WO2002099862A1

WO2002099862A1 - Annealing method, ultra-shallow junction layer forming method and ultr-shallow junction layer forming device

Info

Publication number: WO2002099862A1
Application number: PCT/JP2002/005319
Authority: WO
Inventors: Mitihiko Takase; Akihisa Yoshida; Bunji Mizuno
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2001-06-04
Filing date: 2002-05-30
Publication date: 2002-12-12
Also published as: TW541628B

Abstract

An annealing method for annealing an impurity-introduced substrate, comprising the recrystallizing step of heat treating a substrate at a substrate temperature low enough not to activate the impurities introduced into the substrate so as to bring the substrate into a thermal equilibrium to thereby recrystallize atoms constituting the substrate, and, after the recrystallizing step, the electromagnetic wave irradiation step of irradiating the substrate with an electromagnetic wave having a specified frequency band so as to excite directly the lattice vibration (phonon) of the atoms for the purpose of activating the impurities in a thermal non-equilibrium with the substrate kept at a sufficiently low temperature.

Description

Description: Annealing method, ultra-shallow junction layer forming method and ultra-shallow junction layer forming apparatus

The present invention relates to an annealing method for reactivating atoms introduced into a substrate after recrystallizing the atoms to recover lattice defects generated in atoms constituting the substrate into which the impurities are introduced, and an ultra-shallow junction layer. The present invention relates to a forming method and an ultra-shallow junction layer forming apparatus. Background art

In recent years, in semiconductor devices such as ultra-large-scale integrated circuits (LSIs) formed using a silicon single crystal substrate as a substrate, along with the reduction in the design rule of the semiconductor device, the short channel effect is prevented and the semiconductor device is prevented. In order to operate the device at high speed, it is necessary to reduce the junction depth of a diffusion layer formed in a transistor provided in a semiconductor device. For this reason, in a MOSFET or a bipolar transistor used for a dynamic immediate memory device (DRAM) or the like, for example, a junction depth of a diffusion layer formed in a transistor having a gate having a gate length of about 100 nanometers is It is required to be as shallow as about 50 nanometers. Furthermore, a transistor having a gate with a gate length of about 50 nanometers is required to have a junction depth of a diffusion layer formed as small as about 10 nanometers. For this reason, in addition to the technology of doping impurities into a very shallow junction layer having a depth of about 10 nanometers to 50 nanometers at a high concentration, it is necessary to activate the impurities doped in such a very shallow junction layer. Anneal technology is being considered. One of the conventional annealing technologies is a solid-state diffusion process using infrared rapid heat treatment (RTA), which heats the entire substrate into which impurities have been implanted to approximately 100 ° C using an infrared lamp or the like. An activation method in a thermal equilibrium state using a technique is known.

Also, as a conventional technique using a laser, a technique of irradiating a 310 nm XeC1 excimer laser to melt the surface of a silicon substrate and then recrystallizing silicon atoms is known as laser annealing. . Here, for example, a laser annealing of 0.35 JZ cm ² and 800. Heat treatment is performed in combination with RTA of C 10 seconds (references Ken-ich Goto et al .; 9 31—93 3 3., International Electron Device Meeting 1999 at) Washington DC).

However, the above-described conventional annealing technique utilizing the solid-phase diffusion process by infrared rapid thermal processing (RTA) in a thermal equilibrium state is effective for activating the impurity-doped layer, but the entire substrate is 100,000. Since the substrate is heated to a high temperature of about ° C, there is a problem that the implanted impurities may diffuse deep into the substrate. For example, a boron atom implanted layer with a depth of 20 nanometers obtained by low energy can be heated to a depth of about 50 nanometers by performing rapid heating at 100 ° C for 10 seconds. There was a problem that it would be 2.5 times deeper.

In addition, in the LSI manufacturing process that requires multiple impurity introduction processes, conventional heat treatment technology heats the entire substrate to a high temperature at which the impurities diffuse, and therefore exists at locations where diffusion is unnecessary. There was a problem that it could diffuse to impurities.

