WO2007013753A1 - Semiconductor doping method using pulsed inductively coupled plasma and system therefor - Google Patents

Semiconductor doping method using pulsed inductively coupled plasma and system therefor Download PDF

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Publication number
WO2007013753A1
WO2007013753A1 PCT/KR2006/002909 KR2006002909W WO2007013753A1 WO 2007013753 A1 WO2007013753 A1 WO 2007013753A1 KR 2006002909 W KR2006002909 W KR 2006002909W WO 2007013753 A1 WO2007013753 A1 WO 2007013753A1
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Prior art keywords
pulse
vacuum chamber
wafer
plasma
high voltage
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PCT/KR2006/002909
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French (fr)
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Bong-Ju Lee
Seunghee Han
Hag-Joo Lee
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Sem Technology Co., Ltd
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Publication of WO2007013753A1 publication Critical patent/WO2007013753A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/26—Bombardment with radiation
    • H01L21/263—Bombardment with radiation with high-energy radiation
    • H01L21/265—Bombardment with radiation with high-energy radiation producing ion implantation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/223—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a gaseous phase
    • H01L21/2236—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a gaseous phase from or into a plasma phase
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082—Radio frequency generated discharge
    • H01J37/321—Radio frequency generated discharge the radio frequency energy being inductively coupled to the plasma
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32412—Plasma immersion ion implantation

Definitions

  • the present invention relates to a semiconductor doping method using pulsed inductively coupled plasma and a system for the same, more particularly to a semiconductor doping method using pulsed inductively coupled plasma and a system thereof for doping impurities in order to form an ultra- shallow junction of very large scale integration (VLSI) semiconductor.
  • VLSI very large scale integration
  • Ion implantation using ion beam has been the most widely utilized technique for doping impurities such as B (boron), P (phosphorus), As (arsenic), etc. into a semiconductor. But, as the semiconductors become more and more integrated, a shallow ion implantation depth of dozens of nanometers or less is required for the doping. To attain the ion implantation depth, the ion beam energy of the ion implantation equipment has to be lowered down to 10 keV to hundreds of electron volts. But, when ion implantation is performed with such a low energy, the current of the ion beam decreases because of the phenomenon called "Child-Langmuir current limit", resulting in significantly decreased speed of ion implantation.
  • an ion beam scattering device is required to uniformly implant ions on a large wafer and an additional equipment is needed to prevent charge concentration, which may result in the destruction of thin insulating layers inside the VLSI semiconductor. Accordingly, the ion implantation becomes very expensive.
  • 4,764,394, Korean Patent No. 137,704 is a technique enabling surface modification of three-dimensional objects having a large surface area. It is also advantageous over the conventional ion implantation using ion beam for the purpose of doping impurities into a semiconductor. That is, since the technique is not affected by the Child-Langmuir current limit, it enables very fast and uniform ion implantation on a large-sized wafer and does not require an ion beam scattering equipment, etc. Also, since it uses plasma, the problem of charge concentration at the surface of the wafer is solved. And, with simple equipment, clustering with other semiconductor processing equipments is facile and the cost of equipment can be reduced significantly.
  • the conventional semiconductor doping using plasma implants ions into the surface of a wafer using continuous plasma generated from such gas as B H , BF , PH , AsH , etc. and high voltage pulse.
  • continuous plasma generated from such gas as B H , BF , PH , AsH , etc. and high voltage pulse.
  • utilization of the continuous plasma is disad- vantageous in that the plasma is generated even when the pulse of high voltage is not being applied, which results in the formation of thin films or impurities on the surface of the wafer and badly aggravates the ion implantation characteristics.
  • the present invention was made to solve the problems of the conventional wafer doping techniques using plasma.
  • An object of the present invention is to provide an advanced semiconductor doping method which improves the problems of the impurity doping method using continuous plasma by using pulsed inductively-coupled plasma and enables plasma generation even at low pressure favorable for ion implantation and a system thereof.
