Olivier Mann

Chromatography of bis-(3-sulfopropyl) disulfide and its breakdown products by HPLC coupled with electrochemical detection

A chromatographic method for the detection of bis-(3-sulfopropyl) disulfide (SPS), a common additive in acidic copper plating baths, and its breakdown products is demonstrated. The detection scheme involves a combination of solid-phase extraction for sample pre-treatment, C(18) reversed-phase high-performance liquid chromatography column for separation, and electrochemical sensor for detection of all non-fully oxidized sulfur-containing compounds. We were able to achieve an effective separation and accurately assign chromatographic peaks to all detectable species. Owing to a high sensitivity of the utilized electrochemical detector, detection in low parts per billion range was possible. This can prove crucial for plating bath control, since minute amounts of certain by-products significantly affect the bath performance.

Advanced via filling for improved within-unit distribution

Laser drilling of blind micro vias (BMVs) and subsequent copper filling is now the standard manufacturing technique for high density interconnects. To enable the required interconnect density and to provide the surface for reliable solder attachment in IC packaging these copper filled BMVs are used. To maintain the development in circuit miniaturization together with the reduction in overall processing costs as expected by Moores Law and to meet the demand for ever more filled BMVs on each plated layer, advances in filling processes are required. The filling processes used for a stable production must provide void/inclusion free filling and a minimum of surface plated copper. For the production of the finest lines and spaces for IC substrate technology additives that allow the use of pattern plating in the semi additive process (SAP) to produce structures in the range of 10 μm line and space are available. As the force for miniaturization of consumer electronics continues, even finer lines and spaces are required. Challenges like within-unit distribution become a critical factor for the subsequent processing steps. Modifications in the production process as well as development of new additives show that Moores Law is still valid.

Via filling: Challenges for the plating process for conveyorised production

Copper filling of laser drilled blind micro vias (BMVs) is now the standard production method for high density interconnects. Copper filled BMVs are used as solder bump sites for IC packaging where the filling process enables the required interconnect density and provides the surface to ensure reliable solder attachment. For “smart phone” production use of multiple lamination and typically 10 layers of stacked copper BMV filling is now the preferred technology, this is also known as the “any layer” filling process. Advances in filling processes are required to maintain the development in circuit miniaturization together with the reduction in overall processing costs and to meet the demand for ever more filled BMVs on each plated layer. The required filling processes must provide void or inclusion free filling, a minimum of surface plated copper along with the capability to allow stacked filled structures. This paper describes the function and principles behind BMV filling processes together with methods for non destructive testing of the filled structures. Production processes for BMV filling in vertical and horizontal production equipment with both soluble and insoluble anodes are presented together with a discussion of the plating parameters currently used in volume production. A comparison in filling performance of DC plating with that achieved in reverse pulse plating is also made. Current production systems for BMV filling are usually conveyorized to meet the required production targets in terms of volume and uniformity. High relative electrolyte loading in such systems requires uniform processing parameters and tight control. Examples of fully automatic analysis and control systems for copper plating additives and inorganic components are shown.