Substrate processing method and substrate processing device

Abstract

The object of this invention is to locally control the etching amount when etching the surface of a substrate. The substrate processing method of this invention includes the following steps: a first etching step, in which a pool of a first processing liquid is formed on the entire surface of the substrate, and a second processing liquid is locally sprayed from a nozzle onto a target area locally defined on the surface of the substrate, thereby etching in a manner that makes the etching rate of the target area different from the etching rate of other areas; and a second etching step, in which an etching liquid is supplied while the substrate is rotated, such that a liquid film of the etching liquid covers the entire surface of the substrate, thereby simultaneously etching the entire surface of the substrate; one of the first and second processing liquids used in the first etching step is an etching liquid, and the other is an etching inhibitor liquid that reduces the etching rate of the etching liquid on the surface of the substrate by mixing with the etching liquid.

Description

Technical Field

[0001] This invention relates to a substrate processing method and a substrate processing apparatus. Prior Technology

[0002] In the manufacture of semiconductor devices, wet etching is performed to remove the film formed on the surface of substrates such as semiconductor wafers using a chemical solution. In recent years, there has been a search for ways to further improve the in-plane uniformity of the etching amount. Patent Document 1 describes a substrate processing apparatus that performs wet etching of a substrate by supplying an etching solution to the center of a rotating substrate. The apparatus improves the in-plane uniformity of the etching amount by blowing a temperature-controlled gas onto the periphery of the substrate, which is easier to cool, during the processing. [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2001-085383 Summary of the Invention

[0004] [The problem the invention aims to solve]

[0005] This invention provides a technique for locally controlling the amount of etching when etching the surface of a substrate. [Methods for solving problems]

[0006] According to one embodiment of the present invention, a substrate processing method includes the following steps: a first etching step in which, with a pool of a first processing liquid formed on the entire surface of the substrate, a second processing liquid is partially sprayed from a nozzle onto a target area partially set on the surface of the substrate, thereby etching in a manner that makes the etching rate of the target area different from the etching rate of other areas; and a second etching step in which the etching liquid is supplied while the substrate is rotated, such that a liquid film of the etching liquid covers the entire surface of the substrate, thereby simultaneously etching the entire surface of the substrate; wherein, in the first etching step, one of the first processing liquid and the second processing liquid is the etching liquid, and the other is an etching inhibitor, which reduces the etching rate of the etching liquid on the surface of the substrate by mixing with the etching liquid. [Invention Effects]

[0007] Through the above embodiments of the present invention, the etching amount can be locally controlled when etching the surface of the substrate. Simple Explanation of the Diagram

[0008] Figure 1 is a schematic cross-sectional view of a substrate processing system according to one embodiment of a substrate processing apparatus. Figure 2 is a schematic longitudinal cross-sectional view showing the configuration of the processing unit of the substrate processing system in Figure 1. Figures 3(A) to (E) are schematic diagrams illustrating the etching method of the first embodiment of the substrate processing method. Figures 4(A) to (E) are schematic diagrams illustrating the etching method of the second embodiment of the substrate processing method. Figures 5(A) to (E) are schematic diagrams illustrating the etching method of the third embodiment of the substrate processing method. Figures 6(A) to (E) are schematic diagrams illustrating the etching method of the fourth embodiment of the substrate processing method. Figure 7 is a diagram illustrating how the processing conditions for the first etching step are set. Figure 8 is a graph showing the experimental results of the etching amount distribution in the first etching step. Figure 9 is a schematic diagram illustrating the first deformation implementation state of the second etching step. Figure 10 is a schematic diagram illustrating the second deformation implementation of the second etching step. Implementation

[0009] An embodiment of a substrate processing apparatus is described with reference to the accompanying drawings.

[0010] Figure 1 is a schematic diagram showing the basic configuration of the substrate processing system according to this embodiment. Hereinafter, to clarify the positional relationships, the X-axis, Y-axis and Z-axis are defined as mutually orthogonal, and the positive direction of the Z-axis is set as the vertically upward direction.

[0011] As shown in Figure 1, the substrate processing system 1 includes an inbound / outbound station 2 and a processing station 3. The inbound / outbound station 2 and the processing station 3 are arranged adjacent to each other.

[0012] The loading / unloading station 2 includes a carrier placement section 11 and a transport section 12. The carrier placement section 11 holds a plurality of carriers C, which horizontally accommodate a plurality of substrates (in this embodiment, semiconductor wafers or other substrates W).

[0013] The transport unit 12 is disposed adjacent to the carrier placement unit 11, and includes a substrate transport device 13 and a transfer unit 14 inside it. The substrate transport device 13 has a substrate holding mechanism for holding the substrate W. Furthermore, the substrate transport device 13 can move in the horizontal and vertical directions, and rotate about the vertical axis, and uses the substrate holding mechanism to transport the substrate W between the carrier C and the transfer unit 14.

[0014] Processing station 3 is disposed adjacent to transport section 12. Processing station 3 includes transport section 15 and a plurality of processing units 16. The plurality of processing units 16 are arranged on both sides of transport section 15.

[0015] The transport unit 15 has a substrate transport device 17 inside. The substrate transport device 17 has a substrate holding mechanism for holding the substrate W. Furthermore, the substrate transport device 17 can move in the horizontal and vertical directions, and rotate about the vertical axis, and uses the substrate holding mechanism to transport the substrate W between the transfer unit 14 and the processing unit 16.

[0016] The processing unit 16 performs predetermined substrate processing on the substrate W transported by the substrate transport device 17.

[0017] Furthermore, the substrate processing system 1 includes a control device 4. The control device 4 is, for example, a computer, and includes a control unit 18 and a storage unit 19. The storage unit 19 stores programs that control various processes executed in the substrate processing system 1. The control unit 18 reads and executes the programs stored in the storage unit 19 to control the operation of the substrate processing system 1.

