Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2002-12-23
2004-09-21
Pham, Hoai (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S382000, C257S384000
Reexamination Certificate
active
06794721
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to microelectronic integrated circuits, and more particularly to a metal-oxide-semiconductor field-effect transistor (MOSFET) device and a method for producing the same.
2. Description of the Related Art
Advanced generations of microelectronic integrated circuits use metal-oxide-semiconductor field-effect transistor (MOSFET) devices with gate insulator materials having a dielectric constant greater than that of silicon dioxide and silicon-oxy-nitride materials. HfO
x
and ZrO
x
materials have been proposed as high-k gate insulator materials. In fact, it is desirable to incorporate these gate insulator materials into a complementary n-channel and p-channel MOSFET (CMOS) process. Moreover, these high-k materials have been used as an etch-stop film, wherein after the etching occurs, the stop film in the connect area of the MOSFET device is converted to metal by a specific annealing process.
For example, in studies examining the effects of ZrO
2
and Zr silicate (Zr
27
Si
10
O
63
) gate dielectrics deposited on silicon substrates, these high-k materials showed excellent equivalent oxide thicknesses (EOT) of 9.9 angstroms (ZrO
2
) and 9.6 angstroms (Zr
27
Si
10
O
63
), with very low leakage currents of 20 mA/cm
2
and 23 mA/cm
2
, respectively (C. H. Lee et al., “MOS Characteristics of Ultra Thin Rapid Thermal CVD ZrO
2
and Zr Silicate Gate Dielectrics,” IEEE Tech. Dig., 2000, the complete disclosure of which is herein incorporated by reference). In another study, HfO
2
demonstrated equally as well, having an EOT of 10.4 angstroms and a leakage current of 0.23 mA/cm
2
(S. J. Lee et al., “High Quality Ultra Thin CVD HfO
2
Gate Stack with Poly-Si Gate Electrode,” IEEE Tech. Dig., 2000, the complete disclosure of which is herein incorporated by reference).
However, due to the ever-increasing performance required of MOSFET devices, and the lack of a conventional device capable of meeting performance specifications, there is a need for a new and improved structure and method of manufacturing a high-performance MOSFET device capable of achieving present and future technological specifications for integrated circuit technology.
SUMMARY OF THE INVENTION
The present invention has been devised to provide a structure and method for manufacturing a high performance MOSFET device. The present invention provides a structure which integrates a combination of a high dielectric constant gate insulator and a low-resistance metal silicide source/drain region in a self-aligned manner without incurring extra processing cost. The present invention provides a method which reduces the number of processing steps used to manufacture a MOSFET device having a high-dielectric constant gate insulator and a low-resistance silicide (salicide) source/drain region relative to conventional MOSFET devices. The present invention provides a method for converting a metal oxide thin film to a metallic thin film in selected source/drain regions such that a subsequent annealing process will convert the metallic film to a silicide (salicide) film in order to improve the device series resistance.
There is provided, according to one aspect of the invention a new self-aligned and low-cost silicidation process. While forming a MOS device with a high-k gate dielectric using a proper metal oxide such as HfO
x
or ZrO
x
, the remaining high-k dielectric in the source/drain regions exposed to the air are converted into metal. One feature of the present process is the ability to block the high-k dielectric, which directly contacts the gate conductor, by using a cap dielectric layer. A subsequent silicidation process forms silicide alloy only in the source/drain region to reduce device series resistance. By controlling the metal conversion processing step, the overlap capacitance due to the gate and source/drain overlap with the high-k dielectric is also minimized. The high-k dielectric on top of the insulating substrate can also be used to form resistors. In short, a low-cost fabrication method to integrate very high-performance active and passive devices is taught in this disclosure.
Specifically, according to the present invention, a transistor device, and method of forming the same, is disclosed comprising forming a source region, a drain region, and a trench region in a substrate. Then, a first insulator is formed over the substrate. Next, a gate electrode is formed above the first insulator. Upon completion of this step, a pair of insulating spacers are formed adjoining the electrode. Next, a portion of the first insulator is converted into a metallic film. Then, at least a portion of the metallic film is converted into one of a silicide and a salicide film.
The method further comprises forming an interconnect region above the trench region and forming an etch stop layer above the first insulator, the trench region, the gate electrode, and the pair of insulating spacers. Next, a second insulator is formed above the etch stop layer, and finally, contacts are formed in the second insulator. The first insulator comprises a metal oxide material, and specifically, comprises one of a HfO
x
and a ZrO
x
.
In the step of converting a portion of the first insulator into a metallic film, the portion of the first insulator comprises a region above the source and the drain regions of the substrate. Moreover, the step of converting the metallic film into one of a silicide and a salicide film occurs in a region above the source and drain regions of the substrate. Furthermore, the step of converting a portion of the first insulator into a metallic film occurs by annealing in a reducing ambient environment. Additionally, the step of converting the metallic film into one of a silicide and a salicide film occurs by one of an annealing process and a wet etching process.
Also, a transistor device is disclosed comprising a substrate with a metal oxide film above the substrate, a gate electrode above the metal oxide film, and spacers adjacent to the gate electrode. The metal oxide film has a first region below the gate electrode and second regions not protected by the gate electrode. Moreover, the second regions have a reduced oxygen content when compared to the first region. Also, the second regions extend partially under the spacers. The transistor device in the second portions includes a silicide region and further comprises a source and drain region in the substrate below the second regions. Finally, the first region comprises a gate insulator.
According to the present invention, the performance of a MOSFET device is influenced by the dielectric properties of the thin gate insulator, and the series resistance of the source/drain region of the transistor. Additionally, the device's transconductance is increased, by the introduction of a high-dielectric constant gate insulator.
Moreover, according to the present invention, the series resistance of the source/drain region of the transistor is reduced by the introduction of a metal silicide on the surface of the source/drain region. Also, the gate to source/drain overlap capacitance is reduced by minimizing the overlap area using a self-aligned processing scheme.
REFERENCES:
patent: 6657244 (2003-12-01), Dokumaci et al.
Clevenger Lawrence A.
Hsu Louis L.
Radens Carl J.
Shepard, Jr. Joseph F.
International Business Machines - Corporation
Jennings Derek S.
McGinn & Gibb PLLC
Pham Hoai
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