Plasma treatment method

Abstract

In order to enable uniform etching processing, regardless of pattern density, by independently controlling the etching shapes of a sparse pattern section and a dense pattern section within the same wafer, this plasma processing method is characterized by: comprising a first step for performing reactive ion etching using a gas that forms a taper shape, and a second step for performing radical etching; the first etching and the second etching being alternately repeated a prescribed number of times; and the time taken for the first step being shorter than the time taken for the second step.

Description

Technical Field

[0001] The present invention relates to a plasma processing method.

Background Art

[0002] In recent years, due to the increasing complexity and three-dimensionalization of semiconductor devices, sparse and dense pattern portions coexist within the same wafer, and the demand for uniformly etching them has been growing stronger.

[0003] In conventional RIE (Reactive Ion Etching), when etching is performed to obtain a vertical shape for the dense pattern portion, since there are many reaction products generated due to the large etched area in the sparse portion, the effect of inhibiting etching becomes significant, and it often becomes a tapered shape. To achieve uniform etching regardless of pattern density, independent control of the etching shape of the sparse and dense portions is necessary.

[0004] In Patent Document 1, in an etching process for forming grooves in a semiconductor substrate, a first step of performing etching under conditions with a high etching rate immediately after the start of etching and a second step of performing etching under conditions with a low etching rate thereafter are proposed.

[0005] Also, in Patent Document 2, a technique is proposed in which an etching step in which roughness is formed on the etched surface of a substrate by anisotropic etching mainly using ions and, subsequent to the said step, a step of removing the roughness formed by the said step by isotropic etching mainly using radicals of a non-depositing gas with respect to the said substrate are continuously repeated a plurality of times.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In order to etch the sparse and dense portions of patterns on the same wafer uniformly, independent control of the etching shapes of the sparse and dense portions is required.

[0008] However, the technique described in Patent Document 1 has the same problem of suppressing variations in the etching amount of the sparse and dense patterns, but the solution means is different from the present invention.

[0009] Also, the technique described in Patent Document 2 repeats ionic etching and radical etching in order to achieve both the perpendicularity and smoothness of the pattern after etching, and does not attempt to independently control the etching shapes of the sparse and dense portions of the pattern.

[0010] The present invention provides a plasma processing method that solves the above-described problems of the prior art and enables uniform etching of the sparse and dense portions of patterns on the same wafer.

Means for Solving the Problems

[0011] In order to solve the above-described problems, in the present invention, In a plasma processing method for forming a Gate All Around structure, NF 3 gas and HBr gas a first step of performing Reactive Ion Etching using a mixed gas, and NF 3 gas and a mixed gas of HBr gas are used a second step of performing radical etching, and the first step and the second step are repeatedly performed alternately for a predetermined times, time, and the time of the first step is shorter than the time of the second step, which is a plasma processing method characterized by this.

Effects of the Invention

[0012] According to the present invention, it has become possible to independently control the etching shapes of sparse and dense portions of patterns within the same wafer, and to etch the sparse and dense portions uniformly.

Brief Description of the Drawings

[0013]

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Mode for Carrying Out the Invention

[0014] The present invention uses a plasma processing apparatus equipped with a gas system that is etched into a tapered shape in RIE and allows etching to proceed even in radical etching that shields ions with the same gas system, and repeatedly executes while controlling the processing by RIE and the processing by radical etching, so that the sparse and dense portions of the pattern within the same wafer can be etched homogeneously.

[0015] Also, the present invention uses a plasma processing apparatus equipped with a gas system that is etched into a tapered shape in RIE and allows etching to proceed even in radical etching that shields ions with the same gas system, controls the RIE time ratio (the ratio of the RIE processing time to the total processing time of RIE and radical etching) so as to obtain a desired etching shape, and repeats RIE and radical etching a predetermined number of times, thereby making it possible to independently control the etching shapes of the sparse and dense portions of the pattern within the same wafer and enabling the sparse and dense portions to be etched homogeneously.

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the present embodiment, those having the same function are denoted by the same reference numerals, and repeated explanations thereof are omitted in principle.

[0017] However, the present invention is not to be construed as being limited to the description of the embodiments shown below. It will be easily understood by those skilled in the art that the specific configuration can be changed without departing from the spirit or gist of the present invention.

Example

[0018] FIG. 1 is a longitudinal sectional view showing an outline of the overall configuration of a plasma processing apparatus according to this example. The plasma processing apparatus 10 shown in FIG. 1 has a processing chamber 100 formed inside a vacuum chamber 101. Above the vacuum chamber 101, a shower plate 102 for introducing an etching gas into the processing chamber 100 in the vacuum chamber 101, a dielectric window 103 for hermetically sealing the upper part of the processing chamber 100, and an ion shielding plate 104 are installed to constitute the processing chamber 100.

[0019] In a region 1020 between the shower plate 102 and the dielectric window 103, a gas supply device 107 is connected through a gas supply pipe 1071, and a gas for performing a plasma etching process is supplied. The shower plate 102 is formed with a plurality of small-diameter holes 1021 for passing the gas supplied to the region 1020 to the processing chamber 100 side. Further, a vacuum exhaust device 118 is connected to the vacuum chamber 101 via a pressure regulating valve 117 to control the pressure in the processing chamber 100. The pressure in the processing chamber 100 is measured by a pressure gauge 121.

[0020] In order to transmit power for generating plasma to the processing chamber 100, a waveguide 108 (or antenna) that radiates electromagnetic waves is provided above the dielectric window 103. Electromagnetic waves oscillated from an electromagnetic wave generation power source (also referred to as a high-frequency power source) 110 are transmitted through an electromagnetic wave matcher 111 to the waveguide 108 (or antenna). In this Example 1, the frequency of the high-frequency current output from the electromagnetic wave generation power source 110 is set to a constant frequency. A cavity resonator 109 is arranged to form a standing wave of a specific mode in the processing chamber 100 by the electromagnetic waves propagated from the waveguide 108. Although the frequency of the electromagnetic waves is not particularly limited, in this example, it is a microwave of 2.45 GHz.

