Abstract

A system for measuring the gap in a proximity exposure tool of a plasma display panel (PDP) is developed that uses single or dual position-sensitive detectors (PSD’s). The resolution of the gap distance is 0.5 µm, with a capture range of 500 µm. Signal processing is simple and fast and easy because analogous PSD’s are used as the position sensors. One PSD is used to detect the position of the reference beam, which is reflected from the upper surface of the gap; the other PSD is used to detect the position of the signal beam, which is reflected from the lower surface of the gap. A charge-coupled-device sensor is also employed to monitor the reflected beams and the region of measurement. In the gap-measurement system that uses a single PSD, first the reference beam is incident upon the PSD and then the signal beam is incident upon the same PSD. Then the separation between the two beams is calculated from the position of the reference beam and from the average beam position.

© 2000 Optical Society of America

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  1. H. Jeong, M. A. Hartney, “Optical projection system for gigabit DRAMs,” J. Vac. Sci. Technol. B 11, 2675–2679 (1993).
    [CrossRef]
  2. C. A. Mack, “Trends in optical lithography,” Opt. Photon. News, April1996, pp. 29–35.
  3. J. A. Castellano, Handbook of Display Technology (Academic, San Diego, Calif., 1992).
  4. W. B. Glendinning, J. N. Helbert, Handbook of VLSI Microlithography (Noyes, Park Ridge, N.J., 1991).
  5. M. S. Lucas, “FPD and IC fabrication similarities and differences,” Microlithogr. World 5, 5–8 (1996).
  6. E. E. Moon, P. N. Everett, H. I. Smith, “Simultaneous measurement of gap and superposition in a precision aligner for x-ray nanolithography,” J. Vac. Sci. Technol. B 14, 3969–3973 (1996).
    [CrossRef]
  7. P. J. Thomas, R. Mani, N. Khali, “Noncontact measurement of etalon spacing using a retroreflection technique,” Rev. Sci. Instrum. 70, 2225–2229 (1999).
    [CrossRef]
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    [CrossRef]
  12. Y. Takada, H. Matsuda, T. Nishikawa, “Optical displacement measuring system using a triangulation including a processing of position signals in a time sharing manner,” U.S. patent5,814,808 (29September1996).
  13. G. U. Kalman, “Apparatus for measuring the distance between surfaces of transparent material,” U.S. patent3,807,870 (30April1974).

1999 (1)

P. J. Thomas, R. Mani, N. Khali, “Noncontact measurement of etalon spacing using a retroreflection technique,” Rev. Sci. Instrum. 70, 2225–2229 (1999).
[CrossRef]

1996 (3)

C. A. Mack, “Trends in optical lithography,” Opt. Photon. News, April1996, pp. 29–35.

M. S. Lucas, “FPD and IC fabrication similarities and differences,” Microlithogr. World 5, 5–8 (1996).

E. E. Moon, P. N. Everett, H. I. Smith, “Simultaneous measurement of gap and superposition in a precision aligner for x-ray nanolithography,” J. Vac. Sci. Technol. B 14, 3969–3973 (1996).
[CrossRef]

1994 (1)

1993 (1)

H. Jeong, M. A. Hartney, “Optical projection system for gigabit DRAMs,” J. Vac. Sci. Technol. B 11, 2675–2679 (1993).
[CrossRef]

1991 (1)

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

1990 (1)

1989 (1)

Castellano, J. A.

J. A. Castellano, Handbook of Display Technology (Academic, San Diego, Calif., 1992).

Chim, S. S. C.

Dobson, C. C.

Everett, P. N.

E. E. Moon, P. N. Everett, H. I. Smith, “Simultaneous measurement of gap and superposition in a precision aligner for x-ray nanolithography,” J. Vac. Sci. Technol. B 14, 3969–3973 (1996).
[CrossRef]

Glendinning, W. B.

W. B. Glendinning, J. N. Helbert, Handbook of VLSI Microlithography (Noyes, Park Ridge, N.J., 1991).

Hartney, M. A.

H. Jeong, M. A. Hartney, “Optical projection system for gigabit DRAMs,” J. Vac. Sci. Technol. B 11, 2675–2679 (1993).
[CrossRef]

Helbert, J. N.

W. B. Glendinning, J. N. Helbert, Handbook of VLSI Microlithography (Noyes, Park Ridge, N.J., 1991).

Hell, S.

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

Hunklinger, S.

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

Jeong, H.

H. Jeong, M. A. Hartney, “Optical projection system for gigabit DRAMs,” J. Vac. Sci. Technol. B 11, 2675–2679 (1993).
[CrossRef]

Kalman, G. U.

