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靶基距对Cu/Si(100)薄膜结构和残余应力的影响

  • 孟笛

    机 构：

    大连理工大学 材料科学与工程学院 表面工程实验室, 大连 116024

    ×
  • ， 蒋智韬

    机 构：

    大连理工大学 材料科学与工程学院 表面工程实验室, 大连 116024

    ×
  • ， 李玉阁

    机 构：

    大连理工大学 材料科学与工程学院 表面工程实验室, 大连 116024

    ×
  • ， 高剑英

    机 构：

    大连理工大学 材料科学与工程学院 表面工程实验室, 大连 116024

    ×
  • ， 雷明凯

    机 构：

    大连理工大学 材料科学与工程学院 表面工程实验室, 大连 116024

    ×

大连理工大学 材料科学与工程学院 表面工程实验室, 大连 116024；

Effects of Target-substrate Distance on Structure and Residual Stress of Cu / Si(100) Thin Films

  • MENG Di

    Affiliation：

    Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 , China

    ×
  • ， JIANG Zhitao

    Affiliation：

    Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 , China

    ×
  • ， LI Yuge

    Affiliation：

    Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 , China

    ×
  • ， GAO Jianying

    Affiliation：

    Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 , China

    ×
  • ， LEI Mingkai

    Affiliation：

    Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 , China

    ×

Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 , China；

通讯作者:

雷明凯(1963—),男(汉),教授,博士;研究方向:材料表面工程;E-mail:surfeng@dlut.edu.cn

中图分类号:TG174.444

文献标识码:A

文章编号:1007-9289(2020)06-0086-07

DOI:10.11933/j.issn.1007-9289.20190910002

参考文献 1
MISRA A,NASTASI M.Limits of residual stress in Cr films sputter deposited on biased substrates[J].Applied Physics Letters,1999,75(20):3123-3125.
查找原文
参考文献 2
MENG D,LI Y G,JIANG Z T,et al.Scratch behavior and FEM modelling of Cu/Si(100)thin films deposited by modulated pulsed power magnetron sputtering [J].Surface and Coatings Technology,2019,363:25-33.
查找原文
参考文献 3
ENGWALL A M,RAO Z,CHASON E.Origins of residual stress in thin films:Interaction between microstructure and growth kinetics[J].Materials and Design,2016,110:616-623.
查找原文
参考文献 4
ABADIAS G,CHASON E,KECKES J,et al.Stress in thin films and coatings:Current status,challenges,and prospects [J].Journal of Vacuum Science and Technology A,2018,36(2):020801.
查找原文
参考文献 5
ABERMANN R.Measurements of the intrinsic stress in thin metal films[J].Vacuum,1990,41:1279-1282.
查找原文
参考文献 6
DANIEL R,MARTINSCHITZ K J,KECHES J,et al.The origin of stresses in magnetron-sputtered thin films with zone T structures [J].Acta Materialia,2010,58(7):2621-2633.
查找原文
参考文献 7
JANSSEN G C A M,KAMMINGA J-D.Stress in hard metal films[J].Applied Physics Letters,2004,85:3086-3088.
查找原文
参考文献 8
LIN J L,MOORE J J,SPROUL W D,et al.Modulated pulse power sputtered chromium coatings [J].Thin Solid Films,2009,518(5):1566-1570.
查找原文
参考文献 9
吴志立,朱小鹏,雷明凯.高功率脉冲磁控溅射沉积原理与工艺研究进展[J].中国表面工程,2012,25(5):15-20.WU Z L,ZHU X P,LEI M K.Process in deposition principle and process characteristics of high power pulse magnetron sputtering[J].China Surface Engineering,2012,25(5):15-20(in Chinese).
查找原文
参考文献 10
AISSA K A,ACHOUR A,CAMUS J,et al.Comparision of the structural properties and residual stress of AlN films deposited by dc magnetron sputtering and high power impulse magnetron sputtering at different working pressures[J].Thin Solid Films,2014,550:264-267.
查找原文
参考文献 11
LIN J L,MOORE J J,SPROULW D,et al.The structure and properties chromium nitride coatings deposited using dc,pulsed dc and modulated pulse power magnetron sputtering [J].Surface and Coatings Technology,2010,204:2230-2239.
查找原文
参考文献 12
PETROV I,BARNA P B,HULTMAN L,et al.Microstructural evolution during film growth [J].Journal of Vacuum Science and Technology A,2003,21(5):S117-S128.
查找原文
参考文献 13
CHASON E,KARLSON M,COLIN J J,et al.A kinetic model for stress generation in thin films grown from energetic vapor fluxes [J].Journal of Applied Physics,2016,119(14):145307.
查找原文
参考文献 14
CEMIN F,ABADIAS G,MINEA T,et al.Benefits of energetic ion bombardment for tailoring stress and microstructural evolution during growth of Cu thin films[J].Acta Materialia,2017,141:120-130.
查找原文
参考文献 15
ZHANG X,MISRA A.Residual stresses in sputter-deposited copper/330 stainless steel multilayers[J].Journal of Applied Physics,2004,96(12):7173-7178.
查找原文
参考文献 16
KINBARA A,KUSANO E,KAMIYA T,et al.Evaluation of adhesion strength of Ti films on Si(100)by the internal stress method [J].Thin Solid Films,1998,317:165-168.
查找原文
参考文献 17
OLIVER W C,PHARR GM.An improved technique for determing hardness and elastic modulus using load and displacement sensing indentation experiments [J].Journal of Materials Research,1992,7(6):1564-1583.
查找原文
参考文献 18
LEE H,WONG S W,LOPATIN S D.Correlation of stress and texture evolution during self-and thermal annealing of electroplated Cu films[J].Journal of Applied Physics,2003,93(7):3796-3804.
查找原文
参考文献 19
SAMUELSSON M,LUNDIN D,JENSEN J,et al.On the film density using high power impulse magnetron sputtering [J].Surface and Coatings Technology,2010,205:591-596.
查找原文
参考文献 20
SAVALONI H,TAHERIZADEH A,ZENDEHNAM A.Residual stress and structural characteristics in Ti and Cu sputtered films on glass substrates at different substrate temperatures and film thickness[J].Physica B:Condensed Matter,2004,349:44-55.
查找原文
参考文献 21
MOVCHAN B A,DEMCHISHIN A V.Structure and properties of thick vacuum-condensates of nickel,titanium,tungsten,aluminum oxide,and zirconium dioxide in vacuum [J].Physics of Metal and Metallography,1969,28:653-660.
查找原文
参考文献 22
THORNTON J A.High rate thick film growth[J].Annual Review of Materials Science,1977,7:239-260.
查找原文
参考文献 23
ANDERS A.A structure zone diagram including plasmabased deposition and ion etching [J].Thin Solid Films,2010,518:4087-4090.
查找原文
参考文献 24
KARABACAK T.Thin-film growth dynamics with shadowing and re-emission effects [J].J.Nanomechanics Micromechanics,2011,5(1):1-18.
查找原文
目录contents

