JP2971003B2 - Device to detect dirt on lens of laser repair device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting contamination on a lens of a laser processing apparatus for processing a pattern on a wafer by using a laser.

[0002]

2. Description of the Related Art FIG. 3 shows a path of a processing laser beam in a conventional laser processing apparatus. The laser beam generated by the laser oscillator 10 is reflected via the mirror M1, the mirror M2, and the mirror M3 so as to be vertically input to the wafer to be processed. Then, the laser light is focused on the wafer by the objective lens 11 immediately before the wafer.

[0003]

When the processing on the wafer is to be miniaturized, it is necessary to reduce the laser spot diameter. Therefore, the objective lens 11 and the wafer 12
Distance becomes shorter. As a result, during laser processing, polysilicon scattered from the wafer may adhere to the lens. If the lens adheres to the lens, the power of the laser beam reaching the wafer decreases. Then, if the processing is performed as it is, the power is insufficient and a cutting failure occurs. An object of the present invention is to realize a method and an apparatus for detecting dirt on the surface of an objective lens in a laser processing apparatus.

[0004]

In order to achieve the above object, the present invention realizes the following method and apparatus. That is, the intensity of the laser light output from the laser oscillator 10 is measured by the light receiving unit A15, and the intensity of the laser light passing through the objective lens 11 is measured by the light receiving unit B16 or the light receiving unit B15.
26, the measurement data of the light receiving unit A15 and the light receiving unit B1
By detecting that the ratio of the measurement data of No. 6 or the light receiving unit B26 has changed from the initial state in which the lens is not dirty, the dirt on the lens of the laser processing apparatus is detected.

Further, a light receiving section A for measuring the intensity of the laser beam output from the laser oscillator 10 through the beam splitter 1 is provided, and the laser beam passing through the beam splitter 1 and the beam splitter 2 is transmitted to the quarter wavelength plate 14. A light receiving unit for measuring the intensity of laser light reflected by the standard reflecting plate 13 and transmitted through the objective lens 11 through the quarter-wave plate 14 and the beam splitter 2; B16 is provided to detect contamination of the lens of the laser processing apparatus.

As another method, a light receiving section A15 for measuring the intensity of the laser light output from the laser oscillator 10 through the beam splitter 1 is provided, and the intensity of the laser light passing through the beam splitter 1, the mirror M2 and the objective lens 11 is provided. A light receiving unit B26 for measuring the height is provided to detect contamination of a lens of the laser processing apparatus.

[0007]

When the objective lens 11 is contaminated, the intensity of the laser beam transmitted therethrough is attenuated as compared with the case where there is no contamination. Therefore, the dirt on the lens can be detected by measuring the attenuation. However, since the intensity of the laser light output from the laser oscillator 10 fluctuates, the dirt on the lens cannot be specified only by measuring the intensity of the laser light transmitted through the objective lens 11. Therefore, the intensity of the laser light output from the laser oscillator 10 is also measured, and the laser oscillator 10
The ratio between the intensity of the laser light that has output the laser beam and the intensity of the laser light that has passed through the objective lens is determined, and a change from the initial state can be detected to detect dirt on the lens.

[0008]

【Example】

(Embodiment 1) FIG. 1 shows an embodiment of the present invention. The laser processing device for detecting dirt on the lens includes a light receiving unit A15 for measuring the intensity of the laser light output from the laser oscillator 10 through the mirror M1 and the beam splitter 1, and
The standard reflector 13 for irradiating the laser beam passing through the beam splitter 1 and the beam splitter 2 through the quarter-wave plate 14 and the objective lens 11, and the laser beam reflected by the standard reflector 13 and transmitted through the objective lens 11. Strength is 1 /
It comprises a four-wavelength plate 14 and a light receiving section B16 for measurement through the beam splitter 2.

The laser light output from the laser oscillator 10 is reflected by the mirror M1 and is input to the beam splitter 1. In the beam splitter 1, 50% of the laser light travels toward the beam splitter 2, and the remaining 50% of the laser light travels to the light receiving unit A15. The laser light that has advanced to the beam splitter 2 is reflected by the beam splitter 2 and
The focus is focused on the standard reflection plate 13 through 4 and the objective lens 11. Here, when the laser beam passes through the quarter-wave plate 14, the phase of the laser changes by 90 degrees. The laser uses the standard reflector 13
The light is reflected on the upper side and enters the beam splitter 2 through the objective lens 11 and the 波長 wavelength plate 14. Here, when the laser beam passes through the quarter-wave plate 14, the phase of the laser is further changed by 90 degrees, and the phase of the laser input to the beam splitter 2 is changed by 180 degrees. Beam splitter 2 transmits the laser 180 degree phase changes to the laser beam from the beam splitter 1, the laser beam reaches the light receiving portion B16.

