# Patent

## Title
Spacer scheme for semiconductor device

## Abstract

A manufacturing method for a semiconductor device includes providing a substrate having at least agate structure formed thereon and a first spacer formed on sidewalls of the gate structure, performing an ion implantation to implant dopants into the substrate, forming a disposal spacer having at least a carbon-containing layer on the sidewalls of the gate structure, the carbon-containing layer contacting the first spacer, and performing a thermal treatment to form a protecting layer between the carbon-containing layer and the first spacer.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a division of U.S. application Ser. No. 13/527,608 filed on Jun. 20, 2012, and all benefits of such earlier application are hereby claimed for this division application.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a semiconductor device and a manufacturing method manufacturing method applied with strained-silicon technique.
2. Description of the Prior Art
With semiconductor processes entering the era of the deep submicron meter below 65 nanometer (nm), it has been more and more important to increase the metal-oxide semiconductor (MOS) drive current. To improve device performance, strained-silicon technique such as selective epitaxial growth (hereinafter abbreviated as SEG) method is developed to form epitaxial layers serving as the source/drain of the MOS. Because a lattice constant of the epitaxial layer is different from that of silicon, such characteristic is employed to cause alteration to the band structure of the silicon in the channel region. Accordingly, carrier mobility of the channel region is enhanced and thus device performance is improved.
Those skilled in the art have well known that the conventional MOS applied with SEG method is to form a disposal spacer on sidewalls of the gate structure or on a first spacer of the gate structure in order to define positions for forming recesses. Subsequently, recesses are formed and followed by performing a SEG method. Thus, epitaxial layers are formed in each recess. Thereafter the disposal spacer is removed and an ion implantation is subsequently performed to implant dopants of required conductivity type into the epitaxial layers. Accordingly, source/drain having the epitaxial layer are obtained. The epitaxial layers formed in the source/drain region render compressive or tensile stress to the channel region and thus the carrier mobility in the channel region is enhanced.
However, as size of the semiconductor structure keeps shrinking, semiconductor industries contrive to ensure that the device will not be impacted when forming or removing elements by which the device is constructed. For example, it has been found that the first spacer is always consumed and damaged when removing the disposal spacer. It even damages the profile of the gate structure when removing the disposal spacer. Furthermore, it is found that the size or profile of the second spacer and the source/drain are all adversely impacted when the first spacer is consumed. Seriously, it results that the following manufacturing processes fail to meet expectations.
Therefore, there is still a need for a manufacturing method for a semiconductor device that is able to protect elements of the semiconductor device from being impacted during removing the disposal spacer, and thus to ensure performance of the semiconductor device and the yield of the manufacturing method.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a manufacturing method for a semiconductor device is provided. The manufacturing method includes providing a substrate having at least a gate structure formed thereon, and a first spacer being formed on sidewalls of the gate structure; performing an ion implantation to implant dopants into the substrate; forming a disposal spacer on the sidewalls of the gate structure, the disposal spacer comprising at least a carbon-containing layer, and the carbon-containing layer contacting the first spacer; and performing a thermal treatment to form a protecting layer between the carbon-containing layer and the first spacer.
According to another aspect of the present invention, a manufacturing method for a semiconductor device is provided. The manufacturing method includes providing a substrate having at least a gate structure formed thereon, and a first spacer is formed on sidewalls of the gate structure. Then, at least a carbon-containing layer is formed on the substrate, the carbon-containing layer contacts the first spacer. After forming the carbon-containing layer, a thermal treatment is performed to form a protecting layer between the carbon-containing layer and the first spacer and followed by performing an etching back process to remove portions of the carbon-containing layer and of the protecting layer to form a disposal spacer on the sidewalls of the gate structure.
According to another aspect of the present invention, a semiconductor device is provided. The semiconductor device includes a gate structure, a first spacer positioned on sidewalls of the gate structure, a second spacer positioned on the first spacer, the second spacer comprising a silicon nitride layer and a carbon-containing layer, a SiCN-based protecting layer formed between the first spacer and the second spacer, and epitaxial layers respectively positioned at two sides of the second spacer.
According to the manufacturing method for the semiconductor device provided by the present invention, the thermal treatment is introduced to cause a reaction between the carbon-containing layer of the disposal spacer and the first spacer, so that a SiCN-based protecting layer is formed between the carbon-containing layer and the first spacer. Consequently, the SiCN-based protecting layer serves as an etching stop layer during removing the disposal spacer, and thus the underneath first spacer is protected from consumption. Since the first spacer remains unimpaired and impervious to the disposal spacer removal and possesses its original profile due to the SiCN-based protecting layer, the subsequent steps for forming elements such as the second spacer and the source/drain are performed successfully and the obtained second spacer and source/drain can meet the expectation.
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. 1-4 and FIGS. 8-10 are drawings illustrating a manufacturing method for a semiconductor device provided by a first preferred embodiment of the present invention, wherein
FIG. 2 is a schematic drawing in a step subsequent to FIG. 1,
FIG. 3 is a schematic drawing in a step subsequent to FIG. 2, and
FIG. 4 is a schematic drawing in a step subsequent to FIG. 3.
