Conference Paper

Evaluation of Cu capping alternatives for polyimide-Cu MCM-D

IBM Microelectron., Hopewell Junction, NY
DOI: 10.1109/ECTC.2001.927977 Conference: Electronic Components and Technology Conference, 2001. Proceedings., 51st
Source: IEEE Xplore

ABSTRACT Among the 3 types of polyimide (PI) systems, pre-imidized,
polyamic ester and polyamic acid, the latter has been shown to react
with Cu surfaces when it is spun coated. This paper reviews Cu-polyimide
adhesion and diffusion data and present various wet process alternatives
to minimize Cu diffusion into poly(biphenyl dianhydride-p-phenylene
diamine) (BPDA-PDA) polyamic acid precursor. Two different process
options were investigated: a precoat or adhesion promoters (A1100, AP420
and benzotriazole) prior to the polyamic acid apply, and an additive
(Tetrazole or BTA) formulated in the PAA solution. The 5 processes were
compared with respect to adhesion, capacitance, dielectric constant and
reliability. Only the BTA formulation had adhesion problems which were
attributed to the A1100 precoat used. A1100 as a precoat was further
evaluated on various copper surfaces and curing environments. All
proposed solutions performed well when used on a MCM-D/C module which
was used to extract electrical parametrics and was further subjected to
reliability testing

  • [Show abstract] [Hide abstract]
    ABSTRACT: Copper is one of the common metals used in the semiconductor backend process and wafer level packaging. A photo definable polymer layer is usually used to passivate the Cu metal. Acceptable adhesion between the polymer layer and Cu is a very important factor to achieve high reliability for the IC component. The purpose of this paper is to investigate how to improve the adhesion strength between spin-on polymer dielectric material and electrolytic-plated Cu. Because adhesion strength is affected by the type of metal surface treatment prior to polymer coating, it is important to find a practical method for Cu surface treatment wafer process. Three types of treatment methods, including plasma, thermal, and wet process, were tried on the plated Cu surface. X-ray photoelectron spectroscopy (XPS) results are reported for the surface properties after treatment. Adhesion strength between the polymer layer and the Cu surface is reported as measured by manual tape, nano-indentation scratch, and four-point bending methods. Our results show that cleaning the Cu surface with dilute acetic acid significantly increases the adhesion between Cu and the polymer layer. We also report results for the change in Cu surface properties as a function of time after clean.
    Proceedings - Electronic Components and Technology Conference 01/2010; DOI:10.1109/ECTC.2010.5490840
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Wafer level chip scale packaging (WLCSP) has some advantages, such as real die size packaging, high electrical performance, and low manufacturing cost. However, because the mechanical reliability of a large die can not be guaranteed due to the coefficient of thermal expansion (CTE) mismatch between silicon and organic printed circuit board (PCB), WLCSP technology is still not fully accepted. We have developed a new solder joint protection-WLCSP (SJP-WLCSP) structure with a delamination layer interposed between the top layer of the chip and the bottom insulating layer of the metal redistribution traces. The stress on the solder joints can be released by the cracks forming in the delamination layer, which protects the solder joints from cracking. Since the cracking of the delamination layer is irrelevant to the electrical circuits of the packaging, the packaged integrated circuits (IC) device remains functional. One of the possibilities for processing the SJP-WLCSP was implemented and validated successfully in the SiLK-wafer samples. The board level packaging samples, using the daisy chain resistance measurement passed 1000 cycles of the temperature cycling testing.
    IEEE Transactions on Advanced Packaging 09/2007; DOI:10.1109/TADVP.2007.901773 · 1.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: As WLCSP packaging technology travels the road to ubiquity a transition is unfolding. WLCSP designs and material selection paradigms are moving from a process integration focus to one of product integration. The transition is driven by the application of WLCSP technology to larger die and enabled by the improvement in materials properties and process requirements. Both the driver and the enabler are consequences of the relentless pressure on cost that is the hallmark of the recent industry cycle. Achieving the goal of a low cost, high reliability, product-driven package solution required the balancing a variety of needs and characteristics. Often these are in conflict and detente is needed to ease the tension. The design goals of a Hi Rel WLCSP must provide superior protection, mechanical strength and electrical contact. A successful solution necessitated the need to avoid special tools or processes. The solution also needed to exceed the reliability requirements of the end customer. A key component of the WLCSP structure is the dielectric which is interposed between the solder bumps and the die. It must provide most of the protection functions while supporting the bumps and buffering the bump strains. A negative tone, photosensitive polyimide was ultimately selected. This polymer was designed with the goal of achieving thermal and mechanical cured film properties fully compatible with the stresses and thermal excursions associated with WLP thin-film processing and bumping. Integration of the new polymer require careful characterization and process optimization to assure critical material qualities such adhesion were achieved. Similar optimizations were run for assembly operations. Based on test results described herein, a double-layer polyimide, copper redistributed, eutectic SnPb or Pb-free bumped WLCSP was developed that exceeded all the design goals. Salient differentiators of the WLCSP solution are identified. Improved reliability was achieved, and new design standards were established relative to RF capability and power density.
    Electronic Components and Technology Conference, 2004. Proceedings. 54th; 07/2004