Back-end-of-line

In Reaction (3), the level of impurities (C and O2) remains high and Reaction (2) is usually preferred, although carbon retention is still a problem. These reactions are being considered for semiconductor applications to replace sputtering since their principal advantage is the low deposition temperature compatible with back-end of line (BEOL) processing compatibility in the fabrication of electronic circuits. 

Copper has emerged as the leading contender for back-end-of-line metallization for advanced integrated circuits. Lack of a viable copper etch process and depth-of-focus limitations of advanced lithography leads to the chemical-mechanical polishing (CMP) of Damascene structures as the preferred method by which copper-based metallization is formed. CMP is the only known feasible method by which copper metallization can be patterned to the requisite, feature size and global planarity. 

Electroless copper seed layer on TaN surfaces for Cu metallization in the back-end-of-line semiconductor fabrication was also investigated.38 After etching in diluted HF solution and activation with PdCb, the electroless deposition of copper (to be used as a seed layer) was carried out from CuSCVEDTA solution containing Triton X-100, tetramethyl ammonium hydroxide (TMAH), and formaldehyde as a reducing agent of Cu(II) ions. 

Copper chemical mechanical planarization (Cu CMP) challenges in 22 nm back-end-of-line (BEOL) and beyond... 

A typical semiconductor device (found in the back-end of the line or the interconnects) consists of a layer of glass followed by a sputtered layer of titanium, which is thermally treated to form a titanium silicide. Next, a layer of titanium nitride is deposited on top of the silicide and on the sidewall of the contacts by sputtering or by MOCVD (see Fig. 13.3 in Ch. 13).P ]P ] This layer of TiN acts as a diffusion barrier and an adhesion promoter. It is followed by the main interconnect, which is an aluminum-copper alloy, in turn followed by another layer of TiN, which acts as adhesion and antireflecting layer. 

Today s CMP applications concern both front-end steps such as shallow trench isolation (STI) and inter metal dielectric (IMD) in the back end of the line. 

The element consists of wound corrugated metal strips. The quenching gap size can be adjusted in accordance with the flash-back capability of the explosive mixture. The principle of flame quenching in small gaps is applied in end-of-line flame arresters and in-line flame arresters. 

The thick line in Fig. 5.9 is the result of filtering the raw data in the forward and reverse directions using a fourth-order, low-pass Butterworth filter set at a cutoff frequency of 6 Hz (note that the front and back ends of the raw data were padded). This raises an interesting question, that is, how do we identify an appropriate cutoff frequency for the filter There are a number of methods that can be used to help select an appropriate cutoff frequency. A fast Fourier transform (FFT) can be used to... 

Figure 2 (a) a copper CMOS logic chip from which the SiOx insulator has been selectively removed (h) A schematic dqiiction of the back-end-of-die line wiring... 

Figure I. Back end of the line (BEOL) wiring structure.

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