FIGS. 5-7 and FIGS. 8-10 are drawings illustrating a manufacturing method for a semiconductor device provided by a second preferred embodiment of the present invention, wherein
FIG. 6 is a schematic drawing in a step subsequent to FIG. 5, and
FIG. 7 is a schematic drawing in a step subsequent to FIG. 6.
FIGS. 8-10 are schematic drawings in steps subsequent to FIGS. 4 and 7, wherein
FIG. 8 is a schematic drawing in a step subsequent to FIGS. 4 and 7,
FIG. 9 is a schematic drawing in a step subsequent to FIG. 8, and
FIG. 10 is a schematic drawing in a step subsequent to FIG. 9.
FIGS. 11-15 are drawings illustrating a manufacturing method for a semiconductor device provided by a third preferred embodiment of the present invention, wherein
FIG. 12 is a schematic drawing in a step subsequent to FIG. 11,
FIG. 13 is a schematic drawing in a step subsequent to FIG. 12,
FIG. 14 is a schematic drawing in a step subsequent to FIG. 13, and
FIG. 15 is a schematic drawing in a step subsequent to FIG. 14.
FIGS. 16-20 are drawings illustrating a manufacturing method for a semiconductor device provided by a fourth preferred embodiment of the present invention, wherein
FIG. 17 is a schematic drawing in a step subsequent to FIG. 16,
FIG. 18 is a schematic drawing in a step subsequent to FIG. 17,
FIG. 19 is a schematic drawing in a step subsequent to FIG. 17, and
FIG. 20 is a schematic drawing in a step subsequent to FIG. 19.
FIGS. 21-24 are drawings illustrating a manufacturing method for a semiconductor device provided by a fifth preferred embodiment of the present invention, wherein
FIG. 22 is a schematic drawing in a step subsequent to FIG. 21,
FIG. 23 is a schematic drawing in a step subsequent to FIG. 22, and
FIG. 24 is a schematic drawing in a step subsequent to FIG. 23.
FIGS. 25-28 are drawings illustrating a manufacturing method for a semiconductor device provided by a sixth preferred embodiment of the present invention, wherein
FIG. 26 is a schematic drawing in a step subsequent to FIG. 25,
FIG. 27 is a schematic drawing in a step subsequent to FIG. 26, and
FIG. 28 is a schematic drawing in a step subsequent to FIG. 27.



DETAILED DESCRIPTION
Please refer to FIGS. 1-4, which are drawings illustrating a manufacturing method for a semiconductor device provided by a first preferred embodiment of the present invention. As shown in FIG. 1, the preferred embodiment first provides a substrate 100 having a plurality of shallow trench isolations (STIs) 102 for providing electrical isolation formed therein. A first gate structure 110 and a second gate structure 111 are formed on the substrate 100. The first gate structure 110 and the second gate structure 111 include a gate dielectric layer 112, a gate conductive layer 114, and a cap layer 116 sequentially and upwardly stacked on the substrate 100. It is well-known to those skilled in the art that the cap layer 116 is formed to cover the gate conductive layer 114 to protect the gate conductive layer 114 from damage that may be caused in any process such as photolithograph process, ion implantation, etching process, or any needed cleaning process in the semiconductor fabricating process. Furthermore, a first spacer 120 is formed on sidewalls of the first gate structure 110 and the second gate structure 111, respectively. The first spacer 120 includes, for example but not limited to, a silicon nitride layer preferably formed by bis(tertiary-butylamino) silane (BTBAS). A width of the first spacer 120 is exemplarily 50 angstroms (Å), but not limited to this. Additionally, those skilled in the art would easily realize that the material and width of the first spacer 120 can be modified depending on different process or product requirements.
Please refer to FIG. 1 again. Next, an ion implantation (not shown) is performed to form second lightly-doped drains (LDDs) 137 in the substrate 100 respectively at two sides of the second gate structure 111. Then, a mask layer 118 is formed on the substrate 100 and followed by performing another ion implantation 130. Accordingly, dopants (not shown) are implanted into the substrate 100 at two sides of the first gate structure 110, particularly at two sides of the first spacer 120. Then, a thermal treatment 132 is performed to drive-in the dopants, such that first LDDs 136 are formed in the substrate 100 respectively at two sides of the first spacer 120 of the first gate structure 110. The conductivity types of the dopants for the first LDDs 136 and the second LDDs 137 are complementary to each other. For example, the first gate structure 110 is a p type gate structure and thus the dopants for forming the first LDDs 136 are p-type dopants such as boron (B) or boron difluoride (BF2). The second gate structure 111 is an n type gate structure thus the dopants for forming the second LDDs 137 are n-type dopants such as phosphorous (P) or arsenic (Ar).
Please refer to FIG. 2. Subsequently, the mask layer 118 is removed and a protecting layer 140 is blanketly formed on the substrate 100, subsequently. The protecting layer 140 includes silicon carbon nitride based (SiCN-based) material. For example, the SiCN-based material can be SiCN or silicon oxycarbonitride (SiOCN), but not limited to this.
