JP2003059857A - Annealing method and method and device for forming ultra-shallow junction layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an annealing method for preventing activated impurities from unnecessarily diffusing to the deep part of a substrate. SOLUTION: The annealing method is for annealing the substrate to which impurities are introduced. The method comprises a recrystalization process for recrystallizing atoms constituting the substrate by thermally treating the substrate, so that the substrate becomes thermally balanced state at a substrate temperatures which is sufficiently low, to the degree that the impurities introduced to the substrate are not activated and an electromagnetic wave irradiation process for irradiating the substrate with electromagnetic waves having a prescribed frequency band, so that the lattice vibration (phonons) of the atoms is directly excited for activating the impurities in a thermally non-balanced state, in a state in which the substrate is kept at a sufficiently low substrate temperature after the recrystalization process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reactivates the impurities introduced into a substrate after recrystallizing the atoms to recover the lattice defects generated in the atoms constituting the substrate into which the impurities are introduced. The present invention relates to an annealing method, an ultra-shallow junction layer forming method, and an ultra-shallow junction layer forming apparatus.

[0002]

2. Description of the Related Art In recent years, in a semiconductor device such as an ultra-large scale integrated circuit (LSI) formed by using a silicon single crystal wafer as a substrate, the short channel effect is prevented as the design rule of the semiconductor device is reduced. At the same time, in order to operate the semiconductor device at high speed, it is necessary to reduce the junction depth of the diffusion layer formed in the transistor provided in the semiconductor device. For this reason, in a MOSFET or a bipolar transistor used for a dynamic immediate call storage device (DRAM) or the like, for example, the junction depth of a diffusion layer formed in a transistor having a gate with a gate length of about 100 nanometers is about 50 nanometers. It is required to be shallow.
Furthermore, the junction depth of the diffusion layer formed in a transistor having a gate with a gate length of about 50 nanometers is required to be as shallow as about 10 nanometers. Therefore, an annealing technique for activating the impurities doped in such an ultra-shallow junction layer as well as a technique for doping the ultra-shallow junction layer having a depth of about 10 to 50 nanometers with a high concentration of impurities. Is being considered.

As one of such conventional annealing techniques, an infrared rapid heat treatment (R) in which the entire substrate into which impurities are implanted is heated to about 1000 ° C. using an infrared lamp or the like.
An activation method in a thermal equilibrium state using a solid phase diffusion process by TA) is known. As a conventional technique using a laser, a technique of irradiating a 308 nm XeCl excimer laser to melt the surface of a silicon substrate and then recrystallizing silicon atoms is known as laser annealing.
Here, for example, heat treatment is performed by combining laser annealing of 0.35 J / cm ² and RTA of 800 ° C. for 10 seconds (reference document Ken-ich Goto et al.,
p931-933. , International E
electron Device Meeting 19
99 at Washington DC).

[0004]

However, the above-mentioned conventional annealing technique utilizing the solid-phase diffusion process by infrared rapid thermal annealing (RTA) in a thermal equilibrium state is effective for activating the impurity-doped layer. However, since the whole substrate is heated to a high temperature of about 1000 ° C,
There is a problem that the implanted impurities may diffuse into the deep part of the substrate. For example, a boron atom implantation layer having a depth of 20 nanometers obtained by low energy is 1
By performing the rapid heat treatment at 000 ° C. for 10 seconds, the depth becomes about 50 nanometers, and 2.
There was a problem that the depth would be 5 times.

Further, in the LSI manufacturing process which requires a plurality of impurity introduction processes, the conventional heat treatment technique heats the entire substrate to a high temperature at which the impurities diffuse, so that the diffusion exists at a position where the diffusion is unnecessary. There is a problem that even the impurities that do exist may be diffused.

