In addition, argon ion beam and oxygen plasma was also used for wafer surface treatment before bonding to increase bonding strength of bonded wafer interface. Surface and interface characterization of sequentially plasma. Doi wafer with chemical mechanical polishing cmp on the diamond surface makes a poor bonding to silicon wafers with thermal oxide. Mar, 2006 two lowtemperature wafer bonding methods, namely the mediumvacuum level wafer bonding mvwb and plasmaactivated wafer bonding pawb, are performed. Mechanisms for lowtemperature direct bonding of sisi and. After plasma treatment the wafers were cleaned in rca1 solution andor deionized water. Investigation of plasma activated sisi bonded interface by infrared. Sequentially plasma activated bonding sp ab of silicon wafers has been investigated to facilitate chemical free, room temperature and spontaneous bonding required for integration of. The images, obtained by infrared imaging system, were analyzed by the software based on spatial domain and morphology methods. Lowtemperature wafer bonding is increasingly required due to the increasing. After 96 hours most plasma activated samples reached full bond strength, except for one which was near 2500 mjm2. The spatial domain processing methods, including median. Pdf plasma activated wafer bonding generated a high interest in last decade due to the important process temperature reduction. A new lowtemperature highaspectratio mems process using.
Diamondoninsulator wafers featuring uncd with minimum residual stress are used. A second silicon wafer is then directly bonded on top of the oxide. Annealed sio2 interlayer improves the direct bonding quality. Wiegand semiconductor wafer bonding generally refers to a process where two mirrorpolished wafers adhere to each other at room temperature without the application of any macroscopic gluing layer or outside force. Plasma activated wafer bonding for mems spie digital library. Comparison of argon and oxygen plasma treatments for. Most of the data for plasma activated wafers were in the range of 1500 to 2000 mjm2 after 24 anneal which significantly higher than previous results 2. Aug 01, 2014 bonding of most processed wafers requires a low temperature bonding 1. Plasma activated wafer bonding is a way to reduce the required temperatures significantly by changing the surface chemistry of the materials 2. Low temperature plasma activated direct wafer bonding allows to lower the required.
With sab, the surfaces to be bonded are activated by plasma. The fusion bonding is a twostep process consisting of a room temperature prebond and an annealing step. Plasma activated wafer bonding is an application where the ionized gas atoms are used to modify the surface conditions of a substrate. In order to achieve a strong bonding, the ohmolecules on both surfaces need to react with one another. Plasma activated w afer bonding for thin siliconon. Cleanliness of the patterned wafers becomes difficult to achieve when the low surface roughness of the underlying layer such as silicon dioxide needs to be protected. This paper presents a detection method for characterizing the bonded interface of o2 plasma activated silicon wafer direct bonding. After lowtemperature annealing 500c for a short time activated bonding sab method using argon fast atom beam arfab irradiation was used as a surface pretreatment for direct bonding at low temperatures 1. The plasma is chosen to compliment existing interface conditions and can result in conductive or insulating interfaces. With the main advantage of bringing some applications at industrial. Effect of interfacial sio 2 thickness for low temperature o 2. Nondestructive characterization of fusion and plasma. Plasma activated wafer bonding is a surface activation method in which by applying a plasma treatment to the wafers prior to bringing them in contact for bonding, the surface chemistry can.
For wafer bonding experiments, the specification of each wafer within the wafer pair, the relevant information for wafer preparation and bonding conditions are tabulated in table 1. Plasma activated w afer bonding for thin silicononinsulator. Plasma assisted lowtemperature hydrophobic wafer bonding. Plasma activated wafer bonding for mems request pdf. Although a cleavage method with blade insertion is applicable to quantitatively.
Finally, patterned wafers are bonded to diamondcoated wafers using plasma activated direct wafer bonding technology fig. Systematic experiments of sisio 2 and sio 2 sio 2 wafer bonding are performed for analyzing the evolution of the bonding surface energy with the interfacial oxide thickn. The cornerstone of low temperature bonding is plasma activation. Different plasma treatments were used to modify silicon surfaces and to analyze their effect on the wafer bonding behavior. Kulawski vtt information technology, 02150 espoo, finland plasma assisted direct bonding has been investigated for wafer scale encapsulation of microelectromechanical systems mems. Sequentially plasma activated bonding sp ab of silicon wafers has been investigated to facilitate chemical free, room temperature and spontaneous bonding required for integration of nanostructure on the wafer scale. A historical patent picture of the worldwide moving front of the stateoftheart of contact bonding. Surface analysis of materials for direct wafer bonding. Uncd makes a poor direct bonding to oxidized silicon wafer. Wafer scale packaging of mems by using plasmaactivated wafer bonding t. Plasma activated wafer bonding is a surface activation method in which by applying a plasma treatment to the wafers prior to bringing them in contact for bonding, the surface chemistry can be. The focus behind this book on wafer bonding is the fast paced changes in the research and development in threedimensional 3d integration, temporary bonding and microelectromechanical systems mems with new functional layers. Wafer scale packaging of mems by using plasmaactivated.
