Etching method and etching apparatus

Abstract

To control the etching distribution on the surface of a substrate.SOLUTION: An etching method of the present disclosure comprises: a first storing step for supplying a first etching gas from a first gas supply source to a first gas supply channel, storing it in a first reservoir provided in the first gas supply channel, and raising the pressure inside the first reservoir; a second storing step for supplying a second etching gas from a second gas supply source to a second gas supply channel, storing it in a second reservoir provided in the second gas supply channel, and raising the pressure inside the second reservoir; a first supplying step for supplying the first etching gas from the first reservoir into a processing vessel during a first period; and a second supplying step for supply the second etching gas from the second reservoir into the processing vessel during a second period in which at least one of which the start point and the end point is different from the first period, so that a period is formed in which only one of the first etching gas and the second etching gas is supplied into the processing vessel.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an etching method and an etching apparatus.

Background Art

[0002] In some cases, for processing a substrate such as a semiconductor wafer (hereinafter referred to as a wafer), a gas once stored in a tank is discharged into a processing container for processing. In Patent Document 1, it is described that for a substrate for manufacturing a flat panel display (FPD), etching is performed by discharging each of the gases of He, HCl, and SF6 stored in a tank.

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 capable of controlling an etching distribution on the surface of a substrate.

Means for Solving the Problems

[0005] The etching method of the present disclosure includes a step of storing a substrate in a processing container in which a reaction occurs and surface etching is performed by supplying both a first etching gas and a second etching gas, a first storage step of supplying the first etching gas from a first gas supply source to a first gas supply path, storing the gas in a first storage portion provided in the first gas supply path, and increasing the pressure inside the first storage portion, a second storage step of supplying the second etching gas from a second gas supply source to a second gas supply path, storing the gas in a second storage portion provided in the second gas supply path, and increasing the pressure inside the second storage portion, A first supply step of supplying the first etching gas from the first storage unit into the processing container during the first period, A second supply step involves supplying the second etching gas from the second storage unit into the processing container during a second period in which at least one of the first etching gas and the second etching gas is different from the first period, such that a period is formed in which only one of the first etching gas and the second etching gas is supplied into the processing container. Equipped with, The first storage step is performed in the first storage unit provided in the first gas Close the first valve located downstream of the first storage section in the supply line, and the first gas The process involves supplying the first etching gas from a first gas supply source to the first storage unit with the third valve, which is located upstream of the first storage unit in the supply path, open. The second storage step is performed in the second storage section provided in the second gas Close the second valve located downstream of the second storage section in the supply line, and the aforementioned second gas The process involves supplying the second etching gas from a second gas supply source to the second storage unit from the supply path while the fourth valve, which is located upstream of the second storage unit in the supply path, is open. The first supply step is a step of opening the first valve with the third valve closed and supplying the first etching gas from the first storage unit into the processing container, The second supply step is a step of opening the second valve with the fourth valve closed and supplying the second etching gas from the second storage unit into the processing container, An overlapping period is formed in which the first period and the second period overlap. [Effects of the Invention]

[0006] This disclosure enables control of the etching distribution on the surface of the substrate. [Brief explanation of the drawing]

[0007] [Figure 1]This is a longitudinal cross-sectional side view of an etching apparatus, which is one embodiment of the present disclosure. [Figure 2] A plan view of the wafer. [Figure 3] Plan view of the wafer [Figure 4] This chart shows the timing of gas supply. [Figure 5] This is a longitudinal cross-sectional side view of the wafer. [Figure 6] This is a longitudinal cross-sectional side view of the wafer. [Figure 7] This is an explanatory diagram showing the results of the evaluation test. [Figure 8] This is an explanatory diagram showing the results of the evaluation test. [Figure 9] This is an explanatory diagram showing the results of the evaluation test. [Modes for carrying out the invention]

[0008] An etching apparatus 1, which is one embodiment of the etching apparatus of this disclosure and implements the etching method according to this disclosure, will be described with reference to the longitudinal cross-sectional side view of Figure 1. In the etching apparatus 1, a wafer W, which is a circular substrate, is placed in a processing container 11, the processing container 11 is set to a desired pressure, which is a vacuum atmosphere, and etching is performed by supplying a halogen-containing gas as a first etching gas and a basic gas as a second etching gas. Specifically, in this example, HF (hydrogen fluoride) gas is used as the halogen-containing gas, and a mixed gas of NH3 (ammonia) gas and amine gas is used as the basic gas to etch the SiOx (silicon oxide) film 91 on the surface of the wafer W. For example, trimethylamine (TMA) gas is used as the amine gas.

[0009] Therefore, ammonium fluorosilicate [(NH4)SiF6: AFS], which is a reaction product of HF and NH3 acting on SiOx, and reaction products of HF and TMA acting on SiOx are generated on the surface of the wafer W, and etching is performed by sublimation of these reaction products. In performing this etching, no plasma is formed around the wafer W.

[0010] The above HF gas and basic gas are stored in tanks 81 and 82, and are supplied into the processing container 11 by opening valves V1 and V2 on the downstream side of the tanks 81 and 82 in a pressurized state inside the tanks 81 and 82. As will be described in detail later, a gas supply cycle is set so that the supply of the HF gas and the basic gas is repeated in order to make the etching amount a desired amount. In one cycle thereof, the period for supplying the HF gas into the processing container 11 and the period for supplying the basic gas into the processing container 11 are set to be shifted from each other.

[0011] Hereinafter, the configuration of the apparatus will be specifically described. The wafers W are stored side by side in the left and right directions inside the processing container 11. The two wafers W are etched collectively. The processing of the wafers W is performed in a processing space 21 partitioned from each other. Inside the processing container 11, a processing space forming member 22 for forming the processing space 21 is provided. The processing space forming member 22 is a horizontally long block in the left and right directions, and through holes 23 perforated in the vertical direction are configured to be provided at intervals in the left and right directions. The lower edge of the peripheral surface forming the through holes 23 forms a protruding edge portion 24 protruding inward.

