Oxidation Transformation in Atomic Layer Deposition

Abstract

A method for processing a substrate is described. A first reactant in a gaseous phase is introduced into a reaction chamber having the substrate therein. The first reactant is allowed to adsorb onto the surface of the substrate. After the flow of the first reactant is stopped, the unreacted portion of the first reactant is purged from the reaction chamber. While the first reactant is adsorbed onto the surface of the substrate, a second reactant is introduced into the reaction chamber in a gaseous phase. The second reactant comprises dihydrogen (H2), a nitrogen-containing reactant, and an oxygen-containing reactant in a ratio of 1:1:1. A plasma is ignited based on the second reactant. The surface of the substrate is exposed to the plasma. The plasma is extinguished. Gas is purged from the reaction chamber.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 692,015, filed on June 29, 2018, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to a method for reducing impurities in an atomic layer deposition process, and more particularly to an improved oxidation conversion in an atomic layer deposition process. Background Art

[0004] Silicon-containing films have various physical, chemical, and mechanical properties and are frequently used in semiconductor manufacturing processes. For example, silicon nitride films can be used as diffusion barriers, gate insulators, sidewall spacers, and encapsulation layers, and silicon oxide can be used as a dielectric insulator. In various applications, silicon-containing films are deposited by chemical vapor deposition (CVD) or by atomic layer deposition (ALD). However, some depositions of silicon-containing films may be non-conformal. As device dimensions continue to shrink, there is an increasing need to tailor the deposition profile of silicon-containing films with high aspect ratio topologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Some embodiments are shown by way of example and not limitation in the figures of the accompanying drawings.

[0006] Figure 1 is a flow chart of a method for processing a substrate according to an exemplary embodiment.

[0007] Figure 2 is a flow chart of a method for processing a substrate according to another exemplary embodiment.

[0008] Figure 3 is a block diagram illustrating a system for processing a substrate according to an exemplary embodiment.

[0009] Figure 4 is a graph illustrating complete and incomplete reactions according to an exemplary embodiment.

[0010] Figure 5 FTIP spectrum showing the effect of the presence of H2 gas in the conversion gas on the impurity content in the film according to an exemplary embodiment.

[0011] Figure 6 FTIR spectrum showing the effect of the presence of H2 gas in the conversion gas on the main Si-O peak in the film according to an exemplary embodiment. DETAILED DESCRIPTION

[0012] The following description includes systems, methods, techniques, instruction sequences, and computer program products that embody illustrative embodiments of the present invention. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments. However, it will be apparent to those skilled in the art that the embodiments may be practiced without these specific details.

[0013] A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to any data described below and in the accompanying drawings that constitute a part of this document: Copyright © LAM Research Corporation, 2018. All rights reserved.

[0014] In this application, the terms "semiconductor wafer," "wafer," "substrate," "wafer substrate," and "partially fabricated integrated circuit" are used interchangeably. Those skilled in the art will understand that the term "partially fabricated integrated circuit" can refer to a silicon wafer at any of a number of stages of integrated circuit fabrication. The terms "chamber" and "reactor" are also used interchangeably.

[0015] Wafers include features such as trenches, contacts, and vias where insulation needs to be deposited. As features shrink in size (e.g., below 50nm) or increase in aspect ratio (>5:1), depositing high-quality insulating materials becomes more challenging. Some approaches to address these issues involve chemical vapor deposition (CVD), atomic layer deposition (ALD), and plasma-enhanced atomic layer deposition (PEALD).

[0016] PEALD and ALD are cyclic deposition processes in which a substrate is continuously exposed to various chemicals. Typically, the substrate is exposed to a first chemical or combination of chemicals to form an adsorbed layer. Excess first chemical or chemicals is removed by pumping or purging. A second chemical or combination of chemicals is introduced to react with the first material to form a deposited material layer. The two chemicals or combinations of chemicals are specifically selected to react with each other to form the deposited material layer.

[0017] In ALD processes, the tendency of two chemical groups to react is exploited to drive film formation, typically at elevated deposition temperatures. In PEALD processes, plasma energy is used to enhance the reaction between the two chemical groups or to provide other desired film properties. As such, PEALD offers the advantage of lower processing temperatures, enabling deposition on thermally unstable materials. It also reduces equipment costs and can increase throughput. However, PEALD processes can result in poorer film quality.

