Semiconductor Device and Method

Abstract

Semiconductor device (100) comprising the following: an active region (110) with a rib structure (120) extending in a first direction (X); a first gate structure (151) extending in a second direction (Y) that is different from the first direction; where: the first gate structure (151) contains a first segment (151A) that is arranged above the active region (110) and a second segment (151B) that is not arranged above an active region; the first segment (151A) has a first material composition; and the second segment (151B) has a second material composition that differs from the first material composition; and a second gate structure (152) that extends in the second direction (Y), wherein the second gate structure is spaced apart from the first gate structure (151) in the first direction; where: the second gate structure (152) contains a third segment (152A) that is located above the active region (110), and a fourth segment (152B) that is not located above an active region; the third segment (152A) has a third material composition; and the fourth segment (152B) has a fourth material composition that differs from the third material composition, wherein: the active region has a boundary that extends in the first direction; the second segment is spaced from the boundary of the active region (110) by a first distance (171); the fourth segment (152B) is separated from the boundary of the active region (110) by a second distance (172) which is different from the first distance (172); where the second material composition differs from the fourth material composition; and wherein the second segment (151B) has a first dimension (181), measured in the second direction (Y); the fourth segment (152B) has a second dimension (182), measured in the second direction (Y); and the first dimension (181) is not equal to the second dimension (182).

Description

[0001] US patent 2010 / 0102389A1 relates to a finned FET which is said to have gate electrodes that can be controlled independently of each other. The patent discloses the use of two separate gate electrodes, each with its own gate contact.

[0002] US 9 543 297 B1 relates to a finned FET with a replacement metal gate structure, which is suitable for several threshold voltages V T to be used. For this purpose, it is disclosed to form a gate with two different metal materials, which are arranged congruently on top of each other.

[0003] US 2015 / 0 008 533 A1 reveals a fin FET with two different gates over two different fins, the gates differing in material.

[0004] US 2014 / 0317581A1 concerns a layout for a semiconductor structure to reduce the corner rounding effect.

[0005] DE 10 2015 113 081 A1 relates to a FET structure comprising a transistor of a first conductivity type. BACKGROUND

[0006] In its pursuit of higher device density, increased performance, and reduced costs, the semiconductor industry has advanced into the realm of nanometer-scale process nodes. As part of this progress, challenges arising from manufacturing and design issues have led to the development of three-dimensional designs, such as fin field-effect transistors (FinFETs). A typical FinFET is fabricated with a thin "rib" (or rib-like structure) extending from a substrate. The rib typically contains silicon and forms the body of the transistor. The transistor channel is formed within this vertical rib. A gate is positioned above the rib (for example, around the rib). This type of gate allows for better control of the channel. Other advantages of FinFETs include reduced short-channel effect and higher current handling.

[0007] FinFET devices are compatible with a high-k metal gate (HKMG) process flow. In other words, FinFET devices can be implemented as HKMG devices, featuring a high-k gate dielectric and a metal gate electrode. However, state-of-the-art HKMG FinFET devices still have limitations, such as the lack of threshold voltage (Vt) tuning options, which restricts design freedom in IC development and could also degrade device performance.

[0008] Although the HKMG-FinFET devices of the state of the art are generally sufficient for their intended purposes, they are not yet satisfactory in every respect. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Aspects of the present disclosure are best understood with reference to the following detailed description, when read in conjunction with the accompanying figures. It should be noted that, in accordance with common industry practice, various structural elements are not drawn to scale. The dimensions of the various structural elements may be enlarged or reduced as necessary for the sake of clarity in this discussion. It should also be noted that the attached drawings illustrate only typical embodiments of this invention and should therefore not be interpreted as limiting its scope, since the invention may also be applicable to other equally effective embodiments. Fig. Figure 1 is a perspective view of an example FinFET device. Fig. Figure 2 illustrates a top view of a FinFET device according to an embodiment of the present disclosure. Fig. Figure 3 is a diagram illustrating a relationship between creepage and drive current for a transistor according to an embodiment of the present disclosure. Fig. Figure 4 is a diagram illustrating a relationship between threshold voltage and a distance according to an embodiment of the present disclosure. Fig. Figure 5 illustrates a circuit diagram for an SRAM cell according to an embodiment of the present disclosure. Fig. Figure 6 is a flowchart illustrating a method according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0010] The invention is defined by the subject matter of the independent claims. The dependent claims relate to corresponding embodiments. The following disclosure provides many different embodiments or examples for implementing various features of the subject matter discussed herein. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, only examples and are not intended to limit the scope of the invention.For example, the formation of a first structural element above or on top of a second structural element in the following description may include embodiments in which the first and second structural elements are in direct contact, and may also include embodiments in which additional structural elements may be formed between the first and second structural elements, so that the first and second structural elements are not necessarily in direct contact. Furthermore, this disclosure may repeat reference numerals and / or letters in the various examples. This repetition serves the purpose of simplicity and clarity and does not automatically establish a relationship between the various embodiments and / or configurations discussed.

