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Nondestructive Infrared Testing of Connections

IP.com Disclosure Number: IPCOM000090748D
Original Publication Date: 1969-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 60K

Publishing Venue

IBM

Related People

Jorgensen, RR: AUTHOR [+2]

Abstract

The infrared nondestructive microirradiation and radiation detection technique is for determining the quantitative and qualitative integrity of chip-to-substrate interconnections with regard to their thermal and electrical conducting properties. The technique is described in conjunction with detection of voids within joints or of excessive contact resistance between a semiconductor chip and substrate interface connection.

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Nondestructive Infrared Testing of Connections

The infrared nondestructive microirradiation and radiation detection technique is for determining the quantitative and qualitative integrity of chip-to- substrate interconnections with regard to their thermal and electrical conducting properties. The technique is described in conjunction with detection of voids within joints or of excessive contact resistance between a semiconductor chip and substrate interface connection.

A laser probing technique is used for remotely injecting or irradiating the silicon devices directly above or in the neighborhood of the interconnection with a pulse of electromagnetic radiation. This has a wavelength of lambda 1 within the transmission spectrum of the device, away from the absorption edge of the material, and a pulse width equal to or less than time constant of the material, maximizing thermal contrast. The transient thermal response or radiant flux emission at the metallization via hole area is detected with an infrared detection system for comparison with a standard and subsequent data reduction. The quality of the radiant energy detected has a direct bearing on the time required for heat to propagate across the interconnection and the energy conducting properties of the bond. This is because the bond offers resistance to heat flow, in proportion to its incremental thermal resistance, and absorbs energy in proportion to its heat capacity. Such are directly related to the presence and distribution of voids or gas pockets within the interconnection pads and the contact resistance between the pad, the chip, and the substrate.

In drawing A, if an electromagnetic pulse of coherent radiation has a wavelength lambda 1 in the near infrared region within the transmission spectrum of the silicon device and has uniform flux density, the absorption proceeds in accordance with Lambert's Law. Thus, provided that the absorption coefficients, e.g., of a doped silicon and SiO(2) target area, are sufficiently low at lambda 1, most of the incident radiation propagates through the media and arrives at the metallization with little absorption within its traversed path. Approximately 10t12% of the radiation arriving at the metallization, directly above the via hole area, is absorbed, converted to thermal energy, and conducted to the interconnection. The remainder of the radiation either scatters or deflects or both, retracing its original path.

The target temperature distribution through the media is complex. The target emits thermal radiation as a function of its temperature. If radiation from the target is collected by a reflective objective and focused on a photovoltaic detector, the latter generates a signal voltage proportional to the radiation intensity. The total radiance WT collected from the target is amplified with processing of the detect tor signal to obtain a transient thermal response, drawing B, of the interconnection target. When the latter is compared...