材料研究学报, 2026, 40(8): 613-623 DOI: 10.11901/1005.3093.2025.324

研究论文

制备工艺参数对磁控溅射Ni5Pt薄膜的影响

张铭原1,2, 闻明3, 李思勰3, 张滨4, 张广平,2

1.中国科学技术大学材料科学与工程学院 沈阳 110016

2.中国科学院金属研究所 高性能均质合金国家工程研究中心 沈阳 110016

3.昆明贵金属研究所 贵金属功能材料全国重点实验室 昆明 650106

4.东北大学材料科学与工程学院 材料各向异性与织构教育部重点实验室 沈阳 110819

Effect of Processing Parameters on Magnetron Sputtering Preparation of High-quality Ni5Pt Films for Schottky Diodes

ZHANG Mingyuan1,2, WEN Ming3, LI Sixie3, ZHANG Bin4, ZHANG Guangping,2

1.School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China

2.National Engineering Research Center for High Performance Homogenized Alloys, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

3.State Key Laboratory of Precious Metal Functional Materials, Kunming Institute of Precious Metals, Kunming 650106, China

4.Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China

通讯作者: 张广平,研究员,gpzhang@imr.ac.cn,研究方向为薄膜与微小尺度材料力学行为

收稿日期: 2025-11-03   修回日期: 2026-01-15  

基金资助: 国家自然科学基金(U25A20218)
云南省科技计划(202305AF150171)

Corresponding authors: ZHANG Guangping, Tel:(024)23971938, E-mail:gpzhang@imr.ac.cn

Received: 2025-11-03   Revised: 2026-01-15  

Fund supported: National Natural Science Foundation of China(U25A20218)
Scientific and Technological Project of Yunnan Province(202305AF150171)

作者简介 About authors

张铭原,男,2000年生,硕士生

摘要

分别在面外取向为(001)和(111)的单晶硅基底磁控溅射Ni5Pt合金薄膜,根据动力学标度理论量化研究了基底温度、溅射时间和基底取向对薄膜表面的粗糙度和微观结构的影响,并揭示了薄膜开裂失效的微观机理。结果表明,磁控溅射Ni5Pt合金薄膜的生长模式为层-岛状(SK)生长,其表面粗糙度随沉积时间的延长和基底温度的降低而提高,且与基面的晶体取向有关。给出了制备性能优异Ni5Pt薄膜的工艺参数。基于残余应力超过断裂强度的薄膜的断裂判据,得到了沉积态Ni5Pt薄膜开裂的基底“工程近似”临界厚度和对应的临界沉积时间。

关键词: 金属材料; Ni5Pt薄膜; 表面粗糙度; 残余应力; 磁控溅射; 肖特基二极管

Abstract

With the rapid development of ultra-high-speed and low-power Schottky barrier diode (SBD), the height and stability of the Schottky barrier have become a critical factor driving the continued evolution of the electronic and information technology industry. However, challenges such as uncontrollable surface quality, crack formation, and a lack of theoretical guidance for process optimization limit practical applications. Herein, Ni5Pt alloy films were prepared on substrates of single crystal Si with orientations of (100) and (111) respectively via magnetron sputtering technique by varying the substrate temperature and deposition time. The influence of sputtering parameters on the microstructure and surface morphology of the acquired films was characterized, while the mechanism related to the cracking failure of the films was postulated. Results reveal that the growth mechanism of Ni5Pt conforms to Stranski-Krastanov (SK) model. Surface roughness of films increases with the increasing deposition time and the decreasing substrate temperature, besides, which also depends on the crystallographic orientation of the basal plane of substrates. A cracking criterion based on residual stress was proposed, thereafter, the optimal sputtering parameters were established. The findings provide not only an important theoretical guidance for obtaining a Schottky barrier layer with good interface continuity and high barrier stability, but also a meaningful reference for the R & D of high-performance Schottky barrier diode devices in the future.

Keywords: metallic materials; Ni5Pt film; surface roughness; residual stress; magnetron sputtering; Schottky barrier diode

PDF (10902KB) 元数据 多维度评价 相关文章 导出 EndNote| Ris| Bibtex  收藏本文

本文引用格式

张铭原, 闻明, 李思勰, 张滨, 张广平. 制备工艺参数对磁控溅射Ni5Pt薄膜的影响[J]. 材料研究学报, 2026, 40(8): 613-623 DOI:10.11901/1005.3093.2025.324

ZHANG Mingyuan, WEN Ming, LI Sixie, ZHANG Bin, ZHANG Guangping. Effect of Processing Parameters on Magnetron Sputtering Preparation of High-quality Ni5Pt Films for Schottky Diodes[J]. Chinese Journal of Materials Research, 2026, 40(8): 613-623 DOI:10.11901/1005.3093.2025.324

基于金属-半导体结的肖特基二极管(Schottky barrier diode, SBD)的正向压降较低、超高速响应和低功耗,得到了广泛的应用[1,2]。SBD的整流特性和稳定性决定于其金属-半导体势垒,常用的势垒金属有Au[3]、Pt[4]、Ni[5]和Pd[6]。但是,这些传统贵金属的热稳定性较低且功函数不可调。使用合金材料替代单一贵金属可精准调控势垒高度[7,8]。镍铂(NiPt)合金的热稳定性较高且界面特性可调控,是主流势垒材料[9~11]。制备NiPt基SBD用的是在Si基底磁控溅射的合金薄膜,将其热处理形成热稳定的NiPtSi势垒层可实现反向电流阻断[12]。关于NiPt合金的研究,侧重于NiPt薄膜与Si形成的势垒高度[13]、热稳定性[11]以及高速退火工艺等方面[14]。制备NiPt合金薄膜的工艺参数对SBD器件势垒层微结构和性能的影响尚须进一步深入研究[15~17]。近年来,研究人员通过调控磁控溅射制备参数(如沉积时间、基底温度和沉积速率等)改善NiPt合金薄膜的表面粗糙度并调控残余应力[9,18,19]。Shin等[18]用晶圆曲率法研究了xNi(1-x)Pt (0.02 < x < 0.81)薄膜的应力行为,发现富集Ni的样品对基底温度和沉积速率的变化极其敏感。随着基底温度的降低和沉积速率的提高,薄膜中的残余应力显著增大。Eiler等[19]分析了xNi(1-x)Pt (0.01 < x < 0.39)薄膜的杨氏模量和硬度的变化,发现随着沉积时间的延长表面粗糙度有所提高。Yang等[20]发现,基底取向对ZnO薄膜的表面粗糙度也有显著影响。取向不同的基底其原子排列不同,使在其上制备的薄膜原子的生长能力也不同。在Si(100)基底上制备的薄膜表面粗糙度略比Si(111)基底的低。Tsamouras和Galinski等[21,22]发现,随着基底温度的提高在其上制备的Pt薄膜表面粗糙度提高,因为基底原子的扩散增强和活化能增大。虽然有些工作研究了用不同工艺制备的NiPt合金薄膜的表面粗糙度和残余应力状态的变化,但是关于制备工艺参数不同的Ni5Pt合金薄膜的应力变化和薄膜表面质量仍缺少系统的研究[10,16,23],特别是亟需进一步揭示薄膜制备工艺参数对薄膜的残余应力和表面粗糙度的影响。鉴于此,本文在两种晶体取向的单晶硅基底上磁控溅射Ni5Pt合金薄膜,研究基底温度、沉积时间以及基底取向对薄膜的表面粗糙度和微观结构的影响,并根据薄膜的开裂行为以及残余应力分布建立薄膜开裂的判据。

