JP2006055880A - Method for machining many works for femtosecond laser light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase productivity while suppressing heat storage to workpieces, by frequently and uniformly distributing and emitting femtosecond laser light to the workpieces by the combination of a reflective mirror and a movement stage in microfabrication using a femtosecond laser. <P>SOLUTION: Laser light L emitted from a femtosecond laser system 1 is highly precisely reflected by a mirror 9 whose angle is adjusted by a servomotor 10 for mirror rotation control, and the laser light L can be subjected to positional control freely in a lateral direction as shown in the figure. Further, a box body 7 is integrated with a movement stage 14 movable by orthogonal 3 axes, and is freely movable at high precision. The laser light is frequently and uniformly distributed by the mirror, and irradiates each workpiece. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a processing method for picking a large number of micro workpieces with a femtosecond laser.

Some microfabrication using a laser processing device uses a femtosecond laser as a processing light source. As can be seen from the fact that the unit of one femtosecond is one thousandth of a second, laser processing is performed for a very short time. Since the machining is finished before the heat is generated by driving the workpiece, the heat is hardly generated.
In addition, femtosecond lasers have a very small spot diameter when irradiating lasers, so they are unlikely to be accompanied by heat generation. It is considered.
However, the current technology has not yet left an experimental range, and mass production technology for efficiently processing a large number of workpieces in the manufacturing industry has not been established.
In particular, there is an urgent need for development of efficient mass production processing technology for metal parts of 0.1 mm to 1 mm, which is expected to generate great demand in the industry.

Regarding the use of femtosecond laser light, as described above, it is common that the object to be processed is a fine small workpiece.
These small small workpieces are individually set in a box (chamber), and the workpiece is processed by irradiating femtosecond laser, but the processing is completed with one irradiation. Therefore, the irradiation is repeated many times while moving the irradiation position little by little.
Although it is difficult to generate heat by irradiating for an extremely short time per time, if the number of times of irradiation is accumulated or the number of times of irradiation per unit time is increased, heat is inevitably accumulated in the work piece, and the work piece is altered or generated heat. Undesirable phenomena such as deterioration in accuracy and plasma generation occur.
That is, if the irradiation frequency is increased in order to increase productivity, adverse effects due to heat generation will occur, and if the irradiation interval of the femtosecond laser is set to be long in order to avoid this, the processing efficiency will decrease.

For example, an XY orthogonal biaxial stage is housed in a vacuum chamber of a box, and an observation electron microscope is provided. A femtosecond laser whose optical axis is adjusted by two galvanometer mirrors The workpiece is irradiated from the glass window.
The workpiece assumes a very small semiconductor device. (Patent Document 1)
However, the workpiece assumed in the above apparatus is extremely fine, and no means for efficiently processing a large number of workpieces is disclosed.
JP 2004-53550 A

  As mentioned above, in this processing field that has not yet been pioneered, conventional MEMS technology is inefficient, and in the micro processing of metal parts based on such technology, efficient processing assuming mass production is performed. I could not.

  A problem to be solved by the present invention is that, in a method of processing a fine workpiece by a femtosecond laser, a multi-piece machining method for improving productivity while preventing heat accumulation on the workpiece has not been established. That is.

  The present invention arranges a plurality of workpieces on a moving stage, and irradiates the plurality of workpieces with frequent and even distribution of femtosecond laser light, thereby simultaneously processing a plurality of workpieces, It is characterized in that the continuity of the processing is increased and the productivity is improved by suppressing the temperature rise of the workpiece due to the laser irradiation.

The multi-piece machining method of the present invention relates to a method of freely machining a plurality of minute workpieces with femtosecond laser light, and reduces the time and effort of setup by improving the number of machining simultaneously. There is an advantage that high-precision machining can be realized by avoiding local heat storage on individual workpieces.
As the number of workpieces increases, the heat storage to each workpiece per unit time can be reduced, and the influence of heat can be minimized.

  In the present invention, there is provided a machining method in which femtosecond laser light is frequently and evenly distributed by a reflecting mirror, and multiple pieces of three-dimensional machining are simultaneously performed on workpieces of the same shape arranged on a moving stage in a box. It was realized.

