Substrate processing apparatus and substrate processing method

Abstract

To etch a substrate including a fine pattern at a good etching rate.SOLUTION: A substrate processing apparatus 1 according to the present invention includes chemical solution preparation units 101 and 103 that prepare a chemical solution containing a solute that acts as an etchant and ionizes in the solution, a processing chamber 11 that houses a substrate S and performs etching processing of the substrate with the chemical solution, an ion removal unit 121 that removes at least a part of specific ion species in the chemical solution, and chemical solution supply units 105 and 113 that form a chemical solution flow path for supplying the chemical solution sent from the chemical solution preparation unit to the substrate in the processing chamber via the ion removal unit.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a substrate processing apparatus and a substrate processing method for etching a substrate with a chemical solution containing an ionized solute, and more particularly to a technique for etching narrow spaces such as fine patterns. [Background technology]

[0002] Manufacturing processes for electronic components such as semiconductor devices and liquid crystal display devices include an etching process in which a substrate is partially etched away using a chemical solution to form a desired pattern. In recent years, particularly with the trend toward finer patterns and three-dimensional structuring of electronic components, etching processes are sometimes required to form not only recesses with relatively wide openings but also elongated recesses with narrow and deep openings.

[0003] For example, Patent Document 1 describes a method for manufacturing a semiconductor memory device in which a three-dimensional structure is realized by selectively removing one of the thin films by etching from a stack formed by alternately stacking two types of thin films having different compositions on the surface of a semiconductor substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-027125 Summary of the Invention [Problem to be solved by the invention]

[0005] Although Patent Document 1 does not clearly describe the dimensions of each part of the structure, it has been found that the etching rate drops dramatically in narrow spaces where the opening dimensions of the recesses in the pattern to be etched are minute, for example, 10 nanometers or less. As will be described later, one cause of this phenomenon is thought to be the formation of an electric double layer at the interface between the chemical solution and the surface of the object to be etched that is in contact with it, and the electric field thus formed exerts a repulsive force on the ions in the chemical solution.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a technology in a substrate processing apparatus and a substrate processing method for etching a substrate, which enables a substrate including a fine pattern to be etched at a good etching rate. [Means for solving the problem]

[0007] One aspect of the present invention is A substrate processing apparatus for performing narrow space etching, which etches narrow spaces including recesses whose opening dimensions are 10 nanometers or less, A chemical solution preparation unit that prepares a chemical solution containing a solute that acts as an etchant and ionizes in the solution, a processing chamber that accommodates a substrate and performs an etching process on the substrate with the chemical solution, and Does not contribute to or inhibits the narrow space etching reaction The substrate processing apparatus includes an ion removal unit that removes at least a portion of a specific ion species, and a chemical solution supply unit that forms a flow path for the chemical solution that supplies the chemical solution delivered from the chemical solution preparation unit to the substrate in the processing chamber via the ion removal unit.

[0008] Another aspect of the present invention is A substrate processing method for performing narrow space etching, which etches a narrow space including a portion where the opening dimension of a recess is 10 nanometers or less, a step of preparing a chemical solution containing a solute that acts as an etchant and is ionized in the solution; Does not contribute to or inhibits the narrow space etching reaction The substrate processing method includes a step of removing at least a portion of a specific ion species, and a step of supplying the chemical liquid that has passed through the ion removal section to a substrate to perform an etching process.

[0009] In the invention configured as above, the chemical solution supplied to the substrate , not contributing to the confined space etching or inhibiting the confined space etching reactionThe content of specific ionic species is artificially reduced. A portion of the solute contained in the chemical solution is ionized, and the chemical solution contains a mixture of ions generated by ionization and unionized solute. Normally, ions and unionized solute are present in the solution at concentrations that maintain ionization equilibrium. In the present invention, specific ionic species are removed from the chemical solution before it is supplied to the substrate, so the chemical solution supplied to the substrate is in a state where the ionization equilibrium is disrupted.

[0010] In the following description, a "narrow space" refers to a recess that is formed in advance in the substrate to be processed or in a structure stacked on the substrate, or that is formed as a result of an etching process, and whose minimum dimensions, such as the diameter or width of the opening, are approximately 10 nanometers or less.

[0011] As will be described in more detail later, according to the findings of the present inventors, some ion species contained in the chemical solution as an etchant contribute less to the etching process in a narrow space, which is thought to be the cause of the reduced etching rate in narrow space etching. On the other hand, it is thought that the retention of such ions that do not contribute to the process hinders the supply of other etchants to the processed area.

[0012] Therefore, in the present invention, at least a portion of the specific ion species in the etchant in the chemical solution that contributes little to the narrow space etching process is removed, thereby allowing the etchant that contributes to the process to be efficiently supplied to the processed area, thereby improving the efficiency of the narrow space etching process and suppressing a decrease in the etching rate.

[0013] Even if some ion species are removed from the chemical solution, the ionization equilibrium shifts over time, causing the ion species to increase again. For this reason, it is preferable to remove the ion species immediately before supplying the chemical solution to the substrate. To make this possible, in the present invention, an ion removal unit is provided in the flow path through which the adjusted chemical solution is supplied to the substrate. [Effects of the Invention]

[0014] According to the invention configured in this manner, by reducing the content of ion species in the chemical solution that do not contribute to the etching process, it is possible to perform a good etching process while suppressing a decrease in the etching rate, even in the case of a substrate having a narrow space with an opening dimension of 10 nanometers or less, for example. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams showing examples of structures on a substrate that are the subject of the present invention. [Figure 2] 1A to 1C are diagrams illustrating a part of a process for forming a three-dimensional NAND structure. [Figure 3] 10A and 10B are diagrams showing other examples of structures on a substrate that are the subject of the present invention. [Figure 4] FIG. 10 is a diagram showing examples corresponding to opening dimensions. [Figure 5] FIG. 10 is a diagram showing some examples of experimental results. [Figure 6] FIG. 10 is a diagram for explaining consideration of experimental results. [Figure 7] FIG. 1 is a diagram showing a schematic configuration of first to third embodiments of a substrate processing apparatus. [Figure 8] FIG. 10 is a diagram showing a schematic configuration and operation of a fourth embodiment of a substrate processing apparatus. [Figure 9] FIG. 10 is a diagram showing a schematic configuration of a fifth embodiment of a substrate processing apparatus. [Figure 10] FIG. 10 is a diagram showing a schematic configuration of a substrate processing apparatus according to sixth and seventh embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following, several embodiments of a substrate processing apparatus and a substrate processing method according to the present invention will be described. The present invention relates to an etching process for a substrate. Prior to describing the invention, examples of the structures of a substrate that is the subject of the present invention and a device formed on its surface will be given.

