Etching method and plasma processing device

Abstract

The present invention provides an etching method, wherein the temperature of a workpiece is maintained at 30°C or above and 30°C or below, and when the flow rate of the i-th fluorocarbon gas in one or more fluorocarbon gases used for etching is J(i), the number of fluorine atoms and carbon atoms in the elemental composition of the gas are M(i) and N(i), respectively, for all possible values ​​of i, the sum of all J(i)×N(i) / M(i) is Ua, and the flow rate of the k-th hydrogen-containing gas in one or more hydrogen-containing gases used for etching is J(k), the number of hydrogen atoms in the elemental composition of the k-th hydrogen-containing gas is H(k), and for all possible values ​​of k, the sum of all J(k)×H(k) is Ub, Ua / Ub satisfies 0.04<Ua / Ub<0.22. Thus, a workpiece including a silicon oxide film and a silicon nitride film can be etched at one time under conditions common to both films.

Description

Technical Field

[0001] Illustrative embodiments of the present invention relate to an etching method and a plasma processing apparatus. Background Art

[0002] In the manufacture of a NAND flash memory device having a three-dimensional structure, etching of a multilayer film including a silicon oxide film and a silicon nitride film can be performed. For example, the etching method disclosed in Patent Document 1 includes a first step and a second step. In the first step, a plasma of a first processing gas including a fluorocarbon gas and a hydrofluorocarbon gas is generated in a processing container of a plasma processing device in which a processed object is prepared. In the second step, a plasma of a second processing gas including hydrogen, hydrofluorocarbon gas, and nitrogen is generated in a processing container of the plasma processing device. In this method, the first step and the second step are performed alternately and repeatedly.

[0003] The etching method disclosed in Patent Document 2 includes a first plasma processing step and a second plasma processing step. In the first plasma processing step, a plasma of a first processing gas containing a fluorocarbon gas and an oxygen gas is generated in a processing container of a plasma processing device. In the second plasma processing step, a plasma of a second processing gas containing a hydrogen gas, a nitrogen trifluoride gas, a hydrogen bromide gas, and a carbon-containing gas is generated in the processing container. In the first plasma processing step, the temperature of the electrostatic chuck is set to a first temperature. In the second plasma processing step, the temperature of the electrostatic chuck is set to a second temperature lower than the first temperature.

[0004] In addition, Patent Document 3 discloses an etching method. In this method, plasma is generated from hydrogen-containing gas and fluorine-containing gas using high-frequency electric power for plasma generation, and etching target films of silicon oxide film and silicon nitride film are etched using the generated plasma in an extremely low temperature environment below -30°C. In this etching, the difference between the etching rate of a first etching for etching one etching target film and the etching rate of a second etching for etching another etching target film having a structure different from the one etching target film is controlled within ±20%.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent document 1: Japanese Patent Application Publication No. 2016-192483.

[0008] Patent document 2: Japanese Patent Application Publication No. 2016-225437.

[0009] Patent document 3: Japanese Patent Application Publication No. 2016-207840. Summary of the invention

[0010] The technical problem that the invention is intended to solve

[0011] The present invention provides a technology capable of etching a workpiece including two films, a silicon oxide film and a silicon nitride film, at a time using conditions common to both films.

[0012] Technical solutions to solve problems

[0013] In an exemplary embodiment, a method for etching a workpiece is provided. The method includes: placing the workpiece on a mounting table in a processing container of a plasma processing device, and maintaining the temperature of the workpiece within a preset temperature range. Next, in the method, while maintaining the temperature of the workpiece within the temperature range, a plasma of a processing gas is generated in the processing container, and the workpiece is etched using the plasma. The workpiece includes a silicon oxide film and a silicon nitride film. The processing gas includes a first gas and a second gas. The first gas is a fluorocarbon gas. The second gas is a hydrogen-containing gas. The temperature range is above -30°C and below 30°C. The first gas includes p types (p is an integer greater than 1) of a first fluorocarbon gas to a pth fluorocarbon gas. The second gas includes q types (q is an integer greater than 1) of a first hydrogen-containing gas to a qth hydrogen-containing gas. Let the flow rate of the i-th fluorocarbon gas contained in the first fluorocarbon gas to the pth fluorocarbon gas during the execution of the etching process be J(i). Let the number of fluorine atoms contained in the elemental composition of the i-th fluorocarbon gas be M(i). Let the number of carbon atoms contained in the elemental composition of the i-th fluorocarbon gas be N(i). Let the value obtained by summing all J(i)×N(i) / M(i) for all possible values ​​of i (i is an integer greater than 1 and less than p) be Ua. Let the flow rate of the kth hydrogen-containing gas contained in the 1st hydrogen-containing gas to the qth hydrogen-containing gas during the execution of the etching process be J(k). Let the number of hydrogen atoms contained in the elemental composition of the kth hydrogen-containing gas be H(k). Let the value obtained by summing all J(k)×H(k) for all possible values ​​of k (k is an integer greater than 1 and less than q) be Ub. Ua / Ub satisfies 0.04<Ua / Ub<0.22.

[0014] Effects of the Invention

[0015] According to the present invention, it is possible to provide a technique capable of etching a workpiece including two films, a silicon oxide film and a silicon nitride film, at a time using conditions common to both films. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart showing an example of a method according to an exemplary embodiment.

[0017] Figure 2FIG. 1 is a diagram showing an example of a structure of a plasma processing apparatus according to an exemplary embodiment.

[0018] Figure 3 Yes means that it can be Figure 1 A diagram showing an example of the structure of an object to be processed by the method shown.

[0019] Figure 4 It is used to illustrate Figure 1 A diagram showing the temperature range used for the method shown.

[0020] Figure 5 Is used to explain about Figure 1 A diagram showing the conditions of the process gases used in the method shown.

[0021] Figure 6 Is used to explain about Figure 1 A diagram showing the conditions of the second gas in the process gas used in the method shown.

[0022] Figure 7 It is used to illustrate Figure 1 A diagram showing an example of the effect of the method shown.