[0018] Furthermore, the program can be stored on a computer-readable recording medium and installed from that recording medium into the storage unit 19 of the control device 4. Examples of computer-readable recording media include hard disks (HD), floppy disks (FD), optical discs (CD), magneto-optical discs (MO), and memory cards.

[0019] In the substrate processing system 1 configured as described above, firstly, the substrate transport device 13 of the transfer station 2 takes out the substrate W from the carrier C placed in the carrier placement section 11 and places the taken-out substrate W in the transfer section 14. The substrate W placed in the transfer section 14 is taken out from the transfer section 14 by the substrate transport device 17 of the processing station 3 and transferred into the processing unit 16.

[0020] After being processed by the processing unit 16, the substrate W is removed from the processing unit 16 by the substrate transport device 17 and placed in the transfer unit 14. Then, the processed substrate W placed in the transfer unit 14 is sent back to the carrier C of the carrier placement unit 11 by the substrate transport device 13.

[0021] Next, the configuration of the processing unit 16 will be described with reference to FIG2.

[0022] The processing unit 16 has a chamber 20 that defines the processing space. A fan filter unit (FFU) 21 is provided on the top cover of the chamber 20. The FFU 21 blows clean gas downwards into the chamber 20.

[0023] The processing unit 16 is provided with a rotary chuck (substrate holding and rotating mechanism) 30. The rotary chuck 30 has a substrate holding part (chuck part) 31 that holds the substrate W in a horizontal position, and a rotary drive part 32 that rotates the substrate holding part 31 and the substrate W held therein about a vertical axis.

[0024] The substrate holding part 31 can be a mechanical suction cup that mechanically holds the periphery of the substrate W with holding members such as clamping claws, or it can be a vacuum suction cup that vacuum-adsorbs the center of the back side of the substrate W. The rotation drive part 32 can be, for example, an electric motor.

[0025] The processing unit 16 is provided with a processing fluid supply unit 40, which supplies various processing fluids required for the processing of the substrate W to the substrate W.

[0026] The processing fluid supply unit 40 has a plurality of nozzles 41 (only two are shown in FIG. 2) for spraying processing fluid onto the substrate W. In one embodiment, the processing fluid supplied to the substrate W in the processing unit 16 includes a processing liquid and a processing gas. Examples of processing liquids include DHF (diluted fluoride), DIW (pure water), and IPA (isopropanol). Examples of processing gases include N2 gas (nitrogen). The processing fluid is not limited to the above and can be selected from various conventional processing fluids used in monolithic substrate processing units for wet etching in the field of semiconductor manufacturing technology, as needed.

[0027] In one embodiment, different processing fluids are ejected from different nozzles 41. In this case, the required processing fluid is supplied to each nozzle 41 from the processing fluid supply source 42 via a supply line 43 equipped with a supply control unit 44 (shown schematically as a blank square in Figure 2). The processing fluid supply source 42 may be, for example, a storage tank for storing processing fluids or a plant facility. The supply control unit 44 consists of an on / off valve, a flow meter, a flow control valve, etc. In other embodiments, multiple types of processing fluids (e.g., DHF and DIW) may be ejected from a single nozzle.

[0028] One of the plurality of nozzles 41 may be a two-fluid nozzle (two-fluid spray head). As is generally known in the art, a two-fluid nozzle is a nozzle in which a flow of process gas (e.g., nitrogen) supplied from a process gas supply source and a process liquid (e.g., DHF or DIW) supplied from a process liquid supply source are combined inside to generate a water mist of the mixture of process liquid and process gas and spray it out.

[0029] One of the plurality of nozzles 41 may be a single-fluid nozzle. A single-fluid nozzle only sprays a water mist-like liquid.

[0030] A plurality of nozzles 41 are supported by one or more nozzle arms 45 (only one is shown in Figure 2). The nozzle arms 45 can position each nozzle 41 at any position (radial position) between a position above the center of the substrate W held by the substrate holder 31 and a position above the periphery of the substrate W. The nozzle arms can be of the type that rotates about a vertical axis, or they can be of the type that move side by side along a guide rail.

[0031] Around the substrate holding portion, a liquid collection cup 50 is provided to collect the processing liquid that splashes out from the rotating substrate W. The processing liquid collected by the liquid collection cup 50 is discharged to the outside of the processing unit 16 through a drain port 51 located at the bottom of the liquid collection cup 50. An exhaust port 52 is also provided at the bottom of the liquid collection cup 50, and the interior of the liquid collection cup 50 is drawn in through the exhaust port 52.

[0032] The following describes several embodiments of the etching method. In these embodiments, DIW (pure water), DHF (diluted fluoride), and IPA (isopropanol) are used as processing solutions sprayed from the nozzle. DIW is used as a pre-wetting solution, pool forming solution, and cleaning solution. DHF is used as an etching solution. IPA is used as a drying liquid and / or pool forming solution.

[0033] As an etching solution, SC1 or SPM (sulfuric acid and hydrogen peroxide water) can be used to replace DHF (but not limited to these). Functional water can also be used instead of DIW as a pre-wetting solution, pool forming solution, and cleaning solution. Functional water refers to water in which trace amounts of solutes (such as ammonia, carbon dioxide, etc.) are dissolved in DIW to impart special properties (such as conductivity) that DIW does not possess.

[0034] In the following description, each nozzle 41 will also be referred to as "the name of the treatment fluid that the nozzle sprays or is prepared to spray" + "nozzle". That is, for example, a nozzle that sprays DIW is also called a DIW nozzle.

