JPH10214785A - Thin semiconductor and deposition thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a crystal structure in good order while activating the electric carrier by depositing a thin semiconductor physically or chemically, introducing impurity elements into the thin semiconductor and irradiating the thin semiconductor with a laser light having a wavelength resonance absorption to the lattice vibration of the compositional elements and the impurity elements thereby reforming the thin semiconductor. SOLUTION: A than semiconductor is deposited physically or chemically. More specifically, a thin crystal of 3C-SiC is deposited on a substrate 17 by laser CVD and implanted with N ions. The thin semiconductor is then irradiated with a free electron laser 10 and reformed. The tree electron laser 10 is irradiated at an interval of 100ms in the form of a 20μs wide macropulse light comprising micropulses of less than 10ps having pulse width of less than 10ps and power density of less than 180MW/cm<2> . The irradiation region is 2mm square and since macropulse 3000 shots (5min) are irradiated, an area of 0.942cm<-2> is irradiated when 3000 shots scanning us performed at a beam diameter of 200μmϕ.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor thin film in which a semiconductor material is irradiated with a laser beam to order its crystal structure and activate electric carriers, and a method for forming the same.

[0002]

2. Description of the Related Art When a semiconductor material is formed as a thin film by physical or chemical means, and when an electronic device is formed from this semiconductor thin film, the disordered crystal structure of the semiconductor thin film is ordered and recrystallized, or As one of the processing methods for activating the carrier, a method of performing a high-temperature heat treatment using an electric furnace or the like is known. In this method, a semiconductor material such as silicon carbide needs to be at a high temperature of 1300 ° C. or more, and the heat treatment at such a high temperature causes a narrow selection range of the electrode material, and the order of the steps cannot be optimally selected. There are various restrictions.

[0003] On the other hand, since an attempt to crystallize an ion-implanted amorphous layer by laser irradiation has been proposed as a laser annealing method, it is possible to heat the surface layer only at an arbitrary position in a short time. Attention has been paid to a point different from heating by a conventional electric furnace, for example, the amount of impurities dissolved in a recrystallization region can be increased.

In such a background, Japanese Patent Application Laid-Open No. 7-2231 has been proposed as one of application examples of the laser annealing method in order to obtain the same heat treatment effect at low temperature and locally.
A method for producing a semiconductor material according to Japanese Patent Application Publication No. 1 (JP-A) No. 1 is known.

In this method, a semiconductor thin film having good reproducibility and high carrier mobility is irradiated by irradiating a laser beam of a predetermined intensity in a state where the concentrations of carbon, nitrogen and oxygen in an amorphous semiconductor are reduced to a certain level or less. It is proposed to make.

In the above-described principle of laser annealing, the material is once melted, so that the reproducibility of the electrical characteristics of the semiconductor material is poor. Therefore, in the laser annealing according to the above-mentioned patent publication, the concentrations of carbon, nitrogen and oxygen are kept below a certain level. Irradiation of the amorphous semiconductor with the laser beam causes the material to be ordered without melting the material.

In this case, the surface of the material is not melted by the irradiation of the laser beam, and the amorphous region is mixed (semi-amorphous) in the solid-phase ordered region solid-phase grown by the energy of the absorbed laser beam. It is said that high mobility can be obtained under the condition that the concentrations of carbon, nitrogen and oxygen are low.

[0008]

By the way, it is described that the laser annealing method according to the above-mentioned patent application can be applied to various semiconductor materials. However, it is necessary that the semiconductor material be amorphous. It is not applicable to various semiconductor materials and is not a fundamental solution.

The oscillation conditions of laser light for semiconductor materials are not clear, and the absorption length of laser light for the material depends on the wavelength. Therefore, an excimer laser that is an ultraviolet laser, a YAG laser for visible light, or an infrared laser. The best laser for that material must be selected from the infrared lasers in the country.

Further, in the laser annealing method according to the above-mentioned patent publication, the semiconductor material modified by laser irradiation is semi-amorphous, so that the solid-phase ordered region and the amorphous region coexist. The crystal structure is not homogeneously ordered over the entire region, and there is room for further improvement in mobility in a crystal structure containing an impurity element.

