JPH02146724A - Laser cvd device - Google Patents

Abstract

PURPOSE:To use a pulse laser at an area having a strict size restriction and at an area having a large thermal diffusion, to enable selection such as use of a continuous output laser at an area which requires an accumulated velocity, and to always enable formation of a good thin film by using both a pulse laser of repetition and a continuous output laser as a laser beam source. CONSTITUTION:In a laser CVD device which forms a thin film selectively on only a laser irradiation section of a sample 2 and the periphery thereof using mainly heat dissociation reaction of CVD material gas, both a pulse laser 7 of repetition and a continuous output laser 8 are used by irradiating a laser beam onto a surface of a sample 2 which is in contact with the CVD material gas. For example, second harmonics (lambda=532nm) of continuous excitation Q switch Nd:YAG laser which enables repetition at a fast speed of about 1kHz to 10kHz is used as a pulse laser 7 and argon laser (lambda=514.5nm) is used as a continuous output laser 8. After adjusted to a proper output by the use of attenuators 9 and 10, each laser beam is synthesized by a synthesizing mirror 12.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an OVD (Ohmic
The present invention relates to a laser CVD apparatus that mainly uses a thermal dissociation reaction to selectively form a thin film using a vapor deposition (chemical vapor deposition) method.

[Conventional technology]

Techniques and equipment for selectively forming various thin films of tungsten, molybdenum, and the like using conventional laser CVD equipment, which mainly uses thermal dissociation reactions, have been extremely widely developed. For example, SFM Engineering C0NDUC! TOR engineering N
TERNAT engineering 0NAL, , TAN,.

90 (1986), a continuous output argon laser was used as a laser, and W (CO)6 and At(OH3) were used as raw materials.
) 3 and describes in detail the technique for forming thin films on glass substrates for the purpose of photomask modification. or,
J, Appl Phys.

62.673 (1987) presents an example of research on technology for forming conductive thin films, using wF6. An example is shown in which a krypton laser is used as the laser.

In addition, techniques and equipment for forming various thin films of molybdenum, chromium, copper, gold, aluminum, polysilicon, etc. are being developed.

In these conventional devices, the laser used is a continuous output laser such as an argon laser or a krypton laser, and a mechanical shutter or an A-0 modulation element is used as the shutter.

[Problem to be solved by the invention]

When only a continuous output laser is used, as in the conventional laser CVD apparatus described above, the following secondary problems occur.

The first point is that when forming a linear thin film, the line width cannot be kept small. VLS
When considering conductor wiring on I, the width of the wiring formed by laser CVD must be 2 μm or less.

However.

When irradiating with a continuous output laser beam, the effect of thermal diffusion around the laser beam irradiation area is large, and it is extremely difficult to suppress the thin film formation area to the spot diameter of the laser beam.

In the case of threads that form a linear thin film while scanning the laser beam over the workpiece, it is possible to suppress the line width to some extent by increasing the scanning speed of the laser beam, but in this case the thickness of the thin film becomes thinner. Because of this, it cannot be called a practical method.

Second, a particularly large portion of thermal diffusion (e.g.
One of the points raised is that it is difficult to form a thin film on the aluminum wiring part on an LSI. This does not increase in the case of materials such as aluminum, which have a high reflectance (90 cm or more over almost all wavelengths) and good thermal conductivity, and even if the cutting angle slightly increases, the heat diffuses rapidly, so it is difficult to irradiate with laser light. This is a phenomenon in which the temperature rise in the region is insufficient and the thermal decomposition reaction does not proceed easily. In this case, I carelessly raised the intensity of the irradiated laser beam to the temperature required for the thermal field of the raw material gas (several hundred degrees for W(CO)6).
Due to uncontrollably rapid thin film deposition between fingers on the edges of the workpiece.

This results in a situation where selective formation of a thin film is not possible.

[Failure to solve the problem]

The laser CVD apparatus of the present invention is a laser CVD apparatus that selectively forms a thin film on a laser beam irradiated area mainly by utilizing thermal dissociation reaction of CVD raw material gas, and uses a continuous pulsed laser as the laser light source. This is characterized by the combined use of an output laser.

〔Example〕

Next, two aspects of the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention.

This embodiment is an apparatus for forming metal wiring on a semiconductor substrate 2 placed in a sealed chamber 1 by laser CVD.

In this embodiment, tungsten carbonyl W(CO)6 vapor is used as the CvD source gas.

The raw material is stored in a reservoir 3, heated and vaporized therein, and mixed with argon as a carrier gas. Argon gas is used to purge the inside of sealed chamber 1, and CV is applied to pulps 4 and 5.
Switched to D raw material gas. The inside of the sealed chamber 1 is evacuated by a vacuum pump B.