[0018] Current PEALD processes for depositing SiO2 typically involve the use of Ar / O2 or N2O / O2 plasmas, or some combination thereof. These plasmas are used to affect the second major step of the PEALD SiO2 cycle; namely, creating a hydroxyl-terminated surface for further reaction with silicon-containing precursors. Ar / O2 plasmas are effective in producing high-quality films at low temperatures (due to the advantages of Ar-containing plasmas, such as improved plasma density and ion bombardment). As a result, this process condition is often used for patterning applications.

[0019] However, a major drawback of Ar-containing plasmas is their limited operating window relative to RF power. Above certain watts, plasma and arcing are known to occur within the chamber, severely limiting the application of this process. In contrast, plasmas composed of N2O / O2 gases are known to be more robust, allowing the use of higher-power plasmas. However, this increased process window is associated with reduced oxidation and impurity removal efficiency.

[0020] Alternative plasma chemistries present additional drawbacks and challenges. For example, for certain gases (e.g., O2), the plasma can be difficult to ignite quickly. Certain gas compositions can be expensive or difficult to obtain (e.g., O2 / He, O2 / Ne). Other chemicals can be difficult to deliver due to their physical properties or chemical instability or reactivity (e.g., H2O, O3, H2O2), significantly increasing equipment costs.

[0021] To address the aforementioned challenges, the present disclosure describes an alternative atomic layer deposition (ALD) process based on modified oxidation. This improved oxidation method involves introducing dihydrogen gas (H2) into the plasma. During the atomic layer deposition of SiO2 on the substrate, the surface hydrosilane groups are converted to the corresponding hydrosiloxane-terminated surface. The addition of hydrogen to the N2O / O2 plasma significantly improves the resulting electrical film performance compared to existing 400°C films. This 200°C drop in the necessary operating temperature can save significant costs.

[0022] Additionally, adding H2 to the N2O plasma produces denser / higher quality films. Adding H2 to the O2 plasma has the advantage of reducing oxidation of the underlying metals (if they have reducible metal oxides). If metal oxides are already present, they can also be reduced by adding H2.

[0023] Other benefits of using H2 / O2 in a deposition / etch / deposition process, or when using a suppressive chemistry as part of a PEALD process, include the virtual elimination of F and N from the film. Because the H penetrates deeply into the film, one can maintain the suppressive effect while still removing buried residual chemistry after the chemistry has served its purpose.

[0024] In some exemplary embodiments of the present disclosure, dihydrogen (H2) is added to a plasma gas composition consisting of a 1:1 N2O / O2 mixture. This 1:1:1 mixture (H2:N2O:O2) eliminates the IR band originating from organic film impurities. Furthermore, under these conditions, both breakdown field and leakage current characteristics are improved compared to the baseline.

[0025] Figure 1 is a flow chart of a method for processing a substrate according to an exemplary embodiment. Method 100 begins with operation 102, wherein a substrate having recessed features is provided to a chamber. In operation 104, a dose of a first precursor (also referred to as a reactant) is flowed into the chamber. The first precursor is adsorbed onto the surface of the substrate, including in the recessed features. In the case where the deposited film comprises silicon, the first precursor is typically a silicon-containing reactant. In the case where the deposited film comprises metal, the first precursor is typically a metal-containing reactant. Next, the reaction chamber is purged at operation 106. In some embodiments, purging comprises purging the reaction chamber with a non-reactive gas. Alternatively or additionally, purging can comprise evacuating the reaction chamber by performing an evacuation. In this case, the pressure in the reaction chamber during the evacuation is significantly lower than the pressure during the reactant delivery. The purpose of this purging operation 106 is to remove all or substantially all of the first precursor from the reaction chamber. In some embodiments, the purge / purging may be less than complete, wherein only a portion of the first precursor is removed from the reaction chamber. For example, Figure 4 Complete and incomplete reactions are shown. In a complete reaction, silane 402 reacts with the precursor to form molecular structure 404. However, incomplete reaction results in a molecular structure 406 with aminosilane on the substrate surface. Subsequent oxidation may only partially convert the silane. This partial conversion results in the incorporation of amine, amide, carboxylic acid, ester, and alcohol functional groups, as well as C, N, and H, into the film.

