Method for etching the etching layer
The plasma-assisted ALD method for sidewall passivation in semiconductor etching addresses vertical profile maintenance and reduces sidewall curvature, enhancing etching precision and chamber throughput by using tungsten oxide films formed at controlled temperatures, thus overcoming the limitations of high-temperature passivation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- LAM RES CORP
- Filing Date
- 2026-04-06
- Publication Date
- 2026-07-07
AI Technical Summary
Existing etching methods for semiconductor devices face challenges in maintaining a vertical profile with minimal lateral CD growth while avoiding profile trade-offs such as reduced mask selectivity, decreased etching rate, and feature capping/clogging, particularly when high temperatures are required for sidewall passivation, which can damage semiconductor devices.
A method involving plasma-assisted atomic layer deposition (ALD) is used to deposit a protective film on sidewalls during etching, employing tungsten hexafluoride (WF6) and oxygen plasma at controlled temperatures below 150°C to form a non-conformal tungsten oxide film, followed by alternating etching and deposition cycles to achieve precise feature etching.
This approach maintains a vertical profile with reduced sidewall curvature, prevents damage to semiconductor devices, and enhances throughput by performing etching and ALD in the same plasma processing chamber, ensuring high aspect ratio etching without compromising device integrity.
Smart Images
Figure 2026113643000001_ABST
Abstract
Description
Background Art
[0001] [Cross - reference to Related Applications] This application claims the benefit of priority of U.S. Application No. 62 / 755,707, filed on November 5, 2018, which is incorporated herein by reference for all purposes.
[0002] The present disclosure relates to a method of forming semiconductor devices on a semiconductor wafer. The present disclosure particularly relates to etching concave features in a stacked etching layer.
[0003] In the formation of semiconductor devices, an etching layer may be etched to form contact holes or trenches. Some semiconductor devices may be formed by etching a silicon oxide (SiO2)-based layer.
Summary of the Invention
[0004] To achieve the above and in accordance with the objectives of the present disclosure, a method of etching features in a stack including a dielectric material on a substrate is provided. In step (a), an etching plasma is generated from an etching gas, the stack is exposed to the etching plasma, and the features in the stack are partially etched. In step (b), an atomic layer deposition process is provided after step (a) to deposit a protective film on the sidewalls. The atomic layer deposition process includes a plurality of cycles, and each cycle includes exposing the stack to a first reaction gas containing WF6, where the first reaction gas is adsorbed on the stack, and exposing the stack to a plasma formed from a second reaction gas, where the plasma formed from the second reaction gas reacts with the adsorbed first reaction gas to form a protective film on the stack. In step (c), steps (a) to (b) are repeated at least once.
[0005] In another embodiment, an apparatus for etching features into a stack is provided. A process chamber is provided. A substrate support is located inside the process chamber. A gas inlet supplies gas to the process chamber. A gas source supplies gas to the gas inlet and includes an etching gas source, a WF6 gas source, and a reaction gas source. An exhaust pump is provided to evacuate gas from the process chamber. Electrodes supply RF power to the process chamber. At least one power supply supplies power to the electrodes. A controller is controllably connected to the gas source and at least one power supply and comprises at least one processor and a computer-readable medium. The computer-readable medium comprises computer code for bringing the stack to etching by a first plurality of cycles, each of which includes partially etching the stack and depositing layers on the stack by atomic layer deposition by providing a second plurality of cycles. Each cycle of the second set of cycles includes flowing a WF6-containing gas from a WF6 gas source, adsorbing the WF6-containing gas onto the laminate, stopping the flow of the WF6-containing gas, and exposing the laminate to a plasma of a reaction gas from a reaction gas source, the plasma converting the adsorbed WF6-containing gas into an atomic layer deposition layer.
[0006] These and other features of the present disclosure will be described in more detail in the following embodiments for carrying out the invention of the present disclosure, in conjunction with the following figures. [Brief explanation of the drawing]
[0007] This disclosure is provided for illustrative purposes only, not limitation, and in the figures of the attached drawings, the same reference numerals mean the same elements.
[0008] [Figure 1] A high-level flowchart of one embodiment.
[0009] [Figure 2A] A schematic diagram of a laminate processed according to one embodiment. [Figure 2B] A schematic diagram of a laminate processed according to one embodiment. [Figure 2C] A schematic diagram of a laminate processed according to one embodiment. [Figure 2D] A schematic diagram of a laminate processed according to one embodiment. [Figure 2E] A schematic diagram of a laminate processed according to one embodiment. [Figure 2F] A schematic diagram of a laminate processed according to one embodiment. [Figure 2G] A schematic diagram of a laminate processed according to one embodiment.
