JPH0673754B2 - Laser processing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laser processing apparatus that performs processing using the energy of laser light.

[Conventional technology]

Conventionally, as this type of apparatus, the one described in Japanese Patent Laid-Open No. 59-40526 is known. This laser processing device
A laser light source that emits laser light toward an object to be irradiated, a transmitted light intensity adjuster that is disposed between the laser light source and the object to be irradiated and that adjusts the transmitted light intensity of the laser light, and the transmitted light intensity An optical splitter disposed between the controller and the object to be irradiated, for splitting the laser light before being irradiated on the object to be irradiated or the laser light after being reflected by the object to be irradiated; And a photometer for measuring the intensity of the laser light split by the light splitter, and the output of the laser light is adjusted based on the measurement result of the photometer.

[Problems to be solved by the invention]

As a specific example of the transmitted light intensity adjuster, the publication discloses the following configuration. That is, linearly polarized laser light is generated from a laser light source, and this is used as a polarizing plate (JP-A-55
-109588, JP-A-58-89889, and JP-A-59-228207, installed so as to have plane symmetry with respect to the vertical plane of the optical axis and have Brewster's angle with respect to the optical axis. (Including a set of glass flat plates), and the transmitted light intensity is adjusted by rotating this polarizing plate about the optical axis of the laser light. Therefore, in such an adjuster, the plane of polarization of the transmitted laser light changes as the light intensity is adjusted.
However, since a light splitter (half mirror, dichroic mirror, etc.) generally has a polarization characteristic, when the plane of polarization of the incident laser light rotates, the ratio (split ratio) between the reflected light intensity and the transmitted light intensity changes. Resulting in. Therefore, even if the light split by the light splitter is measured, it is difficult to accurately calculate the intensity of the laser beam applied to the irradiation target, and it is also difficult to control the intensity of the laser beam to a desired value. became.

[Means for solving problems]

In order to solve this problem, the present invention provides an irradiation target (8).
A laser light source (1) which emits a laser beam toward the light source; and a transmitted light intensity adjuster (3) which is disposed between the laser light source and the irradiation target and adjusts the transmitted light intensity of the laser light; An optical splitter which is disposed between the transmitted light intensity adjuster and the object to be irradiated and which divides the laser beam before being irradiated on the object to be irradiated or after being reflected by the object to be irradiated. (6); and a laser processing device having a photometer (10, 100) for measuring the intensity of the laser beam divided by the optical splitter and outputting photometric information, wherein the transmitted light intensity adjuster (3) Has a characteristic of changing the polarization plane direction of the transmitted laser light passing through itself in accordance with the adjustment, and the light splitter (6) divides it according to the polarization plane direction of the incident transmitted laser light. A polarized light having a characteristic that changes the ratio and generating information indicating the direction of the plane of polarization of the transmitted laser light. Based on the light surface information generating means (3, 11) and the photometric information and the polarization surface information, the transmitted light intensity adjuster for adjusting the laser light intensity to be irradiated to the irradiation target to a preset target. A laser processing apparatus comprising: a control means (11) for generating an adjustment signal for controlling (3).

[Action]

With such a configuration, the orientation of the polarization plane of the laser light transmitted through the transmitted light intensity adjuster (3) changes as the intensity is adjusted, and the division ratio of the light splitter (6) changes accordingly. However, reliable processing is possible without being affected by it.

〔Example〕

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

(A) Configuration of Embodiment This embodiment is an apparatus for correcting a circuit pattern of a large number of LSI chips formed on a wafer by laser light.
FIG. 1 is a block diagram showing the overall structure. The laser beam 1a emitted from the laser light source 1 has its beam diameter expanded by the beam expander 2 into a laser beam 1b, which is linearly polarized and enters the transmitted light intensity adjuster 3. This adjuster 3 is a polarizing plate (Gran-Thompson, Glan-Taylor, lotion, etc. prisms can also be adopted)
And an electric drive mechanism that rotates this polarizing plate about the optical axis of the laser light as a center, and changes the intensity of the laser beam 1c that is transmitted according to the rotation angle of the polarizing plate. The electric drive mechanism includes a pulse motor and a drive mechanism that rotates the polarizing plate according to the rotation angle of the motor.

