CN113990927B - 一种减小米勒电容的新型rc-igbt结构 - Google Patents

一种减小米勒电容的新型rc-igbt结构 Download PDF

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CN113990927B
CN113990927B CN202111251255.1A CN202111251255A CN113990927B CN 113990927 B CN113990927 B CN 113990927B CN 202111251255 A CN202111251255 A CN 202111251255A CN 113990927 B CN113990927 B CN 113990927B
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伍伟
李岩松
陈勇
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University of Electronic Science and Technology of China
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    • H01L29/72—Transistor-type devices, i.e. able to continuously respond to applied control signals
    • H01L29/739—Transistor-type devices, i.e. able to continuously respond to applied control signals controlled by field-effect, e.g. bipolar static induction transistors [BSIT]
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    • H01L29/7395—Vertical transistors, e.g. vertical IGBT
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Abstract

本发明提供了一种减小米勒电容的新型RC‑IGBT结构，该结构在常规RC‑IGBT结构的基础上，在沟槽栅下方对应的P型集电区与集电极金属之间增添SiO2氧化层，来增大栅极与集电极间的距离。除此之外，改变RC‑IGBT中IGBT区域的栅极分布，包括沟槽栅与Dummy栅的比例以及栅极之间的间距。通过增大沟槽栅的比率，使沟槽栅底部电势快速提升，当沟槽栅底部电势高于栅极与发射极间电压VGE时，耗尽区将向栅极下方扩展，进一步增大栅极与集电极间的间距，从而减小CGC。CGC的减小使得RC‑IGBT在IGBT工作模式下开启、关断过程中的VCE电压拖尾现象减弱，从而减小RC‑IGBT的开启关断损耗。