[0023] Description of Reference Numerals

[0024] 10 ... plasma processing device, 12 ... processing container, 12a ... ground conductor, 12e ... exhaust port, 12g ... opening, 14 ... support, 16 ... lower electrode, 16a ... first component, 16b ... second component, 16f ... flow path, 18 ... electrostatic chuck, 18a ... electrode, 18h ... heater, 18t ... temperature detector, 22 ... DC power supply, 26a ... piping, 26b ... piping, 28 ... gas supply line, 30 ... upper electrode, 32 ... insulating shielding member, 34 ... top plate, 34a ... gas exhaust hole, 36 ... support, 36a ... gas diffusion chamber, 36b ... gas flow hole, 36c ... gas introduction port, 38 ... gas supply pipe, 40 ... gas source group, 42 ... valve group, 44 ... flow controller group, 46…deposition shield, 48…exhaust plate, 50…exhaust device, 52…exhaust pipe, 54…gate valve, 56…conductive component, 62…first high-frequency power supply, 64…second high-frequency power supply, 66…matching device, 68…matching device, 70…DC power supply unit, Cnt…control unit, CU…refrigeration unit, FL1…first film, FL2…second film, FR…focusing ring, GS…gas supply mechanism, HP…heater power supply, IL1…silicon oxide film, IL2…silicon nitride film, MSK…mask, MT…method, PD…stage, PS…main surface, R1…first region, R2…second region, R3…third region, S…processing space, SW…switch, TS…temperature adjustment mechanism, UL…base layer, W…wafer. DETAILED DESCRIPTION

[0025] Various exemplary embodiments are described below. In an exemplary embodiment, a method for etching a workpiece is provided. The method includes: placing the workpiece on a mounting table in a processing container of a plasma processing device, and maintaining the temperature of the workpiece within a preset temperature range. Next, in the method, while maintaining the temperature of the workpiece within the temperature range, a plasma of a processing gas is generated in the processing container, and the workpiece is etched using the plasma. The workpiece includes a silicon oxide film and a silicon nitride film. The processing gas includes a first gas and a second gas. The first gas is a fluorocarbon gas. The second gas is a hydrogen-containing gas. The temperature range is above -30°C and below 30°C. The first gas includes p types (p is an integer greater than 1) of a first fluorocarbon gas to a pth fluorocarbon gas. The second gas includes q types (q is an integer greater than 1) of a first hydrogen-containing gas to a qth hydrogen-containing gas. Let the flow rate of the i-th fluorocarbon gas contained in the first fluorocarbon gas to the pth fluorocarbon gas during the execution of the etching process be J(i). Let the number of fluorine atoms contained in the elemental composition of the i-th fluorocarbon gas be M(i). Let the number of carbon atoms contained in the elemental composition of the i-th fluorocarbon gas be N(i). Let the value obtained by summing all J(i)×N(i) / M(i) for all possible values ​​of i (i is an integer greater than 1 and less than p) be Ua. Let the flow rate of the kth hydrogen-containing gas contained in the 1st hydrogen-containing gas to the qth hydrogen-containing gas during the execution of the etching process be J(k). Let the number of hydrogen atoms contained in the elemental composition of the kth hydrogen-containing gas be H(k). Let the value obtained by summing all J(k)×H(k) for all possible values ​​of k (k is an integer greater than 1 and less than q) be Ub. Ua / Ub satisfies 0.04<Ua / Ub<0.22.

[0026] So far, a technology has been studied that can etch a workpiece containing two films, a silicon oxide film and a silicon nitride film, at one time using conditions common to both films. Such etching can be achieved by setting the temperature of the workpiece to between -30°C and 30°C, and setting the flow rate and element composition of the processing gas containing fluorocarbon gas and hydrogen-containing gas to satisfy 0.04<Ua / Ub<0.22.

[0027] In an exemplary embodiment, the first gas is any one of C4F8 gas, C3F8 gas, and C4F6 gas, or a mixed gas consisting of at least two of C4F8 gas, C3F8 gas, and C4F6 gas. The second gas is any one of H2 gas and CH4 gas, or a mixed gas of H2 gas and CH4 gas.

[0028] In an exemplary embodiment, the process gas further includes a third gas, and the third gas includes a halogen element other than fluorine. The third gas is HBr gas.

[0029] In an exemplary embodiment, the object to be processed includes a first region, a second region, and a mask. The first region and the second region are arranged along the main surface of the object to be processed. The first region and the second region each extend below the main surface. The mask is arranged on the main surface above the first region and the second region, and provides openings for the first region and the second region, respectively. The first region is composed of a first film. The second region is composed of a second film. The first film is a silicon oxide film. The second film has a structure in which a silicon oxide film and a silicon nitride film are alternately stacked. The first region and the second region are etched simultaneously during the etching process.

[0030] In an exemplary embodiment, the workpiece further includes a third region. The third region extends below the main surface and is arranged along the main surface together with the first region and the second region. The mask is provided on the main surface above the third region and provides an opening to the third region. The third region is composed of the first film and the second film. In the etching process, the first region, the second region, and the third region are etched simultaneously.

