Plasma processing equipment

Abstract

To provide a plasma processing apparatus which can realize both of radical irradiation and ion irradiation with one apparatus, controls the radical distribution on a sample surface in a processing mode with the radical irradiation and can perform uniform processing.SOLUTION: A plasma processing apparatus comprises: a vacuum processing chamber 104 in which plasma processing is performed on a sample; a magnetron 101 which supplies the high-frequency power for plasma generation; a solenoid 105 which forms a magnetic field in the processing chamber; a sample stage 120 on which the sample is placed; a first shielding plate 110 which is arranged on the upper side of the sample stage and has a plurality of openings; a cylindrical shielding part 111 which is arranged on the upper side of the first shielding plate and divides a space on the upper side of the first shielding plate into an inner space 104-3 including an axial line of the plasma processing apparatus and an outer space 104-2 that surrounds the inner space; and a first gas supply port 130 and a second gas supply port 131 which supply different gases to the outer space and the inner space.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, in order to meet the increasing requirements for power saving and high speed of semiconductor devices, the complexity of device structures has been remarkable. For example, in logic devices, a FET (referred to as GAA-FET) having a GAA (Gate All Around) structure in which a channel is formed by stacked nanosheets has been studied. In the etching process of GAA-FET, in addition to anisotropic etching when forming fins, isotropic etching for performing lateral processing when forming nanosheets is required.

[0003] Here, anisotropic etching mainly proceeds by ion-assisted etching that promotes the reaction of radicals by ions. Therefore, anisotropic etching is realized by irradiating both radicals and ions onto the sample surface. On the other hand, since isotropic etching mainly involves the surface reaction of radicals and the sample, it is realized by irradiating only radicals onto the sample surface.

[0004] As described above, plasma processing apparatuses used for semiconductor device processing are required to have both a mode for performing anisotropic etching by both ions and radicals and a mode for performing isotropic etching by radicals.

[0005] In response to such requirements, in Patent Document 1, a shielding plate for shielding ions is installed in a chamber, and a mode of processing a sample with both ions and radicals is realized by generating plasma in a region below the shielding plate (sample side), or a mode of processing a sample with only radicals is realized by generating plasma above the shielding plate. A plasma processing apparatus has been proposed.

[0006] Furthermore, Patent Document 2 discloses a plasma processing apparatus that shields ions in the plasma by arranging two or more shielding plates, each having multiple holes, so that their holes do not overlap, thereby enabling processing using only radicals. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-93226 [Patent Document 2] Japanese Patent Publication No. 2006-86449 [Overview of the project] [Problems that the invention aims to solve]

[0008] By the way, in order to create as many devices as possible from a single sample, it is necessary to control the in-plane distribution of the etching rate and to make the processed shape uniform within a single sample.

[0009] However, in the case of the plasma processing apparatus shown in Patent Document 1, in the processing mode using only radicals, the position of the holes in the shielding plate to which the radicals are supplied is fixed, so the radical distribution on the sample surface cannot be controlled, and the processed shape may become non-uniform.

[0010] Furthermore, in Patent Document 2, in order to improve ion shielding, two or more shielding plates with multiple holes are arranged so that the holes of each shielding plate do not overlap. However, there is no mechanism to control the distribution of radicals, and the processed shape may become non-uniform.

[0011] This invention has been made in view of the problems of the prior art described above, and aims to provide a plasma processing apparatus that can perform both radical irradiation and ion irradiation with a single device, and that can control the radical distribution on the sample surface and perform uniform processing in the radical irradiation processing mode. [Means for solving the problem]

[0012] To solve the above problems, one representative plasma processing apparatus of the present invention comprises: a processing chamber in which a sample is subjected to plasma processing; a high-frequency power supply for supplying high-frequency power for plasma generation; a magnetic field forming mechanism for forming a magnetic field in the processing chamber; a sample stage on which the sample is placed; and a first shielding plate disposed above the sample stage and having a plurality of openings, wherein the plasma processing apparatus comprises: a cylindrical shielding portion disposed above the first shielding plate and dividing the space above the first shielding plate into an inner space including the axis of the plasma processing apparatus and an outer space surrounding the inner space; a supply structure for supplying different gases to the outer space and the inner space; and a second shielding plate disposed in the inner space and having a plurality of openings, which divides the inner space into an upper space and a lower space. The magnetic field formation mechanism causes the upper region of the first shielding plate to By forming an ECR surface, the radical mode is set. and, Lower region of the first shielding plate to This is achieved by forming an ECR surface, which in turn sets the RIE mode. [Effects of the Invention]

