Control of parameters such as bonded wafer stack (BWS)
thickness, total thickness variation (TTV), bow, warp/sori, and flatness, is
essential to successful implementation of a wafer bonding process. These
parameters provide meaningful information about the quality of the wafer
thinning process (if used), the uniformity of the bonding process, and the
amount of deformation induced to the wafer stack by the bonding process. TTV is
also critical in certain bonded wafer manufacturing process steps, since
non-planarity can lead to problems in subsequent processing steps, including
lithographic overlay and intermittent electrical contact between metal layers
in the bonded wafers. This Guide provides a description of tools that can be
used to determine these key parameters before, during, and after the process
steps involved in wafer bonding.
This Guide provides examples of the capabilities and
limitations of various measurement technologies applicable to BWS as well as
their suitability for different applications.
The Guide describes metrology techniques that are
applicable to both temporary and permanently BWSs.
This Guide is complementary to existing SEMI Test Methods
for measuring these parameters on single wafers, in some cases extending
existing metrology techniques to a BWS and in other cases describing metrology
techniques specific to a BWS.
The Guide focuses on general measurement techniques
including infrared (IR) laser profiling, white light confocal microscopy,
visible and IR interferometry, capacitance, back-pressure, and acoustic metrology.
Each technology has unique strengths and weaknesses—some rely on front-surface
illumination, others on back-surface illumination. Some techniques can measure
the thicknesses of individual layers in the BWS, and some are additionally
capable of measuring surface nanotopography.
The metrology examples provided in this Guide originated
from industry experts and are believed to be representative of tool performance
as of the year 2012. However, as tool and measurement techniques continue to
evolve and improve, BWS measurement performance may surpass what is contained
in this Guide. The user should investigate metrology suppliers’ current
capabilities.
Referenced SEMI Standards (purchase separately)
SEMI HB1 — Specification for Sapphire Wafers Intended for
Use for Manufacturing High Brightness-Light Emitting Diode Devices
SEMI MF533 — Test Method for Thickness and Thickness
Variation of Silicon Wafers
SEMI MF1390 — Test Method for Measuring Bow and Warp on
Silicon Wafers by Automated Noncontact Scanning
SEMI MF1451 — Test Method for Measuring Sori on Silicon
Wafers by Automated Noncontact Scanning
Revision History
SEMI 3D4-0915 (Reapproved 0222)
SEMI 3D4-0915 (technical revision)
SEMI 3D4-0613 (first published)