Furthermore, in the above-described conventional technique of irradiating an excimer laser, Unnecessary diffusion into the part is suppressed to a considerable extent, but the lattice defects generated in the atoms that make up the substrate into which the impurities are introduced cannot be sufficiently recovered, so that the There is a problem that the leakage current generated in the transistor may increase.

The present invention has been made to solve the above-mentioned problem, and an object thereof is to provide an annealing method capable of preventing activated impurities from being unnecessarily diffused deep into a substrate. It is in.

Another object of the present invention is to provide an ultra-shallow junction layer forming method and an ultra-shallow junction layer forming apparatus capable of forming an ultra-thin junction layer having a shallow junction depth. Disclosure of the invention

The annealing method according to the present invention is an annealing method for annealing a substrate having impurities introduced therein, wherein the substrate is heated at a substrate temperature sufficiently low that the impurities introduced into the substrate are not activated. A heat treatment of the substrate so as to be in a state of equilibrium, thereby recrystallizing atoms constituting the substrate, and after the recrystallization step, the substrate temperature is lowered to the sufficiently low substrate temperature. In order to activate the impurities in a thermal non-equilibrium state while holding the substrate, an electromagnetic wave having a predetermined frequency band is applied to the substrate so as to directly excite lattice vibration (phonon) of the atoms. And irradiating an electromagnetic wave.

In the above, lattice vibration (phonon) refers to the inter-atomic force that acts as a restoring force (pane force) according to Hooke's law for small displacement of atoms between atoms existing at the crystal lattice position due to thermal motion or forced vibration from the outside. A coupled vibration in which the vibration of an atom caused by a force is transmitted to the next atom.

The method for forming an ultra-shallow junction layer according to the present invention comprises the steps of: A very shallow junction layer for forming an extremely shallow junction layer at a substrate temperature sufficiently low that the impurities introduced into the semiconductor substrate are not activated. A heat treatment of the semiconductor substrate so that the semiconductor atoms constituting the semiconductor substrate are recrystallized, and after the recrystallization step, the semiconductor substrate is cooled to the sufficiently low substrate temperature. While maintaining the semiconductor substrate, in order to activate the impurity in a thermal non-equilibrium state and form an ultra-shallow junction layer, a predetermined lattice vibration (phonon) of the semiconductor element is directly excited. Irradiating the semiconductor substrate with an electromagnetic wave having a frequency band.

In the above, the extremely shallow junction layer is a diffusion layer formed in a transistor provided in a semiconductor device, and has a junction depth of about 20 nm or less and about 1 nm or more.

An ultra-shallow junction layer forming apparatus according to the present invention is an ultra-shallow junction layer forming apparatus for forming an ultra-shallow junction layer on a semiconductor substrate into which impurities are introduced, wherein the impurity introduced into the semiconductor substrate is Recrystallization means for subjecting the semiconductor substrate to heat treatment so that the semiconductor substrate is in a thermal equilibrium state at a substrate temperature sufficiently low that the semiconductor substrate is not activated, thereby recrystallizing semiconductor atoms constituting the semiconductor substrate. Activating the impurities in a thermal non-equilibrium state while maintaining the semiconductor substrate in which the semiconductor atoms have been recrystallized by the recrystallization means at the sufficiently low substrate temperature; Means for irradiating the semiconductor substrate with an electromagnetic wave having a predetermined frequency band so as to directly excite the lattice vibration (phonon) of the semiconductor atoms to form a layer; And characterized in that: BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a cross-sectional view of a semiconductor substrate into which an impurity according to the present embodiment has been introduced.

FIG. 2 is a cross-sectional view schematically showing an electric furnace for performing the recrystallization step according to the present embodiment.

FIG. 3 is a cross-sectional view schematically showing an electromagnetic wave irradiation device for performing the electromagnetic wave irradiation step according to the present embodiment. '

FIG. 4 is a cross-sectional view schematically showing an ultrashallow junction layer forming apparatus for performing both the recrystallization step and the electromagnetic wave irradiation step according to the present embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

In the method for forming an ultra-shallow junction layer according to the present invention, it is preferable that the semiconductor substrate is made of one of silicon and a silicon compound. This is because a semiconductor device formed over a silicon substrate can be obtained.

