JPH04329633A - Treatment of semiconductor substrate - Google Patents

Abstract

PURPOSE:To selectively laser-anneal only microregions of a semiconductor substrate. CONSTITUTION:A mask 4 consisting of an SiO2 film 2 as the thermal insulating film and an Si film 3 as the photoabsorption film is formed on an Si substrate 1, which is in turn irradiated with pulse laser light 12 by excimer laser. This process allows selective laser annealing of the Si substrate 1 at a part uncovered with the mask 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing semiconductor substrates, and more particularly to a laser annealing technique for semiconductor substrates.

0002

2. Description of the Related Art Laser annealing technology is used for forming single crystal semiconductor films on insulators, forming junctions, etc., and has been actively researched. In recent years, laser annealing technology using pulsed laser light in the ultraviolet region using an excimer laser has been attracting attention.

When attempting to selectively laser anneal only minute regions of a semiconductor substrate using such pulsed laser light, a resist pattern is formed on the semiconductor substrate by lithography, and the laser annealing is performed using this resist pattern as a mask. It is possible to do so.

0004

[Problems to be Solved by the Invention] However, ordinary resists with low heat resistance cannot withstand the irradiation of laser light with the energy density necessary for laser annealing. For this reason, it has been difficult to perform laser annealing on minute areas of a semiconductor substrate.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for processing a semiconductor substrate that allows selective laser annealing of only minute regions of the semiconductor substrate.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for processing a semiconductor substrate, which comprises a thermal insulation film (2) and a light absorption film (3) on a semiconductor substrate (1). A mask (4) is selectively formed and the semiconductor substrate (1
) is irradiated with pulsed laser light (12).

[0007]

[Operation] According to the method for processing a semiconductor substrate of the present invention configured as described above, the thermal insulating film (2) and the light absorbing film (3)
) When a pulsed laser beam (12) is irradiated onto a semiconductor substrate (1) on which a mask (4) consisting of In addition, the heat generated by irradiation with the pulsed laser beam (12) can be absorbed by the semiconductor substrate (
1) can be suppressed by the thermal insulating film (2). As a result, the pulsed laser beam (12) is applied only to the part of the semiconductor substrate (1) that is not covered by the mask (4).
is selectively irradiated to perform laser annealing.

On the other hand, since the mask (4) can be formed by lithography and etching, the fine region to be laser annealed can be defined with high dimensional accuracy using the mask (4). As described above, it is possible to selectively laser anneal only the minute regions of the semiconductor substrate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a laser annealing apparatus used in this example. As shown in FIG. 2, in this laser annealing apparatus, a pulsed laser beam 12 having a wavelength of 308 nm is generated from an XeCl excimer laser 11. The pulse width of this pulsed laser beam 12 is, for example, 44 nsec. This pulsed laser beam 12 is reflected by a mirror M1 and then passed through an attenuator 13 to have a desired intensity. Next, this pulsed laser beam 12 is reflected by mirrors M2 and M3, respectively, and then passed through a beam homogenizer 14 to make the energy density uniform.

The pulsed laser beam 12 whose energy density has been made uniform in this manner is incident on a substrate 16 as a sample to be laser annealed, which is placed on a sample stage 15. Then, while moving the beam homogenizer 14 two-dimensionally as shown by the arrow in FIG. 2, the pulsed laser beam 12 is irradiated onto the substrate 16 chip by chip in a step-and-repeat manner to perform laser annealing. here,
Irradiation with this pulsed laser light 12 is performed with a single pulse or multiple pulses. Further, laser annealing by irradiation with this pulsed laser beam 12 is normally performed in a vacuum chamber. When doping the substrate 16 with impurities, laser annealing is performed in a doping gas atmosphere.

Next, the laser annealing method according to this embodiment will be explained. In this embodiment, as shown in FIG. 1A, a silicon dioxide (SiO2
) After forming the film 2, a Si film 3 as a light absorption film is formed on this SiO2 film 2. As the Si film 3, a polycrystalline or amorphous film that is easy to form can be used. The Si substrate 1 is not only a single crystal Si substrate but also a polycrystalline Si film or an amorphous Si film formed on the substrate.

