Work function layer preparation method and MOS tube

Abstract

The invention discloses a work function layer preparation method and an MOS transistor, and belongs to the field of semiconductor integrated circuits, and the method comprises the steps: introducing gas containing oxygen atoms in a process of depositing a plurality of P-type work function layers, and enabling the oxygen atoms to be inserted into the P-type work function layers, forming an oxygen atom-containing P-type work function layer between the P-type work function layers not containing the oxygen atoms so as to form a first work function layer; and depositing a metal-containing N-type work function layer on the surface of the first work function layer to form a second work function layer so as to prepare a work function layer. In the process of depositing the P-type work function layer, an oxidation process is added, oxygen atoms can be inserted to destroy columnar growth of the P-type work function layer and reduce open crystal boundaries while it is ensured that the P-type work function layer is not subjected to peroxidation, and therefore diffusion of metal is effectively prevented; the work function of the oxygen atom-containing P-type work function layer is similar to the work function of the P-type work function layer, so that the influence on the threshold voltage of the P-type work function layer can be eliminated.

Description

Technical Field

[0001] The present application relates to the field of semiconductor integrated circuits, and in particular to a work function layer preparation method and a MOS tube. Background Art

[0002] When depositing the work function layer of a MOS tube with HKMG, it is usually adopted to deposit a P-type work function layer first, and then deposit an N-type work function layer on the P-type work function layer. After the P-type work function layer has gone through the process steps, it will be affected by the upper N-type work function layer. Since the P-type work function layer has a columnar crystal structure, its ability to block metal diffusion is weak. The metal in the N-type work function layer will migrate to the bottom, affecting the P-type work function layer, causing instability and low yield of the component. Therefore, it is necessary to provide a work function layer preparation method to solve the problem of the weak ability of the P-type work function layer to block metal diffusion in the traditional work function layer deposition process. Summary of the invention

[0003] The purpose of the present application is to provide a work function layer preparation method and a MOS tube, so as to solve the problem of weak diffusion ability of the P-type work function layer barrier metal in the traditional work function layer deposition process.

[0004] To achieve the above object, the present application provides a method for preparing a work function layer, comprising:

[0005] In the process of depositing a plurality of P-type work function layers, introducing a gas containing oxygen atoms to insert the oxygen atoms into the P-type work function layers, forming P-type work function layers containing oxygen atoms between the P-type work function layers not containing the oxygen atoms, so as to form a first work function layer;

[0006] A metal-containing N-type work function layer is deposited on the surface of the first work function layer to form a second work function layer, so as to manufacture a work function layer.

[0007] Optionally, the introducing of the gas containing oxygen atoms to insert the oxygen atoms into the P-type work function layer, forming a P-type work function layer containing oxygen atoms between the P-type work function layers not containing the oxygen atoms, so as to form a first work function layer, comprises:

[0008] The flow rate of the gas containing oxygen atoms is controlled by a mass flow controller, and the gas containing oxygen atoms is introduced to insert the oxygen atoms into the P-type work function layer, so as to form the P-type work function layer containing oxygen atoms between the P-type work function layers not containing the oxygen atoms, so as to form the first work function layer.

[0009] Optionally, the P-type work function layer is titanium nitride; and the oxygen-atom-containing P-type work function layer is titanium monoxide.

[0010] Optionally, depositing a plurality of P-type work function layers includes:

[0011] introducing ammonia gas into the reaction chamber;

[0012] After the adsorption is completed, nitrogen is introduced to remove the ammonia gas that has not been adsorbed in the reaction chamber;

[0013] After removing the ammonia, introducing titanium tetrachloride to react with the ammonia;

[0014] After the reaction is completed, nitrogen gas is introduced to remove the unreacted titanium tetrachloride in the reaction chamber to form the P-type work function layer.

[0015] Optionally, the gas containing oxygen atoms is oxygen.

[0016] Optionally, the flow rate of oxygen is 0.6slm-5slm, including both end values.

[0017] Optionally, the metal-containing N-type work function layer is a titanium-aluminum alloy.

[0018] Optionally, during the process of depositing the plurality of P-type work function layers, introducing a gas containing oxygen atoms to insert the oxygen atoms into the P-type work function layers, and forming P-type work function layers containing oxygen atoms between the P-type work function layers not containing the oxygen atoms, so as to form a first work function layer, comprising:

[0019] During the deposition of the plurality of P-type work function layers, the oxygen-atom-containing gas is introduced multiple times to insert the oxygen atoms into the P-type work function layer, so as to form the plurality of oxygen-atom-containing P-type work function layers in the first work function layer.

