Atomic layer etching with chuck zoning adjustment mechanism for enhanced uniformity control

Abstract

The invention relates to atomic layer etching for realizing enhanced uniformity control by utilizing a chuck partition adjustment mechanism. The ALE process comprises a plurality of cycles, each cycle comprising a surface modification step and a sputtering step. The system employs a chuck with independently controlled regions, which may be selectively activated during a sputtering step. And the system controller can configure different sputtering options in different ALE cycles, so that the etching rate adjustment aiming at a specific region is realized. According to the flexibility, the non-uniformity, such as the thickness difference of a target layer, of the to-be-processed substrate can be compensated by performing directional etching on the selected area.

Description

Cross Reference to Related Applications

[0001] This application claims priority to U.S. Patent Application No. 18 / 906,182, filed October 4, 2024. TECHNICAL FIELD

[0002] The present invention relates generally to semiconductor processing equipment, and in particular to systems and methods for improving Atomic Layer Etching (ALE) processes. The core of the invention is to enhance process uniformity by selectively controlling the bias voltage applied to multiple zones of a chuck supporting a substrate during the sputter step of an ALE cycle. The novel chuck design can also be applied to other plasma-based etch and deposition processes. BACKGROUND

[0003] Reactive Ion Etching (RIE) is a primary etching technique in semiconductor manufacturing. During RIE, various species including neutrals, radicals, and ions collectively contribute to the etching process. A key feature of RIE is the synergistic effect of ion and neutral fluxes, which greatly enhances the etch rate. The concept of synergism was first introduced by Coburn and Winters in their paper “Ion-and electron-assisted gas-surface chemistry - an important effect in plasma etching” published in J. Appl. Phys. (Vol. 50, pp. 3189-3196, 1979). They found that the etch rate of silicon was significantly enhanced when using argon ion beams, XeF2 neutral beams, and their combination. Efficient RIE etching requires both ion and neutral fluxes to maximize the synergistic effect. However, in modern etching processes, especially when scaling down to nanometer-sized features and structures with high aspect ratios, balancing these fluxes becomes increasingly complex. Furthermore, achieving uniformity across 300 mm wafers and consistent repeatability in production processes presents challenges.

[0004] ALE technology was developed to overcome the limitations of RIE. ALE process systems evolved from RIE process systems and are not as demanding for uniformity on 300 mm wafers. However, ALE has unique requirements due to the nature of its process steps. Karanik et al., “Overview of atomic layer etching in the semiconductor industry,” J. Vac. Sci. Technol. A33, 020802 1-14 (2015), and Lill, “Atomic layer processing: semiconductor dry etching technology,” Wiley-VCH GmbH, Boschstr. 12, 69469 Weinheim, Germany (2021), provide an overview of ALE technology. ALE enables atomic precision control of material removal and is an etching technique that utilizes sequential self-limiting reactions. An ALE process typically includes two steps: surface modification and material removal. The surface modification step forms a thin reactive layer of a predetermined thickness that is more easily removed than the unmodified material. The material removal step removes the thin reactive layer formed while leaving the underlying unmodified base material intact to reset the surface for the next cycle. Material removal can be achieved by thermal energy from elevated wafer temperature or kinetic energy from inert gas ions. George et al., U.S. Patent No. 10,208,383, discloses an isotropic process that utilizes thermal energy to remove the modified layer (i.e., thin reactive layer). When high energy ions are used, the material removal step is achieved by a sputtering process. Tan et al., U.S. Patent No. 10,727,073, discloses an anisotropic ALE process that demonstrates the versatility of the technology.

[0005] While the ALE process itself is inherently uniform, the non-uniformity of the substrate or material being processed can result in non-uniformity of the substrate surface after etching. For example, layer thickness or critical dimension variations can require directional etching to correct these irregularities. Current ALE systems lack the flexibility to selectively control etching in specific areas of the substrate during the sputtering step, which can result in suboptimal process results.

