Radical assisted ignition plasma system and method

Abstract

Plasma assisted methods and apparatus are disclosed. The methods and apparatus can be used to provide activated species formed in a remote plasma cell to a reaction chamber to assist in igniting a plasma within a reaction chamber coupled to the remote plasma cell.

Description

Technical Field

[0001] This disclosure generally relates to methods for forming apparatus structures and systems for forming said structures. More specifically, this disclosure relates to methods using plasma forming apparatus and systems having plasma reactors. Background Technology

[0002] During the manufacture of electronic devices, fine feature patterns can be formed on the substrate surface by patterning the substrate surface and etching the material from the substrate surface using processes such as plasma-assisted etching. As the density of devices on the substrate increases, it becomes increasingly desirable to form features with smaller dimensions.

[0003] Photoresist is commonly used to pattern a substrate surface prior to etching. The method of forming a pattern in photoresist is to apply a layer of photoresist to the substrate surface, mask the photoresist surface, expose the unmasked portion of the photoresist to radiation (e.g., ultraviolet light or an electron beam), and remove a portion of the photoresist (e.g., the unmasked portion or the masked portion), while leaving a portion of the photoresist on the substrate surface.

[0004] After the removal step, excess residual photoresist can remain at the bottom of the photoresist feature. This excess photoresist can cause deviations from the desired pattern, meaning it will migrate from the photoresist to the underlying layer during subsequent etching.

[0005] Recently, patterns with resolutions exceeding those typically achieved using only photoresist have been formed by using spacers; this technique involves a spacer-defined double patterning (SDDP) process. In SDDP, a feature pattern is formed as a core material using photoresist or spin-on carbon (SOC) on a size that may correspond to or be close to the resolution limit of, for example, photoresist processes. Sidewall spacers are then formed on the sidewalls of the core material. Subsequently, the core material is removed while retaining the sidewall spacers, and the remaining sidewall spacers serve as a mask for etching the underlying layer. Using this technique, fine patterns can be formed in the underlying layer, with widths smaller than the resolution limit of photoresist processes, because the distance between the spacers can be smaller than the width of the sacrificial film (e.g., photoresist).

[0006] To precisely control the critical dimension (CD) of features formed using patterned core materials (such as photoresist), dimensional control of the core material is required. For example, trimming techniques using plasma processing can be used to remove portions of the core material, such as excess material at the bottom of the feature.

[0007] Typically, during the conditioning process, plasma is generated in the reaction chamber. Argon is often used to ignite the plasma because it is relatively easy to ignite. The power used to ignite the plasma depends on several factors, such as the type of gas used to generate the plasma, the pressure within the reaction chamber, and the spacing between the electrodes. Therefore, it is usually necessary to adjust the plasma ignition power to suit various conditioning conditions.

[0008] Unfortunately, some conditions may involve igniting the plasma at relatively high power. High-power conditions during the plasma ignition step can cause undesirable damage to the core material. Furthermore, typical plasma ignition processes can be relatively unstable and unreliable due to other factors. Therefore, there is a need to improve the methods and systems used for igniting the plasma and / or for conditioning the core material.

[0009] Any discussion of the problems and solutions presented in this paragraph is included in this disclosure solely for the purpose of providing background information and should not be construed as an admission that any or all of the topics discussed were known at the time of making this invention. Summary of the Invention

[0010] Various embodiments of this disclosure relate to plasma-assisted methods and apparatus. While the ways in which various embodiments of this disclosure address the shortcomings of existing methods and systems will be discussed in more detail below, in general, various embodiments of this disclosure provide improved methods for igniting plasma within a reaction chamber. The various techniques described herein provide reliable methods for igniting plasma within a reaction chamber and / or methods for reducing damage to materials (e.g., patterned materials, such as photoresists) on substrate surfaces.

[0011] According to at least one embodiment of this disclosure, a method (e.g., forming patterned features on a substrate) includes forming patterned features on a substrate. An exemplary method may include the steps of: providing a substrate in a reaction chamber; forming a first activated species using a remote plasma unit; providing the first activated species to the reaction chamber for a first time interval; and, after initiating the step of providing the first activated species to the reaction chamber, forming a second activated species in the reaction chamber for a second time interval. The first and second time intervals may overlap, such that the first activated species facilitates the ignition of plasma used to form the second activated species. The substrate may include features formed from, for example, a carbon-containing material, such as one or more of photoresist, spin-on carbon (SOC) material, and carbon hard mask (CHM) material. The second activated species may be used to trim the features. The step of forming the second reactive species may include providing an oxygen-containing gas to the reaction chamber. The oxygen-containing gas may include, for example, one or more gases selected from the group comprising O2, CO2, and N2O. The remote plasma unit may be supplied with an inert gas, such as argon, to form the first activated species. The oxygen-containing gas may not be supplied to the remote plasma unit. A first gas can be supplied to a remote plasma unit to form a first activated species. A second gas can be supplied to the reaction chamber to form a second activated species. The first gas and the second gas can be different.

