http://www.ajaint.com/whatis.htm A technique used to deposit thin films of a material onto a surface (a.k.a. substrate). By first creating a gaseous plasma and then accelerating the ions from this plasma into some source material (a.k.a. target), the source material is eroded by the arriving ions via energy transfer and is ejected in the form of neutral particles - either individual atoms, clusters of atoms or molecules. As these neutral particles are ejected they will travel in a straight line unless they come into contact with something - other particles or a nearby surface. If a substrate such as a Si wafer is placed in the path of these ejected particles it will be coated by a thin film of the source material. 溅射是一种在表面（又称为基片，衬底）沉积薄膜材料的技术。首先，形成气态的等离子体，然后将等离子的离子在电场下加速，导向源材料（又名靶材，目标）。等离子的离子轰击碰撞靶材，发生能量转移，使得靶材以中性粒子的形式开始喷射出来，这些中性粒子要么是单个原子，要么就是原子簇团或分子簇团。 当这些中性粒子喷出时，它们将在一直一条直线上运动，除非他们接触到的东西，（中学物理学的弹性碰撞）这些东西可能是其他粒子或附近的表面。如果衬底例如硅晶片，被放置在这些喷射出的粒子的运动路径上，衬底就会覆盖一层源材料的薄膜。 Although SPUTTERING as described above seems relatively intuitive, familiarization with the following terms / concepts will give a more comprehensive understanding of this process: 虽然溅射如上所述似乎比较直观，但是，熟悉一下以下的术语或概念将会使得你对溅射过程有一个更全面的了解： Sometimes described as the fourth state of matter (the first three being solid, liquid, gas), a gaseous plasma is actually a dynamic condition where neutral gas atoms, ions, electrons and photons exist in a near balanced state simultaneously. An energy source (eg. RF, DC, MW) is required to feed and thus maintain the plasma state while the plasma is losing energy into its surroundings. One can create this dynamic condition by metering a gas (e.g. Ar) into a pre-pumped vacuum chamber and allowing the chamber pressure to reach a specific level (eg. 0.1 Torr) and introducing a live electrode into this low pressure gas environment using a vacuum feedthrough. 气态的等离子体有时被描述为物质的第四态（排在前三位的是固体，液体，气体），气态等离子实际上是一种动态条件，其中中性气体原子，离子，电子和光子在接近平衡状态同时存在。等离子体会损失能量在其周围环境中，因而必须通过提供能量来源（如射频，直流，兆瓦）从而保持等离子体状态。待续 POWERING THE ELECTRODE WITH DCV WILL RESULT IN: 1. Ever present free electrons will immediately be accelerated away from the negatively charged electrode (cathode). These accelerated electrons will approach the outer shell electrons of neutral gas atoms in their path and, being of a like charge, will drive these electrons off the gas atoms. This leaves the gas atom electrically unbalanced since it will have more positively charged protons than negatively charged electrons - thus it is no longer a neutral gas atom but a positively charged ion (e.g. Ar +). See animation WhatIs_Sputtering1Anim.swf http://www.ajaint.com/Images/PHOTOGRAPHS/Other/WhatIs_Sputtering1Anim.swf 2. At this point the positively charged ions are accelerated into the negatively charged electrode (a.k.a. cathode) striking the surface and blasting loose electrode material (diode sputtering) and more free electrons by energy transfer. The additional free electrons feed the formation of ions and the continuation of the plasma. See animation WhatIs_Sputtering2Anim.swf http://www.ajaint.com/Images/PHOTOGRAPHS/Other/WhatIs_Sputtering2Anim.swf 3. All the while free electrons find their way back into the outer electron shells of the ions thereby changing them back into neutral gas atoms. Due to the laws of conservation of energy, when these electrons return to a ground state, the resultant neutral gas atom gas gained energy and must release that same energy in the form of a photon. The release of these photons is the reason the plasma appears to be glowing. See animation WhatIs_Sputtering3Anim.swf http://www.ajaint.com/Images/PHOTOGRAPHS/Other/WhatIs_Sputtering3Anim.swf MAGNETRON SPUTTERING The diode sputtering example given above has proven to be a useful technique in the deposition of thin films when the cathode is covered with source material (sputtering target). Diode sputtering however has two major problems - the deposition rate is slow and the electron bombardment of the substrate is extensive and can cause overheating and structural damage. The development of magnetron sputtering deals with both of these issues simultaneously. By using magnets behind the cathode to trap the free electrons in a magnetic field directly above the target surface, these electrons are not free to bombard the substrate to the same extent as with diode sputtering. At the same time the extensive, circuitous path carved by these same electrons when trapped in the magnetic field, enhances their probability of ionizing a neutral gas molecule by several orders of magnitude. This increase in available ions significantly increases the rate at which target material is eroded and subsequently deposited onto the subtrate. See animation WhatIs_MagnetronSputtering.swf http://www.ajaint.com/Images/PHOTOGRAPHS/Other/WhatIs_MagnetronSputtering.swf WHAT IS A MAGNETRON SPUTTERING SOURCE? See photo WhatIs_A_MS_Source.jpg A tool to deposit thin film that mounts to a vacuum chamber by means of either flanges or feedthroughs and consists of a water cooled cathode/target holder with an imbedded magnet array and appropriate grounded shielding. Numerous designs and magnet configurations are employeed to address particular requirements. MODULAR MAGNET ARRAY - MAGNETRON SPUTTER SRC. A special magnetron sputtering source feature developed by AJA International, Inc. in 1991 to allow the end user to convert the specific magnetic field of the source to a variety of configurations. For example, each source can be