Spatial coherence properties of an LED-based illumination system for mask-aligner lithography

Since LED became an attractive alternative for general lighting, the market demand for higher brightness, higher efficiency and lower costs was the motivation for improving the LED technology. Locking in on the LED manufacturing process, most steps are on die-level after chip singularizing and therefore the costs are dominated by the huge number of dies which could often reach several thousand dies on one wafer. It's obvious that WLP has a clear benefit for LED packaging and it is also the path to success for LED manufacturing. Moreover, it also allows the implementation and integration of additional functionalities to the LED chip module, e.g. electrical connects, Zener-Diode, mirrors, optics drivers etc. Nonetheless, a clear important aspect to adopt WLP for LED manufacturing is to benefit from existing know-how of the IC manufacturing technology and of the experience of the equipment suppliers for this industry. However, the equipment needs to be optimized for the dedicated LED-WLP application. For example, microlithography with mask aligners is widely used for LED chip manufacturing, but the illumination system of these mask aligner are typically optimized for highest resolution which means contact lithography. For LED-WLP the optical systems must be capable for customized illumination for proximity lithography, where the photo mask and the wafer are separated by a proximity gap of typically 30 to 200 microns. Here, diffraction effects limit the resolution and fidelity of the pattern generated or printed in the photoresist. These diffraction effects are related to the mask pattern and the angular spectrum of the illumination light. The requirements on the lithography process for LED-WLP will be explained and discussed. Experimental results of perfect 3D patterning on topographies up to several hundred microns will be shown.

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An improved illumination system for spatial coherence control

10.1117/12.560350 ◽

2004 ◽

Cited By ~ 2

Author(s):

Zhiqiang Liu ◽

Takeshi Gemma ◽

Joseph Rosen ◽

Mitsuo Takeda

Keyword(s):

Spatial Coherence ◽

Illumination System

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Improved illumination system for spatial coherence control

Applied Optics ◽

10.1364/ao.49.000d12 ◽

2010 ◽

Vol 49 (16) ◽

pp. D12 ◽

Cited By ~ 10

Author(s):

Zhiqiang Liu ◽

Takashi Gemma ◽

Joseph Rosen ◽

Mitsuo Takeda

Keyword(s):

Spatial Coherence ◽

Illumination System

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Advanced mask aligner lithography: new illumination system

Optics Express ◽

10.1364/oe.18.020968 ◽

2010 ◽

Vol 18 (20) ◽

pp. 20968 ◽

Cited By ~ 61

Author(s):

Reinhard Voelkel ◽

Uwe Vogler ◽

Andreas Bich ◽

Pascal Pernet ◽

Kenneth J. Weible ◽

...

Keyword(s):

Illumination System ◽

Mask Aligner

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Influence of X-Ray Induced Fluorescence on Energy Dispersive X-Ray Analysis of Thin Foils

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100079164 ◽

1977 ◽

Vol 35 ◽

pp. 328-329

Author(s):

E. A. Kenik ◽

J. Bentley

Keyword(s):

Thin Foil ◽

Electron Excitation ◽

Simple Approach ◽

Foil Thickness ◽

X Rays ◽

X Ray ◽

Hole Spectrum ◽

Illumination System ◽

Thin Foils ◽

Intensity Ratios

Cliff and Lorimer (1) have proposed a simple approach to thin foil x-ray analy sis based on the ratio of x-ray peak intensities. However, there are several experimental pitfalls which must be recognized in obtaining the desired x-ray intensities. Undesirable x-ray induced fluorescence of the specimen can result from various mechanisms and leads to x-ray intensities not characteristic of electron excitation and further results in incorrect intensity ratios.In measuring the x-ray intensity ratio for NiAl as a function of foil thickness, Zaluzec and Fraser (2) found the ratio was not constant for thicknesses where absorption could be neglected. They demonstrated that this effect originated from x-ray induced fluorescence by blocking the beam with lead foil. The primary x-rays arise in the illumination system and result in varying intensity ratios and a finite x-ray spectrum even when the specimen is not intercepting the electron beam, an ‘in-hole’ spectrum. We have developed a second technique for detecting x-ray induced fluorescence based on the magnitude of the ‘in-hole’ spectrum with different filament emission currents and condenser apertures.