  • the present invention provides a semiconductor doping method using pulsed inductively-coupled plasma, which comprises the steps of: positioning a wafer on a wafer sample stage in a vacuum chamber; supplying a plasma source gas into the vacuum chamber; and applying RF (radio-frequency) pulse to the gas inside the vacuum chamber through a dielectric plate, which forms one side of the vacuum chamber, using an antenna equipped at the outside to form pulsed inductively-coupled plasma while applying negative high voltage pulse to the wafer sample stage as synchronized with the RF pulse, so that plasma ions are doped into the surface of the wafer.
  • RF radio-frequency
  • the semiconductor doping method in accordance with the present invention is capable of generating plasma at low pressure favorable for plasma ion implantation and the problem of the conventional method using continuous plasma, or the deterioration of doping quality caused by the deposition of films and mixing of impurity particles on the wafer surface while the high voltage pulse is not being applied, can be effectively prevented. Further, the semiconductor doping method of the present invention is advantageous in that, since pulsed RF which offers larger output than continuous RF is used, the plasma density can be increased and the speed and uniformity of impurity doping can be improved.
  • Fig. 1 is a graph showing the voltage applied to the wafer sample in the convent ional semiconductor doping method using continuous plasma.
  • Fig. 2 is a graph showing the voltage applied to the wafer sample in the semiconductor doping method of the present invention using pulsed inductively-coupled plasma.
  • FIG. 3 is a schematic diagram showing a preferred embodiment of the semiconductor doping system using pulsed inductively-coupled plasma in accordance with the present invention.
  • Fig. 4 is a graph showing the SIMS analysis result of the wafer doped with boron in
  • Example 1 in accordance with the present invention. Mode for the Invention
  • the present invention provides a semiconductor doping method using pulsed inductively-coupled plasma, which comprises the steps of: positioning a wafer on a wafer sample stage in a vacuum chamber; supplying a plasma source gas into the vacuum chamber; and applying RF pulse to the gas inside the vacuum chamber through a dielectric plate, which forms one side of the vacuum chamber, using an antenna equipped at the outside to form pulsed inductively-coupled plasma while applying negative high voltage pulse to the wafer sample as synchronized with the RF pulse, so that the ions in the plasma state are doped into the surface of the wafer sample.
  • a pulsed RF having a pulse width of 5 ⁇ s to 500 ⁇ s and a pulse frequency of 10 Hz to 100 kHz is used.
  • the pulsed RF and the high voltage pulse are synchronized with each other.
  • B 2 H 6 or BF 3 gas is used for p-type doping and PH 3 or
  • AsH gas is used for n-type doping.
  • the present invention also provides a semiconductor doping system using pulsed inductively-coupled plasma, which comprises: a vacuum chamber inside of which is maintained in vacuum state; a dielectric plate made of quartz or alumina which is equipped on one side of the vacuum chamber; an antenna which is equipped at the outside of the dielectric plate and applies RF pulse; an RF pulse generator which supplies RF pulse to the RF antenna; a wafer sample stage which is set up inside the vacuum chamber opposing the RF antenna and accommodates a wafer sample; a negative high voltage pulse supplier which supplies negative (-) high voltage pulse to the wafer sample as synchronized with the RF pulse; and a gas supplier which supplies the plasma source gas to the vacuum chamber.
  • the semiconductor doping system of the present invention may further comprise a matcher which connects and electrically matches the RF pulse generator with the RF antenna and a plurality of permanent magnets which are equipped on the inner wall or outer wall of the vacuum chamber and offer uniform plasma distribution inside the vacuum chamber using magnetic field.
  • the wafer sample stage equipped inside the vacuum chamber is electrically insulated from the vacuum chamber.
  • the wafer sample stage shall have a larger diameter than the wafer to be positioned on it to ensure uniform doping of the wafer.
  • the wafer sample stage is equipped with such a current measuring device as Faraday cup inside it to enable the measurement of ion implantation.
  • the semiconductor doping system of the present invention may further comprise a plasma measuring device to measure the characteristics of the pulsed plasma generated inside the vacuum chamber and a gas control device to control the amount of the gas supplied into the vacuum chamber by the gas supplier.
  • Fig. 1 is a graph showing the voltage applied to the wafer sample in the conventional semiconductor doping method using continuous plasma.
