Patent Application
20250183047
The present disclosure relates to a substrate processing method and a substrate processing apparatus.
When manufacturing a semiconductor device, there may be a case where the Si film of a Si film and a SiGe film formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) serving as a substrate is selectively etched. For example, Patent Document 1 describes that the selective etching is performed by using an F2 gas and an NH3 gas as etching gases and setting the ratio of the NH3 gas to the etching gases to a predetermined value.
According to one embodiment of the present disclosure, there is provided a substrate processing method including: a first step of supplying processing gases including a halogen-containing gas and a basic gas to a substrate having a recess with side walls formed of a silicon film and an inner wall formed of a germanium-containing film to alter a surface of the silicon film and produce a reaction product; a second step of removing the reaction product to widen a width of the recess; a step of performing a cycle including the first step and the second step multiple times; and a step of performing the first step of a former cycle under a first processing condition and performing the first step of a latter cycle under a second processing condition different from the first processing condition.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure.
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.
An embodiment of the substrate processing method of the present disclosure will be described.
A mask film 14 is stacked on the uppermost Si film 13 of the above-mentioned repeated structure to prevent the Si film 13 from being etched from above. A recess extending in the vertical direction from the mask film 14 to the upper side of the underlayer film 11 is formed. This recess is a groove 15 extending in the front-to-back direction of the paper surface in
The groove 15 and the recesses 16 are formed to form a symmetrical structure, and the vertical widths of the recesses 16 are the same or approximately the same. Hereinafter, the recesses 16 on the upper side of the Si film 13, the recesses 16 on the lower side of the Si film 13, and the recesses 16 between the upper and lower sides of the Si film 13 may be referred to as a top recess 16, a bottom recess 16, and a middle recess 16, respectively. The height of the stacked body formed by the SiGe film 12 and the Si film 13 (=the height from the upper surface of the underlayer film 11 to the lower end of the mask film 14) is, for example, 4 μm.
When a gas is supplied to the wafer W, the gas is introduced into the groove 15 and further into the recesses 16 of respective stages. In the present embodiment, as described above, the processing gas is introduced into each recess 16 from the surface of the wafer W to thereby etch the lower surface side of the upper wall 21 and the upper surface side of the lower wall 22. That is, the thickness of the Si film 13 forming the side wall of the recess 16 is reduced, and the recess 16 is widened in the vertical direction. Due to this widening, the side wall 23 of the recess 16 after etching is formed of the SiGe film 12 and the Si film 13.
Specifically, the etching process is as follows. An F2 (fluorine) gas, which is a halogen-containing gas, and an NH3 gas, which is a basic gas, are supplied to the wafer W as processing gases, and the surface of the Si film 13 constituting the upper wall 21 and the lower wall 22 is altered to generate a reaction product. The process of altering the Si film 13 by the processing gases is called a processing gas supply process. Then, a heating process is performed in which the wafer W is heated to sublimate the reaction product and widen the recess 16. The reaction product to be sublimated includes various products such as AFS, which will be described later. The vertical width of the recess 16 is made to a desired size by repeating a cycle consisting of the processing gas supply process, which is a first process, and the heating process, which is a second process. Each of the processing gas supply process and the heating process is performed in a state in which the wafer W is accommodated in a processing container in which a vacuum atmosphere is formed under a predetermined pressure.
The above-mentioned processing gases act mainly on the Si film 13 out of the Si film 13 and the SiGe film 12. Therefore, the Si film 13 is etched selectively with respect to the SiGe film 12. The above-mentioned reaction product is ammonia fluorosilicate [AFS:(NH4)SiF6]. In the following description, unless otherwise specified, the processing gas supply time refers to the processing gas supply time in one cycle, and refers to the time during which both the F2 gas as a halogen-containing gas and the NH3 gas as a basic gas are supplied to the wafer W.
It is desired that the recess 16 after etching meets the first to third requirements described below. The first requirement is that the roughness (surface roughness) of the lower surface of the upper wall 21 and the upper surface of the lower wall 22, which are the Si film 13, be relatively small. The second requirement is described below. Even after etching, as before etching, the upper wall 21 and the lower wall 22 and the side wall 23 form an angle of 90° or approximately 90° on the inner side of the recess 16. The formation of such an angle results in high uniformity of the vertical width between the opening side and the inner side of the recess 16. For the sake of convenience of description, the shape of the recess 16 in which such an angle is formed and the uniformity of the vertical width is high will be described as a rectangular shape. On the other hand, the shape of the recess 16 in which such an angle is not formed, the recess 16 is a horizontally inclined U-shape in a vertical cross section, and the vertical width on the inner side is smaller than that on the opening side will be described as a round shape. The second requirement is that the shape of the recess 16 be closer to a rectangular shape (the rectangularity be high).
The third requirement is that the variation in the vertical widths of the recesses 16 at respective heights be suppressed. In other words, the third requirement is that the variation in the amount of etching be suppressed among the top, middle, and bottom recesses 16.
The roughness of the Si film 13 regarding the first requirement will be described in detail. The Si film 13 reacts with the F2 gas and the NH3 gas, which are the processing gases, as shown in the following formula 1 to produce a product (SiF4). This SiF4 reacts as shown in formula 2 to produce AFS. The roughness of the Si film 13 after etching varies depending on the processing conditions, but it is thought that the amount of AFS produced during the processing gas supply process involves the roughness of the Si film 13 after etching.
