Metal hard mask and preparation method and etching method thereof
Through the combination of oxygen plasma treatment and sputtering etching process, the etching residue problem of titanium nitride hard mask layer is solved, more efficient etching hole morphology control is achieved, and the reliability of semiconductor interconnection structure is improved. .
Patent Information
- Application Number
- CN202411257459.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2024-12-17
AI Technical Summary
In the prior art, when chlorine-based gas is used to pattern etch the hard mask layer of titanium nitride, titanium nitride residue will occur in the etching area, resulting in poor etching windows and affecting the reliability of the semiconductor interconnect structure.
The surface of the titanium nitride hard mask layer is converted into a titanium nitride hard mask layer by oxygen plasma treatment, and the titanium nitride hard mask layer is first patterned through sputtering etching process, and then the dry etching method is used. The etching process etches the titanium nitride hard mask layer to reduce the thickness and etching difficulty of the titanium nitride hard mask layer, and improves the purity of the etching hole and the shape accuracy.
It effectively reduces the etching residue of the titanium nitride hard mask layer, improves the purity and shape accuracy of the etching holes, and enhances the reliability of the semiconductor interconnection structure.
Smart Images
Figure CN119153326A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a metal hard mask and a preparation method and an etching method thereof. Background Art
[0002] As chip feature size continues to shrink and chip integration continues to increase, metal interconnects must be wired in multiple layers. For example, for a 45nm chip, the number of metal interconnect layers is as high as 10. This increases the capacitance between metal wires, the interlayer capacitance, and the resistance of metal wires, which leads to an increase in wiring RC delay time, crosstalk noise, and power consumption, ultimately reducing the processing speed of the chip. In order to increase the speed of the chip and reduce the RC delay time of the wiring, on the one hand, Cu is used to replace Al for metal wires, and on the other hand, the dielectric constant k of the insulating layer between metal interconnect layers must be reduced, that is, low-k dielectrics are used instead.
[0003] In order to reduce the damage of the interlayer dielectric layer during the process of dry etching to form the connection hole and ensure the morphology of the contact hole of the interlayer dielectric layer after etching, a metal hard mask (MHM) is introduced when the interlayer dielectric layer is patterned to improve the selectivity between the dielectric layer and the etching process. Among them, the material of the metal hard mask layer is mainly titanium nitride (TiN). Because of the large selectivity between titanium nitride and the dielectric layer and its ability to effectively control the endpoint during chemical mechanical polishing, titanium nitride has become the final choice of the back-end interconnect hard mask layer material, and the thickness of the metal hard mask layer using titanium nitride can be relatively thin, which is conducive to the extension of the subsequent etching process.
[0004] At present, when a titanium nitride hard mask layer is patterned and etched using a chlorine-based gas, titanium nitride residues are generated in the etched area, thereby forming a poor etching window. As a result, the morphology of the connecting holes formed by subsequent dry etching of the interlayer dielectric layer based on the patterned titanium nitride hard mask layer is poor, thereby affecting the reliability of the semiconductor interconnect structure. Summary of the invention
[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a metal hard mask and a preparation method and an etching method thereof, so as to solve the problem that in the prior art, during the process of patterning and etching the titanium nitride hard mask layer using chlorine-based gas, titanium nitride residue will be generated in the etching area, thereby forming a poor etching window, resulting in poor morphology of the connecting holes formed by subsequent dry etching of the interlayer dielectric layer based on the patterned titanium nitride hard mask layer, thereby affecting the reliability of the semiconductor interconnect structure.
[0006] To achieve the above-mentioned object and other related objects, the present invention provides a method for preparing a metal hard mask, the preparation method comprising:
[0007] Providing a wafer with an interlayer dielectric layer deposited on the surface;
[0008] Depositing a titanium nitride hard mask layer on the wafer;
[0009] The titanium nitride hard mask layer is converted into a titanium oxynitride hard mask layer with a preset thickness on the surface thereof by oxygen plasma treatment.
