JPH0691089B2 - Metal film melting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In order to prevent aluminum (Al) wiring of an integrated circuit (hereinafter referred to as IC) from being thinned or broken in a via hole portion,
A high-energy laser beam such as an excimer laser is irradiated for a short time to melt and re-solidify the Al film instantaneously, and the Al is filled in the via hole.
To obtain the filled state. When the irradiation energy is too high in this process and evaporation of Al occurs, visible light is emitted. Therefore, by detecting this with a photosensor, the evaporation of Al is monitored and the laser output is controlled as necessary.

[Industrial application field]

The present invention relates to the improvement of the coverage of the Al wiring of the IC, in particular, the Al film such as a via hole is apt to be melted and resolidified by irradiating a pulsed laser beam to a portion where the Al film is likely to be discontinuous,
Involved in processing equipment that fills holes.

In the manufacture of ICs, the metal film forming the internal wiring is often deposited by sputtering. Sputtering is a process in which a substrate is exposed to metal droplets blown from a target by an electron beam or the like, so that it has a strong anisotropy and has a problem in the coverage of inclined surfaces and vertical surfaces.

In particular, in recent years, the opening area of via holes has become narrower with higher integration of ICs, and discontinuity between the metal film deposited on the insulating layer and the metal film deposited on the bottom of the hole is likely to become discontinuous.

[Conventional technology]

As a measure to solve such a problem, various measures are taken, such as pre-filling holes by a deposition method with good coverage such as CVD and depositing a metal film on them by sputtering. ing. Although effective, such treatment is associated with a large increase in steps.

As a method of improving the coating property of the metal film in a simpler process, it is considered to irradiate a pulsed laser beam to a portion having a problem of the coating property such as a via hole to momentarily melt and re-solidify the metal film. There is. This utilizes the fact that Al changes its shape in the direction in which the surface area decreases due to surface tension during melting, for example, Tuckerman et al, IEEE Elect.
ron Device Letters, Vol.EDL-7, No.1 (Jan., 1986), pp.
1-4, a treatment of irradiating a Au film and an Al film with laser light is disclosed.

This paper is described from the viewpoint of flattening the depression on the surface of the metal film that occurs in the via hole portion, and the treatment for filling the via hole as in the present invention is also included in the flattening in terms of shape. is there. However, in the case of via holes, depending on the shape of the holes and the adherend, cavities may be created inside the holes and only the surface may be flattened, so consideration must be given to dealing with this during the opening process and Al adhesion process. is there.

Instantaneous melting and resolidification of metal film by pulsed laser light
Since the temperature rising area is limited, it has an advantage that the characteristics of the formed element are not changed, but it is necessary to control the amount of energy to be irradiated appropriately. If the injected thermal energy is too large, the substrate temperature rises, which not only changes the characteristics of the formed element, but also changes the boiling point property like Al, and also has a relatively low boiling point like Al. The metal may evaporate and the wiring layer may disappear.

[Problems to be solved by the invention]

As described above, in the momentary melting and resolidification of a metal film by a pulsed laser beam, it is necessary to control the amount of energy to be irradiated to an appropriate amount, but an excimer laser is unstable in the amount of light emitted for each pulse and If the operating conditions are set so that the aluminum melts, the evaporation of Al occurs when the emission output rises.

You can solve this problem by constantly monitoring the state of the Al film, stopping the laser irradiation when evaporation starts, or making the next operation lower output, but to automate it Means must be provided to detect the start of evaporation.

An object of the present invention is to provide an Al film melting apparatus capable of monitoring the state of the Al film and stopping the operation of the laser by detecting the start of evaporation, or lowering the amount of emitted energy in the next time. is there.

[Means for solving problems]

In order to achieve the above-mentioned object, the device of the present invention was irradiated with laser light in addition to a high-power laser device and a stage on which a semiconductor substrate having an Al film formed thereon was placed and moved in a plane.
It is equipped with a light detection control device for detecting visible light emitted from the Al film.

[Action]

When Al is evaporated by the irradiation of ultraviolet laser light, visible light is emitted. If the photo sensor detects this visible light and the laser output is controlled by the detection output, it is possible to reduce the occurrence of wiring defects due to Al evaporation.

