Atomic layer deposition method and atomic layer deposition apparatus

Abstract

The atomic layer deposition apparatus comprises an ALD furnace 205, an ozone supply device 201 that supplies ozone gas to the ALD furnace 205, and an additive gas supply device 202 that supplies one of the following gases to the ALD furnace 205 as an additive gas: water, acetylacetone (C5H8O2), formic acid (CH2O2), or methanol (CH4O).

Description

Technical Field

[0001] The present invention relates to a semiconductor manufacturing process technology for a vacuum process using ozone gas, particularly to a process that actively utilizes radicals generated by mixing ozone and an additive gas.

Background Art

[0002] Semiconductor devices are changing from the conventional planar structure to a three-dimensional structure with stacking for higher integration. In the case of logic semiconductor devices, for example, in the Fin-FET with a structure where channels are distributed on a plane, in recent years, the GAA-FET with a structure distributed in a stacked structure has been put into practical use, and in the future, a CFET with an increased number of stacked layers has been proposed. In the structure of memory semiconductor devices, the number of stacked layers in 3D-NAND with stacked NAND-type operating memory elements is increasing year by year, and this trend will continue in the future. As issues for future semiconductor device manufacturing processes against this trend of increasing stacked structures, there are achieving a film with good coating properties with a uniform film thickness over the entire sidewall of a deep trench, and highly efficient processing over the entire sidewall of etching and cleaning. To solve these issues, a method of highly efficiently transporting highly reactive radicals to the bottom of a deep trench or generating them efficiently at the bottom of the trench is applied to each process.

[0003] In the film formation process for three-dimensional semiconductor devices, the application of atomic layer deposition with good coating properties is expected to continue in the future. The atomic layer deposition method for forming an oxide film such as a gate oxide film is composed of a process of repeatedly supplying a precursor gas and an oxidation source gas alternately with an exhaust process in between, and it is known that the film quality such as coating properties is greatly affected by the selection of the oxidation source gas species.

[0004] The role of the oxidation source gas is to form an oxide film by reacting with the precursor adsorbed in an amount of one atomic layer along the deep trench after precursor supply. When the amount of the oxidation source reaching is insufficient, the oxide film is not formed or impurities remain in the film due to insufficient oxidation reaction, causing film quality deterioration such as a decrease in insulation.

[0005] Conventional oxidation sources include oxygen plasma, water, hydrogen peroxide, ozone, and a mixed gas of ozone and unsaturated hydrocarbons (Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] K. Arts et. al., J. Chem. C 125 8244-8252 (2021). [Non-Patent Document 2] Tsuchibuchi et al., Taiyo Nippon Sanso Technical Report No. 38, p. 16 (2019). [Non-Patent Document 3] T. Nishiguchi et. al., Appl. Phys. Lett. 81 2190 (2002) [Non-Patent Document 4] R. Kobayashi et. al., Jpn. J. Appl. Phys., 60 030903 (2021). [Non-Patent Document 5] RE Buhler et. al., J. Phys. Chem., 88 2560 (1984) [Patent Documents]

[0007] [Patent Document 1] Patent No. 6052470 [Patent Document 2] Patent No. 6677356 [Overview of the project]

[0008] The characteristics and problems of conventional oxidation sources are described below.

[0009] Oxygen plasma involves applying plasma to oxygen molecules, separating them into atomic oxygen, which then undergoes an oxidation reaction. Atomic oxygen has high oxidizing power, and the plasma application arrangement allows for the generation of high-density atomic oxygen near the processing substrate, enabling its supply to the substrate. Therefore, it is frequently used in low-temperature film deposition. On the other hand, atomic oxygen is easily deactivated by collisions with other oxygen molecules or with other atomic oxygen molecules, resulting in poor coverage of deep grooves compared to other oxidation methods. In particular, atomic layer deposition of HfO2 and Al2O3 films, which are commonly used as gate oxide films, will not be able to deposit films deep into grooves with an aspect ratio of 100, which will be required for 3D-NAND in the future (Non-Patent Literature 1). Here, the aspect ratio is an index for groove shape defined as the ratio of groove opening width 102 to groove depth 101 (distance from groove entrance) in the substrate 1, which is the film-deposited body having the groove structure shown in Figure 1.