    摘要

    采用高功率调制脉冲磁控溅射(MPPMS)技术在 Si(100)基体上沉积 Cu 薄膜,SEM 观察薄膜厚度及生长特征、XRD 分析薄膜晶体结构、nanoindentor 测量薄膜纳米硬度和弹性模量、Stoney 公式计算薄膜残余应力,研究沉积过程靶基距对 Cu / Si(100)薄膜沉积速率、微结构及残余应力的影响。 随着靶基距的增大,薄膜沉积速率降低,薄膜的生长结构由致密 T 区向 I 区转变,Cu(111)择优生长的晶粒逐渐减小,薄膜纳米硬度和弹性模量也相应降低,残余拉应力约为 400 MPa。 较小靶基距时增加的沉积离子通量和能量,决定了薄膜晶粒合并长大体积收缩过程的主要生长形式,导致了 Cu / Si(100)薄膜具有的残余拉应力状态。 MPPMS 工艺的高沉积通量和粒子能量可实现对 Cu / Si(100)薄膜残余应力的调控。

    Abstract

    Cu thin films were deposited on the Si(100) substrate by modulated pulsed power magnetron sputtering (MPPMS). The effect of target-substrate distance on film thickness, microstructure, nanohardness and residual stress was systematically investigated by using SEM, analyzing crystal structure by XRD, nanoindentor and Stoney equation methods. With increasing the target-substrate distance, the deposition rates of Cu / Si(100) thin films decrease due to reduction of both the deposition flux and particle energy. The microstructure of the Cu / Si(100) thin films also change from the dense zone T structure to the zone I structure with decrease of the Cu(111) grain size I, the hardness and elastic modulus of the thin films correspondently decrease with residual tensile stress of about 400 MPa. The reduced deposition ion flux and energy with the increase of target-substrate distance determine the main growth mode of the thin film grains as coalesce and shrinkage process, resulting in the Cu / Si(100) films with a residual tensile stress state. The high deposition flux and ion energy of MPPMS could effectively control the residual stress of Cu / Si(100) films.

