METAL GATE STRUCTURE AND MANUFACTURING METHOD THEREOF
A method for manufacturing a metal gate structure includes providing a substrate having a high-K gate dielectric layer and a bottom barrier layer sequentially formed thereon, forming a work function metal layer on the substrate, and performing an anneal treatment to the work function metal layer in-situ.
This application is a division of U.S. application Ser. No. 13/037,383 filed on Mar. 1, 2011, and incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION1. Field of the Invention
The invention relates to a metal gate structure and a manufacturing method thereof, and more particularly, to an n-type metal gate structure and a manufacturing method thereof.
2. Description of the Prior Art
With a trend towards scaling down size of the semiconductor device, conventional methods, which are used to achieve optimization, such as reducing thickness of the gate dielectric layer, for example the thickness of silicon dioxide layer, have faced problems such as leakage current due to tunneling effect. In order to keep progression to next generation, high-K materials are used to replace the conventional silicon oxide to be the gate dielectric layer because it decreases physical limit thickness effectively, reduces leakage current, and obtains equivalent capacitor in an identical equivalent oxide thickness (EOT).
On the other hand, the conventional polysilicon gate also has faced problems such as inferior performance due to boron penetration and unavoidable depletion effect which increases equivalent thickness of the gate dielectric layer, reduces gate capacitance, and worsens a driving force of the devices. Thus work function metals are developed to replace the conventional polysilicon gate to be the control electrode that competent to the high-K gate dielectric layer.
However, there is always a continuing need in the semiconductor processing art to develop semiconductor device renders superior performance and reliability even though the conventional silicon dioxide or silicon oxynitride gate dielectric layer is replaced by the high-K gate dielectric layer and the conventional polysilicon gate is replaced by the metal gate.
SUMMARY OF THE INVENTIONAccording to an aspect of the present invention, there is provided a metal gate structure. The metal gate structure includes a high-K gate dielectric layer, a bottom barrier layer formed on the high-K gate dielectric layer, a titanium tri-aluminide (TiAl3) work function metal layer formed on the bottom barrier layer, a top barrier layer formed on the TiAl3 work function metal layer, and a low-resistance metal layer formed on the top barrier layer.
According to another aspect of the present invention, there is provided a method for manufacturing a metal gate structure. The method includes providing a substrate having a high-K gate dielectric layer and a bottom barrier layer sequentially formed thereon, forming a work function metal layer on the substrate, and performing an anneal treatment to the work function metal layer in-situ.
According to the metal gate structure and the method for manufacturing a metal gate structure provided by the present invention, the anneal treatment is in-situ performed to induce a phase transformation of the work function metal layer to form a TiAl3 work function metal layer and simultaneously to improve Al diffusion and thus the work function of the metal gate structure is tuned to an ideal value: 3.9-4.3 eV. In other word, the method for manufacturing a metal gate structure is performed to provide a metal gate structure having superior reliability.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
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According to the method for manufacturing a metal gate structure provided by the first preferred embodiment, which is integrated with the high-K first process, the anneal treatment 150 is in-situ performed to induce the phase transformation from the TiAl work function metal layer 140 to the TiAl3 work function metal layer 140a, and simultaneously to improve Al diffusion. Accordingly, work function of the metal gate is tuned to the ideal value: 3.9-4.3 eV. In other words, according to the method provided by the first preferred embodiment, a metal gate structure 120a having ideal work function is obtained.
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The semiconductor device 210 further includes LDDs 212. Since the semiconductor device 210 provided by the preferred embodiment is an n-type semiconductor device, the LDDs 212 are n-type LDDs. The semiconductor device 210 further includes a spacer 214 formed on sidewalls of the gate structure, and the spacer 214 is preferably a multi-layered structure. The semiconductor device 210 further includes an n-type source/drain 216 and silicides 218 for reducing resistance formed on the source/drain 216. As mentioned above, the SEG method can be utilized to form a SiC n-type source/drain 216 according to the preferred embodiment. Furthermore, there are a CESL 230 and an ILD layer 232 sequentially formed on the semiconductor device 210 and the substrate 200. Since steps for forming the gate structure, the LDDs 212, the spacer 214, the source/drain 216, the silicides 218, the CESL 230 and the ILD layer 232 are well-known to those skilled in the art, those details are omitted herein in the interests of brevity.
