JP3751897B2 - Substrate processing apparatus and substrate processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate processing apparatus and a substrate processing method that can planarize the surface of a substrate such as a semiconductor substrate or a glass substrate for a liquid crystal display device by etching.
[0002]
[Prior art]
In a so-called damascene process, a wiring groove or hole is formed in an insulating film on a semiconductor substrate, and a copper thin film is embedded in the wiring groove or the like. At that time, first, a copper thin film is formed on the entire surface of the semiconductor substrate including the inside of the wiring groove by plating, and then the copper thin film is left only inside the wiring groove by CMP (Chemical Mechanical Polishing). The copper thin film is removed from other regions.
[0003]
When plating, a seed layer is formed on the surface of the semiconductor substrate in advance by sputtering, and plating is performed using a dedicated plating solution, so that a copper thin film is grown (bottom-up) from the bottom of the wiring groove or hole, wiring groove, etc. It is possible to prevent voids from being formed inside.
In this type of plating, after the wiring groove or the like is filled with a copper thin film, the upper copper thin film such as the wiring groove or the like swells to form a protrusion, and the protrusion forms a step on the substrate surface.
[0004]
The copper thin film having such a step can be planarized to some extent by a subsequent CMP process.
[0005]
[Problems to be solved by the invention]
However, when the pattern formed on the semiconductor substrate becomes dense and narrow wiring grooves and small-diameter holes are arranged close to each other, the protruding portions of the copper thin film overlap to form a larger step. Such a large step is difficult to completely flatten by polishing by CMP.
Further, CMP is a process of polishing by pressing a polishing pad against the entire surface of the substrate. Therefore, if the thickness of the copper thin film formed on the semiconductor substrate is not substantially the same in each part on the semiconductor substrate, the entire surface of the semiconductor substrate is used. The copper thin film cannot be uniformly polished across. However, when a copper thin film is formed on a semiconductor substrate by electrolytic plating, the thickness of the copper thin film does not become uniform between the central portion and the peripheral portion of the semiconductor substrate, which makes the CMP process more difficult.
[0006]
Furthermore, since CMP uses an abrasive, it is not as clean as other processes in the semiconductor device manufacturing process. Therefore, CMP must be performed in an isolated dedicated room, which complicates the semiconductor device manufacturing process.
Further, since the plating apparatus and the CMP apparatus are different from each other, it has been pointed out that in-line installation is meaningless. For this reason, the plating apparatus and the CMP apparatus are prepared separately, and the plating process and the polishing process are not performed as a series of processes.
[0007]
Further, after the copper thin film was formed by plating, uniform polishing could not be performed by CMP unless the copper thin film was baked by annealing. Therefore, an annealing process is always required to perform CMP, and the manufacturing process is complicated.
SUMMARY OF THE INVENTION An object of the present invention is to provide a substrate processing apparatus that can satisfactorily flatten a substrate surface even when a step due to a protrusion on the substrate surface is large.
Another object of the present invention is to provide a substrate processing apparatus capable of uniformly flattening a thin film even when the thickness distribution of the thin film formed on the substrate surface is not uniform.
[0008]
Still another object of the present invention is to provide a substrate processing apparatus capable of flattening or thinning a thin film on a substrate by a clean process.
Still another object of the present invention is to provide a substrate processing apparatus capable of performing the plating process and the flattening process (thinning process) with one apparatus.
Still another object of the present invention is to provide a substrate processing apparatus that can uniformly reduce the surface of a substrate that has not been annealed.
[0009]
Still another object of the present invention is to provide a substrate processing method capable of satisfactorily flattening a substrate surface even when a step due to a protrusion on the substrate surface is large.
Still another object of the present invention is to provide a substrate processing method capable of eliminating the protrusion of the thin film over the entire surface of the substrate even when the thickness distribution of the thin film formed on the substrate surface is not uniform. is there.
Still another object of the present invention is to provide a substrate processing method capable of flattening or thinning the substrate surface in a clean process.
[0010]
Still another object of the present invention is to provide a substrate processing method that does not require an annealing step before the substrate surface is thinned.
[0011]
[Means for Solving the Problems and Effects of the Invention]
  The invention according to claim 1 for solving the above-mentioned problems is as follows.FirstEtching droplet jetting means (10) for jetting the droplet (Ld) generated by mixing the etching liquid (L1) and gas to collide with the surface of the substrate (W).And a processing liquid supply means for discharging, as a processing liquid, a second etching liquid (L2) that advances etching on the surface of the substrate at a higher etching rate than the droplets ejected by the etching liquid droplet ejecting means on the surface of the substrate. (26)An etching processing section (3a-3c) for etching the surface of the substrate;Control for controlling the processing liquid supply means so as to eject the second etching liquid onto the surface of the substrate after controlling the etching liquid droplet ejecting means so that the liquid droplets are ejected and collide with the surface of the substrate. Part (30) withThis is a substrate processing apparatus.
[0012]
  In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
  Etching liquid sprayed by etching droplet spraying means(First etchant)Most of the droplets of the liquid droplets collide with the surface of the substrate and then spread at a high speed along the surface of the substrate without rebounding. For example, when a thin film such as a metal film is formed on the surface of the substrate, and this thin film has a step due to the protruding portion, the etching solution that spreads along the surface of the substrate (thin film) Etching is performed at a higher etching rate than other portions.
[0013]
This is a significant difference from the case where the etching solution is supplied to the substrate surface without forming droplets. When the etching solution is supplied to the substrate surface as it is without forming droplets, the etching solution acts isotropically on the surface of the thin film, so that the thin film is etched with a step on the surface. However, when droplets of etching solution are generated and collide with the substrate, the thin film is not etched isotropically, but the protrusions are selectively etched. As a result, the thin film is planarized with the protrusions removed. Even when the level difference due to the protrusion on the surface of the thin film is large, the surface of the thin film is satisfactorily flattened.
[0014]
The higher the rate at which the droplet of the etching solution collides with the substrate, the greater the rate at which the etching solution spreads along the surface of the substrate, and the thin film protrusions are efficiently etched.