[0011] Furthermore, spatially relative terms, such as "below," "under," "lower," "above," "upper," and the like, may be used in this text to simplify the description and to describe the relationship of one element or structural element to one or more other elements or structural elements, as illustrated in the figures. These spatially relative terms are intended to encompass not only the orientation shown in the figures but also other orientations of the device during use or operation. The device may also be oriented differently (rotated 90 degrees or otherwise), and the spatially relative descriptors used in this text may be interpreted accordingly.

[0012] The present disclosure relates, without being limited thereto, to a rib-like field-effect transistor (FinFET) device. The FinFET device may, for example, be a complementary metal-oxide-semiconductor (CMOS) device comprising a P-type metal-oxide-semiconductor (PMOS) FinFET device and an N-type metal-oxide-semiconductor (NMOS) FinFET device. The following disclosure continues with one or more FinFET examples to illustrate various embodiments of the present disclosure. It is understood, however, that the application may not be limited to a particular type of device unless expressly claimed otherwise.

[0013] The use of FinFET devices has become increasingly prevalent in the semiconductor industry. Fig. Figure 1 illustrates a perspective view of an exemplary FinFET device 50. The FinFET device 50 is a non-planar multi-gate transistor formed on a substrate (such as a bulk substrate). A thin, silicon-containing, rib-like structure (hereinafter referred to as a rib) forms the body of the FinFET device 50. The rib extends along a Fig. 1. X-direction shown. The rib has a rib width W. fin , measured along a Y-direction that runs orthogonal to the X-direction. A gate 60 of the FinFET device 50 wraps around this rib, for example around the top and the opposite sidewall surfaces of the rib. Therefore, a section of the gate 60 is located above the rib in a Z-direction that runs orthogonal to both the X-direction and the Y-direction.

[0014] L Gdenotes a length (or width, depending on the perspective) of the gate 60, measured in the X direction. The gate 60 can contain a gate electrode component 60A and a gate dielectric component 60B. The gate dielectric 60B has a thickness t ox , measured in the Y direction. A section of the gate 60 is located above a dielectric insulating structure, such as shallow trench insulation (STI). A source 70 and a drain 80 of the FinFET device 50 are formed in extensions of the rib on opposite sides of the gate 60. A section of the rib that wraps around the gate 60 serves as a channel for the FinFET device 50. The effective channel length of the FinFET device 50 is determined by the dimensions of the rib.

[0015] FinFET devices offer several advantages over conventional metal-oxide-semiconductor field-effect transistors (MOSFETs) (also known as planar transistors). These advantages can include better chip area utilization, improved carrier mobility, and better fabrication, which is compatible with the manufacturing processes of planar devices. FinFET devices are compatible with a high-k metal gate (HKMG) process flow. Therefore, FinFET devices can be implemented as HKMG devices, where the gates each have a high-k-value gate dielectric and a metal gate electrode. For these benefits discussed above, it may be desirable to design an integrated circuit (IC) chip that uses HKMG FinFET devices for a portion of the IC chip or the entire IC chip.

[0016] However, conventional HKMG FinFET devices can still have weaknesses, such as weaknesses related to threshold voltage (Vt) tuning. Specifically, for many modern devices (e.g., mobile phones, computers, etc.), the ability to fine-tune the threshold voltage can be desirable to optimize a trade-off between performance and power consumption. The threshold voltage of a MOSFET transistor (including FinFETs) is largely determined by the material composition of the exit metal inside the transistor's gate electrode. One way to adjust the threshold voltage is to increase the gate length of the transistor. However, as semiconductor structural elements become increasingly smaller, increasing the gate length is not a realistic option. Ion implantation can also be used to adjust the threshold voltage.However, such ion implantation can damage the FinFET device and degrade its performance. Because of these limitations, IC designers often have to make compromises regarding the threshold voltage, meaning the IC design is often not optimized, for example, in terms of a trade-off between performance and power consumption.

