Method for etching a metal hard mask layer

Abstract

The application provides an etching method of a metal hard mask layer, which comprises the following steps: providing a preset substrate; wherein the preset substrate comprises, from top to bottom, a patterned photoresist layer, an anti-reflection layer and a metal hard mask layer, and the anti-reflection layer comprises an organic anti-reflection layer; a reflow step, wherein argon-containing gas is introduced into a chamber to etch the photoresist layer so that the photoresist layer is reflowed; a repair step, wherein a repair gas of the photoresist layer is introduced into the chamber to modify the edge profile of the photoresist layer; an organic anti-reflection layer etching step, wherein the power supply mode of a radio frequency power source is controlled to be in a pulse mode, fluorine-containing gas is introduced into the chamber, and the organic anti-reflection layer is etched with the patterned photoresist layer as a mask until the next film layer is exposed; and a hard mask etching step, wherein chlorine-containing gas is introduced into the chamber to etch the exposed metal hard mask layer until the next film layer is exposed. The application can effectively improve the line width roughness of the metal hard mask after etching, and improve the stability of a chip.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an etching method for a metal hard mask layer. Background Technology

[0002] Currently, in semiconductor processes, metal is commonly used as the hard mask layer for trench etching in pre-trench processes. This significantly reduces damage to materials with (ultra)low dielectric constants, improves the distortion and roughness of metal interconnects, and controls the smooth transition between vias and trenches in double damascene structures. Line width roughness (LWR), which is three times the standard deviation of linewidth variation, is typically one of the key parameters after metal hard mask etching. High LWR leads to increased resistance of metal wires, parasitic capacitance between metal wires, and parasitic capacitance between metal interconnect layers, thereby increasing signal delay time. Therefore, reducing LWR has become a significant challenge in metal hard mask etching.

[0003] Related metal hard mask etching techniques typically involve plasma treatment or plasma strip doping of the photoresist lines before the main etching process to repair the edge morphology of the photoresist and reduce the linewidth roughness after metal hard mask etching. However, in a plasma environment, ions or free radicals in the plasma can also act on the photoresist, forming a graphite-like layer on the photoresist surface. When the thickness of the graphite-like layer reaches a certain level, it restricts further remelting of the photoresist, failing to effectively improve the linewidth roughness and reducing the stability of the chip. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an etching method for a metal hard mask layer, which can effectively improve the linewidth roughness after etching of the metal hard mask and improve the stability of the chip.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0006] In a first aspect, embodiments of the present invention provide a method for etching a metal hard mask layer, comprising:

[0007] A preset substrate is provided; wherein, the preset substrate includes a patterned photoresist layer, an anti-reflection layer and a metal hard mask layer formed sequentially from top to bottom, and the anti-reflection layer includes an organic anti-reflection layer;

[0008] In the remelting step, argon-containing gas is introduced into the chamber to etch the photoresist layer, thereby remelting the photoresist layer.

[0009] The repair step involves introducing a repair gas into the chamber to modify the edge morphology of the photoresist layer.

[0010] In the organic antireflective layer etching step, the power application mode of the radio frequency power supply is controlled to be pulsed, fluorine-containing gas is introduced into the chamber, and the organic antireflective layer is etched using the patterned photoresist layer as a mask until the next film layer is exposed.

[0011] In the hard mask etching step, chlorine-containing gas is introduced into the chamber to etch the exposed metal hard mask layer until the next film layer is exposed.

[0012] Furthermore, the present invention provides a first possible implementation of the first aspect, wherein the antireflective layer further includes an organic film layer and a dielectric antireflective layer arranged sequentially downward below the organic antireflective layer; after the etching step of the organic antireflective layer, the method further includes:

[0013] The exposed organic film layer and the dielectric anti-reflective layer are etched sequentially until the metal hard mask layer is exposed.

[0014] Furthermore, this embodiment of the invention provides a second possible implementation of the first aspect, wherein the etching step of the organic film layer includes:

[0015] Oxygen-containing gas is introduced into the chamber, and the organic anti-reflective layer is used as a mask to etch the organic film layer until the next film layer is exposed.

[0016] Furthermore, this embodiment of the invention provides a third possible implementation of the first aspect, wherein the etching step of the dielectric anti-reflection layer includes:

[0017] Carbon-containing gas and fluorine-containing gas are introduced into the chamber, and the medium anti-reflection layer is etched using the organic film layer as a mask until the metal hard mask layer is exposed.

[0018] Furthermore, this embodiment of the invention provides a fourth possible implementation of the first aspect, wherein, after the etching step of the dielectric anti-reflection layer, the method further includes:

[0019] The organic film layer is removed by etching with oxygen-containing gas into the chamber.

[0020] Furthermore, this embodiment of the invention provides a fifth possible implementation of the first aspect, wherein, prior to the hard mask etching step, the following steps are further included:

[0021] Fluorine-containing gas is introduced into the chamber to etch and remove the oxides on the surface of the metal hard mask layer.

[0022] Furthermore, this embodiment of the invention provides a sixth possible implementation of the first aspect, wherein, after the hard mask etching step, it further includes:

[0023] Fluorine-containing gas and chlorine-containing gas are introduced into the chamber to re-etch the incompletely etched metal hard mask layer, and to etch part of the dielectric anti-reflection layer.

