# Patent

## Title
Epitaxial growth between gates

## Abstract

An integrated circuit device includes at least two epitaxially grown active regions grown onto a substrate, the active regions being placed between two gate devices. The device further includes at least one dummy gate between two epitaxially grown active regions. Each active region is substantially uniform in length.

## Background
REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 61/779,842 filed on Mar. 13, 2013.


BACKGROUND
Electronic devices that utilize integrated circuits are susceptible to electrostatic discharges (ESDs). An electrostatic discharge may occur from a human holding the device or other source. An electrostatic discharge can pass a large amount of electric current through circuitry that is sensitive to such high currents, thus damaging the circuitry. To reduce the susceptibility to ESD damage, integrated circuits typically include an ESD device that channels ESDs away from sensitive circuitry.
One type of ESD device involves multiple active regions, such as source or drain regions, between an elongated gate device. The gate device is used for the gate of a transistor. The transistor acts as a switch that opens when a high electric current such as an ESD is detected. The open switch allows the ESD passes through in order to avoid flowing through the sensitive circuitry.
One issue involved in forming an ESD device comes from silicide. When forming transistor devices, a silicide material is commonly used at semiconductor-metal junctions to facilitate an efficient junction. This is because silicide conducts electric current relatively well. However, it is desirable that the silicide is not formed over the source or drain regions adjacent to the gate. If silicide layers were to be formed there, the current flowing through the source and drain regions would tend to travel mostly through the silicide, which may cause damage because the current density resulting from the high ESD currents may burn away the silicide and surrounding material.
Another issue involving the formation of ESD devices arises when the source drain regions are formed through an epitaxial growth process. An epitaxial growth process involves growing a semiconductor crystal onto an existing crystal. When forming source or drain regions in such a manner, the length of the regions can affect the uniformity of the epitaxial grown structures. If a structure is too long compared to other nearby structures, a set of non-uniform epitaxially grown structures may be formed. This is referred to as the loading effect. It is thus desirable to fabricate ESD devices, or other devices that utilize epitaxially grown active regions between gates, without too much of an adverse loading effect.



BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
FIG. 1 is a diagram showing an illustrative top view of epitaxial growth between gates, according to one example of principles described herein.
FIG. 2A is a diagram showing an illustrative cross-sectional view of an ESD device with epitaxial growth between gates, according to one example of principles described herein
FIG. 2B is a diagram showing an illustrative cross-sectional view of an ESD device with epitaxial growth between gates, according to one example of principles described herein.
FIG. 3A is a diagram showing an illustrative top view of epitaxial growth between gates, including multiple dummy gates, according to one example of principles described herein.
FIG. 3B is a diagram showing a cross-sectional view of epitaxial growth between gates, including multiple dummy gates, according to one example of principles described herein.
FIG. 4 is a flowchart showing an illustrative method for forming a device with improved epitaxial growth between gates, according to one example of principles described herein.