  • 0 引言

  • Cu作为导电薄膜广泛应用于半导体等领域,残余应力是导致其失效、剥落主要原因之一[1-2]。基于Volmer-Webber方式生长的多晶Cu薄膜,残余应力主要受薄膜生长过程中形成的本征应力和膜基不同晶格膨胀产生的热应力共同影响[3]。而较低沉积温度生长薄膜的残余应力主要源于本征应力。本征应力强烈依赖于沉积工艺对薄膜生长形态的影响,薄膜通过协调生长过程中晶界吸引力产生拉应力和致密结构产生压应力[4]。 ABERMANN等[5]原位测量了不同金属薄膜的本征应力,不同金属的移动能力差别导致薄膜生长模式的转变,进而影响薄膜的残余应力。

  • DANIEL等[6]进一步提出晶粒生长合并体积收缩产生拉应力、吸附原子扩散产生压应力,以及离子轰击薄膜产生压应力。对于荷能粒子沉积技术,离子轰击是独立于薄膜生长的重要影响因素,薄膜的残余应力是各种因素叠加的结果[7]。高功率调制脉冲磁控溅射( Modulated pulsed power magnetron sputtering, MPPMS) 作为一类HiPIMS(High power impulse magnetron sputtering) 沉积技术,由于靶材的高度离化,可促进离子辐照和吸附原子移动对薄膜残余压应力的形成[8-9],在相近的平均功率下,HiPIMS较常规直流磁控溅射沉积的硬质薄膜具有更高的残余压应力[10-11]。

  • HiPIMS沉积工艺,由于沉积粒子的能量和通量是薄膜残余应力演化的重要影响因素,可控制薄膜生长前沿吸附原子的移动能力[12]。但是对于迁移能力较高的金属,如Au、Cu等, 沉积粒子的能量和通量对残余应力的影响更为显著。 CHASON等[13]模拟了生长Mo薄膜的残余应力动力学演变过程,与HiPIMS试验结果吻合,由于金属Mo的移动能力较低,模拟方法不能适用于迁移能力较高的金属。 CEMIN等[14] 在Si基体上改变偏压沉积一系列厚度约为150nm的Cu薄膜,研究高能粒子轰击下薄膜残余应力和微观结构的关联规律,随着薄膜厚度增加,残余应力发生压应力-拉应力-压应力的转变,沉积通量中断再恢复后,由于Cu具有较高的移动能力,薄膜残余应力迅速降低。因此, HiPIMS沉积薄膜残余应力随着沉积粒子能量和通量的变化规律有待深入研究。鉴于MPPMS技术具有的特征放电波形,许多微脉冲组成的低电压长脉冲提供了高离化比例的沉积通量,同时达到高的沉积速率,为分析高功率能量沉积金属薄膜残余应力的演化规律及影响因素提供了有利条件。

  • 文中试验采用MPPMS沉积Cu/Si(100) 薄膜,通过改变靶基距调控沉积粒子通量和能量, 研究MPPMS工艺特征下靶基距对薄膜沉积速率、微结构及残余应力的影响规律。

  • 1 薄膜沉积装置和分析方法

  • 图1 给出了四靶闭合场高功率调制脉冲磁控溅射沉积薄膜系统示意图,系统配置90°均布的4个可独立控制的非平衡磁控靶,相邻阴极磁极相反形成闭合磁路,可有效约束电子提高等离子体密度。溅射腔室为 ϕ800mm×800mm圆形全不锈钢结构,侧面开门。靶材为纯度99.95%的金属Cu,尺寸为440mm×140mm×6mm。磁控溅射靶由10kW的Zpulser AXIS TM 高功率调制脉冲电源控制,采用固定平均功率模式,平均功率设定为2kW,充电电压为600V,微脉冲参数如表1所示。 t total 为微脉冲持续时间,tweak 弱离化时间,t strong 强离化时间,t on 微脉冲开启时间,t off 微脉冲关闭时间。图2给出了沉积过程中由Tektronix TDS2014C示波器记录的放电波形曲线,放电由微脉冲开启和关闭时间(t on/t off)控制, 放电包括弱离化和强离化两个阶段。

  • 图1 四靶闭合场高功率调制脉冲磁控溅射系统示意图

  • Fig.1 Schematic diagram of modulated pulsed power magnetron sputtering system in four-target closed field

  • 表1 MPPMS溅射沉积Cu薄膜的工作参数

  • Table1 Deposition parameters used in MPPMS Cu thin films

  • 图2 MPPMS沉积Cu/Si(100)薄膜的典型放电曲线

  • Fig.2 Typical discharge curve of MPPMS Cu/Si(100) thin films

  • 采用Si(100)基体样品,依次用丙酮和无水乙醇分别清洗30min并吹干后,装入平行于磁控溅射靶面的样品架上。溅射腔室的本底真空达到2.0×10-4 Pa后,引入99.99%Ar气作为工作气体,流量为80sccm,工作气压为0.30Pa。溅射沉积试验前使用AE Pinnacle plus脉冲电源以350V电压溅射清洗样品20min, 频率为100kHz, 占空比为10%, 在溅射沉积前使用MPPMS电源清洗靶面2min。沉积的Cu/Si(100)薄膜厚度控制在1.2 μm左右,沉积过程中未加热和施加负偏压。沉积完毕后停止通气,使样品在高真空状态的真空室内自然冷却3h后取出测试。

