Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Patent
1992-07-16
1994-06-14
Hille, Rolf
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
257435, 257436, 257443, 359619, H01L 2978, H01L 2329, H01L 2504
Patent
active
053212975
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a solid state image pickup device and a method of manufacturing the same.
BACKGROUND OF THE INVENTION
A solid state image pickup device is constructed of a plurality of pixels of image pickup elements, each having a photosensitive section. In each image pickup element, light incident to a light receiving section is converted into electric charge signal by the photosensitive section (e.g., a photodiode). This electric charge signal is outputted from a charge transfer section of the solid state image pickup device.
As a method of improving the light reception sensitivity of such a solid state image pickup device without enlarging any light receiving section, a light converging lens is mounted above a photodiode (photosensitive section) to converge external light onto the photosensitive section.
A conventional method of manufacturing a solid state image pickup device having a light converging lens will be described with reference to FIGS. 13A to 13D.
As seen from FIG. 13A, a plurality of photosensitive sections (photodiodes) 2 are first formed on the surface of a semiconductor substrate 1 at predetermined areas. The surface of each photodiode 2 is covered with a passivation film 3. Color filters 4.sub.1, 4.sub.2 and 4.sub.3 are formed on the surface of the passivation film 3, using a dying film such as gelatin. The color filters 4.sub.1, 4.sub.2 and 4.sub.3 are red, green, and blue, respectively. A passivation film 5 is deposited on the surface of these color filters 4.sub.1, 4.sub.2 and 4.sub.3.
Next, as seen from FIG. 13B, a photoresist film 6A is formed over the whole surface of the passivation film 5. The photoresist film 6A is patterned to form a photoresist film 6 above each photodiode 2.
Thereafter, as shown in FIG. 13C, light 7 is applied to the photoresist films 6 to make them transparent.
Then, as shown in FIG. 13D, the transparent films 6 are thermally deformed to form light converging lenses 6'.
FIGS. 11A to 11C show a conventional solid state image pickup device manufactured by the above-described method. FIG. 11C is a plan view, FIG. 11A is a cross sectional view taken along the A.sub.5 -A.sub.5' of FIG. 11C, and FIG. 11B is a cross sectional view taken along line B.sub.5 -B.sub.5' of FIG. 11C. FIG. 11A corresponds to FIG. 13D.
Another conventional manufacturing method will be described with reference to FIGS. 14A to 14D.
The processes up to forming a passivation film 5 shown in FIG. 11A are the same as those described with FIG. 13A. A transparent film 106 to form light converging lenses 106' (refer to FIG. 14D) is formed on the passivation film 5.
Next, as seen from FIG. 14B, a photoresist layer 107A is formed on the transparent film 106. The photoresist layer 107A is patterned by means of a photoetching method, to form a photoresist film 107 patterned so as to form light converging lenses. Thereafter, as seen from FIG. 14C and 14D, the transparent film 106 and photoresist film 107 are etched by means of an anisotropic etching (e.g., RIE). The shape of the photoresist film 107 is therefore transferred to the transparent film 106 to form the light converging lenses 106'. The plan view and cross sectional view along line B.sub.5 -B.sub.5', of this device are shown in FIGS. 11C and 11B.
As shown in FIG. 14B, the photoresist film 107 of a solid state image pickup device manufactured by the method explained with FIGS. 14A to 14D is formed on a flat passivation film 5. Therefore, the film thickness is substantially the same both in the X- and Y-directions. Thus, the curvatures in the X- and Y-directions are determined by the shape of the photoresist film 107 patterned so as to form the light converging lenses. The light convergence efficiency in the direction along line A.sub.5 -A.sub.5' of the light converging lens 6' (106') shown in FIG. 11A is good because light is refracted by the light converging lens 6' and directed to the center of the photodiode 2. However, the light convergence efficiency in the direction along line B.sub.5 -B.sub.5
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IEEE Transactions on Consumer Electronics, vol. CE-31, No. 2, May 1985, New York US pp. 88-95; H. Saeki et al., Effect of Microlens Array for Mos Color Imager.
Hille Rolf
Kabushiki Kaisha Toshiba
Saadat Mahshid
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