Method of supporting a workpiece during physical vapour deposition

Abstract

Methods and related apparatus support a work piece during a physical vapor deposition. An aluminium support having a support surface coated with a heat absorbent coating is provided. The support is cooled to around 100° C. and a PVD process is performed such that, with cooling, the work piece temperature is between 350° C. and 450° C. The coating is inert and/or ultra-high voltage compatible.

Claims

1. A method of supporting a workpiece during Physical Vapour Deposition (PVD), the method including: (a) providing an aluminium support having a support surface coated with a heat absorbing coating of a metal oxide film, and placing the workpiece on the metal oxide film so as to be supported by the support surface of the support; (b) cooling the support to 100° C.; and (c) executing PVD, to thereby deposit material on the workpiece, while the cooling is being carried out such that, with the cooling, the workpiece temperature is between 350° C. and 450° C. during the depositing of the material on the workpiece.

2. A method as claimed in claim 1 wherein the coating is inert and/or Ultra High Voltage compatible.

3. A method as claimed in claim 2 wherein the coating is a film of CrO.sub.x or Al.sub.2O.sub.3 .

4. A method of supporting a workpiece during Physical Vapour Deposition (PVD), the method including: (a) providing an aluminium support having a support surface coated with a heat absorbing coating of CrO.sub.x or Al.sub.2O.sub.3, and placing the workpiece on the coating of CrO.sub.x or Al.sub.2O.sub.3 so as to be supported by the support surface of the support; (b) cooling the support to 100° C.; and (c) executing PVD, to thereby deposit material on the workpiece, while the cooling is being carried out such that, with the cooling, the workpiece temperature is between 350° C. and 450° C. during the depositing of the material on the workpiece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention may be performed in various ways and specific embodiments will now be described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic view of a sputtering apparatus;

(3) FIG. 2 illustrates the effect of the coating in a particular temperature range for a target having a 26 kw power supplied;

(4) FIG. 3 is a corresponding graph for a 40 kw set up; and

(5) FIG. 4 is a table setting out wafer temperature and deposited film grain size for aluminium and aluminium/CrOx coated platen assemblies with DC power 40 kW and platen temperature controlling at 100 C.

DETAILED DESCRIPTION

(6) In FIG. 1 a vacuum chamber 10 contains a support or platen 11 with an opposed target 12. As known in the art the target has a varying magnetic field generated by magnetron 14 and is powered by DC supply 14. As is also known in the art, a plasma 15 is struck within the chamber and ions are drawn to the target from the plasma to sputter aluminium from the target which descends onto wafer 16 that is carried on the support 11.

(7) In general at above 350° C. to 400° C. a silicon wafer emits significant quantities of thermal radiation. For the most part, due for example to the aluminium coating on top of silicon dioxide layer on a silicon wafer, any heat transfer from the wafer will be restricted to the back surface of the wafer.

(8) As the Applicants were interested in high deposition rate processes involving significant powers, and hence heating, they decided to try an aluminium platen, because of its greater heat conductivity. However, as can be seen in FIGS. 2 and 3 when they experimented with an aluminium platen cooled to 100° C. for two different power regimes, they found that the wafer temperature continued to rise until it was way above 450° C. and so the process was, surprisingly, unacceptable. However, when the platen was coated with an inert ultra high voltage compatible coating, the wafer temperate flattened out at around 350° C. and in both cases kept the platen temperature below 450° C. Indeed in the first instance it was held at 400° C.

(9) This arrangement accordingly, surprisingly, provides a very effective way of cooling the wafer in a high temperature process without the need for gas back side cooling, electrostatic clamps or even mechanical clamping systems.

(10) FIG. 4 illustrates that the 40 kW process on an aluminium platen controlling at 100° C. results in a wafer temperature of 540° C. either on a SiO.sub.2 or the SiO.sub.2/Ti/TiN liner while the platen assembly with the absorbing coating maintains the wafer temperature at 440° C. The smaller grain sizes observed for the coated platen assembly are indicative of the lower wafer temperature. The process requirement for this device restricted the BEOL thermal budget to <450° C. and as such the conventional aluminium platen could not be used.