G. U. Kalman, “Apparatus for measuring the distance between surfaces of transparent material,” U.S. patent3,807,870 (30April1974).

Khali, N.

P. J. Thomas, R. Mani, N. Khali, “Noncontact measurement of etalon spacing using a retroreflection technique,” Rev. Sci. Instrum. 70, 2225–2229 (1999).
[CrossRef]

Kino, G. S.

Lai, G.

Lucas, M. S.

M. S. Lucas, “FPD and IC fabrication similarities and differences,” Microlithogr. World 5, 5–8 (1996).

Mack, C. A.

C. A. Mack, “Trends in optical lithography,” Opt. Photon. News, April1996, pp. 29–35.

Mani, R.

P. J. Thomas, R. Mani, N. Khali, “Noncontact measurement of etalon spacing using a retroreflection technique,” Rev. Sci. Instrum. 70, 2225–2229 (1999).
[CrossRef]

Matsuda, H.

Y. Takada, H. Matsuda, T. Nishikawa, “Optical displacement measuring system using a triangulation including a processing of position signals in a time sharing manner,” U.S. patent5,814,808 (29September1996).

Moon, E. E.

E. E. Moon, P. N. Everett, H. I. Smith, “Simultaneous measurement of gap and superposition in a precision aligner for x-ray nanolithography,” J. Vac. Sci. Technol. B 14, 3969–3973 (1996).
[CrossRef]

Neiger, M.

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

Nishikawa, T.

Y. Takada, H. Matsuda, T. Nishikawa, “Optical displacement measuring system using a triangulation including a processing of position signals in a time sharing manner,” U.S. patent5,814,808 (29September1996).

Schckfus, M. v.

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

Smith, H. I.

E. E. Moon, P. N. Everett, H. I. Smith, “Simultaneous measurement of gap and superposition in a precision aligner for x-ray nanolithography,” J. Vac. Sci. Technol. B 14, 3969–3973 (1996).
[CrossRef]

Smith, L. M.

Smolka, E.

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

Takada, Y.

Y. Takada, H. Matsuda, T. Nishikawa, “Optical displacement measuring system using a triangulation including a processing of position signals in a time sharing manner,” U.S. patent5,814,808 (29September1996).

Thomas, P. J.

P. J. Thomas, R. Mani, N. Khali, “Noncontact measurement of etalon spacing using a retroreflection technique,” Rev. Sci. Instrum. 70, 2225–2229 (1999).
[CrossRef]

Wijnaendts van Resandt, R. W.

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

Witting, S.

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

Yatagai, T.

Appl. Opt. (3)

J. Microsc. (1)

S. Hell, S. Witting, M. v. Schckfus, R. W. Wijnaendts van Resandt, S. Hunklinger, E. Smolka, M. Neiger, “A confocal beam scanning white-light microscope,” J. Microsc. 163, 179–187 (1991).
[CrossRef]

J. Vac. Sci. Technol. B (2)

H. Jeong, M. A. Hartney, “Optical projection system for gigabit DRAMs,” J. Vac. Sci. Technol. B 11, 2675–2679 (1993).
[CrossRef]

E. E. Moon, P. N. Everett, H. I. Smith, “Simultaneous measurement of gap and superposition in a precision aligner for x-ray nanolithography,” J. Vac. Sci. Technol. B 14, 3969–3973 (1996).
[CrossRef]

Microlithogr. World (1)

M. S. Lucas, “FPD and IC fabrication similarities and differences,” Microlithogr. World 5, 5–8 (1996).

Opt. Photon. News (1)

C. A. Mack, “Trends in optical lithography,” Opt. Photon. News, April1996, pp. 29–35.

Rev. Sci. Instrum. (1)

P. J. Thomas, R. Mani, N. Khali, “Noncontact measurement of etalon spacing using a retroreflection technique,” Rev. Sci. Instrum. 70, 2225–2229 (1999).
[CrossRef]

Other (4)

J. A. Castellano, Handbook of Display Technology (Academic, San Diego, Calif., 1992).

W. B. Glendinning, J. N. Helbert, Handbook of VLSI Microlithography (Noyes, Park Ridge, N.J., 1991).

Y. Takada, H. Matsuda, T. Nishikawa, “Optical displacement measuring system using a triangulation including a processing of position signals in a time sharing manner,” U.S. patent5,814,808 (29September1996).

G. U. Kalman, “Apparatus for measuring the distance between surfaces of transparent material,” U.S. patent3,807,870 (30April1974).