[0026] Refer again Figure 1In operation 108, a second reactant is flowed into the reaction chamber. The second reactant is typically dihydrogen (H2), a nitrogen-containing reactant, and / or an oxygen-containing reactant. Each of the first and second reactants can also be a mixture of reactants. In one example, the second reactant can include dihydrogen, oxygen, and nitrous oxide in a ratio of 1:1:1. In the case where more than one reactant is delivered to the reaction chamber simultaneously, the reactants can be mixed before delivery (e.g., in a separate mixing vessel) or after delivery (e.g., in the reaction chamber itself).

[0027] In operation 110, a plasma is ignited in the reaction chamber and exposed to the substrate surface. In various embodiments, operations 108 and 110 occur at least partially simultaneously. In some cases, a second reactant may be pre-flowed into the reaction chamber in 108 before the plasma ignition occurs in 110. In certain examples, the second reactant is provided continuously. In other embodiments, operations 108 and 110 begin simultaneously. In alternative embodiments, the second reactant is flowed into the reaction chamber in 110 and then purged / purged from the reaction chamber before the pulsed plasma ignition occurs in operation 110.

[0028] Next, in operation 112, the plasma is extinguished and the reaction chamber is purged. As mentioned with respect to the purge in operation 106, this may include purging and / or evacuating the reaction chamber. In some cases, this purge / sweep may be optional, although using a post-plasma purge can help promote the formation of high-quality films. Operations 104-112 typically result in the deposition of a monolayer of material, although in some embodiments, less than a monolayer of material may be deposited. As indicated by the dashed arrows, these steps may be repeated multiple times to form a film of the desired thickness.

[0029] As shown, the plasma characteristics can have a significant impact on the deposited film. In many embodiments, the plasma is a capacitively coupled plasma (CCP). However, other types of plasmas, such as inductively coupled plasmas, can also be used. Various types of plasma generators can be used, including RF, DC, and microwave plasma generators. The plasma can be a direct plasma (i.e., a plasma generated in the reaction chamber) or a remotely generated plasma.

[0030] Figure 2 2 is a flow chart of a method for processing a substrate according to another exemplary embodiment. In operation 202 (feeding process), a silane precursor is introduced into the substrate in the reactor. It should be noted that when using other reactors and plasma sources, the operating conditions will vary significantly. The following is an example of parameter ranges for the feeding process of a four-station CCP reactor:

[0031] Gas: Ar (1-30slm), N2 (0-30slm), H2 (0-5slm), silane precursor,

[0032] Pressure: 0.6-6 Torr,

[0033] Temperature: 150-650℃.

[0034] In operation 204 (the sweep process), byproducts and excess reactants are swept from the chamber. The following is an example of a series of parameters during the sweep process:

[0035] Gas: Ar (1-30slm), N2 (0-30slm), H2 (0-5slm), O2 (0.5-15slm), N2O (0.5-5slm), Pressure: 0.6-6 Torr,

[0036] Temperature: 150-650℃.

[0037] In operation 206 (oxidation process), the surface of the substrate is oxidized and cleaned with RF plasma. The following is an example of a series of parameters for the oxidation process:

[0038] Gas: Ar (1-30slm), N2 (0-30slm), H2 (0-5slm), O2 (0.5-15slm), N2O (0.5-5slm),

[0039] RF power: 500W-5000W,

[0040] Pressure: 0.6-6 Torr,

[0041] Temperature: 150-650℃.

[0042] In operation 208 (sweep process), residual oxidant is scavenged from the chamber. The following are examples of parameters for the sweep process:

[0043] Gas: Ar (1-30slm), N2 (0-30slm), H2 (0-5slm), O2 (0.5-15slm), N2O (0.5-5slm), Pressure: 0.6-6 Torr,

[0044] Temperature: 150-650℃.

