FIELD EFFECT TRANSISTOR WITH FIN STRUCTURE
A FET with a fin structure includes a substrate, an isolation structure and a gate structure. The substrate includes at least one fin structure. The fin structure includes two source/drain regions and a gate channel region between the two source/drain regions. The isolation structure is disposed on the substrate and surrounds the fin structure to expose an upper portion of the fin structure. A width of the gate channel region of the exposed upper portion of the fin structure is less than each of widths of the source region and the drain region. A gate structure covering two sidewalls of the gate channel region of the exposed upper portion of the fin structure is formed. Two sidewalls of the gate structure contact two facing sidewalls of the two source/drain regions, respectively.
This application is a division of U.S. application Ser. No. 13/284,987, filed Oct. 31, 2011, the disclosure of which is hereby incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates generally to a field effect transistor (FET) with a fin structure, and more particularly to a field effect transistor fabricated through a damascene-like process.
2. Description of the Prior Art
With the trend of scaling down the size of metal oxide semiconductor transistors (MOS) in the industry, three-dimensional or non-planar transistor technology, such as fin field effect transistor technology (Fin-FET) has been developed to replace planar MOS transistors. The three-dimensional structure of a fin-FET increases the overlapping area between the gate and the fin structure of the silicon substrate, and accordingly, the channel region is more effectively controlled. The short channel effect which miniaturized devices may encounter is therefore reduced. The channel region is also wider under the same gate length, and thus the current between the source and the drain is increased.
Since the fin-FET devices have the aforesaid advantages, there is still a need for novel fin-FET devices and methods of fabricating the same to improve performance.
SUMMARY OF THE INVENTIONAn objective of the present invention is to provide a FET with a fin structure, in which, a width of a gate channel region of an exposed upper portion of the fin structure is less than each of widths of the source region and the drain region and a gate structure is well aligned with the gate channel region.
According to one aspect of an embodiment of the present invention, the FET with a fin structure includes a substrate, an isolation structure and a gate structure. The substrate includes at least one fin structure. The fin structure includes two source/drain regions and a gate channel region between the two source/drain regions. The isolation structure is disposed on the substrate and surrounds the fin structure to expose an upper portion of the fin structure. A width of the gate channel region of the exposed upper portion of the fin structure is less than each of widths of the source region and the drain region. A gate structure covering two sidewalls of the gate channel region of the exposed upper portion of the fin structure is formed. Two sidewalls of the gate structure contact two facing sidewalls of the two source/drain regions, respectively.
In the present invention, a process similar to damascene is utilized to form a trench within an insulation layer to expose an upper portion of a gate channel region of a fin structure, and thereafter agate structure covering the gate channel region is formed within the trench. Accordingly, in the process, the gate structure and the gate channel region are self-aligned with each other. Furthermore, in the process, the insulation layer may include amorphous material to avoid a rough surface due to crystal grains, and accordingly the trench may have a smooth surface and the resultant gate structure may have a relative fine and straight edge with respect to a conventional gate structure obtained from patterning directly through an etching process. Furthermore, in a certain embodiment, a trim process may be further performed to reduce the width of the exposed upper portion of the fin structure; while the source/drain regions may be still in the original width. Accordingly, the problems of short channel effect, such as drain induced barrier lowering (DIBL), sub-threshold slope and Vt roll-off effect, can be improved. Furthermore, the gate structure and the gate channel region are well self-aligned with each other, such that, the two sidewalls of the gate structure contact two sidewalls, which face each other, of the two source/drain regions S/D, respectively. No gap is between the gate structure and the source/drain region. Accordingly, in addition that the problems of short channel effect are improved, a low parasitic resistance between the gate structure and the source/drain can be also obtained.
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.