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Figures (12)

Fig. 1
Fig. 1

Schematic of the gap-measurement system with two PSD’s and a CCD sensor. Two reflected beams, from the lower surface of the mask and the upper surface of the substrate, are incident into the PSD’s and the CCD. The reference PSD detects the reference beam’s position reflected from the lower surface of the mask, and the signal PSD detects the signal beam’s position reflected from the upper surface of the substrate. LD, laser diode; L1, L2, lenses; M1, M2, mirrors; BS1, BS2, beam splitters.

Fig. 2
Fig. 2

Side view of paths of the reference and the signal beams. The two beams are divided by beam splitter BS1 and are incident onto the stacked PSD’s. BS is a beam splitter that divides the reference beam for the CCD sensor. (b) Front view of the stacked PSD’s, showing the positions of the incident beams and the blocking mask. The blocking mask eliminates the signal beam from the reference PSD and the reference beam from the signal PSD.

Fig. 3
Fig. 3

Intensity distributions of the reference and the signal beams. The minimum detectable separation is same as the diameter of the Airy disk, ω0, because the first minimum point at the right-hand side of the reference beam should be the first minimum point at the left-hand side of the signal beam.

Fig. 4
Fig. 4

Geometry of the reference and the signal beams for gap-measurement with a single PSD. Two beams, reflected from the lower surface of the mask and the upper surface of the substrate, are incident onto the single PSD at positions x A and x B , respectively.

Fig. 5
Fig. 5

Schematic of signal processing for the PSD sensor. The beam position information is obtained from the output V 0 = V 1 - V 2/V 1 + V 2, and the incident beam power is obtained from the summed output V sum = V 1 + V 2. R, feedback resistor.

Fig. 6
Fig. 6

Output voltage as a function of the signal beam’s position when the reference beam is stationary. Signal beam power P s is 0.4 mW, and the slope of the signal is 1.545 mV/µm.

Fig. 7
Fig. 7

Dependence of the slope of the output voltage in Fig. 6 on the incident power. The maximum position error that is due variation in beam power from 0.1 to 0.6 mW corresponds to ∼10 µm in a 500-µm range.

Fig. 8
Fig. 8

Comparison of measured gap values obtained with PSD sensor and with CCD sensor.

Fig. 9
Fig. 9

Schematic diagram of the proximity PDP exposure system: S, light source; FE, fly’s-eye lens; FM, folding mirror; CM, concave mirror; G, gap-measurement module; M, mask; S, substrate.

Fig. 10
Fig. 10

Patterns produced from the proximity PDP exposure system. Test patterns produced on the substrate when the gap is (a) 100 µm and (b) 50 µm. A small diffraction pattern appears at the crossing point when the gap is 100 µm; it is negligible when the gap is 50 µm.

Fig. 11
Fig. 11

Change in output voltage when two beams are incident upon the same PSD. The reference beam is stationary, and the signal beam is allowed to move along the x direction. The slope depends on the signal beam power.

Fig. 12
Fig. 12

Change in the slope of the PSD signal as a function of incident beam power for the gap-measurement system with a single PSD. Solid curve, theoretical curve from Eq. (32); filled circles, experimental data.

Equations (34)

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R=k1λ2NA,
R=Qλg/2,
Δs=2g sin θ,
Δs1=2t1 tan φ sin θ,
Δs2=2t2 tan φ sin θ,
Ir1=C21-2L xrPr,
Ir2=C21+2L xrPr,
Is1=C21-2L xsPs,
Is2=C21+2L xsPs,
Vr=G Ir1-Ir2Ir1+Ir2=2GL xr,
Vs=G Is1-Is2Is1+Is2=2GL xs,
Vr=Srxr+Cr,
Vs=Ssxs+Cs,
xr=Mpr+x0,
xs=Mps+x0,
Vr=SrMpr+Srx0+Cr,
Vs=SsMps+Ssxo+Cs.
g=ps-pr=VsMSs-VrMSr+D,
D=CrMSr-CsMSs.
D=g0-Vs0MSs+Vr0MSr.
gmin=2.4fλ/d,
IA1=C21-2L xAPr,
IA2=C21+2L xAPr,
IA=IA1+IA2=CPr,
IB1=C21-2L xBPs,
IB2=C21+2L xBPs,
IB=IB1+IB2=CPs.
I1=IA1+IB1=C2Pr+Ps-2LxAPr+xBPs,
I2=IA2+IB2=C2Pr+Ps+2LxAPr+xBPs.
x¯=xAPr+xBPsPr+Ps=xA+xBr1+r=L2I1-I2I1+I2,
V0=G I1-I2I1+I2=2GL11+r xA+r1+r xB.
S=2GLr1+r=2GLPsPr+Ps.
Δx=xB-xA=1+rrx¯-xA.
xmax=LM sin ϑ=783 μm.

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