[0010] Optionally, the thickness of the titanium oxynitride hard mask layer is
[0011] Optionally, the radio frequency power used in the oxygen plasma treatment is 150W to 200W, and the flow rate of oxygen is 25sccm to 50sccm.
[0012] Optionally, the oxygen plasma treatment is achieved by an in-situ process.
[0013] Furthermore, the in-situ process is to implement the oxygen plasma treatment in different chambers of the same machine or in the same chamber of the same machine.
[0014] Optionally, before forming the titanium nitride hard mask layer, a first cap layer is deposited on the surface of the wafer; after forming the titanium oxynitride hard mask layer, a second cap layer is deposited on the surface of the titanium oxynitride hard mask layer.
[0015] Furthermore, the material of the first capping layer includes silicon oxide; the material of the second capping layer includes silicon oxide.
[0016] The present invention also provides a metal hard mask, which is prepared by using any one of the above methods for preparing the metal hard mask.
[0017] The present invention also provides a method for etching a metal hard mask, the etching method comprising:
[0018] providing a metal hard mask as described above;
[0019] forming a photoresist layer on the metal hard mask, and patterning the photoresist layer to form a patterned photoresist layer;
[0020] Etching the titanium oxynitride hard mask layer of the metal hard mask by using a sputtering etching process based on the patterned photoresist layer;
[0021] The titanium nitride hard mask layer of the metal hard mask is etched by a dry etching process based on the patterned photoresist layer, thereby forming a patterned metal hard mask.
[0022] Optionally, the etching gas used in the sputtering etching process is argon gas or krypton gas; and the etching gas used in the dry etching process includes chlorine gas.
[0023] As described above, the present invention provides a metal hard mask and a preparation method and etching method thereof. The preparation method of the metal hard mask uses oxygen plasma treatment to convert the preset thickness of the titanium nitride hard mask layer into a titanium oxynitride hard mask layer, so that the titanium nitride hard mask layer and the titanium oxynitride hard mask layer are formed together as a metal hard mask. Since the titanium nitride material has a high density, the use of oxygen plasma treatment will convert a very thin layer on the surface of the titanium nitride hard mask layer into a thin and uniform titanium oxynitride hard mask layer. The titanium oxynitride hard mask layer can be used as a hard mask for the opening etching of the titanium nitride hard mask layer, so as to perform patterning in advance, reduce the thickness of the titanium nitride hard mask layer, reduce the etching difficulty and etching byproducts of the titanium nitride hard mask layer, and at the same time improve the conformality of the etched hole of the titanium nitride hard mask layer, and improve the accuracy of the subsequent transfer of the interlayer dielectric layer pattern; and in the etching process, the titanium oxynitride hard mask layer is first physically etched by a sputtering etching process, that is, the metal hard mask is etched in advance. After patterning, the titanium nitride hard mask layer is etched by a dry etching process to achieve complete patterning of the metal hard mask. During this process, since the titanium oxynitride hard mask layer is a thin and uniform material layer and has a high selective etching ratio with the titanium nitride hard mask layer, a sputtering etching process can be selected to achieve complete etching of the titanium oxynitride hard mask layer, so that there will be no residual titanium oxynitride material in the second window. On this basis, the dry etching process is selected to etch the titanium oxynitride hard mask layer without any residual titanium oxynitride material, thereby effectively ensuring the purity of the etched holes and the shape of the etched holes. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 and Figure 2 The cross-sectional structure schematic diagram of each step in the etching process of titanium nitride hard mask according to an example in the prior art is shown.
[0025] Figures 3 to 7 It is a schematic diagram of the cross-sectional structure of each step in the preparation process of the metal hard mask of the present invention.
[0026] Figures 8 to 15 It is a schematic diagram of the cross-sectional structure of each step in the etching process of the metal hard mask of the present invention.
