ION IMPLANTING APPARATUS AND ION IMPLANTING METHOD

• US 20100025821A1
• Filed: 12/20/2007
• Published: 02/04/2010
• Est. Priority Date: 12/25/2006
• Status: Active Grant

• Current Assignee: National University Corporation Chiba University, Tokyo Electron Limited
• Original Assignee: National University Corporation Chiba University, Tokyo Electron Limited
• Inventors: Goto, Tetsuya, Matsuoka, Takaaki, Teramoto, Akinobu, Ohmi, Tadahiro
• Granted Patent: US 8,399,862 B2
• Time in Patent Office: Days
• US Class Current: 257/607
• CPC Class Codes: H01J 2237/20 Positioning, supporting, modifying or maintaining the physical state of objects being observed or treated
• CPC Class Codes: H01J 2237/26 Electron or ion microscopes
• CPC Class Codes: H01J 37/3222 Antennas
• CPC Class Codes: H01J 37/32412 Plasma immersion ion implantation
• CPC Class Codes: H01J 37/32706 Polarising the substrate
• CPC Class Codes: H01L 21/265 producing ion implantation
• CPC Class Codes: H01L 21/26513 of electrically active species
• CPC Class Codes: H01L 21/2658 of a molecular ion, e.g. decaborane
• CPC Class Codes: H01L 29/30 characterised by physical imperfections; having polished or roughened surface
• CPC Class Codes: H01L 29/7833 with lightly doped drain or source extension, e.g. LDD MOSFET's; DDD MOSFET's for thin film transistors H01L29/78618

Abstract

When positively charged ions are implanted into a target substrate, charge-up damage may occur on the target substrate. In order to suppress charge-up caused by secondary electrons emitted from the target substrate when positively charged ions are implanted, a conductive member is installed at a position facing the target substrate and electrically grounded with respect to a high frequency. Further, a field intensity generated in the target substrate may be reduced by controlling an RF power applied to the target substrate in pulse mode.

Claims

1. An ion implanting apparatus comprising:

a depressurizable processing chamber;

a plasma excitation unit for exciting plasma within the processing chamber;

a holding table installed in the processing chamber, for holding a target substrate;

a conductive member disposed so as to face the holding table in the processing chamber, having a portion through which the plasma is transmitted toward the holding table; and

an RF power application unit for applying RF power for substrate bias onto the target substrate held by the holding table,

wherein the conductive member is electrically grounded with respect to a frequency of the RF power.

2. The ion implanting apparatus of claim 1, wherein the plasma excitation unit includes:

a unit for supplying plasma excitation power to an inside of the processing chamber; and

a unit for supplying a plasma excitation gas to the inside of the processing chamber.

3. The ion implanting apparatus of claim 2, wherein the plasma excitation gas includes a source gas for ions to be implanted into the target substrate.

4. The ion implanting apparatus of claim 2, wherein a frequency of the plasma excitation power is in a range of a frequency of a microwave.

5. The ion implanting apparatus of claim 2, wherein the unit for supplying the plasma excitation power to the inside of the processing chamber includes:

a microwave source;

a flat plate antenna; and

a unit for transmitting a microwave from the microwave source to the antenna,

wherein the antenna is disposed to face the holding table with a dielectric plate therebetween, and

the microwave radiated from the antenna propagates through the dielectric plate and irradiates the plasma excitation gas in the processing chamber so as to generate plasma.

6. The ion implanting apparatus of claim 5, wherein the unit for supplying the plasma excitation gas includes a plurality of gas paths for discharging the plasma excitation gas into the processing chamber via a gas supply port and an inside of the dielectric plate, and

wherein the plasma is generated in a space where the plasma excitation gas is discharged into the processing chamber from the dielectric plate or in its vicinity.

7. The ion implanting apparatus of claim 2, wherein in the processing chamber, an electron density of the plasma in a space opposite to the holding table with respect to the conductive member is higher than a cut-off density determined by ω

²m∈

₀/e² where an angular frequency of the plasma excitation power is w, a permittivity in vacuum is ∈

₀, mass of an electron is m, and an elementary electric charge is e.

8. The ion implanting apparatus of claim 4, wherein the plasma excitation gas includes a fluoride gas, and a pressure within the processing chamber is set such that an electron density of the plasma in a space opposite to the holding table with respect to the conductive member is maintained higher than a cut-off density determined by ω

²m∈

₀/e² where an angular frequency of the microwave is w, a permittivity in vacuum is ∈

₀, mass of an electron is m, and an elementary electric charge is e.

