CN1499605A - 在半导体器件中形成隔离膜的方法 - Google Patents
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Abstract
本发明公开了一种在半导体器件中形成隔离膜的方法。在形成衬垫氧化膜和衬垫氮化膜的堆叠结构以暴露隔离区域中的半导体衬底的工艺中,在邻近衬底表面的衬垫氧化膜和衬垫氮化膜的底部侧壁上形成尾形突出部分,并且在蚀刻衬底时,使用突出部分作为抗蚀刻膜使沟槽的顶角成为圆形。因此,可以防止电场集中于沟槽的顶角上,抑制漏电的产生。因此,可改善该工艺的可靠性及器件的电学特性。
Description
技术领域
本发明涉及一种在半导体器件中形成隔离膜的方法,更加特别地,涉及一种在半导体器件中形成能够防止电场集中在浅沟槽隔离(shallow trenchisolation;STI)结构隔离膜中沟槽顶角上的隔离膜的方法。
背景技术
在所有半导体器件中,都要形成用于电隔离形成在半导体衬底中的各种器件的隔离膜。传统上,隔离膜通过局部氧化(local oxidation;LOCOS)工艺的手段形成。但是,在该情形中,在隔离膜的顶角出现鸟喙形。由此,造成器件的电学特性及集成度劣化的问题。
随着半导体器件的集成度越来越高,隔离膜应形成为具有STI(浅沟槽隔离)结构,其可以使隔离膜处的鸟喙形的产生最小化,同时还防止其产生。
参考图1A至1D,说明在半导体器件中形成隔离膜的传统方法。
参考图1A,在半导体衬底101上顺序形成衬垫氧化膜102及衬垫氮化膜103。然后将光致抗蚀剂覆盖于衬垫氮化膜103上。接着,实施曝光及显影工艺,以形成光致抗蚀剂图案104,其中限定了将形成隔离膜的隔离区域。由此,在将要形成隔离膜的区域内的衬垫氮化膜103被曝光。
参考图1B,通过蚀刻工艺移除隔离区域内的衬垫氮化膜103。下面暴露出来的衬垫氧化膜102也被移除。藉此曝光隔离区域内的半导体衬底101。
参考图1C,隔离区域中的半导体衬底101被蚀刻至既定深度以形成沟槽105。接着,移除光致抗蚀剂图案(图1B中的104)。
参考图1D,形成绝缘材料层(未示出),以掩埋沟槽105。接着,通过化学机械抛光工艺移除衬垫氮化膜(图1C中的103)上的绝缘材料层。同样,通过蚀刻工艺,顺序移除衬垫氮化膜和衬垫氧化膜(图1C中的102)。由此,使绝缘材料层仅保留于沟槽中,以形成由绝缘材料层组成的隔离膜106。
对上述隔离膜的形成方法进行检验。若形成的隔离膜具有STI结构,则不会产生鸟喙形缺陷。因此,可防止由于鸟喙造成的电学特性及集成度的降低。
但是,STI结构中隔离膜的最大弱点为,电场集中于沟槽顶角(图1C中的105a)的尖锐部分。若沟槽顶角非常尖锐,则该部分上会形成很薄的栅极氧化膜,这会增加该部分的漏电流。电场集中于该部分还可改变晶体管的阈值电压,产生器件缺陷。因此,将出现器件可靠性降低的问题。
防止该问题的方法为,在蚀刻衬底形成沟槽时,使用光致抗蚀剂图案而不是用衬垫氮化膜当作蚀刻掩模。下面将详细说明该方法。
在图1C中,在光致抗蚀剂图案保持于衬垫氮化膜103上原封未动而不移除该光致抗蚀剂图案的状态下,如图1B所示,若在使用蚀刻剂蚀刻衬底形成沟槽时产生聚合反应,当聚合物产生时则产生聚合物累积于隔离区域角落里的衬底上。因为累积的聚合物中的硅成分和蚀刻选择率不同,所以在蚀刻衬底时,累积聚合物作为抗蚀刻膜。因此,与隔离膜的中心相比,其上累积聚合物的隔离膜的角落几乎未被蚀刻。因而沟槽的顶角形成圆形。
但是,该方法不能准确控制聚合物的产生量。因此,难以将沟槽的顶角均匀地形成圆形。另外,若光致抗蚀剂图案被用作蚀刻掩模,由于在集成图案大小时在光致抗蚀剂中产生聚合物,因此难以蚀刻该半导体衬底。因此,需要移除光致抗蚀剂图案后再蚀刻半导体衬底。但是,若移除光致抗蚀剂图案后使用衬垫氮化膜作为蚀刻掩模,则缺少产生聚合物的碳源。因此,更难以用聚合物将沟槽的顶角制成圆形。
发明内容
因此,本发明的意图主要在于排除由于现有技术的限制及缺点所产生的一种或多种问题。
