Method for adjusting threshold voltage in metal gate manufacturing process

Abstract

The invention provides a method for adjusting a threshold voltage in a metal gate manufacturing process, and the method comprises the steps: 1, providing a substrate, and sequentially forming a first TiN layer and a TiAl layer on the substrate; secondly, the substrate leaves the vacuum environment, and the TiAl layer makes contact with air to be subjected to surface oxidation; and thirdly, a second TiN layer is formed on the TiAl layer. Under the condition that the thickness of the TiAl layer and the thickness of the TiN layer are not changed, adjustment of the threshold voltage is achieved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and specifically to a method for adjusting the threshold voltage in a metal gate process. Background Technology

[0002] In existing metal gate manufacturing processes, such as Figure 1 As shown, the threshold voltage of the device (e.g., ultra-low threshold voltage ULVT, low threshold voltage LVT, and standard threshold voltage SVT) is adjusted by stacking a PMOS work function metal layer (TiN layer, titanium nitride layer) and an NMOS work function metal layer (TiAl layer, titanium aluminum alloy layer) in the trench formed after removing the alternative gate.

[0003] As dimensions shrink and equipment limits are imposed, the aforementioned methods for adjusting the threshold voltage of devices become increasingly limited. Stacked structures that are too thick cannot be filled in the trenches formed after the replacement gate is removed, while stacked structures that are too thin cause problems such as uncontrollable equipment uniformity (U%). Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a method for adjusting the threshold voltage in a metal gate process, so as to solve the problem that the existing methods for adjusting the threshold voltage of devices have limitations.

[0005] To achieve the above and other related objectives, this application provides a method for adjusting the threshold voltage in a metal gate fabrication process, comprising:

[0006] Step 1: Provide a substrate, and sequentially form a first TiN layer and a TiAl layer on the substrate;

[0007] Step 2: Remove the substrate from the vacuum environment, and the TiAl layer will undergo surface oxidation upon contact with air;

[0008] Step 3: Form a second TiN layer on the TiAl layer.

[0009] Preferably, in step two, the contact time between the TiAl layer and the air is determined according to the preset value of the work function.

[0010] Preferably, in step one, a first TiN layer and a TiAl layer are sequentially formed on the substrate using a deposition process.

[0011] Preferably, before forming the first TiN layer and TiAl layer, an interface layer, a high-k dielectric layer, a capping layer and a barrier layer are sequentially formed on the substrate.

[0012] Preferably, an interface layer is formed on the substrate using a thermal oxidation process or a chemical vapor deposition process, and the material of the interface layer is silicon oxide.

[0013] Preferably, an atomic layer deposition process is used to form a high-k dielectric layer on the interface layer, and the material of the high-k dielectric layer includes hafnium oxide.

[0014] Preferably, the material of the capping layer includes titanium nitride, and the material of the barrier layer includes tantalum nitride.

[0015] Preferably, in step three, a second TiN layer is formed on the TiAl layer using a deposition process.

[0016] Preferably, after step three is completed, a metal gate material layer is formed on the second TiN layer.

[0017] Preferably, the metal gate process is a back gate process.

[0018] As described above, the method for adjusting the threshold voltage in the metal gate process provided in this application has the following beneficial effects: the threshold voltage can be adjusted without changing the thickness of the TiAl layer and the TiN layer. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This diagram illustrates the stacked structure used in existing metal gate processes to adjust the threshold voltage of devices.

[0021] Figure 2 The flowchart shown is a method for adjusting the threshold voltage in a metal gate fabrication process provided in an embodiment of this application.

[0022] Figure 3 This diagram illustrates a comparison of the effects of prior art and the methods for adjusting the threshold voltage in the metal gate process provided in the embodiments of this application. Detailed Implementation

[0023] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this invention.

[0024] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0027] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0028] like Figure 1 As shown, Al diffusion from the TiAl layer into the underlying TiN layer reduces the NMOS work function. This reduction in NMOS work function can be avoided by thickening the TiN layer and thinning the TiAl layer. However, with miniaturization and equipment limitations, thickening the TiN layer makes it impossible to effectively fill the trenches formed after removing the replacement gate, while thinning the TiAl layer leads to uncontrollable equipment uniformity (U%).

[0029] To address the aforementioned issues, this application provides a method for adjusting the threshold voltage during metal gate fabrication.

[0030] Please see Figure 2 The diagram illustrates a flowchart of a method for adjusting the threshold voltage in a metal gate process provided in an embodiment of this application.

