# Patent

## Title
Metal gate structure and manufacturing method thereof

## Abstract

A semiconductor structure includes a substrate including a first active region, a second active region and an isolation disposed between the first active region and the second active region; a plurality of gates disposed over the substrate and including a first gate extended over the first active region, the isolation and the second active region, and a second gate over the first active region and the second active region; and an inter-level dielectric (ILD) disposed over the substrate and surrounding the plurality of gates, wherein the second gate is configured not to conduct current flow and includes a first section disposed over the first active region and a second section disposed over the second active region, a portion of the ILD is disposed between the first section and the second section.

## Background
BACKGROUND
The semiconductor integrated circuit (IC) industry has experienced rapid growth. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. As the dimensions of transistors decrease, the thickness of the gate oxide must be reduced to maintain performance with the decreased gate length. However, in order to reduce gate leakage, high dielectric constant (high-k) gate insulator layers are used which allow greater physical thicknesses while maintaining the same effective capacitance as would be provided by a typical gate oxide used in larger technology nodes.
Polysilicon is used as a gate electrode in a semiconductor device such as metal oxide semiconductor (MOS). However, with a trend toward scaling down the size of the semiconductor device, the polysilicon gate has low performance such as reduction of gate capacitance and driving force of the semiconductor device. In some IC designs, there has been a desire to replace the typically polysilicon gate electrode with a metal gate (MG) electrode to improve device performance with the decreased feature sizes. One process of forming the MG electrode is termed “gate last” process, as opposed to another MG electrode formation process termed “gate first”. The “gate last” process allows for reduced number of subsequent processes, including high temperature processing, that must be performed after formation of the gate.
There are many challenges on fabrication of the MG electrode in decreased feature size of the semiconductor device. Thus, there is a continuous need to enhance a metal gate structure, simplifying a manufacturing method of the metal gate on a substrate and improving a performance of the semiconductor device including the MG electrode.



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. 1A is a right side perspective view of a transistor in accordance with some embodiments of the present disclosure.
FIG. 1B is a left side perspective view of a transistor in accordance with some embodiments of the present disclosure.
FIG. 1C is a front cross sectional view of a transistor in accordance with some embodiments of the present disclosure.
FIG. 2A is a front perspective view of a FinFET in accordance with some embodiments of the present disclosure.
FIG. 2B is a rear perspective view of a FinFET in accordance with some embodiments of the present disclosure.
FIG. 2C is a cross sectional view of a FinFET of FIG. 2A along AA′ in accordance with some embodiments of the present disclosure.
FIG. 3 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 4 is a top view of a semiconductor structure of FIG. 3 in accordance with some embodiments of the present disclosure.
FIG. 5 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 6 is a top view of a semiconductor structure of FIG. 5 in accordance with some embodiments of the present disclosure.
FIG. 7 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 8 is a top view of a semiconductor structure of FIG. 5 in accordance with some embodiments of the present disclosure.
FIG. 9 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 10 is a top view of a semiconductor structure of FIG. 9 in accordance with some embodiments of the present disclosure.
FIG. 11 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 12 is a top view of a semiconductor structure of FIG. 11 in accordance with some embodiments of the present disclosure.
FIG. 13 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 14 is a top view of a semiconductor structure of FIG. 13 in accordance with some embodiments of the present disclosure.
FIG. 15 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 16 is a top view of a semiconductor structure of FIG. 15 in accordance with some embodiments of the present disclosure.
FIG. 17 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 18 is a top view of a semiconductor structure of FIG. 17 in accordance with some embodiments of the present disclosure.
FIG. 19 is a schematic view of a semiconductor structure in accordance with some embodiments of the present disclosure.
FIG. 20 is a top view of a semiconductor structure of FIG. 19 in accordance with some embodiments of the present disclosure.
FIG. 21 is a flow diagram of a method of manufacturing a semiconductor structure in accordance with some embodiments of the present disclosure.
FIGS. 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H, 21I, 21J, 21K, 21L, 21M, 21N, 21O, 21P, 21Q, 21R, 21S, 21T, 21U, 21V, 21W, 21X, 21Y, 21Z, 21AA, 21AB, 21AC, 21AD, 21AE, and 21AF are schematic views of showing the manufacturing of a semiconductor structure in accordance with some embodiments of the present disclosure.