[0010] [Figure 3] A schematic diagram of an etching chamber that may be used in one embodiment.
[0011] [Figure 4] A schematic diagram of a computer system that may be used when implementing one embodiment of the system. [Modes for carrying out the invention]
[0012] Herein, this disclosure will be described in detail with reference to several exemplary embodiments, as shown in the accompanying drawings. Many specific details are included in the following description to provide a full understanding of this disclosure. However, it will be apparent to those skilled in the art that this disclosure may be carried out without some or all of these specific details. In other examples, well-known process steps and / or structures are not described in detail so as not to make this disclosure unnecessarily complex.
[0013] High aspect ratio etching requires maintaining a vertical profile with minimum lateral CD (critical dimension) growth (CD curvature). Furthermore, profile trade-offs such as reduced mask selectivity, decreased etching rate, or feature capping / clogging must be avoided. CD curvature is caused by etching of the feature sidewalls. To reduce CD curvature, a passivation layer may be placed on the sidewalls. Some methods deposit sidewall passivation at temperatures above 250°C to provide uniform passivation. Such high temperatures can damage semiconductor devices.
[0014] In one embodiment, Figure 1 is a high-level flowchart of that embodiment. This embodiment may be used to process the laminate 200 as shown in Figure 2A. Figure 2A is a cross-sectional view of the laminate 200 with the substrate 204 positioned beneath an etching layer 208 positioned beneath a mask 212. In this embodiment, the mask 212 is a hard mask, such as a plasma-enhanced chemical vapor deposition (PECVD) amorphous carbon mask. In this embodiment, the etching layer 208 is a dielectric layer made of a dielectric material such as silicon oxide (SiO2). One or more layers (not shown) may be placed between the substrate 204 and the etching layer 208. One or more layers (not shown) may also be placed between the etching layer 208 and the mask 212.
[0015] The features are partially etched into the etching layer 208 (step 104). An example recipe for partially etching the features into the etching layer 208 (step 104) provides a pressure of 5–50 mTorr. Radio frequency (RF) power is provided at a frequency of 60 megahertz (MHz) with a power of 500 watts (W)–10 kilowatts (kW) and at a frequency of 400 kilohertz (kHz) with a power of 1 kW–30 kW. The RF power is pulsed between these power levels. An etching gas is provided. The etching gas contains oxygen (O2), fluorocarbons, and / or hydrofluorocarbons. The etching gas is plasma-generated by the RF power. The plasma provides radical ions responsible for high aspect ratio etching. Such plasma is referred to herein and in the claims as etching plasma. Once partial etching is complete, the flow of etching gas is stopped. The RF power is stopped or reduced so as not to generate plasma. Figure 2B is a cross-sectional view of the stack 200 after feature 216 has been partially etched.
[0016] Following partial etching (step 104), an atomic layer deposition process is provided to deposit a protective film on the sidewalls of feature 216 (step 108). The atomic layer deposition process (step 108) includes a periodic process consisting of multiple cycles. In the first stage of one cycle of the atomic layer deposition process (step 108), the laminate 200 is exposed to a first reaction gas containing tungsten hexafluoride (WF6) (step 112). A gas flow containing WF6 at 0.5 to 200 sccm is provided. In this embodiment, the first reaction gas is not plasma-activated. As a result, this process is plasma-free. The deposition temperature is maintained at a temperature of 40°C to 80°C. The first reaction gas adsorbs onto the surface of the laminate 200. The flow of the first reaction gas is stopped after 3 seconds.
[0017] Without being bound by theory, it is assumed that WF6 chemically reacts with SiO2 to form a layer of tungsten silicide oxide (SiOW). Figure 2C is a cross-sectional view of the laminate 200 after the formation of the SiOW layer 220 on the surface (including the sidewalls) of feature 216. The SiOW layer 220 is not drawn to an accurate scale, but is shown thicker to make the SiOW layer 220 easier to understand.
[0018] After the first reaction gas has been adsorbed (step 112), a first purge is provided to purge the first reaction gas (step 116). In this example, the first purge is provided by flowing O2 through the plasma processing chamber. Other embodiments may have a purge gas of pure nitrogen (N2), or a mixture of N2 and argon (Ar), or pure Ar. An O2 purge gas can generate plasma immediately after the first purge. The purge gas flow is stopped after 5 seconds. The first purge completely removes any unadsorbed tungsten (W) before the plasma is formed in the next step.