[0017] Figure 1 shows an example of a structure on a substrate that is the subject of this invention. Figure 1(a) shows an example of a structure that appears at one stage in the manufacturing process of a replacement gate (RG) type three-dimensional NAND flash memory. This structure has a structure in which multiple insulating layers I are provided parallel to the surface of the substrate S1, separated by minute gaps, and memory pillars P are provided perpendicular to the surface of the substrate S1, penetrating through them.

[0018] 1(b) shows an example of a structure that appears at one stage in the manufacturing process of a floating gate (FG) type 3D NAND flash memory. This structure has a memory hole H formed perpendicular to the substrate S2, and the sidewall of the memory hole H is partially enlarged to form an enlarged portion R.

[0019] To form such a structure or to treat the surface of a structure formed on such a structure, an etching process is performed. For example, the structure shown in Figure 1(b) is formed as follows.

[0020] FIG. 2 is a schematic diagram illustrating a part of the process for forming a three-dimensional NAND structure. As shown in FIG. 2(a), first, two types of thin films made of different materials M1 and M2 are alternately stacked on the surface of a substrate S2. Next, as shown in FIG. 2(b), a memory hole H is formed through the stack. To form the memory hole H, for example, a combination of mask formation by photolithography and anisotropic etching can be applied. Furthermore, as shown in FIG. 2(c), at least a portion of the surface of material M2 facing the memory hole H is removed by an etching process that selectively dissolves material M2. This forms the three-dimensional structure shown in FIG. 1(b).

[0021] Similarly, the structure shown in Figure 1(a) can be formed by alternately stacking layers of material that will become the insulating film I and layers (sacrificial layers) that will ultimately be removed by etching on the substrate S1, forming the pillars P, and then etching away the sacrificial layers.

[0022] The combination of material M1, which remains in the final device as a functional layer, and material M2, at least a portion of which is removed by selective etching, can be various, such as SiO2 and SiN, SiO2 and poly-Si, Si and SiGe, or TiO2 and Si. These materials are not particularly limited in the present invention. Furthermore, in the above combinations, the material that remains in the device and the material that is removed by etching may be reversed.

[0023] Figure 3 shows another example of a structure on a substrate that is the subject of the present invention. In this example, a gap called an air spacer is formed in a semiconductor device formed by stacking multiple functional layers on the surface of a substrate S3. In this example, an air spacer AS is provided to insulate between electrodes E1 to E3 as part of the manufacturing process for a device called a nanosheet device, such as a transistor or switching element. The air spacer AS is formed by etching away a sacrificial layer Ls formed between electrodes E1 to E3.

[0024] As described above, there are various types of device structures to which the present invention can be applied, but the present invention is particularly suitable for the manufacture of devices with process rules of 10 nanometers or less. Devices with such microstructures often employ three-dimensional structures such as those described above to achieve high density. Therefore, a technology for etching narrow spaces on the order of nanometers is required.

[0025] The following describes the problems with "narrow space etching" based on the findings of the present inventors and the means for solving them in this embodiment. Regarding recesses, which are areas to be etched on a substrate and have a recessed surface compared to the surrounding area, there is a phenomenon in which the etching rate is significantly lower in "narrow spaces" with small opening dimensions than when etching recesses with larger opening dimensions.

[0026] Here, a "narrow space" refers to a recess that is formed in advance in a substrate to be processed or in a structure laminated on the substrate, or that is formed as a result of an etching process, and has a minimum dimension, such as the diameter or width, of the opening that is approximately 10 nanometers or less. In a narrower sense, the minimum dimension of the opening is 5 nanometers or less. Hereinafter, the "minimum dimension of the opening" will be abbreviated to simply "opening dimension." Furthermore, the term "substrate" below includes not only base materials such as semiconductor wafers and glass substrates, but also structures with various functional layers laminated on their surfaces.

[0027] FIG. 4 shows an example of what is referred to as "opening dimension" in this specification. When a small, deep recess R1 is provided in a substrate S, as shown in the cross-sectional view of FIG. 4(a), the opening width W1 is the opening dimension. When the recess R1 is, for example, a hole with a circular cross section, its diameter corresponds to the opening dimension. On the other hand, in the case of a recess R2 whose opening shape is anisotropic, as shown in FIG. 4(b), the dimension W2 of the smallest recess among them corresponds to the opening dimension.

[0028] 4(c), when a recess R4 is further formed inside a recess R3 provided in a substrate S, the opening width W3 of the recess R3 and the opening width W4 of the recess R4 can both correspond to the opening dimension as defined in this specification. That is, when the opening width W3 of the recess R3 is 10 nanometers or less, the entire recess R3 corresponds to a "narrow space." On the other hand, even if the opening width W3 of the recess R3 is greater than 10 nanometers, when the opening width W4 of the recess R4 is 10 nanometers or less, each of the recesses R4 corresponds to a "narrow space."

[0029] The findings obtained by the present inventors through various experiments will be described below with reference to FIGS. 5 and 6. FIG. 5 shows an example of some of the experimental results, and FIG. 6 is a diagram for explaining consideration of the experimental results. The present inventors investigated changes in the etching rate during narrow space etching when the SiO2 layer in a silicon (Si) and silicon dioxide (SiO2) laminate was the etching target and the SiO2 layer was selectively removed using an aqueous hydrofluoric acid (HF) solution as the etching solution. Specifically, the etching rate was measured by changing various combinations of the hydrofluoric acid concentration in the etching solution and the opening dimension W of the narrow space. Here, a "blanket" is a so-called solid film with no recesses, which corresponds to a state where W = ∞.

[0030] As shown in FIG. 5(a), the higher the concentration of hydrofluoric acid in the chemical solution, the higher the etching rate, and the smaller the opening dimension W of the narrow space, the lower the etching rate. The etching reaction of silicon dioxide with hydrofluoric acid is represented by the following reaction formula: SiO2+6HF→SiF6 2- +2H2O … (Formula 1) In reality, the contribution of unseparated hydrogen fluoride (HF, more specifically, associated molecule (HF)2) and hydrogen difluoride ions (HF2 - ) and Equation 2 shown in the upper part of FIG. 5(b) is known as an equation that quantitatively expresses the etching rate Re due to these factors.

