Substrate processing apparatus and substrate processing method

Abstract

Disclosed is a substrate processing apparatus and a substrate processing method. The disclosed substrate processing apparatus includes a substrate support section that supports a substrate; a spray section that sprays a chemical liquid toward the substrate; and a cup that includes a collection wall section, a groove section, and a drain, wherein the collection wall section surrounds the substrate support section to collect the chemical liquid that is sprayed to the substrate and then discharged from the substrate support section, the groove section collects the chemical liquid that falls along the collection wall section, and the drain is provided at one side of the groove section to discharge the chemical liquid from the groove section; wherein a bottom of the groove section includes a first bottom and a second bottom that is recessed deeper than the first bottom.

Description

Technical Field

[0001] This invention relates to a substrate processing apparatus and a substrate processing method, which uses a chemical solution to process a substrate used in semiconductor manufacturing. Background Technology

[0002] Semiconductor manufacturing processes may include thin-film deposition, etching, and cleaning. Cleaning involves spraying a chemical solution onto a substrate to remove residual particles or foreign matter. However, the waste chemical solution discharged after spraying onto the substrate increases environmental burden and raises operating costs.

[0003] The background technology of this invention is disclosed in Korean Patent Publication No. 10-2012-0018296 (publication date: March 2, 2012, invention title: semiconductor wafer cleaning method and apparatus). Summary of the Invention

[0004] The present invention was proposed to improve the above-mentioned problems. The present invention provides a substrate processing apparatus and a substrate processing method, which reuses the chemical solution used in substrate processing, thereby reducing the amount of chemical solution consumed in substrate processing.

[0005] The substrate processing apparatus of the present invention is characterized by comprising: a substrate support portion for supporting a substrate; an ejection portion for ejecting a liquid medicine onto the substrate; and a cup having a collecting wall portion, a groove portion, and a drain outlet, wherein the collecting wall portion surrounds the substrate support portion to collect the liquid medicine discharged from the substrate support portion after being ejected onto the substrate, the groove portion collects the liquid medicine falling along the collecting wall portion, and the drain outlet is disposed on one side of the groove portion to allow the liquid medicine to be discharged from the groove portion; wherein the bottom of the groove portion includes: a first bottom portion; and a second bottom portion forming a height difference with the first bottom portion and recessed deeper below the first bottom portion.

[0006] The longitudinal section shape of the second bottom can be an inwardly concave curve.

[0007] The longitudinal section shape of the first bottom may be a line shape that slopes in the width direction of the groove portion in a manner that increases in height as it moves away from the second bottom.

[0008] A pair of first bottoms are provided in the width direction of the groove portion, and a second bottom is located between the pair of first bottoms.

[0009] In the width direction of the groove, the width dimension occupied by the second bottom may be greater than the width dimension occupied by the first bottom.

[0010] The groove can extend along a closed curved path around the substrate support. The bottom height of the groove can be lowest at the location of the drain outlet, and the further away from the location of the drain outlet, the higher the bottom height of the groove.

[0011] The substrate processing apparatus of the present invention is characterized by comprising: a substrate support portion for supporting a substrate; an ejection portion for ejecting a liquid medicine onto the substrate; and a cup having a collecting wall portion, a groove portion, and a drain outlet, wherein the collecting wall portion surrounds the substrate support portion to collect the liquid medicine discharged from the substrate support portion after being ejected onto the substrate; the groove portion extends along a closed curved path surrounding the substrate support portion and collects the liquid medicine falling along the collecting wall portion; the drain outlet is disposed on one side of the groove portion to allow the liquid medicine to be discharged from the groove portion; the bottom height of the groove portion is lowest at the location of the drain outlet, and the bottom height of the groove portion increases with distance from the location of the drain outlet.

[0012] The liquid medicine may include a first liquid medicine and a second liquid medicine different from the first liquid medicine, and the cup may include: a first cup that collects the first liquid medicine; and a second cup that collects the second liquid medicine but not the first liquid medicine.

[0013] The substrate processing apparatus may further include: a drainage path that guides the second liquid discharged from the second cup to the outside of the substrate processing apparatus; and a liquid recovery unit that recovers the second liquid discharged from the second cup.

[0014] The liquid recovery unit may include: a reuse liquid tank for containing the second liquid discharged from the second cup; a liquid recovery flow path branching from the drainage flow path to guide the second liquid flowing along the drainage flow path to the reuse liquid tank; and a flow path switching unit that selectively switches the direction of travel of the second liquid so that the second liquid discharged from the second cup and entering the drainage flow path flows toward either the outside of the substrate processing device or the reuse liquid tank.

[0015] Before the concentration of the second liquid collected in the second cup becomes the same as the concentration of the second liquid supplied to the spray nozzle, the flow path switching unit can be controlled to make the second liquid collected in the second cup flow toward the outside of the substrate processing device; after the concentration of the second liquid collected in the second cup becomes the same as the concentration of the second liquid supplied to the spray nozzle, the flow path switching unit can be controlled to make the second liquid collected in the second cup flow toward the reuse liquid tank.

[0016] The substrate processing apparatus may further include: a first liquid tank containing the first liquid for supplying to the ejection section; and a second liquid tank containing the second liquid for supplying to the ejection section; the liquid recovery section may include: a liquid recovery flow path branching from the drainage flow path and guiding the second liquid flowing along the drainage flow path to the second liquid tank; and a flow path switching section selectively switching the direction of travel of the second liquid so that the second liquid discharged from the second cup and entering the drainage flow path flows toward either the outside of the substrate processing apparatus or one of the second liquid tanks.

[0017] Before the concentration of the second liquid collected in the second cup becomes the same as the concentration of the second liquid in the second liquid container, the flow path switching unit can be controlled to make the second liquid collected in the second cup flow toward the outside of the substrate processing device; after the concentration of the second liquid collected in the second cup becomes the same as the concentration of the second liquid in the second liquid container, the flow path switching unit can be controlled to make the second liquid collected in the second cup flow toward the second liquid container.

[0018] The substrate processing method of the present invention is characterized by comprising: a first cup first liquid spraying step, wherein a first liquid is sprayed onto a substrate supported by the substrate support at a first cup position where the height level of the top of the first cup corresponds to the height level of the substrate support; a first cup second liquid spraying step, wherein a second liquid different from the first liquid is sprayed onto the substrate while the spraying of the first liquid is stopped and the first cup position is maintained; a cup shifting step, wherein a second cup is moved to a second cup position where the height level of the top of the second cup corresponds to the height level of the substrate support; and a second cup second liquid spraying step, wherein the second liquid is sprayed onto the substrate at the second cup position.