[0010] While water has good coating properties, its low reactivity results in poor film quality, including poor insulation. Furthermore, condensation on the inner walls of pipes and inside vacuum pumps due to water supply increases the operating load on the pump, making it difficult to maintain a vacuum level. Therefore, improving film quality through large-scale water supply is not feasible.

[0011] Hydrogen peroxide solution, while providing high coating properties similar to water, decomposes due to its greater thermal instability compared to water, generating highly reactive radicals primarily composed of OH groups. These radicals improve film quality (Non-Patent Literature 2). For this reason, hydrogen peroxide is an effective oxidation source for next-generation semiconductor manufacturing ALD processes. However, similar to the case where water is used as an oxidation source, the supply flow rate of hydrogen peroxide solution is constrained in order to suppress the increased load on the exhaust system due to condensation.

[0012] Ozone improves coating properties and film quality as the ozone concentration in oxygen gas increases. For coating grooves with an aspect ratio exceeding 100, a high concentration of ozone gas (20 vol% or higher) is required. However, when using ozone, the oxidation source is either ozone molecules or atomic oxygen, both of which are formed solely from oxygen atoms and do not contain hydrogen. The reaction may be insufficient depending on the type of precursor.

[0013] A mixed gas of ozone and unsaturated hydrocarbons generates radicals through collision reactions between ozone gas and unsaturated hydrocarbons in the gas phase, leading to the decomposition of the unsaturated hydrocarbons (Patent Document 1). In particular, when ethylene gas is used as the unsaturated hydrocarbon, it reacts with ozone to generate OH radicals as a representative radical. By applying these OH radicals to the resist deposited on the substrate surface, an increase in the ashing rate can be obtained. The increase in the ashing rate is largely related to the ozone concentration; high-concentration ozone gas with an ozone concentration of 80% by volume or more, which has undergone liquefaction and concentration, increases the ashing rate, but ozone gas with a concentration of 20% by volume or less, which has not undergone such liquefaction and concentration, does not increase the ashing rate (same Patent Document). It is assumed that the mixed gas with a high ozone concentration generates a large amount of OH radicals, and the frequency of deactivation of the generated OH radicals due to collisions with oxygen molecules and other inert molecules of reaction byproducts is reduced, so that the OH radicals necessary for resist ashing can reach the substrate surface. Since ozone and ethylene are highly reactive at room temperature, the mixed gas is effective for low-temperature processing at around room temperature. However, the mixing of ozone gas and ethylene gas to supply OH radicals to the substrate must be done near the substrate, a showerhead-type gas supply structure is necessary for uniform treatment of the substrate, and if the substrate temperature is high, the reaction system is accelerated by thermal energy, requiring the gas mixing position to be brought even closer to the substrate, and the OH radicals are quickly deactivated and cannot penetrate into deep grooves.

[0014] To achieve the coating performance required for next-generation semiconductor device manufacturing, it is essential to perform the process within the ALD process window, a temperature range (100-300°C) where the precursor undergoes self-regulation of atom-layer adsorption. In contrast, a mixed gas of ozone and ethylene gas results in a higher temperature range than the process temperature range in which the ALD process window is effective, and also exhibits lower coating performance, making it difficult to apply to next-generation semiconductor device manufacturing.

[0015] As described above, the effectiveness of conventional oxidation methods varies depending on the applications used. For the oxidation source of ALD for next-generation semiconductor devices, hydrogen peroxide water and ozone (high-concentration ozone with a concentration of 20 vol% or more) are considered effective. However, it is necessary to improve the generation amount of OH radicals, which have the highest reactivity, in hydrogen peroxide water and ozone.

[0016] In view of the above circumstances, an object of the present invention is to provide an atomic layer deposition method and an apparatus thereof that can improve the film quality of an oxide film and the etching rate of atomic layer etching.

[0017] One aspect of the present invention is an atomic layer deposition method in which ozone gas is supplied to an atomic layer deposition furnace and a gas of any one of water, acetylacetone, formic acid, and methanol is supplied.

[0018] One aspect of the present invention is that, in the atomic layer deposition method, the ozone gas has an ozone concentration of 80 vol% or more.