Please refer to FIG. 3. After forming the protecting layer 140, a carbon-containing layer 142 and a silicon nitride layer 144 are blanketly and sequentially formed on the substrate 100. In the preferred embodiment, the carbon-containing layer 142 includes, for example but not limited to, a layer formed by carbon source gas and hexachlorodisilane (Si2Cl6, HCD), and the silicon nitride layer 144 preferably includes a silicon nitride layer formed by HCD. Additionally, a thickness of the carbon-containing layer 142 is about 40 Å, and a thickness of the silicon nitride layer 144 is about 130 Å. However, the thickness of the carbon-containing layer 142 and of the silicon nitride layer 144 can be modified depending on different process requirements.
Please refer to FIG. 4. After forming the carbon-containing layer 142 and the silicon nitride layer 144, another mask layer 118a, such as a patterned photoresist, is formed to cover the second gate structure 111. Subsequently, an etching back process 150 is performed to form a disposal spacer 152 respectively on the sidewalls of the first gate structure 110, particularly on the first spacer 120. The disposal spacer 152 including the carbon-containing layer 142 and the silicon nitride layer 144 defines positions of recesses required by the SEG process at the two sides of the first gate structure 110. It is noteworthy that according to the preferred embodiment, the protecting layer 140 positioned between the disposal spacer 152 and the first spacer 120 includes an L shape as shown in FIG. 4.
Please refer to FIGS. 5-10, which are drawings illustrating a manufacturing method for a semiconductor device provided by a second preferred embodiment of the present invention. It should be noted that elements the same in the first and second preferred embodiments are designated by the same numerals, and those elements can include the same materials. Thus those details are omitted hereinafter in the interest of brevity. As shown in FIG. 5, the preferred embodiment first provides a substrate 100 having a plurality of STIs 102 formed therein. A first gate structure 110 and a second gate structure 111 are formed on the substrate 100, and the first gate structure 110 and the second gate structure 111 include a gate dielectric layer 112, a gate conductive layer 114, and a cap layer 116 sequentially and upwardly stacked on the substrate 100. Furthermore, a first spacer 120 is formed on sidewalls of the first gate structure 110 and the second gate structure 111, respectively.
Please still refer to FIG. 5. Next, second LDDs 137 are formed in the substrate 100 at two sides of the second gate structure 111, respectively. Then, a mask layer (not shown) is formed on the substrate 100 and followed by performing an ion implantation (as shown in FIG. 1). Accordingly, dopants 134 are implanted into the substrate 100 at two sides of the first spacer 120 of the first gate structure. After the ion implantation, a carbon-containing layer 142 and a silicon nitride layer 144 are blanketly and sequentially formed on the substrate 100. As shown in FIG. 5, the carbon-containing layer 142 contacts the first spacer 120. In the preferred embodiment, the carbon-containing layer 142 can be a layer formed by carbon source gas and HCD and the silicon nitride layer 144 can be a silicon nitride layer formed by HCD. Additionally, a thickness of the carbon-containing layer 142 is about 40 Å, and a thickness of the silicon nitride layer 144 is about 130 Å. However, the thickness of the carbon-containing layer 142 and of the silicon nitride layer 144 can be modified depending on different process requirements.
Please refer to FIG. 6. After forming the carbon-containing layer 142 and the silicon nitride layer 144, an etching back process 150 is performed to form a disposal spacer 152 respectively on the sidewalls of the first gate structure 110 and the second gate structure 111, particularly on the first spacer 120. The disposal spacer 152 including the carbon-containing layer 142 and the silicon nitride layer 144 defines positions of recesses required by the SEG process at the two sides of the first gate structure 110.
Please refer to FIG. 7. Next, a thermal treatment 132 is performed to cause a thermal reaction between the carbon-containing layer 142 and the first spacer 120. In other words, the carbon-containing layer 142 reacts with the first spacer 120 and thus a protecting layer 140 is formed between the carbon-containing layer 142 and the first spacer 120. In the preferred embodiment, the thermal treatment 132 includes a spike rapid thermal process (spike RTP), and a process temperature of the thermal treatment 132 is between 850° C. and 1000° C. It is noteworthy that since the protecting layer 140 is obtained by reaction between the carbon-containing layer 142 and the first spacer 120 which includes silicon nitride, the protecting layer 140 includes SiCN-based material such as SiCN or SiOCN, but not limited to this. Different from the first preferred embodiment, in which the protecting layer 140 is an L-shaped layer, the protecting layer 140 in the preferred embodiment, which is formed at the interface between the first spacer 120 and the carbon-containing layer 142 does not possess the L shape. More important, the thermal treatment 132 drives-in the dopants 134 in the substrate 100 to form first LDDs 136 simultaneously with forming the protecting layer 140.
Please refer to FIGS. 8-10. It is noteworthy that steps depicted in FIGS. 8-10 are performed after forming the first LDDs 136 and the protecting layer 140 by the thermal treatment 132 in the second preferred embodiment, however those steps can also be performed after forming the disposal spacer 152 in the first preferred embodiment. As shown in FIG. 8, after performing the thermal treatment 132 to simultaneously form the protecting layer 140 and the first LDDs 136, another mask layer (not shown) is formed on the substrate 100. The mask layer, the cap layers 116, the disposal spacers 152, and the STIs 102 serve as an etching mask and an etching process 160 is performed to form a recess 162 in the substrate 100 respectively at two sides of the disposal spacer 152 of the first gate structure 110.
