JP2004095613A - Method of diffusing impurity, and semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device which allows efficient diffusion of only a specified impurity element. <P>SOLUTION: The method of manufacturing a semiconductor device comprises processes of introducing a prescribed impurity element into a semiconductor substrate, forming an impurity diffused region in the semiconductor substrate by radiating the light of a frequency resonating the characteristic frequency of the impurity element to diffuse the impurity element, and forming a semiconductor element on the semiconductor substrate. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to impurity diffusion using resonance absorption by laser irradiation, a semiconductor device using such a diffusion phenomenon, and a method of manufacturing the same. More particularly, to a semiconductor device and a manufacturing method thereof having an impurity diffusion region of the isotope oxygen ^{(18 O).}
[0002]
[Prior art]
BACKGROUND ART In a manufacturing process of a semiconductor device, thermal diffusion is used in various aspects such as formation of a pn junction and doping of impurities. Thermal diffusion is a phenomenon in which impurity atoms move from a high-concentration region to a low-concentration region in a solid crystal in an attempt to approach a thermal equilibrium state. Since the diffused atoms are thermally activated and move over the energy barrier, diffusion is generally promoted at a higher temperature.
[0003]
In the thermal diffusion process, the same oxidation furnace as that of the normal oxidation process is often used. In a semiconductor device, since the distribution of impurities affects element characteristics, control of doping concentration and profile in impurity diffusion is extremely important. In the conventional thermal diffusion technology, diffusion of impurities is controlled by adjusting two parameters, temperature and time.
[0004]
2. Description of the Related Art A semiconductor device manufacturing process includes a number of impurity diffusion steps, and various types of impurities are used. Although the temperature and time of the heat treatment are controlled, since the heat treatment is performed collectively in the furnace, the shape (impurity concentration distribution) of the initially formed impurity diffusion region changes during the heat treatment in the subsequent impurity diffusion process. The problem of doing it always follows. In order to solve this problem, at present, the diffusion conditions are set so that the subsequent diffusion step does not disturb the impurity concentration distribution of the diffusion region formed by the previous diffusion step as much as possible, or Is set in advance and the conditions of all the diffusion steps are set.
[0005]
[Problems to be solved by the invention]
However, under the current situation in which the device structure is extremely miniaturized and complicated, it is extremely difficult to accurately form a wide variety of fine impurity diffusion regions in accordance with the types of the respective dopants. This problem is also caused by the fact that the conventional impurity diffusion technique is controlled only by two parameters of the temperature and time of the diffusion heat treatment. When a heat treatment set under a predetermined temperature condition and processing time is performed to diffuse specific impurities in the wafer, the entire wafer is heated. Another type of impurity contained in the wafer is also activated and diffuses beyond the diffusion barrier in the substrate.
[0006]
For these reasons, it becomes difficult to form an impurity region with a steeper profile according to the miniaturization of the device structure, which also affects the reliability of the operation of the semiconductor device.
[0007]
On the other hand, ion implantation is widely employed as a method for uniformly introducing impurities at a relatively low temperature with good controllability. In ion implantation, collisions of energetic particles cause damage such as crystal defects in the crystal. In addition, there is a problem of channeling in which the implanted energy ions penetrate deeper than expected by several times along the single crystal. In this regard, there is a possibility that steep junction can be realized by thermal diffusion, and various attempts have been made on diffusion methods even at present.
[0008]
Accordingly, an object of the present invention is to provide a novel impurity diffusion method capable of diffusing only a target impurity element with good controllability.
[0009]
It is another object of the present invention to provide a method of manufacturing a semiconductor device in which diffusion of a plurality of types of impurities due to batch heat treatment is prevented, and only predetermined impurities are diffused to form impurity diffusion regions.
[0010]
Still another object is to provide a semiconductor device having a desired impurity diffusion region having a steep profile.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention utilizes the resonance absorption of a specific atom by irradiating light of a specific wavelength to diffuse only a specific atom without affecting other impurity atoms. In particular, by performing a low-temperature heat treatment while irradiating an infrared laser, it becomes possible to efficiently diffuse a target impurity to a desired depth.
