Tesla AI Day 2023 Says 75% Reduction in SiC Usage 

特斯拉在 2023 投資者日表示將減少 75% 的碳化矽用量

Tesla's Colin Campbell discussed about reducing silicon carbide usage by 75% in next generation EV platform in Tesla Investor Day 2023. This has caused big stock price drops on silicon carbide companies including Wolfspeed, Onsemi and STMicroelectronics.  How can Telsa reduce such a large amount of SiC usage?  Should SiC investors worry?

特斯拉的 Colin Campbell 在 Investor Day 2023 中，提到下一代 EV 平台將碳化矽用量減少 75%，導致了隔日 Wolfspeed、Onsemi 和 STMicroelectronics 等碳化矽公司的股價大幅下跌，Telsa 如何能減少如此多的 SiC 用量？碳化矽投資人應該擔心嗎？

1) SiC MOSFET Improvement 碳化矽場效電晶體設計改善

Tesla introduced SiC in Model 3 with support from STMicroelectronics in 2018. In 2022 STMicro launched automotive qualified Gen 3 SiC MOSFET with 40% reduction in specific on resistance normalized the MOSFET array from Gen 2 products. This means 40% less SiC required for the same current. SiC in Tesla EV is at least one generation behind. 

特斯拉在 STMicroelectronics 的支持下，2018 年在 Model 3 車型上採用了 SiC。2022 年 STMicro 推出了符合汽車標準的第 3 代 SiC MOSFET，第 3 代的 MOSFET 陣列導通電阻，相較第 2 代產品降低了 40%，意味著相同電流所需的 SiC 面積可以減少 40%，而 Tesla EV 中的 SiC 至少落後了 STMicro 產品一代。

STMicroelectronics SiC MOSFET die 意法半導體 SiC MOSFET 晶粒

Source: Tech Insights

STMicro achieved the savings by a shell pitch shrink combined with segmenting P+ body contacts along the source array.  All while sticking with the more conservative play in the gate MOSFET array. Trench design can provide even further efficiency savings.

STMicro 通過縮減間距、結合源極陣列、分段 P+ 體接觸點，在維持保守的柵極 MOSFET 陣列設計下，達到了降低電阻的目標，甚至透過溝槽設計的改善，應該還能進一步的改善。

P+ body contacts of STMicroelectronics SiC device

Source: Tech Insights

2) New Package Design 新的封裝設計

Tesla also mentioned that they have designed their own thermally optimized package. Details of this are yet to be revealed so specific efficiency savings are difficult to predict at this stage. However, in principle this means a SiC device within can be driven harder. STMicro's 3rd generation SiC MOSFET are already rated 200oC, the highest available in the market and beyond what Silicon is capable of.

特斯拉還提到他們已經設計了自己優化過散熱的封裝設計，但細節未公佈，因此現階段難以預測具體提升的效率。然而，SiC 可以被更高效的驅動， STMicro 的第三代 SiC MOSFET 額定溫度已經達到 200oC，是市場上最高、遠超過矽晶片的能力。

SiC as a material does not degrade until well over 500oC so there is in fact a huge amount of room to grow here. It's the packaging, wiring and contacts that really need to catch up to the SiC.

碳化矽材料直到超過 500oC 才會降解，因此實際上還有有很大的空間，真正需要趕上 SiC 技術的是封裝、佈線和接觸點。

3) SiC MOSFET Integrate with SiC Schottky Diode 整合 SiC 肖基二極體

There are more novel approaches to the reduction of use of silicon carbide material. Despite silicon carbide MOSFET having their own internal body diode for reverse conduction, they are commonly co-packaged in module configurations with additional silicon carbide schottky diodes to improve system robustness.

目前有更多新穎的方法，來減少碳化矽材料的使用，儘管碳化矽 MOSFET 具有反向傳導的內部二極體效應，它們常與外部的碳化矽肖基二極體，共同封裝在模塊配置中，以提高系統強健性。

Toshiba is the 1st SiC manufacturer taking this approach of integrating a schottky diode into an active silicon carbide MOSFET array seen in the cross-sectional example here. This increase the SiC die size but in fact reduces the overall amount of silicon carbide necessary as a system level. We expect many more manufacturers to go down this route over the coming years.

東芝是第一家將肖特基二極體集成到碳化矽 MOSFET 陣列晶片中的 SiC 製造商，下圖為其橫截面電子顯微鏡照片，雖然如此會增加 SiC 晶片尺寸，但在系統層面上，減少了所需的碳化矽總量，預計未來幾年會有更多製造商走上這個設計方向。

SiC MOSFET with Integrated Schottky Diode

Source: Tech Insights

結  語

Some final point to note. Tesla does estimate a 75% reduction of SiC per car for their next generation vehicle not affecting the current production cars. They also plan to increase the amount of EVs produced to 20 millions per year, a 20-fold increase. Granted this is an ambitious target but with the ever-growing new entrance using silicon carbide in the EV market. I wouldn't be panicking just yet about the prospect for silicon carbide. As Tech Insights forecast shows silicon IGBTs maintaining the larger share of volume for some time, but silicon carbide penetration approaches 30% in 2029.

最後，特斯拉的確估計下一代電動車，每輛將減少 SiC 75% 的用量，但還不會影響當前生產的車款，特斯拉計劃將每年生產的汽車數量增加到 2000 萬輛、代表 20 倍的增加。

儘管這是個雄心勃勃的目標，但隨著電動汽車中使用碳化矽的不斷增長，目前還不需要對碳化矽的前景感到恐慌，Tech Insights 預測，矽基 IGBT 元件將在一段時間內保持較大的銷量份額，但到 2029 年碳化矽的滲透率將接近 30%。