[0020] Optionally, during the process of depositing the plurality of P-type work function layers, introducing the oxygen-atom-containing gas multiple times to insert the oxygen atoms into the P-type work function layer to form the plurality of oxygen-atom-containing P-type work function layers in the first work function layer comprises:

[0021] After each deposition of the P-type work function layer of a preset thickness, the oxygen-atom-containing gas is introduced to insert the oxygen atoms into the P-type work function layer, so as to form a plurality of the oxygen-atom-containing P-type work function layers in the first work function layer.

[0022] To achieve the above object, the present application further provides a MOS tube, comprising: a work function layer prepared by the work function layer preparation method described above;

[0023] The work function layer includes a first work function layer and a second work function layer; the first work function layer includes a plurality of P-type work function layers and a P-type work function layer containing oxygen atoms; the second work function layer includes an N-type work function layer containing metal.

[0024] The present application provides a method for preparing a work function layer, comprising: during the process of depositing multiple P-type work function layers, introducing a gas containing oxygen atoms to insert the oxygen atoms into the P-type work function layer, forming a P-type work function layer containing oxygen atoms between the P-type work function layers that do not contain the oxygen atoms, so as to form a first work function layer; depositing a metal-containing N-type work function layer on the surface of the first work function layer to form a second work function layer, so as to produce a work function layer.

[0025] Obviously, in the process of depositing the P-type work function layer, the present application adds an oxidation process, which ensures that the P-type work function layer will not be over-oxidized, and can insert oxygen atoms to destroy the columnar growth of the P-type work function layer and reduce the open grain boundaries, thereby effectively preventing the diffusion of metal; at the same time, the work function of the P-type work function layer containing oxygen atoms is similar to the work function of the P-type work function layer, which can eliminate the influence on the threshold voltage of the P-type work function layer. The present application also provides a MOS tube with the above-mentioned beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0027] Figure 1 A flow chart of a method for preparing a work function layer provided in an embodiment of the present application;

[0028] Figure 2 A flow chart of another method for preparing a work function layer provided in an embodiment of the present application;

[0029] Figure 3 A schematic diagram of a process for preparing a work function layer provided in an embodiment of the present application;

[0030] Figure 4 A graph showing the mass ratio of each element in the work function layer of the present application as a function of position;

[0031] Figure 5 The side wall slice SEM image and element distribution map of the work function layer of this application;

[0032] Figure 6 is a graph showing the mass ratio of each element in a conventional work function layer as a function of position;

[0033] Figure 7 The side wall slice SEM image and element distribution diagram of the traditional work function layer. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] There are currently two methods for HKMG process: the first method is to process the work function layer of NMOS HKMG and PMOS HKMG separately; this requires the use of photolithography to define the work function layer of NMOS and the work function layer of PMOS respectively. The second method is to generate P-type work function layer first and then generate N-type work function layer.

[0036] The simplified process of the second method is: first form a gate dielectric layer, this step is called GOX Loop (Gate oxide loop), including: sequentially forming an interface layer, a high dielectric constant layer and a titanium nitride layer of a bottom barrier layer. Then form a subsequent tantalum nitride layer of the bottom barrier layer to the metal gate, this step is called NRG Loop (NMOS Remove Gate Loop). The second method can save masks, thereby saving costs and increasing shipments. However, in actual application, after the P-type work function layer has gone through the process steps, its work function layer will be affected by the upper N-type work function layer, and the metal in the N-type work function layer will migrate to the bottom, affecting the P-type work function layer, causing instability and low yield in the components. For example, in the subsequent back-end of line (BEOL) process, the thermal effect of BEOL will cause the metal in HKMG to diffuse downward, bond with other elements and affect the P-type work function layer; in severe cases, the metal passes through the P-type work function layer and the bottom tantalum nitride layer and titanium nitride layer, and combines with the high dielectric constant layer of the gate dielectric layer, which will further deteriorate the PMOS component. Therefore, the present application provides a method for preparing a work function layer, which adds an oxidation process during the deposition of the P-type work function layer, while ensuring that the P-type work function layer will not be over-oxidized, and can insert oxygen atoms to destroy the columnar growth of the P-type work function layer and reduce open grain boundaries, thereby effectively preventing the diffusion of metal.

[0037] Please refer to Figure 1 , Figure 1 A flow chart of a method for preparing a work function layer provided in an embodiment of the present application, the method may include:

[0038] S101: During the deposition of multiple P-type work function layers, a gas containing oxygen atoms is introduced to insert oxygen atoms into the P-type work function layers, and P-type work function layers containing oxygen atoms are formed between P-type work function layers not containing oxygen atoms, so as to form a first work function layer.