[0035] In the specific application of the device, there are often situations where two or more treatment fluids (such as DIW and DHF) are selected to be sprayed from a common nozzle 41. Such nozzles are referred to as "the name of the treatment fluid currently being sprayed or prepared to be sprayed" + "nozzle". That is, for example, a certain nozzle 41 is sometimes called "DIW nozzle" and sometimes "DHF nozzle".

[0036] Furthermore, there are also dual-fluid nozzles that can function as both single-fluid and dual-fluid nozzles. That is, for example, when only a processing fluid (e.g., DHF) is supplied to the dual-fluid nozzle instead of gas (e.g., N2 gas), the dual-fluid nozzle functions as a single-fluid nozzle. When both gas and processing fluid are supplied to the dual-fluid nozzle, it sprays a mixture of water mist from the processing fluid and gas (dual-fluid). Regardless of whether the nozzle is dedicated to single-fluid spraying, dual-fluid spraying, or a combined single-fluid / dual-fluid nozzle, it is always referred to as "the name of the processing fluid currently being sprayed or prepared to be sprayed" + "nozzle". That is, for example, a nozzle may sometimes be called a "DHF single-fluid nozzle" and sometimes a "DHF dual-fluid nozzle". "DHF single-fluid nozzle" may also omit "single-fluid" and simply be called "DHF nozzle".

[0037] [First embodiment of the etching method] The first embodiment of the etching method is illustrated with reference to Figure 3. All nozzles are marked with reference symbol 41, but this does not mean that all nozzles are the same.

[0038] <Pre-wetting steps> The substrate W is held horizontally by a rotating suction cup 30 and rotated about a vertical axis at a first rotational speed (e.g., a relatively high rotational speed of about 1000 rpm). In this state, DIW is supplied from the DIW nozzle to the center of the surface of the substrate W at a first flow rate (e.g., a relatively high flow rate of about 1.5 L / min). The DIW that reaches the center of the surface of the substrate W diffuses and flows to the periphery of the substrate W through centrifugal force, thereby covering the entire surface of the substrate W with a liquid film of DIW (Fig. 3(A)).

[0039] Furthermore, "the center of substrate W" refers to the position of the rotation center of substrate W or the position near the rotation center. Here, "the position near the rotation center of substrate" means the position close to the rotation center of substrate to the extent that "when the processing liquid (here, DIW) arrives at that position from the nozzle (here, DIW nozzle), the processing liquid spreads out immediately upon arrival and covers the surface of the rotation center of substrate by the force of arrival".

[0040] <Steps for forming a liquid pool> After the first time (e.g., about 10 seconds) following the start of the pre-wetting step, while continuously ejecting DIW from the DIW nozzle at the first flow rate, the rotation speed of the substrate W is significantly reduced to a second rotation speed (e.g., an extremely low rotation speed of about 10 rpm). This results in a state where a thicker DIW liquid film (DIW pool) covers the entire surface of the substrate W (Figure 3(B)).

[0041] <First Etching Step (Local Etching Step)> After a second time interval (e.g., approximately 5 seconds) following the start of the liquid pool formation step, DIW ejection from the DIW nozzle stops. Then, while the substrate W continues to rotate at the aforementioned second rotational speed, DHF is ejected from the DHF nozzle onto the substrate W. The DHF nozzle used here may be, for example, a two-fluid nozzle that ejects a mixture of water mist and nitrogen gas for DHF.

[0042] When the DHF nozzle used in the first etching step is a dual-fluid nozzle, DHF (etching solution) is supplied to the DHF dual-fluid nozzle at a flow rate of approximately 10 to 200 ml / min, and nitrogen (inactive gas) is supplied at a pressure of approximately 10 to 100 Pa.

[0043] At this time, the DHF nozzle is positioned at a predetermined radial position that allows the DHF to reach the substrate (this position can be represented by the distance R from the center of rotation of the substrate). The substrate W rotates at the second rotational speed, so the DHF ejected from the DHF nozzle sweeps across the substrate W (i.e., the DIW pool) along a circle of radius R and reaches the DIW pool (Figure 3(C)).

[0044] The DHF arriving at the DIW pool causes a depression in the DIW pool near the arrival point, and is diluted by the DIW constituting the pool and diffuses around the arrival point. Therefore, on the surface of the substrate W, the annular region (target region) surrounded by circles of radius R-ΔR1 and radius R+ΔR2 is locally and slightly etched. Regions outside the target region are completely or almost unetched. Furthermore, when the substrate W rotates at an extremely low speed, for example, about 10 rpm, ΔR1 and ΔR2 can be considered approximately equal.

[0045] As described above, when the substrate W rotates at a speed of 10 rpm, the DHF is ejected from the DHF nozzle and arrives at the entire aforementioned annular region exactly 6 seconds later. In other words, the arrival point surrounds the annular region. Thus, the annular region is etched by a very small amount (e.g., about a few Å) of etched material in a substantially uniform manner.

[0046] Furthermore, strictly speaking, the area near where the DHF initially arrives experiences the most etching, while the area near where the DHF subsequently arrives experiences relatively less etching. However, this degree of etching variation will not cause problems in practical applications (details will be discussed later).

[0047] Alternatively, the first nozzle arm 45 can hold the first DHF nozzle 41, and the second nozzle arm 45 can hold the second DHF nozzle 41, with the arrival points of DHF from the first DHF nozzle and the arrival points of DHF from the second DHF nozzle both located on the circumference of radius R and facing each other in the diametrical direction of the substrate W. This can reduce the deviation of the etching amount in the circumferential direction.

[0048] In this first embodiment, the first etching step etches the area where "the etching amount is inevitably smaller in the second etching step, which sets the processing conditions in a way that maximizes the in-plane uniformity of the etching amount," and the details will be described later.

