JP2024134798A - Substrate processing method and apparatus - Google Patents

Abstract

To appropriately etch a substrate regardless of the size of a recess on the substrate or the size of a layer to be etched.SOLUTION: Since nanobubbles NB+ are positively charged, negative ions (HF2-) of an etching species are attracted to the nanobubbles NB+, and positive ions (H+) of the etching species are repelled by the nanobubbles NB+. Therefore, even in a narrow recess, the active etching species of the etching solution EF circulate one after another. Furthermore, even in a narrow recess, the nanobubbles NB+ do not enter the recess, because their particle size is larger than the thickness of a first layer L1. Therefore, the nanobubbles NB+ exist outside the narrow recess where active etching species are abundant, and contribute to the stirring of the etching solution EF in the narrow recess. As a result, a substrate W can be appropriately etched regardless of the size of the first layer L1 on the substrate W.SELECTED DRAWING: Figure 2

Description

The present invention relates to a substrate processing method and apparatus for processing substrates (hereinafter simply referred to as substrates) such as semiconductor wafers, substrates for liquid crystal displays and organic EL (Electroluminescence) display devices, glass substrates for photomasks, substrates for optical disks, substrates for magnetic disks, ceramic substrates, and substrates for solar cells.

Conventionally, one such method involves supplying an etching liquid to a substrate and etching the substrate (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 9-22891 Japanese Patent Application Publication No. 9-115875

However, the conventional example having such a configuration has the following problems.
That is, in recent years, the patterns formed on the surface of the substrate are becoming finer and more complex three-dimensional structures. Specifically, the patterns have progressed from Fin-type FETs to Gate-All-Around (GAA)-type FETs (nanowires and nanosheets), Nanosheets+BPR (Buried Power Rails), Forksheets+new standard cell arch., CFET (Complementary FET)+BEOL (Back End Of Line) w/air gaps, and CFET w/2D atomic channels. Therefore, etching of narrower and deeper portions is required. For example, the pattern includes multiple convex portions (structures) and multiple concave portions (spaces). The pattern also includes a layer to be etched sandwiched between layers not to be etched. For example, the concave portions and the layer to be etched become narrower. The dimensions of the concave portions and the layer to be etched may be, for example, tens of nanometers or less.

For this reason, in etching processes, etching liquid may be supplied to narrow recesses or layers to be etched. However, the quality of the etching process may be reduced depending on the size of the recesses or layers to be etched. For example, if the recesses or layers to be etched are narrow, the substrate may not be properly etched. For example, if the recesses or layers to be etched are narrow, the etching function may be reduced.

The present invention has been made in consideration of these circumstances, and aims to provide a substrate processing method and apparatus that can properly etch a substrate regardless of the size of the recess on the substrate or the layer to be etched.

The present inventors have conducted intensive research to solve the above problems, and have come to the following findings. Here, reference is made to Figs. 9 and 10. Fig. 9 shows the structure of a sample that has been etched. Fig. 10 is a graph showing the etching rate when etching is performed by applying ultrasonic vibration. The sample substrate W has a first layer L1 made of an oxide film (SiO ₂ ). The first layer L1 is a layer to be etched. In the sample, the second layer L2, which is an upper layer of the first layer L1, is made of polysilicon. In the sample, the third layer L3, which is a lower layer of the first layer L2, is made of silicon. The first layer L1, the second layer L2, and the third layer L3 have different compositions. A process of etching the first layer L1 of this sample was performed. As the etching of the first layer L1 progresses, a recess is formed between the second layer L2 and the third layer L3.

The thickness of the first layer L1 of each sample is different, 3 nm, 5 nm, and 10 nm. The etching solution is a solution composed of a mixture of hydrofluoric acid (HF) and pure water (DIW). The mixture ratio is HF:DIW=1:5. Each sample having the above-mentioned configuration was immersed in this etching solution for 1 minute. The length EL of the first layer L1 etched in the direction perpendicular to the stacking direction of the first layer L1 to the third layer L3 was measured. From the result, the etching rate (nm/min) was obtained. Furthermore, a comparison was made with the case where ultrasonic vibration was applied to the etching solution as a physical assist. The result is graphed in FIG. 10. From this graph, the narrower the first layer L1, the lower the etching rate. Furthermore, even if physical assist was applied, the etching rate did not improve. From this result, the inventors considered that the etching rate was not improved near the narrow first layer L1 because the etching species (HF ₂ ⁻ , H ⁺ ) that contribute to the etching action in the etching solution were not replaced. Based on this finding, the present invention is configured as follows.

That is, the invention described in claim 1 is a substrate processing method for processing a substrate including a first layer, a second layer formed on one side of the first layer and having a composition different from that of the first layer, and a third layer formed on the other side of the first layer and having a composition different from that of the first layer, characterized in that it includes an etching step of etching the first layer by applying to the substrate an etching solution that contains nanobubbles that are larger in diameter than the thickness of the first layer and are electrically charged, and that contains ions or polarized molecules that etch the first layer.

[Actions and Effects] According to the invention described in claim 1, in the etching process, as the etching of the first layer progresses, a recess is formed between the second layer and the third layer. In the etching process, the charged nanobubbles attract or repel the etching species, which are ions or polarized molecules of the etching solution. Therefore, the etching solution supplied to the substrate is stirred, and the active etching species circulate. Even if the recess is narrow, the charged nanobubbles do not enter the recess because their particle size is larger than the thickness of the first layer. Therefore, the nanobubbles exist outside the recess where active etching species are abundant, and contribute to stirring the etching solution in the narrow recess. As a result, the substrate can be appropriately etched regardless of the size of the recess on the substrate or the layer to be etched.