[0027] Component number description
[0028] 10 Wafer
[0029] 100 Interlayer dielectric layer
[0030] 101 First Capping Layer
[0031] 102 Titanium nitride hard mask layer
[0032] 103 Titanium Oxynitride Hard Mask Layer
[0033] 104 Second Cap Level
[0034] 11 Photoresist layer
[0035] 110 Patterned photoresist layer
[0036] 111 First Window
[0037] 112 Second Window
[0038] 113 Third Window
[0039] 20 Wafer
[0040] 200 Interlayer dielectric layer
[0041] 201 Titanium nitride hard mask layer
[0042] 202 Peak point defect
[0043] 203 Etching residue DETAILED DESCRIPTION
[0044] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.
[0045] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.
[0046] For ease of description, spatial relational terms such as “under”, “below”, “below”, “below”, “over”, etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatial relational terms are intended to include other orientations of the device in use or operation in addition to the orientation depicted in the drawings, and may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, so that the first and second features may not be in direct contact. In addition, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or one or more intervening layers may also be present.
[0047] See also Figures 1 to 15It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0048] As described in the background technology, in the semiconductor device back-end metal interconnection process, as the process nodes continue to shrink, the metal spacing is also shrinking, so a metal hard mask is introduced as a mask layer for forming connection holes, wherein the material of the mask layer is mainly titanium nitride. The etching process of the titanium nitride hard mask includes: Figure 1 As shown, firstly, a titanium nitride hard mask layer 201 is formed on a wafer 20 having an interlayer dielectric layer 200 formed thereon; Figure 2 As shown, the titanium nitride hard mask layer 201 is then patterned based on the photoresist layer to obtain a patterned titanium nitride hard mask layer. Subsequently, the interlayer dielectric layer 200 on the wafer 20 is etched based on the patterned titanium nitride hard mask layer. However, after the titanium nitride hard mask layer 201 is patterned, it is found through transmission electron microscopy (TEM) measurement that there is still titanium nitride hard mask residue in the area where the titanium nitride hard mask needs to be removed, such as Figure 2 In the etching window of the patterned titanium nitride hard mask layer, there is an etching residue 203, which will affect the subsequent correct transfer of the interlayer dielectric layer 200 pattern, resulting in poor morphology of the formed connecting hole, thereby affecting the reliability of the subsequent semiconductor interconnection structure. In view of this problem, the inventors have found that if Figure 1 As shown, after the titanium nitride hard mask layer 201 is formed, the surface of the titanium nitride hard mask layer 201 reacts with oxygen to generate titanium nitride oxide (TiN x O y ) has a peak point defect 202, and the thickness distribution of the peak point defect 202 is very uneven. In addition, the selectivity of titanium oxynitride and titanium nitride for chlorine-based etching gas is very high. Figure 2 As shown, when the titanium nitride hard mask layer 201 is etched, the titanium nitride region covered by the peak point defect 202 is difficult to be etched away, resulting in the following Figure 2 The etching residue 203 is formed.
[0049] Based on this research and analysis, this embodiment provides a method for preparing a metal hard mask. The metal hard mask prepared by this preparation method can effectively avoid the following Figure 2 The generation of etching residue 203, such as Figures 3 to 7 As shown, the preparation method comprises:
[0050] S1, providing a wafer 10 with an interlayer dielectric layer 100 deposited on the surface;
[0051] S2, such as Figure 3 and Figure 4 As shown, a titanium nitride hard mask layer 102 is deposited on the wafer 10;
[0052] S3, such as Figure 5 and Figure 6 As shown, oxygen plasma treatment is used to convert the titanium nitride hard mask layer 102 with a preset thickness on the surface into a titanium oxynitride hard mask layer 103 .