[0006] Therefore, there is an urgent need for a system that can more flexibly control the application of ion bombardment in the sputtering step of different ALE cycles to ensure that different areas of the substrate can obtain customized etching processing according to requirements. The present application introduces a chuck with independently controlled areas to provide selective bias voltage options in the sputtering step, thereby improving the uniformity and overall performance of ALE and other plasma-based processes to meet this need. SUMMARY

[0007] The present application relates to a system and method for improving ALE processes, which is to solve the problem of non-uniformity of the material to be processed by using a chuck with multiple independently controlled areas. The areas of the chuck are electrically isolated from each other, and the present application realizes selective control of the ALE process by providing bias voltage options for the sputtering step of each ALE cycle.

[0008] In some embodiments, the chuck is divided into multiple concentric areas (such as a central area, an intermediate area, and an edge area). Here, three areas are taken as an example, and the number of areas can be increased or decreased according to requirements in actual implementation. Each area is used to apply a bias voltage and is configured to be independently activated or deactivated. In other embodiments, the chuck can be divided into grid-shaped areas, each of which can be independently controlled in the sputtering step. The system provides optional bias voltage options in the sputtering step, such as only activating the central area or only activating the edge area, to meet specific etching requirements.

[0009] In some implementations, the areas are connected to a radio frequency (RF) power generator through resonators and are configured with an RF power distributor for distributing power among the areas. In other implementations, each area is connected to an independent custom waveform generator, thereby more accurately controlling ion bombardment in the sputtering step and further optimizing the etching process.

[0010] The system controller is responsible for coordinating the operation of the ALE process and determining the sequence of surface modification steps and sputtering steps according to the data of the substrate to be processed and the required output specifications. In some embodiments, the system controller will use an ALE process simulator to assist in generating a process sequence or process recipe to ensure that the etching process can compensate for the non-uniformity of the substrate and ultimately achieve the desired uniformity on the substrate.

[0011] Although the present application is mainly described for ALE processes, the chuck design has universality and can be adapted to other plasma-based processes that require independent control of substrate areas, such as various plasma etching and deposition applications. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to clearly describe the technical solutions, the following will be described with reference to the accompanying drawings:

[0013] Figure 1 Figure 1 illustrates an exemplary ALE process system including key components such as a process chamber, a gas distribution unit, a plasma source, a chuck, and a system controller.

[0014] Figure 2A Figure 2 illustrates a first implementation of a tunable chuck, which is exemplary divided into three concentric and independently controllable zones for applying bias voltage in an ALE process.

[0015] Figure 2B Figure 3 illustrates a second implementation of a tunable chuck, which is configured to have multiple independently controllable grid-like zones for applying bias voltage.

[0016] Figure 3A Figure 4 illustrates an embodiment of controlling the three zones of the chuck shown in Figure 2 using one RF power generator and one RF power distributor. Figure 2A

[0017] Figure 3B Figure 5 illustrates an embodiment of controlling the three zones of the chuck shown in Figure 2 using three independent RF power generators. Figure 2A

[0018] Figure 3C Figure 6 illustrates an embodiment of controlling the three zones of the chuck shown in Figure 2 using three independent custom waveform generators. Figure 2A

[0019] Figure 3D Figure 7 illustrates an embodiment of controlling the grid-like zones of the chuck shown in Figure 3 using multiple independent RF power generators. Figure 2B

[0020] Figure 3E Figure 8 illustrates an embodiment of controlling the grid-like zones of the chuck shown in Figure 3 using multiple independent custom waveform generators. Figure 2B

[0021] Figure 4 Figure 9 illustrates a flowchart of an ALE process incorporating a substrate non-uniformity elimination mechanism.

[0022] Figure 5 Figure 10 illustrates a sequence diagram of an ALE process, which is configured for a chuck with three independently controllable zones, providing three alternative sputtering steps.

[0023] Figure 6 Figure 11 illustrates a flowchart of an ALE process with multiple alternative sputtering steps, showing multiple options for eliminating substrate non-uniformity.