Even when the substrate surface forms a gentle curved surface as a whole, the etching solution can spread along the substrate surface and can etch local protrusions of the thin film. Therefore, even when the thickness distribution of the thin film formed on the substrate surface is not uniform, it is possible to eliminate the protrusions over the entire surface of the substrate. For example, even when a copper thin film is formed on a semiconductor substrate by electrolytic plating, and the thickness of the copper thin film is different between the central portion and the peripheral portion of the semiconductor substrate, the protruding portion of the copper thin film should be eliminated over the entire surface of the semiconductor substrate. Can do.
[0015]
Moreover, even when the thin film formed on the substrate surface is not baked by annealing, the thin film can be uniformly thinned by the etching solution. Therefore, it is not necessary to perform an annealing step before the substrate surface is thinned by this substrate processing apparatus. “Thinning” includes thinning the thin film until the thin film remains only inside the recess when the thin film is formed on a substrate having a recess such as a wiring groove on the surface. (same as below).
[0016]
When the substrate is a semiconductor substrate and the thin film formed on the substrate surface is a metal film, the metal film may be, for example, an aluminum (Al) thin film in addition to the copper (Cu) thin film.
Such a substrate processing apparatus can flatten a thin film only by a chemical action by an etchant without using physical polishing as in CMP, and can uniformly thin a thin film. That is, these processes are clean without dust generation. For this reason, this substrate processing apparatus can be arranged and used in the same room as the apparatus which performs processes other than a thinning (flattening) process.
[0017]
  The invention according to claim 2 is characterized in that the etching droplet ejecting means isThe firstMix with etchant and gasThe firstThis produces droplets of etchantFirstA two-fluid nozzle (9) for injecting a droplet of etching liquid onto the surface of the substrate, and connected to the two-fluid nozzle,The firstThe etching liquid supply pipe (17) for supplying an etching liquid, and a gas supply pipe (18) connected to the two-fluid nozzle and for supplying gas to the two-fluid nozzle. A substrate processing apparatus.
[0018]
  From the etchant supply pipe into the two-fluid nozzleFirstThe etching solution is discharged, and compressed air or nitrogen (N₂) Discharged by discharging high pressure gas such as gasFirstBy spraying high-pressure gas from the lateral direction on the etchant,FirstThe etching solution can be made into fine droplets. By adjusting the flow rate (pressure) of high pressure gas,FirstIt is possible to control the size of the droplet of the etching solution and the collision speed with respect to the substrate. The two-fluid nozzle is an open space.FirstIt may be one that generates and ejects liquid droplets by spraying gas on the etchant (external mixing).FirstA gas may be sprayed onto the etching solution to generate droplets, and the droplets may be ejected outside the two-fluid nozzle (internal mixing).
[0019]
  By two fluid nozzleThe firstThe distance between the two-fluid nozzle and the substrate when the etching liquid droplets are sprayed onto the substrate can be, for example, 5 mm to 50 mm. Thereby, the droplets of the etching solution collide with the substrate at a sufficiently high collision speed, and the substrate surface can be satisfactorily flattened.
  The invention according to claim 4 is based on the etching droplet ejecting means.The first4. The substrate processing apparatus according to claim 1, wherein an angle formed by a direction in which an etching liquid droplet is jetted and a direction normal to the substrate is within 45 degrees.
[0020]
  Etching solution(First etchant)When the component in the normal direction of the substrate is large in the collision speed of the droplets to the substrate, the moving speed of the etching solution along the substrate surface after the collision becomes large. According to the present invention, the droplets of the etching solution are ejected at a small angle (within 45 °) with respect to the normal direction of the substrate, so that the component in the normal direction of the substrate is large in the collision speed against the substrate. Become. Therefore, the thin film can be preferably planarized.
  More preferably, the angle formed by the etching liquid droplet injection direction by the etching liquid droplet injection means and the normal direction of the substrate is approximately 0 °. That is, it is more preferable that the droplet of the etching solution collides with the substrate substantially perpendicularly.
[0021]
  According to a fifth aspect of the present invention, the etching processing section moves the substrate holding means (11) holding the substrate, and the substrate held by the substrate holding means and the etching droplet ejecting means relatively move. 5. The substrate processing apparatus according to claim 1, further comprising means (15, 21).
  FirstWhen the droplet of the etching solution collides with the substrate and moves an appropriate distance along the substrate surface, the moving speed with respect to the substrate is attenuated and stops. Therefore,FirstWhen the region where the droplet of the etchant collides with the substrate is narrow relative to the substrate surface, the region that is not etched may remain on the substrate surface (thin film).
[0022]
  According to the present invention, the substrate and the etching droplet ejecting means are moved relative to each other, so thatFirstThe thin film can be etched over the entire surface of the substrate by moving the region where the droplets of the etching solution collide.
  For example, the moving means may be capable of arbitrarily moving the etching droplet ejecting means in the in-plane direction of the substrate.
  The invention according to claim 6 further includes a rotation drive mechanism (15) in which the etching processing section rotates the substrate held by the substrate holding means.Thus, the control unit discharges the second etching liquid to the surface of the substrate while controlling the etching droplet ejecting means to eject the droplet and collide with the surface of the substrate. In this way, the rotation drive mechanism is controlled so as to rotate the substrate held by the substrate holding means while controlling the processing liquid supply means.The substrate processing apparatus according to claim 5.
[0023]
  According to this invention, the substrate is rotated by the rotation driving mechanism, and the etching droplet ejecting means is moved between the central portion and the peripheral portion of the substrate by the moving means.FirstBy spraying the droplets of the etching solution, the thin film can be etched over the entire surface of the substrate.
  Also, by rotating the substrate with a rotation drive mechanism,FirstShake off the etchant by centrifugal force and hit the substrate surface anew.FirstEtching liquid droplets can easily spread along the substrate surface.
[0024]
The processing liquid can be supplied to the substrate surface by the processing liquid supply means to perform a process other than the flattening of the thin film. The treatment liquid is, for example, a claim7As statedSecondEtching solutionOthersMay contain pure water. placeBy means of liquid supplySecondAn etching solution can be supplied to the substrate surface to uniformly thin the thin film after the surface is flattened. At this time, since the thin film may be isotropically etched,SecondThe etching solution can be supplied to the substrate surface as it is without forming droplets.
[0025]
  Also, the substrate surface can be cleaned by supplying pure water to the substrate surface by the treatment liquid supply means..
[0026]
  In the thin film flattening process, only the protrusions on the surface of the thin film need be etched and used in this process.FirstThe etching solution is not necessarily suitable for thinning the entire thin film in a short time. Therefore, after the planarization of the thin film surface is completed, for example, the concentration of active ingredients such as acid is high.SecondThe thin film can be thinned as a whole in a short time by supplying the etching liquid by the processing liquid supply means.