Si+F2+NH3→SiF4+NH3 formula 1
SiF4+H2+F2+2NH3→(NH4)SiF6 formula 2
Hereinafter, differences in roughness that are believed to be caused by differences in the amount of AFS produced will be described with reference to
Referring to
The state in which the surface roughness is relatively small as shown in
Next, the shape of the recess 16 after etching regarding the second requirement will be described. Depending on the processing conditions, the shape of the recess 16 after etching is changed between a rectangular shape and a round shape. The process presumed to occur until the rectangular shape and the round shape are formed will be described below. Referring first to
The F2 gas 41 and the NH3 gas 42 act on the side wall 23 in addition to the upper wall 21 and the lower wall 22. The surface layer of the SiGe film 12 constituting the side wall 23 is altered and slightly etched, releasing a GeF4 (germanium tetrafluoride) gas 43. By etching the side wall 23 in this way, a portion of the Si film 13 is newly exposed in the recess 16 on the inner of the recess 16, thereby forming the upper wall 21 and the lower wall 22 of the recess 16 (lower part in
The newly exposed portion 44 is exposed to the recess 16 during the supply of the processing gases and, therefore, is exposed to the F2 gas 41 and the NH3 gas 42 for a shorter period of time than the portions of the Si film 13 that form the upper wall 21 and the lower wall 22 before etching. Therefore, the amount of reaction with the F2 gas 41 and the NH3 gas 42 is relatively small. In addition, the F2 gas 41 and the NH3 gas 42 are less likely to enter the recess 16 toward the inner side. From the above, the amount of reaction with the F2 gas 41 and the NH3 gas 42 is smaller in the inner side of the recess 16 for the upper wall 21 and the lower wall 22 including the newly exposed portion 44. However, the GeF4 gas 43 is reactive with the Si film 13, and is generated from the SiGe film 12. The GeF4 gas 43 reacts relatively strongly with the Si film 13 on the inner side of the recess 16. Therefore, the Si film 13 reacts with high uniformity from the opening of the recess 16 to the inner side (upper part in
Next, the presumed process of forming the round shape will be described. When the reaction between the surface layer of the SiGe film 12 and the processing gases proceeds from the state shown in the lower part in
Next, the variation in the amount of etching among the top, middle, and bottom regarding the third requirement will be described. Since the processing gases are less likely to enter toward the inner side of the groove 15, when the processing gas is supplied for a relatively short time, the upper wall 21 and the lower wall 22 of the recess 16 are more likely to come into contact with the processing gases and react with the processing gases in the order of top>middle>bottom. Accordingly, the amount of etching increases in this order.
However, as shown in the evaluation tests described later, it has been confirmed that the longer the processing gas supply time, the greater the amount of etching becomes in the bottom side (i.e., the order of the amount of etching becomes top<middle<bottom). This is considered to be due in part to the fact that the longer the processing gas supply time, the thicker the AFS layer 31 formed becomes in the top side (the opening side of the groove 15), thereby preventing the upper wall 21 and the lower wall 22 from reacting with the processing gases. Furthermore, the greater the flow rate of the NH3 gas, the easier it is for the thickness of the AFS layer 31 on the top side to increase, and the greater the amount of etching tends to be in the bottom side.
As described above, by setting the processing conditions in which the NH3 gas flow rate ratio is relatively small and/or the processing gas supply time is relatively short, the recess 16 after etching tends to have micro-roughness, a rectangular shape, and a large amount of etching on the top side. Conversely, by setting the processing conditions in which the NH3 gas flow rate ratio is relatively large and/or the processing gas supply time is relatively long, the recess 16 after etching tends to have large roughness, a round shape, and a large amount of etching on the bottom side. Regarding the NH3 gas flow rate ratio and the processing gas supply time, the appropriate range for keeping the roughness within an allowable range, the appropriate range for forming the rectangular shape, and the appropriate range allowing for the uniform amount of etching between the top and bottom do not necessarily coincide. Therefore, when the cycle consisting of the processing gas supply process and the heating process is repeatedly performed, if the processing gas supply process of each cycle is set to the same processing conditions, it is difficult to fully meet all of the above-mentioned first to third requirements.
Therefore, in the present embodiment, the processing conditions are set to be different between the processing gas supply process performed in the former stage cycle and the processing gas supply process performed in the latter stage cycle.
By changing the processing conditions as described above, it is possible to prevent a particular tendency from appearing strongly in the roughness, the shape of the recess, and the etching amount between the top, middle, and bottom, as compared with a case where processing is performed under a single processing condition, and to meet the first to third requirements. However, as will be shown later as an evaluation test, it has been confirmed that the shape and roughness of the recess 16 after etching are relatively more affected by the processing conditions performed in the former stage cycle than in the latter stage cycle. In other words, when the processing gas supply process in the former stage cycle is performed under conditions in which the rectangular shape and the micro-roughness are obtained, the recess 16 after etching tends to have the rectangular shape and the micro-roughness. Conversely, when the processing gas supply process in the former stage cycle is performed under conditions that the round shape and the large roughness are obtained, the recess 16 after etching tends to have the round shape and the large roughness.
It is sufficient that the roughness falls within a tolerance even if it is formed slightly. Therefore, for the purpose of forming the rectangular shape, the first processing condition in the former stage cycle may be a processing condition that tends to obtain the rectangular shape and the micro-roughness, and the second processing condition in the latter stage cycle may be a processing condition that tends to obtain the round shape and the large roughness compared to the first processing condition. Therefore, specifically, the NH3 gas flow rate ratio is made smaller in the first processing condition than in the second processing condition, or the processing gas supply time is made shorter in the first processing condition than in the second processing condition. Furthermore, in order to increase the tendency to form the rectangular shape, it is preferable that after setting the first processing condition in the former stage cycle and the second processing condition in the latter stage cycle, for example, the number of times the former stage cycle is performed (X times) are set to be greater than or equal to the number of times the latter cycle is performed (Y times).
In addition, there may be a case where the first requirement (requirement to reduce roughness) is more important than the second requirement (requirement to increase rectangularity). In that case, as described above, the influence of the first processing condition in the former stage cycle remains relatively large on the recess 16 after etching. Therefore, a condition that relatively reduces roughness is selected as the first processing condition. Then, a condition that corrects the etching amount between the top, middle, and bottom and changes the shape of the recess 16 so as to increase the rectangularity may be selected as the second processing condition in the latter stage cycle. Specifically, the NH3 gas flow rate ratio is made smaller in the first processing condition than in the second processing condition, or the processing gas supply time is made shorter in the first processing condition than in the second processing condition. In this way, even when a high roughness reduction effect is intended to obtain, for the purpose of increasing the effect, it is preferable that, for example, the number of times the former stage cycle is performed (X times) is set to be greater than or equal to the number of times the latter stage cycle is performed (Y times).