[0045] Figure 3 is a block diagram illustrating a system for processing a substrate according to an exemplary embodiment. Suitable apparatus for performing the disclosed methods generally include hardware for performing the process operations and a system controller having instructions for controlling the process operations according to the present invention. For example, in some embodiments, the hardware may include one or more PEALD processing stations included in a processing tool.

[0046] As shown, reactor 300 includes a process chamber 324 that surrounds the other components of the reactor and is used to contain a plasma generated by, for example, a capacitor-type system including a showerhead 314 operating in conjunction with a grounded heater block 320. A high-frequency RF generator 304 is connected to a matching network 306, and a low-frequency RF generator 302 is connected to the showerhead 314. These RF generators are capable of igniting the plasma as described herein. The power and frequency provided by matching network 306 are sufficient to generate a plasma from the process gas. In one exemplary embodiment, both an HFRF generator and a LFRF generator are used. In a typical process, the high-frequency RF component is typically between approximately 2 and 60 MHz; in preferred embodiments, the HF component is approximately 13.56 MHz or 27 MHz. The low-frequency LF component is typically between approximately 0.050 and 2 MHz; in a specific embodiment, the LF component is approximately 350 kHz.

[0047] Within the reactor, a wafer pedestal 318 supports a substrate 316. The pedestal typically includes a chuck, forks, or lift pins to hold and transfer the substrate during and between deposition and / or plasma processing reactions. The chuck can be an electrostatic chuck, a mechanical chuck, or various other types of chucks useful in industry and / or research.

[0048] Process gases are introduced via inlet 312. A plurality of source gas lines 310 are connected to a manifold 308. The gases may or may not be premixed. Appropriate valves and mass flow control mechanisms are employed to ensure the correct gases are delivered during the deposition and plasma treatment phases of the process. In the case where the chemical precursors are delivered in liquid form, a liquid flow control mechanism is employed. The liquid is then vaporized and mixed with the other process gases during its transport through the manifold, which is heated above its vaporization point, before reaching the deposition chamber.

[0049] The process gas leaves the chamber 300 via outlet 322. A vacuum pump 326 (e.g., a one or two stage mechanical dry pump and / or a turbomolecular pump) typically draws the process gas out and maintains a suitable low pressure within the reactor through a closed loop controlled flow restriction device (e.g., a throttle valve or a swing valve).

[0050] Those skilled in the art will recognize that other variations of the reactor 300 can be used to apply the presently described methods. For example, the reactor 300 can include a powered pedestal instead of the sparger 314.

[0051] Figure 5 FTIR spectra showing the effect of the presence of H2 gas in the conversion gas on the impurity content in the film according to an exemplary embodiment.

[0052] Figure 6FTIR spectrum showing the effect of the presence of H2 gas in the conversion gas on the main Si-O peak in the film according to an exemplary embodiment.

[0053] from Figure 5 and Figure 6 As can be seen in Figure 5, the addition of H2 to the oxidation step reduces impurities in ALDSiO2 using aminosilane chemistry; little effect on the Si-O bands is observed.

[0054] Traditional methods to achieve this goal primarily include a) increasing chamber temperature, b) increasing RF power, and c) changing process chemistry. All three strategies have significant drawbacks ranging from higher CoC to process instability.

[0055] Although the embodiments have been described with reference to specific exemplary embodiments, it is apparent that various modifications and changes may be made to these embodiments without departing from the broader scope of the present disclosure. Therefore, the description and drawings should be considered illustrative rather than restrictive. The drawings forming a part thereof show, by way of illustration and not limitation, specific embodiments in which the present subject matter may be practiced. The illustrated embodiments are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom so that structural and logical substitutions and changes may be made without departing from the scope of the present disclosure. Therefore, this detailed description should not be understood in a limiting sense, and the scope of the various embodiments is limited only by the appended claims and the full scope of equivalents to which these claims are assigned.

[0056] Here, such embodiments of the subject matter of the present invention may be referred to individually and / or collectively by the term "invention" merely for convenience, and it is not intended that the scope of the present application be automatically limited to any single invention or inventive concept (if more than one is actually disclosed). Therefore, although specific embodiments have been illustrated and described herein, it should be understood that any arrangement calculated to achieve the same purpose can replace the specific embodiments shown. This disclosure is intended to cover all modifications or variations of the various embodiments. By reading the above description, combinations of the above embodiments, and other embodiments not specifically described herein will be apparent to those skilled in the art.