[0024] Figure 7 ​​​​​Table 1 schematically illustrates the optional sputtering configurations in the ALE process for adjusting substrate inhomogeneity. Specific Implementation

[0025] To facilitate a full understanding of the invention, specific embodiments thereof will be described in detail below. While specific details are provided for ease of explanation, any modifications and variations consistent with the technical principles of the invention are considered appropriate. Certain well-known procedures and components are described selectively only to highlight the unique features of the invention.

[0026] Terminology definition:

[0027] Anisotropic Atomic Layer Etching (ALE) is a precision etching process used in semiconductor manufacturing. This process removes material layer by layer at the atomic scale, allowing for precise control over the etching depth and morphology. ALE operates in a cyclic manner and typically includes a surface modification step (chemically modifying the surface) and a sputtering step (removing the modified surface layer by physical ion bombardment).

[0028] ALE process simulator: A software tool used by the system controller to assist in generating process sequences or recipes based on substrate data.

[0029] Bias Unit: This unit generates a controlled voltage to accelerate ion bombardment of the substrate carried by the electrostatic chuck (ESC). The electric field generated by the bias unit enhances ion bombardment, ensuring precise control over ion energy and directionality during etching.

[0030] Chuck: A component used to carry and hold the position of a substrate in semiconductor manufacturing processes.

[0031] Electrostatic chuck (ESC): A chuck that uses electrostatic force to fix the position of a substrate in a semiconductor manufacturing process, providing uniform clamping force and stability.

[0032] Gas Distribution Unit: This unit distributes process gases to the substrate surface. Gas dispersion can be achieved through injectors, showerhead structures, or lateral jetting mechanisms, thereby improving the uniformity of gas distribution.

[0033] Facility Gas Supply: The source of process gases used in process chambers. It can control and regulate the gas flow rate under controlled pressure conditions.

[0034] Options for Sputtering Step: Refers to different configurations for activating or deactivating selected regions of the chuck during the sputtering step of the ALE process.

[0035] Output Specification: Refers to the expected outcome of the ALE process, such as uniformity of the etched layer.

[0036] Plasma Source: In some embodiments, a plasma source is used to generate plasma for processes such as etching or deposition. As examples, plasma includes Inductively Coupled Plasma (ICP), transformer coupled plasma (TCP), and Capacitively Coupled Plasma (CCP).

[0037] Process Chamber: An enclosed environment used to perform semiconductor manufacturing processes such as etching or deposition.

[0038] Process Recipe: Refers to a predefined set of steps for the ALE process, which can be customized based on substrate data and output specifications.

[0039] Process System: Refers to an integrated device used in semiconductor manufacturing to perform various processes such as deposition, etching, or surface modification.

[0040] Reactive Ion Etching (RIE): A plasma etching technique that combines physical ion bombardment with chemical reactions to remove portions of a substrate material. RIE enables anisotropic etching, which is crucial for complex microfabrication processes.

[0041] Resonator: A device or component that produces resonance at a specific RF, often used for RF impedance matching in semiconductor processing equipment applications.

[0042] RF Power Divider: A component that divides RF power to individual regions of the chuck.

[0043] RF Power Generator: A device that generates RF energy to sustain plasma in semiconductor manufacturing processes such as etching or deposition.

[0044] Substrate: The substrate used in the manufacture of semiconductor devices, usually a silicon wafer.

[0045] System Controller: The central control unit that coordinates and manages the operation of the process system to ensure the efficient and precise execution of semiconductor processes.

[0046] Tailored Waveform Generator: In some implementations, this generator can generate customized electrical waveforms to optimize ion energy distribution and improve etching or deposition performance.

[0047] Transmission line: In RF technology, a conductor used to transmit RF signals with minimal loss and distortion. Transmission lines ensure efficient power transfer in semiconductor manufacturing processes such as etching or deposition.

[0048] Zones in the Chuck: These refer to independently controllable areas of the chuck, each capable of providing bias voltage during the sputtering process. Electrical isolation is used between these zones to allow for independent control of the bias voltage.