In view of the various problems in the conventional laser annealing method as described above, the present invention modifies a semiconductor thin film formed by a physical or chemical method without melting the thin film by irradiating a laser beam. It is an object of the present invention to provide a film forming method capable of improving the order of the crystal structure and activating the electric carrier, and obtaining a semiconductor thin film by the method.

[0012]

According to the present invention, as a means for solving the above problems, a semiconductor thin film is formed by a physical or chemical method, an impurity element is introduced into the thin film, and the lattice vibration of the constituent elements is introduced into the thin film. Irradiating a laser beam with a wavelength that can be resonantly absorbed to the crystallographic structure, and irradiating a laser beam with a wavelength that is resonantly absorbed by the lattice vibration of the impurity element to excite localized vibrations and activate the electric carriers. Thus, a method of forming a semiconductor thin film made of

According to the above method, a laser beam having a wavelength that resonates and absorbs the crystal structure of a constituent element of a thin film obtained by introducing an impurity element into a semiconductor thin film formed by a physical or chemical method. Irradiate and order,
In addition, a semiconductor thin film formed by irradiating a laser beam having a wavelength that is resonantly absorbed by lattice vibration of an impurity element and activating an electric carrier by localized vibration is obtained.

In the method of forming a semiconductor thin film, the method of forming a semiconductor thin film by a physical or chemical method is as follows.
For example, it is a known method such as a physical method by a sputtering method or the like or a chemical method by a laser CVD or the like, and any of them may be used.

Further, in the above-mentioned film forming method, instead of melting the entire material by high-temperature heat treatment using an electric furnace or the like and reconstructing atoms disturbed through a thermal equilibrium state, or disposing atoms at desired lattice positions, By irradiating a laser beam that resonates and absorbs the lattice vibration of the constituent elements, the lattice vibration is directly excited without melting the material, the crystal structure is ordered, and the thin film material is modified. Thereby, the reproducibility of the electrical characteristics of the thin film material is improved.

On the other hand, if the impurity element introduced into the semiconductor thin film stays at a position shifted from the position of the original constituent element, the dopant becomes inactive and the electrical characteristics are not improved.
In order to solve this problem, in this manufacturing method, the electric carrier is activated by irradiating a laser beam having a wavelength that is resonantly absorbed by the lattice vibration of the impurity element different from the lattice vibration of the constituent element. In this case, laser light having a wavelength corresponding to the lattice vibration of any of the constituent element and the impurity element may be irradiated first, and the order does not matter.

When a semiconductor thin film is formed by irradiating a laser beam as described above, the crystal structure can be modified and the electric carrier can be activated for the following reasons. FIG.
Figure 2 shows a model of the atomic structure of a semiconductor material. Reference numerals 1 and 2 in the drawing denote constituent elements and reference numeral 3 denotes an atom in a material at a position slightly shifted from its lattice position. For example, when the material is SiC (silicon carbide), one of constituent elements 1 and 2 is Si or C.

(1) In the above-mentioned SiC material, if atom 3 is a constituent element, it is either Si or C. At this time, the lattice vibration mode between adjacent atoms is a vibration mode peculiar to Si—C, Laser light (1
2.6 μm, 10.3 μm),
The disturbed element at a position deviated from the original lattice position is shaken and enters the original lattice position. As a result, the crystal is reconstructed and ordered, and recrystallization is realized.

(2) On the other hand, if the third atom is an impurity atom that supplies an electric carrier, the atom 3 is, for example, N,
Al, B, etc. come. At this time, the lattice vibration mode between adjacent atoms is a vibration mode peculiar to Si—N in the case of N, and a laser beam (10.4 μm) having a wavelength corresponding to this vibration.
m), the disturbed atoms at positions deviated from the original lattice position are shaken to enter the original lattice position, and as a result, the crystal is reconstructed and the activity of the electric carrier is reduced. It is planned.