[0012] The left and right central lower portions of the processing space forming member 22 are connected to a lifting mechanism 26 provided outside the processing container 11 via columns 25 penetrating the bottom wall of the processing container 11, and can be lifted up and down between an upper position and a lower position inside the processing container 11. A bellows (not shown) surrounding the column 25 is provided outside the processing container 11, and the gap formed between the column 25 and the bottom wall of the processing container 11 is sealed by making the column 25 liftable.

[0013] On the ceiling inside the processing container 11, two circular shower plates 3 are provided in plan view. The shower plates 3 are located above each through-hole 23 of the processing space forming member 22. In some cases, one of the two shower plates 3 is distinguished as 3A and the other as 3B. The gas supplied to the central portion of the shower plate 3 through each of the pipes described later is discharged downward from a large number of discharge ports 31 formed dispersedly on the lower surface of the shower plate 3 through the flow path of the shower plate 3.

[0014] On the left and right of the bottom wall of the processing container 11, upright cylinders 32 are provided respectively. When the processing space forming member 22 is located at an upper position, the O-ring 23A provided at the hole edge of the through-hole 23 is in close contact with the peripheral portion of the lower surface of the shower plate 3, and the O-ring 24A provided on the protruding edge portion 24 is in close contact with the flange formed on the upper edge portion of the cylinder 32. Thereby, the above-described processing space 21 is formed. The processing space 21 is a region above the stage 41 described later among the spaces surrounded by the processing space forming member 22 and the shower plate 3 in this way.

[0015] Through-holes 34 are formed in the side walls of the cylinders 32. And at the left and right central portions of the bottom wall of the processing container 11, an exhaust port 35 is opened at a position behind the support column 25. Outside the bottom wall, an exhaust pipe 36 is connected so that the upstream end opens at the exhaust port 35. The downstream end of the exhaust pipe 36 is connected to an exhaust mechanism 38 constituted by a vacuum pump or the like through a valve 37. By adjusting the opening degree of the valve 37, the pressure in the processing space 21 is adjusted.

[0016] When the processing space forming member 22 is located at a lower position, a transfer port (not shown) provided in front of the processing container 11 is located above the processing space forming member 22. Through this transfer port, a transfer mechanism of the wafer W provided outside the processing container 11 is located above the through-hole 23 and can transfer the wafer W to the stage 41 described later through the pin 52 described later.

[0017] A stage 41 is provided in each through-hole 23. The upper surface of the stage 41 is horizontal and faces the lower surface of the shower plate 3. In a plan view, the center of the shower plate 3 is aligned with the center of the wafer W placed on the upper surface of the stage 41. A fluid channel 42 is formed in the stage 41 to supply a temperature-controlled fluid, so that the temperature of the wafer W on the stage 41 is set to a desired temperature. A concave partition member 43 is provided in a longitudinal cross-sectional view so as to be connected to the lower surface of the stage 41, forming a partitioned space below the stage 41.

[0018] The partition member 43 is connected to a lifting mechanism 45 located outside the processing container 11 via a support column 44 that extends downward through the bottom wall of the processing container 11, allowing the height of the stage 41 to be changed. Therefore, the volume of the processing space 21 can be freely changed by changing the height H between the stage 41 and the shower plate 3 when processing the wafer W. For the purpose of quickly diffusing and exhausting gas throughout the processing space 21, it is preferable to set the height H to a relatively small value, for example, 40 mm or less, for processing.

[0019] Three pins 52 (only two shown in the figure) extending vertically upward are provided, supported by support plates 51 located in the space between the partition member 43 and the lower surface of the stage 41. The support plates 51 are connected to a lifting mechanism 54 located outside the processing container 11 via support columns 53 that extend downward through the partition member 43 and the bottom wall of the processing container 11. The pins 52 can protrude and retract from the upper surface of the stage 41, and as previously described, wafers W are transferred between the transport mechanism and the stage 41. In the figure, 55 is a bellows that surrounds the support columns 44 and 53 and connects the partition member 43 and the bottom wall of the processing container 11, preventing the airtightness inside the processing container 11 from being broken by gaps between the support columns 44 and 53 and the bottom wall.

[0020] The etching apparatus 1 is equipped with pipes 61, 62, 63, and 64. Pipes 61 and 62 are connected to the ceiling of the processing container 11 so as to supply gas from above to the centers of shower plates 3A and 3B, respectively. The upstream sides of pipes 61 and 62 are connected to N2 gas supply sources 71A and 71B, respectively, via a flow rate adjustment mechanism 60. The flow rate adjustment mechanism 60 consists of a valve and a mass flow controller and switches the supply and cut of gas to the downstream side of the flow path and adjusts the gas flow rate. The flow rate adjustment mechanisms 60 provided in pipes other than pipes 61 and 62, which will be described later, have the same configuration as the flow rate adjustment mechanisms 60 interposed in pipes 61 and 62. The N2 (nitrogen) gas supplied from the N2 gas supply source 71 serves as both a carrier gas for the etching gas and a purge gas for purging the inside of the processing container 11. During the processing of the wafer W, the supply of N2 gas from gas supply sources 71A and 71B is continuous.

[0021] Pipes 63 and 64 are configured as gas flow paths with storage sections interposed between them. Pipe 63 forms the first gas supply path, and pipe 64 forms the second gas supply path. The downstream ends of pipes 63 and 64 are connected to the ceiling of the processing container 11 to supply gas from above to the center of shower plates 3A and 3B. Along pipe 63, valve V1, tank 81, and valve V3 are interposed in this order toward the upstream side. Upstream of valve V3, pipe 63 branches into two. One branch is connected to the HF gas supply source 72, which is the first gas supply source, via a flow rate adjustment mechanism 60, and the other branch is connected to the N2 gas supply source 73 via a flow rate adjustment mechanism 60. The N2 gas supplied from the N2 gas supply source 73 is a diluent gas for the HF gas. Valve V3 is open during the period when each gas is supplied to and stored in the first storage unit, tank 81, and is closed when the first valve, valve V1, is open to prevent the gas stored in tank 81 from flowing back through the piping 63.

