GelEtch

The World's Only Chemical Die De-layering System

GelEtchThe GelEtch bare die delayering system uses etch chemicals that are both adsorbed and absorbed onto the surface of a proprietary Carrier Medium (designation 36-6).

Operating Principle

Controlled chemical etching for de-layering of IC die has never been possible due to etch chemicals leaking through vias from one metal layer to another, causing cross contamination and etching of successive die layers. Until now it has only been possible to remove surface passivation layers to expose the uppermost metal layer. This metal layer can be removed by manual chemical etching, but invariably chemicals leak and diffuse through the interconnect vias to contaminate lower layers in the die stack.

To overcome this problem, the process of backside emission microscopy was developed. Backside emission microscopy itself is a very demanding methodology, due to the difficulties of preparing suitable thinned and polished die, while avoiding mechanical and thermal damage to the samples.

GelEtch overcomes the problems associated with front side die de-layering by using etch chemicals that are both adsorbed and absorbed onto the surface of an inert, proprietary Carrier Medium (36-6). This material is available exclusively from Nisene Technology and is perhaps best described as a complex quaternary polysaccharide (for more details please see GelEtch Technical Bulletins 3001, 3002, and 3003).

CARRIER MEDIUM 36-6, Described

Any etch chemistry of choice can be adsorbed/absorbed onto the Carrier Medium surface. This Carrier Medium, now charged with the appropriate etchant, is passed across the surface of the die in a Teflon etch chamber designed to allow an exact laminar flow of etchant across the die surface.

The etchants used in de-layering can be re-circulated. The etchant is pumped from the heated reservoir etchant bottle through the Etch Chamber, and then returns to the reservoir bottle.

The GelEtch is equipped with three supply bottles and one purge bottle housed in a Bottle box compartment that is equipped with double containment and liquid sensors to monitor any possible spilled chemicals.

The system is constructed with all Teflon wetted parts. All mechanical components are manufactured form corrosion resistant polymers.

The pump has variable speed control. The pump head mechanism is separated from the electronic components by a bulkhead that isolates the electrical components from the fluid handling side of the system. The pump and all fluid handling components of the GelEtch are purge-able with nitrogen gas to ensure complete removal of any residual etchant from both the Etch Chamber and supply lines prior to opening the chamber for sample exchange.

GelEtch DESIGN AND OPERATING PARAMETERS

Manual vs. Automated De-layering Procedures

Manual

Manual de-layering is both difficult and time consuming. Sequential layers of a die stack are normally removed by flooding the surface of a die or by immersion of the die in an etch mixture that is chemically specific for the layer to be removed. Depending on the etch recipe, this may or may not require the application of heat.

Chemical de-layering is a trial and error process in which one must balance the removal of a desired layer with chemical specificity of the selected etch mixture. While it is sometimes easy to select an etch recipe that is chemically selective for a given layer composition, it is extremely difficult to prevent the etch chemicals from diffusing into the body of the die stack through the vias to lower layers.

Automated

It is possible to eliminate the problems of etchant penetration into the die stack through the vias by attaching the etch medium onto the surface of a Carrier Medium.

Our 36-6 Carrier Medium is a hydrophilic polymer composed of complex polysaccharides (see Technical Bulletins 3102 and 3103 for more information). The physical properties of 36-6 are such that this polysaccharide complex can retain water through a combination of hydrogen bonding and/or it can be held captive within the extensive network of inter and intra molecular voids found in the quaternary molecular structure.

Chemical etch recipes typically contain water, or are water-soluble. The presence of water as a constituent of the etch recipe, or the miscibility of a recipe with nascent water bound in the molecule of 36-6 results in the etch formula being absorbed onto the surface of the Carrier Medium particles.

The 36-6 Carrier Medium is chemically inert and is fully compatible with all known etch chemistries. Experiments have shown that this Carrier Medium is suitable for a wide range of etch chemistries and conditions and is successful from room temperature up to 45°C.

Questions about the GelEtch?

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