Thin film deposition process

Abstract

A thin film deposition process is provided that allows for high precision control of the in-plane distribution of a thin film deposited on a substrate. The process is a process for depositing a thin film on a substrate in a chamber by atomic layer deposition (ALD) that includes repeating deposition cycles to deposit the thin film on the substrate. The deposition cycles include the steps of: supplying a reactant gas and a carrier gas to the chamber and a source gas of reduced concentration to the chamber to allow the source gas to adsorb on the substrate; supplying the reactant gas and the source gas to the chamber to allow the source gas to adsorb on the substrate; supplying the reactant gas and the carrier gas to the chamber to purge the source gas that is not adsorbed on the substrate from the chamber; applying RF power to the chamber to convert the reactant gas to a plasma such that the source gas activated by the plasma is allowed to contact a surface of the substrate; and supplying the reactant gas and the carrier gas to the chamber to purge unreacted source gas and reactant gas from the chamber.

Description

Technical Field

[0001] The present invention relates to thin film deposition processes. Background Art

[0002] The atomic layer deposition (ALD) process involves controlling the in-plane distribution of a thin film deposited on a substrate, such as a wafer. Methods for controlling the in-plane distribution of the thin film include adjusting parameters such as source input, gas flow ratio, RF power, and intervening by controlling the source purge time during a chemical vapor deposition (CVD) process. Summary of the Invention

[0003] However, even if these parameters are adjusted, it is still difficult to control the in-plane distribution of the thin film with higher precision. Therefore, it is necessary to control the in-plane distribution of the thin film deposited on the substrate with high precision.

[0004] One aspect of the present disclosure relates to a process for depositing a thin film on a substrate in a chamber by atomic layer deposition (ALD), the process comprising repeating a deposition cycle to deposit the thin film on the substrate. The deposition cycle comprises the following steps: supplying a reaction gas and a carrier gas to the chamber, and supplying a source gas with a reduced concentration to the chamber to allow the source gas to adsorb on the substrate; supplying the reaction gas and the source gas to the chamber to allow the source gas to adsorb on the substrate; supplying the reaction gas and the carrier gas to the chamber to purge the source gas that is not adsorbed on the substrate from the chamber; applying RF power to the chamber to convert the reaction gas into plasma, so that the source gas activated by the plasma is allowed to contact the surface of the substrate; and supplying the reaction gas and the carrier gas to the chamber to purge unreacted source gas and unreacted reaction gas from the chamber.

[0005] The present invention allows for high-precision control of the in-plane distribution of a thin film deposited on a substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a vertical sectional view schematically showing a film deposition apparatus according to an embodiment;

[0007] Figure 2 is a diagram showing an ALD process sequence related to an embodiment;

[0008] Figure 3A is a schematic diagram showing gas flows in the purge and source supply steps;

[0009] Figure 3B is a schematic diagram showing the flow of gases in the source gas supply step;

[0010] Figure 3C is a schematic diagram showing the flow of gases during the purge step; and

[0011] Figure 4is a view showing measurement results of a thin film obtained through a thin film deposition process related to the embodiment. DETAILED DESCRIPTION

[0012] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following embodiments are not intended to limit the present invention and can be changed or modified in various ways without departing from the spirit of the present invention.

[0013] <Film deposition equipment>

[0014] Although any type of film deposition equipment may be used in the film deposition process according to the embodiment, in particular Figure 1 The film deposition equipment shown.

[0015] Figure 1 is a vertical cross-sectional view schematically showing a film deposition apparatus 1 according to the embodiment. Figure 1 The film deposition apparatus 1 is configured to deposit a thin film on a substrate W such as a semiconductor wafer W by plasma enhanced atomic layer deposition (PEALD).

[0016] The film deposition apparatus 1 includes a substantially cylindrical chamber 10 opened at the top and closed at the bottom, and a stage 12 provided in the chamber 10 and on which a substrate W is mounted.