Note that nanobubbles here refer to bubbles with a particle size of several nanometers to several hundred nanometers.

In addition, in the present invention, it is preferable to carry out a mixing step immediately before the etching step, in which the dilution liquid containing the nanobubbles is mixed with a chemical liquid to generate the etching liquid (Claim 2).

Nanobubbles are easily crushed by compression, expansion, vortexes, etc. that occur during the liquid flow process. Therefore, an etching solution is produced by mixing a dilution liquid containing nanobubbles with a chemical liquid in a mixing process immediately before the etching process. This makes it possible to carry out the etching process while maximizing the effect of containing nanobubbles. As a result, it is possible to reliably perform appropriate etching on the substrate.

In the present invention, it is preferable that the mixing step generates the etching solution by supplying the dilution solution containing the nanobubbles and the chemical solution near the substrate (Claim 3).

The etching solution is generated by mixing the dilution liquid containing nanobubbles with the chemical solution near the substrate, so the etching process can be carried out before the nanobubbles in the dilution liquid are reduced by collapse. As a result, the effect of containing nanobubbles can be maximized while minimizing the reduction in nanobubbles.

In the present invention, it is also preferable that the mixing step is performed in such a manner that the dilution liquid containing the nanobubbles and the chemical liquid are mixed in a mixing tank upstream of the position where the etching liquid is supplied to the substrate (Claim 4).

The dilution liquid containing nanobubbles and the chemical liquid are mixed in a mixing tank to produce the etching liquid. Therefore, before the nanobubbles in the dilution liquid are significantly reduced due to collapse, the dilution liquid and the chemical liquid are sufficiently mixed in the mixing tank, and then the etching process can be carried out using the etching liquid. As a result, the etching liquid can be supplied without uneven mixing of the chemical liquid. Therefore, unevenness in the etching process can be suppressed.

In the present invention, it is preferable that the mixing step is performed by mixing the dilution liquid containing the nanobubbles and the chemical liquid in a mixing valve upstream from the position where the etching liquid is supplied to the substrate (claim 5).

The dilution liquid containing nanobubbles and the chemical liquid are mixed in the mixing valve to generate the etching liquid. Therefore, the etching liquid can be supplied to the substrate within a short time after generation. As a result, the etching liquid can be supplied in a state where the chemical liquid concentration in the etching liquid is accurately adjusted to the desired concentration, and the etching liquid can be supplied to the substrate with the reduction in nanobubbles kept to a minimum.

In addition, in the present invention, it is preferable that the dilution liquid is generated by passing pure water through a nanobubble generator that generates nanobubbles (Claim 6).

By passing pure water through a nanobubble generator, nanobubbles can be generated in the pure water to produce a diluted solution. Therefore, a diluted solution containing a large amount of nanobubbles can be used in the etching process, allowing the etching solution to be sufficiently agitated.

In addition, in the present invention, it is preferable that the dilution liquid is a solution containing pre-generated nanobubbles in pure water (Claim 7).

It does not take much time to generate nanobubbles in pure water. Therefore, the etching process can be carried out in a short time.

In addition, in the present invention, it is preferable that the method further includes, before the etching step, a step of mixing an adjustment liquid for adjusting the pH of the etching solution (claim 8).

By adjusting the pH of the etching solution in the adjustment liquid mixing process, the zeta potential of the nanobubbles can be adjusted. Therefore, the degree of charge of the nanobubbles can be adjusted, and therefore the degree of agitation of the etching solution can be adjusted.

In the present invention, it is also preferable that the adjusting liquid is a chemical liquid that further strengthens the acidity or alkalinity of the etching liquid (Claim 9).

By further increasing the acidity or alkalinity of the etching solution, the absolute value of the zeta potential can be increased. This increases the degree of charge on the nanobubbles. As a result, the degree of agitation of the etching solution can be increased.

The invention described in claim 10 is a substrate processing apparatus for processing a substrate, characterized in that it comprises a processing section for processing a substrate including a first layer, a second layer formed on one side of the first layer and having a composition different from that of the first layer, and a third layer formed on the other side of the first layer and having a composition different from that of the first layer, a supply section for supplying an etching solution containing nanobubbles having a particle size larger than the thickness of the first layer and charged, and containing ions or polarized molecules that etch the first layer, to the processing section, and a control section for etching the first layer by applying the etching solution supplied from the supply section to the substrate held in the holding section.

[Actions and Effects] According to the invention described in claim 10, the control unit supplies the etching solution from the supply unit to the substrate in the processing unit. As the etching of the first layer progresses, a recess is formed between the second layer and the third layer. In the etching solution, charged nanobubbles attract or repel etching species, which are ions or polarized molecules of the etching solution. Therefore, the etching solution supplied to the substrate is stirred, and active etching species circulate to the substrate. Even if the recess is narrow, the charged nanobubbles do not enter the recess because their particle size is larger than the thickness of the first layer. Therefore, the nanobubbles exist outside the recess where active etching species are abundant, and contribute to stirring the etching solution in the narrow recess. As a result, the substrate can be appropriately etched regardless of the size of the recess on the substrate or the layer to be etched.

According to the substrate processing method of the present invention, in the etching process, as the etching of the first layer progresses, a recess is formed between the second layer and the third layer. In the etching process, the charged nanobubbles attract or repel etching species, which are ions or polarized molecules of the etching solution. Therefore, the etching solution supplied to the substrate is stirred, and active etching species circulate. Even if the recess is narrow, the charged nanobubbles do not enter the recess because their particle size is larger than the thickness of the first layer. Therefore, the nanobubbles exist outside the recess where active etching species are abundant, and contribute to stirring the etching solution in the narrow recess. As a result, the substrate can be appropriately etched regardless of the size of the recess on the substrate or the layer to be etched.

