CN104733392B - 用于绝缘体上硅射频开关器件结构的制造方法 - Google Patents

用于绝缘体上硅射频开关器件结构的制造方法 Download PDF

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CN104733392B
CN104733392B CN201510189304.1A CN201510189304A CN104733392B CN 104733392 B CN104733392 B CN 104733392B CN 201510189304 A CN201510189304 A CN 201510189304A CN 104733392 B CN104733392 B CN 104733392B
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刘张李
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Shanghai Huahong Grace Semiconductor Manufacturing Corp
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    • H01ELECTRIC ELEMENTS
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    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
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    • H01L21/82Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
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    • H01L21/78Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
    • H01L21/82Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
    • H01L21/822Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components the substrate being a semiconductor, using silicon technology
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    • H01L21/8234MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type
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    • H01L21/77Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
    • H01L21/78Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
    • H01L21/82Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices to produce devices, e.g. integrated circuits, each consisting of a plurality of components
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    • H01L21/8232Field-effect technology
    • H01L21/8234MIS technology, i.e. integration processes of field effect transistors of the conductor-insulator-semiconductor type
    • H01L21/8238Complementary field-effect transistors, e.g. CMOS
    • H01L21/823878Complementary field-effect transistors, e.g. CMOS isolation region manufacturing related aspects, e.g. to avoid interaction of isolation region with adjacent structure

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Abstract

一种用于绝缘体上硅射频开关器件结构的制造方法,包括:形成绝缘体上硅射频开关器件的基本结构,基本结构包括在有源层中形成的源极区域、栅极区域和漏极区域,其中在栅极区域上形成了栅极氧化层和栅极多晶硅,有源层上覆盖有介质层,在介质层上形成有通过通孔分别与源极区域和漏极区域连接的源极金属布线和漏极金属布线;沉积介质材料并对沉积的介质材料进行平坦化处理,以使得介质层的厚度变大,其中介质材料完全覆盖源极金属布线和漏极金属布线;在介质层中刻蚀出位于源极金属布线和漏极金属布线之间的凹槽;在凹槽中部分地填充介质材料,以便在凹槽中形成被介质材料包围的空隙。

