JPH0672305B2 - Laser injection deposition method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for modifying a solid surface, and in particular, a solid surface is doped with impurities using a laser to reduce damage.
The present invention relates to a laser injection deposition method, which comprises forming a high-concentration treatment layer and modifying the surface to have a functional surface.

(Prior art and its problems) On solid surfaces, especially metal surfaces, rust prevention, high hardness,
Various surface modification methods have been tried in order to obtain a functional surface having a high friction coefficient and wear resistance. Among the surface modification methods, an ion implantation method is known as a general method, and as a conventional method close to the present invention, laser light is used to alloy a solid surface with a different metal. The meat,
Methods for forming a thin film and making it amorphous have been developed.

The outline and problems of the ion implantation method and the surface modification method using laser light will be described below.

The ion implantation method is a method of ionizing impurities and accelerating with an energy of about 10 to 100 KeV to dope into a solid. Usually, when the metal surface is modified, it is preferable to add it at a higher concentration. However, since ion implantation is forced to implant ions, the higher the concentration, the greater the damage to the substrate. These damages are believed to have a profound effect on the properties of the functional surface. In addition, since the implanted impurities do not bond with the substrate atoms and exist at interstitial positions only by performing ion implantation, the bonding strength is weak. Therefore, in order to recover the damage caused by the implantation and put the implanted impurities in the lattice positions, heat treatment at a high temperature is required. However, there are problems that the entire substrate is affected by heat by this thermal process and that the impurities that are injected with high precision control are redistributed by this thermal process. Further, in order to obtain the highest concentration of impurities added to the extreme surface of the substrate, ion implantation has a problem that the maximum concentration cannot be added to the extreme surface because the implantation profile has a Gaussian distribution. In addition, the ion implantation method has a drawback that it requires a large-scale device, and the work is troublesome.

The alloying method is called alloying, and is a method in which a dissimilar metal is applied or deposited on the surface of a material and irradiated with laser light to be melted to form an amorphous layer. This method first requires the work of coating the surface of the material with a dissimilar metal.

As a method similar to the alloying, there is a cladding in which a dissimilar metal is built up on the substrate surface. Cladding supplies different materials thicker than alloying,
It is a method of melt-coating the feed substance itself. This technique
In addition to having the same problems as alloying, there are problems with adhesion and bonding strength with the base material.

The laser PVD and CVD methods are methods of physically or chemically depositing a thin film on the material surface using a laser, but in this case also, the adhesion and bonding strength with the base material are problems.

The glazing for surface amorphization is to irradiate the surface of a material with a laser beam to melt and amorphize the surface of the material as it is, and to harden the surface by a microstructural change. However, since the constituent substances in the material do not change, it is effective as a surface hardening method for a specific substance, but a dramatic improvement in other properties cannot be expected.

As described above, the conventional surface modification method has advantages and disadvantages,
It has been difficult to obtain an excellent surface structure material having wear resistance, corrosion resistance, heat resistance and the like that can be used under severe conditions.

The present invention uses laser light on the surface of various solid materials,
The purpose is to create a functional surface that is excellent in various properties by doping impurities.

(Means for Solving the Problems) In the present invention, the material substrate surface in a reaction gas atmosphere is irradiated with laser light, the substrate surface is made to have a melting point of the material or higher, and atoms in the reaction gas are injected into the substrate surface. At the same time, it can be achieved by a laser injection deposition method of forming a thin film of the atoms in the reaction gas on the substrate surface.

(Function) Since the excimer laser light has a short wavelength and a short pulse, it is possible to heat and melt an extremely shallow region near the surface when the solid surface is irradiated. FIG. 3A and FIG. 3B are schematic diagrams showing a pattern in which a laser beam is irradiated in an impurity gas atmosphere and the impurity gas is decomposed to be injected and a thin film is formed on the substrate surface. In FIG. 3A, gas molecules 32 are adsorbed on the surface of the substrate 31 in the impurity gas atmosphere. When the gas adsorption surface is irradiated with laser light, the laser light 33 decomposes the adsorbed impurity gas molecules as shown in FIG. 3B, and the decomposed impurity atoms 34 are melted on the substrate surface by laser light irradiation. Can be injected into. The impurity atoms injected into the melting region diffuse in the liquid layer at the melting portion. Further, by selecting the irradiation conditions such as the pulse number, it is possible to coat the material surface with a thin film of the same kind as the implanted atoms at the same time as the implantation is performed. Further, by utilizing the fact that the laser light is excellent in straightness, it is possible to locally heat and inject impurities and form a thin film in a pattern. FIG. 3C is a schematic diagram in which the boundary between the implantation-treated layer 36 on the substrate surface and the bare metal layer 37 of the substrate is expressed at the atomic level. In the lower part of the figure, in the base metal layer, only the atoms of the substrate are arranged in an orderly manner.On the other hand, in the layer in which impurities are implanted, the impurity atoms are taken in and aligned between the substrate atoms, and the atoms are also continuous at this interface. It is considered that they are physically connected. Further, since the thin film layer 38 formed as the uppermost layer is formed only of the impurity atoms and is continuously bonded to the lower doping layer, it is considered that the adhesive force of the film is strong.

