Platinum thin films are used in var

Platinum thin films are used in various microelectronic and
micro-sensor applications. The microstructural, chemical, and electrical
stability of these films under high-temperature conditions
are of major concern. In addition, stability is also a concern for
potential extended use in specialized microelectronic applications,
especially when the films are used as thin, two-dimensional interconnects
or electrodes connecting active components at elevated
temperatures. Typical applications of these high-temperature
films are aligned with electrodes/interconnects for chemical sensors,
micro-heaters and -hotplates within microelectromechanical
systems (MEMS) [1–6]. Recently, more advanced MEM systems
have been applied within extreme environments, which
includes high temperatures and harsh chemical reactants, such as
micro-chemical emission sensors, -structural monitoring sensors,
-thermocouples, and -fuel cell systems that are utilized at temperatures
>600–800 ◦C [7–13].
High melting point noble metals are most suited for extreme
environment applications. Platinum, with its relatively high melting
point (1773 ◦C) and excellent chemical inertness, has long
been utilized for MEMs devices capable of operating at elevated
temperatures. Pt and other noble metals have a great chemical
inertness; however, these metals show poor adhesion and high surface
tension toward oxide surfaces. Budhani et al. demonstrated an
interface modification between thermally grown aluminum oxide
(Al2O3) and thin Pt films via reactive sputtering with low levels
of oxygen in order to obtain a 20–30 nm PtxO1−x layer prior to
pure platinum metal deposition. Adhesion tests showed a higher
level of adhesion compared to the conventional Pt + Al2O3 couple.
The authors indicated that strong PtxO1−x to Al2O3 bonding and
interdiffusion at the interface were responsible for the enhanced
adhesion [14].
Although the controlled oxidation of a sub-layer of Pt showed
promise for enhanced wetting and adhesion to oxide substrates,
various researchers have focused on incorporating alternative
metal/metal oxide layer compositions. These thin coatings
were deposited to improve noble metal adhesion, as well as, to
improve the thermal stability over prolonged exposure to high
temperatures. High temperature operating conditions lead to
the development of many structural defects, such as hillocks,
film delamination, surface cracking, voids and grain coarsening,
which all eventually result in non-uniform film morphology and
variable electrical response [1–5,15–18]. At high temperatures
(≥700 ◦C), grain coarsening and hillock formation are the major
mechanisms that break the percolated granular network across the
polycrystalline film [3,19–22]. Since low-temperature sputtering
and evaporation techniques typically produce films with high
surface area granular structures, these films possess an extremely
high driving force for sintering and grain growth processes. Hightemperature
operation permits the required diffusional kinetics
for accelerated grain growth, resulting in the coalescence of the
grains and the formation of a poorly percolated structure [21,23].
In other words, the total interfacial and surface energy of the thin
film can be minimized by reducing ceramic–metal contact area by
creating islands of Pt material. The destruction of the integrity of
the continuous film eventually results in complete loss of electrical
continuity, which diminishes the functionality, reliability and
sensitivity of the micromachined devices.
Metals such as Ti and Ta have been proposed and demonstrated
with variable success to decrease both Pt grain coarsening and
hillock formation. Lee et al. optimized the procedure first defined by
Budhani et al. for deposition of Pt over insulating oxide layers with
improved adhesion. According to this procedure, platinum deposition
under an oxidation atmosphere, followed by inert atmosphere
deposition of Pt and subsequent annealing of silicon substrate
at 400–1300 ◦C, removed the remaining O2 in the Pt film [24].
Recently, Tiggelaar et al. compared the use of the PtxO1−x adhesion
layer to the use of Ti or Ta adhesion layers. These layers were
deposited by sputtering onto silicon and Si3N4 substrates. After
annealing between 400 and 950 ◦C under inert and oxygen containing
atmospheres, their electrical and structural performances were
characterized [25]. The authors concluded that the operational reliability
of Pt films with Ti and Ta adhesion layers are limited to
temperatures below 650 ◦C and 850 ◦C, respectively. In the same
study, the fast diffusion behavior of Ti and the resultant changes
to the wetting characteristics of Pt on the Ti layer over different
ceramic layers (Al2O3, Ta2O5, SiO2 and Si3N4) were also described.
Firebaugh et al. used a similar Ta adhesion strategy on silicon rich
silicon nitride. This study states that the adhesion layer migration
and co

