Plasma processing apparatus

Abstract

During isotropic etching, the distribution of free radicals on the wafer is controlled, and foreign matter on the upper surface of the second shielding plate is prevented from flying away. The plasma processing apparatus includes: a processing chamber (106) for plasma processing of a sample; a high-frequency power supply (113) for supplying high-frequency power for generating plasma; a sample stage (120) for holding the sample; and a first plate (115) disposed above the sample stage (120) and having a plurality of through holes (170). The plasma processing apparatus further includes: a second plate (116) disposed between the first plate (115) and the sample stage (120) and opposite to the first plate (115); and a gas supply port (150) disposed on the side of the processing chamber (106) between the first plate (115) and the second plate (116) for supplying gas. The through holes (170) are arranged concentrically only on the outer side of a portion at a predetermined distance from the center, and the spacing between adjacent through holes in the circumferential direction is smaller than the diameter of the through holes.

Description

[0001] This application is a divisional application of the invention patent application filed on April 21, 2020, with international application number PCT / JP2020 / 017190, application number 202080004072.7, and entitled "Plasma Processing Apparatus". Technical Field

[0002] This invention relates to plasma processing apparatus. Background Technology

[0003] In the manufacturing process of semiconductor devices, efforts are being made to miniaturize and integrate the components contained within the semiconductor device. For example, in integrated circuits and nanoelectromechanical systems, the nanoscale of structures is being further advanced.

[0004] In semiconductor device manufacturing, photolithography is typically used to create intricate patterns. This technique involves applying a pattern of the device structure to a resist layer and selectively etching away the exposed substrate according to the pattern. In subsequent processing steps, integrated circuits can be formed by depositing other materials within the etched areas.

[0005] Dry etching apparatus is used for etching. For example, Patent Document 1 discloses a dry etching apparatus that has the functions of irradiating both ions and free radicals, and of irradiating only free radicals while blocking ions. In addition, Patent Document 2 discloses a dry etching apparatus that can generate inductively coupled plasma by supplying high-frequency power to a helical coil.

[0006] By switching from a first high-frequency power supply located in the first plasma generation unit to a second high-frequency power supply that supplies high-frequency power to a sample stage located in the second plasma generation unit and on which the sample is placed, capacitively coupled plasma can be generated between the porous metal plate and the sample. The ratio of free radicals to ions can be adjusted by regulating the ratio of power supplied to the helical coil to power supplied to the sample.

[0007] Furthermore, Patent Document 3 discloses an ECR plasma-type dry etching apparatus capable of generating plasma using the electron cyclotron resonance (ECR) phenomenon of a magnetic field generated by a solenoid coil and 2.45 GHz microwaves. In this dry etching apparatus, a DC bias voltage is generated by applying high-frequency power to the sample, and this DC bias voltage is used to accelerate ions and irradiate the wafer.

[0008] Furthermore, Patent Document 4 discloses a plasma processing apparatus that can block ions generated from plasma by providing a partition member that separates the plasma generation chamber from the processing chamber. In this dry etching apparatus, by making the partition member a barrier material that prevents ultraviolet light from passing through, ultraviolet light can be blocked and only hydrogen radicals can be supplied to the processing chamber.

[0009] Furthermore, Patent Document 5 discloses a dry etching apparatus that is capable of replacing free radicals with inactive gases through a supplied second etching gas in an atomic layer etching apparatus. In this dry etching apparatus, free radicals can be generated from the replaced inactive gas, and etching is then performed.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2019-176184

[0013] Patent Document 2: Japanese Patent Application Publication No. 2015-50362

[0014] Patent Document 3: Japanese Patent Application Publication No. 62-14429

[0015] Patent Document 4: Japanese Patent Application Publication No. 2009-016453

[0016] Patent Document 5: Japanese Patent Application Publication No. 2017-228791

[0017] Patent Document 6: Japanese Patent Application Publication No. 2010-21166

[0018] In performing atomic layer etching using conventional methods, the sample needs to be alternately moved via vacuum transport between (1) a device capable of irradiating the sample with only free radicals and (2) a device capable of accelerating ions in plasma to irradiate the sample, as described in Patent Document 3, etc. Therefore, in atomic layer etching using these conventional methods, a significant decrease in production capacity becomes a problem. Therefore, it is desirable to perform both the first step of irradiating the sample with only free radicals and the second step of irradiating the sample with ions using a single dry etching apparatus.

