什么是脉冲直流溅射?/What is Pulsed DC Sputtering?
Written by Matt Hughes - President - Semicore Equipment, Inc.
Published: 14 December 2016
Pulsed DC Sputtering is a physical vapor deposition technique with a wide range of
applications in the semiconductor, optical and industrial coating industries. Pulsed DC Sputtering is particularly effective for the sputtering of metals and dielectric coating –
coatings which are insulating non-conducting materials that can acquire a charge.
脉冲直流溅射是一种物理气相沉积技术，在半导体、光学和工业镀膜等领域有着广泛的应用。脉冲直流溅射尤其适用于金属和介质涂层的溅射，这些涂层是绝缘的非导电材料，可以获得电荷。
It is most often used with Reactive Sputtering where there is a chemical reaction occurring in the plasma between the vaporized target material and ionized gases like Oxygen to form deposition molecules such as silicon oxides. Pulsed DC Sputtering has revolutionized the Reactive Sputtering of “difficult” dielectric materials like Alumina, Titania and Silica with high deposition rates that are impossible with straight DC Sputtering alone.
它最常用于反应溅射，在等离子体中，气化的靶材材料和电离气体(如氧)之间发生化学反应，形成沉积分子(如硅氧化物)。脉冲直流溅射使氧化铝、二氧化钛和二氧化硅等“困难”
介质材料的反应溅射发生了革命性的变化，具有较高的沉积速率，这是单凭直流电溅射无法做到的。
脉冲直流溅射过程示意图
The primary advantages of Pulsed DC Sputtering over conventional DC Sputtering is that it dramatically reduces or eliminates the formation of arcs which occur when the target
material used as a coating takes on a charge. This charge when allowed to build
discharges in high voltage arcs into the plasma forming droplets causing defects in thin film quality control - as well as potentially damaging the DC power system.
与传统的直流溅射相比，脉冲直流溅射的主要优点是，它大大减少或消除了作为涂层的靶材材料带电时产生的电弧。当允许这种电荷在高压电弧中建立放电到等离子体中形成液滴时，会导致薄膜质量控制的缺陷——以及潜在地破坏直流电源系统。
The basic configuration of either a Pulsed or conventional DC Sputtering system is the target material t
o be used as a coating is placed in a vacuum chamber parallel to the substrate to be coated. The vacuum chamber is evacuated to a base pressure removing
H2O, Air, H2, and then backfilled with a high purity inert process gas – usually Argon due to its size and ability to convey kinetic energy upon impact with the target material. For Reactive Sputtering, reactive gases such as Oxygen that will combine with the target material in the plasma to produce oxide molecules are also entered into the vacuum chamber.
无论是脉冲式还是传统的直流溅射系统，其基本结构都是将用作涂层的目标材料放置在与被涂层基体平行的真空室中。真空室被抽真空到一个基本压力，除去H2O，空气，H2，然后用高纯度惰性过程气体回填-通常是氩气，因为它的尺寸和与目标材料碰撞时传递动能的能力。对于反应性溅射，反应性气体如将与等离子体中的目标材料结合产生氧化分子的氧也进入真空室。
A Pulsed DC electrical current typically in the few hundreds of volts range is then applied to the target coating material - which is the cathode or point at which electrons enter the system known as the negative bias – and a positive charge is applied to the substrate to be coated which becomes the anode.
脉冲直流电流通常在几个数百伏范围然后应用到目标涂层材料——阴极或点电子进入系统称为负偏压和
一个正电荷是应用于衬底成为阳极涂层。
The great challenge of the Reactive Sputtering of dielectric materials such as Alumina, Titania and Silica is preventing arcs when the target material takes on a charge that can seriously degrade or destroy the thin film quality.
氧化铝、二氧化钛和二氧化硅等介电材料的反应溅射的最大挑战是防止目标材料带电时产生电弧，这些电弧会严重降低或破坏薄膜质量。
With conventional DC Sputtering of dielectrics, an insulating film forms on the surface of the target coating material around the area commonly referred to as the “racetrack” - a circular depression that forms on the surface of the target that has this shape as a result of the circular magnetic field holding the bombarding gas ions close to the target for maximum sputtering. This insulating layer takes on a positive charge as a result of the gas ion collisions which “Poisons” the t arget - dramatically reducing the sputter rate and ultimately leading to arcing.
传统的介质直流溅射技术，靶材的表面绝缘膜形成涂层材料周围的区域通常被称为“赛马场”——一个圆形萧条形成表面的目标，这种形状的圆形磁场控股轰击气态离子接近靶材最大的溅射。这个绝缘层由于气体离子碰撞而带上了正电荷，“中毒”了靶材——极大地降低了溅射速率，最终导致电弧
Compared to conventional DC Sputtering, arcing can be greatly decreased or even eliminated by pulsing the DC voltage in the 10–350 kHz range with duty cycles in the 50–90% range.
与传统的直流溅射相比，脉冲直流电压在10 ~ 350 kHz范围内，占空比在50 ~ 90%范围内，可以大大减少甚至消除电弧。
During the “on time” part of the duty cycle, a strong ne gative pulse of a few hundred volts is applied to the target to initiate sputtering. The gas in the vacuum chamber is ionized as a result of collisions with the target surface sputtering off atoms, and the plasma glow is ignited. Sputtering only takes plac e while this “on time” negative pulse is being applied to
the target.