  • Cu膜厚度和Si基体的曲率采用Surfcorder ET4000AK表面轮廓仪,对尺寸为30mm×3mm×0.36mm的Si(100)基体上溅射沉积1.2 μm厚Cu薄膜前后的表面弧度进行接触式轮廓测量。测量载荷为50 μN,设置计算机程序使探头在样品中间位置以0.2mm/s的速度平行于长边移动24mm,记录轮廓曲线。用i-Star软件对采集到的轮廓曲线进行分析,得到Si(100)基体沉积Cu薄膜前后的曲率半径。利用式(1)给出的Stoney公式[15]计算薄膜的弯曲应力,即总残余应力。

  • σf=Es1-vsts26tf1R2-1R1
    (1)

  • 式中,Es 和 υs 分别为Si(100)基体的弹性模量和泊松比;t s 和 t f 为基体和薄膜的厚度;R2 和 R1 分别为溅射沉积后和溅射沉积前Si(100) 基体的曲率半径。 Es 取值为1.30 × 10 11 Pa,υs 为0.28 [16],t f 为1.2 μm,t s 为360 μm。

  • 采用ZEISS SUPRA 55-32-76型扫描电子显微镜(SEM)观察Cu/Si(100)薄膜表面和截面生长形貌。采用PANalytical EMPYREAN型x射线衍射仪对Cu/Si(100)薄膜的结构和生长取向进行分析,采用Debye-Scherrer公式计算Cu(111) 晶面的晶粒尺寸。 Cu薄膜纳米硬度和弹性模量采用MTS Nanoindenter XP TM 纳米压痕仪测量并通过Oliver-Pharr法计算[17],薄膜的纳米硬度和弹性模量均为至少9个有效测量点的平均值。

  • 2 试验结果

  • 图3 给出了Cu/Si(100)薄膜沉积速率随靶基距变化曲线。靶基距由50mm增至135mm,Cu/Si(100)薄膜沉积速率迅速下降,由8.30 μm/h降至4.06 μm/h,进一步增加靶基距至250mm,沉积速率逐渐降至1.60 μm/h。薄膜沉积速率随靶基距增加下降,在靶基距135mm附近存在一个沉积速率下降转折点。

  • 图3 Cu/Si(100)薄膜沉积速率随靶基距变化曲线

  • Fig.3 Deposition rate of Cu/Si(100) thin films at varied target-substrate distance

  • 图4 给出了不同靶基距下Cu/Si(100)薄膜生长形貌的表面和横截面SEM图像。随靶基距增加,Cu/Si(100)薄膜表面逐渐由致密的T区结构转变为贯穿柱状晶的I区结构。靶基距为135mm,薄膜的微结构发生明显的转变。结合图3可知,当靶基距大于135mm时,薄膜沉积速率的显著变化造成了薄膜生长微结构的改变。

  • 图4 不同靶基距Cu/Si(100)薄膜生长形貌的表面和横截面SEM图像

  • Fig.4 Surface and cross-sectional SEM images of Cu/Si(100) thin films at varied target-substrate distance

  • 图5(a)给出了Cu/Si(100)薄膜随靶基距离变化的XRD谱。 Cu/Si(100)薄膜主要呈现明显的fcc-Cu(111)择优取向。通过Cu薄膜(111)和(200)衍射峰强度比值( I(111)/I(200))分析薄膜生长的择优取向变化。图5(b)给出了根据XRD图谱计算的晶粒尺寸与衍射峰强度比(I(111)/I(200)) 曲线。靶基距从75mm增至150mm,Cu薄膜(111) 和( 200) 晶面衍射峰强度比值( I(111)/I(200))依次为5.94、9.75、6.30、5.43和3.92,Cu薄膜的择优取向先变强而后转弱。 Debye-Scherrer公式计算了Cu(111) 晶面的晶粒尺寸,晶粒尺寸随靶基距减小,在靶基距大于115mm时迅速降低。

  • 图5 不同靶基距沉积Cu/Si(100)薄膜XRD谱和晶粒尺寸与 I(111) /I(200)衍射峰强度比变化曲线

  • Fig.5 XRD patterns, grain size and I(111)/I(200) ratio at varied target-substrate distance

  • LEE等[18] 对电镀Cu涂层的择优取向研究表明,薄膜生长取向受表面能与应变能竞争控制。因Cu(111) 晶面表面能最低,(200) 晶面应变能最低,表面能最小化趋向于形成(111)织构, 而应变能最小化趋向于形成(200)织构。靶基距离逐渐增大,Cu薄膜表面出现的裂纹释放了薄膜应力,可能进一步导致Cu/Si(100)薄膜择优取向发生变化。