[0019] Furthermore, in isotropic silicon processing, for example, the native oxide film on the silicon surface needs to be removed by irradiation with both ions and free radicals, followed by isotropic etching of silicon by irradiation with only free radicals. In such processing, the time required to remove the native oxide film is as short as a few seconds, so production capacity drops significantly when different equipment is used to handle native oxide film removal and isotropic etching of silicon. Therefore, it is desirable to use a single dry etching equipment to perform both native oxide film removal by irradiation with both ions and free radicals, and isotropic etching of silicon using only free radicals.

[0020] In addition, for example, in medium-scale semiconductor manufacturing processes aimed at producing a large number of products in small quantities, multiple processes are usually performed using a single dry etching device. Therefore, by enabling the aforementioned dry etching device to perform both anisotropic etching that irradiates both ions and free radicals, and isotropic etching that irradiates only free radicals, the device cost can be significantly reduced.

[0021] Given this reality, dry etching equipment used in semiconductor device processing requires both the ability to process by irradiating both ions and free radicals, and the ability to process by irradiating only free radicals.

[0022] Previously, to meet such requirements, the dry etching apparatus described in Patent Document 1 was anticipated. The reasoning was that in this apparatus, during the first step of free radical irradiation, high-frequency microwave power could be supplied to generate ECR plasma, and plasma could be generated on a shield by controlling a magnetic field forming mechanism. Thus, by blocking the incident ions through the shield, only free radicals were supplied to the sample from the ECR plasma. However, in order to irradiate the sample with free radicals using the aforementioned dry etching apparatus, the free radicals generated in the upper region of the processing chamber needed to be supplied through holes penetrating the outer periphery of the shield. Therefore, there were insufficient free radicals in the center of the wafer, resulting in a high etching rate at the periphery and causing processing inhomogeneity.

[0023] It should be noted that the dry etching apparatus disclosed in Patent Document 1 can supply free radicals from the center of the plasma generated in the upper region through the second baffle plate, but it also has the problem of not having the function of actively controlling the airflow.

[0024] Furthermore, the dry etching apparatus disclosed in Patent Document 5 supplies a second gas after etching with the first gas, but it suffers from a problem where the airflow of the first etching gas is not actively controlled. In the dry etching apparatus, the second gas is simply used to replace the products of the first gas.

[0025] Furthermore, Patent Document 6 discloses a technique in which the through holes of two baffles are staggered by half a pitch so that they do not overlap, but there is a problem that such baffles are costly to process. Summary of the Invention

[0026] The problem that the invention aims to solve

[0027] Therefore, the object of the present invention is to provide a plasma processing apparatus capable of performing both free radical irradiation and ion irradiation using a single device, and capable of controlling the free radical irradiation between the first shield and the second shield.

[0028] Methods for solving problems

[0029] To achieve the above objectives, one representative plasma processing apparatus of the present invention includes: a processing chamber for plasma processing of a sample; a high-frequency power supply for supplying high-frequency power for generating plasma; a sample stage for holding the sample; and a first plate disposed above the sample stage and having a plurality of through holes.

[0030] The plasma processing apparatus further comprises: a second plate disposed between the first plate and the sample stage and facing the first plate; and a gas supply port disposed on the side of the processing chamber between the first plate and the second plate and supplying gas.

[0031] The through holes are arranged concentrically only on the outer side of the portion at a predetermined distance from the center, and the spacing between adjacent through holes in the circumferential direction is smaller than the diameter of the through holes, thereby achieving the above-mentioned objective.

[0032] Invention Effects

[0033] According to the present invention, a plasma processing apparatus is provided that can realize both free radical irradiation and ion irradiation using a single device, and can control the free radical irradiation between the first shield and the second shield.

[0034] Other issues, structures, and effects not mentioned above will be clarified through the following description of the implementation methods. Attached Figure Description

[0035] Figure 1 This is a cross-sectional view showing an outline of the plasma processing device.

[0036] Figure 2 This is a schematic diagram showing the magnetic field lines within a plasma processing device.

[0037] Figure 3 This is a top view showing an example of the hole configuration of the first shield in an ECR plasma processing apparatus.

[0038] Figure 4 This is a top view showing an example of the hole configuration of the second baffle in an ECR plasma processing apparatus.

[0039] Figure 5 This is a cross-sectional view of an apparatus used to illustrate the state of free radical flow controlled by multiple gases.

[0040] Figure 6A This is a diagram simulating the airflow of a single baffle structure using streamlines.

[0041] Figure 6B This is a graph showing the relationship between the radial position on the sample in the comparative example and the gas pressure and gas velocity.

[0042] Figure 7A This is a graph showing the actual etching rate of a plasma processing device with a single-sheet baffle structure, illustrated using contour lines.

[0043] Figure 7B This is a graph showing the ER distribution of the comparative example.

