Overcoming dicing challenges for low-K copper wafers using nickel-palladium-gold bond pads for automotive application

2012 ◽  
Author(s):  
Tu Anh Tran ◽  
V. Mathew ◽  
Wen Shi Koh ◽  
K. Y. Yow ◽  
Y. K. Au
Keyword(s):  
Automotive Application ◽  
Copper Wafers ◽  
Bond Pads ◽  
Low K

Dicing Development for low-k Copper Wafers using Nickel-Palladium-Gold Bond Pads for Automotive Application

2012 ◽  
Vol 2012 (1) ◽  
pp. 001085-001096
Author(s):  
Tu Anh Tran ◽  
Varughese Mathew ◽  
Wen Shi Koh ◽  
K. Y. Yow ◽  
Y. K. Au
Keyword(s):  
Production Control ◽  
Low Cost ◽  
Electroless Nickel ◽  
Junction Temperature ◽  
Automotive Application ◽  
Wafer Level ◽  
Plastic Packages ◽  
Wire Material ◽  
Copper Wafers ◽  
Low K

New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on the development of dicing process for low-K-copper wafers having aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold Over Pad Metallization (OPM). Development wafers were pizza mask wafers on which multiple die designs and scribe grid production control (SGPC) modules were designed. SGPC modules are designed with aluminum probe pads that are used to monitor wafer-level process control. All aluminum features on the wafer were plated with nickel/palladium/gold OPM. With nickel about four times as hard as aluminum, OPM plated SGPC's were much more difficult to dice than conventional SGPC's with aluminum pads. Cracking on silicon sidewall with crack propagating towards the die was found to cause back-end-of-line (BEOL) delamination and device failure. Surface roughness and hardness measurements were taken on OPM variations. Extensive mechanical dicing studies were conducted to modulate the failures and resolve the dicing challenge. Laser grooving followed by mechanical dicing of OPM wafers was also performed. Packages underwent extensive reliability stress conditions. The associated process improvements described in this paper supported a successful integration of a 55nm die technology in Low Profile Quad Flat Package with Exposed Pad (LQFP-EP) meeting and exceeding AEC grade 0 requirements.

Dicing Development for low-k Copper Wafers using Nickel-Palladium-Gold Bond Pads for Automotive Application

2013 ◽  
Vol 2013 (1) ◽  
pp. 000657-000662
Author(s):  
Tu Anh Tran ◽  
Varughese Mathew ◽  
Wen Shi Koh ◽  
K. Y. Yow ◽  
Y. K. Au
Keyword(s):  
Production Control ◽  
Low Cost ◽  
Electroless Nickel ◽  
Junction Temperature ◽  
Automotive Application ◽  
Wafer Level ◽  
Plastic Packages ◽  
Wire Material ◽  
Copper Wafers ◽  
Low K

New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on the development of dicing process for low-K-copper wafers having aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold Over Pad Metallization (OPM). Development wafers were pizza mask wafers on which multiple die designs and scribe grid production control (SGPC) modules were designed. SGPC modules are designed with aluminum probe pads that are used to monitor wafer-level process control. All aluminum features on the wafer were plated with nickel/palladium/gold OPM. With the hardness of nickel and palladium being more than 10 to 15 times the hardness of aluminum, OPM-plated SGPC's were much more difficult to dice than conventional SGPC's with aluminum pads. Cracking on silicon sidewall with crack propagating towards the die was found to cause back-end-of-line (BEOL) delamination and device failure. Extensive mechanical dicing studies were conducted to modulate the failures and resolve the dicing challenge. Specifically, dicing was observed to be not centered on SPGC pads on the pizza mask. Off-centered dicing produced drastic change in Ni loading at the center of the blade and on the edges of the blade. Packages underwent extensive reliability stress conditions. The associated process improvements described in this paper supported a successful integration of a 55nm die technology in Low Profile Quad Flat Package with Exposed Pad (LQFP-EP) meeting and exceeding AEC grade 0 requirements.

To Study the High Temperature Effects on Ball Bonds Using Low K Material in Wire Bond Devices

2007 ◽  
Author(s):  
S. A. Kudtarkar ◽  
R. Murcko ◽  
K. Srihari ◽  
S. Saiyed
Keyword(s):  
High Temperature ◽  
Mechanical Stability ◽  
Semiconductor Industry ◽  
Gold Wire ◽  
Wire Bonding ◽  
Mechanical Stresses ◽  
Wire Bond ◽  
Ball Bonds ◽  
Bond Pads ◽  
Low K