  • 图6 给出了Cu/Si(100)薄膜硬度和弹性模量随靶基距变化曲线。在75mm靶基距下薄膜纳米硬度和弹性模量最高, 分别为2.80和135GPa。随靶基距增加,纳米硬度和弹性模量都逐渐变小,在150mm靶基距下分别达到2.23和105GPa的最小值。薄膜硬度降低由其致密度下降导致[19]。通常沉积的金属薄膜结构由T区转变到I区,薄膜硬度增加,但随靶基距增加, Cu/Si(100)薄膜致密性显著降低,其硬度相应下降。而当靶基距为150mm时,薄膜弹性模量迅速降低,下降速率明显高于硬化速率,薄膜表面形成的裂纹导致了薄膜刚度降低。

  • 图6 Cu/Si(100)薄膜硬度和弹性模量随靶基距变化曲线

  • Fig.6 Nanohardness and elastic modulus of Cu/Si( 100) thin films at varied target-substrate distance

  • 图7 给出了Cu/Si(100)薄膜残余应力随靶基距变化曲线。所有Cu/Si(100)薄膜均呈现残余拉应力。当靶基距为50mm时,残余应力为263MPa,增加靶基距,沉积薄膜残余应力逐渐增大,直至靶基距达到135mm时,Cu/Si(100)薄膜残余拉应力迅速降低,并最终稳定在80MPa左右。结合图3和4可知,靶基距增至135mm时, Cu/Si(100)薄膜的沉积速率和微观形貌均发生显著变化,薄膜表面因贯穿柱状晶的阴影效应遮挡逐渐形成微裂纹,薄膜的应力得到释放。但SEM结果表明Cu/Si(100)薄膜厚度约100nm以内的初始生长阶段,薄膜相对致密连续且无明显裂纹, 最终的Cu薄膜残余应力也可稳定在80MPa左右。

  • 薄膜本征的拉应力由生长初期的岛状生长和合并所决定。由于Cu原子异质界面迁移能力较高[5],薄膜生长初期可快速形成连续生长薄膜。忽略热应力影响时,薄膜始终存在残余拉应力,说明Cu/Si(100)薄膜残余应力主要受晶粒合并聚集所产生的残余拉应力主导。当Cu薄膜表面出现裂纹后,薄膜近80MPa的残余拉应力,且后续存在表面裂纹的薄膜残余应力均保持在这一数值,是受到薄膜生长初期残余应力的影响所致。

  • 图8 给出了Cu/Si(100)薄膜沉积速率与残余应力关系曲线。薄膜表面未出现裂纹时,当靶基距由50mm增至115mm时, 沉积速率由8.30 μm/h降至4.06 μm/h,其残余拉应力逐渐升高。而沉积速率小于6.00 μm/h,薄膜残余应力基本稳定。由于所有薄膜厚度均为1.2 μm左右,且基体未加热,薄膜残余应力主要由本征应力决定。在薄膜生长过程中,高沉积速率有利于薄膜残余拉应力形成。仅在薄膜沉积速率大于6.00 μm/h时呈现明显的压应力状态,由MPPMS沉积时粒子能量较大引起的压应力所致。 SAVALONI等[20] 指出,Cu(111) 织构趋向于拉应力状态,而(200)织构趋向于压应力状态。随靶基距增加,沉积通量和粒子能量因碰撞和散射逐渐降低,薄膜微结构由致密T区逐渐向贯穿柱状晶的I区转变,虽然Cu薄膜(111)和(200) 晶面衍射峰强度比值( I(111)/I(200)) 逐渐降低,但贯穿柱状晶“阴影效应”遮蔽形成的缺陷导致薄膜形成裂纹,残余应力得到释放。

  • 图7 Cu/Si(100)薄膜残余应力随靶基距变化曲线

  • Fig.7 Residual stress of Cu/Si(100) thin films at varied target-substrate distance

  • 图8 Cu/Si(100)薄膜不同沉积速率与残余应力关系曲线

  • Fig.8 Effects of deposition rate on residual stress in Cu/Si(100) thin films

  • 3 讨论

  • MPPMS沉积Cu/Si( 100) 薄膜, 靶基距由50mm增至250mm,由于沉积通量和粒子能量的变化,导致薄膜结构逐渐由致密T区向贯穿柱状晶的I区转变。 MOVCHAN和DEMECHISHIN [21]利用薄膜沉积温度与薄膜熔点比的同系温度,建立了结构带图,将薄膜生长结构划分为3个区域。 THORNTON [22] 进一步提出了薄膜的生长结构主要可由溅射气压和基体温度决定, 在低温和高溅射气压时易形成贯穿柱状晶的I区结构。 ANDERS [23] 修正了高功率能量沉积薄膜生长的结构带图,指出了薄膜的生长结构主要由同系温度和归一化能量决定。当同系温度低且溅射粒子能量也低时,由于移动能力较弱,易形成贯穿柱状晶的I区结构。

  • MPPMS技术可提供高离化率的沉积通量, 考虑靶基距对Cu + 沉积通量和能量的影响,Cu + 沉积通量为

  • ΓCu+=ΓCu+0exp⁡(-x/λ)
    (2)