[0017] According to various aspects of this disclosure, different exit work metals are implemented in different segments of the gate structures, which are formed outside or above an active region. By configuring the distance between the active region and the gate segments (which have different exit work metals) that are formed outside the active region, and / or by selecting specific material compositions of these exit work metals, this disclosure provides the ability to tune the threshold voltage with higher resolution. Or, in other words, this disclosure allows for finer tuning of the threshold voltage for FinFET devices, as will be discussed in more detail below.

[0018] Fig. Figure 2 is a fragmentary top view of a semiconductor device 100 according to embodiments of the present disclosure. In some embodiments, the semiconductor device 100 includes a FinFET device, such as the FinFET device 50 of Fig. 1. The semiconductor device 100 contains an active region 110, also referred to as an OD region. In some embodiments, the active region 110 contains a rib structure (for example, similar to that in Fig. 1 rib structure shown), extending in the X direction. The rib structure can contain a semiconductor material, such as silicon or silicon-germanium. Source / Drain regions 120 (similar to Source 70 and Drain 80 of Fig. 1) are also formed in the rib structure. The source / drain regions 120 can be formed by processes such as ion implantation. A dielectric insulating structure 130 (for example, a shallow trench insulation) surrounds the active region 110 (or is located next to it). For example, a boundary 140 (extending in the X direction) separates the active region 110 from the active region 110 of the dielectric insulating structure 130.

[0019] The semiconductor device 100 also includes several elongated gate structures, each extending in the Y direction (perpendicular to the X direction), for example, elongated gate structures 150, 151, 152, and 153. In some embodiments, the elongated gate structures 150-153 are HKMG structures, and each contains a high k-value gate dielectric and a metal gate electrode. A high k-value dielectric material is a material whose dielectric constant is greater than that of SiO₂, which is approximately 4. In one embodiment, the high k-value gate dielectric contains hafnium oxide (HfO₂), which has a dielectric constant in the range of approximately 18 to approximately 40. In alternative embodiments, the gate dielectric with high k-value can contain ZrO2, Y2O3, La2O5, Gd2O5, TiO2, Ta2O5, HfErO, HfLaO, HfYO, HfGdO, HfAlO, HfZrO, HfTiO, HfTaO or SrTiO.

[0020] The metal-gate electrode can contain a work-effect layer and a filler metal layer. The work-effect metal component is configured to tune the work function of its corresponding transistor to achieve a desired threshold voltage, Vt. The work-effect metal component can contain at least one layer or multiple layers made of different materials. The work-effect layer material is selected based on whether the FinFET is an n-type or a p-type FinFET. For example, if the FinFET is an n-type FinFET, the work-effect layer can contain a TaN layer, a titanium-aluminum (TiAl) layer over the TaN layer, and a TiAl layer. If the FinFET is a p-type FinFET, the work-effect layer can contain a TaN layer, a TiN layer over the TaN layer, and a TiAl layer over the TiN layer.Other suitable materials for the exit working layer include titanium aluminum nitride (TiAlN), tantalum carbon nitride (TaCN), titanium nitride (TiN), tungsten nitride (WN), tungsten (W), or combinations thereof. The filler metal layer is applied over the... The exit working layer is formed and serves as the main conductive section of the elongated gate structures 150-153. In various embodiments, the filler metal layer can contain aluminum (Al), tungsten (W), copper (Cu), or combinations thereof.

[0021] In some embodiments, the formation of the elongated gate structures 150-153 involves a gate replacement process. More precisely, several dummy gate structures can first be formed, each containing a dummy gate dielectric, such as silicon oxide, and a dummy gate electrode, such as polysilicon. After the formation of the source / drain regions 120, the dummy gate structures are removed and replaced by the elongated gate structures 150-153, each containing a gate dielectric with a high k-value and a metallic (or conductive) gate electrode. In some embodiments, the gate replacement process involves replacing both the dummy gate dielectric and the dummy gate electrode. In other embodiments, the high k-value gate dielectric is formed under the dummy gate electrode, and only the dummy gate electrode needs to be replaced by the metal gate electrode as part of the gate replacement process.

[0022] As in Fig. As shown in Figure 2, the elongated gate structures 150-153 each have a segment 150A-153A located above the active region 110. The elongated gate structures 150-153 also each have a segment (or section) 150B-153B that is not located above the active region 110. In other words, the segments 150B-153B of the elongated gate structures 150-153 are located outside the active region 110 and are positioned above the dielectric insulating structures 130.