The laser beam used in the above method is a laser beam having a wavelength corresponding to the lattice vibration, and must be a laser beam having a wavelength unique to each semiconductor thin film material. In such a situation, the free electron laser is the optimal light source in that there is no restriction on the oscillation wavelength, but if the above-mentioned unique wavelength is specified in advance by the free electron laser, the As the laser light, another type of laser having a specific oscillation wavelength such as a semiconductor laser may be used.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an apparatus for forming a semiconductor thin film. In this embodiment, a basic semiconductor thin film is formed on a Si substrate by a general thin film manufacturing method, and details thereof are well known, so that illustration and description are omitted.

Reference numeral 10 denotes a free electron laser, and 11 denotes a free electron laser beam generated by the laser. The free electron laser beam is bent by a reflection mirror 12, condensed by a ZnSe lens 13 as convergent light 14, and then scanned by a galvanometer mirror 15 for scanning. The light is reflected and irradiated on the semiconductor thin film 16 as the irradiation sample over the range of the modified portion 16a. Reference numeral 17 denotes an insulating substrate made of Si, and reference numeral 18 denotes a stage plate.

Although the details of the free electron laser 10 are not shown, the electron beam generated by the electron gun is accelerated to near the speed of light by an accelerator and passed through a periodic magnetic field generating means such as a wiggler magnet, so that mutual interaction with the magnetic field is achieved. In this system, laser light having a predetermined wavelength is generated by repeatedly amplifying light induced by the action between reflection mirrors. By adjusting the magnetic field strength, magnet pitch, electron beam energy, etc., from the infrared region, ultraviolet rays, X
This is a laser generator of the type that can change the wavelength freely to the line region.

The galvanometer mirror 15 is of a type in which the reflection mirror is freely rotated at an arbitrary angle, and other members need not be described. It should be noted that the apparatus of this embodiment aims at modifying a semiconductor thin film formed on the substrate 17 on the stage plate 18 in advance, and shows only a configuration directly related thereto. The production of the semiconductor thin film itself is performed by physical means such as a sputtering method or chemical means such as a laser CVD method, and these are well known and will not be described in detail.

The laser beam obtained by the actual free electron laser 10 has a beam diameter of about 50 mmφ and a ZnSe lens 1.
Reference numeral 3 denotes a focal length of 10 inches, an aperture is inserted immediately before the lens, and the diameter of the laser beam irradiated on the sample by the galvanometer mirror 15 is approximately 600 μmφ.

The semiconductor thin film was modified by the above-described apparatus as follows. A crystalline 3C-SiC thin film is previously formed on the substrate 17 (Si) by a laser CVD method,
N was ion-implanted into this. In addition, the ion implantation apparatus is also a publicly known apparatus, and the details are omitted. The N-ion-implanted thin film was irradiated with the free electron laser 10 to modify the semiconductor thin film. The irradiation conditions of the free electron laser 10 at that time were as follows.

That is, the pulse width is 10 ps, the power density of the micro pulse is 180 MW / cm ² , and the details of this laser beam are shown in FIG. 2. 10
Irradiation is performed at intervals of 0 ms. The irradiation area is 2 mm square and 3,000 shots (5
Minutes), 3,000 shots scanning with a beam diameter of 200 μmφ results in an irradiation of 0.942 cm ^{−2 in} area, and simply irradiates the irradiation area uniformly.

Laser light was irradiated under the above irradiation conditions, and the crystal structure of the thin film was first ordered to improve the reproducibility of the electrical characteristics. Fourier transform infrared absorption measurement (FT-IR)
, The change in the absorbance was measured as an IR absorption spectrum. The result is shown in FIG. In the figure, for comparison, a sample thin film (●) not irradiated with the modifying laser light, an N ion implanted thin film (▲) injected with N ions and not irradiated with the modifying laser light, The modified thin film (○) irradiated with a 12.6 μm laser beam is also shown.

In the figure, as a result of changing the wavelength from 9 to 14 μm, peaks are observed at 12.6 μm and 10.3 μm, respectively, which show absorptions corresponding to TO phonon and LO phonon of SiC. It can be seen from FIG. 5 that the peak at 12.6 μm became wider after ion implantation. This is because a damaged layer is formed by ion implantation,
It is presumed that the peak spread. When the free electron laser beam was irradiated at a wavelength of 12.6 μm, the broadening of the peak was reduced again at this wavelength, indicating that the crystallinity of the damaged layer was greatly restored at this wavelength.