The thickness of the SiO2 film 2 is set so as to sufficiently suppress the conduction of heat to the underlying Si substrate 1 during irradiation with the pulsed laser beam 12, that is, to provide sufficient thermal insulation. Specifically, for example, 3
The thickness is selected to be about 000 Å. The thickness of the Si film 3 is selected so that it can sufficiently absorb the pulsed laser beam 12. The absorption coefficient of Si for light in the ultraviolet region is approximately 106 cm
-1, so if the thickness of the Si film 3 is about 100 Å or more, it becomes a light absorption mask for the pulsed laser beam 12. Specifically, the thickness of this Si film 3 is, for example, 200 mm.
Selected around Å.

Next, a resist pattern (not shown) having openings corresponding to the regions to be laser annealed is formed on the Si film 3 by lithography, and then the Si film 3 and the SiO2 film 2 are formed using this resist pattern as a mask.
are sequentially etched using, for example, reactive ion etching (RIE). After this, the resist pattern is removed. As a result, as shown in FIG. 1B, Si
A mask 4 consisting of an O2 film 2 and a Si film 3 formed thereon is formed.

Next, as shown in FIG. 1C, using the laser annealing apparatus shown in FIG. 2, the Si substrate 1 is irradiated with a pulsed laser beam 12 whose energy density is uniformly controlled. As a result, the S of the part not covered by the mask 4 is
The i-substrate 1 is laser annealed. On the other hand, in the part of the Si substrate 1 covered by the mask 4, the pulsed laser beam 12
is completely absorbed by the Si film 3 of the mask 4, and the pulsed laser beam 1 is completely absorbed by the SiO2 film 2 of the mask 4.
The conduction of the heat generated by the irradiation 2 to the underlying Si substrate 1 is completely suppressed.

The energy density of the pulsed laser beam 12 is:
If the Si substrate 1 is a substrate on which a polycrystalline Si film or an amorphous Si film is formed, for example, about 200 mJ/c.
m2, and if the Si substrate 1 is a single-crystal Si substrate, it is, for example, about 800 mJ/cm2. When the Si substrate 1 is a single-crystal Si substrate, this is the case, for example, when bonding is annealed.

[0016] Note that the S of the part to be laser annealed is
The iO2 film 2 is not completely removed by etching, but the SiO2 film 2 is etched by about 50% as shown by the dashed line in FIG. 1C.
If only a film thickness of 0 Å is left, this SiO2
The film 2 has a wavelength of 308 by the XeCl excimer laser 11.
Since it serves as an antireflection film for the nanometer pulsed laser beam 12, it has the advantage of improving the efficiency of laser annealing. After laser annealing the Si substrate 1 as described above, the mask 4 is removed by etching.

As described above, according to this embodiment, a mask 4 consisting of an SiO2 film 2 as a thermal insulating film and a Si film 3 as a light absorbing film is placed on the Si substrate 1 in the area where laser annealing is to be performed. is selectively formed and in this state the pulsed laser beam 12 is irradiated onto the Si substrate 1, so that only the portion of the Si substrate 1 not covered by the mask 4 can be selectively laser annealed. . Furthermore, the region of the Si substrate 1 to be laser annealed by this pulsed laser beam 12 can be defined with high dimensional accuracy close to the accuracy of lithography.

Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the technical idea of the present invention. . For example, in the above embodiment, the pulsed laser beam 12 generated by the XeCl excimer laser 11 is used as the pulsed laser beam for laser annealing. Of course, it is possible to use pulsed laser light generated by an excimer laser other than the laser, and it is also possible to use pulsed laser light generated by a laser other than the excimer laser. Further, in the above embodiment, the SiO2 film 2 and the Si film 3 are used as the thermal insulation film and the light absorption film, respectively, but other materials may be used as the thermal insulation film and the light absorption film. It is possible.

[0019]

[Effects of the Invention] As described above, according to the present invention,
A mask consisting of a thermal insulation film and a light absorption film is selectively formed on the semiconductor substrate, and the semiconductor substrate is irradiated with pulsed laser light, so that only minute areas of the semiconductor substrate can be selectively laser annealed. Can be done.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining a laser annealing method according to an embodiment of the present invention in order of steps.

FIG. 2 is a schematic diagram showing a laser annealing apparatus used in an embodiment of the present invention.

[Explanation of symbols]

1 Si substrate 2　SiO2　film 3 Si film 4 Mask 11 XeCl excimer laser 12 Pulsed laser light

Claims (1)

[Claims] 1. A method for processing a semiconductor substrate, comprising selectively forming a mask made of a thermal insulating film and a light absorption film on the semiconductor substrate, and irradiating the semiconductor substrate with pulsed laser light.