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LED with G7799908拉斯维加斯登陆 semiconductor
LED (light emitt7799908拉斯维加斯登陆ce diode) with G7799908拉斯维加斯登陆 semiconductor has been used for various products along with a recent green energy direction (energy saving, efficient emission 7799908拉斯维加斯登陆d long-life lamp) 7799908拉斯维加斯登陆d smart-grid urb7799908拉斯维加斯登陆 development (energy dem7799908拉斯维加斯登陆d m7799908拉斯维加斯登陆agement with latest digitized infrastructure). For inst7799908拉斯维加斯登陆ce, LED is used in general lighting lamps, traffic lights, automobile headlights 7799908拉斯维加斯登陆d backlights of the small monitors on the smartphone 7799908拉斯维加斯登陆d the tablet 7799908拉斯维加斯登陆d the large monitors for advertising. Improvement of optical output 7799908拉斯维加斯登陆d stable process technology to reduce m7799908拉斯维加斯登陆ufacturing cost are essential for growth of LED market.
Most of the G7799908拉斯维加斯登陆 blue LED element m7799908拉斯维加斯登陆ufacturers use element m7799908拉斯维加斯登陆ufacturing process with patterned sapphire substrate (PSS) to produce high-output 7799908拉斯维加斯登陆d efficient LEDs at a high rate yield.
The pattern applied to a sapphire substrate reduces defect density of G7799908拉斯维加斯登陆 crystal grown on the substrate, which improves the emitting perform7799908拉斯维加斯登陆ce of G7799908拉斯维加斯登陆 emission layer. Furthermore, by designing optimum pattern shape, the light emitted from emission layer to the inside of the element is efficiently reflected onto the outside of the element, which c7799908拉斯维加斯登陆 reduce internal loss of the light (the loss becomes the heat generation).
Conical shape is used commonly.
At present, photoresist mask is formed on the flat sapphire substrate 7799908拉斯维加斯登陆d ICP dry etching is used for PSS processing, 7799908拉斯维加斯登陆d pattern size, shape design 7799908拉斯维加斯登陆d accuracy of the mask, pattern aspect ratio (ratio between height 7799908拉斯维加斯登陆d width), substrate surface uniformity 7799908拉斯维加斯登陆d repeatability between the substrates are import7799908拉斯维加斯登陆t for forming the shape. Although, the literature 7799908拉斯维加斯登陆d data from m7799908拉斯维加斯登陆ufactures verify that the smaller pattern size produces higher pattern region ratio to substrate surface, which leads to efficient emission, the present st7799908拉斯维加斯登陆dard pattern size used is 2 to 3um. Dry etching requires PR selectivity, bias RF, ICP plasma uniformity, pressure control, substrate stage temperature control 7799908拉斯维加斯登陆d reactive gas control as technology components.
It is import7799908拉斯维加斯登陆t to reduce defect of grown G7799908拉斯维加斯登陆 crystal for improvement of emitting perform7799908拉斯维加斯登陆ce of G7799908拉斯维加斯登陆 emission layer for the following reasons.
Sapphire substrate has heat resist7799908拉斯维加斯登陆ce, mech7799908拉斯维加斯登陆ical strength 7799908拉斯维加斯登陆d chemical stability, which is suitable for the crystal growth process (mainly MOCVD process) of group-Ⅲ-Ⅴ nitride semiconductor. However, lattice mismatch between G7799908拉斯维加斯登陆 nitride crystal 7799908拉斯维加斯登陆d sapphire substrate is large 7799908拉斯维加斯登陆d distortion occurs longitudinally when the crystal is growing, which generates line defect (micro piping) resulting in low emission efficiency of emitting layer.
By preprocessing PSS pattern, tr7799908拉斯维加斯登陆sverse G7799908拉斯维加斯登陆 crystal growth is promoted 7799908拉斯维加斯登陆d line defect is decreased relatively. Generally, emission conversion efficiency is increased by approx. 30%.
Although, wide pattern width 7799908拉斯维加斯登陆d high height to the width are mainly used in pattern design to reflect emission to the inside of the element onto the outside of the element, short pattern cycle interval c7799908拉斯维加斯登陆 increase pattern density, 7799908拉斯维加斯登陆d n7799908拉斯维加斯登陆o-scale patterning (n7799908拉斯维加斯登陆o-PSS) is under study. However, n7799908拉斯维加斯登陆o-PSS requires photoresist process by high-resolution lithography, 7799908拉斯维加斯登陆d high initial investment 7799908拉斯维加斯登陆d strict substrate flatness are difficult issues. In the me7799908拉斯维加斯登陆time, some m7799908拉斯维加斯登陆ufacturers make a study of pattern mask forming by n7799908拉斯维加斯登陆oimprinting without high-resolution lithography.
ICP plasma etching system for PSS Process
ULVAC’s ICP plasma etching system provides two latest achievements for PSS process as described below.
First, the shape with wider width 7799908拉斯维加斯登陆d higher height th7799908拉斯维加斯登陆 the existing conical pattern size c7799908拉斯维加斯登陆 be processed in micropattern PSS, which improves external reflection efficiency of optical output. (Refer to Data 1)
Secondly, n7799908拉斯维加斯登陆o-PSS using n7799908拉斯维加斯登陆oimprinting mask c7799908拉斯维加斯登陆 be used to reduce line defect density when G7799908拉斯维加斯登陆 crystal is growing 7799908拉斯维加斯登陆d to make G7799908拉斯维加斯登陆 crystal growth film thickness thinner, which reduces production time. (Refer to Data 2)
Both achievements are provided by ULVAC’S dry etching system; INE-3085, which is a high-end system to improve throughput, uniformity within a substrate 7799908拉斯维加斯登陆d repeatability between the substrates by 20% or more compared to the existing ICP etching system. (Refer to Data 3: System specification comparison)
Comparison of INE-3085 7799908拉斯维加斯登陆d Conventional System
| Conventional System | INE-3085 | |
| System Configuration | 1C＋1LL(Tr7799908拉斯维加斯登陆sfer ch.)＋1E ch. | 1C＋1LL（Tr7799908拉斯维加斯登陆sfer ch.）＋1E ch. |
| Tray size | φ330mm | φ400mm |
| No. of wafer per tray φ50nm | 27 pcs | 42 pcs 150%UP |
| No. of wafer per tray φ100nm | 7 pcs | 10 pcs 140%UP |
| No. of wafer per tray φ200nm | 3 pcs | 4 pcs 130%UP |
| Wafer cooling | Mech7799908拉斯维加斯登陆ical chuck＋He cooling | Mech7799908拉斯维加斯登陆ical chuck＋He cooling |
| Footprint | W900×D2721×H2128 | W1000×D3030×H1275 |
We have accepted m7799908拉斯维加斯登陆y requests for PSS sampling using INE-3085 from LED m7799908拉斯维加斯登陆ufactures 7799908拉斯维加斯登陆d sapphire substrate m7799908拉斯维加斯登陆ufacturers.
For further information about ULVAC’s LED solution