Substrate processing method and substrate processing apparatus

Abstract

This substrate treatment method comprises: a first etching step for, in a state where a puddle of a first treatment liquid is formed on the entirety of the surface of a substrate, performing etching so as to make a difference between the etching rate of a target region locally set to the surface of the substrate and the etching rate of other regions, by locally discharging a second treatment liquid from a nozzle toward the target region; and a second etching step for simultaneously etching the entirety of the surface of the substrate by supplying an etching liquid to the entirety of the surface of the substrate so as to cover the entire surface with a liquid film of the etching liquid while rotating the substrate. One of the first treatment liquid and the second treatment liquid for use in the first etching step is the etching liquid, and the other is an etching suppressing liquid to be mixed with the etching liquid to reduce the rate of etching of the surface of the substrate by the etching liquid.

Description

Technical Field

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus.

Background Art

[0002] In the manufacture of semiconductor devices, wet etching processing is performed to remove a film formed on the surface of a substrate such as a semiconductor wafer with a chemical solution. In recent years, it has been required 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, and by performing the processing while blowing a temperature control gas to the peripheral portion of the substrate that is likely to cool, a technique for improving the in-plane uniformity of the etching amount is described.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique for locally controlling the etching amount when etching the surface of a substrate.

Means for Solving the Problems

[0005] A substrate processing method according to an embodiment of the present disclosure includes a first etching step of performing etching such that an etching rate of a target region is different from that of other regions by locally discharging a second processing liquid from a nozzle toward the target region locally set on the surface of the substrate in a state where a paddle of the first processing liquid is formed on the entire surface of the substrate, and a second etching step of simultaneously etching the entire surface of the substrate by supplying the etching liquid such that the entire surface of the substrate is covered with a liquid film of the etching liquid while rotating the substrate. One of the first processing liquid and the second processing liquid used in the first etching step is the etching liquid, and the other is an etching suppression liquid that is mixed with the etching liquid to reduce the etching rate of the surface of the substrate by the etching liquid.

Effects of the Invention

[0006] According to the above embodiment of the present disclosure, the etching amount can be locally controlled when etching the surface of the substrate.

Brief Description of the Drawings

[0007]

Figure 1

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Figure 10

Embodiments for Carrying Out the Invention

[0008] An embodiment of a substrate processing apparatus will be described with reference to the accompanying drawings.

[0009] FIG. 1 is a diagram showing the schematic configuration of a substrate processing system according to this embodiment. Hereinafter, in order to clarify the positional relationship, X-axis, Y-axis, and Z-axis orthogonal to each other are defined, and the positive direction of the Z-axis is the vertically upward direction.

[0010] As shown in FIG. 1, the substrate processing system 1 includes a loading / unloading station 2 and a processing station 3. The loading / unloading station 2 and the processing station 3 are provided adjacent to each other.

[0011] The loading / unloading station 2 includes a carrier placement unit 11 and a transfer unit 12. On the carrier placement unit 11, a plurality of carriers C for horizontally accommodating a plurality of substrates, in this embodiment, substrates W such as semiconductor wafers, are placed.

[0012] The transfer unit 12 is provided adjacent to the carrier placement unit 11 and includes a substrate transfer device 13 and a delivery unit 14 inside. The substrate transfer device 13 includes a substrate holding mechanism for holding the substrate W. Further, the substrate transfer device 13 can move in the horizontal direction and the vertical direction and turn around the vertical axis, and transfers the substrate W between the carrier C and the delivery unit 14 using the substrate holding mechanism.

[0013] The processing station 3 is provided adjacent to the transfer unit 12. The processing station 3 includes a transfer unit 15 and a plurality of processing units 16. The plurality of processing units 16 are arranged side by side on both sides of the transfer unit 15.

[0014] The transfer unit 15 includes a substrate transfer device 17 inside. The substrate transfer device 17 includes a substrate holding mechanism for holding the substrate W. Further, the substrate transfer device 17 can move in the horizontal and vertical directions and can turn around a vertical axis, and transfers the substrate W between the delivery unit 14 and the processing unit 16 using the substrate holding mechanism.

[0015] The processing unit 16 performs a predetermined substrate process on the substrate W transferred by the substrate transfer device 17.

[0016] In addition, 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. A program for controlling various processes executed in the substrate processing system 1 is stored in the storage unit 19. The control unit 18 controls the operation of the substrate processing system 1 by reading and executing the program stored in the storage unit 19.

[0017] Note that such a program may be recorded on a computer-readable storage medium and installed from the storage medium into the storage unit 19 of the control device 4. Examples of the computer-readable storage medium include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magneto-optical disk (MO), a memory card, and the like.

[0018] In the substrate processing system 1 configured as described above, first, the substrate transfer device 13 of the loading / unloading station 2 takes out the substrate W from the carrier C placed on the carrier placement unit 11 and places the taken-out substrate W on the delivery unit 14. The substrate W placed on the delivery unit 14 is taken out from the delivery unit 14 by the substrate transfer device 17 of the processing station 3 and carried into the processing unit 16.

[0019] The substrate W carried into the processing unit 16 is processed by the processing unit 16, then carried out from the processing unit 16 by the substrate transfer device 17, and placed on the delivery unit 14. Then, the processed substrate W placed on the delivery unit 14 is returned to the carrier C of the carrier placement unit 11 by the substrate transfer device 13.

[0020] Next, the configuration of the processing unit 16 will be described with reference to FIG. 2.

[0021] The processing unit 16 has a chamber 20 that defines a processing space. A fan filter unit (FFU) 21 is provided on the ceiling of the chamber 20. The FFU 21 blows clean gas downward into the chamber 20.