This luminescence is generated by Al-1% Si, Al-1 used for internal wiring of IC.
It is also found in alloys containing Al as the main component, such as% Cu.

〔Example〕

The structure of the device of the present invention is shown in the drawing. In FIG. 1, reference numeral 1 denotes a laser light source section whose main constituent is an excimer laser, and a Q switch may be provided in some cases. The Q-switch is used to control the pulse width and is not necessary. The excimer laser used here is an argon fluoride (Ar
F) A laser, which has an emission wavelength of 193 nm, a pulse width of 15 ns, and an energy amount of 130 mJ to 170 mJ per shot. The thickness of the beam is 2 cm × 1.8 cm at the laser output, and this is condensed by the lens 2 and narrowed down to 1 mm × 0.6 mm to increase the energy density.

Reflection on the Al surface is a problem that cannot be ignored. In the above paper, the Al film is coated with Si to reduce the reflection of laser light, whereas in the present invention, the irradiation energy per unit area is reduced. By increasing the amount and shortening the irradiation time, the required energy is absorbed without coating treatment. The laser used in the experiments in the above paper has a wavelength of 50.
With a 4 nm die laser, the irradiation energy density is 1 J / cm ² and the pulse width is 0.6 to 1 μm.

3 is a silicon substrate on which an Al film is formed, 4 is a stage on which the silicon substrate is mounted and which moves in the XY plane. This is because the irradiation area of the laser beam is small as described above, so all the necessary parts It is used to irradiate a laser beam on the.
If a more powerful laser device can be obtained, it is possible to perform irradiation processing on a chip-by-chip basis by thickening the beam, but it is considered that undesired results will be brought about if the irradiation area for one irradiation is too wide.

5 is a photo sensor. If the Al film is excessively irradiated with laser light, the temperature of Al rises above the boiling point and Al evaporates. At that time, it emits light in the visible range.
Know the evaporation of. The photo sensor may be an ordinary photodiode, but since the laser light is reflected by the Al surface, a filter is used when it is necessary to cut this reflected light.

The light detection control device 6 displays the detection status of the photo sensor 5 and outputs a control signal as necessary to suppress the output of the excimer laser. Output control of excimer laser is Q
This is done by closing the switch or decreasing the amount of light emitted next time.

It is desirable to use the apparatus of the present invention in a non-oxidizing atmosphere, because when the Al film is melted in an oxidizing atmosphere, the surface is oxidized and the shape of the melt does not change.
Treatment in vacuum is also possible, but Al vaporizes quickly.

If you install a heater on the stage and preheat the wafer,
It is possible to reduce the energy density of laser light, that is, to expand the irradiation area. In that case, the preheating temperature must be set within a range that does not delay resolidification.

The patterning of the Al film is performed after the melting process. When the patterned Al film is subjected to the melting treatment, an undesired change may occur, such as a change in the planar shape of the patterned Al film and an increase in the substrate temperature in a portion not covered with the Al film.

〔The invention's effect〕

As described above, since the apparatus of the present invention has the function of detecting the evaporation of Al, it is possible to avoid the situation where the melting process is continued while the output of the unstable excimer laser is excessive, and Since the flattening of holes etc. is performed safely, the yield of IC manufacturing is improved.

In addition, the thickness of the Al film is often biased between the wafers and within the wafer, but according to the present invention, it is possible to perform processing according to the film thickness.

[Brief description of drawings]

 The figure shows the configuration of the apparatus of the present invention. In the figure, 1 is a laser light source section 2, 2 is a lens, 3 is a silicon substrate, 4 is a stage, 5 is a photosensor, and 6 is a photodetection control apparatus.

Claims (2)

[Claims] 1. A high-power laser device (1) and a light having a wavelength longer than that of the laser light emitted from a coating containing aluminum as a main component irradiated with the laser light emitted from the device is detected and controlled. A metal comprising a photodetection control device (6) for outputting a signal, and a stage (4) for placing a semiconductor substrate on the surface of which the film containing aluminum as a main component is formed and moving it in a plane. Film melting equipment. 2. The metal film melting apparatus according to claim 1, wherein the light source of the high-power laser device is an excimer laser.