Hard mask etching method and etching equipment

Abstract

The invention provides a hard mask etching method and etching equipment. The method comprises the following steps: placing a device to be etched in a plasma reaction cavity; applying first radio frequency excitation into the plasma reaction cavity so as to excite the process gas in the plasma reaction cavity into plasma; applying second radio frequency excitation with first fixed power into the plasma reaction cavity to drive the plasma to perform first-stage etching on the hard mask layer; and before the strip-shaped morphology generated by the side wall of the photoresist layer is transmitted to the hard mask layer, applying second radio frequency excitation of pulse power into the plasma reaction cavity so as to drive the plasma to carry out second-stage etching on the hard mask layer until the target film layer is etched. According to the method, the strip-shaped phenomenon of the side wall can be improved in the hard mask dry etching process, and meanwhile, adverse effects caused by a traditional technological parameter regulation and control method are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, and in particular to a hard mask etching method and an etching device. BACKGROUND

[0002] Semiconductor dry etching refers to a method of transferring a pattern of a photoresist (PR) to a target film layer after the PR is developed. The topography formed after etching completely depends on the topography of the PR after development and the dry etching process. In actual operation, in order to ensure the accuracy and stability of the critical dimension, a hard mask layer 2 (such as a SiO2 layer) is usually grown on the target film layer 1 (such as a Si layer) before etching the target film layer 1, so as to perform pattern transfer. In the absence of abnormalities in the photoresist layer 3, the topography quality of the target film layer 1 mainly depends on the dry etching effect of the hard mask layer 2. Figure 1A

[0003] In the dry etching process, a mixture of various hydrofluorocarbons is usually used to generate plasma. The top surface of the photoresist layer 3 is bombarded by high-energy ions during etching, and at the same time interacts with fluorocarbon polymers in the plasma. This microscopic process will cause the top surface of the photoresist layer 3 to change in shape, forming cross-linking points 31 and evaporation points 32, as shown in Figure 1A and 1B .

[0004] The high ion energy in the etching process will exacerbate the deformation of the photoresist layer 3, causing a striation topography to gradually form on the sidewall of the photoresist layer 3. As shown in Figure 2A , when part of the exposed hard mask layer 2 is etched away, a striation topography is formed on the sidewall of the photoresist layer 3, as shown by the hole wall in the red box in Figure 2A . As the etching continues, the deformation of the photoresist layer 3 will continue to be transmitted downward and into the sidewall of the hard mask layer 2, causing a striation to form on the sidewall of the hard mask layer 2, as shown by the hole wall in the red box in Figure 2B . It should be understood that the striation topography of the hard mask layer 2 will affect the topography quality of the subsequent etching of the target film layer 1.

[0005] Considering that the ion density and energy in the plasma, the chemical composition of the gas, the total etching time, and other factors will affect the deformation of the photoresist layer 3 and the formation of the striation topography, the current method mainly adjusts the process parameters to improve the striation phenomenon of the sidewall of the hard mask layer 2. Specifically, the pressure, the ratio of fluorocarbon gas, the radio frequency power, and other parameters of the hard mask etching step are comprehensively adjusted to achieve striation improvement. However, this method can improve the striation topography of the sidewall, but at the same time, it will affect the critical dimension, the selectivity, and the sidewall angle, and the adjustment process is complex and will reduce the process window. SUMMARY ​

[0006] In order to improve the side wall strip phenomenon in the hard mask dry etching process, and avoid the adverse effects caused by the traditional process parameter control method, the present application provides a hard mask etching method and an etching device.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a hard mask etching method, comprising: Placing a device to be etched in a plasma reaction chamber, wherein the device to be etched comprises a target film layer, a hard mask layer and a patterned photoresist layer which are sequentially stacked from bottom to top; Applying a first radio frequency excitation to the plasma reaction chamber to excite the 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 the hard mask layer; Before the strip morphology generated on the sidewall of the photoresist layer is transferred to the hard mask layer, 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.

[0008] Further, after the second stage etching is completed, the method further comprises: Applying a second radio frequency excitation with a second fixed power to the plasma reaction chamber to drive the plasma to perform over-etching on the hard mask layer.

[0009] Further, the duration T1 of the first stage etching does not exceed a duration threshold T, wherein 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 morphology generated on 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.