[0013] According to the present invention, a plasma processing apparatus can be provided that enables both radical irradiation and ion irradiation with a single device, and that, in the processing mode using radical irradiation, the radical distribution on the sample surface can be controlled to perform uniform processing. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a longitudinal cross-sectional view showing the schematic overall configuration of the plasma processing apparatus according to Embodiment 1. [Figure 2A] Figure 2A is a perspective view showing the configuration of the cylindrical shielding portion of the plasma processing apparatus according to Embodiment 1. [Figure 2B]FIG. 2B is a plan view of a shielding plate constituting a shielding portion according to Embodiment 1. [Figure 3A] FIG. 3A is a diagram showing a simulation result of a radical flux distribution on a sample surface when plasma is generated at an outer peripheral portion of an upper part of a shielding plate. [Figure 3B] FIG. 3B is a diagram showing a simulation result of a radical flux distribution on a sample surface when plasma is generated at a central portion of an upper part of a shielding plate. [Figure 4] FIG. 4 is a longitudinal sectional view showing a schematic overall configuration of a plasma processing apparatus according to Embodiment 2. [Figure 5A] FIG. 5A is a plan view of a first shielding plate constituting a shielding portion according to Embodiment 2. [Figure 5B] FIG. 5B is a plan view of a second shielding plate constituting a shielding portion according to Embodiment 2. [Figure 6] FIG. 6 is a diagram schematically showing magnetic field lines in a plasma processing apparatus.

MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, the present invention will be described with reference to embodiments. In this specification, the side of the magnetron 101 is taken as the upper side, and the side of the sample stage 120 is taken as the lower side.

[0016] (Embodiment 1) A schematic overall configuration sectional view of a plasma processing apparatus according to Embodiment 1 of the present invention is shown in FIG. 1. In the plasma processing apparatus of this embodiment, microwaves with a frequency of 2.45 GHz supplied from a magnetron 101, which is a high-frequency power source, through a waveguide 102 and a dielectric window 103 to a vacuum processing chamber 104 (lower region 104-1, upper outer peripheral region 104-2, upper central region 104-3), and electrons that perform cyclotron motion by a static magnetic field generated by a solenoid coil 105 resonate with each other by electron cyclotron resonance (ECR) to generate plasma.

[0017] Furthermore, a high-frequency power supply 123 is connected to the sample stage 120 on which the sample 121 is placed, via a matching unit 122. The inside of the vacuum processing chamber 104 is connected to a pump 124 via a valve 125, and the pressure inside the vacuum processing chamber 104 can be adjusted by the opening of the valve 125.

[0018] Furthermore, this plasma processing apparatus divides the vacuum processing chamber 104 into a lower region 104-1 and an upper region (104-2 and 104-3) by a dielectric shielding plate 110, and further divides the upper region into an upper outer region 104-2 and an upper central region 104-3 by a dielectric cylindrical member (cylindrical shielding part) 111.

[0019] In this plasma processing apparatus, when the frequency of microwaves supplied from the magnetron 101 through the waveguide 102 and dielectric window 103 to the vacuum processing chamber 104 is 2.45 GHz, plasma is generated by ECR on a surface with a magnetic field strength of 0.0875 T generated by the solenoid coil (magnetic field formation mechanism) 105. The plasma generation surface is called the ECR surface.

[0020] Therefore, by adjusting the current of the solenoid coil 105 so that the ECR surface is located between the dielectric window 103 and the shielding plate 110, plasma can be generated in the upper region (104-2 and 104-3) of the shielding plate 110, and since ions are almost completely shielded by the shielding plate 110, a radical mode can be realized in which only radicals are irradiated onto the sample 121. At this time, isotropic etching mainly driven by surface reactions caused by radicals proceeds on the sample surface.