In the recrystallization step, the semiconductor substrate is preferably heat-treated at a substrate temperature of 700 ° C. or less. This is because the substrate temperature is low enough that the impurities introduced into the semiconductor substrate are not activated in a thermal equilibrium state.

In the recrystallization step, it is preferable that the semiconductor substrate is heat-treated by using either an electric furnace or a lamp heating furnace. This is because heat treatment can be performed with a simple configuration.

The coherent electromagnetic wave irradiated in the electromagnetic wave irradiation step preferably includes an ultrashort pulse laser beam having a pulse width of 10 to 1000 femtoseconds, and 10 GHz to 1 GHz. It preferably includes a continuous wave output laser beam having a frequency bandwidth of TH z or less, and has an oscillation frequency of 10 GHz or more and 100 GHz or less. It preferably contains a millimeter wave electromagnetic wave. It is preferable that the coherent electromagnetic wave irradiated in the electromagnetic wave irradiation step also has a frequency band corresponding to a binding energy between the semiconductor atom and the impurity. This is because the lattice vibration (phonon) of semiconductor atoms can be more reliably excited.

In the electromagnetic wave irradiation step, it is preferable that the semiconductor substrate is irradiated with the electromagnetic wave while cooling the semiconductor substrate so as to maintain the semiconductor substrate at the sufficiently low substrate temperature. The cooling ensures that the semiconductor substrate is maintained at a substrate temperature sufficiently low that the impurities are not substantially activated in a thermal equilibrium state, so that the activated impurities are unnecessarily diffused deep into the semiconductor substrate. This is because this can be prevented more reliably.

Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a silicon substrate 2 into which impurities according to the present embodiment have been introduced. On the surface of the silicon substrate 2, an impurity layer 3 is formed. The impurity layer 3 is formed by introducing an impurity into the silicon substrate 2 by, for example, an ion implantation method or a plasma doping method.

FIG. 2 is a cross-sectional view schematically showing an electric furnace 4 for performing the recrystallization step according to the present embodiment. The electric furnace 4 includes a chamber 14. Inside the chamber 114, a silicon substrate 2 on which an impurity layer 3 is formed in advance is accommodated. The chamber 114 is provided with a heater 7 for heating the silicon substrate 2 housed inside the chamber 114. A gas introduction pipe 5 for introducing nitrogen (N ₂ ) gas into the inside of the chamber 14 is provided on one side wall of the chamber 14, and the other side wall of the chamber 14 is provided with the chamber introduction pipe 5. A gas exhaust pipe 6 for exhausting the gas inside the chamber 14 to the outside of the chamber 14 is provided.

In the electric furnace 4 thus configured, the impurity layer 3 is formed in advance. After the silicon substrate 2 was placed in the chamber 114, nitrogen (N ₂ ) gas was introduced into the chamber 114 through the gas introduction pipe 5, and the gas existing in the chamber 114 was introduced. Was discharged through the gas discharge pipe 6 to make the inside of the chamber 14 a nitrogen (N ₂ ) gas atmosphere.

Then, the substrate temperature of the silicon substrate 2 becomes 700 ° C. or less, which is sufficiently low that impurities are not substantially activated in a thermal equilibrium state in which the silicon substrate 2 is in a thermal equilibrium state. As described above, the silicon substrate 2 was heated by the heater 7. For example, the silicon substrate 2 was heated for about 5 hours so that the silicon substrate 2 was in a thermal equilibrium state at a substrate temperature of about 600 ° C. The silicon atoms forming the heated silicon substrate 2 are recrystallized at a substrate temperature of about 600 ° C., and lattice defects generated in the silicon atoms forming the silicon substrate 2 into which impurities are introduced are recovered. did.

By such heat treatment, the silicon atoms constituting the silicon substrate 2 rearranged, and the lattice defects generated in the silicon atoms disappeared. An important point in this heat treatment is to set the substrate temperature at which silicon atoms are recrystallized to 70 ° C or less, which is sufficiently low that impurities are not substantially activated in thermal equilibrium. is there.