本发明的目的在于提供一种在半导体器件中形成隔离膜的方法,在形成衬垫氧化膜和衬垫氮化膜的堆叠结构以暴露隔离区域中的半导体衬底的工艺中,在邻近衬底表面的衬垫氧化膜和衬垫氮化膜的底部侧壁上形成尾形突出部分,并且在蚀刻半导体衬底时,使用突出部分作为抗蚀刻膜使沟槽的顶角形成为圆形,因此可以防止沟槽的电场集中于沟槽的顶角上,抑制漏电的产生,因而改善工艺的可靠性及器件的电学特性,同时由于沟槽的顶角为圆形,即使移除光致抗蚀剂图案,也可解决聚合物工艺的困难。
本发明的其它好处、目的及特征将部分在以下的说明中提出,而部分地可由本领域技术人员在检验以下内容后更加了解,或可由实施本发明来学习到。本发明的目的及其它好处可由下文中的说明及权利要求,以及附图所特别指出的结构来实现及获得。
为实现根据本发明意图的这些目的及其它优点(如本文所体现及广泛说明地),根据本发明优选实施例,一种在半导体器件中形成隔离膜的方法,其特征在于包括步骤:在半导体衬底上顺序形成衬垫氧化膜和衬垫氮化膜;移除隔离区域上的衬垫氮化膜和衬垫氧化膜,从而在隔离区域的顶角处形成尾形的突出部分;蚀刻隔离区域的半导体衬底,同时使用突出部分作为抗蚀刻膜,以形成其顶角形成为圆形的沟槽;以及,用绝缘材料掩埋沟槽,然后移除半导体衬底上的衬垫氮化膜和衬垫氧化膜以形成隔离膜。
在上述说明中,在移除隔离区域内的衬垫氮化膜后,可通过在移除衬垫氮化膜的时间的1至10%的时间段内使用CHF3气体实施过蚀刻工艺形成突出部分。或者,突出部分通过实施在移除衬垫氮化膜与衬垫氧化膜的蚀刻工艺中对氧化物具有高选择率的蚀刻工艺而形成。同时,蚀刻工艺使用CF4气体和CHF3气体作为蚀刻气体来实施,其中,CHF3气体供应得比CF4气体多,从而增大对氧化物的选择率。此时,CHF3气体和气体CF4气体的供应比率为2∶1至10∶1。此蚀刻工艺通过设定探测到衬垫氧化膜的氧化物成分时的时间点为结束点(EOP)而实施。
而且,光致抗蚀剂图案形成于衬垫氮化膜上,以便界定隔离区域。此时,在移除隔离区域上的衬垫氮化膜和衬垫氧化膜后,在形成沟槽前移除光致抗蚀剂图案,从而防止光致抗蚀剂产生的聚合物影响用于形成沟槽的蚀刻工艺。
形成沟槽的蚀刻工艺在移除衬垫氮化膜和衬垫氧化膜后在蚀刻室内就地立即实施,以便防止在隔离区域的半导体衬底上形成原生氧化膜。
形成沟槽的蚀刻工艺可包括步骤:对半导体衬底实施第一次蚀刻工艺,其工艺条件仅为对突出部分具有高选择率,以形成其顶角不为圆形的沟槽;以及,实施第二次蚀刻工艺,使用对突出部分具有低选择率的工艺条件的过蚀刻处理(PET),以便在移除突出部分的同时在沟槽的顶角处形成蚀刻斜面,由此形成为圆形的沟槽。此时,对于突出部分和半导体衬底的蚀刻选择率通过调整蚀刻气体中HBr的气体流量而控制。第一次蚀刻工艺中,通过增加HBr气体的流量来仅蚀刻半导体衬底。在第二次蚀刻工艺中,通过相对减少HBr的气体流量来蚀刻沟槽的顶角及突出部分。
在本发明的另一方面中,应理解,上述对本发明的一般性说明及以下的详细说明均为范例及说明性,意在提供如权利要求的发明的进一步解释。
附图说明
通过以下参考附图对本发明的优选实施例的详细说明,更能明了本发明的上述及其它目的、特征及优点,附图中:
图1A至1D为说明在半导体器件中形成隔离膜的传统方法的半导体器件的截面图;
图2A至2E为说明在本发明优选实施例的半导体器件中形成隔离膜的方法的半导体器件的截面图;以及
图3A和3B为说明形成图2C的沟槽的蚀刻工艺的实施例的半导体器件的截面图,
其中,附图标记说明如下:
101 半导体衬底 102 衬垫氧化膜
103 衬垫氮化膜 104 光致抗蚀剂图案
105 沟槽 105a 沟槽的顶角
106 隔离膜 201 半导体衬底
202 衬垫氧化膜 203 衬垫氮化膜
204 光致抗蚀剂图案 205 沟槽
205a 沟槽的顶角 206 绝缘材料层
207 隔离膜
具体实施方式
现将详细参考本发明的优选实施例,实施例的范例在附图中说明,其中相同的附图标记代表相同或类似的部分。
图2A至2E用于解释在本发明的优选实施例的半导体器件中形成隔离膜的方法的半导体器件的截面图。
参考图2A,在半导体衬底201上顺序形成衬垫氧化膜202及衬垫氮化膜203。然后光致抗蚀剂覆盖于该衬垫氮化膜203上。接着,实施曝光及显影工艺,以形成光致抗蚀剂图案204,其中界定将形成隔离膜的隔离区域。藉此,在待形成隔离膜的区域内暴露衬垫氮化膜203。此时,形成的衬垫氮化膜203的厚度优选在1500以下。