The direction of the plane of polarization of the beam 1c rotates as the intensity changes. The beam 1c is deflected by the reflecting mirror 5 and enters the light splitter 6. The light splitter 6 transmits a part of the beam 1c and reflects a part thereof, but when the polarization plane of the incident laser light rotates, the ratio (division ratio) of the reflected light intensity and the transmitted light intensity is accordingly changed. Has a changing polarization characteristic. The beam 1d that has passed through the light splitter 6 is focused on a wafer 8 as an irradiation target through an objective lens 7. The wafer 8 is placed on the movable stage 9. On the other hand, the laser beam 1e reflected by the light splitter 6 is incident on the photometer 10. The photometer 10 sends the measurement result to the laser light intensity controller 11.

The light intensity control unit 11 sends an adjustment signal to an electric drive mechanism incorporated in the transmitted light intensity adjuster 3 to control the electric drive mechanism, thereby rotating the polarizing plate also incorporated therein to adjust the transmitted light intensity.

This adjustment signal is created as follows. That is,
The relation between the direction of the plane of polarization of the laser light transmitted through the transmitted light intensity adjuster 3 and the division ratio in the light splitter 6 is obtained in advance, and the division ratio indicating what the division ratio is when the polarization plane is at a certain angle. The data is stored in the PROM in the storage device 11a.

The light intensity controller 11 provides information indicating the direction of the polarization plane of the laser light 1c that has passed through the adjuster 3, that is, the transmitted light intensity adjuster 3
It is obtained by monitoring an encoder or a potentiometer that detects the rotation angle of the polarizing plate, and digital data corresponding to this is generated as polarization angle data. This polarization angle data is sent to the storage device 11c as address data.
The storage device 11a reads the division ratio data stored at the address indicated by the address data and sends it to the light intensity control unit 11.

The light intensity control unit 11 obtains the reflection intensity data corresponding to the intensity of the beam 1e reflected by the light splitter 6 from the photometer 10, and from the reflection intensity data and the division ratio data from the storage device 11a, the divider 6 Beam 1d that is transmitted through and irradiates the wafer 8
The processing energy data corresponding to the intensity of is constantly calculated.

Then, the control unit 11 constantly obtains the difference between the processing energy data and the preset target value, and generates a signal for rotating the polarizing plate of the adjuster 3 in the direction of reducing the difference as the adjustment signal. The control unit 11 continues to generate the adjustment signal while the difference remains, and stops it when the difference disappears.

The transmitted light intensity adjuster 3 receives the adjustment signal and rotates the built-in polarizing plate. When the output of the adjustment signal is stopped, the rotation of the polarizing plate is stopped. At this time, the processing energy of the beam 3 with which the wafer 8 is irradiated matches the target value.

The central control unit 12 includes a laser light source 1 and a laser light intensity control unit 1
1. Outputs a signal for centrally controlling the stage control unit 13.

The stage controller 13 drives and controls the stage 9.

(D) Operation of Embodiment Next, the operation of the embodiment will be described.

i. Processing energy initial setting work Before the wafer is actually processed, the processing energy is set appropriately. To start this operation, the central control unit 12 sends a control signal to the stage control unit 13 to drive the stage 9. By driving the stage 9, an ineffective portion of the surface of the wafer 8 on which no circuit is formed is positioned below the optical axis of the objective lens 7. After that, the central control unit 12 causes the laser light source system 1 to emit a laser beam 1a. The beam 1a becomes a beam 1d through the above optical systems 2 to 7 and is applied to an ineffective portion of the wafer 8. When the intensity of this beam 1d is high, this ineffective portion is processed, but there is no effect on the circuit forming portion.

The intensity of the beam 1e reflected by the light splitter 6 is measured by the photometer 10, and based on the resulting reflected light intensity data,
By the above control, the processing energy for the wafer 8 by the beam 1d is adjusted to the target value. When this adjustment is completed, the central control unit 12 sends a control signal to the light source system 1 to stop the emission of the laser beam 1a. This completes the work of setting the processing energy.

Incidentally, if a mechanical shutter, an acousto-optic device, etc. are provided between the light splitter 6 and the wafer 8 so that the beam 1e is not irradiated on the wafer 8 at the time of the initialization work of the processing energy, the wafer 8 It is no longer necessary to position the invalid part with respect to the beam 1d.

ii. Machining work When the machining energy setting work is completed, the central control unit 12
Will proceed with the actual processing according to the following procedure. The storage device built in the central control unit 12 stores the position information of the required processing points on the wafer 8 and the processing order information. This information is sequentially sent to the stage controller 13, the stage 9 is driven according to this information, and the required processing point on the wafer 8 is beam 1d.
Positioned with respect to. When the positioning is completed, the central control unit 12 sends a control signal to the laser light source system 1 to cause the laser beam 1a to be emitted with the intensity set previously. This beam
The beam 1d passes through each of the optical systems 2 to 7 to form a beam 1d, which is used to process a required portion of the wafer 8. Specific examples of this processing include cutting and annealing of circuit lines of an integrated circuit.