[0021] Magnetic field generation coils 112a, 112b, and 112c are provided on the outer peripheral portion of the processing chamber 100. DC coil current power sources 113a and 113b are connected to the magnetic field generation coils 112a and 112b to control their currents, and an AC coil current power source 114 is connected to the magnetic field generation coil 112c. The magnetic field generation coils 112a and 112b are driven by DC currents output from the DC coil current power sources 113a and 113b, and the magnetic field generation coil 112c is driven by an AC current output from the AC coil current power source 114.

[0022] The magnetic field generation coil 112, the DC coil current power sources 113a and 113b, and the AC coil current power source 114 can be referred to as a magnetic field forming mechanism. The magnetic field generation coils 112a and 112b can be referred to as the first coils, and the magnetic field generation coil 112c can be referred to as the second coil.

[0023] The power oscillated from the electromagnetic wave generation power source 110 generates plasma in the processing chamber 100 by electron cyclotron resonance (ECR) with the magnetic field formed by the magnetic field generation coil 112.

[0024] Also, at the lower part of the processing chamber 100 facing the ion shielding plate 104, a substrate electrode 115 that also serves as a mounting table (also referred to as a sample stage) for the sample (semiconductor substrate) 116 is installed. A high-frequency power supply 120 is connected to the substrate electrode 115 via a high-frequency matcher 119. By supplying high-frequency power from the high-frequency power supply 120 connected to the substrate electrode 115, a negative voltage generally called self-bias is generated on the substrate electrode 115. Due to the self-bias, ions in the plasma are accelerated and vertically incident on the sample 116 placed on the substrate electrode 115, whereby the sample 116 is etched.

[0025] The ion shielding plate 104 divides the internal space of the processing chamber 100 into upper and lower regions. Here, in this specification, the region between the shower plate 102 above the ion shielding plate 104 in the internal space of the processing chamber 100 is called the first region or the radical region 105, and the region on the side where the substrate electrode 115 below the ion shielding plate 104 is installed is called the second region or the RIE (Reactive Ion Etching) region 106. The magnetic field generating coils 112a and 112b are arranged above the ion shielding plate 104. The magnetic field generating coil 112c is arranged below the magnetic field generating coils 112a and 112b and in the vicinity of the ion shielding plate 104.

[0026] Also, as shown in FIG. 2, through holes 1041 having the same hole diameter are uniformly arranged on the outer periphery of the ion shielding plate 104. In this embodiment, "uniform" means that when a plurality of concentric circles (including the case where the radius is zero) with equal diameter differences are drawn, the through holes 1041 having a center point on the circumference of each concentric circle are arranged at equal pitches in the circumferential direction.

[0027] When plasma is generated in the radical region 105, the ions generated in the plasma are confined in the radical region 105 by the ion shielding plate 104. On the other hand, the radicals generated in the plasma diffuse inside the radical region 105, and a part of them reaches the RIE region 106 through the through holes 1041 of the ion shielding plate 104.

[0028] To generate plasma by causing electromagnetic waves of 2.45 GHz to cause ECR, a magnetic field with a magnetic flux density of 0.0875 T (tesla) is required. The region in the processing chamber 100 where the magnetic flux density is 0.0875 T is defined as the position of the ECR region. To generate such a strong magnetic field, a magnetic field generation coil 112 having a self-inductance of 100 to 1000 mH is used, and the DC coil current power supplies 113a and 113b, and the AC coil current power supply 114 are capable of supplying a current of about 10 to 60 A. By controlling the current values supplied from the plurality of DC coil current power supplies 113a, 113b and the AC coil current power supply 114 to the magnetic field generation coils 112a to 112c connected thereto respectively, the position of the ECR region in the processing chamber 100 can be precisely controlled, and the plasma generation position with respect to the sample 116 can be moved.

[0029] Also, since the magnetic field generation coils 112a and 112b are located above the ion shielding plate 104, the magnetic field strength created by these magnetic field generation coils 112a and 112b is made stronger in the radical region 105 closer to the magnetic field generation coils 112a and 112b than in the RIE region 106. This is because when it is desired to propagate electromagnetic waves to the ECR region where plasma is generated, it is better to set the magnetic field to weaken from the incident direction of the electromagnetic waves toward the ECR region. This is to make the magnetic field stronger in the direction of the waveguide 108 as seen from the ECR region, that is, in the direction of the radical region 105 as seen from the RIE region 106.

[0030] As described above, the processing chamber 100 includes an ion shielding plate 104 between the shower plate 102 and the substrate electrode 115 which is a mounting table for the sample 116, and is divided into two regions: a radical region 105 above the ion shielding plate 104 and a RIE region 106 below the ion shielding plate 104.

[0031] When the position of the ECR region is set within the radical region 105 to generate plasma, since there is an ion shielding plate 104 between the sample 116 and the plasma, ions in the plasma generated in the approximate center region within the radical region 105 are confined by the magnetic field of the ECR region, are not diffused, are blocked near the center of the ion shielding plate 104, and are confined inside the radical region 105. As a result, ions from the plasma do not reach the sample 116 on the RIE region 106 side. On the other hand, radicals generated within the radical region 105 diffuse within the radical region 105 without being confined by the magnetic field of the ECR region, and a part of them passes through a large number of through-holes 1041 formed around the ion shielding plate 104, so that the radicals are supplied to the RIE region 106 side, and the sample 116 is plasma-processed by radical etching (isotropic etching).

[0032] On the other hand, when the position of the ECR region is set within the RIE region 106 to generate plasma, since there is nothing to block between the plasma generated in the ECR region and the sample 116, both ions and radicals from the plasma are supplied to the sample 116, and the sample 116 is plasma-processed by RIE (anisotropic etching).

[0033] A control unit 130 is connected to the gas supply device 107, the pressure regulating valve 117, the electromagnetic wave generation power source 110, the DC coil current power sources 113a and 113b, the AC coil current power source 114, and the high-frequency power source 120, and controls the plasma processing apparatus 10 according to the process conditions. In the case of process conditions consisting of a plurality of plasma processing steps, the control unit 130 controls each device parameter in order according to each processing step to perform an etching process on the sample 116. Further, information regarding the pressure inside the processing chamber 100 measured by the pressure gauge 121 is sent to the control unit 130 and is used for control of process conditions consisting of a plurality of plasma processing steps.

