Underfill adhesion to BCB (Cyclotene/sup TM/) bumping and redistribution dielectrics

Garrou, P.; Scheck, D.; Im, James S.; Hetzner, J.; Meyers, Gregory F.; Hawn, David D.; Wu, Jiali; Vincent, Michael; Wong, Ching‐Ping

doi:10.1109/6040.861575

Cited by 14 publications

(14 citation statements)

References 13 publications

(10 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Additionally, PBO material is known for its excellent thermal stability and thermo-oxidative resistance, and can be used in and is compatible with various front-end and back-end assembly applications [11], [21]- [25], [27]. The material is also easily processed and with a photosensitizer will act as a photoresist or hardmask during etching, as has been shown with other photosensitive polymer materials [4], [9], [28], [29]. Furthermore, the developer that is usually utilized with this photosensitive PBO is tetramethyl ammonium hydroxide (TMAH) in water, an environmentally benign aqueous solution.…”

Section: Introductionmentioning

confidence: 93%

See 1 more Smart Citation

Variable Frequency Microwave and Convection Furnace Curing of Polybenzoxazole Buffer Layer for GaAs HBT Technology

Yota

Ramanathan

et al. 2007

IEEE Trans. Semicond. Manufact.

View full text Add to dashboard Cite

Photosensitive polybenzoxazole (PBO) film has been used in GaAs heterojunction bipolar transistor (HBT) technology for stress buffer and mechanical protection layer applications. However, this film needs to be cured at high temperatures for a long period of time in order to obtain its desired excellent material characteristics. High-temperature curing can result in degradation to the electrical characteristics and performance of the underlying GaAs devices due to limited thermal budget. In this paper, we have characterized the effects of curing the PBO film on GaAs HBT wafers using a conventional convection furnace and using a variable frequency microwave (VFM) furnace. The results show that a VFM cure can achieve similar excellent physical, mechanical, thermal, and chemical material characteristics at a lower curing temperature and in a much shorter time, as compared to convection furnace curing, therefore resulting in minimal GaAs device degradation. Based on these results, an optimum curing condition using the VFM method can be obtained that satisfies both stress buffer layer material and device requirements for GaAs HBT technology.

show abstract

Section: Introductionmentioning

confidence: 93%

“…They are utilized in both front-end and back-end semiconductor processing, including as interlevel dielectric, redistribution layer, final passivation, stress buffer layer, and as encapsulants in chip-scale and wafer-level packaging [1]- [9]. Some of these polymers include parylene, polyimide, benzocyclobutene, and polybenzoxazole (PBO).…”

Section: Introductionmentioning

confidence: 99%

Variable Frequency Microwave and Convection Furnace Curing of Polybenzoxazole Buffer Layer for GaAs HBT Technology

Yota

Ramanathan

et al. 2007

IEEE Trans. Semicond. Manufact.

View full text Add to dashboard Cite

show abstract

“…Despite their importance, the adhesion and fracture behavior of the underfill interfaces have not been investigated until recently [10]- [21]. There have been a few studies dealing with a single specific interface within a flip-chip structure [22]- [25]. Others have investigated the adhesion based on fracture mechanics [26]- [29].…”

mentioning

confidence: 99%

Study on underfill/solder adhesion in flip-chip encapsulation

Fan

Tison

Wong

2002

IEEE Trans. Adv. Packag.

Self Cite

View full text Add to dashboard Cite

Underfill materials are employed in flip-chip assemblies to enhance solder joint reliability performance. The adhesion of underfills with solders is important to the integrity of the flip-chip structure. We have studied the adhesion strength of two underfill samples with tin/lead (Sn/Pb) eutectic solder and tin/copper (Sn/Cu) lead-free solder, benchmarked with a copper surface. It was found that the adhesion of underfills and both solder materials was about 1/3 of the adhesion between underfills and copper. The effect of temperature and humidity aging as well as flux residue on adhesion strength was also investigated. A loss of adhesion was observed after the pressure cooker test, but 85 C/85% RH aging and flux residue revealed only a slight influence on adhesion strength.Surface analysis was performed on solid surfaces including copper, Sn/Pb eutectic solder, Sn/Cu lead-free solder and cured underfills by using the three-liquid-probe three-component surface tension method with a goniometer. The surface tension of liquid underfills was measured by the pendent drop method, and their contact angles on copper, Sn/Pb eutectic solder and Sn/Cu lead-free solder were also measured with a goniometer. The thermodynamic work of adhesion for underfills with copper and solder surfaces of different conditions was then calculated following these two surface analysis approaches. It was found that the thermodynamic work of adhesion was not correlated with the lap shear strength of underfills with copper and solder materials. Thus, the wetting property of an underfill on a substrate is not the determining factor for its practical adhesion strength.Various possible techniques for improving the adhesion of underfills and solder materials were then considered, and the use of additives in underfill formulations was experimented. However, we have not observed any significant effect of adhesion strength enhancement from any of these additives. Further tests of these additives with the base underfill formulation seemed to reveal a slight possibility to enhance adhesion of underfills and solders by proper manipulation of the underfill and/or flux formulation.