[0022] In the piping 64, valve V2, tank 82, and valve V4 are installed in this order toward the upstream side. Upstream of valve V4, the piping 64 branches into three, and the upstream end of each branch is connected to the TMA gas supply source 74, NH3 gas supply source 75, and N2 gas supply source 76 via the flow rate adjustment mechanism 60. The TMA gas supply source 74 and NH3 gas supply source 75 are second gas supply sources. The N2 gas supplied from the N2 gas supply source 76 is a diluent gas for the NH3 gas and TMA gas. Valve V4 is open during the period when each gas is supplied to and stored in the tank 82, which is the second storage section, and is closed when valve V2, which is the second valve, is open to prevent the gas stored in tank 82 from flowing back through the piping 64.

[0023] The etching apparatus 1 is equipped with a control unit 80, which is a computer. This control unit 80 includes software, memory, and a CPU. The program incorporates instructions (each step) to process the wafer W, which will be described later. This program is stored on a storage medium, such as a compact disk, hard disk, magneto-optical disk, or DVD, and installed in the control unit 80. The control unit 80 outputs control signals to each part of the etching apparatus 1 based on this program, thereby controlling the operation of each part. Specifically, the operation of gas from tanks 81 and 82 by opening and closing valves V1 to V4, supplying gas to tanks 81 and 82, adjusting the flow rate of gas supplied to the downstream side by the flow rate adjustment mechanism 60, raising and lowering the processing space forming member 22, stage 41, and pin 52 by lifting mechanisms 26, 45, and 54, and adjusting the opening degree of valve 37 are all controlled by the control signals.

[0024] As described above, in the etching apparatus 1, etching is performed such that the period during which HF gas is supplied to the processing container 11 and the period during which NH3 gas and TMA gas are supplied to the processing container 11 are staggered (at least one of the start time of supply and the end time of supply is staggered). As previously described, since the etching apparatus 1 is configured as described above, the period during which HF gas is supplied to the processing container 11 and the period during which NH3 gas and TMA gas are supplied to the processing container 11 are the periods during which valves V1 and V2 are open, respectively. Therefore, the opening and closing of valves V1 and V2 are controlled so that at least one of the timings in which valves V1 and V2 are opened or closed is staggered within the same cycle (the period during which HF gas and basic gas are supplied once each).

[0025] The reason for the staggered gas supply periods is explained below. In the etching apparatus 1, each etching gas (HF gas, NH3 gas, and TMA gas) is stored in tanks 81 and 82. When tanks 81 and 82 are pressurized, valves V1 and V2 are opened and the gases are supplied to the processing container 11. This allows the gases to quickly diffuse throughout the processing space 21, thereby improving throughput. In order to improve throughput in this way, valves V1 and V2 are quickly closed after being opened, stopping the supply of each etching gas to the processing space 21, and these gases are exhausted. In one cycle, the period during which valves V1 and V2 are open is, for example, less than 1 second.

[0026] As will be shown in the evaluation tests described later, when gas is supplied while the timing of opening valves V1 and V2 within the same cycle is synchronized, the amount of etching on the central side of wafer W becomes larger than the amount of etching on the peripheral side. The mechanism behind this etching distribution will be explained with reference to Figure 2, a plan view of wafer W.

[0027] Each etching gas is introduced from its respective pipe to the center of the shower plate 3, i.e., above the center of the wafer W. The etching gas is dispersed within the shower plate 3, but because it is pressurized in tanks 81 and 82, a relatively large amount of etching gas is supplied to the center of the wafer W due to the momentum when it is introduced into the shower plate 3. As the processing space 21 is exhausted, the etching gas supplied to the center of the wafer W flows outward from the wafer W, but because valves V1 and V2 are quickly closed after being opened, the supply of each etching gas onto the wafer W is instantaneous. Therefore, if we consider a region R where the etching gas concentration is relatively high in plan view, this region R rapidly changes from a circular shape to a ring shape on the center of the wafer W, and this ring rapidly expands outward from the wafer W while its diameter increases.

[0028] When the supply periods of HF gas and basic gases (NH3 gas and TMA gas) to the wafer W overlap and coincide, these etching gases flow similarly across the wafer W. That is, the region R described in Figure 2 is formed by both HF gas and basic gases. Therefore, from the perspective of one of the etching gases, when it is supplied to the center of the wafer W, there is a sufficient concentration of the other gas in its vicinity, and the reaction products described above are generated between these gases and the SiOx film 91 on the surface of the wafer W. In other words, since much of each etching gas reacts with the other gas and the SiOx film 91 before it spreads to the periphery of the wafer W, the amount of etching is greater in the center of the wafer W than in the periphery, as described above.

[0029] In etching apparatus 1, in order to suppress the difference in etching amount between the peripheral and central parts of the wafer W and to increase the uniformity of etching amount within the surface of the wafer W, the HF gas and basic gas are supplied to the processing container 11 at different times. By staggering the times in this way, when viewed from the perspective of one etching gas supplied to the center of the wafer W, the concentration of the other etching gas in the center is relatively low, thereby suppressing excessive reaction in the center of the wafer W.

[0030] Furthermore, by staggering the supply periods of HF gas and basic gas to the wafer W, etching can be promoted at locations away from the center of the wafer W. The mechanism of this etching promotion is presumed to be as follows: By staggering the supply periods of HF gas and basic gas (NH3 gas and TMA gas) to the wafer W, the timing of their spread across the wafer W can be made different for the region R with a high concentration of HF gas (for convenience, let's call it region R1) and the region R with a high concentration of basic gas (for convenience, let's call it region R2), respectively, as shown in Figure 3.

