laser beam being 45 °, when the diameter of the laser beam guided to the polarization beam splitter is φ35 mm, the laser beam diameter on the window is in the major axis direction. 52 mm, which is about 1.5 times the laser beam diameter, and the effective window diameter of the conventional polarizing beam splitter having an incident angle of Brewster's angle of 2.5 times or more than the incident laser beam diameter, Smaller shapes can be produced. In comparison with the area of the window, since the minor axis direction may be 35 mm, the polarization beam splitter having an incident angle of 45 ° can reduce the area by 44.6% compared to the conventional polarization beam splitter. Thereby, size reduction of a processing apparatus is attained.
Further, in the case of a window having the same diameter, for example, 53 mm, the conventional polarizing beam splitter has a Brewster angle of 67.5 °, so that the spectroscopic laser beam diameter is about φ20 mm, but a polarized beam having an incident angle of 45 °. The splitter has a diameter of 35 mm, and an optical path having a larger laser beam diameter can be formed. Here, when a laser beam having a beam diameter D is incident on an fθ lens having a focal length f and the beam spot diameter collected on the workpiece is d, the beam spot diameter d and the focal length f of the fθ lens are set. The relationship of the incident beam diameter D can be expressed by the following equation.

Equation (1) indicates that the beam spot diameter d collected on the workpiece by the fθ lens having the focal length f is inversely proportional to the beam diameter D of the laser light incident on the fθ lens.
Therefore, when considering the configuration of the polarizing beam splitter with windows having the same diameter, the polarizing beam splitter having an incident angle of 45 ° as described above can more effectively secure the effective diameter of the laser beam, and uses the same fθ lens. In this case, since the beam diameter D incident on the fθ lens can be increased, processing with a smaller beam spot diameter can be performed.
Further, since a mirror that turns the optical path to 90 ° is not required, the polarization beam splitter becomes cheaper, and the cost of the processing apparatus can be reduced.
In the embodiment of the present invention, a polarizing beam splitter having an incident angle of 45 ° is applied because an optical path for turning the laser light back to 90 ° is formed. With this configuration, the scan direction of the biaxial galvano scan mirror is orthogonal on the XY table 18, so that the X direction and the Y direction can be changed by matching the orthogonal direction to the XY direction as shown in FIG. Each of the galvano scan mirrors can be made to correspond one-to-one, and the control of the galvano scan mirror at the time of processing can be easily understood.
When the turning angle of the laser beam at the polarizing beam splitter is set to an acute angle from 90 °, it is possible to increase the effective diameter of the polarizing beam splitter and to perform processing with a smaller beam spot diameter. However, in this case, since the scanning direction of the biaxial galvano scan mirror does not go straight on the XY table, for example, even if the scan direction of one galvano scan mirror is aligned with the X direction, the Y direction is the same as that of the other galvano scan mirror. Since scanning can be performed only by combining with the galvano scan mirror in the direction, the control of the galvano scan mirror during processing is more complicated than the optical path for turning the laser beam back to 90 °.
Embodiment 2. FIG.
Since the two laser beams thus separated pass through the second polarization beam splitter, they need to be guided to the center of the second galvano scan mirror 12 and parallel to the axis in the X direction in FIG. It is necessary to adjust the optical axes of the laser beams 6 and 7 independently.
In order to guide the laser beams 10 and 11 to the second galvano scan mirror 12 with high accuracy, in the optical path after the mirror 4z provided immediately before the first polarization beam splitter 5, it is perpendicular to the traveling direction of the optical path. Thus, at least two mirrors each capable of adjusting the angle in the biaxial directions perpendicular to each other are required. In the present embodiment, the laser beam 10 is separated from the mirror 4z immediately before the first polarization beam splitter 5 and the second mirror 4z. The optical axis can be adjusted by the polarizing beam splitter 8, while the optical axis of the laser beam 11 can be adjusted by the first polarizing beam splitter 5 and the first galvano scan mirror 13. Here, the first galvano scan mirror 13 has two mirrors whose angles can be adjusted in the twisting direction, and can be regarded as having the same function as one mirror whose angle can be adjusted in two axial directions perpendicular to each other.
FIG. 2 is a diagram showing a mechanism capable of adjusting the angle of the polarization beam splitter in two axial directions perpendicular to the traveling direction of the laser beam and perpendicular to each other, according to the second embodiment of the present invention. In FIG. 2, the polarization beam splitter 5 or 8 is supported by a fixed holder 31, and the fixed holder 31 is rotatably supported by a holder support 32 via a first rotation shaft 35a. The holder support 32 is rotatably supported by an optical base 36 that supports the optical system via a second rotation shaft 35b that is orthogonal to the first rotation shaft 35a. Thus, the polarization beam splitter can be adjusted in angle in two axial directions perpendicular to the traveling direction of the optical path and orthogonal to each other. Also, a first adjustment hole 34 a that is long in the rotation direction of the fixing holder 31 is provided at a joint portion of the holder support 32 with the fixing holder 31, and a first fixing screw 33 a passes through and is screwed into the fixing holder 31. After the rotation adjustment, the fixing holder 31 can be fixed to the holder support 32 by tightening the first fixing screw 33a. Similarly, the joint between the holder support 32 and the optical base 36 has a structure that can be fixed after rotation adjustment by the second adjustment hole 34b and the second fixing screw 33b.
