Etching method for improving contact hole metal residue
By employing a progressive three-step etching method, and utilizing combinations of different bias powers and etching gas compositions, the problem of tungsten residue in dry tungsten etching was solved, achieving high selectivity etching results and dielectric layer protection, and improving the stability of electrical parameters.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUA HONG SEMICON WUXI LTD
- Filing Date
- 2023-02-24
- Publication Date
- 2026-08-04
AI Technical Summary
In the dry etching process of tungsten, it is difficult to achieve high selectivity etching to avoid dielectric layer loss and tungsten residue, especially on 12-inch wafers, where existing technologies are not effective in removing tungsten residue.
A progressive three-step etching method is adopted, which gradually controls the etching process of the tungsten layer by adjusting the bias power and the composition of the etching gas. The process consists of main etching, main etching and over-etching, which ensures the complete removal of the tungsten layer and the protection of the dielectric layer.
This method achieves high selectivity control during tungsten dry etching, ensuring no tungsten residue in the dielectric layer and improving etching performance and the stability of electrical parameters.
Smart Images
Figure CN116190313B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to an etching method for improving the removal of metal residue in contact holes. Background Technology
[0002] Tungsten plays an indispensable role in modern integrated circuit processes and is widely used in processes such as through-hole or trench metal interconnects. In dry etching processes, dry etching using plasma etched by fluorine chemical gases, such as contact hole W-Etch Back, is also widely used.
[0003] In dry etching of tungsten, the tungsten layer must be selectively etched while the dielectric layer or TIN is etched to a minimum to avoid excessive loss of the dielectric layer or TIN and the generation of defects such as tungsten residue, which would affect the electrical parameters.
[0004] The tungsten contact via (TIN) etching process on 12-inch wafers primarily utilizes an ICP (transformer-coupled plasma) etching machine, employing gases such as SF6 / Ar as the main etching gases, to etch and stop the etching on the TIN surface. Throughout the etching process, a high W / TIN selectivity ratio must be maintained, and no tungsten residue must remain on the TIN surface after etching.
[0005] To address the above problems, a novel etching method is needed to improve the etching process for metal residue in contact holes. Summary of the Invention
[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an etching method to improve the metal residue in contact holes, which solves the problem in the prior art that it is necessary to ensure a high W / TIN selectivity ratio throughout the etching process and that there is no tungsten residue on the TIN surface after etching.
[0007] To achieve the above and other related objectives, the present invention provides an etching method for improving the etching of residual metal in contact holes, comprising:
[0008] Step 1: Provide a substrate, on which an interlayer dielectric layer is formed, a first metal layer is formed on the interlayer dielectric layer, a contact hole is formed on the metal layer and the interlayer dielectric layer below it, and a second metal layer covering the first metal layer is formed on the contact hole;
[0009] Step 2: Use the first bias power and the first etching gas to etch the second metal layer, so that a portion of the second metal layer remains on the first metal layer. When the first etching gas etches the first and second metal layers, the second metal layer has a first selectivity relative to the first metal layer.
[0010] Step 3: Use a second bias power and a second etching gas to etch and remove the second metal layer retained on the first metal layer. The second bias power is lower than the first bias power. When the first etching gas etches the first and second metal layers, the second metal layer has a second selectivity ratio relative to the first metal layer. The second selectivity ratio is greater than the first selectivity ratio.
[0011] Step 4: Use a third bias power and a third etching gas to etch a portion of the second metal layer in the contact hole. When the third etching gas etches the first and second metal layers, the second metal layer has a third selectivity ratio relative to the first metal layer, and the third selectivity ratio is greater than the second selectivity ratio.
[0012] Preferably, the substrate in step one comprises a bulk semiconductor substrate or a silicon-on-insulator substrate.
[0013] Preferably, the material of the interlayer dielectric layer in step one is silicon dioxide or a material with a low dielectric constant.
[0014] Preferably, the material of the first metal layer in step one includes titanium and titanium nitride.
[0015] Preferably, the material of the second metal layer in step one is tungsten.
[0016] Preferably, in step two, the first bias power does not exceed 120 watts, the first etching gas is a mixture of SF6 and argon, the volume ratio of SF6 to argon is 1.8:1, and the total gas flow rate of the first etching gas does not exceed 300 sccm.
[0017] Preferably, the second bias power in step three does not exceed 100 watts, the second etching gas is a mixture of SF6, argon, nitrogen and oxygen, the volume ratio of SF6 to argon is 2.5:1, the nitrogen accounts for 20% to 40% of the total volume of the second etching gas, the oxygen accounts for 15% to 30% of the total volume of the second etching gas, and the total gas flow rate of the second etching gas does not exceed 300 sccm.