When the objective lens 11 is contaminated, the intensity of the laser transmitted therethrough is attenuated as compared with the case where there is no contamination. Therefore, the dirt on the lens can be detected by measuring the attenuation. However, since the intensity of the laser light output from the laser oscillator 10 fluctuates, the dirt on the lens cannot be specified only by measuring the intensity of the laser light transmitted through the objective lens 11. Therefore, the laser oscillator 10
The intensity of the output laser light is also measured, and the laser oscillator 1
The ratio between the intensity of the laser light that has output 0 and the intensity of the laser light that has passed through the objective lens is obtained, and a change from the initial state can be detected to detect dirt on the lens.
In the example of FIG. 1, the light is reflected using the standard reflecting plate 13, and the ratio of the intensity of the laser beam between the light receiving unit A15 and the light receiving unit B16 is measured in advance. The light receiving section B1
It can be considered that the intensity of the laser light of No. 6 decreased. In this embodiment, since the light passes through the objective lens 11 twice in a reciprocating manner, compared with the single pass in the second embodiment,
It can be said that the light receiving portion B16 has a large attenuation with respect to the dirt on the lens and the detection sensitivity is high.

(Embodiment 2) FIG. 2 shows another embodiment of the present invention. In this embodiment, the apparatus for detecting the dirt on the lens of the laser processing apparatus includes a light receiving unit A15 for measuring the intensity of the laser beam output from the laser oscillator 10 through the mirror M1 and the beam splitter 1, a beam splitter 1, The light receiving unit B26 measures the intensity of the laser beam transmitted through the objective lens 11 via the mirror M2.

The laser light output from the laser oscillator 10 is reflected by the mirror M1 and is input to the beam splitter 1. 50% of the laser beam from the beam splitter 1 is mirror M
2 and the remaining 50% of the laser light is
Go to 5. The laser beam that has traveled to the mirror M2
After being reflected by the objective lens 11 and converging, the light reaches the light receiving unit B26.

When the objective lens 11 is contaminated, the intensity of the laser transmitted therethrough is attenuated as compared with the case where there is no contamination. Therefore, the dirt on the lens can be detected by measuring the attenuation. However, since the intensity of the laser light output from the laser oscillator 10 fluctuates, the dirt on the lens cannot be specified only by measuring the intensity of the laser light transmitted through the objective lens 11. Therefore, the laser oscillator 10
The intensity of the output laser light is also measured, and the laser oscillator 1
The ratio between the intensity of the laser light that outputs 0 and the intensity of the laser light that has passed through the objective lens is obtained, and a change from the initial state can be detected to detect contamination of the lens.
In the example of FIG. 2, the ratio of the intensity of the laser light between the light receiving unit A15 and the light receiving unit B26 is measured in advance, and if the ratio changes thereafter, the dirt is attached to the intermediate lens. It can be considered that the intensity of the laser light has decreased. In this embodiment, since the light passes through the objective lens 11 once, the attenuation of the light receiving portion B26 against the dirt on the lens is smaller and the detection sensitivity is lower as compared with the two passes in the first embodiment.

[0014]

Since the present invention is configured as described above, it has the following effects. First, when the objective lens 11 is contaminated, the intensity of the laser transmitted therethrough is attenuated as compared with the case where there is no dirt. Therefore, the dirt on the lens can be detected by measuring the attenuation. However, since the intensity of the laser light output from the laser oscillator 10 fluctuates, the dirt on the lens cannot be specified only by measuring the intensity of the laser light transmitted through the objective lens 11. Therefore, the intensity of the laser light output from the laser oscillator 10 was also measured, and the ratio of the intensity of the laser light output from the laser oscillator 10 to the intensity of the laser light transmitted through the objective lens was determined. By detecting, dirt on the lens can be detected. Before performing the laser processing, the light receiving unit A15 and the light receiving unit B16 or the light receiving unit B26 are measured, the ratio is obtained, and it is confirmed that there is no change with respect to the initial value at which the lens is not stained. This is an effective invention because it is convinced that there is no dirt, and it is possible to prevent cutting defects due to insufficient laser beam power.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory view showing another embodiment of the present invention.

FIG. 3 is an explanatory view showing a conventional laser processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Laser oscillator 11 Objective lens 12 Wafer 13 Standard reflection plate 14 Quarter-wave plate 15 Light receiving part A 16, 26 Light receiving part B

Claims (1)

(57) [Claims] A lipstick output from a laser oscillator (10)
A light receiving unit A (15) for measuring the intensity of the laser light for a through the beam splitter (1) is provided, and the laser light passing through the beam splitter (1) and the beam splitter (2) is converted into a 波長 wavelength plate ( 14) and a standard reflector (13) for irradiating through the objective lens (11). The intensity of the laser beam reflected by the standard reflector (13) and transmitted through the objective lens (11) is reduced by a 波長 wavelength plate. (14) and the light receiving section B (1) for measurement through the beam splitter (2)
An apparatus for detecting contamination of a lens of a laser repair apparatus, wherein the apparatus is provided with 6).