[0031] The coefficients a, b, c, and d were calculated by applying Equation 2 to the experimental results shown in Figure 5(a) and fitting the curves using the least squares method, for example. The results are shown in the bottom of Figure 5(b). All coefficients become smaller as the aperture dimension W becomes smaller. However, compared to the degree of decrease in coefficients a and b, which represent the contribution of unseparated hydrogen fluoride molecules (HF), the decrease in coefficients a and b is greater for hydrogen difluoride ions (HF2 - The decrease in the coefficients c and d of the term representing the contribution of R 2 is the coefficient of determination, which is close to 1 for all aperture sizes, indicating good accuracy of the curve approximation.

[0032] These results show that in narrow space etching, the contribution of hydrogen difluoride ions is greatly reduced, resulting in a lower etching rate, but the contribution of hydrogen fluoride molecules remains effective. In particular, when the opening dimension W is 3 nanometers, the contribution of hydrogen difluoride ions is almost nonexistent. This result can be explained, for example, as the effect of the electric double layer formed at the interface between the etching target and the chemical solution, as follows:

[0033] Figure 6(a) is a diagram showing a typical relationship between the zeta potential at the interface between the constituent materials (Si, SiO2) of the etching target and the aqueous solution and the hydrogen ion concentration (pH) of the aqueous solution. The zeta potential is a representative measure of the potential that appears on the surface of a material due to the electric double layer formed at the interface between the material and the aqueous solution. Si and SiO2 show the same trend in that the zeta potential shifts to the negative side as the pH value of the aqueous solution increases. However, while SiO2 has a positive potential in strong acidic solutions, Si has a negative potential even in strong acidic solutions, as shown by the dotted line in the figure. The pH value at which the zeta potential of SiO2 becomes zero is approximately 2 to 3. Therefore, in aqueous solutions ranging from weakly acidic to alkaline, the zeta potential is negative.

[0034] In other words, in the etching solution, which is a weakly acidic hydrofluoric acid solution, the surface of the object to be etched is negatively charged, as shown in Figure 6(b). This negative potential does not affect hydrogen fluoride molecules (HF, (HF)2), which are electrically neutral molecules, but it does affect hydrogen difluoride ions (HF2 - ) generates a repulsive force against hydrogen difluoride ions (HF2 - ) is repelled from the etching target, reducing the probability of approaching the surface, and as a result, it cannot contribute to etching. This repulsive force is exerted when the distance from the surface of the etching target is equal to the Debye length λ D It can be considered to be a range of degrees.

[0035] The Debye length is a physical property that indicates the thickness of the electric double layer formed at the interface, and it becomes smaller as the solute concentration in the aqueous solution increases. For example, when the solute concentration is 0.01M, the Debye length is about 1 nanometer, and when the solute concentration is 0.1M, it is about 10 nanometers. The Debye length in the system used in this experiment is about 2.5 nanometers.

[0036] As a result, as shown by the dotted line in Figure 6(b), the surface of the etching target has a thickness equal to the Debye length λ for hydrogen difluoride ions. D In recesses R5 with a relatively large opening dimension W5 (for example, 10 nanometers or more), the potential barrier extends along the inner wall of recesses R5, allowing hydrogen difluoride ions to penetrate into the recesses R5. Therefore, in this case, a certain degree of etching effect by hydrogen difluoride ions can be expected.

[0037] In contrast, in recesses R6 having a relatively large opening dimension W6 (for example, 5 nanometers or less), a potential barrier is formed to block the opening of recesses R5, so hydrogen difluoride ions are hardly able to penetrate into the interior of recesses R6, and therefore no etching effect by hydrogen difluoride ions can be expected.

[0038] On the other hand, unionized hydrogen fluoride molecules (HF, (HF)2) are not affected by the potential barrier. However, as shown in Figure 5(b), the coefficients a and b become somewhat smaller as the opening size of the narrow space becomes smaller, indicating that the etching effect of these molecules also decreases in narrow spaces. This can be explained by the fact that ions that cannot enter the interior of the recess remain around the opening, preventing the molecules from entering the recess.

[0039] For this reason, in each embodiment of narrow space etching described later, a configuration is provided for removing at least a portion of the ion species that do not contribute to the etching reaction as described above from the chemical solution supplied to the etching target. By removing ion species that do not contribute to or inhibit the etching reaction, it is possible to suppress a decrease in the etching rate.

[0040] In the etching of silicon dioxide with the above-mentioned hydrofluoric acid aqueous solution, since the surface of the object to be etched has a negative potential, anions that do not contribute to the etching reaction, specifically hydrogen difluoride ions, are removed while the chemical solution is supplied to the object to be etched, thereby maintaining the etching effect of hydrogen fluoride molecules and suppressing a decrease in the etching rate.

[0041] A similar phenomenon can occur in other material systems. For example, when removing the titanium nitride layer from a laminate of silicon (Si) and titanium nitride (TiN) by selective etching, a hydrogen peroxide (H2O2) solution can be used as the etching solution. An oxide film (titanium dioxide; TiO2) is formed on the exposed titanium nitride surface, but hydrogen ions (H + It is therefore desirable for the chemical solution to contain a large amount of hydrogen ions.

[0042] On the other hand, the titanium nitride layer is ionized by unionized hydrogen peroxide (H2O2) or hydrogen peroxide ions (HO2 - In this case, the surface of the object to be etched has a negative potential, so the anionic hydrogen peroxide ions do not contribute to the etching of the narrow space. By removing them from the chemical solution and increasing the ratio of unionized hydrogen peroxide, it is possible to suppress the decrease in the etching rate.

[0043] As mentioned above, the zeta potential of insulating materials is generally negative except in strong acidic conditions, but for metallic materials such as aluminum oxide (Al2O3), the range in which the zeta potential is positive is wider, and some materials exhibit a positive zeta potential even in neutral conditions (pH = 7). In this case, the cations in the chemical solution do not contribute to the etching reaction, so it is expected that removing the cations from the chemical solution can suppress the decrease in the etching rate.

