JPH0677336A - Method for padding connection hole - Google Patents

Abstract

PURPOSE:To pad a contact hole or a through hole by fusing a metallic film without the fused metallic film increasing the irregularity that it had before application of a laser beam and besides, without alloying the metallic film. CONSTITUTION:A first pulse beam 1, 50nsec or less in pulse width is applied by one pulse to a semiconductor substrate which has, at the surface, a metallic film covering the connection hole opened in an insulating film, and while the metallic film is fusing, a second pulse beam 2 lower in energy density at peak than the first pulse beam and 30nsec or more and 50nsec or less in pulse width is applied by one pulse. Hereby, the reliability on a semiconductor device, the yield rate, and the signal propagation property are improved without deteriorating the processability of the semiconductor device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of burying a connection hole of a semiconductor device, and more particularly to a method of burying a wiring metal film for burying a contact hole and a through hole.

[0002]

2. Description of the Related Art Conventionally, as a method of burying a connection hole using laser light irradiation, a method of irradiating a semiconductor substrate having a metal film on its surface with laser light having a pulse width of about 1 microsecond (IEEE Electron Device Letters Magazine IEEE ELECTRON DEV
ICE LETTERS, VOL. EDL-7, NO.
1, 1 (1986)). Similarly, a method of irradiating a laser beam having a pulse width of approximately 20 nanoseconds (IE ELECTRON DEVICE LETTERS, IEEE ELECTRON DEVICE LET)
TERS, VOL. EDL-8, NO. 2,76 (19
86)).

[0003]

According to the above-mentioned conventional method of irradiating a laser beam having a long pulse width of about 1 microsecond, the metal film is liquefied by the laser beam irradiation, and the liquefied metal film is a laser beam. Since the reflectance for light is lowered, it further absorbs the energy of laser light and is maintained at a temperature much higher than the melting point for a long time.

Therefore, the metal film easily reacts with the base material of the metal film and diffuses into each other to form an alloy. The alloyed metal film has a drawback that the resistance is increased and the characteristics of the semiconductor device such as signal propagation characteristics are deteriorated.

On the other hand, in the method of irradiating a laser beam having a short pulse width of about 20 nanoseconds, since the melting time required for flattening the metal film is longer than the pulse width, a large amount of energy is generated within the short pulse width. Must be given. For this reason, the metal on the surface instantaneously evaporates, and due to the influence, the melted metal film amplifies the unevenness that the metal film had before the laser light irradiation. A film with large irregularities has a drawback that it is difficult to process by lithography and etching.

An object of the present invention is to provide a method of filling a contact hole or a through hole that fills a contact hole or a through hole while maintaining the resistance of the metal itself without causing alloying of the metal.

[0007]

In order to achieve the above object, in the method of filling a connection hole according to the present invention, a semiconductor substrate is pulsed with pulsed light to melt a metal film,
A method of flatly filling a contact hole such as a contact hole or a through hole with a metal film, wherein the semiconductor substrate has a metal film covering the connection hole opened in the insulating film on the surface thereof, and pulse irradiation of pulsed light is performed. Is the first pulsed light,
This is a step of pulse-irradiating the second pulsed light, and the pulsed irradiation of the first pulsed light is one pulsed irradiation of the pulsed light having a pulse width of 50 nanoseconds or less. While the metal film is melting,
The pulsed light has a lower peak energy density than the pulsed light and has a pulse width of 30 nanoseconds or more and 50 nanoseconds or less.

In addition, a method of irradiating a semiconductor substrate with pulsed light in a pulsed manner to melt a metal film and burying contact holes such as contact holes and through holes with the metal film evenly, the semiconductor substrate is an insulating film. It has a metal film on the surface that covers the opened connection hole, and the pulse irradiation of pulsed light reaches the maximum energy density before 30 nanoseconds from the start of emission, and the pulse width is 500 when the pulse width is 80 nanoseconds or more. One pulse of pulsed light of nanosecond or less is irradiated.

[0009]

The metal has a lower reflectance in the liquid phase than in the solid phase, and therefore, when irradiated with light of the same intensity, the liquid phase absorbs more energy. In the case of Al, 632 nm in the solid phase
The reflectance in the liquid phase is about 92%, whereas it is 85% at the same wavelength in the liquid phase. In other words, compared to the solid phase in the liquid phase,
About twice as much energy will be absorbed. Since the amount of absorbed energy varies depending on the phase, the temperature of the molten metal and its melting time can be arbitrarily controlled by appropriately selecting the amount of energy applied in each phase and the pulse width.