configured to operate in the: ●Balanced mode to minimize substrate ion / electron bombardment ●Unbalanced mode to utilizing simultaneous ion bombardment to enhance film properties ●Magnetic material mode to help the magnetic field saturate and overcome the shunting effect of magnetic target materials allowing the magnetron sputter deposition of high permeability targets such as Fe. CONFOCAL SPUTTERING See photo WhatIs_Confocal_Sputtering.gif A sputtering system configuration where multiple magnetron sputtering sources are arranged in a specific circular pattern and are aimed at a common focal point. When a substrate is placed in the vicinity of this focal point and rotated on its own axis, it is possible to deposit highly uniform single layers, multi-layers and co-deposited alloy films. It is an extremely popular technique for the following reasons: ●Exceptional deposition uniformity on substrates twice the diameter of the source targets. ●Ability to easily control the growth of successive layers ranging in thicknesses from less thanone atomic monolayer to thousands of Angstroms. ●Minimizes time delay between subsequent layers since the substrate does not have to be re-positioned for each layer. In a con-focal multi-layer deposition, every source shutter opens about one second after the previous shutter has closed thereby keeping the deposited film surface on the substrate in the plasma. This keeps the interface surface free from contamination by residual gas and prevents nucleation of the next layer material. ●Complete freedom to easily grow alloys of any number of materials in any ratio with precise control. This is ideal for combinatorial chemistry applications and for optimization of compound material target stoichiometries for production applications. ●The con-focal sputtering configuration is compact and maintains the substrate holder in an axial orientation. This allows for much more freedom and sophistication in substrate holder design and keeps overall costs down. ●For low deposition rate materials it is possible to boost the rate by running 2-3 targets of this material simultaneously from a single power supply. IN-SITU TILT SOURCES IN A CONFOCAL SPUTTERING SYSTEM See photo WhatIs_Anim_InSitu.gif In powerful RD sputtering systems with the maximum level of flexibility, end users like to have the ability to operate at different working distances (distance between target and substrate). In order maintain high deposition uniformity, the focal point of the magnetron sputtering sources must be variable by adjusting the source head angle. Also, the deposition profile of materials deposited with DC, with RF and with magnetic materials are all different, so the optimal angle for each material is not identical even if the working distance remains unchanged. In 1991 AJA International, Inc. invented the world's first UHV and HV magnetron sputter sources with IN-SITU TILT. Without breaking vacuum, each source head angle could be individually set with a precision micrometer to a specific angle. If removed for service or cleaning, it could be returned to the system and set to precisely the same angle - this is much more difficult to accomplish with manually adjustable, source head tilt assemblies. IN-SITU TILT combined with a load-lock on the sputtering system also saves a significant amount of time in performing quick test runs in succession to zero in on the optimal source angles. What can be done in a few hours on a system with load-lock and IN-SITU TILT can take weeks on a system with manual source head tilt since adjustment requires venting the chamber each time to reset the angle. Finally, IN-SITU TILT permits the user to tilt the source away from the substrate and grow gradient or wedge films which are popular in combinatorial chemistry applications. DIRECT SPUTTERING See photo WhatIs_Anim_Direct.gif A sputtering system configuration where the substrate is positioned or moving directly in front of and parallel to the magnetron sputtering source targets. As a rule, target diameters (or lengths as in the case of rectangular magnetron sputtering sources) should be about 20% to 30% larger than the substrate to achieve reasonable uniformity. For example a 100 mm wafer would require a 150 mm sputter target to achieve +/- 5% deposition uniformity. Although this configuration is much less flexible and generally more expensive than con-focal sputtering, it has its place in production applications which require maximum deposition rates (semiconductor wafer metallization), applications which utilize large substrates (e.g. flat panel displays) and a few techniques that demand line-of-sight deposition (e.g. lift-off). Utilizing a direct sputtering configuration for RD is justified in certain instances, but often is chosen because it is what the researcher has seen before. Like diode sputtering, this was the original sputter system configuration and old habits die hard. It is important to clearly evaluate your needs before choosing between direct and con-focal deposition orientation. AJA - THE CUTTING EDGE IN SPUTTERING TECHNOLOGY http://www.ajaint.com/ By focusing on high quality, innovative design, product flexibility, customer support and affordability, AJA International, Inc. is the undisputed leader in RD sputtering equipment. The company has pushed the envelope since its founding in 1989 and continues to drive the market. Its designs are often copied but never equaled. http://www.ajaint.com/whatis.htm
标签: 溅射