[0034] In this embodiment, when the position of the ECR region is brought to the radical region 105 above the ion shielding plate 104, radicals are mainly supplied to the sample 116. When the position of the ECR region is brought to the RIE region 106 below the ion shielding plate 104, both radicals and ions are supplied to the sample 116. By periodically setting the position of the ECR region between these two regions, reactive ion etching is performed by controlling the amounts of ions and radicals supplied to the sample 116.

[0035] In normal RIE, plasma is generated in the region corresponding to the RIE region 106 for 100% of the time. In contrast, by switching between plasma generation in the RIE region 106 and plasma generation in the radical region 105 as in this embodiment, it is possible to create a time when radicals are mainly supplied in addition to the time when both ions and radicals are supplied to the sample 116. By periodically switching the region where plasma is generated between the RIE region 106 and the radical region 105, it is possible to perform RIE that reduces the amount of ions supplied to the sample 116 as a whole and increases the amount of radicals.

[0036] Also, since ions are mainly supplied during the time when plasma is generated in the RIE region 106, the amount of ions supplied to the sample 116 is proportional to the ratio of the time set in the RIE region 106 to the time of one cycle in which the position of the ECR region is periodically switched between the radical region 105 and the RIE region 106 with the ion shielding plate 104 in between.

[0037] When the ratio of the time in which the position of the ECR region is set in the RIE region 106 in one cycle of switching the ECR region is increased, the ratio of ions incident on the sample 116 increases. When the ratio of the time in which the position of the ECR region is set in the radical region 105 is increased, the ratio of radicals incident on the sample 116 increases. Thus, by changing the ratio between the time in which the position of the ECR region is set in the RIE region 106 and the time in which the position of the ECR region is set in the radical region 105 within one cycle of switching the ECR region, the amounts of ions and radicals incident on the sample 116 can be changed.

[0038] To control the periodic change of the position of the ECR region between the radical region 105 and the RIE region 106, and to change the ratio of the time for setting the position of the ECR region in the radical region 105 and the RIE region 106, the position serving as the center of the ECR region is set by the direct current output from the direct current coil current power supplies (also referred to as direct current power supplies) 113a and 113b and applied to the magnetic field generating coils 112a and 112b, and the position of the ECR region is moved up and down by the alternating current output from the alternating current coil current power supply (also referred to as alternating current power supply) 114 and applied to the magnetic field generating coil 112c.

[0039] In the plasma processing apparatus 10 of FIG. 1, only the magnetic field generating coil 112c closest to the ion shielding plate 104 is connected to the alternating current coil current power supply 114 with respect to the two types of coil current power supplies of the direct current coil current power supplies 113a and 113b and the alternating current coil current power supply 114, and the magnetic field generating coils 112a and 112b farther from the ion shielding plate 104 than the magnetic field generating coil 112c are connected to the direct current coil current power supplies 113a and 113b.

[0040] This utilizes the characteristic that the magnetic field generated by the coil becomes stronger closer to the coil, and the effect of the current of the magnetic field generating coil 112c closest to the ion shielding plate 104 is the greatest on the magnetic field strength near the ion shielding plate 104. When it is desired to move the ECR region up and down with respect to the ion shielding plate 104 based on this characteristic, the current of the magnetic field generating coil 112c closest to the ion shielding plate 104 may be changed in order to change the magnetic field strength near the ion shielding plate 104.

[0041] FIGS. 3A and 3B show an example in which the output from the alternating current coil current power supply 114 is zero and the position of the ECR region is set by the direct current coil current power supplies 113a and 113b. Here, the position of the ECR region can also be regarded as the position serving as the center of the ECR region.

[0042] The magnetic fields generated by the magnetic field generating coils 112a and 112b weaken from the radical region 105 towards the RIE region 106, and to create a magnetic field stronger than the magnetic field strength in the ECR region above the vacuum chamber 101 (or the processing chamber 100), the larger the current, the more the ECR region moves downward in the vacuum chamber 101 (or the processing chamber 100).

[0043] Therefore, as shown in Fig. 3A, the position 200 of the ECR region created when the currents of the DC coil current power supplies 113a and 113b are small (IaL, IbL) is in the radical region 105 above the ion shielding plate 104.

[0044] On the other hand, as shown in Fig. 3B, the position 200 of the ECR region created when the currents of the DC coil current power supplies 113a and 113b are large (IaH > IaL, IbH > IbL) is in the RIE region 106 below the ion shielding plate 104.

[0045] Figs. 4A and 4B show an example of moving the ECR region up and down by flowing an alternating current Icac through the magnetic field generating coil 112c with respect to the position 200 of the ECR region initially set by flowing a current IaL through the magnetic field generating coil 112a and a current IbL through the magnetic field generating coil 112b.

[0046] In Figs. 4A and 4B, the upper limit U and lower limit L of the position 200 of the ECR region, the position of the ion shielding plate 104, and the respective current values (IU (corresponding to the upper limit U), IL (corresponding to the lower limit L), IP (corresponding to the position of the ion shielding plate 104)) corresponding to those positions are shown.

[0047] By adjusting the AC coil current power supply 114, when the alternating current Icac flowing through the magnetic field generating coil 112c is positive, the position of the ECR region can be moved below the ion shielding plate 104 inside the vacuum chamber 101 (or the processing chamber 100), and when it is negative, it can be moved above the ion shielding plate 104.

[0048] As shown in FIG. 4A, when the position 200 of the ECR region is changed by flowing a relatively weak current IaL through the magnetic field generating coil 112a by the DC coil current power supply 113a, flowing a relatively weak current IbL through the magnetic field generating coil 112b by the DC coil current power supply 113b, and flowing an alternating current Icac through the magnetic field generating coil 112c, the time during which the position 200 of the ECR region is in the radical region 105 is longer than the time in the RIE region 106 during one period of the alternating current Icac.

