JP2565138B2 - Laser CVD apparatus and thin film forming method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser CVD apparatus, and more particularly to a laser CVD apparatus capable of optimizing a film formation state by varying an irradiation distribution of laser light.

[0002]

2. Description of the Related Art A so-called laser CV using a laser as a light source
With regard to D technology and equipment, (1) excimer lasers and other lasers in the wavelength band (mainly in the ultraviolet region) that can directly photodissociate a compound gas have been used, and this laser is parallel to the sample surface. Technique for forming a uniform thin film on the entire surface of the sample by injecting into the sample, and (2)
Research and development have been conducted from two aspects of a technique in which a laser beam is vertically incident on a sample surface, a thin film is locally formed only on a laser beam irradiation portion, and the thin film is patterned on the sample surface.

In the thin film patterning technique by laser CVD of (2) above, (2-1) a mask pattern is reduced and projected using an ultraviolet region laser such as an excimer laser capable of direct photodissociation to cover a certain area. There is a method of performing patterning at once (GSHigashi et al. 1986 DRY PROCESS SYMPOSIUM
Proceedings pp.120-125), but the patterning accuracy is insufficient because it is difficult to develop an objective lens that has a sufficient field size for ultraviolet light and high resolution, and semiconductor elements and photomasks When considering the application to
It is not a practical technique.

(2-2) On the other hand, by using a lens or the like having a small field size and excellent resolution, a thin film formed in a minute size is moved into a band by moving the sample with respect to the laser beam. There is a technology for connecting and patterning (for example, GQZhang et al. J.Appl.Ph
ys. 62 (1987) pp.673-675).

In this technique, an Ar laser or a Kr laser, which is a continuous wave laser in the visible range, is conventionally used, and the laser light is not focused onto an image through a slit or aperture, but is simply focused and irradiated. Therefore, there is an advantage that the heating effect is sufficient and the film quality is excellent as compared with the technique of (2-1) above, but the flatness of the surface, the linearity of the side edges, and the patterned thin film There were points that were not sufficient regarding the guarantee of line width and the variability of line width.

In contrast to the above-mentioned conventional technique (2-2), a laser beam is reduced and transferred through a slit to form a fine thin film, which is disclosed in Japanese Patent Application Laid-Open No. 4-295851, and the fine thin film is connected in a strip shape for patterning. A technology was proposed, and since the central part of the laser beam expanded by the beam expander is used by extracting it with a slit, the irradiation intensity of the laser beam becomes relatively uniform. Since the surface of the thin film is flattened, and the shape of the slit is image-transferred, and the size of this slit is variable, the line width can be changed while ensuring the accuracy of the side edge of the strip-shaped thin film. There were significant improvements such as being possible.

[0007]

However, even in this improved technique, there is a problem as described below regarding the profile of the outermost end of the CVD film. That is, in the laser CVD technique disclosed in Japanese Patent Laid-Open No. 4-295851, the thickness of the tip of the CVD film gradually decreases toward the tip, and the CVD film is hardly formed at the tip. When this is shown in the figure, the cross-sectional shape is as shown by the CVD film (solid line) in the lowermost diagram of FIG.

This is because the surface of the sample is moved relative to the irradiation position of the laser beam passing through the slit by C.
When a VD film is formed, a seed material for forming a new CVD film is formed at the tip of the laser spot (Nu
This is because the reaction of increasing the thickness of the CVD film proceeds only behind the spot and at the portion overlapping with the already formed CVD film. Is uniformized (see, for example, Japanese Patent Laid-Open No. 4-26114), there is no problem to be solved.

Considering that this technique is used for repairing a patterning defect of a photomask used for manufacturing a semiconductor or an LCD (liquid crystal display), the edge precision of the tip cannot be secured in the above-mentioned state, It cannot be said that the pattern correction has been completed normally. Therefore, up to now, a means has been taken to secure the film thickness of the tip portion by continuing the irradiation of the laser beam while stopping the laser spot at the end point of the pattern formation. In this case, since the laser light continues to be radiated to the portion other than the tipmost portion, an unnecessarily thick portion is formed as shown by the broken line in the bottom diagram of FIG. There was a problem.