[0012] According to another exemplary embodiment of this disclosure, a method for trimming features on a substrate is provided. The method for trimming features on a substrate may include: providing a substrate in a reaction chamber; forming a first activated species using a remote plasma unit; providing the first activated species to the reaction chamber for a first time interval; after initiating the step of providing the first activated species to the reaction chamber, forming a second activated species in the reaction chamber for a second time interval, and trimming the feature using the second activated species. The first time interval and the second time interval may overlap, such that the first activated species facilitates the ignition of plasma used to form the second activated species. The feature may be formed from, for example, a carbon-containing material, such as one or more of photoresist, spin-on carbon (SOC) material, and carbon hard mask (CHM) material. The step of forming the second reactive species may include providing an oxygen-containing gas to the reaction chamber. The oxygen-containing gas may include, for example, one or more gases selected from the group comprising O2, CO2, and N2O. The remote plasma unit may be supplied with an inert gas, such as argon, to form the first (e.g., argon) activated species. The oxygen-containing gas may not be supplied to the remote plasma unit.

[0013] According to other additional examples of this disclosure, a deposition apparatus configured to perform the methods described herein is provided.

[0014] According to other exemplary embodiments of this disclosure, the structure includes layers and / or features formed according to the methods described herein.

[0015] These and other embodiments will become apparent to those skilled in the art from the following detailed description of certain embodiments with reference to the accompanying drawings; the invention is not limited to any particular embodiment disclosed. Attached Figure Description

[0016] Exemplary embodiments of this disclosure can be more fully understood by referring to the detailed description and claims when considered in conjunction with the following illustrative figures.

[0017] Figure 1 A timing sequence diagram is shown.

[0018] Figure 2 and 3 A reactor system according to at least one embodiment of the present disclosure is shown.

[0019] Figure 4 A timing sequence diagram according to at least one embodiment of the present disclosure is shown.

[0020] Figure 5 The results of an ignition test using a method according to at least one embodiment of the present disclosure are shown.

[0021] Figure 6 and 7 A comparison of photoresist damage between a method according to at least one embodiment of the present disclosure and another process is shown.

[0022] Figure 8 The ignition delay is shown.

[0023] Figure 9 The ignition power varies with the pressure inside the reaction chamber.

[0024] It should be understood that the elements in the figures are for simplicity and clarity only and are not necessarily drawn to scale. For example, some elements in the figures may be enlarged relative to other elements to help improve the understanding of the embodiments described in this disclosure. Detailed Implementation

[0025] Although certain embodiments and examples are disclosed below, those skilled in the art will understand that the invention extends beyond the specific embodiments and / or uses disclosed herein, as well as obvious modifications and equivalents thereof. Therefore, it is intended that the scope of the invention be limited to the specific disclosed embodiments described below.

[0026] This disclosure generally relates to plasma-assisted methods and apparatus. As described in more detail below, exemplary methods can be used to facilitate plasma ignition within a reaction chamber; reduce, for example, damage to material on a substrate surface during plasma ignition; improve the uniformity of material removal on a substrate surface; and so on. The methods and apparatus described herein can be used to trim features on a substrate surface.

[0027] In this disclosure, depending on the context, "gas" can include materials that are gaseous at room temperature and normal pressure, vaporized solids, and / or vaporized liquids, and can consist of a single gas or a mixture of gases. Non-process gases, i.e., gases introduced without passing through gas distribution components such as spray heads, other gas distribution devices, etc., can be used to, for example, seal the reaction space. These non-process gases can include sealing gases, such as rare gases. The term "inert gas" refers to a gas that does not participate in a chemical reaction and / or a gas that excites precursors when RF power is applied.

[0028] As used herein, the term "substrate" can refer to any one or more underlying materials that can be used to form a device, circuit, or film, or on which a device, circuit, or film can be formed. A substrate can include a bulk material such as silicon (e.g., single-crystal silicon), other group IV materials such as germanium, or compound semiconductor materials such as GaAs, and can include one or more layers applied above or below the bulk material. Additionally, a substrate can include various features, such as recesses, lines, etc., formed within or on at least a portion of the layers of the substrate. According to exemplary aspects of this disclosure, one or more of the features are formed of a carbon-containing material, such as one or more of photoresist, spin-on carbon (SOC) materials, and carbon hard mask (CHM) materials. Features can be formed as a cover layer, an adhesion layer, or a film, etc.