[0049] On the other hand, as shown in FIG. 4B, when the position 200 of the ECR region is changed by flowing a relatively strong current IaH (IaH > IaL) through the magnetic field generating coil 112a by the DC coil current power supply 113a, flowing a relatively strong current IbH (IbH > IbL) through the magnetic field generating coil 112b by the DC coil current power supply 113b, and flowing an alternating current Icac through the magnetic field generating coil 112c, the time during which the position 200 of the ECR region is in the RIE region 106 is longer than the time in the radical region 105 during one period of the alternating current Icac. The time in the radical region 105 is longer than the time in the RIE region 106.

[0050] Therefore, by controlling with the control unit 130 to switch between IaL and IaH, and between IbL and IbH respectively during one period in synchronization with the period of the alternating current Icac flowing through the magnetic field generating coil 112c for the currents flowing through the magnetic field generating coil 112a by the DC coil current power supply 113a and the current flowing through the magnetic field generating coil 112b by the DC coil current power supply 113b, the position 200 of the ECR region can be efficiently (in a relatively short time) moved between the radical region 105 and the RIE region 106 periodically as compared with the case where the respective direct currents are not switched.

[0051] That is, by controlling the DC coil current power supplies 113a and 113b and the AC power supply 114 by the control unit 130, the position 200 of the ECR region generated by the interaction between the microwave and the magnetic field can be periodically changed. During one cycle of the alternating current Icac flowing through the magnetic field generation coil 112c by the alternating current coil current power supply 114, the position 200 of the ECR region can be moved between the radical region 105 above the ion shielding plate 104 and the RIE region 106 below the ion shielding plate 104.

[0052] In this embodiment, the magnetic field is adjusted using the control unit 130 so that the plasma generation region is located in the radical region 105 between the ion shielding plate 104 and the shower plate 102, and the sample 116 is etched by isotropic etching mainly based on the surface reaction by radicals during the radical etching period. Then, the magnetic field is adjusted so that the plasma generation region is located in the RIE region 106 between the ion shielding plate 104 and the sample 116, and the RIE period for vertically etching the sample 116 by anisotropic etching using both ions and radicals is repeated a predetermined number of times.

[0053] At this time, a mixed gas of NF3 / HBr is introduced into the processing chamber 100 for plasma generation. When this mixed gas is used, the pattern formed on the surface of the sample 116 is etched into a tapered shape by RIE, and it is characteristic that etching also proceeds in radical etching with ions shielded in the same gas system.

[0054] FIG. 5 is a schematic diagram of an etching shape showing that the etching shapes of the dense and sparse portions can be independently controlled by controlling the RIE time ratio according to this embodiment.

[0055] As shown in FIG. 5(a), the etching shape of the dense portion 532 of the pattern hardly changes even when the RIE time ratio is changed from 25% to 100%. However, as shown in FIG. 5(b), the etching shape of the sparse portion 533 of the pattern changes greatly by changing the RIE time ratio from 25% to 100%.

[0056] From this, it can be seen that by controlling the RIE time ratio, it is possible to independently control the etching shapes of the sparse pattern portions and the dense pattern portions.

[0057] FIG. 6 is a graph showing that it is possible to make the taper angles of the sparse and dense portions uniform by controlling the RIE time ratio according to this embodiment. 601 shows the RIE time ratio dependence of the taper angle of the dense pattern portion 532 of the pattern in FIG. 5, and 602 shows the RIE time ratio dependence of the taper angle of the sparse pattern corresponding to the sparse pattern portion 533 of the pattern in FIG. 5.

[0058] The taper angles were measured from the schematic diagram of FIG. 5 and are shown in the graph in FIG. The taper angle 601 of the dense pattern portion hardly changes even when the RIE time ratio is changed, but it can be seen that the taper angle 602 of the sparse pattern portion approaches 90 degrees, that is, a vertical shape, by decreasing the RIE time ratio and approaches the taper angle 601 of the dense pattern portion.

[0059] From FIG. 6, it can be seen that in order to make the taper angles after etching of the sparse and dense pattern portions uniform, it is desirable that the RIE time ratio be less than 50%. That is, the control unit 130 controls the electromagnetic wave generation power supply 110, the DC coil current power supplies 113a and 113b, and the AC coil current power supply 114 so that the RIE time ratio (the ratio of the RIE processing time to the total processing time of RIE and radical etching) is shorter than that of radical etching and is controlled to be less than 50% so as to obtain a desired etching shape.

[0060] Next, a plasma processing method using the plasma processing apparatus 10 will be described with reference to the flowchart of FIG. 7.

[0061] First, in order to form a GAA (Gate All Around) structure on the surface of the semiconductor substrate, a step of placing a sample 116 as a sample on the substrate electrode 115 in the processing chamber 100 is performed (S701).

[0062] Next, a step of controlling the pressure in the processing chamber 100 is performed by the pressure regulating valve 117 and the vacuum exhaust device 118 (S702).

[0063] Next, a step of supplying, from the gas supply device 107 through the gas supply pipe 1071, an etching gas generated by mixing a plurality of gases for performing plasma etching treatment into the region between the shower plate 102 and the dielectric window 103 in the processing chamber 100 is performed (S703).

[0064] Next, the electromagnetic wave generation power supply 110, the DC coil current power supplies 113a and 113b, and the AC coil current power supply 114 are operated to set the position 200 of the ECR region to the upper radical region 105 with respect to the ion shielding plate 104 as shown in FIG. 3A, and plasma is generated in the radical region 105 for a first predetermined time (S704). In this state, radicals generated in the radical region 105 are supplied to the side of the RIE region 106 through a large number of through holes 1041 formed around the ion shielding plate 104, and the sample 116 is plasma-treated by radical etching (isotropic etching).

