1. Field of the Invention
The present invention relates to a method for making a transistor having a metal gate, and more particularly, to a method of using an oxide layer as an etch stop layer when removing the dummy gate.
2. Description of the Prior Art
Poly-silicon is conventionally used as a gate electrode in semiconductor devices, such as the metal-oxide-semiconductor (MOS). However, with a trend toward scaling down the size of semiconductor devices, the conventional poly-silicon gate 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. Therefore, work function metals that are suitable for use as the high-K gate dielectric layer are used to replace the conventional poly-silicon gate to be the control electrode.
The present invention therefore provides a method for making a transistor having a metal gate to avoid the oxygen vacancies phenomenon and provide a better work function tuning capability for the transistor.
According one preferred embodiment of the present invention, a method for making a metal gate is provided. A substrate is provided and a transistor is formed on the substrate. The transistor includes a high-k gate dielectric layer, an oxygen containing dielectric layer disposed on the high-k gate dielectric layer, and a dummy gate disposed on the oxygen containing dielectric layer. Then, the dummy gate and the oxygen containing dielectric layer are removed. Lastly, a metal gate is formed and the metal gate directly contacts the high-k gate dielectric layer.
In the present invention, the oxygen containing dielectric layer is utilized as an etch stop layer when removing the dummy gate. The oxygen containing dielectric layer can prevent the high-k gate dielectric layer from experiencing the oxygen vacancies phenomenon during the high temperature annealing process. Moreover, the oxygen containing dielectric layer can be removed in the subsequent steps so the metal gate can directly contact the high-k gate dielectric layer. Consequently, a transistor with good performance can be 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.
To provide a better understanding of the presented invention, preferred embodiments will be made in detail. The preferred embodiments of the present invention are illustrated in the accompanying drawings with numbered elements.
Please refer to
However, the high-k dielectric layer 104 is formed before removing the dummy gate 108, so the high-k dielectric layer 104 will be subjected to normal MOS transistor manufacturing methods, such as some high temperature annealing processes, which would damage the high-k dielectric layer 104. As shown in
Please refer to
Next, an interface layer 301, a high-k dielectric layer 303, an oxide layer 305, a dummy gate layer 307 and a capping layer 309 are in sequence deposited on the substrate 300. The deposition method may include a variety of deposition techniques, such as a chemical vapor deposition (VCD) or a physical vapor deposition (PVD), but is not limited thereto. The interface layer 301 can increase the adhesion ability of the above high-k dielectric layer 303. The material of the interface layer 301 may be silicon dioxide or nitridation silicon dioxide. In another embodiment, the interface layer 301 can be formed on the substrate 300 by an oxidation process. The high-k dielectric layer 303 may include a single-layer or a multi-layer structure containing metal oxide layer such as rare earth metal oxide wherein the dielectric constant thereof is substantially greater than 20. For example, the high-k dielectric layer 303 may include hafnium oxide (HfO2), hafnium silicon oxide (HfSiO), hafnium silicon oxynitride (HfSiON), aluminum oxide (MO), lanthanum oxide (La2O3), lanthanum aluminum oxide (LaAlO), tantalum oxide, Ta2O3, zirconium oxide (ZrO2), zirconium silicon oxide (ZrSiO), hafnium zirconium oxide (HfZrO), strontium bismuth tantalite (SrBi2Ta2O9, SBT), lead zirconate titanate (PbZrxTi1-xO3, PZT) or barium strontium titanate (BaxSr1-zTiO3, BST). The dielectric constant of high-k dielectric layer 303 is greater than that of the oxide layer 305 which is substantially between 4 and 15. The oxide layer 305 includes a variety of oxide materials, such as SiO2. In another embodiment of the present invention, the oxide layer 305 may include fluoride oxide or nitrogen oxide, such as SiOF or SiON. The dummy gate layer 307 includes poly-silicon. In another embodiment, the dummy gate layer 307 is a multi-layered structure including a poly-silicon layer, an amorphous silicon layer or a germanium layer. The capping layer 309 can be a SiN layer.
As shown in
In addition, the transistor 400 can further include other semiconductor structures which are not explicitly shown in
As shown in
As shown in
Next, as shown in
As shown in
It is one salient feature that the oxygen containing dielectric layer 306 has been removed away, so the metal gate 326 in the trench 320 can directly contact the high-k gate dielectric layer 304. Compared to the first embodiment (
In summary, the present invention provides a method for forming a transistor having a metal gate. The oxygen containing dielectric layer is utilized as an etch stop layer when removing the dummy gate. The oxygen containing dielectric layer can prevent the high-k gate dielectric layer from the oxygen vacancies phenomenon during the high temperature annealing process. Moreover, the oxygen containing dielectric layer can be removed in the subsequent steps so the metal gate can directly contact the high-k gate dielectric layer. Consequently, a transistor with good performance can be obtained.