[0039] This embodiment does not limit the specific type of the P-type work function layer, as long as it can be used to adjust the work function of PMOS. For example, the P-type work function layer can be titanium nitride; correspondingly, the oxygen-containing P-type work function layer formed after oxidation can be titanium monoxide. It should be noted that the commonly used P-type work function layer is a P-type work function layer with a columnar crystal structure. This embodiment does not limit the specific method of depositing the P-type work function layer. The specific method of depositing the P-type work function layer can be determined according to the specific type of the P-type work function layer. For example, ammonia can be introduced into the reaction chamber; after adsorption is completed, nitrogen is introduced to remove the unadsorbed ammonia in the reaction chamber; after removing the ammonia, titanium tetrachloride is introduced to react with ammonia; after the reaction is completed, nitrogen is introduced to remove the unreacted titanium tetrachloride in the reaction chamber to form a P-type work function layer. It should be noted that in the process of forming the first work function layer, each layer of the P-type work function layer can be deposited in the above manner. The present embodiment does not limit the specific equipment for depositing the P-type work function layer, as long as it can ensure that the P-type work function layer can be formed, for example, an atomic layer deposition (ALD) furnace tube can be used.

[0040] The present embodiment does not limit the specific type of the gas containing oxygen atoms, for example, it can be oxygen or a gas with weak oxidizing properties such as nitric oxide. Furthermore, in order to prevent the P-type work function layer from being over-oxidized, the present embodiment can control the flow rate of the gas containing oxygen atoms through a mass flow controller, and pass the gas containing oxygen atoms to insert oxygen atoms into the P-type work function layer, so as to form an oxygen-containing P-type work function layer between the P-type work function layers that do not contain oxygen atoms, so as to form a first work function layer. When oxygen is passed to oxidize the P-type work function layer, the present embodiment does not limit the specific flow rate of the oxygen passed, as long as it is ensured that the P-type work function layer will not be over-oxidized, for example, the flow rate of oxygen is 0.6slm-5slm, and includes the values ​​at both ends.

[0041] Furthermore, in order to enhance the ability of the first work function layer to prevent metal diffusion, in the process of depositing multiple P-type work function layers, the present embodiment may introduce a gas containing oxygen atoms multiple times to insert oxygen atoms into the P-type work function layer, so as to form multiple P-type work function layers containing oxygen atoms in the first work function layer. The present embodiment does not limit the specific number of times the gas containing oxygen atoms is introduced. For example, after each P-type work function layer of a preset thickness is deposited, the gas containing oxygen atoms is introduced to insert oxygen atoms into the P-type work function layer, so as to form multiple P-type work function layers containing oxygen atoms in the first work function layer; or after each preset number of P-type work function layers are deposited, the gas containing oxygen atoms is introduced to insert oxygen atoms into the P-type work function layer, so as to form multiple P-type work function layers containing oxygen atoms in the first work function layer. It should be noted that each P-type work function layer containing oxygen atoms is located between adjacent P-type work function layers that do not contain oxygen atoms.

[0042] S102: depositing a metal-containing N-type work function layer on the surface of the first work function layer to form a second work function layer, so as to manufacture a work function layer.

[0043] This embodiment does not limit the specific type of the metal-containing N-type work function layer, as long as it can be used to adjust the work function of NMOS, for example, the metal-containing N-type work function layer can be a titanium-aluminum alloy, or other dielectric layers containing aluminum, tantalum or copper. This embodiment does not limit the deposition of the metal-containing N-type work function layer, as long as it can be ensured that the metal-containing N-type work function layer can be formed on the surface of the first work function layer.

[0044] Based on the above embodiments, the present application adds an oxidation process during the deposition of the P-type work function layer, and while ensuring that the P-type work function layer will not be over-oxidized, oxygen atoms can be inserted to destroy the columnar growth of the P-type work function layer and reduce open grain boundaries, thereby effectively preventing the diffusion of metal; at the same time, the work function of the P-type work function layer containing oxygen atoms is similar to the work function of the P-type work function layer, which can eliminate the impact on the threshold voltage of the P-type work function layer.

[0045] Please refer to Figure 2 , Figure 2 A flow chart of another method for preparing a work function layer provided in an embodiment of the present application, the method may include:

[0046] S201: After each P-type work function layer of a preset thickness is deposited, a gas containing oxygen atoms is introduced to insert oxygen atoms into the P-type work function layer, so as to form a plurality of P-type work function layers containing oxygen atoms in the first work function layer.