Plasma power w time s pressure pa 10 30 60 30 50 75 100 300 30 200 1200 30 table ii. The problem arises when excess ohmolecules are left intermittent on. Pdf role of heating on plasmaactivated silicon wafers. Using a thin pecvdgrown sio2 interlayer on uncd makes a good bonding. However, along with its maturation and introduction of layer splitting technologies, the direct wafer bonding approach is gaining. Atmospheric pressure plasma activated bonding enables the possibility to ignite plasma at specific local areas or the whole surface of the substrate. Sequentially plasma activated bonding for wafer scale nano. The two front run contenders for producing soi wafers are simox, which will initially be used by ibm, and the direct wafer bonding. Oxygen plasma surface activation was seen to indeed yield high sisi bondingstrength at low temperatures. Plasmaactivated direct bonding of patterned siliconon. With the main advantage of bringing some applications at industrial degree of feasibility. Then, two wafers were brought into contact in the bonder followed by annealing in n2 atmosphere for several hours.
Wafer bonding is a packaging technology on wafer level for the fabrication of microelectromechanical systems mems, nanoelectromechanical systems nems, microelectronics and optoelectronics, ensuring a mechanically stable and hermetically sealed encapsulation. Investigation of plasma activated sisi bonded interface by. Experimental conditions of plasma parameters in the o2 rie plasma activated bonding process. To promote the use of plasma technology within the electronics manufacturing industry, plasmatreat usa, inc. Plasmaactivated direct bonding of diamondoninsulator. Pdf wafer bonding of sisi, sisio2, sigaas silita3o, ware successfully achieved at low temperature, with high bond strength and voids. Introduction wafer bonding is a well established technology for micro electro mechanical systems mems applications and wafer level packaging. Apr 10, 20 this paper presents a low temperature wafer direct bonding process assisted by o2 plasma. Between the two electrodes plasma gas is ignited via alternating voltage. Tu chemnitz, center for microtechnologies, 09126 chemnitz, germany. Wafer bonding usually requires hightemperature annealing above c to achieve strong bonding between the wafers. Silicon wafers were treated with wet chemical cleaning and subsequently activated by o2 plasma in the etch element of a sputtering system. Plasma parameters used in the sequential plasma activated bonding spab process. The wafers diameter range from 100 mm to 200 mm 4 inch to 8 inch for memsnems.
Plasma activated wafer bonding for thin silicononinsulator. It was experimentally demonstrated that bonding strength strongly depends on the total sio 2 thickness near the bonding interface for a given o 2 plasma surface activation. Prior to mctw direct bonding, wafer to wafer direct bonding processes are employed to measure oxideoxide bonding energies of cmptreated and plasma activated sio 2 used in our experiments. In wafer bonding applications the goal is to create conditions that promote the development of chemical bonds between two surfaces. With the main advantage of bringing some applications at. Wafer scale packaging of mems by using plasma activated wafer bonding t. Transmission electron microscopy tem then plasma activated, separated using a razor blade and interfaces of bonded wafer pairs. Both plasmaactivated wafers have apparent surface energies near 20 mjm 2, which are in agreement with the values 4075 mjm 2 reported by bodner et al. May 15, 2007 achieving wafer level bonding at low temperature employs a little magic and requires new technology development. Our results show that plasma enhanced chemical vapor deposition of silicon dioxide on top of the. This prevents the bonding temperature from exceeding 400 c, and allows for postcmos mems integration. Oxideoxide thermocompression direct bonding technologies.
With the advent of plasma activation, direct wafer bonding can achieve almost the bulk strength in bonding siliconsilicon surfaces at low temperature 1. Plasma activated wafer bonding is a surface activation method in which by applying a plasma treatment to the wafers prior to bringing them in contact for bonding, the surface chemistry can be tailored in order to obtain maximum bond strength for low temperature thermal annealing. Plasma activated direct bonding of doi wafers to thermal oxide grown silicon wafers is investigated under vacuum. O plasma assisted wafer bonding at room temperature 2. Plasma activated direct wafer bonding technique is a convenient way to bond patterned and unpatterned wafers.
Outline why bond driving forces bonding processes alignment processes pa plasma activated bonding. Pdf new developments in plasma activated wafer bonding. Fraunhofer enas, department of system packaging, 09126 chemnitz, germany. Plasma activated wafer bonding generated a high interest in last decade due to the important process temperature reduction.
This service intents to make it as easy as possible to start using openair plasma and to show its benefits with a short demonstration. In this process, the wafers are submitted to a plasma treatment prior to bringing them into contact for bonding. The two wafers are bonded using a lowtemperature plasma activated fusion bond. Keywords direct wafer bonding, mems, microelectronics, microelectromechanical systems, soi, silicononinsulator, integrated circuits, bond strength measurement, heterogeneous integration, preprocessed soi fabrication, wafer scale packaging, plasma activation abstract direct wafer bonding is a method for fabricating advanced substrates for. Research highlights plasma activated direct bonding is used with a maximum temperature of 550 c. Plasma activation is a powerful technique for hydrophilic wafer bonding 4. Low temperature sisi wafer direct bonding using a plasma. Wafer bonding methods adhesive versatile nonhermetic solder selfaligning solder flow possible thermocompression nonflat surface ok high force surface activated varies varies fusion direct strong bond high temp nonflat surface ok varies hermetic specific metals required nonflat surface ok hermetic flat surface required large area medium. This suggests that the effects of plasma activation are not fully clari. Temperature stabilization of linbo3 using plasma activated. Wafer scale packaging of mems by using plasmaactivated wafer. Sequential plasma activated process for silicon direct bonding. Comparison of mediumvacuum and plasmaactivated low.
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