[0010] Further, the duration T1 of the first stage etching is T, and the duration T2 of the second stage etching is L1 / V2, wherein V2 represents the etching rate of the second stage etching.

[0011] Further, during the second stage etching, whether the target film layer is etched is detected by an end point detection device, and the duration T2 of the second stage etching is the duration from the starting time of the second stage etching to the time when the target film layer is etched.

[0012] Further, the first fixed power ranges from 400W to 800W; The pulse frequency of the pulse power ranges from 1000Hz to 5000Hz, and the pulse duty cycle ranges from 10% to 90%. The high power of the pulse power ranges from 400 W to 800 W, and the low power of the pulse power ranges from 0 W to 400 W.

[0013] Further, the over-etching time T3 = (T1 + T2) × OE%, wherein OE% represents a set over-etching coefficient, OE% ranges from 15% to 50%, T1 represents the first-stage etching time, and T2 represents the second-stage etching time.

[0014] Further, the second fixed power ranges from 100 W to 800 W.

[0015] Further, the process gas comprises etching gas, auxiliary gas, and protective gas, the etching gas is fluorocarbon hydrogen gas, the auxiliary gas is O2, and the protective gas is Ar or N2.

[0016] The second aspect of the present application provides an etching device for etching a device to be etched, the device comprising a plasma reaction chamber, a first radio frequency generator, a second radio frequency generator, and a control device, the device to be etched comprising a target film layer, a hard mask layer, and a patterned photoresist layer stacked in sequence from bottom to top; When 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 process gas in the plasma reaction chamber into plasma, then controls the second radio frequency generator to apply a second radio frequency excitation of a first fixed power to the plasma reaction chamber to drive the plasma to perform first-stage etching on the hard mask layer, and before the strip-shaped morphology generated on the sidewall of the photoresist layer is transferred to the hard mask layer, controls the second radio frequency generator to apply a second radio frequency excitation of pulse power to the plasma reaction chamber to drive the plasma to perform second-stage etching on the hard mask layer until the target film layer is etched.

[0017] By adopting the above technical solution, the present application has the following beneficial effects compared with the prior art: The present application eliminates or weakens the strip-shaped phenomenon of the sidewall of the hard mask layer in the etching process by regulating the power mode of the second radio frequency excitation in stages.

[0018] Specifically, in the first stage etching, continuous fixed power second radio frequency excitation is used to realize high rate etching, and before the critical state of the etching process to the photoresist sidewall strip morphology is transferred to the hard mask layer, it is switched to the second stage etching, and the second radio frequency excitation with pulse power is used. The ion motion difference generated by the high-low power alternation, that is, the ion tends to vertically bombard under high power, and the ion tends to bombard the sidewall under low power, and the accumulated charge amount of the sidewall strip protruding area is more than that of the flat area. The more the charge accumulation, the stronger the bombardment energy, so as to selectively bombard and trim the strip protruding area formed or about to be formed on the sidewall of the hard mask layer, effectively inhibit or even eliminate the strip defects of the sidewall of the hard mask layer without affecting the critical dimension precision and etching selectivity, and significantly improve the sidewall verticality and profile uniformity. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1A A schematic diagram of the deformation of the photoresist layer in the process of dry etching the hard mask; Figure 1B A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 1A A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 2A A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 2B A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 3 A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 4A A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 4B A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 5 A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask; Figure 6 A schematic diagram of the top surface of the photoresist layer in the process of dry etching the hard mask. DETAILED DESCRIPTION

[0020] The embodiments of the present application will be described in detail below with specific reference to specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the present specification. The present application can also be implemented or applied by different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0021] It should be noted that the illustrations provided in the embodiments are only schematic illustrations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation, the form, quantity, positional relationship and proportion of each component in actual implementation can be changed at will under the premise of realizing the technical solution of this party, and the component layout form may also be more complicated.

[0022] As previously mentioned, during the dry etching of the hard mask layer, high ion energy causes deformation of the photoresist layer, gradually forming striped morphologies on the sidewalls of the photoresist layer. As etching continues, the deformation of the photoresist layer is continuously transferred downward to the sidewalls of the hard mask layer, causing striped morphologies to form on the sidewalls of the hard mask layer, ultimately affecting the morphological quality of the subsequent target film layer etching. Existing technologies mainly use process parameter control to improve the sidewall striping phenomenon of the hard mask layer, but this approach has adverse effects.