In the present embodiment, in order to increase the rectangularity, the NH3 gas flow rate ratio is set to be smaller in the first processing condition than in the second processing condition, the processing gas supply time is set to be shorter in the first processing condition than in the second processing condition, and the number of times the first cycle is performed (X times) is set to be greater than the number of times the second cycle is performed.
As a more specific example of the processing conditions, the NH3 gas flow rate ratio (the flow rate of the NH3 gas/the flow rate of the F2 gas) is set to fall, for example, within a range of 0.01 to 0.014 in each of the first processing condition and the second processing condition, based on the results of the evaluation tests described later. Therefore, the NH3 gas flow rate ratio in at least one of the first processing condition and the second processing condition is smaller than 0.014. In addition, the processing gas supply time is set to fall, for example, within a range of 10 seconds to 15 seconds in each of the first processing condition and the second processing condition. In this specification, the processing gas supply time is the time during which the halogen-containing gas (F2 gas in the present embodiment) and the basic gas (NH3 gas in the present embodiment) constituting the processing gases are simultaneously supplied to the wafer W (i.e., the time during which they are supplied into the processing container that accommodates the wafer W).
A substrate processing apparatus 5, which is one embodiment of the apparatus for performing the processing described in the flowchart of
The loading/unloading part 51 includes an atmospheric pressure transfer chamber 53 provided with a first substrate transfer mechanism 52 and kept under an atmospheric pressure, and a carrier placement table 55 on the side of the atmospheric pressure transfer chamber 53 on which a carrier 54 storing wafers W is placed. In the drawing, reference numeral 56 denotes an aligner arranged adjacent to the atmospheric pressure transfer chamber 53. The aligner 56 is provided to rotate the wafer W to optically obtain an amount of eccentricity and to align the wafer W with respect to the first substrate transfer mechanism 52. The first substrate transfer mechanism 52 transfers the wafer W between the carrier 54 on the carrier placement table 55, the aligner 56, and the load lock chamber 61.
A second substrate transfer mechanism 62 having, for example, a multi-joint arm structure is provided in each load lock chamber 61. The second substrate transfer mechanism 62 transfers the wafer W between the load lock chamber 61, the thermal processing module 60, and the processing module 7. The inside of the processing container constituting the thermal processing module 60 and the inside of the processing container constituting the processing module 7 are kept in a vacuum atmosphere, and the inside of the load lock chamber 61 can be switched between an atmospheric pressure atmosphere and a vacuum atmosphere so that the wafer W can be transferred between the inside of the processing container kept in the vacuum atmosphere and the atmospheric pressure transfer chamber 53.
In the drawing, reference numeral 63 denotes openable/closable gate valves that are provided between the atmospheric pressure transfer chamber 53 and the load lock chamber 61, between the load lock chamber 61 and the thermal processing module 60, and between the thermal processing module 60 and the processing module 7, respectively. The thermal processing module 60 includes the above-mentioned processing container, an evacuation mechanism for evacuating the inside of the processing container to form a vacuum atmosphere, and a stage provided in the processing container and capable of heating the wafer W placed thereon, and the like. The thermal processing module 60 is configured to be able to execute the heating process described above.
The processing module 7 will be described with reference to the vertical side view of
A temperature regulator 82 is embedded in the stage 81, and the wafer W placed on the stage 81 is adjusted to the temperature described below. The temperature regulator 82 is configured as a flow path that is a part of a circulation path through which a temperature adjustment fluid such as water or the like flows. The temperature of the wafer W is adjusted by heat exchange with the fluid. However, the temperature regulator 82 is not limited to being a flow path for such a fluid, and may be configured, for example, by a heater for performing resistance heating.
One end of an exhaust pipe 83 is opened into the processing container 71, and the other end of the exhaust pipe 83 is connected to an evacuation mechanism 85 constituted by, for example, a vacuum pump via a valve 84, which is a pressure changing mechanism. By adjusting the opening degree of the valve 84, the pressure inside the processing container 71 is set to the pressure range described later, and processing is performed.
A gas shower head 86, which is a processing gas supply mechanism, is provided at the upper side of the processing container 71 so as to face the stage 81. The downstream sides of gas supply paths 91 to 94 are connected to the gas shower head 86, and the upstream sides of the gas supply paths 91 to 94 are connected to gas supply sources 96 to 99 via flow rate regulators 95, respectively. Each flow rate regulator 95 includes a valve and a mass flow controller. The gases supplied from the gas supply sources 96 to 99 are supplied to the downstream side and cut off by opening and closing a valve included in the flow rate regulator 95.
An F2 gas, an NH3 gas, an Ar (argon) gas, and an N2 (nitrogen) gas are supplied to the gas supply sources 96, 97, 98, and 99, respectively. Thus, the HF gas, the NH3 gas, the Ar gas, and the N2 gas can be supplied into the processing container 71 from the gas shower head 86. The Ar gas and the N2 gas are supplied into the processing container 71 as carrier gases together with the F2 gas and the NH3 gas.
As shown in
The transfer path of the wafer W in the substrate processing apparatus 5 will be described. The carrier 54 storing wafers W on which the respective films are formed as shown in
Among the above cycles, in the first to Xth cycles, the processing gas supply process is performed under the first processing condition as shown in
The processing gas supply process in the above-described cycles will be supplementarily described. In the processing gas supply process, the inside of the processing container 71 of the processing module 7 is evacuated to, for example, 100 mTorr (13.3 Pa) to 10 Torr (1333 Pa), and the temperature of the wafer W is adjusted to, for example, −20 degrees C. to 60 degrees C. In this state, the F2 gas and the NH3 gas are supplied into the processing container 71 in parallel (step T1). The time for supplying the F2 gas and the NH3 gas and the flow rate ratios of the F2 gas and the NH3 gas in step T1 are the processing gas supply time and the NH3 gas flow rate ratio, which have been described so far. After the supply of the F2 gas and the NH3 gas is stopped, an N2 gas is supplied into the processing container 71 together with the evacuation of the inside of the processing container 71, so that the F2 gas and the NH3 gas remaining in the processing container 71 are purged (step T2). After this purging, the wafer W is unloaded from the processing container 71. Supplementarily explaining the heating process in the above-described cycles, in the heating process, the wafer W is heated to a temperature higher than the temperature of the wafer W in steps T1 and T2, for example, to a temperature in a range of 80 degrees C. to 300 degrees C., thereby sublimating the above-mentioned reaction products.
