# Patent

## Title
Method for making semiconductor device with different fin sets

## Abstract

A method for making a semiconductor device may include forming, above a substrate, first and second semiconductor regions laterally adjacent one another and each including a first semiconductor material. The first semiconductor region may have a greater vertical thickness than the second semiconductor region and define a sidewall with the second semiconductor region. The method may further include forming a spacer above the second semiconductor region and adjacent the sidewall, and forming a third semiconductor region above the second semiconductor region and adjacent the spacer, with the second semiconductor region including a second semiconductor material different than the first semiconductor material. The method may also include removing the spacer and portions of the first semiconductor material beneath the spacer, forming a first set of fins from the first semiconductor region, and forming a second set of fins from the second and third semiconductor regions.

## Background
FIELD OF THE INVENTION
The present invention relates to the field of electronic devices and, more particularly, to semiconductor devices and related methods.
JOINT RESEARCH AGREEMENT
The claimed configurations set forth herein were made as a result of activities undertaken within the scope of a joint research agreement. The parties to the joint research agreement are (1) STMicroelectronics, Inc., and (2) International Business Machines Corporation.
BACKGROUND OF THE INVENTION
Fin-based field effect transistors (FINFETs) are vertical transistor devices in which a semiconductor fin is located on a substrate and is used to define the source, drain, and channel regions of the device. The gate structure overlies the fin in the channel area, and in some configurations multiple fins may be used to provide a multi-gate transistor architecture. The multiple gates may be controlled by a single gate electrode, where the multiple gate surfaces act electrically as a single gate, or by independent gate electrodes.
In some implementations, different types of semiconductor materials may be used for different device types, such as silicon for NFET devices and silicon germanium (SiGe) for PFET devices, to provide desired electron or hole conductivity, respectively. With ever-increasing device integration densities, (e.g., 10 nm and beyond), for semiconductor on insulator (SOI) implementations, FINFETS with different types of fin materials may be challenging to implement.
As such, further enhancements in semiconductor devices may be desirable in some applications, such as next generation FINFET devices with relatively small dimensions, for example.
SUMMARY OF THE INVENTION
A method for making a semiconductor device may include forming, above a substrate, first and second semiconductor regions laterally adjacent one another and each comprising a first semiconductor material. The first semiconductor region may have a greater vertical thickness than the second semiconductor region and define a sidewall with the second semiconductor region. The method may further include forming a spacer above the second semiconductor region and adjacent the sidewall, and forming a third semiconductor region above the second semiconductor region and adjacent the spacer, with the second semiconductor region comprising a second semiconductor material different than the first semiconductor material. The method may also include removing the spacer and portions of the first semiconductor material beneath the spacer, forming a first set of fins from the first semiconductor region, and forming a second set of fins from the second and third semiconductor regions.
The method may further include performing a thermal anneal to diffuse the second semiconductor material into the second semiconductor region. Removing the spacer may define a trench having the first semiconductor region on one side, and the second and third semiconductor regions on another side, and the method may further include forming a liner in the trench. More particularly, the liner may include an oxide layer and a nitride layer overlying the oxide layer. Furthermore, an oxide may be formed within the liner to define an isolation pillar with the liner. The isolation pillar may be spaced apart from the first and second sets of fins, or it may be in contact with at least one fin from the first and second sets of fins.
Forming the first and second semiconductor regions may include forming a layer of the first semiconductor material above the substrate, forming a mask overlying the first semiconductor region, and removing portions of the first semiconductor material laterally outside of the mask to define the second semiconductor region. By way of example, the first semiconductor material may comprise silicon, and the second semiconductor material may comprise silicon germanium. The method may further include forming at least one gate overlying the first and second sets of fins, and forming respective source and drain regions electrically coupled with each of the first and second sets of fins. Also by way of example, the substrate may comprise a dielectric material.