DETAILED DESCRIPTION OF THE DISCLOSURE
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. 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. For example, 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. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
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. 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.
A semiconductor device includes a transistor. FIGS. 1A and 1B show right side and left side perspective views of an embodiment of a transistor respectively. FIG. 1C is a front view of the transistor of FIGS. 1A and 1B. The transistor includes a substrate 14 and a metal gate 10 disposed over a surface of the substrate 14. The metal gate 10 is fabricated between an active region including doped regions (11, 12), which can be either a source or a drain.
In another semiconductor device, a transistor is configured with several fins as a FinFET (Fin Field-Effect Transistor). FIGS. 2A and 2B show front and rear views of an embodiment of a FinFET. FIG. 2C is a cross sectional view of the FinFET of FIG. 2A along AA′. The FinFET includes a substrate 14, a dielectric layer 13 and a metal gate 10. The substrate 14 includes doped regions (11, 12), which can be either a source or a drain, extending upright respectively in fin configuration and are partially surrounded by the dielectric layer 13.
The metal gate is formed by depositing a metal film within an opening of an interlayer dielectric (ILD) disposed over the substrate. However, as a dimension of the metal gate is in a high aspect ratio, the opening is very small. The ratio of a width to a height of the metal gate is generally greater than 10. Due to the high aspect ratio, a formation of the metal gate is an issue. Such a small opening of the ILD may not be deposited with the metal film sufficiently and fully. An insufficient metal film deposition would induce an incorrect work function and affect a threshold voltage of the metal gate.
In the present disclosure, a semiconductor structure with a structural improvement on a metal gate is disclosed. The semiconductor structure includes a substrate and an inter interlayer dielectric (ILD) over the substrate. The ILD includes a recessed portion, and a polysilicon is disposed within the recessed portion. The polysilicon is then removed, and the recessed portion is deposited with a metal film. Upon removal of the polysilicon, an opening of the recessed portion is increased due to an internal tensile stress developed within the ILD. The internal stress would shrink the ILD and therefore the opening of the recessed portion would be enlarged. The enlarged opening of the ILD would facilitate the metal film deposition and the formation of the metal gate, ultimately a performance of the semiconductor structure is improved.
FIG. 3 and FIG. 4 respectively are a semiconductor structure 100 in accordance with various embodiments of the present disclosure. FIG. 3 is a perspective view of the semiconductor structure 100, and FIG. 4 is a top plan view of the semiconductor structure 100. In some embodiments, the semiconductor structure 100 includes a substrate 101, several gates and an interlayer dielectric (ILD) 104.
In some embodiments, the substrate 101 includes silicon, germanium, silicon germanium, gallium arsenic or other suitable semiconductor materials. In some embodiments, the substrate 101 is a semiconductor on insulator such as silicon on insulator (SOI). In some embodiments, the substrate 101 is a compound semiconductor substrate in a multilayer silicon structure.
In some embodiments, the substrate 101 includes a first active region 101a, a second active region 101b and an isolation 101c disposed between the first active region 101a and the second active region 101b. In some embodiments, the first active region 101a and the second active region 101b respectively include a transistor. In some embodiments, the first active region 101a is doped with P-type dopants such as boron or N-type dopants such as phosphorus or arsenic. Similarly, the second active region 101b is doped with the P-type or N-type dopants.
The isolation 101c is interposed between the first active region 101a and the second active region 101b to electrically isolate them from each other. In some embodiments, the isolation 101c includes materials such as silicon oxide, silicon nitride, silicon oxynitride, fluoride-doped silicate glass (FSG), a low-k dielectric material and/or combinations thereof. In some embodiments, the isolation 101c is a shallow trench isolation (STI).
There are several gates (102, 103) disposed over the substrate 101. In some embodiments, the gates (102, 103) are surrounded by the ILD 104. In some embodiments, the ILD 104 includes silicon oxide, silicon dioxide, silicon oxynitride, silicon oxynitride doped with hydrogen or silicon oxide doped with carbon. In some embodiments, the ILD 104 includes a high density plasma (HDP) dielectric material (e.g., HDP oxide) and/or a high aspect ratio process (HARP) dielectric material (e.g., HARP oxide). It is understood that the ILD 101 may include one or more dielectric materials and/or one or more dielectric layers.