[0022] The processing unit 16 is provided with a spin chuck (substrate holding and rotating mechanism) 30. The spin chuck 30 has a substrate holding portion (chuck portion) 31 that holds the substrate W in a horizontal posture, and a rotation driving portion 32 that rotates the substrate holding portion 31 and the substrate W held thereon around a vertical axis.

[0023] The substrate holding portion 31 may be of a type called a mechanical chuck that mechanically holds the peripheral portion of the substrate W by a holding member such as a gripping claw, or may be of a type called a vacuum chuck that vacuum-sucks the central portion of the back surface of the substrate W. The rotation driving portion 32 can be constituted by, for example, an electric motor.

[0024] The processing unit 16 is provided with a processing fluid supply unit 40 for supplying various processing fluids necessary for processing the substrate W to the substrate W.

[0025] The processing fluid supply unit 40 has a plurality of nozzles 41 (only two are shown in FIG. 2) that discharge the processing fluid toward 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 the processing liquid include DHF (dilute hydrofluoric acid), DIW (deionized water), and IPA (isopropyl alcohol). An example of the processing gas is N2 gas (nitrogen gas). The processing fluid is not limited to the above, and any one can be selectively used as needed from various known processing fluids used in a single-wafer substrate processing unit for wet etching in the technical field of semiconductor manufacturing.

[0026] In one embodiment, different processing fluids are discharged from different nozzles 41. In this case, each nozzle 41 is supplied with the required processing fluid from the processing fluid supply source 42 via a supply line 43 provided with a supply control unit 44 schematically shown by a white box in FIG. 2. The processing fluid supply source 42 consists of, for example, a tank for storing the processing fluid or a factory power source, etc. The supply control unit 44 is composed of an on-off valve, a flow meter, a flow control valve, etc. In other embodiments, multiple types of processing fluids (for example, DHF and DIW) may be selectively discharged from one nozzle.

[0027] One of the plurality of nozzles 41 may be a two-fluid nozzle (two-fluid spray nozzle). As is well known in the art, a two-fluid nozzle is configured to generate and discharge a mixed fluid of a mist-like processing liquid and a processing gas by merging the processing liquid (for example, DHF or DIW) supplied from the processing liquid supply source into the flow of the processing gas (for example, nitrogen gas) supplied from the processing gas supply source inside the nozzle.

[0028] One of the plurality of nozzles 41 may be a single-fluid spray nozzle. The single-fluid spray nozzle discharges only the liquid in a mist form.

[0029] The plurality of nozzles 41 are carried by one or a plurality of nozzle arms 45 (only one is shown in FIG. 2). The nozzle arm 45 is configured to position each nozzle 41 at an arbitrary position (radial position) between a position above the center of the substrate W held by the substrate holding unit 31 and a position above the peripheral edge of the substrate W. The nozzle arm may be of a type that can rotate around a vertical axis, or may be of a type that can translate along a guide rail.

[0030] Around the substrate holding unit, a liquid receiving cup 50 for collecting the processing liquid scattered from the rotating substrate W is provided. The processing liquid collected by the liquid receiving cup 50 is discharged to the outside of the processing unit 16 from a liquid discharge port 51 provided at the bottom of the liquid receiving cup 50. An exhaust port 52 is also provided at the bottom of the liquid receiving cup 50, and the inside of the liquid receiving cup 50 is sucked through the exhaust port 52.

[0031] Some embodiments of the etching method will be described below. In the following embodiments, as the processing liquid, DIW (deionized water), DHF (dilute hydrofluoric acid), IPA (isopropyl alcohol), etc. are discharged from the nozzles. DIW is used as a pre-wet liquid, a paddle forming liquid, a rinse liquid, etc. DHF is used as an etching liquid. IPA is used as a drying liquid and / or a paddle forming liquid.

[0032] As the etching liquid, for example, SC1, SPM (sulfuric acid peroxide) can be used instead of DHF (however, it is not limited to these). Instead of DIW as the pre-wet liquid, the paddle forming liquid, and the rinse liquid, functional water can be used. Functional water means DIW in which a trace amount of solutes (such as ammonia and carbon dioxide) are dissolved to give a special function (such as conductivity) that DIW does not have.

[0033] In the following description, each nozzle 41 will also be referred to as the "name of the processing liquid that the nozzle is discharging or attempting to discharge" + "nozzle". That is, for example, a nozzle that discharges DIW is also called a DIW nozzle.

[0034] In the operation of a specific apparatus, it often happens that two or more types of processing liquids (for example, DIW and DHF) are selectively discharged from a common single nozzle 41. Such a nozzle will be referred to as the "name of the processing liquid that is being discharged or attempting to be discharged at that time" + "nozzle". That is, for example, a certain single nozzle 41 may be called a "DIW nozzle" at one time and a "DHF nozzle" at another time.

[0035] There are also two-fluid nozzles that function as either single-fluid nozzles or two-fluid nozzles. That is, for example, when only a processing liquid (for example, DHF) is supplied to the two-fluid nozzle without supplying gas (for example, N2 gas), the two-fluid nozzle acts as a single-fluid nozzle, and when both gas and the processing liquid are supplied to the two-fluid nozzle, the two-fluid nozzle acts to discharge a mixed fluid (two-fluid) of the mist of the processing liquid and the gas. Regardless of whether it is a nozzle dedicated to single-fluid discharge, a nozzle dedicated to two-fluid discharge, or a nozzle shared for single-fluid discharge / two-fluid discharge, the nozzle will be referred to as the "name of the processing liquid that is being discharged or attempting to be discharged at that time" + "nozzle". That is, for example, a certain single nozzle may be called a "DHF single-fluid nozzle" at one time and a "DHF two-fluid nozzle" at another time. The "DHF single-fluid nozzle" may also be simply called a "DHF nozzle" by omitting "single-fluid".