[0012]
Generally, an impurity element in a crystal vibrates at a unique frequency νimp for each impurity. Since its natural frequency is strongly localized at the place where impurities are collected, irradiation with infrared light having a frequency νir which is the same as or very close to the natural frequency νimp causes a very sharp resonance absorption, The mode is excited. As a result, only the vibration of the impurity atoms corresponding to the wavelength of the irradiation light obtains a large energy and easily jumps over the potential barrier of the crystal lattice and diffuses. The present invention applies such a principle to impurity diffusion and the manufacture of a semiconductor device using impurity diffusion.
[0013]
In a first aspect of the present invention, an impurity diffusion method includes:
(A) a step of introducing a predetermined impurity element into the substrate;
(B) irradiating a predetermined portion on the substrate with light having a wave number that resonates with the natural frequency of the impurity element to excite the predetermined impurity element and diffuse the impurity element into the substrate.
[0014]
According to this method, it is not necessary to subject the substrate to high-temperature heat treatment at once, and it is possible to diffuse only the target impurity. Further, in the irradiation step, when the substrate is irradiated with light having a wave number that resonates with the natural frequency while performing low-temperature heat treatment, the diffusion speed of the target element can be increased without causing the diffusion of other impurity elements contained in the substrate. it can.
[0015]
Further, when a light beam narrowed down in the irradiation step, for example, a light beam having a beam diameter of 10 mm or less is used, the diffusion of impurities in the depth direction can be accurately controlled.
[0016]
According to a second aspect of the present invention, a method of manufacturing a semiconductor device includes:
(A) a step of introducing a predetermined impurity element into a semiconductor substrate;
(B) a step of irradiating a predetermined portion on the substrate with light having a wave number that resonates with the natural frequency of the introduced impurity element to diffuse the impurity element and form an impurity diffusion region; Forming a semiconductor element.
[0017]
The impurity element is, for example, isotope oxygen ( ¹⁸ O). In this case, the isotope oxygen ( ¹⁸ O) is diffused by irradiating a laser beam having a wave number of 1085 ± 10 cm ⁻¹ . As means for realizing light in this wavenumber band, for example, a carbon dioxide laser is used.
[0018]
Impurity diffusion region formed by diffusion of isotopic oxygen ^{(18 O),} an element isolation region or a gettering site.
[0019]
According to such a method for manufacturing a semiconductor device, an impurity diffusion region of a target element can be formed at a desired position and at a desired depth without causing diffusion of another impurity element.
[0020]
In a third aspect of the present invention, a semiconductor device includes a semiconductor substrate, an impurity diffusion region of the isotope oxygen ^{(18 O)} is located in the semiconductor substrate, and a semiconductor device formed on a semiconductor substrate. The concentration of isotope oxygen ( ¹⁸ O) in the impurity diffusion region is 1 × 10 ¹⁵ / cm ³ to 2 × 10 ¹⁸ / cm ³ .
[0021]
Other features and advantages of the present invention will become more apparent in the following detailed description with reference to the accompanying drawings.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a graph showing measurement results of impurity diffusion by resonance absorption.
[0023]
As described above, the impurity element in the crystal vibrates at a unique frequency νimp for each impurity. Irradiation with light having a frequency ｉir substantially equal to the natural frequency ｉimp causes sharp resonance absorption to excite this specific impurity, and diffuses beyond the diffusion potential barrier in the crystal.
[0024]
For example, isotopes of oxygen in the silicon crystal ^{(18 O)} is in the natural frequency just with the natural frequency that resonates with the frequency of the carbon dioxide laser (expressed in wave number 1085 cm ^-1). Therefore, first, an isotope oxygen ( ¹⁸ O) was introduced into the silicon substrate by forming an ¹⁸ O oxide film on the silicon substrate by, for example, a normal oxide film forming process, thereby preparing a sample. Then, using a carbon dioxide gas laser having a beam diameter of 8 mm and an irradiation energy of 3.6 × 10 ⁴ J per hour, a predetermined portion of the silicon substrate is vertically irradiated by continuous oscillation irradiation for 4 hours, and isotopes are obtained. oxygen ⁽¹⁸ O) was diffused into the silicon substrate. At this time, the silicon substrate was heat-treated at 1150 ° C. in an argon gas atmosphere while irradiating with a carbon dioxide gas laser to promote diffusion by resonance absorption. Thereafter, the substrate was cooled at a cooling rate of 60 ° C./min.
