MOS管为什么会静(jing)电击穿详解及MOS管击穿原因与解决方案-KIA MOS管
信息(xi)来源：本(ben)站 日期：2018-12-05
（1）穿(chuan)通(tong)击(ji)穿(chuan)的击(ji)穿(chuan)点软，击(ji)穿(chuan)过程中(zhong)，电流(liu)有逐(zhu)渐增大(da)的特(te)征，这是(shi)因为耗(hao)尽(jin)层(ceng)扩展较宽，发生电流(liu)较大(da)。另(ling)一方面，耗(hao)尽(jin)层(ceng)展广大(da)容易发生DIBL效应，使源衬底结正偏呈现电流(liu)逐(zhu)渐增大(da)的特(te)征。
（2）穿(chuan)(chuan)(chuan)(chuan)通击(ji)(ji)(ji)穿(chuan)(chuan)(chuan)(chuan)的(de)(de)(de)(de)软击(ji)(ji)(ji)穿(chuan)(chuan)(chuan)(chuan)点(dian)(dian)发生在源(yuan)漏的(de)(de)(de)(de)耗(hao)尽(jin)层相(xiang)接时(shi)，此刻源(yuan)端(duan)的(de)(de)(de)(de)载(zai)流(liu)子(zi)注入到耗(hao)尽(jin)层中， 被耗(hao)尽(jin)层中的(de)(de)(de)(de)电场(chang)加快到达漏端(duan)，因此，穿(chuan)(chuan)(chuan)(chuan)通击(ji)(ji)(ji)穿(chuan)(chuan)(chuan)(chuan)的(de)(de)(de)(de)电流(liu)也(ye)有急剧增大(da)(da)点(dian)(dian)，这(zhei)(zhei)个电流(liu)的(de)(de)(de)(de)急剧增大(da)(da)和雪(xue)崩击(ji)(ji)(ji)穿(chuan)(chuan)(chuan)(chuan)时(shi)电流(liu)急剧增大(da)(da)不(bu)同，这(zhei)(zhei)时(shi)的(de)(de)(de)(de)电流(liu)相(xiang)当于源(yuan)衬底PN结正向(xiang)导通时(shi)的(de)(de)(de)(de)电流(liu)，而(er)雪(xue)崩击(ji)(ji)(ji)穿(chuan)(chuan)(chuan)(chuan)时(shi)的(de)(de)(de)(de)电流(liu)主要为PN结反向(xiang)击(ji)(ji)(ji)穿(chuan)(chuan)(chuan)(chuan)时(shi)的(de)(de)(de)(de)雪(xue)崩电流(liu)，如不(bu)作限流(liu)，雪(xue)崩击(ji)(ji)(ji)穿(chuan)(chuan)(chuan)(chuan)的(de)(de)(de)(de)电流(liu)要大(da)(da)。
（3）穿(chuan)通击穿(chuan)一(yi)般不会呈现破坏性击穿(chuan)。因为穿(chuan)通击穿(chuan)场强没有(you)到(dao)达雪崩击穿(chuan)的场强，不会发生许多(duo)电子空穴对。
（4）穿(chuan)(chuan)通击穿(chuan)(chuan)一(yi)般(ban)发生在沟道(dao)体内(nei)，沟道(dao)外表不(bu)容(rong)易发生穿(chuan)(chuan)通，这主要是因为(wei)沟道(dao)注(zhu)入使(shi)外表浓度比浓度大构(gou)成，所以(yi)，对NMOS管一(yi)般(ban)都(dou)有防穿(chuan)(chuan)通注(zhu)入。
（5）一般(ban)的，鸟嘴边际的浓度(du)比沟道中心浓度(du)大，所以穿通击穿一般(ban)发(fa)生在沟道中心。
（6）多晶栅(zha)长(zhang)度对穿(chuan)通击(ji)穿(chuan)是有(you)影响的，跟着栅(zha)长(zhang)度添加，击(ji)穿(chuan)增大。而(er)对雪崩击(ji)穿(chuan)，严(yan)格来说也(ye)有(you)影响，可是没有(you)那么(me)明显。