[0023] In view of this, the present invention provides a hard mask etching method and etching equipment to improve the stripe phenomenon of the sidewall of the hard mask layer during dry etching, while avoiding problems such as key dimension changes and sidewall angle changes caused by traditional parameter control methods.

[0024] Example 1 This embodiment provides a hard mask etching method, such as Figure 3 As shown, the method includes the following steps: Step S1: Place the device to be etched in a 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 in sequence from bottom to top.

[0025] In step S2 , a first radio frequency excitation is applied to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma.

[0026] Step S3 : applying a second radio frequency excitation of a first fixed power into the plasma reaction chamber to drive the plasma to perform a first stage etching on the hard mask layer 2 .

[0027] In step S4, before the stripe morphology generated on the sidewall of the photoresist layer 3 is transferred to the hard mask layer 2, a second RF excitation of pulse power is applied to the plasma reaction chamber to drive the plasma to perform a second stage of etching on the hard mask layer 2 until the target film layer 1 is etched.

[0028] In the embodiment, the patterned photoresist layer 3 is used to expose part of the hard mask layer 2, so that the exposed part is etched to transfer 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, and the embodiment does not make any specific limitation on this.

[0029] In the embodiment, the first radio frequency excitation is applied by the first radio frequency generator, and the second radio frequency excitation is applied by the second radio frequency generator. The radio frequency of the first radio frequency excitation is higher than the radio frequency of the second radio frequency excitation. Preferably, the radio frequency of the first radio frequency excitation ranges from 27 MHZ to 60 MHZ, and the radio frequency of the second radio frequency excitation ranges from 2 MHZ to 13 MHZ.

[0030] In an implementable manner, the substrate can be a high-quality Si (silicon) or SiC (silicon carbide) substrate, or a first, second or third generation semiconductor substrate such as high-quality Si, SiC, GaN (gallium nitride), GaAs (gallium arsenide) epitaxially grown on a low-quality Si, and the embodiment does not make any specific limitation on this.

[0031] In an implementable manner, the hard mask layer 2 is a SiO2 (silicon oxide) or SiN (silicon nitride) layer, but the embodiment is not limited thereto.

[0032] In an implementable manner, the pattern of the photoresist layer 3 includes one or more of line, via and trench patterns.

[0033] In an implementable manner, the photoresist layer 3 can use photoresists of different wavelengths, such as I-line, KrF (krypton fluoride), ArF (argon fluoride), etc.

[0034] In the embodiment, before step S2 is performed, a process gas is introduced into the plasma reaction chamber, and the process gas includes etching gas, auxiliary gas and protective gas.

[0035] In an implementable manner, the etching gas is a fluorocarbon hydrogen 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 dielectric etching, CF* is deposited or attached to the sidewall during etching, Ar is a dilution gas, Ar* generated can be physically bombarded, and O* can be used to remove by-products generated during the reaction and adjust the selectivity. * can represent relevant ions and radicals.

[0036] Preferably, the flow ratio of the auxiliary gas is 0-20% and the flow ratio of the protective gas is 0-90% in the process gas.

[0037] In step S3, a second radio frequency excitation of a first fixed power is applied to the plasma reaction chamber to drive the plasma to perform the first stage etching on the hard mask layer 2. As described in the background, the top surface of the photoresist layer 3 is bombarded by ions and mixed with fluorocarbon polymers in the plasma, so that the top surface of the photoresist layer 3 will change, forming cross-linking points and evaporation points, and the thickness and selectivity of the photoresist layer 3 will change. As the etching continues, the continuous bombardment of ions will intensify the deformation of the photoresist layer 3, causing the sidewall of the photoresist layer 3 to have a strip-shaped appearance. Due to the pattern inheritance, the strip-shaped appearance will gradually be transmitted downward.

[0038] In this embodiment, the duration T1 of the first stage etching 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 strip-shaped appearance generated by the sidewall of the photoresist layer 3 is about to be transmitted to the hard mask layer 2; and V1 represents the etching rate of the first stage etching.

[0039] The first stage etching stops after the duration T1. Since T1 does not exceed the duration threshold T, the first stage etching will stop before the strip-shaped appearance generated by the sidewall of the photoresist layer 3 is transmitted to the hard mask layer 2. That is, after the first stage etching is completed, the sidewall of the hard mask layer 2 does not have a strip-shaped appearance.