According to the present embodiment described above, the first to third requirements can be met by setting different processing conditions in the processing gas supply processes for the former stage cycle and the latter stage cycle. That is, for the recess 16 after etching, the roughness of the Si film 13 forming the upper wall 21 and the lower wall 22 can be reduced, the recess 16 can be made rectangular, and the variation in the vertical width of the recess 16 between the top, middle, and bottom can be suppressed. Accordingly, it is possible to increase the yield of semiconductor products manufactured from the wafer W after etching.
Although the number of times the former stage cycle is performed, X times, and the number of times the latter stage cycle is performed, Y times, have been described as being multiple times, the X times and/or the Y times may be one time. Therefore, the former stage cycle and the latter stage cycle do not have to be performed repeatedly. Furthermore, in the examples described above, the NH3 gas flow rate ratio or the processing gas supply time in the processing gas supply process is changed only once, resulting in a two-stage process consisting of the former stage cycle and the subsequent latter stage cycle. The process is not limited to being two-stage, and the processing conditions may be changed two or more times to result in a three or more stage process.
As described above, when performing the two-stage process, in order to form the rectangular shape, it is preferable to set the NH3 gas flow rate ratio to be smaller in the former stage cycle than in the latter stage cycle, or to set the processing gas supply time to be shorter in the former stage cycle than in the latter stage cycle. Furthermore, as described above, it is preferable to set the number of cycles in the former stage cycle to be equal to or greater than the number of cycles in the latter stage cycle. In the case of performing a three or more stage process, for example, the processing conditions of the first stage and the processing conditions of the second and subsequent stages may have such a relationship, and the number of cycles may be set such that, for example, the number of cycles of the first stage is greater than or equal to the number of cycles of the second and subsequent stages.
In the present embodiment, the atmosphere around the wafer W is kept in a vacuum atmosphere from the start of the first cycle to the end of the last cycle. However, for example, the respective cycles may be performed in different apparatuses, and the wafer W may be moved between the apparatuses through an air atmosphere. From the viewpoint of preventing a decrease in throughput, it is preferable to perform processing in a vacuum atmosphere around the wafer W from the first cycle to the last cycle, as in the case of using the above-described substrate processing apparatus 5.
Incidentally, after the processing gas supply process is performed and before the heating process is performed in any cycle, a second fluorine-containing gas may be supplied to further reduce the roughness after the etching of the Si film 13. The second fluorine-containing gas (i.e., halogen-containing gas) is, for example, a HF (hydrogen fluoride) gas, and is therefore a different type of gas from the first fluorine-containing gas, F2 gas, constituting the process gases. The HF gas is supplied to the wafer W in the processing module 7.
The processing procedure in the processing module 7 when supplying the HF gas will be described. After the supply of processing gas (step T1) and the purging of the inside of the processing container 71 (step T2) described above are performed in order, the HF gas is supplied into the processing container 71 (step T3). After the supply of the HF gas is stopped, in step T4, the processing container 71 is supplied with an N2 gas and evacuated as in step T2, and the remaining HF gas is purged. Thereafter, the wafer W is unloaded from the processing module 7. In addition, when supplying the HF gas, which is a roughness reducing gas, in this way, steps T1 to T4 correspond to a first process, step T1 in which both the halogen-containing gas (F2 gas) and the basic gas (NH3 gas) are supplied corresponds to a first supply process, and step T3 in which only one of these gases is supplied corresponds to a second supply process.
It is believed that the supply of the HF gas causes the NH3 contained in the AFS layer 31 formed in step T1 to react with the HF gas to produce a reaction product, and the reaction product slightly etches the surface layer of the Si film 13 coated on the AFS layer 31, thereby reducing roughness.
The processing module 7 performing the above steps T1 to T4 is configured such that, in addition to the gas supply sources 96 to 99 already described, a HF gas supply source is provided and connected to the gas shower head 86 via a flow path. A flow rate regulator 95 is provided in the HF gas flow path, as in the flow paths of other gases, and the HF gas is supplied into the processing container 71 via the gas shower head 86 at a desired flow rate. When the HF gas is supplied into the processing container 71, for example, an Ar gas and an N2 gas are also supplied into the processing container 71 as a carrier gas.
Furthermore, instead of supplying the HF gas to the wafer W as the roughness reducing gas, an NH3 gas may be supplied to the wafer W. When the NH3 gas is supplied in this manner, the NH3 gas reacts with the fluorine component contained in the AFS layer 31 formed in step T1 to generate a reaction product. It is considered that the reaction product slightly etches the surface layer of the Si film 13 coated on the AFS layer 31, thereby reducing roughness.
When the NH3 gas is used as the roughness reducing gas, for example, the F2 gas and the NH3 gas may be supplied together as the processing gases, and the NH3 gas may be continued to be supplied to the wafer W even after the supply of the F2 gas is stopped, thereby omitting the purge with the N2 gas in step T2. In addition, the supply of each of the above-mentioned roughness reducing gases may be performed in any cycle. For example, the supply of each of the above-mentioned roughness reducing gases may be performed in the last cycle of the cycles in each stage, or may be performed in every cycle.