[0031] In an exemplary embodiment, a plasma processing device for performing an etching process on a workpiece is provided. The plasma processing device includes: a processing container; and a mounting table arranged in the processing container, capable of mounting the workpiece when performing the etching process. The plasma processing device also includes a temperature regulating mechanism for regulating the temperature of the workpiece mounted on the mounting table when performing the etching process. The plasma processing device also includes a gas supply mechanism for supplying a processing gas into the processing container when performing the etching process. The plasma processing device also includes a high-frequency power supply for generating a plasma of the processing gas in a processing space in the processing container when performing the etching process. The plasma processing device also includes a control unit for controlling the temperature regulating mechanism, the gas supply mechanism, and the high-frequency power supply. The control unit controls the temperature regulating mechanism, the gas supply mechanism, and the high-frequency power supply so that while maintaining the temperature of the workpiece mounted on the mounting table within a preset temperature range, a plasma of the processing gas is generated in the processing container, and the workpiece is etched using the plasma. The processing gas includes a first gas and a second gas. The first gas is a fluorocarbon gas. The second gas is a hydrogen-containing gas. The temperature range is above -30°C and below 30°C. The first gas includes p types (p is an integer greater than 1) of the first to p-th fluorocarbon gases. The second gas includes q types (q is an integer greater than 1) of the first to q-th hydrogen-containing gases. Let the flow rate of the i-th fluorocarbon gas included in the first to p-th fluorocarbon gases during the etching process be J(i). Let the number of fluorine atoms included in the elemental composition of the i-th fluorocarbon gas be M(i). Let the number of carbon atoms included in the elemental composition of the i-th fluorocarbon gas be N(i). For all possible values ​​of i (i is an integer greater than 1 and less than p), the value obtained by summing all J(i)×N(i) / M(i) is Ua. Let the flow rate of the k-th hydrogen-containing gas included in the first to q-th hydrogen-containing gases during the etching process be J(k). Let the number of hydrogen atoms included in the elemental composition of the k-th hydrogen-containing gas be H(k). For all possible values ​​of k (k is an integer from 1 to q), the value obtained by summing all J(k)×H(k) is Ub. Ua / Ub satisfies 0.04<Ua / Ub<0.22.

[0032] So far, a technology has been studied that can etch a workpiece containing two films, a silicon oxide film and a silicon nitride film, at one time using conditions common to both films. Such etching can be achieved by setting the temperature of the workpiece to between -30°C and 30°C, and setting the flow rate and element composition of the processing gas containing fluorocarbon gas and hydrogen-containing gas to satisfy 0.04<Ua / Ub<0.22.

[0033] Hereinafter, various exemplary embodiments will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in each of the drawings.

[0034] Figure 1 A flow chart of method MT showing an exemplary embodiment of an etching method. Method MT can be used, for example, in the manufacture of a NAND flash memory having a three-dimensional structure. Method MT uses, for example Figure 2 The plasma processing device 10 shown in FIG. Figure 3 A method for etching a wafer W (workpiece) having the structure shown.

[0035] Figure 2 The structure of a plasma processing apparatus 10 according to an exemplary embodiment of a plasma processing apparatus is shown. The plasma processing apparatus 10 can perform an etching process (process included in method MT) on a wafer W using plasma.

[0036] Figure 2 The plasma processing apparatus 10 shown is a capacitively coupled plasma etching apparatus. The plasma processing apparatus 10 has a substantially cylindrical processing container 12. The material of the processing container 12 may be aluminum, for example. The inner wall surface of the processing container 12 is anodized. The processing container 12 is kept grounded.

[0037] The support part 14 is disposed on the bottom of the processing container 12. The support part 14 has a substantially cylindrical shape. The material of the support part 14 can be an insulating material such as quartz or alumina. The support part 14 extends from the bottom of the processing container 12 in the vertical direction.

[0038] The stage PD is provided in the processing container 12, and the wafer W is placed thereon when the etching process (process included in the method MT) is performed. The stage PD is provided in the processing container 12. The stage PD is supported by the support unit 14. The stage PD includes a lower electrode 16 and an electrostatic chuck 18.

[0039] The lower electrode 16 includes a first component 16a and a second component 16b. The first component 16a and the second component 16b can each be made of a metal such as aluminum. The first component 16a and the second component 16b each have a substantially disc shape. The second component 16b is disposed on the first component 16a. The second component 16b is electrically connected to the first component 16a.

[0040] The electrostatic chuck 18 is provided on the lower electrode 16. Specifically, the electrostatic chuck 18 is provided on the second member 16b. The electrostatic chuck 18 is configured to be able to hold the wafer W placed on the upper surface of the electrostatic chuck 18.

[0041] Specifically, the electrostatic chuck 18 has a substantially disk-shaped insulating film. The electrode 18a is included in the insulating film of the electrostatic chuck 18. The DC power supply 22 is connected to the electrode 18a via the switch SW.

[0042] The electrostatic chuck 18 generates electrostatic force such as Coulomb force when a DC voltage is applied to the electrode 18a from the DC power supply 22. The electrostatic chuck 18 attracts and holds the wafer W by the generated electrostatic force.

[0043] The focus ring FR is provided on the peripheral portion of the lower electrode 16. The focus ring FR has an annular plate shape and is arranged so as to surround the edge of the wafer W and the edge of the electrostatic chuck 18.

[0044] The material of the focus ring FR can be appropriately selected according to the material of the film to be etched. The material of the focus ring FR is, for example, silicon, silicon carbide (SiC), or quartz.

[0045] The plasma processing apparatus 10 includes a temperature adjustment mechanism TS for controlling the temperature of the electrostatic chuck 18. The temperature adjustment mechanism TS adjusts the temperature of the wafer W when the etching process (process included in the method MT) is performed. The temperature adjustment mechanism TS includes a cooling unit CU, a heater 18h, a heater power supply HP, and a temperature detector 18t.

[0046] The temperature detector 18t detects the temperature of the wafer W placed on the mounting table PD, and sends the detection result to the control unit Cnt. The control unit Cnt controls the cooling unit CU and the heater power supply HP based on the detection result sent from the temperature detector 18t.

[0047] The refrigeration unit CU is provided outside the processing container 12. The refrigeration unit CU is connected to the pipe 26a and the pipe 26b. The pipe 26a and the pipe 26b are connected to the flow path 16f. The flow path 16f for the fluid is formed inside the lower electrode 16.

[0048] The refrigeration unit CU supplies the heat medium to the flow path 16f through the pipe 26a. The heat medium supplied to the flow path 16f returns to the refrigeration unit CU through the pipe 26b. The heat medium circulates between the flow path 16f and the refrigeration unit CU.