FIG. 3 is a cross-sectional view schematically showing an electromagnetic wave irradiation device 8 for performing the electromagnetic wave irradiation step according to the present embodiment. The electromagnetic wave irradiation device 8 includes a chamber 9. A mounting table 13 is provided inside the chamber 19. On the mounting table 13, the silicon substrate 2 heat-treated by the electric furnace 4 described above is mounted such that the impurity layer 3 is on the upper side. The electromagnetic wave irradiation device 8 has a coherent electromagnetic wave source 10. The coherent electromagnetic wave source 10 generates an incident coherent electromagnetic wave 12. The irradiation optical system 11 is provided in the chamber 9 so as to face the impurity layer 3 formed on the silicon substrate 2 mounted on the mounting table 13. Irradiation light ί1 converts the incident coherent electromagnetic wave 12 generated by the coherent electromagnetic wave source 10 into an irradiation coherent electromagnetic wave 1, and irradiates the silicon substrate 2 on which the impurity layer 3 is formed. The irradiation optical system 11 is also configured by predetermined optical components necessary for ensuring irradiation uniformity of the irradiation coherent electromagnetic wave 1 irradiated to the silicon substrate 2. The inside of the chamber 19 is maintained in an atmosphere of an inert gas such as nitrogen, helium, or argon.

In the electromagnetic wave irradiation apparatus 8 configured as described above, the silicon substrate 2 that has been heat-treated at a substrate temperature of about 600 ° C. by the electric furnace 4 described above is placed inside the chamber 19 maintained in an inert gas atmosphere. When placed on a mounting table 13 provided in the semiconductor device, the substrate temperature of the silicon substrate 2 is kept at 500 ° C. or less, which is sufficiently low that impurities are not substantially activated in a thermal equilibrium state. I was drunk.

The incident coherent electromagnetic wave 12 was generated by the coherent electromagnetic wave source 10. The irradiation optical system 1 1 converts the incident coherent electromagnetic wave 1 2 into the irradiation coherent electromagnetic wave 1 so that the silicon substrate 2 is irradiated with light so as to secure the irradiation uniformity of the irradiation coherent electromagnetic wave 1 applied to the silicon substrate 2. In the thermal non-equilibrium state, which is a thermal non-equilibrium state, the silicon substrate 2 was irradiated with the irradiation coherent electromagnetic wave 1 having a predetermined frequency band so as to activate the impurities contained in the impurity layer 3.

In the solid crystal of the silicon substrate 2 irradiated with the irradiation coherent electromagnetic wave 1 having a predetermined frequency band, the atoms are regularly arranged, and an interatomic force acts between the atoms existing at the crystal lattice position. . This interatomic force acts as a restoring force (pane force) according to Hooke's law with respect to minute displacement of an atom, so if an atom vibrates due to thermal motion or forced vibration from the outside, the vibration of the atom will be changed to the next atom To generate coupled vibration. this This is called lattice vibration and is called phonon because it is quantized in a solid. In addition, since the atomic force, which is equivalent to the panel constant of the restoring force, as well as the atomic mass and interatomic distance, has a unique value according to each substance, the frequency and wave number of lattice vibration (phonon) are mutually different. There is a dependency, this dispersion relation and Rereu _σ

When a solid crystal is irradiated with electromagnetic waves, a local temperature rise (thermal coupling) or a disturbance of dielectric polarization (photoelastic coupling) causes elastic strain coupled with light. When this elastic strain is used as an external force to irradiate a solid crystal with light (electromagnetic waves) in the frequency range of lattice vibration (phonon), stimulated coherent lattice vibration (phonon) is excited by stimulated Raman scattering. Can be done.

For example, the dispersion relations of phonons known in silicon single crystals (references, for example, F. Fabotand AD Corso, Phys. Rev. B60, 1 1 4 2 7 (1 9 9 9 According to), the frequency of lattice vibration (phonon) exists between 10 GHz and 10 TH z

1 0 GH _Z ~ 1 0 0 in order to obtain a coherent electromagnetic wave in the frequency band (the millimeter wave region) of GH z, the silicon coherent electromagnetic wave of a millimeter wave region more obtained the millimeter-wave oscillator tube of Jai port Tron etc. By irradiating the single crystal and coherently oscillating the induced polarization on the surface of the silicon single crystal by an alternating electric field caused by coherent electromagnetic waves, lattice vibration (phonon) can be excited.

