Hard mask etching method and etching apparatus

Abstract

The application provides a hard mask etching method and an etching device. The method comprises the following steps: placing a device to be etched in a plasma reaction chamber; applying a first radio frequency excitation to the plasma reaction chamber to excite a process gas in the plasma reaction chamber into plasma; applying a second radio frequency excitation with a first fixed power to the plasma reaction chamber to drive the plasma to perform a first stage etching on a hard mask layer; and applying a second radio frequency excitation with a pulse power to the plasma reaction chamber to drive the plasma to perform a second stage etching on the hard mask layer until the target film layer is etched, before a strip-shaped morphology generated on a sidewall of the photoresist layer is transferred to the hard mask layer. The application can improve the strip-shaped phenomenon of the sidewall in the hard mask dry etching process, and avoid the adverse effects caused by the traditional process parameter control method.

Description

Technical Field

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

[0002] Semiconductor dry etching refers to a method of transferring a pattern to a target film layer based on the pattern of the photoresist (PR) after development. The resulting morphology depends entirely on the morphology of the photoresist after development and the dry etching process. In actual operation, to ensure the accuracy and stability of critical dimensions, such as... Figure 1A As shown, a hard mask layer 2 (such as a SiO2 layer) is usually grown on the target film layer 1 before etching the target film layer 1 (such as a Si layer) to facilitate pattern transfer. Assuming no abnormalities in the photoresist layer 3, the morphology quality of the target film layer 1 mainly depends on the dry etching effect of the hard mask layer 2.

[0003] In dry etching, plasma is typically generated using a mixture of various hydrocarbon and fluorine compounds. During etching, the top surface of photoresist layer 3 is bombarded by high-energy ions and interacts with the fluorocarbon polymers in the plasma. This microscopic process causes a change in the morphology of the top surface of photoresist layer 3, forming crosslinking points 31 and evaporation points 32, such as... Figure 1A and 1B As shown.

[0004] During the etching process, high ion energy intensifies the deformation of photoresist layer 3, leading to the gradual formation of striation morphology on the sidewalls of photoresist layer 3. For example... Figure 2A As shown, after partially exposing the hard mask layer 2 is etched away, strip-shaped morphology is formed on the sidewalls of the photoresist layer 3. Figure 2A The hole wall is shown in the red box. As etching continues, the deformation of the photoresist layer 3 is continuously propagated downwards and enters the sidewall of the hard mask layer 2, causing the sidewall of the hard mask layer 2 to form stripes, as shown in the image. Figure 2B The hole wall is shown in the red box. It should be understood that the strip-shaped morphology of the hard mask layer 2 will affect the morphology quality of the subsequent etching of the target film layer 1.

[0005] Considering that factors such as ion density and energy in the plasma, gas chemical composition, and total etching time all affect the deformation and stripe morphology of the photoresist layer 3, the current approach mainly focuses on improving the sidewall stripe phenomenon of the hard mask layer 2 by controlling process parameters. Specifically, stripe improvement is achieved by comprehensively adjusting parameters such as pressure, fluorine gas ratio, and RF power in the hard mask etching step. However, while this method can improve the sidewall stripe morphology, it also affects critical dimensions, selectivity, and sidewall angles, and the control process is complex and reduces the process window. Summary of the Invention

[0006] In order to improve the sidewall striping phenomenon during hard mask dry etching and avoid the adverse effects of traditional process parameter control methods, this invention provides a hard mask etching method and etching equipment.

[0007] To achieve the above objectives, a first aspect of the present invention provides a hard mask etching method, comprising:

[0008] The device to be etched is placed in a plasma reaction chamber. The device to be etched includes a target film layer, a hard mask layer and a patterned photoresist layer stacked from bottom to top.

[0009] A first radio frequency excitation is applied to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma;

[0010] A second radio frequency excitation with a first fixed power is applied into the plasma reaction chamber to drive the plasma to perform a first-stage etching of the hard mask layer;

[0011] Before the strip-shaped morphology generated on the sidewalls of the photoresist layer is transferred to the hard mask layer, a second radio frequency excitation with pulsed power is applied to the plasma reaction chamber to drive the second-stage etching of the hard mask layer in the plasma until the target film layer is etched.

