JPH03261127A - Processor - Google Patents

Abstract

PURPOSE:To remove the adhering pollutant with an optical protective member being fixed by providing it with an optical protective member, which prevents the adhesion to an optical system of the vaporizing ingredients of the film generated by the irradiation with a laser beam, and a pollution removing means, which removes the ingredients adhering to the optical protective member. CONSTITUTION:In case of removing a resist layer, a pollution preventive means is provided, which prevents the resist having evaporated receiving the energy of a laser beam from adhering onto an objective 6 and a wafer 7. That is, a chamber 26 is provided between the objective 6 and the wafer 7, and at the position opposite to the objective 6 is provided an optical protective member 20 such as quartz or the like as a window. And a discharge electrode 17, connected to a power source 16 for discharge, and others are installed opposite in the vicinity of the optical protective member 20, and the adhering ingredients are removed before the light transmittance of the optical protective member 20 reaches the allowable value by pollution. Hereby, the resist and others adhering to the optical protective member can be removed with the optical protective member 20 being fixed.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a processing device for partially removing a thin film laminated on the surface of a substrate [Background of the Invention] In recent years, 4M Alignment precision is required to withstand the production of 16Mbit and 16Mbit capacity memories. Most of this type of exposure equipment exposes the semiconductor wafer by overlapping the circuit pattern of the mask (or reticle) many times, but the mask (or reticle) and wafer, which mainly determine the overlay accuracy, The alignment accuracy with the wafer varies greatly depending on how precisely the position of the alignment mark formed on the wafer is detected.

Typically, wafer alignment is performed by irradiating an alignment mark with light and photoelectrically detecting reflected light, scattered light, diffracted light, etc. from the mark.

Since a resist is necessarily applied to the wafer before exposure, detection of alignment marks is performed on the resist layer (1 to 2).
(thickness on the order of μm). Furthermore, since the alignment mark of the resist layer has a fine step structure, it is inevitable that the film thickness will be non-uniform around the mark. For this reason, the optical information generated from the alignment mark may be weakened by the influence of the resist layer, the interference effect inherent to the thin film may become noticeable near the mark, or the unevenness of the resist film thickness may become asymmetrical on both sides of the mark. The resist layer covering the alignment mark is removed so that the alignment accuracy (mark position detection accuracy) does not deteriorate. This is especially important when using a multilayer resist to miniaturize patterns on a wafer, in order to avoid the phenomenon in which the alignment mark itself becomes optically invisible under illumination light at the exposure wavelength. It's a process. As a method for removing this resist, a method has been devised in which the resist is irradiated with laser light energy to remove a desired region of the resist layer. In a conventional device of this type, as shown in FIG.
3. The gas injected from step 24 blows off the scattered objects from above the wafer 7 placed on the stage 9.

Here, in order to prevent the vaporized resist from adhering to the objective lens 6 and the wafer 7,
A chamber 26 is provided between the two. A chamber lid 22 provided with a hole 22a sufficient for the laser beam LB to pass through is fixed to the wafer 7 side of the chamber 26 so as to seal the chamber 26. The pressure inside the chamber 26 is reduced by the exhaust pump 25 via the trap 27 .

As a result, the vaporized resist is transferred to the chamber 26.
This prevents the resist from being sucked into the wafer 7 and re-adhering onto the wafer 7. Further, a removable optical protection member 20 made of a quartz plate or the like and having light transmittance is provided as a window at a position facing the objective lens 6 of the chamber 26. This prevents the resist from adhering to the objective lens 6 body.

Further, gas is blown onto the inner surface of the chamber 26 of the optical protection member 20 through the nozzle 21, so that the optical protection member 2
The amount of resist adhesion to 0 is reduced. Furthermore, since the optical protection member 20 is removable, even if the optical transparency of the optical protection member 20 is reduced due to resist adhesion, it can be easily cleaned and replaced.