Further, in the above-mentioned conventional technique of irradiating the excimer laser, unnecessary diffusion to the deep portion of the substrate is suppressed to a considerable extent, but the lattice defects generated in the atoms constituting the substrate into which impurities are introduced are sufficiently reduced. However, there is a problem that the leakage current generated in the transistor formed in the manufactured semiconductor device may be large because it cannot be recovered.

The present invention has been made to solve the above problems, and an object thereof is to provide an annealing method capable of preventing activated impurities from unnecessarily diffusing into a deep portion of a substrate. Especially.

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.

[0009]

An annealing method according to the present invention is an annealing method for annealing a substrate having impurities introduced therein, and is sufficiently low so that the impurities introduced into the substrate are not activated. A recrystallization step of recrystallizing atoms constituting the substrate by heat-treating the substrate so that the substrate is in a thermal equilibrium state at the substrate temperature; In order to activate the impurities in a thermal non-equilibrium state while keeping the substrate at a low substrate temperature, an electromagnetic wave having a predetermined frequency band is directly excited so as to directly excite the lattice vibration (phonon) of the atom. And an electromagnetic wave irradiation step of irradiating the substrate.

In the above, the lattice vibration (phonon) is
Due to thermal motion or forced vibration from the outside, atomic vibration caused by the interatomic force acting as a restoring force (spring force) according to Hooke's law between the atoms existing at the crystal lattice position according to Hooke's law It is a coupled vibration transmitted to atoms.

An ultra-shallow junction layer forming method according to the present invention is an ultra-shallow junction layer forming method for forming an ultra-shallow junction layer on a semiconductor substrate having impurities introduced therein, A recrystallization step of recrystallizing semiconductor atoms constituting the semiconductor substrate by heat-treating the semiconductor substrate so that the semiconductor substrate is in a thermal equilibrium state at a substrate temperature sufficiently low that impurities are not activated. And in order to form the ultra-shallow junction layer by activating the impurities in a thermal non-equilibrium state in a state where the semiconductor substrate is kept at the sufficiently low substrate temperature after the recrystallization step, An electromagnetic wave irradiation step of irradiating the semiconductor substrate with an electromagnetic wave having a predetermined frequency band so as to directly excite atomic lattice vibrations (phonons).

In the above description, the ultra-shallow junction layer is a diffusion layer formed in a transistor provided in a semiconductor device and has a junction depth of about 20 nanometers or less and about 1 nanometer or more.

An ultra-shallow junction layer forming device according to the present invention is an ultra-shallow junction layer forming device for forming an ultra-shallow junction layer on a semiconductor substrate having impurities introduced therein, wherein the ultra-shallow junction layer forming device is provided on the semiconductor substrate. Recrystallization means for recrystallizing semiconductor atoms constituting the semiconductor substrate by heat-treating the semiconductor substrate so that the semiconductor substrate is in a thermal equilibrium state at a substrate temperature sufficiently low that impurities are not activated. And, 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 impurities are activated in a thermal non-equilibrium state to form an ultra-shallow junction layer. In order to directly excite the lattice vibration (phonon) of the semiconductor atom, an electromagnetic wave irradiating means for irradiating the semiconductor substrate with an electromagnetic wave having a predetermined frequency band. Characterized by including the.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the ultra-shallow junction layer forming method according to the present invention, it is preferable that the semiconductor substrate is made of either silicon or a silicon compound. This is because a semiconductor device formed on a silicon substrate can be obtained. In the recrystallization process, 700
It is preferable to heat-treat the semiconductor substrate at a substrate temperature of ℃ or less. This is because the substrate temperature is sufficiently low that the impurities introduced into the semiconductor substrate are not activated in the thermal equilibrium state. In the recrystallization step, it is preferable that the semiconductor substrate be heat-treated by either an electric furnace or a lamp heating furnace. This is because the heat treatment can be performed with a simple structure. The coherent electromagnetic wave irradiated in the electromagnetic wave irradiation step preferably contains ultrashort pulsed laser light having a pulse width of 10 femtoseconds or more and 1000 femtoseconds or less.
It is preferable to include a continuous wave output laser beam having a frequency bandwidth of 1 Hz or higher and 10 GHz or lower.
It is preferable to include a millimeter wave band electromagnetic wave having an oscillation frequency of z or more and 100 GHz or less. The coherent electromagnetic wave irradiated in the electromagnetic wave irradiation step also includes
It is preferable to have a frequency band corresponding to the binding energy between the semiconductor atom and the impurity. This is because the lattice vibration (phonons) of semiconductor atoms can be excited more reliably. 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 keep the semiconductor substrate at the sufficiently low substrate temperature. Cooling ensures that the semiconductor substrate is kept at a substrate temperature that is low enough that the impurities are not substantially activated in thermal equilibrium, so that activated impurities do not needlessly diffuse deep into the semiconductor substrate. This is because it is possible to more reliably prevent