[0024] Furthermore, this embodiment of the invention provides a seventh possible implementation of the first aspect, wherein the method further includes:

[0025] Oxygen-containing gas is introduced into the chamber to etch and remove residual polymer.

[0026] Furthermore, the present invention provides an eighth possible implementation of the first aspect, wherein the fluorine-containing gas introduced in the organic antireflective layer etching step includes CF4 and CHF3, and the ratio of CF4 to CHF3 is greater than 1:1;

[0027] And / or,

[0028] The plasma duty cycle in the pulsed mode ranges from 15% to 30%.

[0029] Furthermore, the present invention provides a ninth possible implementation of the first aspect, wherein, in the etching steps of the organic film layer and the dielectric antireflection layer, the power application mode of the radio frequency power supply is a pulse mode or a continuous wave mode.

[0030] This invention provides a method for etching a metal hard mask layer. The method includes: providing a preset substrate; wherein the preset substrate includes a patterned photoresist layer, an anti-reflection layer, and a metal hard mask layer formed sequentially from top to bottom, and the anti-reflection layer includes an organic anti-reflection layer; a remelting step, in which argon-containing gas is introduced into a chamber to etch the photoresist layer to remelt it; a repair step, in which a repair gas for the photoresist layer is introduced into the chamber to modify the edge morphology of the photoresist layer; an organic anti-reflection layer etching step, in which the power application mode of the radio frequency power supply is controlled to be pulsed, a fluorine-containing gas is introduced into the chamber, and the organic anti-reflection layer is etched using the patterned photoresist layer as a mask until the next film layer is exposed; and a hard mask etching step, in which chlorine-containing gas is introduced into the chamber to etch the exposed metal hard mask layer until the next film layer is exposed. This invention improves the linewidth roughness after etching the metal hard mask by adding a pre-processing step of remelting and using argon-containing plasma to generate vacuum deep ultraviolet (VUV) light, which remelts the photoresist. Simultaneously, when etching the organic anti-reflective layer, a novel pulse mode is used instead of the traditional continuous wave mode to reduce plasma energy, decrease molecular decomposition in the plasma, and reduce its chemical molecular activity. This reduces the thickness of the graphite layer on the photoresist surface and also reduces the consumption of photoresist, effectively improving the linewidth roughness after etching the metal hard mask and enhancing chip stability.

[0031] Other features and advantages of the embodiments of the present invention will be set forth in the following description, or some features and advantages may be inferred from the description or determined without doubt, or may be learned by practicing the techniques described above in the embodiments of the present invention.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in 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 the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 A flowchart of an etching method for a metal hard mask layer provided by an embodiment of the present invention is shown;

[0035] Figure 2a A schematic diagram of a preset substrate structure provided by an embodiment of the present invention is shown;

[0036] Figures 2b to 2f This diagram illustrates an etching process for a metal hard mask layer provided in an embodiment of the present invention.

[0037] Figure 3a This diagram illustrates the linewidth roughness (LWR) after etching the metal hard mask layer without any processing.

[0038] Figure 3b This diagram illustrates the linewidth roughness (LWR) of the metal hard mask layer after etching when only HBr is used to repair photoresist.

[0039] Figure 3c This diagram illustrates the linewidth roughness (LWR) of a metal hard mask layer after etching when using Ar to remelt a photoresist and HBr to repair the photoresist, according to an embodiment of the present invention.

[0040] Figure 3d This illustration shows a schematic diagram of the linewidth roughness (LWR) of a metal hard mask layer after etching when using Ar-refused photoresist, HBr to repair the photoresist, and pulse mode in the etching of the organic antireflective layer, according to an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0042] Currently, in order to reduce the linewidth roughness after etching of metal hard masks, the relevant metal hard mask layer etching techniques generally include three categories:

[0043] One method involves exposing and developing a silicon wafer coated with photoresist, then cleaning the surface of the wafer with a solution containing plasticizer, followed by baking the wafer at a high temperature for a period of time. This method increases the cleaning and baking steps, increases wafer costs, and may also lead to a decrease in wafer yield.

[0044] Another method involves placing a substrate with a photoresist pattern on its surface in a vacuum chamber and using a strip ion beam to implant ions into the photoresist pattern. This method can reduce the linewidth roughness after etching the metal hard mask to some extent. However, with the development of wafer fabrication processes, the spacing of the metal hard mask is gradually decreasing, and the requirements for LWR are becoming increasingly stringent. The method of using a strip ion beam to implant ions into the photoresist pattern has limited effect on improving LWR and cannot meet the higher process requirements.

[0045] Another method involves depositing a certain thickness of carbon-containing organic layer on the surface of the photoresist pattern in situ. VUV rays and plasma gas are used to modify the morphology of the photoresist to improve LWR. However, depositing a certain thickness of carbon-containing organic layer on the surface of the photoresist pattern in situ can lead to uneven deposition, resulting in polymer or residual defects after etching.

[0046] Therefore, the relevant metal hard mask etching technology still has the problem of not being able to effectively improve the linewidth roughness after metal hard mask etching, or not being able to meet the requirements of advanced processes, thus reducing the stability of the chip.