[0018] Preferably, the third bias power in step four is 30 to 50 watts, the third etching gas is a mixture of SF6, argon, nitrogen, and oxygen, the volume ratio of SF6 to argon is 2:1, the nitrogen accounts for 20% to 40% of the total volume of the second etching gas, the oxygen accounts for 15% to 30% of the total volume of the second etching gas, and the total gas flow rate of the third etching gas does not exceed 300 sccm.
[0019] Preferably, the method is used for 12-inch wafers.
[0020] As described above, the etching method for improving contact hole metal residue of the present invention has the following beneficial effects:
[0021] This invention uses a progressive three-step method to reduce the bias power for etching the tungsten layer. The first etching ensures that a large amount of tungsten on the TIN surface is completely etched; the second etching stops on the TIN surface to ensure a high W / TIN selectivity; and the third etching ensures that the remaining tungsten is completely etched. The higher W / TIN selectivity can ensure a certain TiN thickness. Attached Figure Description
[0022] Figure 1 The diagram shown is a schematic representation of the process flow of the present invention.
[0023] Figure 2 This is a schematic diagram of the contact hole before etching according to the present invention;
[0024] Figure 3 The diagram shown is a schematic diagram of the first etching step of this invention.
[0025] Figure 4 This is a schematic diagram of the second etching step of the present invention;
[0026] Figure 5 This is a schematic diagram of the third etching step of the present invention. Detailed Implementation
[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention 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 the present invention.
[0028] Please see Figure 1 The present invention provides an etching method for improving the removal of metal residue in contact holes, comprising:
[0029] Step 1, please refer to Figure 2 A substrate (not shown in the figure) is provided, an interlayer dielectric layer 101 is formed on the substrate, a first metal layer 102 is formed on the interlayer dielectric layer 101, a contact hole is formed on the metal layer and the interlayer dielectric layer 101 below it, and a second metal layer 103 covering the first metal layer 102 is formed on the contact hole.
[0030] In embodiments of the present invention, the substrate in step one comprises a bulk semiconductor substrate or a silicon-on-insulator (SOI) substrate. The SOI substrate includes an insulating layer located beneath a thin semiconductor layer serving as the active layer of the SOI substrate. The semiconductor of the active layer and the bulk semiconductor typically comprise the crystalline semiconductor material silicon, but may also include one or more other semiconductor materials, such as germanium, silicon-germanium alloys, compound semiconductors (e.g., GaAs, AlAs, InAs, GaN, AlN, etc.) or alloys thereof (e.g., GaxAl1-xAs, GaxAl1-xN, InxGa1-xAs, etc.), oxide semiconductors (e.g., ZnO, SnO2, TiO2, Ga2O3, etc.), or combinations thereof. The semiconductor material may be doped or undoped. Other substrates that may be used include multilayer substrates, gradient substrates, or mixed-orientation substrates.
[0031] In an embodiment of the present invention, the material of the interlayer dielectric layer 101 in step one is silicon dioxide or a low dielectric constant material.
[0032] In an embodiment of the present invention, the material of the first metal layer 102 in step one includes titanium and titanium nitride, typically including a titanium layer and a titanium nitride layer formed on the titanium layer.
[0033] In an embodiment of the present invention, the material of the second metal layer 103 in step one is tungsten.
[0034] Step Two, please refer to Figure 3 The second metal layer 103 is etched using a first bias power and a first etching gas 104. By controlling the bias power, the directionality of the plasma can be enhanced, the depth during the etching process can be changed, and the sidewall angle load effect can be applied, so that part of the second metal layer 103 remains on the first metal layer 102. When the first etching gas 104 etches the first and second metal layers, the second metal layer 103 has a first selectivity ratio relative to the first metal layer 102. The first etching in this step is the main etching, which can remove most of the second metal layer 103.
[0035] In an embodiment of the present invention, the first bias power in step two does not exceed 120 watts, the first etching gas 104 is a mixture of SF6 and argon, the volume ratio of SF6 to argon is 1.8:1, and the total gas flow rate of the first etching gas 104 does not exceed 300 sccm. The first etching in this step is the main etching, which can remove most of the second metal layer 103, i.e., the tungsten layer, for example, 60% of the tungsten layer.
[0036] Step 3, please refer to Figure 4The second metal layer 103 retained on the first metal layer 102 is removed by etching with a second bias power and a second etching gas 105. The second bias power is lower than the first bias power. When the first etching gas 104 etches the first and second metal layers, the second metal layer 103 has a second selectivity ratio relative to the first metal layer 102, which is greater than the first selectivity ratio. The second etching in this step is the main etching, which can remove the second metal layer 103 retained on the first metal layer 102.