[0065] Next, the electromagnetic wave generation power supply 110, the DC coil current power supplies 113a and 113b, and the AC coil current power supply 114 are operated to set the position 200 of the ECR region to the lower RIE region 106 with respect to the ion shielding plate 104 as shown in FIG. 3B, and plasma is generated in the RIE region 106 for a second predetermined time (S705). Since there is nothing to block between the plasma generated in the ECR region and the sample 116, both ions and radicals from the plasma are supplied to the sample 116, and the sample 116 is plasma-treated by RIE (anisotropic etching).

[0066] The processes of step S704 and step S705 are alternately repeated a predetermined number of times (S706).

[0067] After alternately repeating the processes of step S704 and step S705 a predetermined number of times (Yes in S706), the operations of the electromagnetic wave generation power supply 110, the DC coil current power supplies 113a and 113b, and the AC coil current power supply 114 are stopped, and the supply of the etching gas from the gas supply device 107 is stopped (S707).

[0068] Next, the sample 116 placed on the substrate electrode 115 is taken out (S708), and a series of processes is terminated.

[0069] In addition, in the radical etching (isotropic etching) process of S704 and the RIE (anisotropic etching) process of S705, the control unit 130 may control to switch the high-frequency power supplied from the electromagnetic wave generation power supply 110 to values suitable for the respective processes.

[0070] According to this embodiment, the following effects can be obtained.

[0071] 1) With a single plasma processing apparatus 10, both anisotropic etching that supplies ions and radicals and isotropic etching that supplies only radicals can be realized.

[0072] 2) In anisotropic etching that supplies ions and radicals, a technique can be provided that can more directly control the ratio of the densities of ions and radicals.

[0073] 3) In anisotropic etching that supplies radicals and ions for processing, since the radical density supplied to the surface of the sample (semiconductor substrate) can be controlled with high precision, a high-precision plasma etching technique can be provided.

[0074] 4) The etching shapes of the sparse and dense portions of the pattern within the same wafer can be independently controlled, and the rough and dense portions of the pattern can be etched uniformly.

[0075] In this embodiment, three magnetic field generating coils 112a, 112b, and 112c are used, but the number is not limited to this. When there are a plurality of magnetic field generating coils, an alternating current coil current power supply may be connected in order from the one closest to the ion shielding plate 104, and a direct current coil current power supply may be connected to the remaining magnetic field generating coils.

[0076] Generally, when the magnetic field in the plasma processing chamber is changed using a high-frequency power supply, there is a risk of generating an inductively coupled plasma in which a high-frequency induced current flows in the plasma and the generation of the plasma is maintained by the induced current. In that case, since a plasma different from the plasma generated by ECR is generated, the control of the plasma generation position through the control of the ECR region position becomes impossible. Therefore, it is preferable to use a frequency of 1 kHz or less so that an inductively coupled plasma is not generated for the frequency of the alternating current coil current power supply.

[0077] Also, in FIGS. 4A and 4B, the output of the alternating current coil current power supply 114 is illustrated as a sine wave, but it is not limited to a sine wave. Any alternating current power supply that can output a waveform that changes periodically, such as a square wave, other than a sine wave may be used.

[0078] [Modification Example] FIG. 8 is a longitudinal sectional view showing an outline of the overall configuration of a plasma processing apparatus 11 according to a modification example of Example 1. In Example 1, the control of the ECR region position was controlled by changing the current applied to the magnetic field generating coils 112a to 112c. In this modification example, the control of the ECR region position is controlled by switching the frequency of the electromagnetic wave generating power supply.

[0079] For the same configuration as the plasma processing apparatus 10 described in Example 1, the same part numbers are assigned. This modification example is configured by replacing the electromagnetic wave generating power supply (high-frequency power supply) 110 described in Example 1 with a variable frequency electromagnetic wave generating power supply (also referred to as a variable frequency high-frequency power supply) 301, replacing the control unit 130 of Example 1 with a control unit 230, and replacing the alternating current coil current power supply 114 of Example 1 with a direct current coil current power supply 113c.

[0080] The electromagnetic wave oscillated from the variable-frequency electromagnetic wave generating power supply 301 is transmitted through the electromagnetic wave matcher 111, and a standing wave of a specific mode is formed in the cavity resonator 109 of the processing chamber 100 by the electromagnetic wave propagating from the waveguide 108.

[0081] In this modification, the frequency range of the variable-frequency electromagnetic wave oscillated from the variable-frequency electromagnetic wave generating power supply 301 is not particularly limited, but in this modification, it is a microwave of 1.80 GHz to 2.45 GHz. Magnetic field generating coils 112a, 112b, and 112c are provided on the outer peripheral portion of the processing chamber 100, and DC coil current power supplies 113a, 113b, and 113c are respectively connected to the magnetic field generating coils 112a, 112b, and 112c to control their currents. The magnetic field generating coils 112a, 112b, and 112c and the DC coil current power supplies 113a, 113b, and 113c can be referred to as a magnetic field forming mechanism.

[0082] The power oscillated from the variable-frequency electromagnetic wave generating power supply 301 generates plasma in the processing chamber 100 by electron cyclotron resonance (ECR) with the magnetic field formed by the magnetic field generating coils 112a, 112b, and 112c.

[0083] To cause ECR with an electromagnetic wave of 1.80 GHz to 2.45 GHz and generate plasma, a magnetic field of 0.0643 T to 0.0875 T is required. The region where the magnetic field intensity causes resonance corresponding to each frequency in the processing chamber 100 is defined as the ECR region. To generate such a strong magnetic field, magnetic field generating coils 112a, 112b, and 112c having a self-inductance of 100 to 1000 mH are used, and DC coil current power supplies 113a, 113b, and 113c are capable of supplying a current of about 10 to 60 A.

[0084] By controlling the current values supplied from the plurality of DC coil current sources 113a to 113c to the magnetic field generating coils 112a, 112b, and 112c connected thereto by the control unit 230, the position of the ECR region in the processing chamber 100 can be precisely controlled, and the plasma generation position with respect to the sample 116 can be moved.

[0085] In addition, since the magnetic field generating coils 112a and 112b are located above the ion shielding plate 104, the magnetic field intensity created by these magnetic field generating coils 112a and 112b is stronger in the radical region 105 closer to the magnetic field generating coils 112a and 112b than in the RIE region 106.