[0019] The substrate processing method may further include a second liquid recovery step, wherein the concentration of the second liquid sprayed onto the substrate and collected in the second cup becomes the same as the concentration of the second liquid sprayed into the second cup, and then the second liquid is recovered.

[0020] At the beginning of the second liquid spraying step in the second cup, the concentration of the second liquid collected in the second cup may be different from the concentration of the second liquid sprayed into the second cup.

[0021] The second liquid recovery step can begin after a set time elapsed from the start time of the second liquid spraying step.

[0022] The set time can be the time required for the concentration of the second medicine collected in the second cup to become the same as the concentration of the second medicine contained in the second medicine container.

[0023] The second cup may have a collecting wall, a groove, and a drain outlet, wherein the collecting wall surrounds the substrate support to collect the second liquid that is sprayed onto the substrate and discharged from the substrate support, the groove collects the second liquid that falls along the collecting wall, and the drain outlet is disposed on one side of the groove to allow the second liquid to be discharged from the groove; wherein the bottom of the groove may include: a first bottom; and a second bottom, which forms a height difference with the first bottom and is recessed deeper below the first bottom.

[0024] The second cup may have a collecting wall, a groove, and a drain outlet. The collecting wall surrounds the substrate support to collect the second liquid that is sprayed onto the substrate and then discharged from the substrate support. The groove extends along a closed curved path around the substrate support and collects the second liquid that falls along the collecting wall. The drain outlet is located on one side of the groove to allow the second liquid to be discharged from the groove. The bottom height of the groove may be lowest at the location of the drain outlet, and the bottom height of the groove increases as it moves away from the drain outlet.

[0025] According to the present invention, the chemical solutions used in substrate processing are reused, which can reduce the amount of chemical solutions consumed in substrate processing, thereby reducing operating costs.

[0026] According to the present invention, the amount of waste liquid generated from substrate processing is reduced, thereby alleviating the environmental pollution burden and reducing the cost of waste liquid purification. Attached Figure Description

[0027] Figure 1 This is a configuration diagram of the substrate processing apparatus according to the first embodiment of the present invention.

[0028] Figure 2 yes Figure 1 Diagram of the processing chamber.

[0029] Figure 3 It is shown Figure 2 The diagram shows the composition of the first and second cups in their rising state.

[0030] Figure 4 It is Figure 2 and Figure 3 The second cup is shown in the cross-sectional view.

[0031] Figure 5 It is Figure 4The diagram shown in enlarged form is part A.

[0032] Figure 6 It is along S1-S1 pair Figure 4 A cross-sectional view shown after cutting.

[0033] Figure 7 This is a block diagram illustrating an example of a substrate processing method according to an embodiment of the present invention.

[0034] Figure 8 This is a configuration diagram of the substrate processing apparatus according to the second embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures

[0036] 10: Substrate; 100A, 100B: Substrate processing apparatus; 101: Processing chamber; 110: Substrate support; 120: Ejection section; 130: Second cup; 140: Groove section; 144: First bottom; 147: Second bottom; 150: Drain outlet; 160: First cup; 190: Drainage path; 200A, 200B: Liquid recovery section; 201: Reusable liquid tank; 204, 210: Liquid recovery path; 207, 213: Path conversion section; 220: Reusable liquid supply section; 230: Second liquid supply section; 240: First liquid supply section; 270: Lifting driver. Detailed Implementation

[0037] The substrate processing apparatus of the present invention will now be described in detail with reference to the accompanying drawings. The terminology used in this specification is for the proper expression of preferred embodiments of the invention and may vary depending on the intent of the user or operator, or the conventions of the technical field to which this invention pertains. Therefore, the definitions of these terms should be based on the entire text of this specification.

[0038] Figure 1 This is a configuration diagram of the substrate processing apparatus according to the first embodiment of the present invention. Figure 2 yes Figure 1 Diagram of the processing chamber. Figure 3 It is shown Figure 2 The diagram shows the composition of the first and second cups in their rising state. Figure 4 It is Figure 2 and Figure 3 The second cup is shown in the cross-sectional view. Figure 5 It is Figure 4 The diagram shown in enlarged form is part A. Figure 6 It is along S1-S1 pair Figure 4 A cross-sectional view shown after cutting.

[0039] Reference Figures 1 to 6The substrate processing apparatus 100A of the first embodiment of the present invention may be, for example, an apparatus that sprays a chemical solution onto the upper surface 11 and the lower surface 12 of a substrate 10 to clean the substrate 10. The substrate 10 may be, for example, a disk-shaped semiconductor wafer.

[0040] The substrate processing apparatus 100A includes a processing chamber 101. The processing chamber 101 includes a substrate support 110, an ejection section 120, and a second cup 130. The processing operation of the substrate 10 is performed within the processing chamber 101. The substrate processing apparatus 100A may also include a first solution supply section 240, a second solution supply section 230, and a solution recovery section 200A.

[0041] The substrate support 110 supports the substrate 10. The substrate support 110 may include a worktable 115 that supports the substrate 10, and a spindle 112 that causes the worktable 115 to rotate at high speed around a vertical axis AX.

[0042] The ejection section 120 ejects a liquid medicine onto the substrate 10. The ejection section 120 may include a first liquid medicine nozzle 122 for ejecting the first liquid medicine onto the surface of the substrate 10 (e.g., the upper surface 11). The ejection section 120 may include: a second liquid medicine nozzle 125 for ejecting a second liquid medicine, different from the first liquid medicine, onto the upper surface 11 of the substrate 10; and a third liquid medicine nozzle 127 for ejecting the second liquid medicine onto the lower surface 12 of the substrate 10.

[0043] The second liquid nozzle 125 can move along axis AX when spraying the second liquid so that the second liquid is sprayed to the center of the substrate 10, and move to the outer periphery of the substrate 10 when not spraying the second liquid. The first liquid nozzle 122 can move along axis AX when spraying the first liquid so that the first liquid is sprayed to the center of the substrate 10, and move to the outer periphery of the substrate 10 when not spraying the first liquid.