A related semiconductor device may include a substrate, a first set of fins above the substrate comprising a first semiconductor material, a second set of fins above the substrate and comprising a second semiconductor material different than the first semiconductor material, and an isolation pillar extending above the substrate and positioned between the first and second sets of fins. The isolation pillar may include an inner oxide portion, a nitride layer on the inner oxide portion, and an outer oxide layer on the nitride layer.
Another related semiconductor device may include a substrate, a first set of fins above the substrate comprising a first semiconductor material, and a second set of fins above the substrate and comprising a second semiconductor material different than the first semiconductor material. The substrate may have an isolation trench therein positioned between the first and second sets of fins, and a nitride liner in the isolation trench.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of a semiconductor device in accordance with an example embodiment including an isolation pillar between adjacent sets of semiconductor fins.
FIGS. 2-14 are a series of cross-sectional diagrams taken from the perspective of line A-A in FIG. 1 and illustrating a method for making the device of FIG. 1.
FIG. 15 is cross-sectional diagram similar to FIG. 14, and illustrating an approach for making another example embodiment of the semiconductor device of FIG. 1.
FIG. 16 is cross-sectional diagram similar to FIG. 14, and illustrating an approach for making another example embodiment of the semiconductor device of FIG. 1.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime or multiple prime notation is used to illustrate similar elements in different embodiments.
By way of background, uniform SiGe formation may be challenging to implement in relatively small scale devices, such as FINFETs, due to thermal budget concerns. More particularly, non-uniform SiGe material layers may cause a non-uniform response when performing fin etching. However, to form a relatively uniform SiGe fin layer, a very high thermal budget may be required. Yet, this may also cause the germanium to laterally diffuse into the material used for forming the NFET fins (e.g., into the adjacent semiconductor fin layer), which in turn may impact the adjacent NFET silicon fins. This problem may become particularly acute with smaller, advanced processing nodes. To avoid the diffusion problem, one might consider making the base silicon layer upon which the SiGe is deposited thin enough so that adequate germanium diffusion into this thin silicon layer may be accomplished without excessive diffusion into the NFET silicon region. Yet, the use of such thin “seed” silicon layers for the SiGe may result in other problems, such as agglomeration during the epitaxial deposition process, which may in turn lead to performance problems.
Turning now initially to FIGS. 1-2, a semiconductor device 30 and related method for making the device are first described. In the illustrated embodiment, the semiconductor device 30 is a FINFET which is formed from a semiconductor layer 31 (e.g., silicon) on a dielectric substrate 32 (e.g., SiO2). By way of example, the semiconductor layer 31 and dielectric substrate 32 may be implemented as a fully depleted SOI (FDSOI) wafer, but the configurations described herein may also be implemented with other substrates such as partially-depleted SOI (PDSOI), Ultra-Thin Body and BOX (UTBB), etc. A dielectric (e.g., SiO2) layer 33 may be formed overlying the semiconductor layer 31, and a nitride (e.g., SiN) layer 34 may be formed overlying the dielectric layer, which serves as a hard mask. The dielectric layer 33 and nitride layer 34 may then be patterned to cover the areas where NFET fins 35 are to be formed, and to expose the areas where PFET fins 36 are to be formed, as seen in FIG. 3.
The silicon layer 31 may be etched in areas exposed by the nitride mask layer 34 to provide a thinned silicon region 37 (FIG. 4), which will provide a seed layer for deposition of a second semiconductor material, such as SiGe, as will be discussed further below. That is, the silicon region 38 that will be used to define or form the fins 35 for the NFET device will have a greater vertical thickness or height than the silicon region 37 after the etch, and the boundary between the two defines a sidewall 39 of the silicon region 38.
It should be noted that the silicon in the region 37 need not be overly etched to an undesirably small thickness (e.g., less than 10 nm), which may lead to other problems such as agglomeration, for example, as discussed above. Rather, a thickness greater than 10 nm, and more preferably from 10 nm to 20 nm, may advantageously be used, to avoid such agglomeration issues. This is because the present approach may be used with relatively high thermal budgets to provide uniform germanium diffusion, yet while avoiding undesired diffusion of germanium into the silicon region 38 that will be used to define or form the fins for the NFET device.