[0049] The heater 18h is provided inside the electrostatic chuck 18. The heater 18h is connected to the heater power supply HP. The heater 18h generates heat by the electric power supplied by the heater power supply HP. In addition, in the plasma processing, when the amount of heat removed from the plasma to the mounting table PD is large, the heater 18h and the heater power supply HP may not be used.

[0050] In addition, a gas supply line 28 is provided as a part of the temperature control mechanism TS in the plasma processing apparatus 10. The gas supply line 28 supplies a heat transfer gas such as He gas from the heat transfer gas supply mechanism between the upper surface of the electrostatic chuck 18 and the back surface of the wafer W.

[0051] In addition, the temperature sensor or temperature detector not shown in the figure included in the temperature detector 18t can directly detect the temperature of the wafer W, but is not limited to this. For example, the temperature value of the stage PD or the temperature value of the heat transfer medium supplied from the refrigeration unit CU to the flow path 16f can be used. In the plasma processing, the wafer W is exposed to the plasma, and the temperature of the wafer W rises due to the ion irradiation or light from the plasma, thereby generating a temperature difference between the wafer W and the stage PD or the heat transfer medium. Therefore, the temperature of the wafer W can be estimated based on the structure between the wafer W and the stage PD or the heat transfer medium and the temperature difference data estimated from the relationship with the process conditions or the temperature difference data measured in advance.

[0052] The upper electrode 30 is provided above the mounting table PD and is arranged to face the mounting table PD. A processing space S for performing plasma processing on the wafer W is defined between the upper electrode 30 and the mounting table PD.

[0053] The upper electrode 30 is supported on the upper portion of the processing container 12 via an insulating shielding member 32. The upper electrode 30 may include a top plate 34 and a support body 36.

[0054] The top plate 34 faces the processing space S. A plurality of gas exhaust holes 34a are formed in the top plate 34. The material of the top plate 34 may be a low-resistance conductor or semiconductor with relatively little Joule heat.

[0055] The support body 36 detachably supports the top plate 34. The material of the support body 36 can be, for example, a conductive material such as aluminum. The support body 36 may have a water-cooling structure.

[0056] The plasma processing apparatus 10 includes a gas supply mechanism GS. The gas supply mechanism GS supplies a processing gas (hereinafter sometimes referred to as a processing gas G) into the processing container 12 when an etching process (step ST3 described later) included in the method MT is performed.

[0057] The processing gas G includes a first gas, a second gas, and a third gas. The gas source group 40 includes a plurality of gas sources corresponding to the first gas, the second gas, and the third gas, respectively.

[0058] The first gas is a fluorocarbon gas. The first gas includes p types (p is an integer greater than or equal to 1, the same below) of the first to p-th fluorocarbon gases. The second gas is a hydrogen-containing gas. The second gas includes q types (q is an integer greater than or equal to 1, the same below) of the first to q-th hydrogen-containing gases. The third gas includes a halogen element that is not fluorine.

[0059] More specifically, the first gas may be, for example, any one of C4F8 gas, C3F8 gas, and C4F6 gas (when p=1), or a mixed gas consisting of at least two of C4F8 gas, C3F8 gas, and C4F6 gas (when p=2 or 3). The second gas may be, for example, H2 gas (when q=1), or a mixed gas of H2 gas and CH4 gas (when q=2). The third gas may be HBr gas.

[0060] The gas supply mechanism GS includes a gas source group 40, a valve group 42, and a flow controller group 44. The gas source group 40 is connected to the gas supply pipe 38 via the valve group 42 and the flow controller group 44. The gas source group 40 supplies the processing gas G into the processing space S when the etching process (process included in the method MT) is performed.

[0061] The valve group 42 has a plurality of valves. The flow controller group 44 includes a plurality of flow controllers such as mass flow controllers. The plurality of gas sources of the gas source group 40 are connected to the gas supply pipe 38 via corresponding flow controllers of the flow controller group 44 and corresponding valves of the valve group 42 .

[0062] The gas diffusion chamber 36a is provided inside the support body 36. A plurality of gas flow holes 36b extend downward from the gas diffusion chamber 36a. The gas flow holes 36b communicate with the gas discharge holes 34a.

[0063] The gas introduction port 36c is formed in the support body 36. The gas introduction port 36c introduces the processing gas G into the gas diffusion space 36a. The gas supply pipe 38 is connected to the gas introduction port 36c.

[0064] The ground conductor 12 a has a substantially cylindrical shape and is provided so as to extend from the side wall of the processing container 12 to a position above the height of the upper electrode 30 .

[0065] The sediment shield 46 is detachably provided along the inner wall of the processing container 12. The sediment shield 46 is also provided on the outer periphery of the support portion 14.

[0066] The deposition shield 46 prevents the etching byproducts from being attached to the processing container 12. The deposition shield 46 may be formed by coating an aluminum material with ceramic such as Y2O3, for example.

[0067] The exhaust plate 48 is provided between the support portion 14 and the inner wall of the processing container 12. A plurality of through holes penetrating the exhaust plate 48 in the thickness direction thereof are provided. The exhaust plate 48 may be formed by coating, for example, an aluminum material with ceramic such as Y2O3.

[0068] The exhaust port 12e is provided in the processing container 12 below the exhaust plate 48. The exhaust device 50 is connected to the exhaust port 12e via an exhaust pipe 52.

[0069] The exhaust device 50 includes a pressure regulating valve and a vacuum pump such as a turbomolecular pump. The exhaust device 50 can reduce the pressure in the processing container 12 to a desired vacuum level.

[0070] An opening 12g is provided in the side wall of the processing container 12. The opening 12g is provided for conveying the wafer W. The opening 12g can be opened and closed by a gate valve 54.

[0071] The conductive component 56 is installed on the inner wall of the processing container 12. The conductive component 56 is installed on the inner wall of the processing container 12 in a manner that it is located at approximately the same height as the wafer W in the height direction. The conductive component 56 is connected to the ground DC to play an effect of preventing abnormal discharge. The conductive component 56 can be installed in the plasma generation area, and the installation position of the conductive component 56 is not limited to Figure 2 Position shown.