[0012] Furthermore, after the second stage of etching is completed, the method further includes:

[0013] A second radio frequency excitation with a second fixed power is applied to the plasma reaction chamber to drive the plasma to over-etch the hard mask layer.

[0014] Furthermore, the etching duration T1 of the first stage does not exceed the duration threshold T, where T = (L - L1) / V1, L represents the initial thickness of the hard mask layer, L1 represents the remaining thickness of the hard mask layer when the strip-shaped morphology generated by the sidewall of the photoresist layer is about to be transferred to the hard mask layer, and V1 represents the etching rate of the first stage etching.

[0015] Furthermore, the etching duration of the first stage is T1=T, and the etching duration of the second stage is T2= L1 / V2, where V2 represents the etching rate of the second stage.

[0016] Furthermore, during the second stage etching process, the endpoint detection device detects whether the target film layer has been etched. The duration T2 of the second stage etching is the duration from the start time of the second stage etching to the time when the target film layer is etched.

[0017] Furthermore, the range of the first fixed power is 400W~800W;

[0018] The pulse frequency range of the pulse power is 1000Hz~5000Hz, and the pulse duty cycle range is 10% to 90%.

[0019] The high power range of the pulse power is 400W~800W, and the low power range of the pulse power is 0W~400W.

[0020] Furthermore, the over-etching duration T3 = (T1 + T2) × OE%, where OE% represents the set over-etching coefficient, and the range of OE% is 15%~50%, T1 represents the duration of the first stage of etching, and T2 represents the duration of the second stage of etching.

[0021] Furthermore, the range of the second fixed power is 100W to 800W.

[0022] Furthermore, the process gas includes an etching gas, an auxiliary gas, and a protective gas. The etching gas is a hydrocarbon gas, the auxiliary gas is O2, and the protective gas is Ar or N2.

[0023] A second aspect of the present invention provides an etching apparatus for etching a device to be etched. The apparatus includes a plasma reaction chamber, a first radio frequency generator, a second radio frequency generator, and a control device. The device to be etched includes a target film layer, a hard mask layer, and a patterned photoresist layer stacked sequentially from bottom to top.

[0024] After the device to be etched is placed in the plasma reaction chamber, the control device controls the first radio frequency generator to apply a first radio frequency excitation to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma; then controls the second radio frequency generator to apply a second radio frequency excitation with a first fixed power to the plasma reaction chamber to drive the plasma to perform a first-stage etching of the hard mask layer; and before the strip-shaped morphology generated by the sidewall of the photoresist layer is transmitted to the hard mask layer, the second radio frequency generator is controlled to apply a second radio frequency excitation with pulsed power to the plasma reaction chamber to drive the plasma to perform a second-stage etching of the hard mask layer until the target film layer is etched.

[0025] By adopting the above technical solution, the present invention has the following advantages over the prior art:

[0026] This invention eliminates or reduces the sidewall stripe phenomenon of the hard mask layer during the etching process by controlling the power mode of the second radio frequency excitation in stages.

[0027] Specifically, in the first stage of etching, high-rate etching is achieved using a second radio frequency excitation with continuous fixed power. Before the etching process reaches the critical state where the strip-shaped morphology of the photoresist sidewall is transferred to the hard mask layer, the process switches to the second stage of etching, using a second radio frequency excitation with pulsed power. The difference in ion movement generated by the alternation of high and low power is utilized. That is, under high power, ions tend to bombard vertically, while under low power, ions tend to bombard the sidewall. Moreover, the amount of charge accumulated in the strip-shaped protrusion area of ​​the sidewall is greater than that accumulated in the flat area. The more charge accumulated, the stronger the bombardment energy. This allows for selective bombardment and trimming of the strip-shaped protrusion areas that have formed or are about to form on the sidewall of the hard mask layer. Without affecting the critical dimensional accuracy and etching selectivity, the strip-shaped defects on the sidewall of the hard mask layer are effectively suppressed or even eliminated, significantly improving the verticality and contour uniformity of the sidewall. Attached Figure Description

[0028] Figure 1A This is a schematic diagram showing the deformation of the photoresist layer during the dry etching process of a hard mask.

