Method of predicting the curvature radius of the microlens

Details Method of predicting the curvature radius of the microlens Method of predicting the curvature radius of the microlens

2000-05-19

2001-10-16

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

C359S648000, C359S664000, C359S362000, C427S164000, C065S017300, C264S001320, C264S002200

Reexamination Certificate

active

06304387

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 89103233, filed Feb. 24, 2000.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a microlens. More particularly, the present invention relates to a method of predicting the curvature radius of the microlens.
2. Description of Related Art
Microlens technology is now widely used in many optoelectronical products, for example, color digital cameras, endoscopes and color liquid crystal displays (LCD). The microlens is used to control the traveling directions of each light ray, so that the light can be precisely converged or diverged. Furthermore, through the control of digital devices, light and electricity can be interchanged digitally with each other.
For example, the converged digital camera is usually constituted by superimposing color filter arrays (CFA) either on a charge-coupled device (CCD) image sensor or on a complementary metal-oxide-semiconductor (CMOS) image sensor. In general, CFA contains three or more color filter channels arranged alternately, where each color filter channel only lets light with a specific frequency pass through, projecting to the corresponding image sensor. Therefore, the color of the image is interpreted by CFA, and then transferred to each corresponding sensor device for further processing. Furthermore, microlens arrays coupled with CFA can be used to focus the light rays, so that either the layout area of each sensor device on the substrate can be increased or the integrity can be raised.
Referring to
FIG. 1
, illustrating the cross-sectional view of the prior art structure containing the microlens and the sensor device, light-sensitive regions
12
are formed in a chip substrate
10
. Sensor devices
14
, for example, CCD or CMOS, are formed on the substrate
10
. A planarized transparent layer
16
is formed on the substrate
10
, with a CFA layer
18
formed thereon. Microlenses
20
are formed on the CFA layer
18
, which refract light rays
22
coming from the outside to focus on the light-sensitive regions
12
. Through the refraction of microlenses
20
, light rays
22
are focused onto smaller areas in the light-sensitive regions
12
, so that smaller areas are needed to form light-sensitive regions
12
. Consequently, either the layout areas of sensor devices
14
can be increased or the integrity can be further raised.
For manufacturing the microlens in the prior art, a thermal process is usually performed to melt the patterned microlens material layer to form the microlens. In this way, it is difficult to obtain an important parameter, a curvature radius. In the past, the curvature radius was obtained by experience or by testing responses from the customers. The trial-and-error method is not only time-consuming but also imprecise.
SUMMARY OF THE INVENTION
The invention provides a method of predicting the curvature radius of the microlens through simple calculations, while using the easily adjustable process parameters, spin speed and exposure energy, for calculations. The predicted result is then used to control precisely the real curvature radius of the microlens.
The invention provides a method of predicting the curvature radius of the microlens. A substrate is provided. A microlens material layer is spin-coated on the substrate and a thickness of the microlens material layer is adjusted by controlling the spin speed for spin coating. A photolithography step is performed to pattern the microlens material layer with a first volume. A diameter of the patterned microlens material layer can be controlled by adjusting the exposure energy during the photolithography step. Then a lens-forming step is performed to transform the patterned microlens material layer into a microlens with a diameter and a second volume. After measuring the diameter of the microlens, the first volume multiplies with a contraction coefficient to calculate the second volume. The diameter and the second volume of the microlens are used to calculate the curvature radius.
The invention provides a method of predicting the curvature radius of the microlens, wherein the curvature radius can be predicted precisely because the process parameters, the spin speed and the exposure energy, can be accurately controlled. Consequently, the required standards can be reached readily by accurately controlling the process parameters.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 5036971 (1991-08-01), Seden

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