The present embodiment will be described below with reference to the drawings. FIG. 1 is a sectional view of a silicon substrate 2 having impurities introduced therein according to the present embodiment. An impurity layer 3 is formed on the surface of the silicon substrate 2. The impurity layer 3 is formed by introducing impurities into the silicon substrate 2 by, for example, an ion implantation method or a plasma doping method.

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

In the electric furnace 4 thus constructed,
After accommodating the silicon substrate 2 on which the impurity layer 3 is formed in advance in the chamber 14, nitrogen (N ₂ ) gas is introduced into the chamber 14 through the gas introduction pipe 5 to remove the gas existing in the chamber 14. By discharging the gas through the gas discharge pipe 6, the inside of the chamber 14 is filled with nitrogen (N
₂ ) A gas atmosphere was used.

The substrate temperature of the silicon substrate 2 is sufficiently low 700 that impurities are not substantially activated in the thermal equilibrium state in which the silicon substrate 2 is in the thermal equilibrium state 700.
The silicon substrate 2 was heated by the heater 7 so as to be equal to or lower than ° C. 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. Heated silicon substrate 2
Was 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 forming the silicon substrate 2 are rearranged, and the lattice defects generated in the silicon atoms disappear. An important point in this heat treatment is to set the substrate temperature at the time of recrystallizing silicon atoms to 700 ° C. or lower, which is sufficiently low so that impurities are not substantially activated in a thermal equilibrium state.

FIG. 3 is a 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 9. On the mounting table 13, the silicon substrate 2 heat-treated by the electric furnace 4 described above is mounted with the impurity layer 3 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. An 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. The irradiation optical system 11 is a coherent electromagnetic wave source 1
The incident coherent electromagnetic wave 12 generated by 0 is converted into the irradiation coherent electromagnetic wave 1 and irradiated on the silicon substrate 2 on which the impurity layer 3 is formed. The irradiation optical system 11 is also composed of predetermined optical components necessary for ensuring irradiation uniformity of the irradiation coherent electromagnetic wave 1 with which the silicon substrate 2 is irradiated. The inside of the chamber 9 is kept in an inert gas atmosphere such as nitrogen, helium, or argon.

In the electromagnetic wave irradiation device 8 thus constructed, the silicon substrate 2 heat-treated at the substrate temperature of about 600 ° C. by the above-mentioned electric furnace 4 is placed inside the chamber 9 kept in the inert gas atmosphere. When mounted on the mounting table 13 provided, the substrate temperature of the silicon substrate 2 was kept at 500 ° C. or lower, which was sufficiently low so that impurities were not substantially activated in the thermal equilibrium state.