In some embodiments, the ILD 104 includes several recesses (104a, 104b, 104c), and the gates (102, 103) are disposed within the recesses (104a, 104b, 104c) correspondingly. In some embodiments, each recess (104a, 104b, 104c) has a sidewall 104d substantially orthogonal to the substrate 101.
Each of the recesses (104a, 104b, 104c) has a width (W1, W2) and a height (H1, H2). In some embodiments, the recesses (104a, 104b, 104c) have a consistent width (W1, W2), for example the width W1 is substantially equal to the width W2. In some embodiments, the recesses (104a, 104b, 104c) have a consistent height (H1, H2), for example the height H1 is substantially equal to the height H2. An aspect ratio of each recess (104a, 104b, 104c) is high. In some embodiments, the aspect ratio of each recess (104a, 104b, 104c) is substantially greater than about 10. In some embodiments, a ratio of the width W1 to the height H1 or the width W2 to the height H2 is substantially greater than 1:10.
In some embodiments, the gates include a first gate 102 and a second gate 103. In some embodiments, the first gate 102 and the second gate 103 respectively includes a polysilicon or a gate fill metal. In some embodiments, an oxide layer 105 is disposed at a bottom of the first gate 102 and is contacted with the substrate 101. In some embodiments, a spacer 106 is disposed along the sidewall 104d of the recess (104a, 104b, 104c) or a sidewall of the first gate 102.
In some embodiments, the first gate 102 is extended over the first active region 101a, the isolation 101c and the second active region 101b, and the second gate 103 is disposed over the first active region 101a and the second active region 101b. In some embodiments, the first gate 102 has a width W1 and a height H1, while the second gate 103 has a width W2 and a height H2. An aspect ratio of the first gate 102 or the second gate 103 is high. In some embodiments, the aspect ratio of the first gate 102 or the second gate 103 is substantially greater than about 10. In some embodiments, a ratio of the width W1 to the height H1 or the width W2 to the height H2 is substantially greater than 1:10.
In some embodiments, the second gate 103 is configured not to conduct current flow. In some embodiments, the first gate 102 is a control gate, while the second gate 103 is a dummy gate. The second gate 103 is divided into two sections (103a, 103b). In some embodiments, the second gate 103 includes a first section 103a and a second section 103b. In some embodiments, the first section 103a is disposed over the first active region 101a, and the second section 103b is disposed over the second active region 101b. 
The first section 103a is distanced from the second section 103b. In some embodiments, a portion 104e of the ILD 104 is disposed between the first section 103a and the second section 103b. The portion 104e of the ILD 104 separates the first section 103a from the second section 103b. In some embodiments, the portion 104e of the ILD 104 is disposed over the isolation 101c. Referring to FIG. 4, the first section 103a and the second section 103b are separated from each other in a distance D.
FIG. 5 and FIG. 6 respectively are a semiconductor structure 200 in accordance with various embodiments of the present disclosure. FIG. 5 is a perspective view of the semiconductor structure 200, and FIG. 6 is a top plan view of the semiconductor structure 200. The semiconductor structure 200 has similar configuration as the semiconductor structure 100 of FIG. 3 and FIG. 4.
In some embodiments, the recess 104a of the ILD 104 is extended in an inconsistent width. In some embodiments, a portion of the recess 104a disposed opposite to the portion 104e of the ILD 104 has a width W1′, and the width W1′ is substantially greater than the width W1 or the width W2 of the recess 104b or the recess 104c. In some embodiments, the recess 104a disposed over the isolation 101c has the width W1′.
In some embodiments, the first gate 102 is elongated over the substrate 101 in an inconsistent width. In some embodiments, a portion of the first gate 102 disposed opposite to the portion 104e of the ILD 104 has the width W1′, and the width W1′ is substantially greater than the width W1 or the width W2 of the second gate 103. In some embodiments, the first gate 102 disposed over the isolation 101c has the width W1′.
FIG. 7 and FIG. 8 respectively are a semiconductor structure 300 in accordance with various embodiments of the present disclosure. FIG. 7 is a perspective view of the semiconductor structure 300, and FIG. 8 is a top plan view of the semiconductor structure 300. The semiconductor structure 300 has similar configuration as the semiconductor structure 100 of FIG. 3 and FIG. 4.
In some embodiments, the recess 104a of the ILD 104 has a larger opening. The recess 104a is in a tapered configuration, that a width W1′ of a top part of the recess 104a is greater than a width W1 of a bottom part of the recess 104a. In some embodiments, the width W1′ of the top part of the recess 104a is greater than a width W2 of the recess 104b. 
Similarly, the first gate 102 is in a tapered configuration. A top part of the first gate 102 has the width W1′ greater than the width W1 of a bottom part of the first gate 102. In some embodiments, the width W1′ of the top part of the first gate 102 is greater than the width W2 of the second gate 103.
