JPH0251224A - Method for implanting impurity - Google Patents

Abstract

PURPOSE:To largely shorten a processing time as compared with that of selective formation by a laser scanning by irradiating an impurity film with a patterned high energy beam, and implanting impurity into a substrate to be processed. CONSTITUTION:A sample stage 5 is driven in a two-dimensional manner, one chip of a semiconductor wafer 6 is positioned to a reticle mask 3, and a laser beam is oscillated by an excimer laser oscillator 1. The intensity distribution of this beam is made uniform and enlarged by a homogenizer 2, and the beam is incident to the mask 3. The beam patterned by passing it through the mask 3 is contracted to the size to be projected to the one chip through a projecting contraction lens 4 and introduced into the one chip of the wafer 6. Here, a substrate 10 is melted at the irradiated position, and the As of an impurity layer 16 formed on the molten part is injected into the substrate. When the laser beam is extinguished, the Si substrate 10 is recrystallized, and a chip having a junction layer 18 containing the impurity can be formed.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for implanting impurities.

(Prior Art) Conventionally, in a circuit patterning process, which is one of the main fM manufacturing processes for semiconductor integrated circuits, impurities are implanted into a semiconductor substrate such as silicon using an ion implantation device.

In the ion implantation method using this ion implantation device, the impurity to be implanted, that is, the ion particles, is accelerated with a constant acceleration voltage and the ions are implanted into the semiconductor substrate, so the impurity tends to be implanted deeply into the substrate. It was there.

In recent years, semiconductor devices have become more dense and highly integrated, and currently, for example, IMDRAM is the mainstream.
In the near future, 4MDRAM, 16MDRAM, 64MD
It is expected that they will be gradually migrated to RAM. The impurity implant width W and depth D of each DRAM become more strict as the degree of integration increases, and for IMDRAM: W=1.2 μm.

D = 0, 2~0, 3 AZ rn4MDRAM:
W=0.8 μrn.

D=0.2μm 16MDRAM: W=0.5. urr+.

D = 0, 1 to 0, 15, L (approximately m).The method using the ion implantation device described above can produce up to 4M DRAM, but up to 16M DRAM.
The realization of DRAM manufacturing has been questioned, and it has become difficult to manufacture highly integrated semiconductor devices beyond 64M DRAM. Laser doping is attracting attention as a suitable method for forming shallow junctions.

This laser doping method has not yet been put to practical use, but in principle, laser light is irradiated onto the surface of a semiconductor such as silicon to melt it, and this is recrystallized to inject impurities into the semiconductor substrate. Note 1) that it is possible to implant impurities more shallowly than with an ion implanter.

(Problem to be solved by the invention) In realizing the above laser doping,
A method has been announced in academia and the like in which laser light is scanned to selectively irradiate a large number of impurity implantation positions within each chip of a semiconductor wafer, and this is applied to all chips within the wafer.

However, there are usually as many as one million ion implantation locations in one chip, and there are as many as 200 chips in a 6-inch wafer, so if impurity implantation is performed using this scanning method, one semiconductor wafer can be implanted. It took several hours to process and was not suitable for mass production. Furthermore, since a laser beam scanning optical system is also required, there is a problem that the apparatus becomes larger and more complicated.

Therefore, an object of the present invention is to provide an impurity implantation method that solves the above-mentioned conventional problems, performs laser doping in a relatively short time, and has a simple configuration. It's about doing.

[Structure of the Invention (Means for Solving Problems)] The present invention provides the following method: After forming an impurity film on a substrate to be processed (2), the impurity film described in (1) is irradiated with a patterned high-energy beam. The present invention provides an impurity implantation method for implanting the impurity into a substrate to be processed.

(Function) The method of the present invention is characterized in that impurity implantation can be effectively performed in a short period of time by irradiating a patterned high-energy beam.

(Example) Hereinafter, an example in which the method of the present invention is not applied to implanting impurities into each chip of a semiconductor wafer will be specifically described with reference to the drawings.

First, to explain about the impurity implantation device, as a laser light source, for example, the wavelength of 308nn+ ultraviolet KI region is
An excimer laser QNN13 that outputs a high energy beam of j/cl11 is provided. The beam output from this excimer laser oscillator 1 is homogenizer 2
The beam size is adjusted and the beam is shaped to have a uniform intensity distribution. In other words, since the intensity distribution of the excimer laser has a rectangular spread and is distributed in a Gaussian distribution, the homogenizer 2 is generally made of two orthogonal sets of cylindrical lenses for creating parallel beams or a light distribution equalizer. A fly-eye lens is used to shape the beam to the desired size.

