HAYASHI PURE CHEMICAL IND., LTD. (President: Mr.Masakatsu Irie,hereinafter, HAYASHI PURE CHEMICAL) has succeeded to develop high performance etchant to make roughness on surface of AlGaInP layer (Semiconductor Layer) in Light Emitting Diode process (hereinafter, LED). With this newly developed etchant, surface of semiconductor layer that consists of light output surface can be etched efficiently. As the result, roughness is easily obtained without using specialized process technique. HAYASHI PURE CHEMICAL contributes to increase in High Brightness LED products that high growth is expected in future, and improve processing accuracy and reliability, and is planning to propose and distribute our ideas to various market as well as LED production market.
Generally, LED requires high luminous efficiency. And its efficiency is etermined by multiplication of internal quantum efficiency and light extraction efficiency. Therefore, to enhance luminous efficiency, this multiplication number is required to be increased. As technology to enhance light extraction efficiency, it is proposed that preventing light reflection by roughness on semiconductor layer of light output surface.
In recent years, AlGaInP layer is used for yellowish green ~ red high brightness LED. As the methods to make roughness on AlGaInP layer surface, following processes are proposed at present.
(1) Method of etching with Sulfuric Acid.
(2) Etching with Hydrochloric Acid – Phosphoric Acid system or Hydrobromic Acid system.
(3) Etching with Acetic Acid – Sulfuric Acid – Hydrochloric Acid – Hydrogen Peroxide system.
(4) Etching with Phosphoric Acid – Hydrogen Peroxide system or Hydrochloric Acid added in this system.
However, it is difficult to make roughness on AlGaInP layer efficiently and to make intended roughness with above conventional processes. On the other hand, dry etching technology is proposed. For example,
(5) Method of dry etching after forming etching mask on AlGaInP layer, or dry etching after forming self composition etching mask.
(6) Method of forming etching mask with concentrated metal powder. etc. are proposed.
By dry etching process described above, process to form etching mask, and also special technique to form the etching mask are required. Therefore, these processes cause complicated process, throughput degradation, and increasing of process cost.
HAYASHI PURE CHEMICAL has been developing new etchant for the purpose of solving these problems, as well as finding chemical composition to make efficient etching on semiconductor layer of LED light output to obtain roughness on surface without using specialized process technique.
Ⅲ. Development Result
Features of this newly developed high performance surface roughness etchant are as below.
(1) Surface roughness can be obtained on semiconductor layer, as AlGaInP, AlGaAs, GaAsP, GaInP, AlGaP, AlInP, GaP etc.
(2) Lower temperature and room temperature (25 degree C) processes are available.
(3) Forming both large (Chart 1) and small asperity (Chart 2) are available.
And desirable asperity can be formed by combination of etchant.
(4) Both Dipping and Spray methods are available.
Ⅳ. Explanation of Terms
(1) Light Emitting Diode
It is called LED, and semiconductor device that emits light when voltage is given.
(2) Dipping Method
Method of dipping substrate to etchant directly, and keep substrate still or vibrate, or agitate the etchant.
(3) Spray Method
Provide etchant on substrate through spray nozzle.
〔Contact Information for Press〕
HAYASHI PURE CHEMICAL IND.,LTD.
3-2-12 UCHIHIRANOMACHI, CHUO-KU, OSAKA 540-0037, JAPAN
TEL +81-6-6910-7336 FAX +81-6-6910-7330
Information on this document is as of press released.
Please note this may differ from latest information.