show abstract

“…This technique is explored because of the reported improved adhesion between copper and BCB [7][8]. This data suggests that a tradeoff may exist between BCB-to-BCB and BCB-to-copper adhesion energies using this surface preparation technique.…”

Section: Resultsmentioning

confidence: 95%

“…Ideally, all should be capable of being bonded to one another without interfering with the electrical characteristics of the Cu-to-Cu interconnection. Surface preparation techniques for improving adhesion of BCB to silicon and silicon nitride [7] as well as copper [8] have been discussed in the literature, but not with respect to a wafer bonding application. Further, wafer bonding of soft baked BCB has been well documented for the 3D application [9][10], as has damascene patterning of copper in fully cured BCB [11][12].…”

Section: Multi-level On-chip Interconnectsmentioning

confidence: 99%

Wafer bonding of damascene-patterned metal/adhesive redistribution layers for via-first three-dimensional (3D) interconnect

McMahon

Lü

Gutmann

Proceedings Electronic Components and Technology, 2005. ECTC '05.

View full text Add to dashboard Cite

A novel via-first, back-end-of-the-line (BEOL) compatible, monolithic wafer-level three-dimensional (3D) integration technology platform is being developed, which employs wafer bonding of damascene-patterned metal/adhesive redistribution layers on two wafers, thus facilitating both high density of inter-wafer electrical interconnects and strong adhesive bond of two wafers in one unit processing step. Two key steps for this approach are 1) fabrication of a metal/adhesive redistribution layer on the top of the BEOL-processed wafer by damascene patterning and 2) face-to-face alignment and bonding of two wafers utilizing the metal/adhesive redistribution layers. Repeating a whole 3D process flow, the third wafer (or more) can then be added. Copper/tantalum (Cu/Ta) and Benzocyclobutene (BCB) are selected as the metal and adhesive for the feasibility demonstration of the via-first 3D approach.Critical processing challenges are investigated, including 1) BCB partial curing and patterning; 2) Ta and Cu deposition; 3) Cu/BCB chemical mechanical planarization (CMP); 4) post-CMP treatment; and 5) bonding process parameters.Wet chemical and dry plasma surface preparation techniques are used for post-CMP treatment and pre-bonding surface preparation, a critical step in facilitating a strong, reliable bond between BCB-to-BCB regions as well as a low contact resistance between Cu-to-Cu regions. Results on blanket BCB/Si wafers show a strong BCB-to-BCB bond with mean critical adhesion energy in a range of 14-31 J/m 2 . For patterned Cu/BCB wafers, interfaces of bonded BCB-to-BCB, Cu-to-Cu, and BCB-to-Cu areas are imaged by focused ion beam scanning electron microscopy (FIB/SEM), showing the feasibility of these bonds. Specific contact resistance of the Cu-to-Cu interconnect is on the order of 1x10 -7 Ω-cm 2 , a promising preliminary result indicting electrical contact is possible using this new 3D technology platform. IntroductionThree-dimensional (3D) integration technology holds promise for reducing interconnect delays in future integrated circuits (ICs) by reducing length and number of long interconnect lines [1-3] as well as offering heterogeneous integration of processes and devices through die-to-die, dieto-wafer, or wafer-to-wafer approaches [4][5][6]. Of these approaches, monolithic wafer-level processing also holds promise for decreasing cost through parallel fabrication methods for high volume manufacturing. Various wafer-level approaches have been demonstrated [1-3], with each approach having its own advantages. For example, the dielectric bonding technology platform offers a robust bonding

show abstract

Underfill adhesion to BCB (Cyclotene/sup TM/) bumping and redistribution dielectrics

Cited by 14 publications

References 13 publications

Variable Frequency Microwave and Convection Furnace Curing of Polybenzoxazole Buffer Layer for GaAs HBT Technology

Variable Frequency Microwave and Convection Furnace Curing of Polybenzoxazole Buffer Layer for GaAs HBT Technology

Study on underfill/solder adhesion in flip-chip encapsulation

Wafer bonding of damascene-patterned metal/adhesive redistribution layers for via-first three-dimensional (3D) interconnect

Contact Info

Product

Resources

About