[0017] The chamber 10 is electrically grounded through a ground conductor (not shown). The chamber 10 has an inner wall, for example, a surface of which is covered with a coating (not shown) made of a plasma-resistant material.

[0018] The workbench 12 is made of a metal material such as an aluminum alloy. The bottom of the workbench 12 is supported by a support member 13 made of a conductive material and is electrically connected. The support member 13 is electrically connected to the bottom surface of the chamber 10. Therefore, the workbench 12 is grounded through the chamber 10 and serves as a lower electrode, which is paired with a gas supply 14 serving as an upper electrode. The workbench 12 has a built-in heater (not shown) configured to heat the substrate W on the workbench 12 to a desired temperature.

[0019] In this apparatus, a distance D is provided between the stage 12 serving as a lower electrode and the gas supplier 14 serving as an upper electrode. The distance D may be within a range capable of generating plasma between the stage 12 and the gas supplier 14, for example, within a range of 7 mm to 15 mm.

[0020] The lower portion of the support member 13 extends downward through an insertion hole 11 provided at the center of the bottom of the chamber 10. The support member 13 is vertically movable by a raising and lowering mechanism (not shown) that raises and lowers the workbench 12.

[0021] Below the stage 12, a plurality of support pins (not shown) are provided inside the chamber 10, and the stage 12 has insertion holes (not shown) configured to receive the support pins. When the stage 12 is lowered, the support pins pass through the insertion holes in the stage 12 to support the substrate W with their upper ends so that the substrate W can be transferred to a transfer arm (not shown) that enters the chamber 10 from the outside.

[0022] Above the stage 12, a gas supplier 14 is provided parallel to and facing the stage 12. In other words, the gas supplier 14 is provided facing the substrate W mounted on the stage 12. The gas supplier 14 is configured to supply a process gas for processing the substrate W. For example, the gas supplier 14 is made of a conductive metal such as an aluminum alloy, which also serves as an upper electrode.

[0023] The upper circumference of the gas supply 14 is held by an annular support member 16. The support member 16 is made of an insulating material such as quartz. The gas supply 14 and the chamber 10 are electrically insulated from each other. A heater (not shown) may also be provided on the upper surface of the gas supply 14.

[0024] The gas supplier 14 is connected to a reaction gas supply source (not shown), a carrier gas supply source (not shown), and a reservoir 19 through gas supply lines L1, L2, L3, and L4 outside the chamber 1. Source gas, reaction gas, and carrier gas are supplied to the gas supplier 14 and then introduced into the chamber 10 through the gas supply holes 15 in a shower-like manner.

[0025] Outside the film deposition apparatus 1, the gas supply lines L1, L2, L3, and L4 are provided with valves V1, V2, V3, V4, and V5, as well as other components such as mass flow controllers (not shown), which allow control of the conditions of the supplied process gases, such as the gas type, gas mixture ratio, and flow rate. Specifically, the gas supply line L1 is provided with valve V1, the gas supply line L2 is provided with valves V2 and V3, the gas supply line L3 is provided with valve V4, and the gas supply line L4 is provided with valve V5. Valves V3, V4, and V5 are also referred to as pass-through switch (PS) valves, inlet valves, and outlet valves, respectively.

[0026] The reservoir 19 contains source gas precursors. The reservoir 19 is connected to the chamber 10 via gas supply lines L2, L3, and L4. The gas supply line L2 is connected to the gas supply lines L3 and L4. The gas supply line L3 is connected to the gas supply line L4 via the reservoir 19. The gas supply line L3 is connected upstream of the valve V3 in the gas supply line L2. The gas supply line L4 is connected downstream of the valve V3 in the gas supply line L2. When only the carrier gas is supplied, the valve V3 is opened, while the valves V4 and V5 are closed, and the carrier gas is supplied to the chamber 10 via the gas supply line L2 and the valve V3. When the carrier gas and the source gas are supplied, the valve V3 is closed, and the valves V4 and V5 are opened at the same time, and the carrier gas and the source gas are supplied to the chamber 10 via the gas supply lines L2, L3, and L4 and the valves V4 and V5.