[0044] exist Figure 2 and Figure 3 In the illustrated embodiment, the first liquid nozzle 122 sprays the first liquid only onto the upper surface 11 of the substrate 10. However, in other embodiments of the present invention, a first liquid nozzle may also be included that sprays the first liquid onto the lower surface 12 of the substrate 10.

[0045] The second liquid supply unit 230 can supply liquid to the spraying unit 120. For example, the second liquid supply unit 230 can supply second liquid to the second liquid nozzle 125 and the third liquid nozzle 127.

[0046] The second drug supply unit 230 may include a second drug tank 231, a second drug supply flow path 234, a pump 236, and a valve 238. The second drug tank 231 may contain a second drug. The second drug may be, for example, any one or a combination of HF (Hydrogen Fluoride), SP (Sulfate Peroxide), SPM (Sulfate Acid Peroxide Mixture), FPM (Fluoric Acid Peroxide Mixture), SC-1 (Standard Clean 1), and SC-2 (Standard Clean 2).

[0047] The second drug supply path 234 guides the second drug from the second drug tank 231 to the spray nozzle 120. The second drug supply path 234 may include, for example, a pipe. A pump 236 can pump the second drug released from the second drug tank 231 to the spray nozzle 120. A valve 238 opens and closes the second drug supply path 234 to selectively supply the second drug to the spray nozzle 120.

[0048] Although not in Figure 1 As shown, the second medicine supply unit 230 may also include a filter. The filter can remove impurities from the medicine supplied from the second medicine tank 231 to the spray unit 120.

[0049] The first liquid supply unit 240 supplies a first liquid to the spraying unit 120. The first liquid supply unit 240 may include a first liquid tank 241, a first liquid supply flow path 244, a pump 246, and a valve 248. The first liquid tank 241 can contain the first liquid. For example, the first liquid may be DIW (deionized water).

[0050] The first liquid supply path 244 guides the first liquid from the first liquid tank 241 to the spray nozzle 120. For example, the first liquid may be supplied to the first liquid nozzle 122. The first liquid supply path 244 may include, for example, a pipe. The pump 246 may pump the first liquid released from the first liquid tank 241 to the spray nozzle 120 side. The valve 248 opens and closes the first liquid supply path 244 to allow the first liquid to be selectively supplied to the spray nozzle 120.

[0051] Although not in Figure 1 As shown, the first medicine supply unit 240 may also include a filter. The filter can remove impurities from the first medicine supplied from the first medicine tank 241 to the spray unit 120.

[0052] For example, the second liquid sprayed from the second liquid nozzle 125 to the upper surface 11 of the substrate 10, and the second liquid sprayed from the third liquid nozzle 127 to the lower surface 12 of the substrate 10, are discharged from the outer periphery of the worktable 115 in the radial direction by means of the centrifugal force generated by the rotation of the worktable 115.

[0053] The second cup 130 collects the liquid medicine that is sprayed onto the substrate 10 and discharged from the substrate support portion 110 as described above. The liquid medicine collected in the second cup 130 may be the second liquid medicine. The first liquid medicine may not be collected into the second cup 130.

[0054] The second cup 130 includes a collecting wall 131, a groove 140, and a drain outlet 150. The collecting wall 131 surrounds the substrate support 110. For example, the collecting wall 131 may stand upright around the worktable 115 in the vertical direction. The upper end of the collecting wall 131 may extend obliquely in a direction closer to the axis AX as it moves upward.

[0055] by Figures 2 to 6 Using this as a reference, the horizontal direction can be parallel to a plane including the X and Y axes, and the vertical direction can be parallel to the Z-axis. The up-down direction can be a direction intersecting the plane including the X and Y axes. Alternatively, the up-down direction can be the same as the vertical direction.

[0056] The medicinal liquid that falls along the collecting wall 131 is collected in the groove section 140. For example... Figure 6 As shown, when viewed from above, the groove portion 140 may have an annular planar shape centered on the axis AX. In other words, the groove portion 140 may extend along a circular path centered on the axis AX.

[0057] It should be noted that, in another embodiment of the present invention, the groove portion of the second cup may also extend around the substrate support portion along a non-circular closed curve path.

[0058] A drain outlet 150 is located on one side of the groove section 140. The liquid medicine discharged from the workbench 115 and collected in the groove section 140 is discharged through the drain outlet 150 to the outside of the second cup 130. The liquid medicine discharged through the drain outlet 150 can move to the drainage path 190 through the drain pipe 152.

[0059] The groove portion 140 may include a first groove 140a and a second groove 140b. The first groove 140a may include a first bottom 144, and the second groove 140b may include a second bottom 147. The second groove 140b may be recessed downward from the first bottom 144 of the first groove 140a. That is, the groove portion 140 may be an integral type formed by connecting the first groove 140a and the second groove 140b. The width (TL1+TL2) of the first groove 140a may be greater than the width CU of the second groove 140b.

[0060] The bottom of the groove portion 140 includes a first bottom portion 144 and a second bottom portion 147. The second bottom portion 147 forms a height difference with the first bottom portion 144 and is recessed deeper below the first bottom portion 144.

[0061] The longitudinal section shape of the second bottom 147 may be an inwardly concave curved shape. The longitudinal section shape of the first bottom 144 may be a linear shape that slopes in the width direction of the groove portion 140 in a manner that increases in height as it moves away from the second bottom 147.

[0062] A pair of first bottoms 144 may be provided in the width direction of the groove portion 140, and a second bottom 147 may be provided between the pair of first bottoms 144. The longitudinal section shape of the first bottom 144 may coincide with a diagonal line that intersects at the center point WC of the groove portion 140 along the width direction of the groove portion 140 and is symmetrical from left to right.

[0063] For example, after machining a bottom with a V-shaped cross-section using a tool, the bottom can be further machined with a U-shaped cross-section to form a second bottom 147 with a U-shaped cross-section.

[0064] Thus, the bottom of the groove portion 140 can be formed, which includes a pair of first bottoms 144 spaced apart from each other and a second bottom 147 between the pair of first bottoms 144.

[0065] In the width direction of the groove portion 140, the width CU occupied by the second bottom 147 can be larger than the width (TL1+TL2) occupied by the first bottom 144. Since the bottom of the groove portion 140 includes the second bottom 147 in addition to the first bottom 144, it is deeper than a groove portion with only a V-shaped inclined bottom in longitudinal section, which can accommodate a larger liquid flow rate and allows the liquid flowing along the length direction of the groove portion 140 to flow at a faster rate.