Although it has been described that the temperature of the wafer W is made higher than the temperature during the processing gas supply process in order to remove the reaction products, the present disclosure is not limited thereto. For example, after the above steps T1 and T2 are performed in the processing module 7, the opening degree of the valve 74 arranged in the exhaust pipe 73 may be increased to reduce the pressure in the processing container 71, thereby lowering the sublimation temperature of the reaction products. Accordingly, the present disclosure is not limited to performing one cycle in different processing containers.
As described above, the timings of the ends of supply and the timings of the starts of supply of the F2 gas and the NH3 gas, which are processing gases, may be shifted from each other. In addition, the fluorine-containing gas included in the processing gases is not limited to the F2 gas, and may be, for example, an IF7 gas, an IF5 gas, a ClF3 gas, or an SF6 gas. Incidentally, “containing fluorine” does not mean that fluorine is contained as an impurity, but means that fluorine is contained as a constituent. Similarly, “containing Ge”, which will be described later, means that Ge is contained as a constituent, not as an impurity.
Moreover, the recess 16 is not limited to being laid horizontally. The present disclosure may be applied to a case where the recess 16 is open vertically and the Si film forming the side wall of such a recess 16 is etched. In that case, the recess 16 can be etched so as to meet the first and second requirements (requirements regarding the roughness and the rectangular shape) among the first to third requirements described above.
It is considered that even if the side wall 23 of the recess 16 is formed by a Ge film instead of the SiGe film 12, it is possible to produce GeF4 using a fluorine-containing gas and to etch the inner side of the recess 16. Therefore, the side wall 23 of the recess 16 is not limited to being formed by the SiGe film 12, and may be formed by any film including a Ge film.
The embodiments disclosed herein should be considered to be exemplary and not limitative in all respects. The above-described embodiments may be omitted, substituted, modified, or combined in various forms without departing from the scope and spirit of the appended claims.
Evaluation tests 1 to 5 performed on this technique will now be described. In each test, a cycle consisting of a processing gas supply process and a heating process is performed on the substrate having the film structure described in
The following three kinds of dimensions were measured in each evaluation test. One dimension is the horizontal width of the groove 15. Hereinafter, this horizontal width is referred to as a groove width dimension. Another dimension is the vertical width of the recess 16 at a position spaced by a predetermined small distance from the opening of the recess 16 toward the inner side of the recess 16. Hereinafter, this vertical width is referred to as an opening side dimension. A further dimension is the vertical width of the recess 16 at a position spaced by a predetermined small distance from the side wall 23 of the recess 16 toward the opening of the recess 16. Hereinafter, this vertical width is referred to as an inner side dimension.
Among the recesses 16 formed in multiple stages, a plurality of recesses 16 in predetermined stages are regarded as top recesses 16 in the evaluation tests. For each of the groove width dimension, the opening side dimension, and the inner side dimension of the top recesses 16, (dimension after etching—dimension before etching)/2 is calculated. This calculation is performed for each of the plurality of top recesses 16. Then, for each of the calculated values obtained from the groove width dimension, the calculated values obtained from the opening side dimension, and the calculated values obtained from the inner side dimension, average values among the recesses 16 are calculated, and the obtained average values are regarded as a groove width etching amount, an opening side etching amount, and an inner side etching amount in the top recesses 16. The groove width dimension of each top recess 16 is obtained from between the upper walls 21 of the recesses 16 facing each other in the horizontal direction.
Similarly, a plurality of recesses 16 in predetermined stages are regarded as middle recesses 16 and bottom recesses 16, respectively. A groove width etching amount, an opening side etching amount, and an inner side etching amount are calculated for each of the middle recesses 16 and the bottom recesses 16. The etching amounts calculated in this way are divided by a predetermined reference amount, and standardized values are obtained as shown in
In evaluation tests 1-1 to 1-3, substrates were etched by repeating a cycle of a processing gas supply process and a heating process. The combination of the number of cycles and the pressure in the processing container 71 during the processing gas supply process was changed between evaluation tests 1-1 to 1-3. In evaluation test 1-1, the pressure in the processing container 71 was 200 Pa (1.5 Torr), and the number of cycles was 9. In evaluation test 1-2, the pressure in the processing container 71 was 666.6 Pa (5 Torr), and the number of cycles was 9. In evaluation test 1-3, the pressure in the processing container 71 was 666.6 Pa (5 Torr), and the number of cycles was 3. Each processing condition, such as the temperature of the wafer W during the processing gas supply, the supply time of the process gases, or the NH3 gas flow rate ratio, was set to a value falling within the range described in the embodiment.
The results of evaluation test 1 indicate the average values of the values obtained from the top, middle, and bottom recesses 16. In evaluation test 1-1, the groove width etching amount was 1.26, the opening side etching amount was 1.62, and the inner side etching amount was 1.66. In evaluation test 1-2, the etching progressed significantly, causing the upper wall 21 and the lower wall 22 to disappear, and each etching amount could not be measured. In evaluation test 1-3, the disappearance of the upper wall 21 and the lower wall 22 was prevented, and the groove width etching amount was 1.78, the opening side etching amount was 1.9, and the inner side etching amount was 1.9.
From the above results of evaluation test 1, it is noted that the etching rate can be increased by relatively increasing the pressure in the processing container 71 when the processing gases are supplied, and excessive etching can be prevented by appropriately setting the number of cycles. It is also noted that the pressure in the processing container 71 is preferably greater than 1.5 Torr (200 Pa), and more preferably equal to or greater than 5 Torr (666.6 Pa).
In evaluation tests 2-1 to 2-5, each substrate was processed by performing the processing gas supply process and the heating process once, without repeating the cycle of these processes. The processing gas supply time was set to different values between evaluation tests 2-1 to 2-5, and was set to 5 seconds, 10 seconds, 15 seconds, 25 seconds, and 35 seconds in evaluation tests 2-1, 2-2, 2-3, 2-4, and 2-5, respectively. In addition, each processing condition, such as the NH3 gas flow rate ratio, the temperature of the wafer W during the processing gas supply, or the pressure inside the processing container 71, was set to a value falling within the range described in the embodiment.