[0027] The gas supply 14 also serves as the upper electrode. The gas supply 14 is electrically connected to a high-frequency power supply 17 via a matching box. The high-frequency power supply 17 provides high-frequency power for generating plasma. The high-frequency power supply 17 is configured to output high-frequency power at a frequency of, for example, 100 kHz to 100 MHz. The matching box is used to match the internal impedance of the high-frequency power supply with the load impedance. When plasma is generated within the chamber 10, the matching box provides an apparent match between the internal impedance of the high-frequency power supply and the load impedance.

[0028] The chamber 10 is also connected to an exhaust system 18 configured to evacuate the interior of the chamber 10. When the exhaust system 18 is driven, the atmosphere in the chamber 10 is evacuated so that the pressure is reduced to a predetermined vacuum level.

[0029] The deposition apparatus 1 includes one or more controllers (not shown) that are programmed or configured to perform the deposition process. Those skilled in the art will appreciate that the one or more controllers are connected to components including power supplies, heating systems, pumps, chambers, mass flow controllers, and valves.

[0030] [Substrate preparation]

[0031] To deposit a thin film, first, a substrate W is introduced into the chamber 10 and mounted on the stage 12. The substrate W may be, but is not limited to, a silicon substrate or a germanium substrate. The substrate W may be introduced into the chamber 10 under vacuum using a load lock chamber (not shown) or other apparatus.

[0032] The heater is used to heat the substrate W on the stage 12 . For example, the substrate W may be heated at a temperature in the range of 50 to 500° C. During heating, a carrier gas is supplied into the chamber 10 .

[0033] The carrier gas may be, for example, one or more selected from the group consisting of helium (He), argon (Ar), and hydrogen (H 2 ). During the supply process, the pressure in the chamber 10 is usually at least 50 Pa or higher, preferably 300 Pa or higher, and usually up to 1300 Pa or lower, preferably 1000 Pa or lower. While the carrier gas is being supplied, the reaction gas described later may also be supplied.

[0034] [Sedimentation Cycle]

[0035] Figure 2 is a diagram showing the ALD process sequence related to the embodiment. Figure 2 The ALD process sequence in includes a conventional sequence (current sequence) and a sequence according to an embodiment (new sequence).

[0036] The deposition cycle includes a purge and source supply step, a source gas supply step, a purge step, a plasma contact step, and a post-purge step. Throughout the deposition cycle, the reaction gas and the carrier gas are continuously supplied to the chamber 10 .

[0037] Depending on the target film thickness, composition, and quality, the deposition cycle can be repeated as many times as desired, although repetition is not required. The sequence according to the embodiment differs from the conventional sequence, in particular, it includes purge and source supply steps. In the following, each step of the deposition cycle will be described in detail.

[0038] [Purge and source supply steps]

[0039] First, when the reaction gas and the carrier gas are supplied to the chamber 10, the source gas is supplied to the chamber 10 with a reduced concentration. As a result, the source gas is allowed to be adsorbed on the substrate W. Figure 3A Schematic diagram showing the gas flow in the purge and source supply steps. Figure 3A As shown, valve V1 is opened, so that the reaction gas is supplied to the chamber 10 through the gas supply line L1. Valves V2, V3, V4, and V5 are also opened, so that the carrier gas is supplied to the chamber 10 through the gas supply lines L2, L3, and L4. The source gas in the reservoir 19 is carried by the carrier gas, which flows through the gas supply line L3 and is supplied to the chamber 10 through the gas supply lines L4 and L2.

[0040] In this step, since valves V3, V4, and V5 are opened, the source gas is diluted with the carrier gas and then supplied to chamber 10. The concentration of the diluted source gas supplied to chamber 10 is lower than that of the source gas supplied in the source gas supply step described later.