Even if the intensity of the beam 1d fluctuates for some reason during this processing, the beam 1d will be controlled by the same control as above.
The intensity of 1d is kept constant.

When this processing is completed, the central control unit 12 sends a control signal to the laser light source system 1 to stop the light emission of the beam 1a, and then sends a control signal to the stage control unit 13 to beam the next processing point. Position below 1d. Then, the processing here is performed in the same manner as described above. The above operation is repeated until there are no more processing points.

The photometer 100 receives the laser light reflected from the wafer 8 from the light splitter 6 and detects it, and can be used in exactly the same manner as the photometer 10. Also, the measurement result of this and the photometer 10 is compared. By doing so, the division ratio of the optical splitter 6 and
As shown in No. 59-40526, the energy absorbed by the wafer 8 can be calculated.

The photometer 1000 is installed on the stage and the beam 1d
Then, the intensity can be directly detected. As a result, the processing energy can be initialized without irradiating the invalid portion of the wafer 8 with the beam 1e. Also, by comparing the measurement results of this photometer 1000 and photometer 10,
It is also possible to know the division ratio of the light splitter 6.

When the required processing energy is different for each required processing portion of the wafer 8, the information is stored in the storage device in the central control unit 12, and this information is read out each time one processing is completed, The processing energy may be reset by the same method as the above-mentioned processing energy initial setting work.

Next, another example of the control for matching the processing laser beam 1d with the target value will be described.

The light intensity control unit 11 obtains data corresponding to the intensity of the laser beam 1d currently transmitted through the divider 6 and irradiated on the wafer 8 from the measurement result of the photometer 100 or 1000, which is preset with this. The ratio with the target value is calculated, and the data corresponding to this is generated as ratio data. Then, the control unit 11 obtains the polarization angle data indicating the direction of the polarization plane of the laser light 1c transmitted through the adjuster 3 by monitoring the encoder that detects the rotation angle of the polarizing plate. Then, the address data having the ratio data and the polarization angle data as upper and lower bits, respectively, is generated. This address data is used to read out adjustment data stored in advance in the PROM in the storage device 11a. This adjustment data is used to set the combined transmittance of the polarizing plate and the light splitter 6 in order to eliminate the difference between the current light intensity of the laser beam 1d and the target value. It indicates in what direction and to what extent from the current state it should be rotated, and is obtained in advance by an experiment and stored in the storage device 11a. That is, this adjustment data is set in consideration of the division ratio of the light splitter 6 that changes according to the rotation angle of the polarizing plate. In response to this adjustment data, the light intensity controller 11 generates an adjustment signal.

In response to this adjustment signal, the adjuster 3 adjusts the light intensity of the laser beam to be transmitted, and makes the beam 1d from the light splitter 6 a target light intensity.

〔The invention's effect〕

As described above, according to the laser processing apparatus of the present invention, the direction of the plane of polarization of the laser light transmitted through the transmitted light intensity adjuster (3) changes as the intensity is adjusted, and accordingly the optical splitter (6) changes its direction. No matter how the division ratio changes, reliable processing is possible without being affected by it.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. [Explanation of symbols of main parts] 8 ... Irradiation object 1 ... Laser light source 3 ... Transmitted light intensity adjuster 6 ... Optical splitter 10, 100 ... Photometer 3, 11 ... Polarization plane information generating means 11 ... Control means

Claims (1)

[Claims] 1. A laser light source that emits laser light toward an object to be irradiated; and a laser light source disposed between the laser light source and the object to be irradiated,
A transmitted light intensity controller for adjusting the transmitted light intensity of the laser beam; disposed between the transmitted light intensity controller and the object to be irradiated, before being irradiated to the object to be irradiated, or the object to be irradiated. A light splitter that splits the laser light after being reflected by the illuminating object;
In a laser processing device having a photometer that measures the intensity of the laser light divided by the light splitter and outputs photometric information, the transmitted light intensity adjuster changes the polarization plane direction of the transmitted laser light transmitted through itself. It has the property of changing with the adjustment,
Further, the light splitter has a characteristic of changing a division ratio according to a polarization plane direction of the incident transmitted laser light, and generates a plane of polarization information generating information indicating a direction of a plane of polarization of the transmitted laser light. A control means for generating an adjustment signal for controlling the transmitted light intensity adjuster so that the intensity of the laser light applied to the object to be irradiated is made to correspond to a preset target based on the photometric information and the polarization plane information. A laser processing apparatus having means.