JP5460176B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus used for cutting a silicon wafer or the like.

  A processed decomposition product (debris) generated in laser processing using a pulse laser light source contaminates the surface in the vicinity of the processing point and degrades the product quality. Therefore, it is desired to remove debris during processing.

  Various measures against debris have been proposed. For example, a nozzle having a gas outlet coaxially with the optical axis of laser processing is configured so as to cover a processing point and remove and recover debris. There is also a method in which a gas blowing nozzle is disposed at a position different from the laser processing point, and the moving direction of the laser processing point is aligned with the direction of the maximum pressure gradient formed by the gas flow.

  Further, in the technique disclosed in Patent Document 1, the optical axis of laser processing is arranged obliquely with respect to the processing object to provide a flow along the processing surface and at the same time to remove the scattered decomposition products. A tube is provided across the optical axis, and an air flow is formed in the tube. At the same time, air is sprayed from the opening of the tube so that the debris is not further scattered.

  In the configuration disclosed in Patent Document 2, the jet and suction nozzles are arranged near the surface of the workpiece to form a flow along the surface, and at the same time, a high-pressure gas is jetted from the jet side to the vicinity of the machining point. Remove debris from the point. At the same time, high-pressure gas is sprayed, and debris scattered from the high-pressure gas is carried away by the flowing low-pressure gas air curtain, avoiding the high-pressure portion, and removed and collected by the suction nozzle. In particular, in an apparatus for processing using an fθ lens, the entire processing point is disposed so as to be blown away by high-pressure gas.

JP-A-2005-219108 JP 2005-305537 A

  However, in laser cutting of a silicon wafer, the processing itself is close to the end of the manufacturing process, and a semiconductor element is constructed near the processing point. There are two cutting directions, which are in the form of a lattice. The shorter the distance between the laser processing point and the semiconductor element, the better, and usually it is 1 mm or less.

Various elements are formed in such a semiconductor element, and contaminants such as debris should not be attached. Conventionally, rotary cutting is performed while flowing an abrasive using a rotating grindstone called a dicing saw. In this method, a cleaning process is always required after cutting. However, in such a system, it is difficult to manage the liquid abrasive or the cleaning agent in the cleaning process, and at the same time, the maintenance cost of the additional process becomes enormous, which has been a problem as described above. In the conventional configuration having a gas jet port at the bottom, the debris scattering direction is unstable, and a stagnation state with a very low flow velocity is formed where the jetted gas collides with the processing surface. This stagnation state indicates a state where the pressure is high but the flow velocity is low. On the other hand, when laser processing is performed, a high-pressure shock wave front formed by a shock wave generated in the processing process propagates, and debris recombines inside to receive the force toward the surface and reach the surface. The pressure of the shock wave front is significantly larger than the stagnation point pressure, and it is impossible to suppress debris scattering only by jetting in the coaxial direction.

  In the configuration where the laser machining point is arranged at the position where the pressure gradient formed by the gas flow is maximized and the feed direction of the machining point coincides with the direction of the pressure gradient, the pressure of the gas flow is accompanied by a shock wave front. It will be better. Further, a large pressure gradient does not necessarily correspond to a large velocity of the fluid, but a large velocity difference. In order to remove debris, the speed at the processing position is a problem, and it is difficult to directly apply it to a phenomenon involving a shock wave front.

  The one disclosed in Patent Document 1 uses a fluid mainly as protection of an optical element in laser processing. Therefore, debris removal is performed by installing a component in the vicinity of the optical element away from the processing point, but in the vicinity of the processing point, a jet nozzle and a suction nozzle are arranged to form and remove the fluid flow. is there. In this case, as described above, it is difficult to completely recover the debris with respect to the processing having the shock wave front, and the contamination of the surface is generated from the processing position.

  Similarly, the pressure disclosed in Patent Document 2 is high due to the processing having a shock wave front, and debris generation is not prevented. In particular, in the recovery with a low-pressure gas, it is difficult to prevent debris scattering in processing with a strong shock wave.

  An object of this invention is to provide the laser processing apparatus which can suppress generation | occurrence | production of a debris and can avoid the contamination of the surface of a workpiece.

