MOS transistor
A method of forming a MOS transistor, in which a co-implantation is performed to implant an implant into a source region and a drain region or a halo implanted region to effectively prevent dopants from over diffusion in the source region and the drain region or the halo implanted region, for obtaining a good junction profile and improving short channel effect. The implant comprises carbon, a hydrocarbon, or a derivative of the hydrocarbon, such as one selected from a group consisting of C, CxHy+, and (CxHy)n+, wherein x is a number of 1 to 10, y is a number of 4 to 20, and n is a number of 1 to 1000.
This is a divisional application of U.S. patent application Ser. No. 11/278,434 filed on Apr. 3, 2006, and the contents of which are included herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates a method of forming a MOS transistor, and particularly a method of forming a MOS transistor having an improved short channel effect, comprising a step of co-implantation using an implant comprising carbon, hydrocarbon, or a derivative thereof.
2. Description of the Prior Art
Field effect transistors (FETs) are important electronic devices in the fabrication of integrated circuits, and as the size of the semiconductor device becomes smaller and smaller, the fabrication of the transistors also improves and is constantly enhanced for fabricating transistors with smaller sizes and higher quality.
In the conventional method of fabricating transistors, a gate structure is first formed on a substrate, and a lightly doped drain (LDD) is formed on the two corresponding sides of the gate structure. Next, a spacer is formed on the sidewall of the gate structure and an ion implantation process is performed to form a source/drain region within the substrate by utilizing the gate structure and spacer as a mask. Finally, an anneal process is performed.
Refer to
With the device scaling down, it's difficult to control the junction depth (Xj) and also reduce the access resistance. The short channel effect (SCE) noticeably depends on the junction depth. The junction depth for the source/drain of a transistor must be reduced to avoid the short channel effect of the MOS arisen from the shrinkage of the MOS size to increase the integration of the device. A lot of papers have demonstrated many approaches to improve the pFET SCE. But from 65 nm node and beyond, the conventional As implantation and spike RTP can hardly meet the nFET SCE requirement.
From the above viewpoint, the shallower as-implant depth by heavy ions or less diffusion activation tool is needed. Unfortunately the advanced activation tools (for example, flash or laser anneal) are under development and not mature.
A method of manufacturing a PMOS transistor has been disclosed to implant fluorine in a source/drain extension region or source/drain region to be with the dopants thereat together. The diffusion for the dopants can be improved during a subsequent annealing process, to alleviate the SCE.
However, due to transistors with smaller sizes and higher quality are constantly desired, an FET with an improved SCE and a good junction profile and a method of manufacturing it are still needed.
SUMMARY OF THE INVENTIONOne object of the present invention is to provide a method of forming a MOS transistor with an improved short channel effect.
The method of forming a MOS transistor according to the present invention comprises the steps as follows. First, a substrate having a gate thereon, a source region and a drain region therein with a channel region under the gate therebetween is provided. Next, the source region and the drain region are pre-amorphized to form amorphized regions. Subsequently, a first ion implantation is performed to implant a first dopant in the source region and the drain region to form a first doped region. At least a spacer is formed on the sidewalls of the gate. A second ion implantation is performed to implant a second dopant in the source region and the drain region to form a second doped region. The source region and the drain region are annealed to activate the first dopant, regrow the amorphized regions to a substantially crystalline form, and form a junction profile. Among these steps, a co-implantation process is performed after pre-amorphizing the source region and the drain region and before annealing the source region and the drain region, to implant an implant in the source region and the drain region, wherein the implant comprises carbon, a hydrocarbon compound, or a derivative of the hydrocarbon compound.