FIG. 1 shows a basic configuration of a processing apparatus according to the present invention. Signals are distributed at a terminal 15 via a control unit 11 by software processing of a computer 12, and positioning and adjustment of laser light are performed from a signal line 13. Do the following operations.
Since the laser light L emitted from the femtosecond laser device 1 is reflected with high accuracy by the mirror 9 whose angle is adjusted by the mirror rotation control servomotor 10, the laser light L can be freely positioned in the left-right direction in the figure. Control is possible.
The pulsed femtosecond laser light L is distributed and irradiated to the fine workpieces W frequently and evenly by the mirror.
The moving stage 14 on which the workpiece W is mounted can be freely moved with high accuracy by servo motors 3, 4 and 5 of the X, Y and Z axes.

FIG. 2 shows a processing apparatus according to a second embodiment in which airtightness is taken into consideration in the basic configuration shown in FIG.
The box 7 on which the work is placed is airtight, and a glass window 8 through which the laser beam L can be transmitted is provided on the top of the box 7.
The box 7 is integrated with the orthogonal three-axis moving stage 14 and can be freely moved with high accuracy.

FIG. 3 shows that the inside of the box body can be decompressed in the configuration of FIG. 2, and a pipe 18 is connected to the box body 7, and the inside of the box body 7 is decompressed by the decompression pump 3.
When it is desired to control the degree of decompression in the box 7 such as pressure adjustment, the pressure inside the box is monitored in real time by the pressure sensor S and adjusted appropriately by the pressure reducing valve V1. Can be maintained at a desired pressure.

Next, a method of filling the box with various gases is shown in FIG.
First, with the gas adjustment valve V2 closed, the pressure inside the box 7 is adjusted by the pressure reduction pump 11 until the desired pressure is obtained while checking the air inside the box 7 with the pressure sensor S, and then the pressure reduction adjustment valve V1 is closed. Then, by opening the gas adjustment valve V2 little by little, the gas G flows from the gas cylinder B through the pipe 18 into the box, and the gas adjustment valve V2 is closed when it reaches a desired atmospheric pressure.
Thereafter, the pressure adjustment valve V1 and the gas adjustment V2 are appropriately controlled according to the measured value of the atmospheric pressure sensor S to stabilize the gas pressure in the box.

Although the present invention assumes application to a fine workpiece, it is difficult to visually confirm a workpiece having a size of less than 1 mm.
In particular, in the case of a processed work that does not have sufficient processing results, as shown in FIG. 5, while confirming the processed work and its processing status with a microscope M, the processing work is observed and adjustment of laser irradiation is appropriately performed. Become.
The microscope M is connected to the image processing unit 16 through a signal line 13, and after performing image processing such as digital conversion, the personal computer 12 displays data processing status, work images, and the like.

Further, as shown in FIG. 6, the glass window 8 at the top of the box 7 is in close contact with the packing 17, so that the glass window 8 is removed and the workpiece is observed with the microscope M from directly above the workpiece. Is also possible.
In this case, as shown in FIG. 7, positioning of the moving stage 14 and image input of the microscope M are performed together, thereby inspecting the workpiece surface before processing and recognizing position errors of a large number of workpieces arranged. It is also possible to automatically inspect workpieces after processing.
If the glass window 8 is close to the workpiece W, it can be observed with the microscope M through the glass window.

Next, description will be given in accordance with an actual processing procedure.
As shown in FIG. 8, a large number of workpieces W01, W02,... Are arranged on the workpiece workpiece plate P in an orderly manner and placed on a moving stage or stored in a box.
The femtosecond laser light is distributed frequently and evenly within the range of the movable range of the reflection mirror. In this arrangement, irradiation to W01, W02,. ... By repeating W10, the processing by multi-cavity progresses with apparently simultaneous progress.
When the processing steps from W01 to W10 are completed, the box body is moved by the moving stage 14, and W11 to W20 are now processed.