Results (English) 3:

铂薄膜应用于各种微电子和微传感器应用。的微观结构，化学和电气这些薄膜在高温条件下的稳定性是主要关注的。此外，稳定也是一个值得关注的问题潜在的扩展在专门的微电子应用中的应用，特别是当薄膜被用来作为薄的，二维的互连或连接在高架上的活性成分的电极温度.这些高温的典型应用薄膜与电极/互连化学传感器，微加热器和加热板在微机电系统（MEMS）[ 1 - 6 ]。最近，更先进的微机电系统已被应用在极端的环境中，这包括高温和苛刻的化学反应物，如微型化学发射传感器，结构监测传感器，用于在温度下使用的热电偶和燃料电池系统> 600–800◦C [ 13 ] 7–。高熔点贵金属最适合于极端环境中的应用。铂金，以其相对高的熔点点（1773◦C）和良好的化学惰性，具有长用于在高架操作的微机电系统装置温度.铂等贵金属有很大的化学成分然而，这些金属的惰性；附着力差和高的表面向氧化物表面张力。budhani等人。展示了一个热生长氧化铝的界面改性低浓度反应溅射（氧化铝）和薄的铂薄膜为了在获得20–30 nm ptxo1−X层氧纯铂金属沉积。粘附试验显示出较高的粘附水平相比，传统的铂+氧化铝的夫妇。作者指出，强ptxo1−X氧化铝粘结在界面扩散是负责增强粘附[ 14 ]。虽然控制氧化的一个子层的铂显示增强润湿性和对氧化物衬底的粘附性的承诺，不同的研究人员专注于结合替代金属/金属氧化物层组合物。这些薄涂层沉积，以提高贵金属的粘附性，以及，以提高长时间暴露在高的热稳定性温度.高温操作条件导致许多结构性缺陷的发展，如小丘，薄膜脱层，表面裂纹，空隙和晶粒粗化，这最终会导致非均匀膜的形态和变电响应––18 ]、[ 1。在高温下（700≥◦C），晶粒粗化和沙丘的形成是主要的机制，打破了网络在颗粒[ 22 ]–3多晶薄膜。由于低温溅射和蒸发技术通常生产高的薄膜表面积颗粒结构，这些薄膜具有一个非常烧结和晶粒生长过程的高驱动力。高温经营许可证要求的扩散动力学对于加速晶粒的生长，导致在聚结的谷物和低渗透结构[ 21,23 ]的形成。换言之，总的界面和表面能的薄通过减少陶瓷-金属接触面积，薄膜可以被最小化创建铂材料岛屿。破坏的完整性连续膜最终导致电气损耗连续性，这削弱了功能性，可靠性和微机械器件的灵敏度。金属如Ti、Ta已经提出和论证具有可变的成功，以减少两个的铂晶粒粗化和小丘形成。Lee et al。优化了第一个定义的过程budhani等人。用于沉积在绝缘氧化物层上的铂提高附着力。根据此程序，铂沉积在氧化气氛下，其次是惰性气氛硅衬底的沉积及硅衬底的后续退火在400–1300◦C，除去剩余的O2在Pt薄膜[ 24 ]。最近，tiggelaar等人。比较了ptxo1−X粘附的使用层的Ti或Ta粘附层的使用。这些层溅射沉积到硅和氮化硅衬底。后退火之间的400和950◦C在惰性和含氧气氛，他们的电气和结构性能特点[ 25 ]。作者的结论是，操作可靠性用Ti和Ta黏附层Pt薄膜有限公司在650 C和850 C的温度◦◦，分别。在相同的研究中，钛的快速扩散行为以及由此产生的变化PT的润湿特性的钛层不同陶瓷层（Al2O3、Ta2O5、SiO2和Si3N4）也进行了描述。王志鹏等人。在富硅上使用了类似的钽粘附策略氮化硅。本研究指出，粘附层迁移和CO