JPS63144889A - Laser beam processing device - Google Patents

Abstract

PURPOSE:To permit partial and satisfactory removal of a resist film on a prescribed substrate or the like by condensing laser light of a CW laser, scanning said light on an object and processing the object while monitoring the processing condition of the object. CONSTITUTION:Reflected light is generated from a wafer W or resist and further, fluorescence is generated from the resist when said wafer or resist is irradiated by the laser light LB outputted from a light source 10 of the CW laser. Such reflected light and fluorescence are partly entered by the effect of a beam splitter 20 and a fluorescent lens 36 to a photodetector by which the light is photoelectrically converted and a detection signal is outputted to a system controller 34. The presence or absence of the resist is judged in said controller. The reflectivity to the laser light LB varies with the resist and the wafer W in a mode in which the reflected light is selected and, therefore, whether the resist is satisfactorily removed or not is judged by the change in the intensity of the incident light on the photodetector 38.

Description

[Detailed Description of the Invention] [Field of Application in Industry] The present invention relates to a laser processing device that partially removes a photoresist film formed on the surface of a semiconductor substrate in the manufacturing process of integrated circuits, etc. It is.

[Prior Art] In the manufacturing process of integrated circuits, a process of partially removing or peeling a resist on a wafer is sometimes performed due to the necessity of alignment between a mask and a wafer. The area of the resist to be removed is, for example, about 300 μm square.

As such a means for removing resist on a wafer, there is a method using a pulse laser disclosed in Japanese Patent Application No. 61-95511, for example.

Furthermore, in addition to such a pulsed laser, a method using a CW laser as a light source is also conceivable.

[Problems to be Solved by the Invention] However, the above techniques have the following problems.

First, in the method that uses a pulsed laser as a light source, a large amount of light energy is instantaneously applied to the resist.
The resist on the wafer is also heated rapidly, causing its rapid expansion.

Therefore, there is a problem that the resist in the molten state is likely to scatter and contaminate the surrounding area.

Further, when the resist is removed to some extent and the alignment mark formed on the wafer is exposed, the alignment mark itself is rapidly heated and expands. If the stress at this time is concentrated at the corner of the alignment mark, there is a problem that the mark may collapse.

If such an alignment mark is used to align the mask and the sea urchin, the alignment accuracy will be lower than before the resist is removed.

On the other hand, in the case of a method using a CW laser as a light source, the power of the laser beam is much smaller than that of a pulsed laser, so it is difficult to peel off a resist having an area of about 300 μm square.

In addition, with either method, if the entire area from which you want to remove resist is irradiated with a laser beam, the beam profile of the laser beam will cause the resist to be removed even though some parts of the area remain. There is an inconvenience that the alignment mark is damaged.

The present invention has been made in view of this point, and an object of the present invention is to provide a laser processing apparatus that can partially remove a resist film or the like on a predetermined substrate.

[Means for Solving the Problems] The present invention uses a CW laser as a light source of laser light, and also includes a condensing means for condensing the laser light to form a beam, and a combination of the laser beam and the object. relatively 8
beam scanning means for scanning an object with a laser beam by irradiating the object; processing state detection means for monitoring the processing state of the object using detection light obtained from the object by irradiation with the laser beam; and the beam scanning means. The technical point is that the apparatus further includes a control means for controlling the intensity of the laser beam based on the detection result of the processing state detection means during the operation of the laser beam.

[Function] According to the present invention, a relatively low output CW laser is used as the laser light source. For this reason, the laser beam focused by the focusing means scans the processing range on the object by the scanning means, and thereby the object is processed, but the processing state is determined by the processing state detection means. , monitored. Then, based on the results of this monitoring, it is determined whether the processing is finished or not, and the control means stops the laser beam irradiation.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 mainly shows an optical system portion of an embodiment of the present invention, and FIG. 2 mainly shows a control device portion of this embodiment.

In FIGS. 1 and 2, laser light LB for resist removal is output from a laser light source 10. In FIG. As this laser light source 10, for example, C.
A W laser (continuous wave laser light source) having an oscillation line from the ultraviolet region to the visible region is used. For example, He-C
Laser beams of 325 nm from a D laser and 514.5 nm from an A laser are suitable.