在占空比的“on time”部分，一个几百伏特的强负脉冲被施加到目标上以启动溅射。真空
室中的气体由于与靶材表面的碰撞而电离，溅射出原子，等离子体发光被点燃。溅射只
发生在“on time”负脉冲作用于目标时。
什么是reactive
At the end of this high voltage “on time” part of the duty cycle the voltage is ei ther turned off - or more
frequently reversed with a low voltage positive charge to “cleanse” the target of any charge buildup. This is a low voltage short duration cycle reversal, usually around a 20 volt positive reversal that is about one tenth of the “on time” duration and about ten to twenty percent of the on time voltage. During this positive cycle, the target’s surface is discharged or “scrubbed” making it ready for the next negative voltage pulse sputtering the target coating material into the plasma.
在占空比的高压“on time”部分结束时，电压要么被关闭，要么更频繁地用低电压正电荷
来“清理”目标的任何电荷积聚。这是一个低电压短持续周期逆转，通常在20伏左右的正逆转，大约是“on time ”持续时间的十分之一，大约是准时电压的10%到20%。在这个
正循环中，目标的表面被放电或“擦洗”，为下一个负电压脉冲溅射目标涂层材料到等离
子体做好准备。
Because this buildup of dielectric charge develops over time, problems with maintaining process stability and control that are not evident at the beginning of a run can change dramatically thirty minutes later as the thin film process environment changes. Continuously pulsing the DC circuit also in and of itself is usually not enough to totally eliminate arcs from forming which can be a very expensive, quality control breakdown event that can require a restarting of the run.
由于这种介电电荷的积聚是随着时间的推移而形成的，因此，随着薄膜工艺环境的变化，在运行开始时不明显的保持工艺稳定性和控制方面的问题可能在30分钟后发生显著变化。连续脉冲直流电路本身通常不足以完全消除形成的电弧，这可能是非常昂贵的，质
量控制击穿事件，可能需要重新启动运行。
Today most state-of-the-art Pulsed DC power sources also contain arc suppression
circuitry to detect and extinguish an arc at the moment it forms by detecting changes in the target voltage. When the rapid fall in the target voltage associated with an arc is detected - typically between 50 and 150V - it activates a reverse voltage pulse in an attempt to quench the arc.
今天，最先进的脉冲直流电源还包含电弧抑制电路，以检测和熄灭电弧在瞬间形成，通过检测目标电压的变化。当检测到与电弧相关的目标电压迅速下降(通常在50到150V
之间)时，它会启动一个反向电压脉冲，试图熄灭电弧。
An arc which is eliminated with a single reversal of the voltage pulse is known as a “micro-arc”. Those that require more than one reversal of the voltage pulse to suppress are called “hard-arcs” after which time the normal Pulsed DC cycle resumes.
用电压脉冲的一次反转消除的电弧称为“微弧”。那些需要超过一次电压脉冲反转来抑制的被称为“硬电弧”，在此之后正常的脉冲直流循环恢复。
Output cabling of the sputtering coating equipment can also acquire a charge that contributes to arcing. In addition to the basic Pulsed DC power supply arc handling circuitry is designed to detect and dissipate charge buildups, be proactive inhibiting arc formation, extinguishing arcs that do form, and compensate for charge buildups in a system’s cabling to prevent expensive breakdowns in the thin film quality control environment.
溅射镀膜设备的输出布线也可以获得导致电弧的电荷。除了基本的脉冲直流电源电弧处理电路设计，以检测和消散电荷积聚，主动抑制电弧形成，熄灭形成的电弧，并补偿电荷积聚在一个系统的电缆，以防止昂贵的故障在薄膜质量控制环境。
There are also two types of Pulsed DC Magnetron Sputtering. Uni-Polar Pulsed and
Bi-Polar Pulsed Sputtering where two pulses from adjacent magnetrons set 180 degrees out of phase with each can also greatly reduces the effects of dielectric buildup. The combination of a Pulsed DC power source with a high voltage “on time” cycle followed by a low voltage reversal of current, combined with arc handling circuitry has enable the deposition of even the most difficult to sputter diele
ctric coating materials such as AZO, ZnO and Al2 O3.
还有两种类型的脉冲直流磁控溅射。在单极脉冲和双极脉冲溅射中，相邻磁控管的两个脉冲相互相差180度，也可以大大降低介质堆积的影响。脉冲直流电源具有高电压“on time”周期，随后是低电压反转电流，结合电弧处理电路，可以沉积即使是最难溅射的介质涂层材料，如AZO, ZnO和Al2O3。
While Pulsed DC Sputtering was initially developed for its arc handling capabilities for sputtering dielectric materials, it has also been found that by changing the pulse parameters other beneficial results can be controlled like the presence of more gas ions in the plasma flux which improves film adhesion, and enables the control of other important thin film deposition properties.
虽然脉冲直流溅射最初是为了其溅射介质材料的电弧处理能力而开发的，但人们也发现，通过改变脉冲参数，可以控制其他有益的结果，比如等离子体通量中存在更多的气体离子，从而提高薄膜的附着力。并使控制薄膜其他重要的沉积性能成为可能。
The primary advantages of Pulsed DC Sputtering is that at optimum pulsing frequencies and duty cycles, higher thin film deposition rates can be achieved compared to RF Sputtering without the problems with arcing that results in expensive quality control issues.
脉冲直流溅射的主要优点是在最佳的脉冲频率和占空比下，可以实现比射频溅射更高的薄膜沉积速率，而不会出现导致昂贵的质量控制问题的电弧问题。

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。