JP2707858B2 - Laser assisted electroless plating apparatus and method for filling metal film in fine hole - 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-assisted electroless plating apparatus for selectively forming a metal layer on a main surface of a semiconductor substrate and a method for filling a metal film in a fine hole.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing the structure of a conventional laser-assisted electroless plating apparatus, wherein 1 is a semiconductor substrate, 2 is a stage on which the semiconductor substrate 1 is mounted, and 3 is a plating cup. 3a is the quartz window, 3b is the plating solution inlet, 3
c is a plating solution outlet. Reference numeral 4 denotes a plating solution accommodated in the plating cup 3, and reference numeral 4a denotes a flow of the plating solution 4. Reference numeral 7 denotes a laser light source, 8 denotes laser light, and 9 denotes a lens.

Next, functions and operations will be described.
The semiconductor substrate 1 is placed on the stage 2 in the plating cup 3 with the main surface on which the metal layer is formed facing upward. The plating solution 4 is introduced into the plating cup 3 from the plating solution inlet 3b, passes through the main surface of the semiconductor substrate 1, and is drawn out from the plating solution outlet 3c. Laser light 8 emitted from a laser light source 7 is converged by a lens 9 and is irradiated on the main surface side of the semiconductor substrate 1 through a quartz window 3a. Laser assist processing mainly uses the thermal action of the laser.
As the laser light source 7, a YAG or Ar laser is used. Further, in processing utilizing a photochemical reaction, an example in which a short wavelength region of the Ar laser or DeepUV is used as a light source has been reported. The circulation of the plating solution 4 prevents the laser light 8 from being scattered by air bubbles generated from the portion of the semiconductor substrate 1 irradiated with the laser light 8 during processing. If the plating conditions (solution temperature, etc.) are selected so that plating hardly grows in the non-irradiated portion, the laser light 8 can be generated by the above-mentioned thermal action.
The plating film can be selectively grown only on the irradiated portion. However, the above method is not suitable for performing plating growth on a large number of regions at once from the point of throughput. For this reason, an electroless plating method using a selective film mask is used.

FIGS. 4 (a) to 4 (c) are main cross-sectional views showing a process flow for forming plating in a fine hole using a conventional electroless plating method using a selective film mask. In this figure, 1 is a semiconductor substrate such as GaAs, 11 is a fine hole, 12 is a plating layer, 12a is a swelling of the plating layer 12, 12b is a void formed in the plating layer 12, 1
Reference numeral 3 denotes an insulating film.

Next, a forming process will be described. As shown in FIG. 4A, after the insulating film 13 is formed on the semiconductor substrate 1, the insulating film 13 is subjected to plasma etching using a photoresist or the like as a mask, and the semiconductor substrate 1 such as GaAs is subjected to reactive ion etching to form a fine After the holes 11 are formed, as shown in FIG. 4B, a plating layer 12 is formed in the fine holes 11 by electroless plating. In this case, if the growth rate in the vicinity of the opening of the fine hole 11 is high, as shown in FIG. 4C, the swelling 12a of the plating layer 12 is generated, and the gap 12b is generated in the plating layer 12. In this step, the insulating film 13 functions as a plating growth mask.

[0006]

In the conventional laser-assisted electroless plating apparatus configured as described above, a maskless metal film is formed on a very limited area, for example, a metal film is printed on the semiconductor substrate 1. Although suitable for trimming metal wiring of a circuit pattern, it is not practical due to poor throughput in mass production.

On the other hand, in the method of forming a metal film using ordinary electroless plating on a large number of fine holes 11 formed in the semiconductor substrate 1, if the growth rate near the opening of the fine hole 11 is high, the opening may be reduced. Closes quickly and the plating layer 12
Not only the air gap 12b is formed but also the plating layer 1 near the opening.
There is a problem that a bulge 12a occurs, which hinders circuit pattern formation in a subsequent process.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has excellent mass productivity and can be selectively used without forming a mask pattern such as a photoresist or an insulating film on a semiconductor substrate. Another object of the present invention is to provide a laser-assisted electroless plating apparatus and a method for filling a metal film in a fine hole, which prevent the occurrence of a plating swell.

[0009]

A laser assisted electroless plating apparatus according to the present invention collects laser light emitted from a plurality of laser light sources by an optical fiber so as to have an area equivalent to that of a semiconductor substrate. A quartz photomask is arranged between the laser light source and the semiconductor substrate to add an alignment function.

According to a second aspect of the present invention, in the method of filling a metal film in a fine hole, the laser-assisted electroless plating apparatus irradiates a laser beam only to a bottom portion of a large number of fine holes formed in a semiconductor substrate. To promote plating growth.

[0011]

In the laser-assisted electroless plating apparatus of the present invention, laser light emitted from a plurality of laser light sources is collected by an optical fiber so as to have an area equivalent to that of a semiconductor substrate. By arranging a quartz photomask between semiconductor substrates and adding an alignment function, it is possible to select plating films of various patterns without forming mask patterns such as photoresist and insulating films on the semiconductor substrate. It can be formed on a semiconductor substrate efficiently and in a short time.