  • Fig. 2 is a graph showing the voltage applied to the wafer sample in the semiconductor doping method of the present invention using pulsed inductively-coupled plasma.
  • Fig. 3 is a schematic of a preferred embodiment of the semiconductor doping system using pulsed inductively-coupled plasma in accordance with the present invention.
  • Fig. 4 is a graph showing the SIMS (secondary ion mass spectroscopy) analysis result of the wafer doped with boron in Example 1, in accordance with the present invention.
  • SIMS secondary ion mass spectroscopy
  • a wafer sample (7) is positioned on a wafer sample stage (6) installed inside a vacuum chamber (1) using a wafer load lock system (20). Then, a plasma source gas is supplied into the vacuum chamber from a gas supply container (13) by a gas controller (12). The pressure of the gas supplied into the vacuum chamber is maintained at an adequate value using an ion gauge (11) or other vacuum gauge.
  • a pulsed RF power (21) generated by a pulsed RF generator (3) is applied to an RF antenna (2) equipped outside of a dielectric plate (18), which forms one side of the vacuum chamber, passing through an impedance matcher (4). The RF power (21) applied to the antenna (2) ionizes the gas inside the vacuum chamber and generates inductively coupled plasma (5).
  • the resultant inductively coupled plasma generated by the pulsed RF power is not a continuous plasma but a pulsed plasma. While the pulsed RF power (21) is applied, high voltage pulse (22) generated by a high voltage pulse generator (14) is applied to the wafer (7) on the wafer sample stage (6), as synchronized with the pulsed RF power (21). The high voltage pulse (22) extracts ions from the pulsed inductively-coupled plasma (5) generated by the pulsed RF power (21) and implants them on the surface of the wafer (7).
  • the aforementioned wafer doping system using pulsed inductively-coupled plasma also comprises a vacuum pump (9) and the vacuum chamber (1) should be earthed by a ground (19).
  • a plurality of permanent magnets may be equipped on the walls of the vacuum chamber (1). They form a magnetic field, so that the pulsed inductively-coupled plasma (5) generated inside the vacuum chamber (1) may be distributed uniformly inside the vacuum chamber (1).
  • the characteristics and distribution of the pulsed inductively-coupled plasma inside the vacuum chamber (1) are measured using a plasma measuring device (10) such as Langmuir probe.
  • the wafer sample stage (6) is equipped with an ion implantation current measuring device (8) such as Faraday cup. It is also equipped with a current measuring device (15) and a voltage measuring device (16) for measuring the current and the voltage applied to the wafer sample stage (6), respectively. The signals of these devices are transmitted to a doping system controller (17), so that the entire doping system can be controlled adequately.
  • an ion implantation current measuring device (8) such as Faraday cup. It is also equipped with a current measuring device (15) and a voltage measuring device (16) for measuring the current and the voltage applied to the wafer sample stage (6), respectively.
  • the signals of these devices are transmitted to a doping system controller (17), so that the entire doping system can be controlled adequately.
  • This wafer doping method is advantageous in that, since pulsed inductively-coupled plasma is used, plasma can be generated at low pressure favorable for ion implantation and the problem of the conventional method using continuous plasma, or the deterioration of doping quality caused by the deposition of films and mixing of impurity particles on the wafer surface while the high voltage pulse is not being applied, can be effectively prevented. Further, since pulsed RF which offers larger output than continuous RF is used, the plasma density can be increased and the speed and uniformity of impurity doping can be improved.
  • the pulsed RF power (21) which is applied to the RF antenna (2) and generates inductively-coupled pulsed plasma, has an RF frequency of 1 MHz to 50 MHz, a pulse width of 5 ⁇ s to 500 ⁇ s and a pulse frequency of 10 Hz to 100 kHz.
  • the negative high voltage pulse (22) applied to the wafer sample (7) has a pulse width of 5 ⁇ s to 500 ⁇ s, a pulse frequency of 10 Hz to 100 kHz and a voltage of -0.1 kV to -20 kV.
  • the pulsed RF power and the high voltage pulse should be synchronized with each other.
