后段干法去除光刻胶工艺研究
摘要
在现代集成电路制造中,去胶工艺加氟可有效地提高去除光刻胶的能力,特别是在离子注入之后的去胶工艺。但在后段去胶工艺中,由于含氟气体的引入,会产生一系列的问题。一、灰化率不稳定呈大幅度下跌趋势。二、由于氟离子化学性质活跃,对这些零部件会造成较大损耗,使其使用寿命急速缩短。三、含氟气体的引入容易产生一种缺陷,这种缺陷会造成每片晶圆良率减少3%~5%。这对设备的产能,工艺成本以及产品质量均有较大影响。
本文采用XPS(X射线光电子能谱)对应用在含氟去胶设备中的气体扩散器表面成分进行了分析,进而讨论了气体扩散器对含氟去胶设备灰化率降低的机理,并由此提出了气体扩散器表面氟钝化层生成的物理化学模型。采用SEM(扫描电子显微镜)对缺陷表面进行了分析,并使用FIB(聚焦离子束)对缺陷内部形态进行了分析,进而讨论了缺陷形成的机理。
研究表明:对于氧-氟接触过的气体扩散器,表面复合覆盖层最厚,主要为铝氟氢氧类化合物,这主要是由于氟易与表面氧化铝层反应所致;对于氧-氟接触的气体扩散器,由于氟对扩散器表面氧化铝层的侵蚀形成表面的疏松结构,易使下面的金属铝层曝露出来与等离子体的活性氧原子反应生成氧化铝,如此往复,即造成灰化工艺氧原子的不足,最终导致光刻胶灰化率的下降。对缺陷分析发现,这种缺陷只发生在密集深孔区域,深孔内的阻挡层被挤到表面形成突起,而内部形成空洞。进而研究发现,在去胶过程中加入了含氟气体(四氟化碳)就容易有这种缺陷出现。
基于以上结论,我们提出了对去胶气体组合配比进行改良,以达到稳定并提高灰化率,减少机器零部件损耗和解决缺陷的目的。具体方法为:将去胶气体组合配比由大量氧气加少量四氟化碳加少量氮气改为大量氧气加少量氮气。为进一步提高灰化率,我们还将晶圆的反应温度做了适当的提高。试验对比验证表明:大量氧气加少量氮气的气体组合可以得到稳定的灰化率,且能减少机器零部件损耗和解决缺陷问题。提高晶圆反应温度可以大幅度提高灰化率,从而提高去胶设备的产能,降低工艺成本。
In modern VLSI fabrication, fluorine gas are usually added into photoresist ashing process to remove the residue of crust formed after the implantation with higher energy. However, in BEOL ashing process, because of the introduction of fluorinated gases, will produce a series of problems. 1. Ashing rate was a significant decline of instability. 2. As the F-ion chemical properties of active and cause greater wear and tear of these parts, so that rapid shortening life. 3. Fluorinated gases into a kind of blind prone to defects, such defects would result in yield per wafer reduction of 3% to 5%. That capacity of equipment, process costs and product quality have a greater impact.
In this paper, XPS(X-ray Photoelectron Spectroscopy)are used to analysis the surface composition of the diffuser used in the asher with fluorine and oxygen thoroughly, and then the mechanism of the ashing rate’s decrease are discussed. After that,the physical chemical model about the surface fluorine passivation layer forming are proposed. Using SEM (scanning electron microscope) of the blind analysis of surface defects, and use the FIB (focused ion beam) defect on the blind analysis of the internal morphology, and then discussed the formation mechanism of blind defects.
The study shows that the surface coverage layer on the diffuser contacted with F-O is the thickest and mainly porous aluminum hydro-oxide which is the byproducts of the reaction between fluorine and aluminum oxide on the diffuser’s surface. For O-F contacted gas diffuser, because of attack from fluorine, the surface structure is porous, which makes beneath metal uncovered and easily reacts with radical oxygen to form aluminum oxide. It happens repeatedly to cause the consumption of oxygen and leads to the dropping of ash rate. Analysis of the blind defect, the defect occurs only in dense hole area, hole in the barrier layer are pushed into the surface processes and internal cavities. Further study found that added the F-gases
(CF_4) during the process there be such defects occur. Base on previous conclusion, we propose to optimize the ashing gas composition and ratio to improve stability and the ashing rate, reduce the machine parts wear and tear and solve blind defects. Specific methods are: the ashing gas composition change from mass O_2+ little CF_4+ little N_2 to mass O_2+ little N_2.To further improve the ashing rate, wafer temperature we will do the appropriate increase.
Comparison of validation tests showed that: mass O_2+ little N_2 gas mix can be a stable rate of ash, and can reduce machine parts damage and to solve defects issue. Increase the wafer temperature can greatly improve the ashing rate, thereby enhancing the capacity to dispensing equipment, reduce technology costs.