[0036] [First Embodiment of the Etching Method] The first embodiment of the etching method will be described with reference to FIG. 3. Although all nozzles are labeled with the reference numeral 41, this does not mean that they are all the same nozzle.

[0037] [Pre-wet Process] The substrate W is held in a horizontal posture by the spin chuck 30 and rotated at a first rotation speed (for example, a relatively high rotation speed of about 1000 rpm) around the vertical axis. In this state, DIW is supplied from the DIW nozzle to the central portion of the surface of the substrate W at a first flow rate (for example, a relatively large flow rate of about 1.5 L / min). The DIW that has landed on the central portion of the surface of the substrate W flows while spreading toward the periphery of the substrate W by centrifugal force, whereby the entire surface of the substrate W is covered with a liquid film of DIW (Fig. 3(A)).

[0038] Note that the "central portion of the substrate W" means the position of the rotation center of the substrate W or a position near the rotation center. Here, the "position near the rotation center of the substrate" means a position close to the rotation center of the substrate to such an extent that when the processing liquid (here, DIW) lands at this position from a nozzle (here, the DIW nozzle), the surface of the rotation center of the substrate is covered by the processing liquid that spreads with the momentum of the landing immediately after the landing.

[0039] <Paddle formation step> When the first hour (for example, about 10 seconds) has elapsed since the start of the pre-wet step, while continuously discharging 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 (for example, an extremely low rotation speed of about 10 rpm). As a result, the entire surface of the substrate W is covered with a relatively thick liquid film of DIW (DIW paddle) (Fig. 3(B)).

[0040] <First etching step (local etching step)> When the second hour (for example, about 5 seconds) has elapsed since the start of the paddle formation step, the discharge of DIW from the DIW nozzle is stopped, and while continuously rotating the substrate W at the above second rotation speed, DHF is discharged from the DHF nozzle onto the substrate W. The DHF nozzle used here may be, for example, a two-fluid nozzle that discharges a mixed fluid of DHF mist and nitrogen gas.

[0041] When the DHF nozzle used in the first etching process is a two-fluid nozzle, the DHF (etching solution) is supplied to the DHF two-fluid nozzle at a flow rate of about 10 to 200 ml / min, and nitrogen gas (inert gas) is supplied at a pressure of about 10 to 100 Pa.

[0042] At this time, the DHF nozzle is positioned such that DHF lands at a predetermined radial position of the substrate (this position can be represented by the distance R from the rotation center of the substrate). Since the substrate W is rotating at the second rotation speed, the DHF discharged from the DHF nozzle lands on the DIW paddle so as to scan the substrate W (i.e., the DIW paddle) along a circle of radius R (Fig. 3(C)).

[0043] The DHF that has landed on the DIW paddle diffuses around the landing point while denting the DIW paddle near the landing point and being diluted by the DIW that constitutes the paddle. For this reason, a ring-shaped region (target region) surrounded by a circle of radius R - ΔR1 and a circle of radius R + ΔR2 on the surface of the substrate W is locally etched in a small amount. The regions other than the target region are not etched at all or are hardly etched. When the rotation speed of the substrate W is an extremely low speed of about 10 rpm, for example, it is acceptable to consider that ΔR1 and ΔR2 are substantially equal.

[0044] Assuming that the substrate W is rotating at a rotation speed of 10 rpm as described above, by discharging DHF from the DHF nozzle for exactly 6 seconds, the DHF lands on the entire ring-shaped region described above. In other words, the landing point goes around the ring-shaped region. As a result, the ring-shaped region is etched in a substantially uniform and very small amount (for example, about several Å).

[0045] Strictly speaking, the vicinity of the position where the DHF first lands is etched the most, and the etching amount in the vicinity of the position where the DHF lands later is relatively small. However, this degree of variation in the etching amount does not pose a practical problem (details will be described later).

[0046] Mount the first DHF nozzle 41 on the first nozzle arm 45, mount the second DHF nozzle 41 on the second nozzle arm 45, and arrange the landing point of DHF from the first DHF nozzle and the landing point of DHF from the second DHF nozzle such that both are located on the circumference of a circle with a radius R and are opposed to each other in the diameter direction of the substrate W. By doing so, variations in the etching amount in the circumferential direction can be reduced.

[0047] As will be described in detail later, in this first embodiment, in the first etching step, the regions where the etching amount inevitably becomes small in the second etching step in which the processing conditions are set to enhance the in-plane uniformity of the etching amount as much as possible are etched.

[0048] <Second Etching Step (Overall Etching Step)> After the completion of the first etching step (local etching step), DHF (single-fluid DHF) is discharged from the DHF nozzle to the central portion of the substrate W, and the rotational speed of the substrate W is increased to a third rotational speed (for example, 1000 rpm). As a result, the DIW covering the surface of the substrate W (which is slightly mixed with DHF in the first etching step) is replaced with DHF. By continuing this state for a third time (for example, about 30 seconds), the surface of the substrate W is etched (Fig. 3(D)).

[0049] The transition from the first etching step to the second etching step can be achieved, for example, as follows. When discharging two-fluid DHF from a two-fluid nozzle that can be used as a single-fluid nozzle in the first etching step, after the completion of the first etching step, move the two-fluid nozzle above the central portion of the surface of the substrate W, stop the supply of nitrogen gas to the two-fluid nozzle, and increase the discharge flow rate of DHF.