[0031] Furthermore, if the difference in supply periods between the HF gas and the basic gas is small, regions R1 and R2 approach each other as the wafer W expands, at positions offset from the center of the wafer W, and the HF gas forming region R1 and the basic gas forming region R2 mix with each other. As a result, regions with high concentrations of both HF gas and basic gas are formed on the peripheral side offset from the center in the radial direction of the wafer W, and etching is promoted in these regions. Therefore, as shown in Figure 2, when the gas supply periods are staggered, it is possible to equalize the amount of etching between the center and the periphery of the wafer W compared to when the gas supply periods are matched.

[0032] Furthermore, if the etching gases are supplied from the gas supply source into the processing container 11 for a relatively long period of time without storing them in tanks 81 and 82, the etching gas will be supplied to the processing space 21 with relatively high uniformity after being diffused within the shower plate 3, and the gas will also be diffused with relatively high uniformity in the processing space 21. Therefore, it is considered that the uniformity of the etching distribution within the surface of the wafer W will be relatively high. Accordingly, this technology is particularly effective when the etching gas is stored in a tank (storage section), and the valve on the downstream side of the tank is opened and then quickly closed to supply the etching gas for the short period of time described above.

[0033] Next, the processing procedure for wafer W in etching apparatus 1 will be explained with reference to the timing chart in Figure 4. This timing chart shows the timing of opening and closing valves V1 and V2. Therefore, it shows the timing of supplying HF gas, NH3 gas, and TMA gas to wafer W in processing container 11. Figures 5 and 6 are longitudinal cross-sectional side views of wafer W, showing the state before etching and the state after etching, respectively. A Si film 92 is formed on the lower layer film 90 of wafer W, and grooves 93 are formed in the Si film 92. The SiOx film 91 before etching covers the Si film 92 and is positioned to enter the grooves 93.

[0034] In this example, etching is performed to remove the SiOx film 91 on the Si film 92 and to remove a portion of the SiOx film 91 within the groove 93. That is, the process in this example includes etching of the SiOx film 93 within the recess where the sidewalls are formed by the Si film 92. During etching, both the SiOx film 91 and the Si film 92 are exposed on the surface of the wafer W, but by using the etching gas described above, the SiOx film 91 is selectively etched from the SiOx film 91 and the Si film 92. As shown in Figure 6, the etching is completed with some of the SiOx film 91 remaining in the groove 93.

[0035] With the processing space forming member 22 in the lower position, two wafers W in the state shown in Figure 5 are transported from outside the processing container 11 to above each stage 41 by a transport mechanism (not shown). Each wafer W is then placed on the stage 41 via pins 52 and its temperature is adjusted to a predetermined temperature, for example, -20°C to 150°C. The processing space forming member 22 is then in the upper position, and the processing space 21 is formed inside the processing container 11. The stage 41 is also positioned at a predetermined height, and the height H between the stage 41 and the lower surface of the shower plate is as described above. With N2 gas supplied into the processing container 11 from gas supply sources 71A and 71B, the pressure in the processing space 21 is set to 0.133 Pa to 666 Pa by exhaust by the exhaust mechanism 38.

[0036] With valves V1 and V2 closed, valves V3 and V4 are opened. Then, HF gas and N2 gas are supplied to tank 81 from gas supply sources 72 and 73, while basic gas (NH3 gas + TMA gas) and N2 gas are supplied to tank 82 from gas supply sources 74-76, and the inside of tanks 81 and 82 is pressurized. In other words, the first and second storage processes are carried out. Then, valve V2 is opened (time t1 in the chart), and the gas (basic gas + N2 gas) inside tank 82 is supplied to each processing space 21. As described above, because the inside of tank 82 is pressurized, a relatively large amount of basic gas (NH3 gas and TMA gas) is supplied to the center of the wafer W. Then, the basic gas flows outward from the wafer W, and NH3 and TMA are adsorbed to various parts of the wafer W.

[0037] Then, at time t2, for example, 0.3 seconds after time t1, valve V1 is opened, and the gas (HF gas + N2 gas) in tank 81 is supplied to each processing space 21. This HF gas is also pressurized in tank 82 and supplied to the processing space 21, so a relatively large amount of HF gas is supplied to the center of the wafer W. As a result of the supply of basic gas and HF gas to the center of the wafer W in this manner, the SiOx film 91 in the center reacts with these gases, producing the reaction products described above.

[0038] However, since the basic gas was supplied before the HF gas, it began to flow outward from the wafer W. This prevents both the basic gas and the HF gas from becoming highly concentrated in the center of the wafer W, thus preventing excessive alteration (formation of reaction products) of the SiOx film 91 in that center. The HF gas supplied to the center of the wafer W then flows outward from the wafer W, and HF is adsorbed onto various parts of the wafer W's surface. Together with the previously adsorbed NH3 and TMA, it reacts with the SiOx film 91, generating reaction products.

[0039] Then, at time t3, for example 0.2 seconds after time t2, valve V2 is closed, stopping the supply of gas from tank 82 to each processing space 21. Subsequently, at time t4, for example 0.3 seconds after time t3, valve V1 is closed, stopping the supply of gas from tank 81 to each processing space 21. During this time t3 to t4, only one of the basic gas and HF gas is supplied to the center of wafer W, preventing both gases from becoming highly concentrated, thus preventing excessive deterioration of the SiOx film 91 in the center of wafer W. Between times t1 and t4, as explained in Figure 3, a region R1 with a relatively high concentration of basic gas and a region R2 with a relatively high concentration of HF gas spread outward from wafer W, and the gases forming these regions mix on the periphery of wafer W, causing a relatively large reaction to proceed at the mixed location.