1 实验方法

1.1 薄膜样品的制备

实验用磁控溅射靶材是纯度为99.99%、Ni∶Pt质量比为95∶5的Ni5Pt合金,在厚度为675 μm的面外取向分别为(100)和(111)的商用单晶Si基底(Si(100)和Si(111))上直流磁控溅射Ni5Pt合金薄膜。磁控溅射前,先将真空腔室的本体真空度预抽至2 × 10-3 Pa,然后通入纯度为99.999%的氩气维持1 Pa的溅射气压,预溅射时基板转速为10 r/min,预溅射时间为5 min。然后分别在基底温度为室温、50 ℃和100 ℃三种条件下进行溅射沉积,溅射功率为100 W,溅射时间分别为1、5、10、15和30 min,制备出五种不同厚度的Ni5Pt合金薄膜。制备出的30种样品的编号和名称,列于表1

表1   Ni5Pt样品的编号和名称

Table 1  Codes and nomenclature of Ni5Pt film

NumbersNamesSubstrate orientationSubstrate temperatureSputtering time / min
1#Si(100)-RT1M(100)RT1
2#Si(100)-RT5M(100)RT5
3#Si(100)-RT10M(100)RT10
4#Si(100)-RT15M(100)RT15
5#Si(100)-RT30M(100)RT30
6#Si(100)-50 oC1M(100)50 oC1
7#Si(100)-50 oC5M(100)50 oC5
8#Si(100)-50 oC10M(100)50 oC10
9#Si(100)-50 oC15M(100)50 oC15
10#Si(100)-50 oC30M(100)50 oC30
11#Si(100)-100 oC1M(100)100 oC1
12#Si(100)-100 oC5 M(100)100 oC5
13#Si(100)-100 oC10M(100)100 oC10
14#Si(100)-100 oC15M(100)100 oC15
15#Si(100)-100 oC30M(100)100 oC30
16#Si(111)-RT1M(111)RT1
17#Si(111)-RT5M(111)RT5
18#Si(111)-RT10M(111)RT10
19#Si(111)-RT15M(111)RT15
20#Si(111)-RT30M(111)RT30
21#Si(111)-50 oC1M(111)50 oC1
22#Si(111)-50 oC5M(111)50 oC5
23#Si(111)-50 oC10M(111)50 oC10
24#Si(111)-50 oC15M(111)50 oC15
25#Si(111)-50 oC30M(111)50 oC30
26#Si(111)-100 oC1M(111)100 oC1
27#Si(111)-100 oC5M(111)100 oC5
28#Si(111)-100 oC10M(111)100 oC10
29#Si(111)-100 oC15M(111)100 oC15
30#Si(111)-100 oC30M(111)100 oC30

新窗口打开| 下载CSV


1.2 薄膜的表征

用Supra 35场发射扫描电子显微镜(SEM)观察薄膜表面的形貌,用SEM配备的X射线能量分散谱仪(EDS)定量分析薄膜表面的元素;用CSPM-3400型原子力显微镜(AFM)表征薄膜表面粗糙度;用D8 A型X射线衍射仪(XRD)测定薄膜的XRD谱,靶材为Cu靶,扫描速率为1 (°)/min,扫描范围20°~100°。用Tecnai 20透射电子显微镜(TEM)表征Ni5Pt薄膜中晶粒的特性。TEM样品的制备:先用STX-202A金刚石线切割机将薄膜切割成截面积为2 mm × 1 mm的矩形块,再将其研磨后用Gatan Model 695精密离子减薄仪减薄。

2 结果和讨论

2.1 基底温度和沉积时间对Ni5Pt薄膜微结构的影响

图1给出了分别在室温、50  ℃和100  ℃的Si(100)基底上溅射1、5、10、15和30 min制备的5种厚度的Ni5Pt薄膜样品的SEM照片。可以看出,除了沉积时间为1 min的薄膜,其余4种的表面都出现了不同程度的开裂。为了评估样品表面的开裂程度,统计了薄膜表面的裂纹密度(即SEM照片下裂纹面积占总面积的百分比),如图2所示。可以看出,随沉积时间(薄膜厚度)的增加薄膜的裂纹密度显著提高,表明裂纹的形成可能与薄膜内的应力密切相关,因为应力随着膜厚的增加而增大[24]

图1

图1   在三种温度的Si(100)基底沉积不同时间的Ni5Pt合金薄膜的表面SEM照片

Fig.1   SEM images of Ni5Pt films deposited on Si(100) substrates at room temperature (a-e), 50 oC (f-j), and 100 oC (k-o) with varying sputtering time of 1 min (a, f, k), 5 min (b, g, l), 10 min (c, h, m), 15 min (d, i, n), and 30 min (e, j, o)


图2

图2   在三种温度的基底沉积不同时间的Ni5Pt合金薄膜的表面裂纹密度

Fig.2   Crack density of Ni5Pt films deposited at three different substrate temperatures with varying sputtering time