[0050] In the first etching process and the second etching process, different DHF nozzles may be used. That is, after the first etching process is completed, the DHF nozzle that has stopped discharging DHF is retracted from above the substrate, and DHF may be supplied to the substrate from another DHF nozzle positioned above the central portion of the substrate to perform the second etching process.

[0051] <Rinse process> When the second etching process (overall etching process) is executed for a predetermined time, the discharge of DHF from the DHF nozzle is stopped, and DIW is discharged from the DIW nozzle to the central portion of the surface of the substrate W. Further, preferably, the rotation speed of the substrate W is further increased to a fourth rotation speed (for example, 1500 rpm). Thereby, DHF on the surface of the substrate W, by-products due to etching, etc. are washed away by DIW (FIG. 3(E)).

[0052] <Drying process> Next, a drying process for drying the substrate W is performed. In this drying process, various known drying methods can be used. For example, as a first method, while continuously rotating the substrate W from the end stage of the rinsing process, the discharge of DIW from the DIW nozzle is stopped, and spin drying may be performed. As a second method, the DIW on the surface of the substrate W may be replaced with IPA to form an IPA paddle, and then supercritical drying treatment may be performed. As a third method, the drying process may be carried out in two stages, an IPA replacement stage and a subsequent N2 gas drying stage. In the IPA replacement stage, while continuously rotating the substrate W from the end stage of the rinsing process, the discharge of DIW from the DIW nozzle is stopped, and IPA is discharged 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, while blowing N2 gas from the N2 nozzle onto the substrate W, the blowing position of the N2 gas is moved toward the periphery of the substrate W to expand the drying core and dry the substrate W. In the N2 gas drying stage, IPA may be discharged from the IPA nozzle while N2 gas is discharged from the N2 nozzle. In this case, while maintaining the relationship that the radial position of the liquid landing point of IPA on the substrate W is always radially outside the radial position of the collision point of N2 gas on the substrate W, the IPA nozzle and the N2 nozzle are moved radially outward. In each of the embodiments described below, the same drying method can be appropriately selected and used.

[0053] According to the first embodiment of the etching method described above, even when the in-plane uniformity of the etching amount cannot be sufficiently obtained only in the second etching step (overall etching step), the in-plane uniformity of the etching amount can be improved by performing the first etching step (local etching step). In many cases, the etching amount at the same radial position in the second etching step (that is, the etching amount within a ring-shaped region having a narrow radial width) is generally the same over the entire circumferential direction, and the variation in the etching amount appears along the radial direction. Therefore, by using the first etching step described above in combination with the second etching step, it becomes possible to improve the in-plane uniformity of the etching amount.

[0054] In the second etching process, if there are two or more ring-shaped regions (regions with different radii) where the etching amount is relatively small compared to other regions, the first etching process may be performed two or more times. In this case, after the completion of the first first etching process, a DIW rinse process, a paddle formation process, and a second first etching process can be sequentially executed. If there are a plurality of DHF nozzles (DHF two-fluid nozzles) carried by separate nozzle arms, it is also possible to perform the first etching process simultaneously on two or more ring-shaped regions.

[0055] The first embodiment is also beneficial for correcting the film thickness non-uniformity when the film thickness of the film to be etched is locally thick due to the processing conditions of the previous process (for example, the film formation process).

[0056] The purpose of performing the first etching process is not limited to enhancing the in-plane uniformity of the etching amount, and it may be to form a region with a large (small) etching amount locally on a single substrate.

[0057] [Second Embodiment of the Etching Method] The second embodiment of the etching method will be described with reference to FIG. 4. The second embodiment is different only in the first etching process (FIG. 4(B)) from the first embodiment, and the other processes, that is, the pre-wet process in FIG. 4(A), the second etching process in FIG. 4(C), the rinse process in FIG. 4(D), and the drying process (not shown) are all the same. In the first etching process in the second embodiment, the rotation of the substrate W is stopped, and DHF is discharged from the DHF nozzle so that the DHF lands on a desired position of the DIW paddle on the surface of the substrate W. As a result, a generally circular region (target region) where the DHF diffuses around the landing point of the DHF is slightly etched.

[0058] This second embodiment can cope with a case where in the second etching step (overall etching step), a region with a small etching amount occurs not in a ring shape but at a specific circumferential position. Also, when the film thickness of the film to be etched is locally thick due to processing conditions of the previous step (for example, a film forming step), it is also useful for correcting this film thickness non-uniformity.

[0059] In the second embodiment as well, the first etching step may be performed two or more times.

[0060] The first etching step according to the first embodiment and the first etching step according to the second embodiment may be combined. Specifically, for example, after the completion of the first etching step according to the first embodiment, a rinse step and a paddle formation step may be performed, and then the first etching step according to the second embodiment may be performed.

[0061] In the above first and second embodiments, the first etching step was performed first and the second etching step was performed later, but the order can also be reversed. The procedure in this case will be briefly described. First, a pre-wet step with DIW is performed, then the second etching step is performed, then a rinse step with DIW is performed, then a paddle formation step is performed, then the first etching step is performed, then a rinse step with DIW is performed, and finally a drying step is performed. Regarding which of the first etching step and the second etching step is performed first, it can be arbitrarily selected in consideration of the throughput of the process and the like. However, when the surface of the substrate changes from hydrophilic to hydrophobic by the second etching step, it becomes difficult to stably form a DIW paddle thereafter, so it is preferable to perform the first etching step first.