The graphs of
As is clear from the graph of
In evaluation tests 3-1 to 3-6, substrates were processed by making the combination of the NH3 gas flow rate ratio and the processing gas supply time different for each substrate. The number of cycles was 3. The processing gas supply time was set to 10 seconds in evaluation tests 3-1 to 3-3, and to 15 seconds in evaluation tests 3-4 to 3-6. The NH3 gas flow rate ratio was set to 0.01 in evaluation tests 3-1 and 3-4, 0.014 in evaluation tests 3-2 and 3-5, and 0.02 in evaluation tests 3-3 and 3-6. Other processing conditions were the same as those in evaluation test 2. Table 1 below summarizes the results obtained in evaluation Test 3. In evaluation test 3, the etching amount of each portion was obtained in the same way as in evaluation test 2.
Regarding the roughness of the upper wall 21 and the lower wall 22 of the recess 16 after etching, micro-roughness was confirmed in the middle and bottom recesses 16 of evaluation test 3-1. Furthermore, large roughness was confirmed in the top recess 16 of evaluation test 3-3 and in the top, middle, and bottom recesses 16 of evaluation test 3-6. Regarding the shape of the recess 16 after etching, the top, middle, and bottom recesses 16 of evaluation tests 3-1 and 3-4 and the bottom recess 16 of evaluation test 3-2 were rectangular.
Therefore, it was confirmed from evaluation test 3 that micro-roughness was obtained when the NH3 gas flow rate ratio is relatively small and the etching time is relatively short. It was also confirmed that large roughness was obtained when the NH3 gas flow rate ratio is relatively large. As described in the embodiment, it is considered that the roughness states are different due to the difference in the amount of AFS produced. It was also confirmed from evaluation test 3 that there is a tendency for a rectangular shape to be formed when the NH3 gas flow rate ratio is relatively small. It can be seen that in order to form a rectangular shape, it is preferable to make the flow rate ratio smaller than 0.014, and more preferably 0.01 or less.
However, in evaluation tests 3-1, 3-4, and 3-5 in which the NH3 gas flow rate ratio is set to 0.01 to obtain the rectangular shape, the variation in the amount of etching between the top and bottom was relatively large. Therefore, the results of evaluation tests 3-1 to 3-6 did not sufficiently meet one or more of the first to third requirements.
In evaluation tests 4-1 to 4-5, substrates were processed by making the combination of the NH3 gas flow rate ratio, the processing gas supply time, and the number of cycles different for each substrate. The processing gas supply time was set to 10 seconds, 15 seconds, 15 seconds, 12.5 seconds, and 10 seconds in evaluation tests 4-1, 4-2, 4-3, 4-4, and 4-5, respectively. The NH3 gas flow rate ratio in the processing gases was set to 0.01 in evaluation tests 4-1, 4-2, and 4-4, and to 0.014 in evaluation tests 4-3 and 4-5, respectively. The number of cycles was set to 3 in evaluation tests 4-1 to 4-4, and 4 in evaluation test 4-5. Other processing conditions were the same as those in evaluation tests 2 and 3. Table 2 below summarizes the results of evaluation Test 4. In evaluation test 4 and evaluation test 5 described below, the etching amount of each portion was obtained in the same way as in evaluation test 3.
Regarding the roughness of the upper wall 21 and lower wall 22 of the recess 16 after etching, micro-roughness was confirmed in the middle and bottom recesses 16 of evaluation tests 4-1 and 4-4 and in the bottom recess 16 of evaluation test 4-5. The roughness of other recesses 16 was kept within a desirable range. The comparison among evaluation tests 4-1, 4-2, and 4-4, which have the same number of cycles and the same NH3 gas flow rate ratio indicates that micro-roughness is more likely to obtain when the processing gas supply time is short as described in the embodiment.
Regarding the shape of the recesses 16 after etching, the top, middle, and bottom recesses 16 in evaluation tests 4-1 and 4-2 and the middle and bottom recesses 16 in evaluation tests 4-4 and 4-5 were rectangular, while other recesses 16 were round. The comparison between evaluation tests 4-1, 4-2, and 4-4 indicates that there is a tendency for the recesses 16 to have a rectangular shape when the processing gas supply time is relatively short as described in the embodiment. In addition, in evaluation tests 4-1, 4-2, and 4-4 in which the NH3 gas flow rate ratio was set to 0.01, two or three of the top, middle, and bottom recesses are rectangular. Therefore, it is noted that in order to obtain a rectangular shape, it is preferable to set the NH3 gas flow rate ratio to 0.01 or less.
As for the opening side etching amount and the inner side etching amount, in evaluation tests 4-2, 4-4, and 4-5, the top etching amount was larger than the middle and bottom etching amounts. In other words, there was a relatively large variation in the etching amount between the top, middle, and bottom. Furthermore, in evaluation test 4-3, the top etching amount was smaller than the middle and bottom etching amounts. The above results indicate that the recesses 16 of each substrate in evaluation test 4 did not sufficiently meet one or more of the first to third requirements.
By the way, further verification of the results of evaluation test 4 indicates that when the NH3 gas flow rate ratio is 0.01, the recess 16 tends to be rectangular and the amount of etching of the top tends to be large. Furthermore, when the NH3 gas flow rate ratio is 0.014, the recess 16 tends to be round and the tendency for the amount of etching of the top to be large is alleviated compared to when the flow rate ratio is 0.01. Moreover, when the NH3 gas flow rate ratio is 0.01 and 0.014, there are cases where the roughness is reduced within a desirable range. However, when the NH3 gas flow rate ratio in the processing gases is 0.01 and 0.014, the desired result was not obtained for the roughness when the processing gas supply time is 10 seconds.
