JPH04370925A - Mask for laser annealing, laser annealing method and device - Google Patents

Abstract

PURPOSE:To prevent contamination or the like due to evaporation of a mask material, which is caused by laser irradiation. CONSTITUTION:When a silicon film 21 is subjected to local laser annealing, a mask 19 is used for limiting a laser beam irradiation region. The mask is composed of Si or the same material as the material of the objed to be treated containing Si as its main component, such as SiC and SiO2, whereby the silicon film, which is free from contamination or the like and has good characteristics, can be locally annealed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask for limiting the irradiation area of a laser beam used when locally laser annealing a semiconductor thin film, a laser annealing method using the same, and an apparatus therefor.

0002

[Prior Art] Conventionally, when a semiconductor thin film is irradiated with laser light to modify its crystallinity or dopant activation, a shielding member (mask) having an opening is used to limit the laser beam irradiation area. ) is used. By using this mask, it becomes possible to modify only a limited area of the substrate. Furthermore, even when modifying the entire surface of a substrate, when the size of the laser beam is smaller than the substrate, it is possible to prevent overlapping of laser irradiation areas and improve uniformity within the substrate. The pattern of the opening is processed to match the desired laser irradiation area, so that only a limited area is irradiated with the laser beam. The mask is made of highly reflective aluminum plate. A conventional example of this type is JP-A-1-260812.

0003

[Problems to be Solved by the Invention] When a mask such as an aluminum plate is inserted to limit the laser irradiation area as in the above-mentioned prior art, the high energy required for crystallization (100 mJ/cm2 in general analysis) When irradiated with a laser beam of 100% or less, the mask deteriorates and aluminum etc. evaporates and scatters during laser irradiation. The scattered aluminum and the like adhere to the irradiated sample, causing a contamination effect and degrading the characteristics of the polycrystalline semiconductor film. Furthermore, since the mask is repeatedly irradiated with a high-energy laser beam, the mask becomes hot and deforms. Due to the deformation of the mask, the accuracy of region definition during laser annealing also decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser annealing mask, a laser annealing method, and an apparatus therefor, which eliminate the above-mentioned problems and locally form a semiconductor film with good characteristics.

[0005]

Means for Solving the Problems In order to achieve the above object, a mask that limits the laser irradiation area is formed of the same composition as the sample to be irradiated. That is, the present invention provides a laser annealing mask that has an opening that limits a laser irradiation area and that locally modifies the surface layer of the substrate by irradiating a laser beam onto a limited area of the substrate through the opening. ,
The material of the mask is characterized in that it is made of the same component as the surface layer of the substrate to be irradiated.

[0006] The present invention also provides laser annealing, which has an opening that limits the laser irradiation area and locally modifies the surface layer of the substrate by irradiating the limited area of the substrate with laser light through the opening. The material of the mask is characterized in that its surface layer is made of the same composition as the surface layer of the substrate to be irradiated.

Further, the present invention has an opening that limits the laser irradiation area, and the surface layer of the silicon film is locally modified by irradiating the limited area of the silicon film with laser light through the opening. The mask for laser annealing is characterized in that the mask is made of a material whose main component is silicon. Here, the material of the mask is preferably silicon, silicon carbide (SiC), silicon oxide, or silicon nitride. Or, the surface layer of the mask material is silicon, silicon carbide (S).
iC), silicon oxide or silicon nitride.

Further, the present invention has an opening that limits the laser irradiation area, and the surface layer of the silicon film is locally modified by irradiating the limited area of the silicon film with laser light through the opening. In laser annealing masks,
The material of the mask is characterized in that it is made of a silicon base material containing boron nitride (BN) when the silicon film is p-type, and phosphorus nitride (PN) when it is n-type.

Further, the present invention has an opening that limits a laser irradiation area, and a limited area of the silicon film is irradiated with laser light through the opening to locally modify the surface layer of the silicon film. In laser annealing masks,
The surface layer of the material of the mask is boron nitride (BN) when the silicon film is p-type, and phosphorous nitride (PN) when the silicon film is n-type.
It is characterized by being made of a silicon-based material containing as a component.

Further, the present invention includes a laser irradiation means and an opening provided in the laser optical path to limit the laser irradiation area, and irradiates the limited area of the substrate with laser light through the opening to illuminate the surface of the substrate. A laser annealing apparatus comprising a laser annealing mask for locally modifying a layer and a chamber for holding the substrate, characterized in that the laser annealing mask is one of the above-mentioned ones. It is. Here, the mask for laser annealing is preferably formed to also serve as a light entrance window of the chamber.