Next, FIG. 9 shows a method for distributing femtosecond laser light.
In addition, in order to make it easy to understand, the case where the number of workpieces is two will be described.
First, the mirror rotation control servo motor 10 adjusts the reflection angle of the mirror 9, and the first laser beam L1 is applied to the workpiece W01.
Next, the mirror rotation control servomotor 10 changes the reflection angle of the mirror 9, and the workpiece W02 is irradiated with the laser light L2.
Next, the workpiece work plate P is moved and positioned at the next irradiation position while returning the reflection angle of the mirror to the angle at which L1 was first irradiated.
Then, distributed irradiation of femtosecond laser light and a plate for processing workpiece, such as moving the processing workpiece plate P by irradiating the laser beams L11 and L12 and moving the processing workpiece plate P by irradiating the laser beams L21 and L22. By repeating the movement of P, machining is simultaneously performed on a large number of workpieces.
Regarding the laser beam irradiation shown in FIG. 9, L1, L11, and L12 are normally irradiated to the same position, and the same applies to L2, L12, and L22.
In normal use, the workpiece side is moved by the moving stage, and the light source side is fixed and relatively moved. However, this is described in this way for easy understanding.

The moving stage can be freely positioned by three orthogonal axes.
For example, as shown in FIG. 10, if the moving stage is moved in the direction of the area 21 indicated by the broken line frame and the femtosecond laser is irradiated, the two-dimensional shape can be created.

  FIG. 11 shows a simplified cross-section of the workpiece. For example, the processing unit 22 emits 1 unit of femtosecond laser and the processing unit 23 emits 2 units. In addition, the processing depth can be adjusted by controlling the number of times of laser light irradiation.

As described above, three-dimensional machining can be performed simultaneously on a plurality of workpieces by adjusting the table movement and the number of irradiations.
In particular, in the case of three-dimensional processing using femtosecond laser light, the number of times of irradiation is inevitably increased, and thus the conventional method is concerned about heat storage on the workpiece. However, according to the present invention, femtosecond laser light is frequently used. Since it is distributed evenly, the amount of laser irradiation to each workpiece per unit time can be kept low and the adverse effect of heat can be suppressed. This can be further reduced as the number of workpieces increases.

Then, as shown in FIG. 12, when the processing of the workpiece in one row (or one column) is completed, the workpiece is positioned on the work plate in the next row indicated by the broken line frame 25, and the workpiece in the next row (or next column) is displayed. Will be started.
In addition, when the work is very easy to store heat, or when the work is very sensitive to heat, especially when heat consideration is required, it is possible to process in the order of W01, W02, ..., W11, W12. By reducing the amount of laser light irradiated to each workpiece per unit time and taking a longer cooling period of the workpiece, it is possible to suppress the adverse effect of heat due to laser light irradiation.

In the above description, the method of reflecting the femtosecond laser beam by the mirror has been described, but it is also possible to use the polygon mirror 19 instead of the reflecting mirror, and this is shown in FIG.
The femtosecond laser light L emitted from the femtosecond laser apparatus 1 controls the position of the femtosecond laser light L by adjusting the angle of the polygon mirror 19 with high precision and flexibility by the mirror rotation control servo motor 10.

In a normal reflection mirror, the position of the laser beam is controlled by swinging the reflection angle. However, it is difficult to significantly improve the control speed of such an angle control.
However, it is possible to further increase the speed by rotating the polygon mirror 19 having a plurality of reflecting surfaces instead of swinging.
When the number of workpieces to be processed simultaneously is very large, it is necessary to have a femtosecond laser beam distribution capability corresponding to this, but it can be handled by the above method.

Further, as shown in FIG. 14, the reflecting surfaces R1, R2,... Of the polygon mirror 19 can be distributed two-dimensionally on the polygon mirror side by giving each plane an inclination. It becomes.
As a result, femtosecond laser light can be distributed to a larger number of workpieces at high speed, and heat storage to each workpiece per unit time can be suppressed.

In the three-dimensional processing using femtosecond laser light, the processing depth can be adjusted by controlling the number of times the laser light is applied to the workpiece W.
That is, a free shape can be created with high precision by numerically managing the amount of processing removed by one irradiation of the laser beam L.

With respect to the processing accuracy and processing time, as shown in FIG. 15, it is possible to perform processing in a short time while paying attention to heat generation with a strong laser beam LA, and conversely, a weak laser as shown in FIG. With LB, it is possible to pursue accuracy and quality.
Depending on the combination of conditions such as the intensity of the laser beam, the spot diameter of the laser beam, and the amount of heat generated, the optimum setting is made according to the situation.