[0023] According to various aspects of the present disclosure, at least some of the segments not located above active region 110 are configured to have a different material composition than the segments located above active region 110. For example, segment 151B and segment 151A have different material compositions, segment 152B and segment 152A have different material compositions, and segment 153B and segment 153A have different material compositions.

[0024] In some embodiments, at least some of the segments 150A-153A have identical material compositions, but the segments 151B-153B may have identical or different material compositions. For example, in some embodiments, segments 150A-153A may each have a first material composition, and segments 151B-153B may each have a second material composition that is different from the first. In some other embodiments, segments 150A-153A may each have a first material composition, segment 151B may have a second material composition, segment 152B may have a third material composition, and segment 153B may have a fourth material composition.The second, third and fourth material compositions may be the same in some embodiments (but still different from the first material composition), or they may be different from each other in other embodiments.

[0025] The different material compositions of segments 151B-153B (which differ, for example, from those of segments 151A-153A) help in tuning the threshold voltage Vt, as will be discussed in more detail below. In some embodiments, the respective material compositions of segments 151B-153B can be configured by one or more metal deposition processes performed as part of the gate replacement process (for example, when forming the gate structures 151-153).

[0026] We'll stick with it Fig. 2. Segments 151B-153B are spaced apart from segments 151A-153A. For example, segment 151B is separated from the boundary 140 of active region 110 by a distance of 171, segment 152B is separated from the boundary 140 of active region 110 by a distance of 172, and segment 153B is separated from the boundary 140 of active region 110 by a distance of 173, with distances 171-173 all measured in the Y direction.

[0027] In some embodiments, at least some of the distances 171, 172, and 173 are different from one another. For example, distances 171 and 172 may be essentially the same, but distance 173 may also be greater (or smaller) than either distance 171 or distance 172. As another example, distance 172 may be greater than distance 171, while distance 173 may be greater than both distance 171 and distance 172. In some embodiments, the difference between each of the distances 171 / 172 / 173 and the remaining distances 171 / 172 / 173 may be greater than 10% of the distances 171 / 172 / 173. For example, distances 171 and 172 can each be equal to M nanometers (nm), and distance 173 is larger than distances 171 and 172, and distance 173 can range from about 15 nm to an acceptable distance, depending on how much Vt shift the designer wants to achieve.

[0028] We'll stick with it Fig. 2. Segments 151B-153B can also have different sizes or dimensions. For example, segment 151B can have a dimension of 181, segment 152B can have a dimension of 182, and segment 153B can have a dimension of 183, with dimensions 181-183 each measured in the Y direction.

[0029] In some embodiments, dimensions 181-183 may be substantially the same as one or another. In other embodiments, however, at least some of dimensions 181-183 differ from the other dimensions 181-183. For example, in some embodiments, dimension 183 may be smaller (or larger) than dimension 181 or dimension 182. In some embodiments, the difference between each of dimensions 181 / 182 / 183 and the other dimensions 181 / 182 / 183 may be greater than 10% of each of dimensions 181 / 182 / 183. If, for example, dimensions 181 and 182 are each equal to N nm, and dimension 183 is larger than dimensions 181 and 182, then dimension 183 is greater than 1.1 × N nm, where N is greater than approximately 26 nm. It is understood that dimensions 181 / 182 / 183 are correlated with distances 171 / 172 / 173.For example, as the dimensions 181 / 182 / 183 increase, the distances 171 / 172 / 173 can each decrease while still allowing the desired Vt adjustment. Conversely, as the distances 171 / 172 / 173 increase, the dimensions 181 / 182 / 183 can decrease while still allowing the desired Vt adjustment. Thus, it can be seen that the dimensions 181 / 182 / 183 and the distances 171 / 172 / 173 are practically independent of each other.

[0030] A novel aspect of the present disclosure is that it allows flexible tuning of the threshold voltage Vt by implementing segments 151B-153B with different material compositions than segments 151A-153A. As discussed above, segments 151B-153B are sections of the elongated gate structures that are not located above the active region 110, while segments 151A-153A are sections of the elongated gate structures that are located above the active region 110. Since the threshold voltage Vt of a given transistor depends on the material composition of the gate electrode (for example, the material composition of the exit layer), The different material compositions of segments 151B-153B influence the overall Vt of each corresponding transistor. Or, put another way: By configuring the material composition of each of segments 151B-153B, the corresponding transistor threshold voltage can be adjusted accordingly (either upwards or downwards).