DETAILED DESCRIPTION
It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Moreover, the performance of a first process before a second process in the description that follows may include embodiments in which the second process is performed immediately after the first process, and may also include embodiments in which additional processes may be performed between the first and second processes. Various features may be arbitrarily drawn in different scales for the sake of simplicity and clarity. Furthermore, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as being “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
FIG. 1 is a diagram showing an illustrative top view 100 of epitaxial growth between gates. According to certain illustrative examples, an integrated circuit device includes at least two gate device 104. The device includes active regions 102 between the two gate devices 104. Additionally, at least one dummy gate 108 is placed within the middle of the two gate devices 104. Metal contacts 106 may also be formed adjacent to the gate devices 106 and dummy gate 108.
According to the present example, the active regions 102 may be formed within a well 110. As mentioned above, the active regions 102 can be formed through an epitaxial process. Such a process involves the deposition of a crystalline overlayer onto a crystalline substrate. For example, the active region structures 102 may be formed onto a silicon substrate.
The active regions 102 may be n-type doped or p-type doped. The doping may occur in-situ with the epitaxial formation. Alternatively, a non-doped epitaxial structure may be formed. Then, a doping process may dope the epitaxially grown structures 102. The type of well 110 will depend on the type of dopant. For example, if the active regions 102 are to be n-type, then the well 110 in which the n-type active regions are formed is a p-type well. Conversely, if the active regions 102 are to be p-type, then the well 110 in which the p-type active regions are formed will be an n-type well. The active regions 102 are substantially uniform in length. The length refers to the long dimension between a real gate 104 and the dummy gate 108.
The gate structures 104, 108 may be formed with the same mask. Specifically, a gate layer may be deposited and patterned using standard photolithographic techniques. Specifically, a photoresist layer may be exposed to a light source through a photomask. Regions of the photoresist layer may then be developed away. The remaining photoresist layer acts as a protection from an etching process. The etching process may remove the gate material at all regions where the gates are not intended to be formed. The gate material that was protected by the photoresist layer thus leaves the gate devices 104, 108 intact.
In some examples, the gate devices 104 and the dummy gate 108 may be formed using the same mask and may thus be made out of the same material. The gate devices 104 may be used as gate terminals for a transistor device of an ESD device. The dummy gate 108 may be left as is and is not used for any transistor device. In some cases, the dummy gate 108 may be biased. Alternatively, the dummy gate 108 may be floated. That is, it is not connected to anything, including ground.
The placement of the dummy gate 108 is such that the epitaxial window is reduced. The epitaxial window refers to the length of the epitaxial structures. If there were no dummy gate 108 in place, the epitaxial window would be relatively long as indicated by the line 112. With the dummy gate 108 in place, however, the epitaxial window is reduced as indicated by the line 114. Thus, the epitaxial window 114 on both sides of the dummy gate is substantially the same and smaller. This allows for a more uniform epitaxial process.
The dotted lines 116, 118 represent cross sections of the device. The first dotted line 116 represents a cross-section along a fin structure as illustrated in FIG. 2A. The second dotted line 118 represents a cross section between the fin structures as illustrated in FIG. 2B.
FIG. 2A is a diagram showing an illustrative cross-sectional view 200 of an ESD device with epitaxial growth between gates. According to the present example, the active regions 102 are shown as being formed into the well 110. The well 110 may be formed on top of a base substrate 202. The base substrate 202 may be made of a semiconductor material such as silicon.
The spaces 206 between the active regions 102 are where the gates 104, 108 are formed. As described above, the dummy gate 108 is placed in between the two normal gates 104. The dummy gate 108 reduces the epitaxial window and allows for more uniform active region structures 102.
As mentioned above, contacts 106 may be formed adjacent to the gates 104, 108. The contacts 106 are used to connect the gate devices to the active regions. In the case of the actual gates 104, the contacts connect the source or drain regions to a source or drain terminal. This is typically done on an overlaying metal layer (not shown). Specifically, an interlayer dielectric layer 208 may be formed on top of the gate devices.
Vias are then formed into the interlayer dielectric layer 208. The vias extend down to the substrate regions. A silicide material is then formed within the vias. The vias are then filled with a metal material to form the contacts 106. Forming the contacts in such a manner is referred to as a silicide last process. After the contacts 106 have been formed into the interlayer dielectric layer 208, a metal layer can be formed on top that connects the contacts 106 to other devices.
Similar procedures may be used to connect the gate devices 104 to other elements within the integrated circuit. Specifically, vias may be formed into the interlayer dielectric layer 208 that extend down to the gate devices 104. These vias are then filled with silicide and then with metal. In some cases, the vias that extend to the gate devices 104 may extend from a different layer than the layer that uses the contacts 106 to connect with the active regions 102.
FIG. 2B is a diagram showing an illustrative cross-sectional view of an ESD device with epitaxial growth between gates and between fin structures. According to the present example, the space between parallel active regions may be a shallow trench isolation material. Such a material is a dielectric material such as silicon dioxide in order to prevent electric current from passing between devices.
The shallow trench isolation structures 204 may be formed in a variety of ways. In one example, trenches are etched into the underlying material, in this case the well 110. The trenches are then filled with the dielectric material to form the shallow trench isolation 204. These trenches are patterned using standard photolithographic techniques. From this cross-sectional view, the active regions 102 are still visible because they extend about the shallow trench isolation feature 204.
FIG. 3A is a diagram showing an illustrative top view 300 of epitaxial growth between gates, including multiple dummy gates. According to the present example, more than one dummy gate may be placed between the two real gates 104. Specifically, two dummy gates 302, 304 are placed between the real gates 104.
The dummy gates are spaced so that the active regions between each gate structure 104, 302, 304 are substantially equal in length. Thus, the epitaxial window 308 is approximately equal in length for each active region. By reducing the size of the epitaxial window 302 and maintaining a uniform length among the active regions, the loading effect can be reduced. As mentioned above, the loading effect occurs when an epitaxial growth process is performed at multiple regions on a substrate. If these regions vary in size, then some regions will experience the growth slightly different than other regions. This non-uniformity can have adverse effects on the integrated circuit.
The number of dummy gates and thus size of the epitaxial window can be selected to reduce the loading effect below a threshold level. That threshold level may be predetermined during the design phase or may be determined during the fabrication phase. The epitaxial windows between gates are defined by the following equation:

Wd=(W−n*L)/(n+1)

Where:
Wd is the reduced epitaxial window 308;
W is the original window 310 between the real gates 104
n is the number of dummy gates; and
L is the width of the dummy gates.
The epitaxial window 308 may be fine tuned by selecting the number of dummy gates and the size of the window 310 between the real gates 104. Having the dummy gates 304, 302 allows for more control over the epitaxial window 308 and thus the ESD device may be optimized by adjusting the window 308. In general, the ESD device performs better when a higher electric current can pass through the transistor.
FIG. 3B is a diagram showing a cross-sectional view 320 of epitaxial growth between gates, including multiple dummy gates. The cross-sectional view 320 is along a fin structure as represented by the dotted line 312 in FIG. 3A. According to the present example, the active regions may be formed as described above.
In this example, instead of having a contact on each side of the dummy gate as illustrated in FIG. 1 and FIGS. 2A-2B, only a single contact 306 is positioned between the two dummy gates 302, 304. Other positions for contacts 306 may be used as well. In some examples, the contacts may be used to bias the dummy gates. In some examples, the contact 306 may be used for other circuit design purposes.
While a fin structure transistor is illustrated, the principles described herein may be used with conventional Complementary Metal Oxide Semiconductor (CMOS) architecture as well. For example, a standard active region may be epitaxially grown between gates and dummy gates instead of multiple fin active regions grown between the gates.
Having more uniform active regions between the gates can allow for a higher quality replacement gate process. In some cases, real gates are made of a polysilicon material and are then replaced with a metal material. This process involves forming sidewalls spacer on the sides of the polysilicon gate, removing the polysilicon, and then replacing the space left behind with a metal material.
The dummy gates 304, 302 may also be used to help with thermal dissipation. Because an ESD device is intended to handle higher electric currents, it will be subject to high temperatures due to electric current flowing through narrow structures. The dummy gates 304, 302 may act as a heat sink and thus keep the ESD device relatively cool.
FIG. 4 is a flowchart showing an illustrative method for forming a device with improved epitaxial growth between gates. According to certain illustrative examples, the method includes a step of forming 402 a plurality of active regions using an epitaxial growth process. The method further includes a step of forming 404 at least two gate devices and at least one dummy gate within spaces between the active regions, the gate devices and dummy gate running perpendicular to the active regions, wherein each of the active regions is substantially uniform in dimensions.
According to certain illustrative examples, an integrated circuit device includes at least two epitaxially grown active regions grown onto a substrate, the active regions being placed between two gate devices. The device further includes at least one dummy gate between two epitaxially grown active regions. Each active region is substantially uniform in length.
According to certain illustrative examples, a method for forming an Electro-Static Discharge (ESD) device includes forming a plurality of active regions using an epitaxial growth process, and forming at least two gate devices and at least one dummy gate within spaces between the active regions, the gate devices and dummy gate running perpendicular to the active regions. Each of the active regions is substantially uniform in length.
According to certain illustrative examples, an Electro-Static Discharge (ESD) device includes at least two elongated gate devices running parallel, at least one elongated dummy gate between and running parallel to the gate devices, and a number of epitaxially grown fin active regions between the gate devices and the at least one dummy gate, the active regions running parallel to each other and perpendicular to the gate devices. The length of the active regions between a gate device and a dummy gate is selected to be such that a loading effect is reduced below a threshold level. The optimized length of the active regions between a gate device and a dummy gate could be tradeoff by loading effect and ESD performance. A longer length of the active region between a gate device and a dummy gate gets larger drain-ballasting to boost ESD performance.
It is understood that various different combinations of the above-listed embodiments and steps can be used in various sequences or in parallel, and there is no particular step that is critical or required. Additionally, although the term “electrode” is used herein, it will be recognized that the term includes the concept of an “electrode contact.” Furthermore, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. Accordingly, all such modifications are intended to be included within the scope of this invention.
The foregoing has outlined features of several embodiments. Those of ordinary skill in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those of ordinary skill in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