[0072] The first high-frequency power source 62 is a power source that generates a first high frequency for plasma generation. When the etching process (process included in the method MT) is performed, the first high-frequency power source 62 generates plasma of the processing gas G in the processing space S in the processing container 12 by the first high frequency. The first high frequency can be 27 to 100 [MHz], and in one example can be 40 [MHz]. The first high-frequency power source 62 is connected to the lower electrode 16 via a matching device 66.

[0073] The matching device 66 has a circuit for matching the output impedance of the first high-frequency power source 62 with the input impedance of the load side (the side of the lower electrode 16 ). The first high-frequency power source 62 can be connected to the upper electrode 30 via the matching device 66 .

[0074] The second high frequency power source 64 is a power source for generating a second high frequency, i.e., a high frequency bias, for introducing ions into the wafer W. The second high frequency may be a frequency in the range of 400 [kHz] to 13.56 [MHz], and in one example is 3 [MHz]. The second high frequency power source 64 is connected to the lower electrode 16 via a matching device 68. The matching device 68 has a circuit for matching the output impedance of the second high frequency power source 64 with the input impedance of the load side (lower electrode 16 side).

[0075] The DC power supply unit 70 is connected to the upper electrode 30 . The DC power supply unit 70 generates a negative DC voltage and can apply the DC voltage to the upper electrode 30 .

[0076] The control unit Cnt is a computer having a processor, a storage unit, an input device, a display device, etc., and uniformly controls the various parts of the plasma processing device 10. The control unit Cnt particularly controls the temperature adjustment mechanism TS, the gas supply mechanism GS, and the first high-frequency power supply 62. The storage unit of the control unit Cnt stores a computer program. The computer program includes a control program for causing the processor to control various processes performed by the plasma processing device 10, and particularly a program (processing plan) for causing the processor to cause the various parts of the plasma processing device 10 to perform processes according to process conditions.

[0077] The control unit Cnt controls each unit of the plasma processing apparatus 10 in each step of the method MT according to the processing plan of the method MT. More specifically, the control unit Cnt generates plasma of the processing gas G in the processing space S of the processing container 12 while maintaining the temperature of the wafer W mounted on the mounting table PD within a preset temperature range. The control unit Cnt controls the temperature adjustment mechanism TS, the gas supply mechanism GS, and the first high-frequency power supply 62 so that the wafer W is etched using the generated plasma (processing included in the method MT).

[0078] Figure 3 The structure of a wafer W of an exemplary embodiment of a workpiece is shown. The wafer W includes a base layer UL, a first region R1, a second region R2, a third region R3, and a mask MSK. The base layer UL may be, for example, a polysilicon layer provided on a substrate. The first region R1, the second region R2, and the third region R3 are provided on the base layer UL.

[0079] The first region R1 , the second region R2 , and the third region R3 are arranged along the main surface PS of the wafer W. The first region R1 , the second region R2 , and the third region R3 each extend below the main surface PS.

[0080] The first region R1 is composed of the first film FL1. The second region R2 is composed of the second film FL2. The third region R3 is composed of the first film FL1 and the second film FL2. The first film FL1 is a silicon oxide film IL1. The second film FL2 has a structure in which silicon oxide films IL1 and silicon nitride films IL2 are alternately stacked.

[0081] The mask MSK is provided on the main surface PS in the first region R1, the second region R2, and the third region R3. The mask MSK has openings in the first region R1, the second region R2, and the third region R3. The material of the mask MSK may be, for example, amorphous carbon. The material of the mask MSK may be an organic polymer.

[0082] illustrate Figure 1 The method MT shown in FIG. The method MT can be executed by the plasma processing apparatus 10 under the control of the control unit Cnt. The method MT includes steps ST1 to ST4. First, in step ST1, a wafer W is placed on the mounting table PD (step ST1).

[0083] In step ST2 following step ST1, the temperature of the wafer W is maintained within a preset temperature range (hereinafter referred to as temperature range TE) (step ST2). In step ST3 following step ST2, while the temperature of the wafer W is maintained within the temperature range TE, a plasma of a processing gas G is generated in the processing space S of the processing container 12, and the wafer W is etched using the plasma under the process conditions PP described later (step ST3). The first region R1, the second region R2, and the third region R3 are etched simultaneously (at the same time) by the etching process of step ST3.

[0084] In step ST4 following step ST3, it is determined whether to terminate the method MT (step ST4). More specifically, in step ST4, it is determined whether the etching process in step ST3 reaches a preset etching depth (corresponding to the determination of whether to terminate the method MT). The etching depth can be obtained by the etching rate and the processing time, or it can be the end point detection result detected by using an EPD (End Point Detector) or the like. The preset etching depth can be stored in the storage unit of the control unit Cnt.

[0085] In step ST4, when it is determined that the method MT is not to be terminated (step ST4: No), step ST3 is continued. In step ST4, when it is determined that the method MT is to be terminated (step ST4: Yes), the method MT is terminated.

[0086] Reference Figure 4 Indicates the temperature range TE. Figure 4 An example of the correlation between the temperature [° C.] of the wafer W and the etching rate ratio of the first film FL1 and the second film FL2 in the etching process of the method MT is shown. Figure 4 The horizontal axis represents the temperature of the wafer W [° C.]. Figure 4 The vertical axis represents the ratio (ER1 / ER2) of the etching rate (ER1 [nm / min]) of the first film FL1 to the etching rate (ER2 [nm / min]) of the second film FL2. ER1 / ER2 represents the value obtained by dividing the value of ER1 by the value of ER2.

[0087] When the temperature of the wafer W is between -30[°C] and 30[°C], ER1 / ER2 may be a value in the range of 0.8 to 1.2 including 1 (ER1=ER2). Therefore, as the temperature range TE of the wafer W for achieving ER1=ER2, a range of between -30[°C] and 30[°C] may be adopted.