  Claim8The described invention is supplied by the processing liquid supply means.SecondThe etching solution heating means (25) for heating the etching solution is further included.1 to 7It is a substrate processing apparatus of description.
[0027]
  According to this invention, the etching solution heating meansSecondThe etching solution is heated, and the processing solution supply meansSecondAn etching solution can be supplied to the substrate surface. As a result, the thin film after flatteningSecondAn etchant can be supplied.
  Heated by the etching solution heating means and supplied by the processing solution supply meansSecondThe temperature of the etching solution is jetted from the etching droplet jetting means.FirstetchingofIt can be higher than the temperature of the droplet. Thereby, it is supplied by the processing liquid supply means.SecondInjected from etching liquid and etching droplet injection meansFirstEven if the etching solution is the same type and the concentration of the active ingredient is the same, the thin film after planarization can be thinned in a short time.
[0028]
  Claim9The invention described in claim 1 further includes a plating processing section (2a to 2c) for performing a plating process on the substrate.8The substrate processing apparatus according to any one of the above.
  This substrate processing apparatus can continuously perform a plating process and an etching process for flattening or thinning. Since the etching processing unit processes the substrate by a chemical action using a processing solution in the same manner as the plating processing unit, such in-line processing is possible.
[0029]
The substrate processing apparatus may further include a transfer robot that transfers the substrate and loads / unloads the substrate to / from the plating processing unit or the etching processing unit. In this case, the operation of the plating processing unit, the etching processing unit, and the transfer robot is controlled by the control unit, so that the plating process to the etching process can be performed automatically and continuously.
The substrate processing apparatus may further include a substrate storage unit that stores unprocessed and processed substrates. In this case, the transfer robot is between the substrate storage unit and the plating processing unit or the etching processing unit. The substrate may be transportable.
[0030]
  Claim 10The invention described in claim 1 further includes an annealing treatment section (6a, 6b) for annealing the substrate.9The substrate processing apparatus according to any one of the above.
  Annealing treatment can improve the characteristics (denseness) of the thin film formed on the substrate surface.
  Claim 11The described inventionFirstA droplet generated by mixing an etching solution and a gas is made to collide with the surface of the substrate.ConcernedFirst etching step for etching the surface of the substrateThen, after the first etching step, a second etching solution is applied to the surface of the substrate to etch the surface of the substrate by supplying a second etching solution that advances etching on the surface of the substrate at an etching rate faster than the droplet. Etching processThe substrate processing method characterized by including.
[0031]
  The present invention can be implemented by the substrate processing apparatus according to the first aspect, and can achieve the same effects as the substrate processing apparatus according to the first aspect.
  Claim 12The described invention is the first etching step.The firstThe collision velocity of the droplet of the etching solution against the substrate is 10 m / s to 300 m / s.1It is a substrate processing method of description.
  This substrate processing method spreads along the substrate surface after colliding with the substrate.FirstThe speed of the etching solution can be sufficiently increased, and the thin film formed on the substrate surface can be satisfactorily flattened. Colliding with the substrate at such a speedFirstThe droplet of the etching solution can be generated, for example, by the substrate processing apparatus according to claim 2.
[0032]
  Claim 13The described invention is the first etching step.The firstThe diameter of the droplet of the etching solution is 0.1 μm to 100 μm.1Or 12It is a substrate processing method of description.
  Of such diameterFirstThe thin film formed on the substrate surface can be satisfactorily flattened by the droplets of the etching solution. Of such diameterFirstThe droplet of the etching solution can be generated, for example, by the substrate processing apparatus according to claim 2.
[0033]
  Claim 14The described invention further includes a substrate rotation step of rotating the substrate, and the first etching step.And the second etching stepIs performed on the substrate rotated in the substrate rotation step.113The substrate processing method according to any one of the above.
  This substrate processing method can be carried out by the substrate processing apparatus according to the sixth aspect, and can provide the same effects as the substrate processing apparatus according to the sixth aspect.
[0034]
  Claim 15In the described invention, the first etching step is performed on the substrate.The firstA droplet collision region moving step for moving the droplet collision region (A) where the droplets of the etching solution collide between the central portion and the peripheral portion of the substrate, and the droplet in the droplet collision region moving step 2. A moving speed control step of changing the moving speed of the collision area so that the peripheral edge portion of the substrate is slower than the central portion of the substrate.4It is a substrate processing method of description.
[0035]
When the substrate rotates about its center, the region where the etching liquid droplet collides with the substrate moves with respect to the substrate except for the central portion of the substrate. For this reason, the area of the droplet collision area at the peripheral edge of the substrate is larger than the area of the droplet collision area at the center of the substrate. For this reason, when the droplet amount of the etching solution supplied per unit time is constant and the moving speed of the droplet collision region is the same between the central portion and the peripheral portion of the substrate, the peripheral portion of the substrate is at the central portion of the substrate. In comparison, the amount of droplets of the etching solution supplied per unit area is reduced. As a result, the amount of etching of the thin film formed on the substrate surface in the peripheral portion of the substrate is smaller than that in the central portion, and the degree of flattening becomes worse.
[0036]
  According to this invention, the etching liquid supplied per unit area at the substrate peripheral portion and the substrate central portion is made slower by moving the movement speed of the droplet collision region at the substrate peripheral portion than at the substrate central portion.(First etchant)The droplet amount can be made substantially equal. As a result, the etching amount of the thin film formed on the substrate surface can be made substantially equal between the peripheral edge portion of the substrate and the central portion of the substrate, and the entire surface of the substrate can be satisfactorily flattened.
  Claim 16In the described invention, the first etching step is discharged at a first flow rate.The firstBlowing the gas discharged at the second flow rate into the etchantThe first2. An etching droplet generating step for generating a droplet of an etching solution, wherein the etching droplet generating step includes a step of changing the second flow rate.115The substrate processing method according to any one of the above.
[0037]
  According to this invention,FirstMix the etchant and gasFirstWhen creating droplets of etchant,FirstThe gas flow rate can be changed with respect to the flow rate of the etching solution. Thereby, for example, against the substrateFirstThe collision speed of the etching liquid droplets can be changed.