[0047] To address the aforementioned issues, this invention provides a method for etching a metal hard mask layer. The following provides a detailed description of this invention.

[0048] This embodiment provides a method for etching a metal hard mask layer, which can be applied to semiconductor process equipment. See [link to documentation]. Figure 1 The flowchart shown illustrates the etching method for a metal hard mask layer. This method mainly includes the following steps:

[0049] Step S102: Provide a preset substrate;

[0050] A preset substrate is provided and then introduced into the etching chamber. See also... Figure 2a The schematic diagram of the preset substrate structure shown includes a patterned photoresist layer 20, an anti-reflection layer 30 and a metal hard mask layer 40 formed sequentially from top to bottom. The anti-reflection layer 30 includes an organic anti-reflection layer 31.

[0051] like Figure 2a As shown, the preset substrate provided in this embodiment may also include a dielectric material layer 50, an ultra-low dielectric constant dielectric material layer 60, and an etch stop layer 70 arranged sequentially below the metal hard mask layer 40.

[0052] Step S104, remelting step: Argon gas is introduced into the chamber to etch the photoresist layer so that the photoresist layer is remelted.

[0053] The plasma generated by argon gas can remelt the photoresist layer, and the loss of photoresist is small during the process, which can achieve the purpose of optimizing the linewidth roughness after etching the metal hard mask layer.

[0054] In the remelting step, the chamber settings can include: chamber pressure 3–10 mT; upper electrode power 200–400 W, no lower electrode power, and the current ratio of the upper electrode power is 0.4–0.6; the introduced argon gas can be argon gas with a flow rate of 150–200 sccm; and the process time can be 10–15 s. Since a high upper electrode power would result in significant photoresist consumption, failing to optimize the linewidth roughness after etching the metal hard mask layer, and even worsening the linewidth roughness, using a lower upper electrode power and no lower electrode power can further reduce photoresist consumption.

[0055] Step S106, Repair step: Introduce repair gas into the chamber to modify the edge morphology of the photoresist layer;

[0056] By introducing a repair gas into the chamber, the edge morphology of the photoresist layer can be repaired, ensuring accurate pattern transfer. In one specific embodiment, the repair gas includes a hydrogen-containing gas; such as hydrogen (H2) and / or hydrogen bromide (HBr).

[0057] In the repair step, the chamber settings can include: chamber pressure 3–10 mT, upper electrode power 800–1500 W, no lower electrode power to reduce bombardment of organic materials, upper electrode power current ratio of 0.4–0.6, and process time 20–40 s. When the repair gas is HBr, 150–200 sccm of HBr can be introduced as the main etching gas.

[0058] Step S108, Organic antireflective layer etching step: control the power application mode of the radio frequency power supply to pulse mode, introduce fluorine-containing gas into the cavity, use the patterned photoresist layer as a mask to etch the organic antireflective layer until the next film layer is exposed.

[0059] The main components of the organic antireflective layer are C, N and Si (14% to 40%). Fluorine gas is introduced into the chamber, and the power application mode of the upper and lower electrodes is controlled to be pulsed to reduce the energy of the plasma, reduce the dissociation of molecules in the plasma, reduce their chemical molecular activity, reduce the thickness of the graphite-like layer on the photoresist surface, and also reduce the consumption of photoresist, which can significantly improve the line width roughness.

[0060] In the organic antireflective layer etching step, the chamber settings parameters may include: chamber pressure 10-15 mT; upper electrode power 500-700 W; lower electrode power 50-100 W; pulse frequency 90-110 Hz; current ratio of upper electrode power to lower electrode power 0.4-0.6; and process time 30-50 s.

[0061] In one specific implementation, the plasma duty cycle in the above-mentioned pulse mode ranges from 15% to 30%.

[0062] In one specific embodiment, the fluorinated gas introduced in the organic antireflective layer etching step includes CF4 and CHF3, and 50-100 sccm of CF4 and 50-100 sccm of CHF3 can be introduced as the main etching gas. The ratio of CF4 to CHF3 is an important way to improve critical dimensions, and the ratio of CF4 to CHF3 can be greater than 1:1, which can increase the etching rate while reducing the amount of polymer generated.

[0063] In one embodiment, the etching gas introduced during the organic antireflective layer etching step may further include nitrogen gas. 60–100 sccm of N2 gas can be introduced as a dilution gas to control the reaction process and simultaneously remove byproducts generated during etching. See also... Figures 2b to 2f The etching flowchart of the metal hard mask layer is shown. During the etching of the organic anti-reflective layer, part of the photoresist layer is also etched. The substrate morphology after etching the organic anti-reflective layer is shown in the figure. Figure 2b As shown, the main chemical reactions involved in etching the antireflective layer of the organic material are:

[0064] Si + 4F → SiF4↑

[0065] Step S110, hard mask etching step, chlorine-containing gas is introduced into the chamber to etch the exposed metal hard mask layer until the next film layer is exposed.