Two laser oscillators are prepared. As the pulsed laser 7, a second harmonic (λ=532 nm) of a continuous excitation Q-switched Nd:YAG laser capable of high-speed repetition from about 1 kHz to about 10 kHz is used.As the continuous output laser 8, an argon laser (λ514.5 nm) is used. Each laser beam is used after being adjusted to an appropriate output with attenuators 9 and 10.The output of the pulsed laser can be turned on and off using a Q switch as a shutter mechanism.Furthermore, on the continuous output laser 8 side, A shutter is provided to stop the laser beam irradiation.The pulse laser can also be turned on and off by providing a mechanical shutter in the device.

The two types of laser beams are combined by a combining mirror 12.

As the combining mirror 12, a polarizing beam splitter, a half mirror (if there is enough laser output), or a movable mirror is used. The pulsed and continuous output laser beams are focused and irradiated onto the semiconductor substrate 2 by an objective lens 13 (this objective lens is corrected by a window glass 17), and tungsten produced by the thermal dissociation reaction of tungsten carbonyl is deposited on this substrate. Forms a thin film. The semiconductor substrate can be moved by an XY stage 14, and wiring made of tungsten can be obtained by scanning the XY stage at a speed of several μm/B.

A heating mechanism is built into the holder 15 that holds the semiconductor substrate 2, and serves to maintain the semiconductor substrate 2 at an appropriate temperature (because the tungsten carbonyl does not re-solidify) depending on the concentration of tungsten carbonyl.

FIG. 2 shows the aluminum wiring 21 on the substrate 22 and the laser CV through the via pole 25 formed in the insulating film 26.
It is a vertical cross-sectional view schematically showing how to make contact with the tungsten wiring 26 by the D method, and (a)
(b) at the start of tungsten deposition, (C) at the time of filling the via hole 25, (d) at the start of laser beam irradiation,
1 and 2 respectively show the state in which the tungsten wiring is formed.

In the above case, a repetitive pulse laser (with a peak output higher than a continuous output laser) is used on the via hole 25
When the aluminum wiring 21 is irradiated with a pulse width of about 1 oons), the aluminum wiring 21 is heated to a temperature (several hundred degrees) that can thermally dissociate the CVD raw material for a period of about the same time as the laser irradiation time.
Thin film formation progresses. Furthermore, since the amount of heat conducted and accumulated is smaller than that in the case of continuous laser beam irradiation, it is possible to form a thin film with minute dimensions without causing damage to one periphery, and the above-mentioned problems can be avoided. Furthermore, the reduction in deposition rate due to pulsed laser light irradiation is about one order of magnitude lower than when continuous laser light is used. Furthermore, since it can be used at a peak output that is higher than that of a continuous output laser, it is possible to stably form a thin film particularly on areas where heat diffusion is large, such as aluminum wiring on an LSI.

The two horizontal arrows in the figure indicate the increased heat diffusion when using a continuous output laser, and the two upward arrows indicate the location of the resulting damage. .

A continuous output laser 8 is used when the width of the deposited layer to be formed is wide, or when a metal whose reflectance is not very high is used.

FIG. 3 is a schematic diagram showing the configuration of a second embodiment of the present invention. This embodiment is a CV system that has a margin for the output intensity of the continuous output laser and allows the dissociation reaction to proceed even at a relatively low temperature.
This is effective when using D raw material gas. In this embodiment, one continuous output laser 8 serves both pulse output and continuous output. When it is desired to obtain a pulsed output, a modulator 61 (for example, a mechanical chopper, etc.) placed in the middle is used to modulate the light into a pulsed light.

〔Effect of the invention〕

As explained above, the present invention uses a repetitive pulse laser and a continuous output laser in combination as a laser light source of a laser CVD apparatus.

Processing using a pulsed laser is used for areas with strict dimensional restrictions or large heat diffusion, while processing using a continuous output laser is used for areas that require a high deposition rate (drawing speed when forming a linear thin film).

This makes it possible to make a selection, and it is possible to always form a high-quality thin film.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the first embodiment of the present invention, and FIG. 2 is a configuration diagram of the first embodiment of the present invention.
A vertical cross-sectional view showing an example of the thin film forming process in the apparatus shown in the figure.
FIG. 6 is a block diagram of the second embodiment. Explanation of symbols: 1... Sealed chamber, 2... Semiconductor substrate, 3... Reservoir, 7... Pulse laser, 8...
・Continuous output laser, 16...Objective lens, 17...
Window glass, 21... Aluminum wiring, 23... Insulating film, 25... Via hole, 26... Tungsten wiring, 31... Modulator.

Claims (1)

[Claims] 1. By irradiating a laser beam onto the sample surface that comes into contact with the CVD raw material gas, the thermal dissociation reaction of the CVD raw material gas is mainly used to selectively apply only the laser beam irradiated portion of the sample surface and its surroundings. A laser CVD apparatus for forming a thin film, characterized in that a repetitive pulse laser and a continuous output laser are used together as a laser light source.