Then, an incident coherent electromagnetic wave 12 is generated by the coherent electromagnetic wave source 10. The irradiation optical system 11 converts the incident coherent electromagnetic wave 12 into the irradiation coherent electromagnetic wave 1 so as to ensure the irradiation uniformity of the irradiation coherent electromagnetic wave 1 with which the silicon substrate 2 is thermally unbalanced. In the thermal non-equilibrium state, which is the above 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 the interatomic force acts between the atoms existing at the crystal lattice position. ing. This interatomic force acts as a restoring force (spring force) according to Hooke's law for minute displacement of an atom, so when an atom vibrates due to thermal motion or forced vibration from the outside, the vibration of that atom will be transmitted to the adjacent atom. It produces a coupled vibration. This is called lattice vibration and is called phonon because it is quantized in a solid. Furthermore, since the atomic mass, the interatomic distance, and the interatomic force corresponding to the spring constant of the restoring force have unique values depending on the individual substance, the lattice vibration (phonon) frequency and wave number are dependent on each other. And this is called the distributed relationship.

When a solid crystal is irradiated with an electromagnetic wave, an elastic strain coupled with light occurs due to a local temperature rise (thermal coupling) or a disturbance of dielectric polarization (photoelastic coupling). When the solid crystal is irradiated with light (electromagnetic wave) in the frequency range of lattice vibration (phonon) by using this elastic strain as an external force, coherent lattice vibration (phonon) with coherent phase can be excited by stimulated Raman scattering. .

For example, the phonon dispersion relation known in silicon single crystals (reference literature, eg, F. Fa.
vot and A. D. Corso, Phys. Re
v. B 60, 11427 (1999). )according to,
Lattice vibration (phonon) frequency is 10 GHz to 10 TH
exists between z.

In order to obtain a coherent electromagnetic wave in the frequency band of 10 GHz to 100 GHz (millimeter wave region), a silicon single crystal is irradiated with a coherent electromagnetic wave in the millimeter wave region obtained by a millimeter wave oscillator such as a gyrotron to obtain coherent electromagnetic waves. Lattice vibration (phonons) can be excited by coherently vibrating the dielectric polarization of the silicon single crystal surface by an alternating electric field caused by electromagnetic waves.

Incident coherent electromagnetic wave 12 generated by coherent electromagnetic wave source 10 and irradiation optical system 11
The irradiation coherent electromagnetic wave 1 converted from the incident coherent electromagnetic wave 12 is composed of a millimeter wave band electromagnetic wave having an oscillation frequency of 10 GHz or more and 100 GHz or less. 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 silicon atoms and impurities constituting the silicon substrate 2.

Oscillation frequency is 10 GHz or more and 100 GHz
When the irradiation coherent electromagnetic wave 1 composed of the following millimeter band electromagnetic waves is irradiated to the silicon substrate 2, lattice vibrations (phonons) of silicon atoms are directly excited, and impurities are activated and activated in a thermal nonequilibrium state. The impurities were diffused to form an ultra-thin bonding layer.

The activated impurities diffused at a substrate temperature of 500 ° C. or lower, which is low enough that the impurities are not substantially activated in the thermal equilibrium state. Therefore, the impurities did not unnecessarily diffuse into the deep portion of the silicon substrate. As a result, it was possible to form an ultra-shallow junction layer having a junction depth of about 20 nanometers or less and about 1 nanometer or more.

As described above, according to the present embodiment, the silicon substrate 2 is placed in a thermal equilibrium state at a substrate temperature sufficiently low that the impurities introduced into the silicon substrate 2 are not activated. A recrystallization process of recrystallizing silicon atoms constituting the silicon substrate 2 by heat treatment, and a thermal non-equilibrium state after the recrystallization process in a state where the silicon substrate 2 is kept at a sufficiently low substrate temperature. An electromagnetic wave irradiation step of irradiating the silicon substrate 2 with an electromagnetic wave having a predetermined frequency band so as to directly excite lattice vibrations (phonons) of silicon atoms in order to activate the impurities to form an ultra-shallow junction layer. Includes.

Therefore, in the thermal equilibrium state, the impurities are activated at a substrate temperature sufficiently low so that the impurities are not substantially activated, and the activated impurities diffuse at such a sufficiently low substrate temperature. As a result, it is possible to prevent the activated impurities from unnecessarily diffusing into the deep portion of the silicon substrate 2, so that it is possible to form an extremely shallow junction layer having a shallow junction depth.