  Regarding the angle of the laser beam, if it is a general use, since the workpiece is fine with respect to the distance between the reflecting mirror and the workpiece to be processed, the influence of the change in the angle of the laser beam is considered to be negligible. When it is desired to consider the position error due to the angle, the position can be corrected by moving the moving stage in the Z direction, which will be described with reference to FIGS.

First, as shown in FIG. 17, when the laser beam L1 is irradiated onto the workpiece W1 directly below, the position of the focal point 20 of the laser beam is set according to the processing part.
Next, when the reflecting mirror is rotated, the focal point 20 is shifted above the portion to be processed when the workpiece W2 is irradiated with the laser beam L2 having an angle.

This is a problem that can be numerically processed as shown in FIG.
The amount of movement in the horizontal direction of the laser beam L2 changed by the angle θ with respect to the laser beam L1 irradiated immediately below can be expressed as (distance) × sin θ.
Since the height direction D can be expressed by tan (θ / 2) × (distance) × sin θ, this error is verified in advance, and the moving stage is set so that the overall position error falls within an allowable range. May be positioned.
By doing so, as shown in FIGS. 19 (a) and 19 (b), as shown in FIG. 19 (a) when machining the workpiece W1, and as shown in FIG. 19 (b) when machining the workpiece W1. The moving stage may be corrected in the Z direction by the amount shown above.
In this way, it is possible to cope with the shift of the focal position of the laser beam due to the change of the irradiation angle.

  In addition, regarding the airtightness in the box, in addition to placing the box on the moving stage as shown in FIG. 2 and placing the work in the box, as shown in FIG. Depending on the size and number of workpieces, it is possible to appropriately select whether to store only the workpiece or to include the moving stage.

Further, as shown in FIG. 21, by increasing the number of femtosecond laser light reflecting mirrors from one to two, the femtosecond laser light can be two-dimensionally and evenly distributed to the workpiece.
First, the reflection angle of the femtosecond laser light is controlled by the first reflecting mirror 9 within a range where it can be reflected by the second reflecting mirror 9 ', and then the femtosecond laser light is reflected by the second reflecting mirror 9'. Laser light reaches the workpiece.
The positional relationship between the reflecting mirrors 9 and 9 ′ needs to be considered so that the femtosecond laser light can be easily distributed.
By examining the correlation between the angle of each reflecting mirror and the plane coordinates when actually reaching the workpiece, it can be handled by mapping this and reflecting it in each reflecting mirror angle control. When such coordinate conversion is performed, the calculation load of a processing system such as a personal computer increases accordingly.

As for the coordinate origin of the workpiece, the workpieces are accurately arranged based on the reference position of the workpiece workpiece plate, and the position of each workpiece workpiece is determined from the relative positional relationship based on this workpiece workpiece reference position. It becomes.
If the relative position of the workpiece and the irradiation pattern of the laser beam corresponding to the relative position of the workpiece are registered in advance for each of the workpiece workpiece plates, switching between a plurality of types of workpieces can be quickly handled.

According to the embodiment of the present invention, the following effects can be obtained.
In the femtosecond laser, fine workpieces can be produced efficiently and in large quantities, so that the cost can be greatly reduced in the production of micromachines and the like.
According to the present invention, as the number of workpieces increases, the amount of heat by laser irradiation to each workpiece per unit time decreases, and the merit of the present invention becomes more prominent as mass production is performed.
In addition, even when using high-power femtosecond laser light, it is possible to effectively dissipate heat and greatly improve processing efficiency.

  The present invention aims at efficient operation of femtosecond laser processing in the processing of fine workpieces. However, even if the light source is other than femtosecond laser light, a workpiece that is easily affected by heat from laser light is used. It can be mass-produced efficiently, and can be applied to various light source processing machines that generate heat.