[0049] <Second Etching Step (Overall Etching Step)> After the first etching step (partial etching step) is completed, while spraying DHF (single-fluid DHF) from the DHF nozzle towards the center of the substrate W, the rotation speed of the substrate W is increased to a third rotation speed (e.g., 1000 rpm). This replaces the DIW (which was mixed with a small amount of DHF in the first etching step) covering the surface of the substrate W with DHF. By maintaining this state for a third time (e.g., approximately 30 seconds), the surface of the substrate W is etched (Figure 3(D)).

[0050] For example, the transition from the first etching step to the second etching step can be achieved in the following manner. In the case where dual-fluid DHF is ejected from a dual-fluid nozzle that can be used as a single-fluid nozzle in the first etching step, after the first etching step is completed, the dual-fluid nozzle is moved above the center of the surface of the substrate W and the supply of nitrogen to the dual-fluid nozzle is stopped, while the ejection flow rate of DHF is increased.

[0051] The first etching step and the second etching step can utilize different DHF nozzles. That is, after the first etching step is completed, the DHF nozzle that has stopped spewing DHF is retracted from above the substrate, and DHF is supplied to the substrate from other DHF nozzles located above the center of the substrate to perform the second etching step.

[0052] <Cleaning Steps> After the predetermined time for the second etching step (overall etching step) is completed, the ejection of DHF from the DHF nozzle is stopped, and DIW is ejected from the DIW nozzle toward the center of the surface of the substrate W. Furthermore, it is preferable to increase the rotational speed of the substrate W to a fourth rotational speed (e.g., 1500 rpm). This removes DHF and etching byproducts from the surface of the substrate W through the DIW (Figure 3(E)).

[0053] <Drying Steps> Next, a drying step is performed to dry the substrate W. Various conventional drying methods can be used in this drying step. For example, as a first method, the substrate W can be continuously rotated and the ejection of DIW from the DIW nozzle can be stopped at the final stage of the cleaning step, thus performing spin drying. As a second method, the DIW on the surface of the substrate W can be replaced with IPA to form an IPA pool, and then supercritical drying is performed. As a third method, the drying step can be performed in two stages: an IPA replacement stage and a subsequent N2 gas drying stage. In the IPA replacement stage, the substrate W is continuously rotated and the ejection of DIW from the DIW nozzle is stopped after the cleaning step, and IPA is ejected from the IPA nozzle onto the surface of the substrate W to replace the DIW on the surface of the substrate W with IPA. In the N2 gas drying stage, N2 gas is blown onto the substrate W from the N2 nozzle, and the blowing position of the N2 gas is moved towards the periphery of the substrate W to diffuse the drying center, thereby drying the substrate W. During the N2 gas drying stage, IPA can be sprayed from the IPA nozzle while N2 gas is sprayed from the N2 nozzle simultaneously. In this case, the relationship is maintained such that "the radial position of the IPA's arrival point on the substrate W is always radially outside the radial position of the N2 gas's contact point on the substrate W," and both the IPA nozzle and the N2 nozzle are moved radially outward. In the various embodiments described later, the same drying method can also be appropriately selected.

[0054] Through the first embodiment of the above etching method, when sufficient in-plane uniformity of the etching amount cannot be obtained through the second etching step (overall etching step) alone, the in-plane uniformity of the etching amount can be improved by performing the first etching step (local etching step). Furthermore, in most cases, the etching amount at the same radial position in the second etching step (i.e., the etching amount within an annular region with a narrow radial width) is approximately the same throughout the circumference, and the deviation in etching amount occurs along the radial direction. Therefore, the in-plane uniformity of the etching amount can be improved by using both the first and second etching steps in combination.

[0055] In the second etching step, if there are two or more annular regions (regions with different radii) with relatively smaller etching amounts than other regions, the first etching step can be performed more than twice. In this case, after the first etching step, the DIW cleaning step, the liquid pool formation step, and the second first etching step can be performed sequentially. If there are multiple DHF nozzles (DHF dual-fluid nozzles) respectively mounted on different nozzle arms, the first etching step can also be performed on two or more annular regions simultaneously.

[0056] In the first embodiment described above, if the processing conditions in the previous step (e.g., the film formation step) cause the film thickness of the etched object to be locally thicker, this uneven film thickness can also be corrected and is beneficial.

[0057] The purpose of performing the first etching step is not limited to improving the in-plane uniformity of the etching amount, but also to create areas with larger (smaller) local etching amounts on a substrate.

[0058] [Second embodiment of the etching method] The second embodiment of the etching method is illustrated with reference to FIG4. The second embodiment differs from the first embodiment only in the first etching step (FIG. 4(B)). The other steps are the same: the pre-wetting step in FIG. 4(A), the second etching step in FIG. 4(C), the cleaning step in FIG. 4(D), and the drying step (not shown). In the first etching step of the second embodiment, the rotation of the substrate W is stopped, and DHF is ejected from the DHF nozzle in a manner that allows DHF to reach the desired position of the DIW pool on the surface of the substrate W. Thereby, the DHF diffuses around the point of arrival, etching a small, approximately circular area (target area).

[0059] This second embodiment can address situations where, during the second etching step (overall etching step), there are areas with less etching in a specific circumferential direction (rather than a ring). Furthermore, it can also correct uneven film thickness caused by processing conditions in previous steps (e.g., film formation steps) that result in locally thicker films.

[0060] In the second embodiment, the first etching step can also be performed more than twice.

[0061] The first etching step according to the first embodiment and the first etching step according to the second embodiment can also be combined. Specifically, for example, after the first etching step according to the first embodiment is completed, a cleaning step and a liquid pool formation step can be performed, and then the first etching step according to the second embodiment can be performed.