[0047] It should be noted that each P-type work function layer containing oxygen atoms is located between adjacent P-type work function layers not containing oxygen atoms.

[0048] S202: depositing a metal-containing N-type work function layer on the surface of the first work function layer to form a second work function layer, so as to manufacture a work function layer.

[0049] Based on the above embodiments, the present application adds an oxidation process after each deposition of a P-type work function layer of a preset thickness. While ensuring that the P-type work function layer will not be over-oxidized, oxygen atoms are inserted at multiple positions of the first work function layer. By destroying the columnar growth of the P-type work function layer at multiple positions and reducing open grain boundaries, the purpose of destroying the overall columnar crystal structure of the first work function layer is achieved, thereby more effectively preventing the diffusion of metal. At the same time, the work function of the P-type work function layer containing oxygen atoms is similar to the work function of the P-type work function layer, which can eliminate the influence on the threshold voltage of the P-type work function layer.

[0050] The embodiment of the present application further provides a MOS tube, which may include: a work function layer prepared by the work function layer preparation method described above;

[0051] The work function layer includes a first work function layer and a second work function layer; the first work function layer includes a plurality of P-type work function layers and a P-type work function layer containing oxygen atoms; the second work function layer includes an N-type work function layer containing metal.

[0052] Based on the embodiment of the above work function layer preparation method, the present application adds an oxidation process during the deposition of the P-type work function layer, and while ensuring that the P-type work function layer will not be over-oxidized, oxygen atoms can be inserted to destroy the columnar growth of the P-type work function layer and reduce the open grain boundaries, thereby effectively preventing the diffusion of metal; at the same time, the work function of the P-type work function layer containing oxygen atoms is similar to the work function of the P-type work function layer, which can eliminate the influence on the threshold voltage of the P-type work function layer. The MOS tube provided by the present application includes a work function layer prepared by the above work function layer preparation method, and also has the above beneficial effects.

[0053] The following is a specific example to illustrate the above work function layer preparation process. Please refer to Figures 3 to 7 , Figure 3 A schematic diagram of a process for preparing a work function layer provided in an embodiment of the present application; Figure 4 A graph showing the mass ratio of each element in the work function layer of the present application as a function of position; Figure 5 The side wall slice SEM image and element distribution map of the work function layer of this application; Figure 6 is a graph showing the mass ratio of each element in a conventional work function layer as a function of position; Figure 7 The side wall slice SEM image and element distribution diagram of the traditional work function layer.

[0054] The work function layer preparation process specifically includes:

[0055] 1. Load the wafers onto the wafer boat;

[0056] 2. Pump down the ALD furnace tube to control the pressure inside the ALD furnace tube;

[0057] 3. Ammonia (NH3) is introduced into the reaction chamber of the ALD furnace tube; after the adsorption is completed, nitrogen (N2) is introduced to remove the unadsorbed ammonia in the reaction chamber; after the ammonia is removed, titanium tetrachloride (TiCl4) is introduced to react with the ammonia; after the reaction is completed, nitrogen is introduced to remove the unreacted titanium tetrachloride in the reaction chamber to form a layer of titanium nitride (TiN);

[0058] 4. Repeat step 3, and whenever the thickness of the formed titanium nitride reaches When the reaction is repeated for about 40 times, oxygen (O2) is introduced, and the flow rate of oxygen is controlled at 0.6slm-5slm by a mass flow controller (MFC) to oxidize the formed titanium nitride and form titanium monoxide (TiO) between the titanium nitride layers.

[0059] 5. After the deposition is completed, the first functional layer obtained includes a plurality of titanium nitride layers and a plurality of titanium monoxide layers arranged alternately;

[0060] 6. Unload the wafer boat and unload the wafers from the wafer boat;

[0061] 7. Subsequently, titanium aluminum alloy (TiAl) is deposited on the surface of the first work function layer.

[0062] The curve of the mass ratio of each element (aluminum Al, titanium Ti, nitrogen N, chlorine Cl, oxygen O, and silicon Si) in the work function layer after the oxidation process obtained by EDS (Energy Dispersive Spectroscopy, X-ray spectrometer) as a function of position is as follows: Figure 4 The obtained side wall slice SEM (Transmission Electron Microscope) image of the work function layer and the distribution map of each element are shown in Figure 5 As shown. Figure 4 It can be seen that the penetration of Al in this embodiment is significantly improved, and the penetration depth is only 4.5 nm.