[0031] Furthermore, the threshold voltage can be further tuned by configuring the distances 171-173, which separate segments 151B-153B from the boundary 140 of the active region 110, via a metal boundary effect (MBE). For example, as the distance 171 / 172 / 173 decreases, the influence exerted by segments 151B / 152B / 153B on the Vt of their respective transistor can increase. Conversely, as the distance 171 / 172 / 173 increases, the influence exerted by segments 151B / 152B / 153B on the Vt of their respective transistor can decrease. Thus, the threshold voltage Vt of a corresponding transistor can be further tuned by configuring the value of the distance 171 / 172 / 173. In some embodiments, the value of the distance 171 / 172 / 173 can be set using a logic operation (LOP) computer-aided design (CAD) layer as part of the IC design / layout.

[0032] Furthermore, the threshold voltage can also be adjusted by configuring the dimensions 181-183 of segments 151B-153B. For example, as the dimension 181 / 182 / 183 decreases, the influence exerted by segments 151B / 152B / 153B on the Vt of their respective transistors can also decrease. Conversely, as the dimension 181 / 182 / 183 increases, the influence exerted by segments 151B / 152B / 153B on the Vt of their respective transistors can also increase. Therefore, the threshold voltage Vt of a corresponding transistor can be further adjusted by configuring the value of dimension 181 / 182 / 183. In some embodiments, the value of dimension 181 / 182 / 183 can be set using a logic operation (LOP) computer-aided design (CAD) layer as part of the IC design / layout.

[0033] From the above discussions, it can be seen that the threshold voltage Vt of an HKMG FinFET transistor is a function of the exit-work layer material composition of the gate segment not located over the active region, the distance separating this gate segment from the active region boundary, and / or the size of this gate segment. It should be noted that not all gate structures necessarily have such a segment. For example, while gate structure 150 does have a segment 150B not located over the active region 110, this segment 150B has the same material composition as segment 150A, which is located over the active region 110.

[0034] The Vt voting flexibility offered by the present disclosure can be visually represented in Fig. Figure 3 illustrates a diagram 200 that depicts the relationship between the leakage and drive current for a transistor (for example, an HKMG FinFET transistor) according to embodiments of the present disclosure. The diagram 200 includes an X-axis representing the drive current for the transistor and a Y-axis representing the leakage current (for example, source turn-off current (Isoff)) for the transistor. Each region or point in the diagram 200 can correspond to a specific threshold voltage Vt. Or, in other words, each different threshold voltage is associated with a corresponding drive current and leakage current.

[0035] As the drive current for the transistor increases, its power output increases. As the leakage current for the transistor decreases, its power consumption decreases. Therefore, it is desirable for a transistor to simultaneously achieve a high drive current (moving, for example, "to the right" on the X-axis) and a low leakage current (moving, for example, "down" on the Y-axis). Or, put another way: It is desirable for the transistor to be located near the "lower right corner" of diagram 200.

[0036] Unfortunately, in reality, transistor devices often require a compromise between drive current and leakage current, such that as the transistor's drive current performance improves, its leakage current performance deteriorates, and vice versa. This compromise can be described as a power-current trade-off. It can be advantageous for an IC designer to have a range of transistors with different corresponding Vt profiles, allowing the designer to select the most suitable transistor (with its corresponding Vt profile) for the specific circuit or IC application in which the transistor will be implemented. For example, in applications where device performance is critical, the IC designer might want to use transistors with a high drive current at the cost of a relatively high leakage current.Conversely, in applications where the component's readiness time is important, the IC designer may want to use transistors that have a low leakage current at the cost of a reduced drive current.

[0037] To provide sufficient flexibility in IC design, a semiconductor manufacturer can offer IC designers transistors with various predefined threshold voltages. For example, the semiconductor manufacturer can offer a standard threshold voltage (SVt) device, a low threshold voltage (LVt) device, and an ultra-low threshold voltage (ULVt) device. In some embodiments, the SVt, LVt, and ULVt devices can be fabricated by configuring the material composition of the exit layer for the gate segments formed above the active region, for example, segments 150A-153A of the gate.SVt components, LVt components and ULVt components can be offered to the IC designer as part of an IC design, an IC layout package or an IC layout library, allowing the IC designer to freely select the appropriate transistor components to use in implementing their IC design.