Please still refer to FIG. 8. After forming the recess 162, a pre-clean process is performed by using diluted hydrofluoric acid or SPM solution containing sulfuric acid, hydrogen peroxide, and deionized water to remove native oxides or other impurities from the surface of the recesses 162. Subsequently, a selective epitaxial growth (SEG) process 170 is performed to an epitaxial layer 172 such as an epitaxial silicon-germanium (SiGe) layer or an epitaxial silicon carbide (SiC) layer along the surface of the recess 162. Because a lattice constant of the epitaxial layers 172 is different from that of silicon, such characteristic is employed to cause alteration to the band structure of the silicon in the channel region. Accordingly, carrier mobility of the channel region of the semiconductor device is enhanced and thus device performance is improved. Subsequently, the mask layer is removed.
Please refer to FIG. 9. After forming the epitaxial layers 172, the disposal spacers 152 are removed. It is noteworthy that during removing the disposal spacers 152, the protecting layer 140 serves as an etching stop layer and protects the underneath first spacers 120. Accordingly, the first spacers 120 of both first gate structure 110 and the second gate structure 111 are impervious to the disposal spacer removal, and thus its profile and width are not consumed. As shown in FIG. 9, after removing the disposal spacers 152, the protecting layers 140 are exposed on the substrate 100.
Please refer to FIG. 10. After removing the disposal spacers 152, a second spacer 180 is respectively formed on the first gate structure 110 and the second gate structure 111, particularly on the exposed protecting layer 140, and followed by performing another ion implantation (not shown). Consequently, a first source/drain 182 is formed in the epitaxial layers 172 at two sides of the second spacer 180. And another ion implantation (not shown) is performed to form a second source/drain 183 in the substrate 100 at two sides of the second spacer 180 of the second gate structure 111. Since the details of forming the second spacer 180, the first source/drain 182, and the second source/drain 183 are well-known to those skilled in the art, those details are omitted in the interest of brevity.
According to the manufacturing method for the semiconductor device provided by the first and second preferred embodiments, the SiCN-based protecting layers 140 are formed on the first spacer 120 before forming the disposal spacers 152 or formed between the carbon-containing layer 142 of the disposal spacer 152 and the first spacer 120 simultaneously with forming the first LDDs 136 by the thermal treatment 132. Since etching rate of the SiCN-based the protecting layer 140 is different from that of the disposal spacer 152 and of the first spacer 120, the SiCN-based protecting layer 140 protects the first spacer 120, and thus the width and the profile of the first spacer 120 are unimpaired and impervious during removing the disposal spacer 152. Additionally, the profile of the first gate structure 110 and the second gate structure 111 remains un-damaged. Therefore distances between the first source/drain 182, the first gate structure 110, and its channel region, and distances between the second source/drain 183, the second gate structure 111, and its channel region all meet the expectation. Hence, yield of the manufacturing method and reliability of the obtained semiconductor device are ensured without increasing process complexity.
Please refer to FIGS. 11-15, which are drawings illustrating a manufacturing method for a semiconductor device provided by a third preferred embodiment of the present invention. It is noteworthy that elements the same in the first, second, and third preferred embodiments can include the same materials. Those details are therefore omitted for simplicity. As shown in FIG. 11, the preferred embodiment first provides a substrate 200 having a plurality of STIs 202 for providing electrical isolation formed therein. A first gate structure 210 and a second gate structure 211 are formed on the substrate 200, and the first gate structure 210 and the second gate structure 211 include a gate dielectric layer 212, a gate conductive layer 214, and a cap layer 216 sequentially and upwardly stacked on the substrate 200. Furthermore, a first spacer 220 is formed on sidewalls of the first gate structure 210 and the second gate structure 211, respectively. A width of the first spacer 220 is exemplarily 50 Å, but not limited to this.
Please refer to FIG. 11 again. Next, second LDDs 237 are formed in the substrate 200 at two sides of the second gate structure 211, respectively. Then, a mask layer (not shown) is formed on the substrate 200 and followed by performing an ion implantation as described in the aforementioned preferred embodiments. Accordingly, dopants 234 are implanted into the substrate 200 at two sides of the first spacer 220. After performing the ion implantation, a carbon-containing layer 242 and a silicon nitride layer 244 are blanketly and sequentially formed on the substrate 200. As shown in FIG. 11, the carbon-containing layer 242 contacts the first spacer 220. In the preferred embodiment, the carbon-containing layer 242 can be a layer formed by carbon source gas and HCD and the silicon nitride layer 144 can be a silicon nitride layer formed by HCD. Additionally, a thickness of the carbon-containing layer 242 is about 40 Å, and a thickness of the silicon nitride layer 244 is about 130 Å. However, the thickness of the carbon-containing layer 242 and of the silicon nitride layer 244 can be modified depending on different process requirements.
Please still refer to FIG. 11. After forming the carbon-containing layer 242 and the silicon nitride layer 244, an etching back process 250 is performed to form a disposal spacer 252 respectively on the sidewalls of the first gate structure 210 and the second gate structure 211, particularly on the first spacer 220. The disposal spacer 252 including the carbon-containing layer 242 and the silicon nitride layer 244 further defines positions of recesses required by the SEG process at the two sides of the first gate structure 210.