(Effect of the invention) According to the present invention, since a gas is used as a raw material of impurity atoms to be injected, the degree of freedom in selecting an additive element is high, and
Since the impurity injection layer to be formed is to melt and melt only a small number of surface layers to add atoms in the reaction gas,
There is no thermal effect inside the substrate. The present invention is
Compared with the conventional technique such as ion implantation, the processed surface layer is formed by two layers, that is, an implantation layer of impurity atoms and a layer of impurities, formed on the substrate atomic layer, and these layers are formed after the layers are once melted. As a result, a very tightly bonded layer is formed. Therefore, the functional surface with abrasion-resistant, corrosion-resistant, and strengthening film produced by the present method can be used under severe conditions. Furthermore, this method can achieve a desired surface only by irradiating a laser beam while spraying a raw material gas onto the sample, which requires few control conditions, is simple in equipment, is easy to operate, is easy to carry out and move, etc. There is an advantage, and the economic ripple effect is large.

(Example) Below, the Example of this invention is described in detail.

A KrF excimer laser device (wavelength:
248 nm, pulse width: 23 ns), and 10% SiH ₄ gas diluted with He as a dopant source, metallic material (SUS304)
The sample surface of which was mirror-polished was irradiated. The irradiation conditions were such that the gas pressure was constant at 100 Torr, the laser fluence was changed at 450 mJ / cm ² , and the pulse number was changed within the range of 5 to 100 pulses.

FIG. 1 shows the laser pulse implantation conditions of 30, 5
It is a graph which measured the distribution in the depth direction of Si in a sample when changing it with 0, 100 pulses by the secondary ion mass spectrometer (SIMS). Raising the number of pulses from 30 to 50
The Si concentration increases, but since the Si thin film is deposited almost uniformly on the surface of the material after 50 pulses, the Si concentration does not change even if the number of pulses increases up to about 10 nm on the surface.
In addition, as the number of pulses of doped Si increases,
It can be seen that the distribution is deeper. For example, laser fluence 450 mJ / cm ² , 100 pulses, SiH ₄ gas pressure 100 Torr
In the case of performing the treatment in step 1, the Si doping depth is 220 nm, and the thickness of the deposited Si thin film is several tens nm. The thickness of this Si thin film increases as the number of pulses increases.

FIG. 2 is a graph showing the results of measuring the change in surface hardness when the number of pulses is changed. For the measuring device, an ultrafine indenter (~ 10 μm) in the shape of an equilateral triangular pyramid is used to measure the sample depending on the depth of penetration of the indenter when a load is applied to the sample to reduce The surface hardness was measured using an ultra-micro hardness meter. In the figure,
The vertical axis represents the penetration depth of the indenter into the sample when the indenter was pressed down with the indenter load of 500 mg for the sample in which the present invention was carried out under the above conditions. That is, the shallower the penetration depth means that the surface is harder, and it can be seen from the figure that the penetration depth of the indenter becomes shallower as the number of pulses increases, and thus the surface is hardened. The surface hardening with the increase in the number of pulses is that the thin film of the Si element deposited on the surface is thick,
This is due to the high concentration and deep distribution of the implanted Si element.

[Brief description of drawings]

Figure 1 shows the laser pulse implantation conditions of 30, 50,
S on each sample surface of the present invention when changed with 100 pulses
The graph which measured the depth direction distribution of the i element, FIG. 2 is the graph which shows the result of having measured the change of the surface hardness when changing the pulse number by this invention, FIG. 3A, FIG. Fig. 3C is a schematic diagram showing how the gas is decomposed by irradiating laser light in the gas to inject and form a thin film on the substrate surface. Fig. 3C shows the boundary between the injection-treated layer and the bare metal layer of the substrate. Schematic representation of the atomic level. (Explanation of symbols) 31 ... Substrate, 32 ... Gas molecule, 33 ... Laser light, 34 ... Decomposed impurity atom, 35 ... Melting region, 36 ... Injection treatment layer, 37 ... Base metal layer, 38 ... Thin film layer.

Claims (1)

[Claims] 1. A material substrate surface in a reaction gas atmosphere is irradiated with laser light to bring the substrate surface to a temperature equal to or higher than the melting point of the material, atoms in the reaction gas are injected into the substrate surface, and the reaction gas is formed on the substrate surface. A laser injection deposition method for forming a thin film of said atoms therein.