[0062] [Third Embodiment of the Etching Method] Referring to FIG. 5, a third embodiment of the etching method will be described. In the third embodiment, compared with the first embodiment, IPA is used instead of DIW in the pre-wetting step (FIG. 5(A)) and the paddle formation step (FIG. 5(B)), and DHF is supplied to the IPA paddle in the first etching step (FIG. 5(C)) (local etching step). The other steps (the rinse step in FIG. 5(D) and the drying step not shown) are all the same.

[0063] When the surface of the substrate W is hydrophobic (has a large contact angle), with DIW having a high surface tension, it may not be possible to form a paddle that covers the entire surface of the substrate W, or even if it is formed, it may not be stable. In this case, by using IPA with a low surface tension, it is possible to form a paddle that covers the entire surface of the substrate W.

[0064] The paddle may be formed with a mixed solution of IPA and DIW. The surface tension of the mixed solution increases as the content of DIW increases, but in some cases, a surface tension as low as that of pure IPA may not be required for paddle formation. In such a case, by diluting IPA with DIW to such an extent that it does not cause problems in paddle formation, the usage amount of expensive IPA can be reduced, and the running cost of the apparatus can be lowered.

[0065] Other suitable low surface tension liquids (liquids with a lower surface tension than DIW) can also be used instead of IPA. However, it is preferable that the low surface tension liquid has compatibility with the etching solution and does not inhibit the reaction between the etching solution and the surface of the substrate W.

[0066] In the third embodiment, since a paddle can be stably formed even when the etching target surface is hydrophobic, it is possible to arbitrarily select which of the first etching step and the second etching step to execute first, considering the throughput of the process and the like.

[0067] [Fourth Embodiment of the Etching Method] A fourth embodiment of the etching method will be described with reference to FIG. 6. In the fourth embodiment, compared with the first embodiment, in the paddle formation step (FIG. 6(B)), a paddle is formed with an etching solution (DHF), and in the first etching step (local etching step) of FIG. 6(C), DIW is discharged from a nozzle to the paddle of the etching solution, which is different. The other steps (the pre-wet step with DIW in FIG. 6(A), the rinse step in FIG. 6(D), and the drying step not shown) are all the same.

[0068] In the first etching step of the first embodiment described above, by discharging DHF from the DHF nozzle to the DIW paddle, only a partial region (target region) on the surface of the substrate W is locally etched. In contrast, in the first etching step of this fourth embodiment, by discharging DIW from the DIW nozzle to the DHF paddle, the DHF in a partial region (target region) on the surface of the substrate W is diluted with DIW, and etching is locally suppressed only in the said region.

[0069] Similar to the second embodiment of the etching method described above, in the first etching step, the rotation of the substrate W is stopped, DHF and the liquid is made to land on a desired position of the DIW paddle on the surface of the substrate W DHF from the nozzle DHF by discharging. Thereby, etching within a generally circular region centered on the liquid landing point is locally suppressed.

[0070] Note that depending on the concentration of DHF supplied from the DHF nozzle, the etching rate may increase due to dilution with DIW (due to a change in the ionization state). For this reason, this fourth embodiment may also be used as a technique for locally promoting etching of the target region.

[0071] [Determination of conditions for the first etching step (local etching step)] The determination of the conditions for the first etching step (local etching step) in the first to fourth embodiments will be described below.

[0072] The first embodiment will be described as an example. First, under the same conditions as the first embodiment, a substrate is processed (hereinafter, for simplicity, referred to as "normal processing") by sequentially performing a pre-wet process, a second etching process (overall etching process), a rinse process, and a drying process. In the normal processing, a paddle formation process and a first etching process (local etching process) are not performed. The conditions for this normal processing (particularly the second etching process) are determined based on the conventional method (trial and error through preliminary tests, etc.) so that the in-plane uniformity of the etching amount is as high as possible.

[0073] For the substrate subjected to the above normal processing, the distribution of the etching amount is measured using a known non-destructive inspection method (for example, spectroscopic ellipsometry). Specifically, for example, measurement points are set at equal intervals (for example, intervals of about 5 mm) along the diameter of the substrate, and the etching amount at each measurement point is measured. Note that the measurement points may be set along the radius (that is, on a line connecting the center to a point on the periphery), may be set along two straight lines extending in two mutually perpendicular diameter directions, or may be set along four straight lines extending in four diameter directions that are rotated by 45 degrees relative to each other.

[0074] An example of the distribution of the etching amount measured along the diameter of the substrate is shown by a solid line in the graph of FIG. 7 with significant simplification. The vertical axis of the graph is the etching amount (EA), and the horizontal axis is the position in the diameter direction POS (unit: mm) of each measurement point with the position of the center of the substrate being ±0 mm. In the example shown in the graph of FIG. 7, the etching amount becomes smaller by about several Å (angstroms) within a ring-shaped region around 50 mm from the center of the substrate, and in other regions, the target etching amount is generally achieved and the etching amount is also generally uniform.

[0075] If the etching amount distribution in the second etching process is as shown by the solid line in the graph of FIG. 7, and the first etching process is performed under conditions such that the etching amount distribution shown by the chain line in the graph of FIG. 7 is obtained, then etching with high in-plane uniformity will be achieved by the first and second etching processes.

[0076] The conditions of the first etching process can be determined through preliminary tests. Examples of parameters for determining the conditions of the first etching process include etching time, the type of liquid forming the paddle, paddle thickness, substrate rotation speed, discharge flow rate of the etching liquid from the nozzle (gas discharge flow rate in the case of two fluids), discharge form of the etching liquid from the nozzle, and the like.