1 is a block diagram showing a schematic configuration of a substrate processing apparatus according to a first embodiment; FIG. 1 is a schematic diagram illustrating the action of nanobubbles with a positive zeta potential. FIG. 1 is a schematic diagram illustrating the action of nanobubbles with a negative zeta potential. FIG. 11 is a block diagram showing a schematic configuration of a substrate processing apparatus according to a second embodiment. FIG. 11 is a block diagram showing a schematic configuration of a substrate processing apparatus according to a third embodiment. FIG. 13 is a block diagram showing a schematic configuration of a substrate processing apparatus according to a modified example. 1 is a graph showing an example of the relationship between zeta potential and pH. 1 is a graph showing experimental results of the present invention. FIG. 1 is a diagram for explaining the prior art, showing the structure of an etched sample. 1 is a graph for explaining the prior art, showing an etching rate when etching is performed by applying ultrasonic vibrations.

The present invention will be explained below with reference to examples.

The following describes Example 1 of the present invention with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a substrate processing apparatus according to Example 1. FIG. 2 is a schematic diagram explaining the action of nanobubbles with a positive zeta potential. FIG. 3 is a schematic diagram explaining the action of nanobubbles with a negative zeta potential.

＜1-1. Device configuration＞

The substrate processing apparatus 1 processes a substrate W. The substrate W has, for example, a circular shape in a plan view. The substrate W is, for example, a thin plate. The substrate W is, for example, made of a semiconductor. The substrate W is, for example, silicon.

The substrate processing apparatus 1 performs a predetermined process on the substrate W. The substrate processing apparatus 1 is a single-wafer type apparatus that processes the substrates W one by one in sequence. The substrate processing apparatus 1 performs, for example, an etching process on the substrate W. The etching process chemically etches various films formed on the substrate W. The etching process processes the shapes of various films formed on the substrate W. The etching process is carried out in an etching step.

The substrate processing apparatus 1 includes a processing section 3, a supply section 5, and a control section 7.

The processing section 3 accommodates the substrate W. The processing section 3 processes the substrate W. The processing section 3 includes a chuck 9, a rotating shaft 11, an electric motor 13, and a guard 15.

The chuck 9 holds the substrate W in a horizontal position. The chuck 9, for example, holds the substrate W by suction at the center of its lower surface. The chuck 9 supports the substrate W by abutting it with its upper surface. The chuck 9 is smaller than the diameter of the substrate W. The rotating shaft 11 is cylindrical. The rotating shaft 11 extends in the vertical direction. The lower surface of the chuck 9 is attached to the upper end of the rotating shaft 11. The lower end of the rotating shaft 11 is connected to the electric motor 13. The electric motor 13 rotates the rotating shaft 11 around the axis P1. The electric motor 13 rotates the substrate W together with the rotating shaft 11 and the chuck 9 around the axis P1. A guard 15 is arranged on the outer periphery of the chuck 9. The guard 15 prevents the processing liquid supplied to the substrate W from scattering around. The guard 15 moves up and down between a standby position where its upper end is lower than the chuck 9 and a processing position where its upper end is higher than the chuck 9.

The chuck 9 may be of a so-called mechanical type that supports the substrate W by contacting the outer edge of the substrate W. The mechanical chuck 9 has an outer diameter that is slightly larger than the outer diameter of the substrate W.

The supply unit 5 includes a first nozzle 17, a second nozzle 19, a first supply pipe 21, a second supply pipe 23, a first supply tank 25, and a second supply tank 27. The first nozzle 17 and the second nozzle 19 are configured to be movable between a supply position for supplying the processing liquid to the position where the axis P1 and the upper surface of the substrate W intersect, and a standby position located to the side of the guard 15. The first nozzle 17 and the second nozzle 19 supply the processing liquid to the upper surface of the substrate W at the supply position. The supply position is located above the substrate W. The standby position is a position located to the side of the substrate W.

The first supply pipe 21 is connected to the first nozzle 17 at one end. The first supply pipe 21 is connected to the first supply tank 25 at the other end. The first supply tank 25 stores the first processing liquid. The first supply pipe 21 is provided with a control valve 29, a pump 31, and a flow meter 33 from the first supply tank 25 toward the first nozzle 17. The control valve 29 adjusts the flow rate of the first processing liquid in the first supply pipe 21. The control valve 29 switches to block the flow of the first processing liquid or to allow the flow at a set flow rate. The pump 31 supplies the first processing liquid stored in the first supply tank 25 to the first nozzle 17 via the first supply pipe 21. The flow rate of the first processing liquid at that time depends on the setting of the control valve 29. The flow meter 33 detects the flow rate of the first processing liquid.

The first processing liquid is, for example, pure water (DIW). The first processing liquid is pure water containing nanobubbles. Nanobubbles are air bubbles with a diameter of about several nm to several hundred nm. The diameter of the nanobubbles is larger than the dimensions of the layer to be etched or the recess. The first processing liquid is nanobubble water. The first processing liquid is, for example, commercially available nanobubble water containing nanobubbles of the above-mentioned diameter. The first processing liquid is, for example, nanobubble water containing nanobubbles of the above-mentioned diameter that is generated and then stored in the first supply tank 25.

The first treatment liquid corresponds to the "dilution liquid" in this invention.