[0029] Figure 1B for Figure 1A A schematic diagram of the top surface of the intermediate photoresist layer;

[0030] Figure 2A This is a cross-sectional view of the device obtained after partially exposing the hard mask layer using existing dry etching technology.

[0031] Figure 2B A cross-sectional view of the device obtained after dry etching of all exposed hard mask layers using existing technology;

[0032] Figure 3 This is a flowchart of the hard mask etching method of the present invention;

[0033] Figure 4A This is a schematic diagram of ion movement during the second stage of etching in this invention when the pulse power is high.

[0034] Figure 4B This is a schematic diagram of ion movement during the second stage of etching in this invention when the pulse power is low.

[0035] Figure 5 This is a cumulative electron distribution diagram of the sidewall of the hard mask layer in this invention;

[0036] Figure 6 This is a cross-sectional view of the device obtained after etching all hard mask layers using the etching method of the present invention. Detailed Implementation

[0037] 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.

[0038] It should be noted that the illustrations provided in the embodiments are only schematic representations of the basic concept of the present invention. Although the illustrations 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, the shape, quantity, positional relationship and proportion of each component in the actual implementation can be changed at will under the premise of realizing the technical solution of the present invention, and the layout of the components may also be more complex.

[0039] As mentioned earlier, during dry etching of the hard mask layer, high ion energy causes deformation of the photoresist layer, gradually forming stripe-like morphologies on the sidewalls. As etching continues, the deformation of the photoresist layer propagates downwards into the sidewalls of the hard mask layer, causing stripe-like morphologies to also form on the sidewalls, ultimately affecting the morphology quality of subsequent target film etching. Existing technologies primarily employ process parameter control to mitigate the stripe-like phenomenon on the hard mask layer sidewalls, but this method has adverse effects.

[0040] In view of this, the present invention provides a hard mask etching method and etching equipment to improve the stripe phenomenon on the sidewalls of the hard mask layer during dry etching, while avoiding problems such as changes in key dimensions and sidewall angles caused by traditional parameter control methods.

[0041] Example 1

[0042] This embodiment provides a hard mask etching method, such as Figure 3 As shown, the method includes the following steps:

[0043] Step S1: Place the device to be etched inside the plasma reaction chamber, such as... Figure 4A and 4B As shown, the device to be etched includes a target film layer 1, a hard mask layer 2, and a patterned photoresist layer 3 stacked sequentially from bottom to top.

[0044] Step S2: Apply a first radio frequency excitation to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma.

[0045] Step S3: Apply a second radio frequency excitation with a first fixed power to the plasma reaction chamber to drive the plasma to perform a first-stage etching of the hard mask layer 2.

[0046] Step S4: Before the strip-shaped morphology generated on the sidewall of the photoresist layer 3 is transferred to the hard mask layer 2, a second radio frequency excitation with pulsed power is applied to the plasma reaction chamber to drive the second stage etching of the hard mask layer 2 in the plasma until the target film layer 1 is etched.

[0047] In this embodiment, the patterned photoresist layer 3 is used to expose a portion of the hard mask layer 2 so that the exposed portion can be etched subsequently, thereby transferring the pattern to the hard mask layer 2. The target film layer 1 can be the substrate itself or a functional film layer formed on the substrate; this embodiment does not impose any specific limitations on this.

[0048] In this embodiment, the first radio frequency excitation is applied by a first radio frequency generator, and the second radio frequency excitation is applied by a second radio frequency generator. The radio frequency frequency of the first radio frequency excitation is higher than that of the second radio frequency excitation. Preferably, the radio frequency range of the first radio frequency excitation is 27MHz to 60MHz, and the radio frequency range of the second radio frequency excitation is 2MHz to 13MHz.

[0049] In one feasible approach, the substrate can be a high-quality Si (silicon) or SiC (silicon carbide) substrate, or a high-quality first, second, or third-generation semiconductor substrate such as Si, SiC, GaN (gallium nitride), or GaAs (gallium arsenide) grown epitaxially on low-quality Si. This embodiment does not impose any specific limitations on this.

[0050] In one possible implementation, the hard mask layer 2 is a SiO2 (silicon oxide) or SiN (silicon nitride) layer, but this embodiment is not limited to this.