图3给出了磁控溅射参数不同的Ni5Pt合金薄膜的XRD谱,可见所有样品的谱中都出现了与(111)和(200)晶面对应的衍射峰,其中较为显著的(111)峰表明薄膜中的晶粒具有一定的择优取向。随着薄膜沉积时间的延长衍射峰强度逐渐提高,表明薄膜的结晶度提高,且晶体的择优取向更加明显,生长织构逐渐增强。需要指出的是,Ni-Pt合金体系中可能存在多种中间相(如NiPt、Ni3Pt、NiPt3等[25]),且这些相的衍射峰位与Ni5Pt相的(111)和(200)面峰位较为接近。为了准确判断薄膜的相结构,将样品的XRD谱与文献中的Ni5Pt薄膜的衍射谱比较。根据Ni-Pt二元合金的平衡相图[25],在Pt含量低于约20% (原子分数)的Ni富集区间体系处于稳定的面心立方(FCC)置换固溶体区域,不生成有序金属间化合物或第二相,据此判定薄膜中出现的衍射峰对应Ni5Pt相[9,16,19]。此外,所有Ni5Pt薄膜的衍射峰均向低角度偏移,表明晶格常数有所增大,其原因可能是原子半径较大的Pt原子(0.139 nm)部分取代Ni原子(0.125 nm)进入晶格位置形成了置换型固溶体,使晶胞体积膨胀[14]。这种在取向和温度不同的基底制备的薄膜相同的衍射峰偏移,进一步证实了成分主导的晶格膨胀机制[26]。衍射峰展宽的原因有:在低温沉积薄膜中晶粒较小和在制备过程中薄膜出现一定程度的晶格畸变或微应变,特别是Pt原子非均匀分布或局部固溶在晶格内产生了弹性畸变场[27]

图3

图3   在三种温度的Si(100)和Si(111)基底沉积不同时间的Ni5Pt薄膜的XRD谱

Fig.3   XRD patterns of Ni5Pt films deposited with different sputtering time on Si(100) (a-c) and Si(111) (d-f) substrates at room temperature (a, d), 50 oC (b, e), and 100 oC (c, f)


图4给出了Si(100)-RT1M和Si(111)-RT1M样品的TEM照片和晶粒尺寸分布直方图。从图4a,b可见,Ni5Pt薄膜由纳米晶组成,没有孪晶。右上角的插图是对应的选区电子衍射(SAED)图样,可见明显的衍射环,表明晶粒具有FCC结构。图4c,d分别给出了Si(100)-RT1M和Si(111)-RT1M样品的HRTEM像,可见Si(100)-RT1M薄膜样品的(200)晶面间距为0.18 nm,Si(111)-RT1M薄膜样品的(111)晶面间距为0.21 nm。两者均大于Ni对应晶面的理论值((200):0.1762 nm,(111):0.2034 nm),与XRD谱给出的结果相符。图4e给出了Si(100)-RT1M和Si(111)-RT1M样品的晶粒尺寸分布直方图,可见Si(100)基底的晶粒尺寸((16.0 ± 7.1) nm)与Si(111)基底的晶粒((18.1 ± 6.9) nm)接近,表明不同基底取向对薄膜晶粒尺寸的影响较小。

图4

图4   Ni5Pt薄膜表面的TEM照片和晶粒尺寸分布直方图

Fig.4   Bright field TEM images (a, b) and HRTEM images (c, d) of Si(100)-RT1M (a, c) and Si(111)-RT1M (b, d), and corresponding grain size distribution (e), the insets are the fast FFT patterns


2.2 基底温度和沉积时间对Ni5Pt薄膜表面粗糙度的影响

图5给出了Si(100)基底上不同溅射参数的Ni5Pt合金薄膜的AFM照片,可见所有样品的表面均由不同尺寸的白色团簇状颗粒构成,且颗粒的尺寸和密度随着沉积时间的增加而显著增大和提高。假设薄膜原子在基底上生成一球冠状晶核,根据界面张力的平衡关系[28]

γfcosθ+γi=γs

图5

图5   在三种温度的Si(100)基底上沉积不同时间的Ni5Pt合金薄膜的表面AFM照片

Fig.5   AFM observations of Ni5Pt films deposited on Si(100) substrates at room temperature (a-e), 50 oC (f-j), and 100 oC (k-o) with varying sputtering time of 1 min (a, f, k), 5 min (b, g, l), 10 min (c, h, m), 15 min (d, i, n), and 30 min (e, j, o)


金属Ni、Pt的(111)晶面以及基底Si在(111)和(100)面的表面能分别为γNi(111) = 2.20 J/m2γPt(111) = 1.50 J/m2γSi(100) γSi(111) = 1.23 J/m2 [29~31]式 (1)中γfγs分别为薄膜材料原子和基底材料的表面能,γi为薄膜原子与基底材料之间的界面能,θ为接触角。根据混合法则[32]可计算出Ni5Pt合金在(111)晶面的表面能为γNi5Pt(111) = 2.165 J/m2,且Ni与Si之间的界面能γi ≈ 1.80 J/m2 [33]。于是可得Ni5Pt薄膜与Si基底的(111)晶面的表面能之差以及表面能之和分别为

γNi5Pt(111) - γSi(111) = 0.935 J/m2γNi5Pt(111) + γSi(111) = 3.395 J/m2,可见满足γNi5Pt - γSi < γi < γNi5Pt + γSi (0.935 J/m2 < 1.80 J/m2 < 3.395 J/m2)条件[34]。这表明,Ni5Pt薄膜在Si基底上的生长模式符合典型的层-岛状(Stranski-Krastanov, SK)生长模式。

图6给出了用台阶法测量的在三种温度基底上制备的Ni5Pt薄膜其厚度与沉积时间的关系。可以看出,随着沉积时间的增加,在不同温度基底制备的薄膜厚度均线性增加。同时,进行线性拟合可得薄膜在基底温度为室温、50 ℃和100  ℃时溅射速率分别为8.86、8.50和8.68 nm/min。

图6

图6   在三种温度的基底沉积不同时间的Ni5Pt薄膜的厚度

Fig.6   Thickness of Ni5Pt films at three substrate temperatures with different sputtering time


制备参数不同的Ni5Pt合金薄膜样品的表面粗糙度,如图7所示。可见,在Si(111)基底上制备的Ni5Pt薄膜其表面粗糙度均高于在Si(100)基底制备的薄膜样品。图7a给出了Ni5Pt薄膜的表面粗糙度与制备参数的关系:随着沉积时间(薄膜厚度)的增加,表面粗糙度随之提高。可用动力学标度理论[35]描述Ni5Pt薄膜的表面粗糙度(Sa)与薄膜厚度(h)的关系