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Injector for a 100-500 kV Linac Electron Microscopy Source

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100061380 ◽

1967 ◽

Vol 25 ◽

pp. 274-275

Author(s):

John W. Coleman

Keyword(s):

Electron Microscopy ◽

Linear Accelerator ◽

Beam Current ◽

Ion Trapping ◽

University Of Virginia ◽

Electron Injector ◽

Illumination System ◽

Radio Corporation Of America ◽

The University ◽

Optical Integration

The injector to be described is a component in the Electron Injector-Linear Accelerator—Condenser Module for illumination used on the variable 100-500kV electron microscope being built at the Radio Corporation of America for the University of Virginia.The injector is an independently powered, autonomous unit, operating at a constant 6kV positive with respect to accelerator potential, thereby making beam current independent of accelerator potential. The injector provides for on-axis ion trapping to prolong filament lifetime, and incorporates a derived Einzel lens for optical integration into the overall illumination system for microscopy. Electrostatic beam deflectors for alignment are an integral part of the apparatus. The entire injector unit is cantilevered off a door for side loading, and is topped with a 4-filament turret released electrically but driven by a self-contained Negator spring motor.

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Electron spectroscopic imaging and diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087847 ◽

1991 ◽

Vol 49 ◽

pp. 706-707

Author(s):

M. Rühle ◽

J. Mayer ◽

J.C.H. Spence ◽

J. Bihr ◽

W. Probst ◽

...

Keyword(s):

Materials Science ◽

Electron Spectroscopic Imaging ◽

Magnetic Filter ◽

Magnetic Imaging ◽

Illumination System ◽

Probe Size ◽

Diffraction Patterns ◽

Fritz Haber ◽

Koehler Illumination ◽

First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

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A comparative study on the cold type and thermal type field emission guns used in the same electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107435 ◽

1978 ◽

Vol 36 (1) ◽

pp. 58-59

Author(s):

M. Iwatsuki ◽

Y. Kokubo ◽

Y. Harada

Keyword(s):

Electron Microscope ◽

Field Emission ◽

Signal To Noise Ratio ◽

Electron Source ◽

Resolving Power ◽

Optical Source ◽

Experimental Conditions ◽

High Brightness ◽

Illumination System ◽

Transmission Electron

On accout of its high brightness, small optical source size, and minimal energy spread, the field emission gun (FEG) has the advantage that it provides the conventional transmission electron microscope (TEM) with a highly coherent illumination system and directly improves the resolving power and signal-to-noise ratio of the scanning electron microscope (SEM). The FEG is generally classified into two types; the cold field emission (C-FEG) and thermal field emission gun (T-FEG). The former, in which a field emitter is used at the room temperature, was successfully developed as an electron source for the SEM. The latter, in which the emitter is heated to the temperature range of 1000-1800°K, was also proved to be very suited as an electron source for the TEM, as well as for the SEM. Some characteristics of the two types of the FEG have been studied and reported by many authors. However, the results of the respective types have been obtained separately under different experimental conditions.

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Computer analysis of side-band holography in STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087732 ◽

1991 ◽

Vol 49 ◽

pp. 684-685

Author(s):

M.A. Gribelyuk ◽

J.M. Cowley

Keyword(s):

Interference Pattern ◽

Computer Analysis ◽

Side Band ◽

Diffraction Plane ◽

Illumination System ◽

Probe Size

Recently the use of a biprism in a STEM instrument has been suggested for recording of a hologram. A biprism is inserted in the illumination system and creates two coherent focussed beams at the specimen level with a probe size d= 5-10Å. If one beam passes through an object and another one passes in vacuum, an interference pattern, i.e. a hologram can be observed in diffraction plane (Fig.1).

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Quanitative aspects of electron diffraction using electron holography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100139457 ◽

1995 ◽

Vol 53 ◽

pp. 616-617

Author(s):

E. Völkl ◽

L.F. Allard ◽

B. Frost ◽

T.A. Nolan

Keyword(s):

Electron Beam ◽

Electron Diffraction ◽

Software Package ◽

Spatial Coherence ◽

Electron Holography ◽

Image Intensity ◽

Interference Fringes ◽

Complex Image ◽

The Difference ◽

Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

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