  • 式中,x为Cu +输运距离,ΓCu + 0 为x=0处的Cu +通量,λ=1/nArσCu+,Ar为Cu +在Ar中的平均自由程,σCu +,Ar 为Cu +与Ar原子碰撞截面。沉积通量随着输运距离呈指数下降趋势,因此沉积速率随靶基距降低。沉积的Cu +动能为

  • WK=12mCu+v2=mCu2ΓCu+nCu+2
    (3)

  • 式中, nCu+为Cu +密度,在输运过程中Cu + 密度变化较小,Cu +动能随靶基距降低,且下降速率较沉积通量更大。

  • 靶基距增加,沉积速率降低,溅射粒子到达基体的沉积通量和能量均呈逐渐减小趋势。沉积通量和粒子能量不仅决定沉积速率,也影响涂层初期阶段的生长模式。高沉积通量倾向形成薄膜高密度形核,而低沉积通量薄膜则促进岛状生长状态。粒子能量主要影响吸附原子到达基体表面的运动状态,即迁移能力。当靶基距小于75mm时,沉积通量高且粒子能量也高,高沉积速率造成薄膜生长初期易呈连续状态,吸附原子在薄膜表面迁移能力增强,粒子从生长表面的高处向低处迁移,如阴影部分或岛间缝隙处,这些区域的填充避免了孔隙,薄膜呈致密T区结构, 晶粒生长合并体积收缩产生较高拉应力。高粒子能量进一步驱动吸附原子向晶界移动,同时离子轰击作用较强,产生的压应力抵消了T区结构的拉应力,有效降低了薄膜的残余拉应力。当靶基距增至135mm时,沉积通量和粒子能量均下降,薄膜沉积速率降低,表面形核率和粒子表面迁移能力也相应降低,薄膜呈纤细晶粒I区结构, 晶粒生长产生的拉应力有所降低。但随靶基距增加,粒子能量下降速率更快,轰击作用降低,产生的压应力减小,导致薄膜生长过程的残余拉应力升高。当靶基距大于135mm时,沉积通量低同时粒子能量也低,沉积速率下降减缓,离子轰击能力减弱,吸附原子表面迁移率有限。因阴影效应和低表面迁移率,沉积粒子无法有效填充柱状晶之间的孔隙,导致涂层呈I区的贯穿柱状晶结构[24],特别是在薄膜本征拉应力作用下表面出现裂纹,导致薄膜残余应力大大降低。

  • 沉积通量和粒子能量是高功率能量沉积金属薄膜残余应力的关键影响因素。随靶基距增加,沉积通量和粒子能量均下降,薄膜沉积速率降低的同时薄膜结构由致密T区向贯穿柱状晶结构I区转变,微观结构和离子轰击共同作用导致残余应力呈现随靶基距先增加后减小的变化趋势。 MPPMS的高沉积通量和粒子能量实现了对Cu/Si(100)薄膜残余应力的有效调控。

  • 4 结论

  • (1) 采用MPPMS沉积了不同结构的Cu/Si(100)薄膜。靶基距由50mm增至135mm,薄膜沉积速率因减小的沉积通量和粒子能量而降低。

  • (2) Cu/Si(100)薄膜增加靶基距由致密的T区结构逐渐转变为贯穿柱状晶的I区结构。薄膜呈现明显的(111)择优取向,且晶粒尺寸随靶基距增加逐渐降低,在靶基距大于115mm时迅速下降,相应的薄膜硬度和弹性模量均降低。

  • (3) Cu/Si(100)薄膜均呈现残余拉应力,在靶基距较小时,沉积速率较高,沉积通量和粒子能量均较高,残余应力为400MPa左右,薄膜残余应力主要由晶粒合并体积收缩产生的拉应力控制,增加靶基距可实现对薄膜残余拉应力调节。

  • 参考文献

    • [1] MISRA A,NASTASI M.Limits of residual stress in Cr films sputter deposited on biased substrates[J].Applied Physics Letters,1999,75(20):3123-3125.

    • [2] MENG D,LI Y G,JIANG Z T,et al.Scratch behavior and FEM modelling of Cu/Si(100)thin films deposited by modulated pulsed power magnetron sputtering [J].Surface and Coatings Technology,2019,363:25-33.

    • [3] ENGWALL A M,RAO Z,CHASON E.Origins of residual stress in thin films:Interaction between microstructure and growth kinetics[J].Materials and Design,2016,110:616-623.

    • [4] ABADIAS G,CHASON E,KECKES J,et al.Stress in thin films and coatings:Current status,challenges,and prospects [J].Journal of Vacuum Science and Technology A,2018,36(2):020801.

    • [5] ABERMANN R.Measurements of the intrinsic stress in thin metal films[J].Vacuum,1990,41:1279-1282.

    • [6] DANIEL R,MARTINSCHITZ K J,KECHES J,et al.The origin of stresses in magnetron-sputtered thin films with zone T structures [J].Acta Materialia,2010,58(7):2621-2633.