Please refer to FIG. 12. After forming the disposal spacer 252, a mask layer 218 is formed on the substrate 200. Subsequently, the mask layer 210, the cap layers 216, the disposal spacers 252, and the STIs 202 serve as an etching mask and an etching process 260 is performed to form a recess 262 in the substrate 200 respectively at two sides of the disposal spacer 252 of the first gate structure 210.
Please refer to FIG. 13. After the etching process 260, a thermal treatment 232 is performed to cause a thermal reaction between the carbon-containing layer 242 and the first spacer 220. In other words, the carbon-containing layer 242 reacts with the first spacer 220 and thus a protecting layer 240 is formed therebetween. The parameters of the thermal treatment 232 can be the same with those described in the aforementioned preferred embodiment, therefore those details are omitted for simplicity. It is noteworthy the protecting layer 240 is formed at the interface between the first spacer 220 and the carbon-containing layer 242 and includes SiCN-based material such as SiCN or SiOCN in accordance with the preferred embodiment. More important, the thermal treatment 232 drives-in the dopants 234 in the substrate 200 to form first LDDs 236 simultaneously with forming the protecting layer 240.
Please refer to FIG. 14. After the thermal treatment 232, a SEG process (as shown in FIG. 8) is performed to form an epitaxial layer 272 such as an epitaxial SiGe layer or an epitaxial SiC layer along the surface of the recess 262. After forming the epitaxial layers 272, the disposal spacers 252 are removed. It is noteworthy that during removing the disposal spacers 252, the protecting layer 240 serves as an etching stop layer and protects the underneath first spacer 220. Accordingly, the first spacers 220 are impervious to the disposal spacer removal, and thus its profile and width are not consumed. As shown in FIG. 14, after removing the disposal spacers 252, the protecting layers 240 are exposed on the substrate 200.
Please refer to FIG. 15. After removing the disposal spacer 252, a second spacer 280 is respectively formed on the first gate structure 210 and second gate structure 211, particularly on the exposed protecting layer 240, and followed by performing another ion implantation (not shown). Consequently, a first source/drain 282 is formed in the epitaxial layers 272 at two sides of the second spacer 280. And another ion implantation (not shown) is performed to form a second source/drain 283 in the substrate 200 at two sides of the second spacer 280 of the second gate structure 211. Since the details of forming the second spacer 280, the first source/drain 282, and the second source/drain 283 are well-known to those skilled in the art, those details are omitted for simplicity.
According to the manufacturing method for the semiconductor device provided by the third preferred embodiment, the SiCN-based protecting layer 240 is formed in the SEG-related processes, particularly formed after the etching process 260 that is used to form the recesses 262. Simultaneously with forming the first LDDs 236 by the thermal treatment 232, the carbon-containing layer 242 of the disposal spacer 252 and the first spacer 220 react to form the SiCN-based protecting layer 240. Since etching rate of the SiCN-based the protecting layer 240 is different from that of the disposal spacer 252 and of the first spacer 220, the SiCN-based protecting layer 240 protects the first spacer 220, therefore the width and the profile of the first spacer 220 are unimpaired and impervious during removing the disposal spacers 252. Additionally, the profiles of the first gate structure 210 and the second gate structure 211 remain un-damaged. Therefore the distances between the first source/drain 282, the first gate structure 210, and its channel region and distances between the second source/drain 283, the second gate structure 211, and its channel region all meet the expectation. Hence, yield of the manufacturing method and reliability of the obtained semiconductor device are ensured without increasing process complexity.
Please refer to FIGS. 16-20, which are drawings illustrating a manufacturing method for a semiconductor device provided by a fourth preferred embodiment of the present invention. It is noteworthy that elements the same in the first to fourth preferred embodiments can include the same materials. Those details are therefore omitted for simplicity. As shown in FIG. 16, the preferred embodiment first provides a substrate 300 having a plurality of STIs 302 for providing electrical isolation formed therein. A first gate structure 310 and a second gate structure 311 are formed on the substrate 300, and the first gate structure 310 and the second gate structure 311 include a gate dielectric layer 312, a gate conductive layer 314, and a cap layer 316 sequentially and upwardly stacked on the substrate 300. Furthermore, a first spacer 320 is formed on sidewalls of the first gate structure 310 and the second gate structure 311, respectively.
Please refer to FIG. 16 again. Next, second LDDs 337 are formed in the substrate 300 at two sides of the second gate structure 311, respectively. Then, a mask layer (not shown) is formed on the substrate 300 and followed by performing an ion implantation as described in the aforementioned preferred embodiments. Accordingly, dopants 334 are implanted into the substrate 300 at two sides of the first spacer 320 of the first gate structure 310. After the ion implantation, a carbon-containing layer 342 and a silicon nitride layer 344 are blanketly and sequentially formed on the substrate 300. As shown in FIG. 16, the carbon-containing layer 342 contacts the first spacer 320. In the preferred embodiment, the carbon-containing layer 342 can be a layer formed by carbon source gas and HCD and the silicon nitride layer 344 can be a silicon nitride layer formed by HCD. Additionally, a thickness of the carbon-containing layer 342 is about 40 Å, and a thickness of the silicon nitride layer 344 is about 130 Å. However, the thickness of the carbon-containing layer 342 and of the silicon nitride layer 344 can be modified depending on different process requirements.