[0086] This is because when it is desired to propagate electromagnetic waves to the ECR region where plasma is generated, it is better to set the magnetic field to weaken from the incident direction of the electromagnetic waves toward the ECR region. This is to make the magnetic field stronger in the direction of the waveguide 108 as seen from the ECR region, that is, in the direction of the radical region 105 as seen from the RIE region 106.

[0087] As described in Example 1, the processing chamber 100 includes an ion shielding plate 104 between the shower plate 102 and the sample 116, and is divided into two regions: a radical region 105 above the ion shielding plate 104 and a RIE region 106 below the ion shielding plate 104.

[0088] When the position 200 of the ECR region is set in the radical region 105 to generate plasma, since there is an ion shielding plate 104 between the sample 116 and the plasma, due to the effect of the ion shielding plate 104, ions from the plasma do not reach the sample 116 and only radicals are supplied, and the sample 116 is plasma-processed by radical etching.

[0089] When the position 200 of the ECR region is set in the RIE region 106 to generate plasma, since there is nothing to block between the plasma and the sample 116, both ions and radicals from the plasma are supplied to the sample 116, and the sample 116 is plasma-processed by RIE.

[0090] A control unit 230 is connected to the gas supply device 107, the pressure regulating valve 117, the variable frequency electromagnetic wave generating power source 301, the DC coil current power source 113, and the high-frequency power source 120, and controls the plasma processing apparatus according to the process conditions. In the case of process conditions consisting of a plurality of plasma processing steps, the control unit 230 controls each device parameter in order according to each processing step, thereby performing an etching process on the sample 116.

[0091] In this modification, when the position of the ECR region is brought above the ion shielding plate 104, only radicals are supplied to the sample 116, and when the position of the ECR region is brought below the ion shielding plate 104, both radicals and ions are supplied to the sample 116. By periodically setting the position of the ECR region between these two regions (105, 106), reactive ion etching with controlled density ratio of ions and radicals is performed.

[0092] In normal RIE, plasma is generated in the RIE region 106 for 100% of the time. On the other hand, by generating plasma in the radical region 105 in addition to generating plasma in the RIE region 106, it is possible to create a time when only radicals are supplied to the sample 116 in addition to the time when both ions and radicals are supplied to the sample 116.

[0093] By periodically switching the region where plasma is generated between the RIE region 106 and the radical region 105, it is possible to perform RIE with a reduced ion density and an increased radical density ratio as a whole. Also, since ions are supplied to the sample 116 only during the time when plasma is generated in the RIE region 106, the amount of ions supplied to the sample 116 is proportional to the ratio of the time set in the RIE region 106 in one cycle in which the position of the ECR region is periodically switched.

[0094] When increasing the time during which the position of the ECR region is set in the RIE region 106, the ratio of ions increases, and when increasing the time during which the position of the ECR region is set in the radical region 105, the ratio of radicals increases. Therefore, the ratio of the density of ions to radicals can be changed by the ratio of the time during which the position of the ECR region is set in the RIE region 106 to the time during which the position of the ECR region is set in the radical region within one cycle.

[0095] For the periodic control of the position of the ECR region and for changing the ratio of the time during which the position of the ECR region is set in the radical region 105 and the RIE region 106, by means of the currents output from the DC coil current power supplies 113a, 113b, and 113c, the position of the ECR region corresponding to the center frequency in the frequency range of the variable frequency electromagnetic wave generating power supply 301 is set. For example, when the frequency range is from 1.80 GHz to 2.45 GHz, the position corresponding to the center frequency of 2.13 GHz is set, and the position of the ECR region is moved up and down by changing the output frequency of the variable frequency electromagnetic wave generating power supply 301 with respect to that magnetic field.

[0096] Figures 9A and 9B show examples of setting the position 200 of the ECR region corresponding to the center frequency by the DC coil current power supplies 113a, 113b, and 113c. Here, the position of the ECR region can also be regarded as the position at the center of the ECR region.

[0097] The magnetic field created by the magnetic field generating coils 112a, 112b, and 112c weakens from the radical region 105 towards the RIE region 106, and a magnetic field stronger than the magnetic field strength of the ECR region is created above the vacuum chamber 101. Therefore, the greater the current, the more the ECR region moves downward in the vacuum chamber 101.

[0098] Therefore, when the currents of the DC coil current sources 113a, 113b, and 113c in FIG. 9A are small (IaL, IbL, IcL), the position 200 of the ECR region created is in the radical region 105 above the ion shielding plate 104, and when the currents of the DC coil current sources 113a, 113b, and 113c in FIG. 9B are large (IaH > IaL, IbH > IbL, IcH > IcL), the position 200 of the ECR region created is in the RIE region 106 below the ion shielding plate 104.

[0099] FIGS. 10A and 10B show an example in which the position of the ECR region is moved up and down by the frequency of the variable frequency electromagnetic wave generation power supply 301 with respect to the position 200 of the ECR region of the center frequency set by the magnetic field generation coils 112a, 112b, and 112c.

[0100] FIG. 10A shows the upper limit U and lower limit L of the position 200 of the ECR region, the position of the ion shielding plate 104, and the corresponding frequencies (fU, fL, fP). When the frequency is lower than the center frequency fc, the magnetic field strength required for resonance also becomes weaker. Therefore, when the frequency decreases, the position of the ECR region moves downward in the vacuum chamber 101, and when it becomes higher than the center frequency, it moves upward. As shown in FIG. 10A, when the position 200 of the ECR region corresponding to the center frequency fc is set in the radical region 105 by the DC coil current sources 113a, 113b, and 113c, the time that the ECR region is in the radical region 105 becomes longer than the time in the RIE region 106.

[0101] As shown in FIG. 10B, when the position of the ECR region corresponding to the center frequency fc is set in the RIE region 106 by the DC coil current sources 113a, 113b, and 113c, the time in the RIE region 106 becomes longer than the time in the radical region 105.