In some embodiments, a sidewall 102a of the first gate 102 is tilted in an angle θ. The angle θ is defined between the sidewall 102a of the first gate 102 and an axis orthogonal to the substrate 101. In some embodiments, the angle θ is about 1° to about 10°.
FIG. 9 and FIG. 10 respectively are a semiconductor structure 400 in accordance with various embodiments of the present disclosure. FIG. 9 is a perspective view of the semiconductor structure 400, and FIG. 10 is a top plan view of the semiconductor structure 400. The semiconductor structure 400 has similar configuration as the semiconductor structure 100 of FIG. 3 and FIG. 4.
In some embodiments, the semiconductor structure 400 includes one or more second gates 103. As shown in FIG. 9 and FIG. 10, there are two second gates 103 surrounding the first gate 102. The two second gates 103 are interposed by the first gate 102. In some embodiments, two second gates 103 are in same configuration.
FIG. 11 and FIG. 12 respectively are a semiconductor structure 500 in accordance with various embodiments of the present disclosure. FIG. 11 is a perspective view of the semiconductor structure 500, and FIG. 12 is a top plan view of the semiconductor structure 500. The semiconductor structure 500 has similar configuration as the semiconductor structure 200 of FIG. 5 and FIG. 6.
In some embodiments, the semiconductor structure 500 includes one or more second gates 103. As shown in FIG. 11 and FIG. 12, there are two second gates 103 surrounding the first gate 102. The two second gates 103 are interposed by the first gate 102. In some embodiments, two second gates 103 are in same configuration. In some embodiments, a portion of the first gate 102 with a greater width W1′ is interposed between two portions 104e of the ILD 104.
FIG. 13 and FIG. 14 respectively are a semiconductor structure 600 in accordance with various embodiments of the present disclosure. FIG. 13 is a perspective view of the semiconductor structure 600, and FIG. 14 is a top plan view of the semiconductor structure 600. The semiconductor structure 600 has similar configuration as the semiconductor structure 300 of FIG. 7 and FIG. 8.
In some embodiments, the semiconductor structure 600 includes one or more second gates 103. As shown in FIG. 13 and FIG. 14, there are two second gates 103 surrounding the first gate 102. The two second gates 103 are interposed by the first gate 102. In some embodiments, two second gates 103 are in same configuration. In some embodiments, the width W1′ of the first gate 102 is substantially greater than the width W2 of one of the second gates 103.
FIG. 15 and FIG. 16 respectively are a semiconductor structure 700 in accordance with various embodiments of the present disclosure. FIG. 15 is a perspective view of the semiconductor structure 600, and FIG. 16 is a top plan view of the semiconductor structure 700. The semiconductor structure 700 has similar configuration as the semiconductor structure 100 of FIG. 3 and FIG. 4.
In some embodiments, the semiconductor structure 700 is a FinFET (fin field effect transistor). In some embodiments, the substrate 101 of the semiconductor structure 700 includes several semiconductor fins 107. The semiconductor fin 107 is disposed over the first active region 101a or the second active region 101b. The semiconductor fin 17 is extended between the first gate 102 and the second gate 103 over the first active region 101a or the second active region 101b. The semiconductor fin 107 is across the first gate 102 and the second gate 103. In some embodiments, the semiconductor fins 107 are surrounded by the ILD 104. In some embodiments, the semiconductor fins 107 are separated by shallow trench isolation (STI) 108.
In some embodiments, the semiconductor fin 107 includes silicon or silicon germanium. In some embodiments, the semiconductor fin 107 includes various doped regions comprising lightly doped source/drain (LDD) regions and source/drain (S/D) regions (also referred to as heavily doped S/D regions). The S/D regions are doped with p-type dopants, such as boron or BF2; n-type dopants, such as phosphorus or arsenic. In some embodiments, the source region and the drain region of each of the plurality of fins are interposed by the first gate or the second gate. In some embodiments, each of the semiconductor fins 107 has a height of about 10 nm to about 30 nm and a width of about 10 nm to about 25 nm.
FIG. 17 and FIG. 18 respectively are a semiconductor structure 800 in accordance with various embodiments of the present disclosure. FIG. 17 is a perspective view of the semiconductor structure 800, and FIG. 18 is a top plan view of the semiconductor structure 800. The semiconductor structure 800 has similar configuration as the semiconductor structure 100 of FIG. 3 and FIG. 4. The semiconductor structure 800 is a FinFET and includes several semiconductor fins 107. The semiconductor structure 800 has similar configuration as the semiconductor structure 700 of in FIGS. 15 and 16.