[0040] From time t4 onward, while the supply of basic gas and HF gas to the processing space 21 is stopped, the sublimation of the reaction products proceeds, etching the SiOx film 91. Meanwhile, valves V3 and V4 are opened, and tank 81 is filled with the HF gas and N2 gas released between times t1 and t3, and tank 82 is filled with the basic gas and N2 gas released between times t2 and t4. Thus, the first and second storage processes are repeated. Then, valves V3 and V4 are closed, and at time t5, a predetermined time has elapsed from time t4, valve V2 is opened as at time t1, and the gas from tank 82 is supplied to the processing space 21.

[0041] Next, at time t6, 0.3 seconds after time t5, valve V1 is opened, just as at time t2, and gas from tank 81 is supplied to each processing space 21. Then, at time t7, 0.2 seconds after time t6, valve V2 is closed, stopping the supply of gas from tank 82 to each processing space 21. Subsequently, at time t8, for example, 0.3 seconds after time t7, valve V1 is closed, stopping the supply of gas from tank 82 to each processing space 21. As the gas is supplied in this manner and the sublimation of the reaction products proceeds, the SiOx film 91 is further etched. Meanwhile, the gas released into tanks 81 and 82 is refilled. After that, at time t9, valve V2 is opened again. Therefore, if the processing operation of the apparatus from time t1 to just before time t5 is considered the first cycle, then from time t5 to just before time t9, a second cycle similar to the first cycle is performed, and the SiOx film 91 is etched. From time t9 onward, the same cycle is repeated, and etching progresses each time the cycle is performed.

[0042] Once the cycle is repeated a predetermined number of times and a predetermined amount of SiOx film 91 has been etched, resulting in the wafer W being in the state shown in Figure 6, the wafer W is removed from the etching apparatus 1 in the reverse operation of when it was loaded into the etching apparatus 1. Compared to the case where the supply periods of HF gas and basic gas are synchronized, as explained in Figure 4, the reaction at the center of the wafer W is suppressed and the reaction at the periphery of the wafer W is promoted in each cycle, as described above. As a result, as will be shown in the evaluation test described later, the difference in the amount of etching between the center and periphery of the wafer W is suppressed, and the SiOx film 91 is etched with high uniformity across the surface of the wafer W.

[0043] The supply of basic gas to the processing container 11 takes place during the first period from t1 to t3 and from t5 to t7, with t1 and t5 being the start and t3 and t7 being the end points. The supply of basic gas to the processing container 11 during this first period constitutes the first supply step. The supply of halogen-containing gas to the processing container 11 takes place during the second period from t2 to t4 and from t6 to t8, with t2 and t6 being the start and t4 and t8 being the end points. The supply of basic gas to the processing container 11 during this second period constitutes the second supply step. Therefore, in the above-described process, etching is performed such that the start of one of the first and second periods is earlier than the start of the other, and the end of the other is earlier than the end of the other. Furthermore, times t2-t3 and t6-t7 are overlapping periods where the first and second periods overlap.

[0044] By appropriately adjusting the relationship between the supply period of HF gas and the supply period of basic gas, it is possible to adjust the position in the radial direction of the wafer W where the HF gas and basic gas are mixed relatively large, as explained in Figure 3. In other words, it is possible to control the position in the radial direction of the wafer W where etching progresses relatively large. By utilizing this, it is not only possible to equalize the amount of etching between the center and the periphery of the wafer W, but also to make the amount of etching at the periphery greater than that at the center of the wafer W. Furthermore, as shown in the evaluation test, it is possible to further increase the amount of etching at the center of the wafer W by making the supply periods of HF gas and basic gas not match rather than matching them. Therefore, this technology can control the etching distribution within the plane of the wafer W.

[0045] In the processing example above, the basic gas is supplied first among the HF gas and basic gas in the same cycle, but the basic gas may also be supplied first. However, considering the results of the evaluation test described later, it is preferable to supply the basic gas first.

[0046] In the above process, TMA gas is used as the amine gas, but other amine gases may also be used. Specifically, various amine compounds such as dimethylamine, dimethylethylamine, diethylamine, triethylamine, monotertiary butylamine, pyrrolidine, and pyridine can be used as etching gases. Therefore, any of primary, secondary, or tertiary amines may be used as the etching gas.

[0047] Furthermore, the use of a mixed gas of NH3 gas and amine gas as the basic gas is to improve the uniformity of etching within the groove 93 when etching the SiOx film 91 within the groove 93. More specifically, when using only NH3 gas, the amount of etching near the interface with the Si film 92 tends to be relatively large when etching the SiOx film 91 within the groove 93. This is thought to be because the AFS generated from SiOx, NH3, and HF does not easily adsorb to Si, so the thickness of the AFS layer formed on the SiOx film 92 is relatively thin near the interface and relatively thick near the interface. Therefore, the etching gas can easily come into contact with the SiOx film 91 near the interface, and etching proceeds more easily there.

[0048] Furthermore, when using only amine gas among NH3 gas and amine gas, the etching of the SiOx film 91 in the groove 93 tends to be relatively large at positions relatively far from the interface with the Si film 92. This is because the sublimation temperature of the products generated from SiOx, amine, and HF is relatively low, so the contact of the etching gas with the SiOx film 91 in the groove 93 is not easily hindered by these products. Therefore, the probability of gas collision with the SiOx film 91 is higher at positions far from the Si film 92, which is thought to be why etching proceeds more easily at positions relatively far from the interface with the Si film 92.

[0049] As described above, the etching apparatus 1 utilizes the difference in sublimation properties of the reaction products generated from NH3 gas and amine gas to balance the amount of etching near the interface and at a position relatively far from the interface. However, etching may be performed using only one of the NH3 gas or amine gas. In addition, although the above example etches the SiOx film 91 in a recess that opens upward, the SiOx film 91 in a recess that opens laterally may also be etched, and the method is not limited to etching the SiOx film 91 in a recess; for example, the SiOx film 91 may be formed on a flat surface.

[0050] Incidentally, the etching target is not limited to SiOx films; silicon films containing oxygen other than SiOx films may also be etched. Specifically, for example, films such as SiOCN films and tetraethyl orthosilicate may be etched. Note that in this specification, when a film or gas contains a component, it means that it contains that component as a main component, not as an impurity. In addition, for example, a Si film may also be etched.