[0025]
The graph of FIG. 1 shows SIMS (secondary ion mass spectrometry) of the depth distribution of isotope oxygen immediately after the introduction of isotope oxygen ( ¹⁸ O) and the depth distribution in the irradiated portion and the non-irradiated portion after irradiation with a carbon dioxide gas laser. 2) shows the results of the measurement.
[0026]
Immediately after the introduction of isotope oxygen ( ¹⁸ O), isotope oxygen (impurities) is concentrated on the substrate surface, and the number decreases as the depth increases. When a certain region of such a substrate was irradiated with a carbon dioxide gas laser while performing a low-temperature heat treatment, and the number of counts was measured after cooling, the impurity profile was almost uniformly spread from the substrate surface in the depth direction at the laser irradiated portion. I knew it was there. On the other hand, in the non-irradiated portion, isotope oxygen diffuses to some extent due to heat treatment performed in parallel with laser irradiation to promote diffusion by resonance absorption, but the distribution shape in the depth direction is not uniform. When the isotope oxygen ( ¹⁸ O) concentration was compared between the irradiated portion and the non-irradiated portion at 30 μm from the surface, the difference was 0.7 × 10 ¹⁷ / cm ³ .
[0027]
Although the graph of FIG. 1 combines laser irradiation and heat treatment in order to increase the measurement efficiency, even at a lower temperature treatment, the impurity is uniformly diffused by resonance absorption of laser light. For example, in general, when the temperature is 900 ° C. or lower, thermal diffusion of impurities hardly occurs. However, even in such a low-temperature process, by irradiating the impurities with light having a wavelength matching the natural frequency of the impurities, the impurities can be controlled with good controllability. Can be diffused.
[0028]
The low-temperature heat treatment is not limited to being performed in an argon gas atmosphere, and may be performed in an inert gas atmosphere of oxygen or nitrogen. Further, the cooling rate after the heat treatment can be appropriately set between 100 ° C./min and 1 ° C./min.
[0029]
In the graph of FIG. 1, the measurement is performed up to a depth of 80 μm, but by adjusting the beam diameter and the irradiation energy density, it can be diffused to a depth of about 500 μm. When the heat treatment at about 1150 ° C. is combined, the difference in the concentration of isotope oxygen ( ¹⁸ O) between the laser irradiation area and the non-irradiation area at an arbitrary depth up to a depth of 500 μm is 1 × 10 ¹⁵ / cm ³ to 1 × 10 ¹⁷ particles / cm ³ .
[0030]
In the graph of FIG. 1, a carbon dioxide gas laser having a wave number of 1085 cm ⁻¹ was used to diffuse the isotope oxygen. However, even when irradiated with light having a wave number of 1085 ± 10, sufficient resonance absorption occurred, and isotope oxygen was emitted. Oxygen diffuses. When the diameter of the beam is reduced to 10 mm or less, a fine impurity diffusion region can be formed accurately in the depth direction.
[0031]
As described above, since the impurity diffusion method of the present invention is based on the principle of resonance absorption at a natural frequency in the infrared region, it is possible to diffuse impurities uniformly in the depth direction without melting the substrate surface. become.
[0032]
FIG. 2 shows, as a first embodiment, an example in which the resonance absorption / diffusion by laser irradiation of the present invention is applied to a semiconductor device manufacturing process. In the example of FIG. 2, isotope oxygen ( ¹⁸ O) is diffused by irradiation with a carbon dioxide gas laser to form an element isolation region (STI).
[0033]
First, as shown in FIG. 2A, an oxide film 12 of isotope oxygen ( ¹⁸ O) having a thickness of about 20 nm is formed on a silicon substrate 11, and an impurity ( ¹⁸ O) is introduced into the silicon substrate 11. . The isotope oxygen ( ¹⁸ O) oxide film 12 can be formed by a known method such as thermal oxidation.
[0034]
Next, as shown in FIG. 2B, a predetermined portion of the silicon substrate 11 on which the oxide film 12 of isotope oxygen ( ¹⁸ O) is formed is irradiated with a carbon dioxide gas laser having a beam diameter of 1 mm at an irradiation energy of 3.6 ×. Irradiate vertically at 10 ⁵ J.