In this embodiment, an example using the silicon substrate 2 is shown, but the present invention is not limited to this. A substrate made of a glass material, a polymer material, or the like on which a silicon film or the like is formed may be used.
A compound semiconductor substrate such as s may be used. Further, a mask material such as photoresist may be used.

Although the irradiation coherent electromagnetic wave 1 is composed of a millimeter wave band electromagnetic wave, the present invention is not limited to this. The irradiation coherent electromagnetic wave 1 is
You may comprise by the continuous wave output laser beam whose frequency bandwidth is 10 GHz or more and 1 THz or less. The continuous wave output laser light can be generated by using, for example, a semiconductor laser device as the coherent electromagnetic wave source 10. The irradiation coherent electromagnetic wave 1 also has a pulse width of 10 femtoseconds or more 10
00 femtoseconds or less (frequency bandwidth is 1 THz or more ~ 1
It may be configured by ultrashort pulse laser light of 00 THz or less). The ultrashort pulsed laser light can be generated by using, for example, a titanium sapphire laser device for 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-mentioned ultrashort pulse laser light, continuous wave output laser light and millimeter wave band electromagnetic wave.

Even when the surface of the impurity layer 3 formed on the silicon substrate 2 melts when the silicon substrate 2 is irradiated with the above-mentioned ultrashort pulse laser light having a pulse width of 10 femtoseconds or more and 1000 femtoseconds or less. The melting and solidification phenomenon of the impurity layer 3 occurs adiabatically and locally, so there is no problem. This is because the pulse width of the emitted ultra-short pulse is 1
This is because it is as short as 0 femtoseconds or more and 1000 femtoseconds or less, so that the influence on the temperature of the entire silicon substrate 2 is negligibly small.

Although an example in which the inside of the chamber 9 provided in the electromagnetic wave irradiation device 8 is kept in an inert gas atmosphere is shown, it may be kept at a vacuum degree of 1 × 10 ^-6 Torr or less. Here, 1 Torr = 133.322 Pa.

Although the example in which the silicon substrate 2 is heat-treated by the electric furnace 4 is shown, the heat treatment may be carried out by the lamp annealing furnace.

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

FIG. 4 is a sectional view schematically showing an ultra-shallow junction layer forming apparatus 21 for carrying out 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 components of the electric furnace 4 described above with reference to FIG. 2 and the electromagnetic wave irradiation device 8 described above with reference to FIG.
The same components as the components of the above are given the same reference numerals. Therefore, detailed description of these components will be omitted.

The ultra-shallow junction layer forming device 21 includes a chamber 9
Equipped with A. The mounting table 1 is provided inside the chamber 9A.
3A is provided. The silicon substrate 2 is mounted on the mounting table 13A with the impurity layer 3 on the upper side. The mounting table 13A is provided with a channel (not shown) through which liquid nitrogen for keeping the silicon substrate 2 at a sufficiently low substrate temperature is maintained so that impurities introduced into the silicon substrate 2 are not activated in a thermal equilibrium state. There is. 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 the 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 chamber 9A is provided on one side wall of the chamber 9A, and the other side wall of the chamber 9A is provided inside the chamber 9A. A gas discharge pipe 6 for discharging gas to the outside of the chamber 9A is provided.

Inside the chamber 9A, there is a mounting table 13A.
An infrared lamp 22 for heating the silicon substrate 2 placed on the above is provided.

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

In the ultra-shallow junction layer forming apparatus 21 thus constructed, the silicon substrate 2 on which the impurity layer 3 is formed in advance is placed on the placing table 13A in the chamber 9A, and then nitrogen (N ₂ ) A gas is introduced into the chamber 9A through the gas introduction pipe 5, and the gas existing inside the chamber 9A is discharged through the gas discharge pipe 6, whereby the inside of the chamber 9A is made into a nitrogen (N ₂ ) gas atmosphere.

