Center for Materials for Information Technology an NSF Materials Science and Engineering Center Sputter Deposition Lecture 9 G.J. Mankey

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Sputter Deposition Magnetron sputtering is the most widely used method for vacuum thin film deposition. Although the basic diode sputtering method (without magnetron or magnetic enhanced) is still used in some application areas, magnetron sputtering now serves over 90% of the market for sputter deposition. Magnetron sputtering can be used to coat virtually anything with a wide range of materials - any solid metal or alloy and a variety of compounds. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Sputtering System A typical sputtering system consists of a vacuum chamber with substrate holders and magnetron guns, vacuum pumps and gauging, a gas supply system, power supplies and a computer control system. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center The Magnetron A Magnetron is comprised of : A CATHODE = electron source An ANODE = electron collector A combined ELECTRIC & MAGNETIC FIELD B X E ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center The Plasma Discharge Plasma is a fluid of positive ions and electrons in a quasi-neutral electrical state. The vessel that contains this fluid is formed by electric and magnetic fields. In many plasma coating applications positive ions are generated by collisions between neutral particles and energetic electrons. The electrons in a plasma are highly mobile, especially compared to the larger ions (typically argon for sputtering). Control of the highly mobile plasma electrons is the key to all forms of plasma control. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Microscopic View of Sputtering The impact of an atom or ion on a surface produces sputtering from the surface as a result of the momentum transfer from the incoming particle. Unlike many other vapor phase techniques there is no melting of the material. History of Sputtering –The verb to SPUTTER originates from Latin SPUTARE(To emit saliva with noise). –Phenomenon first described 150 years ago... Grove (1852) and plücker (1858) first reported vaporization and film formation of metal films by sputtering. –Key for understanding discovery of electrons and positive ions in low pressure gas discharges and atom structure (J.J. Thomson, Rutherford), –Other names for SPUTTERING were SPLUTTERING and CATHODE DESINTEGRATION. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center The Magnetron Gun A magnetron consists of a target with magnets arranged behind it to make a magnetic trap for charged particles, such as argon ions, in front of the target. Atoms are knocked out of the target surface by the ions - this is sputtering. These sputtered atoms aren’t charged negatively or positively, so they go straight out of the magnetic trap to coat the substrate. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center The Magnetron Plasma Confinement between a negatively biased target and closed magnetic field produces a dense plasma. High densities of ions are generated within the confined plasma, and these ions are subsequently attracted to the negatively biased target, producing sputtering at high rates. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Target Erosion Target erosion is greatest where the magnetic field and the subsequent plasma density is greatest. This leads to inefficient use of target material, particularly in the case of ferromagnetic targets. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Sputtering Insulators For an insulator target, the ions bombarding the target will create charging, and the electric field necessary to maintain a plasma is greatly diminished. To alleviate this problem, an RF power supply is used to generate the electric field. ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center Magnetron Guns ref:

Center for Materials for Information Technology an NSF Materials Science and Engineering Center The Latest in UHV Sputtering A UHV, magnetron sputter source that fits through the port of a 2.75" CF flange complete with its tilt gimbals assembly. The AJA International new A310-XP only needs a 2.75" CF to accommodate the source head, tilt gimbals and gas injection/isolation chimney. This revolutionary new design is true UHV - all ceramic to metal construction.