Sa~hα

图7

图7   在三种温度的基底沉积不同时间的Ni5Pt薄膜的表面粗糙度与膜厚度的关系,以及表面粗糙度指数α随基底温度的变化

Fig.7   Variation of surface roughness with Ni5Pt film thickness (a) and variation of the roughness exponent α with deposition temperature (b)


式中α为薄膜表面粗糙度指数,表征薄膜表面高度的起伏程度,较大的α表示表面更粗糙,起伏较大;较小的α表示表面较平滑,局部起伏小。对 式(2)取对数得

ln(Sa)~αln(h)

式(3)表明,ln(Sa)-ln(h)呈线性关系,进行线性拟合可得磁控溅射参数不同的Ni5Pt薄膜的α值。图7b给出了Ni5Pt薄膜的α与基底温度的关系。可以看出,与在Si(100)基底制备的薄膜相比,在Si(111)基底上制备的Ni5Pt薄膜其α更大。这一差异,与两种取向基底的原子排列方式以及Ni和Pt原子在Si基底表面的扩散特性密切相关。虽然Si(100)基底与Si(111)基底的表面能接近(γSi(100)γSi(111) = 1.23 J/m2)[31],且Ni和Pt原子在两种取向基底表面上的扩散能力接近,但是Si(111)基底原子的排列更紧密,原子扩散激活能较高((0.97 ± 0.07) eV)[36],溅射出的Ni和Pt原子局部聚集形成较大的颗粒或岛状结构,使薄膜的表面粗糙度提高。而Si(100)基底表面的低能台阶和活性位点较多,原子激活能较低(~0.60 eV)[37],Ni和Pt原子更容易沿着台阶移动填充空位而生成表面较为平整的薄膜。

同时,由图7b可见,在两种取向的基底上生长的Ni5Pt合金薄膜表面粗糙度指数都随着基底温度的升高而减小。这种趋势,主要与Ni和Pt原子的迁移热能有关[22,38~40]。随着基底温度的提高Ni和Pt原子的扩散能力增强,生成的薄膜表面更加均匀和起伏较小。同时,较高的基底温度有助于释放界面应力,使晶体沿能量最低方向生长并通过晶界弛豫降低应力集中造成的表面不平整[41~43]。但是,过高的基底温度使溅射原子的扩散能力过强而使薄膜表面的粗糙度提高[44~46]

2.3 基底温度和沉积时间对Ni5Pt薄膜中残余应力和开裂的影响

图1中沉积时间不同的Ni5Pt合金薄膜的SEM照片可见,除沉积时间为1 min的Ni5Pt薄膜外,其余薄膜均发生了不同程度的开裂,且开裂程度与沉积时间(薄膜厚度)相关。从图3给出的溅射参数不同的Ni5Pt薄膜的XRD谱可见,(111)衍射峰发生了明显偏移,表明薄膜中存在残余应力。根据图3中(111)峰位的偏移结果,由

σ=-E2ν(dθd0-1)

可计算出溅射参数不同的薄膜中的残余应力值[27],结果如图8所示。 式(4)中Eν分别为Ni5Pt薄膜的弹性模量和泊松比,θ为布拉格衍射角,dθ 为在θ角下测得的晶面间距,d0为无应力状态晶面的晶面间距。由图8可见,随着Ni5Pt薄膜厚度的增加残余应力由压应力转变为拉应力。这一转变,可能与薄膜生长过程中内部积累的生长应力、界面失配应力和热应力有关[47~49]。首先,Ni5Pt薄膜与Si基底的晶格常数和表面能不同,且Ni5Pt合金的(111)和(200)晶面间距也不同,分别为dNi5Pt(111) = 0.21 nm, dNi5Pt(200) = 0.18 nm,Si基底的(100)和(111)晶面间距分别为dSi(100) = 0.5431 nm和dSi(111) = 0.3135 nm[50];两种材料的表面能也不同,分别为γNi5Pt(111) = 2.165 J/m2 [30]γSi(100)γSi(111) = 1.23 J/m2 [31]。在磁控溅射过程中,薄膜与基底的界面晶格失配,在界面产生了失配应力[48]。但是,Yang等[51]和Wang等[52]认为,厚度在亚微米范围内的薄膜,其界面失配应力与总残余应力相比并不起关键作用。其次,Ni5Pt薄膜与单晶Si基底的热膨胀系数不同也在沉积和冷却过程中产生热应力[49]。计算结果表明,Ni5Pt薄膜中的热应力只有0.07~0.22 GPa,占总残余应力的2.2%~6.3%,可以忽略不计。这表明,引起Ni5Pt薄膜开裂的是薄膜生长过程中微观结构变化产生的薄膜生长应力。在Ni5Pt薄膜生长的初期,“原子喷丸”效应是引起薄膜残余应力的主要机制[53]。在溅射沉积过程中,入射Ar⁺的轰击使部分原子偏离晶位而产生残余压应力[52]。随着沉积时间的延长表面原子的扩散不足而产生亚稳态结构,在沉积后的有序化过程填补缺陷、体积收缩使其转变为残余拉应力。当拉应力超过“原子喷丸”效应产生的压应力时,薄膜呈拉应力状态[24]

图8

图8   制备工艺参数不同的Ni5Pt薄膜的残余应力和Griffith计算断裂强度与薄膜厚度的关系,以及残余应力与计算断裂强度交汇区域 (图中虚线为计算断裂应力,实线为薄膜残余应力且由于不同基底温度的薄膜溅射速率不同,因而计算得到的断裂强度略有不同,这里仅给出溅射速率为8.50 nm/min所对应的断裂强度用以示意)

Fig.8   Relationship between residual stress and fracture strength calculated by Griffith criterion with thickness for Ni5Pt films (a) and intersection map of residual stress and the fracture strength (b) (Dashed line represents the fracture strength, the solid line represents residual stress and since the sputtering rates of films deposited at different temperatures vary, the fracture strength also shows slight differences. Here, only the fracture strength corresponding to a sputtering rate of 8.50 nm/min is provided for illustration)