    • [7] JANSSEN G C A M,KAMMINGA J-D.Stress in hard metal films[J].Applied Physics Letters,2004,85:3086-3088.

    • [8] LIN J L,MOORE J J,SPROUL W D,et al.Modulated pulse power sputtered chromium coatings [J].Thin Solid Films,2009,518(5):1566-1570.

    • [9] 吴志立,朱小鹏,雷明凯.高功率脉冲磁控溅射沉积原理与工艺研究进展[J].中国表面工程,2012,25(5):15-20.WU Z L,ZHU X P,LEI M K.Process in deposition principle and process characteristics of high power pulse magnetron sputtering[J].China Surface Engineering,2012,25(5):15-20(in Chinese).

    • [10] AISSA K A,ACHOUR A,CAMUS J,et al.Comparision of the structural properties and residual stress of AlN films deposited by dc magnetron sputtering and high power impulse magnetron sputtering at different working pressures[J].Thin Solid Films,2014,550:264-267.

    • [11] LIN J L,MOORE J J,SPROULW D,et al.The structure and properties chromium nitride coatings deposited using dc,pulsed dc and modulated pulse power magnetron sputtering [J].Surface and Coatings Technology,2010,204:2230-2239.

    • [12] PETROV I,BARNA P B,HULTMAN L,et al.Microstructural evolution during film growth [J].Journal of Vacuum Science and Technology A,2003,21(5):S117-S128.

    • [13] CHASON E,KARLSON M,COLIN J J,et al.A kinetic model for stress generation in thin films grown from energetic vapor fluxes [J].Journal of Applied Physics,2016,119(14):145307.

    • [14] CEMIN F,ABADIAS G,MINEA T,et al.Benefits of energetic ion bombardment for tailoring stress and microstructural evolution during growth of Cu thin films[J].Acta Materialia,2017,141:120-130.

    • [15] ZHANG X,MISRA A.Residual stresses in sputter-deposited copper/330 stainless steel multilayers[J].Journal of Applied Physics,2004,96(12):7173-7178.

    • [16] KINBARA A,KUSANO E,KAMIYA T,et al.Evaluation of adhesion strength of Ti films on Si(100)by the internal stress method [J].Thin Solid Films,1998,317:165-168.

    • [17] OLIVER W C,PHARR GM.An improved technique for determing hardness and elastic modulus using load and displacement sensing indentation experiments [J].Journal of Materials Research,1992,7(6):1564-1583.

    • [18] LEE H,WONG S W,LOPATIN S D.Correlation of stress and texture evolution during self-and thermal annealing of electroplated Cu films[J].Journal of Applied Physics,2003,93(7):3796-3804.

    • [19] SAMUELSSON M,LUNDIN D,JENSEN J,et al.On the film density using high power impulse magnetron sputtering [J].Surface and Coatings Technology,2010,205:591-596.

    • [20] SAVALONI H,TAHERIZADEH A,ZENDEHNAM A.Residual stress and structural characteristics in Ti and Cu sputtered films on glass substrates at different substrate temperatures and film thickness[J].Physica B:Condensed Matter,2004,349:44-55.

    • [21] MOVCHAN B A,DEMCHISHIN A V.Structure and properties of thick vacuum-condensates of nickel,titanium,tungsten,aluminum oxide,and zirconium dioxide in vacuum [J].Physics of Metal and Metallography,1969,28:653-660.

    • [22] THORNTON J A.High rate thick film growth[J].Annual Review of Materials Science,1977,7:239-260.

    • [23] ANDERS A.A structure zone diagram including plasmabased deposition and ion etching [J].Thin Solid Films,2010,518:4087-4090.

    • [24] KARABACAK T.Thin-film growth dynamics with shadowing and re-emission effects [J].J.Nanomechanics Micromechanics,2011,5(1):1-18.

  • 基本信息

    中图分类号: TG174.444
    文献标识码: A
    DOI: 10.11933/j.issn.1007-9289.20190910002
    文章编号: 1007-9289(2020)06-0086-07

    基金信息

    国家自然科学基金(51575077, 51601029, U1508218)；
    Supported by National Natural Science Foundation of China (51575077, 51601029, U1508218)；

    引用信息

    孟笛, 蒋智韬, 李玉阁, 等. 靶基距对 Cu / Si(100)薄膜结构和残余应力的影响[J]. 中国表面工程, 2020, 33(6): 86-92

    MENG D, JIANG Z T, LI Y G, et al. Effects of target-substrate distance on structure and residual stress of Cu / Si(100) films[J]. China Surface Engineering, 2020, 33(6): 86-92.

    稿件历史

    收稿日期: 2020-05-10

  • 参考文献

    • [1] MISRA A,NASTASI M.Limits of residual stress in Cr films sputter deposited on biased substrates[J].Applied Physics Letters,1999,75(20):3123-3125.