Please still refer to FIG. 16. After forming the carbon-containing layer 342 and the silicon nitride layer 344, an etching back process 350 is performed to form a disposal spacer 352 respectively on the sidewalls of the first gate structure 310 and the second gate structure 311, particularly on the first spacer 320. The disposal spacer 352 including the carbon-containing layer 342 and the silicon nitride layer 344 further defines positions of recesses required by the SEG process at the two sides of the first gate structure 310.
Please refer to FIG. 17. After forming the disposal spacer 352, another mask layer 318 is formed on the substrate 300. Subsequently, the mask layer 318, the cap layers 316, the disposal spacers 352, and the STIs 302 serve as an etching mask and an etching process 360 is performed to form a recess 362 in the substrate 200 respectively at two sides of the disposal spacer 352 of the first gate structure 310. Subsequently, a pre-clean process is performed to remove native oxides or other impurities from the surface of the recesses 362. Next, a SEG process 370 is performed to form an epitaxial layer 372 such as an epitaxial SiGe layer or an epitaxial SiC layer along the surface of the recess 362.
Please refer to FIG. 18. After performing the SEG process 370, the mask layer 318 is removed and a thermal treatment 332 is subsequently performed to cause a thermal reaction between the carbon-containing layer 342 and the first spacer 320. In other words, the carbon-containing layer 342 reacts with the first spacer 320 and thus a protecting layer 340 is formed therebetween. The parameters of the thermal treatment 332 can be the same with those described in the aforementioned preferred embodiments, therefore those details are omitted for simplicity. It is noteworthy the protecting layer 340 is formed at the interface between the first spacer 320 and the carbon-containing layer 342, and includes SiCN-based material such as SiCN or SiOCN in accordance with the preferred embodiment. More important, the thermal treatment 332 drives-in the dopants 334 in the substrate 300 to form first LDDs 336 simultaneously with forming the protecting layer 340.
Please refer to FIG. 19. After performing the thermal treatment 332 to form the SiCN-based protecting layer 340 and the LDDs 336, the disposal spacers 352 are removed. It is noteworthy that during removing the disposal spacers 352, the protecting layer 340 serves as an etching stop layer and protects the underneath first spacer 320. Accordingly, the first spacers 320 are impervious to the disposal spacer removal, and thus its profile and width are not consumed. As shown in FIG. 19, after removing the disposal spacers 352, the protecting layers 340 are exposed on the substrate 300.
Please refer to FIG. 20. After removing the disposal spacer 352, a second spacer 380 is respectively formed on the first gate structure 310 and the second gate structure 311, particularly on the exposed protecting layer 340, and followed by performing another ion implantation (not shown). Consequently, a first source/drain 382 is formed in the epitaxial layers 372 at two sides of the second spacer 380. And another ion implantation (not shown) is performed to form a second source/drain 383 in the substrate 300 at two sides of the second spacer 380 of the second gate structure 311. Since the details of forming the second spacer 380, the first source/drain 382, and the second source/drain 383 are well-known to those skilled in the art, those details are omitted for simplicity.
According to the manufacturing method for the semiconductor device provided by the fourth preferred embodiment, the SiCN-based protecting layer 340 is formed after the SEG process 370. Simultaneously with forming the LDDs 336 by the thermal treatment 332, the carbon-containing layer 342 of the disposal spacer 352 and the first spacer 320 react to form the SiCN-based protecting layer 340. The SiCN-based protecting layer 340 protects the first spacer 320, therefore the width and the profile of the first spacer 320 are unimpaired and impervious during removing the disposal spacers 352. Additionally, the profile of the first gate structure 310 and the second gate structure 311 remains un-damaged. Therefore distances between the first source/drain 382, the first gate structure 310, and its channel region, and distances between the second source/drain 383, the second gate structure 311, and its channel region all meet the expectation. Hence, yield of the manufacturing method and reliability of the obtained semiconductor device are ensured without increasing process complexity.
Please refer to FIGS. 21-24, which are drawings illustrating a manufacturing method for a semiconductor device provided by a fifth preferred embodiment of the present invention. It is noteworthy that elements the same in the first to fifth preferred embodiments can include the same materials. Those details are therefore omitted for simplicity. As shown in FIG. 21, the preferred embodiment first provides a substrate 400 having a plurality of STIs 402 for providing electrical isolation formed therein. A first gate structure 410 and a second gate structure 411 are formed on the substrate 400, and the first gate structure 410 and the second gate structure 411 include a gate dielectric layer 412, a gate conductive layer 414, and a cap layer 416 sequentially and upwardly stacked on the substrate 400. Furthermore, a first spacer 420 is formed on sidewalls of the first gate structure 410 and the second gate structure 411, respectively. A width of the first spacers 420 is about 50 Å, but not limited to this.