[0040] In this embodiment, L1 is an empirical value obtained by pre-experiment calibration.

[0041] In an implementable manner, the first fixed power ranges from 400W to 800W, for example, 400W, 500W, 600W, 700W, 800W, etc. The first etching stage is performed by applying a second radio frequency excitation of continuous high power to the plasma reaction chamber to accelerate ions, thereby providing continuous and high-energy ion bombardment, and thus obtaining high etching efficiency.

[0042] Preferably, the duration T1 of the first stage etching is T, that is, the first stage etching stops at the critical point when the strip-shaped appearance generated by the sidewall of the photoresist layer 3 is about to be transmitted to the hard mask layer 2, thereby ensuring the etching rate and preventing the strip-shaped appearance from being transmitted to the hard mask layer 2.

[0043] After the first stage etching in step S3 is completed, the second stage etching in step S4 is performed. In the process of the second stage etching, the second radio frequency excitation is switched from continuous high power to pulsed power, that is, a second radio frequency excitation of pulsed power is applied to the plasma reaction chamber.

[0044] It should be understood that the pulse power includes periodically alternating high power and low power, and the difference in ion movement generated by the high-low power alternation thereof can weaken or eliminate the strip phenomenon of the sidewall of the hard mask layer 2, and the specific implementation principle is as follows: First, in the etching process, the electrons in the plasma continuously accumulate on the surface of the photoresist layer 3, the sidewall and the bottom of the hard mask layer 2. Assuming that the diffusion of the electrons is isotropic, due to the difference between the surface area and the volume, the amount of charge accumulated in the flat area 21 and the strip protruding area 22 of the sidewall of the hard mask layer 2 is different, and the amount of charge accumulated in the sidewall strip protruding area 22 is much greater than that in the flat area 21, as shown in Figure 5 The sidewall bombardment energy will be different according to the difference in charge accumulation, and the more the charge accumulation, the stronger the bombardment energy, that is, the strip protruding area 22 will be relatively subjected to stronger bombardment.

[0045] Secondly, under high power, ions tend to vertically bombard, because the bias voltage applied is large, the potential barrier at the top and bottom is large, the ions in the plasma obtain energy and move in the vertical direction, and perform vertical physical bombardment, as shown in Figure 4A When switched to low power, the potential barrier in the vertical direction is reduced, and part of the ions are obliquely moved and bombarded to the sidewall due to the action of the Coulomb force, as shown in Figure 4B

[0046] According to Coulomb's law: where k is the Coulomb constant, q1 and q2 are the charge amount of the charge, and r is the distance between the two charges. Assuming that the ion density in the horizontal direction entering the etching space is the same, compared with the flat area 21, the sidewall strip protruding area 22 is closer to the ion (i.e. r is smaller), and the accumulated charge amount is more, due to the vector superposition principle of the Coulomb force, the ion is more inclined to bombard the sidewall, and then etches the strip protruding area 22, thereby weakening or eliminating the sidewall protruding strip area.

[0047] Therefore, the second stage etching of the embodiment can selectively bombard and trim the strip protruding area 22 of the sidewall of the hard mask layer 2 which has been formed or is about to be formed, effectively inhibits or even eliminates the strip defect of the sidewall of the hard mask layer 2, and significantly improves the verticality and contour uniformity of the sidewall. At the same time, without the need for complex multi-parameter optimization, the process debugging difficulty is greatly simplified, the process window is widened, the process stability and repeatability are enhanced, and it is suitable for various semiconductor devices, which is conducive to reducing production cost and improving device manufacturing yield.

[0048] In the second stage etching process, the pulse frequency of the pulse power ranges from 1000HZ to 5000Hz. For example, the pulse frequency is 1000Hz, 2000Hz, 3000Hz, 4000Hz and 5000Hz, etc.

[0049] ​In the second stage etching process, the pulse duty cycle of the pulse power ranges from 10% to 90%. For example, the pulse duty cycle is 10%, 50%, 60%, 90%, etc.

[0050] In the second stage etching process, the high power of the pulse power ranges from 400W to 800W (e.g. 500W), and the low power of the pulse power ranges from 0W to 400W (e.g. 50W), and the high power should be greater than the low power.