[0102] By periodically changing the frequency of the power supply 301 for generating variable-frequency electromagnetic waves, the position of the ECR region can be periodically moved between the radical region 105 and the RIE region 106 without changing the magnetic field strength. That is, by controlling the power supply 301 for generating variable-frequency electromagnetic waves with the control unit 230, the position 200 of the ECR region generated by the interaction between the microwave and the magnetic field can be periodically changed. Thereby, during one cycle, the position 200 of the ECR region can be moved from above the ion shielding plate 104 to below the ion shielding plate 104 or from below the ion shielding plate 104 to above the ion shielding plate 104.

[0103] The plasma processing method using the plasma processing apparatus 11 according to this modification is the same as the processing flow described with reference to FIG. 7 in Example 1, and thus the detailed description thereof is omitted. However, in this modification, in the step of generating plasma in the radical region of S704 for a first predetermined time and the step of generating plasma in the RIE region of S705 for a second predetermined time, the ECR region is changed by periodically changing the frequency of the power supply 301 for generating variable-frequency electromagnetic waves, which is different from the case of Example 1.

[0104] According to this modification, a technique can be provided that can more directly control the density ratio of ions and radicals in anisotropic etching for supplying ions and radicals.

[0105] Further, as a combination of the configuration described in Example 1 and the configuration described in the above-described modification, in the plasma processing apparatus 11 described in the modification, the DC coil current power supply 113c may be changed to the AC coil current power supply 114 described in Example 1. In this case, in anisotropic etching, it is necessary to set the frequency of the power supply 301 for generating variable-frequency electromagnetic waves and the frequency of the AC coil current power supply 114 so that the density ratio of ions and radicals becomes as desired.

[0106] In addition, in the plasma processing apparatus 11 described in the modified example, a configuration may be adopted in which both the variable frequency electromagnetic wave generation power source 301 and the electromagnetic wave generation power source 110 of the first embodiment are provided. In this case, when performing isotropic etching, the electromagnetic wave generation power source 110 is operated in the configuration shown in FIG. 9A instead of the variable frequency electromagnetic wave generation power source 301. Further, when performing anisotropic etching, the electromagnetic wave generation power source 110 is operated in the configuration shown in FIG. 9B instead of the variable frequency electromagnetic wave generation power source 301. On the other hand, when performing anisotropic etching with highly precise control of the density ratio between ions and radicals, as shown in FIGS. 10A and 10B, the variable frequency electromagnetic wave generation power source 301 is operated.

[0107] Thereby, with a single plasma processing apparatus, both anisotropic etching processing for supplying ions and radicals and isotropic etching processing for supplying only radicals can be realized.

Example

[0108] [[ID=II]]A second embodiment of the present invention will be described with reference to FIGS. 11 and 12. In the first embodiment, as shown in the processing flowchart of FIG. 7, the etching shape of the dense and sparse portions of the pattern formed on the surface of the sample can be independently controlled by switching the ECR region. In this embodiment, in addition to this, the mixing ratio of the mixed gas is also switched according to the switching of the ECR region.

[0109] The configuration of the plasma processing apparatus 20 according to this embodiment shown in FIG. 11 is different from the configuration of the plasma processing apparatus 10 described with reference to FIG. 1 in the first embodiment in the configuration of the gas supply device 107 and the control unit 130. Since the other configurations are the same as those in the first embodiment, the same numbers are assigned and the detailed description thereof is omitted.

[0110] In the configuration of the plasma processing apparatus 20 shown in FIG. 11, gas supply devices 1107 and 1108 are provided, and the mixing ratio of the gases supplied from the gas supply devices 1107 and 1108 is adjusted by the control device 1130, so that a mixed gas with an adjusted mixing ratio is supplied from the gas supply pipe 1171 to the region 1020 between the shower plate 102 and the dielectric window 103 according to the steps.

[0111] During the etching process, switching the ECR region to the radical region above the ion shielding plate 104 and the RIE region 106 below the ion shielding plate 104, and alternately executing the etching process mainly based on radical reaction and the etching process using ions and radicals is the same as in the case of Example 1 or a modification of Example 1.

[0112] In this embodiment, the difference from Example 1 is that in the etching process mainly based on radical reaction and the etching process using ions and radicals, the mixing ratio of a plurality of gases (such as NF3 / HBr) constituting the mixed gas supplied to the processing chamber 100 is switched.

[0113] That is, in this embodiment, the control device 1130 controls the gas supply devices 1107 and 1108 to switch the mixing ratio of HBr gas to NF3 gas in the etching process using ions and radicals with respect to the etching process mainly based on radical reaction.

[0114] The flow of the etching process according to this embodiment will be described with reference to FIG. 12. First, in order to form a GAA structure on the surface of the semiconductor substrate, a step of placing a sample 116 as a sample on the substrate electrode 115 in the processing chamber 100 is performed (S1201).

[0115] Next, a step of evacuating the inside of the processing chamber 100 by the vacuum exhaust device 118 via the pressure adjustment valve 117 and controlling the pressure of the processing chamber 100 is performed (S1202).

[0116] Next, an etching gas for performing a plasma etching process supplied from gas supply devices 1107 and 1108 is supplied from a gas supply pipe 1171 in a state where it is adjusted to a first mixing ratio suitable for a radical etching process in a region between a shower plate 102 and a dielectric window 103 in a processing chamber 100 (S1203).

[0117] Next, an electromagnetic wave generation power source 110, a DC coil current power source 113, and an AC coil current power source 114 are operated, and as shown in FIG. 3A, the position 200 of the ECR region is set to an upper radical region 105 with respect to an ion shielding plate 104, and plasma is generated in the radical region 105 for a first predetermined time (S1204). In this state, radicals generated in the radical region 105 are supplied to the side of an RIE region 106 through a large number of through holes 1041 formed around the ion shielding plate 104, and a sample 116 is plasma-processed by radical etching (isotropic etching).

[0118] Next, an etching gas for performing a plasma etching process supplied from gas supply devices 1107 and 1108 is supplied from a gas supply pipe 1171 in a state where it is adjusted to a second mixing ratio suitable for RIE (anisotropic etching) in a region between a shower plate 102 and a dielectric window 103 in a processing chamber 100 (S1205).