[0051] The etching gas should be selected appropriately according to the material of the film to be etched. When etching an SiOx film, for example, in addition to HF, halogen-containing gases such as HCl, HBr, HI, and SF6 can be used. When etching the Si film described above, for example, tank 81 can be filled with the halogen gas F2 gas, and tank 82 can be filled with the basic gas NH3 gas, and the process can be carried out in the same way as when etching the SiOx film 91. Instead of F2 gas, halogen-containing gases such as IF7 gas, IF5 gas, ClF3 gas, and SF6 gas may be used.

[0052] The processing temperature of wafer W should be set appropriately according to the film to be etched and the etching gas used. Specifically, it should be set to a temperature at which the products generated from the film and etching gas sublimate and etching occurs. When etching a Si film using F2 gas and NH3 gas as described above, the processing temperature of wafer W should be set to, for example, -50°C to 150°C.

[0053] As described above, silicon-containing films such as SiOx films and Si films can be selected as the films to be etched. This technology can be applied to any process that generates reaction products using both the first etching gas and the second etching gas, as well as the film on the surface of the wafer W, and then removes these reaction products by vaporization (including sublimation) to perform etching, and is not limited to the examples described herein.

[0054] Furthermore, in the process shown in the time chart of Figure 4, the cycle is repeated multiple times, but if the required etching amount is very small, the cycle may be omitted and the process may be performed only once. Also, in the example shown in the time chart, the supply period of HF gas and the supply period of basic gas are supplied so that they overlap, but these supply periods may not overlap. In other words, the supply of one gas may be started after the supply of the other gas has finished, or the supply of the other gas may be started at the same time as the supply of the other gas has finished. However, it is preferable to have the supply periods of these gases overlap, as mixing of the gases on the periphery of the wafer W as described above may not occur, and the etching amount at the periphery may be insufficient.

[0055] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The above embodiments may be omitted, replaced, modified, or combined in various ways without departing from the scope and spirit of the appended claims.

[0056] [Evaluation Test] Evaluation tests 1 to 3 conducted in relation to this technology are described below. A wafer W with an SiOx film formed on its surface was etched using an etching apparatus 1. After etching, the amount of etching of the SiOx film at numerous different locations on the wafer W was measured. This etching was performed by carrying out a predetermined number of cycles of supplying each gas as described in the embodiment, but the relationship between the supply period of HF gas and the supply period of basic gases (NH3 gas and TMA gas) within the same cycle was changed for each wafer W. In this evaluation test, the SiOx film to be etched differed from that shown in the embodiment; it was a flat film formed on a wafer W with a flat surface.

[0057] In Evaluation Test 1 (1-1 to 1-5), etching was performed so that the start timing of the supply of basic gases (NH3 gas and TMA gas) and the start timing of the supply of HF gas coincided within the same cycle. In Evaluation Test 2 (2-1 to 2-5), etching was performed so that the end timing of the supply of basic gases and the end timing of the supply of HF gas coincided within the same cycle. In Evaluation Test 3 (3-1 to 3-3), etching was performed so that the start timing of the supply of basic gases and the start timing of the supply of HF gas did not coincide within the same cycle, and the end timing of the supply of basic gases and the end timing of the supply of HF gas did not coincide. In this Evaluation Test 3, the supply time of HF gas and the supply period of basic gas within the same cycle were set to the same length. In each evaluation test, a predetermined time interval was set between the cessation of supply of both HF gas and basic gas into the processing container 11 and the start of the next cycle to allow for sublimation of the product. In other words, if we were to supply each gas as shown in the chart in Figure 4, we would have set the timings for time t4 to time t5 to be predetermined.

[0058] In these evaluation tests 1-3, an index value for in-plane etching uniformity was obtained from the etching amount at each location within the surface of wafer W. This index value is calculated by determining 3σ of the obtained etching amount, dividing this value by the average value of each etching amount, and multiplying by 100 (unit: %). A lower index value indicates higher uniformity of etching within the surface of wafer W. In addition, an image of the etching distribution within the surface of wafer W was created from the etching amount at each location within the surface of wafer W. This etching distribution image is a computer-generated color gradient image of wafer W, showing the etching amount at any location within the surface of wafer W with a color corresponding to that etching amount.

[0059] Figures 7, 8, and 9 show the results of evaluation tests 1, 2, and 3, respectively, and illustrate schematic diagrams of wafer W corresponding to the etching distribution images above. In these schematic diagrams, the wafer W is divided into contour lines according to the colors of the image applied to the wafer W, and the etching distribution is represented by applying different patterns to each divided region. In other words, different patterns are applied to each predetermined etching amount range. Note that since these patterns are applied individually for evaluation tests 1, 2, and 3, even if the same pattern is used between evaluation tests 1 to 3, the etching amount range represented by that pattern differs between evaluation tests 1 to 3.

[0060] Furthermore, the two bars shown for each evaluation test in Figures 7 to 9 represent the supply period of HF gas and the supply period of basic gas in one cycle. HF gas and basic gas are supplied to the processing container 11 for a time corresponding to the length of each bar. The further to the left a bar is, the earlier the timing. Therefore, periods where the bars overlap vertically represent periods when both HF gas and basic gas are supplied to the processing container 11, while periods where they do not overlap represent periods when only one of the gases is supplied to the processing container 11.