On the other hand, the amount of change in the optical axis of the laser beam transmitted through the polarization beam splitter by adjusting the angle of the polarization beam splitter is extremely small and negligible compared to the reflected laser beam, and is reflected by the first polarization beam splitter 5. Even if the optical axes of the laser beams 7 and 11 to be adjusted are adjusted, the optical axes of the transmitted laser beams 6 and 10 are hardly affected, and the optical axes of the laser beams 6 and 10 reflected by the second polarizing beam splitter 8 are reflected. Even if is adjusted, the optical axes of the transmitted laser beams 7 and 11 are hardly affected, so that adjustment can be made independently.
Further, when the angles of the mirror 4z and the first and second polarizing beam splitters 5 and 8 are adjusted, the incident angle to the polarizing beam splitter may deviate from 45 °, and at this time, the energy loss of the laser light increases. However, the angle adjustment is usually minute and the energy loss is also minute. In addition, since correction by the output of the laser oscillator is possible, it is desirable to give priority to the improvement of processing accuracy by adjusting the optical axis.
Next, adjustment of the optical axis by a polarizing beam splitter or the like equipped with the adjustment mechanism will be described.
When the angle adjustment of the mirror 4z immediately before the first polarization beam splitter 5 is performed, the laser beams 10 and 11 move on the second galvano scan mirror 13 in the same direction. Therefore, as the order of the optical axis adjustment direction, it is necessary to first adjust the optical axis of the laser beam 11 after the adjustment of the optical axis of the laser beam 10 using the mirror 4z acting on the two laser beams is completed. Further, once the adjustment of the optical axis is completed, the angle of the mirror 4z immediately before the first polarization beam splitter 5 is adjusted, so that the two laser beams on the second galvano scan mirror 12 are relatively adjusted. The optical axes of the laser beams 10 and 11 can be adjusted while maintaining the positional relationship, and the optical axis adjustment for guiding the two laser beams to the center of the second galvano scan mirror 12 with high accuracy is facilitated. .
Embodiment 3 FIG.
FIG. 3 relates to Embodiment 3 of the present invention, and drilling can be performed simultaneously at two locations by splitting one laser beam into two laser beams and independently scanning the two laser beams. In a laser processing apparatus for use, a mirror 4a, 4b or 14a, 14b, which is a set of optical components having an optical system for performing mask transfer, and having substantially the same surface shape disposed after the mask is used as a beam of one mirror. Arranged so that the incident surface is perpendicular to the beam incident surface of the other mirror and the beam incident angle to one mirror is the same (for example, 45 °) to the other mirror (for example, one of the mirrors) It is a block diagram showing a configuration in which laser light incident from the X direction is reflected by a mirror in the Z direction and then reflected by the other mirror in the Y direction.
In FIG. 3, 4a and 4b are mirrors having substantially the same surface shape for guiding the laser beam 2 from the mask 3 to the first polarizing beam splitter 5, and 14a and 14b are second mirrors from the first polarizing beam splitter 5. It is a mirror having substantially the same surface shape for guiding to the polarization beam splitter 8.
Although the third embodiment is the same as the first embodiment with respect to the polarization beam splitter, the arrangement of the mirrors 4 and 14 or the surface shape is different. Therefore, FIG. 4 shows the arrangement of the optical components that is a feature of the present invention. It explains using.
In FIG. 4, Pru (α) and Prv (α) are the refractive powers in the u direction and the v direction related to the reflected beam in which the incident beam incident at the beam incident angle α is reflected by the mirror, and Ptu (α) , Ptv (α) is the refractive power in the u and v directions related to the transmitted beam through which the incident beam incident at the beam incident angle α passes through the mirror. Here, the u direction is perpendicular to the traveling direction of each beam and parallel to the beam incident surface (the surface formed by the incident beam and the reflected beam), and the v direction is perpendicular to the traveling direction of each beam and the beam. The direction is perpendicular to the incident surface.
Here, refracting power (Power) is one of the parameters representing the refracting performance of the optical component, indicates the state of the refracting surface, and is generally inversely proportional to the surface curvature radius R and proportional to the refractive index n. In FIG. 4, the surface curvature radius R is concentrically uniform and sufficiently large with respect to the optical system (assuming that the surface shape of the optical component is substantially flat), and the refractive index is n, the refractive power Pru (α) and Prv (α) are given by the following equations.