The incident coherent electromagnetic wave 12 generated by the coherent electromagnetic wave source 10 and the irradiation coherent electromagnetic wave 1 converted from the incident coherent electromagnetic wave 12 by the irradiation optical system 11 have an oscillation frequency of 10 GHz or more and 100 GHz or less. Of the millimeter-wave band. Millimeter wave electromagnetic waves Could be generated by using a gyrotron oscillation tube, a klystron oscillation tube, or a traveling wave tube as the coherent electromagnetic wave source 10.

The millimeter-band electromagnetic wave constituting the irradiation coherent electromagnetic wave 1 applied to the silicon substrate 2 had a frequency band corresponding to the binding energy between the silicon atoms constituting the silicon substrate 2 and the impurities.

When the coherent electromagnetic wave 1 composed of millimeter-wave electromagnetic waves having an oscillation frequency of 10 GHz or more and 100 GHz or less is irradiated on the silicon substrate 2, the lattice vibration (phonon) of silicon atoms is directly excited. As a result, the impurities were activated in a thermally unbalanced state, and the activated impurities were diffused to form an ultrathin junction layer.

The activated impurities diffused at a substrate temperature of 500 ° C. or lower, which was sufficiently low that the impurities were not substantially activated in a thermal equilibrium state. Therefore, the impurities did not diffuse unnecessarily into the deep part of the silicon substrate. As a result, an ultra-shallow junction layer with a junction depth of about 20 nm or less and about 1 nm or more could be formed.

As described above, according to the present embodiment, heat treatment is performed on silicon substrate 2 so that silicon substrate 2 is in a thermal equilibrium state at a substrate temperature sufficiently low that impurities introduced into silicon substrate 2 are not activated. The recrystallization step of recrystallizing the silicon atoms constituting the silicon substrate 2 and the thermal non-equilibrium in the state where the silicon substrate 2 is maintained at a sufficiently low substrate temperature after the recrystallization step. In order to activate the impurity in the state and form an ultra-shallow junction layer, an electromagnetic wave having a predetermined frequency band is applied to the silicon substrate 2 so as to directly excite the lattice vibration (phonon) of silicon atoms. Irradiation step.

For this reason, the impurities are activated at a substrate temperature sufficiently low that the impurities are not substantially activated in a thermal equilibrium state, and the activated impurities are no longer activated. At sufficiently low substrate temperatures. As a result, the activated impurities can be prevented from being unnecessarily diffused into the deep portion of the silicon substrate 2, so that an ultra-shallow junction layer having a small junction depth can be formed.

In this embodiment, an example in which the silicon substrate 2 is used has been described, but the present invention is not limited to this. A substrate formed of a glass material, a polymer material, or the like on which a silicon film or the like is formed may be used, or a compound semiconductor substrate such as GaAs may be used. Further, a mask material such as a photo resist may be used.

Further, an example has been shown in which the irradiation coherent electromagnetic wave 1 is configured by a millimeter wave band electromagnetic wave, but the present invention is not limited to this. The irradiation coherent electromagnetic wave 1 may be configured by a continuous wave output laser beam having a frequency bandwidth of 10 GHz or more and 1 THz or less. The continuous wave output laser light can be generated, for example, by using a semiconductor laser device as the coherent electromagnetic wave source 10. Irradiating coherent electromagnetic wave 1 is also the pulse width is constituted by a 0 femtosecond than the 1 0 0 0 ultrashort pulse laser beam Fuemuto seconds (frequency bandwidth 1 TH _Z or ~ 1 0 0 TH z below) You may. The ultrashort pulse laser light can be generated, for example, by using a titanium sapphire laser device as the coherent electromagnetic wave source 10. The irradiation coherent electromagnetic wave 1 may be configured by further combining any two or more of the above-described ultrashort pulse laser light, continuous wave output laser light, and millimeter wave band electromagnetic waves.