[0051] In one feasible approach, the pattern of the photoresist layer 3 includes one or more of the following patterns: lines, vias, and trenches.

[0052] In one feasible approach, the photoresist layer 3 can be a photoresist of different wavelengths, such as I-line, KrF (krypton fluoride), ArF (argon fluoride), etc.

[0053] In this embodiment, before performing step S2, process gas needs to be introduced into the plasma reaction chamber. The process gas includes etching gas, auxiliary gas and protective gas.

[0054] In one feasible embodiment, the etching gas is a hydrocarbon gas, which can be one or more of CF4, CHF3, CH2F2, C4F6, and C4F8; the auxiliary gas is O2; and the protective gas (i.e., dilution gas) is Ar or N2. Based on this, the plasma generated in step S2 contains particles such as F*, CF*, O*, Ar*, N*, and electrons. F* is mainly used for etching the medium; CF* will deposit or adhere to the sidewalls during the etching process; Ar is the dilution gas, and the generated Ar* can be used for physical bombardment; O* can be used to remove byproducts generated in the reaction and adjust the selectivity; and * can represent relevant ions and free radicals.

[0055] Preferably, in the process gas, the flow rate ratio of the auxiliary gas is 0~20%, and the flow rate ratio of the protective gas is 0~90%.

[0056] In step S3, during the process of applying a second radio frequency excitation with a first fixed power to the plasma reaction chamber to drive the plasma to perform the first stage etching of the hard mask layer 2, as described in the background art, the top surface of the photoresist layer 3 is bombarded by ions and mixed with the fluorocarbon polymer in the plasma. This causes a change in the morphology of the top surface of the photoresist layer 3, forming crosslinking points and evaporation points, thus altering the thickness and selectivity of the photoresist layer 3. As etching continues, the continuous bombardment of ions intensifies the deformation of the photoresist layer 3, causing strip-shaped morphologies to appear on its sidewalls. Due to pattern inheritance, these strip-shaped morphologies gradually propagate downwards.

[0057] In this embodiment, the etching duration T1 of the first stage does not exceed the duration threshold T. The duration threshold T = (L-L1) / V1, where L represents the initial thickness of the hard mask layer 2; L1 represents the remaining thickness of the hard mask layer 2 when the stripe-like morphology generated by the sidewalls of the photoresist layer 3 is about to be transferred to the hard mask layer 2; and V1 represents the etching rate of the first stage.

[0058] The first stage of etching stops after a time T1. Since T1 does not exceed the time threshold T, the first stage of etching will stop before the stripe-like morphology generated on the sidewalls of the photoresist layer 3 is transmitted to the hard mask layer 2. That is, after the first stage of etching is completed, the stripe-like morphology has not yet appeared on the sidewalls of the hard mask layer 2.

[0059] In this embodiment, L1 is an empirical value obtained in advance through experimental calibration.

[0060] In one feasible embodiment, the first fixed power ranges from 400W to 800W, for example, 400W, 500W, 600W, 700W, 800W, etc. The first etching stage accelerates ions by applying a continuous high-power second radio frequency excitation to the plasma reaction chamber, thereby providing continuous and high-energy ion bombardment and achieving high etching efficiency.

[0061] Preferably, the etching duration of the first stage is T1=T, that is, the first stage etching stops when the strip-shaped morphology generated by the sidewall of the photoresist layer 3 is about to be transmitted to the critical point of the hard mask layer 2, so as to ensure the etching rate and prevent the strip-shaped morphology from being transmitted to the hard mask layer 2.

[0062] After the first stage of etching is completed in step S3, the second stage of etching is performed in step S4. During the second stage of etching, the second radio frequency excitation is switched from continuous high power to pulsed power, that is, pulsed power second radio frequency excitation is applied to the plasma reaction chamber.