Then, the silicon substrate 2 was heated by the infrared lamp 22 so that the substrate temperature of the silicon substrate 2 was 700 ° C. or lower, which was sufficiently low so that impurities were not substantially activated in the thermal equilibrium state. 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. About 6 silicon atoms are contained in the heated silicon substrate 2.
It was recrystallized at a substrate temperature of 00 ° 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 forming the silicon substrate 2 were 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 in the mounting table 13A on which the silicon substrate 2 which had been subjected to the above-mentioned heat treatment was mounted. And
Due to the heat conduction from the liquid nitrogen flowing through the flow path formed in the mounting table 13A on which the silicon substrate 2 is mounted, the silicon is kept at 500 ° C. or lower, which is sufficiently low that impurities are not substantially activated in a thermal equilibrium state. The liquid nitrogen flowing through the flow path formed in the mounting table 13A was cooled by the cooling device 23 so as to maintain the substrate temperature of the substrate 2.

After that, the incident coherent electromagnetic wave 12 was generated by the coherent electromagnetic wave source 10. The irradiation optical system 11 converts the incident coherent electromagnetic wave 12 into the irradiation coherent electromagnetic wave 1 so as to ensure the irradiation uniformity of the irradiation coherent electromagnetic wave 1 with which the silicon substrate 2 is thermally unbalanced. In a thermal non-equilibrium state, which is in such a state, the irradiation coherent electromagnetic wave 1 is applied to the silicon substrate 2 kept at the substrate temperature of 500 ° C. or lower by the cooling device 23 so as to activate the impurities contained in the impurity layer 3. . The irradiating coherent electromagnetic wave 1 has an oscillation frequency of 10 GH, like the electromagnetic wave irradiating device 8 described above.
It is constituted by millimeter wave electromagnetic waves of z or more and 100 GHz or less.

Oscillation frequency is 10 GHz or more and 100 GHz
When the irradiation coherent electromagnetic wave 1 composed of the following millimeter band electromagnetic waves is irradiated to the silicon substrate 2, lattice vibrations (phonons) of silicon atoms are directly excited, and impurities are activated and activated in a thermal nonequilibrium state. The impurities were diffused to form an ultra-thin bonding layer.

Similar to the electromagnetic wave irradiation device 8 described above, the activated impurities diffused at a substrate temperature of 500 ° C. or lower, which is low enough that the impurities are not substantially activated in the thermal equilibrium state. Therefore, the impurities did not unnecessarily diffuse into the deep portion of the silicon substrate. As a result, the junction depth is about 2
It was possible to form an ultra-shallow junction layer of 0 nanometer or less and about 1 nanometer or more.

As described above, according to the ultra-shallow junction layer forming device 21, the ultra-shallow junction layer can be formed by a single device. The mounting table 13 on which the silicon substrate 2 is mounted
The liquid nitrogen flowing through the flow path formed in A is cooled by the cooling device 23.
Although an example is shown in which the substrate temperature of the silicon substrate 2 is kept at 500 ° C. or lower, which is sufficiently low so that impurities are not substantially activated in the thermal equilibrium state, by cooling by The substrate temperature of the silicon substrate 2 may be kept at 500 ° C. or lower.

[0052]

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

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

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor substrate having an impurity introduced according to the present embodiment.

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

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

FIG. 4 is a cross-sectional view schematically showing an ultra-shallow junction layer forming device for performing both the recrystallization step and the electromagnetic wave irradiation step according to the present embodiment.

