Isolation region fabrication for replacement gate processing
A method for isolation region fabrication for replacement gate integrated circuit (IC) processing includes forming a plurality of dummy gates on a substrate; forming a block mask over the plurality of dummy gates, such that the block mask selectively exposes a dummy gate of the plurality of dummy gates; removing the exposed dummy gate to form an isolation region recess corresponding to the removed dummy gate; filling the isolation region recess with an insulating material to form an isolation region; removing the block mask to expose a remaining plurality of dummy gates; and performing replacement gate processing on the remaining plurality of dummy gates to form a plurality of active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region.
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This disclosure relates generally to the field of integrated circuit (IC) manufacturing, and more specifically to isolation region fabrication for electrical isolation between semiconductor devices on an IC.
ICs are formed by connecting isolated active devices, which may include semiconductor devices such as field effect transistors (FETs), through specific electrical connection paths to form logic or memory circuits. Therefore, electrical isolation between active devices is important in IC fabrication. Isolation of FETs from one another is usually provided by shallow trench isolation (STI) regions located between active silicon islands. An STI region may be formed by forming a trench in the substrate between the active devices by etching, and then filling the trench with an insulating material, such as an oxide. After the STI trench is filled with the insulating material, the surface profile of the STI region may be planarized by, for example, chemical mechanical polishing (CMP).
However, use of raised (or regrown) source/drain structures, which may be employed to achieve lower series resistances of the IC or to strain FET channels, may exhibit significant growth non-uniformities at the boundary between a gate and an STI region, or when the opening in which the source/drain structure is formed is of variable dimensions. This results in increased variability in FET threshold voltage (Vt), delay, and leakage, which in turn degrades over-all product performance and power. One solution to such boundary non-uniformity is to require all STI regions to be bounded by isolation regions. However, inclusion of such isolation region structures may limit space available for wiring, device density, and increase the load capacitance, thereby increasing switching power of the IC.
BRIEF SUMMARYIn one aspect, a method for isolation region fabrication for replacement gate integrated circuit (IC) processing includes forming a plurality of dummy gates on a substrate; forming a block mask over the plurality of dummy gates, such that the block mask selectively exposes a dummy gate of the plurality of dummy gates; removing the exposed dummy gate to form an isolation region recess corresponding to the removed dummy gate; filling the isolation region recess with an insulating material to form an isolation region; removing the block mask to expose a remaining plurality of dummy gates; and performing replacement gate processing on the remaining plurality of dummy gates to form a plurality of active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region.
In another aspect, a semiconductor structure, includes a silicon-on-insulator (SOI) substrate, the SOI substrate comprising a bottom silicon layer, a buried oxide (BOX) layer, and a top silicon layer; a plurality of active devices formed on the top silicon layer; and an isolation region located between two of the active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region, and wherein the isolation region extends through the top silicon layer to the BOX layer.
Additional features are realized through the techniques of the present exemplary embodiment. Other embodiments are described in detail herein and are considered a part of what is claimed. For a better understanding of the features of the exemplary embodiment, refer to the description and to the drawings.
Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:
Embodiments of a method for isolation region fabrication for replacement gate processing, and an IC including isolation regions, are provided, with exemplary embodiments being discussed below in detail. Instead of placing isolation regions at STI region boundaries, isolation regions may replace STI regions, as is described in U.S. patent application Ser. No. 12/951,575 (Anderson et al.), filed Nov. 22, 2010, which is herein incorporated by reference in its entirety. A relatively dense, low-capacitance IC may be formed by replacement gate (i.e., gate-last) processing through use of a block mask that selectively allows removal of active silicon in a gate opening to form an isolation region. The active silicon is removed in a manner that is self-aligned to the dummy gate, such that there is no overlap of gate to active area and hence minimal capacitance penalty.
Returning to method 100, in block 102, a block mask is applied to the top surface of the dummy gates and the ILD, and the block mask is patterned to selectively expose the dummy gates that are to become isolation regions. The block mask may comprise, for example, photoresist.