9. The ion implanting apparatus of claim 6, wherein within the processing chamber, an electron density of the plasma in a space opposite to the holding table with respect to the conductive member and at a position where the plasma is in contact with the dielectric plate at a side of the conductive member with a plasma sheath therebetween is higher than a cut-off density determined by ω

²m∈

₀/e² where an angular frequency of the microwave supplied to the antenna is ω

, a permittivity in vacuum is ∈

₀, mass of an electron is m, and an elementary electric charge is e.

10. The ion implanting apparatus of claim 6, wherein when a plasma angular frequency determined by the following formula 1 (where, n is an electron density of plasma at a position where the plasma is in contact with the dielectric plate at a side of the conductive member with a plasma sheath therebetween, ∈

₀ is a permittivity in vacuum, m is mass of an electron, and e is an elementary electric charge) is ω

_pe and an angular frequency of the microwave supplied to the antenna is ω

, a distance between the dielectric plate and the conductive member is longer than a microwave penetration depth determined by the following formula 2 (here, c is speed of light in vacuum).

√

{square root over (ne²/(m∈

₀))} 

 

[Formula 1]

c/√

{square root over (ω

_pe²−

ω

²)} 

 

[Formula 2]

11. The ion implanting apparatus of claim 6, wherein when a plasma angular frequency determined by the following formula 3 (where n is an electron density of plasma at a position where the plasma is in contact with the dielectric plate at a side of the conductive member with a plasma sheath therebetween, ∈

₀ is a permittivity in vacuum, m is mass of an electron, and e is an elementary electric charge) is ω

_pe and an angular frequency of the microwave supplied to the antenna is ω

, a distance between the dielectric plate and the conductive member is three or more times longer than a microwave penetration depth determined by the following formula 4 (here, c is speed of light in vacuum).

√

ne²/(m∈

₀) 

 

[Formula 3]

c/√

{square root over (ω

_pe²−

ω

²)} 

 

[Formula 4]

12. The ion implanting apparatus of claim 5, wherein the antenna is a radial line slot antenna.

13. The ion implanting apparatus of claim 1, wherein the conductive member is electrically grounded with respect to a direct current.

14. The ion implanting apparatus of claim 1, wherein at least a portion of inner walls of the processing chamber in contact with the plasma and a surface of the conductive member are coated with at least one of metal oxide and metal nitride.

15. The ion implanting apparatus of claim 1, wherein the conductive member includes therein a unit through which a temperature control medium flows.

16. The ion implanting apparatus of claim 1, wherein a period of the frequency of the RF power is longer than a time during which implantation atom ions or implantation molecule ions released from the plasma toward a plasma sheath formed on a surface of the target substrate reaches the target substrate.

17. The ion implanting apparatus of claim 6, wherein a porous ceramic member is installed at each gas discharge position of the plurality of gas paths, and the plasma excitation gas is introduced into the processing chamber from the porous ceramic member.

18. The ion implanting apparatus of claim 6, wherein each gas discharge hole of the plurality of gas paths has a diameter two or less times larger than a thickness of a sheath formed between the dielectric plate and the plasma, and the plasma excitation gas is introduced into the processing chamber from the gas discharge hole.

19. The ion implanting apparatus of claim 1, further comprising:

a unit for cooling the holding table.

20. (canceled)

21. (canceled)

22. A semiconductor device manufacturing method comprising:

exciting plasma;

applying RF power onto a target substrate to generate substrate bias; and

performing an ion implantation plural times by applying the RF power in the form of pulses.

23. The semiconductor device manufacturing method of claim 22, wherein the pulse has a predetermined width and interval and the interval of the pulse is longer than the product of a reciprocal of a ratio of the number of electrons to the total number of ion electric charges in the plasma for a unit volume, a coefficient of secondary electrons emitted from the target substrate and the width of the pulse.

24. The semiconductor device manufacturing method of claim 22, wherein the plasma is excited by a plasma excitation gas which is a fluoride gas of atom ions to be implanted or a mixed gas made by diluting the fluoride gas of the atom ions to be implanted with a rare gas.

25. The semiconductor device manufacturing method of claim 22, wherein the plasma is excited by a plasma excitation gas which is a gas selected from BF₃, PF₃ and AsF₃ or a mixed gas made by diluting a gas selected from BF₃, PF₃ and AsF₃ with at least one kind of rare gas selected from Ar, Kr and Xe.

26. The semiconductor device manufacturing method of claim 24, wherein the target substrate includes silicon and the target substrate is cooled to a temperature lower than a volatilization temperature of a silicon fluoride under a pressure of the processing chamber.

28. A semiconductor device manufactured by using the semiconductor device manufacturing method as claimed in claim 22.

27. (canceled)

29. (canceled)