[0044] Thus, in narrow space etching using a chemical solution containing a solute that ionizes in the solution as an etchant, it is possible to suppress a decrease in the etching rate by removing specific ion species that have a small contribution to the etching reaction from the chemical solution and supplying them to the object to be etched. The ion species to be removed depends on the combination of the object to be etched and the chemical solution. In other words, the ion species to be removed can be determined based on the relationship between the function of the ion species as an etchant in the chemical solution and the polarity of the potential that the object to be etched assumes in the chemical solution.

[0045] Furthermore, the size of the opening that qualifies as a "narrow space" also depends on the combination of the object to be etched and the chemical solution, as well as the concentration of the chemical solution. Generally, it is possible to determine the size that should be treated as a narrow space from the magnitude of the zeta potential resulting from the electric double layer formed at the interface between the two and the Debye length, which is an indicator of the range over which the effect of that potential effectively extends.

[0046] In the combinations of etching target materials and chemicals that are currently widely used, the Debye length is on the order of a few nanometers, so it is safe to assume that the effect of ion repulsion due to the electric double layer at the interface appears when the aperture size is approximately 10 nanometers or less, and this effect is particularly noticeable when the aperture size is 5 nanometers or less.

[0047] Below, based on the above principle, several embodiments of a substrate processing apparatus having a configuration for suppressing a decrease in the etching rate during narrow space etching will be illustrated, and their configurations will be explained in order. Note that when it is necessary to show a specific example of etching processing below, silicon dioxide etching using a hydrofluoric acid solution (dilute hydrofluoric acid) as the chemical solution will be taken as an example, but the configurations of each embodiment can be similarly applied even when the etching target and chemicals are different.

[0048] Fig. 7 is a diagram showing the schematic configuration of first to third embodiments of a substrate processing apparatus according to the present invention, Fig. 8 is a diagram showing the schematic configuration and operation of a fourth embodiment of a substrate processing apparatus according to the present invention, and Fig. 9 is a diagram showing the schematic configuration of a fifth embodiment of a substrate processing apparatus according to the present invention.

[0049] 7(a), the substrate processing apparatus 1 of the first embodiment includes a substrate processing unit 10, a chemical solution supply unit 100, and a control unit 19 for controlling the operation of each part of the apparatus. The substrate processing unit 10 is the main body that performs the etching process, and has a configuration in which a substrate holding part 13 and a chemical solution discharge part 15 are arranged inside a processing chamber 11. The processing chamber 11 receives a substrate S to be processed from outside via a shutter part that can be opened and closed (not shown).

[0050] The substrate holding unit 13 holds the substrate S in a horizontal position and rotates it about a vertical axis. A known spin chuck mechanism can be used as the substrate holding unit 13. The chemical solution discharge unit 15 has a structure in which a nozzle 15a is attached to the tip of a swing arm 15b. The nozzle 15a discharges the etching chemical solution toward the upper surface of the substrate S being rotated by the substrate holding unit 13. The swing arm 15b swings about a predetermined swing axis to position the nozzle 15a relative to the substrate S.

[0051] Since the substrate processing unit 10 having such a configuration is well known, detailed description thereof will be omitted. Furthermore, in the second to fifth embodiments described later, the configuration of the substrate processing unit 10 is generally the same. Therefore, in the following description, the same components as those described above will be assigned the same reference numerals, and description thereof will be omitted.

[0052] The chemical supply unit 100 has the function of preparing an etching chemical and supplying it to the substrate processing unit 10 configured as described above. The chemical supply unit 100 includes a mixer 101 that mixes a chemical supplied from an external supply source (not shown) with DIW (deionized water) to prepare an etching chemical of a predetermined concentration. The chemical is a solute that functions as an etchant, such as hydrogen fluoride in an etching process using a hydrofluoric acid solution. Alternatively, the chemical is hydrogen peroxide in an etching process using a hydrogen peroxide solution. Various other chemical substances that function as etchants, such as electrolytes, liquids, and gases, can also be used as the chemical. The prepared chemical solution CS is temporarily stored in a storage tank 103.

[0053] Pipe 105, which forms a circulation flow path for the chemical liquid, is connected to storage tank 103, and the chemical liquid discharged from the bottom of storage tank 103 flows through pipe 105 and is returned to the top of storage tank 103. In pipe 105, a temperature regulator 111, a liquid delivery pump 113, and a particle filter 115 are inserted in this order from the upstream side along the flow direction of the chemical liquid. In the following description, when the terms "upstream side" and "downstream side" are simply used, these refer to the upstream side and downstream side, respectively, in the flow direction of the chemical liquid within the flow path.

[0054] Temperature regulator 111 adjusts the temperature of the chemical liquid flowing through pipe 105 to a predetermined target temperature. Liquid feed pump 113 circulates the chemical liquid through pipe 105. Particle filter 115 removes foreign matter such as particles from the chemical liquid. These configurations are well known, so detailed explanations will be omitted.

[0055] An output pipe 107 communicating with the nozzle 15a of the substrate processing unit 10 is connected to the pipe 105 downstream of the particle filter 115. A control valve 117 and an ion removal filter 121 are inserted in the output pipe 107. The control valve 117 controls the on / off and flow rate of the chemical liquid supplied to the nozzle 15a.

[0056] The ion removal filter 121 has an ion exchange resin or an ion exchange membrane and removes at least some of the anions or cations in the chemical solution. It is sufficient to significantly reduce the content of specific ion species in the chemical solution; it is not necessary to remove all ions. While there are already examples of ion removal filters installed in the flow path for the purpose of removing foreign matter from the chemical solution, in this case, ion species that would otherwise function effectively as etchants are removed with the goal of improving the etching rate in narrow spaces.

[0057] Ion exchange resins suitable for use in removing anions include those having, for example, quaternary ammonium groups as functional groups, and ion exchange resins suitable for removing cations include those having, for example, sulfonic acid, sulfate ester, carboxylic acid, or other functional groups.

[0058] In a chemical solution containing partially ionized solutes, even if a specific ion species is temporarily removed, the concentration of the removed ion species increases over time due to a shift in ionization equilibrium. For this reason, it is preferable to remove ions immediately before the chemical solution is supplied to the substrate S. To make this possible, an ion removal filter 121 is inserted into the output piping 107 branching off from the circulation flow path. In particular, by placing the ion removal filter 121 in the processing chamber 11, the length of the piping downstream of the ion removal filter 121 can be minimized, making it possible to supply the chemical solution to the substrate S before the ion concentration recovers.