[0066] Therefore, in the groove 140 of the second cup 130, more medicine can be quickly discharged to the outside of the second cup 130 through the drain outlet 150.

[0067] In the groove portion 140, the bottom height of the groove portion 140 can be the lowest at the location of the drain outlet 150 (bottom height LP), and the further away from the location of the drain outlet 150, the higher the bottom height of the groove portion 140.

[0068] For example, with axis AX as the center, the bottom height of the groove 140 can be highest at a point FA (bottom height HP) opposite to the location of the drain outlet 150 in the groove 140. The virtual straight line DL connecting the location of the drain outlet 150 in the bottom of the groove 140 to the point FA where the bottom height of the groove 140 is highest can be inclined at an acute angle AN relative to the horizontal line PL.

[0069] As described above, along the length of the bottom of the groove 140, the closer to the drain outlet 150, the lower the bottom height. Therefore, the medicine collected in the groove 140 can move towards the drain outlet 150 more quickly and be discharged to the outside of the second cup 130 more quickly through the drain outlet 150.

[0070] The substrate processing apparatus 100A may also include a first cup 160 and a lifting driver 270 inside the processing chamber 101.

[0071] The first cup 160 collects the liquid medicine that is sprayed onto the substrate 10 and discharged from the substrate support portion 110. At least one of the first liquid medicine and the second liquid medicine can be collected in the first cup 160.

[0072] For example, the first liquid sprayed from the first liquid nozzle 122 onto the surface of the substrate 10 is discharged from the outer periphery of the worktable 115 in a radial direction by means of the centrifugal force generated by the rotation of the worktable 115, and the first cup 160 can collect the first liquid that is sprayed onto the substrate 10 and discharged from the substrate support portion 110.

[0073] As another example, the second liquid sprayed onto the surface of the substrate 10 from the second liquid nozzle 125 and the third liquid nozzle 127 is discharged from the outer periphery of the worktable 115 in a radial direction by means of the centrifugal force generated by the rotation of the worktable 115. The first cup 160 can collect the second liquid that is sprayed onto the substrate 10 and discharged from the substrate support portion 110.

[0074] If the first solution is sprayed onto the surface of the substrate 10 and then the second solution is sprayed, the first solution that was originally left on the surface of the substrate 10 can be washed away and discharged from the substrate support portion 110 together with the second solution. Therefore, the mixture of the first solution and the second solution can be collected in the first cup 160.

[0075] The first cup 160 includes a collecting wall 161, a groove 170, and a drain outlet 180. The collecting wall 161 surrounds the substrate support 110. For example, the collecting wall 161 can stand upright around the worktable 115 in the vertical direction. The upper end of the collecting wall 161 can extend obliquely in a direction closer to the axis AX as it moves upward.

[0076] The height level of the top of the first cup 160 may be different from the height level of the top of the second cup 130. For example, the upper height of the collection wall 161 of the first cup 160 may be higher than the upper height of the collection wall 131 of the second cup 130.

[0077] The groove portion 170 collects the liquid medicine that falls along the collecting wall portion 161. The groove portion 170 is the same as the groove portion 140 of the second cup 130, and may have an annular planar shape centered on the axis AX. It should be noted that, in another embodiment of the present invention, the groove portion of the first cup may also extend around the substrate support portion along a non-circular closed curve path.

[0078] A drain outlet 180 is located on one side of the groove section 170. The medicine liquid discharged from the workbench 115 and collected in the groove section 170 is discharged through the drain outlet 180 to the outside of the first cup 160. The medicine liquid discharged through the drain outlet 180 can move to the drainage path 190 through the drain pipe 182.

[0079] Similar to the bottom of the groove portion 140 of the second cup 130, the bottom of the groove portion 170 of the first cup 160 may include a first bottom 174 and a second bottom 177. The second bottom 177 forms a height difference with the first bottom 174 and is recessed deeper below the first bottom 174.

[0080] The longitudinal section shape of the second bottom 177 may be an inwardly concave curved shape. The longitudinal section shape of the first bottom 174 may be a linear shape that slopes in the width direction of the groove portion 170 in a manner that increases in height as it moves away from the second bottom 177.

[0081] In the width direction of the groove portion 170, a pair of first bottoms 174 may be provided, and a second bottom 177 is located between the pair of first bottoms 174. Since the shapes of the first bottoms 174, the second bottoms 177 and the drain outlet 180 of the groove portion 170 of the first cup 160 are the same as the shapes of the first bottoms 144, the second bottoms 147 and the drain outlet 150 of the groove portion 140 of the second cup 130, they will not be described again.

[0082] Along the length of the bottom of the groove 170, the closer to the drain outlet 180, the lower the bottom height. Therefore, the medicine collected in the groove 170 can move towards the drain outlet 180 more quickly and be discharged to the outside of the first cup 160 more quickly through the drain outlet 180.

[0083] The lifting actuator 270 can raise and lower the first cup 160 and the second cup 130. The second cup 130 is engaged with the first cup 160, so that the lifting actuator 270 can raise and lower the first cup 160 and the second cup 130 simultaneously.

[0084] For example, when the first liquid is sprayed from the first liquid nozzle 122 and discharged to the outer periphery of the worktable 115, the upper height of the collection wall 161 of the first cup 160 can be set to be higher than the height of the substrate 10, while the upper height of the collection wall 131 of the second cup 130 can be set to be lower than the height of the substrate 10.

[0085] In addition, when the second liquid is sprayed from the second liquid nozzle 125 and the third liquid nozzle 127 and the second liquid or the mixture of the first liquid and the second liquid is discharged to the outer periphery of the worktable 115, the upper end height of the collection wall 161 of the first cup 160 can be set to be higher than the height of the substrate 10, and the upper end height of the collection wall 131 of the second cup 130 can be set to be lower than the height of the substrate 10.

[0086] In this case, the height level of the top of the first cup 160 corresponds to the height level of the substrate support 110, and the position of the first cup 160 in this state will be referred to as the first cup position below.

[0087] When the second liquid is sprayed from the second liquid nozzle 125 and the third liquid nozzle 127 and discharged to the outer periphery of the worktable 115, the lifting driver 270 can raise the second cup 130 and the first cup 160, so that the upper height of the collection wall 131 of the second cup 130, which is lower than the upper height of the collection wall 161 of the first cup 160, is higher than the height of the substrate 10.