[Explanation of symbols]

1 Irradiation coherent electromagnetic wave 2 Silicon substrate 3 Impurity layer 4 electric furnace 5 gas introduction pipes 6 gas discharge pipe 7 heater 8 Electromagnetic wave irradiation device 9 chambers 10 Coherent electromagnetic sources 11 Irradiation optical system 12 Incident coherent electromagnetic waves 13 table 14 chambers 21 Ultra shallow junction layer forming equipment 22 Infrared lamp 23 Cooling device 24 Liquid Nitrogen Supply Device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Bunji Mizuno             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (11)

[Claims] 1. An annealing method for annealing a substrate having impurities introduced therein, wherein the substrate is in a thermal equilibrium state at a sufficiently low substrate temperature that the impurities introduced into the substrate are not activated. By heat-treating the substrate, a recrystallization step of recrystallizing atoms constituting the substrate, and a state in which the substrate is kept at the sufficiently low substrate temperature after the recrystallization step, An electromagnetic wave irradiating step of irradiating the substrate with an electromagnetic wave having a predetermined frequency band so as to directly excite the lattice vibration (phonon) of the atom in order to activate the impurities in the thermal non-equilibrium state. An annealing method characterized by the above. 2. An ultra-shallow junction layer forming method for forming an ultra-shallow junction layer on a semiconductor substrate having impurities introduced therein, the substrate being sufficiently low that the impurities introduced into the semiconductor substrate are not activated. By heat-treating the semiconductor substrate so that the semiconductor substrate is in a thermal equilibrium state at a temperature, a recrystallization step of recrystallizing semiconductor atoms forming the semiconductor substrate, and after the recrystallization step , In the state where the semiconductor substrate is kept at the sufficiently low substrate temperature, the lattice vibration (phonon) of the semiconductor atom is directly excited in order to activate the impurities and form an ultra-shallow junction layer in the thermal non-equilibrium state. As described above, the method for forming an ultra-shallow junction layer, which comprises irradiating the semiconductor substrate with an electromagnetic wave having a predetermined frequency band. 3. The semiconductor substrate is composed of either silicon or a silicon compound.
The method for forming an ultra-shallow junction layer as described. 4. The ultra-shallow junction layer forming method 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 either an electric furnace or a lamp heating furnace. 6. The ultra-shallow junction layer formation according to claim 2, wherein the electromagnetic wave irradiated in the electromagnetic wave irradiation step includes ultrashort pulse laser light having a pulse width of 10 femtoseconds to 1000 femtoseconds. Method. 7. The method for forming an ultra-shallow junction layer according to claim 2, wherein the electromagnetic wave irradiated in the electromagnetic wave irradiation step includes continuous wave output laser light having a frequency bandwidth of 10 GHz or more and 1 THz or less. 8. The electromagnetic wave irradiated in the electromagnetic wave irradiation step includes a millimeter wave band electromagnetic wave having an oscillation frequency of 10 GHz or more and 100 GHz or less.
The method for forming an ultra-shallow junction layer as described. 9. The ultra-shallow junction layer formation 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. Method. 10. The ultra-shallow junction according to claim 2, wherein the electromagnetic wave irradiation step irradiates the semiconductor substrate with the electromagnetic wave while cooling the semiconductor substrate so as to keep the semiconductor substrate at the sufficiently low substrate temperature. Layer forming method. 11. An ultra-shallow junction layer forming apparatus for forming an ultra-shallow junction layer on a semiconductor substrate having impurities introduced therein, the substrate being sufficiently low that the impurities introduced into the semiconductor substrate are not activated. Recrystallization means for recrystallizing semiconductor atoms constituting the semiconductor substrate by heat treating the semiconductor substrate so that the semiconductor substrate is in a thermal equilibrium state at a temperature; and the semiconductor by the recrystallization means. In the state where the semiconductor substrate in which the atoms are recrystallized is kept at the sufficiently low substrate temperature, the lattice vibration of the semiconductor atoms (in order to activate the impurities to form an ultra-shallow junction layer in a thermal non-equilibrium state). An electromagnetic wave irradiating means for irradiating the semiconductor substrate with an electromagnetic wave having a predetermined frequency band so as to directly excite phonons). Bonding layer forming apparatus.