  As described above, when the substrate is rotating, if the etching liquid droplets collide with each other under the same conditions in the central portion of the substrate and the peripheral portion of the substrate, the etching amount of the thin film is reduced in the peripheral portion of the substrate. Therefore, the etchant is more at the periphery of the substrate than at the center of the substrate.(First etchant)By increasing the collision speed of the liquid droplets, the etching amount of the thin film formed on the substrate surface can be made almost equal at the peripheral edge of the substrate and the central portion of the substrate. it can.
[0038]
  Claim 17The described inventionthe aboveA cleaning process for cleaning the substrate by supplying pure water to the surface of the substrate after the second etching step.AboutFurther comprising:116The substrate processing method according to any one of the above.
  The substrate processing method is claimed in claim7It can be implemented by the described substrate processing apparatus,7The same effects as those of the described substrate processing apparatus can be obtained.
According to an eighteenth aspect of the present invention, the first etching step is performed on the substrate held by the substrate holding unit, and the second etching step is performed on the substrate held by the substrate holding unit. The substrate processing method according to claim 11, wherein the substrate processing method is a substrate processing method.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic plan view showing a layout of a substrate processing apparatus according to an embodiment of the present invention. In this substrate processing apparatus, after a copper thin film is formed on the surface of a semiconductor wafer (hereinafter simply referred to as “wafer”) W which is an example of a substrate, the surface of the copper thin film can be thinned. That is, this substrate processing apparatus can perform a so-called damascene process.
[0040]
This substrate processing apparatus includes a cassette mounting portion 1 in which a plurality of cassettes C for storing unprocessed wafers W and processed wafers W are arranged along a predetermined direction, and an electrolytic plating process for the wafers W. A plurality of (three in this embodiment) plating processing portions 2a to 2c for forming a copper thin film, a plurality (three in this embodiment) etching processing portions 3a to 3c for etching a copper thin film, and a wafer An annealing process part 6a, 6b for performing an annealing process on W is provided.
[0041]
The unprocessed wafer W stored in the cassette C has, for example, fine wiring grooves or holes (for example, for interlayer connection of multilayer wiring) formed on the surface, and a seed layer by sputtering is formed on the surface in advance. It is a thing. In the plating units 2a to 2c, a plating process (bottom-up type plating process) is performed on the wafer W having a wiring groove or the like formed on the surface thereof so that a copper thin film grows from the bottom of the wiring groove or the like. it can.
[0042]
The plurality of plating processing units 2 a to 2 c and the annealing processing unit 6 a and the plurality of etching processing units 3 a to 3 c and the annealing processing unit 6 b are arranged along both sides of the straight conveyance path 4. The cassette mounting portion 1 is disposed on one end side of the linear conveyance path 4. The annealing treatment units 6 a and 6 b are arranged opposite to each other with the straight conveyance path 4 in between near the other end of the straight conveyance path 4. The straight transfer path 4 is provided with a main transfer robot 5 that can reciprocate along the straight transfer path 4.
[0043]
A loading / unloading robot 7 is disposed in a portion of the linear conveyance path 4 facing the annealing treatment units 6 a and 6 b, and a delivery table 8 is disposed at the center of the linear conveyance path 4 of the loading / unloading robot 7. Is arranged.
Unprocessed wafers W are taken out one by one from the cassette C by the main transfer robot 5, and are loaded into one of the plating processing units 2a to 2c, where one surface is plated. The wafer W subjected to the plating process is unloaded from any of the plating processing units 2 a to 2 c by the main transfer robot 5 and placed on the delivery table 8. The wafer W placed on the delivery table 8 is loaded into the annealing unit 6a or 6b by the loading / unloading robot 7 and subjected to annealing. Thereby, the characteristic (denseness) of a copper thin film can be improved. The annealing process is usually performed on a plurality of wafers W at the same time.
[0044]
The wafer W that has been annealed is unloaded from the annealing section 6 a or 6 b by the loading / unloading robot 7 and placed on the delivery table 8. The wafer W placed on the delivery table 8 is carried into one of the etching processing units 3a to 3c by the main transfer robot 5, and is subjected to etching processing, cleaning and drying. By the etching process, the copper thin film is flattened and thinned so that the copper thin film is left only inside the wiring groove or the like. The wafer W subjected to these processes is unloaded from one of the etching processing units 3 a to 3 c by the main transfer robot 5 and stored in the cassette C mounted on the cassette mounting unit 1.
[0045]
FIG. 2 is a schematic perspective view showing a common configuration of the etching processing units 3a to 3c. The etching processing units 3 a to 3 c include a spin base 11 that rotates while holding the wafer W substantially horizontally, and an etching droplet ejecting apparatus 10 that ejects a droplet of an etching solution toward the wafer W held by the spin base 11. And a processing liquid supply device 26 capable of switching and supplying the etching liquid and pure water to the wafer W held on the spin base 11.
[0046]
The spin base 11 can hold the wafer W by adsorbing the center of the bottom surface of the wafer W. The spin base 11 has a rotating shaft 14 arranged along the vertical direction, and a rotational driving force is applied to the rotating shaft 14 from a rotational driving mechanism 15.
The etching liquid droplet ejecting apparatus 10 includes a two-fluid nozzle 9, an etchant pipe 17 and a compressed air pipe 18 that are connected to the two-fluid nozzle 9. The etching solution pipe 17 is connected to the etching solution supply source 17S. The etching solution supply source 17S can supply a first etching solution that can dissolve copper. As the first etching solution, for example, a mixed solution of hydrofluoric acid, nitric acid, and water, or a mixed solution of sulfuric acid, hydrogen peroxide solution, and water can be used.
[0047]
The compressed air pipe 18 is connected to a compressed air supply source 18S (for example, a compressor).
The etchant pipe 17 is provided with a valve 17B having a flow rate adjusting function, and the first etchant can be supplied into the two-fluid nozzle 9 by opening the valve 17B. Further, the flow rate of the first etching solution flowing through the etching solution pipe 17 can be adjusted by the valve 17B. The compressed air pipe 18 is provided with a valve 18B having a flow rate adjusting function, and the compressed air can be supplied into the two-fluid nozzle 9 by opening the valve 18B. Further, the flow rate of the compressed air flowing through the compressed air pipe 18 can be adjusted by the valve 18B.
[0048]
FIG. 3 is a schematic sectional view showing the structure of the two-fluid nozzle 9.