MOS管(guan)一(yi)个ESD敏感(gan)器件(jian)，它本身(shen)的(de)(de)输(shu)入(ru)电(dian)(dian)(dian)(dian)(dian)阻(zu)很高(gao)，而(er)栅(zha)-源极(ji)间(jian)(jian)(jian)电(dian)(dian)(dian)(dian)(dian)容(rong)又(you)非(fei)常小，所(suo)以极(ji)易受外界电(dian)(dian)(dian)(dian)(dian)磁(ci)场或静电(dian)(dian)(dian)(dian)(dian)的(de)(de)感(gan)应(ying)而(er)带(dai)电(dian)(dian)(dian)(dian)(dian)(少(shao)量电(dian)(dian)(dian)(dian)(dian)荷就可能在极(ji)间(jian)(jian)(jian)电(dian)(dian)(dian)(dian)(dian)容(rong)上(shang)形(xing)成相(xiang)当高(gao)的(de)(de)电(dian)(dian)(dian)(dian)(dian)压(ya)(想(xiang)想(xiang)U=Q/C)将管(guan)子损坏(huai))，又(you)因在静电(dian)(dian)(dian)(dian)(dian)较(jiao)强的(de)(de)场合(he)难于泄放电(dian)(dian)(dian)(dian)(dian)荷，容(rong)易引起静电(dian)(dian)(dian)(dian)(dian)击(ji)穿(chuan)(chuan)。静电(dian)(dian)(dian)(dian)(dian)击(ji)穿(chuan)(chuan)有(you)两种方(fang)式：一(yi)是(shi)电(dian)(dian)(dian)(dian)(dian)压(ya)型，即栅(zha)极(ji)的(de)(de)薄氧化层发(fa)生击(ji)穿(chuan)(chuan)，形(xing)成针孔(kong)，使栅(zha)极(ji)和源极(ji)间(jian)(jian)(jian)短路(lu)，或者使栅(zha)极(ji)和漏极(ji)间(jian)(jian)(jian)短路(lu);二(er)是(shi)功率(lv)型，即金(jin)属(shu)化薄膜铝(lv)条被(bei)熔断，造成栅(zha)极(ji)开路(lu)或者是(shi)源极(ji)开路(lu)。JFET管(guan)和MOS管(guan)一(yi)样，有(you)很高(gao)的(de)(de)输(shu)入(ru)电(dian)(dian)(dian)(dian)(dian)阻(zu)，只是(shi)MOS管(guan)的(de)(de)输(shu)入(ru)电(dian)(dian)(dian)(dian)(dian)阻(zu)更高(gao)。
静电(dian)(dian)(dian)放(fang)电(dian)(dian)(dian)形(xing)(xing)成的(de)是(shi)短时(shi)大电(dian)(dian)(dian)流，放(fang)电(dian)(dian)(dian)脉冲(chong)的(de)时(shi)间常(chang)数(shu)远小(xiao)于器(qi)(qi)件散热(re)的(de)时(shi)间常(chang)数(shu)。因(yin)此，当静电(dian)(dian)(dian)放(fang)电(dian)(dian)(dian)电(dian)(dian)(dian)流通过(guo)面积很小(xiao)的(de)pn结(jie)或肖特基结(jie)时(shi)，将产生(sheng)(sheng)很大的(de)瞬间功(gong)率(lv)(lv)密度，形(xing)(xing)成局部(bu)过(guo)热(re)，有可能(neng)使(shi)局部(bu)结(jie)温(wen)达到甚至(zhi)超过(guo)材料的(de)本征温(wen)度(如硅的(de)熔点1415℃)，使(shi)结(jie)区局部(bu)或多处(chu)熔化导致pn结(jie)短路，器(qi)(qi)件彻(che)底失效(xiao)。这种失效(xiao)的(de)发生(sheng)(sheng)与否，主要取决(jue)于器(qi)(qi)件内部(bu)区域的(de)功(gong)率(lv)(lv)密度，功(gong)率(lv)(lv)密度越(yue)小(xiao)，说明器(qi)(qi)件越(yue)不(bu)易受到损伤。