[0035]
Next, as shown in FIG. 2C, the isotope oxygen ( ¹⁸ O) is absorbed to the depth of 1 μm of the silicon substrate 11 by the resonance absorption of the isotope oxygen ( ¹⁸ O) included in the laser irradiation region 13. ) Spread. At this time, in order to suppress the diffusion of isotope oxygen ( ¹⁸ O) in the non-irradiated region 14, it is desirable to perform the treatment at a low temperature. Alternatively, although not shown, laser irradiation may be performed after patterning the isotope oxygen ( ¹⁸ O) oxide film 12 so as to leave only the laser irradiation region 13. In the latter case, the combined use of heat treatment at room temperature to 1200 ° C., it is possible to promote diffusion in the depth direction of the isotope oxygen ^{(18 O).} Through these steps, the element isolation region 15 of the ¹⁸ O oxide insulating film is formed.
[0036]
Finally, as shown in FIG. 2D, the oxide film 12 of isotope oxygen ( ¹⁸ O) formed on the surface of the silicon substrate 11 in FIG. The element 19 is formed in the region by an arbitrary method. For example, a gate electrode 16 is formed by forming a gate oxide film 18, depositing and patterning a polysilicon film by a CVD method or the like, and forming a source / drain 17 by ion implantation in a self-aligned manner. create. Alternatively, the source / drain 17 may be formed first using a dummy gate, and then the gate insulating film 18 and the gate electrode 16 may be formed.
[0037]
Thus, the semiconductor device 10 having the isotope oxygen ( ¹⁸ O) diffusion region 15 as an element isolation region is completed.
[0038]
If in resonance absorption diffusion by laser irradiation to form the isolation region 15, it can be accurately diffused in the depth direction only isotope of oxygen ^{(18 O)} alone. Further, by narrowing the beam diameter, it is possible to sufficiently cope with miniaturization of devices.
[0039]
The conventional STI forming technique requires a process of forming a trench in a substrate by dry etching, filling the trench with an insulating film, and then planarizing the surface by CMP. There was a problem of voids remaining inside. In contrast, in the method of the present invention, since the element isolation region is formed using resonance absorption diffusion by laser irradiation, the number of steps can be reduced and the contents of the steps themselves can be simplified. Further, by adjusting the beam diameter and the energy density of the carbon dioxide laser, the depth of the element isolation region can be accurately controlled, and a uniform and void-free element isolation region can be formed.
[0040]
FIG. 3 shows, as a second embodiment, an example in which the resonance absorption / diffusion by laser irradiation of the present invention is applied to the formation of a gettering site. Many metal elements have a detrimental effect on semiconductor devices. Therefore, for the purpose of removing metal impurities from the element active region, a gettering function for intentionally depositing metal impurities on a gettering site in the semiconductor substrate other than the element active region is required. Gettering technology has become indispensable in the manufacture of semiconductor devices because metal impurities penetrate into a substrate in a wide variety of steps, not only a wiring step but also a cleaning step, a high-temperature heat treatment step, and a dry step.
[0041]
First, as shown in FIG. 3A, isotope oxygen ( ¹⁸ O) is uniformly introduced into the silicon substrate 21 by a known method such as thermal diffusion or ion implantation.
Next, as shown in FIG. 3B, a predetermined portion of the silicon substrate 21 is vertically irradiated with a carbon dioxide gas laser having a beam diameter of 1 mm at an irradiation energy of 3.6 × 10 ⁵ J.
[0042]
By such laser irradiation, as shown in FIG. 3C, diffusion of only isotope oxygen ( ¹⁸ O) proceeds inside the silicon substrate 21 corresponding to the irradiation region 23, and precipitation is promoted. The oxygen precipitate in the deep part of the silicon substrate 21 constitutes a gettering site 22 and aggregates metal impurities in the element region.
[0043]
Next, as shown in FIG. 3D, an element isolation region 25 and an element 29 are formed on the silicon substrate 21 by a known method. The element 29 has, for example, a gate electrode 26 and a source / drain 27 via a gate insulating film 28. Thus, a semiconductor device 20 having the isotope oxygen ( ¹⁸ O) diffusion region 22 as a gettering site is manufactured.
[0044]
Generally, when a silicon wafer formed by the CZ method is heat-treated, oxygen precipitates and minute crystal defects are generated. Such oxygen precipitates are actively used as gettering sites. However, the presence of gettering sites in the element active region near the substrate surface adversely affects electrical characteristics. Therefore, when a silicon substrate formed by the CZ method is used, high-temperature heat treatment is required to eliminate solid solution oxygen near the substrate surface and prevent formation of gettering sites in the element active region.
