Featured Article: Next Generation Power Semiconductor: What is GaN / SiC ? Sanken and Next Generation Semiconductors

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Part 3. Sanken Electric's Strengths in SiC and GaN Devices

Sanken Electric's approach to next generation devices

Sanken Electric is a semiconductor manufacturer with more than 70 years of history since its establishment in 1946.
As a specialized manufacturer of power electronics, we recognized the importance of compound semiconductors for next-generation power devices and have been conducting research and development since the 1990s.

Sanken Electric's GaN power devices originated in blue LED substrate technology. Sanken was ahead of the industry in developing InGaN on Silicon LED (Patented by Sanken Electric), a gallium nitride compound mixed with indium on a silicon substrate. This has contributed to making a low cost blue LED possible.
Furthermore, since 2002, Sanken has succeeded in the development of high voltage elements for power devices with support from NEDO. Using these elements, Sanken has introduced motors and power supply applications since 2004.

As for SiCs, Sanken has been participating in NEDO'S projects for the development of next generation power electronics technology since 2009 while developing SiC devices in parallel, and announcing applications examples for power supplies.
NEDO: New Energy and Industrial Technology Development Organization.



Sanken Electric's Strengths in SiC and GaN Power Devices

Sanken Electric commercialized silicon diodes for electric power in 1959, and have manufactured numerous power devices since then, including transistors, power MOSFETs, and IGBTs. Based on these achievements, Sanken is now advancing with the development of both SiC and GaN power devices.

Therefore, Sanken is familiar with the advantages and disadvantages of each element, and our strength lies in our ability to develop products in accordance with the objective.
Sanken can develop products that optimally and flexibly combine SiC, GaN and silicon devices to meet the wide range of requirements for electronic circuits, including high voltage, high current, and downsizing.
It is important to accumulate proprietary know-how for each material in the manufacturing process as well. By exploiting our long experience in the field of silicon devices, together with our patents and proprietary know-how, Sanken Electric is undergoing research and development of the manufacturing process to achieve maximization of the SiC / GaN performance and improved productivity.

Strengths


SiC - Vg=15V Realized with SiC by Proprietary Manufacturing Technology

Silicon ingots are manufactured by the pull-up method. However, SiC is manufactured by the sublimation method, which grows crystals at high temperatures above 2000°C.
Therefore, it was difficult to manufacture wafers with few crystal defects and hindered their widespread use due to their small wafer diameter. However, recent technological innovations in wafer manufacturing have led to the supply of 6-inch wafers, resulting in lower wafer prices.

Sanken Electric's SiC MOSFET is characterized by its simple, easy-to-build trench structure, similar to that of low-voltage silicon MOSFETs.
It also has a unique gate characteristic. SiC MOSFETs are expected to be used as a replacement for silicon IGBTs, but in general, the gate characteristics of SiC is inferior to that of silicon, and many SiC MOSFETs require higher drive voltage than silicon IGBTs. As a result, gate drive voltage must be adjusted when replacing silicon IGBTs with SiC MOSFETs. Sanken Electric has developed an original manufacturing process that makes it possible to drive SiC MOSFETs at the same Vg=15V as silicon IGBTs. This makes it possible to easily replace SiC MOSFETs.

Advantages of using SiC


Example of SiC Application: Inverter Using a Full SiC Module

Sanken Electric has created a 10 kW inverter module using a full-SiC module. A full-SiC module is a module with three half-bridge circuits, in other words, six built-in SiC MOSFETs.
SiC devices not only have low losses, but they can operate continuously at temperatures as high as 200 degrees Celsius, making it possible to significantly reduce the size of heat sinks.
This has enabled the volume of the inverter to be reduced to 1/36th that of a general-purpose inverter using silicon IGBTs as the main element. (Compared to Sanken's conventional product)





Topic: SiC Wafers are Translucent

Translucent SiC Wafers


Unlike silicon, SiC wafers are translucent.
Sanken Electric logo is visible through an unprocessed SiC wafer.
Various electrodes are formed on the SiC substrate to make diodes and power MOSFETs.



GaN - For a Stable Mass Production With Manufacturing Technology That Suppresses the Collapse Phenomenon

Like SiC, it is difficult to manufacture GaN wafers with few crystal defects, and wafers are expensive. Therefore, Sanken Electric has been focusing on the research and development of "GaN on Silicon" (Sanken Electric proprietary), a method of growing GaN epitaxial layers on low-cost silicon substrates.
GaN-based devices are generally made of a wafer with GaN grown on the silicon substrate in a horizontal structure, and Sanken Electric is also undergoing development of horizontal structured GaN devices.
Unlike the vertical structured silicon and SiC, horizontal structures have source and drain electrodes placed on the wafer surface, making it difficult to manufacture high-voltage, high-current devices at low cost. However, because GaN uses a conduction mechanism based on the quantum effect, it is possible to create a device with extremely high speed and low on-resistance, making it ideal for use in 100W-class power supplies.

The biggest challenge in manufacturing GaN devices was the collapse phenomenon, which took a long time to establish mass production technology. The "Collapse Phenomenon" is a phenomenon in which the on-resistance of the element fluctuates after a high voltage is applied during switching.
In order to solve this problem, it is very important to have a technology that can precisely control all processes in a GaN device, including the multi-layered epitaxial layers and the numerous wiring layers, and also detect and inspect various collapse phenomenon.
Sanken Electric has accumulated manufacturing and inspection technologies, including the epitaxial growth processes, and is on track to achieve stable mass production.

Advantages of using GaN

Example of GaN Applications: Realizing a PFC Circuit Operating at 1 MHz

One of the major features of GaN is its ability to switch in MHz, as opposed to silicon, which has been limited to switching at a few hundred kHz. By using this performance to achieve higher frequencies in circuits, it can significantly reduce the mounting area of the transformer, making it possible to achieve a compact, high output power supply.
In particular, GaN's fast switching performance is very effective in realizing the USB Power Delivery standard, which requires compact size with high output power.
Sanken Electric has realized a PFC circuit with 1 MHz operation, using GaN FETs with a dedicated gate driver.
The gate driver is digitally controlled by a microcontroller.
(Sanken Electric's MD660x series microcontrollers for digital power supply is used)

Realize PFC circuit with 1MHz operation using GaN FET



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Part 1. Next Generation Power Semiconductors: What is GaN / SiC?
   ■ Characteristic of SiC / GaN Devices
   ■ Application of SiC / GaN Devices to Replace Silicon Devices

Part 2. Application of SiC / GaN Devices
   ■ 9 Applications Where SiC and GaN Devices are Expected to be Used

Part 3. Sanken Electric's Strengths in SiC and GaN Devices
   ■ Engagement in Semiconductor Development of GaN Devices Since 2002 and SiC Devices Since 2009
   ■ Sanken Electric's Strengths in Each of the SiC and GaN Devices

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