为了找出薄膜的开裂条件,假设薄膜表面的裂纹为贯穿裂纹,即裂纹的长度是薄膜的厚度,则可将薄膜开裂近似为脆性断裂。根据Griffith准则[54],薄膜材料发生断裂所需的临界应力为

σc=2Efγfπa

式中Ef为薄膜的弹性模量,γf为薄膜的表面能,a为裂纹的半长度。由 式(5)可计算出不同厚度Ni5Pt薄膜的临界断裂应力(即断裂强度,图8a)。根据图8a和XRD谱计算出残余应力,可建立薄膜发生失效断裂的判据:薄膜的残余应力小于其断裂强度即σσc时,薄膜不会发生开裂;当σ > σc时,薄膜表面发生失效开裂。图8b给出了较薄Ni5Pt薄膜的残余应力与其断裂强度交汇区域数据。表2进一步汇总了不同制备参数下Ni5Pt薄膜发生断裂时对应的临界厚度和临界沉积时间。结果表明,在基底温度相同的条件下,在Si(100)基底上制备的薄膜发生开裂的临界厚度均高于在Si(111)上制备的薄膜,与在Si(111)基底上制备的Ni5Pt薄膜的失配应变比在Si(100)基底上制备的薄膜大有关。Ni原子在Si(100)基底上外延生长时,其晶格可相对于Si基底晶格旋转45°实现匹配,从而大大降低晶格失配,使其失配应变大约为9%[55],而Si(111)基底无法实现旋转匹配,其失配应变高达35%[56]。此外,随着基底温度的升高薄膜开裂的临界厚度有所增大。基底温度的提高增大了Ni5Pt原子的扩散能力,使薄膜表面更加均匀和残余应力减小,从而增大了薄膜断裂的临界厚度。结合图6拟合得到的溅射速率与临界薄膜厚度,可推算出在不同条件下制备的薄膜发生开裂的临界沉积时间,如表2所示。结果表明,沉积时间为1 min的薄膜不发生开裂,沉积时间大于等于5 min的薄膜都因超过临界厚度而开裂。上述结果表明,制备高性能肖特基势垒二极管使用的Ni5Pt/Si势垒层Ni5Pt薄膜,宜在Si(100)单晶衬底上生长并适当提高基底温度以降低Ni5Pt薄膜的开裂倾向。

表2   Ni5Pt薄膜发生断裂的临界厚度和临界沉积时间

Table 2  Critical thickness and critical sputtering time for fracture of Ni5Pt films

Substrate conditionsThickness / nmSputtering time / min
Si(100)-RT38.744.37
Si(100)-50 oC39.204.61
Si(100)-100 oC41.544.79
Si(111)-RT36.264.09
Si(111)-50 oC37.424.40
Si(111)-100 oC39.814.59

新窗口打开| 下载CSV


3 结论

(1) 在(100)和(111)取向Si基底上磁控溅射沉积的Ni5Pt合金薄膜,均为层-岛状(SK)生长模式。薄膜表面的粗糙度随着厚度的增大而提高,随着基底温度的提高而降低;与Si(100)基底相比,在Si(111)基底上生长的Ni5Pt薄膜粗糙度更高。

(2) 基于残余应力超过断裂强度的薄膜的断裂判据,可得到沉积态Ni5Pt薄膜开裂的基底“工程近似”临界厚度和对应的临界沉积时间。

参考文献

Qin Y, Albano B, Spencer J, et al.

Thermal management and packaging of wide and ultra-wide bandgap power devices: a review and perspective

[J]. J. Phys., 2023, 56D(9) : 093001

[本文引用: 1]

Song Y, Li X M, Mackin C, et al.

Role of interfacial oxide in high-efficiency graphene-silicon Schottky barrier solar cells

[J]. Nano Lett., 2015, 15(3): 2104

DOI      PMID      [本文引用: 1]

The advent of chemical vapor deposition (CVD) grown graphene has allowed researchers to investigate large area graphene/n-silicon Schottky barrier solar cells. Using chemically doped graphene, efficiencies of nearly 10% can be achieved for devices without antireflective coatings. However, many devices reported in past literature often exhibit a distinctive s-shaped kink in the measured I/V curves under illumination resulting in poor fill factor. This behavior is especially prevalent for devices with pristine (not chemically doped) graphene but can be seen in some cases for doped graphene as well. In this work, we show that the native oxide on the silicon presents a transport barrier for photogenerated holes and causes recombination current, which is responsible for causing the kink. We experimentally verify our hypothesis and propose a simple semiconductor physics model that qualitatively captures the effect. Furthermore, we offer an additional optimization to graphene/n-silicon devices: by choosing the optimal oxide thickness, we can increase the efficiency of our devices to 12.4% after chemical doping and to a new record of 15.6% after applying an antireflective coating.

Hövel M, Gompf B, Dressel M.

Electrodynamics of ultrathin gold films at the insulator-to-metal transition

[J]. Thin Solid Films, 2011, 519(9): 2955

DOI      URL     [本文引用: 1]

Roccaforte F, Iucolano F, Giannazzo F, et al.

Electrical properties of inhomogeneous Pt/GaN Schottky barrier

[J]. Mater. Sci. Forum, 2007, 600-603: 1341

DOI      URL     [本文引用: 1]

Kang M S, Ahn J J, Moon K S, et al.

Metal work-function-dependent barrier height of Ni contacts with metal-embedded nanoparticles to 4H-SiC

[J]. Nanoscale Res. Lett., 2012, 7(1): 75

DOI      [本文引用: 1]

Metal, typically gold [Au], nanoparticles [NPs] embedded in a capping metal contact layer onto silicon carbide [SiC] are considered to have practical applications in changing the barrier height of the original contacts. Here, we demonstrate the use of silver [Ag] NPs to effectively lower the barrier height of the electrical contacts to 4H-SiC. It has been shown that the barrier height of the fabricated SiC diode structures (Ni with embedded Ag-NPs) has significantly reduced by 0.11 eV and 0.18 eV with respect to the samples with Au-NPs and the reference samples, respectively. The experimental results have also been compared with both an analytic model based on Tung's theory and physics-based two-dimensional numerical simulations.

Gorji M S, Razak K A, Cheong K Y.

Gold nanoparticles deposited on linker-free silicon substrate and embedded in aluminum Schottky contact

[J]. J. Colloid Interface Sci., 2013, 408: 220

DOI      URL     [本文引用: 1]

Gorji M S, Cheong K Y.