[0045]
On the other hand, when a gettering site is formed using resonance absorption and diffusion by laser irradiation as in the second embodiment of the present invention, the gettering site is formed at a desired position in the silicon substrate by laser irradiation. It can be formed. Further, by adjusting the energy and beam diameter of the carbon dioxide laser, the depth position of the gettering site can be controlled, and the element active region is not adversely affected. Further, even when a wafer prepared by a method other than the CZ method is used, a gettering site can be formed at an arbitrary position.
[0046]
In the example of FIG. 2 and FIG. 3, but by introducing isotopic oxygen ^{(18 O)} to the silicon substrate described by taking an example of the laser irradiation, not only the silicon substrate, to Ge substrate or a compound semiconductor substrate, the The resonance absorption diffusion by laser irradiation according to the invention is applicable.
[0047]
Further, in the above embodiment, an example in which isotope oxygen ( ¹⁸ O) is diffused as an impurity has been described. However, by combining an arbitrary kind of impurity with light having a wavelength that resonates with the natural frequency of the impurity. In addition, various impurity diffusion regions can be formed. Irradiation with infrared laser light is particularly suitable for a region that requires uniform diffusion in the depth direction, and can be applied to, for example, formation of a well.
[0048]
The frequency of the infrared laser can be adjusted by, for example, combining an existing IV-IV semiconductor infrared laser with a nonlinear optical system and performing optical frequency conversion. Alternatively, the adjustment can be made by using a Raman laser to obtain emission laser light having a frequency shifted from the incident laser light. Thereby, the infrared laser light in the range of 8 to 13 μm can be selected according to the type of the impurity used.
(Supplementary Note 1) A step of introducing a predetermined impurity element into the substrate, and irradiating a predetermined portion on the substrate with light having a wave number that resonates with a natural frequency of the impurity element to excite the predetermined impurity element. And diffusing it into a substrate.
(Supplementary Note 2) The impurity is isotope oxygen ( ¹⁸ O), and the isotope oxygen ( ¹⁸ O) is diffused by irradiating a laser beam having a wave number of 1085 ± 10 cm ^−1. 3. The impurity diffusion method according to item 1.
(Supplementary Note 3) The impurity diffusion according to Supplementary Note 1, wherein the impurity is isotope oxygen ( ¹⁸ O), and isotope oxygen ( ¹⁸ O) is diffused by irradiating a laser beam of a carbon dioxide gas laser. Method.
(Supplementary Note 4) The impurity diffusion method according to Supplementary Note 1, wherein the irradiation step performs laser irradiation using a combination of an infrared laser and a nonlinear optical system.
(Supplementary Note 5) The impurity diffusion method according to any one of Supplementary Notes 1 to 4, wherein a predetermined portion on the substrate is irradiated, and a heat treatment is performed at a temperature of room temperature to 1200 ° C.
(Supplementary Note 6) A step of introducing a predetermined impurity into the semiconductor substrate, and irradiating a predetermined portion on the substrate with light having a wave number that resonates with a natural frequency of the impurity to diffuse the introduced impurity element, A method of manufacturing a semiconductor device, comprising: a step of forming an impurity diffusion region therein; and a step of forming a semiconductor element on a semiconductor substrate.
(Supplementary Note 7) The method for manufacturing a semiconductor device according to Supplementary Note 6, wherein the irradiation step includes irradiating light with a desired wavelength by combining an infrared laser and a nonlinear optical system.
(Supplementary Note 8) introducing a semiconductor substrate isotopic oxygen ⁽¹⁸ O), at a predetermined point on the substrate, wherein by irradiating a laser beam of wave number 1085 ± 10 cm ^-1 isotope oxygen ⁽¹⁸ O A method for manufacturing a semiconductor device, comprising: a step of diffusing impurities to form an isotope oxygen ( ¹⁸ O) impurity diffusion region in a semiconductor substrate; and a step of forming a semiconductor element on the semiconductor substrate.
(Supplementary Note 9) A step of introducing isotope oxygen ( ¹⁸ O) into the semiconductor substrate, and irradiating a predetermined portion on the substrate with laser light from a carbon dioxide gas laser to diffuse the isotope oxygen ( ¹⁸ O) impurity. A method for manufacturing a semiconductor device, comprising: forming an isotope oxygen ( ¹⁸ O) impurity diffusion region in a semiconductor substrate; and forming a semiconductor element on the semiconductor substrate.