[0019] After the first purging is complete (step 116), the laminate 200 is exposed to a plasma formed from a second reaction gas (step 120). The laminate 200 and the chamber are maintained at a temperature below 150°C. A second reaction gas is provided. In this example, the second reaction gas is O2. The second reaction gas is plasma-generated by providing excitation energy with a power of 200 W to 20 kW and a frequency of 60 MHz. A bias RF signal is provided with a power of 200 W to 50 kW and a frequency of 100 kHz to 27 MHz. The plasma disappears after 3 seconds.
[0020] After the stack 200 is exposed to the plasma formed from the second reaction gas (step 120), a second purge is provided (step 124) to purge the remaining plasma ion radicals. In this example, the second purge is provided without RF power for forming the appropriate plasma by flowing a second reaction gas into the plasma processing chamber. The second reaction gas is used to purge the remaining plasma. Other embodiments may have other purge gases. Some embodiments may stop the RF power. The purge gas flow is stopped after 5 seconds. The second purge completely removes the plasma ion radicals from the plasma processing chamber. Thereafter, the atomic layer deposition cycle is repeated. In this example, the atomic layer deposition process (step 108) is performed for 3 to 100 cycles.
[0021] FIG. 2D is a cross-sectional view of the stack 200 after a plurality of cycles of an atomic layer deposition process (step 108) have been provided to form a protective film 224 on the sidewalls of the feature 216. In this example, the protective film 224 includes tungsten oxide. The protective film 224 is not drawn to an exact scale. Since the atomic layer deposition process (step 108) uses plasma rather than a plasma-free heat treatment, the protective film 224 is not as conformal as a film deposited using a plasma-free heat treatment. Also, the protective film 224 may not be as high quality as a film deposited using a plasma-free heat treatment. Since the protective film 224 is not conformal, in this embodiment, the protective film 224 does not extend to the bottom of the feature 216.
[0022] After the atomic layer deposition process (step 108) is completed, feature 216 is further etched (step 128). An example of a recipe for further etching the feature into the etch layer 208 provides a pressure of 5 to 50 mTorr. The RF power is provided at a frequency of 60 MHz with a power of 2 kW to 8 kW, and at a frequency of 400 kHz with a power of 4 kW to 25 kW. The RF power is pulsed between these power levels. An etching gas is provided. The etching gas includes O2, fluorocarbon, and / or hydrofluorocarbon. The etching gas is converted into an etching plasma by the RF power. FIG. 2E is a cross-sectional view of the stack 200 after feature 216 has been further etched.
[0023] If the etching of the feature is not completed (step 132) (i.e., the feature is not etched to the final depth), the process returns to the atomic layer deposition process (step 108). The atomic layer deposition process (step 108) is repeated. FIG. 2F is a cross-sectional view of the stack 200 after the atomic layer deposition process (step 108) has been repeated and a new protective film 228 has been formed. The new protective film 228 is not conformal because it is formed using plasma.
[0024] Feature 216 is further etched (step 128). The cycle of the atomic layer deposition process (step 108) and the further etching (step 128) are repeated until the etching of feature 216 is completed (step 132). FIG. 2G is a cross-sectional view of the stack 200 after feature 216 has been etched to the final depth.
[0025] The above embodiment provides sidewall passivation that prevents or reduces feature curvature by using plasma during the atomic layer deposition process (step 108). When a thermal atomic layer deposition process is used to deposit tungsten, a deposition temperature or chamber temperature higher than 250°C would be used. Temperatures higher than 250°C can damage the semiconductor device being formed. An atomic layer deposition process (step 108) using plasma to deposit a tungsten-containing protective film provides a low-quality protective film with low conformability. However, tungsten-containing non-conformable protective films have been shown to be sufficient to prevent or reduce sidewall curvature.
[0026] In various embodiments, the atomic layer deposition process (step 108) is carried out at a deposition temperature or chamber temperature below 100°C. In various embodiments, the plasma formed by the second reaction gas provides either oxidation or nitriding. If the plasma by the second reaction gas provides oxidation, in various embodiments, the second reaction gas contains an oxygen-containing component (e.g., at least one of oxygen (O2), ozone (O3), carbonyl sulfide (COS), carbon dioxide (CO2), sulfur dioxide (SO2), and carbon monoxide (CO)). Argon (Ar) or krypton (Kr) may also be used as a carrier gas. If the plasma by the second reaction gas provides nitriding, the second reaction gas contains a nitrogen-containing component (e.g., at least one of nitrogen (N2) and ammonia (NH3)). Ar or Kr may also be used as a carrier gas. If the second reaction gas contains N2, the second reaction gas may further contain H2.