## Claims

1. An integrated circuit device comprising:
a plurality of parallel, epitaxially grown fin structures comprising active regions, the fin structures grown onto a substrate, the fin structures being placed between two gate devices; and
at least one dummy gate between the two gate devices and between at least two of the plurality of epitaxially grown fin structures;
wherein each fin structure is substantially uniform in length; and
wherein at least two of the plurality of epitaxially grown fin structures extend from a same one of the gate devices to the at least one dummy gate without extending directly below one of the gate devices.

2. The device of claim 1, wherein at least two of the plurality of epitaxially grown fin structures are longitudinally aligned.

3. The device of claim 1, wherein the integrated circuit device comprises a snapback Electro-Static Discharge (ESD) device.

4. The device of claim 1, further comprising a substrate contact on both sides of the at least one dummy gate.

5. The device of claim 1, further comprising a substrate contact in a middle of an epitaxially grown active region that is positioned between two dummy gates.

6. The device of claim 1, wherein the at least one dummy gate is biased.

7. The device of claim 1, wherein the at least one dummy gate is floated.

8. The device of claim 1, wherein the gate devices and the at least one dummy gate are formed using the same mask.

9. The device of claim 1, further comprising substrate contacts comprising a silicide layer formed through a silicide last process.

10. A method for forming an Electro-Static Discharge (ESD) device, the method comprising:
forming a plurality of parallel sets of longitudinally aligned fin structures comprising active regions using an epitaxial growth process; and
forming at least two gate devices and at least one dummy gate within spaces between the fin structures, the at least one dummy gate between positioned between the at least two gate devices, the gate devices and the at least one dummy gate running perpendicular to the active regions;
wherein each of the fin structures' active regions is substantially uniform in length and at least two of the fin structures extend from a same one of the at least two gate devices to the at least one dummy gate without extending directly below one of the at least two gate devices.

11. The method of claim 10, further comprising, selecting a length of the fin structures such that a loading effect is reduced below a threshold level.

12. The method of claim 10, wherein the ESD device comprises a snapback ESD device.

13. The method of claim 10, further comprising forming a substrate contact on both sides of the at least one dummy gate.

14. The method of claim 10, further comprising forming a substrate contact in a middle of an active region that is positioned between two dummy gates.

15. The method of claim 10, wherein the at least one dummy gate is biased.

16. The method of claim 10, wherein the at least one dummy gate is floated.

17. The method of claim 10, wherein the gate devices and dummy gates are formed using a same mask.

18. The method of claim 10, further comprising forming substrate contacts including a silicide layer formed through a silicide last process.

19. The method of claim 10, further comprising forming a plurality of dummy gates between the at least two gate devices.

20. An Electro-Static Discharge (ESD) device comprising:
at least two elongated gate devices running parallel;
at least one elongated dummy gate between and running parallel to the gate devices; and
a plurality of epitaxially grown fin active regions between the gate devices and the at least one dummy gate, the active regions running parallel to each other and perpendicular to the gate devices;
wherein at least two parallel fin active regions extend from a same one of the at least two of the elongated gate devices to the at least one elongated dummy gate without extending directly below one of the at least two elongated gate devices; and
wherein a length of the active regions between a gate device and a dummy gate is selected to be such that a loading effect is reduced below a threshold level.