[0049] like Figure 1 As shown, the gas distribution unit 104 draws gas from the gas tank 106 through the gas manifold 105. Depending on the system design, the gas distribution unit 104 can be configured as a shower head or an injector. Before the gas is introduced into the process chamber 101, it is mixed through the gas manifold 105. The gas tank 106 typically includes components such as mass flow controllers (MFCs), gas pressure regulators, particle filters, gas mixers, and safety sensors. Valves 135 and 137 are provided between the gas tank 106 and the gas manifold 105 to control the flow of the first gas 108 and the second gas 110, respectively. Two gas lines are used as an example here; in actual implementation, more gas lines can be installed as needed. A valve 116 is provided between the gas manifold 105 and the gas distribution unit 104 to regulate the gas flow rate entering the process chamber 101. The gas tank 106 is connected to a central gas supply device 107.

[0050] In the lower part of chamber 101, chuck 121 is used to support substrate 120 during the process. Chuck 121 is typically an electrostatic chuck (ESC) suitable for etching applications. To increase ion energy during the etching process (especially for etching high aspect ratio structures), bias unit 119 is used to accelerate ions generated in the plasma, causing them to move towards the substrate surface. Depending on the design, bias unit 119 may be an RF power generator connected to chuck 121 via a DC blocking capacitor, or a specially designed custom waveform generator. Within the framework of this invention, multiple RF power generators or multiple custom waveform generators may be used.

[0051] The gas (including reaction byproducts) in chamber 101 is discharged through pump 124. A vacuum valve 122 is installed upstream of pump 124 to control the gas discharge rate. The discharged gas is introduced into exhaust port 126 via exhaust line 125. The chamber pressure is controlled by balancing the gas injection rate and the discharge rate: the pressure is adjusted using a proportional-integral-derivative (PID) control loop based on the reading of pressure gauge 127.

[0052] The ALE process operates in a cyclic manner and typically involves two gases. These two gases are delivered in two separate steps: a surface modification step and a sputtering step. These two steps are often referred to as a "semi-cycle," together forming a complete ALE cycle. The surface modification step is usually referred to as "Step A," and the sputtering step is usually referred to as "Step B."

[0053] The operation of the process system 100 is managed by a system controller 128 (including a computer and various software modules). The process system 100 may include an ALE recipe generator 130 for generating process recipes for the ALE process. The ALE recipe generator 130 takes into account the characteristics and output specifications of the substrate to be processed. Substrate data may include (but is not limited to) critical dimensions and the thickness of the target layer on the substrate. The ALE recipe generator 130 may also include a process simulator to ensure that the generated recipe can compensate for various non-uniformities of the substrate to be processed by simulating the ALE process.

[0054] like Figure 2A A top view of the chuck in Embodiment 200 is shown, comprising three regions: a central region 204, an intermediate region 206, and an edge region 208. Each region is designed to provide an independently controlled bias voltage during the sputtering step. In this step, ions are selectively accelerated by a bias voltage based on their radial position within the chamber in the plasma, to bombard the substrate surface upon reaching the desired energy. In some implementations, one or more regions may not be biased during a specific sputtering step of a selected ALE cycle. Electrical isolation between regions is achieved by providing independent electrodes at the bottom of the chuck.

[0055] Figure 3A A connection scheme 302 for the three regions of the chuck of embodiment 200 is shown. Here, the center region 204, the intermediate region 206, and the edge region 208 are connected to the RF power generator 312 through a resonator 314. An RF power distributor 316 distributes the RF power among the three regions according to the instructions of the system controller 128.

[0056] Figure 3B A connection scheme 304 for the three regions of the chuck of embodiment 200 is shown. Here, the three regions (204, 206, 208) are connected to respective independent RF power generators (318, 324, 328) through independent resonators (320, 326, 330), respectively.

[0057] Figure 3C A connection scheme 306 for the three regions of the chuck of embodiment 200 is shown. Here, the three regions (204, 206, 208) are connected to respective independent custom waveform generators (332, 334, 336).