[0041] In this step, the source gas can be a material used in plasma excited atomic layer deposition (PEALD), preferably aminosilane, more specifically one or more selected from the group consisting of: bis(diethylamino)silane (BDEAS), diisopropylaminosilane (DIPAS), tetrakis(dimethylamino)silane (4DMAS), tris(dimethylamino)silane (3DMAS), bis(dimethylamino)silane (2DMAS), tetrakis(ethylmethylamino)silane (4EMAS), tris(ethylmethylamino)silane (3EMAS), bis(tert-butylamino)silane (BTBAS) and bis(ethylmethylamino)silane (BEMAS).

[0042] The reactive gas may be a gas capable of reacting with the source gas in the presence of a plasma of a gas component. More specifically, the reactive gas is preferably one or more selected from the group consisting of oxygen (O2), nitrous oxide (N2O), carbon dioxide (CO2), nitrogen (N2), and ammonia (NH3).

[0043] The reaction gas supplied to the chamber 10 may have a flow rate of about 50 sccm or more, preferably at least 3,000 sccm or more, and may have a flow rate of at most 10,000 sccm or less, preferably 6,000 sccm or less.

[0044] The carrier gas and source gas supplied to the chamber 10 may have a flow rate of about 500 sccm or higher, preferably at least 2000 sccm or higher, and may have a flow rate of at most 10000 sccm or lower, preferably 5000 sccm or lower.

[0045] The source gas may be supplied together with the carrier gas for a period of time, for example, 0.05 seconds or longer, preferably at least 0.1 seconds or longer and at most 10 seconds or shorter, preferably 5 seconds or shorter.

[0046] The purge and source supply step may be performed before or after the source gas supply step. The sequence according to the above embodiment includes performing the purge and source supply step once and performing the source gas supply step once. Alternatively, the purge and source supply step and the source gas supply step may each be performed two or more times.

[0047] [Source Gas Supply Step]

[0048] Next, reaction gas and source gas are supplied into the chamber 10 . Figure 3B Schematic diagram showing the flow of gas in the source gas supply step. Figure 3BAs shown, valve V1 is opened, allowing the reactant gas to be supplied to chamber 10 through gas supply line L1. Valves V2, V4, and V5 are also opened, and valve V3 is closed, allowing the source gas to be supplied to chamber 10 through gas supply lines L2 and L4. Switching between the purge and source supply step and the source gas supply step is typically performed by opening and closing PS valve V3. As a result, the source gas is allowed to adsorb on substrate W, thereby forming a layer of source gas molecules on the surface of substrate W.

[0049] The source gas supplied to the chamber 10 along with the carrier gas may have a flow rate of about 500 sccm or more, preferably at least 2000 sccm or more, and may have a flow rate of up to 10,000 sccm or less, preferably 5000 sccm or less. The source gas may be supplied along with the carrier gas for a period of time, for example, at least 0.05 seconds or more, preferably 0.1 seconds or more and up to 10 seconds or less, preferably 5 seconds or less. The optimal time period for supplying the source gas may be selected based on the type of source gas, the pressure in the chamber 10, and other conditions.

[0050] [Purge Step]

[0051] After the source gas is supplied, a reaction gas and a carrier gas are supplied to the chamber 10 so that the source gas that is not adsorbed on the substrate W is purged from the chamber 10 . Figure 3C Schematic diagram showing the gas flow during the purge step. Figure 3C As shown, valve V1 is open, allowing reactant gas to be supplied to chamber 10 through gas supply line L1. Valves V2 and V3 are also open and valves V4 and V5 are closed, allowing carrier gas to be supplied to chamber 10 through gas supply line L2.

[0052] The purging step allows for a smoother film to be obtained because it reduces contamination of the film by source gas remaining in the atmosphere. When source gas that has not been adsorbed on substrate W is exhausted from chamber 10 in this manner, contamination of the film by source gas remaining in the atmosphere in chamber 10 is reduced, resulting in a smoother film. Specifically, the source gas can be purged at a rate that allows for the initiation of high-frequency power application, allowing for smooth plasma generation and plasma-assisted deposition of the film, as described later.