Please still refer to FIG. 21. Next, second LDDs 437 are formed in the substrate 400 at two sides of the second gate structure 411, respectively. Then, a mask layer (not shown) is formed on the substrate 400 and followed by performing an ion implantation as described in the aforementioned preferred embodiments. Accordingly, dopants 434 are implanted into the substrate 400 at two sides of the first spacer 420 of the first gate structure 410.
Please refer to FIG. 22. After the ion implantation, a carbon-containing layer 442 and a silicon nitride layer 444 are blanketly and sequentially formed on the substrate 400. As shown in FIG. 22, the carbon-containing layer 442 contacts the first spacer 420. In the preferred embodiment, the carbon-containing layer 442 can be a layer formed by carbon source gas and HCD and the silicon nitride layer 444 can be a silicon nitride layer formed by HCD. Additionally, a thickness of the carbon-containing layer 442 is about 40 Å, and a thickness of the silicon nitride layer 444 is about 130 Å. However, the thickness of the carbon-containing layer 442 and of the silicon nitride layer 444 can be modified depending on different process requirements.
Please refer to FIG. 23. After forming the carbon-containing layer 442 and the silicon nitride layer 444, a thermal treatment 432 is subsequently performed to cause a thermal reaction between the carbon-containing layer 442 and the first spacer 420. In other words, the carbon-containing layer 442 reacts with the first spacer 420 and thus a protecting layer 440 is formed therebetween. The parameters of the thermal treatment 432 can be the same with those described in the aforementioned preferred embodiments, therefore those details are omitted for simplicity. It is noteworthy the protecting layer 440 is formed at the interface between the first spacer 420 and the carbon-containing layer 442, and includes SiCN-based material such as SiCN or SiOCN in accordance with the preferred embodiment. More important, the thermal treatment 432 drives-in the dopants 434 in the substrate 400 to form first LDDs 436 simultaneously with forming the protecting layer 440.
Please refer to FIG. 24. After forming the protecting layer 440 and the first LDDs 436, an etching back process 450 is performed to form a disposal spacer 452 respectively on the sidewalls of the first gate structure 410 and the second gate structure 411, particularly on the first spacer 420. The disposal spacer 452 including the carbon-containing layer 442 and the silicon nitride layer 444 further defines positions of recesses required by the SEG process at the two sides of the first gate structure 410.
After forming the disposal spacers 452, steps for forming recesses, performing SEG process, and forming source/drain as mentioned above can be performed. Since those steps are detailed in the aforementioned preferred embodiments, those details are omitted for simplicity.
According to the manufacturing method for the semiconductor device provided by the fifth preferred embodiment, the SiCN-based protecting layer 440 is formed before the SEG-related processes, particularly before the etching back process 450 that is used to form the disposal spacers 452. Simultaneously with forming the first LDDs 436 by the thermal treatment 432, the carbon-containing layer 442 of the disposal spacer 452 and the first spacer 420 react to form the SiCN-based protecting layer 440. Since etching rate of the SiCN-based the protecting layer 440 is different from that of the disposal spacer 452 and of the first spacer 420, the SiCN-based protecting layer 440 protects the first spacer 420, therefore the width and the profile of the first spacer 420 are unimpaired and impervious during removing the disposal spacers 452. Additionally, the profiles of the first gate structure 410 and the second gate structure 411 remain un-damaged. Therefore the distances between the source/drain, the gate structure, and its channel region all meet the expectation. Hence, yield of the manufacturing method and reliability of the obtained semiconductor device are ensured without increasing process complexity.
Please refer to FIGS. 25-28, which are drawings illustrating a manufacturing method for a semiconductor device provided by a sixth preferred embodiment of the present invention. It is noteworthy that elements the same in the first to fifth preferred embodiments can include the same materials. Those details are therefore omitted for simplicity. As shown in FIG. 25, the preferred embodiment first provides a substrate 500 having a plurality of STIs 502 for providing electrical isolation formed therein. A first gate structure 510 and a second gate structure 511 are formed on the substrate 500, and the first gate structure 510 and the second gate structure 511 include a gate dielectric layer 512, a gate conductive layer 514, and a cap layer 516 sequentially and upwardly stacked on the substrate 500. Furthermore, a first spacer 520 is formed on sidewalls of the first gate structure 510 and the second gate structure 511, respectively.
Please still refer to FIG. 25. Next, a carbon-containing layer 542 and a silicon nitride layer 544 are blanketly and sequentially formed on the substrate 500. As shown in FIG. 25, the carbon-containing layer 542 contacts the first spacer 520. In the preferred embodiment, the carbon-containing layer 542 can be a layer formed by CHCD and the silicon nitride layer 544 can be a silicon nitride layer formed by HCD. Additionally, a thickness of the carbon-containing layer 542 is about 40 Å, and a thickness of the silicon nitride layer 544 is about 130 Å. However, the thickness of the carbon-containing layer 542 and of the silicon nitride layer 544 can be modified depending on different process requirements.
Please refer to FIG. 26. After forming the carbon-containing layer 542 and the silicon nitride layer 544, different ion implantations are performed to implant first dopants 534 into the substrate 500 respectively at two sides of the first gate structure 510, and to implant second dopants 535 into the substrate 500 respectively at two sides of the second gate structure 511. The first dopants 534 and the second dopants 535 are complementary to each other. It is noteworthy that according to the preferred embodiment, the carbon-containing layer 542 and the silicon nitride layer 544 serve as a multiple seal layer, thus the first dopants 534 and the second dopants 535 must penetrate through the multiple seal layer to get into the substrate 500.