Description

一种减小米勒电容的新型RC-IGBT结构
技术领域
本发明涉及半导体领域，具体涉及一种减小米勒电容的新型RC-IGBT结构。
背景技术
为了缩减功率器件的尺寸和生产成本，学者们提出将反向续流二极管寄生在IGBT内部，从而研究出了逆导型IGBT(Reverse Conducting-IGBT，RC-IGBT)。RC-IGBT目前受到广泛研究，相比IGBT与续流二极管反向并联的电路结构，RC-IGBT具备更良好的散热性能，可以减小热阻变化和温度波动对器件的影响，因此可以对RC-IGBT施加更大的电流密度。然而在高电流密度条件下，RC-IGBT在IGBT工作模式下进行开启和关断都会产生明显的电压拖尾现象。电压拖尾无疑会严重增加器件的使用损耗。
根据目前的研究可知，对于电压拖尾现象的产生，影响最大的因素是米勒电容，即栅极与集电极间电容CGC。因此如果可以降低RC-IGBT在IGBT工作模式下开启、关断时的米勒电容，即可有效抑制开关过程的电压拖尾现象，从而降低器件损耗。
发明内容
针对RC-IGBT在IGBT工作模式下开启、关断时的米勒电容，进而降低器件损耗的需求，本发明提供了一种减小动态米勒电容的新型RC-IGBT结构。
本发明解决上述技术问题所采用的技术方案是：一种减小米勒电容的新型RC-IGBT结构，其元胞结构包括P型集电区(1)和N型集电区(2)，位于集电区(1)、(2)上方的N型缓冲层(3)和N型漂移区(4)，载流子存储层(5)及P型基区(6)，所述P型基区(6)上设有N+型发射区(7)和P+型发射区(8)，发射区间有多晶硅(9)和SiO2氧化层(10)构成的栅极。结构图中A1、A2、A3为沟槽栅，D1、D2、D3为Dummy栅。并在沟槽栅下方对应的P型集电区(1)与集电极金属之间增添SiO2氧化层(11)，以增大栅极与集电极之间的间距。沟槽栅上方SiO2氧化层，避免栅极与发射极短路。
本发明的技术方案相对常规RC-IGBT结构，主要针对IGBT区域背面结构以及栅极结构进行改进。在沟槽栅下方对应的P型集电区(1)部分与集电极金属之间，增添SiO2氧化层，以增大栅极与集电极之间的间距。同时改变沟槽栅占栅极总数的比率以及栅间距，从而影响栅极底部电势分布以及耗尽层的分布，最终减小IGBT器件在开启和关断过程中的米勒电容CGC，降低器件损耗。
进一步地，改变器件沟槽栅与Dummy栅的比率，增大沟槽栅比例。
进一步地，改变栅间间距，增大栅间间距，减小因增大沟槽栅密度所造成电流分布不均的影响，同时减小Dummy栅对于沟槽栅底部电势分布的影响。
进一步地，在改变栅极分布以及栅间距之后，还需调整N+型发射区(7)的浓度与尺寸，使得本结构与常规RC-IGBT结构具有相似的注入效率与沟道密度。
本发明的有益效果为：本发明提供了一种减小米勒电容的新型RC-IGBT结构，该结构在常规RC-IGBT结构的基础上，在沟槽栅下方对应的P型集电区与集电极金属之间增添SiO2氧化层，来增大栅极与集电极间的距离。除此之外，改变RC-IGBT中IGBT区域的栅极分布，包括沟槽栅与Dummy栅的比例以及栅极之间的间距。通过增大沟槽栅的比率，使沟槽栅底部电势快速提升，当沟槽栅底部电势高于栅极与发射极间电压VGE时，耗尽区将向栅极下方扩展，进一步增大栅极与集电极间的间距，从而减小CGC。CGC的减小使得RC-IGBT在IGBT工作模式下开启、关断过程中的VCE电压拖尾现象减弱，从而减小RC-IGBT的开启关断损耗。
附图说明
图1为本发明的结构示意图；
图2为常规RC-IGBT结构示意图；
图3为本发明RC-IGBT开启时栅极底部电势示意图；
图4为本发明RC-IGBT与常规RC-IGBT开启过程电压曲线示意图。
具体实施方式
下面对本发明的具体实施方式进行描述，以便于本技术领域的技术人员理解本发明，但应该清楚，本发明不限于具体实施方式的范围，对本技术领域的普通技术人员来讲，只要各种变化在所附的权利要求限定和确定的本发明的精神和范围内，这些变化是显而易见的，一切利用本发明构思的发明创造均在保护之列。
本发明提出了减小米勒电容的新型RC-IGBT结构，其元胞结构包括P型集电区(1)和N型集电区(2)，位于集电区(1)、(2)上方的N型缓冲层(3)和N型漂移区(4)，载流子存储层(5)及P型基区(6)，所述P型基区(6)上设有N+型发射区(7)和P+型发射区(8)，发射区间有多晶硅(9)和SiO2氧化层(10)构成的栅极。结构图中A1、A2、A3为沟槽栅，D1、D2、D3为Dummy栅。并在沟槽栅下方对应的P型集电区(1)与集电极金属之间增添SiO2氧化层(11)，以增大栅极与集电极之间的间距。沟槽栅上方SiO2氧化层，避免栅极与发射极短路。
本发明的方案相对常规RC-IGBT结构，主要针对IGBT区域的背面结构及栅极结构进行改进。在沟槽栅下方对应的P型集电区(1)部分与集电极金属之间，增添SiO2氧化层，以增大栅极与集电极之间的间距，以减小米勒电容CGC。栅极结构的改变包括对IGBT区域的栅极间距以及沟槽栅占据栅极总数的比率进行调整，达到改变栅极底部电势分布的效果，进而减小米勒电容CGC以及器件损耗。器件结构优化的具体实现为：增大沟槽栅占据栅极总数的比例，即增大了沟槽栅密度，使得相邻沟槽栅间的电势在相互影响下可以更快速的增大，沟槽栅底部的电势即可更快超越栅极与发射极间的电压VGE，进一步使得耗尽区向下扩展，从而等效于增加了栅极到集电极的距离，减小米勒电容CGC。在IGBT器件开启和关断过程中，造成电压拖尾现象产生的最主要因素即为米勒电容CGC，故减小米勒电容即可改善器件在开关过程中的电压拖尾现象，降低器件损耗。
在一次实施例中，对本发明与常规的RC-IGBT进行实验测试，均选取8V的栅极电压。如图3所示，本发明器件结构在任何集电极与发射极电压下，栅极底部电势都高于常规RC-IGBT器件，即本发明器件栅极底部电压可更快超过栅极与发射极间电压，使得耗尽层向下进行扩展，减小米勒电容CGC。图中纵坐标VT为栅极底部电势。
在一次实施例中，如图4所示，在施加相同的栅极电压及集电极电压测试条件下，IGBT开启过程中，本方案所提出结构的电压拖尾现象得到明显改善。进一步可说明器件的开启、关断损耗得到优化改善。
进一步地，改变器件沟槽栅与Dummy栅的比率，在IGBT区域增加沟槽栅的密度，沟槽栅与总栅比例的典型值为1/2。
进一步地，改变栅间间距，增大栅间间距，减小因增大沟槽栅密度所造成电流分布不均的影响，同时减小Dummy栅对于沟槽栅底部电势分布的影响。
进一步地，在改变栅极分布以及栅间距之后，还需调整N+型发射区(7)的浓度与尺寸，使得本结构与常规RC-IGBT结构具有相似的注入效率与沟道密度。
综上所述，本发明提供了一种减小米勒电容的新型RC-IGBT结构，该结构在常规RC-IGBT结构的基础上，在沟槽栅下方对应的P型集电区与集电极金属之间增添SiO2氧化层，来增大栅极与集电极间的距离。除此之外，改变RC-IGBT中IGBT区域的栅极分布，包括沟槽栅与Dummy栅的比例以及栅极之间的间距。通过增大沟槽栅的比率，使沟槽栅底部电势快速提升，当沟槽栅底部电势高于栅极与发射极间电压VGE时，耗尽区将向栅极下方扩展，进一步增大栅极与集电极间的间距，从而减小CGC。CGC的减小使得RC-IGBT在IGBT工作模式下开启、关断过程中的VCE电压拖尾现象减弱，从而减小RC-IGBT的开启关断损耗。