[0063] The same is obtained through EDS Figure 6 The curve diagram of the mass ratio of each element in the traditional work function layer as a function of position is shown. And the following is obtained: Figure 7 The side wall slice SEM (Transmission Electron Microscope) image and element distribution map of the conventional work function layer are shown. Figure 6It can be seen that the Al penetration depth in the work function layer obtained by the traditional work function layer preparation method is deeper, reaching 6.5nm.

[0064] By comparison Figure 4 , Figure 5 and Figure 6 , Figure 7 It can be seen that compared with the work function layer obtained by the traditional work function layer preparation method, the addition of the oxidation process in this embodiment has a significant effect on preventing Al diffusion.

[0065] Specific examples are used herein to illustrate the principles and implementation methods of the present application, and the embodiments are in a progressive relationship, each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. The description of the above embodiments is only used to help understand the method and core ideas of the present application. For ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0066] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

Claims

1. A method for preparing a work function layer, characterized in that: include: In the process of depositing a plurality of P-type work function layers, introducing a gas containing oxygen atoms to insert the oxygen atoms into the P-type work function layers, forming P-type work function layers containing oxygen atoms between the P-type work function layers not containing the oxygen atoms, so as to form a first work function layer; A metal-containing N-type work function layer is deposited on the surface of the first work function layer to form a second work function layer, so as to manufacture a work function layer.

2. The method for preparing a work function layer according to claim 1, characterized in that: The step of introducing a gas containing oxygen atoms to insert the oxygen atoms into the P-type work function layer, and forming a P-type work function layer containing oxygen atoms between the P-type work function layers not containing the oxygen atoms, so as to form a first work function layer, comprises: The flow rate of the gas containing oxygen atoms is controlled by a mass flow controller, and the gas containing oxygen atoms is introduced to insert the oxygen atoms into the P-type work function layer, so as to form the P-type work function layer containing oxygen atoms between the P-type work function layers not containing the oxygen atoms, so as to form the first work function layer.

3. The method for preparing a work function layer according to claim 1, characterized in that: The P-type work function layer is titanium nitride; the P-type work function layer containing oxygen atoms is titanium monoxide.

4. The method for preparing a work function layer according to claim 3, characterized in that: The depositing of a plurality of P-type work function layers comprises: introducing ammonia gas into the reaction chamber; After the adsorption is completed, nitrogen is introduced to remove the ammonia gas that has not been adsorbed in the reaction chamber; After removing the ammonia, introducing titanium tetrachloride to react with the ammonia; After the reaction is completed, nitrogen gas is introduced to remove the unreacted titanium tetrachloride in the reaction chamber to form the P-type work function layer.

5. The method for preparing a work function layer according to claim 1, characterized in that: The gas containing oxygen atoms is oxygen.

6. The method for preparing a work function layer according to claim 1, characterized in that: The flow rate of oxygen is 0.6 slm-5 slm, including both end values.

7. The method for preparing a work function layer according to claim 1, characterized in that: The metal-containing N-type work function layer is a titanium-aluminum alloy.

8. The method for preparing a work function layer according to any one of claims 1 to 7, characterized in that: In the process of depositing a plurality of P-type work function layers, a gas containing oxygen atoms is introduced to insert the oxygen atoms into the P-type work function layers, and a P-type work function layer containing oxygen atoms is formed between the P-type work function layers not containing the oxygen atoms, so as to form a first work function layer, comprising: During the deposition of the plurality of P-type work function layers, the oxygen-atom-containing gas is introduced multiple times to insert the oxygen atoms into the P-type work function layer, so as to form the plurality of oxygen-atom-containing P-type work function layers in the first work function layer.

9. The method for preparing a work function layer according to claim 8, characterized in that: In the process of depositing the plurality of P-type work function layers, the gas containing oxygen atoms is introduced multiple times to insert the oxygen atoms into the P-type work function layer, so as to form the plurality of P-type work function layers containing oxygen atoms in the first work function layer, comprising: After each deposition of the P-type work function layer of a preset thickness, the oxygen-atom-containing gas is introduced to insert the oxygen atoms into the P-type work function layer, so as to form a plurality of the oxygen-atom-containing P-type work function layers in the first work function layer.

10. A MOS tube, characterized in that: include: A work function layer prepared by the work function layer preparation method according to any one of claims 1 to 9; The work function layer includes a first work function layer and a second work function layer; the first work function layer includes a plurality of P-type work function layers and a P-type work function layer containing oxygen atoms; the second work function layer includes an N-type work function layer containing metal.

Images