Description

用于绝缘体上硅射频开关器件结构的制造方法
技术领域
本发明涉及半导体制造领域,更具体地说,本发明涉及一种用于绝缘体上硅射频开关器件结构的制造方法。
背景技术
硅材料是半导体行业应用最广泛的主要原材料,大多数芯片都是用硅片制造的。绝缘体上硅(SOI,Silicon-on-insulator)是一种特殊的硅片,其结构的主要特点是在有源层和衬底层之间插入绝缘层(掩埋氧化物层)来隔断有源层和衬底之间的电气连接,这一结构特点为绝缘体上硅类的器件带来了寄生效应小、速度快、功耗低、集成度高、抗辐射能力强等诸多优点。
现在,已经采用绝缘体上硅技术来制造开关器件。优值(Figure of Merit,简称FOM)是评价开关器件性能或工艺的特征测试参数。FOM=Ron*Coff,其中Ron是器件栅极电压等于器件处于导通状态时的等效电阻值,Coff是器件处于关断状态时的等效电容值。优值越低则表示器件性能越好。晶体管源漏之间金属层的电容将影响关态电容Coff。
具体地,图1示意性地示出了根据现有技术的绝缘体上硅射频开关器件结构的俯视示意图。图2示意性地示出了根据现有技术的绝缘体上硅射频开关器件结构沿图1的线A-A’的截面示意图。如图1和图2所示,根据现有技术的绝缘体上硅射频开关器件结构包括:梳状栅结构G01、梳状源结构S01以及梳状漏结构D01,其中梳状栅结构G01、梳状源结构S01以及梳状漏结构D01的梳齿相互平行,而且梳状源结构S01以及梳状漏结构D01的梳齿交替布置(在梳齿的延伸方向上彼此重叠),而且在梳状源结构S01的梳齿与梳状漏结构D01的梳齿之间布置有梳状栅结构G01的梳齿;并且,梳状源结构S01以及梳状漏结构D01处于同一层,梳状源结构S01以及梳状漏结构D01处于梳状栅结构G01的上层。
如图2所示,晶体管源漏之间金属层的电容100将影响关态电容Coff。具体地说,金属层面对面的电容,可以理解成平板电容;由此,正对面积越大,电容值则越大。
由此,可以通过减薄金属层厚度来减小金属层面对面的电容,但是,在减薄金属层厚度的时候,会使空气隙由形貌较好的空气隙(如图3的空气隙200所示)变成形貌变差的空气隙(如图4的空气隙200所示)。
发明内容
本发明所要解决的技术问题是针对现有技术中存在上述缺陷,提供一种能够在通过减薄金属层厚度来减小晶体管源漏之间金属层电容的同时保持形貌较好的空气隙的方法。
为了实现上述技术目的,根据本发明,提供了一种用于绝缘体上硅射频开关器件结构的制造方法,包括:首先,形成绝缘体上硅射频开关器件的基本结构,所述基本结构包括布置在衬底上的掩埋氧化物层上的有源层,所述有源层中形成有源极区域、栅极区域和漏极区域,而且在栅极区域上形成了栅极氧化层和栅极多晶硅,有源层上覆盖有介质层,在介质层上形成有通过通孔分别与源极区域和漏极区域连接的源极金属布线和漏极金属布线;其次,沉积介质材料并对沉积的介质材料进行平坦化处理,以使得介质层的厚度变大,其中介质材料完全覆盖源极金属布线和漏极金属布线;随后,在介质层中刻蚀出位于源极金属布线和漏极金属布线之间的凹槽;此后,在凹槽中部分地填充介质材料,以便在凹槽中形成被介质材料包围的空隙。
优选地,源极金属布线和漏极金属布线具有减薄的厚度。
优选地,源极金属布线和漏极金属布线的厚度不大于
优选地,源极金属布线和漏极金属布线的厚度介于之间。
优选地,厚度变大后的介质层的顶部与源极金属布线和漏极金属布线的顶部之间的距离根据所述凹槽的期望深宽比进行调整。
优选地,厚度变大后的介质层的顶部与源极金属布线和漏极金属布线的顶部之间的距离介于之间。
优选地,平坦化处理为化学机械研磨。
优选地,在CMOS工艺中执行所述制造方法。
凹槽中形成的空隙的形貌的好坏取决于凹槽的高宽比,在减薄的金属层的情况下,由于覆盖源极金属布线和漏极金属布线的介质层的厚度加大,使得形成空隙的凹槽的高度能够不会由于金属布线的变小而变小,从而保持凹槽的高宽比基本不变甚至变大,从而得到良好的空隙形貌;继而利用良好的空隙形貌实现绝缘体上硅射频开关器件的良好绝缘特性。由此,根据本发明的用于绝缘体上硅射频开关器件结构的制造方法使得绝缘体上硅射频开关器件不仅具有理想的关态电容,而且具有实现良好的绝缘特性。
