AVS 50th International Symposium
    QSA-10 Topical Conference Monday Sessions
       Session QS-MoA

Invited Paper QS-MoA1
Metrology Needs for Ultrathin Films in the Wafer Processing Industry. What is Needed? What is Available?

Monday, November 3, 2003, 2:00 pm, Room 320

Session: Thin-Film Metrology
Presenter: C.R. Brundle, C.R. Brundle and Associates
Authors: C.R. Brundle, C.R. Brundle and Associates
C.A. Evans, Evans FWA
Correspondent: Click to Email
Single layer films of less than 1nm (eg Si/O/N) or stacks of less than 4nm (eg TaN/Cu) are already in production or under development. The ITRS required metrology for these, however, has been lagging because this presents major instrumentation challenges. Thickness SPC specs across wafers and from wafer to wafer are typically 3% RSD, or better, which implies a measurement precision (at 1 sigma) of at least 1%, ie 0.01nm for a 1nm film. Elemental composition precision may need to be similarly tight (eg for N concentration in a 1nm Si/O/N film). More esoteric parameters, such as depth distribution (elemental or even chemical), interface mixing, roughness, or reaction, or surface contamination, may also have to be under SPC, but even if they do not, these variables must not compromise the metrology used. Finally there may be requirement to make such measurements on restricted areas on production wafers. In this paper we review the capabilities of some of the analytical technologies beginning to find their way into the industry to deal with these issues. They include such methods as VUV spectroscopic ellipsometry, XRR/XRF and XRR/ellipsometry combinations, acoustic sonar methods, non-contact electrical methods, Low Energy X-Ray Emission Spectroscopy (LEXES), and XPS and ARXPS. Examples of their use are presented. It is natural that new measurement instrumentation should penetrate the the "lab" first, where the requirement for throughput and non-expert, recipe driven, automation of both data collection and processing are far less demanding than in "the fab", but even in the lab the instrumentation must must handle full 300mm wafers in a manner where the "time to answer" is acceptable. We discuss what attributes are likely to lead to a transition to fab use.