Claims

1. A method for treating a substrate to reduce impurities in an oxidative conversion process during atomic layer deposition, the method comprising: delivering a first reactant gas into a reaction chamber having the substrate therein, a reactive portion of the first reactant gas being adsorbed onto a surface of the substrate; purging an unreacted portion of the first reactant gas from the reaction chamber, the unreacted portion of the first reactant gas not being adsorbed onto the surface of the substrate; delivering a second reactant gas into the reaction chamber, the second reactant gas comprising hydrogen (H2) gas, a nitrogen-based reactant gas, and an oxygen-based reactant gas; igniting a plasma within the reaction chamber using the second reactant gas, the plasma being exposed to the surface of the substrate; extinguishing the plasma; as well as The reaction chamber is purged after extinguishing the plasma.

2. The method according to claim 1, wherein The plasma gas consists of a mixture of H2, nitrous oxide (N2O) and oxygen (O2).

3. The method according to claim 1, further comprising: The hydrogen gas, the nitrogen-based reactant gas, and the oxygen-based reactant gas are mixed in a mixing vessel coupled to the reaction chamber before delivering the second reactant gas to the reaction chamber.

4. The method according to claim 1, wherein Delivering the second reactant gas further comprises: The hydrogen gas, the nitrogen-based reactant gas, and the oxygen-based reactant gas are respectively delivered into the reaction chamber.

5. The method according to claim 1, wherein The plasma is ignited while delivering the second reactant gas into the reaction chamber.

6. The method according to claim 1, further comprising: applying a pressure of 0.6 Torr to 6 Torr in the reaction chamber; heating the reaction chamber to a temperature of 150 degrees Celsius to 650 degrees Celsius; as well as A radio frequency (RF) power of 500 W to 5000 W is applied to an RF generator coupled to the reaction chamber.

7. A method for treating a substrate to reduce impurities in an oxidative conversion process during atomic layer deposition, the method comprising: introducing a first reactant in a gas phase into a reaction chamber having the substrate therein, and allowing the first reactant to adsorb onto a surface of the substrate; purging the reaction chamber after the flow of the first reactant is stopped; while the first reactant is adsorbed onto the surface of the substrate, introducing a second reactant in a gas phase into the reaction chamber, the second reactant comprising hydrogen (H2), a nitrogen-containing reactant, and an oxygen-containing reactant in a ratio of 1:1:1; igniting a plasma based on the second reactant; exposing the surface of the substrate to the plasma to drive a surface reaction between the first reactant and the second reactant on the surface of the substrate to form a film layer; extinguishing the plasma; as well as The reaction chamber is purged.

8. A system for processing a substrate to reduce impurities in an oxidative conversion process during atomic layer deposition, the system comprising: a reaction chamber having the substrate therein; A controller configured with instructions to: delivering a first reactant gas into the reaction chamber, a reactive portion of the first reactant gas being adsorbed onto the surface of the substrate, and delivering a second reactant gas into the reaction chamber, the second reactant gas comprising hydrogen (H2) gas, a nitrogen-based reactant gas, and an oxygen-based reactant gas; a pump coupled to the reaction chamber, the pump configured to purge an unreacted portion of the first reactant gas from the reaction chamber after delivering the first reactant gas, the unreacted portion of the first reactant gas not being adsorbed onto the surface of the substrate; as well as An RF generator is coupled to the reaction chamber, the RF generator being configured to ignite a plasma in the reaction chamber using the second reactant gas, the plasma being exposed to the surface of the substrate.

9. The system according to claim 8, wherein: The second reactant includes H2, nitrous oxide (N2O) and oxygen (O2) in a ratio of 1:1:

1.

10. The system according to claim 8, further comprising: A mixing vessel is coupled to the reaction chamber, the mixing vessel being configured to mix the hydrogen gas, the nitrogen-based reactant gas, and the oxygen-based reactant gas before delivering the second reactant gas into the reaction chamber.

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