[0066] The aforementioned chlorine-containing gas can be Cl2, used as the main etching gas. The generated plasma can react with TiN, the main component of the metal hard mask layer, ultimately producing volatile TiCl4 and N2, which are then pumped away. The chemical reactions generated during the etching process are as follows:

[0067] Ti3N4 + 6Cl2 → 3TiCl4↑ + 2N2↑

[0068] In the hard mask etching step, the chamber settings parameters may include: chamber pressure 5-10 mT; upper electrode power 600-800 W; lower electrode power 60-100 W; the power application method of the upper and lower electrodes is continuous wave (CW); the current ratio of the upper electrode power to the lower electrode power is 0.4-0.6; when the etching gas is Cl2, the flow rate of the introduced Cl2 is 150-100 sccm.

[0069] In one embodiment, the gas introduced in the hard mask etching step may also include a protective gas and a dilution and bombardment gas. The protective gas may be a hydrocarbon-containing gas, such as CH4, and the dilution and bombardment gas may be Ar. The Ar flow rate may be 50-100 sccm, and the CH4 flow rate may be 30-50 sccm. Under the action of plasma, CH4 can react with Ti and O in the chamber to generate non-volatile byproducts that adhere to the sidewalls of the metal hard mask. This can protect the sidewalls of the metal hard mask and prevent lateral depression of the metal hard mask. However, the more CH4 is introduced, the more byproducts are generated. Excessive byproduct accumulation will not only cause the TiN film layer to be non-vertical after etching, but also cause etching stoppage. It will also increase the critical size load of the dense-sparse region, which can easily affect the subsequent metal layer etching or even affect the copper filling process of electrochemical electroplating. Therefore, in order to avoid the influence of excessive byproducts, the ratio of Cl2 to CH4 can be set to greater than 3:1.

[0070] The etching method for the metal hard mask layer provided in this embodiment improves the linewidth roughness after etching by adding a remelting pretreatment step and using argon-containing plasma to generate vacuum deep ultraviolet (VUV) light to remelt the photoresist. Simultaneously, when etching the organic antireflective layer, a novel pulse mode is used instead of the traditional continuous wave mode to reduce plasma energy, decrease molecular decomposition in the plasma, and reduce its chemical molecular activity, thereby reducing the thickness of the graphite layer on the photoresist surface and also reducing the consumption of photoresist. This effectively improves the linewidth roughness after etching the metal hard mask and enhances the stability of the chip.

[0071] In one implementation, such as Figure 2a As shown, the anti-reflection layer provided in this embodiment further includes an organic film layer 32 and a dielectric anti-reflection layer 33 arranged sequentially downwards below the organic anti-reflection layer; after the etching step of the organic anti-reflection layer, it further includes:

[0072] The exposed organic film layer 32 and dielectric anti-reflection layer 33 are etched sequentially until the metal hard mask layer 40 is exposed.

[0073] In one embodiment, the etching step of the organic film layer provided in this embodiment includes:

[0074] Oxygen-containing gas is introduced into the chamber, and the organic film is etched using the organic anti-reflective layer as a mask until the next film is exposed.

[0075] The main costs of organic films are C and O. Organic films and dielectric anti-reflection layers are sequentially set under the photoresist layer, mainly to solve the problem of insufficient photoresist layer thickness that prevents accurate image transmission.

[0076] The oxygen-containing gas mentioned above can be oxygen. In the step of etching the organic film, the chamber settings parameters may include: chamber pressure 3–10 mT, upper electrode power 300–600 W; lower electrode power 100–300 W, upper electrode power and lower electrode power current ratio both 0.4–0.6, and process time 50–80 s. Using the oxygen-containing gas as the main etching gas, the chemical reactions for etching the organic film include:

[0077] C + O₂ → CO₂↑

[0078] 2C + O2 → 2CO↑

[0079] In one embodiment, the oxygen-containing gas can be oxygen, and the oxygen flow rate can be 90-150 sccm. When etching the organic film layer, the gas introduced can also include passivating gases such as N2, HBr and Cl2, and the passivating gas flow rate can be 30-80 sccm, thereby adjusting the angle of the organic film layer.

[0080] During the etching of the organic film layer 32, the photoresist layer 20 is also etched away. The substrate morphology after etching the organic film layer 32 is shown in the figure. Figure 2c As shown.

[0081] In one embodiment, the etching step of the dielectric anti-reflection layer provided in this embodiment includes:

[0082] Carbon-containing and fluorine-containing gases are introduced into the chamber, and the dielectric anti-reflection layer is etched using the organic film layer as a mask until the metal hard mask layer is exposed.

[0083] The dielectric anti-reflective layer primarily serves as a mask layer for etching the metal hard mask layer. Its main component is SIOC, with carbon-containing and fluorine-containing gases as the primary etching gases. The chemical reactions generated during etching include:

[0084] SiO₂ + 4F → SiF₄↑ + O₂↑

[0085] SiO2 + 2CF2 → SiF4↑ + 2CO↑

[0086] When etching the antireflective layer of the medium, the chamber settings parameters may include: chamber pressure 3-10 mT; upper electrode power 400-700 W; lower electrode power 80-160 W; current ratio of upper electrode power to lower electrode power 0.4-0.6; and etching time 30-50 s.

[0087] In one embodiment, the carbon-containing gas and fluorine-containing gas may include CF4 and CHF3, and 80-120 sccm of CF4 and 20-40 sccm of CHF3 may be introduced as the main etching gas; when etching the anti-reflection layer of the medium, the introduced gas may also include diluent gases such as He, and the flow rate of the introduced He may be 80-120 sccm.