Next, in method 100 of
Lastly, in block 106 of method 100 of
The technical effects and benefits of exemplary embodiments include formation of an IC having relatively high device density and low capacitance through replacement gate processing.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
Claims
1. A method for isolation region fabrication for replacement gate integrated circuit (IC) processing, the method comprising:
- forming a plurality of dummy gates on a substrate;
- forming a block mask over the plurality of dummy gates, such that the block mask selectively exposes a dummy gate of the plurality of dummy gates;
- removing the exposed dummy gate to form an isolation region recess corresponding to the removed dummy gate;
- filling the isolation region recess with an insulating material to form an isolation region;
- removing the block mask to expose a remaining plurality of dummy gates; and
- performing replacement gate processing on the remaining plurality of dummy gates to form a plurality of active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region.
2. The method of claim 1, wherein the substrate comprises a silicon-on-insulator substrate comprising a bottom silicon layer, a buried oxide (BOX) layer located on the bottom silicon layer, and a top silicon layer located on the BOX layer, wherein the plurality of dummy gates are formed on the top silicon layer, and wherein the isolation region recess extends through the top silicon layer down to the BOX layer.
3. The method of claim 1, wherein the insulating material comprises one of silicon dioxide and silicon nitride.
4. The method of claim 1, wherein removing the exposed dummy gate to form the isolation region recess comprises a sequential multilevel etch.
5. The method of claim 4, wherein the sequential multilevel etch comprises:
- etching the exposed dummy gate using a first etch;
- etching a gate dielectric layer corresponding to the exposed dummy gate using a second etch; and
- etching a top silicon layer of the substrate down to a buried oxide (BOX) layer of the substrate using a third etch.
6. The method of claim 5, wherein the exposed dummy gate comprises polysilicon, and the first etch comprises a bromine-based dry etch.
7. The method of claim 5, wherein the second etch comprises a hydrofluoric etch.
8. The method of claim 5, wherein the gate dielectric layer comprises a bottom dielectric layer located on the substrate, and a top metal layer located on the bottom dielectric layer, and wherein the second etch comprises a two-stage etch.
9. The method of claim 5, wherein the third etch comprises a bromine-based dry etch.
10. The method of claim 1, further comprising forming a hardmask layer over the isolation region before performing the replacement gate processing on the remaining plurality of dummy gates to form the plurality of active devices.
11. The method of claim 10, further comprising removing the hardmask layer after formation of the plurality of active devices.
12. The method of claim 10, wherein the hardmask layer comprises silicon nitride.
13. The method of claim 1, wherein the block mask comprises photoresist.
14. The method of claim 1, wherein the isolation region extends between a pair of spacers that are located on the substrate on either side of the isolation region, and through an interlevel dielectric (ILD) layer that is located over the pair of spacers.
15. A method of manufacturing a semiconductor device, the method comprising:
- forming a plurality of dummy gates on a substrate;
- forming an interlevel dielectric layer over the substrate including the plurality of dummy gates;
- forming a block mask over the plurality of dummy gates and over the interlevel dielectric layer, such that the block mask selectively exposes a dummy gate of the plurality of dummy gates;
- removing the exposed dummy gate to form an isolation region recess corresponding to the removed dummy gate;
- filling the isolation region recess with an insulating material to form an isolation region;
- removing the block mask to expose a remaining plurality of dummy gates; and
- performing replacement gate processing on the remaining plurality of dummy gates to form a plurality of active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region.
16. The method of claim 15, further comprising:
- planarizing the interlevel dielectric layer to expose top surfaces of the plurality of dummy gates.
17. The method of claim 15, wherein the isolation region extends through the interlevel dielectric layer.
18. The method of claim 15, wherein forming the block mask comprises forming the block mask to expose a portion of the interlevel dielectric layer, and
- wherein removing the exposed dummy gate comprises removing the exposed dummy gate using the block mask and the exposed portion of the interlevel dielectric layer as etching masks.
19. The method of claim 15 wherein the substrate includes a fin for a finFET.
20. The method of claim 15 further comprising:
- forming spacers on opposing side walls of the plurality of dummy gates beneath the interlevel dielectric layer.