[0088] Figure 4 and the following Figure 5 to Figure 7 The results shown are obtained based on the process conditions PP including the following conditions Pa. The process conditions PP can be used for the execution of step ST3 (etching process), but in the process conditions PP used in step ST3, the content of the condition Pa is not limited to the following.

[0089] (Condition Pa)

[0090] ·Pressure in the processing container 12: 15 to 30 [mTorr].

[0091] Frequency and electric power of the first high-frequency power source 62: 40 [MHz], 2 to 5 [kW].

[0092] The frequency and electric power of the second high-frequency power source 64 are: 3 [MHz], 7 to 9 [kW].

[0093] ·DC voltage of DC power supply unit 70: 0 [V].

[0094] Figure 4 The results shown are obtained by performing etching processing (step ST3) under process conditions PP including the following conditions regarding the flow rate of the processing gas G in addition to the condition Pa. The first gas can use C4F8 gas (p=1). The second gas can use H2 gas (q=1). The inequality IEQ described later for the processing gas G is satisfied.

[0095] ·Flow rate of processing gas G: (C4F8 gas) 50 [sccm], (H2 gas) 160 [sccm], (HBr gas) 20 [sccm].

[0096] The process gas G may further include O 2 gas. The flow rate of the O 2 gas may be determined according to a desired shape of the mask MSK used in the etching process of step ST3 .

[0097] The process gas G condition in the process condition PP including the condition Pa used in the etching process of step ST3 satisfies 0.04<Ua / Ub<0.22 (hereinafter sometimes referred to as the case of inequality IEQ). Ua / Ub represents the value obtained by dividing the value of Ua by the value of Ub. The values ​​of Ua and Ub are defined as follows.

[0098] (Value of Ua)

[0099] Let the flow rate of the i-th fluorocarbon gas (i is an integer greater than 1 and less than p) contained in the first fluorocarbon gas to the p-th fluorocarbon gas of the first gas of the processing gas G during the execution of the etching process be J(i). Let the number of fluorine atoms contained in the elemental composition of the i-th fluorocarbon gas be M(i), and the number of carbon atoms contained in the elemental composition of the i-th fluorocarbon gas be N(i). Ua is the value obtained by summing all J(i)×N(i) / M(i) for all possible values ​​of i.

[0100] (Value of Ub)

[0101] Let the flow rate of the kth hydrogen-containing gas included in the first hydrogen-containing gas to the qth hydrogen-containing gas of the second gas of the processing gas G during the etching process be J(k) (k is an integer greater than 1 and less than q). Let the number of hydrogen atoms included in the elemental composition of the kth hydrogen-containing gas be H(k). Ub is the value obtained by summing all J(k)×H(k) for all possible values ​​of k.

[0102] The inequality IEQ is based on Figure 5 The results shown were adopted. Figure 5 It shows the results obtained by measuring the correlation between Ua / Ub and ER1 / ER2. Figure 5 The horizontal axis represents Ua / Ub. Figure 5 The vertical axis represents ER1 / ER2.

[0103] Figure 5 The results shown are obtained by performing etching processing (step ST3) under process conditions PP including the following conditions regarding the flow rate of the processing gas G in addition to the condition Pa. Regarding the first gas, three types of fluorocarbon gases (C4F8 gas, C3F8 gas, C4F6 gas) are used respectively in each etching process (p=1). H2 gas (q=1) is used as the second gas. The temperature of the wafer W is about 0[°C], which satisfies the temperature range TE.

[0104] Flow rate of the processing gas G: (first gas) 30 to 80 [sccm], (H2 gas) 50 to 240 [sccm], (HBr gas) 20 [sccm].

[0105] The process gas G may further include O 2 gas. The flow rate of the O 2 gas may be determined according to the desired shape of the mask MSK used in the etching process.

[0106] Multiple determination results PL1a in Figure 5 The black triangles in the figure are the measurement results when C4F8 gas is used as the first gas. Figure 5The white rectangle in the figure shows the measurement result when C3F8 gas is used as the first gas. Figure 5 The white circle in the middle represents the measurement result when C4F6 gas is used as the first gas.

[0107] Line LN1 is used Figure 5 The regression line obtained from all the measurement results PL1a, PL1b, and PL1c shown in FIG. 1 is a linear function represented by ER1 / ER2=2.2943×Ua / Ub+0.7066 calculated by the least square method in one exemplary embodiment.

[0108] The range of Ua / Ub is determined by using the straight line LN1 so that the value of ER1 / ER2 is within the range of 0.8 to 1.2 including 1 (ER1=ER2). When Ua / Ub satisfies the inequality IEQ, the value of ER1 / ER2 is within the range of 0.8 to 1.2 including 1 (ER1=ER2). Therefore, in step ST3 (etching process) of method MT, when Ua / Ub satisfies the inequality IEQ, the etching rates of the first film FL1 and the second film FL2 can be the same.

[0109] The second gas contained in the processing gas G used in step ST3 of method MT may contain not only H 2 gas but also, for example, CH 4 gas as a hydrogen-containing gas. Figure 6 The results of measuring the correlation between Ua / Ub and ER1 / ER2 are shown in FIG. Figure 6 The horizontal axis represents Ua / Ub. Figure 6 The vertical axis represents ER1 / ER2.

[0110] Figure 6 The results shown are obtained by performing etching processing (step ST3) under process conditions PP including the following conditions regarding the flow rate of the processing gas G in addition to the condition Pa. As for the first gas, three types of fluorocarbon gases (C4F8 gas, C3F8 gas, C4F6 gas) are used separately (p=1). The temperature of the wafer W is about 0 [°C], which satisfies the temperature range TE. The inequality IEQ regarding the processing gas G is satisfied.

[0111] (When H2 gas is used as the second gas)

[0112] Flow rate of the processing gas G: (first gas) 30 to 80 [sccm], (H2 gas) 50 to 240 [sccm], (HBr gas) 20 [sccm].