The two-fluid nozzle 9 is a so-called internal mixing type two-fluid nozzle, and is configured by connecting a gas introducing unit 211, a liquid introducing unit 210, and a droplet forming / discharging unit 212. The gas introduction part 211, the liquid introduction part 210, and the droplet formation / discharge part 212 all have a tube shape, and are connected in series to form the two-fluid nozzle 9.
[0049]
The droplet forming / discharging unit 212 is connected to the lower end of the liquid introducing unit 210, and is connected to the tapered portion 212a whose inner diameter decreases toward the lower side and the lower end of the 212a, and has a straight tube shape with a uniform inner diameter. And a straight portion 212b.
The gas introduction part 211 has a large diameter part that engages with the upper part of the liquid introduction part 210, and a small diameter part that continues to the lower part of the large diameter part and reaches the internal space of the droplet formation and discharge part 212. A tapered gas introduction path 211a is formed inside.
[0050]
In the liquid introduction part 210, a liquid introduction path 210a for introducing a liquid (first etching solution) is formed so as to open to the side, and the liquid introduction path 210a is connected to a small diameter part of the gas introduction part 211. It communicates with a ring-shaped space SP1 between the inner wall of the liquid introduction part 210. This space SP1 is connected to the internal space SP3 (mixed space) of the tapered portion 212a of the droplet forming / discharging portion 212 via a ring-shaped space SP2 between the small diameter portion of the gas introducing portion 211 and the inner wall of the droplet forming / discharging portion 212. Room).
[0051]
A compressed air pipe 18 is connected to the gas introduction path 211 a of the gas introduction part 211. An etchant pipe 17 is connected to the liquid introduction path 210a.
In the two-fluid nozzle 9, the compressed air supplied from the gas introduction path 211a and the first etching liquid supplied from the liquid introduction path 210a via the spaces SP1 and SP2 are mixed in the space SP3. One droplet of the etching solution is formed. The liquid droplets are accelerated by the taper portion 212a and ejected toward the wafer W through the straight portion 212b. This droplet jet has a very good straightness due to the action of the straight portion 212b.
[0052]
Referring to FIG. 2, a horizontally extending arm 19 is coupled to a side surface of the two-fluid nozzle 9 (liquid introducing portion 210), and the arm 19 is coupled to a rotating shaft 20 extending in the vertical direction. The rotary shaft 20 is coupled with a swing mechanism 21 that swings the rotary shaft 20 about the axis. By the swing mechanism 21, the two-fluid nozzle 9 coupled to the rotating shaft 20 via the arm 19 can be moved in an arc shape above the wafer W held by the spin base 11. At this time, the two-fluid nozzle 9 moves so as to pass above the center of the wafer W. The swing mechanism 21 can also move the two-fluid nozzle 9 to a retracted position that does not face the wafer W held on the spin base 11.
[0053]
When the two-fluid nozzle 9 faces the wafer W held on the spin base 11, the distance between the two-fluid nozzle 9 and the wafer W is set to 5 mm to 50 mm. Further, the direction of the straight portion 212 b is such that the first etching liquid droplets are ejected substantially perpendicularly to the wafer W held on the spin base 11. In other words, the angle formed between the jet direction of the first etching liquid droplet and the normal direction of the wafer W is set to approximately 0 °.
[0054]
The processing liquid supply device 26 includes a pure water supply source 23S in which pure water is stored, and an etching liquid storage tank 24S in which a second etching liquid is stored. One end of the pure water pipe 23 is connected to the pure water supply source 23S, and one end of the etchant pipe 24 is connected to the etchant storage tank 24S. The other ends of the pure water pipe 23 and the etching liquid pipe 24 are connected to one end of the processing liquid pipe 22, and the processing liquid supply nozzle 13 is connected to the other end of the processing liquid pipe 22.
[0055]
The second etching solution stored in the etching solution storage tank 24S is, for example, the same type as the first etching solution and a high concentration of an active component such as an acid. An electrothermal heater 25 is disposed around a part of the etchant pipe 24 so that the second etchant can be heated.
A three-way valve 24 </ b> B is interposed downstream of the heater 25 in the etching solution pipe 24. A return pipe 28 is attached to the three-way valve 24B, and the return pipe 28 extends inside the etching solution storage tank 24S. By operating the three-way valve 24B, the second etching liquid is circulated between the etching liquid storage tank 24S, the etching liquid pipe 24, and the return pipe 28 by a pump (not shown), or the processing liquid is supplied from the etching liquid storage tank 24S. It can supply to the nozzle 13.
[0056]
A valve 23B is interposed in the pure water pipe 23. By preventing the second etching liquid from being supplied to the processing liquid supply nozzle 13 by the three-way valve 24B and opening the valve 23B, pure water can be supplied from the processing liquid supply nozzle 13, the valve 23B is closed, and the three-way valve 24B is The second etching liquid can be supplied from the processing liquid supply nozzle 13 by supplying the two etching liquids to the processing liquid supply nozzle 13.
[0057]
A moving mechanism (not shown) is coupled to the processing liquid pipe 22, and the moving mechanism causes the processing liquid supply nozzle 13 to face the wafer W held by the spin base 11 and to the side of the spin base 11. It is possible to move between the retracted position and the retracted position.
The controller 30 controls the opening and closing of the valves 17B, 18B, and 23B, the operation of the three-way valve 24B, the operations of the rotation driving mechanism 15 and the swing mechanism 21, the energization of the heater 25, and the like.
[0058]
FIG. 4 is a schematic sectional view showing the surface state of the wafer W in the etching process. With reference to FIG. 2 and FIG. 4, the procedure of the etching process in the etching process parts 3a thru | or 3c is demonstrated.
First, the control unit 30 closes the valves 17B, 18B, and 23B so that the second etching solution is not supplied to the processing solution supply nozzle 13 through the three-way valve 24B. Moreover, the heater 25 is energized by the control unit 30, and heating of the second etching solution stored in the etching solution storage tank 24S is started.
[0059]
Then, the control unit 30 controls the swing mechanism 21 and a moving mechanism (not shown), and the two-fluid nozzle 9 and the processing liquid supply nozzle 13 are moved to the retracted positions, respectively. Subsequently, the main transfer robot 5 (see FIG. 1) carries in the wafer W on which the copper thin film is formed on the surface of any of the plating processing units 2a to 2c and the annealing process is performed by the annealing processing unit 6a or 6b. Thus, the wafer W is held on the spin base 11 so that the center of the wafer W is positioned on the central axis of the rotation shaft 14. At this time, the wafer W is held with the surface subjected to the plating process directed upward.