Next, the laser light LB output from the laser light source 10 as described above is incident on the beam splitter 12, and the laser light LB that has passed through the beam splitter is made to enter the shutter 14.

This shutter 14 transmits or blocks the incident laser beam LB based on a command from a control means to be described later, and the laser beam LB transmitted through the shutter 14 is reflected by a galvano mirror 16° 18 that performs scanning. After that, the light passes through a beam splitter 20 and enters an objective lens 22.

Furthermore, the laser beam LB imaged by the objective lens 2°2 is
The light is configured to be incident on the substrate or wafer W in the form of a beam. This wafer W is placed on an XY stage 24 that performs two-dimensional BwJ in the X direction and the Y direction.

It is placed on an XY stage 9 that is controlled by a stage controller 13 and moves two-dimensionally in the X and Y directions.

The XY coordinate position of the XY stage 24 is constantly detected by a position measuring device 26 such as a laser interferometer, and is fed back to the stage controller 28 as position information.
This allows the necessary position control of the XY stage 24 to be performed. The positioning of the XY stage 24, that is, the positioning of the wafer W is, for example, ±0.01.
This is performed with an accuracy of μm, and the irradiation position of the laser beam LB on the wafer W is determined by driving the XY stage 24.

Next, an alignment optical system 30 for detecting alignment marks formed on the wafer W is arranged near the above-mentioned optical system, and the detection light of the alignment marks by this detects the alignment marks including photoelectric elements and the like. Mark detector 32
It is designed to be incident on . Connection is made so that the detection signal obtained by the mark detector 32 is input to a system controller 34 that controls the operation of the entire system.

Next, a beam splitter (or dichroic mirror) 20 disposed in the optical path partially converts the reflected light from the wafer W or resist to the laser beam LB and the fluorescence from the resist generated by laser irradiation into detection light LD. These detection lights LD are condensed by a condenser lens 36 and then incident on a photodetector 38.

This photodetector 38 has a built-in filter (not shown), and by switching this filter, the mode can be switched between reflected light detection and fluorescence detection.

This photodetector 38 is connected to the system controller 34, and a detection signal corresponding to the incidence of the detection light LD is input to the system controller 34. No matter which mode is used, the detection signal changes when the resist is completely removed from the wafer W, and the completion of resist removal can be visually determined by the detection signal.

Next, the laser light LB output from the laser light source 10 is
A portion of the light is reflected by the beam splitter 12 described above and enters the photodetector 40. This light detection M40 is for measuring the intensity of laser light B, and its detection signal is sent to the system controller 34.

Based on the light intensity signal, the system controller 34 sends a control command signal to the laser control device 42 to control the laser light source 10, so that the laser light LB with an appropriate intensity is output.

Further, the irradiation of the laser beam LB is performed by the shutter 1 according to a control command signal output from the system controller 34.
It is controlled by the opening/closing operation of 4.

Next, the overall operation of the above embodiment will be explained.

First, as described above, the system controller 34 issues a control command to the laser control device based on the detection signal of the photodetector 40, and the intensity of the laser beam LB output from the laser light source 10 is adjusted to a necessary appropriate level. adjusted to size. The intensity adjustment of the laser beam LB is appropriately performed as necessary during operation. Note that while the laser beam LB is processing the wafer W, it is desirable to control the laser beam intensity to be constant.

Next, the alignment optical system 30 and the mark detector 3
2, the alignment mark on the wafer W is detected, and thereby the alignment mark on the wafer W is detected.

Global alignment is performed.

When the global alignment of this wafer W is completed,
In response to a control command from the system controller 34, the shutter 14 is opened, and the laser beam LB is transmitted to the shutter 1.
4 and is then irradiated onto the wafer W.

At this time, due to the action of the galvano mirrors 16 and 18, the beam spot of the laser beam LB scans the set range of the resist on the wafer W two-dimensionally.

Here, by irradiation with the laser beam LB, reflected light is generated from the wafer W and the resist, and furthermore, fluorescent light is generated from the resist. A portion of these reflected lights and fluorescent light is condensed by the action of the beam splitter 20 and the condensing lens 36, and enters the photodetector 38 as detection light LD. In the photodetector 38, a suitable one of the incident detection lights LD is selected using a filter, photoelectrically converted, and a detection signal is output to the system controller 34.