[0088] In this case, the height level of the top of the second cup 130, which is different from the height level of the top of the first cup 160, corresponds to the height level of the substrate support 110. The position of the second cup 130 in this state will be referred to as the second cup position below.

[0089] When the second liquid stops spraying and the first liquid resumes spraying from the first liquid nozzle 122 and is discharged towards the outer periphery of the worktable 115, the lifting driver 270 can lower the second cup 130 and the first cup 160 to their original heights, such that the upper end of the collection wall 161 of the first cup 160 is higher than the height of the substrate 10, and the upper end of the collection wall 131 of the second cup 130 is lower than the height of the substrate 10. That is, the first cup 160 can be reset to the first cup position.

[0090] The substrate processing apparatus 100A may also include a drainage path 190, through which the liquid discharged from the second cup 130 is guided to the outside of the substrate processing apparatus 100A via a drain outlet 150.

[0091] The drainage path 190 can be connected to the drain pipe 152 of the second cup 130 and the drain pipe 182 of the first cup 160. Therefore, after the first liquid or the second liquid is discharged to the outside of the first cup 160, it can be discharged to the outside of the substrate processing apparatus 100A through the drainage path 190.

[0092] The liquid recovery unit 200A recovers the second liquid discharged from the second cup 130 through the drain outlet 150. The liquid recovery unit 200A may include a reuse liquid tank 201, a liquid recovery flow path 204, and a flow path conversion unit 207.

[0093] The reuse medicine tank 201 can hold the second medicine discharged from the second cup 130. The medicine recovery flow path 204 can branch from the drainage flow path 190, guiding the medicine flowing along the drainage flow path 190 to the reuse medicine tank 201.

[0094] The flow path switching unit 207 selectively switches the direction of travel of the second liquid, so that the second liquid discharged from the second cup 130 and flowing into the drain flow path 190 flows toward either the outside of the substrate processing apparatus 100A or the reuse liquid tank 201. The flow path switching unit 207 may include, for example, a three-way valve.

[0095] The substrate processing apparatus 100A may also include a reuse solution supply unit 220 and a control unit 260.

[0096] The reused medicine supply unit 220 can supply the second medicine, namely the reused medicine, contained in the reused medicine tank 201 to the spraying unit 120. The reused medicine supply unit 220 may include a reused medicine supply flow path 221, a pump 224, and a valve 226.

[0097] The reused medicine supply path 221 guides the reused medicine from the reused medicine tank 201 to the spray nozzle 120. The reused medicine supply path 221 may include, for example, a pipe. A pump 224 pumps the reused medicine released from the reused medicine tank 201 to the spray nozzle 120. A valve 226 opens and closes the reused medicine supply path 221 to selectively supply the reused medicine contained in the reused medicine tank 201 to the spray nozzle 120.

[0098] Although not in Figure 1 As shown, the reuse medicine supply unit 220 may also include a filter. The filter can remove impurities from the reuse medicine supplied from the reuse medicine tank 201 to the spray unit 120.

[0099] The control unit 260 can control the operation of the first liquid supply unit 240, the second liquid supply unit 230, the substrate support unit 110, the ejection unit 120, the first cup 160, the second cup 130, the lifting driver 270, the liquid recovery unit 200A, and the reuse liquid supply unit 220 according to the operation sequence executed by the substrate processing device 100A.

[0100] For example, the control unit 260 can control the switching of pumps 224, 236, and 246, the opening and closing of valves 226, 238, and 248, the opening and closing of nozzles 122, 125, and 127, the switching of spindle 112, the upward and downward driving of lifting driver 270, and the operation of flow path conversion unit 207 included in the substrate processing apparatus 100A.

[0101] For example, when the first cup 160 is in the first cup position, when the first liquid is sprayed from the first liquid nozzle 122 of the spraying section 120, the first liquid collected in the first cup 160 is discharged to the outside of the substrate processing apparatus 100A through the drainage path 190. When the spraying of the first liquid through the first liquid nozzle 122 of the spraying section 120 stops and the second liquid is sprayed through the second liquid nozzle 125 and the third liquid nozzle 127, the flow path switching section 207 can be controlled by the control section 260 to discharge the second liquid collected in the first cup 160 to the outside of the substrate processing apparatus 100A through the drainage path 190.

[0102] Furthermore, when the second cup is in the second cup position, and the second liquid is sprayed onto the substrate 10 from the second liquid nozzle 125 and the third liquid nozzle 127, the flow path switching unit 207 can be controlled by the control unit 260 to make the second liquid collected in the second cup 130 flow toward the outside of the substrate processing apparatus 100A before the concentration of the second liquid collected in the second cup 130 becomes the same as the concentration of the second liquid sprayed onto the substrate 100A.

[0103] After the concentration of the second liquid collected in the second cup 130 becomes the same as the concentration of the second liquid sprayed onto the substrate 10, the flow path switching unit 207 can be controlled by the control unit 260 to cause the second liquid collected in the second cup 130 to flow toward the reuse liquid tank 201 of the liquid recovery unit 200A. The concentration of the second liquid sprayed onto the substrate 10 can be the same as the concentration of the second liquid contained in the second liquid tank 231 of the second liquid supply unit 230.

[0104] For example, the first liquid supplied to the spraying part 120 through the first liquid supply unit 240 may be DIW, while the second liquid supplied to the spraying part 120 through the second liquid supply unit 230 may be HF (Hydrogen Fluoride).

[0105] When the first cup 160 is in the first cup position, the first liquid is sprayed onto the substrate 10 through the first liquid nozzle 122, and then the second liquid is sprayed onto the substrate 10 through the second liquid nozzle 125 and the third liquid nozzle 127.

[0106] During the process of spraying the second liquid onto the substrate 10, the first cup 160 and the second cup 130 can be moved from the substrate 10 by means of the lifting driver 270. Figure 2 The height shown rises to Figure 3 The height shown. In other words, the second cup 130 can be moved to the second cup position.

[0107] In the second cup 130, there may be residual second liquid that was collected in the second cup 130 during the processing of the previous substrate 10 but was not discharged through the drain outlet 150. The residual second liquid in the second cup 130 may become more concentrated over time due to solvent evaporation or other reasons, resulting in a higher concentration. Alternatively, the concentration of the residual second liquid in the second cup 130 may also become lower.