反(fan)(fan)偏(pian)(pian)(pian)pn结(jie)(jie)比正偏(pian)(pian)(pian)pn结(jie)(jie)更容易发生热(re)致失效，在(zai)反(fan)(fan)偏(pian)(pian)(pian)条件下(xia)使结(jie)(jie)损坏所(suo)需要的(de)(de)能量(liang)只有正偏(pian)(pian)(pian)条件下(xia)的(de)(de)十分(fen)之一左右。这(zhei)是(shi)因(yin)为反(fan)(fan)偏(pian)(pian)(pian)时，大(da)部分(fen)功率消耗在(zai)结(jie)(jie)区中心，而正偏(pian)(pian)(pian)时，则多消耗在(zai)结(jie)(jie)区外(wai)的(de)(de)体电(dian)(dian)(dian)阻上。对(dui)于(yu)双极器件，通常发射(she)结(jie)(jie)的(de)(de)面积比其它结(jie)(jie)的(de)(de)面积都(dou)小，而且(qie)结(jie)(jie)面也比其它结(jie)(jie)更靠近表面，所(suo)以(yi)常常观察到的(de)(de)是(shi)发射(she)结(jie)(jie)的(de)(de)退(tui)化。此外(wai)，击穿电(dian)(dian)(dian)压高于(yu)100V或漏电(dian)(dian)(dian)流小于(yu)1nA的(de)(de)pn结(jie)(jie)(如JFET的(de)(de)栅结(jie)(jie))，比类似尺寸的(de)(de)常规(gui)pn结(jie)(jie)对(dui)静电(dian)(dian)(dian)放电(dian)(dian)(dian)更加敏感。
所(suo)有的(de)(de)(de)东西是(shi)(shi)相(xiang)对(dui)(dui)的(de)(de)(de)，不(bu)是(shi)(shi)绝对(dui)(dui)的(de)(de)(de)，MOS管(guan)(guan)(guan)(guan)只是(shi)(shi)相(xiang)对(dui)(dui)其它的(de)(de)(de)器件(jian)(jian)要敏感些，ESD有一(yi)(yi)个(ge)很大的(de)(de)(de)特点就是(shi)(shi)随机性，并不(bu)是(shi)(shi)没有碰到MOS管(guan)(guan)(guan)(guan)都能(neng)(neng)够把它击穿。另外，就算是(shi)(shi)产(chan)(chan)(chan)生(sheng)ESD，也不(bu)一(yi)(yi)定(ding)会(hui)(hui)把管(guan)(guan)(guan)(guan)子(zi)(zi)击穿。静(jing)电(dian)(dian)的(de)(de)(de)基本物理特征为：(1)有吸引或排斥的(de)(de)(de)力量;(2)有电(dian)(dian)场存在(zai)(zai)(zai)，与大地有电(dian)(dian)位差;(3)会(hui)(hui)产(chan)(chan)(chan)生(sheng)放电(dian)(dian)电(dian)(dian)流(liu)。这(zhei)三种(zhong)情(qing)(qing)形即ESD一(yi)(yi)般会(hui)(hui)对(dui)(dui)电(dian)(dian)子(zi)(zi)元(yuan)(yuan)件(jian)(jian)造成以下三种(zhong)情(qing)(qing)形的(de)(de)(de)影(ying)响(xiang)：(1)元(yuan)(yuan)件(jian)(jian)吸附灰尘，改变线路间(jian)的(de)(de)(de)阻(zu)抗，影(ying)响(xiang)元(yuan)(yuan)件(jian)(jian)的(de)(de)(de)功能(neng)(neng)和寿命;(2)因电(dian)(dian)场或电(dian