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As mentioned above, during forming the work function metal layer, that is the TiAl layer 240 or the Ti/Al bi-layered structure 240, the work function metal layer 240 is formed in a vacuum environment. According to the preferred embodiment, an anneal treatment 250 is in-situ performed to the work function metal layer 240 after forming the TiAl layer 240 without removing the vacuum environment. In other words, the step of forming the work function metal layer 240 and the step of performing the anneal treatment 250 are in-situ performed in a vacuum environment. In the second preferred embodiment, the anneal treatment 250 is performed at a temperature and in a duration the same with those described in the first preferred embodiment, therefore those details are omitted for the sake of simplicity.
As mentioned above, the anneal treatment 250 is performed to the work function metal layer 240 to induce a phase transformation from the TiAl layer 240 to a TiAl3 layer 240a. More important, during the phase transformation from the TiAl work function metal layer 240 to the TiAl3 work function metal layer 240a, Al in the aforementioned layer diffuses to the interface between the TiN layer 224 and the high-K gate dielectric layer 222 and finally arrives at the surface of the high-K gate dielectric layer 222. Simultaneously, work function of the gate structure is tuned. Accordingly, by in-situ performing the anneal treatment 250, Al diffusion is improved, and work function of the n-type metal gate is tuned to the ideal value: 3.9-4.3 eV. Furthermore, since the anneal treatment 250 is performed without removing the vacuum environment, the TiAl layer 240 is avoided from contacting the air, and thus is prevented from forming oxide or nitride that deteriorates the performance.
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According to the method for manufacturing a metal gate structure provided by the second preferred embodiment, which is integrated with the high-K last process, the anneal treatment 250 is in-situ performed to induce the phase transformation from the TiAl work function metal layer 240 to the TiAl3 work function metal layer 240a and simultaneously improves Al diffusion. Accordingly, work function of the metal gate is tuned to an ideal value: 3.9-4.3 eV. In other words, according to the method provided by the second preferred embodiment, a metal gate structure 220a having ideal work function is obtained.
Accordingly, the present invention provides a method for manufacturing metal gate structure performed with the gate-last process and can be integrated alternatively with high-K first or high-K last process. More important, the provided method utilizes the in-situ performed anneal treatment to induce the phase transformation of the work function metal layer from the TiAl work function metal layer to the TiAl3 work function metal layer. Simultaneously, Al diffusion is improved and thus the work function of the metal gate is tuned to the ideal value: 3.9-4.3 eV. In other word, the method for manufacturing a metal gate structure is performed to provide an n-type metal gate structure having superior reliability.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Claims
1. A metal gate structure comprising:
- a high-K gate dielectric layer;
- a bottom barrier layer formed on the high-K gate dielectric layer;
- a titanium tri-aluminide (TiAl3) work function metal layer formed on the bottom barrier layer;
- a top barrier layer formed on the TiAl3 layer; and
- a low-resistance metal layer formed on the top barrier layer.
2. The metal gate structure according to claim 1, wherein the bottom barrier layer comprises titanium nitride (TiN).
3. The metal gate structure according to claim 1, wherein the bottom barrier layer comprises titanium nitride or tantalum nitride (TaN).
4. The metal gate structure according to claim 1, wherein the top barrier layer comprises titanium nitride or titanium oxynitride (TiON).
5. The metal gate structure according to claim 1, wherein the high-K gate dielectric layer comprises materials selected from the group consisting of hafnium oxide (HfO2), hafnium silicon oxide (HfSiO4), hafnium silicon oxynitride (HfSiON), aluminum oxide (Al2O3), lanthanum oxide (La2O3), tantalum oxide (Ta2O5), yttrium oxide (Y2O3), zirconium oxide (ZrO2), strontium titanate oxide (SrTiO3), zirconium silicon oxide (ZrSiO4), and hafnium zirconium oxide (HfZrO4).
6. The metal gate structure according to claim 1, wherein the low-resistance metal layer comprises aluminum (Al).
7. The metal gate structure according to claim 1, wherein cross-sectional views of the high-K gate dielectric layer, the bottom barrier layer, the TiAl3 layer, and the top barrier layer comprise a U-shape.
8. The metal gate structure according to claim 1, wherein cross-sectional views of the TiAl3 layer and the top barrier layer comprise a U-shape.
Type: Application
Filed: Sep 9, 2015
Publication Date: Dec 31, 2015
Inventors: Chan-Lon Yang (Taipei City), Chi-Mao Hsu (Tainan City), Chun-Yuan Wu (Yunlin County), Tzyy-Ming Cheng (Hsinchu City), Shih-Fang Tzou (Hsinchu County), Chin-Fu Lin (Tainan City), Hsin-Fu Huang (Tainan City), Min-Chuan Tsai (New Taipei City)
Application Number: 14/848,362