In general, even if an optical component is manufactured with a flat surface shape, it has a slight distortion in the manufacturing process, and the general processing accuracy is about λ / 10 to λ / 20, which is higher than λ / 20. In order to finish the surface shape, enormous time and cost are required. Therefore, it can be said that a general optical component has a surface curvature radius R of about λ / 10 to λ / 20. For example, in the case of a polarizing beam splitter having a beam incident angle of 45 ° obtained by applying a dielectric multilayer coating to ZnSe (n = 2.41), the following equations are obtained from equations (2) and (3), respectively.

As is clear from the equations (4) and (5), at the beam incident angle of 45 °, the refractive power in the u direction is larger than the refractive power in the v direction at the time of reflection. When the difference in refractive power between the u direction and the v direction propagates to the processing point, astigmatism occurs, and it may be difficult to obtain stable processing quality.
On the other hand, in the present invention, when constructing an optical system, a set of optical components having substantially the same surface shape among a plurality of optical components is used, and the beam incident surface of one optical component is the beam incident surface of the other optical component. And the beam incident angle to one optical component is the same as the beam incident angle to the other optical component.
Here, the configuration will be described using the mirrors 14a and 14b. In FIG. 5, the mirror 14a reflects the laser beam incident from the X direction in two directions, and the mirror 14b is arranged to reflect the laser beam reflected by the mirror 14a in the Y direction. The mirror surface radius of curvature of the mirror 14a is Ra, and the mirror surface radius of curvature of the mirror 14b is Rb. The refractive power in the u direction of the mirror 14a is Paru (45 °), the refractive power in the v direction is Parv (45 °), the refractive power in the u direction of the mirror 14b is Pbru (45 °), and the refractive power in the v direction is Pbrv. Assuming (45 °), the combined refractive power Pru in the u direction and the refractive power Prv in the v direction of the mirror 14a and the mirror 14b of the laser light reflected by the mirror 14b are as follows.

Here, since the mirror 14a and the mirror 14b have substantially the same surface shape, Ra≈Rb and the above Pru and Prv are substantially equal, thereby canceling the difference in refractive power between the u direction and the v direction, resulting in a processing point. Astigmatism can be reduced, and stable processing quality can be obtained. Since the mirror 4a and the mirror 4b have the same configuration, the same effect can be obtained.
The above was examined at α = 45 °, but at a general angle, it is as follows.