Wire bonding is widely used as one of the main interconnect alternatives. This technique applies significant mechanical stresses on the bond pads along with heat and ultrasonic energy to form a bond. An interconnection of copper plus low k material has been a focus of the semiconductor industry with the goal of reducing interconnection delays. The material is below the wire bond pads and complicates the mechanical stability of the device during wire bonding. The low k materials that are suggested are very sensitive to these mechanical stresses. This generates a significant reliability concern for the underlying metal structures. In addition, the integrity of the bond formed may be negatively impacted from a reliability perspective because of the softer material properties of the dielectric. This research explores the ball bond integrity for die with SiO2 and low k dielectric underlying material respectively, using 0.8 mil thick (20 microns) gold wire. Accelerated tests, such as high temperature storage at 150°C and 175°C, were conducted to assess the reliability of these bonds. The results of this investigation reveal that the ball bond’s strength degrades after high temperature tests due to the occurrence of Kirkendall voids between the gold wire and the aluminum bond pad. The degradation recorded was more severe for regular die than its low k counterpart.

Mechanical and Electrical Characterization of an IC Bond Pad Stack Using a Novel In-Situ Methodology

2003 ◽  
Author(s):  
C.D. Hartfield ◽  
J.J. Broz ◽  
T.M. Moore
Keyword(s):  
Integrated Circuit ◽  
Electrical Characterization ◽  
Dynamic Contact ◽  
Wafer Level ◽  
New Class ◽  
Increased Risk ◽  
Bond Pads ◽  
Low K

Abstract The semiconductor industry’s efforts to integrate dielectrics into Si devices has driven characterization efforts to address the challenges presented by adoption of this new class of materials. Abundant literature exists on the considerations required for CMP process recommendations for successful fabrication, adhesion requirements for both fabrication and assembly, and considerations for interconnect structure to enable wire-bonding. There is also interest in understanding the wafer level test challenges presented by the low-K devices. In addition to the typical concerns about reaching the best compromise of good contact resistance (CRES) performance with a minimum amount of probe damage, low-K materials present an increased risk of compromising the dielectric or barrier layers beneath bond pads. For a better understanding of the dynamic contact phenomenon of probing and its effect on the integrated circuit (IC) metal stack, a specialized in-situ nanomanipulator tool was developed for simultaneous visualization of probing events with data recording of electrical and load measurements. This paper describes initial research with this new tool.

Comparison of Gold and Copper Wire Bonding on Aluminum and Nickel-Palladium-Gold Bond Pads for Automotive Application

2011 ◽  
Vol 2011 (1) ◽  
pp. 000589-000599
Author(s):  
Tu Anh Tran ◽  
Varughese Mathew ◽  
Harold Downey
Keyword(s):  
High Temperature ◽  
Copper Wire ◽  
Low Cost ◽  
Electroless Nickel ◽  
Wire Bonding ◽  
Junction Temperature ◽  
Automotive Application ◽  
Plastic Packages ◽  
Wire Material ◽  
Bond Pads

New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on evaluating Au and Cu wire bonding on low-K-copper wafers having two types of bonding surfaces, the conventional aluminum pad and aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold. Ni thickness ranging from 1μm to 3μm was evaluated. Defects on as-plated Ni/Pd/Au bond pads such as color difference and surface roughness were determined to be due to nodule growth and plating non-uniformity. Wire bonded strip-level thermal aging was conducted to compare the high-temperature performance of the four interconnect types. Packages underwent extensive reliability stress conditions. Cross-sectioning through the ball bonds was also conducted to examine the welding region between the ball bond and bond pad. Defects in plating and wire bonding processes causing package reliability failures were identified. Recommendations for plating and wire bonding processes were derived to ensure high quality and reliable interconnect exceeding AEC grade 0 requirements.

Comparison of Gold and Copper Wire Bonding on Aluminum and Nickel-Palladium-Gold Bond Pads for Automotive Application

2012 ◽  
Vol 9 (2) ◽  
pp. 65-77 ◽  
Author(s):  
Tu Anh Tran ◽  
Varughese Mathew ◽  
Harold Downey
Keyword(s):  
Copper Wire ◽  
Chemical Properties ◽  
Automotive Application ◽  
Plastic Package ◽  
Copper Wire Bonding ◽  
Prolonged Duration ◽  
Environmental Requirements ◽  
Higher Temperature ◽  
Materials Used ◽  
Bond Pads

New automotive specifications derived from higher module integration and more stringent environmental requirements expect plastic packages to operate at higher junction temperatures with prolonged duration. Temperature is a key accelerating factor for failures in electronic package devices because of the thermo-mechanical, metallurgical and chemical properties of the materials used in the package. Failures in conventional plastic package at high temperatures such as 175 °C often originate from aluminum – gold wirebonding system because of the formation of Au-Al intermetallic phases and associated Kirkendall voiding which degrades the interface. Methods to overcome such reliability issues in wire bonded devices are to change either the wire material or the bond pad metallurgy or pad finishing other than aluminum which can reliably withstand operations at higher temperature and longer duration.

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