[0038] In Fig. In diagram 200, the SVt device corresponds to region 210, the LVt device to region 211, and the ULVt device to region 212. However, given the complexity and sophistication of modern IC applications, having only three different transistors with their respective threshold voltages (e.g., SVt, LVt, and ULVt) may be insufficient. An IC designer may require transistors with more versatile threshold voltage (Vt) tuning capabilities.

[0039] As discussed above, the present disclosure allows flexible tuning of the threshold voltage Vt by implementing a different exit metal in a section of the gate formed outside (for example, not above) the active region. For example, each of the SVt transistor device, the LVt transistor device, and the ULVt transistor device can be modified using the information provided in Fig. The two HKMG FinFET transistors shown are implemented. Segments 151B, 152B and 153B of Fig. 2 can each contain a different exit work metal material than their corresponding segments 151A, 152A, and 153A of the gate structures. By carefully configuring the material composition of the exit work layers of segments 151A, 152A, and 153A, the threshold voltage Vt of their respective transistor can be adjusted. Fig. 3. Changing or adjusting the threshold voltage Vt can be represented by shifting regions 210 / 211 / 212 in a direction indicated by arrows 220 / 221 / 222. For example, by configuring the material composition of the exit working metal material for segments 151B, 152B, or 153B, regions 210, 211, and / or 212 can be shifted "up and right" or "down and left" in diagram 200 of Fig. 3 move as indicated by arrows 220 / 221 / 222.

[0040] Since the threshold voltage of a transistor can also be tuned by configuring the distances 171, 172, or 173 between the boundary 140 of active region 110 and segments 151B, 152B, and 153B, regions 210, 211, and / or 212 can similarly be shifted further in the direction indicated by arrows 220 / 221 / 222. And since the dimensions 181, 182, and 183 of segments 151B, 152B, and 153B can also affect the threshold voltage of the corresponding transistor, these dimensions 181, 182, and / or 183 can also be configured to support the shifting of regions 210, 211, and / or 212.In this manner discussed above, regardless of whether an SVt transistor device, an LVt transistor device, or a ULVt transistor device is used, the corresponding threshold voltage of this transistor device can still be flexibly adjusted on the basis of the various aspects of the present disclosure.

[0041] It is understood that the threshold voltage Vt for a given transistor can also be tuned by increasing the gate length and / or by performing one or more implantation processes on the gate. This aspect of tuning the threshold voltage Vt can be described in Fig. 3. Regions 210, 211, and / or 212 can be visually represented by shifting them in the direction indicated by arrows 230, 231, and 232, respectively. The resulting regions 240, 241, and 242 can still correspond to an SVt device, an LVt device, and a ULVt device, respectively. Naturally, the transistor corresponding to regions 240, 241, and 242 in diagram 200 can still be tuned in a similar manner to the transistor corresponding to regions 210, 211, and 212.For example, the gate structure can include a different exit-work metal segment located outside the active region 210, and the distance between the boundary of the active region and the other exit-work metal segment can be configured, as can the dimensions of the other exit-work metal segment, to flexibly adjust the threshold voltage Vt of the transistors corresponding to regions 240, 241, and / or 242. As a result, regions 240, 241, and / or 242 can be shifted in a direction indicated by arrows 250, 251, and / or 252. In this way, the present disclosure offers even greater flexibility in adjusting the threshold voltage compared to conventional devices.

[0042] Fig. Figure 4 illustrates a diagram 300 that demonstrates a relationship between a threshold voltage and a distance, where the distance is the distance separating the boundary of the active region and the segment of the gate structure containing a different exit working metal. For example, the distance may be the distance 171, 172, or 173 from Fig. 2. An X-axis of diagram 300 represents the distance, and a Y-axis of diagram 300 represents the threshold voltage Vt of the corresponding transistor.

[0043] Diagram 300 contains a curve 310 and a curve 311. In some embodiments, curve 310 represents the threshold voltage of an NFET, and curve 311 represents the threshold voltage of a PFET. In some other embodiments, curve 310 represents the threshold voltage of a PFET, and curve 311 represents the threshold voltage of an NFET. As in Fig. As illustrated in Figure 4, curves 310 and 311 are each a function of distance. As the distance (for example, distance 171, 172, or 173 from) increases, the curves change. Fig. 2) As the value of curve 310 increases (from a positive number towards 0), the value of curve 311 increases (from a negative number towards 0). Therefore, diagram 300 visually indicates that the threshold voltage Vt of a transistor can be adjusted by configuring the distance 171, 172, or 173 from the Fig. 2 can be voted on.

