Self-annealing

It is sometimes necessary to remove rapidly renaturing sequences from DNA samples before measuring the extent of relatedness, and this can be done on HA columns as described by Price et al.6 Self-annealing of the radiolabeled probe DNA can be minimized if the ratio of target to probe is kept to at least 1000 1. It may also be useful to determine the amount of self-annealing to be certain that this does not bias the calculated relatedness. Finally, a simplified version of the HA procedure was described by Lachance24 in which HA-containing minicolumns maintained under controlled temperatures are used to separate the duplexed DNAs. 

Fig.2 displays the normalized Cu removal rate as a function of storage time. For reference, the sheet resistance self-annealing curve is also displayed in the graph. As the graph demonstrates, during film transformation, the CMP removal rate increased by -35%. TTie increase of Cu removal rate over time was in part caused by the 43% mechanical softening of the... 

Cu film. It is obvious that room temperature self-annealing would result in high variations in CMP process in a real production environment, which is unacceptable for IC manufacturing. In order to ensure consistent Cu film properties and stable CMP removal rates, the electroplated Cu films have to be stabilized. 

Fig. 2 CMP removal rate increased 35% during Cu film self annealing.

Film hardness of electrodeposited Cu film was found to reduce over time at room temperature by 43%. The hardness reduction was caused by Cu film self anneal where Cu grains grow fi om the initial 0.1 pm at as-deposit to 1 pm at the final stage. The significant hardness reduction and changes in film microstructure resulted in a 35% CMP removal rate increase. This removal rate increase translates to variations in manufacturing environment and are therefore simply unacceptable. It was found that anneals at temperatures around 100°C for several minutes in inert gas will stabilize blanket Cu films and provide consistent CMP removal rate. 

Since 1/3 of the absolute melting temperature is usually sufficient for an effective stress-relief, some materials may self-anneal during the filing. One of the examples is lead (Pb), which is a ductile metal and has melting temperature 601 K. Lead powder self-anneals at room temperature (-298 K), thus producing sharp Bragg peaks in the as-filed state. 

Resistivity of copper film and its self-annealing characteristic are important aspects of its quality. Fig. 5 shows sheet resistance of two copper films deposited at different stages of the bath. The copper film deposited in aged bath has the same sheet resistance as the film deposited in the fresh bath. Furthermore, the selfannealing curves of these two films are almost identical. 

Deposition process parameters are known to affect the properties of copper films. These process parameters include applied current density and additives in the bath chemistry, as well as the concentrations of these additives (1). Our focus in this work was to investigate the effect of current density on the self-annealing behavior of copper. Blanket copper films deposited at higher current densities were found to change more over time than those deposited at lower current densities. Films deposited at low current densities contain more impurities than those deposited at high current densities. Resistivity transients for a blanket film were compared and found to be similar to copper electrodeposited in lines. 

Changes in the degree of self-annealing and the rate of self-annealing were studied by altering toe applied deposition current density as well as changing the deposition waveform. Typical impurities of C, S, O and Cl are incorporated in electrodeposited copper films. These impurities were measured in order to correlate impurity concentrations to the self-annealing phenomenon. 

In addition to monitoring the self-annealing of copper films with resistance and stress measurements on blanket films, resistivity changes in copper electrodeposited into lines were also measured. 

In order to determine the mechanism by which these films self-anneal, it will be necessary to monitor the microstructure of the deposits as they self-anneal. In addition to ion beam imaging, orientation in the film via XRD as a function of time needs to be studied. With this additional information, the role that impurities and microstructure play in self-annealing may be better understood. 

The method described here for the manufacture of an aluminum-stabilized multifilamentary superconductor is essentially a two-step process, as illustrated in Fig. 1. First, a composite of multifilamentary NbTi embedded in an aluminum alloy (1100 Al or 6061 Al) matrix is prepared in the usual manner. The extruded NbTi-Al alloy composite is then inserted into a high-purity Al tube, and the whole composite is drawn in a Cu jacket. In this way, the high-strength NbTi filaments are supported in a stronger and work-hardenable Al matrix. As far as the softer, self-annealing pure Al is concerned, the center core, i.e., the NbTi-Al composite, can be considered as a unit, such as a NbTi monofilament. The whole composite can be reduced without localized nonhomogeneous deformation. 

Mur] Murakam, K., Okamoto, T., Miyamoto, Y, Nakazono, S., Rapid Solidifieation and Self-Annealing of Fe-C-Si Alloys by Low-Pressure Plasma Spraying , Mat. Scl Eng. A -Struct. Mai Prop. Microstr. Proc., 117, 207-214 (1989) (Experimental, Meehan. Prop., Morphology, 14)... 

The same authors noted that almost 20% of the polyribonucleotides obtained in vitro formed ribonuclease-resistant double-stranded RNA after self-annealing. They concluded that this ribonuclease-resistant RNA arose from partly symmetric transcription and that at most 12-15 of the RNA formed in vitro was complementary to the L strand. The asymmetry of transcription was thought to result from damage of the organelles. These experiments were extended (Aloni and Attardi, 1971). Using HeLa... 

A high proportion of the fast sedimenting mt RNA was made ribo-nuclease-resistant by self-annealing or by annealing with unlabeled mt RNA. Up to 85% of the fraction with the highest molecular weight was... 

After self-annealing (48 hours) or annealing with unlabeled mt RNA (10-35 S). 

Lower concentration of PE-PCR primers used is to avoid of self-annealing of the long adaptors, which will further block the DNA polymerase annealing on the cDNA templates. Single primer control in this PCR reaction should also be done to monitor potential faulty amplification. 

Similarly, Cu oxide DE growth post-CMP exhibits queue time effects as previous studies have indicated [19,20,22]. One study pointed out that a certain amount of lag time between plating and furnace anneal can help extend the post-CMP queue time DE free for up to 144 h [22]. The plating-anneal lag time dependence of DE implies that room temperature self-annealing of Cu during the lag time can alter the Cu microstructure to the extent that it enhances surface passivation and/or reduces Cu oxide... 

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