[0062] In the first and second embodiments described above, the first etching step is performed before the second etching step, but the order can also be reversed. The steps in this case are briefly explained below. First, a pre-wetting step for the DIW is performed, followed by the second etching step, then a cleaning step for the DIW, then a liquid pool formation step, then the first etching step, then a cleaning step for the DIW, and finally a drying step. The order in which the first and second etching steps are performed can be arbitrarily chosen, considering factors such as the processing volume. However, if the second etching step causes the substrate surface to change from hydrophilic to hydrophobic, it becomes more difficult to stably form the DIW liquid pool subsequently; therefore, it is preferable to perform the first etching step first.

[0063] [Etching Method, Third Embodiment] The third embodiment of the etching method is illustrated with reference to FIG5. Compared with the first embodiment, the third embodiment uses IPA instead of DIW in the pre-wetting step (FIG. 5(A)) and the liquid pool formation step (FIG. 5(B)), and differs in the point at which DHF is supplied to the IPA liquid pool in the first etching step (FIG. 5(C)) (partial etching step). The other steps (the cleaning step in FIG. 5(D) and the drying step not shown) are the same.

[0064] When the surface of substrate W is hydrophobic (with a large contact angle), it may be impossible to form a liquid pool covering the entire surface of substrate W using DIW with a high surface tension, or even if formed, it may be unstable. In this case, IPA with a low surface tension can be used to form a liquid pool covering the entire surface of substrate W.

[0065] A mixture of IPA and DIW can also be used to form a pool. The surface tension of the mixture increases with the DIW content, but sometimes the formation of a pool does not require the low surface tension of pure IPA. In such cases, IPA can be diluted with DIW to a degree that does not cause problems in forming the pool, thereby reducing the amount of expensive IPA used and thus reducing the operating costs of the equipment.

[0066] Alternatively, other suitable low surface tension liquids (liquids with surface tension lower than DIW) can be used instead of IPA. However, it is preferable that the low surface tension liquid is compatible with the etching solution and does not hinder the reaction between the etching solution and the surface of the substrate W.

[0067] In the third embodiment, a liquid pool can be stably formed even if the etched object surface is hydrophobic. Therefore, the choice between performing the first etching step and the second etching step can be arbitrarily made based on factors such as the amount of processing.

[0068] [Etching Method, Embodiment 4] The fourth embodiment of the etching method is illustrated with reference to FIG6. Compared with the first embodiment, the fourth embodiment differs in that the pool is formed with etchant (DHF) in the pool formation step (FIG. 6(B)) and the point at which DIW is sprayed from the nozzle into the pool of etchant in the first etching step (partial etching step) in FIG. 6(C). The other steps (the pre-wetting step of DIW in FIG. 6(A), the cleaning step in FIG. 6(D), and the drying step not shown) are the same.

[0069] In the first etching step of the previously described first embodiment, DHF was sprayed from a DHF nozzle into a DIW pool, thereby locally etching only a portion of the surface of the substrate W (the target area). In contrast, in the first etching step of this fourth embodiment, DIW is sprayed from a DIW nozzle into a DHF pool, thereby diluting the DHF in a portion of the surface of the substrate W (the target area) with DIW, thus locally suppressing the etching of that area.

[0070] Furthermore, similar to the second embodiment of the aforementioned etching method, the first etching step can also stop the rotation of the substrate W and eject the DIW from the DIW nozzle in a manner that allows the DIW to reach the desired position of the DHF liquid pool on the surface of the substrate W. This locally suppresses etching within a roughly circular area centered on the point of arrival.

[0071] Furthermore, depending on the concentration of DHF supplied from the DHF nozzle, there are cases where the DIW dilution increases the etching rate (caused by changes in the ionization state). Therefore, this fourth embodiment can also be used as a method to locally promote etching of the target area.

[0072] [Conditions for the first etching step (local etching step)] The following explains the conditions for determining the first etching step (partial etching step) of embodiments 1 to 4.

[0073] Taking the first embodiment as an example, the substrate is processed under the same conditions as the first embodiment, sequentially performing a pre-wetting step, a second etching step (overall etching step), a cleaning step, and a drying step (hereinafter referred to as "normal processing" for convenience). In the normal processing, the liquid pool formation step and the first etching step (partial etching step) are not performed. The conditions of this normal processing (especially the second etching step) are determined based on conventional methods (trial and error in preliminary experiments, etc.) to maximize the in-plane uniformity of the etching amount.

[0074] For substrates that have undergone the aforementioned conventional treatment, the distribution of etching amount is determined using a conventional non-destructive inspection method (e.g., elliptic polarization). Specifically, for example, measurement points are set at equal intervals (e.g., approximately 5 mm intervals) along the diameter of the substrate, and the etching amount at each measurement point is measured. Alternatively, the measurement points can be set along the radius (i.e., a line connecting the center to a point on the periphery), along two mutually perpendicular straight lines extending in the diameter direction, or along four straight lines that are rotated 45 degrees in sequence in the diameter direction.

[0075] Figure 7 shows a simplified representation of the etching amount distribution along the diameter of the substrate, indicated by a solid line. The vertical axis represents the etching amount (EA), and the horizontal axis represents the diameter position (POS) of each measurement point with the substrate center set at ±0 mm. In the example shown in Figure 7, the etching amount in the annular region approximately 50 mm from the center of the substrate is only a few Å, while other areas generally achieve the target etching amount, and the etching amount is also roughly uniform.

[0076] If the etching amount distribution of the second etching step is as shown by the solid line in the graph of Figure 7, and the first etching step is performed under the condition that the etching amount distribution shown by the chain line in the graph of Figure 7 can be obtained, then high in-plane uniformity etching can be achieved through the first and second etching steps.