)(dian)流(liu)破(po)坏元(yuan)(yuan)件(jian)(jian)绝缘层和导体，使(shi)元(yuan)(yuan)件(jian)(jian)不(bu)能(neng)(neng)工作(完全破(po)坏);(3)因瞬间(jian)的(de)(de)(de)电(dian)(dian)场软击穿或电(dian)(dian)流(liu)产(chan)(chan)(chan)生(sheng)过(guo)热，使(shi)元(yuan)(yuan)件(jian)(jian)受伤，虽(sui)然仍能(neng)(neng)工作，但(dan)是(shi)(shi)寿命受损(sun)。所(suo)以ESD对(dui)(dui)MOS管(guan)(guan)(guan)(guan)的(de)(de)(de)损(sun)坏可(ke)能(neng)(neng)是(shi)(shi)一(yi)(yi)，三两种(zhong)情(qing)(qing)况，并不(bu)一(yi)(yi)定(ding)每(mei)次都是(shi)(shi)第二种(zhong)情(qing)(qing)况。上述(shu)这(zhei)三种(zhong)情(qing)(qing)况中(zhong)(zhong)，如果元(yuan)(yuan)件(jian)(jian)完全破(po)坏，必能(neng)(neng)在(zai)(zai)(zai)生(sheng)产(chan)(chan)(chan)及(ji)品质测(ce)试中(zhong)(zhong)被察觉而排除，影(ying)响(xiang)较少。如果元(yuan)(yuan)件(jian)(jian)轻微(wei)受损(sun)，在(zai)(zai)(zai)正常(chang)测(ce)试中(zhong)(zhong)不(bu)易被发(fa)现，在(zai)(zai)(zai)这(zhei)种(zhong)情(qing)(qing)形下，常(chang)会(hui)(hui)因经过(guo)多次加(jia)工，甚(shen)至已在(zai)(zai)(zai)使(shi)用(yong)时(shi)，才被发(fa)现破(po)坏，不(bu)但(dan)检查不(bu)易，而且损(sun)失亦(yi)难以预(yu)测(ce)。静(jing)电(dian)(dian)对(dui)(dui)电(dian)(dian)子(zi)(zi)元(yuan)(yuan)件(jian)(jian)产(chan)(chan)(chan)生(sheng)的(de)(de)(de)危害(hai)不(bu)亚于严重(zhong)火灾和爆炸事故(gu)的(de)(de)(de)损(sun)失。
电(dian)(dian)(dian)子元件(jian)及产(chan)(chan)(chan)品在什么(me)情况下会(hui)遭(zao)受(shou)静(jing)电(dian)(dian)(dian)破坏?可(ke)(ke)以(yi)(yi)这么(me)说(shuo)：电(dian)(dian)(dian)子产(chan)(chan)(chan)品从(cong)生产(chan)(chan)(chan)到(dao)使用的(de)(de)(de)(de)全过(guo)程都遭(zao)受(shou)静(jing)电(dian)(dian)(dian)破坏的(de)(de)(de)(de)威胁。从(cong)器件(jian)制造到(dao)插件(jian)装焊、整机装联(lian)、包装运输直至产(chan)(chan)(chan)品应(ying)用，都在静(jing)电(dian)(dian)(dian)的(de)(de)(de)(de)威胁之下。在整个(ge)电(dian)(dian)(dian)子产(chan)(chan)(chan)品生产(chan)(chan)(chan)过(guo)程中，每一个(ge)阶段(duan)中的(de)(de)(de)(de)每一个(ge)小步骤，静(jing)电(dian)(dian)(dian)敏感元件(jian)都可(ke)(ke)能遭(zao)受(shou)静(jing)电(dian)(dian)(dian)的(de)(de)(de)(de)影响或受(shou)到(dao)破坏，而实际上(shang)最主要(yao)而又容易(yi)疏忽的(de)(de)(de)(de)一点却是在元件(jian)的(de)(de)(de)(de)传(chuan)(chuan)送与(yu)运输的(de)(de)(de)(de)过(guo)程。