Embedded nanoparticles in Schottky and Ohmic contacts: A review

[J]. Crit. Rev. Solid State Mater. Sci., 2015, 40(4): 197

DOI      URL     [本文引用: 1]

Pearton S J, Yang J C, Cary P H, et al.

A review of Ga2O3 materials, processing, and devices

[J]. Appl. Phys. Rev., 2018, 5(1): 011301

[本文引用: 1]

Mallett J J, Svedberg E B, Bonevich J E, et al.

Compositional control in electrodeposited Ni x Pt1- x films

[J]. J. Electrochem. Soc., 2008, 155(1): D1

DOI      URL     [本文引用: 3]

Panciera F, Hoummada K, Perrin C, et al.

Ni(Pt)-silicide contacts on CMOS devices: Impact of substrate nature and Pt concentration on the phase formation

[J]. Microelectron. Eng., 2014, 120: 34

DOI      URL     [本文引用: 1]

Lai J, Chen Y W, Ho N T, et al.

NiPt salicide process improvement for 28 nm CMOS with Pt(10%) additive

[J]. Microelectron. Eng., 2012, 92: 137

DOI      URL     [本文引用: 2]

Xu X L, Huang Y Y, Guo R S, et al.

Tailoring the electronic properties of nickel silicide by interfacial modification

[J]. AIP Adv., 2022, 12(7): 075112

[本文引用: 1]

Imbert B, Pantel R, Zoll S, et al.

Nickel silicide encroachment formation and characterization

[J]. Microelectron. Eng., 2010, 87(3): 245

DOI      URL     [本文引用: 1]

Delwail C, Dabertrand K, Joblot S, et al.

Nanoscale effect on the formation of the amorphous Ni silicide by rapid thermal annealing from crystalline and pre-amorphized silicon

[J]. Acta Mater., 2024, 262: 119430

DOI      URL     [本文引用: 2]

Xu Y T, Guo J M, Wang C J, et al.

Research progress on precious metal sputtering target

[J]. Mater. Mech. Eng., 2021, 45(8): 8

DOI      [本文引用: 1]

Sputtering targets are the key raw materials for the preparation of thin films by magnetron sputtering, and their quality determines the performance of the sputtered thin films. Precious metal sputtering targets are widely used in the preparation of high-performance thin films because of their excellent physical and chemical properties. The research progress on the preparation methods, technical requirements and application of precious metal sputtering targets is reviewed. The development direction of high purity, large size, high utilization rate, and integrated development of target production and sputtering film is put forward.

许彦亭, 郭俊梅, 王传军 .

贵金属溅射靶材的研究进展

[J]. 机械工程材料, 2021, 45(8): 8

DOI      [本文引用: 1]

溅射靶材是磁控溅射制备薄膜的关键原材料,其质量决定着溅射薄膜的性能。贵金属溅射靶材因具有优异的物理和化学性能而广泛应用于高性能薄膜的制备。综述了贵金属溅射靶材制备方法、技术要求和应用情况的研究进展,指出高纯化、大尺寸、高利用率以及靶材生产与溅射镀膜一体化是贵金属靶材未来发展方向。

Wang Y Q, Xu Y T, Wen M, et al.

Microstructure evolution and magnetic properties of Ni-5Pt alloy during cold rolling

[J]. Chin. J. Nonferrous Met., 2020, 30(3): 559

DOI      URL     [本文引用: 2]

王一晴, 许彦亭, 闻 明 .

冷轧过程中NiPt5合金的结构演变及磁性能

[J]. 中国有色金属学报, 2020, 30(3): 559

[本文引用: 2]

Tan Z L, Yin C C, Wen M, et al.

Hot deformation behavior and hot processing maps of NiPt15 alloys

[J]. Rare Metal Mater. Eng., 2021, 50(11): 4149

[本文引用: 1]

谭志龙, 尹畅畅, 闻 明 .

NiPt15合金热变形行为及热加工图研究

[J]. 稀有金属材料与工程, 2021, 50(11): 4149

[本文引用: 1]

Shin J W, Hangarter C, Bertocci U, et al.

In situ stress measurement during electrodeposition of Ni x Pt1- x alloys

[J]. J. Electrochem. Soc., 2012, 159(8): D479

DOI      URL     [本文引用: 2]

Eiler K, Fornell J, Navarro-Senent C, et al.

Tailoring magnetic and mechanical properties of mesoporous single-phase Ni-Pt films by electrodeposition

[J]. Nanoscale, 2020, 12(14): 7749

DOI      PMID      [本文引用: 3]

Homogeneous mesoporous Ni-rich Ni-Pt thin films with adjustable composition have been synthesised by one-step micelle-assisted electrodeposition. The films exhibit a face-centred cubic solid solution (single phase) and their magnetic and mechanical properties can be tuned by varying the alloy composition. In particular, the Curie temperature (T) is shown to decrease with the Pt content and thin films with a T close to room temperature (i.e. NiPt) and below can be produced. Hysteresis loops show a decrease of saturation magnetisation (M) and coercivity (H) with decreasing Ni content. A comparison of porous and dense films reveals significantly lower saturation magnetic field strength for porous films. Concerning mechanical properties, mainly two trends can be observed: a decrease of the Young's modulus of the nanoporous films with respect to dense films by 10% in average and a progressive increase of Young's modulus with the Ni content from 4.2 GPa to 5.7 GPa in both types of films. The tunability of properties and facility of synthesis make this alloy a promising material for microelectromechanical systems (MEMS).

Yang W J, Liu J J, Guan Z Y, et al.

Morphology, electrical and optical properties of magnetron sputtered porous ZnO thin films on Si(100) and Si(111) substrates

[J]. Ceram. Int., 2020, 46(5): 6605

DOI      URL     [本文引用: 1]

Tsamouras D, Palasantzas G.

Temperature dependence of the growth front roughening of oligomer films

[J]. Appl. Phys. Lett., 2002, 80(24): 4528

DOI      URL     [本文引用: 1]

Growth front roughening characteristics of vacuum deposited pentamer 2,5-di-n-octyloxy-1,4-bis[4-(styryl)styryl]-benzene oligomer thin films, onto silicon substrates, strongly depend on the substrate temperature in the range ∼20 °C–100 °C. The measured roughness exponents H increase from H≈0.4 at low substrate temperatures where growth is dominated by vacancy formation, to H≈0.7–0.8 at elevated temperatures where diffusive growth takes place. Moreover, the root-mean-square roughness amplitude and the correlation length evolve with temperature closely as an Arrhenius process with activation barrier comparable to molecule transnational and rotational barriers on oligomer surfaces.

