Lithographic projection apparatus, device manufacturing method, device manufactured thereby and gas composition

• US 20020045113A1
• Filed: 07/06/2001
• Published: 04/18/2002
• Est. Priority Date: 07/14/2000
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: van de Pasch, Engelbertus Antonius Fransiscus, Beems, Marcel Hendrikus Maria, Pril, Wouter Onno, Henshaw, Philip Dennis
• Granted Patent: US 6,747,729 B2
• Time in Patent Office: Days
• US Class Current: 430/22
• CPC Class Codes: C01B 23/00 Noble gases; Compounds thereof liquefying F25J ; noble gases obtained by rectification F25J3/028
• CPC Class Codes: G03F 7/70775 Position control, e.g. interferometers or encoders for determining the stage position
• CPC Class Codes: G03F 7/70866 of mask or workpiece
• CPC Class Codes: G03F 7/70933 Purge, e.g. exchanging fluid or gas to remove pollutants

Abstract

A lithographic projection apparatus which uses one, and optionally also two or more color interferometric devices to accurately determine the position of a movable table within the apparatus. The apparatus comprises a purge gas source to supply purge gas to a space accommodating at least a part of said movable table, the purge gas being selected such that leakage of the purge gas into the area of operation of the interferometric devices does not cause significant error in the interferometric measurements.

Claims

1. A lithographic projection apparatus comprising:

a radiation system to provide a projection beam of radiation;

patterning structure to pattern the projection beam according to a desired pattern;

a substrate table to hold a substrate;

a projection system to image the patterned beam onto a target portion of the substrate,

a displacement measuring interferometer having an operating wavelength λ

₁ for measuring at least one of the position of said substrate table and the position of a table which is a part of said patterning structure;

a purge gas source to supply purge gas to a space, to displace therefrom ambient air, said space accommodating at least one of at least a part of said substrate table and at least a part of said table which is a part of said patterning structure, wherein said purge gas is substantially non-absorbent of said projection beam of radiation and has a refractive index at a wavelength λ

₁ which is substantially the same as that of air when measured at equal wavelength, temperature and pressure.

2. An apparatus according to claim 1 wherein the purge gas comprises two or more components selected from N₂, He, Ar, Kr, Ne and Xe.

3. An apparatus according to claim 2 wherein said purge gas comprises at least 95% by volume N₂ and at least 1% by volume He.

4. An apparatus according to claim 2 wherein said purge gas comprises at least 95% by volume Ar and at least 1% by volume Xe.

5. An apparatus according to claim 2 wherein said purge gas comprises at least 90% by volume Ar and at least 5% by volume Kr.

6. An apparatus according to claim 2, wherein said purge gas comprises at least 95% by volume N₂ and at least 1% by volume Ne.

7. An apparatus according to claim 2, wherein said purge gas comprises at least 50% by volume N₂ and at least 35% by volume Ar.

8. An apparatus according to claim 2 wherein said purge gas comprises at least 94% by volume N₂, at least 0.5% by volume He and at least 0.5% by volume Xe.

9. An apparatus according to claim 1, which further comprises a second harmonic interferometer having operating wavelengths λ

₂ and λ

₃ to adjust measurements of said displacement measuring interferometer to substantially eliminate effects of variation in pressure and temperature, and

wherein said purge gas comprises at least three different components, each component having refractivities at the wavelengths λ

₂ and λ

₃ such that the following equations are substantially fulfilled;

$\begin{array}{cc}\stackrel{k}{\underset{j}{\sum <br><br>}}<br><br>F_j<br><br>{\mathrm{\alpha <br><br>}}_{\mathrm{j1}}={\mathrm{\alpha <br><br>}}_{\mathrm{a1}}& \left(1\right)\\ \stackrel{k}{\underset{j}{\sum <br><br>}}<br><br>F_{j<br><br>\text{\hspace{1em}<br><br>}}<br><br>\left({\mathrm{\alpha <br><br>}}_{\mathrm{j3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{j2}}\right)={\mathrm{\alpha <br><br>}}_{\mathrm{a3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{a2}}& \left(2\right)\end{array}$

wherein F_j is the fraction by volume of component j in the purge gas, which purge gas contains a total of k components, α

_j1 is the refractivity of component j at a wavelength λ

₁, α

_j2 is the refractivity of component j at a wavelength λ

₂, α

_j3 is the refractivity of component j at a wavelength λ

₃, α

_a1 is the refractivity of air at a wavelength λ

₁, α

_a2 is the refractivity of air at a wavelength λ

₂ and α

_a3 is the refractivity of air at a wavelength λ

₃; and

wherein;

$\begin{array}{cc}\stackrel{k}{\underset{j}{\sum <br><br>}}<br><br>F_j=1.& \left(3\right)\end{array}$

10. An apparatus according to claim 9, wherein said purge gas comprises at least three different components selected from N₂, He, Ar, Kr, Ne and Xe.