[0113] (When a mixed gas of H2 gas and CH4 gas is used as the second gas)

[0114] ·Flow rate of processing gas G: (first gas) 30~80 [sccm], (H2 gas) 10~30 [sccm], (CH4 gas) 50~70 [sccm], (HBr gas) 10~30 [sccm].

[0115] The process gas G may further include O 2 gas. The flow rate of the O 2 gas may be determined according to the desired shape of the mask MSK used in the etching process.

[0116] Multiple determination results PL2a in Figure 6 The black circle in the figure is the measurement result when H2 gas is used as the second gas. Figure 5 The multiple measurement results PL1a, PL1b, and PL1c shown are all plotted. One measurement result PL2b is Figure 6 The white triangles in the figure are the measurement results when the second gas is a mixed gas of H2 gas and CH4 gas. Figure 6 The regression line obtained from the multiple measurement results PL2a shown in FIG. Figure 5 The straight line LN1 shown is the same.

[0117] The measurement result PL2b when the second gas is a mixed gas of H2 gas and CH4 gas is plotted near the regression line LN2 obtained by the measurement result PL2a when the second gas is H2 gas. That is, even when the second gas is a mixed gas of H2 gas and CH4 gas, when Ua / Ub satisfies the inequality IEQ, the value of ER1 / ER2 can be within the range of 0.8 to 1.2 including 1 (ER1=ER2). Therefore, in step ST3, even when the second gas is H2 gas, or when the second gas is a mixed gas of H2 gas and CH4 gas, when Ua / Ub satisfies the inequality IEQ, the etching rates of the first film FL1 and the second film FL2 can be the same.

[0118] Figure 7 The figure shows the results of measuring the correlation between the etching time [min] and the normalized etching depth [au] in the etching process (step ST3) performed on the wafer W using two types of openings of the mask MSK having different opening areas. Figure 7 The horizontal axis represents etching time [min]. Figure 7 The vertical axis represents the normalized etching depth [au].

[0119] Figure 7The results shown are obtained under process condition PP including the following conditions regarding the flow rate of the process gas G in addition to condition Pa. C4F8 gas (p=1) is used as the first gas. H2 gas (q=1) is used as the second gas. The temperature of the wafer W is about 0[°C], which satisfies the temperature range TE. The inequality IEQ regarding the process gas G is satisfied.

[0120] Flow rate of process gas G: (C4F8 gas) 70 [sccm], (H2 gas) 140 [sccm], (HBr gas) 20 [sccm]. The process gas G also contains O2 gas.

[0121] Multiple determination results PL3a in Figure 7 The white circle in FIG. 1 shows the measurement result of the etching process on the second film FL2 through the opening of the first opening area of ​​the mask MSK. Figure 7 The black triangles in FIG. 1 represent the measurement results of the etching process on the second film FL2 performed through the opening of the second opening area of ​​the mask MSK. The first opening area and the second opening area are different from each other. Figure 7 In FIG. 1 , the etching depth in which the etching time is 10 [min] among the plurality of measurement results PL3a is normalized to 1, and the plurality of measurement results PL3a are plotted respectively.

[0122] according to Figure 7 As shown in the results, it can be seen that the correlation between the etching time and the etching depth is equal in the etching process performed through the opening of the first opening area of ​​the mask MSK and the etching process performed through the opening of the second opening area of ​​the mask MSK. Therefore, it can be seen that according to step ST3 (etching process) of the method MT, even when the etching process of the second film FL2 is performed through the openings of various opening areas of the mask MSK, it is possible to achieve a substantially equal etching rate. In addition, according to a plurality of measurement results PL3a, it can be seen that as the etching time increases, the etching depth increases linearly, so etching that does not depend on the aspect ratio can be achieved.

[0123] Various exemplary embodiments have been described above, but the present invention is not limited to the exemplary embodiments described above, and various omissions, substitutions, and changes may be made. In addition, elements in different exemplary embodiments may be combined to form other exemplary embodiments.

[0124] According to the above description, various illustrative embodiments of the present invention are described in this specification for the purpose of explanation, and it should be understood that various changes can be made without departing from the scope and spirit of the present invention. Therefore, the various illustrative embodiments disclosed in this specification are not intended to be limiting, and the scope and spirit of the present invention are represented by the scope of the attached claims.

Claims

1. A method for etching a workpiece, characterized in that: A workpiece is placed on a placing table in a processing container of a plasma processing device. The temperature of the workpiece is maintained within a preset temperature range. while maintaining the temperature of the workpiece within the temperature range, generating plasma of a processing gas in the processing container, and etching the workpiece using the plasma, The workpiece includes a silicon oxide film and a silicon nitride film, The processing gas includes a first gas and a second gas, The first gas is a fluorocarbon gas, The temperature range is above -30℃ and below 30℃. The first gas includes p types of first to p-th fluorocarbon gases, wherein p is an integer greater than 1, The second gas includes q types of first to qth hydrogen-containing gases, wherein q is an integer greater than 1, Let the flow rate of the i-th fluorocarbon gas included in the first to p-th fluorocarbon gases during the execution of the etching process be J(i), the number of fluorine atoms included in the elemental composition of the i-th fluorocarbon gas be M(i), the number of carbon atoms included in the elemental composition of the i-th fluorocarbon gas be N(i), for all possible values ​​of i, the value obtained by summing all J(i)×N(i) / M(i) is Ua, let the flow rate of the k-th hydrogen-containing gas included in the first to q-th hydrogen-containing gases during the execution of the etching process be J(k), the number of hydrogen atoms included in the elemental composition of the k-th hydrogen-containing gas is H(k), for all possible values ​​of k, the value obtained by summing all J(k)×H(k) is Ub, Ua / Ub satisfies 0.04<Ua / Ub<0.22, wherein i is an integer greater than 1 and less than p, and k is an integer greater than 1 and less than q, The second gas is any one of H 2 gas and CH 4 gas, or a mixed gas of H 2 gas and CH 4 gas.