[0021] In contrast, by adjusting the current of the solenoid coil 105 so that the ECR surface is located between the shielding plate 110 and the sample 121, plasma can be generated in the lower region 104-1 on the sample 121 side of the shielding plate 110, and an RIE mode can be realized in which both radicals and ions can be supplied to the sample 121. At this time, anisotropic etching mainly consisting of ion-assisted etching proceeds on the sample surface, where the radical reaction is promoted by ion irradiation.

[0022] In this embodiment, the shielding plate 110 and the cylindrical member 111 are made of dielectric material, and microwaves can propagate from the shielding plate 110 to the lower region 104-1 on the sample side.

[0023] Furthermore, this plasma processing apparatus is equipped with a supply structure comprising a first gas supply port 130 formed on the inner circumferential surface of the vacuum processing chamber 104 and supplying gas to the upper outer circumferential region 104-2, and a second gas supply port 131 that opens at the lower central surface, passing through the interior from the outer circumferential surface of the dielectric window 103 and supplying gas to the upper central region 104-3. The first gas supply port 130 and the second gas supply port 131 are independent of each other and connected to different gas sources (not shown), so that different types of gas can be supplied to the upper outer circumferential region 104-2 and the upper central region 104-3. This supply structure that supplies different gases allows control of the distribution of radicals irradiated onto the sample 121 in the case of radical mode. The method for controlling the radical distribution will be described below.

[0024] An etching gas that generates radicals is supplied from the first gas supply port 130 to the upper outer peripheral region 104-2, and a rare gas is supplied from the second gas supply port 131 to the upper central region 104-3, generating plasma by ECR in the region above the shielding plate 110. At this time, since the rare gas does not generate radicals, radicals are supplied to the sample 121 only from the opening 141, and the etching rate can be increased in the outer peripheral portion of the sample 121.

[0025] In response to this, a rare gas is supplied from the first gas supply port 130 to the upper outer peripheral region 104-2, and an etching gas that generates radicals is supplied from the second gas supply port 131 to the upper central region 104-3, generating plasma by ECR in the region above the shielding plate 110. At this time, since radicals are supplied to the sample 121 only from the opening 140, the etching rate can be increased in the central part of the sample 121.

[0026] Figures 2A and 2B show the structure of the shielding portion according to this embodiment. Here, Figure 2A is a perspective view of the cylindrical member 111, and Figure 2B is a plan view of the shielding plate 110.

[0027] As shown in Figure 2A, the cylindrical member 111 has a cylindrical structure with an inner diameter R1, an outer diameter R2, and a height h1.

[0028] As shown in Figure 2B, the shielding plate 110 has a disc-shaped structure. With respect to the center of the shielding plate 110, one or more openings (through holes) 201 are formed in the inner region with a diameter R3 smaller than the inner diameter R1 of the cylindrical member 111, and one or more openings (through holes) 202 are formed in the outer region with a diameter R4 larger than the outer diameter R2 of the cylindrical member 111. Preferably, the smallest circumscribed circle diameter of the circumferentially aligned openings 201 is equal to the diameter R3, and the largest inscribed circle diameter of the circumferentially aligned openings 202 is equal to the diameter R4.

[0029] The shielding plate 110 has an annular groove 203 with a depth of h2, which is concentrically formed in the upper surface region between diameter R1 and diameter R2. The groove 203 engages with the end of the cylindrical member 111 to prevent displacement when installed on the shielding plate 110.

[0030] There is a relationship h1-h2=h3 between the height h1 of the cylindrical member 111, the depth h2 of the groove 203 of the shielding plate 110 from the dielectric window side surface, and the distance h3 (Figure 1) between the dielectric window side surface of the shielding plate 110 and the shielding plate side surface of the dielectric window 103. Therefore, by engaging the lower end of the cylindrical member 111 with the groove 203 and placing the upper end of the cylindrical member 111 in contact with the lower surface of the dielectric window 103, the space between the dielectric window 103 and the shielding plate 110 is divided by the cylindrical member 111 into exactly two spaces (an inner space including the axis of the plasma processing apparatus (upper central region 104-3), and an outer space surrounding the inner space (upper outer peripheral region 104-2)).

