In September this year, Enkris Semiconductor declared an advancement when it showed top quality 300 mm GaN-on-silicon HEMT epiwafers, for 200V, 650V and 1200V power applications. In reaction to market demand, the China-based pure epi-foundry, moved its 200 mm AlGaN/GaN HEMT epitaxy process to 300 mm silicon substrates, an accomplishment that business chief executive, Kai Cheng, says was a collective effort of both hardware adjustment and procedure control.
Enkris had developed its 200 mm process back in 2014. However as Cheng mentions: “We decided to transfer to 300 mm following market requests. Thanks to constant research study and development throughout the years, we moved our technology to the larger wafer size after we had actually optimized parts of the procedure, such as deposition and metrology tools.”
At the heart of Enkris’ structures lies a high crystalline quality AlN-based nucleation layer onto which Al-containing buffer layers are grown to alleviate the lattice and thermal growth mismatches between the silicon substrate and active GaN layers. Thanks to the AlN nucleation layer, Enkris handled to fabricate 300 mm GaN-on-silicon HEMTs with relatively thin buffer layers that fulfill leakage current requirements whilst keeping overall gadget costs down.According to Enkris,
the buffer layers in its latest epiwafers are likewise only 2 to 6 microns thick, have consistent structure across the entire wafer and deliver consistent electrical homes. Company figures indicate wafer bow remains within an appropriate 50 micron while leakage present can be found in at 1μA/ mm2 at room temperature.Enkris Semiconductor CEO, Kai Cheng.As Cheng explains: “Thanks to our aluminium nitride nucleation layer, we have a quite big procedure window to handle
the stress in thick buffer layers and keep the wafer bow appropriate for the 300 millimetre fab.””In addition, the high quality aluminium nitride also implies that problems, such as V-pits and meltback etching defects at the nitride/silicon interface
, are decreased,”he adds.”Therefore, the leakage existing in the vertical direction can be substantially lowered and meet the requirements for high voltage applications on large-size silicon substrates up to 300 millimetre.”Cheng emphasizes that in spite of the industry-wide difficulties associated with epitaxy, strain management and problem control when transferring to 300mm wafer size, his business has actually accomplished excellent structural quality and electrical properties in its AlGaN/GaN HEMT structures.”This will definitely motivate the development of high-power incorporated circuits … [and] decrease the cost of gallium nitride power gadgets,”he says.Tackling tough concerns However what about yield figures? It’s no secret that bad yields have actually held back lots of market gamers, keen to deal with larger wafers sizes and enjoy the cost benefits this shift brings.Cheng is positive about yields at 300 mm wafer sizes, but says:”It
‘s still prematurely to speak about the yields of our twelve inch wafers in terms of substrates and epitaxy at this minute.”Still, as he includes:”We have not seen any genuine challenging hurdles of physics yet, however the last yield improvement depends on the entire market’s efforts including metrology tool suppliers, processing tool vendors, growers and gadget makers.”Back in 2014, Enkris likewise worked closely with Aixtron on its high voltage GaN HEMT structures on 200 mm silicon, using a high throughput Crius II Close Coupled Showerhead Reactor. This time around, such system details are not disclosed, however Cheng is specific that devices produced from Enkris’300 mm GaN-on-silicon epiwafers will be cost-competitive.”
The gallium nitride-on-silicon wafer costs are typically greater than silicon products, but gallium nitride materials have extremely unique residential or commercial properties,”he says.”And if we look at silicon power devices, more than three times more gallium nitride gadgets can be produced from the very same wafer size, making the gallium nitride gadget costs equivalent or perhaps lower than its silicon rivals.
“So where next for Enkris Semiconductor? Today, the pure-play epi-foundry is delivering its plus size GaN-on-silicon HEMT epiwafers worldwide- Cheng says his company is seeing interest from China, the rest of Asia, the United States and Europe. He also points out how vertical breakdown measurements show the structures can run at 200V, 650V and 1200V voltage ranges for a vast array of power applications
such as consumer electronics and information centre applications. And while Enkris also establishes GaN-on-SiC, GaN-on-sapphire and GaN-on-GaN epiwafers, GaN-on-silicon wafers are presently in the best need, being required for RF, power and microLED show applications.” We are growing different fascinating structures, but we do pay attention to consumer requirements,” he says.”As an industrial business, we are creating world class items for market.”Source