The laser processing apparatus of the present invention is a laser processing apparatus for processing a processing object with laser light, a stage for moving the processing object relative to the laser light, and the stage along the surface of the processing object. A pair of gas flows extending in the moving direction of the stage on the upper layer side of the first gas port pair for forming a pair of gas flow paths extending in the moving direction A second gas port pair that forms a path, and the first gas port pair ejects gas from the pair of gas flow paths toward the processing point of the laser beam, respectively. The gas port pair is configured such that at least one of the pair of gas flow paths sucks gas in the moving direction of the stage from the laser beam processing point , and the pressure setting is asymmetric. Said The pair of gas flow paths of the two gas port pairs are configured to be capable of switching between gas ejection and suction, and configured to switch the asymmetric pressure setting according to the moving direction of the stage. The high-pressure portion formed by the first gas port pair is formed at a position shifted from the processing point of the laser beam by asymmetric pressure setting by the second gas port pair. .

  A high-speed flow is formed along the surface of the workpiece in the space near the laser processing point, and the debris and stagnation point pressure flowed by the flow is used to force the suction side gas port using a high-pressure gas flow To guide. At the same time, the shock wave propagation velocity is increased by lowering the upper portion of the space so that the flow effectively acts on debris that is generated with a time delay.

  By adding such a debris collection mechanism to the laser processing apparatus, it is possible to eliminate the wet cleaning process and the like, and a completely dry laser processing system can be realized.

It is a schematic diagram which shows the laser processing apparatus by one Embodiment. FIG. 2 shows only the recovery unit of the apparatus of FIG. 1, (a) is a sectional view thereof, and (b) is a partially enlarged sectional view showing an enlarged main part of (a).

  A laser processing apparatus shown in FIG. 1 includes an XY stage 1 that is a stage for moving a processing object relative to a laser beam, a rotating stage 2 that rotates around a Z axis, and a processed decomposition product (debris) generated by laser processing. ) Is collected. The workpiece to be supported on the rotary stage is a silicon wafer, and is cut by the laser beam condensed by the condenser lens 4.

  Furthermore, it has a heater 5 for adjusting the temperature of gas ejected from the recovery unit 3, a fan motor 6 for ejecting gas from the recovery unit 3, a filter 7 for removing dust in the gas, and the like. Further, adjustment valves 8 and 9 for adjusting the flow rate and pressure of the gas ejected from the recovery unit 3, filters 10 and 11 for removing dust from the suction gas, temperature control heaters 12 and 13, and two-way electromagnetic for switching between suction and ejection. Valves 14 and 15 are provided. Further, a fan 16, a suction pump 17, a dust filter 18, a control unit 19 for controlling the whole, and the like are provided. The solenoid valves 14 and 15 have a pressure adjustment function. Therefore, it is possible to switch between suction and ejection and adjust the pressure by the command of the control unit 19.

  The XY stage 1 moves in the XY direction according to a command from the control unit 19. The laser beam is condensed by the condenser lens 4 on the surface of the workpiece placed on the rotary stage 2. In this state, when the XY stage 1 moves in the orthogonal direction, laser processing is performed in a lattice shape. The rotary stage 2 rotates 90 ° as necessary when the XY stage 1 reaches the end of the processing range. Of course, other angles can also be set, so this apparatus can also perform laser processing in a shape other than the lattice shape.

  The recovery unit 3 includes four gas ports 21 to 24 for forming gas flow paths. The gas ports 21 and 22 constituting the first gas port pair form a pair of gas flow paths extending in the moving direction of the XY stage 1 along the surface of the workpiece. The gas ports 23 and 24 constituting the second gas port pair form a pair of gas flow paths extending in the moving direction of the XY stage 1 on the upper layer side than the gas ports 21 and 22. The gas ports 23 and 24 each have a cross section having a size of □ 1 mm, and at least one of the gas ports 24 sucks gas upstream in the moving direction (traveling direction) of the XY stage 1. The other gas port 23 ejects gas toward the processing point. The gas ports 21 and 22 are only ejected, but the gas ports 23 and 24 can be switched between ejection and suction.