[0061] Refer to Figure 7 to describe Evaluation Test 1 (1-1 to 1-5) in detail. In Evaluation Test 1, etching was performed in the same cycle, with the start time of HF gas supply and the start time of basic gas supply being the same. In Evaluation Tests 1-1, 1-2, 1-3, 1-4, and 1-5, the supply times for basic gas were 0.3 seconds, 0.3 seconds, 0.3 seconds, 0.4 seconds, and 0.5 seconds, respectively, and the supply times for HF gas were 0.5 seconds, 0.4 seconds, 0.3 seconds, 0.3 seconds, and 0.3 seconds, respectively. Consequently, the supply time of basic gas was relatively longer than the supply time of HF gas in the order of Evaluation Tests 1-1, 1-2, 1-3, 1-4, and 1-5, and the longer the supply time of basic gas, the larger the index value of in-plane uniformity of etching (i.e., the lower the in-plane uniformity). Specifically, the index values ​​for in-plane etching uniformity in evaluation tests 1-1, 1-2, 1-3, 1-4, and 1-5 were 10.4%, 12.5%, 18.4%, 21.3%, and 23.3%, respectively.

[0062] In evaluation test 1, the etching distribution showed that the amount of etching varied along the radial direction of wafer W, with the etching amount being greater in the center of wafer W than in the periphery. Figure 7 shows the etching distributions of evaluation tests 1-1, 1-3, and 1-5 as representative examples from evaluation tests 1-1 to 1-5. Furthermore, the shorter the HF gas supply time relative to the basic gas supply time, the greater the etching amount in the center of wafer W compared to the periphery.

[0063] In evaluation test 1-3, the supply period of HF gas and the supply period of basic gas coincided, and the gases were supplied as explained in Figure 2. In evaluation tests 1-1 and 1-2, where the supply period of HF gas was longer than that of basic gas, and the supply of HF gas continued even after the supply of basic gas was stopped, the index value of uniformity within the etching plane was smaller compared to evaluation test 1-3, and the amount of etching in the center of the wafer W relative to the peripheral edge was suppressed. Therefore, evaluation test 1 showed that in order to perform etching with high uniformity within the plane of the wafer W, it is preferable to continue supplying HF gas even after the supply of basic gas has ended. Furthermore, the results of evaluation tests 1-3 to 1-5 showed that in order to etch a larger area in the center of the wafer W, it is preferable to continue supplying basic gas even after the supply of HF gas has ended.

[0064] Next, we will refer to Figure 8 and describe evaluation tests 2 (2-1 to 2-5) in detail. In evaluation tests 2, etching is performed in the same cycle, with the end of HF gas supply and the end of basic gas supply being synchronized. In evaluation tests 2-1, 2-2, 2-3, 2-4, and 2-5, the supply times for basic gas were 0.3 seconds, 0.3 seconds, 0.3 seconds, 0.4 seconds, and 0.5 seconds, respectively, and the supply times for HF gas were 0.5 seconds, 0.4 seconds, 0.3 seconds, 0.3 seconds, and 0.3 seconds, respectively.

[0065] Therefore, relative to the HF gas supply time, the supply time of the basic gas was relatively longer in evaluation tests 2-1, 2-2, 2-3, 2-4, and 2-5, and the longer the supply time of the basic gas, the smaller the index value of the in-plane uniformity of etching (i.e., the higher the in-plane uniformity). Specifically, the index values ​​of the in-plane uniformity of etching in evaluation tests 2-1, 2-2, 2-3, 2-4, and 2-5 were 23.6%, 20.8%, 18.1%, 13.8%, and 10.5%, respectively.

[0066] In evaluation test 2, the etching distribution showed that the amount of etching varied along the radial direction of wafer W, with greater etching in the center of wafer W compared to the periphery. Figure 8 shows the etching distributions for evaluation tests 2-1, 2-3, and 2-5 as representative examples from evaluation tests 2-1 to 2-5. Furthermore, the longer the HF gas supply time relative to the basic gas supply time, the greater the etching in the center of wafer W compared to the periphery.

[0067] In evaluation test 2-3, the supply period of HF gas and the supply period of basic gas coincided, and the gases were supplied as explained in Figure 2. In evaluation tests 2-4 and 2-5, where the supply period of basic gas was longer than that of HF gas, and the supply of basic gas began before the supply of HF gas, the index value of uniformity within the etching plane was smaller compared to evaluation test 2-3, and the amount of etching in the center of the wafer W was suppressed relative to the peripheral edge. Therefore, evaluation test 2 showed that in order to etch with high uniformity within the plane of the wafer W, it is preferable to start supplying basic gas before supplying HF gas. Furthermore, the results of evaluation tests 2-1 to 2-3 showed that in order to etch a larger area in the center of the wafer W, it is preferable to start supplying HF gas before supplying basic gas.

[0068] Next, referring to Figure 9, we will explain evaluation test 3 (3-1 to 3-3). In this evaluation test 3, based on the results of evaluation tests 1 and 2, the aim is to further improve the uniformity of etching within the wafer W by supplying basic gas before the start of HF gas supply and continuing to supply HF gas after the end of basic gas supply. As mentioned above, the supply time for HF gas and basic gas is the same, so in evaluation test 3, the supply times of each gas are staggered, and this stagger time differs between evaluation tests 3-1 to 3-3.

[0069] In evaluation tests 3-1, 3-2, and 3-3, the supply time for HF gas and basic gas in one cycle was set to 0.5 seconds. Furthermore, in evaluation tests 3-1, 3-2, and 3-3, the start time of HF gas supply was delayed by 0.2 seconds, 0.3 seconds, and 0.4 seconds, respectively, compared to the start time of basic gas supply. The relationship between the HF gas supply time and the basic gas supply time in evaluation test 3-2 is shown in the time chart in Figure 4.

[0070] In evaluation test 3, the etching distribution also showed that the amount of etching varied along the radial direction of the wafer W, but the relationship between the central and peripheral areas differed between evaluation tests 3-1 to 3-3. Specifically, in evaluation test 3-1, the amount of etching was greater in the central part of the wafer W than in the peripheral area, similar to the results of evaluation tests 1 and 2, but in evaluation tests 3-2 and 3-3, the peripheral area of ​​the wafer W was larger than the central area. Furthermore, the index values ​​for in-plane etching uniformity in evaluation tests 3-1, 3-2, and 3-3 were 4.6%, 2.2%, and 7.4%, respectively, indicating higher in-plane uniformity than in evaluation tests 1 and 2.