[0077] The conditions of the first etching process are arbitrary as long as the desired etching amount distribution is achieved, but can preferably be determined based on the following considerations.

[0078] The rotation speed of the substrate is preferably low, specifically 100 rpm or less, and more preferably 30 rpm or less. When the rotation speed of the substrate increases, the liquid (DIW) forming the paddle flows, and the etching liquid (DHF) adhering to the paddle may not stay in place and may be etched to an unintended area. In a preferred embodiment, the rotation speed of the substrate is 10 rpm. At such a low rotation speed, the flow of the liquid forming the paddle occurs only to an extent that can be ignored, so the etching liquid adhering to the paddle spreads within the paddle substantially due to the mutual diffusion of the etching liquid (DHF) and the paddle liquid (DIW) and the stirring effect during liquid adhesion. When the etching liquid is discharged in a two-fluid state, the stirring effect is enhanced (see also the test results described later).

[0079] The number of rotations of the substrate (which corresponds to the processing time if the rotation speed is fixed) should also be as small as possible. If the number of rotations increases, the etching solution may spread from the liquid landing point to a position far away, and there is a risk that unintended areas may be etched. In the above-mentioned preferred example where the rotation speed of the substrate is 10 rpm, the number of rotations of the substrate is set to 1 (that is, the time of the first etching step is 6 seconds).

[0080] If the rotation speed and the number of rotations (processing time) of the substrate are determined as described above (although not limited to the above conditions), the discharge form of the etching solution from the nozzle and the discharge flow rate of the etching solution from the nozzle (the gas discharge flow rate in the case of two fluids) may be determined.

[0081] The discharge form of the etching solution is classified into the form of a liquid column or the form of a spray (liquid droplets). The spray form is classified into a single fluid (simply spraying the etching solution as liquid droplets) or a two-fluid (spraying a mixed fluid of liquid droplets of the etching solution and an inert gas). When the etching solution is discharged in the form of liquid droplets, the spray angle is also considered.

[0082] When the spray angle is increased, local etching can be performed over a relatively wide radial range, and when the spray angle is decreased, local etching can be performed over a relatively narrow radial range. When the etching solution is discharged in the form of a thin liquid column (single fluid), local etching can be performed over a relatively narrow radial range.

[0083] As described above, the etching solution may be discharged in either the two-fluid or single-fluid form. As a result of experiments, when the etching solution is discharged in the two-fluid form, a wider radial width of local etching and higher in-plane and inter-plane uniformity of the etching amount are obtained compared to the case of a single fluid (details will be described later). Therefore, except when it is particularly desired to etch a narrow radial region, it is preferable to discharge the etching solution in the two-fluid form.

[0084] For example, when an etching solution (e.g., DHF) is discharged by a two-fluid nozzle, tests are conducted with parameters such as the spray angle of the two-fluid nozzle, the flow rate of the etching solution, and the flow rate of the gas. It is only necessary to find the discharge conditions of the etching solution under which the width of an appropriate etching region can be stably obtained. Generally, it is preferable (but not limited thereto) that the two-fluid discharged from the two-fluid nozzle impinges on the paddle with such a force that the surface of the paddle is slightly recessed.

[0085] It is obvious that those skilled in the art who have read the present specification can easily find the processing conditions of the first etching step capable of etching a desired radial region with a desired etching amount by conducting tests while changing various parameter values while considering the above-described matters.

[0086] [Test on the First Etching Step] A test was conducted to confirm the etching amount distribution when the first etching step was performed alone. As the substrate to be etched, a substrate in which an oxide film was formed on a bare silicon wafer by thermal CVD was prepared. With respect to this substrate, while rotating the substrate on which a DIW paddle was formed at a rotation speed of 10 rpm, DHF was supplied from the nozzle for 6 seconds at a position 100 mm away from the center of the substrate. The discharge flow rate of DHF from the nozzle was 100 ml / min both in the case of single-fluid discharge and in the case of two-fluid discharge. In the case of two-fluid discharge, a pressure of 10 kPa was further applied to the nozzle and nitrogen gas was supplied. Four substrates were processed for each of the single-fluid and two-fluid treatments. After the treatment, film thickness measurement was performed on the substrate using spectroscopic ellipsometry to obtain the distribution of the etching amount.

[0087] The test results are shown in the graph of FIG. 8. The upper part of the graph shows the results in the case of two-fluid discharge, and the upper part shows the results in the case of single-fluid discharge. The horizontal axis of the graph indicates the distance from the center of the substrate at each measurement point (unit: mm), and the measurement points on the right side of the center of the substrate are shown as positive values, and the measurement points on the left side are shown as negative values. The vertical axis of the graph is the etching amount (unit: Å).

[0088] From the graph of FIG. 8, it can be visually seen that the two-fluid process has a wider etched radial width and higher stability of the etching amount between wafers.

[0089] Also, based on the acquired data, the variation in the etching amount was confirmed. The results are shown in Tables 1 and 2 below. In the following tables, for example, the region "-100±10" means that the data obtained within the region between position -90 mm and position -110 mm when discharging the two-fluid (or single-fluid) aiming at the position of -100 mm was processed. Regardless of the region width, all the discharge conditions of the two-fluid and the single-fluid are the same. σ is the standard deviation, which indicates the standard deviation of all the etching amounts obtained within the corresponding regions on four substrates.