In another embodiment of the present invention, the method of forming a MOS transistor comprises the steps as follows. First, a substrate having a gate thereon, a source region and a drain region therein with a channel region under the gate therebetween is provided. Next, an implant is implanted into the source region and the drain region for achieving both pre-amorphization and co-implantation of the source region and the drain region to form amorphized regions with the implant, wherein the implant comprises carbon, a hydrocarbon compound, or a derivative of the hydrocarbon compound. Next, a first ion implantation is performed to implant a first dopant in the source region and the drain region to form a first doped region. At least one spacer is formed on the sidewalls of the gate. A second ion implantation is performed to implant a second dopant in the source region and the drain region to form a second doped region. Finally, the source region and the drain region are annealed to activate the first dopant, regrow the amorphized regions to a substantially crystalline form, and form a junction profile.
Furthermore, the MOS transistor according to the present invention comprises a substrate having a gate thereon, a source region and a drain region therein with a channel region under the gate therebetween; at least a spacer disposed on a side wall of the gate; a light doped source region and a light doped drain region disposed in the source region and the drain region; a source and a drain disposed respectively in the source region and the drain region at a side of the light doped source region and a side the light doped drain region; and a halo implanted region formed between the channel region and the source region and between the channel region and the drain region, wherein the halo implanted region comprises an implant comprising carbon, a hydrocarbon compound, or a derivative of the hydrocarbon compound.
In another embodiment according to the present invention, the MOS transistor comprises a substrate having a gate thereon, a source region and a drain region therein with a channel region under the gate therebetween; at least a spacer disposed on a side wall of the gate; a light doped source region and a light doped drain region disposed in the source region and the drain region; a source and a drain disposed respectively in the source region and the drain region at a side of the light doped source region and a side the light doped drain region; and a halo implanted region formed between the channel region and the source region and between the channel region and the drain region, wherein the halo implanted region comprises an implant comprising carbon, a hydrocarbon compound, or a derivative of the hydrocarbon compound.
The method of forming a MOS transistor comprises a step of co-implantation to implant carbon, a hydrocarbon compound, or a derivative of the hydrocarbon compound, such as one selected from a group consisting of C, CxHy+, and (CxHy)n+, wherein x is a number of 1 to 10, y is a number of 4 to 20, and n is a number of 1 to 1000, within substantially the same place as that of the lightly doped drain or source, the source region and the drain region, or the halo implanted region. Therefore, after a rapid thermal process is performed, for example, by a conventional implanter and a spike annealing tool, the diffusion of dopants co-existing with the implants from the co-implantation can be reduced. That is, the diffusion of the dopants within the lightly doped drain or source, the source region and the drain region, or the halo implanted region can be effectively controlled, to obtain a good junction profile and an improved short channel effect.
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.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 3 to 6 show cross sectional views for the method of forming a MOS transistor according to the present invention;
Refer to FIGS. 2 to 6 for illustration of an embodiment according to the present invention.
FIGS. 3 to 6 show cross sectional views for the method of forming a MOS transistor according to the present invention. As shown in
The co-implantation 302 is performed to implant an implant into the source region and the drain region. For example, as shown in
Referring to
After the LDD implantation, a spike rapid thermal process may be further performed to activate dopants. Alternatively, the spike rapid thermal process is not performed at this manufacturing stage, and an anneal process is performed after the source/drain implantation.
Subsequently, the source/drain implantation 304 is performed. As shown in
Finally, the anneal process 305 is performed, such as a rapid thermal process, or a spike anneal process to activate the dopant in the substrate 200 at a high temperature of, for example, 1000 to 1050° C. to form a desired junction profile and regrow the damaged lattice structure of the surface of the substrate 200 caused by ion implantations to a substantially crystalline form.
In the flow chart shown in
Referring to
As shown in
In case the halo implantation is included to form the transistor, the implant of the co-implantation may be implanted in the substrate at a place substantially the same as that of the halo implant, in addition to the place substantially the same as that of the light dopant in the lightly doped region or that of the heavy dopant in the source/drain.
When carbon, hydrocarbon, or a derivative thereof is implanted as an implant into the doped region and exists with dopants together, the diffusion of the dopants (such as, B or P) can be controlled because the implant occupies the interstitials of the silicon crystalline structure. This situation facilitates the control for the diffusion of dopants, and thus a good junction profile can be obtained.