[0027] In various embodiments, the hard mask may be formed from amorphous carbon, boron-doped carbon, boron-doped silicon, metal-doped carbon, or polysilicon. In various embodiments, the etching layer 208 is a silicon oxide-based dielectric layer. In various embodiments, the etching layer 208 is a stack of different material layers. In various embodiments, at least one layer of the etching layer 208 is a layer of dielectric material. In various embodiments, the atomic layer deposition process (step 108) provides a non-conformal protective film 228 that does not reach the bottom of the feature 216. In various embodiments, the RF power may be a continuous wave. In other embodiments, the RF power may be pulsed power. In various embodiments, the pulsed RF power may have a pulse repetition rate between 100 Hz and 5 kHz. In various embodiments, the pulsed RF power may have a duty cycle between 5% and 95%.
[0028] Furthermore, since the atomic layer deposition process (step 108) uses plasma rather than heat treatment, it may be carried out in situ in the same plasma processing chamber as the etching process (step 128). Because all steps are carried out in the same plasma processing chamber, the throughput is increased by providing an in-situ atomic layer deposition process (step 108).
[0029] In an exemplary embodiment, Figure 3 is a schematic diagram of an etching reactor that may be used in one embodiment. In one or more embodiments, the plasma processing chamber 300 comprises a gas distribution plate 306 providing a gas inlet and an electrostatic chuck (ESC) 308 inside an etching chamber 349 surrounded by chamber walls 352. Inside the etching chamber 349, the laminate 200 is placed on the ESC 308. The ESC 308 also serves as a substrate support. An edge ring 309 surrounds the ESC 308. A gas source 310 is connected to the etching chamber 349 through the gas distribution plate 306. In this embodiment, the gas source 310 includes an etching gas source 312, a WF6 gas source 316, and a reaction gas source 318. An ESC temperature controller 350 is connected to a chiller 314. In this embodiment, the chiller 314 provides a coolant to a flow path 315 inside or near the ESC 308 to cool the ESC 308. A radio frequency (RF) source 330 provides RF power to the lower electrode. In this embodiment, ESC308 is the lower electrode. In an exemplary embodiment, 400 kHz and 60 MHz power supplies constitute the RF source 330. In this embodiment, the upper electrode and gas distribution plate 306 are grounded. In this embodiment, one generator is provided for each frequency. In other embodiments, other arrangements of the RF source and electrodes may be used. The controller 335 is controllably connected to the RF source 330, the exhaust pump 320, and the gas source 310. An example of such an etching chamber is the Flex® etching system manufactured by Lamb Research Corporation in Fremont, California. The processing chamber is a CCP (capacitively coupled plasma) reactor or an ICP (inductively coupled plasma) reactor.
[0030] Figure 4 is a high-level block diagram showing a computer system 400 suitable for implementing the controller 335 used in the embodiment. This computer system may have many physical forms, ranging from integrated circuits, printed circuit boards, and small handheld devices to large supercomputers. The computer system 400 may comprise one or more processors 402, and further comprise an electronic display device 404 (for displaying images, text, and other data), main memory 406 (e.g., random access memory (RAM)), storage device 408 (e.g., hard disk drive), removable storage device 410 (e.g., optical disc drive), user interface device 412 (e.g., keyboard, touch screen, keypad, mouse, or other pointing device), and communication interface 414 (e.g., wireless network interface). The communication interface 414 allows software and data to be transferred between the computer system 400 and external devices via a link. The system may also comprise a communication infrastructure 416 (e.g., communication bus, crossover bar, or network) to which the aforementioned devices / modules are connected.
[0031] The information transferred through the communication interface 414 may be in the form of an electronic signal, electromagnetic signal, optical signal, or other signal that the communication interface 414 can receive through a signal-transmitting communication link, and may be implemented using wiring or cables, optical fibers, telephone lines, mobile phone links, radio frequency links, and / or other communication paths. Through such a communication interface, one or more processors 402 may receive information from the network or output information to the network in the process of carrying out the steps of the method described above. Furthermore, embodiments of the method may be executed in a single processor or in cooperation with remote processors that share part of the processing, via a network such as the Internet.
[0032] The term “non-temporary computer-readable medium” generally refers to main memory, secondary memory, removable storage, and storage devices (hard disks, flash memory, disk drive memory, CD-ROMs, and other forms of persistent memory), and should not be interpreted to include temporary objects such as carriers or signals. Examples of computer code include machine code generated by a compiler and files containing higher-level code executed by a computer using an interpreter. Computer-readable medium may also be computer code embodied in a carrier and transmitted by computer data signals representing a sequence of instructions executable by a processor.