[Problems to be Solved by the Invention] However, in the conventional method of reinstalling and replacing the optical protection member 20 after cleaning, it is necessary to adjust the position and angle of the optical protection member 20, which causes a decrease in the operating rate of the device. It became.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a processing device equipped with a contamination removal device that can remove contaminants attached to the optical protection member 20 while the optical protection member 20 is fixed.

[Means for Solving the Problems] The present invention includes a contamination prevention means including an optical protection member 20 that prevents contaminants such as resist from adhering to the objective lens 6, It was decided to provide a decontamination means for chemically or physically removing contaminants.

[Function] According to the present invention, contaminants such as resist attached to the optical protection member 20 can be removed in a short time while the optical protection member 20 is fixed.

[Examples] Examples of the present invention will be described below with reference to FIGS. 1, 2, and 3.

FIG. 1 is a block diagram showing a schematic configuration of the processing device, in which a laser beam LB having an oscillation wavelength in the ultraviolet rays emitted from a laser light source 1 is shaped into a predetermined beam shape by a variable aperture 2, and then Most of the light passes through the beam splitter 3 and reaches the shutter 4. The shutter 4 transmits or blocks the laser beam LB, and the shutter 4
The laser beam that has passed through is reflected by a mirror 5 and then enters an objective lens 6. The laser beam LB imaged by the objective lens 6 forms an aperture shape of an aperture 2 on the wafer 7 and irradiates the resist layer on the wafer 7 .

The laser beam LB for removing such a resist layer includes excimer laser, third harmonic of Nd:YAG laser,
The wavelength range is 150 to 360 nm, such as the 4th harmonic, the 2nd harmonic of the 514.5 nm oscillation line of an argon ion laser, etc.
It is preferable to have an oscillation line at m.

Now, the wafer 7 is placed on an XY stage 9 that is controlled by a stage controller 8 and moves two-dimensionally in the X direction and the y direction. The position of the XY stage 9 is constantly detected by a laser interferometer, etc., and is fed back to the stage controller 8 as position information, and the laser beam LB
The irradiation position can be determined on the wafer 7 with an accuracy of ±0.01 μm, for example, by moving the XY stage 9. On the other hand, the small amount of laser light reflected by the beam splitter 3 is collected by the condenser lens 10 onto the light receiving surface of the light meter 11, and the light meter 11 sends a photoelectric signal corresponding to the amount of light (light intensity) to the system controller 12. Output. The system controller 12 issues a command to the stage controller 8 for positioning the wafer 7 with respect to the laser beam LB, and also sends a control signal to the control system 15 of the laser light source 1 or the shutter 4 so as to obtain the optimum amount of laser irradiation. emits. For example, if the laser light source l generates pulsed laser light, such as an excimer, the system controller 12 calculates the optimal laser output value and the required number of pulses based on the photoelectric signal from the light meter 11. , outputs a corresponding control signal to the laser control system 15.

Here, if the laser light source 1 generates CW laser light, the system controller 12 calculates the optimal laser output value and the required irradiation time based on the photoelectric signal, and then the controller 12 A control signal corresponding to the output value is output to the laser control system 15, and a control signal corresponding to the irradiation time is sent to the shutter 4.

Further, an alignment optical system 13 for detecting alignment marks formed on the wafer 7 is fixedly installed at a different position than the objective lens 6, and together with a photoelectric detector 14,
Alignment of the wafer 7 is performed using an off-axis method.
An alignment signal is provided from the photoelectric detector 14 to the system controller 12 . This alignment signal is generated when the center of a mark provided at a specific position on the wafer 7 is captured, and the system controller 12 stores the position of the XY stage 9 at the time of generation as a reference point. , the association (global alignment) between the irradiation position of the laser beam LB and an arbitrary point on the wafer 7 is completed.