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.
Number | Name | Date | Kind |
---|---|---|---|
5319319 | Kerth | Jun 1994 | A |
5892282 | Hong | Apr 1999 | A |
5915203 | Sengupta | Jun 1999 | A |
6025627 | Forbes | Feb 2000 | A |
6043157 | Gardner | Mar 2000 | A |
6093590 | Lou | Jul 2000 | A |
6096659 | Gardner | Aug 2000 | A |
6100118 | Shih | Aug 2000 | A |
6251761 | Rodder | Jun 2001 | B1 |
6291282 | Wilk | Sep 2001 | B1 |
6303418 | Cha | Oct 2001 | B1 |
6444139 | Minamihaba | Sep 2002 | B1 |
6506682 | Lee | Jan 2003 | B1 |
6514827 | Kim | Feb 2003 | B2 |
6653698 | Lee | Nov 2003 | B2 |
6696345 | Chau | Feb 2004 | B2 |
6743669 | Lin | Jun 2004 | B1 |
6790719 | Adetutu | Sep 2004 | B1 |
6794234 | Polishchuk | Sep 2004 | B2 |
6797622 | Brask | Sep 2004 | B2 |
6806146 | Brask | Oct 2004 | B1 |
6825117 | Miller | Nov 2004 | B2 |
6864163 | Yu et al. | Mar 2005 | B1 |
6867084 | Chiu | Mar 2005 | B1 |
6872627 | Chen | Mar 2005 | B2 |
6902969 | Adetutu | Jun 2005 | B2 |
6924184 | Cave | Aug 2005 | B2 |
6960416 | Mui | Nov 2005 | B2 |
7045428 | Brask | May 2006 | B2 |
7098516 | Colombo | Aug 2006 | B2 |
7108579 | Wada | Sep 2006 | B2 |
7112486 | Cho | Sep 2006 | B2 |
7138323 | Kavalieros | Nov 2006 | B2 |
7148548 | Doczy | Dec 2006 | B2 |
7153784 | Brask | Dec 2006 | B2 |
7157378 | Brask | Jan 2007 | B2 |
7166913 | Chinthakindi | Jan 2007 | B2 |
7196010 | Park | Mar 2007 | B2 |
7208361 | Shah | Apr 2007 | B2 |
7217611 | Kavalieros | May 2007 | B2 |
7220635 | Brask | May 2007 | B2 |
7314793 | Frohberg | Jan 2008 | B2 |
7381619 | Wang | Jun 2008 | B2 |
7488656 | Cartier | Feb 2009 | B2 |
7517746 | Lin | Apr 2009 | B2 |
20020058374 | Kim et al. | May 2002 | A1 |
20030003645 | Besser | Jan 2003 | A1 |
20050239273 | Yang | Oct 2005 | A1 |
20050253173 | Wang | Nov 2005 | A1 |
20050275035 | Mathew | Dec 2005 | A1 |
20060001095 | Doris | Jan 2006 | A1 |
20060024953 | Papa Rao | Feb 2006 | A1 |
20060102964 | Huang | May 2006 | A1 |
20070037335 | Chambers | Feb 2007 | A1 |
20070138559 | Bohr | Jun 2007 | A1 |
20070145591 | Yano | Jun 2007 | A1 |
20070259519 | Yang | Nov 2007 | A1 |
20070262451 | Rachmady | Nov 2007 | A1 |
20080029478 | Hsu | Feb 2008 | A1 |
20080311713 | Lu | Dec 2008 | A1 |
20090039433 | Yang et al. | Feb 2009 | A1 |
20090057769 | Wei | Mar 2009 | A1 |
20090057787 | Matsuki | Mar 2009 | A1 |
20090101989 | Chen | Apr 2009 | A1 |
20090134466 | Cho | May 2009 | A1 |
20090166769 | Metz | Jul 2009 | A1 |
20090186458 | Yu | Jul 2009 | A1 |
20100062592 | Clark | Mar 2010 | A1 |
20100065926 | Yeh | Mar 2010 | A1 |
20100068877 | Yeh | Mar 2010 | A1 |