[0060]
As shown in FIG. 4A, a copper thin film F is formed on the wafer W at this time so as to cover the entire surface. A large number of wiring grooves or wiring holes H (hereinafter referred to as “wiring grooves H”) are formed on the surface of the wafer W (for example, the surface of an insulating film formed on the wafer W). F is formed so as to fill the wiring groove H and the like. The wiring groove etc. H of the wafer W includes a wiring groove etc. Hn having a narrow width (diameter) and a wiring groove etc. Hw having a wide width (diameter). Since the wafer W is subjected to a bottom-up type plating process, the copper thin film F grows thick above the narrow wiring groove Hn and the like, and a protruding portion P protruding from the other portion is formed. Yes. On the other hand, a recess C lower than other portions is formed on the surface of the copper thin film F above the wiring groove Hw having a wide width.
[0061]
  Although not shown in FIG. 4A, the thickness of the copper thin film F differs between the central portion and the peripheral portion of the wafer W because it is formed by electrolytic plating. For this reason, the surface of the wafer W (copper thin film F) forms a gentle curved surface as a whole.
  Next, the swing mechanism 21 is controlled by the control unit 30 so that the two-fluid nozzle 9 is moved so as to face the central portion of the wafer W, and is driven to rotate.mechanism15 is controlled, and the wafer W held on the spin base 11 is rotated. Thereafter, the control unit 30 opens the valves 17B and 18B at a predetermined opening, and the first etching liquid and the compressed air are respectively supplied from the etching liquid supply source 17S and the compressed air supply source 18S at a predetermined flow rate. 9 is supplied.
[0062]
As a result, a droplet of the first etching solution is generated in the space SP3 and sprayed from the straight portion 212b toward the wafer W (see FIG. 3), and the first etching step is performed. The diameter of the first etching liquid droplet is 0.1 μm to 100 μm, and the collision speed at which the first etching liquid droplet collides with the wafer W is 10 m / s to 300 m / s (more preferably, 50 m / s to 300 m / s).
Since the inner diameter of the straight portion 212b is significantly smaller than the diameter of the wafer W, the area A (hereinafter referred to as “droplet collision area A”) where the droplets of the first etching liquid collide with the surface of the wafer W is referred to. This is a limited area on the W surface. The droplet collision area Ac when the two-fluid nozzle 9 faces the center of the wafer W is a substantially circular area near the center of the wafer W. If the two-fluid nozzle 9 is located at a position away from the center of the wafer W, an annular droplet collision area Ap is formed as the wafer W rotates.
[0063]
In the first etching step, when the droplet Ld of the first etching liquid L1 collides with the copper thin film F formed on the surface of the wafer W as shown in FIG. 4B, the surface of the copper thin film F does not bounce off. It spreads quickly along. At this time, the protrusion P of the copper thin film F is etched at a higher etching rate than other portions.
After colliding with the copper thin film F, the first etching liquid L1 whose moving speed along the copper thin film F is attenuated is swung off to the side by the centrifugal force accompanying the rotation of the wafer W. Thereby, the droplet Ld of the first etching liquid L1 that newly collides with the copper thin film F is likely to spread along the surface of the wafer W. In this way, when the droplet Ld of the first etching liquid L1 is sprayed toward the surface of the copper thin film F for an appropriate time, the protrusion P is etched with good selectivity, and the copper thin film F The surface is flattened.
[0064]
This is a point that is greatly different from the case where the first etching liquid L1 is supplied as it is to the surface of the wafer W without making it into droplets. When the first etching liquid L1 is supplied to the surface of the wafer W as it is without forming the droplet Ld, the first etching liquid L1 acts isotropically on the surface of the copper thin film F, so that the copper thin film F has a step on the surface. Etching is carried out as it is. As a result, as shown in FIG. 4E, when etching is performed so that the copper thin film F in portions other than the wiring trenches H is eliminated, the copper thin film F has a surface of the wafer W in the narrow wiring trenches Hn. In the wiring groove Hw having a wide width, a recess C is formed reflecting the shape of the wiring groove Hw.
[0065]
The control unit 30 controls the swing mechanism 21 in parallel with the ejection of the liquid droplet Ld of the first etching liquid L1 by the two-fluid nozzle 9 from the position where the two-fluid nozzle 9 is opposed to the central portion of the wafer W. Slowly move to a position facing the peripheral edge of W. Accordingly, the droplet collision area A moves from the central portion of the wafer W to the peripheral portion. Since the wafer W is rotating, the copper thin film F is flattened over the entire surface of the wafer W by the movement of the droplet collision area A in this way. At this time, the swinging mechanism 21 is controlled so that the moving speed of the two-fluid nozzle 9 becomes slower from the position facing the center of the wafer W toward the position facing the peripheral edge of the wafer W.
[0066]
Since the area of the droplet collision area Ap is larger than the area of the droplet collision area Ac, when the moving speed of the droplet collision area A is the same between the central portion and the peripheral portion of the wafer W, the peripheral portion of the wafer W is the central portion. Compared to the above, the amount of droplets of the first etching liquid L1 supplied per unit area is reduced. As a result, the peripheral portion of the wafer W has a smaller amount of etching of the copper thin film F than the central portion, and the degree of planarization becomes worse.
The above-described control of the moving speed of the two-fluid nozzle 9 is for solving such a problem, and the moving speed of the droplet collision area A is made slower at the periphery of the wafer W than at the center of the wafer W. As a result, the amount of droplets of the first etching liquid L1 supplied per unit area between the central portion and the peripheral portion of the wafer W is made substantially equal. Thereby, the etching amount of the copper thin film F can be made substantially equal between the central portion and the peripheral portion of the wafer W, and the copper thin film F can be satisfactorily flattened over the entire surface of the wafer W.
[0067]
Further, the first etching liquid L1 can spread along the surface of the wafer W having a gently curved surface, and only the local protrusions P of the copper thin film F can be etched. Therefore, even if the thickness distribution of the copper thin film F is not uniform, the protrusion P can be eliminated over the entire surface of the wafer W.
