Xiaoyun Cui

The Evolution of Pd ∕ Sn Catalytic Surfaces in Electroless Copper Deposition

This paper describes the different catalytic surfaces of Pd/Sn formed before electroless copper deposition onto a glass substrate. In this study, silanization of the glass surfaces with (3-aminopropyl) trimethoxysilane was used to provide a surface-coupled layer of functional molecules to assist in the adsorption of Pd/Sn catalyst and the subsequent copper deposition. The composition and microstructure of the modified glass surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry. These showed that catalytic Pd/Sn structures on the surface changed with increasing immersion time in the catalyst bath. The core-level XPS spectrum of Pd indicated that metallic Pd(0) became more significant in the catalyst layer than Pd(II) with the increasing immersion time. A model of the adsorption process is proposed to explain these changes. It was observed that too high a quantity of Pd(0) does not always improve the adhesion of the Cu deposits in the electroless process.

Glass as a Substrate for High Density Electrical Interconnect

The high volume production of substrates able to support high density interconnection is becoming increasingly difficult as the pitch of devices continues to decrease. An important issue is the alignment of microvias and pads which is made particularly challenging by the dimensional instability of traditional organic substrates. In this work, glass has been investigated as an alternative substrate material. Glass offers potential advantages including: electrical insulation, dimensional stability, thermal expansion similar to Si and optical transparency. This paper examines manufacturing processes for the preparation of substrates built up from 50 to 100 ¿m thick glass sheets. Excimer laser machining was used to form microvias and tracks in the glass which were metallised using electroless plating methods. Using a photoresist layer during the laser machining process helped to reduce debris on the glass surface and could be used to direct the subsequent deposition of electroless copper or nickel such that circuit patterns could be created. Lamination of the thin glass sheets was investigated using direct glass to glass bonding and through the use of an intermediate layer. A method for the combination of these techniques to create multilayer substrates is proposed.

Challenges in the manufacture of glass substrates for electrical and optical interconnect

For high density electrical interconnect, the production of fine feature, fine pitch substrates is difficult, due to limitations in manufacturing processes and the dimensional stability of conventional laminate materials. In order to enable the further uptake of flip-chip technology, new materials and methods for substrate manufacture are required. Glass as a substrate material offers a number of potential advantages including dimensional stability and close coefficient of thermal expansion match to Si. Furthermore, its optical clarity makes it suitable as a conduit for the transmission of light signals for applications in the growing area of optical interconnect. This paper describes preliminary work to investigate the key challenges of laser machining, metallization and lamination that are involved in the manufacture of multilayer substrates from thin glass sheets. Laser machining has been used to create microvias and other features in the glass and work is underway to determine appropriate process windows. The metallization of glass using electroless copper has been investigated and found to be very dependent on the surface pre-treatments. Finally, pressure assisted-low temperature bonding has been considered as a method for the lamination of the glass sheets to create a multilayer structure

Copper Deposition and Patterning for Glass Substrate Manufacture

Glass is a potential substrate material for the manufacture of substrates for high density electrical and optical interconnect. However, in order to realize such substrates, metallization is required to form conductive tracks and pads. In this work, electroless copper was used due to its relatively low cost, fast speed and potential for high volume production. Silanisation of the glass surfaces with (3-aminopropyl) trimethoxysilane (APTS) was used to provide a surface-coupled layer of functional molecules to assist in the adhesion of Pd/Sn catalyst and the subsequent copper deposition. The composition and microstructure of the modified glass surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Tape peel testing was used to qualitatively assess the adhesion of the copper to the smooth glass surface. For layers less than 150 nm thick, adhesion was good, but thicker coatings tended to peel away easily. Preliminary analysis of the peeled surfaces indicated that failure occurred at the interface between the copper and the catalyst. As an alternative approach for improving adhesion, laser machining was used to roughen the glass and direct the deposition of electroless copper, such that circuit patterns with good adhesion were formed.