Galinski H, Ryll T, Reibisch P, et al.

Temperature-dependent 2-D to 3-D growth transition of ultra-thin Pt films deposited by PLD

[J]. Acta Mater., 2013, 61(9): 3297

DOI      URL     [本文引用: 2]

Wang Y Q, Guo J M, Guan W M, et al.

Application and development trend of NiPt alloy sputtering target in semiconductor manufacturing

[J]. Precious Met., 2016, 37(3): 87

[本文引用: 1]

王一晴, 郭俊梅, 管伟明 .

镍铂合金溅射靶材在半导体制造中的应用及发展趋势

[J]. 贵金属, 2016, 37(3): 87

[本文引用: 1]

Xi Y T, Gao K W, Pang X L, et al.

Film thickness effect on texture and residual stress sign transition in sputtered TiN thin films

[J]. Ceram. Int., 2017, 43(15): 11992

DOI      URL     [本文引用: 2]

Cadeville M C, Dahmani C E, Kern F.

Magnetism and spatial order in Ni-Pt and Co-Pt alloys

[J]. J. Magn. Magn. Mater., 1986, 54-57: 1055

DOI      URL     [本文引用: 2]

Cheng F Y, Ma H, Li Y M, et al.

Ni1- x Pt x (x = 0-0.12) hollow spheres as catalysts for hydrogen generation from ammonia borane

[J]. Inorg. Chem., 2007, 46(3): 788

DOI      URL     [本文引用: 1]

Welzel U, Ligot J, Lamparter P, et al.

Stress analysis of polycrystalline thin films and surface regions by X-ray diffraction

[J]. J. Appl. Crystallogr., 2005, 38(1): 1

DOI      URL     [本文引用: 2]

The components of the macroscopic mechanical stress tensor of a stressed thin film, coating, multilayer or the region near the surface of a bulk material can in principle be determined by X-ray diffraction. The various analysis methods and measurement strategies, in dependence on specimen and measurement conditions, are summarized and evaluated in this paper. First, different X-ray diffraction geometries (conventional or grazing incidence) are described. Then, the case of macroscopically elastically isotropic, untextured specimens is considered: from the simplest case of a uniaxial state of stress to the most complicated case of a triaxial state of stress. The treatment is organized according to the number of unknowns to be determined (i.e.the state of stress, principal axes known or unknown), the use of one or several values of the rotation angle φ and the tilt angle ψ of the sample, and one or multiplehklreflections. Next, the focus is on macroscopically elastically anisotropic (e.g.textured) specimens. In this case, the use of diffraction (X-ray) elastic constants is not possible. Instead, diffraction (X-ray) stress factors have to be used. On the basis of examples, it is demonstrated that successful diffraction stress analysis is only possible if an appropriate grain-interaction model is applied.

Kumar V, Majumder A.

Effect of low surface energy material deposition on the wettability and corrosion resistance characteristics of a copper substrate

[J]. J. Taibah Univ. Sci., 2025, 19(1): 2444095

DOI      URL     [本文引用: 1]

Wen Z Q, Hou H, Zhao Y H, et al.

First-principle study of interfacial properties of Ni-Ni3Si composite

[J]. Comput. Mater. Sci., 2013, 79: 424

DOI      URL     [本文引用: 1]

Kim J S, Seol D, Lee B J.

Critical assessment of Pt surface energy-An atomistic study

[J]. Surf. Sci., 2018, 670: 8

DOI      URL     [本文引用: 1]

Jaccodine R J.

Surface energy of germanium and silicon

[J]. J. Electrochem. Soc., 1963, 110(6): 524

DOI      URL     [本文引用: 3]

Semiatin S L, Piehler H R.

Deformation of sandwich sheet materials in uniaxial tension

[J]. Metall. Trans., 1979, 10A(1) : 85

[本文引用: 1]

Zhao Y H, Wen Z Q, Hou H, et al.

Density functional theory study of the interfacial properties of Ni/Ni3Si eutectic alloy

[J]. Appl. Surf. Sci., 2014, 303: 205

DOI      URL     [本文引用: 1]

Venables J A, Spiller G D T, Hanbucken M.

Nucleation and growth of thin films

[J]. Rep. Prog. Phys., 1984, 47(4): 399

DOI      URL     [本文引用: 1]

Family F, Vicsek T.

Scaling of the active zone in the Eden process on percolation networks and the ballistic deposition model

[J]. J. Phys., 1985, 18A(2) : L75

DOI      URL     [本文引用: 1]

Kodiyalam S, Khor K E, Das Sarma S.

Calculated Schwoebel barriers on Si(111) steps using an empirical potential

[J]. Phys. Rev., 1996, 53B(15) : 9913

[本文引用: 1]

Brocks G, Kelly P J, Car R.

Binding and diffusion of a Si adatom on the Si(100) surface

[J]. Phys. Rev. Lett., 1991, 66(13): 1729

PMID      [本文引用: 1]

Imran M, Hussain F, Rashid M, et al.

Molecular dynamics simulation of nanoscale surface diffusion of heterogeneous adatoms clusters

[J]. Chin. Phys., 2016, 25B(7) : 076601

[本文引用: 1]

Zarshenas M, Sangiovanni D G, Sarakinos K.

Diffusion and magnetization of metal adatoms on single-layer molybdenum disulfide at elevated temperatures

[J]. J. Vac. Sci. Technol., 2024, 42A(2) : 023409

Baski A A, Fuchs H.

Epitaxial growth of silver on mica as studied by AFM and STM

[J]. Surf. Sci., 1994, 313(3): 275

DOI      URL     [本文引用: 1]

Kasai M, Dohi H.

Growth temperature and relaxation of lattice strain in epitaxial Pt films exhibiting diffraction fringes

[J]. Surf. Sci., 2019, 689: 121461

DOI      URL     [本文引用: 1]

Bathe R, Vispute R D, Habersat D, et al.

Stress origin and relaxation in epitaxial AIN thin films on SiC

[J]. MRS Online Proc. Libr., 2001, 696: 320

Zhou H, Liao X X, Ke S M.