[0059] Furthermore, as the equilibrium shifts to restore the amount of removed ions, the concentration of other etchants in the chemical solution, particularly unionized solutes that function effectively in narrow spaces, may decrease. To prevent this decrease in etching rate, it is preferable to increase the solute concentration in the chemical solution in advance. For example, a chemical solution with a high concentration, about 10 times higher than the concentration of the chemical solution used to etch a target object with a large opening, can be used.

[0060] According to the above-described configuration, it is possible to supply a chemical solution with a reduced content of ion species that do not contribute to narrow space etching but may actually hinder it to the substrate S. Therefore, it is possible to suppress a decrease in the etching rate even in narrow space etching, and to perform the etching process well.

[0061] 7(b), a substrate processing apparatus 2 according to a second embodiment includes a substrate processing unit 10 and a control unit 19 similar to those of the first embodiment, and a chemical liquid supply unit 200. The chemical liquid supply unit 200 includes a mixer 201, a storage tank 203, piping 205, a temperature regulator 211, a liquid feed pump 213, a particle filter 215, an output piping 207, and a control valve 217. The structures and functions of these components are the same as those of the corresponding components in the first embodiment.

[0062] In this embodiment, ion removal filters 221 and 223 are inserted in series on the output pipe 207. One of the ion removal filters 221 and 223 removes anions, and the other removes cations. By removing both anions and cations in this way, the chemical solution becomes mainly composed of unionized solutes. When unionized solutes contribute significantly to the etching reaction, removing both anions and cations in this way enables stable etching that is not affected by the surface potential of the object to be etched.

[0063] 7(c) includes a substrate processing apparatus 3 according to a third embodiment, which includes a substrate processing unit 10 and a control unit 19 similar to those of the first embodiment, and a chemical liquid supply unit 300. In this embodiment, the ion removal filter is provided outside the processing chamber 11, and a configuration for adjusting the ion concentration in the chemical liquid circulating through the circulation flow path is provided.

[0064] Specifically, the chemical solution supply unit 300 includes a mixer 301, a storage tank 303, piping 305, a temperature regulator 311, a liquid delivery pump 313, a particle filter 315, an output piping 307, and a control valve 317. The structures and functions of these components are the same as those of the corresponding components in the first embodiment.

[0065] However, unlike the first embodiment, the pipe 305 branches into two between the liquid feed pump 313 and the particle filter 315. A control valve 321 is inserted in one pipe 305a. A control valve 323 and an ion removal filter 325 are inserted in the other pipe 305b. In other words, the pipe 305a functions to form a bypass flow path that bypasses the ion removal filter 325. In addition, a concentration meter 327 is inserted in the pipe 305 after the two pipes 305a and 305b join together again.

[0066] If a concentration meter 327 is used that measures the conductivity of the chemical solution to determine the ion concentration, the concentrations of various ion species will be measured all at once. This measurement method is practical enough for chemicals with relatively simple components, such as a hydrofluoric acid solution. On the other hand, if it is necessary to measure the concentration of each ion species more precisely, a method using infrared spectroscopy, for example, can be used. For example, this method can be used when preparing a chemical solution by mixing multiple chemicals.

[0067] In this embodiment, the ion removal filter 325 is incorporated into the circulation flow path upstream of the branch to the output pipe 307 that ultimately delivers the chemical solution toward the substrate processing unit 10. In this case, the removed ion species increase again over time due to equilibrium shift. Therefore, in this embodiment, a concentration meter 327 is provided in the circulation flow path to measure the ion concentration in the chemical solution, and the amount of ions removed by the ion removal filter 325 is adjusted based on the measurement result. As in the second embodiment, a filter that removes anions and a filter that removes cations may be used in combination.

[0068] Specifically, by controlling the opening and closing of control valves 321 and 323 in accordance with the ion concentration measurement result by concentration meter 327, the flow path of the chemical solution is switched between a flow path via pipe 305a without an ion removal filter and a flow path via pipe 305b provided with ion removal filter 325. This makes it possible, for example, to not remove ions when the chemical solution is not being supplied to substrate S, but to switch the flow path to remove ions before supplying the chemical solution, thereby supplying the chemical solution with an optimized ion concentration to substrate S.

[0069] 8(a), the substrate processing apparatus 4 of the fourth embodiment has a configuration basically similar to that of the third embodiment. That is, a chemical liquid supply unit 400 of this embodiment includes a mixer 401, a storage tank 403, a pipe 405 and pipes 405a and 405b branching from the pipe 405, a temperature regulator 411, a liquid feed pump 413, a particle filter 415, an output pipe 407, control valves 417, 421, and 423, an ion removal filter 425, a concentration meter 427, and the like. The structures and functions of these components are the same as those of the corresponding components in the third embodiment.

[0070] In this embodiment, as shown by the dotted arrow in Fig. 8(a), a flow path is added that allows a drug (solute) supplied from an external supply source to be directly injected into the storage tank 403 without going through the mixer 401. This is a configuration for performing so-called spiking, in which the drug concentration in the storage tank 403 is increased by temporarily injecting the drug directly into the storage tank 403. Although detailed configuration illustrations are omitted, spiking can be performed, for example, by combining a pipe branching from the drug supply pipe from the outside with a control valve.

[0071] As the ion-removed chemical solution circulates and the ionization equilibrium shifts, the concentration of unionized solutes in the chemical solution in the storage tank 403 decreases. This causes a decrease in the etching rate when etching in a narrow space. Therefore, in this embodiment, the timing of ion removal by the ion removal filter 425 and chemical spiking is controlled as follows, so that the concentrations of both unionized hydrogen fluoride and hydrogen difluoride ions can be maintained within appropriate ranges.

[0072] 8(b) is a timing chart showing concentration control in this embodiment. The mixer 401 mixes an externally supplied chemical with DIW at a predetermined ratio, and supplies the chemical solution, in which the hydrogen fluoride concentration Cm is adjusted to be between the upper limit USL1 and the lower limit LSL1 of the appropriate range, to the storage tank 403. The concentration meter 427 measures the concentration Cm of unionized hydrogen fluoride (HF) molecules in the chemical solution and the concentration Cm of hydrogen difluoride ions (HF2 - The control unit 19 controls the opening and closing of the control valves 421 and 423 based on the measurement result of the concentration of hydrogen difluoride ions, and switches between a flow path that does not pass through the ion removal filter, as indicated by arrow A in FIG. 8(a), and a flow path that passes through the ion removal filter 425, as indicated by arrow B.