[0011] Furthermore, the present invention limits the laser irradiation area using a laser annealing mask having an opening provided in the laser beam path, and irradiates the limited area of the substrate with the laser beam, thereby locally damaging the surface layer of the substrate. This laser annealing method is characterized in that one of the following laser annealing masks is used as a laser annealing mask.

0012

[Action] Surface modification such as crystallization or ion implantation
The mask deteriorates due to irradiation with the high-energy laser beam necessary for punt activation, and the material of the mask evaporates and scatters during laser irradiation. This scattered material adheres to the sample, causing contamination to the sample. but,
According to the present invention, even if the mask material evaporates due to laser irradiation, its components are almost the same as those of the sample, so there is no influence of contamination, etc., and local laser annealing with even better characteristics is possible.

Furthermore, if a heat-resistant material is used as the mask material and the surface is coated with the material, deformation of the mask due to the influence of heat can be prevented and laser annealing can be performed with high precision. .

Furthermore, by using a laser annealing apparatus equipped with the mask of the present invention, localized laser annealing with excellent throughput can be realized with high precision without the influence of contamination.

[0015]

[Examples] Examples of the present invention will be described below. In the present invention, when laser annealing an amorphous silicon (hereinafter referred to as a-Si) film, the mask is made of a material whose main component is Si, or the surface is It is coated with a material whose main component is Si. Typical examples include using a mask made of Si or SiC, or using a traditionally used metal such as an aluminum plate as a core material and coating the surface with Si, SiC, SiO2, or silicon nitride. There is a way to do that. The coating is
CVD (Chemical Vapor Deposit)
This can be achieved by depositing a Si film or the like using the ion method.

The present invention will be explained below with reference to the drawings. Figure 1
1 is a schematic diagram of a laser annealing apparatus showing an embodiment of the present invention. The laser is a XeCl excimer laser (λ=30
8 nm, pulse oscillation, pulse width 28 ns) 10 was used. Furthermore, in order to make the laser beam intensity uniform within the beam, a beam homogenizing mechanism 12 is introduced in the optical system after the reflecting mirror 11, thereby realizing annealing with excellent uniformity. The sample 15 was placed in a chamber 14 with a light entrance window 13 made of quartz.
It is set on a Y movable stage 16 and laser annealed while scanning in the X and Y directions. The chamber 14 is equipped with an evacuation system 17 and a gas introduction mechanism 18, and can perform laser annealing in a vacuum or in an inert gas such as Ar or He. Further, by providing a heating mechanism on the stage 16, it is possible to perform laser annealing while heating the substrate. As shown in FIG. 2 as sample 15, an a-Si film 2 formed on a glass substrate 20
In order to perform local laser annealing on the films 21b and 21c of the films 1a, 21b and 21c, a mask 19 made of a Si wafer, which is one means of the present invention shown in FIG. 3, is inserted. Openings 22 are provided in portions corresponding to the membranes 21b and 21c. 200-300mJ/cm2 required for crystallization
Although the material of the Si mask 19 is evaporated and scattered by irradiation with a XeCl excimer laser with a high energy level, the use of a Si wafer in this way does not affect the sample by contamination or the like. Further, since a mask with a desired pattern can be easily formed, laser annealing of a fine pattern is also possible.

[0017] Here, the laser used for laser annealing was an XeCl excimer laser, but the above means can also be applied to crystallization processes using different lasers such as other pulsed lasers, CW (continuous wave), and Ar ion lasers. By doing so, local laser annealing can be performed well. Moreover, in the case of a gas atmosphere that does not require sealing of the chamber 14, instead of the light entrance window 13,
A mask 19 having minute openings can be used.

Next, a method for manufacturing the above mask will be explained in detail. (1) High-purity silicon single crystal was used as the material. Its quality is 200 μm thick, 25 mm in diameter, (100) crystal orientation, and mirror polished. An opening with a size of 8 mm square was provided in the center. The formation of the opening is
A silicon single crystal is oxidized to a thickness of 1.6 μm on both main surfaces.
A SiO2 film was formed, the SiO2 film was opened by photolithography, and the remaining SiO2 film was used as a mask for anisotropic etching with a KOH water-isopropyl alcohol mixed solution. As a result, a highly accurate opening can be obtained. Furthermore, since the surface is mirror-polished, it has a high light reflectance and is effective in preventing deterioration. Moreover, a polycrystalline silicon wafer can also be used as the material.

(2) A sintered wafer containing SiC as a main component was used as the material. Thickness approximately 100μm, diameter size 1
It is an 8mm polycrystalline wafer with a mirror polished finish. The opening was formed by a sandplast method using 600 mesh diamond powder. In addition, BN wafers and PN wafers for silicon semiconductor processing can also be masked in the same manner.