In the case of Ra≈Rb, as is clear from the equations (8) and (9), Pru and Prv are substantially equal, thereby canceling the difference in refractive power between the u direction and the v direction, and when α = 45 °. Similarly, astigmatism at the processing point can be reduced, and stable processing quality can be obtained.
By the way, the holder member that fixes the optical component has a structure with directionality, and when the surface curvature radius of the mirror supported by the holder changes along the directionality and astigmatism occurs, The mirrors supported by the pair of holders are aligned in the same direction with respect to each incident surface, and the beam incident surface of one optical component is perpendicular to the beam incident surface of the other optical component. And the beam incident angle to one optical component is the same as the beam incident angle to the other optical component.
An example is shown in FIG. In FIG. 6, the first optical component 37a and the second optical component 37b are optical components having the same surface shape, and the first holder member 38a and the second holder member 38b are optical component fixing members having the same shape. A and B respectively indicate direction axes of the holder member. When an optical component such as a mirror is attached to the holder, the radius of curvature of the mirror surface is RA in the A direction and RB in the B direction.
As shown in FIG. 6, the first optical component 37a and the second optical component 37b are arranged such that the beam incident surface of the first optical component 37a is perpendicular to the beam incident surface of the second optical component 37b, and The beam is incident so that the beam incident angle on the first optical component 37a is the same as the beam incident angle on the second optical component 37b (for example, 45 °), and the direction A is incident to match the direction of the holder member. When parallel to the surface, the refractive powers Pru and Prv in the u direction and the v direction when the second optical component 37b is reflected are as follows.

(10) As is clear from the equations (11), Pru and Prv are equal, and astigmatism due to a directional holder can be canceled. Thereby, astigmatism at the processing point can be reduced, and stable processing quality can be obtained. As described above, astigmatism can be canceled even when the incident angle is other than 45 °.
In addition, an inexpensive holder member having directionality can be used, and the cost of the processing apparatus is reduced.
In the present embodiment, a plurality of optical components arranged after the mask have been described in the optical system that performs mask transfer. This is because, in mask transfer, the aberration of the optical component after masking mainly affects the beam quality at the processing point. Furthermore, it goes without saying that a plurality of optical components before the mask can be more effectively arranged by the same concept.
Further, not only the optical system that performs mask transfer but also the effect of reducing optical aberrations by arranging optical components based on the same concept.
Embodiment 4 FIG.
FIG. 7 relates to a fourth embodiment of the present invention, and a polarization beam splitter having a convex shape on the front surface and a concave shape on the back surface as the first polarization separation means, and a concave shape on the surface as the second polarization separation means. Using a polarizing beam splitter with a convex back surface, splitting one laser beam into two laser beams and independently scanning the two laser beams for drilling at two locations simultaneously It is a block diagram which shows a laser processing apparatus.
In FIG. 7, a polarizing beam splitter 22 has a convex shape on the front surface and a concave shape on the back surface (see FIG. 8 (a)), and 23 has a concave shape on the front surface and has a convex shape on the back surface (eighth). FIG. Here, each surface shape is determined by the shape of the polishing machine that is the production machine, so by controlling the production method, select either concave or convex shape with flatness of the desired processing accuracy, Can be produced.
The fourth embodiment is different from the first embodiment in the configuration of the surface shape of the polarizing beam splitter, and the shape of the polarizing beam splitter, which is a feature of the present invention, will be described.
In FIG. 4, Ptu (α) and Ptv (α) are the refractive powers in the u and v directions of the transmitted beam through which the incident beam incident at the beam incident angle α passes through the optical component, and the surface curvature radius R Is concentrically uniform and sufficiently large with respect to the optical system (assuming that the surface shape of the optical component is a substantially flat surface), and the refractive index is n, the refractive powers Ptu (α), Ptv (α) Is given by:

For example, in the case of a polarizing beam splitter having a beam incident angle of 45 ° obtained by coating a dielectric layer coating on ZnSe (n = 2.41), the following equations are obtained from equations (12) and (13), respectively.

As is clear from the equations (4), (5), (14), and (15), at the beam incident angle of 45 °, the refractive power in the u direction is larger than the refractive power in the v direction not only during reflection but also during transmission. When the difference in refractive power between the u direction and the v direction propagates to the processing point, astigmatism occurs, and it may be difficult to obtain stable processing quality.
Here, attention is paid to the refractive power upon transmission through the polarizing beam splitter. In addition to the refractive power at the surface of the polarizing beam splitter, the refractive power at the back surface is added to the refractive power at the time of transmission. That is, the refractive powers Ptua (45 °) and Ptva (45 °) in the u direction and the v direction at the time of transmission from the equations (14) and (15) It becomes like this.