11. An apparatus according to claim 10, wherein said purge gas comprises (i) N₂ and/or Ar in an amount of from 50-90% by volume, (ii) Xe and/or Kr in an amount of from 0.5 to 40% by volume and (iii) He and/or Ne in an amount of from 2 to 20% by volume.

13. An apparatus according to claim 12, wherein said purge gas comprises at least two gases selected from N₂, He, Ar, Kr, Ne and Xe.

14. An apparatus according to claim 13, wherein said purge gas comprises (i) N₂, He, Ar and/or Ne in an amount of from 65 to 99.5% by volume and (ii) Kr and/or Xe in an amount of from 0.5 to 35% by volume.

16. An apparatus according to claim 15, wherein said purge gas has a refractive index at a wavelength λ

₁ which is substantially the same as that of air when measured at the same wavelength, temperature and pressure.

17. An apparatus according to claim 15, wherein K is given by the equation:

18. An apparatus according to claim 15, wherein the purge gas comprises at least 95% by volume He.

19. An apparatus according to claim 15, wherein the purge gas comprises from 94 to 96% by volume N₂ and from 4 to 6% by volume He.

20. An apparatus according to claim 1 wherein λ

₁ is about 633 nm, λ

₂ is about 532 nm and λ

₃ is about 266 nm.

21. An apparatus according to claim 1, wherein said purge gas supply comprises a gas flow regulator to control a rate of flow of purge gas to said space and a pump to remove purge gas from said space.

22. An apparatus according to claim 21 wherein said flow regulator comprises a flow restrictor.

23. An apparatus according to claim 21 wherein said flow regulator comprises a blower.

24. An apparatus according to claim 1 wherein said radiation of said projection beam has a wavelength less than about 180 nm.

25. An apparatus according to claim 24 wherein said radiation of said projection beam has a wavelength selected from the group comprising about 157 nm and about 180 nm.

27. A method according to claim 26, which further comprises adjusting the measurement of said displacement measuring interferometer to substantially eliminate effects of variation in pressure and temperature using a second harmonic interferometer having operating wavelengths λ

₂ and λ

₃, and

wherein said purge gas comprises at least three different components, each component having refractivities at the wavelengths λ

₂ and λ

₃ such that the following equations are substantially fulfilled;

$\begin{array}{cc}\stackrel{k}{\underset{j}{\sum <br><br>}}<br><br>F_j<br><br>{\mathrm{\alpha <br><br>}}_{\mathrm{j1}}={\mathrm{\alpha <br><br>}}_{\mathrm{a1}}& \left(1\right)\\ \stackrel{k}{\underset{j}{\sum <br><br>}}<br><br>F_{j<br><br>\text{\hspace{1em}<br><br>}}<br><br>\left({\mathrm{\alpha <br><br>}}_{\mathrm{j3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{j2}}\right)={\mathrm{\alpha <br><br>}}_{\mathrm{a3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{a2}}& \left(2\right)\end{array}$

wherein F_j is a fraction by volume of component j in the purge gas, which purge gas contains a total of k components, α

_j1 is a refractivity of component j at a wavelength λ

₁, α

_j2 is a refractivity of component j at a wavelength λ

₂, α

_j3 is a refractivity of component j at a wavelength α

₃, α

_a1 is a refractivity of air at a wavelength λ

₁, α

_a2 is a refractivity of air at a wavelength λ

₂ and α

_a3 is a refractivity of air at a wavelength λ

₃, and wherein;

$\begin{array}{cc}\underset{j}{\overset{k}{\sum <br><br>}}<br><br>F_j=1.& \left(3\right)\end{array}$

30. A device manufactured according to the method of claim 26.

31. A purge gas as defined in claim 3.

12. A lithographic projection apparatus comprising:

a radiation system to provide a projection beam of radiation;

patterning structure to pattern the projection beam according to a desired pattern;

a substrate table to hold a substrate;

a projection system to image the patterned beam onto a target portion of the substrate;

a displacement measuring interferometer having an operating wavelength λ

₁ to measure at least one of a position of said substrate table and a position of a table which is a part of said patterning structure;

a second harmonic interferometer having operating wavelengths λ

₂ and λ

₃ to adjust measurements of the displacement measuring interferometer to substantially eliminate the effects of variation in pressure and temperature;

a purge gas source to supply purge gas to a space, to displace therefrom ambient air, said space accommodating at least one of at least a part of said substrate table and at least a part of said table which is a part of said patterning structure, wherein said purge gas is substantially non-absorbent of said projection beam of radiation and comprises at least two components, each component having refractivities at the wavelengths λ

₁, λ

₂ and λ

₃ such that the following equation is substantially fulfilled;

$\begin{array}{cc}\frac{{\mathrm{\alpha <br><br>}}_{\mathrm{m1}}}{\left({\mathrm{\alpha <br><br>}}_{\mathrm{m3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{m2}}\right)}=K_a& \left(4\right)\end{array}$

wherein α

_m1 is the refractivity of the purge gas at a wavelength λ

₁, α

_m2 is the refractivity of the purge gas at a wavelength λ

₂, α

_m3 is the refractivity of the purge gas at a wavelength λ

₃ and

$\begin{array}{cc}{K}_a=\frac{{\mathrm{\alpha <br><br>}}_{\mathrm{a1}}}{\left({\mathrm{\alpha <br><br>}}_{\mathrm{a3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{a2}}\right)}& \left(5\right)\end{array}$

wherein α

_a1 is the refractivity of air at a wavelength λ

₁, α

_a2 is the refractivity of air at a wavelength λ

₂ and α

_a3 is the refractivity of air at a wavelength λ

₃.