[0088] When etching the medium anti-reflection layer 33 using the organic film layer 32 as a mask, the organic anti-reflection layer 31 is also etched away simultaneously. The morphology after etching the medium anti-reflection layer 33 is as follows: Figure 2d As shown.

[0089] In one embodiment, after the etching step of the dielectric anti-reflection layer, the method provided in this embodiment further includes:

[0090] The organic film layer is removed by etching oxygen-containing gas into the chamber.

[0091] Oxygen-containing gas is used as the main etching gas to react with silicon and carbon in the organic film to generate byproducts that are then removed. When etching the organic film, the chamber settings can include: chamber pressure 3-10 mT, upper electrode power 500-800 W, lower electrode power 50-100 W, the upper and lower electrode power are applied in a continuous wave (CW) manner, the current ratio of the upper and lower electrode power is 0.4-0.6, and the etching time is 30-50 s.

[0092] The oxygen-containing gas mentioned above can be O2, with an O2 flow rate of 100–300 sccm. To completely remove the organic film layer, the introduced gas may also include Cl2, with a Cl2 flow rate of 50–100 sccm. Adding Cl2 can completely remove the organic film layer and avoid defects. The substrate morphology after etching to remove the organic film layer 32 is as follows. Figure 2e As shown.

[0093] In one embodiment, prior to the hard mask etching step, the method provided in this embodiment further includes:

[0094] Fluorine-containing gas is introduced into the chamber to etch and remove oxides from the surface of the metal hard mask layer.

[0095] During the etching process to remove the organic film layer, the oxygen introduced reacts with the TiN on top of the metal hard mask layer to generate TiO2. By introducing fluorine-containing gas into the chamber, the TiO2 on top of the metal hard mask layer can be etched away, thus avoiding etching stoppage issues that could lead to wafer scrap.

[0096] In the step of etching to remove oxides from the surface of the metal hard mask layer, the introduced fluorine-containing gas can be fluorine-based gases such as CF4 and / or CHF3. During the etching process, the chamber settings parameters can include: chamber pressure 3-10 mT, upper electrode power 200-400 W, lower electrode power 30-60 W, power application method continuous wave (CW), current ratio 0.4-0.6, etching time 5-10 s, and the introduction of 40-80 sccm of CF4 and 20-40 sccm of CHF3 as the main etching gases. The chemical reactions generated during etching include:

[0097] TiO₂ + 4F → TiF₄↑ + O₂↑

[0098] In one embodiment, after the hard mask etching step, the method provided in this embodiment further includes:

[0099] Fluorine-containing and chlorine-containing gases are introduced into the chamber to re-etch the incompletely etched metal hard mask layer and etch part of the dielectric anti-reflection layer.

[0100] To prevent incomplete etching of the metal hard mask layer, fluorine-containing and chlorine-containing gases are introduced into the chamber to re-etch the incompletely etched metal hard mask layer, while also etching part of the dielectric reflective layer. The fluorine-containing gas introduced can include etching gases such as NF3, and the chlorine-containing gas can include Cl2.

[0101] During the etching process, the chamber settings can include: chamber pressure 10–20 mT, upper electrode power 500–700 W, lower electrode power 30–50 W, and continuous wave (CW) power application; current ratio 0.4–0.6, and etching time 6–10 s. 100–300 sccm of NF3 and 50–100 sccm of Cl2 can be introduced as the main etching gases. To reduce etching of the dielectric reflective layer, 80–150 sccm of SiCl4 and 10–20 sccm of CH4 can also be introduced as etching protective gases.

[0102] After etching the metal hard mask layer 40 using the dielectric antireflection layer 33 as a mask layer, the incompletely etched metal hard mask layer is etched again. The morphology of the substrate after etching is as follows: Figure 2f As shown.

[0103] In one embodiment, the method provided in this embodiment further includes:

[0104] Oxygen-containing gas is introduced into the chamber to etch and remove residual polymer.

[0105] Because a large amount of passivation gas is used in the etching process of the metal hard mask layer, polymers are generated during the etching process. Some areas still have polymer residues after etching. If the residual polymers are not removed, they will affect the device performance and thus affect the product yield. By introducing oxygen-containing gas into the chamber, the residual polymers in the chamber can be etched away.

[0106] The oxygen-containing gas mentioned above can be oxygen. During the etching process to remove residual polymer, the chamber settings can include: chamber pressure 8-15 mT, upper electrode power 1000-1500 W; lower electrode power 10-30 W, current ratio 0.4-0.6, O2 flow rate 100-300 sccm, and etching time 30-50 s. 30-80 sccm of N2 can also be introduced as a dilution gas to make the reaction process controllable and to remove byproducts generated during the etching process.

[0107] In one embodiment, during the etching steps of the organic film layer and the dielectric antireflection layer provided in this embodiment, the power of the radio frequency power supply is applied in either pulse mode or continuous wave mode.

[0108] During the etching of organic films using an organic antireflective layer as a mask, the power application method of the radio frequency power supply can be either pulsed mode or continuous wave mode. Using pulsed mode can reduce the energy of the plasma, further reducing the consumption of photoresist, and significantly improving the linewidth roughness after etching the metal hard mask layer. On the other hand, using continuous wave mode can reduce the etching time of the organic film layer and increase the etching rate of the organic film layer.

