Physical Vapor Deposition (PVD) S. 1

Transcription

1 Physical Vapor Deposition (PVD) S. 1

2 PVD proceses are atomistic where material vaporized from a solid or liquid source is transported as a vapor through a vacuum or low-pressure gaseous or plasma environment and then condensed. PVD processes are used to deposited films with thickness in the range of a few to thousands nanometers. Solid or liquid In vacuum, plasma or low-pressure Vapor (e.g. element, alloy or compound) condensation substrate PVD@Rattanachan S. 2

3 What is Magneton Sputtering? S. 3

4 Steps of PVD (Bunshah 1982) Step 1: Creation of deposition species Step 2: Transport from source to substrate (collision + ionized) Stop 3: Film growth on substrate (condensation, nucleation and growth) PVD@Rattanachan S. 4

5 Sputtering deposition Target Vapor Non-thermal vaporization process where surface atoms are physically ejected by a momentum transfer from an energetic bombarding particles that is usually a gaseous ion accelerated from a plasma or an ion gun. substrate The most common sputtering sources are the planar magnetons where the plasma is magnetically confined close to the target surface and ions are accelerated from the plasma to the target surface. PVD@Rattanachan S. 5

6 Advantages of sputter deposition Elements, alloys and compounds can be sputtered and deposited. The sputtering target provides a stable, long-lived lived vaporization source. In some configurations, reactive deposition can be easily accomplished using reactive gaseous species that are activated in i plasma. Low radiant heat in the deposition process. The source and substrate can be spaced close together. The sputter deposition chamber can have a small volume. PVD@Rattanachan S. 6

7 Disadvantages of sputter deposition Sputtering rates are low compared to those that can be attained in thermal evaporation. In many configurations, the deposition flux distribution is non-uniform, requiring moving fixturing to obtain films of uniform thickness. Target is expensive and may be poor Target becomes heat, which must be cooled. In some cases, gaseous contaminants are activated in plasma, making film contamination. S. 7

8 Sputtering S. 8

9 Sputtering E-beam Laser ablation Heat S. 9

10 DC Plasma sputtering S. 10

11 A schematic drawing of a sputtering deposition reactors PVD@Rattanachan S. 11

12 Reactive sputtering S. 12

13 Magnetron sputtering S. 13

14 In addition to sputtering neutral species, electrons are also emitted from the target as a consequence of gas ion bombardment. Most of these electrons enter the plasma (a random motion) and engage in ionizing collisions with gas atoms, thereby producing the ions that sustain the discharge. These electrons cause changes in film composition and thickness due to local biasing and local heating of the substrate. PVD@Rattanachan S. 14

15 A sophisticated sputtering system is available to coat variety of materials. The system consist of three targets, out of these two are connected to RF and one DC. The three targets could be sputter simultaneously while rotating the substrate which can be biased and rotated. Mass flow controller allows to precise control of the deposition process. It is also possible insitu to monitor the thickness of the deposited films. The large number of targets available with this system to deposit multilayers or n a n o c o m p o s i t e t h i n f i l m s. PVD@Rattanachan S. 15

16 PVD reactor S. 16

17 Microstructure of coating PVD CVD S. 17

18 Evaporation process characteristics S. 18

19 Reactive evaporation S. 19

20 Process parameters & limitation of evaporation and sputtering process S. 20

21 Advantage of vacuum evaporation High-purity film can be deposited from high-purity source material Source of material to be vaporized may be a solid in any form and purity The line-of of-sight trajectory (prevent contamination) Deposition rate monitoring and control are relatively easy Least expensive of the PVD processes. PVD@Rattanachan S. 21

22 Disadvantages of vacuum evaporation Many compounds and alloy compositions can be deposited difficulty. Line-of of-sight and limited-area sources result in poor surface. Line-of of-sight trajectories (ว ถ โคจร ว ถ โคจร) and limited-area sources result in poor film-thickness uniformity over large areas. Few processing variables are available for film property control. S. 22