参考图2B,通过蚀刻工艺移除隔离区域内的衬垫氮化膜203。然后,移除在衬垫氮化膜203下暴露的衬垫氧化膜202,藉此,暴露隔离区域内的半导体衬底201。此时,在移除隔离区域内的衬垫氮化膜203与衬垫氧化膜202的工艺中,在与半导体衬底201的表面接触的衬垫氮化膜203与衬垫氧化膜202的底部侧壁上形成尾形的突出部分230。此时,突出部分230作为抗蚀刻膜,在随后蚀该半导体衬底201以形成沟槽的工艺中防止隔离区域的角被蚀刻。
尽管有许多方法可形成突出部分230,下面将说明作为范例的两个实施例。
第一种方法,在移除隔离区域的衬垫氮化膜203的蚀刻工艺中,通过控制有关蚀刻气体及过蚀刻的工艺条件的方法可形成突出部分230。更具体而言,在蚀刻隔离区域内的衬垫氮化膜203后移除衬垫氮化膜203的时间的1至10%时间内,使用CHF3气体实施过蚀刻。此时,若过蚀刻工艺是使用CHF3气体实施,则将产生聚合物。但是,因为过蚀刻工艺在短时间内实施,在形成突出部分230的同时聚合物累积于衬垫氮化膜203与衬垫氧化膜202的底部侧壁上。
第二种方法,在移除隔离区域内的衬垫氮化膜203与衬垫氧化膜202的蚀刻工艺中,通过控制衬垫氮化膜203与衬垫氧化膜202的蚀刻选择率可形成突出部分230。更具体而言,衬垫氮化膜203通常通过使用CF4气体与CHF3气体的蚀刻工艺移除。一般而言,CF4气体的供应量多于CHF3气体。但是,若CHF3气体供应得更多,氧化物的选择率则会降低。因此,在形成由氮化物/氧化物组成的尾形突出部分230的同时,在衬垫氧化膜202的下部侧壁也形成蚀刻斜面。此时,CHF3气体与CF4气体的供应比例可为2∶1至10∶1。同时,在此情况下,当蚀刻衬垫氮化膜203与衬垫氧化膜202时,探测到半导体衬底201的硅成分时的时间点未被设定为结束点(EOP)。相反,探测到垫氧化膜202的氧化成分时的时间点被设定为EOP。
如上所述,若通过蚀刻气体及过蚀刻工艺、或通过控制衬垫氮化膜203与衬垫氧化膜202的蚀刻选择率来移除隔离区域内的衬垫氮化膜203与衬垫氧化膜202,则尾形突出部分230即形成于衬垫氮化膜203与衬垫氧化膜202的底部侧壁上。
参考图2C,该光致抗蚀剂图案(图2B中的204)被移除。然后,隔离区域内的半导体衬底201被蚀刻既定深度以形成沟槽205。此时,因形成于隔离区域顶角的突出部分(图2B的230)阻碍隔离区域的角被蚀刻,在沟槽205的顶角205a处形成蚀刻斜面。因此,沟槽205的顶角205a即被制成圆形。
在上述说明中,在移除隔离区域的衬垫氮化膜与衬垫氧化膜后形成沟槽205前,通常实施蚀刻工艺,以便移除在暴露的半导体衬底表面上形成的原生氧化膜。但是,若实施该蚀刻工艺移除该原生氧化膜,则可能损坏突出部分230。因此,为从开始即防止形成原生氧化膜,在移除衬垫氮化膜与衬垫氧化膜后,在蚀刻室内原位立即在隔离区域内形成沟槽。这样,若半导体衬底201原位蚀刻形成沟槽,就可省略移除原生氧化膜的蚀刻工艺。因此,具有减少工艺步骤的优点。
同时,在形成沟槽205的蚀刻工艺中,可在各种方法中实施利用突出部分使沟槽205的顶角制成圆形的蚀刻工艺。下面将作更详细的说明。
作为第一种方法,若沟槽205通过普通半导体衬底201的蚀刻工艺形成,则在蚀刻半导体衬底201时对突出部分230更慢地蚀刻,同时在隔离区域的角处自然形成了蚀刻斜面,藉此形成呈圆形的沟槽205。
作为第二种方法,通过控制对于由氮化物和氧化物构成的突出部分230与半导体衬底201的蚀刻选择率,可形成由两次蚀刻工艺使其顶角为圆形的沟槽205。参考图3A与图3B,进行更详细地说明。图3A与图3B为说明形成图2C的沟槽的蚀刻工艺的实施例的半导体器件的截面图。
参考图3A,在由氮化物和氧化物构成的突出部分230形成于衬垫氮化膜203和衬垫氧化膜202的底部侧壁的状态中,仅蚀刻半导体衬底201,使用的工艺条件为对突出部分230具有高选择率,因而形成其预角205a未被圆化的沟槽205。