The second supply pipe 23 is connected to the second nozzle 19 at one end. The second supply pipe 3 is connected to the second supply tank 27 at the other end. The second supply tank 23 stores the second processing liquid. The second supply pipe 23 is provided with a control valve 35, a pump 37, and a flow meter 39 from the second supply tank 27 toward the second nozzle 19. The control valve 35 adjusts the flow rate of the second processing liquid in the second supply pipe 23. The control valve 35 switches to block the flow of the second processing liquid or to allow the flow at a set flow rate. The pump 37 supplies the second processing liquid stored in the second supply tank 27 to the second nozzle 19 via the second supply pipe 23. The flow rate of the second processing liquid at that time depends on the setting of the control valve 35. The flow meter 39 detects the flow rate of the second processing liquid.

The second processing liquid is different from the first processing liquid. The second processing liquid is a chemical liquid. The chemical liquid is, for example, hydrofluoric acid (HF).

The first processing liquid and the second processing liquid are mixed to form an etching liquid. The mixing ratio of the first processing liquid supplied from the first nozzle 17 to the second processing liquid supplied from the second nozzle 19 is, for example, 5:1. This ratio is adjusted according to the desired etching rate of the layer to be etched and the recess on the substrate W.

The control unit 7 controls the above-mentioned parts in an integrated manner. The control unit 7 includes a CPU and a memory (not shown). The memory stores a control program and a recipe that defines the conditions for processing the substrate W. The control unit 7 controls the movement of the first nozzle 17 and the second nozzle 19. The control unit 7 controls the elevation of the guard 15. The control unit 7 operates the control valves 29 and 35 to control the flow rate of the first processing liquid in the first supply pipe 21 and the flow rate of the second processing liquid in the second supply pipe 23. The control unit 7 receives the flow rates detected by the flow meters 33 and 39. The control unit 7 operates the control valves 29 and 35 to perform feedback control of the flow rates of the first processing liquid and the second processing liquid.

<1-2. Processing process>

An example of a specific processing step for the etching process on the substrate W performed by the substrate processing apparatus 1 described above will be described.

A substrate W on which a film to be processed is formed is placed on the chuck 9. The substrate W is transported from a transport arm (not shown). The substrate W is adsorbed to the chuck 9. The substrate W has a layer to be etched formed on its upper surface.

The control unit 7 raises the guard 15 to the processing position. The control unit 7 moves the first nozzle 17 and the second nozzle 19 to the supply position. The control unit 7 operates the electric motor 13 to rotate the substrate W at a processing rotation speed according to the recipe. The processing rotation speed is slower than the drying rotation speed described below. The processing rotation speed is, for example, several hundred rpm. The control unit 7 operates the control valves 29, 35 and the pumps 31, 37 to circulate the first processing liquid and the second processing liquid at a predetermined ratio. At this time, the control valves 29, 35 may be operated to perform feedback control based on the detection results of the flow meters 33, 39.

In this manner, the first processing liquid and the second processing liquid are supplied near the center of rotation of the substrate W. The first processing liquid and the second processing liquid are supplied to the substrate W in a predetermined ratio and mixed to generate an etching liquid on the upper surface of the substrate W. The control unit 7 maintains this state for the etching time according to the recipe. The etching time is, for example, several tens of minutes. Since the rotation speed of the substrate W is relatively low, a sufficient thickness of the etching liquid is stored on the upper surface of the substrate W, and the etching liquid is further discharged from the outer periphery to the surrounding area. This causes etching of the layer to be etched formed on the surface of the substrate W. An etching process using the etching liquid is carried out.

The supply of the first processing liquid and the second processing liquid to the substrate W and mixing them corresponds to the "mixing process" in the present invention. The supply of the first processing liquid and the second processing liquid to the substrate W in a predetermined ratio and the etching liquid acting on the substrate W corresponds to the "etching process" in the present invention.

When the etching time has elapsed, the control unit 7 closes the control valves 29 and 35. When the etching time has elapsed, the control unit 7 stops the pumps 31 and 37. The control unit 7 moves the first nozzle 17 and the second nozzle 19 to the standby position. The control unit 7 moves a nozzle (not shown) onto the axis P1 of the substrate W to supply a rinsing liquid. The rinsing liquid is, for example, pure water. This washes away the etching liquid adhering to the upper surface of the substrate W. A rinsing process using the rinsing liquid is performed.

When the rinsing time according to the recipe has elapsed, the control unit 7 stops the supply of rinsing liquid from the nozzle (not shown). After retracting the nozzle (not shown), the control unit 7 increases the rotation speed of the electric motor 13 to the drying rotation speed according to the recipe. The drying rotation speed is higher than the processing rotation speed. The drying rotation speed is, for example, several thousand rpm. This drying rotation speed is maintained for the drying time according to the recipe. This causes the substrate W to undergo a shake-off drying process. A drying process by shake-off is carried out.

After drying for the drying time, the control unit 7 stops the electric motor 13. This stops the rotation of the substrate W. The control unit 7 lowers the guard 15 to the standby position and releases the suction by the chuck 9. The control unit 7 causes the substrate W to be removed by a transport arm (not shown).

The etching process for one substrate W is completed through the above-described series of steps.

Here, reference is made to Figures 2 and 3. Figure 2 is a schematic diagram explaining the action of nanobubbles with a positive zeta potential. Figure 3 is a schematic diagram explaining the action of nanobubbles with a negative zeta potential.