从而,本发明提出一种改善射频开关隔离特性的技术方案,其中在减薄金属层厚度的基础上,通过工艺方法改善深宽比,形成形貌更优的空气隙结构。
附图说明
结合附图,并通过参考下面的详细描述,将会更容易地对本发明有更完整的理解并且更容易地理解其伴随的优点和特征,其中:
图1示意性地示出了根据现有技术的绝缘体上硅射频开关器件结构的俯视示意图。
图2示意性地示出了根据现有技术的绝缘体上硅射频开关器件结构沿图1的线A-A’的截面示意图。
图3示意性地示出了根据现有技术的绝缘体上硅射频开关器件结构的空气间隙的示意图。
图4示意性地示出了根据现有技术的绝缘体上硅射频开关器件结构在减薄金属层厚度之后的空气间隙的示意图。
图5至图8示意性地示出了根据本发明优选实施例的用于绝缘体上硅射频开关器件结构的制造方法的各个步骤。
需要说明的是,附图用于说明本发明,而非限制本发明。注意,表示结构的附图可能并非按比例绘制。并且,附图中,相同或者类似的元件标有相同或者类似的标号。
具体实施方式
为了使本发明的内容更加清楚和易懂,下面结合具体实施例和附图对本发明的内容进行详细描述。
图5至图8示意性地示出了根据本发明优选实施例的用于绝缘体上硅射频开关器件结构的制造方法的各个步骤。
如图5至图8所示,根据本发明优选实施例的用于绝缘体上硅射频开关器件结构的制造方法包括:
首先,形成绝缘体上硅射频开关器件的基本结构,所述基本结构包括布置在衬底10上的掩埋氧化物层20上的有源层,所述有源层中形成有源极区域30、栅极区域40和漏极区域50,而且在栅极区域40上形成了栅极氧化层和栅极多晶硅80,有源层上覆盖有介质层90,在介质层90上形成有通过通孔分别与源极区域30和漏极区域50连接的源极金属布线60和漏极金属布线70,如图5所示。
其中,源极金属布线60和漏极金属布线70具有减薄的厚度,即该厚度小于现有技术中一般采用的金属布线的厚度。
优选地,源极金属布线60和漏极金属布线70的厚度不大于进一步优选地,源极金属布线60和漏极金属布线70的厚度介于之间。
其次,沉积介质材料并对沉积的介质材料进行平坦化处理(例如,化学机械研磨),以使得介质层90的厚度变大,其中介质材料完全覆盖源极金属布线60和漏极金属布线70,如图6所示。其中,优选地,厚度变大后的介质层的顶部与源极金属布线60和漏极金属布线70的顶部之间的距离h可以根据所述凹槽的期望深宽比进行调整;例如,在具体实施例中,优选地,该距离h介于 之间。
随后,在介质层90中刻蚀出位于源极金属布线60和漏极金属布线70之间的凹槽91,如图7所示。
此后,在凹槽91中部分地填充介质材料,以便在凹槽91中形成被介质材料包围的空隙92,如图8所示。例如,该步骤可包括:沉积介质材料以部分地填充凹槽91,随后执行平坦化处理。
凹槽中形成的空隙的形貌的好坏取决于凹槽的高宽比,在减薄的金属层的情况下,由于覆盖源极金属布线和漏极金属布线的介质层的厚度加大,使得形成空隙的凹槽的高度能够不会由于金属布线的变小而变小,从而保持凹槽的高宽比基本不变甚至变大,从而得到良好的空隙形貌;继而利用良好的空隙形貌实现绝缘体上硅射频开关器件的良好绝缘特性。由此,根据本发明优选实施例的用于绝缘体上硅射频开关器件结构的制造方法使得绝缘体上硅射频开关器件不仅具有理想的关态电容,而且具有实现良好的绝缘特性。
而且,根据本发明优选实施例的用于绝缘体上硅射频开关器件结构的制造方法与CMOS工艺兼容,所以可以在CMOS工艺中执行。
此外,需要说明的是,除非特别说明或者指出,否则说明书中的术语“第一”、“第二”、“第三”等描述仅仅用于区分说明书中的各个组件、元素、步骤等,而不是用于表示各个组件、元素、步骤之间的逻辑关系或者顺序关系等。
可以理解的是,虽然本发明已以较佳实施例披露如上,然而上述实施例并非用以限定本发明。对于任何熟悉本领域的技术人员而言,在不脱离本发明技术方案范围情况下,都可利用上述揭示的技术内容对本发明技术方案作出许多可能的变动和修饰,或修改为等同变化的等效实施例。因此,凡是未脱离本发明技术方案的内容,依据本发明的技术实质对以上实施例所做的任何简单修改、等同变化及修饰,均仍属于本发明技术方案保护的范围内。