Considering the results of evaluation test 4 and the results of evaluation test 2 in which the processing gas supply time is preferably 10 to 15 seconds, the NH3 gas flow rate ratio in the processing gases may be set to a range greater than 0.01 and less than 0.014, and the processing gas supply time may be set to a range greater than 10 seconds and less than 15 seconds. In other words, it is considered that an allowable range which is more suitable for the first to third requirements than the processing conditions set in evaluation test 4 is searched from such ranges of respective parameters, and processing is performed using values within the allowable range. However, the allowable range for the NH3 gas flow rate ratio is an even narrower range in the relatively narrow range of 0.01 to 0.014. Therefore, for example, when the film structure to be etched is changed slightly, it is difficult to deal with the change by changing the flow rate ratio, which may lead to a concern that the practicality is low. Therefore, the multi-stage processing performed by changing the processing conditions described in the embodiment is effective.
In evaluation tests 5-1 to 5-5, two-stage processing (former stage cycle and latter stage cycle) was performed by changing the processing conditions as described in the embodiment. The combination of the processing conditions in the former stage cycle and the latter stage cycle was changed for each substrate. The processing conditions other than the NH3 gas flow rate ratio, the processing gas supply time, and the number of cycles were the same as the processing conditions in evaluation test 4.
The NH3 gas flow rate ratio and the processing gas supply time in the former stage cycle of evaluation tests 5-1, 5-2, and 5-4 and in the latter stage cycle of evaluation tests 5-3 and 5-5 were set to the same processing conditions as the processing conditions under which the rectangular shape is obtained in evaluation test 4. The NH3 gas flow rate ratio and the processing gas supply time in the latter stage cycle of evaluation tests 5-1, 5-2, and 5-4 and in the former stage cycle of evaluation tests 5-3 and 5-5 were set to the same processing conditions under which the roughness is reduced to fall within a desirable range in evaluation test 4. Table 3 below summarizes the processing conditions and the results of evaluation test 5.
Considering the difference in the number of cycles in addition to the NH3 gas flow rate ratio and the processing gas supply time, the tendency to form a rectangular shape is as follows: former stage of evaluation test 5-1>former stage of evaluation test 5-2 and latter stage of evaluation test 5-3>former stage of evaluation test 5-4>latter stage of evaluation test 5-5. The tendency to reduce roughness is as follows: latter stage of evaluation test 5-2, former stage of evaluation test 5-3 and former stage of evaluation test 5-5>latter stage of evaluation test 5-1 and latter stage of evaluation test 5-4.
The results of evaluation tests 5-1 to 5-5 are verified for the difference in the amount of etching between the top and bottom. Stating the outline of this verification, the difference in the amount of etching of the recess 16 between the top and bottom obtained from evaluation test 4 is corrected according to the number of cycles. Thus, the expected difference in the amount of etching between the top and bottom when only the former stage cycle in evaluation test 5 is performed and the expected difference in the amount of etching between the top and bottom when only the latter stage cycle in evaluation test 5 is performed are calculated. The expected differences in the amount of etching between the top and bottom are summed up to obtain an expected difference in the amount of etching. This expected difference in the amount of etching and the expected difference in the amount of etching obtained in the process of obtaining the difference in the expected amount of etching are compared with the actual difference in the amount of etching between the top and bottom obtained from evaluation test 5.
To explain more specifically, in evaluation test 5-1, the amount of etching on the opening side of the top and the amount of etching on the inner side of the top are referred to as A1X1 and A2X2, respectively, and the average value thereof is referred to as A3X3. The amount of etching on the opening side of the bottom and the amount of etching on the inner side of the bottom are referred to as B1Y1 and B2Y2, respectively, and the average value thereof is referred to as B3Y3. The value calculated as A3X3-B3Y3 is referred to as a difference in the amount of etching between the top and bottom in evaluation test 5-1. The difference in the amount of etching between the top and bottom calculated in this way was a positive value. Therefore, in evaluation test 5-1, the amount of etching on the top was greater than that on the bottom.
Evaluation tests 4-1 and 4-3 were conducted under the same conditions as the former and latter stage cycles of evaluation test 5-1 except for the number of cycles. For evaluation test 4-1, (average value of the opening side etching amount of the top and the inner side etching amount of the top)−(average value of the opening side etching amount of the bottom and the inner side etching amount of the bottom)=C1A1 was obtained. The number of cycles in evaluation test 4-1 is 3, but the number of cycles in the former stage of evaluation test 5-1 is 4. Therefore, C1A1 was corrected by multiplying by 4/3, and the obtained value was set as a difference in the expected etching amount C2A2 (=C1A1×4/3). The value of C2A2 was a positive value. In other words, the etching amount of the top is larger than that of the bottom.
Similarly, for evaluation test 4-3, which was performed under the same conditions as the latter stage cycle, the difference in the expected etching amount was calculated. Specifically, for evaluation test 4-3, (average value of the etching amount on the opening side of the top and the etching amount on the inner side of the top)−(average value of the etching amount on the opening side of the bottom and the etching amount on the inner side of the bottom)=C1A′1 was calculated. The number of cycles in evaluation test 4-3 is 3, but the number of latter stage cycles in evaluation test 5-1 is 1. Therefore, C1A′1 was corrected by multiplying by ⅓, and the obtained value was set as a difference in the expected etching amount C2A′2(=C′A′1×⅓). The value of C2A′2 was a negative value. In other words, the etching amount of the bottom is larger than that of the top.
The expected total etching amount C2A2+C2A′2 was compared with A3X3-B3Y3 in evaluation test 5-1, indicating that they are almost the same. Furthermore, C2A2 was larger than A3X3-B3Y3. The above calculation results indicate that, even if a relatively large bias in the etching amount occurs between the top side and the bottom side at the end of the first stage of the two-stage processing described in the embodiment, the bias can be offset by performing the second stage processing in which the etching amount is increased on the opposite side of the top side or bottom side in the first stage processing.
As described above, in evaluation test 4-1, each recess 16 was rectangular, and microroughness was obtained in the middle and bottom recesses 16. In evaluation test 4-3, each recess 16 was intermediate in shape, and the roughness of each recess 16 was within a desirable range. In contrast, the test results in evaluation test 5-1 indicate that the middle and bottom recesses 16 were rectangular, and microroughness was obtained in the top, middle, and bottom recesses 16. Therefore, the shape and roughness of the recesses 16 were relatively significantly affected by the processing conditions of the former stage cycle.