[0109] During the etching of a dielectric antireflective layer using an organic film as a mask, the power applied by the radio frequency power supply can be in pulse mode or continuous wave mode. Using pulse mode can reduce the energy of the plasma, reduce the consumption of the organic film, and significantly improve the linewidth roughness after etching the metal hard mask layer. On the other hand, using continuous wave mode can reduce the etching time of the dielectric antireflective layer and increase the etching rate of the dielectric antireflective layer.

[0110] In one embodiment, to improve the etching rate, when etching the organic antireflective layer using the patterned photoresist layer as a mask, the power application mode of the radio frequency power supply can be controlled to be pulsed. During the etching of the organic film layer using the organic antireflective layer as a mask and the etching of the dielectric antireflective layer using the organic film layer as a mask, the power application mode of the radio frequency power supply can be controlled to be continuous wave mode. This improves the etching rate of the product while also improving the linewidth roughness.

[0111] The etching method for the metal hard mask layer provided in this embodiment optimizes the etching process by increasing the pretreatment of the photoresist layer, using argon gas to remelt the photoresist layer, and modifying the edge morphology of the photoresist layer. Furthermore, a novel pulse mode is used in the organic anti-reflection layer etching step to reduce the linewidth roughness after metal hard mask etching. This comprehensive optimization effectively improves the linewidth roughness after metal hard mask etching, thereby reducing the resistance of metal wires and the parasitic capacitance and RC delay between metal interconnect layers, increasing product yield, and playing a crucial role in the subsequent etching of ultra-low dielectric material layers. Without changing the current wafer mass production technology roadmap and equipment hardware structure, improvements to the etching process menu further reduce linewidth roughness, meeting the requirements of advanced processes.

[0112] Based on the foregoing embodiments, this embodiment provides an example of optimizing the linewidth roughness after etching of metal hard masks MHM (1-7) using the aforementioned etching method for metal hard mask layers. The metal hard mask (M*HM) pre-etching film structure provided in this embodiment is as follows: Figure 2a As shown, the film layers from top to bottom are: photoresist layer 20, organic antireflective layer (Si-Barc) 31, organic film layer 32, dielectric antireflective layer 33, metal hard mask layer 40, dielectric material layer 50, ultra-low dielectric constant dielectric material layer 60, and etching stop layer 70. An ICP plasma etching machine can be used for etching. The upper and lower power supply frequencies are 13.56MHz. The upper electrode power application method is continuous wave, and the lower electrode power application method is either continuous wave or pulse wave. The electrostatic chuck temperature during the process is 25-40℃, the electrostatic adsorption voltage is 2200-2600V, and the helium pressure on the back side of the wafer is 6-10T. Figures 2a to 2f As shown, the etching steps can be performed as follows:

[0113] The remelting step (Descum step) involves etching the photoresist layer with argon gas to remelt the photoresist layer. During the etching process, the chamber pressure is 3–10 mT; the upper electrode power is 200–400 W, there is no lower electrode power, and the current ratio of the upper electrode power is 0.4–0.6; the introduced argon gas is used as the main etching gas with a flow rate of 150–200 sccm, and the process time is 10–15 s.

[0114] The principle of photoresist can be achieved by using plasma generated by inert gases such as argon to re-fuse the photoresist, and the loss of photoresist is not significant during the process, thus achieving the goal of optimizing LWR.

[0115] The repair step (Cure step) involves introducing a repair gas into the photoresist layer to repair the edge morphology of the photoresist and ensure accurate pattern transfer. During the etching process, the chamber pressure is 3-10 mT, the upper electrode power is 800-1500 W, and there is no lower electrode power to reduce the bombardment of organic materials. The current ratio of the upper electrode power is 0.4-0.6, the process time is 20-40 s, and 150-200 sccm HBr is introduced as the main etching gas.

[0116] The organic antireflective layer etching step (Si-Barc step) etches the organic antireflective layer, whose main components include C, N and Si (14% to 40%).

[0117] During the etching process, the chamber pressure is 10–15 mT; the upper electrode power is 500–700 W; the lower electrode power is 50–100 W; the pulse frequency is 90–110 Hz; the current ratio of the upper electrode power to the lower electrode power is 0.4–0.6; the process time is 30–50 s; the power application method is a novel pulse mode; the plasma duty cycle is 15%–30%; and the pulse frequency is 100 Hz. The purpose is to reduce the plasma energy, reduce the dissociation of molecules in the plasma, reduce its chemical molecular activity, reduce the thickness of the graphite-like layer on the photoresist surface, and also reduce the consumption of photoresist, thus significantly improving the LWR.

[0118] 50–100 sccm of CF4 and 50–100 sccm of CHF3 are introduced as the main etching gases, and 60–100 sccm of N2 gas can also be introduced as a dilution gas, which can remove byproducts generated during the etching process. The ratio of CF4 to CHF3 is an important way to improve critical dimensions. By making the ratio of CF4 to CHF3 greater than 1:1, the etching rate can be increased while the amount of polymer generated can be reduced.