[0073] Due to the shift in ionization equilibrium that occurs in the circulating chemical solution, the concentration Cm of hydrogen fluoride molecules in the chemical solution in the storage tank 403 decreases over time. As shown by the white arrow in Figure 8(b), when the hydrogen fluoride concentration Cm falls to the lower limit LSL1, spiking is performed to inject a certain amount of chemical into the storage tank 403. This causes the hydrogen fluoride concentration Cm to temporarily increase, and then decrease again. By repeating this process, the hydrogen fluoride concentration Cm in the chemical solution can be maintained within the appropriate range.

[0074] On the other hand, the hydrogen difluoride ion concentration Ci increases when the chemical solution flows through flow path A, which does not pass through the ion removal filter, and decreases when the chemical solution flows through flow path B, which passes through the ion removal filter 425. Therefore, when the hydrogen difluoride ion concentration Ci reaches the upper limit USL2 of the appropriate range, the chemical solution flow path is switched from flow path A to flow path B. This activates the ion removal function of the ion removal filter 425, and the ion concentration decreases. Then, when the ion concentration Ci reaches the lower limit LSL2 of the appropriate range, the chemical solution flow path is switched back from flow path B to flow path A. This stops the ion removal function, and the ion concentration increases due to equilibrium shift. By repeating this process, the hydrogen difluoride ion concentration Ci in the chemical solution can also be maintained within the appropriate range.

[0075] These two controls are independent of each other, and the timing of spiking and the timing of flow path switching are not necessarily synchronized. However, because spiking also temporarily increases the hydrogen difluoride ion concentration Ci, it is thought that there is some correlation between the two.

[0076] In this embodiment, as in the third embodiment, it is possible to supply a chemical solution with an optimized ion concentration to the substrate S. Then, by performing spiking as needed, it is possible to stabilize both the hydrogen fluoride concentration and the hydrogen difluoride ion concentration for a longer period of time. In this embodiment, too, an anion removal filter and a cation removal filter may be used in combination.

[0077] 9 corresponds to the substrate processing apparatus 5 of the third embodiment with a filter regeneration function added. Specifically, a chemical liquid supply unit 500 of this embodiment includes a mixer 501, a storage tank 503, piping 505, a temperature regulator 511, a liquid feed pump 513, a particle filter 515, an output piping 507, and a control valve 517. The structures and functions of these components are the same as those of the corresponding components in the third embodiment.

[0078] Additionally, this embodiment includes a filter regeneration pipe 531 shown by a dotted line in the figure, and control valves 533 and 535 inserted in the pipe. Control valve 533 is provided in a pipe connected to an external sodium hydroxide (NaOH) supply source, while control valve 535 is provided in a pipe connected to an external DIW supply source.

[0079] When ion removal treatment is performed continuously, the ion exchange capacity of the ion exchange resin decreases due to the absorption of the removed ions. It is possible to recover the ion exchange capacity by performing a regeneration treatment to discharge the absorbed ions. For anion exchange resin, hydroxide ions (OH) are introduced into the resin using, for example, an aqueous solution of sodium hydroxide (NaOH). - The filter can be regenerated by supplying an aqueous solution of sodium chloride (NaCl) to the cation exchange resin.

[0080] The filter regeneration is performed while the flow of chemical liquid to the ion removal filter 525 is stopped, and after the regeneration process, the DIW is removed by the ion removal filter 525, thereby discharging any remaining ions. The liquid discharged from the ion removal filter 525 during the regeneration process is discharged to the outside and is prevented from flowing into the piping 505. Note that this filter regeneration function can be applied to any of the first to fourth embodiments.

[0081] The substrate processing unit 10 of the first to fifth embodiments described above is a so-called single-wafer type substrate processing apparatus that accommodates substrates S to be processed one by one in the processing chamber 11 and processes them. However, the configuration of the substrate processing apparatus to which the present invention is applicable is not limited to this. For example, as exemplified below, the present invention can also be applied to a so-called batch type substrate processing apparatus that processes multiple substrates simultaneously.

[0082] 10A and 10B are diagrams showing the schematic configurations of sixth and seventh embodiments of a substrate processing apparatus according to the present invention. Of these, FIG. 10A shows the sixth embodiment. The substrate processing apparatus 6 of the sixth embodiment shown in FIG. 10A includes a substrate processing unit 60 and a chemical liquid supply unit 600. The substrate processing unit 60 is equipped with a processing tank 61 capable of accommodating the entire substrate S therein and storing a liquid. In this substrate processing unit 60, the substrate S is immersed in the chemical liquid CS stored in the processing tank 61 to perform an etching process on the substrate S. In this case, by using a processing tank having a capacity large enough to simultaneously accommodate multiple substrates S, it is possible to simultaneously process multiple substrates, i.e., perform so-called batch processing.

[0083] The chemical liquid supply unit 600 has the same configuration as the chemical liquid supply unit 100 described in the first embodiment. Specifically, the chemical liquid supply unit 600 includes a mixer 601, a storage tank 603, piping 605, a temperature regulator 611, a liquid delivery pump 613, a particle filter 615, an output piping 607, and a control valve 617, and the structures and functions of these components are the same as those of the corresponding components in the first embodiment.

[0084] An ion removal filter 621 is also inserted in the output pipe 607. This configuration and function are also the same as the ion removal filter 121 of the first embodiment. The chemical solution that has passed through the ion removal filter 621 is supplied into the treatment tank 61 from the bottom thereof. The etching process is carried out by immersing the substrate S in the treatment tank 61 that is filled with fresh chemical solution in which the ion concentration has been properly adjusted. The chemical solution that overflows from the top of the treatment tank 61 is discharged to the outside.

[0085] 10(b), the substrate processing apparatus 7 of the seventh embodiment differs from that of the sixth embodiment in the configuration of the chemical liquid supply unit 700. The chemical liquid supply unit 700 of the seventh embodiment has the same configuration as the chemical liquid supply unit 300 of the third embodiment. That is, the chemical liquid supply unit 700 of this embodiment includes a mixer 701, a storage tank 703, a pipe 705 and pipes 705a and 705b branching from the pipe 705, a temperature regulator 711, a liquid feed pump 713, a particle filter 715, an output pipe 707, control valves 717, 721, and 723, an ion removal filter 725, a concentration meter 727, and the like. The structures and functions of these components are the same as those of the corresponding components in the third embodiment.