[0019] One aspect of the present invention is that, in the atomic layer deposition method, the additive gas is supplied in a time zone when the ozone gas is supplied to the atomic layer deposition furnace.

[0020] One aspect of the present invention is that, in the atomic layer deposition method, the mixing ratio of the additive gas to the ozone gas is 300% or less with respect to the supply flow rate of the ozone gas.

[0021] One aspect of the present invention is that, in the atomic layer deposition method, the processing substrate in the atomic layer deposition furnace is heated to 100°C or higher, the wall temperature of the atomic layer deposition furnace is heated to 50 to 100°C, and the partial pressure of the additive gas is not higher than the vapor pressure corresponding to the wall temperature.

[0022] One aspect of the present invention is that, in the atomic layer deposition method, water vapor is supplied to an atomic layer deposition furnace and atomic oxygen generated by oxygen plasma is supplied to the atomic layer deposition furnace.

[0023] One aspect of the present invention is an atomic layer deposition apparatus including an atomic layer deposition furnace to which ozone gas is supplied, and an additive gas supply device that supplies any one of water, acetylacetone, formic acid, and methanol gases as an additive gas to the atomic layer deposition furnace.

[0024] One aspect of the present invention is an atomic layer deposition apparatus including an atomic layer deposition furnace to which water vapor is supplied, and a plasma generator that supplies atomic oxygen generated by oxygen plasma to the atomic layer deposition furnace.

[0025] According to the present invention as described above, it is possible to provide an atomic layer deposition method and apparatus capable of improving the film quality of an oxide film and enhancing the etching rate of atomic layer etching.

Brief Description of Drawings

[0026] [Figure 1] (a) Schematic cross-sectional view of a channel formed on the surface of a substrate, (b) Enlarged view of a deep groove of the channel. [Figure 2] Schematic configuration diagram of an atomic layer deposition apparatus related to semiconductor manufacturing to which the present invention is applied. [Figure 3] Schematic configuration diagram of an additive gas supply device related to the atomic layer deposition apparatus of FIG. 2. <00...​​​​​​​​​​​​(a) A schematic diagram of an atomic layer deposition apparatus according to one aspect of the present invention that utilizes the thermal decomposition of ozone, and (b) A schematic diagram illustrating the generation of OH radicals in the atomic layer deposition apparatus. [Figure 9] (a) schematic diagram of the sample before the ashing process according to the present invention, (b) schematic diagram of the sample after the ashing process according to the present invention. [Figure 10] A characteristic diagram showing the relationship between the mixing ratio of water vapor to ozone gas and the ashing rate. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below with reference to the drawings.

[0028] This invention achieves both OH radical generation and coating properties by supplying one of the following gases—water, acetylacetone (C5H8O2), formic acid (CH2O2), or methanol (CH4O)—as an additive gas to ozone, which is less reactive than ethylene gas.

[0029] The atomic layer deposition apparatus (hereinafter referred to as ALD apparatus) for semiconductor manufacturing to which the present invention is applied, as shown in Figure 2, is equipped with an ozone supply device 201 and an additive gas supply device 202 in the configuration of a typical ALD apparatus.

[0030] In other words, the atomic layer deposition reactor 205 (hereinafter referred to as ALD reactor 205) is connected to an ozone supply device 201, an additive gas supply device 202, a purge gas supply cylinder 203, and a precursor supply device 204 as gas supply sources. The exhaust system of the ALD reactor 205 is equipped with an exhaust pump 206, a decontamination cylinder 207, and an exhaust duct 208.

[0031] The connection line between the ozone supply unit 201, additive gas supply unit 202, purge gas supply cylinder 203, precursor supply unit 204, and exhaust pump 206 and the ALD furnace 205 is equipped with an ozone gas ALD furnace supply valve 211, an additive gas ALD furnace supply valve 212, a purge gas ALD furnace supply valve 213, a precursor ALD furnace supply valve 214, and an exhaust valve 215, respectively. The opening and closing operation of each of these valves controls the gas supply as part of the ALD process. In addition, the ALD furnace 205 is equipped with a pressure gauge 221, which measures the pressure trend in real time and controls the opening and closing times of each of the aforementioned valves.