Claims (6)

1.一种用于绝缘体上硅射频开关器件结构的制造方法,其特征在于包括:
首先,形成绝缘体上硅射频开关器件的基本结构,所述基本结构包括布置在衬底上的掩埋氧化物层上的有源层,所述有源层中形成有源极区域、栅极区域和漏极区域,而且在栅极区域上形成了栅极氧化层和栅极多晶硅,有源层上覆盖有介质层,在介质层上形成有通过通孔分别与源极区域和漏极区域连接的源极金属布线和漏极金属布线,其中,源极金属布线和漏极金属布线的厚度不大于
其次,沉积介质材料并对沉积的介质材料进行平坦化处理,以使得介质层的厚度变大,其中厚度变大后的介质层的顶部与源极金属布线和漏极金属布线的顶部之间的距离介于之间,介质材料完全覆盖源极金属布线和漏极金属布线;
随后,在介质层中刻蚀出位于源极金属布线和漏极金属布线之间的凹槽;
此后,在凹槽中部分地填充介质材料,以便在凹槽中形成被介质材料包围的空隙。
2.根据权利要求1所述的用于绝缘体上硅射频开关器件结构的制造方法,其特征在于,源极金属布线和漏极金属布线具有减薄的厚度。
3.根据权利要求1或2所述的用于绝缘体上硅射频开关器件结构的制造方法,其特征在于,源极金属布线和漏极金属布线的厚度介于之间。
4.根据权利要求1或2所述的用于绝缘体上硅射频开关器件结构的制造方法,其特征在于,厚度变大后的介质层的顶部与源极金属布线和漏极金属布线的顶部之间的距离根据所述凹槽的期望深宽比进行调整。
5.根据权利要求1或2所述的用于绝缘体上硅射频开关器件结构的制造方法,其特征在于,平坦化处理为化学机械研磨。
6.根据权利要求1或2所述的用于绝缘体上硅射频开关器件结构的制造方法,其特征在于,在CMOS工艺中执行所述制造方法。
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CN106656128A (zh) * 2016-12-31 2017-05-10 唯捷创芯(天津)电子技术股份有限公司 用于多晶体管串联射频开关的电压均匀化方法及射频开关
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08227935A (ja) * 1994-12-20 1996-09-03 Matsushita Electric Ind Co Ltd 半導体装置の製造方法
US5972761A (en) * 1997-12-29 1999-10-26 Texas Instruments - Acer Incorporated Method of making MOS transistors with a gate-side air-gap structure and an extension ultra-shallow S/D junction
WO2002007213A1 (en) * 2000-07-17 2002-01-24 Advanced Micro Devices, Inc. Deliberate void in innerlayer dielectric gapfill to reduce dielectric constant
CN1641847A (zh) * 2003-12-29 2005-07-20 三星电子株式会社 半导体器件及制造半导体器件的方法
CN103839884A (zh) * 2014-03-10 2014-06-04 上海华虹宏力半导体制造有限公司 半导体器件结构及其形成方法
CN103855166A (zh) * 2012-12-04 2014-06-11 三星电子株式会社 半导体存储器件及其制造方法
CN104485361A (zh) * 2014-12-25 2015-04-01 上海华虹宏力半导体制造有限公司 绝缘体上硅射频开关器件结构

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9634645B2 (en) * 2013-03-14 2017-04-25 Qualcomm Incorporated Integration of a replica circuit and a transformer above a dielectric substrate

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08227935A (ja) * 1994-12-20 1996-09-03 Matsushita Electric Ind Co Ltd 半導体装置の製造方法
US5972761A (en) * 1997-12-29 1999-10-26 Texas Instruments - Acer Incorporated Method of making MOS transistors with a gate-side air-gap structure and an extension ultra-shallow S/D junction
WO2002007213A1 (en) * 2000-07-17 2002-01-24 Advanced Micro Devices, Inc. Deliberate void in innerlayer dielectric gapfill to reduce dielectric constant
CN1641847A (zh) * 2003-12-29 2005-07-20 三星电子株式会社 半导体器件及制造半导体器件的方法
CN103855166A (zh) * 2012-12-04 2014-06-11 三星电子株式会社 半导体存储器件及其制造方法
CN103839884A (zh) * 2014-03-10 2014-06-04 上海华虹宏力半导体制造有限公司 半导体器件结构及其形成方法
CN104485361A (zh) * 2014-12-25 2015-04-01 上海华虹宏力半导体制造有限公司 绝缘体上硅射频开关器件结构

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