JP2012058118A - On-machine measuring device for laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-machine measuring device for a laser beam machine using weak light of a light source for laser beam machining for a light source for measurement.SOLUTION: The on-machine measuring device includes a stage 6 for the on-machine measuring device provided freely movably on a pedestal. The stage 6 for the on-machine measuring device includes: spectroscopic means for dispersing weak continuous light and attaining a reference optical axis and a positioning mechanism 2 for positioning the on-machine measuring device by the reference optical axis; and spectroscopic means 4 and 5 for dispersing reflected light from a machining object 7 of the weak continuous light and a displacement detection mechanism 3 for detecting the displacement of the surface shape of the machining object by the dispersed reflected light. During machining, the stage 6 for the on-machine measuring device is moved to withdraw both the spectroscopic means 4 and 5 from a laser beam for machining. During measurement, the stage 6 for the on-machine measuring device is moved, the stage 6 for the on-machine measuring device is positioned to an irradiation optical axis by the positioning mechanism 2 by using the reference optical axis from the weak continuous light, and the displacement of the surface shape of the machining object 7 is detected by the displacement detection mechanism 3.

Description

  The present invention relates to a laser beam machine, and more particularly to an on-machine measuring device for a laser beam machine.

In laser processing, for example, laser repair processing that removes wiring short-circuit defects in a manufactured semiconductor integrated circuit with a short pulse laser can repair a product that cannot be used as it is due to a manufacturing error in a short time. The importance is great. In recent years, it is desired to increase the precision of laser repair processing technology in accordance with the current state of the semiconductor industry which is becoming increasingly dense.
In order to identify the location of the wiring to be processed and accurately evaluate the processing amount, not only the observation under the microscope that has been used in the past, but also the incorporation of a measuring device using on-machine measurement technology into the processing system It is desirable.

In a laser processing machine, non-contact measurement using light is effective for performing on-machine measurement at high speed. As an idea of an on-machine measuring device for a conventional laser processing machine so far, as in Patent Documents 1 and 2, a measurement light source different from the processing laser is added to the system, and the processed shape is measured. An example is given.
On the other hand, even when processing light is used as in Patent Documents 3 to 6, the processing surface or the processing state is only provided with a monitoring function, and the surface shape displacement is measured numerically. It is not applied to the technique, nor does it temporarily retract the measuring device during processing.

JP 11-245059 A JP 2008-209299 A Japanese Patent Laid-Open No. 5-228671 JP 2001-179470 A JP 2007-54881 A JP 2008-290117 A

In the on-machine measurement by the laser micro-machining machine, if the irradiation point on the processing object of the processing light and the measuring light is not matched, an error between the processing position and the measurement position occurs. This error causes an unintended point to be processed by mistake. Even when the adjustment has been made in advance, there is a possibility that the irradiation point may be shifted over time or due to processing heat, and there is a problem that frequent adjustment is required. For this reason, it is advantageous to perform measurement using weak continuous light of the processing laser light as a light source, rather than using separate light sources for the processing light and the measurement light.
On the other hand, further to perform highly accurate measurement, it is desirable to place the measuring device to the processing target near by repair processing laser is said to reach several hundred MW / cm ² at the time of processing, the measuring device is easily broken There is a risk. In order to avoid destruction, after measuring the shape, it is necessary to retract the measuring device once before processing and install this device again after processing to evaluate the measurement. However, in this case, if the measuring device is not accurately positioned, an error of the measurement zero point occurs, and there is a problem that high-precision comparative measurement of the processing amount before and after the processing cannot be performed.
The object of the present invention is to solve the above-mentioned problems, avoid the position error between the machining point and the measurement point by using the same processing and measurement light source, avoid the destruction of the measuring device due to the powerful laser beam during machining, An object of the present invention is to provide an on-machine measuring device for a laser beam machine capable of performing highly accurate shape measurement in the vicinity of a machining point.