More particularly, this is achieved by first forming a spacer 40 (e.g., SiN) above the silicon region 37 and adjacent or along the sidewall 39, as seen in FIG. 5. A semiconductor region 41 of a semiconductor material different than silicon (e.g., SiGe) may be formed or deposited above the silicon region 37 and adjacent the spacer 40, as seen in FIG. 6. Thus, the spacer 40 is positioned laterally between the silicon region 38 and the SiGe region 41. Generally speaking, the amount of deposition of the SiGe may be such that the top of the SiGe region 41 is relatively close to level with the top of the silicon region 38, although different thicknesses may be used in different embodiments depending on the thickness of the underlying silicon region 37 used, as well as the desired silicon/germanium concentrations in the PFET fins 36, as will be appreciated by those skilled in the art.
An oxide may then be formed over the structure and planarized down to the nitride layer 34 via chemical mechanical polishing (CMP), for example, which creates oxide region 42 overlying the SiGe region 41 (FIG. 7). The nitride layer 34 and spacer 40 may then be removed, as shown in FIGS. 8 and 9. By way of example, the nitride layer 34 may be removed using a dry etch, such as a reactive ion etch (RIE), for example, and the spacer 40 may be removed using a wet etch (e.g., hot phosphorus acid, etc). However, both the nitride layer 34 and the spacer 40 could be removed in a single etch step (e.g., hot phosphorus acid), if desired. Removing the spacer 40 defines a trench 43 having the silicon region 38 on one side (the left side in FIG. 9), and the SiGe region 41 on another side (the right side in FIG. 9). Since the trench 43 is defined based upon the width of the nitride spacer 40, the trench may be relatively small and accordingly not occupy an excessive amount of surface area or “real estate” that would otherwise be used for semiconductor fins.
The oxide layers 32, 42 may then be used as a hard mask for etching the silicon region 37 in the bottom of the trench 43. This extends the trench to the dielectric substrate 32, which in turn separates or isolates the silicon region 38 from the silicon region 37. An oxide deglazing step may then be performed to remove the oxide hard mask regions 32, 42, followed by deposition of a liner above the silicon region 38 and SiGe region 41, and within the trench (FIG. 12). By way of example, the liner may include a relatively thin layer of SiO2 45 and an SiN layer 44 overlying the SiO2 layer.
Because the silicon region 38 is physically separated from the SiGe region 41 and isolated therefrom by the trench 43, a high temperature anneal may be performed to diffuse the germanium from the SiGe region 41 into the silicon region 37 to create a uniform SiGe region 48, without germanium diffusion into the silicon region 38, as seen in FIG. 12. Since a high thermal budget may accordingly be used without germanium “bleed” into the silicon region 38, desired uniformity of the germanium diffusion may be achieved in the SiGe region 48.
In the present example, the trench 43 is further filled with a flowable oxide (FIG. 13) to define an oxide region 49 within the trench. Upon etching or patterning of the silicon fins 35 and SiGe fins 36 from the silicon region 38 and uniform SiGe region 48, respectively, the SiO2 layer 45, SiN layer 44, and oxide region 49 define an isolation pillar 50 extending above the substrate 32 and positioned laterally between the silicon and SiGe fins sets, as seen in FIG. 14. In the illustrated example, a space is etched on either side of the isolation pillar 50 so that the isolation pillar is physically separated or spaced apart from the laterally adjacent silicon fin 35 and SiGe fin 36. However, it should be noted that in other embodiments, the isolation pillar 50′ may be in contact with the laterally adjacent silicon fin 35′ and/or SiGe fin 36′, as shown in FIG. 15.
In accordance with another approach, rather than forming the oxide region 49 within the trench 43 as shown in FIG. 13 above, the trench may instead be left open, such that when the fins 35′′, 36′′ are patterned a residual portion of the nitride liner 44′′ remains in the isolation trench 43′′ in the substrate 32′′ and positioned between the first and second sets of fins, as shown in FIG. 16.
As seen in FIG. 1, further device processing may be performed to define a gate 55 overlying the fins 35, 36, as well as respective source and drain regions 56, 57 and 58, 59 for each of the sets of fins 35, 36. In addition to the above described advantages, the methods and devices described herein may advantageously be used for relatively small processing nodes (e.g., 7 nm, 10 nm, 14 nm, etc.). It should also be noted that in some embodiments nanowire fins may be formed. For example, the height of the silicon region 38 and SiGe region 41 may be made thinner than shown in the illustrated examples, which in turn may be patterned and formed into respective silicon and SiGe nanowire fins, such as by the approach described in U.S. application Ser. No. 14/182,601 filed Feb. 18, 2014, which is assigned to the present Applicant and is hereby incorporated herein in its entirety by reference.
Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.