[0063] It should be understood that pulse power includes periodically alternating high and low power. By utilizing the difference in ion movement generated by the alternation of high and low power, the stripe phenomenon on the sidewalls of the hard mask layer can be weakened or eliminated. The specific implementation principle is as follows:

[0064] First, during the etching process, electrons in the plasma continuously accumulate on the surface of the photoresist layer 3, the sidewalls of the hard mask layer 2, and the bottom. Assuming that electron diffusion is isotropic, due to differences in surface area and volume, the amount of charge accumulated in the flat region 21 and the strip-shaped protrusion region 22 on the sidewalls of the hard mask layer 2 is different, and the amount of charge accumulated in the strip-shaped protrusion region 22 is much greater than the amount of charge accumulated in the flat region 21. Figure 5 As shown. The bombardment energy of the sidewall varies depending on the amount of charge accumulated. The more charge accumulated, the stronger the bombardment energy, meaning that the strip-shaped protrusion 22 will be bombarded relatively more strongly.

[0065] Secondly, at high power, ions tend to bombard vertically because the applied bias voltage is large, creating a large potential barrier at the top and bottom. This allows ions in the plasma to gain energy and move vertically, engaging in vertical physical bombardment. Figure 4A As shown. However, when switching to low power, the vertical potential barrier decreases, and some ions, due to the Coulomb force, move obliquely to bombard the sidewalls, such as... Figure 4B .

[0066] Because according to Coulomb's law: Where k is the Coulomb constant, q1 and q2 are the charge amounts, and r is the distance between the two charges. Assuming the ion density in the horizontal direction is the same in the etching space, compared with the flat region 21, the sidewall strip protrusion region 22 is closer to the ions (i.e., r is smaller) and accumulates more charge. Due to the principle of vector superposition of Coulomb forces, the ions are more inclined to bombard the sidewall, thereby etching the strip protrusion region 22, thus weakening or eliminating the sidewall protrusion strip region.

[0067] Therefore, the second-stage etching in this embodiment can selectively bombard and refine the strip-shaped protrusions 22 that have already formed or are about to form on the sidewalls of the hard mask layer 2, effectively suppressing or even eliminating strip-shaped defects on the sidewalls of the hard mask layer 2, and significantly improving the verticality and contour uniformity of the sidewalls. At the same time, it eliminates the need for complex multi-parameter co-optimization, greatly simplifying process debugging, widening the process window, enhancing process stability and repeatability, and making it suitable for various semiconductor devices. This helps reduce production costs and improve device manufacturing yield.

[0068] During the second-stage etching process, the pulse frequency range of the pulse power is 1000Hz~5000Hz. For example, pulse frequencies are 1000Hz, 2000Hz, 3000Hz, 4000Hz, and 5000Hz.

[0069] During the second-stage etching process, the pulse duty cycle of the pulse power ranges from 10% to 90%. For example, the pulse duty cycle can be 10%, 50%, 60%, 90%, etc.

[0070] During the second stage of etching, the high power of the pulse is in the range of 400W~800W (e.g., 500W), and the low power of the pulse is in the range of 0W~400W (e.g., 50W), and the high power should be greater than the low power.

[0071] During the second-stage etching process, the endpoint detection device can be used to detect whether the target film layer 1 has been etched. When the target film layer 1 is detected to have been etched, the second-stage etching ends. The duration T2 of the second-stage etching is the time from the start of the second-stage etching to the time when the target film layer 1 is etched.

[0072] When the first stage etching duration T1=T, that is, the first stage etching stops when the strip-shaped morphology produced by the sidewall of the photoresist layer 3 is about to be transferred to the critical point of the hard mask layer 2. The second stage etching duration T2 can also be calculated by monitoring the etching rate V2 of the second stage etching. The calculation formula is: T2=L1 / V2. When the duration T2 has elapsed, the second stage etching ends.

[0073] After the second stage of etching, the pattern formed by the hard mask layer 2 is consistent with the pattern of the photoresist layer 3. It can be one or more of the following: lines, holes, trenches, etc. The sidewalls of the hard mask layer 2 have a stripe-less morphology or a weak stripe morphology.

[0074] Preferably, in order to prevent the hard mask layer 2 from remaining, after the second stage etching is completed, this embodiment further includes: step S5, applying a second fixed power second radio frequency excitation to the plasma reaction chamber to drive the plasma to perform a third stage etching on the hard mask layer 2, that is, to perform over-etching.

[0075] In one feasible approach, the second fixed power ranges from 100 to 800 W, for example, 100 W, 400 W, 500 W, 600 W, 700 W, 800 W, etc. The third etching stage accelerates ions by applying a second radio frequency excitation with continuous power to the plasma reaction chamber, thereby providing continuous ion bombardment, thoroughly removing the hard mask layer 2 residue, and ensuring that the pattern can be completely transferred to the target film layer 1.