FIG. 19 and FIG. 20 respectively are a semiconductor structure 800 in accordance with various embodiments of the present disclosure. FIG. 19 is a perspective view of the semiconductor structure 900, and FIG. 20 is a top plan view of the semiconductor structure 900. The semiconductor structure 900 is also a FinFET with several semiconductor fins 107, similar to the semiconductor structure 700 of in FIGS. 15 and 16.
In the present disclosure, a method of manufacturing a semiconductor structure is also disclosed. In some embodiments, a semiconductor structure is formed by a method 1000. The method 1000 includes a number of operations and the description and illustration are not deemed as a limitation as the sequence of the operations.
FIG. 21 is a diagram of a method 1000 of manufacturing a semiconductor device in accordance with various embodiments of the present disclosure. The method 1000 includes a number of operations (1001, 1002, 1003, 1004 and 1005).
In operation 1001, a substrate 101 is received or provided as in FIG. 21A. In some embodiments, the substrate 101 includes silicon, germanium, silicon germanium, gallium arsenic or other suitable semiconductor materials. In some embodiments, the substrate 101 has similar configuration as the substrate 101 in one of FIGS. 3-20.
In operation 1002, a first active region 101a, a second active region 101b and an isolation 101c disposed between the first active region 101a and the second active region 101b are patterned as in FIG. 21B. In some embodiments, the first active region 101a and the second active region 101b are formed by various doping operations, depending on design requirements. In some embodiments, the first active region 101a or the second active region 101b is doped with n-typed dopants or p-typed dopants. In some embodiments, the isolation 101c is formed by pattering the substrate 101 through photolithography operation, forming a trench in the substrate 101 through dry etching, wet etching or plasma etching operation, and filing the trench by a dielectric material. In some embodiments, the first active region 101a, the second active region 101b and the isolation 101c are configured as in one of FIGS. 3-14. In some embodiments, the first active region 101a, the second active region 101b and the isolation 101c are patterned upon the receipt or provision of the substrate 101 (the operation 1001).
In some embodiments for forming a semiconductor structure as a FinFET, the substrate 101 is patterned with the first active region 101a, the second active region 101b, the isolation 101c and several fins 107 as in FIG. 21C and FIG. 21D. In some embodiments, the fins 107 are patterning by hardmask deposition and reactive ion etching (RIE) operations. In some embodiments, the first active region 101a, the second active region 101b, the isolation 101c and the fins 107 are configured as in one of FIGS. 15-20. In some embodiments, the semiconductor fins 107 are separated by shallow trench isolation (STI) 108.
In operation 1003, an inter-level dielectric (ILD) 104 is disposed over the substrate 101 as in FIGS. 21E-21H. In some embodiments, the ILD 104 includes a dielectric material. In some embodiments, the ILD 104 includes silicon oxide, silicon dioxide, silicon oxynitride, silicon oxynitride doped with hydrogen or silicon oxide doped with carbon. In some embodiments as in FIG. 21G and FIG. 21H, the ILD 104 is disposed around the fins 107. In some embodiments, the ILD 104 has similar configuration as in one of FIGS. 3-20.
In operation 1004, a first gate 102 is formed as in FIGS. 21I-21T. In some embodiments, the first gate 102 is extended over the first active region 101a, the isolation 101c and the second active region 101b. In some embodiments, the first gate 102 includes a gate fill metal.
In some embodiments, the formation of the first gate 102 includes forming a first recess 104a of the ILD 104. In some embodiments, the first recess 104a is formed by any suitable operations such as etching. The first recess 104a is formed through the ILD 104 and is extended over the first active region 101a, the second active region 101b and the isolation 101. In some embodiments, the first recess 104a is in a high aspect ratio of greater than about 10. In some embodiments, the first recess 104a is filled by a polysilicon and then is annealed at a predetermined temperature of about 200 degree Celsius to about 800 degree Celsius.
In some embodiments as in FIGS. 21M-21T, the polysilicon within the first recess 104a is removed from the first recess 104a, thereby a width of a portion or a whole of the first recess 104a is increased. In some embodiments, the removal of the polysilicon from the first recess 104a includes pulling a sidewall 104d of the first recess 104a to increase the width of the portion of the first recess 104a. In some embodiments, the width of the first recess 104a is increased from W1 (as in FIGS. 21I-21L) to W1′ (as in FIGS. 21M-21T). In some embodiments, the sidewall 104d of the first recess 104a is tilted in an angle θ when the polysilicon is removed from the first recess 104a. The angle θ between the sidewall 104d and an axis orthogonal to the substrate 101 is about 1° to about 10°. After the polysilicon is removed from the first recess 104a, the first recess 104a is filled by the gate fill metal. As a result, the first gate 102 is formed.