[0108] When the second cup 130 is in the second cup position, and the second liquid is sprayed onto the substrate 10 through the second liquid nozzle 125 and the third liquid nozzle 127, the second liquid that remains in the second cup 130 and whose concentration has changed will mix with the second liquid that is sprayed onto the substrate 10 and discharged from the substrate support portion 110.

[0109] Therefore, at the initial time point when the second liquid begins to be collected in the second cup 130, the concentration of the second liquid collected in the second cup 130 may differ from the concentration of the second liquid sprayed onto the substrate 10. For example, at the initial time point when the second liquid begins to be collected in the second cup 130, the concentration of the second liquid collected in the second cup 130 may be higher than the concentration of the second liquid sprayed onto the substrate 10. The concentration of the second liquid sprayed onto the substrate 10 may be the same as the concentration of the second liquid contained in the second liquid container 231.

[0110] However, when the second cup 130 is in the second cup position, the second liquid is continuously collected into the second cup 130 and continuously discharged through the drain outlet 150. Therefore, the concentration of the second liquid collected in the second cup 130 can become the same as the concentration of the second liquid sprayed onto the substrate 10. In other words, the concentration of the second liquid collected in the second cup 130 can be adjusted to a recyclable concentration.

[0111] After the concentration of the second medicine collected in the second cup 130 and retained in the groove 140 becomes the same as the concentration of the second medicine contained in the second medicine tank 231, the second medicine in the drainage path 190 can be switched to flow toward the reuse medicine tank 201 by the flow path switching section 207 and supplied to the reuse medicine tank 201.

[0112] As described above, since the bottom of the groove portion 140 has a second bottom 147, the second liquid is quickly discharged from the groove portion 140 to the outside of the second cup 130. Therefore, the time required from the point when the second liquid is sprayed onto the substrate 10 and begins to be collected in the second cup 130 until the concentration of the second liquid collected in the second cup 130 becomes the same as the concentration of the second liquid contained in the second liquid container 231 can be shortened.

[0113] For example, for a second cup that does not have a second bottom 147, the time required from the point when the second liquid is sprayed onto the substrate 10 and begins to be collected in the second cup until the concentration of the second liquid collected in the second cup becomes the same as the concentration of the second liquid contained in the second liquid container 231 may be greater than the time required for the second cup 130 of the first embodiment of the present invention from the point when the second liquid is sprayed onto the substrate 10 and begins to be collected in the second cup 130 until the concentration of the second liquid collected in the second cup 130 becomes the same as the concentration of the liquid in the second liquid supply section 230.

[0114] In other words, in one embodiment of the present invention, within a set time period from the point when the second liquid begins to be collected in the second cup 130, the second liquid is discharged to the outside through the drainage path 190. After the set time has elapsed since the point when the second liquid begins to be collected in the second cup 130, the control unit 260 can control the flow path switching unit 207 to allow the second liquid to be recycled back to the reuse liquid tank 201 for reuse. Therefore, the reuse rate of the liquid can be improved.

[0115] Figure 7 This is a block diagram illustrating an example of a substrate processing method according to an embodiment of the present invention. Figure 7 The substrate processing method shown can be an example of the substrate processing method using the substrate processing apparatus 100A of the first embodiment of the present invention.

[0116] Reference Figures 1 to 7 One embodiment of the substrate processing method of the present invention can be a method of cleaning substrate 10 using substrate processing apparatus 100A of the first embodiment of the present invention.

[0117] The substrate processing method includes: a first liquid ejection step S110, a second liquid ejection step S120, a cup shifting step S130, a second liquid ejection step S140, and a second liquid recovery step S150.

[0118] The first cup first liquid spraying step S110 is a step in which the first liquid is sprayed onto the substrate 10 supported by the substrate support 110 from the first cup position, where the height level of the top of the first cup 160 corresponds to the height level of the substrate support 110.

[0119] The first liquid, which is sprayed onto the substrate 10 from the first cup position and discharged from the substrate support 110 and collected in the first cup 160, is discharged from the first cup 160 through the drain port 180 and discharged to the outside of the substrate processing apparatus 100A through the drain path 190.

[0120] The position of the first cup has already been mentioned in the description of the substrate processing apparatus 100A of the present invention, and therefore will not be repeated here. Figure 2 As shown, at the first cup position, the upper end of the first cup 160 may be slightly higher than the height of the substrate 10 supported by the substrate support portion 110, and the upper end of the second cup 130 may be slightly lower than the height of the substrate 10.

[0121] The first cup second liquid spraying step is a step in which a second liquid, different from the first liquid, is sprayed onto the substrate 10 while the first liquid spraying is stopped and the first cup position is maintained. The second liquid, which is sprayed onto the substrate 10 from the first cup position and discharged from the substrate support 110 and collected in the first cup 160, is discharged from the first cup 160 through the drain port 180 and discharged to the outside of the substrate processing apparatus 100A through the drain path 190.

[0122] The cup shifting step S130 is a step of moving the second cup 130 to a second cup position where the height level of the top of the second cup 130 corresponds to the height level of the substrate support 110. The cup shifting step S130 can be performed by means of the operation of the lifting driver 270.

[0123] The location of the second cup has already been mentioned in the description of the substrate processing apparatus 100A of the present invention, and will not be repeated here. Figure 3 As shown, at the second cup position, the upper end of the second cup 130 may be slightly higher than the height of the substrate 10 supported by the substrate support portion 110, and the upper end of the first cup 160 may be higher than the upper end of the second cup 130.

[0124] The second cup second liquid spraying step S140 is the step of spraying the second liquid onto the substrate 10 at the second cup position. If the cup shifting step S130 is performed during the process of spraying the second liquid onto the substrate 10, the second cup second liquid spraying step S140 can be performed at the same time as the second cup 130 moves to the second cup position.

[0125] In the second cup second liquid spraying step S140, the second liquid sprayed onto the substrate 10 and discharged from the substrate support 110 is collected in the second cup 130. As mentioned in the description of the substrate processing apparatus 100A, at the beginning of the second cup second liquid spraying step S140, the second liquid collected in the second cup 130 may include the second liquid that remained in the second cup 130 due to the previous substrate processing.

[0126] Therefore, at the start time of the second liquid spraying step, the concentration of the second liquid collected in the second cup 130 may differ from the concentration of the second liquid sprayed onto the substrate 10, i.e., the concentration of the second liquid contained in the second liquid container 231. For example, at the start time of the second liquid spraying step, the concentration of the second liquid collected in the second cup 130 may be higher than the concentration of the second liquid sprayed onto the substrate 10, i.e., the concentration of the second liquid contained in the second liquid container 231.

