Replacement metal gate

Emerging front-end CMP applications can gain from the experience of STI CMP. The replacement metal gate process, for example, comprises two CMP damascene steps (one oxide and metal) with comparable geometry dimensions. The know-how in terms of consumables, tools, process parameters, and... 

Lagudu, U.R.K., Chockalingam, A.M., Babu, S.V., 2013. Chemical mechanical polishing of Al-Co films for replacement metal gate applications. ECS J. Solid State Sci. Technol. 2, Q77-Q82. 

The ISFET is an electrochemical sensor based on a modification of the metal oxide semiconductor field effect transistor (MOSFET). The metal gate of the MOSFET is replaced by a reference electrode and the gate insulator is exposed to the analyte solution or is coated with an ion-selective membrane as illustrated in Fig. 

The metal gate may also be replaced with silicon nitride or polymeric pH-selective membranes58. 

Ion-Selective Field Effect Transistors [22b,c,d] An ion-selective field effect transistor (ISFET) is a hybrid of an ion-selective electrode and a metal-oxide semiconductor field effect transistor (MOSFET), the metal gate of the MOSFET being replaced by or contacted with a thin film of a solid or liquid ion-sensitive material. The ISFET and a reference electrode are immersed in the solution containing ion i, to which the ISFET is sensitive, and electrically connected as in Fig. 5.37. A potential which varies with the activity of ion i, o(i), as in Eq. (5.38), is developed at the ion-sensitive film ... 

This feature of the FET is transformed into high sensitivity in the ISFET. That is, in order to go over from the FET to the ISFET it is sufficient to replace the insulating layer by an ion-selective membrane permeable only to one sort of iont and the metal gate by an electrolyte solution, which contains a reference electrode needed to short circuit the electric circuit (Fig. 19b). The potential, which develops across the membrane in the presence in the solution of that sort of ions for which the membrane is selectively permeable, acts here as an external voltage on the gate. This potential can be determined from Nernst s equation [cf. Eq. (4)]... 

Figure 6.1. Structure of a metal-oxide-semiconductor field-effect transistor (MOSFET) and an ion-sensitive field-effect transistor (ISFET). (a) Cross section of an n-type MOSFET (b) An ISFET is created by replacing the metal gate of the MOSFET by an electrolyte and a reference electrode.

Figure 3 Schematic diagram of an iSFET 1, drain 2, source 3, substrate 4, insulator 5, metai iead 6, reference eiectrode 7, sample solution 8, ion-selective membrane and 9, encapsul-ant. 6, 7 and 8 replace the original metal gate of the FET. (Reprinted with permission from Janata J and Huber RJ (1979) Ion-selective field effect transistors. Ion-selective Electrode Reviews 1 31-79 Elsevier.)...

In ISFETs and ChemFETs, the transistor metal gate electrode is replaced by an electrolyte solution, in the case of ChemFETs probably with a modifier film being placed on top of the gate region to condition access of the species which can influence the source-drain current (see Fig. 14.3). 

Semiconductor technology will also prove to play an important role in the future of ion-selective electrodes as shown by the first attempts using ion-selective transistor electrodes [441—443]. In this case the metal gate of a MOS-FET unit was replaced with a thin (> 100 ju) ion-selective membrane, contacting the sample solution. With... 

In principle the ISFET is derived from a MOSFET, where the metal is replaced by the couple solution-reference electrode and where a CIM (Chemically Interactive Material) is deposited on the S1O2, the gate oxide. 

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