In the above-mentioned etching process, an etching solution is generated on the upper surface of the substrate W. This etching solution is a mixture of pure water containing nanobubbles as a first processing solution and hydrofluoric acid as a second processing solution. This etching solution is acidic. When the etching target layer is an oxide film (SiO ₂ ), the etching species that contribute to etching are HF ₂ ⁻ , H ⁺ , and H ₂ F ₂ . Therefore, among these etching species, when HF ₂ ⁻ and H ⁺ are circulated to the etching target layer one after another, the active etching species that are not acting on the etching act on the etching target layer, so that the decrease in the etching rate can be suppressed. If the etching target layer is narrow, it is difficult for the active etching species to circulate to the etching target layer. In particular, when the etching target layer is a recess or becomes a recess as etching progresses, the etching rate is likely to decrease.

＜1-3. Special effects＞

In this embodiment, nanobubble water is mixed into the etching solution. This etching solution is acidic. The nanobubbles are dispersed in the acidic etching solution. Therefore, in this etching solution, the zeta potential of the nanobubbles is positive. The nanobubbles in the etching solution are positively charged. The nanobubbles in the etching solution are positive poles. Since the nanobubbles are charged with the same polarity, they can be dispersed in the etching solution without agglomerating. As shown in FIG. 2, if the first layer L1 is sandwiched between the second layer L2 and the third layer L3 and is narrow, the etching rate decreases.

In this embodiment 1, the etching solution EF is acidic. Therefore, since the nanobubbles NB+ are positively charged, the negative ions (HF ₂ ⁻ ) of the etching species are attracted to the nanobubbles NB+, and the positive ions (H ⁺ ) of the etching species are repelled by the nanobubbles NB+. Therefore, even in a narrow recess, the active etching species of the etching solution EF circulate one after another. Furthermore, even in a narrow recess, the nanobubbles NB+ have a particle size larger than the thickness of the first layer L1, so they do not enter the recess. Therefore, the nanobubbles NB+ exist outside the narrow recess where the active etching species are abundant, and contribute to the stirring of the etching solution EF in the narrow recess. As a result, the substrate W can be appropriately etched regardless of the size of the first layer L1 on the substrate W.

In the above example, the etching solution EF is acidic. On the other hand, when the etching solution EF is alkaline with SC1, it acts as shown in FIG. 3. That is, when the etching solution EF is alkaline, the nanobubbles NB- are negatively charged. Therefore, the negative ions of the etching species (HO ₂ ^- , OH ^- ) are repelled by the nanobubbles NB-, and the positive ions of the etching species (H ⁺ ) are attracted to the nanobubbles NB+. Therefore, similarly to the above, the active etching species of the etching solution EF circulate one after another. As a result, the substrate W can be appropriately etched regardless of the size of the first layer L1 on the substrate W.

In the present invention, etching species ions are agitated with charged nanobubbles. In other words, the etching species ions are moved by charged nanobubbles without forming an electric field. Therefore, no power is required to form an electric field, and power saving can be achieved compared to a configuration in which an electric field is formed to move the etching species ions and nanobubbles.

Second Embodiment A second embodiment of the present invention will now be described with reference to the drawings.
FIG. 4 is a block diagram showing a schematic configuration of a substrate processing apparatus according to the second embodiment.

＜2-1. Device configuration＞

The same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. The substrate processing apparatus 1A includes a processing section 3, a supply section 5A, and a control section 7.

The supply unit 5A is equipped with a third nozzle 17A. The third nozzle 17A is connected to one end of a third supply pipe 41. The other end of the third supply pipe 41 is connected to a mixing tank 43. The third supply pipe 41 is equipped with a control valve 45, a pump 47, and a flow meter 49, in that order, from the mixing tank 43 side toward the third nozzle 17A side. The third nozzle 17A is configured to be movable between a supply position above the axis P1 and a standby position spaced to the side of the guard 15. The supply position is located above the substrate W. The standby position is spaced to the side of the substrate W.

The control valve 45 adjusts the flow rate of the third processing liquid in the third supply pipe 41. The control valve 45 switches between blocking the flow of the third processing liquid or allowing the flow at a set flow rate. The pump 47 supplies the third processing liquid stored in the mixing tank 43 to the third nozzle 17A via the third supply pipe 41. The flow rate of the third processing liquid at that time depends on the setting of the control valve 45. The flow rate of the third processing liquid at that time is detected by the flow meter 49.

The third processing liquid is a mixture of a diluent containing nanobubbles and a chemical liquid. The mixture is an etching liquid. The etching liquid is generated in a mixing tank 43. The mixing tank 43 is connected to a first supply pipe 21A and a second supply pipe 23A. One end of the first supply pipe 21A is connected to a pure water supply source. The other end of the first supply pipe 21A is connected to the mixing tank 43. The first supply pipe 21A is equipped with a control valve 29, a pump 31, a flow meter 33, and a nanobubble generator 51, in this order from the pure water supply source side.

The nanobubble generator 51 is supplied with gas from a gas supply source. The gas is, for example, an inert gas. The inert gas is, for example, nitrogen gas. The nanobubble generator 51 generates nanobubbles in the first processing liquid flowing through the first supply pipe 21A. The nanobubble generator 51 mixes nanobubbles into the first processing liquid flowing through the first supply pipe 21A. The nanobubbles contain gas supplied from the gas supply source. The second supply pipe 23A generates nanobubbles in the first processing liquid and supplies it to the mixing tank 43. The first processing liquid is, for example, pure water (DIW). The first processing liquid is pure water containing nanobubbles.