[0044] The various aspects of this disclosure can be useful in many IC applications. For example, flexible threshold voltage tuning can be implemented in SRAM cells. As an example, this is illustrated below. Fig. 5 A circuit diagram for an SRAM cell 400 to which the threshold voltage tuning according to the present disclosure can be applied. In some embodiments, the SRAM cell 400 can be a 1-bit SRAM cell. The SRAM cell 400 contains pull-up transistors PU1, PU2; pull-down transistors PD1, PD2; and pass-gate transistors PG1, PG2. As shown in the circuit diagram, transistors PU1 and PU2 are p-type transistors, such as the p-type FinFETs discussed above, and transistors PG1, PG2, PD1, and PD2 are the n-type FinFETs discussed above.

[0045] The drains of pull-up transistor PU1 and pull-down transistor PD1 are coupled together, and the drains of pull-up transistor PU2 and pull-down transistor PD2 are coupled together. Transistors PU1 and PD1 are cross-coupled with transistors PU2 and PD2 to form a first data buffer. The gates of transistors PU2 and PD2 are coupled to each other and to the drains of transistors PU1 and PD1 to form a first memory node SN1, and the gates of transistors PU1 and PD1 are coupled to each other and to the drains of transistors PU2 and PD2 to form a complementary first memory node SNB1. The sources of the pull-up transistors PU1 and PU2 are coupled to a power voltage Vcc (also called Vdd), and the sources of the pull-down transistors PD1 and PD2 are coupled to a voltage Vss, which in some embodiments may be an electrical ground.

[0046] The first memory node SN1 of the first data buffer is coupled to the bit line BL through the pass-gate transistor PG1, and the complementary first memory node SNB1 is coupled to the complementary bit line BLB through the pass-gate transistor PG2. The first memory node N1 and the complementary first memory node SNB1 are complementary nodes that are often at opposite logic levels (logic high or logic low). The gates of the pass-gate transistors PG1 and PG2 are coupled to a word line WL.

[0047] Fig. Figure 6 is a flowchart illustrating a method 500 according to an embodiment of the present disclosure. The method 500 includes a step 510 in which a rib structure is formed. The rib structure extends in a first direction.

[0048] Procedure 500 includes a step 520 of forming a dummy gate structure that extends in a second direction that is different from the first direction.

[0049] The procedure 500 includes a step 530 of forming source / drain regions in the rib structure.

[0050] Method 500 includes a step 540 for replacing the dummy gate structure with a metal gate structure after the formation of the source / drain regions. The metal gate structure comprises a first section formed over the rib structure and a second section not formed over the rib structure. The first and second sections contain different exit metals.

[0051] In some embodiments, forming the dummy gate structure includes forming a first dummy gate structure and a second dummy gate structure spaced apart from the first dummy gate structure in the first direction. Replacing the dummy gate structure can be accomplished by having a first metal gate structure and a second metal gate structure replace the first dummy gate structure and the second dummy gate structure, respectively. The first metal gate structure can include the first section and the second section. The second metal gate structure can include a third section formed above the rib structure and a fourth section not formed above the rib structure. The third and fourth sections can contain different exit metals.In some embodiments, the replacement of the dummy gate structure is carried out such that: the second section is separated from the rib structure by a first distance, measured in the second direction; the fourth section is separated from the rib structure by a second distance, measured in the second direction; and the second distance is greater or less than the first distance. In some embodiments, the replacement of the dummy gate structure is carried out such that: the second section has a first dimension, measured in the second direction; the fourth section has a second dimension, measured in the second direction; and the second dimension is greater or less than the first dimension.

[0052] It is understood that further processes may be performed before, during, or after steps 510-540 of procedure 500. For example, procedure 500 may include additional steps such as forming conductive vias or contacts, interconnect layers, encapsulation, testing, etc. For the sake of simplicity, other additional steps are not discussed in detail in this text.