Claims (5)

1.一种减小米勒电容的RC-IGBT结构，其元胞结构从下往上依次为：P型集电区(1)和N型集电区(2)，位于P型集电区(1)和N型集电区(2)上方的N型缓冲层(3)和N型漂移区(4)，载流子存储层(5)及P型基区(6)，所述P型基区(6)上设有N+型发射区(7)和P+型发射区(8)，发射区间依次设置有多晶硅(9)和SiO2氧化层(10)构成的沟槽栅极A1、A2、A3，以及由多晶硅(9)和SiO2氧化层(10)构成的Dummy栅极D1、D2、D3，并在沟槽栅极A1、A2、A3下方对应的P型集电区(1)与集电极金属之间增添SiO2氧化层(11)，以增大栅极A1、A2、A3与集电极之间的间距；沟槽栅极A1、A2、A3上方SiO2氧化层，避免栅极与发射极短路。
2.根据权利要求1所述的减小米勒电容的RC-IGBT结构，其特征在于，在沟槽栅极A1、A2、A3下方对应的部分P型集电区(1)与集电极金属之间，增添SiO2氧化层，以增大沟槽栅极A1、A2、A3与集电极之间的间距。
3.根据权利要求1所述的减小米勒电容的RC-IGBT结构，其特征在于，改变沟槽栅与Dummy栅的比率，增大沟槽栅比例。
4.根据权利要求1所述的减小米勒电容的RC-IGBT结构，其特征在于，改变栅间间距，增大栅间间距，减小因增大沟槽栅密度所造成电流分布不均的影响，同时减小Dummy栅对于沟槽栅底部电势分布的影响。
5.根据权利要求4所述的减小米勒电容的RC-IGBT结构，其特征在于，改变沟槽栅极A1、A2、A3及Dummy栅极D1、D2、D3的分布以及栅间距之后，还需调整N+型发射区(7)的浓度与尺寸。
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