[0090]

Table 1

[0091]

Table 2

[0092] From the data in Tables 1 and 2, it can also be seen that the two-fluid process has a wider etched region in the radial direction and higher stability of the etching amount between substrates. That is, if importance is attached to the stability of the process, the two-fluid process is more preferable. However, this does not deny the use of the single-fluid process. If local etching in a narrower range is desired, the single-fluid process may be performed.

[0093] Note that the radial width of the etched region at the -100 mm position tends to be wider than that at the +100 mm position, and the variation in the etching amount also tends to be smaller. This is presumably because the -100 mm position is closer to the position where the etching solution first lands, and the diffusion of the etching solution has progressed further. Such variation in the etching results is inevitable as long as the first etching step is carried out by fixing the nozzle and rotating the substrate once. However, the inventor believes that such a degree of variation does not pose a practical problem. Also, by arranging two nozzles at positions diametrically opposed at an equal distance from the center of the substrate and starting the discharge of the etching solution simultaneously from these two nozzles and rotating the substrate, for example, once, it is considered that the above-mentioned variation can be alleviated.

[0094] [Fifth Embodiment of the Etching Method] In the above first to fourth embodiments, the first etching step (local etching step) and the second etching step (overall etching step) are performed as a series of processes, but it is not limited to this. A modified etching process including a pre-wetting step, a paddle formation step, a first etching step, a rinse step, and a drying step may be performed on a substrate (for example, a dried substrate) that has been subjected to a conventional etching process (a process including the second etching step and not including the first etching step).

[0095] Specifically, for example, a substrate that has been subjected to a conventional etching process is carried into an inspection unit, where the in-plane distribution of the etching amount is investigated using a known non-destructive inspection method such as spectroscopic ellipsometry. When the in-plane distribution of the etching amount does not meet the standard, a modified etching process is performed on the substrate.

[0096] The relationship between the inspection results of a substrate that has undergone a conventional etching process (for example, the in-plane distribution of the etching amount) and the conditions of the corrective etching process necessary to correct the distribution (non-uniform distribution) may be stored in a database in a storage unit. In this case, the control device 4 that has received the inspection results may refer to the database and automatically determine the conditions of the corrective etching process.

[0097] Also, for all the substrates that have undergone a conventional etching process in the first substrate processing apparatus, corrective etching may be performed in the second substrate processing apparatus under predetermined etching conditions. Further, if it is known that the etching amount distribution obtained by the conventional etching process in the first substrate processing apparatus is stably within a predetermined range, it may not be necessary to inspect the etching amount distribution of the substrate before performing corrective etching in the second substrate processing apparatus.

[0098] [Modified Embodiment of the Second Etching Step] Next, a modified embodiment of the second etching step will be described with reference to FIGS. 9 and 10. The modified embodiment of the second etching step described below can be used to adjust the distribution of the etching amount in the plane of the substrate in the second etching step in the first to fifth embodiments of the etching method.

[0099] [First Modified Embodiment]< In the first modified embodiment, when performing the second etching step, as shown in FIG. 9, the DHF nozzle 41 that discharges DHF is reciprocally moved (also referred to as "scanned") between above the central portion and above the peripheral portion of the substrate W. Further, a low-humidity gas is discharged from the central discharge portion 21C of the FFU 21, and the low-humidity gas is selectively blown onto the central portion of the substrate W. The low-humidity gas may be a gas having a humidity sufficiently lower than the air in the clean room. For example, it is preferably a gas having a humidity of 1% or less such as dry air or nitrogen gas. Clean air (air having the same humidity as the air in the clean room) may be discharged from the peripheral discharge portion 21P of the FFU 21.

[0100] An FFU configured to be able to supply different gases (for example, clean air, dry gas) to a central portion and a peripheral portion is known in the art, and a detailed description of the structure will be omitted.

[0101] Selective spraying of low-humidity gas onto the central portion of the substrate W may be performed by disposing a movable gas nozzle above the central portion of the substrate W and discharging the low-humidity gas therefrom toward the central portion of the substrate W.

[0102] According to this modified embodiment, by selectively spraying low-humidity gas onto the central portion of the substrate W, evaporation of moisture in the liquid film of DHF is promoted at the central portion of the substrate W, thereby increasing the concentration of DHF. Further, by reciprocally moving the liquid landing point of DHF from the DHF nozzle onto the surface of the substrate W between the central portion and the peripheral portion of the substrate W, the liquid film of DHF existing in the central portion of the substrate W becomes thinner while the liquid landing point of DHF is away from the central portion of the substrate W (compared with the case where the liquid landing point of DHF is fixed at the central portion of the substrate W). Therefore, when the same amount of moisture evaporates, the degree of increase in the concentration of DHF becomes larger. As a result, the etching rate at the central portion of the substrate W becomes larger than that at the peripheral portion. By utilizing this phenomenon, the etching amount distribution within the substrate surface can be adjusted.

[0103] <Second Modified Embodiment> In the second modified embodiment, when performing the second etching step, as shown in FIG. 10, the DHF nozzle 41 is fixed above the central portion of the substrate W. Further, low-humidity gas is discharged from the peripheral discharge portion 21P of the FFU 21 toward the peripheral portion of the substrate W, and low-humidity gas is selectively sprayed onto the peripheral portion of the substrate W. Clean air (air having the same humidity as the air in the clean room) is discharged from the central discharge portion 21C of the FFU 21.

[0104] In this case, evaporation of moisture in the liquid film of DHF is promoted at the peripheral portion of the substrate W, thereby increasing the concentration of DHF. Therefore, the etching rate at the peripheral portion of the substrate W becomes larger than that at the central portion. By utilizing this phenomenon, the etching amount distribution within the substrate surface can be adjusted.