在这个(ge)过(guo)程中，运输因移(yi)动(dong)容易(yi)暴露(lu)在外界电(dian)(dian)(dian)场(如经过(guo)高压(ya)设(she)备附近、工人移(yi)动(dong)频繁、车(che)辆迅速移(yi)动(dong)等)产(chan)(chan)(chan)生静(jing)电(dian)(dian)(dian)而受(shou)到(dao)破坏，所以(yi)(yi)传(chuan)(chuan)送与(yu)运输过(guo)程需(xu)要(yao)特(te)别注(zhu)意，以(yi)(yi)减少损失，避(bi)免无所谓(wei)的(de)(de)(de)(de)纠(jiu)纷(fen)。防护(hu)的(de)(de)(de)(de)话加(jia)齐纳稳压(ya)管保护(hu)。
现在(zai)的mos管(guan)没有那(nei)么容易被击穿，尤其是是大功率的vmos,主要是不(bu)(bu)少都有二极(ji)管(guan)保护。vmos栅极(ji)电容大，感应不(bu)(bu)出高压。与(yu)干燥的北方不(bu)(bu)同，南方潮湿不(bu)(bu)易产生静电。还有就是现在(zai)大多(duo)数CMOS器件内部已经增加了IO口保护。但(dan)用(yong)手直(zhi)接接触CMOS器件管(guan)脚不(bu)(bu)是好习惯。至少使管(guan)脚可(ke)焊性变(bian)差。
第一(yi)、MOS管本(ben)身(shen)的(de)(de)输入电(dian)阻很(hen)高(gao)，而(er)(er)栅(zha)-源极(ji)间(jian)电(dian)容又十(shi)分小，所以极(ji)易受外(wai)界(jie)电(dian)磁场或(huo)静电(dian)的(de)(de)感应(ying)而(er)(er)带(dai)电(dian)，而(er)(er)少数(shu)电(dian)荷就可在极(ji)间(jian)电(dian)容上构(gou)成相当(dang)高(gao)的(de)(de)电(dian)压(ya)(U=Q/C)，将管子损坏。尽(jin)管MOS输入端有抗静电(dian)的(de)(de)维护措施(shi)，但仍需当(dang)心对待，在存储(chu)和运送中(zhong)(zhong)最好用金属(shu)容器或(huo)许导电(dian)资料包装，不要放在易发生静电(dian)高(gao)压(ya)的(de)(de)化(hua)(hua)工资料或(huo)化(hua)(hua)纤织物中(zhong)(zhong)。
拼装、调试时(shi)，东(dong)西、外(wai)表、工(gong)作台等(deng)均应杰出接地。要避免操作人员的(de)静电(dian)搅(jiao)扰构成(cheng)的(de)损坏，如不(bu)宜穿(chuan)尼(ni)龙、化纤衣(yi)服，手或(huo)东(dong)西在触(chu)摸集(ji)成(cheng)块前最好先接一下(xia)地。对器材引(yin)线矫直曲折或(huo)人工(gong)焊接时(shi)，运用(yong)的(de)设备有必要杰出接地。
第二、MOS电(dian)(dian)(dian)路输入端(duan)的(de)(de)(de)维(wei)护(hu)二极管(guan)，其(qi)导通时电(dian)(dian)(dian)流(liu)容限一(yi)般为(wei)1mA 在(zai)可(ke)能呈(cheng)现(xian)过大瞬态输入电(dian)(dian)(dian)流(liu)(超越10mA)时，应串(chuan)接(jie)输入维(wei)护(hu)电(dian)(dian)(dian)阻(zu)。而(er)129#在(zai)初期设(she)计时没有参加维(wei)护(hu)电(dian)(dian)(dian)阻(zu)，所(suo)以(yi)(yi)这也(ye)是MOS管(guan)可(ke)能击穿的(de)(de)(de)原因，而(er)经过替换(huan)一(yi)个内部有维(wei)护(hu)电(dian)(dian)(dian)阻(zu)的(de)(de)(de)MOS管(guan)应可(ke)避免此(ci)种失效(xiao)的(de)(de)(de)发生(sheng)。