  Since the collection unit 3 is close to the surface of the workpiece by a distance of about 1 mm, the height of the gas ports 21 and 22 is about 1 mm. The surface of the optical window 25 through which the laser beam passes is arranged so as not to become a flow resistance in the gas flow path formed by the gas ports 23 and 24. The upper and lower gas port pairs are blocked by members, and the portion irradiated with the laser is opened as an opening. The end face shape of the opening may be R-shaped or tapered.

  When laser processing starts, as shown in FIG. 2A, gas is ejected and sucked from the gas ports 21 to 24 according to the setting. The gas ports 21 and 22 eject gas toward the processing point. The gas to be ejected is taken in by the fan 6 from the filter 7, the temperature is set through the heater 5, and the pressures of the gas ports 21 and 22 are controlled using the regulating valves 8 and 9. The heater 5 may be disposed on the output side of the regulating valves 8 and 9. The heater 5 is managed by the control unit 19. In the part end region, the pressures of the gas ports 21 to 24 are set so that the debris is not recovered by the recovery unit 3 but pushed out directly. For example, when a part is processed in the direction of the gas port 24, debris generated in the processing is pushed out in the direction of the gas port 23. Therefore, the pressure is set such that the gas port 23 is sucked or stopped and the remaining gas ports 21, 22, 24 are ejected. At this time, the pressure of the gas ports 21 and 22 is made higher than that of the gas port 24 so that the jet from the gas port 24 does not flow to the gas ports 21 and 22. When the processing progresses and the end surface of the component is on the gas port 23 side from the opening, the gas port 23 is ejected, and the gas ports 21 and 22 are switched to suction or ejection.

  The gas pressure is controlled by the regulating valves 8 and 9 as follows. In laser processing, debris generally comes out on the opposite side of the direction of travel of the XY stage 1, and in order to effectively remove the debris, the scattered debris surely enters the suction port. It is necessary to configure.

  The gas pressure ejected from the gas ports 21 and 22 is the same, but the gas port 24 in the traveling direction of the XY stage 1 is suctioned and the gas port 23 on the opposite side is ejected or sucked out of the gas ports 23 and 24. It has become. When the gas port 23 is used for suction, the pressure of the gas port 24 is lowered.

  By making the pressure settings of the gas ports 23 and 24 asymmetric in this way, as shown in FIG. 2 (b), the high-pressure part formed by the gas ports 21 and 22 moves from the center of each gas port pair to the XY stage 1. Move to a position shifted in the moving direction. That is, the shift is made to the gas port 24 side.

  The same thing can be realized by making the pressures of the gas ports 21 and 22 asymmetrical. For example, when the suction side is the gas port 24, the pressure of the gas port 21 is made higher than that of the gas port 22.

  When the high-pressure part is shifted in the traveling direction of the XY stage 1, a very high-speed flow field is formed on the side opposite to the traveling direction, and in particular, it becomes stronger in the direction along the surface. In the case of pulse laser processing with a shock wave, the pressure of the shock wave is such a pressure that cannot be prevented by such a gas, so that the generated shock wave propagates over the high-speed flow field to the upper part. In regions other than the flow field, the pressure is relatively low. When a shock wave reaches this region, the propagation velocity increases and disappears rapidly. On the other hand, debris is generated with a time delay from the generation of the shock wave. At this stage, the shock wave is not protected and is affected by the flow field, and is scattered along the high-speed flow. That is, debris generated by laser processing propagates according to this flow field, and reaches the gas port 24 on the upper layer side so as to avoid the high-pressure portion described above. As a result, debris is recovered by this flow.

  When debris is caused to flow by such a high-speed flow field, heat is also expected to be taken away at the same time. Therefore, stabilization is achieved by changing the settings of the heaters 12, 13, and 5. This is effective when processing a substance whose temperature change greatly contributes to the light absorption coefficient. For the gas used, air is usually used. However, a gas with a low molecular weight is desirable for putting debris on the flow field. On the other hand, if processing is performed only with a gas having a low molecular weight, there is a problem in that the gas cost increases. Therefore, a method of adding a slightly light molecular weight gas (argon, helium, etc.) to air is used. As a means for removing debris, there is a method of adding a reactive gas that can be gasified by reacting with a target substance. In the same manner as when a gas having a low molecular weight is used, a method of adding and flowing a reactive gas may be used. In this case, it is necessary to select a substance that does not react with a substance constituting an article arranged in the flow path such as a gas port or a solenoid valve. Even if these normally used gases are added, it is necessary to supplement the heat removal by the flow by heating with a heater.

