Inter metal dielectric

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. 

Since one major motivation behind the use of plasma BPSG was to provide an improved passivation barrier, the better crack resistance is an advantage, but the greater sodium penetration is a negative. Therefore, it is not clear if it would be advantageous to make this replacement11 for a final passivation film. Its use as an inter-metallic dielectric may be more useful. 

Avigal, I., Inter-metal dielectric and passivation-related properties of plasma... 

A field shielded pixel structure is used. The cross-section of the active-matrix stack is shown in Fig. 14.6. The first four layers, defining the TFT, are identical with the stack presented in Section 14.2. The rows of the display are processed on the first metal level whereas the columns are processed on the second metal level. In the field-shielded pixel design, the pixel electrode is defined in a third metal level of gold, resulting in a six-mask process. The pixel pad overlaps the storage capacitor, TFT, and column lines with a 6 pm thick polyvinylphenol layer acting as inter-layer dielectric. The optical aperture thereby increases to over 95%. The TFT channel length (L) and width (W) are 5 pm and 140 pm, respectively. 

W. Ong, S.Robles, S. Sdhn, B. C. Nguymi Characterization of Inter-metal and Pre-metal Dielectric Oxides for Chemical Mechanical Polishing Process Integration , Proc. of lEEE-VMIC (1993) P.197... 

One important difference between the damascene and the plating through mask procedures is the way the trenches and vias are filled with electrochemically deposited Cu, either tlirough electro or electroless techniques. In multi-level metal slruclures. the vias provide paths for connecting two conductive regions separated by inter-level dielectric (ILD). In a damascene process the Cu deposit grows from the active bottom and the sidewalls, as shown in Fig. 7a. 

Macroscopic experiments allow determination of the capacitances, potentials, and binding constants by fitting titration data to a particular model of the surface complexation reaction [105,106,110-121] however, this approach does not allow direct microscopic determination of the inter-layer spacing or the dielectric constant in the inter-layer region. While discrimination between inner-sphere and outer-sphere sorption complexes may be presumed from macroscopic experiments [122,123], direct determination of the structure and nature of surface complexes and the structure of the diffuse layer is not possible by these methods alone [40,124]. Nor is it clear that ideas from the chemistry of isolated species in solution (e.g., outer-vs. inner-sphere complexes) are directly transferable to the surface layer or if additional short- to mid-range structural ordering is important. Instead, in situ (in the presence of bulk water) molecular-scale probes such as X-ray absorption fine structure spectroscopy (XAFS) and X-ray standing wave (XSW) methods are needed to provide this information (see Section 3.4). To date, however, there have been very few molecular-scale experimental studies of the EDL at the metal oxide-aqueous solution interface (see, e.g., [125,126]). 

Fluorine-based plasmas are currently employed in microelectronics industry for etching processes of metal (W), semiconductors (Si, Ge), or dielectrics (Si02, Si3N4). Mechanistic studies have shown that the key parameters of the plasma-surface inter-... 

Metal-RIE process was/is used in the fabrication of Al inter-coimects on chips." This process is depicted in four steps in Fig. 2. The first step in the metal-RIE process is sputter deposition of a blanket thin film of Al (or Al alloys, such as Al-Cu, Al-Si) over a planerized dielectric (e.g., silicon dioxide). In the next step, the unwanted metal is etched away by reactive ion etching (RIE) through a photoresist mask. The features produced this way are separated, electrically isolated, metal Al conductor lines. In the RIE process chemicaly active ions such as F or Cl bombard the Al surface and form volatile aluminum fluorides or chlorides, which are then pumped away in the vacuum system. After etcliing, a dielectric is deposited in such a fashion that it fills the gaps between the lines as well as above them. In the last step, the dielectric is planarized using the chemical mechanical polishing (CMP) technique. ... 

Nevertheless the use of dielectric materials obtained by conductive filler dispersion (carbon black, graphite fibres, metallic powders) is limited. As a matter of a fact material performances are dependent on the filler content as well as particle aggregation phenomena. These composites require a high level of reproducibility and their behaviour is linked to the control of electronic inter-particular transfer. The measured parameter (complex permittivity) depends on the texture of the percolation aggregates and consequently on the processing conditions. The percolation threshold (the particle concentration, after which particles are in contact and the electrical current exists) depends on the particle shape (sphere, plates or fibres). 

A corresponding response has been obtained from complex impedance measurements on a monolayer of Ag nanopartides with 2R = 3.5 nm. Heath and coworkers, when analyzing the complex dielectric modulus (which is the inverse of the complex dielectric permittivity for details, see Ref [84]), reported a reversible metal-insulator transition. In this case, a transition was observed from RC relaxational behavior to an inductive metallic-like response, when the monolayer was compressed to decrease the inter-particle spacing to <0.6 nm (Figure 5.57). This suggests that a sequential transition from hopping transport between localized states via turmeling to metallic transport appears, accompanied by a rapid decay in the relaxation time. 

Adhesion of metals to polymers has been an intensively studied subject over the past decades This is due to the wide application of polymers to electronic packaging and, to a lesser extent, to device inter-connect The increasing demand in density for devices and speed for packaging, in turn, prompts searches for polymers with reduced dielectric constants than that of the widely used polyimide. Some fluorocarbon polymers, notably Teflon, have lower dielectric constants, 2.1, vis-i-vi the values of 3.0-3.5 for polyimides. The fluorocarbon polymers, however, have very weak adhesion to metals. An enhancement in adhesion is thus a primary requirement for the application of such polymers to technologies. A wide range of studies have been made in the past to understand and enhance the adhesion between metals and fluorocarbon polymers In this paper we review some of our earlier work, and present new observations related to the enhanced adhesion between metals and fluorocaiton polymers. We present results address three contributions to enhanced adhesion between metals and fluorocarbon polymers chemical, mechanical, and thermal. 

Moura-Ramos and Williams have studied LC siloxane polymer P/Si/8/CN in the pressure range 0.1-152 MPa, the temperature range 50-75°C, and the frequency range 10-10 Hz. The substance exhibits a smectic phase between 363 K (the clearing temperature) and 274 K (the glass transition temperature, T ). Dielectric studies were performed with disk samples placed between metal electrodes of a three-terminal high-pressure cell. The results are presented as loss curves in terms of G/w = e"C , where G is the measured equivalent parallel conductivity of the sample, e" is the dielectric loss factor, and Q the inter-electrode geometric capacitance. 

In noble or coinage metals (Cu, Ag, Au), the optical response does not reduce to the response of the free electron gas. Noble metals consist of atoms with completely filled 3d, 4d, and 5d shells and just a single electron in the 4s, 5s, and 6s bands, respectively this last electron in not completely free to move and the dielectric response is essentially influenced by optical transitions of electrons in deeper (e.g. core) levels. These inter-band excitations alter the dielectric function considerably. This contribution can be described using a full quantum mechanical treatment, which is introduced in the next section. 

---