    • [2] MENG D,LI Y G,JIANG Z T,et al.Scratch behavior and FEM modelling of Cu/Si(100)thin films deposited by modulated pulsed power magnetron sputtering [J].Surface and Coatings Technology,2019,363:25-33.

    • [3] ENGWALL A M,RAO Z,CHASON E.Origins of residual stress in thin films:Interaction between microstructure and growth kinetics[J].Materials and Design,2016,110:616-623.

    • [4] ABADIAS G,CHASON E,KECKES J,et al.Stress in thin films and coatings:Current status,challenges,and prospects [J].Journal of Vacuum Science and Technology A,2018,36(2):020801.

    • [5] ABERMANN R.Measurements of the intrinsic stress in thin metal films[J].Vacuum,1990,41:1279-1282.

    • [6] DANIEL R,MARTINSCHITZ K J,KECHES J,et al.The origin of stresses in magnetron-sputtered thin films with zone T structures [J].Acta Materialia,2010,58(7):2621-2633.

    • [7] JANSSEN G C A M,KAMMINGA J-D.Stress in hard metal films[J].Applied Physics Letters,2004,85:3086-3088.

    • [8] LIN J L,MOORE J J,SPROUL W D,et al.Modulated pulse power sputtered chromium coatings [J].Thin Solid Films,2009,518(5):1566-1570.

    • [9] 吴志立,朱小鹏,雷明凯.高功率脉冲磁控溅射沉积原理与工艺研究进展[J].中国表面工程,2012,25(5):15-20.WU Z L,ZHU X P,LEI M K.Process in deposition principle and process characteristics of high power pulse magnetron sputtering[J].China Surface Engineering,2012,25(5):15-20(in Chinese).

    • [10] AISSA K A,ACHOUR A,CAMUS J,et al.Comparision of the structural properties and residual stress of AlN films deposited by dc magnetron sputtering and high power impulse magnetron sputtering at different working pressures[J].Thin Solid Films,2014,550:264-267.

    • [11] LIN J L,MOORE J J,SPROULW D,et al.The structure and properties chromium nitride coatings deposited using dc,pulsed dc and modulated pulse power magnetron sputtering [J].Surface and Coatings Technology,2010,204:2230-2239.

    • [12] PETROV I,BARNA P B,HULTMAN L,et al.Microstructural evolution during film growth [J].Journal of Vacuum Science and Technology A,2003,21(5):S117-S128.

    • [13] CHASON E,KARLSON M,COLIN J J,et al.A kinetic model for stress generation in thin films grown from energetic vapor fluxes [J].Journal of Applied Physics,2016,119(14):145307.

    • [14] CEMIN F,ABADIAS G,MINEA T,et al.Benefits of energetic ion bombardment for tailoring stress and microstructural evolution during growth of Cu thin films[J].Acta Materialia,2017,141:120-130.

    • [15] ZHANG X,MISRA A.Residual stresses in sputter-deposited copper/330 stainless steel multilayers[J].Journal of Applied Physics,2004,96(12):7173-7178.

    • [16] KINBARA A,KUSANO E,KAMIYA T,et al.Evaluation of adhesion strength of Ti films on Si(100)by the internal stress method [J].Thin Solid Films,1998,317:165-168.

    • [17] OLIVER W C,PHARR GM.An improved technique for determing hardness and elastic modulus using load and displacement sensing indentation experiments [J].Journal of Materials Research,1992,7(6):1564-1583.

    • [18] LEE H,WONG S W,LOPATIN S D.Correlation of stress and texture evolution during self-and thermal annealing of electroplated Cu films[J].Journal of Applied Physics,2003,93(7):3796-3804.

    • [19] SAMUELSSON M,LUNDIN D,JENSEN J,et al.On the film density using high power impulse magnetron sputtering [J].Surface and Coatings Technology,2010,205:591-596.

    • [20] SAVALONI H,TAHERIZADEH A,ZENDEHNAM A.Residual stress and structural characteristics in Ti and Cu sputtered films on glass substrates at different substrate temperatures and film thickness[J].Physica B:Condensed Matter,2004,349:44-55.

    • [21] MOVCHAN B A,DEMCHISHIN A V.Structure and properties of thick vacuum-condensates of nickel,titanium,tungsten,aluminum oxide,and zirconium dioxide in vacuum [J].Physics of Metal and Metallography,1969,28:653-660.

    • [22] THORNTON J A.High rate thick film growth[J].Annual Review of Materials Science,1977,7:239-260.

    • [23] ANDERS A.A structure zone diagram including plasmabased deposition and ion etching [J].Thin Solid Films,2010,518:4087-4090.

    • [24] KARABACAK T.Thin-film growth dynamics with shadowing and re-emission effects [J].J.Nanomechanics Micromechanics,2011,5(1):1-18.

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