MEMS Process Equipment, Through silicon vias (TSV’s), an enabling feature of 3D interconnects, are critical to the continued overall performance and form factor improvement of semiconductor devices and systems. TSV allows the integration of RF, logic, memory and sensor devices in a single compact package. They support improved speed as well as reduced RC delays and parasitic power consumption. They provide high device density with conventional die designs. And TSV may deliver a superior cost structure as compared to moving to the next sequential lithography node.
Critical to proper TSV integration are the wet processing steps necessary to electrochemically deposit (ECD) the copper and solder interconnect features, as well as related stripping and etching. Electrochemically-deposited copper offers the device designer and integrator a high purity, low resistivity solution which has virtually no size or shape limitation.
ECD copper for TSV applications typically requires plating bath chemistries specifically developed for deep via plating in order deliver void-free feature fill with optimal grain structure. Power supply wave forms are a second critical ingredient to proper TSV formation; reverse pulse plating operating well below the LCD (limiting current density) is typical. A third critical TSV requirement is management of fluid velocity and boundary layer across the top of the plated feature. These flow dynamics have a dramatic effect on the convection of copper ions within the plating solution (and therefore the plating rate profile), especially in the upper regions of the via. In higher aspect ratio vias, molecular diffusion through the plating liquid becomes the primary factor which controls the mass transfer rate, and therefore, deposition rate in the lower portions of the vias. Successful TSV deposition typically requires dramatically longer process times as compared to conventional damascene copper plating in order to achieve uniform, void-free filling without unnecessary over plating.
Amerimade has been developing and delivering both R&D and full production electro-chemical deposition systems for 15 years. Our experience includes copper, gold, cobalt, ruthenium and NiFe. Amerimade’s earliest efforts focused on the challenging deposition of NiFe (a.k.a.-Permalloy) used as the active magnetic feature in direct access storage devices, including GMR (Giant Magneto-Resistive) and Spin-Valve heads. The same Amerimade production systems developed and delivered to leading edge developers and manufacturers of these devices in the 1990’s remain in production today. Many of the equipment features we developed for NiFe, including solution flow, boundary layer management, electrical contact schemes, temperature control and current density control, provide the performance required for TSV applications.
Amerimade’s TSV equipment suite includes manual, semi-automatic and fully-automatic versions (for high volume manufacturing HVM) of the following types of processing systems:
Electro-deposition (electroplating) systems including:
Paddle plating cells for boundary layer management
Vertical and horizontal models
Single and multi-wafer cells
Sinusoidal and constant speed options
Single and multiple blade options
Adjustable anode shields for virtual anode control
Cathode (wafer) fixtures:
Front or back-side contact
Discrete or ring contacts
Multi-segment, separately biased current thieves
Automatic contact verification and identification
Recirculating plating solution reservoirs:
Stand-alone or integral with plating system
Carbon filtration loop
Precision bleed and feed enabled
Compatible with leading bath metrology systems
Acidic or surfactant/water
Ultra-sonic or vibratory enhanced