[0051] In the second stage etching process, whether the target film layer 1 is etched can be detected by the end point detection device. When the target film layer 1 is detected to be etched, the second stage etching is ended. The time length T2 of the second stage etching is the time length from the starting time of the second stage etching to the time when the target film layer 1 is etched.

[0052] When the time length T1 of the first stage etching is T, that is, the first stage etching stops at the critical point when the strip-shaped morphology generated by the sidewall of the photoresist layer 3 is about to be transferred to the hard mask layer 2, the time length T2 of the second stage etching can also be calculated by monitoring the etching rate V2 of the second stage etching, and the calculation formula is: T2=L1 / V2. When the time length T2 is passed, the second stage etching is ended.

[0053] After the second stage etching, the pattern of the hard mask layer 2 is consistent with the pattern of the photoresist layer 3, which can be one or more of a line, a hole, a trench, etc., and the sidewall of the hard mask layer 2 has no strip-shaped morphology or weak strip-shaped morphology.

[0054] Preferably, in order to prevent the hard mask layer 2 from being left, after the second stage etching is completed, the embodiment further includes: step S5, a second radio frequency excitation of a second fixed power is applied to the plasma reaction cavity to drive the plasma to perform a third stage etching on the hard mask layer 2, that is, to perform over-etching.

[0055] In an implementable manner, the second fixed power ranges from 100W to 800W, for example, 100W, 400W, 500W, 600W, 700W, 800W, etc. The third etching stage can provide continuous ion bombardment by applying a second radio frequency excitation of a continuous power to the plasma reaction cavity to accelerate ions, so as to completely remove the hard mask layer 2 residue and ensure that the pattern can be completely transferred to the target film layer 1.

[0056] After the third stage etching and the removal of the top photoresist layer 3, the final morphology as shown in FIG. 4 can be obtained. Figure 6 As shown in FIG. 4, the sidewall of the hard mask layer 2 (i.e. the etched hole wall) has no obvious strip-shaped phenomenon. Figure 6 As shown in FIG. 4, the sidewall of the hard mask layer 2 (i.e. the etched hole wall) has no obvious strip-shaped phenomenon.

[0057] In an implementable manner, the third stage etching (i.e. over-etching) has a time length T3 = (T1 + T2) x OE%, wherein OE% represents a set over-etching coefficient, OE% ranges from 15% to 50%, T1 represents the time length of the first stage etching, and T2 represents the time length of the second stage etching.

[0058] In the embodiment, the etching temperature of each stage etching ranges from 10°C to 60°C. For example, the temperature can be 10°C, 10.1°C, 11°C, 22°C, 28°C, 35°C, 36°C, 44°C, 49°C or 60°C, but is not limited thereto.

[0059] In the embodiment, the etching pressure of each stage etching ranges from 1mtorr to 150mtorr. For example, the etching pressure can be 1mtorr, 1.2mtorr, 20mtorr, 40mtorr, 55mtorr, 80mtorr, 100mtorr, 125mtorr, 140mtorr or 150mtorr, but is not limited thereto.

[0060] In the embodiment, when steps S3-S5 are performed, step S2 is continuously performed at the same time to maintain the plasma in the reaction chamber.

[0061] By using the etching method of the embodiment, the side wall strip phenomenon of the hard mask layer 2 in the etching process can be eliminated or weakened, and the technical problems such as difficult to simultaneously realize improving strip morphology and stable feature size transmission, ensuring etching selectivity ratio and the like in the traditional hard mask etching can be solved.

[0062] Embodiment 2 The embodiment provides an etching device for implementing the hard mask etching method of embodiment 1. The etching device mainly comprises a plasma reaction chamber, a first radio frequency generator, a second radio frequency generator and a control device. The device to be etched comprises a target film layer 1, a hard mask layer 2 and a patterned photoresist layer 3 which are sequentially stacked from bottom to top.

[0063] In the embodiment, after the device to be etched is placed into 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 on the hard mask layer 2; and before the strip morphology generated by the sidewall of the photoresist layer 3 is transmitted to the hard mask layer 2, the control device controls the second radio frequency generator to apply a second radio frequency excitation with a pulse power to the plasma reaction chamber to drive the ions in the plasma to perform the second stage etching on the hard mask layer 2 until the target film layer 1 is etched.