  • the pulsed RF power (21) and the high voltage pulse (22) are synchronized with each other with the same frequency, their pulse widths and relative positions on the time axis may be varied to optimize the doping characteristics.
  • the wafer sample stage (6) shall have a larger diameter than the wafer (7) to be positioned on it to ensure uniform doping of the wafer. Further, the wafer sample stage is equipped with an ion implantation current measuring device (8) such as Faraday cup to enable accurate measurement of ion implantation.
  • an ion implantation current measuring device (8) such as Faraday cup to enable accurate measurement of ion implantation.
  • a silicon wafer (7) having a diameter of 100 mm was positioned on a 200 mm-wide wafer sample stage (6) of a wafer doping system using pulsed inductively-coupled plasma.
  • Boron (B) doping test was performed using pulsed RF (21) and high voltage pulse (22), while maintaining the pressure of B 2 H 6 gas at 1 mTorr. Pulsed RF power of
  • the boron-doped silicon wafer was activated under nitrogen atmosphere by rapid thermal annealing.
  • SIMS analysis was performed before and after the thermal annealing (Fig. 4). Further, sheet resistance of the silicon wafer was measured after the thermal annealing by the 4-point probing technique.
  • boron was doped up to the shallow thickness of 250 A from the silicon surface. The depth increased to about 350 A after the thermal annealing. Sheet resistance of the silicon wafer after boron doping and thermal annealing was 330 ⁇ /sq.

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Abstract

Provided is a semiconductor doping method using pulsed inductively-coupled plasma, which comprises the steps of: positioning a wafer on a wafer sample stage in a vacuum chamber; supplying a plasma source gas into the vacuum chamber; and applying RF (radio-frequency) pulse to the gas inside the vacuum chamber through a dielectric plate, which forms one side of the vacuum chamber, using an antenna equipped at the outside to form pulsed inductively- coupled plasma while applying negative high voltage pulse to the wafer sample stage as synchronized with the RF pulse, so that plasma ions are doped into the surface of the wafer. Since pulsed inductively-coupled plasma is used, the problem of the impurity doping method using continuous plasma is solved and plasma generation becomes possible even at low pressure.

Description

Description
SEMICONDUCTOR DOPING METHOD USING PULSED INDUCTIVELY COUPLED PLASMA AND SYSTEM THEREFOR
Technical Field
[1] The present invention relates to a semiconductor doping method using pulsed inductively coupled plasma and a system for the same, more particularly to a semiconductor doping method using pulsed inductively coupled plasma and a system thereof for doping impurities in order to form an ultra- shallow junction of very large scale integration (VLSI) semiconductor. Background Art
[2] Ion implantation using ion beam has been the most widely utilized technique for doping impurities such as B (boron), P (phosphorus), As (arsenic), etc. into a semiconductor. But, as the semiconductors become more and more integrated, a shallow ion implantation depth of dozens of nanometers or less is required for the doping. To attain the ion implantation depth, the ion beam energy of the ion implantation equipment has to be lowered down to 10 keV to hundreds of electron volts. But, when ion implantation is performed with such a low energy, the current of the ion beam decreases because of the phenomenon called "Child-Langmuir current limit", resulting in significantly decreased speed of ion implantation. Further, an ion beam scattering device is required to uniformly implant ions on a large wafer and an additional equipment is needed to prevent charge concentration, which may result in the destruction of thin insulating layers inside the VLSI semiconductor. Accordingly, the ion implantation becomes very expensive.
[3] Plasma ion implantation using plasma and high voltage pulse (U.S. Patent No.
4,764,394, Korean Patent No. 137,704) is a technique enabling surface modification of three-dimensional objects having a large surface area. It is also advantageous over the conventional ion implantation using ion beam for the purpose of doping impurities into a semiconductor. That is, since the technique is not affected by the Child-Langmuir current limit, it enables very fast and uniform ion implantation on a large-sized wafer and does not require an ion beam scattering equipment, etc. Also, since it uses plasma, the problem of charge concentration at the surface of the wafer is solved. And, with simple equipment, clustering with other semiconductor processing equipments is facile and the cost of equipment can be reduced significantly.