[0032] The ozone supply device 201 supplies high-concentration ozone gas to the ALD furnace 205. A higher ozone concentration is preferable for high-concentration ozone gas. For example, the ozone concentration of high-concentration ozone gas is preferably 20-100% by volume, and more preferably 80-100% by volume. High-concentration ozone gas can be obtained by liquefying and separating only the ozone from an ozone-containing gas based on the difference in vapor pressure, and then vaporizing the liquefied ozone again. For obtaining high-concentration ozone gas, a well-known ozone generator described in Patent Document 2 can be used.

[0033] The additive gas supply device 202 supplies additive gases, such as water, acetylacetone, formic acid, and methanol, to the ALD furnace 205. In particular, the additive gas supply device 202 supplies the additive gases during the time period when the ozone gas is supplied to the ALD furnace 205. The mixing ratio of the additive gases to the ozone gas is adjusted, for example, to 300% or less, preferably 100% or less, and more preferably 50% or less, relative to the supply flow rate (volume flow rate) of the ozone gas.

[0034] The purge gas supply cylinder 203 supplies purge gas to the ALD furnace 205. The purge gas can be a well-known purge gas used in a typical ALD apparatus (Patent Document 2). Examples of the purge gas include inert gases such as argon or nitrogen.

[0035] The precursor supply device 204 supplies the precursor (raw material gas) to the ALD furnace 205. The precursor used is a raw material gas that contains elements that form an oxide film as constituent elements (see the same patent document).

[0036] As shown in Figure 3, the additive gas supply device 202 has a piping configuration designed to control the supply amount of the additive gas liquid by vapor pressure and to reproducibly adjust the dilution ratio with the carrier gas in each ALD cycle.

[0037] In other words, the additive gas supply device 202 includes an additive gas supply line, a carrier gas supply line, and an exhaust line.

[0038] The aforementioned additive gas supply line includes an additive gas introduction valve 312, a buffer container 303, a buffer container pressure gauge 321, and an additive gas ALD furnace supply valve 314, which supplies the additive gas liquid 302 in the additive gas liquid storage container 301 to the ALD furnace 205. The additive gas ALD furnace supply valve 314 corresponds to the additive gas ALD furnace supply valve 212 shown in Figure 2.

[0039] The carrier gas supply line is equipped with a carrier gas introduction valve 311 and supplies carrier gas from the carrier gas supply port to the additive gas supply line. The carrier gas can be a well-known carrier gas used in a typical ALD apparatus (see the same patent document).

[0040] The exhaust line is equipped with an additive gas exhaust valve 313, which supplies the gases (additive gas and carrier gas) accumulating in the additive gas supply line and the carrier gas supply line to the exhaust port.

[0041] The additive gas liquid 302 is sealed inside a storage container 301 made of stainless steel or quartz glass that can be vacuum-sealed to a vacuum of 0.1 Pa or less. The piping system 331, including the additive gas supply line, is equipped with a heating mechanism that heats it to 100°C or less. The temperature of the heating mechanism is constantly controlled to a constant temperature, including before and after the ALD process.

[0042] The buffer container 303 provides space for mixing the additive gas and carrier gas before supplying them to the ALD furnace 205. Furthermore, to prevent the carrier gas from mixing with the additive gas liquid storage container 301, the area between the additive gas liquid storage container 301 and the buffer container 303 is separated by an additive gas introduction valve 312. The volume of the buffer container 303 is set, for example, to less than 1 / 10 of the volume of the ALD furnace 205. The amount of additive gas supplied is controlled to be the same each time by checking the target pressure with a pressure gauge 321 or by adjusting the opening and closing times of valves 311-314 according to the heating temperature.

[0043] An example of the operation of the ALD device of this embodiment will be described with reference to Figure 2 and Table 1.

[0044] [Table 1]

[0045] The valve opening and closing operations for one ALD process cycle shown in Table 1 consist of steps 1 to 10. Step 10 results in the same valve opening and closing state as step 1, and subsequent steps return to step 1. The characteristics of the valve opening and closing operation steps of the ALD device are shown below.

[0046] Step 1: The valve opening and closing operation in Step 1 of the same table creates a vacuum inside the ALD furnace 205.