[0119] The etching step (ODL step) of the organic film layer etches the organic film layer, whose main components are C and O. The photoresist layer, the organic material anti-reflective layer, and the organic film layer form a sandwich structure, mainly to solve the problem of insufficient photoresist thickness preventing accurate pattern transfer.

[0120] During the etching process, the chamber pressure is 3–10 mT, the upper electrode power is 300–600 W, and the lower electrode power is 100–300 W. Both upper and lower electrode powers are applied using continuous wave (CW), with a current ratio of 0.4–0.6. The process time is 50–80 s. 90–150 sccm of oxygen is introduced as the main etching gas, and 30–80 sccm of N2, HBr, and Cl2 are introduced as passivation gases to adjust the angle of the organic film.

[0121] The etching step of the dielectric anti-reflective layer (CAP step) etches the dielectric anti-reflective layer (SIOC), which is intended to serve as a mask for etching the metal hard mask layer.

[0122] During the etching process, the chamber pressure was 3–10 mT; the upper electrode power was 400–700 W; and the lower electrode power was 80–160 W. The upper and lower electrode powers were applied using continuous wave (CW) etching, with a current ratio of 0.4–0.6 for both. The etching time was 30–50 s. 80–120 sccm of CF4 and 20–40 sccm of CHF3 were introduced as the main etching gases; 80–120 sccm of He was introduced as the dilution gas.

[0123] Organic film removal step (Asher step): Etching removes the organic film layer;

[0124] During the etching process, the chamber pressure is 3-10 mT, the upper electrode power is 500-800 W, and the lower electrode power is 50-100 W. The upper and lower electrode powers are applied using continuous wave (CW) with a current ratio of 0.4-0.6. The etching time is 30-50 s. 100-300 sccm of O2 and 50-100 sccm of Cl2 are introduced as the main etching gases. The main purpose of adding Cl2 is to completely remove the organic material layer and avoid defects.

[0125] In the oxide removal step (BT step), the oxygen introduced during the organic film removal step will react with the TiN on top of the metal hard mask layer to generate TiO2, which is removed by fluorine-based gas. Otherwise, it will cause problems such as etching stoppage, resulting in wafer scrap.

[0126] During the etching process, the chamber pressure is 3-10 mT, the upper electrode power is 200-400 W, the lower electrode power is 30-60 W, the power application method is continuous wave (CW), the current ratio is 0.4-0.6, the etching time is 5-10 s, and 40-80 sccm of CF4 and 20-40 sccm of CHF3 are introduced as the main etching gases.

[0127] The hard mask etching step (ME step) etches the metal hard mask layer (TiN). The use of this film layer allows subsequent metal layers to be etched in one step (All In One), avoiding multiple damages to porous dielectric materials with ultra-low dielectric constants, and can also improve the distortion and roughness of metal interconnects.

[0128] During the etching process, the chamber pressure is 5–10 mT; the upper electrode power is 600–800 W; the lower electrode power is 60–100 W; the power application method for the upper and lower electrodes is continuous wave (CW); the current ratio of the upper electrode power to the lower electrode power is 0.4–0.6; the flow rate of the main etching gas Cl2 is 150–100 sccm; the flow rate of the dilution and bombardment gas Ar can be 50–100 sccm; and the flow rate of CH4 can be 30–50 sccm. Under the action of plasma, CH4 can react with Ti and O in the chamber to form non-volatile byproducts that adhere to the sidewalls of the metal hard mask, which can protect the sidewalls of the metal hard mask and prevent lateral indentation of the metal hard mask.

[0129] The metal hard mask layer re-etching step (OE step) involves re-etching the incompletely etched metal hard mask layer within the wafer, and also etching part of the dielectric anti-reflective layer (SIOC).

[0130] During the etching process, the chamber pressure was 10–20 mT, the upper electrode power was 500–700 W, and the lower electrode power was 30–50 W. The power application method was continuous wave (CW); the current ratio was 0.4–0.6, and the etching time was 6–10 s. 100–300 sccm of NF3 and 50–100 sccm of Cl2 were introduced as the main etching gases. To reduce the etching of the dielectric reflective layer, 80–150 sccm of SiCl4 and 10–20 sccm of CH4 were introduced as etching protective gases.

[0131] The polymer etching step (PET step) is necessary because a large amount of passivation gas is used during the etching of TiN, which generates polymers. Some areas still have polymer residues after etching. If these residues are not removed, they will affect device performance and thus product yield. Therefore, the main purpose of this step is to remove the residual polymers.

[0132] During the etching process, the chamber pressure is 8–15 mT, the upper electrode power is 1000–1500 W, the lower electrode power is 10–30 W, the current ratio is 0.4–0.6, the O2 flow rate is 100–300 sccm, the etching time is 30–50 s, and 30–80 sccm of N2 is introduced as a dilution gas.