本文采用XPS(X射线光电子能谱)对应用在含氟去胶设备中的气体扩散器表面成分进行了分析,进而讨论了气体扩散器对含氟去胶设备灰化率降低的机理,并由此提出了气体扩散器表面氟钝化层生成的物理化学模型。采用SEM(扫描电子显微镜)对缺陷表面进行了分析,并使用FIB(聚焦离子束)对缺陷内部形态进行了分析,进而讨论了缺陷形成的机理。
研究表明:对于氧-氟接触过的气体扩散器,表面复合覆盖层最厚,主要为铝氟氢氧类化合物,这主要是由于氟易与表面氧化铝层反应所致;对于氧-氟接触的气体扩散器,由于氟对扩散器表面氧化铝层的侵蚀形成表面的疏松结构,易使下面的金属铝层曝露出来与等离子体的活性氧原子反应生成氧化铝,如此往复,即造成灰化工艺氧原子的不足,最终导致光刻胶灰化率的下降。对缺陷分析发现,这种缺陷只发生在密集深孔区域,深孔内的阻挡层被挤到表面形成突起,而内部形成空洞。进而研究发现,在去胶过程中加入了含氟气体(四氟化碳)就容易有这种缺陷出现。
基于以上结论,我们提出了对去胶气体组合配比进行改良,以达到稳定并提高灰化率,减少机器零部件损耗和解决缺陷的目的。具体方法为:将去胶气体组合配比由大量氧气加少量四氟化碳加少量氮气改为大量氧气加少量氮气。为进一步提高灰化率,我们还将晶圆的反应温度做了适当的提高。试验对比验证表明:大量氧气加少量氮气的气体组合可以得到稳定的灰化率,且能减少机器零部件损耗和解决缺陷问题。提高晶圆反应温度可以大幅度提高灰化率,从而提高去胶设备的产能,降低工艺成本。
In modern VLSI fabrication, fluorine gas are usually added into photoresist ashing process to remove the residue of crust formed after the implantation with higher energy. However, in BEOL ashing process, because of the introduction of fluorinated gases, will produce a series of problems. 1. Ashing rate was a significant decline of instability. 2. As the F-ion chemical properties of active and cause greater wear and tear of these parts, so that rapid shortening life. 3. Fluorinated gases into a kind of blind prone to defects, such defects would result in yield per wafer reduction of 3% to 5%. That capacity of equipment, process costs and product quality have a greater impact.
In this paper, XPS(X-ray Photoelectron Spectroscopy)are used to analysis the surface composition of the diffuser used in the asher with fluorine and oxygen thoroughly, and then the mechanism of the ashing rate’s decrease are discussed. After that,the physical chemical model about the surface fluorine passivation layer forming are proposed. Using SEM (scanning electron microscope) of the blind analysis of surface defects, and use the FIB (focused ion beam) defect on the blind analysis of the internal morphology, and then discussed the formation mechanism of blind defects.
The study shows that the surface coverage layer on the diffuser contacted with F-O is the thickest and mainly porous aluminum hydro-oxide which is the byproducts of the reaction between fluorine and aluminum oxide on the diffuser’s surface. For O-F contacted gas diffuser, because of attack from fluorine, the surface structure is porous, which makes beneath metal uncovered and easily reacts with radical oxygen to form aluminum oxide. It happens repeatedly to cause the consumption of oxygen and leads to the dropping of ash rate. Analysis of the blind defect, the defect occurs only in dense hole area, hole in the barrier layer are pushed into the surface processes and internal cavities. Further study found that added the F-gases
(CF_4) during the process there be such defects occur. Base on previous conclusion, we propose to optimize the ashing gas composition and ratio to improve stability and the ashing rate, reduce the machine parts wear and tear and solve blind defects. Specific methods are: the ashing gas composition change from mass O_2+ little CF_4+ little N_2 to mass O_2+ little N_2.To further improve the ashing rate, wafer temperature we will do the appropriate increase.
Comparison of validation tests showed that: mass O_2+ little N_2 gas mix can be a stable rate of ash, and can reduce machine parts damage and to solve defects issue. Increase the wafer temperature can greatly improve the ashing rate, thereby enhancing the capacity to dispensing equipment, reduce technology costs.