15. A lithographic projection apparatus comprising:

a radiation system to provide a projection beam of radiation;

patterning structure to pattern the projection beam according to a desired pattern;

a substrate table to hold a substrate;

a projection system to image the patterned beam onto a target portion of the substrate;

a purge gas source to supply purge gas to a space, to displace therefrom ambient air, said space accommodating at least one of at least a part of said substrate table and at least a part of said table which is a part of said patterning structure, wherein said purge gas is substantially non-absorbent of said projection beam of radiation;

an displacement measuring interferometer having an operating wavelength λ

₁ for measuring at least one of the position of said substrate table and the position of said table which is a part of said patterning structure; and

a second harmonic interferometer having operating wavelengths λ

₂ and λ

₃ to adjust measurements of the displacement measuring interferometer (DI) according to the following equation;

L=(DI)−

K(SHI) 

 

(9)

wherein L is the adjusted displacement measuring interferometer measurement, SHI is the measurement of the second harmonic interferometer and K is a coefficient, the value of which is optimized such that effects of variation in pressure, temperature and purge gas composition are partially eliminated from the adjusted measurement L.

26. A device manufacturing method comprising:

projecting a patterned beam of radiation onto a target area of a layer of radiation-sensitive material on a substrate;

determining the position of a table using a displacement measuring interferometer having an operating wavelength λ

₁, said table comprising at least one of a substrate holder and a patterning structure;

providing purge gas to a space accommodating at least a part of said table to displace therefrom ambient air, wherein said purge gas is substantially non-absorbent of said patterned beam of radiation and has a refractive index at a wavelength λ

₁ which is substantially the same as that of air when measured at the same wavelength, temperature and pressure.

28. A device manufacturing method comprising:

projecting the patterned beam of radiation onto a target area of the layer of radiation-sensitive material,

determining a position of a table using a displacement measuring interferometer having an operating wavelength λ

₁, said table comprising at least one of a substrate holder and a patterning structure;

adjusting a measurement of said displacement measuring interferometer to substantially eliminate effects of variation in pressure and temperature using a second harmonic interferometer having operating wavelengths λ

₂ and λ

₃;

providing purge gas to a space accommodating at least a part of said table to displace therefrom ambient air, wherein said purge gas is substantially non-absorbent of said patterned beam of radiation and comprises at least two components, each component having refractivities at the wavelengths λ

₁, λ

₂ and λ

₃ such that the following equation is substantially fulfilled;

$\begin{array}{cc}\frac{{\mathrm{\alpha <br><br>}}_{\mathrm{m1}}}{\left({\mathrm{\alpha <br><br>}}_{\mathrm{m3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{m2}}\right)}=K_a& \left(4\right)\end{array}$

wherein α

_m1 is a refractivity of the purge gas at a wavelength λ

₁, α

_m2 is a refractivity of the purge gas at a wavelength λ

₂, α

_m3 is a refractivity of the purge gas at a wavelength λ

₃ and

$\begin{array}{cc}{K}_a=\frac{{\mathrm{\alpha <br><br>}}_{\mathrm{a1}}}{\left({\mathrm{\alpha <br><br>}}_{\mathrm{a3}}-{\mathrm{\alpha <br><br>}}_{\mathrm{a2}}\right)}& \left(5\right)\end{array}$

wherein α

_a1 is a refractivity index of air at a wavelength λ

₁, α

_a2 is a refractivity of air at a wavelength λ

₂ and α

_a3 is a refractivity of air at a wavelength λ

₃.

29. A device manufacturing method comprising:

projecting a patterned beam of radiation onto a target area of a layer of radiation-sensitive material on a substrate,

providing purge gas to a space accommodating at least a part of a table to displace therefrom ambient air, said table comprising at least one of a substrate holder and a patterning structure, wherein said purge gas is substantially non-absorbent of said projection beam of radiation;

determining a position of said table using a displacement measuring interferometer having an operating wavelength λ

₁; and

adjusting the measurement of said displacement measuring interferometer (DI) using a second harmonic interferometer having operating wavelengths λ

₂ and λ

₃ according to the following equation;

L=(DI)−

K(SHI) 

 

(9)

wherein L is an adjusted displacement measuring interferometer measurement, SHI is a measurement of the second harmonic interferometer and K is a coefficient, a value of which is optimized such that the effects of variation in pressure, temperature and purge gas composition are partially eliminated from the adjusted value L.