The relative alignment between the laser beam LB and the wafer 7 is achieved by scanning the wafer with the laser beam LB, vibrating it, photoelectrically detecting the resulting diffracted light, and aligning the center of the mark based on the signal. A similar effect can be obtained by determining the position and using that position as the reference point.

In addition to the off-axis method, it is also possible to align the wafer 7 through the objective lens 6 using a TTL (through-the-lens) method.

Now, FIG. 2 is a diagram showing an example of a reflectance measurement system provided at the rear 3 of the mirror 5. In this case, the mirror 5 shown in FIG. 2 is a dichromic mirror, and has a characteristic that light having a longer wavelength than the laser beam LB is transmitted. light source(
51 (including an optical system) has a wavelength (single wavelength,
The illumination light LA may be one having multiple wavelengths or a bandwidth. After the illumination light LA is reflected by the half mirror 52,
The light passes through the mirror 5 and enters the objective lens 6, illuminating the wafer 7 with a predetermined intensity. The reflected light of the illumination light LA on the wafer 7 enters the condenser lens 53 via the objective lens 6, the mirror 5, and the half mirror 52, and is collected on the light receiving surface of the photoelectric detector 54. The photoelectric signal of the photoelectric detector 54 is sent to the system controller 12. The photoelectric signal reflects the reflectance of the removed portion of the resist layer of the wafer 7, and the system controller 12 detects the end point of resist layer removal based on the change in reflectance (change in signal intensity). If the laser light source 1 continues to irradiate the laser beam LB even after the end point is detected, the system controller 12 forcibly stops the irradiation using the control system 15 and the shutter 4. This function is effective in preventing damage to underlying marks when the resist layer is thinner than originally planned due to uneven thickness of the resist layer. Of course, conversely, even if the resist layer is too thick, this is advantageous in that it provides a guideline for extra laser irradiation to completely remove the resist.

Note that similar effects can be obtained by using a fluorescence detection system instead of the reflectance measurement system. This takes advantage of the property of ordinary resists to emit fluorescence when exposed to ultraviolet light, and the fluorescence is photoelectrically detected through a wavelength selection filter, etc., and the point at which the fluorescence emission becomes almost zero is detected. Laser light LB
What is necessary is to configure a feedback system that stops the irradiation.

By the way, when removing the resist layer as described above, the resist is vaporized by receiving the energy of the laser beam LB. Therefore, as shown in FIG. 3, a contamination prevention means is provided to prevent the vaporized resist from adhering to the objective lens 6 and the wafer 7. In FIG. 3, a chamber 26 is provided between the objective lens 6 and the wafer 7, and an optical protection member 20 such as a quartz plate is provided as a window at a position facing the objective lens 6. Gas is then sprayed onto the inner surface of the optical protection member 20 (inside the chamber 26) through the nozzle 21. This prevents the resist from adhering to the main body of the objective lens 6, and also reduces the adhesion of the resist to the inside of the optical protection member 20 by blowing the gas. However, even with this gas blowing, contamination of the wafer 7 by resist components cannot be completely prevented, and the laser beam LB is gradually attenuated. Therefore, the discharge power supply 1
A discharge electrode 17 connected to the optical protection member 20 is installed near the optical protection member 20 so as to face it. Then, before the light transmittance of the optical protection member 20 reaches a permissible value or less due to contamination, the adhered component removal process is performed as follows. First, place the lid 19 in position I.
Move from B to position A and seal the chamber 26. Next, the chamber 2 is pumped through the trap 27 with the exhaust pump 25.
Vacuum the inside of 6.

Further, the discharge electrode 17 is initially installed at a position that does not prevent the laser beam LB from irradiating the wafer 7, and the discharge electrode 17 is moved from this position to the position C.

The discharge electrode 17 may be a flat plate electrode or a mesh plate electrode.

Next, etching gas is introduced into the chamber 26 from the nozzle 21, causing discharge between the discharge electrode 17 and the chamber 26, and generating plasma 18.