[0058] Figure 2B A top view of the chuck of embodiment 202 is shown, in which the substrate is divided into a plurality of grid-like regions, labeled as region 1, region 2, region 3, region 4,..., region i,..., region n. Each region can provide an independently controlled bias voltage to the substrate, so that the ion state of the plasma in the sputtering step can be adjusted in selected cycles of the ALE process. Figure 3D A connection scheme 308 for the plurality of regions of the chuck of embodiment 202 is shown, in which each region (region 1, region 2,..., region i,..., region n) is connected to a respective independent RF power generator (338, 340,..., 342,..., 344) through a resonator (339, 341,..., 343,..., 345), respectively. Figure 3E A connection scheme 310 for the plurality of regions of the chuck of embodiment 202 is shown, in which the above combination of RF power generators and resonators is replaced by custom waveform generators (346, 348,..., 350,..., 352).

[0059] Figure 4An exemplary ALE process 400 incorporating a non-uniformity control mechanism is shown. Process 400 begins at step 402, where system controller 128 optionally receives data regarding the substrate to be processed and analyzes the data to determine the desired etch performance (e.g., to compensate for non-uniformities in the substrate). For example, system controller 128 can determine that additional etching is required in the central region of the substrate to correct for thickness differences in the target layer. At step 404, system controller 128 determines the counts for steps A and B based on the desired etch performance. In one implementation, an ALE simulator can be used to determine an ALE process recipe for each individual region. System controller 128 can then integrate the recipes for the various regions and configure the corresponding sputtering steps while maintaining consistency in the surface modification steps.

[0060] One key feature of the present application is that step B has multiple selectable configurations (as shown in Table 1 for embodiment 200) in different ALE cycles. B1 mode: all three regions (204, 206, 208) have their bias voltages activated, resulting in uniform sputtering across the substrate; B2 mode: only the central region 204 has its bias voltage activated, resulting in enhanced sputtering in the central region of the substrate; B3 mode: only the edge region 208 has its bias voltage activated, resulting in focused sputtering in the edge region of the substrate. The above three modes are merely examples, and more modes can be designed even if the chuck only has three regions; in other embodiments, the number of chuck regions can be increased or decreased, and the operating modes can be adjusted accordingly.

[0061] At step 406, step A of the ALE cycle is performed: chemically active neutral particles in the plasma diffuse to the substrate surface and modify it. This step is typically self-limiting and only occurs while the surface is exposed to the neutral particles. To ensure the desired effect of the ALE process, ion bombardment of the substrate surface is typically avoided during step A, so the bias unit is typically inactive.

[0062] At step 408, system controller 128 selects one of the options (B1, B2, or B3) for step B of the current ALE cycle. At step 410, the selected sputtering step is performed, removing the modified layer formed in step A. Depending on the selected option, the removal process can be targeted to specific regions of the substrate. Note that because of the self-limiting nature of the surface modification step, the thickness of the modified layer in regions that were not subjected to ion bombardment during the selected sputtering step will not increase in subsequent ALE cycles.

[0063] At step 412, system controller 128 updates the step counts. At step 414, system controller 128 determines whether the ALE process is complete: if so, process 400 ends; if not, process 400 returns to step 406 and repeats.

[0064] Figure 5An exemplary ALE process sequence 500 is shown, which starts with three cycles of step 502, each cycle performing step A and step B; then two cycles of step 504, each cycle performing step A and step B1; and finally two cycles of step 506, each cycle performing step A and step B. This sequence can result in a larger etch amount in the center region of the substrate than in the edge region, forming a customized etch profile to address the particular non-uniformity of the substrate.

[0065] Figure 6 A flow chart of an ALE process 600 based on the chuck of embodiment 202 is shown. Process 600 starts at step 602, where system controller 128 optionally receives data of the substrate to be processed, which can include but is not limited to the thickness of the target layer on the substrate, the thickness of the mask layer, and the critical dimension of the mask layer. The desired output specification of the ALE process can be stored in a memory unit of the system controller. In step 604, system controller 128 determines the count of step A and step B for each region. To compensate for the non-uniformity of the substrate to be processed, the count of step B can be different for different regions. In step 606, system controller 128 generates a process recipe, which includes a plurality of ALE cycles, each cycle having a uniform step A and the option of step B determined in step 604. In step 608, the ALE process is performed according to the generated process recipe.