Further, in the method for filling a metal film in a fine hole according to the present invention, the plating film is promoted by irradiating laser light only to the bottom of the fine hole to promote plating growth. Can be formed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a structural view of a main part of a laser assisted electroless plating apparatus showing one embodiment of the present invention, and FIG. 2 is a main sectional view showing a method of filling a metal film in a fine hole. In these figures, the same reference numerals as in FIGS. 3 and 4 denote the same components, and 5 denotes a quartz window 3a of the plating cup 3.
, A reference numeral 6 denotes a bundle of optical fibers, 6a denotes an optical fiber, 7 denotes a laser light source, 8 denotes laser light, 11 denotes micro holes, and 12 denotes a plating layer. I have.

First, the function and operation of the laser assisted electroless plating apparatus will be described. In FIG. 1, laser light 8 emitted from a plurality of laser light sources 7 is once collected by a bundle 6 of optical fibers, and expanded to a large area without reducing the intensity. The semiconductor substrate 1 to be an irradiated portion in this way
The optical fiber bundle 6 having the same area as that of the semiconductor substrate 1 is irradiated on the semiconductor substrate 1 through the quartz photomask 5 and the quartz window 3a disposed between the laser light source 7 and the semiconductor substrate 1. Since an alignment function by moving the quartz photomask 5 in the X and Y directions with respect to the substrate position is added, the laser light 8 having various patterns can be generated by changing the quartz photomask 5 only. Can be irradiated. In the plating cup 3, the plating solution 4 is constantly circulating, so that the plating solution 4 can prevent the laser light 8 from being scattered by bubbles generated at the top of the plating process.

Next, a method for filling the metal film in the micropores will be described. The laser light 8 is aligned with the fine holes 11 formed in the semiconductor substrate 1 by the quartz photomask 5 provided in the laser-assisted electroless plating apparatus. It is selectively irradiated. Since the plating growth is promoted only in the portion irradiated with the laser beam 8, the plating layer 12 is selectively grown from the bottom of the fine hole 11 toward the opening, and a mask pattern such as a photoresist or an insulating film is formed on the semiconductor. Plating films of various patterns can be selectively and quickly formed on a semiconductor substrate without being formed on the substrate 1.

[0016]

As described above, according to the laser-assisted electroless plating apparatus of the present invention, laser light emitted from a plurality of laser light sources is made to have an area equivalent to that of a semiconductor substrate by an optical fiber. And a quartz photomask arranged between the laser light source and the semiconductor substrate, and by adding an alignment function, without forming a mask pattern such as a photoresist or an insulating film on the semiconductor substrate. A laser-assisted electroless plating apparatus excellent in mass productivity capable of selectively forming plating films of various patterns on a semiconductor substrate in a short time can be obtained.

Further, according to the method of filling a metal film in a fine hole of the present invention, the plating film is promoted by irradiating laser light only to the bottom of the fine hole to promote plating growth. It can be formed toward the opening, and has the effect that the fine hole can be filled without generating a bulge of the plating layer in the opening of the fine hole or the gap of the plating layer in the fine hole.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a laser assisted electroless plating apparatus showing an embodiment of the present invention.

FIG. 2 is a main cross-sectional view showing one embodiment of a method for filling a metal film in a fine hole using a laser-assisted electroless plating apparatus of the present invention.

FIG. 3 is a sectional view showing a configuration of a conventional laser assisted electroless plating apparatus.

FIG. 4 is a main cross-sectional view showing a process flow of forming plating in a fine hole using a conventional electroless plating method using a selective film mask.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 stage 3 plating cup 3a quartz window 3b plating solution inlet 3c plating solution outlet 4 plating solution 4a plating solution flow 5 quartz photomask 6 bundle of optical fibers 6a optical fiber 7 laser light source 8 Laser light 11 Micro holes 12 Plating layer

Claims (2)

(57) [Claims] A plating solution circulating function of a pump;
In an electroless plating apparatus having a plating cup for containing a plating solution which always overflows and circulates, and a stage for installing a semiconductor substrate provided in the plating cup, a plurality of laser light sources are provided. An optical fiber serving as a guide for laser light generated from these laser light sources, and arranged so that the cross-sectional area of the bundle of optical fibers is at least equivalent to the area of the semiconductor substrate; Laser light emitted from the emission end of the fiber bundle is passed through a quartz photomask having a desired aperture pattern from a quartz window provided above the plating cup onto a semiconductor substrate installed in the plating cup. A laser-assisted electroless plating apparatus comprising an alignment mechanism for performing selective plating by irradiation. 2. A laser-assisted electroless plating apparatus according to claim 1, wherein the bottom of the fine hole formed in the semiconductor substrate is irradiated with laser light by an alignment mechanism, and the opening is formed from the bottom of the fine hole. A method of filling a metal film in a micropore, wherein a metal film is selectively grown toward a portion and the micropore is filled.