[0053] The preparation method of the metal hard mask of the present embodiment uses oxygen plasma treatment to convert the preset thickness of the titanium nitride hard mask layer into a titanium oxynitride hard mask layer, so that the titanium nitride hard mask layer and the titanium oxynitride hard mask layer are formed together as a metal hard mask. Since the titanium nitride material has a high density, the use of oxygen plasma treatment will convert a very thin layer on the surface of the titanium nitride hard mask layer into a thin and uniform titanium oxynitride hard mask layer, and the titanium oxynitride hard mask layer can be used as a hard mask for the opening etching of the titanium nitride hard mask layer, so as to perform patterning in advance, reduce the thickness of the titanium nitride hard mask layer, reduce the etching difficulty and etching byproducts of the titanium nitride hard mask layer, and at the same time improve the conformality of the etched hole of the titanium nitride hard mask layer, and improve the accuracy of the subsequent transfer of the interlayer dielectric layer pattern.
[0054] The method for preparing the metal hard mask of the present embodiment is mainly applied to the back-end interconnection process of semiconductor devices, so the wafer 10 has the corresponding structure formed in the front-end and middle-end processes of the semiconductor device, which is specifically configured according to different semiconductor device structures and is not excessively limited here. In addition, the method for preparing the metal hard mask of the present embodiment is applicable to any one or more interconnection processes that require the use of a metal hard mask in the back-end interconnection process of a semiconductor device.
[0055] According to the actual needs of the device structure to be prepared, the titanium nitride hard mask layer 102 can be directly deposited on the surface of the wafer 10 (eg Figure 3 As shown); a cap layer may also be deposited on the surface of the wafer 10 before forming the titanium nitride hard mask layer 102, such as Figure 4 The first capping layer 101, the material of the first capping layer 101 is generally selected to be a silicon dioxide material formed by thermal decomposition reaction of TEOS. The first capping layer 101 of silicon dioxide material can be used as a protective layer of the interlayer dielectric layer 100, and can also improve the adhesion between the interlayer dielectric layer 100 and the titanium nitride hard mask layer 102.
[0056] As an example, Figure 7As shown, after forming the titanium oxynitride hard mask layer 103, a second cap layer 104 is deposited on the surface of the titanium oxynitride hard mask layer 103. The second cap layer 104 is generally used as a protective layer to improve the adhesion with the bottom anti-reflective coating BARC and avoid photoresist contamination during the subsequent photolithography process. The material of the second cap layer 104 is generally selected from silicon oxide material.
[0057] The oxygen plasma treatment of this embodiment is an efficient surface modification technology. The high-frequency power supply ionizes oxygen to generate plasma, converts oxygen molecules into active substances such as active oxygen ions, oxygen molecules, and oxygen atoms, and uses high-energy electrons and oxygen ions to chemically modify the material surface to oxidize the titanium nitride material into a titanium oxynitride material. The thickness of the titanium oxynitride hard mask layer is For example, it can be In this embodiment, the thickness of the titanium oxynitride hard mask layer is preferably The parameters used in the oxygen plasma treatment are generally selected as follows: RF power is 150W to 200W, and oxygen flow rate is 25sccm to 50sccm. The parameters of the oxygen plasma treatment can be adjusted within this range according to different requirements.
[0058] As a preferred solution, the oxygen plasma treatment is achieved through an in-situ process. The so-called in-situ process refers to a process method in which a material or device is synthesized, processed or assembled directly at the final use location through specific technical means during the preparation process. In this embodiment, after the titanium nitride hard mask layer 102 is formed, the oxygen plasma treatment is performed without changing the environmental parameters or close to the final environmental parameters, thereby effectively avoiding the risk of the titanium nitride material contacting the air to oxidize and form spike point defects during the wafer transfer process as described in the background technology. For example, the oxygen plasma treatment can be achieved between different chambers of the same machine without breaking the vacuum, or the oxygen plasma treatment can be achieved in the same chamber of the same machine.
[0059] This embodiment also provides a metal hard mask, which is prepared by the method for preparing the metal hard mask described in this embodiment. The beneficial effects that can be achieved can be found in the preparation method of the metal hard mask, which will not be described in detail below.