[4] The conventional semiconductor doping using plasma implants ions into the surface of a wafer using continuous plasma generated from such gas as B H , BF , PH , AsH , etc. and high voltage pulse. However, utilization of the continuous plasma is disad- vantageous in that the plasma is generated even when the pulse of high voltage is not being applied, which results in the formation of thin films or impurities on the surface of the wafer and badly aggravates the ion implantation characteristics.
[5] In order to solve this problem of continuous plasma, a technique of directly generating plasma using high voltage pulse applied to a wafer (U.S. Patent No. 5,654,043), a technique of generating plasma through pulsed cold-cathode discharge (U.S. Patent No. 5,354,381), a technique of generating plasma using an auxiliary electrode (Korean Unexamined Patent No. 2002-0047294), etc. have been proposed, so that the plasma is generated only while the high voltage pulse is being applied. However, utilization of the pulsed cold-cathode is disadvantageous in that the cold- cathode material may contaminate the wafer. And, the plasma using high voltage pulse or auxiliary electrode is problematic in that plasma is not generated at low pressure because a direct current voltage is used. A high pressure of dozens of millitorr or higher is required, at which pressure the ion implantation energy is reduced and varied because of collision with the ion source gases. Disclosure of Invention Technical Problem
[6] The present invention was made to solve the problems of the conventional wafer doping techniques using plasma. An object of the present invention is to provide an advanced semiconductor doping method which improves the problems of the impurity doping method using continuous plasma by using pulsed inductively-coupled plasma and enables plasma generation even at low pressure favorable for ion implantation and a system thereof. Technical Solution
[7] The present invention provides a semiconductor doping method using pulsed inductively-coupled plasma, which comprises the steps of: positioning a wafer on a wafer sample stage in a vacuum chamber; supplying a plasma source gas into the vacuum chamber; and applying RF (radio-frequency) pulse to the gas inside the vacuum chamber through a dielectric plate, which forms one side of the vacuum chamber, using an antenna equipped at the outside to form pulsed inductively-coupled plasma while applying negative high voltage pulse to the wafer sample stage as synchronized with the RF pulse, so that plasma ions are doped into the surface of the wafer.
Advantageous Effects
[8] Since pulsed inductively-coupled plasma is used, the semiconductor doping method in accordance with the present invention is capable of generating plasma at low pressure favorable for plasma ion implantation and the problem of the conventional method using continuous plasma, or the deterioration of doping quality caused by the deposition of films and mixing of impurity particles on the wafer surface while the high voltage pulse is not being applied, can be effectively prevented. Further, the semiconductor doping method of the present invention is advantageous in that, since pulsed RF which offers larger output than continuous RF is used, the plasma density can be increased and the speed and uniformity of impurity doping can be improved. Brief Description of the Drawings
[9] Fig. 1 is a graph showing the voltage applied to the wafer sample in the convent ional semiconductor doping method using continuous plasma.
[10] Fig. 2 is a graph showing the voltage applied to the wafer sample in the semiconductor doping method of the present invention using pulsed inductively-coupled plasma.
[11] Fig. 3 is a schematic diagram showing a preferred embodiment of the semiconductor doping system using pulsed inductively-coupled plasma in accordance with the present invention.
[12] Fig. 4 is a graph showing the SIMS analysis result of the wafer doped with boron in
Example 1, in accordance with the present invention. Mode for the Invention
[13] The present invention provides a semiconductor doping method using pulsed inductively-coupled plasma, which comprises the steps of: positioning a wafer on a wafer sample stage in a vacuum chamber; supplying a plasma source gas into the vacuum chamber; and applying RF pulse to the gas inside the vacuum chamber through a dielectric plate, which forms one side of the vacuum chamber, using an antenna equipped at the outside to form pulsed inductively-coupled plasma while applying negative high voltage pulse to the wafer sample as synchronized with the RF pulse, so that the ions in the plasma state are doped into the surface of the wafer sample.