[0033] While this disclosure has been described in terms of several exemplary embodiments, there are many variations, modifications, reorders, and various alternative equivalents that fall within the scope of this disclosure. It should also be noted that there are many other ways of carrying out the methods and apparatus of this disclosure. Therefore, the following appended claims are intended to be construed as encompassing all such variations, modifications, reorders, and various alternative equivalents that fall within the true spirit and scope of this disclosure.
Claims
1. A method for etching features into a laminate containing dielectric material on a substrate, (a) A step of generating etching plasma from etching gas, exposing the laminate to the etching plasma, and partially etching features in the laminate, (b) A step of providing an atomic layer deposition process after (a) to deposit a protective film on the sidewall, wherein the atomic layer deposition process includes a plurality of cycles, each cycle being: (i) WF 6 Exposing the laminate to a first reaction gas containing, wherein the first reaction gas is adsorbed onto the laminate, (ii) Exposing the laminate to a plasma formed from a second reaction gas, wherein the plasma formed from the second reaction gas reacts with the adsorbed first reaction gas to form the protective film on the laminate, a step comprising: (c) A step of repeating (a) to (b) at least once, Methods that include...
2. The method according to claim 1, The step of providing the atomic layer deposition process further includes maintaining the deposition temperature below 150°C.
3. The method according to claim 1, The method wherein the second reaction gas comprises at least one of an oxygen-containing component and a nitrogen-containing component.
4. The method according to claim 1, The second reaction gas is COS, CO 2 CO, SO 2 , O 2 , N 2 NH 3 , and O 3 A method that includes at least one of the following.
5. The method according to claim 1, The aforementioned laminate is SiO 2 Methods that include...
6. The method according to claim 5, The lamination method further includes a hard mask.
7. The method according to claim 6, The hard mask comprises one or more amorphous carbon, boron-doped carbon, boron-doped silicon, metal-doped carbon, and polysilicon.
8. The method according to claim 1, The process providing the atomic layer deposition process is carried out for 2 to 100 cycles.
9. The method according to claim 1, Each cycle further, The first reaction gas is purged after the laminate has been exposed to the first reaction gas and before it has been exposed to the plasma formed by the second reaction gas. After exposing the laminate to the plasma formed from the second reaction gas, the plasma formed from the second reaction gas is purged. Methods that include...
10. The method according to claim 1, A method wherein the step of exposing the laminate to the first reaction gas is a plasma-free step.
11. The method according to claim 1, Steps (a) to (c) are methods performed in situ.
12. A device for etching features into a stack, Processing chamber and The substrate support in the processing chamber, A gas inlet for supplying gas to the processing chamber, A gas source for supplying the gas to the gas inlet, Etching gas source and WF 6 a gas source, A reaction gas source, including a gas source, An exhaust pump for discharging gas from the processing chamber, An electrode for supplying RF current to the processing chamber, At least one power source for supplying power to the electrode, A controller controllably connected to the gas source and the at least one power source, wherein the controller is At least one processor, A computer-readable medium comprising computer code for causing etching of a stack by a first plurality of cycles, wherein each of the first plurality of cycles is Partially etching the aforementioned layer, The method includes providing a second set of cycles to deposit layers in the stack by atomic layer deposition, wherein each cycle of the second set of cycles is The aforementioned WF 6 WF from gas source 6 Discharging the contained gas, The WF 6 Adsorbing the contained gas, The aforementioned WF 6 Stopping the flow of the contained gas, The laminate is exposed to the plasma of the reaction gas from the reaction gas source, wherein the plasma is adsorbed WF 6 A controller including a computer-readable medium that includes a method for converting a contained gas into an atomic layer deposition layer, A device equipped with the following features.
13. The apparatus according to claim 12, further, An apparatus comprising a chiller for cooling the substrate support.
14. The apparatus according to claim 12, The apparatus further comprises a computer-readable medium and computer code for cooling the substrate support to a temperature of 150°C or less.
15. The apparatus according to claim 12, WF 6 The apparatus is such that the process of flowing the contained gas is a plasma-free process.
16. The apparatus according to claim 12, The reaction gas source is COS, CO 2 CO, SO 2 , O 2 , N 2 NH 3 , and O 3 A device that is at least one source of [something].
17. The apparatus according to claim 12, The apparatus provides the atomic layer deposition process, which is carried out in 2 to 100 cycles.
18. The apparatus according to claim 12, Each cycle of the second plurality of cycles further, The aforementioned WF 6 After stopping the flow of the contained gas and before exposing the stack to the plasma formed by the second reaction gas, the first reaction gas is purged. After exposing the laminate to the plasma formed from the second reaction gas, the plasma formed from the second reaction gas is purged. A device including a device.