When the two-fluid nozzle 9 is moved to a position facing the outermost peripheral portion of the wafer W, the control unit 30 controls to stop the operation of the swing mechanism 21, and the movement of the two-fluid nozzle 9 is stopped. . At the same time, the control unit 30 controls to close the valves 17B and 18B, and the injection of the droplet Ld of the first etching liquid L1 onto the wafer W is stopped. Thereby, the first etching step is completed.
[0068]
Next, a control mechanism 30 controls a moving mechanism (not shown) to move the processing liquid supply nozzle 13 to a position facing the wafer W. Then, the three-way valve 24B is brought into a state in which the second etching liquid is supplied to the processing liquid supply nozzle 13 by the control of the control unit 30, and the heated second etching liquid is discharged from the processing liquid supply nozzle 13, and the second etching liquid is discharged. An etching process is performed. During this time, the rotation of the wafer W by the rotation driving mechanism 15 is continued.
[0069]
At this time, as shown in FIG. 4C, the second etching liquid L2 flows so as to cover the surface of the copper thin film F already planarized by the first etching process. Thereby, the copper thin film F is isotropically etched. That is, the copper thin film F is thinned while maintaining the flatness of the surface. Since the second etching solution L2 has a higher concentration of active components and a higher temperature than the first etching solution L1, the copper thin film F is etched quickly.
[0070]
When the supply of the second etching solution L2 to the wafer W is continued for a predetermined time, the surface of the wafer W is in a state in which the copper thin film F exists only inside the wiring groove H or the like as shown in FIG. It becomes. In this state, the surface of the copper thin film F is substantially flush with the surface of the wafer W both in the wiring groove Hn having a narrow width (diameter) and in the wiring groove Hw having a wide width (diameter).
Next, under the control of the control unit 30, the three-way valve 24 </ b> B is brought into a state in which the second etching liquid is not supplied to the processing liquid supply nozzle 13, and the valve 23 </ b> B is opened for a predetermined time. Pure water is discharged. Thereby, the surface of the wafer W is cleaned, and the first and second etching liquids L1, L2, etc. are removed. Subsequently, the rotation drive mechanism 15 is controlled by the control unit 30, the spin base 11 is rotated at a high speed for a certain period of time, and after the moisture of the wafer W is shaken and dried, the rotation of the spin base 11 is stopped.
[0071]
Thereafter, the control unit 30 controls the swing mechanism 21 and a moving mechanism (not shown) to move the two-fluid nozzle 9 and the processing liquid supply nozzle 13 to the retreat positions, respectively, and the processed wafer W is unloaded by the main transfer robot 5. Thus, the etching process for one wafer W is completed.
The above substrate processing apparatus is an in-line arrangement of the plating processing units 2a to 2c and the etching processing units 3a to 3c, and the plating process and the etching process can be performed in the same apparatus. Since the etching processing units 3a to 3c process the wafer W by a chemical action using a processing solution (etching solution) in the same manner as the plating processing units 2a to 2c, such in-line processing is possible.
[0072]
The above etching process is performed only by the chemical action of the first and second etching liquids L1 and L2 without physical polishing as in CMP. Therefore, the copper thin film F formed on the surface of the wafer W can be flattened and thinned in a clean process without generating dust. For this reason, this substrate processing apparatus can be arranged and used in the same room as the apparatus which performs other processes other than the process of flattening and thinning.
[0073]
The description of one embodiment of the present invention is as described above, but the present invention can be implemented in other forms. For example, in the above embodiment, by controlling the moving speed of the two-fluid nozzle 9 to be slower at the position facing the peripheral edge of the wafer W than the position facing the central area of the wafer W, the central portion and the peripheral edge of the wafer W are controlled. The copper thin film F is flattened almost equally at the portion. However, instead of such control, by changing the collision speed of the droplet Ld of the first etching liquid L1 that collides with the surface of the wafer W between the central portion and the peripheral portion of the wafer W, the copper thin film F becomes You may make it planarize substantially equally.
[0074]
In this case, the opening degree of the valve 17B is made constant by the control unit 30, and the opening degree of the valve 18B is changed as the two-fluid nozzle 9 moves from a position facing the central part of the wafer W to a position facing the peripheral part. Controlled to increase. Thereby, the flow rate of the first etching liquid L1 supplied to the two-fluid nozzle 9 is constant, but the flow rate of the compressed air supplied to the two-fluid nozzle 9 is such that the droplet collision area A is from the center of the wafer W. It becomes larger as it moves to the periphery. As a result, the collision speed of the droplet Ld of the first etching liquid L1 with respect to the surface of the wafer W and the movement speed of the first etching liquid L1 along the surface of the copper thin film F are Grows as you move on. Thereby, the etching amount of the copper thin film F becomes substantially equal between the central portion and the peripheral portion of the wafer W.
[0075]
In the first etching step, the two-fluid nozzle 9 moves from the center portion of the wafer W toward the peripheral portion. However, the movement of the two-fluid nozzle 9 is not limited to this. For example, the two-fluid nozzle 9 may move from the peripheral edge of the wafer W toward the center, and the center of the wafer W You may reciprocate between a part and a peripheral part.
In the above embodiment, the wafer W is annealed, but this is for the purpose of improving the characteristics of the copper thin film F, not for performing the etching uniformly. That is, even when the annealing step is omitted and the copper thin film F is not baked by annealing, the copper thin film F can be uniformly etched by the first etching liquid L1. Therefore, when the surface of the wafer W is etched by this substrate processing apparatus, an annealing process is not necessarily required.
[0076]
The above-described two-fluid nozzle 9 generates droplets Ld by spraying compressed air on the first etching liquid L1 in the space SP3 in the two-fluid nozzle 9 and jets the droplets Ld to the outside of the two-fluid nozzle 9 ( (Internal mixing) However, it is also possible to generate and eject droplets Ld by spraying compressed air on the first etching liquid L1 in an open space (external mixing).
When the first etching solution and the second etching solution are the same type and the concentration of the effective component of the second etching solution is sufficiently higher than the concentration of the effective component of the first etching solution, the heater 25 may be eliminated. In addition, when the second etching solution can be heated so that the second etching solution has good etching characteristics, the first etching solution and the second etching solution may be the same. In any case, the copper thin film F whose surface is planarized can be quickly etched with the second etching solution.