引文
[1] Michael Quirk,Julian Serda著,韩郑生译.半导体制造技术.电子工业出版社.2005:310-316
[2]朱正涌编著.半导体集成电路.清华大学出版社. 2003:150-154
[3] Hai-Au Phan-vu,Fund of photolithography and resist partⅠ,2000,41-42
[4] Hai-Au Phan-vu,Fund of photolithography and resist partⅡ,2000,42-44
[5] Hai-Au Phan-vu,Fund of photolithography and resist partⅢ,2000,44-47
[6]王万琪.光刻胶处理系统.电子工业专用设备. 1988年01期; 59-63
[7] Rene Gorge,X-ray photoelectron spectroscopy of Fluorine-exposed Aluminum for determination of Fluorine reactions with Aluminum surfaces,Mattson internal, 1999:10-20
[8] QingyuanHan,TeresaBausum ,PalaniSakthivel ,GaryDahrooge , AxcelisTechnologies.180nm及更深技术中去除过度注入光刻胶的干剥离工艺.半导体技术. 2003年第5期
[9] Hai-Au Phan-vu,Fund of Mattson ICP partⅡ,Mattson internal,1997,72-74
[10]关旭东.硅集成电路工艺基础.北京大学出版社.2002:101-103
[11] Hai-Au Phan-vu,Fund of Mattson ICP partⅢ,Mattson internal,1997,74-77
[12] Hai-Au Phan-vu,Fund of Mattson ICP partⅡ,Mattson internal,1997,88-89
[13] Rene Gorge,X-ray photoelectron spectroscopy of Fluorine-exposed Aluminum for determination of Fluorine reactions with Aluminum surfaces,Mattson internal,1999,23-30
[14]冯伟.含氟气体的去光刻胶工艺灰化率提高的研究[硕士论文].上海:上海交通大学. 2007.
[15] D.Behrens.Corrosion Handbook,VCH Publishers,NY.
[16] Songlin Xu,Fund of Mattson Strip,Mattson internal,2000,45-47
[17]A.Li,A.Belkind,F.Jansen,Z.Orban.Surface and Coating Technology,92 (1997) 171-177.
[18] Mary L.Long,樊代文.微电子学.超大规模集成电路微细光刻中光刻胶的粒子控制. 1984年04期:69-72+89
[19] Hai-Au Phan-vu,Fund of Mattson ICP partⅢ,Mattson internal,1997:7-10
[20]管慧.光刻胶处理系统的国内外现状.半导体技术. 1992年05期; 11-14
[21] Peter Singer. 45nm节点清洗_光刻胶去除的挑战.集成电路应用. 2007年08期
[22] Ruth DeJule.光刻胶去胶难度渐增.集成电路应用. 2008年10期
[2]朱正涌编著.半导体集成电路.清华大学出版社. 2003:150-154
[3] Hai-Au Phan-vu,Fund of photolithography and resist partⅠ,2000,41-42
[4] Hai-Au Phan-vu,Fund of photolithography and resist partⅡ,2000,42-44
[5] Hai-Au Phan-vu,Fund of photolithography and resist partⅢ,2000,44-47
[6]王万琪.光刻胶处理系统.电子工业专用设备. 1988年01期; 59-63
[7] Rene Gorge,X-ray photoelectron spectroscopy of Fluorine-exposed Aluminum for determination of Fluorine reactions with Aluminum surfaces,Mattson internal, 1999:10-20
[8] QingyuanHan,TeresaBausum ,PalaniSakthivel ,GaryDahrooge , AxcelisTechnologies.180nm及更深技术中去除过度注入光刻胶的干剥离工艺.半导体技术. 2003年第5期
[9] Hai-Au Phan-vu,Fund of Mattson ICP partⅡ,Mattson internal,1997,72-74
[10]关旭东.硅集成电路工艺基础.北京大学出版社.2002:101-103
[11] Hai-Au Phan-vu,Fund of Mattson ICP partⅢ,Mattson internal,1997,74-77
[12] Hai-Au Phan-vu,Fund of Mattson ICP partⅡ,Mattson internal,1997,88-89
[13] Rene Gorge,X-ray photoelectron spectroscopy of Fluorine-exposed Aluminum for determination of Fluorine reactions with Aluminum surfaces,Mattson internal,1999,23-30
[14]冯伟.含氟气体的去光刻胶工艺灰化率提高的研究[硕士论文].上海:上海交通大学. 2007.
[15] D.Behrens.Corrosion Handbook,VCH Publishers,NY.
[16] Songlin Xu,Fund of Mattson Strip,Mattson internal,2000,45-47
[17]A.Li,A.Belkind,F.Jansen,Z.Orban.Surface and Coating Technology,92 (1997) 171-177.
[18] Mary L.Long,樊代文.微电子学.超大规模集成电路微细光刻中光刻胶的粒子控制. 1984年04期:69-72+89
[19] Hai-Au Phan-vu,Fund of Mattson ICP partⅢ,Mattson internal,1997:7-10
[20]管慧.光刻胶处理系统的国内外现状.半导体技术. 1992年05期; 11-14
[21] Peter Singer. 45nm节点清洗_光刻胶去除的挑战.集成电路应用. 2007年08期
[22] Ruth DeJule.光刻胶去胶难度渐增.集成电路应用. 2008年10期