When irradiating the silicon substrate 2 with the above-mentioned ultrashort pulse laser beam having a pulse width of not less than 100 femtoseconds and not more than 100 femtoseconds, the surface of the impurity layer 3 formed on the silicon substrate 2 is melted. However, there is no problem because the solidification of the impurity layer 3 occurs adiabatically and locally. This is because the pulse width of the irradiated ultrashort pulse is as short as 10 femtoseconds or more and less than 100 femtoseconds, so that the influence on the temperature of the entire silicon substrate 2 is affected. The sound is so small that it can be ignored.

An example is shown in which the chamber 9 provided in the electromagnetic wave irradiation unit 8 is kept in inert gases atmosphere, it may be kept at a degree of vacuum below 1 X 1 0- ⁶ T orr. Here, lTorr = 13.33.322Pa.

Although the example in which the silicon substrate 2 is heat-treated by the electric furnace 4 has been described, the heat treatment may be performed by a lamp annealing furnace.

As shown in FIGS. 1 and 2, an example in which the silicon substrate 2 on which the impurity layer 3 is formed in advance has been heat-treated has been described, but an ion source is provided inside the chamber 14 of the electric furnace 4. The impurity layer 3 may be formed by introducing an impurity into the silicon substrate 2 before the impurity layer 3 is formed. In addition, a plasma electrode is provided inside the chamber 14, diporane or the like is introduced as a gas containing impurities into the chamber 14, and impurities are introduced into the silicon substrate by plasma doping during discharge generated by the plasma electrode. 2 to form the impurity layer 3.

FIG. 4 is a cross-sectional view schematically showing an ultra-shallow junction layer forming apparatus 21 for performing both the heat treatment step and the electromagnetic wave irradiation step in the ultra-shallow junction layer forming method according to the present embodiment. The same components as those of the electric furnace 4 described above with reference to FIG. 2 and the components of the electromagnetic wave irradiation device 8 described above with reference to FIG. 3 are denoted by the same reference numerals. Therefore, a detailed description of these components will be omitted.

The ultra-shallow junction layer forming apparatus 21 includes a chamber 9A. A mounting table 13 A is provided inside the chamber 19 A. The silicon substrate 2 is mounted on the mounting table 13 A such that the impurity layer 3 is on the upper side. On the mounting table 13 A, the silicon substrate 2 is set at a substrate temperature sufficiently low that the impurities introduced into the silicon substrate 2 are not activated in a thermal equilibrium state. A flow path (not shown) through which liquid nitrogen for keeping the liquid nitrogen flows is formed. The ultra-shallow junction layer forming device 21 is provided with a liquid nitrogen supply device 24 for supplying liquid nitrogen to the mounting table 13A. The mounting table 13A is provided with a cooling device 23 for controlling the temperature of liquid nitrogen flowing through the flow path formed in the mounting table 13A.

A gas inlet pipe 5 for introducing nitrogen (N ₂ ) gas into the inside of the chamber 9 A is provided on one side wall of the chamber 9 A, and a chamber 9 is provided on the other side wall of the chamber 9 A. A gas exhaust pipe 6 for exhausting gas inside the chamber A to the outside of the chamber 9A is provided.

Inside the chamber 19A, an infrared lamp 22 for heating the silicon substrate 2 placed on the mounting table 13A is provided.

The ultra-shallow junction layer forming apparatus 21 has a coherent electromagnetic wave source 10. The coherent electromagnetic wave source 10 generates an incident coherent electromagnetic wave 12. The illumination optical system 11 is provided on the champer 9A so as to face the impurity layer 3 formed on the silicon substrate 2 mounted on the mounting table 13A. Irradiation optical system 11 converts incident coherent electromagnetic wave 12 generated by coherent electromagnetic wave source 10 into irradiation coherent electromagnetic wave 1 and irradiates silicon substrate 2 on which impurity layer 3 is formed.