[0053] It is evident from the above discussions that the present disclosure offers advantages over conventional methods and components for tuning the threshold voltage. It is understood, however, that other embodiments may offer further advantages, and that not all advantages are necessarily disclosed in the present text, nor is a single advantage required for all embodiments. One advantage is that the present disclosure allows for more flexible tuning of a threshold voltage Vt. For example, the threshold voltage for a high-k metal gate (HKMG) FinFET transistor can be tuned by implementing a segment of the gate structure outside the active region, such that the segment contains a different exit metal material than sections of the gate formed above the active region.The threshold voltage can also be tuned by adjusting the distance between the active region boundary and the segment of the gate structure that is not located over the active region. Furthermore, the threshold voltage can be tuned by configuring the dimensions or size of this gate structure segment. Being able to offer transistors with different threshold voltages is advantageous for the IC designer, as they may need access to a variety of transistors with different threshold voltages to fine-tune the IC design, for example, to optimize the power-to-current trade-off. This power-to-current trade-off is relevant in many IC application areas, such as mobile communication devices.Another advantage is that the present disclosure does not involve extensive layout changes and is compatible with the existing HKMG-FinFET process flow. Therefore, the present disclosure can be implemented easily and cost-effectively.

Claims

[1] Semiconductor device (100) comprising the following: an active region (110) with a rib structure (120) extending in a first direction (X); a first gate structure (151) extending in a second direction (Y) that is different from the first direction; where: the first gate structure (151) contains a first segment (151A) that is arranged above the active region (110) and a second segment (151B) that is not arranged above an active region; the first segment (151A) has a first material composition; and the second segment (151B) has a second material composition that differs from the first material composition; and a second gate structure (152) extending in the second direction (Y), wherein the second gate structure is spaced apart from the first gate structure (151) in the first direction; where: the second gate structure (152) contains a third segment (152A) that is located above the active region (110) and a fourth segment (152B) that is not located above an active region; the third segment (152A) has a third material composition; and the fourth segment (152B) has a fourth material composition that differs from the third material composition, wherein: the active region has a boundary that extends in the first direction; the second segment is spaced from the boundary of the active region (110) by a first distance (171); the fourth segment (152B) is separated from the boundary of the active region (110) by a second distance (172) which is different from the first distance (172); where the second material composition differs from the fourth material composition; and wherein the second segment (151B) has a first dimension (181), measured in the second direction (Y); the fourth segment (152B) has a second dimension (182), measured in the second direction (Y); and the first dimension (181) is not equal to the second dimension (182). [2] Semiconductor device according to claim 1, wherein the first segment (150A, 151A) of the first gate structure (150, 151) is located at least partially around the rib structure. [3] Semiconductor device according to any one of the preceding claims, wherein: the first segment (150A, 151A) of the first gate structure (150, 151) contains a first exit working metal material; and the second segment (150B, 151B) of the first gate structure (150, 151) contains a second exit working metal material that is different from the first metal material composition. [4] Semiconductor device according to one of the preceding claims, wherein the first material composition and the third material composition are the same. [5] Method (500) comprising the following: Forming (510) a rib structure (120) extending in a first direction (X); Forming (520) a dummy gate structure extending in a second direction (Y) that is different from the first direction; Formation (530) of source / drain regions (120) in the rib structure; and After forming the source / drain regions, replacing (540) the dummy gate structure with a metal gate structure (151), wherein the metal gate structure includes a first section (151A) formed over the rib structure and a second section (151B) not formed over the rib structure, and wherein the first section (151A) and the second section (151B) contain different exit working metals, wherein: forming (520) the dummy gate structure includes forming a first dummy gate structure and a second dummy gate structure spaced apart from the first dummy gate structure in the first direction; the replacement (540) of the dummy gate structure is carried out in such a way that a first metal gate structure (151) and a second metal gate structure (152) replace the first dummy gate structure and the second dummy gate structure respectively; the first metal gate structure contains the first section (151A) and the second section (151B); the second metal gate structure (152) contains a third section (152A) formed above the rib structure (120) and a fourth section (152B) not formed above the rib structure; and the third section and the fourth section contain different exit working metals, wherein the replacement (540) of the dummy gate structure is carried out such that: the second section (151B) is separated from the rib structure by a first distance (171), measured in the second direction (Y); the fourth section (152B) is separated from the rib structure by a second (172) distance, measured in the second direction (Y); the second distance (172) is greater or smaller than the first distance (171), wherein the replacement (540) of the dummy gate structure is carried out such that: the second section (151B) has a first dimension (181), measured in the second direction (Y); the fourth section (152B) has a second dimension (182), measured in the second direction (Y); and the second dimension (182) is larger or smaller than the first dimension (181); and the second section (151B) and the fourth section (152B) contain different exit working metals.

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