Browse Prior Art Database

Method for inspection of interfaces in 3-D stacked wafers or dice

IP.com Disclosure Number: IPCOM000132113D
Publication Date: 2005-Dec-01
Document File: 4 page(s) / 835K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for inspection of interfaces in three-dimensional (3-D) stacked wafers or dice. Benefits include improved functionality and improved throughput.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Method for inspection of interfaces in 3-D stacked wafers or dice

Disclosed is a method for inspection of interfaces in three-dimensional (3-D) stacked wafers or dice. Benefits include improved functionality and improved throughput.

Background

      A nondestructive inspection method is required for detecting defects, such as delamination, voids, and the lack of bonding; during the wafer-to-wafer stacking process for 3-D interconnect technology. The conventional solution can cause wafer chipping and fracturing when a wafer is thinned. Significant equipment down time results when damaged wafers must be removed, making the process not feasible for high volume manufacturing.

              To attempt to prevent problems, wafers are visually inspected for bulges and large defects after die thinning. Acoustic inspection of stacked wafers has been evaluated but the technique requires immersion of the wafers in water, a long inspection through-put time, and artifacts of water seeping between the wafers.

              A C-mode scanning acoustic microscopy (CSAM ) image of a thinned bonded wafer reveals a light contrast region in the wafer center. This area is a void between the two wafers. Voids can lead to catastrophic failure during wafer processing (see Figure 1).

General description

      The disclosed method is thermal inspection to evaluate the integrity of bonded interfaces in 3-D stacked wafers, stacked dice, and stacked dice in packages.

      The key elements of the disclosed method include:

•     Heat pulse to locally heat the stacked wafers or dice

•     Temperature mapping across the surfaces (top and bottom of sample) as a function of time using a high-speed infrared (IR) camera

•     Local variations of temperature or kinetics of temperature change are used to detect wafer-to-wafer bonding defects, such as delamination, voids, and poor bonds

•     Heat pulse and IR detector to raster scan the stacked wafers to improve the resolution of defect detection

•             Image processing software to identify the type of defect/abnormality and location and to quantify the defect size/magnitude

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to providing nondestructive, noncontact inspection of 3-D stacked wafers using image analysis
•             Improved functionality due to enabling inline wafer inspection at multiple manufacturing stages

•             Improved functionality due to enabling the inline inspection of local wafer areas

•             Improved throughput due to quickly detecti...