[0086] Even with this configuration, it is possible to supply a chemical solution with an optimized ion concentration to the processing tank 61 and perform a good etching process on the substrate S. As in the fourth embodiment, a spiking function may be further added.

[0087] In these embodiments, an anion removal filter and a cation removal filter may be used in combination, as in the second embodiment. Furthermore, a filter regeneration function may be further added, as in the fifth embodiment. In this way, the chemical solution supply units shown in the first to fifth embodiments can also be combined with substrate processing units that perform batch processing.

[0088] As described above, in the substrate processing apparatus of the first embodiment, the mixer 101 and the storage tank 103 function together as the "chemical liquid preparation unit" of the present invention, and the storage tank 103 corresponds to the "storage container" of the present invention. The ion removal filter 121 functions as the "ion removal unit" of the present invention. The piping 105 and the liquid transfer pump 113 function together as the "chemical liquid supply unit" of the present invention. The output piping 107 corresponds to the "supply piping" of the present invention. The same applies to the configurations corresponding to the above in each of the second and subsequent embodiments.

[0089] In addition, the concentration meter 327 and the like in the third, fourth, fifth and sixth embodiments function as the "concentration measuring unit" of the present invention, and the control valves 321, 323 and the like function as the "concentration adjusting unit" of the present invention. In addition, the regeneration pipe 531 and the control valves 533, 535 in the fifth embodiment function as the "regeneration unit" of the present invention.

[0090] The present invention is not limited to the above-described embodiments, and various modifications other than those described above are possible without departing from the spirit of the present invention. For example, in the first and second embodiments, the ion removal filter 121 and the like are provided inside the processing chamber 11 for the purpose of removing ions at a position close to the nozzle 15a that ultimately supplies the chemical solution to the substrate S. Alternatively, the ion removal filter may be integrated with the processing chamber and attached to, for example, the outer wall surface thereof.

[0091] For example, although a temperature regulator and a particle filter are provided in the flow path of the chemical solution in each of the above embodiments, these are not essential requirements. Also, although a circulation flow path for the chemical solution is provided in each of the above embodiments, the effect of improving the etching rate in narrow space etching by ion removal according to the present invention is effective even in substrate processing apparatuses that do not have such a circulation flow path.

[0092] Furthermore, the types of chemical substances (materials to be etched, solutes, solvents, etc.) listed in the above embodiments are only examples, and the present invention is also applicable to processes using various substances other than those listed above.

[0093] As described above with reference to specific embodiments, in the substrate processing apparatus according to the present invention, the ion removal unit can be provided in the processing chamber. For example, it may be provided inside the processing chamber. Even if some ion species are removed from the chemical solution, the concentration increases over time due to a shift in ionization equilibrium. By performing ion removal at a position as close as possible to the position where the chemical is supplied to the substrate, the effects of the present invention can be more reliably achieved.

[0094] Furthermore, for example, the chemical solution preparation unit may have a storage container that temporarily stores the prepared chemical solution, the chemical solution supply unit may have a circulation flow path that circulates the chemical solution delivered from the storage container to the storage container, and the ion removal unit may be provided in a flow path branching from the circulation flow path. With this configuration, the chemical solution in an equilibrium state is circulated within the circulation flow path, and by providing the ion removal unit in a flow path branching from the circulation flow path and heading toward the substrate, the ion concentration of the chemical solution supplied to the substrate can be reliably reduced.

[0095] On the other hand, for example, the chemical solution preparation unit may include a storage container for temporarily storing the prepared chemical solution, the chemical solution supply unit may include a circulation flow path for circulating the chemical solution delivered from the storage container to the storage container and a supply flow path branching from the circulation flow path for supplying the chemical solution to the substrate, and the circulation flow path leading from the storage container to the branch point with the supply flow path may be provided with an ion removal unit, a concentration measurement unit for measuring the concentration of ion species in the chemical solution, and a concentration adjustment unit for adjusting the ion concentration in the chemical solution based on the measurement results of the concentration measurement unit. With this configuration, it is possible to supply the chemical solution to the substrate while maintaining the ion concentration in the chemical solution appropriately.

[0096] In this case, the concentration adjusting unit may include a bypass flow path connected to the circulation flow path and bypassing the ion removal unit, and a control valve that controls the flow rate of the chemical solution in the bypass flow path based on the measurement results of the ion concentration measuring unit. With this configuration, it is possible to increase or decrease the ion concentration in the chemical solution by changing the ratio of the chemical solution from which ions have been removed to the chemical solution before ion removal.

[0097] Furthermore, for example, the ion removal unit may be one that removes ionic species using an ion exchange resin or an ion exchange membrane. Ion removal according to the present invention can be achieved using such known materials.

[0098] In this case, a regeneration unit may be further provided that regenerates the ion exchange resin contained in the ion removal unit. By adding the function of regenerating the ion exchange resin, it becomes possible to perform ion removal stably over a long period of time.

[0099] Furthermore, for example, the chemical solution preparation unit may be configured to control the amount of solute added to the chemical solution based on the measurement results of the concentration of unionized solute in the chemical solution. Removal of a specific ion species may shift the ionization equilibrium, which may result in a decrease in the concentration of unionized solute in the chemical solution. Unionized solute also contributes to the etching reaction, and a decrease in its concentration may cause a decrease in the etching rate. By controlling the amount of solute in the solution according to the concentration of unionized solute, it is possible to avoid such problems.

[0100] Furthermore, in the substrate processing apparatus and substrate processing method according to the present invention, the portion of the substrate to be etched can be a recess with a minimum opening dimension of 10 nanometers or less, more preferably 5 nanometers or less. In the typical combination of etching target and chemical solution used in the manufacture of semiconductor devices, etc., the Debye length, which is a measure of the distance affected by the potential of the electric double layer formed on the material surface, is on the order of several nanometers. When the opening dimension is this small, the etching rate drops significantly, making the present invention particularly effective.