In operation 1005, a second gate 103 is formed as in FIGS. 21U-21AF. In some embodiments, the second gate 103 is disposed over the first active region 101a and the second active region 101b. In some embodiments, the second gate 103 includes a gate fill metal. In some embodiments, the second gate 103 includes a first section 103a disposed over the first active region 101a and a second section 103b disposed over the second active region 101b. In some embodiments, a portion 104e of the ILD 104 is disposed between the first section 103a and the second section 1036b. 
In some embodiments, the formation of the second gate 103 includes forming a second recess (104b, 104c) of the ILD 104. In some embodiments, the second recess (104b, 104c) is formed by any suitable operations such as etching. In some embodiments, the second recess (104b, 104c) is formed through the ILD 104 and is disposed over the first active region 101a and the second active region 101b. In some embodiments, the second recess (104b, 104c) is in a high aspect ratio of greater than about 10.
In some embodiments, the second recess (104b, 104c) is formed by disposing a photoresist over a portion 104e of the ILD 104 and removing the ILD 104 uncovered by the photoresist through photolithography and etching operations. In some embodiments, the second recess (104b, 104c) includes a first section 104b and a second section 104c. The portion 104e of the ILD 104 is disposed between the first section 104b and the second section 104c. 
In some embodiments, the second recess 104b is filled by a polysilicon and then is annealed at a predetermined temperature of about 200 degree Celsius to about 800 degree Celsius. In some embodiments, the polysilicon within the second recess 104b is removed from the second recess 104b, and then the second recess 104b is filled by the gate fill metal. As a result, the second gate 103 is formed.
In some embodiments, the first recess 104a and the second recess 104b are formed simultaneously, and then the first recess 104a and the second recess 104b are filled by to polysilicon and annealed at a predetermined temperature of about 200 degree Celsius to about 800 degree Celsius. After the annealing operation, the polysilicon is removed from the first recess 104a and the second recess (104b, 104c). When the polysilicon is removed, a sidewall 104d of the first recess 104a is pulled towards the portion 104e of the ILD 104 disposed between the first section 104b and the second section 104c, thereby a width of a portion of the first recess 102 opposite to the portion 104e of the ILD 104 disposed between the first section 103a and the second section 103b is increased as shown in FIGS. 21Y-21AB. In some embodiments, a width of the first recess 102 is increased as shown in FIGS. 21AC-21AF when the polysilicon is removed from the first recess 102. In some embodiments, the width of the first recess 102 is increased from W1 to W1′. In some embodiments, when the polysilicon is removed from the first recess 102, the sidewall 104d of the first recess 102 is tilted in an angle θ. The angle θ between the sidewall 104d and an axis orthogonal to the substrate 101 is about 1° to about 10°.
After the removal of the polysilicon from the first recess 104a and the second recess (104b, 104c), the first recess 104a and the second recess (104b, 104c) are filled by a gate fill metal to form the first gate 102 and the second gate 103 respectively. As the width of the first recess 104a is widened during the formation of the first gate 102, deposition of the gate fill metal into the first recess 104a is improved. Therefore, an improved first gate 102 is formed.
A semiconductor structure with a metal gate is improved. The semiconductor structure includes a first gate and a second gate includes a first section and a second section. An improved first gate is formed, since a first recess for forming the first gate is widen by an internal tensile stress developed within the ILD. The enlarged first recess would facilitate the formation of the first gate, ultimately a performance of the semiconductor structure is improved.
In some embodiments, a semiconductor structure includes a substrate including a first active region, a second active region and an isolation disposed between the first active region and the second active region; a plurality of gates disposed over the substrate and including a first gate extended over the first active region, the isolation and the second active region; and a second gate over the first active region and the second active region; and an inter-level dielectric (ILD) disposed over the substrate and surrounding the plurality of gates, wherein the second gate is configured not to conduct current flow and includes a first section disposed over the first active region and a second section disposed over the second active region, a portion of the ILD is disposed between the first section and the second section.