[0029] In some embodiments, "membrane" refers to a layer extending in a direction perpendicular to the thickness direction that covers the entire target or related surface, or simply refers to a layer covering the target or related surface. In some embodiments, "layer" refers to a structure or membrane or non-membrane structure formed on a surface with a certain thickness. A membrane or layer may consist of discrete individual membranes or layers with certain properties, or it may consist of multiple membranes or layers, and the boundaries between adjacent membranes or layers may be clear or unclear and may or may not be created based on the physical, chemical and / or any other properties, formation processes or sequences and / or functions or purposes of adjacent membranes or layers.

[0030] Furthermore, in this disclosure, any two numbers of a variable may constitute a working range of the variable, and any indicated range may include or exclude endpoints. Additionally, any indicated variable value (whether or not it is indicated by “about”) may refer to an exact value or an approximate value and include equivalent values, and in some embodiments may refer to the mean, median, representative value, multi-value, etc. Furthermore, in this disclosure, in some embodiments, the terms “comprising,” “consisting of,” and “having” independently mean “generally or broadly comprising,” “including,” “substantially consisting of,” or “consisting of.” In this disclosure, in some embodiments, the meaning of any definition does not necessarily exclude the common and conventional meaning.

[0031] In some embodiments of this disclosure, “continuous” may refer to one or more of the following: without loss of vacuum, without interruption of the timeline, without any material insertion step, without change of processing conditions, immediately thereafter, as the next step, or without the insertion of discrete physical or chemical structures between two structures other than two structures.

[0032] Now refer to the attached diagram. Figure 1 A conventional timing sequence 100 for the trimming process is shown. The timing sequence 100 includes the following steps: start (step 101), raise the sensor (step 102), introduce gas into the reaction chamber (step 103), set the pressure (step 104), stabilize the gas flow (step 105), ignite the plasma (step 106), provide RF power (step 107), provide the reaction gas (step 108), perform trimming (step 109), purify the reaction chamber (step 110), and reduce the pressure inside the reaction chamber (step 111).

[0033] During step 101, the substrate may be loaded onto the sensor in the reaction chamber. Once the substrate is loaded onto the sensor, the gate valve may be closed and the sensor may be moved to the operating position (step 102).

[0034] During step 103, an inert gas (e.g., argon) may be introduced into the reaction chamber. During step 104, the pressure may be increased to the desired operating pressure, and the flow rate of the inert gas may be set to the desired level. Additionally, a rare gas (e.g., helium) may be supplied to the reactor containing the reaction chamber to provide a gas curtain between the reaction space and another section of the reactor (e.g., the loading / unloading space). The gas flow rate and the pressure within the reaction chamber may be stabilized for a period of time (step 105).

[0035] During step 106, the plasma within the reaction chamber is ignited. During this time, relatively high radio frequency (RF) power (e.g., approximately 90 W to 130 W) can be applied, for example, to a parallel plate within the reaction chamber to bombard the plasma. Then, during step 107, the power is reduced to process or operational levels. In step 108, a reactive gas (oxygen) and additional or diluting gas (e.g., nitrogen) are supplied to the reaction chamber. During step 109, activated reactant species are used to trim the characteristics. At step 110, the plasma generator power is shut off and the reaction chamber is purged. Then, during step 111, the pressure within the reaction chamber is reduced.

[0036] like Figure 1 As shown, during step 106, the power supplied to the reaction chamber to ignite the plasma is relatively high compared to the power level supplied to the reaction chamber during the trimming process. This relatively high power can lead to damage to features and / or the layers or films forming those features. Furthermore, the relatively high power can result in relatively high inhomogeneities within the wafer during the trimming process, and / or relatively high feature heights after the trimming process. As described below, embodiments of this disclosure provide improved apparatus and methods to reduce power requirements, improve plasma ignition, enhance plasma stability, and, particularly, reduce feature and / or layer damage during the plasma ignition step.

[0037] Figure 2 and 3 A reactor system 200 according to an exemplary embodiment of the present disclosure is shown. The reactor system 200 includes a reactor 202 with a reaction chamber 204, a sensor 206, a gas distribution device 208, a gate valve 210, and a remote plasma unit (RPU) 212. Figure 2 The reactor system 200 is shown when the gate valve 210 is in the closed position, and Figure 3 The reactor system 200 is shown when the gate valve 210 is in the open position.