[0066] It is important to note that although the present application is primarily described in the context of ALE processes, the chuck design is versatile and can be adapted to other plasma-based processes that require independent control of substrate regions, such as various plasma etching and deposition applications.

Claims

1. A process system, characterized in that, include: The process chamber is configured to have a vacuum environment; A gas distribution unit is used to introduce gas into the chamber; A plasma source, connected to an RF power generator, is used to generate plasma in the chamber; A chuck for supporting a substrate during a process, wherein the chuck includes multiple regions, each region being used to apply a bias voltage and configured to be independently activated or deactivated; and A system controller, configured to coordinate the operation of the process system to execute an ALE process according to a process recipe comprising multiple cycles, each cycle including a surface modification step and a sputtering step, wherein... The sputtering step includes multiple options, and different ALE cycles can select different sputtering step options. These options are used to selectively activate or deactivate selected areas of the chuck.

2. The system according to claim 1, wherein, The multiple regions are connected to an RF power generator via a resonator, and the system is equipped with an RF power divider for distributing power to each region.

3. The system according to claim 1, wherein, Each of the multiple regions is connected to its corresponding RF power generator via its own resonator.

4. The system according to claim 1, wherein, Each of the multiple regions is connected to its own custom waveform generator.

5. The system according to claim 1, wherein, Several options for the sputtering step include: Activate the selected area at the center of the substrate while deactivating all other areas; and Activate the selected area at the edge of the substrate while deactivating all other areas.

6. The system according to claim 1, wherein, The multiple regions are electrically isolated from each other.

7. The system according to claim 1, wherein, The system controller determines the sequence of ALE processes based on the data of the substrate to be processed and the output specifications of the ALE process.

8. The system according to claim 7, wherein, The system controller determines the sequence using an ALE process simulator.

9. The system according to claim 1, wherein, The multiple regions are arranged concentrically.

10. The system according to claim 1, wherein, The multiple regions are arranged in a grid pattern.

11. A method for processing a substrate using ALE technology, characterized in that, include: a. Providing a process chamber with a vacuum environment, wherein a plasma source is capable of generating plasma within the chamber; b. Place the substrate on a chuck in the chamber, wherein the chuck includes multiple regions, each region being used to apply a bias voltage and configured to be independently activated or deactivated; c. Perform the surface modification steps via the system controller; d. Select one of several options for multiple selectable activation regions in the sputtering step via the system controller; e. Execute the selected sputtering step option via the system controller; and f. Repeat steps c through e until the ALE process is complete.

12. The method according to claim 11, wherein, Several options for the sputtering step include: Activate the selected area at the center of the substrate while deactivating all other areas; and Activate the selected area at the edge of the substrate while deactivating all other areas.

13. The method according to claim 11, wherein, The method further includes: the system controller generating a process recipe based on the data of the substrate to be processed and the output specifications of the ALE process.

14. The method according to claim 11, wherein, The multiple regions are connected to an RF power generator via a resonator, and power is distributed to each region by configuring an RF power divider.

15. The method according to claim 11, wherein, Each of the multiple regions is connected to its corresponding RF power generator via its own resonator.

16. The method according to claim 11, wherein, Each of the multiple regions is connected to its own custom waveform generator.

17. An electrostatic chuck for supporting a substrate in a process chamber, characterized in that, The electrostatic chuck includes multiple independently controllable regions, wherein the multiple regions are electrically isolated from each other, and each region can independently provide a bias voltage to the substrate.

18. The electrostatic chuck according to claim 17, wherein, The regions are arranged in a concentric or grid pattern.

19. The electrostatic chuck according to claim 17, wherein, Each of the multiple regions is connected to its corresponding RF power generator via its own resonator.

20. The electrostatic chuck according to claim 17, wherein, Each of the multiple regions is connected to its own custom waveform generator.

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