In order to solve the above-described problems, the on-machine measuring device for a laser beam machine according to the present invention is a laser beam machine that performs processing by irradiating a laser beam for processing from a laser light source onto a workpiece to be processed placed on a machining stage. In the on-machine measuring device to be used, the laser light source selectively irradiates the processing laser beam and the weak continuous light used as the measuring light on the same irradiation optical axis from the same light source. An on-machine measuring device stage movably provided on a pedestal is provided, and the on-machine measuring device stage is configured to perform on-machine measurement using a spectroscopic means that splits weak continuous light into a reference optical axis and the reference optical axis. A positioning mechanism for positioning the apparatus; a spectroscopic unit that divides the reflected light from the processing object of weak continuous light; and a displacement detection mechanism that detects the displacement of the surface shape of the processing object by the spectrally reflected light. ,processing In this case, the on-machine measuring device stage is moved to retract both the spectroscopic means from the processing laser beam, and at the time of measurement, the on-machine measuring device stage is moved and positioned using the reference optical axis from the weak continuous light. The on-machine measuring device stage is positioned with respect to the irradiation optical axis by the mechanism, and the displacement of the surface shape of the workpiece is detected by the displacement detection mechanism.
Furthermore, the present invention is characterized in that in the on-machine measuring device for a laser beam machine, the pedestal is provided on a machining stage.
Furthermore, the present invention is characterized in that in the on-machine measuring device for a laser beam machine, the pedestal is provided at a fixed portion other than the machining stage.

When repairing a highly integrated semiconductor, it is necessary to select a processing location by prior measurement, then perform processing and evaluate again. At that time, if a processing laser is irradiated to a place different from the intended point, there is a possibility that an adjacent circuit is erroneously destroyed. In the case of the conventional technique using the processing light and the measurement light of another light source, frequent adjustment is necessary to eliminate this error.
In the present invention, since the weak light of the processing light source is used as the measurement light source, no position error between the processing point and the measurement point occurs, and these adjustments are unnecessary. In addition, since measurement is performed at a location close to the object to be processed, it is difficult to be affected by air fluctuations, and high-precision measurement is possible. Further, since the on-machine measuring device itself can be positioned with reference to the machining / measurement optical axis, a zero point error in measurement before and after the machining does not occur, and the machining amount can be accurately measured and evaluated.

It is a figure explaining the outline | summary of one Example of this invention. It is a figure which shows the external appearance at the time of a measurement in the Example of FIG. It is a figure which shows the general view at the time of the process which retracted | retracted the measuring device in the Example of FIG. It is a figure explaining the outline | summary of the other Example of this invention. An overview of the experimental system. Graph of position detection result (sensor moved in x-axis direction). Graph of position detection result (sensor moved in y-axis direction). Graph of the result of repositioning. Graph of on-machine measurement system output result.

Example 1
FIG. 1 shows an embodiment of the present invention. The integrated circuit 7 to be processed is installed on a processing stage 8. On-machine measuring devices 2 to 6 are installed between the processing laser irradiation port 1 and the stage 8. This on-machine measuring device includes a positioning mechanism 2, a displacement detecting mechanism 3, beam splitters 4 and 5, and an on-machine measuring device stage 6.
FIG. 2 shows an overview at the time of measurement of this example.
When measuring the surface shape of the integrated circuit 7 before and after processing, first, the processing laser is weakly continuous light to weaken the output, and then the light split by the beam splitter 4 is used as a reference optical axis to determine the positioning mechanism 2. The on-machine measuring device is positioned based on the output of the light receiving element. As the light receiving element, an element capable of detecting the position of the light spot, such as a quadrant photodiode, PSD, or CCD, is used. Thereafter, the reflected light from the integrated circuit 7 is bent by the beam splitter 5 and guided to the displacement detection mechanism 3, and the displacement of the surface shape is measured by the displacement detection optical system and the light receiving element in this mechanism. In the embodiment shown in FIG. 1, the astigmatism method using a cylindrical lens and two convex lenses is used as a measurement principle, but the measurement may be performed by a trigonometric method or a knife edge method.
Even when the stage 8 is moved to scan the surface of the integrated circuit 7, the displacement of the surface shape can be measured by following the optical axis using the positioning mechanism 2 and the stage 6.
FIG. 3 shows an overview at the time of processing, and the on-machine measuring device is retracted by the on-machine measuring device stage 6 to avoid the destruction of the light receiving element by the processing light.

(Example 2)
FIG. 4 shows another embodiment of the present invention. This embodiment is different from the embodiment of FIG. 1 in that the on-machine measuring device is installed at a fixed portion other than the stage 8, and the other portions are the same as the configuration of FIG. As shown in FIG. 4, when the on-machine measuring device is installed on a fixed part other than the stage 8, it is possible to perform surface scan measurement just by positioning with respect to the optical axis before and after processing, and follow the stage 6. No action is required.