The method of forming a MOS transistor according to the present invention can be used to form a pPFET or an nFET. For example, when carbon is used as a co-implant in the light doped drain/source, an NLDD can be formed using, for example, As or P as a light dopant in the source region and the drain region, and a PLDD can be formed using, for example, B or BF2 as a light dopant in the source region and the drain region. When CxHy+ or (CxHy)n+ is used as a co-implant in the light doped drain/source, a PLDD can be formed using, for example, B, BF2, BwHz+, or (BwHz)m+ as a light dopant in the source region and the drain region.
According to still another embodiment according to the present invention, using hydrocarbon or a derivative thereof (such as CxHy+ or (CxHy)n+) as a co-implant, and in such situation, the process flow is the same as that shown in
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 MOS transistor, comprising:
- a substrate having a gate thereon, a source region and a drain region therein with a channel region under the gate therebetween;
- at least a spacer disposed on a side wall of the gate;
- a light doped source region and a light doped drain region disposed in the source region and the drain region; and
- a source and a drain disposed respectively in the source region and the drain region at a side of the light doped source region and a side the light doped drain region;
- wherein one of the light doped source region, the light doped drain region, the source region, and the drain region comprises an implant comprising carbon, a hydrocarbon compound, or a derivative of the hydrocarbon compound.
2. The MOS transistor as claimed in claim 1, further comprising a halo implanted region formed between the channel region and the source region and between the channel region and the drain region.
3. The MOS transistor as claimed in claim 1, wherein the implant comprises one selected from the group consisting of C, CxHy+, and (CxHy)n+, wherein x is a number of 1 to 10, y is a number of 4 to 20, and n is a number of 1 to 1000.
4. The MOS transistor as claimed in claim 1, wherein the implant comprises C and the light doped source region and the light doped drain region comprise As or P.
5. The MOS transistor as claimed in claim 1, wherein the implant comprises C and the light doped source region and the light doped drain region comprise B or BF2.
6. The MOS transistor as claimed in claim 1, wherein the implant comprises CxHy+ or (CxHy)n+ and the light doped source region and the light doped drain region comprise B, BF2, BwHz+, or (BwHz)m+, wherein w is a number of 2 to 30, z is a number of 2 to 40, and m is a number of 10 to 1000.
7. A MOS transistor, comprising:
- a substrate having a gate thereon, a source region and a drain region therein with a channel region under the gate therebetween;
- at least a spacer disposed on a side wall of the gate;
- a light doped source region and a light doped drain region disposed in the source region and the drain region;
- a source and a drain disposed respectively in the source region and the drain region at a side of the light doped source region and a side the light doped drain region; and
- a halo implanted region formed between the channel region and the source region and between the channel region and the drain region, wherein the halo implanted region comprises an implant comprising carbon, a hydrocarbon compound, or a derivative of the hydrocarbon compound.
8. The MOS transistor as claimed in claim 7, wherein the implant comprises one selected from the group consisting of C, CxHy+, and (CxHy)n+, wherein x is a number of 1 to 10, y is a number of 4 to 20, and n is a number of 1 to 1000.
9. The MOS transistor as claimed in claim 7, wherein the light doped source region and the light doped drain region comprise B, BF2, BwHz+, or (BwHz)m+, wherein w is a number of 2 to 30, z is a number of 2 to 40, and m is a number of 10 to 1000.
Type: Application
Filed: May 14, 2007
Publication Date: Oct 4, 2007
Inventors: Hsiang-Ying Wang (Chia-Yi Hsien), Chin-Cheng Chien (Tainan Hsien), Tsai-Fu Hsiao (Hsin-Chu City), Ming-Yen Chien (Kao-Hsiung Hsien), Chao-Chun Chen (Kao-Hsiung City)
Application Number: 11/748,479
International Classification: H01L 29/772 (20060101);