[0038] Reactor 202 may include any suitable reactor. For example, a reactor system with a reactor suitable for use as reactor 202 may be obtained from ASM International N.V.

[0039] The sensor 206 is capable of vertical movement to load and unload the substrate 214. Lifting pins and a robotic arm (not shown) are available for loading and unloading the substrate from the surface of the sensor 206. The sensor 206 may also form electrodes for generating direct plasma within the reaction chamber 204.

[0040] The gas distribution device 208 may include, for example, a nozzle gas distribution device. Furthermore, the gas distribution device 208 may form electrodes for forming direct plasma within the reaction chamber 204.

[0041] Gate valve 210 can be used to control the flow rate of activated species between RPU 212 and reaction chamber 204. Gate valve 210 can be opened during the direct plasma ignition step and can be opened or closed during processing (e.g., trimming) steps.

[0042] RPU 212 may include any suitable remote plasma unit. According to an example of this disclosure, RPU 212 is coupled to an inert gas source 216 such that inert gas from the inert gas source can be supplied to RPU 212, and RPU 212 can generate activated species from the inert gas. Examples of suitable inert gases include argon. The power used to generate the remote plasma can be any power suitable for producing plasma.

[0043] Figure 4 Exemplary timing sequences 400 according to various exemplary embodiments of the present disclosure are illustrated. Timing sequence 400 can be used to perform various methods described herein, including methods for forming patterned features on a substrate and methods for trimming features on a substrate as described herein. System 200 can be used to perform the timing sequences and / or methods described herein.

[0044] The timing sequence 400 includes the following steps: starting (step 401), raising the sensor (step 402), introducing gas into the reaction chamber (step 403), setting the pressure (step 404), stabilizing the airflow (step 405), remotely generating activated species (step 406), providing RF power to the direct plasma and trimming it (step 407), purifying the reaction chamber (step 408), and reducing the pressure inside the reaction chamber (step 409).

[0045] Similar to step 101, during step 401, the substrate can be loaded onto the sensor in the reaction chamber. Once the substrate is loaded onto the sensor, the reaction chamber gate valve can be closed, and the sensor can be moved to the operating position (step 402).

[0046] During step 403, an inert gas, such as argon, may be introduced into the RPU, for example, RPU 212. Additionally, gases such as dilution gases (e.g., nitrogen or argon, labeled “additional gas”), reactants (e.g., one or more of O2, CO2, and N2O) and inert gases (RC - inert) may be supplied to the reaction chamber—for example, reaction chamber 204.

[0047] During step 404, the pressure may be increased to the desired operating pressure, and the gas flow rates to the reaction chamber and to the RPU may be set to desired levels. During step 404, a rare gas (e.g., helium) may also be supplied to the reactor to provide a gas curtain, for example, between the reaction space and another section of the reactor (e.g., the loading / unloading section of the reactor). The gas flow rates and pressure within the reaction chamber and / or RPU may be stabilized for a period of time (step 405).

[0048] During step 406, power is supplied to the RPU and / or activated species from the RPU are introduced into the reaction chamber. Activated species (e.g., first) from the RPU are provided to the reaction chamber to ignite the direct plasma within the reaction chamber at a lower power and / or in a more stable manner than without activated species from the RPU. In some cases, the RPU may be continuously on, and activated species may be provided to the reaction chamber by opening a gate valve between the RPU and the reaction chamber. Alternatively, as shown, the RPU may be on only during steps 406 and optionally 407.

[0049] During step 407, processes such as trimming are performed within the reaction chamber. During this step, power is supplied to electrodes (e.g., gas distribution device 208 and / or sensor 206 (if only one electrode is energized, the other electrode may be grounded)) to form a second activated species within the reaction chamber. During step 407, the power used to ignite the direct plasma within the reaction chamber can be approximately the same as the power used to maintain the plasma during step 407 (e.g., in the range of approximately 10%).

[0050] In step 408, the power supply to the direct plasma generator is turned off, and optionally the power supply to the RPU is turned off and the reaction chamber is purged. Figure 4 As shown, the reaction chamber can be purged by flowing one or more RPU inert gases into the RPU and / or by flowing one or more gases (in any combination) containing reactants, additional gases, and reaction chamber (RC) inert gases into the reaction chamber. Subsequently, during step 409, the pressure inside the reaction chamber can be reduced. Table 1 below shows exemplary process conditions for steps 406 and 407.

[0051] Table 1 below shows exemplary process conditions for steps 406 and 407.

[0052]

[0053] Table 1

[0054] The power rating indicated above for a 300mm wafer can be converted to W / cm². 2(Watts per unit area of ​​wafer), which can be applied to wafers with different diameters such as 200mm or 450mm. Substrate temperature can be considered as the temperature of the reaction space during the process.

