Etching Aluminum

Minor and potential new uses include flue-gas desulfurization (44,45), silver-cleaning formulations (46), thermal-energy storage (47), cyanide antidote (48), cement additive (49), aluminum-etching solutions (50), removal of nitrogen dioxide from flue gas (51), concrete-set accelerator (52), stabilizer for acrylamide polymers (53), extreme pressure additives for lubricants (54), multiple-use heating pads (55), in soap and shampoo compositions (56), and as a flame retardant in polycarbonate compositions (57). Moreover, precious metals can be recovered from difficult ores using thiosulfates (58). Use of thiosulfates avoids the environmentally hazardous cyanides. 

Barrier anodic oxides covering the surface of aluminum etched foil are usually formed in borate or phosphate solutions. To improve capacitor characteristics, high-purity aluminum is desirable with as low a concentration of impurities as is acceptable in terms of cost. 

An aluminum etching mask is deposited (Fig. 14 e) and patterned corresponding to the shapes of the devices. RIE is used to etch the polyimide down to the support wafer and to separate all devices in one etching step. After removing the aluminum and the resist, the single devices are separated from the support wafer. The resulting components have a total thickness of 10 pm (Fig. 14 f). 

Fig. 11.2 AFM image of aluminum etched for 20s at 10V in a Type III eutectic of 1 choline chloride 2 ethylene glycol (right side of image masked during experiment).

All plasma exposures were carried out in an IPC (International Plasma Corporation) 2005 capacitance-coupled barrel reactor at 13.56MHz. The reactor was equipped with an aluminum etch tunnel and a temperature controlled sample stage. Pressure was monitored with an MKS capacitance manometer RF power was monitored with a Bird R.F. power meter and substrate temperature was measured with a Fluoroptic thermometer utilizing a fiber optic probe which was immune to R.F. noise. 

Use In derusting and descaling processes for metal concrete admixtures to retard set and reduce water required textile applications aluminum etching and caustic bottle washing. 

See Tokunaga and Hess for a discussion of aluminum etching using carbon tetrachloride. 

Aluminum etching takes place in the NaOH bath. Dissolution rate of aluminum during NaOH etch can be determined [5]. From the AFM scans, surfaces of the aluminum are roughened slightly during the 15 s bath time. 

Aluminum is used as a metallization material in current microelectronic devices. It can be etched by chlorine containing plasmas, provided that the native aluminum oxide is removed. This is accomplished with oxide scavengers such as BCI3 added to the plasma. Aluminum etching is isotropic in fact a clean aluminum surface reacts with atomic and molecular chlorine even in the absence of a plasma [225]. Anisotropy is achieved by the wall passivation mechanism (Fig. 16d). 

Aluminum is often used as an alloy with a few atomic % Si and/or Cu to reduce electromigration (Fig. 1). This alloy is difficult to etch because copper does not form readily volatile compounds [73]. Fleating of the wafer to some 200 °C and intense ion bombardment to sputter off involatile products are then necessary to effect etching. Residual chlorine remaining on the wafer after aluminum etching can be deleterious because it can promote corrosion, especially in Al-Cu alloys. Hence wafer rinsing with DI water is common. Dry passivation by exposure to a fluorocarbon plasma has... 

Aluminum Etching Procedure. The following procedure should be done in a class 100 clean room ... 

Meeks E., Ho P., Buss R. Modeling aluminum etch chemistry in high density plasmas. Proc. 

Aluminum can be cleaned in the same fashion as steel. Alternatively, it may be prepared for bonding by chemical etching. For instance, cyanoacrylates cure rapidly to give strong, durable bonds on aluminum etched by Forest Products Laboratory (FPL) chromic acid etching solution. 

The boron carbide coated chamber is also qualified through a 2,000 wafer marathon for etching of 0.15 pm feature size. Excellent aluminum etching performance is demonstrated as shown in Fig. 17 [48]. 

On a 300mm etch tool, boron carbide coated chamber was also used in a 1,000 wafer marathon. The boron carbide coated chamber meets all the requirements including aluminum etch rate and etch rate non-uniformity, etch profiles, defects and particles, metal contamination [49]. The particle performance at 0.12 pm or larger is the critical requirement. It is obvious that the boron carbide coated chamber can meet the requirement. The up limit of particle allowance at 0.12 pm or larger is defined as 50 adders/ per wafer. 

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