参考图3B,通过实施工艺条件为对突出部分230具有低选择率的PET(后蚀刻处理)工艺,蚀刻斜面形成于沟槽205的顶角205a,以形成圆化的沟槽205,同时移除突出部分(图3A中的230)。此时,对突出部分(图3A中的230)和半导体衬底201的蚀刻选择率可通过仅调整蚀刻气体中的HBr气体流量而控制。换言之,在第一次蚀刻工艺中,通过增加HBr气体的流量来仅对半导体衬底201进行蚀刻。在第二次蚀刻工艺中,相对减少HBr气体流量,蚀刻沟槽205的顶角205a及突出部分(图3A中的230)。
此时,本发明的最重要特征之一,即通过上述方法形成沟槽的原因如下。由于沟槽在移除光致抗蚀剂图案后形成,沟槽不会受光致抗蚀剂产生的聚合物的影响。因此,可更准确地控制蚀刻工艺,从而工艺的可靠性也可改善。
参考图2D,在整个结构上形成绝缘材料层206,从而掩埋沟槽205。
参考图2E,衬垫氮化膜(图2D中的203)上的绝缘材料层(图2D中的206)通过化学机械抛光工艺移除。然后,通过蚀刻工艺顺序移除衬垫氮化膜和衬垫氧化膜(图2D中的202)。藉此,绝缘材料层仅保留在其顶角为圆形的沟槽(图2D的205)处,因而形成由绝缘材料层构成的隔离膜207。
如上所述,当使用上述方法形成STI结构的隔离膜时,本发明具有以下有益效果。
第一,因为突出部分通过调整实施过蚀刻工艺所需的时间或调整其形成时蚀刻气体的混合比率而形成,因而可精确控制突出部分的形状。因此,因沟槽的顶角可均匀地形成为圆形,从而改善了工艺的可靠性。
第二,在移除衬垫氮化膜与衬垫氧化膜后,通过在蚀刻室内就地立即蚀刻半导体衬底而形成沟槽。由此能够防止形成原生氧化膜。因此,可省略移除原生氧化膜的清除工艺,因而减少工艺步骤与时间。
第三,由于沟槽的顶角形成为圆形,因此防止了电场的集中。因此,可防止半导体器件(如晶体管)的阈值电压发生变化。
第四,由于沟槽的顶角形成为圆形,因此防止了电场的集中。因此,可产生硅位错(dislocation)。
第五,由于沟槽的顶角形成为圆形,因此防止了在后续工艺中形成薄弱的栅极氧化膜。因此,可能防止漏电的增加。
第六,由于即使移除光致抗蚀剂图案,沟槽的顶角也可形成为圆形,因此可解决工艺中存在的难以移除光致抗蚀剂图案及使沟槽的顶角形成为圆形的问题。
上述实施例仅为示范,不应解释为限制本发明。本发明很容易应用于其它类型的设备。本发明的介绍是说明性的,并非限制权力要求的范围。本领域技术人员清楚地知道本发明的各种替换、修改及变化。
Claims (11)
1.一种在半导体器件中形成隔离膜的方法,包括步骤:
在半导体衬底上顺序形成衬垫氧化膜和衬垫氮化膜;
移除隔离区域上的衬垫氮化膜和衬垫氧化膜,从而在隔离区域的顶角处形成尾形突出部分;
蚀刻隔离区域的半导体衬底,同时使用突出部分作为抗蚀刻膜,以形成其顶角形成为圆形的沟槽;以及
用绝缘材料掩埋沟槽,然后移除半导体衬底上的衬垫氮化膜和衬垫氧化膜以形成隔离膜。
2.如权利要求1所述的方法,其中在移除隔离区域内的衬垫氮化膜后,通过在移除衬垫氮化膜所用时间的1至10%的期间内使用CHF3气体实施过蚀刻工艺来形成突出部分。
3.如权利要求1所述的方法,其中突出部分通过实施在移除衬垫氮化膜与衬垫氧化膜的蚀刻工艺中对氧化物具有高选择率的蚀刻工艺而形成。
4.如权利要求3所述的方法,其中蚀刻工艺使用CF4气体和CHF3气体作为蚀刻气体来实施,其中,CHF3气体供应得比CF4气体多,从而增大对氧化物的选择率。
5.如权利要求4所述的方法,其中CHF3气体与CF4气体的供应比率为2∶1至10∶1。
6.如权利要求3所述的的方法,其中蚀刻工艺通过设定探测到衬垫氧化膜的氧化物成分时的时间点为结束点(EOP)而实施。
7.如权利要求1所述的方法,其中光致抗蚀剂图案形成于衬垫氮化膜上,以便界定隔离区域,并且,其中在移除隔离区域上的衬垫氮化膜和衬垫氧化膜后,在形成沟槽前移除光致抗蚀剂图案,从而防止光致抗蚀剂产生的聚合物影响用于形成沟槽的蚀刻工艺。
8.如权利要求1所述的方法,其中形成沟槽的蚀刻工艺在借以移除衬垫氮化膜和衬垫氧化膜的蚀刻室内立即就地实施,以便防止在隔离区域的半导体衬底上形成原生氧化膜。
9.如权利要求1所述的方法,其中形成沟槽的蚀刻工艺包括步骤:
在对突出部分具有高选择率的工艺条件下仅对半导体衬底实施第一次蚀刻工艺,以形成其顶角不为圆形的沟槽;以及
使用对突出部分具有低选择率的工艺条件的后蚀刻处理(PET)实施第二次蚀刻工艺,以便在移除突出部分的同时在沟槽的顶角处形成蚀刻斜面,由此形成呈圆角的沟槽。
10.如权利要求9所述的方法,其中对于突出部分和半导体衬底的蚀刻选择率通过调整蚀刻气体中HBr气体的流量来控制。
11.如权利要求9所述的方法,其中在第一次蚀刻工艺中,通过增加HBr气体的流量来仅对半导体衬底进行蚀刻,而在第二次蚀刻工艺中,通过相对减少HBr气体的流量来蚀刻沟槽的顶角及突出部分。
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CN104124163A (zh) * | 2013-04-23 | 2014-10-29 | 中国科学院微电子研究所 | 半导体器件制造方法 |
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US7396738B1 (en) | 2006-12-13 | 2008-07-08 | Hynix Semiconductor Inc. | Method of forming isolation structure of flash memory device |
US7553717B2 (en) * | 2007-05-11 | 2009-06-30 | Texas Instruments Incorporated | Recess etch for epitaxial SiGe |
US8329578B2 (en) * | 2009-03-27 | 2012-12-11 | Taiwan Semiconductor Manufacturing Company, Ltd. | Via structure and via etching process of forming the same |
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TW313696B (en) * | 1996-12-18 | 1997-08-21 | Vanguard Int Semiconduct Corp | Method of forming contact window |
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US6214747B1 (en) | 1999-10-28 | 2001-04-10 | United Microelectronics Corp. | Method for forming opening in a semiconductor device |
KR100447263B1 (ko) * | 1999-12-30 | 2004-09-07 | 주식회사 하이닉스반도체 | 식각 폴리머를 이용한 반도체 소자의 제조방법 |
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US6890859B1 (en) * | 2001-08-10 | 2005-05-10 | Cypress Semiconductor Corporation | Methods of forming semiconductor structures having reduced defects, and articles and devices formed thereby |
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CN103400795A (zh) * | 2013-08-14 | 2013-11-20 | 上海华力微电子有限公司 | 浅沟槽隔离工艺 |
CN103400795B (zh) * | 2013-08-14 | 2015-06-24 | 上海华力微电子有限公司 | 浅沟槽隔离工艺 |
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