On the other hand, for comparison, FIG. 4 shows the results when the modified wavelength was irradiated at 10.3 μm, which is another peak. This example also shows the absorption spectra of the sample thin film (●), the N ion-implanted thin film (▲), and the modified thin film (）) at a wavelength of 10.3 μm. As can be seen from the figure, in this example, there is no change in the spread of the wavelength peak at a wavelength of 12.6 μm, and the crystallinity of the damaged layer is remarkable while the damaged layer caused by N ion implantation remains. It is considered that he has not recovered.

As described above, this SiC thin film material has an Si-Si thin film at a specific wavelength at which the absorption characteristic of the irradiated laser beam becomes a peak.
It was shown that local crystallization could be performed at room temperature in response to strong resonance absorption due to C stretching vibration.

Next, in order to see the activation of the electric carrier by the impurities injected into the thin film material, the wavelength dependence of the electric characteristics was examined by changing the irradiation wavelength of the free electron laser to 13 to 10 μm. . The Hall effect of the sample after the irradiation with the laser light was measured, and the relationship between the carrier concentration and the wavelength dependence of the hole mobility with respect to the irradiation light wavelength obtained by the measurement is shown in FIG. In the figure, Δ indicates a change in carrier concentration, and ● indicates a hole mobility.

As can be seen from FIG.
A large change is observed around 0.4 μm. This is wavelength 1
This is because the localized vibration Si-N of the impurity is excited at 0.4 μm. When the activation rate of the carrier concentration was estimated, it was found that an activation rate of almost 100% was obtained at the peak position of ion implantation. Such a value cannot be obtained at all by the conventional heat treatment method.

From the above, it has been shown that the local electric carrier can be activated at room temperature by irradiating a free electron laser beam having a wavelength corresponding to the strong resonance absorption due to the stretching vibration of Si—N.

Furthermore, the effect of free electron laser light irradiation on the thin film material 6H-SiC was measured. Crystal Si
C has many crystal forms and is used industrially, and a similar measurement was attempted using 6H-SiC. Specifically, p-type (5 × 10 ¹² cm ⁻³ ) 6H
—SiC was formed by laser CVD, and an n-type (5 × 10 ¹⁵ cm ⁻³ ) 6H—SiC single crystal thin film was formed thereon.

Then, N ions were implanted into the single crystal thin film at room temperature. The implantation condition is 200 Ke at the implantation energy.
V, the implantation dose is 5 × 10 ¹⁴ cm ⁻² . The apparatus including the used free electron laser was the same as that used in the previous measurement, and the target thin film was irradiated with free electron laser light having the same pulse width and the same pulse power density through the same optical system.

In this thin film material, though not shown, the peak of the absorption wavelength due to the irradiation with the free electron laser was 12.6 μm, which is the same as the previous thin film material.

Thereafter, as a process based on the wavelength dependence of the electrical characteristics, the lattice vibration wavelength of the impurity element (N) is 10.4 μm.
m, and photoluminescence measurement was performed to evaluate the characteristics. FIG. 6 shows a photoluminescence measurement result of the thin film material modified by the laser beam. 325mm wavelength as excitation light for measurement
Was measured using a He-Cd laser. The measurement temperature is 10K.

In this measurement, a typical donor / acceptor pair emission of 6H—SiC was observed. In the figure, (a) shows a case where a laser beam is irradiated at 10.4 μm.
(B) is a comparative example, in which N ions were implanted and 10.4 μm was implanted.
m laser light is a case of non-irradiation. In the case of (a), it can be seen that the luminous intensity with respect to the photon energy (eV) = wavelength increases particularly at a specific value. This is considered to be because the inactive N in the SiC was activated by the irradiation of the 10.4 μm laser light. It also indicates that the change in emission intensity due to this photoluminescence irradiation has wavelength dependence, which indicates that vibration at a wavelength of 10.4 μm that resonates with lattice vibration of the impurity element N is directly excited. .