One end of the second supply pipe 23A is connected to the second supply tank 27. The other end of the second supply pipe 23A is connected to the mixing tank 43. The second supply pipe 23A is equipped with a control valve 35, a pump 37, and a flow meter 39. The second supply pipe 23A supplies a second processing liquid to the mixing tank 43. The second processing liquid is different from the first processing liquid. The second processing liquid is a chemical liquid. The chemical liquid is, for example, hydrofluoric acid (HF).

The control unit 7 operates the flow rate of the second processing liquid in the first supply pipe 21A and the flow rate of the second processing liquid in the second supply pipe 23A to generate a mixed liquid, a third processing liquid, in the mixing tank 32. The first processing liquid is nanobubble water. The second processing liquid is a chemical liquid. The third processing liquid is an etching liquid. The control unit 7 mixes the first processing liquid and the second processing liquid in the mixing tank 43 so that the mixing ratio of the first processing liquid and the second processing liquid is, for example, 5:1. This ratio is adjusted according to the desired etching rate of the etching target layer in the substrate W. When the liquid level height of the third processing liquid stored in the mixing tank 43 reaches a predetermined position, the control unit 7 stops the supply of the first processing liquid and the second processing liquid.

The mixing of the first and second processing liquids in the mixing tank 32 corresponds to the "mixing process" in the present invention.

The mixing tank 43 is preferably equipped with a liquid level sensor. In this case, the control unit 7 replenishes the first processing liquid and the second processing liquid from the first supply pipe 21A and the second supply pipe 23A when the detection position of the liquid level sensor drops below a predetermined position. The predetermined position is a position corresponding to the amount of etching liquid required for at least one etching process. This makes it possible to maintain a state in which the amount of etching liquid required for one etching process can always be supplied.

＜2-2. Processing process＞

An example of a specific processing step for the etching process on the substrate W performed by the above-mentioned substrate processing apparatus 1A will be described.

The operations of transferring the substrate W to the processing section 3 and rotating the substrate W are the same as those in Example 1 described above.

The control unit 7 generates an etching liquid of a predetermined concentration in the mixing tank 43 in advance. The control unit 7 moves the third nozzle 17A to a supply position. While the substrate W is rotating at the processing rotation speed, the control unit 7 operates the control valve 45 and the pump 47 to supply the third processing liquid from the third nozzle 17A to the center of rotation of the substrate W. In other words, the third processing liquid is supplied near the axis P1.

When the etching time has elapsed, the control unit 7 closes the control valve 45 and stops the pump 47. Thereafter, as in Example 1, a rinsing process and a drying process are carried out in that order. Through these processes, the etching process for one substrate W is completed.

According to this embodiment 2, the same effect as that of the above-mentioned embodiment 1 is achieved. That is, the nanobubbles are present outside the narrow recess where active etching species are abundant, and contribute to the stirring of the etching liquid in the narrow recess. As a result, the substrate W can be appropriately etched regardless of the size of the first layer L1 on the substrate W. In addition, in this embodiment 2, the dilution liquid containing nanobubbles and the chemical liquid are mixed in the mixing tank 43 to generate the etching liquid. Therefore, before the nanobubbles in the dilution liquid are significantly reduced by collapse, the dilution liquid and the chemical liquid are sufficiently mixed in the mixing tank 43, and then the etching process can be performed using the etching liquid. As a result, the etching liquid can be supplied without uneven mixing of the chemical liquid. Therefore, uneven etching processing can be suppressed.

Next, a third embodiment of the present invention will be described with reference to the drawings.
FIG. 5 is a block diagram showing a schematic configuration of a substrate processing apparatus according to the third embodiment.

＜3-1. Device configuration＞

The same components as those in the first embodiment are denoted by the same reference numerals and detailed description thereof will be omitted. The substrate processing apparatus 1B includes a processing section 3, a supply section 5B, and a control section 7.

The supply unit 5B includes a fourth nozzle 17B. The fourth nozzle 17B is connected to one end of the second supply pipe 21B. The other end of the second supply pipe 21B is connected to the first supply tank 25. The second supply pipe 21B includes a control valve 29, a pump 31, a flow sensor 33, and a mixing valve 53, in that order, from the first supply tank 25 side to the fourth nozzle 17B side. The first supply tank 25 stores a first processing liquid. The fourth nozzle 17B is movable between a supply position above the axis P1 and a standby position away from the side of the guard 15. The supply position is located above the substrate W. The standby position is away from the side of the substrate W. The first supply tank 25 stores a first processing liquid. The first processing liquid is, for example, pure water (DIW). The first processing liquid contains nanobubbles in pure water.

The mixing valve 53 has a sub-flow path that is connected to the main flow path. The mixing valve 53 has a sub-flow path that is connected to the main flow path from a direction perpendicular to the main flow path. The mixing valve 53 can mix the fluid from the sub-flow path with the fluid in the main flow path. The main flow path in this mixing valve 53 is the first supply pipe 21B.

One end of the second supply pipe 23B is connected to the sub-flow path of the mixing valve 53. The other end of the second supply pipe 23B is connected to the second supply tank 27. The second supply tank 27 stores a second processing liquid. The second processing liquid is different from the first processing liquid. The second processing liquid is a chemical liquid. The chemical liquid is, for example, hydrofluoric acid (HF).

The control unit 7 adjusts the ratio between the flow rate of the first processing liquid in the first supply pipe 21B and the flow rate of the second processing liquid in the second supply pipe 23B according to the recipe. In other words, the control unit 7 adjusts the mixing ratio of the first processing liquid and the second processing liquid according to the concentration of the etching liquid specified in the recipe. Specifically, the control unit 7 adjusts the control valves 29 and 31 to adjust the chemical concentration in the etching liquid supplied from the fourth nozzle 17B.