In some embodiments, the first section is distanced from the second section. In some embodiments, a ratio of a distance between the first section and the second section to a length of the first section protruded from the first active region is about 1:1, or a ratio of a distance between the first section and the second section to a length of the second section protruded from the second active region is about 1:1. In some embodiments, the first section has a length substantially greater than a length of the first active region, or the second section has a length substantially greater than the a length of the second active region. In some embodiments, each of the plurality of gates has a high aspect ratio of greater than about 10. In some embodiments, the first gate is a control gate, and the second gate is a dummy gate. In some embodiments, the substrate further includes a plurality of fins extending between the first gate and the second gate over the first active region or the second active region. In some embodiments, the substrate further includes a plurality of fins surrounded by the ILD. In some embodiments, the first gate and the second gate respectively includes a polysilicon or a gate fill metal. In some embodiments, an oxide layer is disposed at a bottom of the first gate and is contacted with the substrate, or a spacer is deposited along a sidewall of the first gate. In some embodiments, the ILD includes silicon oxide, silicon dioxide, silicon oxynitride, silicon oxynitride doped with hydrogen or silicon oxide doped with carbon.
In some embodiments, a method of manufacturing a semiconductor structure includes receiving a substrate; patterning a first active region, a second active region and an isolation between the first active region and the second active region over the substrate; disposing an inter-level dielectric (ILD) over the substrate; forming a first gate extended over the first active region, the isolation and the second active region; and forming a second gate over the first active region and the second active region, wherein the second gate includes a first section disposed over the first active region and a second section disposed over the second active region, a portion of the ILD is disposed between the first section and the second section.
In some embodiments, the forming the first gate or the forming the second gate includes annealing the semiconductor structure at a predetermined temperature of about 200 degree Celsius to about 800 degree Celsius. In some embodiments, the forming the first gate includes forming a sidewall of the first gate tilted in an angle, and the angle between the sidewall and an axis orthogonal to the substrate is about 1° to about 10°. In some embodiments, the forming the first gate includes widening a width of a portion of the first gate opposite to the portion of the ILD disposed between the first section and the second section.
In some embodiments, a method of manufacturing the semiconductor structure includes receiving a substrate patterned with a first active region, a second active region, an isolation and a plurality of fins; disposing an inter-level dielectric (ILD) over the substrate and around the plurality of fins; forming a first recess through the ILD and extended over the first active region, the isolation and the second active region; forming a second recess through the ILD and disposed over the first active region and the second active region; disposing a polysilicon within the first recess and the second recess; annealing the semiconductor structure at a predetermined temperature; removing the polysilicon from the first recess and the second recess, thereby a width of a portion of the first recess opposite to the portion of the ILD disposed between a first section of the second recess and the second section of the second recess is increased; and filling the first recess and the second recess by a gate fill metal.
In some embodiments, the removing the polysilicon includes pulling a sidewall of the first recess towards the portion of the ILD disposed between the first section and the second section to increase the width of the portion of the first recess. In some embodiments, the removing the polysilicon includes forming a sidewall of the first recess tilted in an angle, and the angle between the sidewall and an axis orthogonal to the substrate is about 1° to about 10°. In some embodiments, the forming the second recess includes disposing a photoresist over a portion of the ILD between the first section and the second section, and removing the ILD uncovered by the photoresist through photolithography and etching operations. In some embodiments, the first recess and the second recess are in a high aspect ratio of greater than about 10.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled 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 skilled 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. A semiconductor structure, comprising:
a substrate including a first active region, a second active region and an isolation disposed between the first active region and the second active region;
a plurality of gates disposed over the substrate and including:
a first gate extended over the first active region, the isolation and the second active region; and
a second gate over the first active region and the second active region; and