[0105] The selective spraying of the low-humidity gas onto the peripheral portion of the substrate W may be performed by disposing a movable gas nozzle above the peripheral portion of the substrate W and discharging the low-humidity gas from there toward the peripheral portion of the substrate W.

[0106] In addition, in any of the first modified embodiment and the second modified embodiment, depending on the type and original concentration of the chemical solution, the etch rate may decrease due to the evaporation of the moisture in the chemical solution. In this case, the etch rate at the central portion (or peripheral portion) of the substrate W can be made smaller than that at the peripheral portion (or central portion).

[0107] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The above embodiments may be omitted, replaced, or changed in various forms without departing from the scope and gist of the appended claims.

[0108] The substrate to be processed is not limited to a semiconductor wafer, and may be other types of substrates used in the manufacture of semiconductor devices such as glass substrates and ceramic substrates.

Claims

1. While paddles of a first treatment liquid are formed over the entire surface of a substrate, by locally discharging a second treatment liquid from a nozzle toward a target region locally set on the surface of the substrate, a first etching step of performing etching such that an etching rate of the target region is different from an etching rate of other regions; A second etching step of simultaneously etching the entire surface of the substrate by supplying the etching liquid such that the entire surface of the substrate is covered with a liquid film of the etching liquid while rotating the substrate; comprising; One of the first treatment liquid and the second treatment liquid used in the first etching step is the etching liquid, and the other is an etching inhibition liquid that is mixed with the etching liquid to reduce the etching rate of the surface of the substrate by the etching liquid, A substrate processing method.

2. The substrate processing method according to claim 1, wherein the first etching step is performed with the rotation of the substrate stopped.

3. The target region is a ring-shaped region concentric with a periphery of the substrate, and the first etching step includes rotating the substrate at least once while discharging the second treatment liquid from the nozzle with the position of the nozzle fixed. The substrate processing method according to claim 1.

4. When rotating the substrate in the first etching step, the substrate is rotated at a low speed such that the paddles of the first treatment liquid are not broken. The substrate processing method according to claim 3.

5. When rotating the substrate in the first etching step, a rotation speed of the substrate is 100 rpm or less. The substrate processing method according to claim 3.

6. During execution of the first etching step, the first treatment liquid is not supplied to the substrate to maintain the paddles of the first treatment liquid. The substrate processing method according to claim 1.

7. In the first etching step, the second processing liquid is in the form of a mist and is discharged from the nozzle toward the target area in a two-fluid form mixed with a gas, according to the substrate processing method of claim 1.

8. A step of obtaining an etching amount distribution in the surface of the substrate when the second etching step is performed without performing the first etching step; A step of determining processing conditions for the first etching step based on the etching amount distribution; The substrate processing method according to claim 1, further comprising:

9. The processing conditions for the first etching step are determined such that the etching amount distribution when both the first etching step and the second etching step are performed is made uniform compared to when only the second etching step is performed, according to the substrate processing method of claim 8.

10. The first processing liquid is an etching inhibitor, and the second processing liquid is an etching solution, according to the substrate processing method of claim 1.

11. The first processing liquid is an etching solution, and the second processing liquid is an etching inhibitor, according to the substrate processing method of claim 1.

12. The etching inhibitor is DIW (pure water), functional water, IPA (isopropyl alcohol), or a mixture thereof, according to the substrate processing method of claim 1.

13. The first etching step is performed prior to the second etching step, according to the substrate processing method of claim 1.

14. The second etching step is performed prior to the first etching step, according to the substrate processing method of claim 1.

15. The second etching step is performed while blowing a low-humidity gas onto only one of the peripheral portion and the central portion of the substrate, according to the substrate processing method of claim 1.

16. The second etching step is performed while moving the liquid landing point of the etching solution on the substrate between the central portion and the peripheral portion of the substrate and blowing a low-humidity gas only onto the central portion of the substrate. The substrate processing method according to claim 15.

17. The second etching step is performed while maintaining the liquid landing point of the etching solution on the substrate at the central portion of the substrate and blowing a dry gas only onto the peripheral portion of the substrate. The substrate processing method according to claim 15.

18. A local etching step of performing etching such that the etching rate of a target region is different from that of other regions by locally discharging a second processing liquid from a nozzle toward a target region set locally on the surface of the substrate in a state where a paddle of a first processing liquid is formed on the entire surface of the substrate. One of the first processing liquid and the second processing liquid is an etching solution, and the other is an etching inhibitor that is mixed with the etching solution to reduce the etching rate of the surface of the substrate by the etching solution. Substrate processing method.

19. A substrate holding unit that holds the substrate horizontally; A rotation driving unit that rotates the substrate holding unit around a vertical axis; A processing fluid supply unit that supplies a processing fluid to the surface of the substrate held by the substrate holding unit; A control unit that controls the substrate holding unit, the rotation driving unit, and the processing fluid supply unit to execute the substrate processing method according to claim 1 or 18. A substrate processing apparatus comprising:

20. A substrate holding unit that holds the substrate horizontally; A rotation driving unit that rotates the substrate holding unit around a vertical axis; A processing fluid supply unit that supplies a processing fluid to the surface of the substrate held by the substrate holding unit; A gas supply unit configured to selectively blow dry gas only to either the central portion or the peripheral portion of the surface of the substrate; A control unit configured to control the substrate holding unit, the rotational drive unit, the processing fluid supply unit, and the gas supply unit to execute the substrate processing method according to claim 15; A substrate processing apparatus comprising the above.

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