[0037] In an embodiment of the present invention, the second bias power in step three does not exceed 100 watts, the second etching gas 105 is a mixture of SF6, argon, nitrogen, and oxygen, the volume ratio of SF6 to argon is 2.5:1, nitrogen accounts for 20% to 40% of the total volume of the second etching gas 105, oxygen accounts for 15% to 30% of the total volume of the second etching gas 105, and the total gas flow rate of the second etching gas 105 does not exceed 300 sccm. The second etching in this step is the main etching, which can remove the tungsten layer retained on the titanium nitride layer.
[0038] Step 4, please refer to Figure 5 A portion of the second metal layer 103 in the contact hole is etched using a third bias power and a third etching gas 106. When the third etching gas 106 etches the first and second metal layers, the second metal layer 103 has a third selectivity ratio relative to the first metal layer 102, which is greater than the second selectivity ratio. This third etching step is an over-etching process, which can etch the second metal layer 103 in the contact hole to the required thickness.
[0039] In an embodiment of the present invention, the third bias power in step four is 30 to 50 watts, and the third etching gas 106 is a mixture of SF6, argon, nitrogen, and oxygen, with a volume ratio of SF6 to argon of 2:1. Nitrogen accounts for 20% to 40% of the total volume of the second etching gas 105, and oxygen accounts for 15% to 30% of the total volume of the second etching gas 105. The total gas flow rate of the third etching gas 106 does not exceed 300 sccm. This third etching step is an over-etching process, which can etch the tungsten layer in the contact hole to the required thickness.
[0040] In an embodiment of the present invention, the above method is used for 12-inch wafers.
[0041] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the 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.
[0042] In summary, this invention reduces the bias power for tungsten layer etching using a progressive three-step method. The first etching step ensures complete etching of a large amount of tungsten on the TIN surface; the second etching stops at the TIN surface, ensuring a high W / TIN selectivity; and the third etching step ensures complete etching of any remaining tungsten. This higher W / TIN selectivity ensures a certain TiN thickness. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.
[0043] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. An etching method for improving contact hole metal residue, characterized by, At least including: Step 1: Provide a substrate, on which an interlayer dielectric layer is formed, a first metal layer is formed on the interlayer dielectric layer, a contact hole is formed on the metal layer and the interlayer dielectric layer below it, and a second metal layer covering the first metal layer is formed on the contact hole. The material of the first metal layer includes titanium and titanium nitride, and the material of the second metal layer is tungsten. Step 2: Use the first bias power and the first etching gas to etch the second metal layer, so that a portion of the second metal layer remains on the first metal layer. When the first etching gas etches the first and second metal layers, the second metal layer has a first selectivity relative to the first metal layer. Step 3: Use a second bias power and a second etching gas to etch and remove the second metal layer retained on the first metal layer. The second bias power is lower than the first bias power. When the second etching gas etches the first and second metal layers, the second metal layer has a second selectivity ratio relative to the first metal layer. The second selectivity ratio is greater than the first selectivity ratio. Step 4: Use a third bias power and a third etching gas to etch a portion of the second metal layer in the contact hole. When the third etching gas etches the first and second metal layers, the second metal layer has a third selectivity ratio relative to the first metal layer, and the third selectivity ratio is greater than the second selectivity ratio.
2. The method of claim 1, wherein the method is characterized by: The substrate in step one includes a bulk semiconductor substrate or a silicon-on-insulator substrate.
3. The method of claim 1, wherein the method is used to improve etch of metal residue in a contact hole. The material of the interlayer dielectric layer in step one is silicon dioxide or a material with a low dielectric constant.
4. The method of claim 1, wherein the method is used to improve etch of metal residue in contact holes. In step two, the first bias power does not exceed 120 watts, the first etching gas is a mixture of SF6 and argon, the volume ratio of SF6 to argon is 1.8:1, and the total gas flow rate of the first etching gas does not exceed 300 sccm.
5. The method of claim 1, wherein the method is used to improve etch of metal residue in contact holes. In step three, the second bias power does not exceed 100 watts, the second etching gas is a mixture of SF6, argon, nitrogen and oxygen, the volume ratio of SF6 to argon is 2.5:1, the nitrogen accounts for 20% to 40% of the total volume of the second etching gas, the oxygen accounts for 15% to 30% of the total volume of the second etching gas, and the total gas flow rate of the second etching gas does not exceed 300 sccm.
6. The method of claim 1, wherein the method is used to improve etch of metal residue in contact holes. The third bias power in step four is 30 to 50 watts, the third etching gas is a mixture of SF6, argon, nitrogen and oxygen, the volume ratio of SF6 to argon is 2:1, the nitrogen accounts for 20% to 40% of the total volume of the third etching gas, the oxygen accounts for 15% to 30% of the total volume of the third etching gas, and the total gas flow rate of the third etching gas does not exceed 300 sccm.
7. The method of claim 1, wherein the method is used to improve etch of metal residue in contact holes. The method is used for 12-inch wafers.