In the ultra-shallow junction layer forming apparatus 21 configured as described above, after the silicon substrate 2 on which the impurity layer 3 is formed in advance is mounted on the mounting table 13A in the chamber 19A, nitrogen ( N ₂ ) Gas is introduced into chamber 19A through gas introduction pipe 5 and gas existing in chamber 19A is exhausted through gas exhaust pipe 6, whereby nitrogen inside chamber 19A is discharged. (N ₂ ) gas atmosphere.

The silicon is set so that the substrate temperature of the silicon substrate 2 becomes 700 ° C. or less, which is sufficiently low that impurities are not substantially activated in a thermal equilibrium state. The substrate 2 was heated by the infrared lamp 22. For example, the silicon substrate 2 was heated for about 5 hours so that the silicon substrate 2 was in thermal equilibrium at a substrate temperature of about 600 ° C. The silicon atoms constituting the heated silicon substrate 2 were recrystallized at a substrate temperature of about 600 ° C., and the lattice defects generated in the silicon atoms constituting the silicon substrate 2 into which the impurities were introduced were recovered. By such heat treatment, the silicon atoms constituting the silicon substrate 2 rearranged, and the lattice defects generated in the silicon atoms disappeared.

Next, liquid nitrogen was supplied from the liquid nitrogen supply device 24 to the flow path formed on the mounting table 13A on which the silicon substrate 2 subjected to the heat treatment described above was mounted. Then, due to heat conduction from liquid nitrogen flowing through the channel formed on the mounting table 13 A on which the silicon substrate 2 is mounted, the temperature is sufficiently low that impurities are not substantially activated in a thermal equilibrium state. Liquid nitrogen flowing through the flow path formed in the mounting table 13A was cooled by the cooling device 23 so that the substrate temperature of the silicon substrate 2 was maintained at 500 ° C. or lower.

After that, the incident coherent electromagnetic wave 12 was generated by the coherent electromagnetic wave source 10. The irradiation optical system 1 1 converts the incident coherent electromagnetic wave 1 2 into the irradiation coherent electromagnetic wave 1 so that the irradiation coherent electromagnetic wave 1 irradiating the silicon substrate 2 can maintain the irradiation uniformity. In a thermal non-equilibrium state where the substrate is in a thermal non-equilibrium state, the cooling device 23 was used to maintain the substrate temperature at 500 ° C. or lower so as to activate the impurities contained in the impurity layer 3. The silicon substrate 2 was irradiated with the irradiation coherent electromagnetic wave 1. The irradiation coherent electromagnetic wave 1 was constituted by a millimeter-wave band electromagnetic wave having an oscillation frequency of 10 GHz or more and 100 GHz or less, similarly to the electromagnetic wave irradiation device 8 described above.

Irradiation coherent electromagnetic wave 1 composed of millimeter-band electromagnetic waves with an oscillation frequency of 10 GHz or more and 100 GHz or less is irradiated on silicon substrate 2. As a result, the lattice vibration (phonon) of the silicon atoms was directly excited, and the impurities were activated in a thermally unbalanced state, and the activated impurities were diffused to form an ultrathin junction layer.

As in the case of the electromagnetic wave irradiation device 8 described above, the activated impurities diffused at a substrate temperature of 500 ° C. or lower, which is sufficiently low that the impurities are not substantially activated in a thermal equilibrium state. For this reason, the impurities did not needlessly diffuse into the deep portion of the silicon substrate. As a result, an ultra-shallow junction layer with a junction depth of about 20 nm or less and about 1 nm or more could be formed.

Thus, according to the ultra-shallow junction layer forming apparatus 21, the ultra-shallow junction layer could be formed by a single apparatus. By cooling the liquid nitrogen flowing through the flow path formed on the mounting table 13 A on which the silicon substrate 2 is mounted by the cooling device 23, impurities are substantially activated in a thermal equilibrium state. Although the example in which the substrate temperature of the silicon substrate 2 is maintained at 500 ° C. or less, which is sufficiently low to prevent the substrate temperature of the silicon substrate 2 from decreasing by 500 ° C. ° C or lower. Industrial applicability

As described above, according to the present invention, it is possible to provide an annealing method capable of preventing activated impurities from being unnecessarily diffused into a deep portion of a substrate.

