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structure and method to suppress gatestack regrowth in FinFET RMG with HKGM _b Disclosure Number: IPCOM000232334D
Publication Date: 2013-Nov-01
Document File: 3 page(s) / 41K

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Disclosed are a structure and method to avoid oxygen ingress and gate dielectric regrowth and maintain semiconductor chip performance by low temperature nitridation of the exposed high-K dielectric, after the metal gate formation within Standard High-K metal gate (HKMG) Complimentary Metal-Oxide Semiconductor (CMOS) technologies fabricated using the replacement metal gate (RMG).

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structure and method to suppress gatestack regrowth in FinFET RMG with HKGM _b

High-K dielectric with Metal Gate electrodes (HKMG) is a critical innovation that allows further gate thickness scaling, which in turn enables the active channel length scaling and the overall performance boost in advanced Complimentary Metal-Oxide Semiconductor (CMOS) technology. Furthermore, the Replacement Gate (RMG) integration flow for HKMG provides an additional advantage in terms of thermal budget control. However, in a typical HKMG RMG flow, gate dielectric, including the high-K gate, can become exposed after the metal gate Chemical Mechanical Planarization (CMP) process. This provides an oxygen ingress path and leads to oxide regrowth at the gate channel interface during the subsequent Middle of Line (MOL) dielectric deposition and Back End Of the Line (BEOL) processing. The oxide regrowth increases the effective dielectric thickness and shifts the transistor threshold voltage, both of which can cause severe device degradation in terms of performance and variability. Thus, the oxygen ingress and regrowth at high-K gate dielectric to semiconductor channel interface needs to be avoided.

In the prior art, after the metal-gate CMP is completed, the next layer, usually silicon nitride, is deposited at temperatures high enough (>500°C) to enable the exposed high-K gate dielectric material to absorb any oxygen present during the deposition process, and transport the oxygen toward the gate dielectric to channel interface region, where the oxygen causes an unwanted regrowth. The deposition temperature is important because higher temperatures increase the absorption and diffusion of oxygen into the high-K gate dielectric, towards the gate dielectric to channel interface.

The novel contribution is a structure and method to minimize the oxygen ingress and diffusion into the gate dielectric to semiconductor channel interface in RMG Field Effect Transistor (FET) structure and process.

The solution is to perform a nitridation process at low temperature (less than 500°C) after the CMP process, but prior to the standard MOL dielectric deposition. Hence, the top of the exposed HiK dielectric layer is nitridized and this forms an Oxygen ingress barrier located between the active gate area and the MOL dielectric layer. Because the Nitridation process is performed at a low temperature of 500°C or less, oxygen ingress and diffusion into the high-K gate dielectric layer is effectively suppressed. Furthermore, once the top of the high-K dielectric has been nitridized, it serves as an Oxygen barrier to protect the active gate area against any subsequent processing steps, such as MOL dielectric deposition, above 5...