First, the metal film is melted in a short time of 30 nanoseconds or less by irradiating the light whose pulsed light energy peak is about 30 nanoseconds after the light is emitted. After that, the energy of the pulsed light to be irradiated is reduced to keep the temperature of the liquefied metal as low as possible, and the pulse width is shortened as much as possible to give the minimum melting time required for filling the contact holes and through holes. To do. The melting time of the metal required to fill the contact hole and the through hole is approximately 50 nanoseconds or more and 500 nanoseconds or less.

The pulse width of the laser beam required for embedding is about 80 nanoseconds to 500 nanoseconds or less, including the time required for melting the metal of about 30 nanoseconds and the melting time required for embedding. When irradiating two laser beams having different intensities and pulse widths, the sum of the pulse widths of these laser beams may be set to about 80 nanoseconds to 500 nanoseconds or less.

As a result, the reaction between the metal film and the base of the metal film is suppressed, and the increase in the resistance value of the metal film itself can be suppressed. Furthermore, since the temperature of the liquefied metal film is always maintained near the melting point, the metal film does not evaporate. Therefore, the metal film can be flattened over the entire pulsed light irradiation region.

[0013]

The present invention will be described below with reference to the drawings. FIG. 1 shows the intensity changes with time of the energy densities of the first pulsed light and the second pulsed light in an embodiment according to claim 1 of the present invention. In this embodiment, the metal film on the semiconductor substrate is covered with a contact hole 500 formed in a silicon oxide film having a film thickness of 1 μm on a silicon substrate.
The second harmonic is obtained by modulating an Al film having a thickness of nm with an output light of a krypton fluoride excimer laser as a first pulse light and an Nd: YAG laser excited by a flash lamp as a second pulse light with a Pockels cell. A case where wave light is used will be illustrated.

The Al film is irradiated with krypton fluoride excimer laser light 1 having a maximum energy density of 1 J / cm ² , a pulse width of 20 nanoseconds and a wavelength of 248 nm. Then Al
The temperature of the film reached the melting point, and about 2 from the start of laser irradiation.
The Al film melts in 0 nanosecond. Then, it overlaps with the output light of the krypton fluoride excimer laser for 5 nanoseconds, and Nd:
Irradiate the second harmonic wave 2 of the YAG laser. Nd: YA
The maximum energy density of the second harmonic of the G laser is 0.5 J / cm ² , pulse width 100 nanoseconds, wavelength 532
nm.

As a result, the Al film is liquefied for about 100 nanoseconds. During the liquefaction, Al flows into the contact hole formed in the substrate, and flat filling becomes possible. In this case, even if silicon or TiN that is a barrier metal is used as the base film, the melting time is as short as about 100 nanoseconds and the temperature of Al is about 700 ° C.
Therefore, significant interdiffusion between the base film and Al does not occur. Further, since the temperature of the molten Al is lower than the melting point, the laser irradiation does not amplify the unevenness that the Al film had before the laser light irradiation.

In the present embodiment, the case where the output light of the krypton fluoride excimer laser is used as the first pulsed light and the second harmonic of the Nd: YAG laser light is used as the second pulsed light is exemplified. As pulsed light, in addition to gas lasers such as excimer lasers and carbon dioxide gas lasers, solid-state lasers such as glass lasers, fundamental waves and harmonics of liquid lasers such as dye lasers, and light and flash lamps obtained by chopping continuous wave lasers, etc. It is also possible to use chopped lamp light or continuous lamp light.

Although the case where Al is used as the target metal film has been illustrated, it goes without saying that the same effect can be obtained by using gold, copper, tungsten, titanium or other alloys.

Further, in this embodiment, the case where the contact hole formed on the substrate is filled has been exemplified, but the same effect can be obtained when the through hole formed on the metal wiring is filled. The time during which the metal film is melted can be arbitrarily selected by changing the pulse width of the second pulsed light.

FIG. 2 (a) shows changes in the voltage applied to the Pockels cell for modulating the pulsed light in the embodiment for claim 2 of the present invention. FIG. 2B shows the energy density change with time of the pulsed light. In this embodiment, as the metal film on the semiconductor substrate, an Al film having a film thickness of 500 nm covering a contact hole opened in a silicon oxide film having a film thickness of 1 μm on a silicon substrate, and using a Nd: YAG laser as a Pockels cell as pulsed light. The case of using a pulsed laser beam externally modulated in 1. will be exemplified.

