JPS62220922A - Laser beam machine - Google Patents

Abstract

PURPOSE:To hold the split ratio of laser light by a light splitter at a specific value by transmitting laser light through a polarizing plate before the laser light transmitted through a transmitted light intensity controller is split and made incident on light measuring instruments. CONSTITUTION:The laser light transmitted through the transmitted light intensity controller 3 is transmitted through the polarizing plate 4, split by the light splitter 6 and made incident on the light measuring instruments 10,100. The polarizing plate 4 on which a beam 1c is made incident makes the direction of the plane of polarization of a transmitted beam 1d constant regardless of the direction of the plane of polarization of the beam 1c. Further, the light splitter 6 has polarization characteristics and transmit part of the beam 1b while reflecting the remainder. Consequently, even however the direction of the plane of polarization of laser light changes through the light intensity control of the transmitted light intensity controller 3, the polarizing plate 4 holds the direction of the plane of polarization of the laser light incident on the light splitter 6 constant and holds the split ratio of the laser ratio by the light splitter 6 at the specific value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser processing device that performs processing using the energy of laser light.

[Conventional technology]

Conventionally, as this type of device, one described in Japanese Patent Application Laid-Open No. 59-40526 is known. This laser processing device includes a laser light source that emits a laser beam toward an object to be irradiated; and a transmitted light intensity adjustment that is disposed between the laser light source and the object to adjust the transmitted light intensity of the laser beam. a device disposed between the transmitted light intensity adjuster and the object to be irradiated, and splits the laser beam before being irradiated to the object to be irradiated or after being reflected by the object to be irradiated; It includes a light splitter and a photometer that measures the intensity of the laser light split by the light splitter, and adjusts the output of the laser light based on the measurement results of the photometer.

[Problem that the invention seeks to solve]

As a specific example of the transmitted light intensity adjuster, the publication discloses the following configuration. In other words, a linearly polarized laser beam is generated from a laser light source, and this is polarized by a polarizing plate (a set of glass flat plates installed so as to have plane symmetry with respect to a plane perpendicular to the optical axis and a Brewster angle with respect to the optical axis). The transmitted light intensity is adjusted by rotating this polarizing plate around the optical axis of the laser beam. Therefore, in such an adjuster, the polarization plane of the transmitted laser light changes as the light intensity is adjusted. Since it is necessary to monitor the adjustment results, such a regulator is disposed closer to the laser light source than the light splitter.

However, since light splitters (so-called half mirrors, gicroic mirrors, etc.) generally have polarization characteristics,
When the polarization plane of the incident laser light is rotated, the ratio between the intensity of the reflected light and the intensity of the transmitted light changes, causing a problem in which it is difficult to accurately calculate the laser light output.

[Means to solve the problem]

In order to solve this problem, the present invention provides that before the laser light transmitted through the transmitted light intensity adjuster (3) is split by the light splitter (6) and enters the photometer (10, 100), It is made to transmit through the polarizing plate (4).

[Effect]

This polarizing plate (4) allows the laser light incident on the light splitter (6) to be The direction of the polarization plane is kept constant and the division ratio of the laser beam by the light splitter (6) is set to a predetermined value.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

(a) Structure of the Embodiment The present embodiment is an apparatus for correcting circuit patterns of LSI chips formed in large numbers on a wafer using a laser beam, and FIG. 1 is a block diagram showing the overall structure thereof. A laser beam 1a emitted from a laser light source 1 is expanded in beam diameter by a beam expander 2 and becomes a laser beam 1b.
The light enters the transmitted light intensity adjuster 3 in a linearly polarized state. This regulator 3 is a polarizing plate (Glan-Thompson, Glan-Tiller, Lotion, etc. prisms can be adopted)
and an electric drive mechanism that rotates this polarizing plate around the optical axis of the laser beam, and changes the intensity of the transmitted laser beam 1c according to the rotation angle of the polarizing plate. With this change, the direction of the polarization plane of the beam IC rotates. The polarizing plate 4 on which this beam IC enters is
Regardless of the direction of the polarization plane of the transmitted beam 1d, the direction of the polarization plane of the transmitted beam 1d is made constant. The beam 1d transmitted through the polarizing plate 4 is deflected by a reflecting mirror 5 and enters a light splitter 6.

The light splitter 6 has polarization characteristics, and this beam 1d
Transmits some of it and reflects some of it. The transmitted beam 1e is focused through an objective lens 7 onto a wafer 8 as an object to be irradiated. This wafer 8 is placed on a movable stage 9
is placed on top. On the other hand, the laser beam 1f reflected by the light splitter 6 enters the photometer 10. The photometer 10 sends this measurement result to the laser light intensity control section 11. Based on the output from the photometer 10, the control unit 11 drives and controls a motor built in the transmitted light intensity adjuster 3 to adjust the transmitted light intensity, so that the beam 1f from the light splitter 6 becomes a desired light beam. For example, make sure that the intensity is constant at all times. The central control unit 12 includes a laser light source 1, a laser light intensity control unit 11,
A signal for controlling the stage control section 13 is output.

The stage control unit 13 drives the stage 9.

(b) Operation of the embodiment Next, the operation of the embodiment will be explained.

i. Initial Setting of Processing Energy Before the wafer is actually processed, work is performed to appropriately set the processing energy.