[0055] Figure 5 The advantages of the exemplary method compared to conventional methods that do not include free radical-assisted ignition are shown. Figure 5 The results in Table 1 show the ignition test results of 20 ignition tests. RAI indicates that the test was performed using radical-assisted ignition (RAI), and w / o RAI indicates that the test was performed without RAI. As shown, the use of radical-assisted ignition significantly reduces many false ignitions (e.g., failure to form plasma), reduces or eliminates ignition delay (e.g., ignition delay greater than or equal to 0.1 seconds), and / or provides good ignition (in plasma form) under the conditions shown in Table 1 above.

[0056] Figure 6 and 7 The results of the methods described herein are shown when used to trim features (e.g., photoresist features) on the surface of a substrate. Figure 6 As shown, using the method described herein, the amount of feature (e.g., photoresist) damage (etching) can be significantly reduced in the absence of reactants. Figure 7 The method described herein demonstrates that, in the absence of reactants, 1σ (standard deviation) within wafer uniformity with characteristic defects can be significantly reduced.

[0057] Figure 8 Ignition delay is shown, defined as a delay time exceeding 0.1 seconds. Without RAI, the ignition delay frequency is approximately 100%. However, according to an example of the invention, with RAI, for example using the conditions described in Table 1, the ignition delay is zero or approximately zero percent.

[0058] Figure 9 The diagram shows that the ignition power typically increases with increasing pressure within the reaction chamber, up to approximately 360 Pa. In the example shown, under the conditions indicated in Table 1, the power saturates at approximately 20 W.

[0059] The exemplary embodiments of this disclosure described above do not limit the scope of the invention, as these embodiments are merely examples of embodiments of the invention. Any equivalent embodiments are intended to be included within the scope of the invention. In fact, those skilled in the art will readily recognize various modifications to this disclosure beyond the embodiments shown and described herein, such as alternative applicable combinations of the described elements. Such modifications and embodiments are also intended to be within the scope of the appended claims.

Claims

1. A method of forming patterned features on a substrate, the method comprising the steps of: providing the substrate within a reaction chamber; providing an inert gas to a remote plasma unit; providing a reactive gas to the reaction chamber; forming a first activated species from the inert gas by generating a remote plasma within the remote plasma unit; providing the first activated species to the reaction chamber for a first time interval; and forming a second activated species from the reactive gas within the reaction chamber using direct plasma formed within the reaction chamber for a second time interval, wherein the first time interval and the second time interval overlap; and wherein the reactive gas is not supplied to the remote plasma unit, wherein the substrate comprises features, the method further comprising the step of trimming the features using the second activated species.

2. The method of claim 1, wherein, The inert gas is argon.

3. The method of claim 1, wherein the features comprise carbon.

4. The method of claim 3, wherein the features comprise one or more of photoresist, spin-on carbon (SOC) material, and carbon hard mask (CHM) material.

5. The method of claim 1, wherein the step of forming the second activated species comprises providing an oxygen-containing gas to the reaction chamber.

6. The method of claim 5, wherein the oxygen-containing gas comprises one or more gases selected from the group comprising O2, CO2, and N2O.

7. The method of claim 5, wherein the oxygen-containing gas is not supplied to the remote plasma unit.

8. A method of trimming features on a substrate, the method comprising the steps of: providing the substrate within a reaction chamber; providing an inert gas to a remote plasma unit; providing a reactive gas to the reaction chamber; forming a first activated species from the inert gas by generating a remote plasma within the remote plasma unit; providing the first activated species to the reaction chamber for a first time interval; forming a second activated species from the reactive gas within the reaction chamber using direct plasma formed within the reaction chamber for a second time interval, wherein the first time interval and the second time interval overlap; and trimming the features using the second activated species, wherein the reactive gas is not supplied to the remote plasma unit.

9. The method of claim 8, wherein the features comprise carbon.

10. The method of claim 8, wherein the features comprise one or more of photoresist, spin-on carbon (SOC) material, and carbon hard mask (CHM) material.

11. The method of claim 8, wherein the reactive gas is an oxygen-containing gas.

12. The method of claim 11, wherein the oxygen-containing gas comprises one or more gases selected from the group comprising O2, CO2, and N2O.

13. The method of claim 8, wherein the pressure within the reaction chamber during the step of forming the second activated species is between 200 Pa and 600 Pa.

14. The method of claim 8, wherein the first activated species comprises an argon activated species.

15. A system configured to perform any of the methods of claims 1-14.

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