[0031] Alternatively, the cylindrical member 111 and the shielding plate 110 may be integrally formed. In that case, there is a relationship h1 = h3 between the height h1 of the cylindrical member 111 and the distance h3 between the dielectric window side surface of the shielding plate 110 and the shielding plate side surface of the dielectric window 103, and the space between the dielectric window 103 and the shielding plate 110 is divided into exactly two spaces by the cylindrical member 111.

[0032] Figure 3A shows the distribution of O radical flux within the wafer surface when O2 is plasma-generated in the upper outer region 104-2 of Figure 1, and Figure 3B shows the distribution of O radical flux within the wafer surface when O2 is plasma-generated in the upper central region 104-3. In each figure, the vertical axis represents the value of O radical flux, and the horizontal axis represents the radial position of the wafer (center is set to 0). In the figures, the O radical flux values ​​are normalized by the average value. Furthermore, the uniformity shown in the graphs is expressed by the following equation (1), using the O radical flux Γm at the wafer center (wafer diameter 0 mm), the radical flux Γe at the wafer edge (wafer diameter 140 mm), and the average value Γa of the O radical flux within the wafer surface. (Uniformity)=(Γm-Γe) / (Γa) (1)

[0033] According to equation (1), when the O radical flux is high at the outer edge of the wafer, the uniformity will be a negative value, and conversely, when the O radical flux is high at the center of the wafer, the uniformity will be a positive value, and the smaller the absolute value, the higher the uniformity.

[0034] Figure 3A shows that when O2 is plasma-generated in the upper outer peripheral region 104-2 of Figure 1, the in-plane distribution of radical flux becomes negative, and etching is promoted at the outer edge of the wafer. In contrast, Figure 3B shows that when O2 is plasma-generated in the upper central region 104-3 of Figure 1, the in-plane distribution of radical flux becomes positive, and etching is promoted at the center of the wafer.

[0035] Figures 3A and 3B confirm that the in-wafer distribution of the etching rate can be controlled by switching the etching gas supply destination to either the upper outer region 104-2 or the upper central region 104-3 in Figure 1.

[0036] (Embodiment 2) Figure 4 shows a schematic cross-sectional view of the overall configuration of a plasma processing apparatus according to Embodiment 2 of the present invention. The configuration, excluding the (first) shielding plate 110 and the second shielding plate 112, is the same as that of Embodiment 1 described using Figure 1, so its description is omitted.

[0037] In Embodiment 2, a second shielding plate 112 is further fixed inside the cylindrical member 111 to the plasma processing apparatus of Embodiment 1, and is arranged coaxially with the first shielding plate 110. The second shielding plate 112 divides the inner space of the cylindrical member 111 into an upper central region (upper space) 104-4 above the second shielding plate 112 and a lower central region (lower space) 104-5 below the second shielding plate 112.

[0038] Figures 5A and 5B show the structure of the shielding portion according to this embodiment. Here, Figure 5A is a plan view of the first shielding plate 110, and Figure 5B is a plan view of the second shielding plate 112.

[0039] As shown in Figure 5A, the first shielding plate 110 has a disc-shaped structure. With respect to the center of the first shielding plate 110, one or more openings (through holes) 301 are formed in the region inside the cylindrical member 111 with a diameter R3 smaller than the inner diameter R1, and one or more openings (through holes) 302 are formed in the region outside the cylindrical member 111 with a diameter R4 larger than the outer diameter R2. Here, the openings 301 are preferably single circles with a diameter R3 and concentric with the first shielding plate 110, but are not limited to this.

[0040] As shown in Figure 5B, the second shielding plate 112, which is arranged coaxially with the first shielding plate 110, has a disc-shaped structure. With respect to the center of the second shielding plate 112, one or more openings 303 are formed in the outer region with a diameter R5 that is greater than diameter R3, but no openings are formed on the side of diameter R3 that is closer to the center. It is preferable that the maximum inscribed circle diameter of the openings 303 arranged in the circumferential direction is equal to the diameter R5.

[0041] The reason why the above configuration improves ion shielding performance is explained below. It is known that ions move along magnetic field lines when a magnetic field is present. Figure 6 is a cross-sectional view illustrating the shape of magnetic field lines in the plasma processing apparatus shown in Figure 1. The magnetic field lines 400 are located longitudinally within the plasma processing apparatus, and the spacing between the magnetic field lines widens as you move from the dielectric window 103 toward the sample 121.