[0071] The results of evaluation tests 1-3 showed that by not matching the supply period of HF gas and the supply period of basic gas, it is possible to increase the etching amount at the center of the wafer W and reduce the difference in etching amount between the center and the periphery, thereby increasing the uniformity of etching within the plane, compared to when the supply periods are matched. Furthermore, it was shown that by adjusting the relationship between the supply period of HF gas and the supply period of basic gas, it is possible to switch the relationship between the magnitude of etching between the center and the periphery within the plane of the wafer W. In addition, it was confirmed that in order to increase the uniformity of etching within the plane of the wafer W, it is preferable to supply basic gas before the start of HF gas supply and to continue supplying HF gas after the end of basic gas supply. In other words, it was confirmed that it is preferable to etch so that the start point of one of the first and second periods is earlier than the start point of the other, and the end point of the other first and second period is earlier than the end point of the other first and second period.

[0072] Furthermore, under each processing condition of evaluation tests 1 to 3, etching was also performed on the SiOx film 91 within the grooves 93 formed in the Si film 92, as explained in Figure 5, and the shape of each film after etching was confirmed. As a result, it was confirmed that etching was performed with high selectivity for the Si film 92, as shown in Figure 6. Therefore, it was confirmed that even if the supply periods for HF gas and basic gas were not matched, it was prevented that the etched shape would deviate from the desired shape. [Explanation of Symbols]

[0073] W wafer 11 Processing container 63, 64 Gas supply pipes 72 HF gas supply sources 74 TMA gas supply sources 75 NH3 gas supply sources 81, 82 tanks

Claims

1. A process in which a substrate is placed in a processing container to undergo surface etching by a reaction that occurs when both a first etching gas and a second etching gas are supplied, A first storage step involves supplying the first etching gas from a first gas supply source to a first gas supply path, storing it in a first storage section provided in the first gas supply path, and increasing the pressure inside the first storage section. A second storage step involves supplying the second etching gas from a second gas supply source to a second gas supply path, storing it in a second storage section provided in the second gas supply path, and increasing the pressure inside the second storage section. A first supply step of supplying the first etching gas from the first storage unit into the processing container during the first period, A second supply step involves supplying the second etching gas from the second storage unit into the processing container during a second period in which at least one of the start and end points differs from that of the first period, such that a period is formed in which only one of the first etching gas and the second etching gas is supplied into the processing container. Equipped with, The first storage step is a step of supplying the first etching gas from the first gas supply source to the first storage unit while closing the first valve provided downstream of the first storage unit in the first gas supply path where the first storage unit is provided, and opening the third valve provided upstream of the first storage unit in the first gas supply path. The second storage step is a step of supplying the second etching gas from the second gas supply source to the second storage section while closing the second valve provided downstream of the second storage section in the second gas supply path where the second storage section is provided, and opening the fourth valve provided upstream of the second storage section in the second gas supply path. The first supply step is a step of opening the first valve with the third valve closed and supplying the first etching gas from the first storage unit into the processing container, The second supply step is a step of opening the second valve with the fourth valve closed and supplying the second etching gas from the second storage unit into the processing container, An etching method in which an overlapping period is formed in which the first period and the second period overlap.

2. The etching method according to claim 1, wherein the first period and the second period are 1 second or less.

3. During the period in which the first etching gas and the second etching gas are supplied to the processing container once each, The starting point of one of the first and second periods is earlier than the starting point of the other. Furthermore, the etching method according to claim 1, wherein the endpoint of one of the first period and the second period is earlier than the endpoint of the other.

4. The etching method according to claim 3, wherein the length of the first period and the length of the second period are the same.

5. In order to repeatedly etch the surface of the substrate, the first supply step and the second supply step are repeatedly performed. The etching method according to claim 1, further comprising the step of exhausting the inside of the processing container after the first supply step and the second supply step have been performed, before the next time the first supply step and the second supply step are performed.

6. The etching method according to claim 1, wherein the first etching gas is a halogen-containing gas, the second etching gas is a basic gas, and the surface of the substrate to be etched is composed of a silicon-containing film.

7. The etching method according to claim 6, wherein the silicon-containing film is silicon oxide.

8. A processing container for storing a substrate in which a reaction occurs and the surface is etched by supplying both a first etching gas and a second etching gas, A first gas supply path through which the first etching gas is supplied from a first gas supply source, A first storage section is provided in the first gas supply passage, which stores the first etching gas and increases the internal pressure, A second gas supply path through which the second etching gas is supplied from a second gas supply source, A second storage section is provided in the second gas supply passage, which stores the second etching gas and increases the internal pressure, A first valve is provided downstream of the first storage section of the first gas supply passage and opens to supply the first etching gas from the first storage section into the processing container during the first period, A second valve is provided downstream of the second storage section of the second gas supply path, and opens to supply the second etching gas during a period in which only one of the first etching gas and the second etching gas is supplied from the second storage section into the processing container, and the second etching gas is supplied during a second period in which at least one of the start and end points differs from that of the first period. A third valve is provided on the upstream side of the first storage section in the first gas supply line, A fourth valve is provided on the upstream side of the second storage section in the second gas supply passage, With the first valve closed and the third valve open, the first etching gas is supplied to the first storage section from the first gas supply source to increase the internal pressure of the first storage section, and with the second valve closed and the fourth valve open, the second etching gas is supplied to the second storage section from the second gas supply source to increase the internal pressure of the second storage section. A control unit controls the opening and closing of the first valve, second valve, third valve, and fourth valve so that the first valve is opened with the third valve closed in order to supply the first etching gas into the processing container, the second valve is opened with the fourth valve closed in order to supply the second etching gas into the processing container, and an overlapping period is formed in which the first period and the second period overlap. An etching apparatus equipped with the following features.

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