Accordingly, as shown in FIG. 8 (a), when the surface has a convex shape (R1> 0) and the back surface has a concave shape (R2 <0), the refractive power of the front surface and the back surface cancels out. Becomes smaller. As a result, since the difference in refractive power between the u direction and the v direction is reduced, there is an effect of reducing astigmatism.
Also, when the surface is concave (R1 <0) and the back is convex (R2> 0) as shown in FIG. 8 (b), the refractive power of the front and back surfaces cancels out in the same manner. As a result, the refractive power is reduced, and as a result, the difference in refractive power between the u direction and the v direction is reduced, which has the effect of reducing astigmatism.
The surface shape of the polarizing beam splitter in the present invention needs to have the same absolute value of the radius of curvature of the front surface and the back surface, so that it is desirable to improve the processing accuracy than usual, and is preferably λ / 20 or less.
Next, the optimum shape of the first polarizing beam splitter and the second polarizing beam splitter in the entire optical system will be described.
As in the previous discussion of refractive power, the refractive power of individual optical components is added to the entire optical system, and as a result, it is determined whether the aberration is large or small. Accordingly, the optical path A of the laser beam 6 that passes through the first polarizing beam splitter with respect to the optical component between the first polarizing beam splitter 22 and the second polarizing beam splitter 23 used in the optical system of FIG. And the optical path B of the reflected laser beam 7 will be described separately.
In the optical path A, the laser beam 6 transmitted through the first polarizing beam splitter 22 is guided to the second polarizing beam splitter 23 by the mirrors 14a and 14b. Since the mirrors 14a and 14b are relatively easy to manufacture, the accuracy of the finished flatness is about λ / 10 to λ / 20. However, since the flatness of the galvano scan mirror tends to be relatively deteriorated as shown below, it is desirable to finish with an accuracy of about λ / 15 to λ / 20.
On the other hand, in the optical path B, the laser beam 7 reflected from the first polarization beam splitter 22 is positioned by the first galvano scan mirrors 13 a and 13 b and guided to the second polarization beam splitter 23. The first galvano scan mirrors 13a and 13b need to be very light in order to move at high speed, and the area needs to be increased in order not to deteriorate the processing quality as described in the equation (1). Therefore, the thin and wide shape is very difficult to manufacture, and the flatness to be finished tends to be worse than that of the mirror, which is about λ / 10 to λ / 15. In addition, the surface shape is more strongly dependent on the production machine, for example, a strong concave shape.
If the flatness differs between the optical path A and the optical path B, a difference may occur in the added refractive power. This difference in refractive power may be a focal difference between the optical path A and the optical path B.
In the present invention, when the surface shape of the first galvano scan mirrors 13a and 13b is a strong concave shape, the surface shape of the first polarizing beam splitter 22 is a convex shape, the back surface shape is a concave shape, and the second polarizing beam splitter The surface shape of 23 is a concave shape, and the back surface shape is a convex shape.
With this configuration, almost no refractive power is generated in the optical path A during transmission through the first polarization beam splitter 22, and the mirrors 14a and 14b have a slightly converging direction from a slightly concave shape on the surface. And is guided to the second polarizing beam splitter 23, and when reflecting off the second polarizing beam splitter 23, the refractive power in the convergence direction is added slightly from the slightly concave shape of the surface shape. As a result, the laser beam has a refractive power slightly in the convergence direction.
On the other hand, in the optical path B, the light is guided to the first galvano scan mirrors 13 a and 13 b with a slight refracting power from the convex shape of the surface when reflected by the first polarizing beam splitter 22. Since the first galvano scan mirrors 13a and 13b have a strong concave shape, a strong refracting power is added in the converging direction. As a result, the laser light 7 having a slightly converging refracting power passes through the second polarizing beam splitter 23. Transmits with almost the same refractive power.
In the above description, the surface shape of the mirrors 14a and 14b is a slight concave shape. However, even in the case of a slight convex shape, when the surface shape of the first galvano scan mirrors 13a and 13b is a strong concave shape, The surface shape of the polarizing beam splitter 22 is convex, the back surface shape is concave, the surface shape of the second polarizing beam splitter 23 is concave, and the back surface shape is convex. Can be reduced. However, the concave shape is desirable because the surface shape of the mirrors 14a and 14b is reduced to a slight concave shape because the reduction effect is high.
As described above, according to the present invention, the aberration component of each optical component is canceled in the optical system, and as a result, an optical system with less optical aberration such as astigmatism and focal difference is obtained. effective.
In the present embodiment, the first polarization separation means is a polarization beam splitter having a convex surface and the back surface is concave, and the second polarization separation means is a concave surface and the back surface is convex. Although the polarization beam splitter is used, when the first galvano scan mirrors 13a and 13b have a strong convex shape, a polarization beam splitter having a concave shape on the front surface and a convex shape on the back surface as the first polarization separation means, If the polarizing beam splitter has a convex shape on the front surface and a concave shape on the back surface as the polarization separating means, the aberration component of each optical component can be canceled in the optical system.
As is clear from the above description, it goes without saying that the optimum values of the shape and flatness differ depending on the optical system or the optical component used in the optical system.
In the present embodiment, attention is paid to the shapes of the first and second polarization separation means. However, as is apparent from the above description, it is needless to say that other optical components have optimum values based on the same concept. .
Further, although the embodiments have been described separately as 1, 2, and 3, it goes without saying that these can be combined.