[0053] [Plasma contact step]

[0054] Next, a reactive gas and a carrier gas are supplied into the chamber 10, and high-frequency power is applied to the gas supply 14, causing the reactive gas components (gas components that can be activated by plasma generation) in the process gas to become plasma. The reactive gas activated by plasma generation is allowed to contact the surface of the substrate W, thereby allowing the reactive gas components to react with the source gas components adsorbed on the substrate W. This makes it possible to deposit a thin film having a uniform thickness on the surface even when the surface of the substrate W has a three-dimensional structure.

[0055] More specifically, when the reaction gas and the carrier gas are supplied into the chamber 10, this step may include applying high-frequency power to convert reaction gas components including one or both of the reaction gas and the carrier gas into plasma; and allowing the reaction gas components activated by the plasma to contact the source gas components adsorbed on the substrate W, thereby allowing the reaction gas components to react with the source gas components. This makes it possible to deposit a thin film having a uniform thickness on the surface of the substrate W.

[0056] [Post-Purge Step]

[0057] After forming a single layer for the thin film, byproducts generated during the reaction between the reactive gas component and the source gas component are exhausted from the chamber. In this step, the byproducts can be exhausted from the chamber using a device for supplying at least one of a reactive gas and a carrier gas into the chamber to purge the source gas components that are not adsorbed on the substrate, a device for evacuating the chamber 10 to exhaust the source gas components, or a combination thereof.

[0058] [Depositing a thin film with a desired thickness]

[0059] After exhausting the byproducts from chamber 10, a cycle can be repeated, including: allowing source gas components to adsorb on substrate W; exhausting excess source gas components from chamber 10; supplying process gas including a reactive gas into chamber 10; applying high-frequency power to gas supply 14 to convert the reactive gas components in the process gas into plasma and allow them to react with the source gas components to form a thin film; and exhausting the byproducts from the chamber. This allows a thin film having a desired thickness to be deposited on substrate W. The resulting thin film can have a thickness of at least 0.0001 μm, which corresponds to the thickness of a monomolecular layer, and can have a thickness of at most 1 μm or less, preferably 0.1 μm or less.

[0060] In embodiments, the resulting thin film can be, for example, a SiO2 film, a SiN film, or a SiC film.Deposition of such useful thin films by plasma enhanced atomic layer deposition (PEALD) allows the production of semiconductor devices with higher quality and reliability.

[0061] Example

[0062] Next, examples of the present invention will be described, which are not intended to limit the scope of the present invention. Figure 4 is a view showing analysis results of a thin film obtained through a thin film deposition process related to the embodiment. Figure 4 The table shows the GPC (growth per cycle) with different PS valve V3-closing time ( / cycle), uniformity range / average (%), center / edge ratio, and in-plane distribution profile (+ / - 0.25%) across the wafer. Figure 4 Also shown is the relationship between PS valve V3 - closing time and center / edge ratio.

[0063] As described above, switching between the purge and source supply step and the source gas supply step can generally be performed by opening and closing the PS valve V3. In the example, the purge and source supply step is performed and then the PS valve V3 is closed to switch from the purge and source supply step to the source gas supply step.

[0064] Figure 4 It is shown that as the closing time of the PS valve V3 is delayed, that is, as the time period for performing the purge and source supply steps increases, the GPC decreases, that is, the atomic layer thickness per cycle decreases.

[0065] Figure 4 It is also shown that as the PS valve V3-closing time is delayed, both the uniformity range / average value (%) and the center / edge ratio increase, and the film thickness difference between the center and edge of the wafer increases.

[0066] Furthermore, the thin film deposition process according to the embodiment allows for control of the in-plane distribution profile on the wafer within a range of ±0.25%, whereas conventional processes have difficulty controlling the in-plane distribution profile on the wafer within a range of ±0.25%. As shown above, by controlling the closing time of PS valve V3 to the millisecond level, the in-plane distribution of the thin film is successfully controlled.