[14] For the pulsed RF source, a pulsed RF having a pulse width of 5μs to 500μs and a pulse frequency of 10 Hz to 100 kHz is used. For the negative (-) high voltage pulse applied to the wafer sample, a pulse having a pulse width of 5 μs to 500 μs, a pulse frequency of 10 Hz to 100 kHz and a voltage of -0.1 kV to -20 kV is used. The pulsed RF and the high voltage pulse are synchronized with each other.
[15] For the plasma source gas, B 2 H 6 or BF 3 gas is used for p-type doping and PH 3 or
AsH gas is used for n-type doping.
[16] The present invention also provides a semiconductor doping system using pulsed inductively-coupled plasma, which comprises: a vacuum chamber inside of which is maintained in vacuum state; a dielectric plate made of quartz or alumina which is equipped on one side of the vacuum chamber; an antenna which is equipped at the outside of the dielectric plate and applies RF pulse; an RF pulse generator which supplies RF pulse to the RF antenna; a wafer sample stage which is set up inside the vacuum chamber opposing the RF antenna and accommodates a wafer sample; a negative high voltage pulse supplier which supplies negative (-) high voltage pulse to the wafer sample as synchronized with the RF pulse; and a gas supplier which supplies the plasma source gas to the vacuum chamber.
[17] The semiconductor doping system of the present invention may further comprise a matcher which connects and electrically matches the RF pulse generator with the RF antenna and a plurality of permanent magnets which are equipped on the inner wall or outer wall of the vacuum chamber and offer uniform plasma distribution inside the vacuum chamber using magnetic field.
[18] The wafer sample stage equipped inside the vacuum chamber is electrically insulated from the vacuum chamber. The wafer sample stage shall have a larger diameter than the wafer to be positioned on it to ensure uniform doping of the wafer. Further, the wafer sample stage is equipped with such a current measuring device as Faraday cup inside it to enable the measurement of ion implantation.
[19] The semiconductor doping system of the present invention may further comprise a plasma measuring device to measure the characteristics of the pulsed plasma generated inside the vacuum chamber and a gas control device to control the amount of the gas supplied into the vacuum chamber by the gas supplier.
[20] Hereinafter, the embodiment of the present invention will be described in detail with reference to accompanying drawings.
[21] Fig. 1 is a graph showing the voltage applied to the wafer sample in the conventional semiconductor doping method using continuous plasma. Fig. 2 is a graph showing the voltage applied to the wafer sample in the semiconductor doping method of the present invention using pulsed inductively-coupled plasma. Fig. 3 is a schematic of a preferred embodiment of the semiconductor doping system using pulsed inductively-coupled plasma in accordance with the present invention. And, Fig. 4 is a graph showing the SIMS (secondary ion mass spectroscopy) analysis result of the wafer doped with boron in Example 1, in accordance with the present invention.
[22] Now, the principle of the wafer doping method using pulsed inductively-coupled plasma in accordance with the present invention will be described referring to Fig. 3.
[23] A wafer sample (7) is positioned on a wafer sample stage (6) installed inside a vacuum chamber (1) using a wafer load lock system (20). Then, a plasma source gas is supplied into the vacuum chamber from a gas supply container (13) by a gas controller (12). The pressure of the gas supplied into the vacuum chamber is maintained at an adequate value using an ion gauge (11) or other vacuum gauge. A pulsed RF power (21) generated by a pulsed RF generator (3) is applied to an RF antenna (2) equipped outside of a dielectric plate (18), which forms one side of the vacuum chamber, passing through an impedance matcher (4). The RF power (21) applied to the antenna (2) ionizes the gas inside the vacuum chamber and generates inductively coupled plasma (5). The resultant inductively coupled plasma generated by the pulsed RF power is not a continuous plasma but a pulsed plasma. While the pulsed RF power (21) is applied, high voltage pulse (22) generated by a high voltage pulse generator (14) is applied to the wafer (7) on the wafer sample stage (6), as synchronized with the pulsed RF power (21). The high voltage pulse (22) extracts ions from the pulsed inductively-coupled plasma (5) generated by the pulsed RF power (21) and implants them on the surface of the wafer (7).