Effects of strain on ultrahigh-performance optoelectronics and growth behavior of high-quality indium tin oxide films on yttria-stabilized zirconia (001) substrates

[J]. J. Mater. Sci.: Mater. Electron., 2021, 32(16): 21462

DOI      [本文引用: 1]

Kim J A, Park J H, Park S G, et al.

Effect of substrate temperature on variations in the structural and optical properties of Cu2O thin films deposited via RF magnetron sputtering

[J]. Crystals, 2023, 13(4): 643

DOI      URL     [本文引用: 1]

In the present study, Cu2O films were deposited on a glass substrate via RF (radio frequency) magnetron sputtering under substrate temperature conditions that ranged from room temperature (RT, 25 °C) to 400 °C. The structural, compositional, and optical properties of the Cu2O films were analyzed in relation to the experimental variables by applying various measurement methods. The substrate temperature was a crucial factor in shaping the structural, compositional, and optical properties of the Cu2O films that were synthesized via RF-magnetron sputtering. Our findings revealed that the Cu2O films exhibited a cubic structure, which was confirmed by XRD analysis. Specifically, the (111) and (200) planes showed different trends with respect to the substrate temperature. The intensity of the (111) peak increased at 250 °C, and above 300 °C, the preferred orientation of the (111) plane was maintained. The grain size, which was determined via FE-SEM, displayed a positive correlation with the substrate temperature. Additionally, XPS analysis revealed that the binding energy (BE) of the Cu2O film sputtered at 400 °C was similar to that which was previously reported. Notably, the as-grown Cu2O film demonstrated the highest transmittance (15.9%) in the visible region, which decreased with increasing substrate temperature. Furthermore, the energy band gap (Eg) of the Cu2O films remained constant (2.51 eV) at low substrate temperatures (25 °C to 200 °C) but exhibited a slight increase at higher temperatures, reaching 2.57 eV at 400 °C.

Li Z Y, Li M M.

Effect of silicon substrate temperature on properties of Ti films prepared by electron beam evaporation

[J]. Plat. Finish., 2024, 46(3): 1

李兆营, 李萌萌.

硅衬底温度对电子束蒸发钛薄膜性能的影响

[J]. 电镀与精饰, 2024, 46(3): 1

Yang P H, Zeng Z G, Hu Z Y.

Influence of substrate temperature on growth of RF sputtered bismuth telluride films

[J]. Chin. J. Vac. Sci. Technol., 2012, 32(6): 504

[本文引用: 1]

杨鹏辉, 曾志刚, 胡志宇.

基片温度对射频磁控溅射碲化铋薄膜微结构和表面形貌的影响

[J]. 真空科学与技术学报, 2012, 32(6): 504

[本文引用: 1]

Koch R.

The intrinsic stress of polycrystalline and epitaxial thin metal films

[J]. J. Phys.: Condens. Matter, 1994, 6(45): 9519

DOI      URL     [本文引用: 1]

Frank F C, Van der Merwe J H.

One-dimensional dislocations. II. Misfitting monolayers and oriented overgrowth

[J]. Proc. Roy. Soc. Lond., 1949, 198A(1053) : 216

[本文引用: 1]

Teixeira V.

Mechanical integrity in PVD coatings due to the presence of residual stresses

[J]. Thin Solid Films, 2001, 392(2): 276

DOI      URL     [本文引用: 2]

Kittel C. Introduction to Solid State Physics [M]. 8th ed. New York: John Wiley & Sons, 2004

[本文引用: 1]

Yang Z, Ko C, Ramanathan S.

Metal-insulator transition characteristics of VO2 thin films grown on Ge(100) single crystals

[J]. J. Appl. Phys., 2010, 108(7): 073708

[本文引用: 1]

Wang Y M, Li X A, Yan X Q, et al.

Effects of film thickness on the residual stress of vanadium dioxide thin films grown by magnetron sputtering

[J]. Materials, 2023, 16(14): 5093

DOI      URL     [本文引用: 2]

Vanadium dioxide (VO2) thin films of different thicknesses were prepared by regulating the deposition time (2, 2.5, 3, and 3.5 h). The impact of deposition time on the microstructure, surface morphology, and cross-section morphology was investigated. The results showed that the grain size increased with the film thickness. Meanwhile, the influence of film thickness on the residual stress was evaluated by X-ray diffraction. The phenomenon of “compressive-to-tensile stress transition” was illustrated as the thickness increased. The change of dominant mechanism for residual stress was used for explaining this situation. First, the composition of residual stress indicates that growth stress play a key role. Then, the effect of “atomic shot peening” can be used to explain the compressive stress. Lastly, the increased grain size, lower grain boundary density, and “tight effect” in the progress of film growth cause tensile stress.

Windischmann H.

Intrinsic stress in sputter-deposited thin films

[J]. Crit. Rev. Solid State Mater. Sci., 1992, 17(6): 547

DOI      URL     [本文引用: 1]

Ambati M, Gerasimov T, De Lorenzis L.

A review on phase-field models of brittle fracture and a new fast hybrid formulation

[J]. Comput. Mech., 2015, 55(2): 383

DOI      URL     [本文引用: 1]

Kreuzpaintner W, Störmer M, Lott D, et al.

Epitaxial growth of nickel on Si(100) by DC magnetron sputtering

[J]. J. Appl. Phys., 2008, 104(11): 114302

DOI      URL     [本文引用: 1]

The influence of the substrate temperature on the growth of highly textured Ni(111) and epitaxial Ni(200) with the relationships Ni[100]∥Si[110] and Ni(001)∥Si(001) on hydrogen terminated Si(100) wafer substrates by means of direct current magnetron sputtering is reported. In order to minimize crystal defect formation and to achieve a high quality epitaxial growth of Ni on Si, a two step deposition process was developed whereby different deposition conditions were used for an initial nickel seed layer and the remaining nickel film. The in-plane and out-of-plane structural properties of the films were investigated using x-ray scattering techniques, whereas magneto-optical Kerr effect and neutron reflectometry were used to confirm the magnetic nature of the epitaxially deposited nickel films.

Matthews J W, Blakeslee A E.

Defects in epitaxial multilayers: I. Misfit dislocations

[J]. J. Cryst. Growth, 1974, 27: 118

[本文引用: 1]

/