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Patent Issued for Optical Device Processing Method

August 29, 2014



By a News Reporter-Staff News Editor at Health & Medicine Week -- From Alexandria, Virginia, NewsRx journalists report that a patent by the inventor Sekiya, Kazuma (Tokyo, JP), filed on June 4, 2013, was published online on August 12, 2014 (see also Disco, Corporation).

The patent's assignee for patent number 8802470 is Disco, Corporation (Tokyo, JP).

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to an optical device processing method.

"A plurality of optical devices such as LEDs (Light Emitting Diodes) and LDs (Laser Diodes) are formed by growing an epitaxial layer (crystal layer) on a substrate for crystal growth and forming a plurality of crossing division lines for partitioning the epitaxial layer into a plurality of regions where the plural optical devices are respectively formed. The crystal growth substrate having the plural optical devices is divided along the division lines to obtain a plurality of individual optical device chips.

"In an optical device chip having a light emitting layer of InGaN for emitting green or blue light, sapphire is generally used for the crystal growth substrate. An n-type GaN semiconductor layer, an InGaN light emitting layer, and a p-type GaN semiconductor layer are sequentially formed on the sapphire substrate by epitaxial growth. Further, electrodes for external connection are respectively formed on the n-type GaN semiconductor layer and the p-type GaN semiconductor layer, thus forming an optical device.

"In an optical device such as LEDs, higher luminance is demanded, and it is therefore desired to improve light extraction efficiency. In recent years, an optical device mounted by flip-chip bonding as disclosed in Japanese Patent Laid-open No. Hei 4-10670 has already been widely spread in the market. In such a flip-chip mounted optical device, light emitted from the light emitting layer toward the outside is not blocked by the electrodes, so that the light extraction efficiency is improved over an optical device mounted by conventional wire bonding."

As a supplement to the background information on this patent, NewsRx correspondents also obtained the inventor's summary information for this patent: "It is known that the luminous efficiency of a flip-chip mounted LED is improved by tens of percents over an LED mounted by wire bonding. However, a further improvement in light extraction efficiency is desired.

"It is therefore an object of the present invention to provide an optical device processing method which can further improve the light extraction efficiency.

"In accordance with an aspect of the present invention, there is provided an optical device processing method for processing an optical device wafer having a plurality of optical devices formed on a front side and a plurality of crossing division lines for partitioning the optical devices, each of the optical devices having electrodes formed on the front side. The optical device processing method includes: a protective layer forming step of forming a protective layer of an insulator on the front side of the optical device wafer so as to insulate at least the electrodes from each other; a groove forming step of forming a groove on the front side of the optical device wafer along each division line after performing the protective layer forming step, the groove having a depth reaching a finished thickness; a reflective film forming step of forming a reflective film on the front side of the optical device wafer after performing the groove forming step, thereby forming the reflective film on at least side surfaces of the groove; an electrode exposing step of removing the protective layer formed on the electrodes on the front side of the optical device wafer after performing the reflective film forming step, thereby exposing the electrodes; and a grinding step of grinding a back side of the optical device wafer before or after performing the electrode exposing step, thereby reducing the thickness of the optical device wafer to the finished thickness until the groove is exposed to the back side of the optical device wafer to divide the optical device wafer into individual optical device chips.

"Preferably, the protective layer is formed over the entire surface on the front side of the optical device wafer in the protective layer forming step; and the protective layer formed on the front side of the optical device wafer is cut off by using tool cutting means to thereby expose the electrodes in the electrode exposing step.

"Preferably, the optical device processing method of the present invention further includes: a mounting step of flip-chip mounting each optical device chip on a substrate after performing the grinding step; and a sealing step of sealing each optical device chip mounted on the substrate with a sealing member.

"According to the optical device processing method of the present invention, the reflective film is formed on the side surfaces of each optical device chip to thereby prevent the problem that light emitted from a light emitting layer may emerge from the side surfaces of the optical device chip. Furthermore, the back side of each optical device chip is a ground surface having minute irregularities formed by the grinding step. Accordingly, totally reflected light in the optical device chip can be reduced by the minute irregularities to thereby improve the light extraction efficiency.

"The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention."

For additional information on this patent, see: Sekiya, Kazuma. Optical Device Processing Method. U.S. Patent Number 8802470, filed June 4, 2013, and published online on August 12, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8802470.PN.&OS=PN/8802470RS=PN/8802470

Keywords for this news article include: Electronics, Semiconductor, Crystal Growth, Disco Corporation.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Health & Medicine Week


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