[0047] Steps 2-4: After the atmosphere inside the ALD furnace 205 is evacuated, the precursor is filled into the ALD furnace 205 by the valve opening and closing operations in steps 2-4 of the table.

[0048] Steps 6-8: The valve opening and closing operations in Steps 2-4 of the same table fill the ALD furnace 205 with oxidizing gas (ozone or a mixture of ozone and additive gas). At this time, the processing substrate inside the ALD furnace 205 is heated to, for example, 100°C or higher, the wall temperature of the ALD furnace is heated to 50-100°C, and the partial pressure of the additive gas is set to be less than or equal to the vapor pressure corresponding to the wall temperature.

[0049] Steps 4 and 9: The valve opening and closing operations in steps 4 and 9 of the same table facilitate gas replacement in the initial vacuuming stage by introducing purge gas into the ALD furnace 205.

[0050] Steps 6-7: After the valve opening and closing operations in Steps 6-7 of the same table initiate the supply of ozone gas to the ALD furnace 205, the supply of additive gas to the ALD furnace 205 is initiated once the ozone gas flow rate stabilizes. By initiating the supply of additive gas in an ozone gas atmosphere within the ALD furnace 205 in this way, it becomes possible to mix the ozone gas and additive gas to uniformly generate radicals within the ALD furnace 205.

[0051] Referring to Figure 3 and Table 2, an example of valve opening and closing operation of the additive gas supply device 202 will be explained.

[0052] [Table 2]

[0053] The valve opening and closing operations shown in Table 2 aim to secure gas pressure by pressurizing the additive gas from a liquid state to a constant temperature of 100°C or less, thereby achieving saturated vapor pressure, and then diluting it with a carrier gas using an inert gas such as nitrogen or argon before supplying it to the ALD furnace 205.

[0054] The valve opening and closing operations for one ALD process cycle shown in the table consist of steps 1 to 8. Step 8 results in the same valve opening and closing state as step 1, and subsequent steps return to step 1.

[0055] Since the additive gas ALD furnace supply valve 314 is identical to the additive gas ALD furnace supply valve 212, steps 7-8 in operation shown in Table 1 and steps 5-7 in operation shown in Table 2 are synchronized. The additive gas and carrier gas are mixed in the buffer container 303 and then supplied to the ALD furnace 205 (steps 3-6).

[0056] The objective is to reproduce the gas mixing ratio for each cycle of the ALD process by supplying the gas to the ALD furnace 205, exhausting the residual gas from the buffer container 303, and repeating the gas mixing process. The reason for mixing the carrier gas is that the supply amount of the additive gas is less than that of ozone, so when ozone and the additive gas are supplied to the ALD furnace 205 simultaneously, the pressure difference on the primary side of each gas prevents backflow, and also ensures uniform diffusion of the additive gas within the ALD furnace 205.

[0057] The following is an overview of the valve opening and closing operation steps of the additive gas supply device 202.

[0058] 1. The valve opening and closing operations in steps 1 to 6 of the table begin with the vacuum sealing of the buffer container 303 (step 1). First, the additive gas is filled into the buffer container 303 (step 2), then mixed with the carrier gas (steps 3 to 4), and supplied to the ALD furnace 205 (steps 5 to 6). Finally, the valve opening and closing operations in steps 7 to 8 of the table discharge the residual gas from the buffer container 303, the additive gas supply line, the carrier gas supply line, and the exhaust line (step 7), and then the inside of the buffer container 303 is maintained under vacuum (step 8).

[0059] 2. In supplying to the ALD furnace 205, the valve opening and closing operations in steps 5 and 6 of the table first supply the mixed gas in the buffer container 303 to the ALD furnace 205 (step 5), and then the mixed gas remaining in the buffer container 303 is supplied to the ALD furnace 205 by the carrier gas push-out flow (step 6).

[0060] According to the ALD apparatus of this embodiment, by adding and mixing high-concentration ozone gas with an additive gas (water, acetylacetone, formic acid, or methanol) in the ALD furnace 205, the components of the additive gas undergo a decomposition reaction accelerated by collision reactions with heat and ozone, enabling the generation of radicals. Therefore, it is possible to improve the film quality of the oxide film on the processed substrate in the ALD furnace 205 and to improve the etching rate of atomic layer etching. In particular, compared to oxidation by ozone alone, OH radicals become newly available.