From the above, it can be understood that, in this example as well, the local activation of impurities in 6H-SiC can be realized at room temperature by irradiating a laser beam corresponding to strong resonance absorption due to the stretching vibration of Si—N. Is done.

In the measurement of the characteristics of each of the above-mentioned thin film materials, 12.6 μm, 10.3 μm, and 10.4 μm are obtained by changing the laser light using a free electron laser as the laser light.
m is irradiated with laser light of each wavelength, but when irradiating laser light of a specific wavelength for each thin film material,
After the resonance absorption wavelength is determined by measurement in advance, a laser other than the free electron laser may be used as long as it can irradiate a laser beam of the specific wavelength.

Although an example has been shown in which N ions are implanted as impurities, any of Al and B ions may be implanted instead of N ions.

[0044]

As described above in detail, the method for forming a semiconductor thin film of the present invention aims at ordering the crystal structure by irradiating a laser beam having a wavelength that is resonantly absorbed by the lattice vibration of the constituent elements of the thin film. Since the activation of the electrical carrier is intended by irradiating laser light having a wavelength that is resonantly absorbed by the lattice vibration of the impurity element, the reproducibility of the electrical characteristics of the thin film obtained by this film formation method is due to the ordered crystal structure. It has a remarkable effect of improving the electrical characteristics itself.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a semiconductor thin film manufacturing apparatus according to an embodiment.

FIG. 2 is an explanatory diagram of a pulse structure of a free electron laser.

FIG. 3 shows a laser (wavelength 1) of a semiconductor thin film material 3C-SiC.
2.6 μm) Infrared absorption spectrum before and after irradiation

FIG. 4 shows a laser (wavelength 1) of a semiconductor thin film material 3C—SiC.
0.3μm) Infrared absorption spectrum before and after irradiation

FIG. 5 is a diagram showing the laser wavelength dependence of the electric carrier concentration and the mobility of the semiconductor thin film material 3C-SiC after laser irradiation.

FIG. 6 shows a semiconductor thin film material 6H—SiC laser (wavelength 1);
0.4μm) Photoluminescence spectrum before and after irradiation

FIG. 7 is an explanatory diagram of ordering of a crystal structure and activation of an electric carrier by a modeled atomic structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Free electron laser 11 Free electron laser beam 12 Reflection mirror 13 ZnSe lens 14 Convergent light 15 Galvanometer mirror 16 Semiconductor thin film 17 Insulating substrate 18 Stage plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuneo Sanroku 2-9-5 Tsuda Yamate, Hirakata City Inside Free Electron Laser Laboratory Co., Ltd. (72) Inventor Takio Tomimas 2-9-5 Tsuda Yamate, Hirakata City Free Electron Laser Laboratory Inc.

Claims (5)

[Claims] 1. A semiconductor thin film formed by a physical or chemical method, into which an impurity element is introduced, is ordered by irradiating a laser beam having a wavelength that is resonantly absorbed by lattice vibrations of the constituent element. A semiconductor thin film formed by irradiating a laser beam having a wavelength that is resonantly absorbed by lattice vibration of an impurity element and activating an electric carrier by localized vibration. 2. The semiconductor thin film according to claim 1, wherein the semiconductor thin film is a silicon carbide film, and the impurity element is any one of nitrogen, aluminum, and boron. 3. A semiconductor thin film is formed by a physical or chemical method, an impurity element is introduced into the semiconductor thin film, and the thin film is irradiated with a laser beam having a wavelength that is resonantly absorbed by lattice vibration of the constituent elements to order the crystal structure. A method of forming a semiconductor thin film, comprising irradiating a laser beam having a wavelength that is resonantly absorbed by lattice vibration of an impurity element to excite localized vibration and activate an electric carrier. 4. The semiconductor thin film according to claim 3, wherein a laser beam having a wavelength that resonates and absorbs the lattice vibrations of the constituent elements and impurity elements of the thin film is selectively irradiated by a free electron laser. Membrane method. 5. The method according to claim 4, wherein the irradiation light of the free electron laser has a pulse width of 10 ⁻¹¹ seconds or less and a peak power of 1,000,000 W or more.