Challenges in the Manufacture of Glass Substrates for Electrical and Optical Interconnect

For high density electrical interconnect, the production of fine feature, fine pitch substrates is difficult, due to limitations in manufacturing processes and the dimensional stability of conventional laminate materials. In order to enable the further uptake of flip-chip technology, new materials and methods for substrate manufacture are required. Glass as a substrate material offers a number of potential advantages including dimensional stability and close coefficient of thermal expansion match to Si. Furthermore, its optical clarity makes it suitable as a conduit for the transmission of light signals for applications in the growing area of optical interconnect. This paper describes preliminary work to investigate the key challenges of laser machining, metallization and lamination that are involved in the manufacture of multilayer substrates from thin glass sheets. Laser machining has been used to create microvias and other features in the glass and work is underway to determine appropriate process windows. The metallization of glass using electroless copper has been investigated and found to be very dependent on the surface pre-treatments. Finally, pressure assisted ? low temperature bonding has been considered as a method for the lamination of the glass sheets to create a multilayer structure.

An investigation of electroless copper films deposited on glass

This paper describes the characterization of electroless copper deposition on glass substrates with respect to surface morphology and adhesion. Silanisation of the glass surfaces with (3-aminopropyl)-trimethoxysilane (APTS) was used to provide a surface-coupled layer of functional molecules to assist in the improvement of adhesion of a Pd/Sn catalyst and the subsequent copper deposition. Surface morphology of the deposited films was characterized by field emission scanning electron microscopy (SEM) and together with atomic force microscopy (AFM), showed that the roughness and grain size tended to increase with the plating time. Tape peel testing was used to assess the adhesion of the coatings. All the deposits prepared with an electroless bath temperature of 40degC with a thickness up to 150 nm were found to adhere well to the glass substrate. Copper films were peeled off easily with increased thickness. This paper focuses on the development of thin copper films (Lt 200 nm thick) and considers the early stages of deposition in order to investigate further the role of the catalyst on adhesion.

A multi‐electrode array (MEA) biochip with excimer laser‐produced micro‐well features

Purpose – The purpose of this paper is to highlight a novel manufacturing process for a biochip with a multi‐electrode array (MEA) that is specifically designed for use in characterising cardio‐active substances and to demonstrate a novel proposed solution prototype that has been constructed to meet the needs of end‐users.Design/methodology/approach – Practical problems encountered with conventional MEA biochips are described and a novel biochip design to tackle these problems is presented. The manufacturing approach used to produce the prototypes of that design is described and depicted.Findings – The novel prototype MEA biochips were successfully manufactured using conventional electronics manufacturing approaches. Prototypes demonstrated limited successes in the early stages of testing. Further revisions of the feature geometry are required to implement an alternative MEA biochip that is suitably reliable.Research limitations/implications – Basic photolithography techniques have been used to construct ...

Investigation of the Adhesion of Electroless Copper to Glass Substrates

This paper reports the effect of a Pd/Sn catalyst treatment process on the adhesion of electroless copper deposited onto a glass substrate. Adhesion of the copper varied with catalyst treatment time: short or extended catalyst immersion times led to lower adhesion. In this work silanisation of the glass surface with (3-aminopropyl)-trimethoxysilane was used to provide a layer of functional molecules to assist the adhesion of the Pd/Sn catalyst. Surface analysis of the catalyzed glass was carried out by X-ray Photoelectron Spectroscopy (XPS) and together with Time-of-Flight Secondary Ion Mass Spectrometry, showed that the Pd/Sn structures changed with increasing immersion time in the catalyst bath. The Pd XPS core level peaks indicated that Pd(0) became more significant in the catalyst layer than Pd(II) with increasing immersion time. Tape peel testing was used to assess the adhesion of the coatings: thin layers adhered well to the glass, but for layers thicker than 160 nm tape tests removed large areas. The failure surfaces of copper layers peeled off the glass were also examined by XPS which indicated that the failure occurred between the copper and catalyst.