When the above verification using calculation was performed for evaluation tests 5-2 to 5-5 in the same manner as in evaluation test 5-1, it was estimated that the bias in the amount of etching between the top side and the bottom side is offset by the execution of the former stage cycle and the latter stage cycle. In the verification, the processing conditions of evaluation tests 4-1 and 4-3 were used in evaluation tests 5-2 and 5-3 as in evaluation test 5-1, but the processing conditions of evaluation test 4-2 were used in evaluation tests 5-4 and 5-5. Therefore, the verification was performed using the data of evaluation test 4-2. In addition, the processing conditions of the former stage cycle and the latter stage cycle of evaluation test 5-2 were the same as those of evaluation test 5-1, and the same as those of evaluation test 4-1 and 4-3 except for the number of cycles. As shown in Table 3, in evaluation test 5-2, the bottom recess 16 was rectangular, and micro-roughness was obtained in each of the middle and bottom recesses 16. Therefore, in even evaluation test 5-2, as in evaluation test 5-1, the influence of the processing conditions of the former stage cycle on the shape and roughness of the recess 16 is relatively large.
Regarding evaluation test 5-3, the former stage cycle and the latter stage cycle are the same as those of evaluation test 4-3 and evaluation test 4-1, respectively, except for the number of cycles. As shown in Table 3, in evaluation test 5-3, the top, middle, and bottom recesses 16 were intermediate in shape, while the roughness thereof was reduced to fall within an allowable range. In evaluation test 4-3, each recess 16 was intermediate in shape, and the roughness of each recess 16 was within an allowable range, whereas in evaluation test 4-1, each recess 16 was rectangular, and micro-roughness was obtained in the middle and bottom recesses 16. Therefore, in evaluation test 5-3 as well, the influence of the processing conditions of the former stage cycle on the shape and roughness of the recess 16 was relatively large.
Regarding evaluation test 5-4, the former stage cycle and the latter stage cycle are the same as those of evaluation test 4-2 and evaluation test 4-3, respectively, except for the number of cycles. As shown in Table 3, in evaluation test 5-4, the bottom recess 16 was rectangular, and micro-roughness was obtained in the bottom recess 16. On the other hand, in evaluation test 4-2, each recess 16 was rectangular, and micro-roughness was obtained in the bottom recess 16. In evaluation test 4-3, each recess 16 was intermediate in shape, and the roughness of each recess 16 was within a desirable range. Therefore, in evaluation test 5-4 as well, the influence of the processing conditions of the former stage cycle on the shape and roughness of the recess 16 was relatively large.
Regarding evaluation test 5-5, the former stage cycle and the latter stage cycle are the same as those of evaluation test 4-3 and evaluation test 4-2, respectively, except for the number of cycles. Furthermore, as described above, in evaluation test 5-5, the roughness of each of the top, middle, and bottom recesses 16 was reduced to fall within an allowable range, and the shape thereof was intermediate. On the other hand, in evaluation test 4-3, each recess 16 was intermediate in shape, and the roughness of each recess 16 was within a desirable range. In evaluation test 4-2, each recess 16 has a rectangular shape, and the bottom recess 16 has micro-roughness. Therefore, in evaluation test 5-5 as well, the influence of the processing conditions of the former stage cycle on the shape and roughness of the recess 16 was relatively large. Incidentally, in evaluation test 5-5, the roughness of the top, middle, and bottom was reduced, and the difference A3X3-B3Y3 in the etching amount between the top and bottom was the smallest in evaluation test 5. The shape of each recess 16 was slightly rounder than that of the recess 16 in evaluation test 5-1 and more rectangular than that of the recess 16 in evaluation test 4-3, and was therefore practical. Therefore, among evaluation tests 5-1 to 5-5, evaluation test 5-5 has the most favorable results.
As described above, it was confirmed from evaluation test 5 that the bias in the amount of etching between the top side and the bottom side in the former stage cycle and the latter stage cycle is offset, and as a result, the amount of etching from the top side to the bottom side can be made highly uniform. It was also confirmed that the processing conditions used in the former stage cycle have a large influence on the shape and roughness of the recess 16 after etching. As described above, the roughness is reduced at the top, middle, and bottom in evaluation tests 5-3 and 5-5. Therefore, it was noted that in order to reduce the roughness in this way, as described in the embodiment, it is preferable to make the NH3 gas flow rate ratio smaller in the first processing condition of the former stage cycle than in the second processing condition of the latter stage cycle. When evaluation tests 5-3 and 5-5 are compared, the differences in the amount of etching between the top and bottom are different, and the difference in the amount of etching is smaller in evaluation test 5-5 than in evaluation test 5-3. Since the processing gas supply time under the second processing condition differs between evaluation tests 5-3 and 5-5, it can be seen that by adjusting the processing gas supply time between the first and second processing conditions, it is possible to control the balance of the etching amount between the top, middle, and bottom while reducing the roughness of each recess 16.
Regarding the rectangularity of the recess 16, the results of evaluation tests 5-1, 5-2, and 5-4 indicate that in order to improve the rectangularity, it is preferable to make the NH3 gas flow rate ratio smaller under the first processing condition than under the second processing condition. Since evaluation test 5-1 has the highest rectangularity, it was confirmed that in order to obtain a higher rectangularity, it is preferable to make the processing gas supply time shorter under the first processing condition than under the second processing condition.
According to the present disclosure, it is possible to reduce the roughness of an etched surface of a silicon film that forms a recess, and to control the shape of the recess.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-150573 | Sep 2022 | JP | national |
This application is a bypass continuation application of international application No. PCT/JP2023/033433 having an international filing date of Sep. 13, 2023 and designating the United States, the international application being based upon and claiming the benefit of priority from Japanese Patent Application No. 2022-150573, filed on Sep. 21, 2022, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/033433 | Sep 2023 | WO |
| Child | 19042043 | US |