[0042] Therefore, ions supplied from the upper outer peripheral region 104-2 to the lower region 104-1 through the opening 141 are lost when they strike the inner wall of the vacuum processing chamber 104 along the magnetic field lines.

[0043] In contrast, ions supplied from the upper central region 104-3 to the lower region 104-1 through the opening 140 are incident on the sample 121 along the magnetic field lines. To avoid this, it is desirable to improve the ion shielding performance of the opening 140.

[0044] According to this embodiment, by arranging the first shielding plate 110 and the second shielding plate 112 as shown in Figure 5, when plasma is formed in the central upper region 104-4, ions supplied to the central lower region 104-5 through the opening 142 of the second shielding plate 112 shown in Figure 4 are absorbed along the magnetic field lines by the cylindrical member 111 and the upper surface of the first shielding plate 110. As a result, only neutral particles containing radicals are supplied to the lower region 104-1 from the opening 140 of the first shielding plate 110, thereby improving the shielding of ions. [Explanation of Symbols]

[0045] 101...Magnetron, 102...Waveguide, 103...Dielectric window, 104...Vacuum processing chamber, 104-1...Lower region, 104-2...Upper outer region, 104-3...Upper central region, 104-4...Upper central region, 104-5...Lower central region, 105...Solenoid coil, 110...Shielding plate (first shielding plate), 111...Cylindrical member, 112...Second shielding plate, 120...Sample stage, 121...Sample, 122...Matching unit, 123...High-frequency power supply, 124...Pump, 125...Valve, 130...First gas supply port, 131...Second gas supply port, 140...Opening, 141...Opening, 142...Opening, 201...Opening, 202...Opening, 203...Groove

Claims

1. A plasma processing apparatus comprising: a processing chamber in which a sample is subjected to plasma treatment; a high-frequency power supply for supplying high-frequency power for plasma generation; a magnetic field forming mechanism for forming a magnetic field within the processing chamber; a sample stage on which the sample is placed; and a first shielding plate positioned above the sample stage and having a plurality of openings, A cylindrical shielding portion is positioned above the first shielding plate and divides the space above the first shielding plate into an inner space including the axis of the plasma processing apparatus and an outer space surrounding the inner space, A supply structure that supplies different gases to the outer space and the inner space, It includes a second shielding plate having multiple openings, which is positioned in the inner space and divides the inner space into an upper space and a lower space, The magnetic field formation mechanism sets a radical mode by forming an ECR surface in the upper region of the first shielding plate, and sets an RIE mode by forming an ECR surface in the lower region of the first shielding plate. A plasma processing apparatus characterized by the following:

2. In the plasma processing apparatus according to claim 1, The plasma processing apparatus is characterized in that the first shielding plate has one or more openings in an inner region with a diameter R3 smaller than the inner diameter R1 of the cylindrical shielding portion, with respect to its center, and one or more openings in an outer region with a diameter R4 larger than the outer diameter R2 of the cylindrical shielding portion.

3. In the plasma processing apparatus according to claim 1, The plasma processing apparatus is characterized in that the first shielding plate has an annular groove into which the end of the cylindrical shielding portion fits.

4. In the plasma processing apparatus according to claim 1, A plasma processing apparatus characterized in that a dielectric window is arranged above the first shielding plate, and the cylindrical shielding portion divides the space between the first shielding plate and the dielectric window into an outer space and an inner space.

5. In the plasma processing apparatus according to claim 1, The first shielding plate has one or more openings in an inner region with a diameter R3 smaller than the inner diameter R1 of the cylindrical shielding portion, with respect to its center, and one or more openings in an outer region with a diameter R4 larger than the outer diameter R2 of the cylindrical shielding portion. The plasma processing apparatus is characterized in that the second shielding plate has the opening in an outer region with a diameter R5 greater than the diameter R3, with respect to its center, and does not have an opening on the central side of the diameter R3.

6. In the plasma processing apparatus according to claim 5, The first shielding plate has a single opening in the region inside the diameter R3. A plasma processing apparatus characterized by the following:

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