In this case, in the mode in which reflected light is selected, the reflectance for the laser beam LB is different between the resist and the wafer W, so that due to a change in the intensity of the incident light on the photodetector 38,
It is determined whether the resist has been successfully removed.

In addition, in the mode in which fluorescent light is selected, the fluorescent light is emitted only when the resist is irradiated with the laser beam LB, so similarly, whether or not the resist is removed is determined based on changes in the intensity of the incident light. .

This determination of whether or not to remove the resist is made by the system controller 34.

When the system controller 34 determines that resist removal is complete based on the detection signal from the photodetector 38,
A control signal is output to the shutter 14, and the shutter 1
4 is controlled to the "closed" state. With the above operations,
Removal of the resist at the corresponding location is completed. In addition, when scanning the laser beam and spot B, it is better to scan the same part of the resist multiple times and not remove the resist with just one scan, as this will damage the surface of the wafer W (marks, patterns, etc.). This is preferable because it reduces the risk.

Next, if there are other resist removal locations, the stage controller 28 is operated by the system controller 34.
A control signal is output to the XY stage 24, and the XY stage 24 moves eight times so that the beam spot of the laser beam LB is irradiated onto the next resist removal location.

As mentioned above, this embodiment uses a CW laser as a light source,
The amount of laser light outputted from this is controlled, and the laser light is focused onto a smaller area than the desired area and irradiated onto the resist. Then, the positions of the wafer and the laser beam spot are changed relative to each other, and the resist is scanned by the laser beam spot to remove the entire desired range of resist. At this time, the removal end point is monitored by detecting fluorescence or the like from the resist.

According to this embodiment, since a CW laser is used as the light source, there is an effect that contamination of the surrounding area due to scattering of melted resist is reduced and alignment marks on the substrate are not damaged.

Further, since the resist in a predetermined range is removed by focusing the laser light on a small area and scanning it, there is an effect that the resist does not remain partially due to the beam profile of the laser light.

Using such a device, a He-Cd laser with an oscillation line at 325 nm is used as a laser light source, and this is
0FPR-800 resist film coated to a thickness of 1 μm on a silicon substrate was focused at
When the resist film was removed over an area of m, the resist film could be completely removed without causing any damage to the silicon substrate.

Note that the present invention is not limited to the above embodiments in any way.

For example, in the above embodiment, the relative g motion between the laser beam LB and the wafer W, that is, the scanning of the laser beam spot on the resist, was performed by two sets of galvanometer mirrors 16 and 18, but instead, Such beam scanning may be performed by moving the XY stage 24 eight times.

Further, in the above embodiments, the resist was removed, but the present invention is also applicable to cases where other materials are subjected to appropriate processing.

[Effects of the Invention] As described above, according to the present invention, the laser beam of the CW laser is focused, the laser beam is scanned on the object, and the object is processed while monitoring the processing state of the object. Therefore, there is an effect that good processing can be applied to a part of the object.

[Brief explanation of the drawing]

FIG. 1 is a perspective view mainly showing optical components of an embodiment of the present invention, and FIG. 2 is a circuit block diagram mainly showing a control device part of the embodiment of FIG. DESCRIPTION OF SYMBOLS 10... Laser light source, 12.20... Beam splitter, 14... Shutter, 16.18... Galvano mirror 122... Objective lens, 24... XY stage, 28... Stage controller , 30... Alignment optical system, 32... Mark detector, 34...
System controller, 38.40... Photodetector, 4
2... Laser control device, LB... Laser light, LD.
...Detection light, W...Wafer.

Claims (3)

[Claims] (1) In a laser processing device that performs necessary processing on an object by irradiating a laser beam, a CW laser is used as the light source of the laser beam, and the laser beam is focused to form a spot. a focusing means; a scanning means for scanning the object with the spot by relatively moving the spot and the object; and processing the object using detection light obtained from the object by irradiation with the laser spot. A laser processing apparatus comprising: a processing state detection means for monitoring a state; and a control means for controlling irradiation of the laser beam to a target object based on a detection result of the processing state detection means. (2) The object is a semiconductor substrate undergoing a lithography process, which has an alignment mark and has a resist layer formed on its surface.
The laser processing device described in Section 1. (3) The laser processing apparatus according to claim 2, wherein the detection light is either reflected light of a laser beam obtained from the resist layer or fluorescent light.