## Claims

1. A method for making a semiconductor device comprising:
forming, above a substrate, first and second semiconductor regions laterally adjacent one another and each comprising a first semiconductor material, the first semiconductor region having a greater vertical thickness than the second semiconductor region and defining a sidewall with the second semiconductor region;
forming a spacer above the second semiconductor region and adjacent the sidewall;
forming a third semiconductor region above the second semiconductor region and adjacent the spacer, the third semiconductor region comprising a second semiconductor material different than the first semiconductor material;
removing the spacer and portions of the first semiconductor material beneath the spacer; and
forming a first set of fins from the first semiconductor region, and forming a second set of fins from the second and third semiconductor regions.

2. The method of claim 1 further comprising performing a thermal anneal to diffuse the second semiconductor material into the second semiconductor region.

3. The method of claim 1 wherein removing the spacer defines a trench having the first semiconductor region on one side, and the second and third semiconductor regions on another side; and further comprising forming a liner in the trench.

4. The method of claim 3 wherein the liner comprises an oxide layer and a nitride layer overlying the oxide layer.

5. The method of claim 3 further comprising forming an oxide within the liner to define an isolation pillar with the liner.

6. The method of claim 5 wherein the isolation pillar is spaced apart from the first and second sets of fins.

7. The method of claim 5 wherein the isolation pillar is in contact with at least one fin from the first and second sets of fins.

8. The method of claim 1 wherein forming the first and second semiconductor regions comprises:
forming a layer of the first semiconductor material above the substrate;
forming a mask overlying the first semiconductor region; and
removing portions of the first semiconductor material laterally outside of the mask to define the second semiconductor region.

9. The method of claim 1 wherein the first semiconductor material comprises silicon, and the second semiconductor material comprises silicon germanium.

10. The method of claim 1 further comprising forming at least one gate overlying the first and second sets of fins.

11. The method of claim 10 further comprising forming respective source and drain regions electrically coupled with each of the first and second sets of fins.

12. The method of claim 1 wherein the substrate comprises a dielectric material.

13. A method for making a semiconductor device comprising:
forming a silicon layer above a substrate;
forming a mask overlying a first region of the silicon layer;
removing portions of silicon from the silicon layer laterally outside of the mask to define a second region in the silicon layer, the first region having a greater vertical thickness than the second region and defining a sidewall with the second region;
forming a spacer above the second region and adjacent the sidewall;
forming a third region comprising silicon germanium above the second region and adjacent the spacer;
removing the mask, spacer and portions of the second region beneath the spacer; and
forming a first set of fins from the first region, and forming a second set of fins from the second and third regions.

14. The method of claim 13 further comprising performing a thermal anneal to diffuse germanium into the second region.

15. The method of claim 13 wherein removing the spacer defines a trench having the first region on one side, and the second and third regions on another side; and further comprising forming a liner in the trench.

16. The method of claim 15 wherein the liner comprises an oxide layer, and a nitride layer overlying the oxide layer.

17. The method of claim 15 further comprising forming an oxide within the liner to define an isolation pillar with the liner.

18. A method for making a semiconductor device comprising:
forming a first set of fins above a substrate and comprising a first semiconductor material;
forming a second set of fins above the substrate and comprising a second semiconductor material different than the first semiconductor material; and
forming an isolation pillar extending above the substrate and positioned between the first and second sets of fins, the isolation pillar comprising an inner oxide portion, a nitride layer on the inner oxide portion, and an outer oxide layer on the nitride layer.

19. The method of claim 18 comprising forming at least a portion of the isolation pillar to extend into the substrate.

20. The method of claim 18 comprising forming the isolation pillar to be spaced apart from the first and second sets of fins.

21. The method of claim 18 comprising forming the isolation pillar to be in contact with at least one fin from the first and second sets of fins.

22. The method of claim 18 wherein the first semiconductor material comprises silicon, and the second semiconductor material comprises silicon germanium.

23. The method of claim 18 further comprising:
forming at least one gate overlying the first and second sets of fins; and
forming respective source and drain regions electrically coupled with each of the first and second sets of fins.

24. A method for making a semiconductor device comprising:
forming a first set of fins above a substrate and comprising a first semiconductor material;
forming a second set of fins above the substrate and comprising a second semiconductor material different than the first semiconductor material;
forming an isolation trench in the substrate between the first and second sets of fins; and
forming a nitride liner in the isolation trench.

25. The method of claim 24 wherein the first semiconductor material comprises silicon, and the second semiconductor material comprises silicon germanium.

26. The method of claim 24 further comprising:
forming at least one gate overlying the first and second sets of fins; and
forming respective source and drain regions electrically coupled with each of the first and second sets of fins.