[0060] Based on the metal hard mask and the preparation method thereof provided in this embodiment, this embodiment further provides an etching method for the metal hard mask, the etching method comprising:
[0061] S1, such as Figure 6 and Figure 7As shown, a metal hard mask prepared by the method for preparing a metal hard mask provided by this embodiment is provided, that is, a metal hard mask composed of a titanium nitride hard mask layer 102 and a titanium oxynitride hard mask layer 103;
[0062] S2, such as Figure 8 and Fig. 9 As shown, a photoresist layer 11 is formed on the metal hard mask and patterned to form a Fig.10 and Fig.11 The patterned photoresist layer 110 is formed with a first window 111, and the first window 111 defines the etching area of the subsequent metal hard mask and the interlayer dielectric layer 100;
[0063] S3, such as Fig.12 and Fig.13 As shown, the titanium oxynitride hard mask layer 103 of the metal hard mask is etched by a sputtering etching process based on the patterned photoresist layer 110, so as to form a second window 112 penetrating the titanium oxynitride hard mask layer 103 based on the first window 111;
[0064] S4, such as Fig.14 and Fig.15 As shown, the titanium nitride hard mask layer 102 of the metal hard mask is etched by a dry etching process based on the patterned photoresist layer 110 to form a patterned metal hard mask, thereby forming a third window 113 penetrating the titanium nitride hard mask layer 102 based on the second window 112 .
[0065] The etching method of the metal hard mask of the present embodiment adopts a sputtering etching process to first physically etch the titanium oxynitride hard mask layer 103, that is, the metal hard mask is patterned in advance, and then the titanium nitride hard mask layer 102 is etched by a dry etching process to achieve complete patterning of the metal hard mask. In this process, since the titanium oxynitride hard mask layer 103 is a thin and uniform material layer, and has a high selective etching ratio with the titanium nitride hard mask layer 102, the sputtering etching process can be selected to achieve complete etching of the titanium oxynitride hard mask layer 103, so that there will be no residual titanium oxynitride material in the second window 112. On this basis, the dry etching process is selected to achieve the etching of the titanium oxynitride hard mask layer without the residual titanium oxynitride material, thereby effectively ensuring the purity of the etched hole and the shape of the etched hole.
[0066] As an example, when the photoresist layer 11 is formed in step S2 , a bottom anti-reflection layer is formed under the photoresist layer 11 as needed.
[0067] The sputtering etching process is a dry etching technology that uses high-energy ions to impact the surface of the material and remove the material through physical bombardment. The process generally uses an inert gas, which is given high energy at low pressure to decompose the gas into atoms and electrons, and then uses an electric field to accelerate the atoms to impact the surface of the etched material to achieve material removal. In this embodiment, argon or krypton is preferably used as the etching gas for the sputtering etching process.
[0068] When dry etching is performed on the titanium nitride hard mask layer 102, in this embodiment, chlorine gas is preferably used as an etching gas to etch the titanium nitride hard mask layer 102.
[0069] like Fig. 9 As shown, as an example, when the second capping layer 104 is formed on the surface of the titanium oxynitride hard mask layer 103, the photoresist layer 11 is formed on the second capping layer 104. Fig.11 As shown, after the photoresist layer 110 is patterned, the first window 111 of the patterned photoresist layer 110 exposes the surface of the second capping layer 104. Fig.13 As shown, before etching the titanium oxynitride hard mask layer 103 based on the patterned photoresist layer 110 , it is necessary to select appropriate dry etching gas and parameters according to the material of the second cap layer 104 to etch the second cap layer 104 .
[0070] After forming the patterned metal hard mask, the step of removing the patterned photoresist layer 110 is also included.