It is a block diagram of the processing apparatus by this invention. (Example 1) It is a block diagram of the processing apparatus by this invention. (Example 2) FIG. 3 is an operation diagram illustrating a method for decompressing a box according to the present invention. It is an operation figure which shows the gas filling method to a box. It is a block diagram at the time of equip | installing a microscope. It is a block diagram of a box and a glass window. It is explanatory drawing at the time of performing a workpiece | work inspection etc. with a microscope. It is a state figure showing arrangement of a work on a work plate. It is explanatory drawing of several simultaneous processing. It is explanatory drawing at the time of processing by a two-dimensional shape. It is explanatory drawing at the time of adjusting in the depth direction by laser processing. It is explanatory drawing at the time of distributing a laser beam with respect to more workpieces. It is a block diagram which shows reflection of the laser beam by a polygon mirror. It is explanatory drawing of the polygon mirror which has a different reflective surface. It is a related figure which shows the intensity | strength of a laser beam, and a process depth. It is a related figure which shows the intensity | strength of a laser beam, and a process depth. It is explanatory drawing which shows the shift | offset | difference of the Z direction by the inclination of a laser beam. It is a geometric diagram which shows the shift | offset | difference of the Z direction by the inclination of a laser beam. It is an operation | movement figure of the movement stage for correct | amending the shift | offset | difference of a Z direction. It is a block diagram at the time of accommodating in a box to a moving stage. It is a block diagram in case there are two reflection mirrors.

Explanation of symbols

1 Femtosecond laser device 2 Air filter 3 Pressure reducing pump 4 Servo motor 1 (X axis)
5 Servo motor 2 (Y axis)
6 Servo motor 3 (Z axis)
7 Box 8 Glass window 9 Mirror 10 Mirror rotation control servo motor 11 Control unit 12 Computer 13 Signal line 14 Moving stage 15 Terminal 16 Image processing unit 17 Packing 18 Piping 19 Polygon mirror 20 Focus of laser beam A Air B Gas cylinder G Gas H Machining area K Machining area per pulse K1, K2 Machining area per pulse L Laser light L1, L2 Laser light LA, LB Laser light (strong, weak)
M Microscope P Machining work plate S Air pressure sensor W Machining work W1, W2 ・ ・ Machining work W01, W02 ・ ・ Machining work V1 Vacuum adjustment valve V2 Gas adjustment valve θ Reflection angle

Claims (6)

A plurality of workpieces are arranged side by side on the upper surface of a moving stage having a three-dimensional movement axis composed of three orthogonal axes,
The femtosecond laser light emitted from the separately installed femtosecond laser device is reflected by a reflection mirror whose reflection angle can be freely changed by servo control.
In the laser processing method of irradiating the workpiece with the femtosecond laser light,
By controlling the reflection angle of the reflection mirror, the femtosecond laser beam is distributed and irradiated frequently and evenly to a plurality of workpieces, while the workpiece is moved three-dimensionally by the moving stage, and heat is generated by continuous irradiation of the femtosecond laser beam. A multi-piece machining method for femtosecond laser light characterized in that a plurality of machining workpieces are simultaneously machined while dispersing a plurality of machining workpieces while preventing heat accumulation in each machining workpiece.   2. The multi-cavity processing method for femtosecond laser light according to claim 1, wherein a polygon mirror having a plurality of reflecting surfaces with a polyhedral structure is used instead of the reflecting mirror. In claim 1, a box having airtightness inside is joined to the upper surface of the moving stage,
So that the box moves integrally with the moving stage,
A glass window is provided at the top of the box,
A plurality of workpieces are placed side by side inside the box,
Femtosecond laser light is emitted from the glass window at the top of the box to the workpiece placed in the box,
A multi-cavity processing method for femtosecond laser light, characterized in that the box body and a vacuum pump are connected by piping, and the box body is processed under reduced pressure. In claim 1, the moving stage and the entire workpiece are housed in an airtight box.
A glass window is provided at the top of the box,
Femtosecond laser light is emitted from the glass window at the top of the box to the workpiece placed in the box,
A multi-cavity processing method for femtosecond laser light, characterized in that the box body and a vacuum pump are connected by piping, and the box body is processed under reduced pressure.   2. A large number of femtosecond laser beams according to claim 1, wherein the number of reflecting mirrors is set to two so that the femtosecond laser beams are two-dimensionally and evenly distributed to the workpiece. The processing method of the single piece. In Claim 3 and Claim 4, after decompressing the inside of the box,
A large number of femtosecond laser beams, wherein the box is filled with a mixed gas composed of any combination of nitrogen, carbon dioxide, carbon monoxide, oxygen, argon, and helium and processed by femtosecond laser beams. The processing method of the single piece.

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