(3) As the material, an electrolytically polished mirror-finished aluminum plate with high light reflectance is used, and after forming an opening by etching, a silicon nitride film and polycrystalline S are formed on the surface.
i-film was coated. Coating was performed by RF plasma CVD method, with a substrate temperature of 350 to 380°C, and silicon nitride was first deposited using SiH4 and NH3 as raw material gases, and then a Si film was successively deposited using only SiH4. . After that, in order to improve the adhesion of the deposited film,
Heat treatment was performed at 00°C for 30 minutes in air. The deposited film thickness is 2000 to 2500 Å for the silicon nitride film and 300 Å for the Si film.
It is 0 to 5000 Å. The silicon nitride film is a barrier for preventing reaction between aluminum and the Si film during laser irradiation. As the barrier film, an alumina film formed by plasma anodization of aluminum or the like can also be used. As the surface coating material, SiO2 or the like can be used in addition to the Si film.

(4) A high purity quartz plate was used as the material. It has a thickness of 1.1 mm and a diameter of 25 mm. After coating the surface with a polycrystalline Si film to a thickness of 6000 Å by low pressure CVD using SiH4 gas as a raw material, openings were formed by patterning the Si film and quartz plate by photolithography. Note that even if only the Si film is patterned by photolithography, it can be used as a mask; however, ■ the focus of the laser beam may shift due to the quartz plate; Since cloudiness occurs on the surface of the quartz plate due to evaporation and scattering of the Si film, it can be used more stably if the quartz plate is also etched.

[0022]

According to the present invention, it is possible to limit the crystallized region during laser annealing without affecting the sample by contamination, and it is possible to locally form a polycrystalline semiconductor film with good characteristics. Furthermore, the durability and reliability of the mask are also improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a laser annealing apparatus according to the present invention.

FIG. 2 is a perspective view of a substrate being laser annealed.

FIG. 3 is a perspective view of a laser annealing mask.

[Explanation of symbols]

10 Laser 14 Chamber 15 Sample (substrate) 19 Si mask 21 a-Si film 22 Opening

Claims (10)

[Claims] 1. A laser annealing mask that has an opening that limits a laser irradiation area and locally modifies a surface layer of the substrate by irradiating a laser beam onto a limited area of the substrate through the opening. A mask for laser annealing, characterized in that the material of the mask is made of the same composition as the surface layer of the substrate to be irradiated. 2. A laser annealing mask that has an opening that limits a laser irradiation area and locally modifies the surface layer of the substrate by irradiating a laser beam onto a limited area of the substrate through the opening. A mask for laser annealing, characterized in that the surface layer of the mask is made of the same composition as the surface layer of the substrate to be irradiated. 3. For laser annealing, which has an opening that limits the laser irradiation area and locally modifies the surface layer of the silicon film by irradiating the limited area of the silicon film with laser light through the opening. 1. A mask for laser annealing, characterized in that the mask is made of a material whose main component is silicon. 4. The laser annealing mask according to claim 3, wherein the material of the mask is silicon, silicon carbide (SiC), silicon oxide, or silicon nitride. 5. The laser annealing mask according to claim 3, wherein the surface layer of the mask material is made of silicon, silicon carbide (SiC), silicon oxide, or silicon nitride. 6. For laser annealing, which has an opening that limits a laser irradiation area and locally modifies the surface layer of the silicon film by irradiating a laser beam onto a limited area of the silicon film through the opening. In the mask, the material of the mask is boron nitride (BN) when the silicon film is p-type.
), a mask for laser annealing characterized by being made of a silicon base material containing phosphorus nitride (PN) as a component in the case of n-type. 7. For laser annealing, which has an opening that limits a laser irradiation area and locally modifies the surface layer of the silicon film by irradiating a laser beam onto a limited area of the silicon film through the opening. In the mask, the surface layer of the material of the mask is made of a silicon base material containing boron nitride (BN) when the silicon film is p-type, and phosphorus nitride (PN) when the silicon film is n-type. Mask for laser annealing. 8. Laser irradiation means, and an opening provided in the laser optical path to limit the laser irradiation area, the laser beam being irradiated to a limited area of the substrate through the opening to locally damage the surface layer of the substrate. A laser annealing apparatus comprising a laser annealing mask for selectively modifying the substrate, and a chamber for holding the substrate, wherein the laser annealing mask is the one according to any one of claims 1 to 7. Laser annealing equipment. 9. The laser annealing apparatus according to claim 8, wherein the laser annealing mask is formed to also serve as a light entrance window of the chamber. 10. The surface layer of the substrate is locally modified by limiting the laser irradiation area using a laser annealing mask having an opening provided in the laser beam path and irradiating the limited area of the substrate with the laser beam. 8. A laser annealing method characterized in that a mask for laser annealing according to any one of claims 1 to 7 is used as a laser annealing mask.