[0127] On the other hand, in another embodiment of the present invention, at the beginning of the second liquid spraying step, the concentration of the second liquid collected in the second cup 130 may be lower than the concentration of the second liquid sprayed onto the substrate 10, that is, the concentration of the second liquid contained in the second liquid container 231.

[0128] The second drug recovery step S150 is a step of recovering the second drug after the concentration of the second drug sprayed to the substrate 10 and discharged from the substrate support 110 and collected in the second cup 130 becomes the same as the concentration of the second drug sprayed to the second cup 130, that is, the concentration of the second drug contained in the second drug tank 231.

[0129] The second drug solution recovery step S150 can be performed by the drug solution recovery unit 200A. The recovered second drug solution can be contained in the reuse drug solution tank 201.

[0130] The second medicine recovery step S150 can begin after a set time elapsed from the starting time of the second medicine spraying step S140. The following time can be determined in advance through repeated experiments: the time elapsed from the starting time of the second medicine spraying step S140 until the concentration of the medicine collected in the second cup 130 becomes the same as the concentration of the second medicine contained in the second medicine container 231, and this determined time is set as the aforementioned set time.

[0131] Between the start time of the second liquid spraying step S140 and the start time of the second liquid recovery step S150, the second liquid collected in the second cup 130 can be discharged from the second cup 130 through the drain outlet 150 and discharged to the outside of the substrate processing apparatus 100A through the drain path 190.

[0132] The second liquid recovered from the liquid tank 201 can be sprayed onto the substrate 10 to perform substrate processing on the substrate 10 supported by the substrate support portion 110. Alternatively, the recovered second liquid can be sprayed onto the next substrate 10, or used for subsequent processing of the substrate 10.

[0133] Although not in Figure 7 As shown in the figure, however, the substrate processing method of one embodiment of the present invention may include a step of loading the substrate 10 onto the substrate support portion 110 before the first cup of first liquid spraying step S110.

[0134] Furthermore, the substrate processing method of one embodiment of the present invention may further include the following steps: after removing impurities from the substrate 10 through the second liquid spraying step S140, the first cup 160 is reset to the first cup position. In other words, it may further include the following steps: lowering the first cup 160 and the second cup 130 to a position such that... Figure 2 The process includes: spraying the first liquid onto the substrate 10 to rinse the substrate 10; drying the substrate 10; and unloading the substrate 10 from the substrate support 110.

[0135] Figure 8 This is a configuration diagram of the substrate processing apparatus according to a second embodiment of the present invention. (Refer to...) Figure 2 and Figure 8 The substrate processing apparatus 100B of the second embodiment of the present invention may include a processing chamber 101, a second liquid supply unit 230, a first liquid supply unit 240, a liquid recovery unit 200B, a drainage path 190, and a control unit 260.

[0136] The processing chamber 101 may include, within it, items such as Figure 2 and Figure 3 The substrate support 110, ejection section 120, first cup 160, second cup 130, drain pipes 152 and 182, and lifting driver 270 are shown. The substrate support 110, ejection section 120, first cup 160, second cup 130, drain pipes 152 and 182, and lifting driver 270 have been mentioned in the description of the substrate processing apparatus 100A of the first embodiment of the present invention, and will not be described again.

[0137] The first liquid supply unit 240, the second liquid supply unit 230, the drainage path 190, and the control unit 260 have already been mentioned in the description of the substrate processing apparatus 100A of the first embodiment of the present invention, and therefore will not be repeated here.

[0138] The liquid medicine recovery unit 200B may include a liquid medicine recovery flow path 210 and a flow path conversion unit 213. The liquid medicine recovery flow path 210 branches off from the drainage flow path 190 and guides the second liquid medicine flowing along the drainage flow path 190 to the second liquid medicine tank 231.

[0139] The flow path switching unit 213 can selectively switch the direction of travel of the second liquid, so that the second liquid discharged from the second cup 130 and entering the drain flow path 190 flows toward the outside of the substrate processing apparatus 100B and one of the second liquid tank 231. The flow path switching unit 213 may include, for example, a three-way valve.

[0140] Before the concentration of the second liquid collected in the second cup 130 becomes the same as the concentration of the second liquid in the second liquid tank 231, the flow path switching unit 213 is controlled to make the second liquid collected in the second cup 130 flow toward the outside of the substrate processing apparatus 100B.

[0141] On the other hand, after the concentration of the second liquid collected in the second cup 130 becomes the same as the concentration of the second liquid in the second liquid tank 231, the flow path switching unit 213 is controlled to make the second liquid collected in the second cup 130 flow toward the second liquid tank 231. The reused second liquid flowing into the second liquid tank 231 can be combined with the original second liquid in the second liquid tank 231 and then sprayed onto the substrate 10 through the spraying unit 120.

[0142] According to the substrate processing apparatus 100A, 100B and substrate processing method described above, the chemical solution used in substrate processing can be reused to reduce the amount of chemical solution consumed in substrate processing, thereby reducing operating costs.

[0143] In addition, the amount of waste liquid generated from substrate processing is reduced, which can alleviate the environmental pollution burden and reduce the cost of waste liquid purification and treatment.

[0144] The present invention has been described with reference to one embodiment shown in the accompanying drawings, but this is merely an example, and those skilled in the art will understand that various modifications and equivalent embodiments can be implemented based on it. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims

1. A substrate processing apparatus, characterized in that, include: A substrate support portion that supports the substrate; The ejection section ejects liquid medicine onto the substrate; as well as A cup having a collecting wall, a groove, and a drain outlet, wherein the collecting wall surrounds the substrate support to collect the liquid medicine discharged from the substrate support after being sprayed onto the substrate, the groove collects the liquid medicine falling along the collecting wall, and the drain outlet is provided on one side of the groove to allow the liquid medicine to be discharged from the groove. The bottom of the groove includes: First bottom; and The second bottom has a height difference with the first bottom and is recessed deeper below the first bottom.

2. The substrate processing apparatus according to claim 1, characterized in that, The longitudinal section of the second bottom has an inwardly concave curved shape.

3. The substrate processing apparatus according to claim 1, characterized in that, The longitudinal section shape of the first bottom is a line shape that slopes in the width direction of the groove portion in a manner that increases in height as it moves away from the second bottom.