The present invention has been made in view of the above points, and an object thereof is to make it possible to flatten the film thickness profile at the patterning end portion.

[0011]

In the laser CVD apparatus of the present invention, when the laser irradiation for securing the film thickness at the most distal end portion is performed at the end point of pattern formation by laser CVD, the center of the opening is The center of the optical axis of the laser beam to CV
A mechanism for shifting to the tip side of the D film was provided, and a level difference was provided so that the laser light intensity became higher toward the tip side.

[0012]

When the center of the optical axis of the laser beam is shifted to the tip side of the CVD film, the laser beam intensity at the tip portion is increased to promote film formation at the tip portion, while the laser intensity is reduced except for the tip portion. Since film formation is suppressed in this way, the film thickness profile is flattened.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an apparatus according to an embodiment of the present invention, and this embodiment shows a case where a movable mirror 17 is used as a means for shifting a laser optical axis with respect to an aperture. . In the following examples, a mixed gas of chromium carbonyl (Cr (Co) ₆ ) and molybdenum carbonyl (Mo (Co) ₆ ) is used as a CVD raw material, and the second harmonic of a continuously excited Q-switched Nd: YAG laser is used as a laser ( SHG, wavelength 0.53 μm) is used.

Since Cr (Co) ₆ and Mo (Co) ₆ are solids at room temperature, the gas which is heated and sublimated is used as the source gas (compound gas). In this embodiment, Cr (Co)
₆ and Mo (Co) ₆ were used after being vaporized at 46 ° C. in Reservoir 1 prepared independently. Although only one system of the reservoir 1 is shown in FIG. 1, a plurality of reservoirs having the same shape are used when a mixed gas is used. Ar gas was used as the carrier gas. When the carrier gas flowing through each reservoir 1 is equal, the partial pressure in the mixed gas is Cr.
(Co) ₆ is about 0.58 Torr, and Mo (Co) ₆ is about 0.51 Torr. The partial pressure can be changed by changing the flow rate ratio of the carrier gas.

The raw material gas is carried by the carrier gas into the chamber 2 which is kept airtight and flows on the surface of the sample 3.
Here, the laser light that has passed through the slit 7 through the glass window 4 provided on the upper surface of the chamber 2 is reduced and transferred onto the sample 3 by the objective lens 8, whereby a metal thin film is deposited on the laser light irradiation portion. For example, when a photomask is used as the sample 3 in the case of the above gas concentration, a metal thin film is deposited on the surface of the sample by irradiation with laser light having an average output of about 0.1 mW / μm ² . The sample 3 in the chamber 2 is heated to about 40 ° C. by the heater 5 in order to balance the concentration with the source gas and to control the deposition rate by limiting the amount of metal carbonyl molecules adsorbed on the surface. In order to move the sample 3 relative to the laser light,
The XY stage 6 is used.

In FIG. 1, 10 is a laser light source, 9 is a beam expander for expanding the beam diameter of the laser light, and 17
Is a movable mirror, 21 is a fixed mirror facing the movable mirror 17, and 7 is a slit (or aperture) as described above. The slit 7 has a plurality of movable knife edges, and the laser beam is shaped by the opening formed by the knife edges. Further, 11 is a dichroic mirror, 8 is an objective lens, laser light passes through the above-mentioned members in order, and the opening of the slit 7 is image-transferred onto the sample 3.

The movable mirror 17 is rotated by the rotating mechanism 23 as shown by the arrow in the figure, and the optical axis of the laser light is shifted. If the slit 7 and the movable mirror 17 are sufficiently separated from each other, it may be considered that the laser optical axis is actually shifted in parallel to the slit 7. Movable mirror 17
As the rotation mechanism 23, for example, a galvanometer (device that moves an optical mirror at high speed) can be considered, and there is no problem in response speed. Of course, other drive devices such as motors can be used.

Above the dichroic mirror 11, an eyepiece device for observation and a CC are provided via a half mirror 25.
The D camera 12 is arranged, and the image read by the CCD camera 12 can be observed by the monitor 13.