[0077] The conditions for the first etching step can be determined through preliminary experiments. Parameters for determining the conditions for the first etching step include, for example, etching time, type of etchant used to form the pool, pool thickness, substrate rotation speed, flow rate of etchant from the nozzle (including gas flow rate if it is a two-fluid system), and etchant spray pattern from the nozzle.

[0078] The conditions for the first etching step are arbitrary as long as the desired etching amount distribution can be achieved, but it is preferable to determine them based on the following methods.

[0079] The substrate rotation speed is preferably low, specifically below 100 rpm, and more preferably below 30 rpm. Higher substrate rotation speeds result in greater flow of the liquid forming the pool (DIW), raising concerns that the etchant (DHF) arriving at the pool may not remain in the intended area and could etch into unintended regions. In a preferred embodiment, the substrate rotation speed is set to 10 rpm. At this low speed, the liquid forming the pool experiences only negligible flow; therefore, the etchant arriving at the pool diffuses substantially within the pool through the interdiffusion of the etchant (DHF) and the pool liquid (DIW) and the agitation effect upon arrival. If the etchant is sprayed in a two-fluid configuration, the agitation effect is improved (see experimental results described later).

[0080] The number of times the substrate is rotated (corresponding to the processing time when the rotation speed is fixed) is also preferably as few as possible. With more rotations, there is a concern that the etchant may spread to locations far from the arrival point, etching into unintended areas. In the above preferred example where the substrate rotation speed is set to 10 rpm, the substrate is rotated once (that is, the time for the first etching step is 6 seconds).

[0081] After determining the substrate's rotation speed and number of rotations (processing time) in the manner described above (but not limited to the above conditions), the ejection pattern of the etchant from the nozzle and the ejection flow rate of the etchant from the nozzle (if it is a two-fluid system, it also includes the gas ejection flow rate) can be determined.

[0082] As for the ejection form of etching solution, it can be classified into liquid column form or spray (droplet) form. Spray form is classified into single fluid (only spraying droplets of etching solution) or two fluid (spraying a mixture of droplets of etching solution and inactive gas). In the case of ejecting etching solution in droplet form, the spray angle is also considered.

[0083] A larger spray angle allows for localized etching over a wider radial area, while a smaller spray angle allows for localized etching over a narrower radial area. Spraying the etching solution in a thin liquid column (single-fluid) allows for localized etching over a narrower radial area.

[0084] As mentioned above, the etchant can be sprayed in either a two-fluid or single-fluid configuration. According to experimental results, spraying the etchant in a two-fluid configuration results in a wider radial width of localized etching compared to single-fluid spraying, and also exhibits higher in-plane and inter-plane uniformity of the etching amount (details will be discussed later). Therefore, except in cases where it is desirable to etch a particularly narrow radial region, spraying the etchant in a two-fluid configuration is preferable.

[0085] For example, when spraying etchant (e.g., DHF) through a two-fluid nozzle, experiments can be conducted using parameters such as the nozzle's spray angle, etchant flow rate, and gas flow rate to find etchant spraying conditions that consistently produce an appropriate width of etched area. Furthermore, generally speaking, the two-fluid sprayed from the nozzle should ideally contact the liquid pool with a force that slightly concaves the surface of the pool (but is not limited to this).

[0086] Those skilled in the art who refer to this specification should be able to easily obtain the processing conditions for the first etching step, which allows etching of the desired radial region with the desired etching amount, by taking into account the above circumstances and conducting experiments with varying parameter values.

[0087] [Experiment regarding the first etching step] We conducted an experiment to confirm the etching amount distribution when performing the first etching step alone. The substrate to be etched was a bare silicon wafer with an oxide film formed by thermal CVD. For this substrate, while rotating the substrate with the DIW pool at 10 rpm, DHF was supplied from a nozzle to a position 100 mm from the center of the substrate for 6 seconds. The DHF flow rate from the nozzle was 100 ml / min in both single-fluid and two-fluid scenarios; in the two-fluid scenario, a pressure of 10 kPa was applied to the nozzle and nitrogen was supplied. Four substrates were processed using both single-fluid and two-fluid methods. The film thickness was measured using ellipsometry after processing to determine the etching amount distribution.

[0088] The experimental results are shown in Figure 8. The upper section of the figure represents the results of two-fluid jetting, and the lower section represents the results of single-fluid jetting. The horizontal axis of the figure represents the distance (in mm) from each measurement point to the center of the substrate. Measurement points to the right of the substrate center are represented by positive values, and measurement points to the left of the substrate center are represented by negative values. The vertical axis of the figure represents the etching amount (in Å).

[0089] As shown in Figure 8, the etching radius is wider in the two-fluid process, and the etching amount between wafers is more stable.

[0090] Furthermore, based on the obtained data, the deviation in etching amount was confirmed. The results are shown in Tables 1 and 2 below. In the tables below, for example, the area "-100±10" represents the data obtained in the area between -90mm and -110mm when processing two-fluid (or single-fluid) spraying at a position aligned to -100mm. Regardless of the area width, the spraying conditions for both two-fluid and single-fluid are the same. σ is the standard deviation, which represents the standard deviation of the total etching amount obtained in the corresponding areas of the four substrates.

[0091] [Table 1] Area (mm) σ (Two-fluid) σ (Single fluid) -100±10 0.085 0.377 -100±20 0.189 0.230 -100±30 0.147 0.172

[0092] [Table 2] Area (mm) σ (Two-fluid) σ (Single fluid) +100±10 0.250 0.598 +100±20 0.188 0.355 +100±30 0.145 0.265

[0093] As can be seen from the data in Tables 1 and 2, the etched area in the two-fluid process is wider in the radial direction, and the etching amount between substrates is more stable. That is, if the stability of the process is important, the two-fluid process is better. However, this does not negate the use of the single-fluid process. If a narrower local etching range is desired, the single-fluid process can be used.