4. The substrate processing apparatus according to claim 1, characterized in that, A pair of first bottoms are provided in the width direction of the groove portion, and a second bottom is located between the pair of first bottoms.

5. The substrate processing apparatus according to claim 1, characterized in that, In the width direction of the groove portion, the width dimension occupied by the second bottom is greater than the width dimension occupied by the first bottom.

6. The substrate processing apparatus according to claim 1, characterized in that, The groove extends along a closed curved path surrounding the substrate support. The bottom of the trench is lowest at the location of the drain outlet, and the further away from the drain outlet, the higher the bottom of the trench becomes.

7. The substrate processing apparatus according to claim 1, characterized in that, The medicinal solution includes a first medicinal solution and a second medicinal solution that is different from the first medicinal solution. The cup includes: The first cup collects at least one of the first and second medicinal solutions; and The second cup collects the second medicinal liquid but not the first medicinal liquid.

8. A substrate processing apparatus, characterized in that, include: A substrate support portion that supports the substrate; The ejection section ejects liquid medicine onto the substrate; as well as A cup having a collecting wall, a groove, and a drain outlet, wherein the collecting wall surrounds the substrate support to collect the liquid medicine discharged from the substrate support after being sprayed onto the substrate, the groove extends along a closed curved path around the substrate support and collects the liquid medicine falling along the collecting wall, and the drain outlet is provided on one side of the groove to allow the liquid medicine to be discharged from the groove; The bottom of the trench is lowest at the location of the drain outlet, and the further away from the drain outlet, the higher the bottom of the trench becomes.

9. The substrate processing apparatus according to claim 8, characterized in that, The medicinal solution includes a first medicinal solution and a second medicinal solution that is different from the first medicinal solution. The cup includes: The first cup collects at least one of the first and second medicinal solutions, and The second cup collects the second medicinal liquid but not the first medicinal liquid.

10. The substrate processing apparatus according to claim 9, characterized in that, The substrate processing apparatus further includes: A drainage path that guides the second liquid discharged from the second cup to the outside of the substrate processing device; and The liquid recovery unit recovers the second liquid discharged from the second cup.

11. The substrate processing apparatus according to claim 10, characterized in that, The drug solution recovery unit includes: The medicine container is reused to hold the second medicine discharged from the second cup; A liquid medicine recovery path, branching off from the drainage path, guides the second liquid medicine flowing along the drainage path to the reuse liquid medicine tank; and The flow path switching unit selectively switches the direction of travel of the second liquid, so that the second liquid discharged from the second cup and entering the drainage flow path flows toward either the outside of the substrate processing device or the reuse liquid tank.

12. The substrate processing apparatus according to claim 11, characterized in that, Before the concentration of the second liquid collected in the second cup becomes the same as the concentration of the second liquid supplied to the ejector, the flow path switching unit is controlled to make the second liquid collected in the second cup flow toward the outside of the substrate processing device; After the concentration of the second medicine collected in the second cup becomes the same as the concentration of the second medicine supplied to the spray nozzle, the flow path switching unit is controlled to make the second medicine collected in the second cup flow toward the reuse medicine tank.

13. The substrate processing apparatus according to claim 10, characterized in that, The substrate processing apparatus further includes: A first liquid container holds the first liquid for supplying to the spray nozzle; and A second liquid container holds the second liquid for supplying to the spray nozzle; The drug solution recovery unit includes: A liquid medicine recovery path, branching off from the drainage path, guides the second liquid medicine flowing along the drainage path to the second liquid medicine tank; and The flow path switching unit selectively switches the direction of travel of the second liquid, so that the second liquid discharged from the second cup and entering the drainage flow path flows toward either the outside of the substrate processing device or into the second liquid tank.

14. The substrate processing apparatus according to claim 13, characterized in that, Before the concentration of the second liquid collected in the second cup becomes the same as the concentration of the second liquid in the second liquid tank, the flow path switching unit is controlled to make the second liquid collected in the second cup flow toward the outside of the substrate processing device; After the concentration of the second medicine collected in the second cup becomes the same as the concentration of the second medicine in the second medicine container, the flow path switching unit is controlled to make the second medicine collected in the second cup flow toward the second medicine container.

15. A substrate processing method, characterized in that, include: In the first cup first liquid spraying step, the first liquid is sprayed onto the substrate supported by the substrate support at the first cup position, where the height level of the top of the first cup corresponds to the height level of the substrate support. In the first cup second liquid spraying step, while stopping the spraying of the first liquid and maintaining the position of the first cup, a second liquid different from the first liquid is sprayed onto the substrate; The cup-shifting step involves moving the second cup to a position where the height level of the top of the second cup corresponds to the height level of the substrate support; and The second cup second liquid spraying step involves spraying the second liquid onto the substrate at the second cup position.

16. The substrate processing method according to claim 15, characterized in that, The substrate processing method further includes: In the second drug recovery step, the second drug is recovered after the concentration of the second drug sprayed onto the substrate and collected in the second cup becomes the same as the concentration of the second drug sprayed into the second cup.

17. The substrate processing method according to claim 16, characterized in that, At the beginning of the second cup second liquid spraying step, the concentration of the second liquid collected in the second cup is different from the concentration of the second liquid sprayed into the second cup.

18. The substrate processing method according to claim 16, characterized in that, The second liquid recovery step begins after a set time elapsed from the starting point of the second liquid spraying step from the second cup.

19. The substrate processing method according to claim 15, characterized in that, The second cup has a collecting wall, a groove, and a drain outlet. The collecting wall surrounds the substrate support to collect the second liquid that is sprayed onto the substrate and then discharged from the substrate support. The groove collects the second liquid that falls along the collecting wall. The drain outlet is located on one side of the groove to allow the second liquid to be discharged from the groove. The bottom of the groove includes: First bottom; and The second bottom has a height difference with the first bottom and is recessed deeper below the first bottom.

20. The substrate processing method according to claim 15, characterized in that, The second cup has a collecting wall, a groove, and a drain outlet. The collecting wall surrounds the substrate support to collect the second liquid that is sprayed onto the substrate and then discharged from the substrate support. The groove extends along a closed curved path around the substrate support and collects the second liquid that falls along the collecting wall. The drain outlet is provided on one side of the groove to allow the second liquid to be discharged from the groove. The bottom of the trench is lowest at the location of the drain outlet, and the further away from the drain outlet, the higher the bottom of the trench becomes.

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