  Next, the gas ports 23 and 24 will be described in detail. The gas ports 23 and 24 are connected to the filters 10 and 11, the heaters 12 and 13, and the two-way solenoid valves 14 and 15, respectively, and control the two-way solenoid valves 14 and 15 based on a command from the control unit 19. The suction pressure is also set. In the suction, the above-described high pressure section is configured to shift in the traveling direction of the XY stage 1. The gas sucked into the gas port 24 passes through the filter 11 and reaches the heater 13. Since it is a gas to be discharged, temperature management is unnecessary, but if it is arranged in a closed space, it will cause a temperature change in that space, so temperature management is also required in the discharge section. Thereafter, the pressure is adjusted via the two-way electromagnetic valve 15 and discharged by the pump 17. Similarly, if the gas port 23 is on the suction side, the sucked gas passes through the filter 10 to the heater 12 and is discharged by the pump 17 through the two-way solenoid valve 14.

  When gas is ejected from the gas port 23, the gas passes through the filter 18 and reaches the two-way electromagnetic valve 14 via the fan 16. As in the case of gas suction, the pressure is also adjusted by the two-way solenoid valve 14. Thereafter, the temperature of the gas is set via the heater 12 and is ejected from the gas port 23 through the filter 10.

  As described above, when the gas port 23 is ejected, an air curtain for reducing the contamination of the optical window 25 disposed in the recovery unit 3 is formed.

  Further, when the machining position changes due to the movement of the XY stage 1, a command is given from the position information of the XY stage 1 from the control unit 19 to change the configuration of the gas ports 21 to 24. At that time, the information of the rotary stage 2 is also taken into consideration, and the settings of the gas ports 21 to 24 are changed so that the high pressure part can be formed in the traveling direction of the XY stage 1.

DESCRIPTION OF SYMBOLS 1 XY stage 2 Rotating stage 3 Recovery unit 4 Condensing lens 14, 15 Two-way solenoid valve 21-24 Gas port

Claims (4)

In a laser processing apparatus that processes an object to be processed with laser light,
A stage for moving the workpiece relative to the laser beam;
A first gas port pair for forming a pair of gas flow paths extending in the moving direction of the stage along the surface of the workpiece;
A second gas port pair forming a pair of gas flow paths extending in the moving direction of the stage on the upper layer side of the first gas port pair;
The first gas port pair ejects gas from the pair of gas flow paths toward the laser beam processing point,
The second gas port pair is configured such that at least one of the pair of gas flow paths sucks gas from the laser beam processing point in the moving direction of the stage , and the pressure setting is asymmetric. And
The pair of gas flow paths of the second gas port pair are configured to be able to switch between gas ejection and suction, respectively, so that the asymmetric pressure setting is switched according to the moving direction of the stage. Composed of
The high-pressure portion formed by the first gas port pair is formed at a position shifted from the processing point of the laser beam by asymmetric pressure setting by the second gas port pair. apparatus.   The laser processing apparatus according to claim 1,
The pair of gas flow paths of the second gas port pair is configured to switch the asymmetric pressure setting by lowering the pressure on the stage moving direction side,
  The high pressure portion formed by the first gas port pair is formed at a position shifted in the moving direction of the stage from the laser beam processing point by asymmetric pressure setting by the second gas port pair. A featured laser processing apparatus. In the laser processing apparatus according to claim 1 or 2 ,
The other of the pair of gas flow paths of the second gas port pair is configured to eject gas toward a processing point of the laser beam. In the laser processing apparatus according to any one of claims 1 to 3 ,
A laser processing apparatus comprising: a heater for heating gas ejected from the first gas port pair and the second gas port pair .

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