[0076] After the third stage of etching and removal of the top photoresist layer 3, the following can be obtained: Figure 6 The final morphology shown. According to... Figure 6 It can be seen that the sidewalls of the hard mask layer 2 (i.e., the etched hole walls) do not show obvious stripe-like phenomena.

[0077] In one feasible approach, the duration of the third-stage etching (i.e., over-etching) is T3 = (T1 + T2) × OE%, where OE% represents the set over-etching coefficient, and the range of OE% is 15% to 50%, T1 represents the duration of the first-stage etching, and T2 represents the duration of the second-stage etching.

[0078] In this embodiment, the etching temperature range for each etching stage is 10℃ to 60℃. For example, the temperature can be 10℃, 10.1℃, 11℃, 22℃, 28℃, 35℃, 36℃, 44℃, 49℃ or 60℃, but is not limited to these.

[0079] In this embodiment, the etching pressure range for each etching stage is 1 mtorr to 150 mtorr. For example, the etching pressure can be 1 mtorr, 1.2 mtorr, 20 mtorr, 40 mtorr, 55 mtorr, 80 mtorr, 100 mtorr, 125 mtorr, 140 mtorr, or 150 mtorr, but it is not limited to these.

[0080] In this embodiment, when steps S3 to S5 are executed, step S2 continues simultaneously to maintain the plasma in the reaction chamber.

[0081] By adopting the etching method of this embodiment, the sidewall stripe phenomenon of the hard mask layer 2 during the etching process can be eliminated or reduced, solving the technical problems in traditional hard mask etching such as difficulty in simultaneously improving stripe morphology and stabilizing feature size transfer, and ensuring etching selectivity.

[0082] Example 2

[0083] This embodiment provides an etching apparatus for implementing the hard mask etching method of Embodiment 1. The etching apparatus mainly includes a plasma reaction chamber, a first radio frequency generator, a second radio frequency generator, and a control device. The device to be etched includes a target film layer 1, a hard mask layer 2, and a patterned photoresist layer 3, stacked sequentially from bottom to top.

[0084] In this embodiment, after the device to be etched is placed in the plasma reaction chamber, the control device controls the first radio frequency generator to apply a first radio frequency excitation to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma; then controls the second radio frequency generator to apply a second radio frequency excitation with a first fixed power to the plasma reaction chamber to drive the plasma to perform a first-stage etching of the hard mask layer 2; and before the strip-shaped morphology generated by the sidewall of the photoresist layer 3 is transmitted to the hard mask layer 2, the second radio frequency generator is controlled to apply a second radio frequency excitation with pulsed power to the plasma reaction chamber to drive the ions in the plasma to perform a second-stage etching of the hard mask layer 2 until the target film layer 1 is etched.

[0085] In this embodiment, the first radio frequency generator is a high-frequency generator, and the second radio frequency generator is a low-frequency generator; that is, the operating frequency of the first radio frequency generator is higher than that of the second radio frequency generator. Preferably, the operating frequency range of the first radio frequency generator is 27MHz to 60MHz, and the operating frequency range of the second radio frequency generator is 2MHz to 13MHz.

[0086] In this embodiment, the plasma reaction chamber is a dual-frequency plasma reaction chamber, which supports the simultaneous operation of the first radio frequency generator and the second radio frequency generator, and the power of the first radio frequency generator and the second radio frequency generator can be controlled independently or simultaneously.

[0087] The first radio frequency generator has a power range of 100W to 1000W and is used to generate high-density plasma, including electrons, ions and free radicals. The strength of its power affects the particle density, thereby determining the etching rate. The second radio frequency generator has a power range of 0W to 1000W and is mainly used to accelerate ions for ion physical bombardment.

[0088] In one feasible embodiment, the total power of the first RF generator and the second RF generator does not exceed 1200W.

[0089] In one feasible embodiment, the plasma reaction chamber is a dual-frequency capacitively coupled plasma reaction chamber, with an upper electrode and a lower electrode inside the reaction chamber, the lower electrode being connected to a first radio frequency generator and a second radio frequency generator.