[24] The aforementioned wafer doping system using pulsed inductively-coupled plasma also comprises a vacuum pump (9) and the vacuum chamber (1) should be earthed by a ground (19). Although not illustrated in the figure, a plurality of permanent magnets may be equipped on the walls of the vacuum chamber (1). They form a magnetic field, so that the pulsed inductively-coupled plasma (5) generated inside the vacuum chamber (1) may be distributed uniformly inside the vacuum chamber (1). The characteristics and distribution of the pulsed inductively-coupled plasma inside the vacuum chamber (1) are measured using a plasma measuring device (10) such as Langmuir probe.
[25] The wafer sample stage (6) is equipped with an ion implantation current measuring device (8) such as Faraday cup. It is also equipped with a current measuring device (15) and a voltage measuring device (16) for measuring the current and the voltage applied to the wafer sample stage (6), respectively. The signals of these devices are transmitted to a doping system controller (17), so that the entire doping system can be controlled adequately.
[26] This wafer doping method is advantageous in that, since pulsed inductively-coupled plasma is used, plasma can be generated at low pressure favorable for ion implantation and the problem of the conventional method using continuous plasma, or the deterioration of doping quality caused by the deposition of films and mixing of impurity particles on the wafer surface while the high voltage pulse is not being applied, can be effectively prevented. Further, since pulsed RF which offers larger output than continuous RF is used, the plasma density can be increased and the speed and uniformity of impurity doping can be improved.
[27] Although not limiting the scope of the present invention, the pulsed RF power (21), which is applied to the RF antenna (2) and generates inductively-coupled pulsed plasma, has an RF frequency of 1 MHz to 50 MHz, a pulse width of 5 μs to 500 μs and a pulse frequency of 10 Hz to 100 kHz. And, although not limiting the scope of the present invention, the negative high voltage pulse (22) applied to the wafer sample (7) has a pulse width of 5 μs to 500 μs, a pulse frequency of 10 Hz to 100 kHz and a voltage of -0.1 kV to -20 kV. The pulsed RF power and the high voltage pulse should be synchronized with each other. Although the pulsed RF power (21) and the high voltage pulse (22) are synchronized with each other with the same frequency, their pulse widths and relative positions on the time axis may be varied to optimize the doping characteristics.
[28] The wafer sample stage (6) shall have a larger diameter than the wafer (7) to be positioned on it to ensure uniform doping of the wafer. Further, the wafer sample stage is equipped with an ion implantation current measuring device (8) such as Faraday cup to enable accurate measurement of ion implantation.
[29] Practical and preferred embodiment of the present invention is illustrated in the following example. However, it will be appreciated that those skilled in the art may, in consideration of this disclosure, make modifications and improvements within the spirit and scope of the present invention.
[30] Example 1
[31] A silicon wafer (7) having a diameter of 100 mm was positioned on a 200 mm-wide wafer sample stage (6) of a wafer doping system using pulsed inductively-coupled plasma. Boron (B) doping test was performed using pulsed RF (21) and high voltage pulse (22), while maintaining the pressure of B 2 H 6 gas at 1 mTorr. Pulsed RF power of
13.56 MHz, 1 kW, a pulse width of 30 μs and a pulse frequency of 2 kHz was applied from a pulsed RF generator (3) to generated pulsed inductively-coupled plasma. And, negative high voltage pulse of - 1 kV, a pulse width of 20 μs and a pulse frequency of 2 kHz was applied to the wafer sample stage (6), as synchronized with the pulsed RF power. Doping was performed for 20 seconds (2x10 /cm ).
[32] The boron-doped silicon wafer was activated under nitrogen atmosphere by rapid thermal annealing. SIMS analysis was performed before and after the thermal annealing (Fig. 4). Further, sheet resistance of the silicon wafer was measured after the thermal annealing by the 4-point probing technique.
[33] As shown in Fig. 4, boron was doped up to the shallow thickness of 250 A from the silicon surface. The depth increased to about 350 A after the thermal annealing. Sheet resistance of the silicon wafer after boron doping and thermal annealing was 330 Ω/sq.