In order to start this work, the central control section 12 sends a control signal to the stage control section 13 to drive the stage 9. By driving the stage S, the invalid portion of the surface of the wafer 8 where no circuit is formed is moved to the objective lens 7.
positioned below the optical axis. Thereafter, the central control unit 12 causes the laser light source system 1 to emit the laser beam 1a.

This beam 1a passes through each of the optical systems 2 to 7, becomes a beam 1e, and is irradiated onto an ineffective portion of the wafer 8.

If the intensity of the beam 1e is high, this ineffective portion will be processed, but the circuit forming portion will not be affected. The intensity of the beam 1f reflected by the light splitter 6 is measured by a photometer 10, and the intensity information is sent to a laser light intensity control section 11. The light intensity control unit 11 controls the intensity of this beam 1f,
The control signal is compared with a target value that has already been input from the central control unit 12, and a control signal based on this comparison value is sent to the transmitted light intensity regulator 3. In response to this, the light intensity adjuster 3 rotates the built-in polarizing plate to change the polarization characteristics of the linearly polarized incident beam 1b. Therefore, the beam 1c transmitted through the adjuster 3 changes in its light intensity and also changes in its polarization plane. However, when this beam 1c passes through the polarizing plate 4, it becomes a beam 1d whose plane of polarization is aligned in a certain direction. As a result, the splitting ratio of the beam 1d in the light splitter 6 is always constant, and the intensity of the transmitted beam 1e can be accurately calculated from the intensity of the reflected beam 1r. The light intensity controller 11 drives the light intensity adjuster until the beam 1r reaches the target value. In this way, when the intensity of beam 1[ is set to the target value by negative feedback control and the intensity of processing beam 1e is set to a predetermined value,
The central control unit 12 sends a control signal to the light source system 1 to stop emitting the laser beam la. This completes the machining energy setting work.

Incidentally, if a mechanical shutter, an acousto-optic element, etc. is provided between the light splitter 6 and the wafer 8 to prevent the beam 1e from being irradiated to the wafer 8 during the initial setting of processing energy, the wafer 8 can be There is no need to position the invalid portion with respect to the beam 1e.

ii. When the machining work machining energy setting work is completed, the central control unit 12
Proceed with the actual processing using the following steps. A storage device built into the central control unit 12 stores information on the positions of required processing points on the wafer 8 and information on the order of processing. This information is sequentially sent to the stage control section 13, and the stage 9 is driven according to this information to position the required processing portion of the wafer 8 with respect to the beam 1e. When the positioning is completed, the central control unit 12 sends a control signal to the laser light source system 1 to emit the laser beam 1a with the previously set intensity.

This beam 1a passes through each optical system 2 to 7, and the beam 1a passes through each optical system 2 to 7.
e, and the required processing portions of the wafer 8 are processed. Specific examples of this processing include fusing and annealing. Even if the intensity of the beam 1a fluctuates for some reason during this processing, the intensity of the beam 1e is kept constant by the feedback control described above. When this processing is completed, the central control unit 12 sends a control signal to the laser light source system 1 to stop sending the beam 1a, and then sends a control signal to the stage control unit 13 to start the beam from the next point to be processed. 1e
Position it below. Then, processing here is performed in the same manner as described above. The above operations are repeated until there are no more parts to be machined.

The photometer 100 receives the laser beam reflected from the wafer 8 from the light splitter 6 and detects it.
By comparing the measurement results of
As shown in No. 526, the energy absorbed by the wafer 8 can be calculated.

The photometer 1000 is provided on a stage and can receive the beam 1e and directly detect its intensity. Thereby, the processing energy can be initialized without irradiating the beam 1e onto the ineffective portion of the wafer 8.

If the required processing energy is different for each location on the wafer 8 that requires processing, this information is stored in a storage device within the central control unit 12, and this information is read out each time one processing is completed. The machining energy may be reset by the same method as the machining energy initial setting work described above.

〔Effect of the invention〕

As explained above, according to the laser processing apparatus of the present invention, the laser light transmitted through the transmitted light intensity adjuster (3) is split by the light splitter (6) and enters the photometer (10, 100). Before doing so, I made it so that it would pass through the polarizing plate (4), so
No matter how the direction of the polarization plane of the laser beam changes as the transmitted light intensity adjuster (3) adjusts the light intensity, the light splitter (6)
), the direction of the polarization plane of the laser beam incident on the
Therefore, the division ratio of the laser light by the light splitter (6) can be maintained at a predetermined value.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. [Explanation of symbols of main parts]

Claims (1)

[Claims] (1) a laser light source that emits laser light toward an irradiated object; a transmitted light intensity adjuster that is disposed between the laser light source and the irradiated object and adjusts the transmitted light intensity of the laser beam; a light splitter that is disposed between the transmitted light intensity adjuster and the irradiated object and splits the laser beam before it is irradiated onto the irradiated object or after it is reflected by the irradiated object; and; a photometer that measures the intensity of the laser light split by the light splitter, wherein the transmitted light intensity adjuster adjusts the polarization plane direction of the transmitted laser light according to the adjustment. The light splitter has a property that the splitting ratio changes depending on the direction of the polarization plane of the incident light, and a polarizing plate is provided between the transmitted light intensity adjuster and the light splitter. , and the polarizing plate sets the plane of polarization of the laser light incident on the light splitter in a predetermined direction so that the splitting ratio of the laser light by the light splitter becomes a predetermined value. Laser processing equipment.