[0090] In one feasible embodiment, the plasma reaction chamber is a dual-frequency inductively coupled plasma reaction chamber, with a coil at the top of the reaction chamber and electrodes inside the reaction chamber, the electrodes being connected to a first radio frequency generator and a second radio frequency generator.

[0091] The control device in this embodiment can improve the sidewall stripe phenomenon of the hard mask layer 2 during the etching process by adjusting the power mode of the second radio frequency generator in stages. For the specific improvement principle, please refer to Embodiment 1, which will not be repeated here.

[0092] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A hard mask etching method, characterized in that, include: The device to be etched is placed in a plasma reaction chamber. The device to be etched includes a target film layer, a hard mask layer and a patterned photoresist layer stacked from bottom to top. A first radio frequency excitation is applied to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma; A second radio frequency excitation with a first fixed power is applied into the plasma reaction chamber to drive the plasma to perform a first-stage etching of the hard mask layer; Before the strip-shaped morphology generated on the sidewalls of the photoresist layer is transferred to the hard mask layer, a second radio frequency excitation with pulsed power is applied to the plasma reaction chamber to drive the plasma to perform a second-stage etching of the hard mask layer until the target film layer is etched.

2. The hard mask etching method as described in claim 1, characterized in that, After the second stage of etching is completed, the method further includes: A second radio frequency excitation with a second fixed power is applied to the plasma reaction chamber to drive the plasma to over-etch the hard mask layer.

3. The hard mask etching method as described in claim 1, characterized in that, The etching duration T1 of the first stage does not exceed the duration threshold T, where T = (L-L1) / V1, L represents the initial thickness of the hard mask layer, L1 represents the remaining thickness of the hard mask layer when the strip-shaped morphology generated by the sidewall of the photoresist layer is about to be transferred to the hard mask layer, and V1 represents the etching rate of the first stage.

4. The hard mask etching method as described in claim 3, characterized in that, The etching duration of the first stage is T1=T, and the etching duration of the second stage is T2=L1 / V2, where V2 represents the etching rate of the second stage.

5. The hard mask etching method as described in claim 1, characterized in that, During the second stage etching process, the endpoint detection device detects whether the target film layer has been etched. The second stage etching duration T2 is the duration from the start time of the second stage etching to the time when the target film layer is etched.

6. The hard mask etching method as described in claim 1, characterized in that, The first fixed power range is 400W~800W; The pulse frequency range of the pulse power is 1000Hz~5000Hz, and the pulse duty cycle range is 10% to 90%. The high power range of the pulse power is 400W~800W, and the low power range of the pulse power is 0W~400W.

7. The hard mask etching method as described in claim 2, characterized in that, The over-etching duration T3 = (T1 + T2) × OE%, where OE% represents the set over-etching coefficient, and the range of OE% is 15%~50%. T1 represents the duration of the first stage of etching, and T2 represents the duration of the second stage of etching.

8. The hard mask etching method as described in claim 2, characterized in that, The range of the second fixed power is 100W~800W.

9. The hard mask etching method according to any one of claims 1-8, characterized in that, The process gases include etching gas, auxiliary gas, and protective gas. The etching gas is a hydrocarbon gas, the auxiliary gas is O2, and the protective gas is Ar or N2.

10. An etching apparatus for etching a device to be etched, the apparatus comprising a plasma reaction chamber, a first radio frequency generator, a second radio frequency generator, and a control device, wherein the device to be etched comprises a target film layer, a hard mask layer, and a patterned photoresist layer stacked sequentially from bottom to top, characterized in that: After the device to be etched is placed in the plasma reaction chamber, the control device controls the first radio frequency generator to apply a first radio frequency excitation to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma; then controls the second radio frequency generator to apply a second radio frequency excitation with a first fixed power to the plasma reaction chamber to drive the plasma to perform the first stage etching of the hard mask layer. Before the strip-shaped morphology generated on the sidewall of the photoresist layer is transmitted to the hard mask layer, the second radio frequency generator is controlled to apply a second radio frequency excitation with pulsed power to the plasma reaction cavity to drive the plasma to perform a second stage of etching on the hard mask layer until the target film layer is etched.

Images