The beam that has passed through the homogenizer 2 passes through the reticle mask 3, thereby becoming a patterned beam that passes through only the area corresponding to the impurity implantation area. This reticle mask 3 is constructed by forming a chromium film using an EB lithography method or the like only in the areas where the laser beam does not pass through the 5i02 substrate 7, for example, and covers at least all the areas in one chip of the semiconductor wafer where impurities are to be implanted. (for example, 1 million locations) are formed as a transparent pattern. Note that the pattern of this reticle mask 3 is formed to be enlarged to about five times the size of one chip of a semiconductor wafer.

A reduction projection lens 4 is provided to reduce and project the beam patterned by passing through the reticle mask 3 onto one chip of a semiconductor wafer. A sample aW table 5 such as an X-Y stage that is movable in directions is arranged, and a semiconductor wafer 6, which is a substrate to be processed, is placed and supported on the sample mounting table 5.

Next, an example of the method of the present invention using the above impurity implantation apparatus will be explained with reference to FIG.

FIG. 2(A) shows a cross section of the NMO 8 of the semiconductor wafer before processing. :S
i02 jPJl 2.12 and a polycrystalline 5i14 serving as a gate electrode is formed in the center thereof.

First, as a first step, it is necessary to form a thin film of impurities, and a thin film 16 of As, which is an impurity in the case of NMO3, is formed to a thickness of about 100 mm by, for example, CVD (see Figure 2 (B)). ).

Next, an impurity implantation process using the impurity implantation apparatus described above is performed.

Here, first, one chip of the semiconductor wafer 6 is positioned with respect to the reticle mask 3 by two-dimensional driving of the sample a mounting table 5, and when the positioning is completed, a laser beam is oscillated by an excimer laser oscillation trigger.

Then, the intensity distribution of this beam is made uniform and expanded by the homogenizer 2, and the beam is made incident on the reticle mask 3. The reticle mask 3 has a transmission pattern that is enlarged approximately five times as large as one chip of the semiconductor wafer 6, and allows the laser beam to pass therethrough in correspondence with each impurity implantation position within one chip.

Then, the patterned beam transmitted through this reticle mask 3 is reduced to a size that can be projected onto one chip by a reduction projection lens 4, and is guided to one chip of the semiconductor wafer 6. .

Here, the above laser beam is, for example, 500 nij/
- If it has a laser energy of more than
The irradiated portion of the substrate 10 is melted, and the As of the impurity layer 16 formed on the melted portion is trapped inside the substrate.

Then, as the laser beam is extinguished, the Si substrate 70 is recrystallized, and a chip having a junction M18 containing impurities can be formed as shown in FIG. 2<C>. Incidentally, FIG. 2(C) shows a state in which the impurity layer 16 is subsequently removed.

At this time, the portions of the SXM that are not irradiated with the laser beam do not dissolve As into the interior, and therefore selective formation of impurities can be realized by the beam patterned by the reticle mask 3.

From then on, such an operation will be performed using IIn of the sample mounting table 5.
The bonding layer 18 of As can be formed on the chips over the entire surface of the semiconductor wafer 5 while performing subsequent movement, for example, step-and-repeat driving for each chip.

Here, in the method using such a reticle mask 3, for example, the excimer laser which is a pulse oscillation is
Assuming that 10 pulses of laser irradiation are performed on one chip by oscillating every rns, 1 second is sufficient for the processing time per chip, including positioning time, and 6
In the case of inch wafers, 20
The processing time is approximately 0 seconds. Therefore, the processing time is significantly shortened compared to the conventional laser scanning method, and an improvement in throughput can be ensured when the laser doping method is put into practical use.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible within the scope of the invention.

For example, in the above embodiment, the semiconductor wafer and NMO3
Although the case has been described as an example, the present invention can be similarly applied to various other substrates to be processed that require implantation of impurities.

Furthermore, the beam source that emits a single high-energy beam is not limited to an excimer laser oscillator as long as it can melt the substrate to be processed. It is necessary to form a thin film of impurities, and various film forming methods other than CVD can be used to form the thin film of impurities.

[Effects of the Invention] As explained above, according to the method of the present invention, the patterned high-energy beam is irradiated onto the impurity Ml on the substrate to be processed, so the processing time is 3 times shorter than that in which selective formation is performed by laser scanning. It can be significantly shortened.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram for explaining one embodiment of an impurity implantation apparatus for carrying out the method of the present invention, and FIG. 2 is a schematic explanatory diagram for explaining one embodiment of the method of the present invention. be. DESCRIPTION OF SYMBOLS 1... Laser source, 2... Homogenizer 3... Reticle mask, 4... Reduction projection lens, 5... Sample mounting stage, 6... Substrate to be processed, 16... Impurity layer, 18... Bonding layer.

Claims (1)

[Claims] An impurity implantation method comprising forming an impurity film on a substrate to be processed, and then irradiating the impurity film with a patterned high-energy beam to implant the impurity.