[0067] As described above, the thin film deposition process according to the embodiment includes a deposition cycle including a purge and source supply step, which includes supplying a reaction gas and a carrier gas to the chamber 10 and supplying a source gas with a reduced concentration to the chamber 10 to allow the source gas to adsorb on the substrate W. When the source gas is diluted in this manner, the source gas can be diluted for a desired period of time by utilizing the tendency of source gas adsorption to be more likely to occur in the central region of the wafer (or the tendency of source gas adsorption to be less likely to occur in the peripheral portion of the wafer). Therefore, the thin film deposition process according to the embodiment allows for high-precision control of the in-plane distribution of the thin film deposited on the wafer W.

[0068] The thin film deposition process according to the embodiment can eliminate the need to use an intrusion mode by unstably controlling the source purge time during a chemical vapor deposition (CVD) process and make it possible to produce a thin film with a desired in-plane distribution using an existing ALD system.

[0069] Furthermore, the thin film deposition process according to the embodiment controls the in-plane distribution of the thin film in the ALD atmosphere, thereby achieving a very stable process. Furthermore, the thin film deposition process according to the embodiment can control the duration of the purge and source supply steps, as well as the duration of the source gas supply step, which allows for more stringent control of the in-plane distribution of the thin film.

[0070] Although the embodiments of the present invention have been described above, it should be understood that these embodiments are not intended to limit the present invention. It should also be understood that the advantageous effects shown in the embodiments are merely examples of the most advantageous effects of the present invention and are not intended to limit the advantageous effects of the present invention.

Claims

1. A process for depositing thin films on a substrate in a chamber by atomic layer deposition (ALD), The process includes repeating deposition cycles to deposit a thin film on a substrate, The deposition cycle comprises the following steps in order: supplying a reaction gas through a first line and a carrier gas through a second line to a chamber, and supplying a source gas with a reduced concentration through a third line and a fourth line to the chamber to allow the source gas to be adsorbed on a substrate, the second line being connected to the third line and the fourth line, the third line being connected to the fourth line through a reservoir containing the source gas, the third line being connected upstream of a valve in the second line, and the fourth line being connected downstream of the valve in the second line, the valve being open; closing the valve to supply the reaction gas and the source gas to the chamber to allow the source gas to be adsorbed onto the substrate; supplying a reaction gas and a carrier gas to the chamber to purge the source gas not adsorbed on the substrate from the chamber; applying RF power to the chamber to convert the reaction gas into plasma, so that the source gas activated by the plasma is allowed to contact the surface of the substrate; and The reaction gas and the carrier gas are supplied to the chamber to purge unreacted source gas and unreacted reaction gas from the chamber.

2. The process of claim 1, wherein: Before the step of supplying the reaction gas and the source gas to the chamber to allow the source gas to be adsorbed on the substrate, the step of supplying the reaction gas and the carrier gas to the chamber and supplying the source gas with reduced concentration to the chamber to allow the source gas to be adsorbed on the substrate is performed.

3. The process of claim 1, wherein: After supplying the reaction gas and the source gas to the chamber to allow the source gas to be adsorbed on the substrate, supplying the reaction gas and the carrier gas to the chamber and supplying the source gas with reduced concentration to the chamber to allow the source gas to be adsorbed on the substrate is performed.

4. The process of claim 1, wherein: The reaction gas is selected from the group consisting of oxygen (O2), nitrous oxide (N2O), carbon dioxide (CO2), nitrogen (N2) and ammonia (NH3).

5. The process of claim 1, wherein: The carrier gas is selected from the group consisting of helium (He), argon (Ar) and hydrogen (H2).

6. The process of claim 1, wherein: The source gas includes aminosilane.

7. The process of claim 1, wherein: The thin film includes a SiO2 film, a SiN film or a SiC film.

8. The process of claim 1, wherein: The deposition cycle is repeated until the desired film thickness is achieved.

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