低功率損耗670伏超級接面金氧半場效電晶體元件之微縮設計;Device Scaling of 670V-class Super Junction MOSFETs with Low Power Loss

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Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/68945

Title:	低功率損耗670伏超級接面金氧半場效電晶體元件之微縮設計;Device Scaling of 670V-class Super Junction MOSFETs with Low Power Loss
Authors:	鐘俊逸;Jhong,Jyun-yi
Contributors:	電機工程學系
Keywords:	超級接面;功率金氧半場效電晶體;Super junction;Power MOSFETs
Date:	2015-08-19
Issue Date:	2015-09-23 14:47:10 (UTC+8)
Publisher:	國立中央大學
Abstract:	超級接面金氧半場效電晶體(SJ MOSFET)關鍵技術在於精確地設計電荷平衡的元件結構。首先，我們分別模擬整理出未達電荷平衡時以及達成電荷平衡時，所對應之最大電場發生位置，以利於後續在模擬製程條件時，可以藉由調整N-epi的濃度、P-pillar寬度、P-pillar摻雜劑量等條件，來迅速達成電荷平衡的設計。綜合考量製程變異對於耐壓的變化(Process window)以及權衡兼顧崩潰電壓與導通電阻的優化，以下是我們經過多方模擬測試之後，針對主動區Cell pitch : 20m至14m元件的結構微縮所提出的設計法則：(1) WP = WN = CP/2；(2) Poly Gate Width = 0.7CP；(3) 保持總電荷相等 (WP × NP = WN × NN)。超級接面金氧半場效電晶體的結構設計，除了需優化主動區的元件之外，為了避免元件在周邊區域發生提早崩潰之情事，更需避免在周圍區域有大電場的聚集的情況發生。因此，我們提出使周圍區域的電場得以均勻分佈的方法：(1)以漸進梯度的方式來縮減周邊區域P型柱與柱間的距離；(2)周圍區域場板(Field plate)的長度優化設計。本論文利用Silvaco的Athena與Atlas，分別模擬製程流程與電性分析，並與實際元件，進行比對分析，確認優化設計之可行性。總整模擬設計與實驗元件之測量結果可知，將元件Cell pitch從20m微縮至16m，雖然導致崩潰電壓從724降至678伏，但可以有效地調降特性導通電阻從3.4至2.45-mm2、也可調降閘極電荷(QG)從9.6至6.2nC，大幅降低功率損耗品質因子(FOM=Rdson×QG)約55%。模擬結果的趨勢與實驗結果吻合。為了進一步優化功率損耗品質因子，我們依Cell pitch=16m的條件為基準，藉由調變閘極寬從11m至9m，模擬結果顯示可再優化調降功率損耗品質因子約20%。根據此一模擬設計的元件結構，已有實際元件晶片產出，且驗證模擬設計法則之功效。 ;The challenges for the production of SJ MOSFET lies in the exquisite design of charge-balancing. In this thesis, we systematically analyze the depth profile of E-field across p-pillars under various conditions including charge imbalance and charge balance. This allows us to gain insight on the E-field distribution, facilitating the design of p-pillar dosage, p-pillar width and n-epi concentration to achieve “charge balance” precisely and rapidly. Considering the process variations and following the charge balance principle, we have proposed a simple, effective design rule for downscaling the SJ MOSFETs with cell pitch of 1420m. The design rule is briefed as follows: (1) WP = WN = CP/2, (2) Poly Gate Width = 0.7CP, (3) achieving charge balance at the condition of WP × NP = WN × NN. In addition to the device structure design in the cell, the structural design for the termination regions are also important in order to sustain high break down voltage for the entire system. We utilize two methods to make the E-field distribution as uniform as possible (to avoid the maximum E-filed occurring in specific regions). (1) A grading separation between pillar to pillar across the termination region, (2) Optimizing the field plate length design. We have used SILVACO Inc. Athena and Atlas simulator to simulate the device process and the corresponding electrical characteristics, respectively. The effectiveness of simulation results has been verified by the experimental data from real devices based on our design. Decreasing the cell pitch from 20m to 16 m, experiment data demonstrate that, although the breakdown voltage declines from 724 to 678V, we are able to reduce the Ron,sp from 3.4 to 2.45 -mm2 and QG from 9.6 to 6.2nC simultaneously, effectively improving the FOM(Rdson×QG) approximately by 55%. For the further advancement of optimal FOM, we modulate the gate electrode width to reduce the gate charge. Simulation results show that decreasing gate electrode width from 11m to 9m, the FOM can be further improves by more than 20%.
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