[0061] Because OH radicals are highly reactive, they improve film quality and GPC (film thickness per ALD cycle). Figure 6 shows a comparative image of GPC. According to Non-Patent Literature 4, improvement in GPC has been observed in gallium oxide films (Ga2O3) by forming OH through surface reactions by alternately supplying ozone and water. However, a similar effect can be expected by directly supplying OH radicals, and it is presumed that the method of the present invention will yield an increase in GPC.

[0062] Furthermore, by using the aforementioned additive gas, which has low reactivity with ozone, the frequency of radical generation reactions is suppressed even after mixing and adding the gas. This allows OH radical generation to occur in the wide space within the ALD furnace 205, and the OH radicals generated near the substrate 1 as illustrated in Figure 1 can diffuse into the depths of the deep grooves 10 within the substrate 1, improving coverage. In particular, compared to the case where ethylene gas is used as the additive gas to ozone, the gas supply arrangement structure can be simplified without the need for a showerhead, coverage is improved, and it becomes possible to use the system at temperatures within the ALD window temperature range.

[0063] Furthermore, by using high-concentration ozone gas, OH radicals can be generated and diffused over a wide area with fewer oxygen molecules, which are the deactivation source. In conventional technology, even with the addition and mixing of ozone gas and ethylene gas, OH radicals can reach the substrate only when the ozone concentration is 80% by volume or higher. Since the radical of interest in this invention is the same OH radical, using high-concentration ozone enables long-distance diffusion of OH radicals.

[0064] Furthermore, the present invention enables the generation of OH radicals by using water as an additive gas along with ozone in a dry process. In conventional technology, ozonated water is produced by bubbling ozone gas into liquid water, in which ozone is dissolved in the water as bubbles (Non-Patent Literature 5). In the ozonated water, the bubble ozone reacts with water to generate OH radicals. However, although this process allows for the process utilization of OH radicals, it is limited to wet processes and cannot be applied to dry processes such as ALD or etching.

[0065] Figure 5(a) is a schematic diagram of an ALD apparatus 700, which is one embodiment of the present invention utilizing oxygen plasma. Figure 5(b) is a schematic diagram illustrating the generation of OH radicals in the region 706 indicated by the dotted line in the ALD apparatus 700.

[0066] The ALD apparatus 700 comprises a plasma generator 701 and an ALD furnace 702.

[0067] The plasma generator 701 generates atomic oxygen (O) from oxygen gas (O2) using an oxygen plasma generated in a quartz tube supplied with oxygen gas (O2), and supplies it to the ALD furnace 702. A well-known inductively coupled plasma generation technique is applied to generate the oxygen plasma.

[0068] The ALD furnace 702 applies OH radicals, generated by mixing water vapor (H2O) from piping 708 and atomic oxygen (O) from plasma generator 701, to the processing substrate on susceptor 704.

[0069] The ALD furnace 702 is maintained at a vacuum of 10 Pa or less by an exhaust pump 206. A susceptor 704 capable of heating to a maximum of 700°C is provided inside the ALD furnace 702. In order to observe the luminescence when OH radicals 707 are generated inside the ALD furnace 702, the ALD furnace 702 is provided with a synthetic silica window 703 that can transmit light in the wavelength range of 200 nm or more, and an emission detector 705 for detecting the luminescence is provided outside the ALD furnace 702. The emission detector 705 detects the OH radicals 707 that are generated by the chemical reaction shown in Figure 5(b) which is expected to occur near the substrate on the susceptor 704.

[0070] Figures 6 and 7 show the emission spectra detected in ALD reactor 702 in Figure 5(a). In particular, in Figure 7, (a) shows the emission spectrum at wavelengths of 280-340 nm, and (b) shows the emission spectrum at wavelengths of 770-790 nm.