Please refer to FIG. 27. After performing the above mentioned ion implantations, a thermal treatment 532 is subsequently performed to cause a thermal reaction between the carbon-containing layer 542 and the first spacer 520. In other words, the carbon-containing layer 542 reacts with the first spacer 520 and thus a protecting layer 540 is formed therebetween. The parameters of the thermal treatment 532 can be the same with those described in the aforementioned preferred embodiments, therefore those details are omitted for simplicity. It is noteworthy the protecting layer 540 is formed at the interface between the first spacer 520 and the carbon-containing layer 542, and includes SiCN-based material such as SiCN or SiOCN in accordance with the preferred embodiment. More important, the thermal treatment 532 further drives-in the first dopants 534 and the second dopants 535 in the substrate 400 to form first LDDs 536 and second LDDs 537 simultaneously with forming the protecting layer 540.
Please refer to FIG. 28. Next, an etching back process 550 is performed to form a disposal spacer 552 respectively on the sidewalls of the first gate structure 510 and the second gate structure 511, particularly on the first spacer 520. The disposal spacer 552 including the carbon-containing layer 542 and the silicon nitride layer 544 further defines positions of recesses required by the SEG process at the two sides of the first gate structure 510.
After forming the disposal spacers 552, steps for forming recesses, performing SEG process, and forming source/drain as mentioned above can be performed. Since those steps are detailed in the aforementioned preferred embodiments, those details are omitted for simplicity.
According to the manufacturing method for the semiconductor device provided by the sixth preferred embodiment, the carbon-containing layer 542 and the silicon nitride layer 544 are formed before the SEG-related processes, even before the ion implantations that is used to implant the dopants 534, 535 for forming the LDDs 536, 537. Simultaneously with forming the first LDDs 536 and the second LDDs 537 by the thermal treatment 532, the carbon-containing layer 542 of the disposal spacer 552 and the first spacer 520 react to form the SiCN-based protecting layer 540. Since etching rate of the SiCN-based the protecting layer 540 is different from that of the disposal spacer 552 and of the first spacer 520, the SiCN-based protecting layer 540 protects the first spacer 520, therefore the width and the profile of the first spacer 520 are unimpaired and impervious during removing the disposal spacers 552. Additionally, the profiles of the first gate structure 510 and the second gate structure 511 remain un-damaged. Therefore the distances between the source/drain, the gate structure, and its channel region all meet the expectation. Hence, yield of the manufacturing method and reliability of the obtained semiconductor device are ensured without increasing process complexity. Furthermore, since the carbon-containing layer 542 and the silicon nitride layer 544 serve as the seal layer, dopants 534, 535 have to penetrate the seal layer to get into the substrate 500. Consequently the following formed first LDDs 536 and the second LDDs 537 obtain the expected ultra-shallow junction profile. Accordingly, SCE is efficiently suppressed and performance of the semiconductor device is improved by improving the ultra-shallow junction profile of the LDDs even when the device size keeps shrinking.
According to the manufacturing method for the semiconductor device provided by the present invention, the thermal treatment is introduced to cause a reaction between the carbon-containing layer of the disposal spacer and the first spacer, so that a SiCN-based protecting layer is formed between the carbon-containing layer and the first spacer before forming the disposal spacer, before forming the recess required by the SEG process, after forming the recess, or after forming the epitaxial layer by the SEG process. Consequently, the SiCN-based protecting layer serves as an etching stop layer during removing the disposal spacer, and thus the underneath first spacer is protected from consumption. Since the first spacer remains unimpaired and impervious to the disposal spacer removal and possesses its original profile due to the protection rendered from the SiCN-based protecting layer, the subsequent steps for forming elements such as the second spacer and the source/drain are performed successfully and the obtained second spacer and source/drain all meet the expectation. Furthermore, since the thermal treatment simultaneously drives-in the dopants to form the LDDs in the substrate, it is conceivable that the manufacturing method for the semiconductor device provided by the present invention can be integrated and practiced in the industries, and to ensure yield of the manufacturing method and reliability of the obtained semiconductor device without increasing process complexity.
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 semiconductor device comprising:
a gate structure;
a first spacer positioned on sidewalls of the gate structure;
a second spacer positioned on the first spacer, the second spacer comprising a silicon nitride layer and a carbon-containing layer;
a SiCN-based protecting layer formed between the first spacer and the second spacer; and
epitaxial layers respectively positioned at two sides of the second spacer.

2. The semiconductor device according to claim 1, wherein the silicon nitride layer is formed by hexachlorodisilane (HCD).

3. The semiconductor device according to claim 1, wherein the carbon-containing layer is formed by a carbon source gas and hexachlorodisilane (HCD).

4. The semiconductor device according to claim 1, wherein the SiCN-based protecting layer comprises silicon oxycarbonitride (SiOCN).

5. The semiconductor device according to claim 1, wherein the SiCN-based protecting layer comprises an L shape.