First, the voltage 3 applied to the Pockels cell is increased up to point a so that the laser light is not transmitted and energy is stored inside the laser medium. Next, when the voltage is made zero in the section ab, the laser light gradually starts to be emitted from the point e, and the energy density 4 of the Nd: YAG laser light becomes maximum at the point f. The ab section is about 10 nanoseconds. When the voltage is applied to the Pockels cell again in the section of bc, the transmittance of the laser light is suppressed and the energy density of the emitted light starts to decrease. The bc section is about 10 nanoseconds. Further, when the voltage applied to the Pockels cell is made zero again in the section cd, the decrease in the energy density of the emitted laser light slows down, and in the section g to h,
After becoming constant at about 1/2 of the energy density at point f,
It becomes zero. The cd interval is about 10 nanoseconds.

This laser light was adjusted with a lens so that the energy density at point f was about 1 J / cm ² , and then 5
When the Al film having a film thickness of 00 nm is irradiated, the Al film is liquefied by the laser irradiation in the section from e to g, and the liquid state is continued by the laser irradiation of about 0.5 J / cm ^{2 in} the section from g to h.

As a result, Al flows into the contact hole formed in the substrate, and flat filling is possible. In this case, even if silicon or TiN that is a barrier metal is used as the base film, the melting time is as short as about 100 nanoseconds and the temperature of Al is as low as about 700 ° C. No significant interdiffusion occurs. Further, since the temperature of the molten Al is low, the laser irradiation does not amplify the unevenness of the surface that the metal film had before the laser light irradiation.

In this embodiment, Nd: YA is used as the pulsed light.
The case where the second harmonic of G laser light is used has been exemplified,
Other solid-state lasers, gas lasers, liquid lasers may be used by modulating the fundamental wave and harmonics.

Although the case where Al is used as the target metal film is exemplified, it is needless to say that the same effect can be obtained by using gold, copper, tungsten, titanium or other alloys.

Further, in the above-mentioned embodiment, the case where the contact hole formed on the substrate is filled has been exemplified, but the same effect can be obtained when filling the through hole formed on the metal wiring. The time during which the metal film is melted can be arbitrarily selected by changing the length of the cd section of the voltage applied to the Pockels cell.

[0026]

As described above, according to the present invention, the contact hole and the through hole can be flatly embedded while the metal film is not alloyed and the low resistance value of the metal film itself is maintained. This has the effect of improving the reliability, yield, and signal propagation characteristics of. In addition, since the contact hole and the through hole can be flatly embedded without amplifying the unevenness that the molten metal film had before the laser light irradiation, the processability of the semiconductor device is not deteriorated and the reliability of the semiconductor device is improved. There is an effect that the yield can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a timing chart of a first pulsed light and a second pulsed light according to an embodiment of the present invention.

2A is a timing chart of a voltage applied to a Pockels cell according to another embodiment of the present invention, and FIG. 2B is a timing chart of an intensity of output light.

[Explanation of symbols]

 1 Krypton Fluoride Excimer Laser Light 2 Second Harmonic Wave of Nd: YAG Laser 3 Voltage Applied to Pockels Cell 4 Nd: YAG Laser Light

Claims (2)

[Claims] 1. A method of irradiating a semiconductor substrate with pulsed light to melt a metal film and burying a contact hole such as a contact hole or a through hole with the metal film evenly, wherein the semiconductor substrate is an insulating film. A metal film covering the opened connection hole is provided on the surface, and the pulse irradiation of the pulsed light is a step of pulse-irradiating the first pulsed light and the second pulsed light. The irradiation is one pulse of pulsed light having a pulse width of 50 nanoseconds or less, and the pulsed irradiation of the second pulsed light is higher than that of the first pulsed light while the metal film is melting. Has a low energy density, and one pulse of pulsed light having a pulse width of 30 nanoseconds or more and 50 nanoseconds or less is irradiated. 2. A method of irradiating a semiconductor substrate with pulsed light to melt a metal film, and burying a contact hole such as a contact hole or a through hole with the metal film evenly, wherein the semiconductor substrate is an insulating film. It has a metal film on the surface that covers the opened connection hole, and the pulse irradiation of pulsed light reaches the maximum energy density before 30 nanoseconds from the start of emission, and the pulse width is 500 nanoseconds at 80 nanoseconds or more. A method of embedding a connection hole, characterized in that one pulse of pulsed light of nanosecond or less is irradiated.