[0071] In summary, the present invention provides a metal hard mask and a preparation method and etching method thereof. The preparation method of the metal hard mask uses oxygen plasma treatment to convert the preset thickness of the titanium nitride hard mask layer into a titanium oxynitride hard mask layer, so that the titanium nitride hard mask layer and the titanium oxynitride hard mask layer are formed together as a metal hard mask. Since the titanium nitride material has a high density, the use of oxygen plasma treatment will convert a very thin layer on the surface of the titanium nitride hard mask layer into a thin and uniform titanium oxynitride hard mask layer. The titanium oxynitride hard mask layer can be used as a hard mask for the opening etching of the titanium nitride hard mask layer, so as to perform patterning in advance, reduce the thickness of the titanium nitride hard mask layer, reduce the etching difficulty and etching byproducts of the titanium nitride hard mask layer, and at the same time improve the conformality of the etched holes of the titanium nitride hard mask layer, and improve the accuracy of the subsequent transfer of the interlayer dielectric layer pattern; and in the etching process, the titanium oxynitride hard mask layer is first physically etched by a sputtering etching process, that is, the metal hard mask is patterned in advance. Patterning treatment is then performed, and then the titanium nitride hard mask layer is etched by a dry etching process to achieve complete patterning of the metal hard mask. In this process, since the titanium oxynitride hard mask layer is a thin and uniform material layer, and based on its high selective etching ratio with the titanium nitride hard mask layer, a sputtering etching process can be selected to achieve complete etching of the titanium oxynitride hard mask layer, so that there will be no residue of titanium oxynitride material in the second window. On this basis, the dry etching process is selected to achieve etching of the titanium oxynitride hard mask layer without the residue of titanium oxynitride material, thereby effectively ensuring the purity of the etched hole and the shape of the etched hole. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.
[0072] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A method for preparing a metal hard mask, It is characterized in that The preparation method comprises: Providing a wafer with an interlayer dielectric layer deposited on the surface; Depositing a titanium nitride hard mask layer on the wafer; The titanium nitride hard mask layer is converted into a titanium oxynitride hard mask layer with a preset thickness on the surface thereof by oxygen plasma treatment.
2. The method for preparing a metal hard mask according to claim 1, Features: The thickness of the titanium oxynitride hard mask layer is 3. The method for preparing a metal hard mask according to claim 1, Features: The radio frequency power used in the oxygen plasma treatment is 150W-200W, and the flow rate of oxygen is 25sccm-50sccm.
4. The method for preparing a metal hard mask according to claim 1, Features: The oxygen plasma treatment is achieved through an in-situ process.
5. The method for preparing a metal hard mask according to claim 4, Features: The in-situ process is to implement the oxygen plasma treatment in different chambers of the same machine or in the same chamber of the same machine.
6. The method for preparing a metal hard mask according to claim 1, Features: Before forming the titanium nitride hard mask layer, a first cap layer is deposited on the surface of the wafer; after forming the titanium oxynitride hard mask layer, a second cap layer is deposited on the surface of the titanium oxynitride hard mask layer.
7. The method for preparing a metal hard mask according to claim 6, Features: The material of the first capping layer includes silicon oxide; the material of the second capping layer includes silicon oxide.
8. A metal hard mask, It is characterized in that The metal hard mask is prepared by the method for preparing the metal hard mask as claimed in any one of claims 1 to 7.
9. A method for etching a metal hard mask, It is characterized in that The etching method comprises: Providing the metal hard mask as claimed in claim 8; forming a photoresist layer on the metal hard mask, and patterning the photoresist layer to form a patterned photoresist layer; Etching the titanium oxynitride hard mask layer of the metal hard mask by using a sputtering etching process based on the patterned photoresist layer; The titanium nitride hard mask layer of the metal hard mask is etched by a dry etching process based on the patterned photoresist layer, thereby forming a patterned metal hard mask.
10. The method for etching a metal hard mask according to claim 9, Features: The etching gas used in the sputtering etching process is argon or krypton; the etching gas used in the dry etching process includes chlorine.