<3-2. Processing process>

An example of a specific processing step for the etching process on the substrate W performed by the substrate processing apparatus 1B described above will be described.

The operations of transferring the substrate W to the processing section 3 and rotating the substrate W are the same as those in Example 1 described above.

The control unit 7 mixes the first processing liquid with the second processing liquid in the mixing valve 53 to generate an etching liquid. The generated etching liquid is supplied to the substrate W from the fourth nozzle 17B. When the etching time has elapsed, the control unit 7 closes the control valves 29 and 31 and stops the pumps 31 and 37. Thereafter, as in Example 1, a rinsing process and a drying process are performed in that order. Through these processes, the processing for one substrate W is completed.

According to this embodiment 3, the same effect as that of the above-mentioned embodiment 1 is achieved. That is, the nanobubbles exist outside the narrow recess where active etching species are abundant, and contribute to the agitation of the etching solution in the narrow recess. As a result, the substrate W can be appropriately etched regardless of the size of the first layer L1 on the substrate W. In addition, in this embodiment 3, the dilution solution containing nanobubbles and the chemical solution are mixed in the mixing valve 53 to generate the etching solution. Therefore, the dilution solution and the chemical solution can be mixed in an accurate ratio. Therefore, the etching solution can be supplied to the substrate W within a short time after generation. As a result, the etching solution can be supplied in a state where the chemical solution concentration in the etching solution is accurately adjusted to the desired concentration, and the etching solution can be supplied to the substrate W in a state where the reduction in nanobubbles is minimized.

<Modifications>

A modified example will be described with reference to Figures 6 and 7. Figure 6 is a block diagram showing a schematic configuration of a substrate processing apparatus according to a modified example. Figure 7 is a graph showing an example of the relationship between zeta potential and pH.

This modified example is a substrate processing apparatus 1C in which a part of the substrate processing apparatus 1 of the first embodiment described above has been modified. The supply section 5C includes a first supply pipe 21, a second supply pipe 23, and an injection pipe 61. The second supply pipe 23 includes a branch section 63. One end of the injection pipe 61 is connected to the branch section 63. The other end of the injection pipe 61 is connected to an adjustment liquid tank 65. The injection pipe 61 is provided with a control valve 67, a pump 69, and a flow meter 71, in that order from the adjustment liquid tank 65 side.

The adjustment liquid tank 65 stores the adjustment liquid. The adjustment liquid adjusts the pH of the medicinal solution. The adjustment liquid is acidic or alkaline. The adjustment liquid is strongly acidic or strongly alkaline. The adjustment liquid further strengthens the acidity or alkalinity of the medicinal solution.

Examples of adjustment liquids that increase the acidity include hydrochloric acid and sulfuric acid. Examples of adjustment liquids that increase the alkalinity include sodium hydroxide and potassium hydroxide.

The control unit 7 mixes the adjustment liquid from the branching portion 63 into the second supply pipe 23. This corresponds to the "adjustment liquid mixing process" in the present invention. The control unit 7 mixes the adjustment liquid so as to further increase the acidity or alkalinity of the chemical liquid in the second supply pipe 23. The second processing liquid, the pH of which has been adjusted in this manner, is supplied from the second nozzle 19 toward the substrate W. Therefore, on the substrate W, the second processing liquid is mixed with the first processing liquid containing nanobubbles supplied from the first nozzle 17, and the etching process is performed on the substrate W.

Refer to Figure 7. As is clear from Figure 7, in a certain chemical solution, as the alkalinity increases, the zeta potential becomes more negative. On the other hand, as the acidity increases, the zeta potential becomes more positive. In other words, by adjusting the pH of the etching solution, the absolute value of the zeta potential of the nanobubbles can be increased. Therefore, by mixing an adjustment liquid, the degree of charge of the nanobubbles can be increased, and the degree of agitation of the etching solution can be increased.

In addition, a nozzle may be further added to mix the first processing liquid, the second processing liquid, and the adjustment liquid on the substrate W to generate an etching liquid in which the nanobubbles are more highly charged. In the second embodiment, the adjustment liquid may be introduced into the mixing tank 43. In the third embodiment, the adjustment liquid may be injected through the mixing valve 53.

<Experimental results of the present invention>

Now, let us refer to FIG. 8. FIG. 8 is a graph showing the experimental results of the present invention. In detail, the etching speed is shown when there is no nanobubbles and when there are nanobubbles, and when the nanobubbles have different particle sizes. The size of the first layer L1 is 5 nm and 10 nm. The etching solution is a solution composed of a mixture of hydrofluoric acid (HF) and pure water (DIW). The mixture ratio is HF:DIW=1:5. The horizontal axis shows the type of gas contained in the nanobubbles. DIW indicates that the etching solution does not contain nanobubbles. The solid film ratio (or blanket ratio) is the ratio of the etching speed of a layer to be etched that is not narrow and a layer to be etched that is narrow. In other words, the closer the solid film ratio (or blanket ratio) is to 1, the better. The small particle size is a nanobubble particle size of 3 to 5 nm. The large particle size is a nanobubble particle size of several tens of nm. In other words, nanobubbles of large particle size do not enter the recesses.

These results show that the same effect cannot be obtained simply by including nanobubbles in the etching solution. In other words, the particle size of the nanobubbles contained in the etching solution must be larger than the size of the layer to be etched. This improves the etching speed compared to conventional methods, even for small layers to be etched.