[0094] Furthermore, the radial width of the etched area at the -100mm position tends to be wider than that at the +100mm position, and the deviation in etching amount tends to be smaller. This is because the -100mm position is closer to the initial arrival point of the etchant, allowing for more efficient diffusion of the etchant. Such deviations in etching results cannot be avoided if the substrate is rotated once while the nozzle is fixed to perform the first etching step. However, the inventors believe that this degree of deviation will not cause problems in practical applications. Moreover, the aforementioned deviations can be mitigated by positioning two nozzles equidistant from the center of the substrate and facing each other in the diametrical direction, and simultaneously starting to spray etchant from both nozzles while rotating the substrate once.

[0095] [Fifth embodiment of the etching method] In the above embodiments 1 to 4, the first etching step (partial etching step) and the second etching step (overall etching step) are performed as a series of processes, but are not limited thereto. A correction etching process including a pre-wetting step, a liquid pool formation step, a first etching step, a cleaning step, and a drying step can also be performed on a substrate (e.g., a dried substrate) that has undergone a conventional etching process (a process that includes the second etching step but not the first etching step).

[0096] Specifically, for example, a substrate that has undergone conventional etching is moved into an inspection unit, and then the in-plane distribution of the etching amount is investigated using conventional non-destructive inspection methods such as elliptic polarization. If the in-plane distribution of the etching amount does not meet the reference, a corrective etching process is performed on the substrate.

[0097] Alternatively, a database can be created to store the relationship between the inspection results of a substrate that has undergone conventional etching (e.g., the in-plane distribution of the etching amount) and the conditions for correcting the etching process required to correct the distribution (non-uniform distribution), and stored in the storage unit. In this case, the control device 4, which receives the inspection results, can automatically determine the conditions for correcting the etching process by referring to the database.

[0098] Alternatively, for all substrates that have undergone conventional etching in the first substrate processing apparatus, corrective etching can be performed in the second substrate processing apparatus under predetermined etching conditions. Furthermore, if it is known that the etching amount distribution obtained by the conventional etching process in the first substrate processing apparatus can stably fall within a predetermined range, the etching amount distribution of the substrate may not need to be checked before performing corrective etching in the second substrate processing apparatus.

[0099] [Deformation of the second etching step] Next, a modified embodiment of the second etching step will be described with reference to FIG8. The modified embodiment of the second etching step described below can be used to adjust the etching amount distribution in the substrate surface in the second etching step of the first to fifth embodiments of the etching method.

[0100] <First Modification Implementation Pattern> In the first modified embodiment, during the second etching step, as shown in Figure 8, the DHF nozzle 41, which sprays DHF, moves back and forth between the center and the periphery of the substrate W (also known as "scanning"). Furthermore, a low-humidity gas is sprayed from the central spray section 21c of the FFU 21, selectively blowing the low-humidity gas onto the center of the substrate W. The low-humidity gas system should be a gas with a humidity sufficiently lower than that of the air in the cleanroom, preferably dry air or nitrogen with a humidity of less than 1%. The peripheral spray section 21p of the FFU 21 sprays clean air (air with the same humidity as the air in the cleanroom).

[0101] FFUs that supply different gases (e.g., clean air, dry gas) to the central and peripheral parts are common knowledge in this technical field, so detailed descriptions of their construction are omitted.

[0102] By positioning a movable gas nozzle above the center of the substrate W, and spraying low-humidity gas towards the center of the substrate W, low-humidity gas can be selectively blown onto the center of the substrate W.

[0103] In this modified embodiment, a low-humidity gas is selectively blown onto the center of the substrate W, thereby promoting the evaporation of moisture in the DHF liquid film at the center of the substrate W and increasing the DHF concentration. Furthermore, by moving the DHF from the DHF nozzle back and forth between the center and periphery of the substrate W, the DHF liquid film present at the center of the substrate W becomes thinner when the DHF arrival point leaves the center (compared to when the DHF arrival point is fixed at the center). Therefore, the increase in DHF concentration is greater when the same amount of moisture evaporates. Consequently, the etching rate at the center of the substrate W is greater than that at the periphery. This phenomenon can be used to adjust the in-plane etching distribution of the substrate.

[0104] <Second Modification Implementation> In the second modified embodiment, during the second etching step, as shown in FIG9, the DHF nozzle 41 is fixed above the center of the substrate W. Furthermore, low-humidity gas is sprayed from the peripheral nozzle 21p of the FFU 21 towards the periphery of the substrate W, selectively blowing low-humidity gas onto the periphery of the substrate W. Clean air (air with the same humidity as the air in the cleanroom) is sprayed from the central nozzle 21c of the FFU 21.

[0105] In this case, the evaporation of water in the DHF liquid film is promoted at the periphery of the substrate W, thereby increasing the DHF concentration. Therefore, the etching rate at the periphery of the substrate W is greater than that at the center. This phenomenon can be used to adjust the etching amount distribution within the substrate surface.

[0106] By positioning a movable gas nozzle above the periphery of the substrate W, and spraying low-humidity gas onto the periphery of the substrate W, low-humidity gas can be selectively blown onto the periphery of the substrate W.

[0107] Furthermore, in either the first or second modified embodiment, depending on the type and original concentration of the etching solution, the etching rate may decrease due to the evaporation of water from the solution. In this case, the etching rate of the center (or periphery) of the substrate W may be lower than that of the periphery (or center).

[0108] It should be understood that all embodiments of the present invention are illustrative and not intended to be limiting. The above embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended patent applications.

[0109] The substrate being processed is not limited to semiconductor wafers, but may also be other types of substrates used in the manufacture of semiconductor devices, such as glass substrates and ceramic substrates.