(Supplementary Note 10) The method according to Supplementary Note 8 or 9, wherein the isotope oxygen ( ¹⁸ O) impurity diffusion region is an element isolation region or a gettering site.
(Supplementary Note 11) The method of manufacturing a semiconductor device according to Supplementary Note 8 or 9, wherein the laser beam has a beam diameter of 10 mm or less.
(Supplementary Note 12) The method of manufacturing a semiconductor device according to any one of Supplementary Notes 8 to 11, further comprising irradiating a predetermined portion on the substrate and performing heat treatment at room temperature to 1200 ° C.
(Supplementary Note 13) and the semiconductor substrate, and the impurity diffusion region of the isotope oxygen ^{(18 O)} is located in the semiconductor substrate, and a semiconductor device formed on a semiconductor substrate, isotope oxygen impurity diffusion region ⁽¹⁸ O A) a semiconductor device having a concentration of 1 × 10 ¹⁵ / cm ³ to 2 × 10 ¹⁸ / cm ³ ;
(Supplementary Note 14) The semiconductor device according to supplementary note 13, wherein the impurity diffusion region is an element isolation region or a gettering site.
[0049]
【The invention's effect】
As described above, according to the present invention, irradiation is performed with light having a wave number corresponding to the natural frequency of a specific impurity element, and the impurity element is diffused by excitation by resonance absorption. With this method, only the target impurity element can be diffused alone into the substrate.
[0050]
In addition, by combining irradiation with low-temperature heat treatment, diffusion of an impurity element can be promoted.
[0051]
By adjusting the diameter and the energy density of the irradiation beam, it is possible to control the diffusion in the depth direction even in fine processing.
[Brief description of the drawings]
FIG. 1 is a graph showing an impurity concentration distribution in a depth direction in impurity diffusion using resonance absorption by laser irradiation.
FIG. 2 is a diagram showing an example in which resonance absorption diffusion by laser irradiation is applied to element isolation formation of a semiconductor device.
FIG. 3 is a diagram showing an example in which resonance absorption diffusion by laser irradiation is applied to formation of a gettering site of a semiconductor device.
[Explanation of symbols]
10, 20 Semiconductor device 11, 21 Silicon substrate 13, 23 Laser irradiation region 14, 24 Non-irradiation region 15 Element isolation region (impurity diffusion region)
19, 29 device 22 gettering site (impurity diffusion region)

Claims (5)

A step of introducing a predetermined impurity element into the substrate,
Irradiating a predetermined portion on the substrate with light having a wave number that resonates with a natural frequency of the impurity element, exciting the predetermined impurity element and diffusing the same into the substrate. Spreading method. A step of introducing a predetermined impurity element into the semiconductor substrate;
Irradiating a predetermined location on the semiconductor substrate with light having a wave number that resonates with the natural frequency of the impurity element to diffuse the introduced impurity element and form an impurity diffusion region in the semiconductor substrate;
Forming a semiconductor element on the semiconductor substrate. A step of introducing isotope oxygen ( ¹⁸ O) into the semiconductor substrate;
At a predetermined point on said semiconductor substrate, wavenumber is irradiated with laser light of 1085 ± 10 cm ^-1 to diffuse the isotope oxygen ⁽¹⁸ O) impurities, isotopic oxygen ⁽¹⁸ O) impurity in the semiconductor substrate Forming a diffusion region;
Forming a semiconductor element on the semiconductor substrate. A step of introducing isotope oxygen ( ¹⁸ O) into the semiconductor substrate;
A predetermined point on said semiconductor substrate, by irradiating a laser beam from a carbon dioxide laser to diffuse the isotope oxygen ^{(18 O)} impurities to form the isotope oxygen ^{(18 O)} impurity diffusion regions in said semiconductor substrate Process and
Forming a semiconductor element on the semiconductor substrate. A semiconductor substrate;
An impurity diffusion region of isotope oxygen ( ¹⁸ O) located in the semiconductor substrate;
A semiconductor element formed on the semiconductor substrate, wherein an isotope oxygen ( ¹⁸ O) concentration of the impurity diffusion region is 1 × 10 ¹⁵ / cm ³ to 2 × 10 ¹⁸ / cm ^3. Characteristic semiconductor device.

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