The discharge electrode 17 is arranged parallel to the optical protection member 20, and the generated plasma 18 uniformly etches the dirt deposited on the optical protection member 20.

During discharge, the etching gas may be kept in the chamber 26, or the trap 27, exhaust pump 2
5 may be allowed to flow. When the deposits on the optical protection member 20 are completely removed, the discharge is stopped and the inside of the chamber 26 is evacuated by the pump 25 via the trap 27. Thereafter, gas is introduced from the nozzle 21 to bring the pressure inside the chamber 26 to atmospheric pressure. Then, move the lid 19 to position B.
At the same time, gas is also blown onto the Eva 7 from the nozzles 23 and 24. The discharge electrode 17 is also returned to its position. This state is the same as before the optical protection member 20 was contaminated by the resist component.

FIG. 4 shows another embodiment of the invention.

The effect of removing deposits on the optical protection member 20 is the same as that shown in FIG.
The electrode is formed in an annular shape so as not to prevent B from irradiating the wafer 7.

Therefore, during plasma discharge and during wafer irradiation, the discharge electrode 2
There is no need to move 8, which simplifies the mechanical structure.

In addition, no matter which discharge electrode is used, the optical protection member 2
If an auxiliary electrode (not shown) having the same potential as the chamber 26 is placed at a position opposite to the discharge electrode with 0 in between, it is easy to concentrate plasma generation on the optical protection member 20 only during plasma discharge.

Further, although the component to be removed is a resist in the above embodiments, other organic substances (polyimide, etc.) or metal components may be used in the same manner.

In addition, in the above embodiments, components such as resist are removed by plasma discharge, but it is also possible to remove them chemically using gas or the like.

Further, according to the present invention, since contaminants can be removed while the optical protection member 20 is fixed, the objective lens 6 and the optical protection member 2 can be removed.
It becomes possible to construct an optical system with an integral structure by covering the lens barrel with the lens barrel. By installing this integrated optical system so as to enter the chamber 26 and following the same procedure as in the above embodiment, the processing apparatus is free from contamination even when the distance between the objective lens 6 and the wafer is desired to be smaller than the height of the chamber 26. is obtained.

[Effects of the Invention] As described above, according to the present invention, the resist etc. attached to the optical protection member can be removed while the optical protection member is fixed, so when removing the resist on the wafer in the lithography process, By peeling off only the resist on the alignment marks without reducing the operating rate of the device, alignment with high precision and high throughput can be expected.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the schematic configuration of the processing device of the present invention, Fig. 2 is a diagram showing the structure of the reflectance measurement system, and Figs.
FIG. 4 is a sectional view showing the contamination removal means of the present invention, and FIG. 5 is a partial sectional view showing a conventional processing device. [Explanation of symbols of main parts] 1. Laser light source 2. Variable aperture 3.
... Beam splitter 4 ... Shutter 5 ...
...Mirror 6...Objective lens 7...
...Wafer 8----Stage controller 9...XY stage lO...Condensing lens 11...Light meter
12- System controller; Roller 13 Alignment optical system 14 Photoelectric detector 15 Laser control system 16 Discharge power source 17 Discharge electrode
18...Plasma 19...Lid 20
・・Optical protection member 21.23.24・・Nozzle
22...Chamber lid 25...Exhaust pump 27...Trap 26...Chamber 28...Annular discharge electrode

Claims (2)

[Claims] (1) A holding means for holding a substrate on which a thin film is laminated to a predetermined thickness on the surface; a laser light source that generates a laser beam; an optical system that irradiates a desired position positioned on the substrate with the laser beam; ; a processing device comprising: an optical protection member disposed between the optical system and the substrate to prevent vaporized components of the thin film generated by irradiation with the laser beam from adhering to the optical system; A processing device comprising: a prevention means; and a contamination removal means for removing the component attached to the optical protection member. (2) The processing apparatus according to claim 1, wherein the contamination removing means removes components attached to the optical protection member using discharge plasma.