[0101] Furthermore, in the present invention, the chemical solution may contain hydrogen fluoride as an etchant, and the ion removal unit may be configured to remove hydrogen difluoride ions. For example, when the object to be removed by the etching process is silicon dioxide, hydrogen fluoride is an effective etchant. On the other hand, the chemical solution may contain hydrogen peroxide as an etchant, and the ion removal unit may be configured to remove hydrogen peroxide ions. For example, when the object to be removed by the etching process is titanium dioxide, hydrogen peroxide is an effective etchant. In these cases, even if ions function effectively as etchants in areas with large openings, their contribution to the etching reaction is reduced in narrow spaces. By removing such ion species, the etching reaction by the unionized etchant can be promoted.

[0102] Furthermore, for example, the substrate processing method according to the present invention may further include the steps of measuring the ion concentration in the chemical solution that has passed through the ion removal unit and adjusting the ion concentration in the chemical solution based on the measurement results. With this configuration, it is possible to supply the chemical solution to the substrate while maintaining the ion concentration in the chemical solution at an appropriate level. [Industrial Applicability]

[0103] The present invention is applicable to a technique for etching a substrate using a chemical solution containing an etchant that is a solute that ionizes in the solution, and is particularly suitable for device manufacturing processes that require etching in narrow spaces with opening dimensions of 10 nanometers or less. [Explanation of symbols]

[0104] 1~7 Substrate processing equipment 10. Substrate Processing Unit 100,200,300,400,500,600,700 Substrate processing unit 101, 203, 303, 403, 503, 603, 703 Mixer (chemical solution preparation section) 105, 205, 305, 405, 505, 605, 705 Piping (chemical supply section, circulation flow path) 113,213,313,413,513,613,713 Liquid transfer pump (chemical supply section) 103, 203, 303, 403, 503, 603, 703 Storage tank (medicine preparation section, storage container) 107,207,307,407,507,607,707 Output piping (supply piping) 121, 221, 223, 325, 425, 525, 621, 725 Ion removal filter (ion removal part) 321, 323, 421, 423, 521, 523, 721, 723 Control valve (concentration adjustment part) 327,427,527,727 Concentration meter (concentration measurement part) 531 Regeneration piping (regeneration part) 533,535 Control valve (regeneration section) S board

Claims

1. A substrate processing apparatus that performs narrow space etching, which etches narrow spaces including a portion where the opening dimension of a recess is 10 nanometers or less, a chemical solution preparation unit that prepares a chemical solution containing a solute that acts as an etchant for the narrow space etching and is ionized in the liquid; a processing chamber that accommodates a substrate and performs an etching process on the substrate with the chemical solution; an ion removal unit that removes at least a portion of specific ion species in the chemical solution that do not contribute to the narrow space etching or that inhibit the narrow space etching reaction; a chemical solution supply unit that forms a chemical solution flow path for supplying the chemical solution delivered from the chemical solution preparation unit to the substrate in the processing chamber via the ion removal unit; A substrate processing apparatus comprising:

2. The substrate processing apparatus according to claim 1 , wherein the ion removal unit is provided in the processing chamber.

3. The substrate processing apparatus according to claim 2 , wherein the ion removal unit is provided inside the processing chamber.

4. the medicinal solution preparation unit has a storage container that temporarily stores the prepared medicinal solution, the chemical solution supply unit has a circulation flow path that circulates the chemical solution delivered from the storage container back to the storage container, 4. The substrate processing apparatus according to claim 1, wherein the ion removal unit is provided in the flow path branched from the circulation flow path.

5. the medicinal solution preparation unit includes a storage container that temporarily stores the prepared medicinal solution, the chemical solution supply unit includes a circulation flow path that circulates the chemical solution delivered from the storage container to the storage container, and a supply flow path that branches off from the circulation flow path and supplies the chemical solution to the substrate; The circulation flow path extending from the storage container to a branch point with the supply flow path includes the ion removal unit, a concentration measurement unit that measures the concentration of the ion species in the chemical solution, and a concentration adjustment unit that adjusts the ion concentration in the chemical solution based on the measurement result of the concentration measurement unit.

4. The substrate processing apparatus according to claim 1, further comprising:

6. a bypass flow path connected to the circulation flow path and bypassing the ion removal unit; a control valve for controlling the flow rate of the chemical solution in the bypass flow path; The substrate processing apparatus according to claim 4 or 5, further comprising:

7. 7. The substrate processing apparatus according to claim 1, wherein the ion removal unit removes the ion species using an ion exchange resin or an ion exchange membrane.

8. The substrate processing apparatus according to claim 7 , further comprising a regenerating section that regenerates the ion exchange resin contained in the ion removing section.

9. 9. The substrate processing apparatus according to claim 1, wherein the chemical solution preparation unit controls the amount of the solute to be added to the chemical solution based on a measurement result of the concentration of the unionized solute in the chemical solution.

10. 10. The substrate processing apparatus according to claim 1, wherein the chemical solution contains hydrogen fluoride as the etchant, and the ion removal unit removes hydrogen difluoride ions.

11. A substrate processing method for performing narrow space etching, which etches narrow spaces including a portion where the opening dimension of a recess is 10 nanometers or less, comprising: preparing a chemical solution containing a solute that acts as an etchant for the narrow space etching and is ionized in the solution; a step of sending the prepared chemical solution to an ion removal unit to remove at least a portion of specific ion species in the chemical solution that do not contribute to the narrow space etching or that inhibit the narrow space etching reaction; supplying the chemical solution that has passed through the ion removal unit to a substrate for etching; A substrate processing method comprising:

12. The substrate processing method according to claim 11 , wherein the minimum opening dimension is 5 nanometers or less.

13. 13. The substrate processing method according to claim 11, wherein the chemical solution contains hydrogen fluoride as the etchant, and the ion removal unit removes hydrogen difluoride ions.

14. The substrate processing method according to claim 13, wherein the material to be removed by the etching process is silicon dioxide.

15. 13. The substrate processing method according to claim 11, wherein the chemical solution contains hydrogen peroxide as the etchant, and the ion removal unit removes hydrogen peroxide ions.

16. 16. The substrate processing method according to claim 15, wherein the object to be removed by the etching treatment is titanium dioxide.

17. measuring the ion concentration in the chemical solution that has passed through the ion removal unit; adjusting the ion concentration in the chemical solution based on the measurement result; The substrate processing method according to claim 11 , further comprising:

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