[0071] As shown in Figure 6, emission was measured at wavelengths of 200-880 nm, and multiple spectra were observed, including spectrum 801 at 309 nm, which is characteristic of OH radical generation, and spectrum 802 at 777 nm, which is characteristic of atomic oxygen (O) generation by oxygen plasma. A characteristic behavior was that the intensity of spectrum 801 increased as the output of the oxygen plasma increased in the output range of 0 W to 500 W. In particular, spectrum 801 did not appear at 0 W output, suggesting that atomic oxygen (O) is necessary for OH radical generation. Furthermore, the change in the intensity of spectrum 802 confirmed that the amount of atomic oxygen (O) generated increased with increasing the output of the oxygen plasma, indicating that a large amount of atomic oxygen (O) is required to increase the efficiency of OH radical generation. Thus, it was confirmed that OH radical generation occurs through the mixing of atomic oxygen (O) and water vapor (H2O). Therefore, with the ALD apparatus 700, the generation of OH radicals in the ALD furnace 702 can improve the film quality of the oxide film on the processing substrate on the susceptor 704 and increase the etching rate of atomic layer etching.

[0072] Figure 8(a) is a schematic diagram of an ALD apparatus 900, which is one embodiment of the present invention utilizing the thermal decomposition of ozone. Figure 8(b) is a schematic diagram illustrating the generation of OH radicals 904 in region 903 of the ALD apparatus 900.

[0073] In the ALD apparatus 900, the ALD furnace 901 supplies OH radicals 904, generated by mixing water vapor (H2O) and atomic oxygen (O), to the processing substrate on the susceptor 902, as shown in Figure (b). The ALD furnace 901 is connected to a pipe 905 through which ozone gas is supplied and a pipe 906 through which water vapor (H2O) is supplied.

[0074] The ALD furnace 901 is maintained at a vacuum level of 10 Pa or less by the exhaust pump 206. The ALD furnace 901 is equipped with a susceptor 902 capable of heating the processing substrate to over 100°C.

[0075] Ozone (O3) is decomposed into atomic oxygen (O) and molecular oxygen (O2) by thermal decomposition. As the temperature of the processed substrate increases, the thermal decomposition of ozone (O3) occurs more significantly near the surface of the processed substrate, thus increasing the oxidation rate of Si in the processed substrate (Non-Patent Literature 3). In particular, when the temperature of the processed substrate is 100°C or higher, the oxidation rate of Si in the processed substrate increases, and atomic oxygen (O) is generated near the surface of the processed substrate. The verification results in Figures 5 and 6 suggest that the radical OH904 is generated by the reaction of atomic oxygen (O) and water vapor (H2O). Therefore, according to the ALD apparatus 900, the generation of OH radicals 904 in the ALD furnace 901 can improve the film quality of the oxide film on the processed substrate on the susceptor 902 and improve the etching rate of atomic layer etching.

[0076] Furthermore, since the thermal decomposition of ozone (O3) occurs probabilistically, atomic oxygen (O) is generated over time after ozone gas is introduced into the ALD furnace 901. In other words, since some of the ozone (O3) in the ozone gas becomes atomic oxygen (O), the supply flow rate of ozone gas should be higher than that of water vapor (H2O) in order to generate OH radicals 904.

[0077] The following describes an example of ash rate evaluation regarding the effect of the water vapor mixing ratio (supply flow rate ratio) on ozone.

[0078] Figure 9(a) is a schematic diagram of the sample used for ashing rate evaluation. This sample has a layered structure in which a resist 1002 is coated on a silicon wafer 1001. The sample, placed on the substrate holder 902 shown in Figure 8(a), is subjected to an ashing process using ozone gas and water vapor. The resist 1002 shown in Figure 9(a) is ashed with an oxidizing agent such as OH radicals generated by the reaction of ozone and water, and becomes a thin film as the resist 1003 shown in Figure 9(b).

[0079] Figure 10 shows the relationship between the mixing ratio of water vapor to ozone gas and the ashing rate. The temperature of the substrate (silicon wafer 1001) is 250°C, and OH radicals are supplied to the substrate by the reaction process shown in Figure 8(b), which is expected to improve the ashing rate. The ashing rate 1103 of the ozone and water vapor mixture increased 1104 due to the generation of OH radicals, as shown in Figure 10, and became a larger value than the ashing rate 1101 with ozone gas alone and the ashing rate 1102 with water vapor alone.