Referring to
Thereafter, according to one feature of the present invention, a planar insulation layer is formed on the substrate to cover the fin structure. The insulation layer is partially removed to a depth to forma trench. The trench is allowed to intersect the fin structure both in their lengthwise direction, such that an upper portion of the fin structure is exposed to the trench. The way for partially removing the insulation layer to a desired depth may be various, for example, but not limited thereto, by means of etching the insulation layer through a patterned mask or hard mask to a desired or predetermined depth to form a trench within the insulation layer; or by means of disposing an etch stop layer between two insulation layers at a desired depth and then carrying out an etching process through a patterned mask or hard mask; or disposing two insulation layers having different etching rates and then carrying out an etching process through a patterned mask or hard mask for a desired etch stop.
Still referring to
Thereafter, referring to
Thereafter, referring to
In another aspect of an embodiment, instead of forming the etch stop layer 20, two insulation layers having different etching rates, i.e. having an etch selection ratio with respect to each other, are formed for an indication for stopping the etch process as aforesaid.
Thereafter, the exposed portion of the fin structure 12 may serve for a gate channel, or it may be further reduced in width through a trim process. For example, in an embodiment illustrated by
A gate dielectric layer (not shown) maybe formed on the exposed upper portion of the fin structure 12. Thereafter, a gate is formed in the trench 24 to cover the channel region of the fin structure 12. Various ways may be available for forming the gate. For example, referring to
Thereafter, a planarization process, such as a CMP process, is performed to planarize the surface of the gate material layer 26 to expose the insulation layer 22. Thereafter, referring to
A source and a drain are formed in the fin structure at two sides of the gate 28. For example, a spacer is formed on the sidewall of the gate and the source/drain regions are implanted with dopants through an ion implantation. The gate 28 covers the exposed upper portion of the fin structure 12 (including two sidewalls and top surface of the fin structure 12), and becomes a tri-gate FET configuration. Furthermore, the gate 28 and the trimmed gate channel are aligned with each other without particular alignment processes. Accordingly, it may be referred to as a self-alignment process.
As aforesaid, after the fin structure 12 is formed, the hard mask layer 14 may be removed or allowed to remain. In the situation that the hard mask layer 14 remains, a trim process can be also performed on the fin structure 12 as described above. For example, an isotropic etching process may be performed on the trench 24. Or, a trim process is performed on the hard mask 14 to reduce the width and thereafter the gate channel region is etched to reduce the width.
In another embodiment, a sacrificial gate is formed as described aforesaid using sacrificial gate material instead of desired gate material. Thereafter, a gate replacement process is performed to replace the sacrificial gate with a desired gate structure. The gate structure may include a gate dielectric layer and a gate. For example, a sacrificial gate is formed of polysilicon, and thereafter a gate dielectric layer and a metal gate are formed through, for example, a conventional gate replacement process.
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 field effect transistor with a fin structure comprising:
- a substrate comprising at least one fin structure comprising two source/drain regions and a gate channel region between the two source/drain regions;
- an isolation structure disposed on the substrate and surrounding the fin structure to expose an upper portion of the fin structure, wherein a width of the gate channel region of the exposed upper portion of the fin structure is less than each of widths of the source region and the drain region; and
- a gate structure covering two sidewalls of the gate channel region of the exposed upper portion of the fin structure, wherein two sidewalls of the gate structure contact two facing sidewalls of the two source/drain regions, respectively.
2. The field effect transistor with a fin structure according to claim 1, further comprising a hard mask atop the gate channel region of the fin structure.
3. The field effect transistor with a fin structure according to claim 1, wherein the gate structure further covers a top of the gate channel region of the fin structure.
4. The field effect transistor with a fin structure according to claim 1, wherein the gate structure further covers the hard mask.
Type: Application
Filed: Sep 11, 2014
Publication Date: Dec 25, 2014
Inventors: Chih-Jung Wang (Hsinchu City), Tong-Yu Chen (Hsinchu City)
Application Number: 14/483,165
International Classification: H01L 29/78 (20060101); H01L 29/06 (20060101);