[0064] In the 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 working frequency of the first radio frequency generator is higher than the working frequency of the second radio frequency generator. Preferably, the working frequency of the first radio frequency generator ranges from 27 MHZ to 60 MHZ, and the working frequency of the second radio frequency generator ranges from 2 MHZ to 13 MHZ.

[0065] In the embodiment, the plasma reaction cavity is a dual-frequency plasma reaction cavity, which supports the first radio frequency generator and the second radio frequency generator to work simultaneously, and the power of the first radio frequency generator and the second radio frequency generator can be controlled independently or simultaneously.

[0066] The power of the first radio frequency generator ranges from 100 W to 1000 W, which is used to generate high-density plasma including electrons, ions and free radicals, and the power affects the particle density and thus determines the etching rate; the power of the second radio frequency generator ranges from 0 W to 1000 W, which is mainly used to accelerate ions for ion physical bombardment.

[0067] In an implementable manner, the total power of the first radio frequency generator and the second radio frequency generator does not exceed 1200 W.

[0068] In an implementable manner, the plasma reaction cavity is a dual-frequency capacitive coupling plasma reaction cavity, which is provided with an upper electrode and a lower electrode inside the reaction cavity, and the lower electrode is connected to the first radio frequency generator and the second radio frequency generator.

[0069] In an implementable manner, the plasma reaction cavity is a dual-frequency inductive coupling plasma reaction cavity, which is provided with a coil at the top of the reaction cavity and an electrode inside the reaction cavity, and the electrode is connected to the first radio frequency generator and the second radio frequency generator.

[0070] The control device in the embodiment can improve the side wall strip phenomenon of the hard mask layer 2 in the etching process by controlling the power mode of the second radio frequency generator in stages. For specific improvement principles, refer to Embodiment 1, which will not be described here.

[0071] Although the specific embodiments of the present application are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present application 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 application, and these changes and modifications all fall within the protection scope of the present application.

Claims

1. A hard mask etching method, characterized in that: include: Placing a device to be etched in a plasma reaction chamber, wherein 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; Applying a first radio frequency excitation into the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma; Applying a second radio frequency excitation of a first fixed power into the plasma reaction chamber to drive the plasma to perform a first stage etching on the hard mask layer; Before the stripe morphology generated on the sidewall of the photoresist layer is transferred to the hard mask layer, a second radio frequency excitation of pulse power is applied to the plasma reaction chamber to drive the plasma to perform a second stage of etching on the hard mask layer until the target film layer is etched.

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

3. The hard mask etching method according to claim 1, wherein: The duration T1 of the first stage etching 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 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.

4. The hard mask etching method according to claim 3, wherein: The duration of the first stage etching is T1=T, and the duration of the second stage etching is T2=L1 / V2, wherein V2 represents the etching rate of the second stage etching.

5. The hard mask etching method according to claim 1, wherein: During the second stage etching process, an endpoint detection device is used to detect whether the target film layer is etched. The duration T2 of the second stage etching is the duration from the start of the second stage etching to the etching of the target film layer.

6. The hard mask etching method according to claim 1, wherein: The first fixed power ranges from 400W to 800W; The pulse frequency of the pulse power is in the range of 1000 Hz to 5000 Hz, and the pulse duty cycle is in the range of 10% to 90%; The high power of the pulse power ranges from 400W to 800W, and the low power of the pulse power ranges from 0W to 400W.

7. The hard mask etching method according to claim 2, wherein: The over-etching duration T3 = (T1 + T2) × OE%, wherein OE% represents a 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.

8. The hard mask etching method according to claim 2, wherein: The second fixed power ranges from 100W to 800W.

9. The hard mask etching method according to any one of claims 1 to 8, wherein: The process gas includes an etching gas, an auxiliary gas and a protective gas. The etching gas is a carbon-fluorine-hydrogen 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 in sequence 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 RF generator to apply a first RF excitation to the plasma reaction chamber to excite the process gas in the plasma reaction chamber into plasma; and then controls the second RF generator to apply a second RF excitation of a first fixed power to the plasma reaction chamber to drive the plasma to perform a first stage of etching on the hard mask layer; Before the stripe morphology generated on the sidewall of the photoresist layer is transferred to the hard mask layer, the second RF generator is controlled to apply a second RF excitation of pulsed power into the plasma reaction chamber to drive the plasma to perform a second stage of etching on the hard mask layer until the target film layer is etched.

Images