[0031] like Figure 2 As shown, the method for adjusting the threshold voltage in this metal gate process includes the following steps:

[0032] Step 1: Provide a substrate, and sequentially form a first TiN layer and a TiAl layer on the substrate;

[0033] Step 2: Remove the substrate from the vacuum environment, and the TiAl layer will undergo surface oxidation upon contact with air;

[0034] Step 3: Form a second TiN layer on the TiAl layer.

[0035] In step one, the substrate can be a semiconductor substrate, such as silicon (Si), germanium (Ge), SiGe substrate, silicon-on-insulator (SOI), or germanium-on-insulator (GOI). In other embodiments, the semiconductor substrate can also be a substrate comprising other elemental semiconductors or compound semiconductors, and can also be a multilayer structure, such as Si / SiGe. Those skilled in the art can select the constituent materials of the substrate according to the type of device structure formed on the substrate; therefore, the type of substrate should not limit the scope of protection of this invention.

[0036] As an example, before forming the first TiN layer and TiAl layer, an interface layer, a high-k dielectric layer, a capping layer and a barrier layer are sequentially formed on the substrate.

[0037] For example, an interface layer is formed on the substrate using a thermal oxidation process or a chemical vapor deposition process, and the material of the interface layer is silicon oxide.

[0038] For example, an atomic layer deposition process is used to form a high-k dielectric layer on the interface layer, and the material of the high-k dielectric layer includes hafnium oxide.

[0039] For example, the material of the capping layer includes titanium nitride, and the material of the barrier layer includes tantalum nitride (TaN).

[0040] For example, a first TiN layer and a TiAl layer are sequentially formed on a substrate using a deposition process.

[0041] In step two, the contact time between the TiAl layer and the air is determined according to the preset value of the work function.

[0042] In step three, a second TiN layer is formed on the TiAl layer using a deposition process.

[0043] like Figure 3As shown, for TiAl layers of the same thickness (whether 15 angstroms or 20 angstroms), compared with the prior art, the method for adjusting the threshold voltage in the metal gate process provided in this application embodiment can significantly improve the NMOS work function by adding a second step, which oxidizes the surface of the TiAl layer and then forms a second TiN layer on it. This is equivalent to the improvement effect of increasing the thickness of the TiN layer and thinning the TiAl layer on the NMOS work function in the prior art, and the thinner the TiAl layer, the greater the improvement in the NMOS work function.

[0044] After step three is completed, a metal gate material layer is formed on the second TiN layer.

[0045] As an example, this metal gate process is a back gate process.

[0046] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0047] In summary, the method for adjusting the threshold voltage in the metal gate process provided in this application achieves adjustment of the threshold voltage without changing the thickness of the TiAl and TiN layers. Therefore, this application effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0048] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this application.

Claims

1. A method for adjusting the threshold voltage in a metal gate fabrication process, characterized in that, The method includes: Step 1: Provide a substrate, and sequentially form a first TiN layer and a TiAl layer on the substrate; Step two: Remove the substrate from the vacuum environment, and the TiAl layer will undergo surface oxidation upon contact with air; Step 3: Form a second TiN layer on the TiAl layer.

2. The method according to claim 1, characterized in that, In step two, the contact time between the TiAl layer and the air is determined according to the preset value of the work function.

3. The method according to claim 1, characterized in that, In step one, the first TiN layer and the TiAl layer are sequentially formed on the substrate using a deposition process.

4. The method according to claim 1, characterized in that, Before forming the first TiN layer and the TiAl layer, an interface layer, a high-k dielectric layer, a capping layer and a barrier layer are sequentially formed on the substrate.

5. The method according to claim 4, characterized in that, The interface layer is formed on the substrate using a thermal oxidation process or a chemical vapor deposition process, and the material of the interface layer is silicon oxide.

6. The method according to claim 4, characterized in that, The high-k dielectric layer is formed on the interface layer using an atomic layer deposition process, and the material of the high-k dielectric layer includes hafnium oxide.

7. The method according to claim 4, characterized in that, The material of the cover layer includes titanium nitride, and the material of the barrier layer includes tantalum nitride.

8. The method according to claim 1, characterized in that, In step three, a deposition process is used to form the second TiN layer on the TiAl layer.

9. The method according to claim 1, characterized in that, After step three is completed, a metal gate material layer is formed on the second TiN layer.

10. The method according to claim 1, characterized in that, The metal gate process is a back gate process.

Images