21. The method of claim 20 wherein forming the block mask comprises forming the block mask so that the block mask selectively exposes the dummy gate of the plurality of dummy gates and a pair of the spacers thereon.
22. The method of claim 21 wherein filling the isolation region recess comprises forming the isolation region to extend through the pair of spacers and the interlevel dielectric layer.
23. The method of claim 15 further comprising:
- forming spacers on opposing side walls of the plurality of dummy gates.
24. The method of claim 15 wherein after performing the replacement gate processing a top surface of the interlevel dielectric layer is coplanar with top surfaces of the plurality of active devices.
25. A method for isolation region fabrication for replacement gate integrated circuit (IC) processing, the method comprising:
- forming a plurality of dummy gates on a substrate;
- forming spacers on opposing side walls of the plurality of dummy gates;
- forming a block mask over the plurality of dummy gates, such that the block mask selectively exposes a dummy gate of the plurality of dummy gates, the exposed dummy gate having a pair of the spacers thereon;
- removing the exposed dummy gate to form an isolation region recess corresponding to the removed dummy gate;
- filling the isolation region recess with an insulating material to form an isolation region extending between the pair of spacers;
- removing the block mask to expose remaining ones of the plurality of dummy gates; and
- performing replacement gate processing on the remaining ones of the plurality of dummy gates to form a plurality of active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region.
26. The method of claim 25, wherein the substrate includes a fin for a finFET.
27. The method of claim 25, further comprising:
- prior to forming the block mask, forming an interlevel dielectric layer over the substrate including the plurality of dummy gates; and
- planarizing the interlevel dielectric layer to expose top surfaces of the dummy gates.
28. The method of claim 27, wherein the isolation region extends through the pair of spacers and the interlevel dielectric layer.
29. The method of claim 27, wherein forming the block mask comprises forming the block mask to expose a portion of the interlevel dielectric layer, and
- wherein removing the exposed dummy gate comprises removing the exposed dummy gate using the block mask and the exposed portion of the interlevel dielectric layer as etching masks.
30. The method of claim 25 further comprising:
- prior to forming the block mask, forming an interlevel dielectric layer over the substrate including the plurality of dummy gates; and
- wherein after performing the replacement gate processing a top surface of the interlevel dielectric layer is coplanar with top surfaces of the plurality of active devices.
31. A method of manufacturing a semiconductor device, the method comprising:
- forming a plurality of dummy gates on a substrate;
- forming a mask over the plurality of dummy gates, such that the mask selectively exposes a dummy gate of the plurality of dummy gates;
- removing the exposed dummy gate to form an isolation region recess corresponding to the removed dummy gate;
- depositing an insulating material in the isolation region recess to form an isolation region;
- removing the mask to expose a remaining plurality of dummy gates; and
- performing replacement gate processing on the remaining plurality of dummy gates to form a plurality of active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region.
32. A method of manufacturing a semiconductor device, the method comprising:
- forming a plurality of dummy gates on a substrate;
- removing a selected dummy gate from the plurality of dummy gates to form an isolation region recess corresponding to the selected dummy gate;
- depositing an insulating material in the isolation region recess to form an isolation region;
- exposing remaining ones of the plurality of dummy gates; and
- performing replacement gate processing on the remaining ones of the plurality of dummy gates to form a plurality of active devices, wherein at least two of the plurality of active devices are electrically isolated from each other by the isolation region.
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Type: Grant
Filed: Oct 1, 2015
Date of Patent: Feb 7, 2017
Assignee: Samsung Electronics Co., Ltd.
Inventors: Brent A. Anderson (Jericho, VT), Edward J. Nowak (Essex Junction, VT)
Primary Examiner: James Menefee
Application Number: 14/872,790
International Classification: H01L 21/338 (20060101); H01L 29/66 (20060101); H01L 21/28 (20060101); H01L 27/12 (20060101); H01L 21/84 (20060101); H01L 21/762 (20060101);