[0119] Next, an electromagnetic wave generation power source 110, a DC coil current power source 113, and an AC coil current power source 114 are operated, and as shown in FIG. 3B, the position 200 of the ECR region is set to a lower RIE region 106 with respect to an ion shielding plate 104, and plasma is generated in the RIE region 106 for a second predetermined time (S1206). Since there is nothing to block between the plasma generated in the ECR region and the sample 116, both ions and radicals from the plasma are supplied to the sample 116, and the sample 116 is plasma-processed by RIE (anisotropic etching).

[0120] The processing from step S1203 to step S1206 is repeated a predetermined number of times (S1207).

[0121] After repeating the processes from the step of S1203 to the step of S1206 a predetermined number of times (Yes in S1207), the operations of the electromagnetic wave generation power supply 110, the DC coil current power supply 113, and the AC coil current power supply 114 are stopped, and the supply of the etching gas from the gas supply devices 1107 and 1108 is stopped (S1208).

[0122] Next, the sample 116 placed on the substrate electrode 115 is taken out (S1209), and a series of processes is terminated.

[0123] In addition, in the radical etching (isotropic etching) step of S1204 and the RIE (anisotropic etching) step of S1206, the control device 1130 may control to switch the high-frequency power supplied from the electromagnetic wave generation power supply 110 to values suitable for the respective processes.

[0124] According to this embodiment, in addition to the effects described in the first embodiment, the etching shapes of the sparse portions and the dense portions of the patterns within the same wafer can be efficiently controlled independently, and the rough and dense portions of the patterns can be etched uniformly.

[0125] In addition, also in this embodiment, the configuration as described in the modification of the first embodiment can be applied.

[0126] The above-described embodiments have been described in detail for easy understanding of the present invention. Needless to say, the present invention is not limited to the above-described embodiments and can be variously modified.

Description of Reference Numerals

[0127] 10, 11, 20: Plasma processing apparatus 100: Processing chamber 101: Vacuum vessel 102: Shower plate 103: Dielectric window 104: Ion shielding plate 1041: Through hole 105: Radical region 106: RIE area 107, 1107, 1108: Gas supply device 108: Waveguide 109: Cavity resonator 110: Power supply for generating electromagnetic waves 111: Electromagnetic wave matcher 112a, 112b, 112c: Magnetic field generating coil 113a, 113b, 113c: DC coil current power supply 114: AC coil current power supply 115: Substrate electrode 116: Sample 117: Pressure regulating valve 118: Vacuum exhaust device 119: High-frequency matcher 120: High-frequency power supply 130, 230: Control unit 200: Position of the ECR area 301: Power supply for generating variable-frequency electromagnetic waves 1071, 1171: Gas supply pipe.

Claims

Claim 1: In a plasma processing method for forming a Gate All Around structure, a first step of performing Reactive Ion Etching using a mixed gas of NF3 gas and HBr gas; a second step of performing radical etching using a mixed gas of NF3 gas and HBr gas; and the first step and the second step are alternately repeated a predetermined number of times, wherein the time of the first step is shorter than the time of the second step. A plasma processing method characterized by this. Claim 2 In the plasma processing method according to Claim 1, the ratio of the time of the first step to the time of the second step is less than 50%. A plasma processing method characterized by this. Claim 3 In the plasma processing method according to Claim 1, by controlling the power source that generates the magnetic field so that the position of the electron cyclotron resonance region generated by the interaction of microwaves and the magnetic field changes periodically above and below a shielding plate that shields the incidence of ions on a sample placed on a sample stage, the first step and the second step are alternately repeated, the position of the electron cyclotron resonance region in the first step is below the shielding plate, and the position of the electron cyclotron resonance region in the second step is above the shielding plate. A plasma processing method characterized by this. Claim 4 In the plasma processing method according to Claim 2, by controlling the power source that generates the magnetic field so that the position of the electron cyclotron resonance region generated by the interaction of microwaves and the magnetic field changes periodically above and below a shielding plate that shields the incidence of ions on a sample placed on a sample stage, the first step and the second step are alternately repeated, the position of the electron cyclotron resonance region in the first step is below the shielding plate, and the position of the electron cyclotron resonance region in the second step is above the shielding plate. A plasma processing method characterized by this. Claim 5 The NF in the first step ３ The ratio of the flow rate of the gas and the flow rate of the HBr gas, and the NF in the second step ３ A plasma processing method characterized in that the ratio of the flow rate of the gas and the flow rate of the HBr gas is different. In the plasma processing method according to Claim 1, Claim 6 In the plasma processing method according to Claim 1, it is characterized by not having any steps other than the first step and the second step. A plasma processing method characterized by this. Claim 7 a first step of performing Reactive Ion Etching using a gas having a tapered shape; and a second step of performing radical etching. The time of the first step is shorter than the time of the second step, by controlling a power supply that generates the magnetic field so as to periodically change the position of the electron cyclotron resonance region generated by the interaction of microwaves and the magnetic field above and below a shielding plate that shields the incidence of ions on a sample placed on a sample stage, the first step and the second step are alternately repeated a predetermined number of times, in the first step, the position of the electron cyclotron resonance region is below the shielding plate, in the second step, the position of the electron cyclotron resonance region is above the shielding plate. A plasma processing method characterized by this.

8. In the plasma processing method according to claim 7, The gas is NF ３ A plasma processing method characterized in that the gas is a mixed gas of NF gas and HBr gas.

9. In the plasma processing method according to claim 8, the second step is characterized by generating plasma using the same gas as the gas. A plasma processing method.

10. In the plasma processing method according to claim 7, the ratio of the time of the first step to the time of the second step is less than 50%. A plasma processing method characterized by this.

11. In the plasma processing method according to claim 7, the gas is a mixed gas, the ratio of the flow rate of the gas constituting the mixed gas in the first step and the ratio of the flow rate of the gas constituting the mixed gas in the second step are different. A plasma processing method characterized by this.

12. In the plasma processing method according to claim 7, A plasma processing method characterized by further having no steps other than the first step and the second step.

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