In order to confirm reproducibility of repositioning in the on-machine measuring device of the present invention, the following experiment was conducted by assembling the experimental system shown in FIG.
A He—Ne laser (Meles Grio 05LHP171, wavelength 632.8 nm, output 7.0 mW) was used instead of the weak continuous light of the processing pulse laser. A convex lens with a focal length of 200 mm is installed directly under the laser head, and the height is adjusted so as to focus on the sample surface. The on-machine measurement system body was constructed using a Tholabs lens tube. A four-divided photodiode of the light receiving element uses Hama Photo S4349.
As the xy stage, a piezoelectric actuator-driven fine movement stage was installed on a coarse movement stepping motor stage (Sigma light machine SGSP20-20). An on-machine measuring device is fixed on the stage. The movement of the stage was measured with a laser linear encoder (Renishaw RLE10-DX-XG) and used for evaluating the characteristics of the sensor system.
An aluminum vapor deposition flat mirror was placed as a sample on the z stage (Sigma optical machine OPT-MIKE), and a simulated shape displacement was given by driving the z stage.
In the original processing system, a plane driving stage is further required in order to give a relative displacement in the xy plane between the sample and the laser beam. However, in this experiment, the purpose was to investigate the basic characteristics of the on-machine measuring device, so this part was omitted.

  6 and 7 show the detected displacements in the respective axial directions when the on-machine measuring device is driven in the xy directions with reference to the optical axis. FIG. 6 shows the output when the sensor is moved in the x-axis direction, and FIG. 7 shows the output when the sensor is moved in the y-axis direction, repeated three times. Each output of the 4-split PD was taken into a measurement personal computer, and the amount of movement in each axis direction was calculated on the program. It can be confirmed that the displacement is repeatable on the order of submicrons. Using this relationship, it is possible to measure the lateral sample position when the laser scans the sample surface.

FIG. 8 shows the result of a repositioning experiment of the on-machine measuring device, assuming a situation before and after repair processing by a laser.
Here, the on-machine measuring device was once moved 5 mm from the optical axis using the coarse movement stage, then returned to the original position, and the stage was repeatedly fed back so that the position detection sensor output of the sensor became constant. The deviation of the laser linear encoder reading at that time is plotted. It was confirmed that the measuring device was fixed with a reproducibility within ± 0.7 μm in both the x and y directions.
The result of examining the output of the on-machine measuring device is shown in FIG. The linear error of output is somewhat conspicuous due to insufficient adjustment of the optical system and poor feed accuracy of the z-axis stage, but it can be confirmed that the surface shape can be measured with this sensor.

In the above, it has been described that the on-machine measuring device for a laser beam machine according to the present invention can be provided with a means for realizing a highly accurate measurement system by incorporating it into an IC repair device. However, the present invention is applied to a general laser beam machine. Thus, it is possible to provide high-precision on-machine measuring means at low cost.
Furthermore, even if the irradiation light cannot be observed with a camera because it is an invisible laser such as an ultraviolet laser, on-machine measurement that matches the processing point is possible according to the present invention, so that highly accurate repair processing can be realized. .

DESCRIPTION OF SYMBOLS 1 Laser irradiation port for processing 2 Positioning mechanism 3 Displacement detection mechanism 4 Beam splitter for positioning mechanism 5 Beam splitter for displacement detection mechanism 6 On-machine measuring device stage 7 Integrated circuit (object to be processed)
8 Processing stage

Claims (3)

In an on-machine measuring device used in a laser processing machine that processes a processing object placed on a processing stage by irradiating a processing laser beam from a laser light source,
The laser light source selectively irradiates a processing laser beam and a weak continuous light used as a measurement beam on the same irradiation optical axis from the same light source,
The on-machine measuring device includes an on-machine measuring device stage movably provided on the pedestal,
The on-machine measuring device stage includes a spectroscopic unit that splits weak continuous light into a reference optical axis, a positioning mechanism that positions the on-machine measuring device using the reference optical axis, and a weak continuous light from the workpiece. A spectroscopic means for splitting the reflected light, and a displacement detection mechanism for detecting the displacement of the surface shape of the workpiece by the split reflected light,
During processing, the on-machine measuring device stage is moved to retract both of the spectroscopic means from the processing laser beam, and at the measuring time, the on-machine measuring device stage is moved to perform positioning using the reference optical axis from weak continuous light. An on-machine measuring device for a laser processing machine, wherein the on-machine measuring device stage is positioned with respect to the irradiation optical axis by a mechanism, and the displacement of the surface shape of the workpiece is detected by a displacement detection mechanism.   The on-machine measuring device for a laser beam machine according to claim 1, wherein the pedestal is provided on a machining stage.   The on-machine measuring device for a laser beam machine according to claim 1, wherein the pedestal is provided at a fixed portion other than the machining stage.