[0080] From the relationship shown in Figure 10, it is assumed that the ashing rate 1103 reaches its maximum value, and the largest amount of OH radicals can be supplied to the substrate, especially when the mixing ratio is 15%. Furthermore, when the mixing ratio is 15% or more, a tendency was observed for the ashing rate 1103 to decrease as the value of the mixing ratio increases. This occurs because excess water vapor deactivates the OH radicals. Note that the mixing ratio at which the ashing rate 1103 is maximized varies depending on process conditions such as temperature, pressure, and flow rate, and for example, it is 300% or less, preferably 100% or less, and even more preferably 50% or less. [Explanation of symbols]

[0081] 1...Substrate, 10...Deep groove 201...Ozone gas supply device, 202...Additive gas supply device, 203...Purge gas supply cylinder, 204...Precursor supply device, 205...ALD furnace, 206...Exhaust pump, 207...Decontamination cylinder, 208...Exhaust duct 211...Ozone gas ALD furnace supply valve, 212...Additive gas ALD furnace supply valve, 213...Purge gas ALD furnace supply valve, 214...Precursor ALD furnace supply valve, 215...Exhaust valve, 221...Pressure gauge 301...Additive gas liquid storage container, 302...Additive gas liquid, 303...Buffer container, 311...Carrier gas introduction valve, 312...Additive gas introduction valve, 313...Additive gas exhaust valve, 314...Additive gas ALD furnace supply valve, 321...Pressure gauge inside buffer container 700...ALD device, 701...Plasma generator, 702...ALD furnace, 703...Window, 704...Susceptor, 708...Piping, 704...Susceptor, 705...Emission sensor 900...ALD equipment, 901...ALD furnace, 902...Susceptor, 905,906...Piping 1001...Silicon wafer, 1002, 1003...Resist 1101, 1102, 1103... Ashing rate, 1104... Ashing rate increase

Claims

1. A method for atomic layer deposition, comprising supplying ozone gas to an atomic layer deposition reactor and supplying one of the following gases as an additive gas: water, acetylacetone, formic acid, or methanol. A method for atomic layer deposition, wherein the processing substrate in the atomic layer deposition furnace is heated to 100°C or higher, the wall temperature of the atomic layer deposition furnace is heated to 50 to 100°C, and the partial pressure of the additive gas is less than or equal to the vapor pressure corresponding to the wall temperature.

2. The atomic layer deposition method according to claim 1, wherein the ozone gas has an ozone concentration of 80% by volume or more.

3. The atomic layer deposition method according to claim 1, wherein the additive gas is supplied to the atomic layer deposition furnace during the time period in which the ozone gas is supplied.

4. The atomic layer deposition method according to claim 1, wherein the mixing ratio of the additive gas to the ozone gas is 300% or less of the supply flow rate of the ozone gas.

5. A method for atomic layer deposition, comprising supplying steam to an atomic layer deposition reactor and supplying atomic oxygen generated by an oxygen plasma to the same atomic layer deposition reactor, A method for atomic layer deposition, wherein the processing substrate in the atomic layer deposition furnace is heated to 100°C or higher, the wall temperature of the atomic layer deposition furnace is heated to 50 to 100°C, and the partial pressure of the water vapor is less than or equal to the vapor pressure corresponding to the wall temperature.

6. Atomic layer deposition reactors supplied with ozone gas, This atomic layer deposit reactor is supplied with an additive gas supply device that provides one of the following gases as an additive gas: water, acetylacetone, formic acid, or methanol. Equipped with, An atomic layer deposition apparatus in which the processing substrate in the atomic layer deposition furnace is heated to 100°C or higher, the wall temperature of the atomic layer deposition furnace is heated to 50 to 100°C, and the partial pressure of the additive gas is less than or equal to the vapor pressure corresponding to the wall temperature.

7. A layered deposition reactor that is supplied with steam, A plasma generator that supplies atomic oxygen generated by oxygen plasma to the atomic layer deposition furnace, Equipped with, An atomic layer deposition apparatus in which the processing substrate in the atomic layer deposition furnace is heated to 100°C or higher, the wall temperature of the atomic layer deposition furnace is heated to 50 to 100°C, and the partial pressure of the steam is less than or equal to the vapor pressure corresponding to the wall temperature.

Images