[0110] 1: Substrate processing system 2: Moving in and out of the station 3: Processing Station 4: Control device 11: Vehicle loading section 12: Transport Department 13: Substrate handling device 14: Transmission Department 15: Transport Department 16: Processing Unit 17: Substrate handling device 18: Control Department 19: Storage Department 20: Chamber 21: Fan Filter Unit (FFU) 21c: Central jet section 21p: Peripheral Spray Section 30: Rotary chuck (substrate holding and rotating mechanism) 31: Substrate holding part (suction cup part) 32: Rotary drive unit 41: Nozzle 42: Processing fluid supply source 43: Supply pipeline 44: Supply Control Department 45: Nozzle Arm 50: Liquid container body 51: Drainage port 52: Exhaust port W: substrate C: Vehicle

Claims

1. A substrate processing method comprising the following steps: a first etching step, wherein, with a pool of a first processing liquid formed on the entire surface of the substrate, a second processing liquid is locally sprayed from a nozzle onto a target area partially defined on the surface of the substrate, thereby etching in such a way that the etching rate of the target area is different from the etching rate of other areas; and a second etching step, wherein the etching liquid is supplied while the substrate is rotated, such that a liquid film of the etching liquid covers the entire surface of the substrate, thereby simultaneously etching the entire surface of the substrate; wherein, in the first etching step, one of the first processing liquid and the second processing liquid is the etching liquid, and the other is an etching inhibitor liquid that reduces the etching rate of the etching liquid on the surface of the substrate by mixing with the etching liquid.

2. The substrate processing method as described in claim 1, wherein, The first etching step is performed while the substrate is stopped from rotating.

3. The substrate processing method as described in claim 1, wherein, The target area is a ring-shaped area concentric with the periphery of the substrate; the first etching step includes the step of spraying the second processing liquid from the nozzle while fixing the position of the nozzle, and rotating the substrate at least once.

4. The substrate processing method as described in claim 3, wherein, When the substrate is rotated in the first etching step, it is rotated at a low speed so as not to damage the pool of the first processing liquid.

5. The substrate processing method as described in claim 3, wherein, In the first etching step, the substrate is rotated at a speed of 100 rpm or less.

6. The substrate processing method as described in any one of claims 2 to 5, wherein, During the execution of the first etching step, the following actions are not performed: supplying the first processing liquid to the substrate to maintain the pool of the first processing liquid.

7. The substrate processing method as described in any one of claims 1 to 5, wherein, In the first etching step, the second processing liquid is in the form of a water mist and is sprayed from the nozzle toward the target area in the form of a two-fluid mixture with gas.

8. The substrate processing method according to any one of claims 1 to 5 further comprises the following steps: obtaining an etching amount distribution within the surface of the substrate when the second etching step has been performed without performing the first etching step; and determining the processing conditions of the first etching step based on the etching amount distribution.

9. The substrate processing method as described in claim 8, wherein, The processing conditions for the first etching step are determined in a way that makes the etching amount distribution more uniform when both the first and second etching steps are performed compared to when only the second etching step is performed.

10. The substrate processing method as described in any one of claims 1 to 5, wherein, The first processing solution is the etching inhibitor, and the second processing solution is the etching solution.

11. The substrate processing method as described in any one of claims 1 to 5, wherein, The first processing solution is the etching solution, and the second processing solution is the etching inhibitor.

12. The substrate processing method as described in any one of claims 1 to 5, wherein, The etching inhibitor is DIW (pure water), functional water, or IPA (isopropyl alcohol), or a mixture thereof.

13. The substrate processing method as described in any one of claims 1 to 5, wherein, The first etching step is performed before the second etching step.

14. The substrate processing method as described in any one of claims 1 to 5, wherein, The second etching step is performed before the first etching step.

15. The substrate processing method as described in any one of claims 1 to 5, wherein, The second etching step is performed by blowing low-humidity gas onto either the periphery or the center of the substrate.

16. The substrate processing method as described in claim 15, wherein, The second etching step is performed while moving the point of arrival of the etching solution on the substrate between the center and the periphery of the substrate, and blowing low-humidity gas only onto the center of the substrate.

17. The substrate processing method as described in claim 15, wherein, The second etching step is performed while maintaining the point of arrival of the etching solution on the substrate at the center of the substrate, and blowing dry gas only onto the periphery of the substrate.

18. A substrate processing method, comprising a local etching step, wherein, with a pool of a first processing liquid formed on the entire surface of the substrate, a second processing liquid is locally sprayed from a nozzle onto a target area locally defined on the surface of the substrate, thereby etching in such a way that the etching rate of the target area is different from the etching rate of other areas; one of the first processing liquid and the second processing liquid is an etching liquid, and the other is an etching inhibitor liquid that reduces the etching rate of the etching liquid on the surface of the substrate by mixing with the etching liquid.

19. A substrate processing apparatus comprising: a substrate holding portion for horizontally holding a substrate; a rotation drive portion for rotating the substrate holding portion about a vertical axis; a processing fluid supply portion for supplying processing fluid to the surface of the substrate held by the substrate holding portion; and a control portion for controlling the substrate holding portion, the rotation drive portion, and the processing fluid supply portion to perform a substrate processing method as described in any one of claims 1 to 5 and claim 18.

20. A substrate processing apparatus comprising: a substrate holding portion for horizontally holding a substrate; a rotation drive portion for rotating the substrate holding portion about a vertical axis; a processing fluid supply portion for supplying processing fluid to the surface of the substrate held by the substrate holding portion; a gas supply portion for selectively blowing dry gas onto either the center or the periphery of the surface of the substrate; and a control portion for controlling the substrate holding portion, the rotation drive portion, the processing fluid supply portion, and the gas supply portion to perform the substrate processing method as described in claim 15.

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