FIG. 2 illustrates a state of film formation at the end point of patterning when a strip-shaped metal thin film is formed by the apparatus having the above-described structure. In order to obtain a film thickness at the tip portion, laser irradiation (referred to as "end point irradiation") is performed with the laser light spot fixed. After that, unlike the conventional method (method without changing the laser intensity distribution in the slit 7), as shown in FIG. 2, the laser beam intensity is increased so that the laser beam intensity increases toward the tip of the CVD film. Shift the optical axis. The shift of the optical axis is performed by the rotating mechanism 23 rotating the movable mirror 17.

For example, the reduction ratio of the slit image is 1/10.
0, the depth of the slit 7 in the direction of film formation on the surface of the sample 3 is 3 μm, and the diameter of the laser light after expanding the laser light from the laser light source 10 by the beam expander 9 is φ5 mm. When the axis is moved to one knife edge position of the slit 7, the difference in average intensity between the center of the slit 7 and the tip edge is about 20% (however, the influence of diffraction is not taken into consideration).

Roughly speaking, since the temperature rise of the sample surface is also determined in proportion to the laser irradiation intensity, if the supply of the source gas molecules is sufficient, the film formation at the tip portion is promoted by this amount, Film formation on portions other than the tip is suppressed.

The intensity distribution of the laser light is generally strong in the central part and weakens toward the peripheral part. However, if it is desired to make the gradient of the intensity distribution gentler, the expansion ratio of the beam expander 9 should be increased. Alternatively, the shift amount of the laser light may be reduced, and the enlargement ratio and the shift amount may be adjusted according to the gas concentration, the type of raw material gas, and the like.

FIG. 3 shows a second laser light shift mechanism.
It is a block diagram which shows an Example. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals. In this embodiment, the laser light is used by passing through the movable glass plate 18, and when the movable glass plate 18 is inclined, the phenomenon that the optical axis is shifted in parallel by refraction is used. The movable glass 18 is tilted by the driving device 27. As the drive device 27, a carbanometer or a motor can be used as in the first embodiment.

In each of the above embodiments, a CVD apparatus of a type in which a thin film is deposited in a strip shape on the sample surface by scanning laser light relative to the sample and thermally decomposing the compound gas has been taken as an example. The invention is not limited to this, but other types of CV
It is also applicable to the D device.

[0025]

As described above, according to the present invention, a mechanism for shifting the center of the optical axis of the laser beam with respect to the center of the opening is provided when the end point irradiation is performed in pattern formation by laser CVD. It is possible to make a level difference so that the light intensity becomes higher toward the tip side, and as a result, film formation at the tip portion is promoted, film formation at other portions is suppressed, and at the final portion of patterning, It has the effect of remarkably improving the film thickness profile, and greatly improves the reliability of thin film patterning by a laser CVD apparatus.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a diagram showing a film thickness profile when a film is formed by the apparatus of FIG.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a film thickness profile when a film is formed by a conventional CVD apparatus.

[Explanation of symbols]

 2 Chamber 3 Sample 4 Glass Window 6 XY Stage 8 Objective Lens 10 Laser 17 Movable Mirror 18 Movable Glass Plate

Claims (4)

(57) [Claims] 1. A metal or dielectric thin film formed by shaping a laser beam emitted from a laser oscillator by an opening and condensing the laser beam onto an object surface placed in a reaction gas atmosphere by an objective lens to react the reaction gas. In the laser CVD apparatus for forming a laser beam, a shift mechanism for shifting the optical axis center of the laser light with respect to the center of the opening is provided. 2. The laser CVD apparatus according to claim 1, wherein the shift mechanism has a movable mirror provided between the laser oscillator and the opening for shifting a laser optical axis. 3. The glass plate which is provided between the laser oscillator and the opening and which transmits the laser light, and the drive mechanism which rotates the glass plate around an axis orthogonal to the optical path of the laser light. The laser CVD apparatus according to claim 1, further comprising: 4. A laser beam emitted from a laser oscillator is shaped by an aperture, condensed by an objective lens on a sample surface placed in a reaction gas atmosphere, and the laser beam is transferred to the sample surface through the aperture, Laser beam while moving relative to the laser beam, the laser spot is stopped at the end of patterning, the laser optical axis is shifted with respect to the opening, and the laser intensity on the CVD film front side of the opening is increased. A method for forming a thin film, characterized in that a CVD film is formed with a high temperature.