an inter-level dielectric (ILD) disposed over the substrate and surrounding the plurality of gates,
wherein the second gate is configured not to conduct current flow and includes a first section disposed over the first active region and a second section disposed over the second active region, a portion of the ILD is disposed between the first section and the second section and separates the first section from the second section.

2. The semiconductor structure in claim 1, wherein the first section is distanced from the second section.

3. The semiconductor structure in claim 1, wherein the first section has a length substantially greater than a length of the first active region, or the second section has a length substantially greater than the a length of the second active region.

4. The semiconductor structure in claim 1, wherein each of the plurality of gates has a high aspect ratio of greater than about 10.

5. The semiconductor structure in claim 1, wherein the first gate is a control gate, and the second gate is a dummy gate.

6. The semiconductor structure in claim 1, wherein the substrate further includes a plurality of fins extending between the first gate and the second gate over the first active region or the second active region.

7. The semiconductor structure in claim 1, wherein the substrate further includes a plurality of fins surrounded by the ILD.

8. The semiconductor structure in claim 1, wherein the substrate further includes a plurality of fins separated from each other by shallow trench isolation (STI).

9. The semiconductor structure in claim 1, wherein the first gate and the second gate respectively includes a polysilicon or a gate fill metal.

10. The semiconductor structure in claim 1, wherein an oxide layer is disposed at a bottom of the first gate and is contacted with the substrate, or a spacer is deposited along a sidewall of the first gate.

11. The semiconductor structure in claim 1, wherein the ILD includes silicon oxide, silicon dioxide, silicon oxynitride, silicon oxynitride doped with hydrogen or silicon oxide doped with carbon.

12. A semiconductor structure, comprising:
a substrate including a first active region and a second active region over the substrate;
a plurality of fins protruded from the substrate and across the first active region or the second active region;
a first gate extending across a portion of each of the plurality of fins and extending from the first active region to the second active region;
a second gate extending across a portion of each of the plurality of fins, disposed opposite to the first gate, and disposed at an edge of the first active region and an edge of the second active region; and
an inter-level dielectric (ILD) interposed between the first gate and the second gate,
wherein the second gate includes a first section along the edge of the first active region and a second section along the edge of the second active region, the first section is distanced away and separated from the second section.

13. The semiconductor structure in claim 12, wherein the second gate disposed between the first active region and the second active region is discontinuous.

14. The semiconductor structure in claim 12, wherein the first gate disposed between the first active region and the second active region has a first width substantially greater than a second width of the first gate disposed within the first active region or the second active region.

15. The semiconductor structure in claim 12, wherein the plurality of fins are integral with the substrate.

16. A semiconductor structure, comprising:
a substrate including an active region within or over the substrate; and
an inter-level dielectric (ILD) disposed over the substrate and including a recess configured to surround a gate structure,
wherein the recess includes a first portion in a first width, a second portion in a second width and a third portion in the first width, the second portion is disposed between the first portion and the third portion, the first width is substantially smaller than the second width.

17. The semiconductor structure in claim 16, wherein the second portion of the recess is tapered towards the substrate.

18. The semiconductor structure in claim 16, wherein the recess has a high aspect ratio of about 10.

19. The semiconductor structure in claim 16, wherein the active region includes a source region and a drain region opposite to the source region, and the gate structure is disposed between the source region and the drain region.

20. The semiconductor structure in claim 16, wherein a spacer is deposited conformal to a sidewall of the recess.