2. The etching method according to claim 1, wherein: The first gas is any one of C4F8 gas, C3F8 gas, and C4F6 gas, or a mixed gas consisting of at least two of C4F8 gas, C3F8 gas, and C4F6 gas.

3. The etching method according to claim 1 or 2, characterized in that: The processing gas further includes a third gas, The third gas contains a halogen element other than fluorine.

4. The etching method according to claim 3, wherein: The third gas is HBr gas.

5. The etching method according to claim 1 or 2, characterized in that: The object to be processed includes a first region, a second region and a mask, The first region and the second region are arranged along the main surface of the workpiece, The first region and the second region each extend below the main surface, The mask is provided on the main surface above the first region and the second region, and has openings for the first region and the second region, respectively. The first region is composed of a first film, The second region is composed of a second film, The first film is a silicon oxide film, The second film has a structure in which silicon oxide films and silicon nitride films are alternately stacked. The first region and the second region are etched simultaneously in the etching process.

6. The etching method according to claim 5, characterized in that: The workpiece further includes a third region, The third region extends below the main surface and is arranged along the main surface together with the first region and the second region. The mask is disposed on the main surface above the third region and provides an opening to the third region. The third region is composed of the first film and the second film, In the etching process, the first region, the second region, and the third region are etched simultaneously.

7. A plasma processing device for etching a workpiece, characterized in that: include: Handling containers; a mounting table disposed in the processing container and capable of mounting the workpiece when the etching process is performed; a temperature regulating mechanism for regulating the temperature of the workpiece placed on the mounting table when the etching process is performed; a gas supply mechanism for supplying a processing gas into the processing container when the etching process is performed; a high frequency power supply for generating plasma of the processing gas in a processing space within the processing container when performing the etching process; and a control unit for controlling the temperature adjustment mechanism, the gas supply mechanism, and the high-frequency power supply, The control unit controls the temperature regulating mechanism, the gas supply mechanism, and the high-frequency power supply so that the temperature of the workpiece placed on the placing table is maintained within a preset temperature range, while plasma of the processing gas is generated in the processing container, and the workpiece is etched using the plasma. The processing gas includes a first gas and a second gas, The first gas is a fluorocarbon gas, The temperature range is above -30℃ and below 30℃. The first gas includes p types of first to p-th fluorocarbon gases, wherein p is an integer greater than 1, The second gas includes q types of first to qth hydrogen-containing gases, wherein q is an integer greater than 1, When the flow rate of the i-th fluorocarbon gas included in the first to p-th fluorocarbon gases during the etching process is J(i), the number of fluorine atoms included in the elemental composition of the i-th fluorocarbon gas is M(i), the number of carbon atoms included in the elemental composition of the i-th fluorocarbon gas is N(i), and for all possible values ​​of i, the value obtained by summing all J(i)×N(i) / M(i) is Ua, and when the flow rate of the k-th hydrogen-containing gas included in the first to q-th hydrogen-containing gases during the etching process is J(k), the number of hydrogen atoms included in the elemental composition of the k-th hydrogen-containing gas is H(k), and for all possible values ​​of k, the value obtained by summing all J(k)×H(k) is Ub, Ua / Ub satisfies 0.04<Ua / Ub<0.22, wherein i is an integer greater than 1 and less than p, and k is an integer greater than 1 and less than q, The second gas is any one of H 2 gas and CH 4 gas, or a mixed gas of H 2 gas and CH 4 gas.

8. A method for etching a workpiece, characterized in that: A workpiece is placed on a placing table in a processing container of a plasma processing device. The temperature of the workpiece is maintained within a preset temperature range. while maintaining the temperature of the workpiece within the temperature range, generating plasma of a processing gas in the processing container, and etching the workpiece using the plasma, The workpiece includes a silicon oxide film and a silicon nitride film, The processing gas includes a first gas and a second gas, The temperature range is above -30℃ and below 30℃. The first gas includes C4F8 gas as a first fluorocarbon gas, C3F8 gas as a second fluorocarbon gas, and C4F6 gas as a third fluorocarbon gas. The second gas includes H2 gas as the first hydrogen-containing gas and CH4 gas as the second hydrogen-containing gas, Let the flow rate of the i-th fluorocarbon gas included in the first to third fluorocarbon gases during the execution of the etching process be J(i), the number of fluorine atoms included in the elemental composition of the i-th fluorocarbon gas be M(i), the number of carbon atoms included in the elemental composition of the i-th fluorocarbon gas be N(i), for all possible values ​​of i, the value obtained by summing all J(i)×N(i) / M(i) is Ua, let the flow rate of the k-th hydrogen-containing gas included in the first to second hydrogen-containing gases during the execution of the etching process be J(k), the number of hydrogen atoms included in the elemental composition of the k-th hydrogen-containing gas is H(k), for all possible values ​​of k, the value obtained by summing all J(k)×H(k) is Ub, Ua / Ub satisfies 0.04<Ua / Ub<0.22, wherein i is an integer greater than 1 and less than 3, and k is 1 or 2.

9. The etching method according to claim 8, wherein: The processing gas further includes a third gas, The third gas contains a halogen element other than fluorine.

10. The etching method according to claim 9, wherein: The third gas is HBr gas.

11. The etching method according to any one of claims 8 to 10, characterized in that: The object to be processed includes a first region, a second region and a mask, The first region and the second region are arranged along the main surface of the workpiece, The first region and the second region each extend below the main surface, The mask is provided on the main surface above the first region and the second region, and has openings for the first region and the second region, respectively. The first region is composed of a first film, The second region is composed of a second film, The first film is a silicon oxide film, The second film has a structure in which silicon oxide films and silicon nitride films are alternately stacked. The first region and the second region are etched simultaneously in the etching process.

12. The etching method according to claim 11, wherein: The workpiece further includes a third region, The third region extends below the main surface and is arranged along the main surface together with the first region and the second region. The mask is disposed on the main surface above the third region and provides an opening to the third region. The third region is composed of the first film and the second film, In the etching process, the first region, the second region, and the third region are etched simultaneously.

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