[0133] For example, this embodiment provides a comparative experiment on the etching method of the metal hard mask layer provided in the above embodiment for the metal hard mask layer, see as follows: Figure 3a The diagram shows the linewidth roughness (LWR) of the metal hard mask layer after etching without any processing, and diagram 3b shows the linewidth roughness (LWR) of the metal hard mask layer after etching when only HBr is used to repair the photoresist. Figure 3aIt can be seen that without any linewidth roughness improvement treatment during the etching of the metal hard mask layer, the linewidth roughness after etching of the metal hard mask layer is quite large, reaching 12.1. Figure 3b It can be seen that when only HBr is used to repair the photoresist, the linewidth roughness after etching the metal hard mask layer can be reduced to 5.5; see [example missing]. Figure 3c The diagram shows the linewidth roughness (LWR) of the metal hard mask layer after etching when using Ar-refused photoresist and HBr to repair the photoresist, and the diagram in 3d shows the linewidth roughness (LWR) of the metal hard mask layer after etching when using Ar-refused photoresist and HBr to repair the photoresist and using a pulse mode in the etching of the organic antireflective layer. Figure 3c It can be seen that when only Ar-refused photoresist is used and HBr is used to repair the photoresist, the linewidth roughness after etching the metal hard mask layer can be reduced to 3.5; from Figure 3d It can be seen that when only Ar re-fused photoresist is used and HBr is used to repair the photoresist, and pulse mode is used in the etching of the organic anti-reflection layer, the linewidth roughness after etching the metal hard mask layer can be reduced to 2.6. Compared with related metal hard mask layer etching techniques, the linewidth roughness after etching the metal hard mask layer can be reduced from 5.5 to 2.6. The metal hard mask layer etching method provided in this embodiment can effectively improve the linewidth roughness after etching the metal hard mask layer, thereby reducing the resistance of the metal wires and the parasitic capacitance and RC delay between the metal interconnect layers, and increasing the product yield.

[0134] This invention provides an electronic device, which includes a processor and a memory. The memory stores a computer program that can run on the processor. When the processor executes the computer program, it implements the steps of the method provided in the above embodiments.

[0135] This invention provides a computer-readable medium storing computer-executable instructions. When these computer-executable instructions are invoked and executed by a processor, they cause the processor to implement the methods described in the above embodiments.

[0136] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the system described above can be referred to the corresponding process in the foregoing embodiments, and will not be repeated here.

[0137] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0138] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0139] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of etching a metal hard mask layer, the method comprising: include: A preset substrate is provided; wherein, the preset substrate includes a patterned photoresist layer, an anti-reflection layer and a metal hard mask layer formed sequentially from top to bottom, and the anti-reflection layer includes an organic anti-reflection layer; In the remelting step, argon-containing gas is introduced into the chamber to etch the photoresist layer, thereby remelting the photoresist layer; wherein, in the remelting step, the upper electrode power ranges from 200 W to 400 W, and the lower electrode power is set to zero; The repair step involves introducing a repair gas into the chamber to modify the edge morphology of the photoresist layer; wherein the repair gas includes hydrogen-containing gas, and the power of the lower electrode is set to zero in the repair step; In the organic antireflective layer etching step, the power application mode of the radio frequency power supply is controlled to be pulsed, a fluorine-containing gas is introduced into the chamber, and the organic antireflective layer is etched using the patterned photoresist layer as a mask until the next film layer is exposed. In the hard mask etching step, chlorine-containing gas is introduced into the chamber to etch the exposed metal hard mask layer until the next film layer is exposed.

2. The method of claim 1, wherein, The anti-reflective layer further includes an organic film layer and a dielectric anti-reflective layer arranged sequentially downwards below the organic anti-reflective layer; after the etching step of the organic anti-reflective layer, the following is also included: The exposed organic film layer and the dielectric anti-reflective layer are etched sequentially until the metal hard mask layer is exposed.

3. The method of claim 2, wherein, The etching step of the organic film layer includes: Oxygen-containing gas is introduced into the chamber, and the organic anti-reflective layer is used as a mask to etch the organic film layer until the next film layer is exposed.

4. The method of claim 2, wherein, The etching step of the dielectric antireflective layer includes: Carbon-containing gas and fluorine-containing gas are introduced into the chamber, and the medium anti-reflection layer is etched using the organic film layer as a mask until the metal hard mask layer is exposed.

5. The method of claim 4, wherein, Following the etching step of the dielectric antireflective layer, the process further includes: The organic film layer is removed by etching with oxygen-containing gas into the chamber.

6. The method of claim 5, wherein, Prior to the hard mask etching step, the method further includes: Fluorine-containing gas is introduced into the chamber to etch and remove the oxides on the surface of the metal hard mask layer.

7. The method according to any one of claims 1 to 6, characterized in that, Following the hard mask etching step, the process further includes: Fluorine-containing gas and chlorine-containing gas are introduced into the chamber to re-etch the incompletely etched metal hard mask layer, and to etch part of the dielectric anti-reflection layer.

8. The method of claim 7, wherein, Also includes: Oxygen-containing gas is introduced into the chamber to etch and remove residual polymer.

9. The method of claim 1, wherein, The fluorine-containing gas introduced in the organic antireflective layer etching step includes CF4 and CHF3, and the ratio of CF4 to CHF3 is greater than 1:1; And / or, The plasma duty cycle in the pulsed mode ranges from 15% to 30%.

10. The method according to claim 2, characterized in that, In the etching steps of the organic film layer and the dielectric anti-reflection layer, the power of the radio frequency power supply is applied in either pulse mode or continuous wave mode.

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