Further, according to the present invention, it is possible to provide an ultra-shallow junction layer forming method and an ultra-shallow junction layer forming apparatus capable of forming an ultra-thin junction layer having a small junction depth.

Claims

The scope of the claims

1. An annealing method for annealing a substrate having impurities introduced therein,

By heat-treating the substrate so that the substrate is in a thermal equilibrium state at a substrate temperature sufficiently low that the impurities introduced into the substrate are not activated, the atoms constituting the substrate are recrystallized. Recrystallization process,

After the recrystallization step, while maintaining the substrate at the sufficiently low substrate temperature, to activate the impurities in a thermal non-equilibrium state

Irradiating the substrate with an electromagnetic wave having a predetermined frequency band so as to directly excite the lattice vibration (phonon) of the atom.

2. A method of forming an ultra-shallow junction layer for forming an ultra-shallow junction layer on a semiconductor substrate into which impurities are introduced,

Heat-treating the semiconductor substrate so that the semiconductor substrate is in a thermal equilibrium state at a substrate temperature sufficiently low that the impurities introduced into the semiconductor substrate are not activated; A recrystallization step of recrystallizing atoms,

After the recrystallization step, in a state where the semiconductor substrate is kept at the sufficiently low substrate temperature, the impurities are activated in a thermal non-equilibrium state to form an ultra-shallow junction layer. Irradiating the semiconductor substrate with an electromagnetic wave having a predetermined frequency band so as to directly excite lattice vibration (phonon).

3. The method for forming an ultra-shallow junction layer according to claim 2, wherein the semiconductor substrate is made of one of silicon and a silicon compound.

4. The method for forming an ultra-shallow junction layer according to claim 2, wherein in the recrystallization step, the semiconductor substrate is heat-treated at a substrate temperature of 700 ° C. or lower.

5. The method for forming an ultra-shallow junction layer according to claim 2, wherein in the recrystallization step, the semiconductor substrate is heat-treated by using either an electric furnace or a lamp heating furnace.

6. The ultra-shallow junction according to claim 2, wherein the electromagnetic wave irradiated in the electromagnetic wave irradiation step includes ultra-short pulse laser light having a pulse width of 10 to 100 femtoseconds or less. Layer forming method.

7. The ultrashallow junction layer formation according to claim 2, wherein the electromagnetic wave applied in the electromagnetic wave irradiation step includes a continuous wave output laser beam having a frequency bandwidth of 10 GHz or more and 1 THz or less. Method.

8. The electromagnetic wave to be irradiated in the electromagnetic wave irradiation process, 1 0 GH z that include a millimeter wave band electromagnetic wave having a 1 0 0 GH _Z following oscillation frequencies above, ultra-shallow junction layer according to claim 2, wherein Forming method.

9. The method for forming an ultra-shallow junction layer according to claim 2, wherein the electromagnetic wave irradiated in the electromagnetic wave irradiation step has a frequency band corresponding to a binding energy between the semiconductor atom and the impurity.

10. The ultra-shallow junction layer according to claim 2, wherein the electromagnetic wave irradiating step irradiates the electromagnetic wave to the semiconductor substrate while cooling the semiconductor substrate so as to maintain the semiconductor substrate at the sufficiently low substrate temperature. Forming method.

11. An ultra-shallow junction layer forming apparatus for forming an ultra-shallow junction layer on a semiconductor substrate into which impurities are introduced,

Heat-treating the semiconductor substrate so that the semiconductor substrate is in a thermal equilibrium state at a substrate temperature sufficiently low that the impurities introduced into the semiconductor substrate are not activated; Recrystallization means for recrystallizing atoms;

In a state in which the semiconductor substrate in which the semiconductor atoms are recrystallized by the recrystallization means is kept at the sufficiently low substrate temperature, the impurity is activated in a thermal non-equilibrium state to form an ultra-shallow junction layer. An electromagnetic wave irradiating means for irradiating the semiconductor substrate with an electromagnetic wave having a predetermined frequency band so as to directly excite the lattice vibration (phonon) of the semiconductor atoms. Ultra-shallow junction layer forming equipment.