[34] As described, it should be evident that the present invention can be implemented through a variety of configurations in the aforementioned technical field without affecting, influencing or changing the spirit and scope of the invention. Therefore, it is to be understood that the example and applications illustrated herein are intended to be in the nature of description rather than of limitation. Furthermore, the meaning, scope and higher conceptual understandings of the present patent application as well as modi- fications and variations that arise therefrom should be understood to be extensions of this application.

Claims

Claims
[1] A semiconductor doping method using pulsed inductively-coupled plasma, which comprises the steps of: positioning a wafer on a wafer sample stage in a vacuum chamber; supplying a plasma source gas into the vacuum chamber; and applying RF (radio-frequency) pulse to the gas inside the vacuum chamber through a dielectric plate, which forms one side of the vacuum chamber, using an antenna equipped at the outside to form pulsed inductively-coupled plasma while applying negative high voltage pulse to the wafer sample stage as synchronized with the RF pulse, so that plasma ions are doped into the surface of the wafer.
[2] The semiconductor doping method as set forth in claim 1, wherein the RF pulse, which is applied to the RF antenna and generates inductively-coupled pulsed plasma, has a RF frequency of 1 MHz to 50 MHz, a pulse width of 5 μs to 500 μs and a pulse frequency of 10 Hz to 100 kHz, the negative high voltage pulse applied to the wafer sample stage has a pulse width of 5 μs to 500 μs, a pulse frequency of 10 Hz to 100 kHz and a voltage of -0.1 kV to -20 kV and the RF pulse and the high voltage pulse are synchronized with each other.
[3] The semiconductor doping method as set forth in claim 1, wherein although the
RF pulse and the high voltage pulse are synchronized with each other with the same frequency, their pulse widths and relative positions on the time axis are different to optimize doping characteristics.
[4] The semiconductor doping method as set forth in claim 1, wherein the plasma source gas is B 2 H 6 or BF 3 gas for p-type doping and PH 3 or AsH 3 gas for n-type doping.
[5] A semiconductor doping system using pulsed inductively-coupled plasma, which comprises: a vacuum chamber inside of which is maintained in a vacuum state; a dielectric plate made of quartz or alumina which is equipped on one side of the vacuum chamber; an antenna which is equipped at outside of the dielectric plate and applies RF pulse; an RF pulse generator which supplies the RF pulse to the RF antenna; a wafer sample stage which is set up inside the vacuum chamber opposing the RF antenna and accommodates a wafer; a negative high voltage pulse supplier which supplies negative high voltage pulse to the wafer sample stage as synchronized with the RF pulse; and a gas supplier which supplies a plasma source gas to the vacuum chamber. [6] The semiconductor doping system as set forth in claim 5, wherein the vacuum chamber further comprises a plurality of permanent magnets which are equipped on the walls of the vacuum chamber and offer uniform plasma distribution inside the vacuum chamber by forming a uniform magnetic field.
[7] The semiconductor doping system as set forth in claim 5, wherein the negative high voltage pulse applied to the wafer sample stage has a pulse width of 5 μs to 500 μs, a pulse frequency of 10 Hz to 100 kHz and a voltage of -0.1 kV to -20 kV.
[8] The semiconductor doping system as set forth in claim 5, wherein the negative high voltage pulse applied to the wafer sample stage has a pulse width of 5 μs to 500 μs, a pulse frequency of 10 Hz to 100 kHz and a voltage of -0.1 kV to -20 kV.
[9] The semiconductor doping system as set forth in claim 5, wherein the plasma source gas is B 2 H 6 or BF 3 gas for p-type doping and PH 3 or AsH 3 gas for n-type doping. [10] The semiconductor doping system as set forth in claim 5, wherein the wafer sample stage has a larger diameter than the wafer to be positioned on it to ensure uniform doping of the wafer and is equipped with an ion implantation current measuring device including Faraday cup for exact measurement of the ion implantation.
PCT/KR2006/002909 2005-07-25 2006-07-24 Semiconductor doping method using pulsed inductively coupled plasma and system therefor WO2007013753A1 (en)

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