  The laser processing apparatus according to the present invention splits one laser beam into two or more laser beams and simultaneously performs laser processing at two or more locations while reducing the manufacturing difficulty and cost while reducing the processing quality. Suitable for improving.

Claims (10)

It has an optical system composed of a plurality of optical components that guide laser light emitted from a laser oscillator to a workpiece, and splits one laser light into two laser lights by a first polarization separation means, And the other is scanned in the biaxial direction by the first galvanometer scan mirror, and after the two laser beams are guided to the second polarization separation means, the second galvanometer scan mirror is scanned and the first polarization In a laser processing apparatus that forms an optical path and processes a workpiece so that the laser light transmitted by the means is reflected by the second polarizing means and the laser light reflected by the first polarizing means is transmitted by the second polarizing means . ,
The first and second polarization separation means are arranged at 45 ° with respect to the optical axis of the laser beam, and the first and second polarization separation means have a concave shape on one surface and a convex shape on the back surface. The laser processing apparatus characterized by the above-mentioned. The first polarized light separating means has a convex shape on the surface that reflects the laser light, and a concave shape on the back surface.
The laser beam reflected by the first polarization separation means is guided to the first galvano scan mirror having a concave surface shape,
2. The laser processing apparatus according to claim 1 , wherein the second polarized light separating means has a concave surface on the side that reflects the laser beam and a convex surface on the back surface thereof. The first polarized light separating means has a concave surface on the side that reflects the laser light, and a convex surface on the back surface.
The laser beam reflected by the first polarization separation means is guided to the first galvano scan mirror having a convex surface shape,
2. The laser processing apparatus according to claim 1 , wherein the second polarized light separating unit has a convex shape on a surface that reflects laser light and a concave shape on a back surface thereof. The convex concave or of the surface of said first and second polarized light separating means from claim 1, characterized in that when the wavelength of the laser light is lambda, and is formed by lambda / 20 or less of accuracy 4. The laser processing apparatus according to any one of 3. In the optical system, a pair of optical components having substantially the same surface shape is formed by making the beam incident surface of one optical component perpendicular to the beam incident surface of the other optical component and the beam incident angle to one optical component. There laser processing apparatus according to any one of claims 1, characterized in that arranged so as to become the same as the angle of incidence of the beam to the other optical components 4. Providing a mask in the laser beam path from the laser beam emitted from the laser oscillator to the first polarized light separating means;
6. The laser processing apparatus according to claim 5 , wherein the set of optical components is disposed between the mask and the workpiece. A holder for individually fixing the set of optical components;
The laser processing apparatus according to claim 5 , wherein when the holder has directionality, the direction is arranged in the same direction with respect to an incident surface of each optical component. Said set optical component of the surface shape is, when the wavelength of the laser beam and λ, λ / 10~λ be formed in / 20 accuracy to claim 4 to 6, characterized in The laser processing apparatus as described. It said first and second polarization separation means, according to claim 1, characterized in that perpendicular to the traveling direction of the laser beam, and those having an angular adjustable mechanism in two directions perpendicular to each other Laser processing equipment. The laser processing apparatus according to claim 1, further comprising a damper to absorb the laser light leaking as energy loss from said second polarized light separating means.

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