The present invention is not limited to the above embodiment, but can be modified as follows:

(1) In each of the above-mentioned embodiments 1 to 3, the single-wafer substrate processing apparatuses 1 to 1C have been described as examples. However, the present invention is not limited to such configurations. For example, the present invention can also be applied to a batch-type substrate processing apparatus that simultaneously immerses multiple substrates W in a processing liquid for processing.

(2) In each of the above-mentioned Examples 1 to 3, the chemical solution contained in the etching solution was hydrofluoric acid (HF), the etching species of the etching solution were HF ₂ ⁻ and H ⁺ , and the first layer L1, which is the layer to be etched, was an oxide film (SiO ₂ ). However, the present invention is not limited to these. For example, the chemical solution, the layer to be etched, and the etching species of the present invention may be as follows:

(a) When the chemical solution is hydrofluoric acid (HF), the etching target layer is silicon nitride film (SiN), and etching species are HF ₂ ⁻ , H ⁺ , F ⁻ , and HF.
(b) When the chemical solution is hydrogen peroxide (H ₂ O ₂ ), the layer to be etched is titanium nitride (TiN), and the etching species are HO ₂ ⁻ , H ⁺ , and OH ^{− .}
(c) When the chemical solution is SC1 (a mixture of DIW, NH ₄ OH, and H ₂ O ₂ ), the layer to be etched is titanium nitride (TiN), and the etching species are HO ₂ ⁻ , H ⁺ , and OH ^{− .}
(d) When the chemical solution is SC2 (a mixture of DIW, HCl, and H ₂ O ₂ ), the layer to be etched is titanium nitride (TiN), and the etching species are HO ₂ ⁻ , H ⁺ , and OH ^{− .}
(e) When the chemical solution is phosphoric acid (H ₃ PO ₄ ), the layer to be etched is silicon nitride (SiN), and the etching species are H ⁺ , H ₂ PO ₄ ⁻ , HPO ₄ ²⁻ , and PO ₄ ^{3− .}

(3) In each of the above-mentioned Examples 1 to 3, the etching species ions are agitated with charged nanobubbles. However, the present invention is not limited to such an embodiment. For example, the present invention can be applied to an embodiment in which polarized molecules of the etching species are agitated with charged nanobubbles.

(4) In each of the above-mentioned Examples 1 to 3, a substrate W having a second layer L2 on one side of a first layer L1 and a third layer L3 on the other side of the first layer L1 has been described as an example. However, the present invention is not limited to a substrate W having such a structure. In other words, the present invention can be applied even to a substrate W in which other layers or the first layer L1, which is the layer to be etched, are stacked on the second layer L2 and the third layer L3.

W... substrate L1... first layer L2... second layer L3... third layer EL... etched length 1, 1A to 1C... substrate processing apparatus 3... processing section 5... supply section 7... control section 9... chuck P1... shaft core 17... first nozzle 19... second nozzle 21... first supply pipe 23... second supply pipe 25... first supply tank 27... second supply tank 29... control valve 31... pump 33... flow meter 35... control valve 37... pump 39... flow meter EF... etching solution NB+, NB-... nanobubbles

Claims (10)

A substrate processing method for processing a substrate including a first layer, a second layer formed on one side of the first layer and having a composition different from that of the first layer, and a third layer formed on the other side of the first layer and having a composition different from that of the first layer, comprising:
1. A substrate processing method comprising: an etching step of etching the first layer by applying to the substrate an etching solution containing nanobubbles having a particle size larger than a thickness of the first layer and electrically charged, the etching solution containing ions or polarized molecules that etch the first layer. 2. The substrate processing method according to claim 1,
a mixing step of mixing a dilution liquid containing the nanobubbles with a chemical liquid to generate the etching liquid, immediately before the etching step. 3. The substrate processing method according to claim 2,
The substrate processing method, wherein the mixing step generates the etching liquid by supplying the dilution liquid containing the nanobubbles and a chemical liquid near the substrate. 3. The substrate processing method according to claim 2,
The substrate processing method, wherein the mixing step includes mixing the dilution liquid containing the nanobubbles and the chemical liquid in a mixing tank upstream of a position where the etching liquid is supplied to the substrate. 3. The substrate processing method according to claim 2,
the mixing step comprises mixing the dilution liquid containing the nanobubbles and the chemical liquid in a mixing valve upstream of a position where the etching liquid is supplied to the substrate. 6. The substrate processing method according to claim 2, further comprising:
The substrate processing method according to claim 1, wherein the dilution liquid is generated by circulating pure water through a nanobubble generator that generates nanobubbles. 6. The substrate processing method according to claim 1,
The substrate processing method according to claim 1, wherein the dilution liquid is a solution containing pre-generated nanobubbles in pure water. 6. The substrate processing method according to claim 1,
The substrate processing method further comprises, before the etching step, a step of mixing an adjusting liquid for adjusting a pH of the etching liquid. 9. The substrate processing method according to claim 8,
4. A substrate processing method, comprising: a control liquid for controlling the acidity or alkalinity of the etching liquid; In a substrate processing apparatus for processing a substrate,
a processing section for processing a substrate including a first layer, a second layer formed on one side of the first layer and having a composition different from that of the first layer, and a third layer formed on the other side of the first layer and having a composition different from that of the first layer;
a supply unit that supplies, to the processing unit, an etching solution that contains nanobubbles having a particle size larger than a thickness of the first layer and that are electrically charged, and that contains ions or polarized molecules that etch the first layer;
a control unit that etches the first layer by applying an etching solution supplied from the supply unit to the substrate held by the holding unit;
A substrate processing apparatus comprising:

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