还有因为(wei)维(wei)护(hu)电(dian)(dian)(dian)路吸收的(de)(de)(de)瞬间(jian)能量有限，太大的(de)(de)(de)瞬间(jian)信号和过高的(de)(de)(de)静电(dian)(dian)(dian)电(dian)(dian)(dian)压将使(shi)维(wei)护(hu)电(dian)(dian)(dian)路失去效(xiao)果。所(suo)以(yi)(yi)焊接(jie)时电(dian)(dian)(dian)烙铁(tie)有必要可(ke)靠接(jie)地，以(yi)(yi)防漏(lou)电(dian)(dian)(dian)击穿器材输入端(duan)，一(yi)般运用时，可(ke)断电(dian)(dian)(dian)后(hou)使(shi)用电(dian)(dian)(dian)烙铁(tie)的(de)(de)(de)余(yu)热(re)进行焊接(jie)，并(bing)先焊其(qi)接(jie)地管(guan)脚。
MOS是电(dian)(dian)压驱动(dong)元件，对电(dian)(dian)压很敏感，悬空(kong)的(de)G很容易接受外部搅(jiao)扰使MOS导通(tong)，外部搅(jiao)扰信(xin)号(hao)对G-S结电(dian)(dian)容充电(dian)(dian)，这(zhei)个细(xi)小的(de)电(dian)(dian)荷能够(gou)贮存(cun)很长时刻。在(zai)实验中G悬空(kong)很风险，许多就因为这(zhei)样爆管，G接个下拉电(dian)(dian)阻对地，旁路搅(jiao)扰信(xin)号(hao)就不会直(zhi)通(tong)了，一(yi)般(ban)能够(gou)10~20K。
这个(ge)电阻(zu)称为栅(zha)(zha)极(ji)(ji)电阻(zu)。效(xiao)(xiao)果(guo)1：为场效(xiao)(xiao)应管(guan)供给偏(pian)置电压(ya)(ya);效(xiao)(xiao)果(guo)2：起到泻(xie)(xie)放电阻(zu)的(de)(de)效(xiao)(xiao)果(guo)(维护(hu)栅(zha)(zha)极(ji)(ji)G~源极(ji)(ji)S)。榜首个(ge)效(xiao)(xiao)果(guo)好了解，这儿解释一下(xia)第二个(ge)效(xiao)(xiao)果(guo)的(de)(de)原理：维护(hu)栅(zha)(zha)极(ji)(ji)G~源极(ji)(ji)S：场效(xiao)(xiao)应管(guan)的(de)(de)G-S极(ji)(ji)间的(de)(de)电阻(zu)值是很大的(de)(de)，这样(yang)只要有(you)(you)少数的(de)(de)静电就能(neng)(neng)(neng)使他的(de)(de)G-S极(ji)(ji)间的(de)(de)等(deng)效(xiao)(xiao)电容两头(tou)发生很高(gao)的(de)(de)电压(ya)(ya)，如(ru)果(guo)不(bu)及时把(ba)这些少数的(de)(de)静电泻(xie)(xie)放掉，他两头(tou)的(de)(de)高(gao)压(ya)(ya)就有(you)(you)可(ke)能(neng)(neng)(neng)使场效(xiao)(xiao)应管(guan)发生误(wu)动(dong)作，甚至有(you)(you)可(ke)能(neng)(neng)(neng)击穿其G-S极(ji)(ji);这时栅(zha)(zha)极(ji)(ji)与(yu)源极(ji)(ji)之间加的(de)(de)电阻(zu)就能(neng)(neng)(neng)把(ba)上述的(de)(de)静电泻(xie)(xie)放掉，然后(hou)起到了维护(hu)场效(xiao)(xiao)应管(guan)的(de)(de)效(xiao)(xiao)果(guo)。
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