[0077]
After the surface of the wafer W is flattened (FIG. 4B), the copper thin film F may be polished and thinned by CMP.
The substrate processing apparatus may further include an organic solvent supply device that supplies an organic solvent to the surface of the wafer W. After the wafer W is washed with pure water, the organic solvent ( For example, it may be washed with isopropyl alcohol).
[0078]
In addition to the copper thin film F, the metal film formed on the surface of the wafer W may be, for example, an aluminum thin film. By selecting an appropriate kind of the first etching solution L1, this thin film can be uniformly thinned even on a substrate having a thin film other than a metal film formed on the surface.
The substrate to be processed may be a square substrate such as a glass substrate for a liquid crystal display device in addition to a circular substrate such as the wafer W.
[0079]
In addition, various modifications can be made within the scope of the matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing a layout of a substrate processing apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic perspective view showing a configuration of an etching processing unit.
FIG. 3 is a schematic cross-sectional view showing the structure of a two-fluid nozzle.
FIG. 4 is a schematic cross-sectional view showing a surface state of a wafer in an etching process.
[Explanation of symbols]
2a ~ 2c Plating part
3a-3c Etching process part
5 Main transfer robot
6 Annealing section
9 Two-fluid nozzle
10 Etching droplet jetting device
11 Spin base
13 Treatment liquid supply nozzle
15 Rotation drive mechanism
17, 24 Etching solution piping
17B, 18B valve
17S, 24S Etch solution supply source
18 Compressed air piping
18S compressed air supply source
21 Swing mechanism
22 Treatment liquid piping
23 Pure water piping
23S source of pure water
25 Heater
26 Treatment liquid supply device
30 Control unit
A Droplet collision area
Ld First etchant droplet
L1 first etchant
L2 Second etchant
W wafer

Claims (18)

Etching droplet ejecting means for ejecting droplets generated by mixing the first etching liquid and gas and colliding with the surface of the substrate; and droplets ejected by the etching droplet ejecting means on the surface of the substrate An etching processing unit that etches the surface of the substrate, including a processing liquid supply unit that discharges, as a processing liquid, a second etching liquid that advances etching on the surface of the substrate at a higher etching rate .
Control for controlling the processing liquid supply means so as to eject the second etching liquid onto the surface of the substrate after controlling the etching liquid droplet ejecting means so that the liquid droplets are jetted and collide with the surface of the substrate substrate processing apparatus is characterized in that a part. The etching liquid droplet ejecting means generates a liquid droplet of the first etching liquid by mixing with the first etching liquid and a gas, and a two-fluid nozzle that ejects the liquid droplet of the first etching liquid onto the surface of the substrate; ,
An etchant supply pipe connected to the two-fluid nozzle and supplying the first etchant to the two-fluid nozzle;
The substrate processing apparatus according to claim 1, further comprising: a gas supply pipe connected to the two-fluid nozzle and configured to supply gas to the two-fluid nozzle. 3. The substrate processing apparatus according to claim 2, wherein a distance between the two-fluid nozzle and the substrate when the droplet of the first etching liquid is sprayed onto the substrate by the two-fluid nozzle is 5 mm to 50 mm. 4. An angle formed by a jet direction of the droplet of the first etching liquid by the etching droplet jetting means and a normal direction of the substrate is within 45 °. Substrate processing equipment. A substrate holding means for holding the substrate;
5. The substrate processing apparatus according to claim 1, further comprising moving means for relatively moving the substrate held by the substrate holding means and the etching droplet ejecting means. The etching processor is further seen including a rotary driving mechanism for rotating the substrate held by the substrate holding means,
The control unit controls the etching droplet ejecting unit to eject the droplet and collide with the surface of the substrate, and discharges the second etching liquid onto the surface of the substrate. 6. The substrate processing apparatus according to claim 5, wherein the rotation driving mechanism is controlled so as to rotate the substrate held by the substrate holding means while the processing liquid supply means is controlled . The treatment liquid discharged by the treatment liquid supply means further contains pure water,
The substrate processing apparatus according to any one of claims 1, wherein said treatment liquid supply means can be supplied to the surface of the substrate by switching between the second etchant and pure water 6. The processing liquid substrate processing apparatus according to any one of claims 1, further comprising an etchant heating means for heating the second etching solution supplied 7 by the supply means. The substrate processing apparatus according to any one of claims 1 to 8, further comprising a plating unit for plating process on the substrate. The substrate processing apparatus according to any one of claims 1 to, further comprising an annealing unit for annealing of the substrate 9. A first etching step of etching the surface of the substrate by colliding droplets a first etchant and the gas is generated are mixed on the surface of the substrate,
After the first etching step, a second etching step for etching the surface of the substrate by supplying a second etching solution that advances etching on the surface of the substrate at an etching rate faster than that of the droplets. And a substrate processing method. The impact velocity relative to the above substrate of droplets of the first etching solution in the first etching step, the substrate processing method according to claim 1 1, wherein the to not 10 m / s is 300 meters / s. The diameter of the first droplet of the first etching solution in the etching step, 0.1 [mu] m to claim 1 1 or 1 2 substrate processing method wherein a is 100 [mu] m. A substrate rotation step of rotating the substrate;
The first etching step and the second etching step, the substrate processing according to any one of 1 3 claims 1 1, characterized in that it is performed on the substrate being rotated at the substrate rotating step Method. The first etching step includes
A droplet collision region moving step of moving a droplet collision region where the droplets of the first etching liquid collide on the substrate between a central portion and a peripheral portion of the substrate;
And a movement speed control step of changing the movement speed of the droplet collision area in the droplet collision area movement step so that the peripheral edge of the substrate is slower than the central portion of the substrate. 1 4 the substrate processing method according. The first etching step includes an etching droplet generation step of generating a droplet of the first etching solution by blowing a gas discharged at a second flow rate to the first etching solution discharged at a first flow rate. Including
The etching droplet generation process, a substrate processing method according to any one of claims 1 1 to 1 5, characterized in that it comprises a step of changing the second flow rate. After the second etching step, the substrate processing according to claim 1 1 to 1 6, characterized in that by supplying pure water to the surface of the substrate further comprises a higher cleaning Engineering for cleaning the substrate Method.   The first etching step is performed on the substrate held by the substrate holding means,
  The substrate processing method according to claim 11, wherein the second etching step is performed on the substrate held by the substrate holding unit.

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