[0044] Figure 8A It is a simulated diagram that uses streamlines to represent the airflow of a two-barrier structure.

[0045] Figure 8B This is a graph showing the relationship between the radial position of the sample and the gas pressure and gas velocity in this embodiment.

[0046] Figure 9A This is a simulated diagram showing the airflow with a second airflow added to the two baffle structures, represented by streamlines.

[0047] Figure 9B This is a graph showing the relationship between the radial position of the sample and the gas pressure and gas velocity in this embodiment.

[0048] Explanation of reference numerals in the attached figures:

[0049] 106-1 Upper region of the processing chamber, 106-2 Middle region of the processing chamber, 106-3 Lower region of the processing chamber, 112 Circular waveguide, 113 Magnetron, 114 Solenoid coil, 115 First shielding plate, 116 Second shielding plate, 117 Dielectric window (top plate), 120 Sample stage, 121 Sample (wafer), 122 Matching device, 123 High-frequency power supply, 124 Pump, 140 Magnetic lines of force, 149 First gas supply port, 150 Second gas supply port, 151 Area without through-hole (free radical shielding area), 170 Through-hole, 171 Through-hole. Detailed Implementation

[0050] The present invention will now be described through embodiments.

[0051] exist Figure 1 The figure shows a schematic overall structural cross-sectional view of the plasma processing apparatus of this embodiment. In the plasma processing apparatus of this embodiment, plasma is generated in the vacuum processing chamber 106 by means of the interaction between 2.45 GHz microwaves (high-frequency power) supplied to the vacuum processing chamber 106 from the magnetron 113, which serves as a high-frequency power source, via the square waveguide 112 and the dielectric window 117, and the magnetic field formed by the solenoid coil 114, which serves as a magnetic field forming mechanism. Such a plasma processing apparatus is called an ECR plasma processing apparatus.

[0052] Additionally, the sample 121 placed on the sample stage 120 is connected to a high-frequency power supply 123 via a matcher 122. The interior of the vacuum chamber 106 is connected to a pump 124 via a valve 125, and the internal pressure can be adjusted by the opening of the valve 125.

[0053] In addition, the plasma processing apparatus has a first shielding plate (first plate) 115 and a second shielding plate (second plate) 116 made of dielectric material inside the vacuum processing chamber 106. The second shielding plate 116 is arranged parallel to the first shielding plate 115 at intervals below it.

[0054] In this embodiment, the first shield 115 and the second shield 116 are formed of a dielectric. The first shield 115 is formed of a non-metallic material, thus allowing microwaves to propagate to the sample side through the first shield 115 and the second shield 116.

[0055] The vacuum processing chamber 106 above the first baffle plate 115 is designated as the upper region 106-1, the vacuum processing chamber 106 between the first baffle plate 115 and the second baffle plate 116 is designated as the middle region 106-2, and the vacuum processing chamber 106 below the second baffle plate 116 is designated as the lower region 106-3.

[0056] The plasma processing apparatus used in this embodiment has the characteristic of generating plasma near a magnetic flux density of 0.0875T when the microwave frequency is 2.45 GHz. Therefore, if the magnetic field is adjusted so that the plasma generation region is located between the first shielding plate 115 and the dielectric window 117 (upper region 106-1) (set as the first control), plasma can be generated on the dielectric window 117 side of the first shielding plate 115. The generated ions pass through the first shielding plate 115, and the ions that have passed through drift along the magnetic field lines and disappear upon collision with the wall surface, thereby irradiating the sample 121 only with free radicals. At this time, isotropic etching, which mainly utilizes the surface reaction of free radicals, is performed on the sample 121.

[0057] Conversely, if the magnetic field is adjusted so that the plasma generation region is located between the second shielding plate 116 and the sample 121 (lower region 106-3) (set as the second control), plasma can be generated on the side closer to the sample 121 than the second shielding plate 116, supplying the sample 121 with both ions and free radicals. At this time, anisotropic etching utilizing ion-assisted reactions is performed in the sample 121, where the reaction of free radicals is promoted by ions.

[0058] It should be noted that the control device 100 can be used to adjust or switch the height position (above or below) of the plasma generation area relative to the height position of the first shielding plate 115 and the second shielding plate 116, adjust the period of maintaining their respective height positions, and switch the power supplied to each solenoid coil when there are multiple solenoid coils.

[0059] Furthermore, in this plasma processing apparatus, the first gas supply port 149 (see below) can be used for processing. Figure 2 The first gas is supplied. Furthermore, a second gas supply port 150 is provided along the entire circumference of the peripheral wall of the vacuum processing chamber 106, communicating with the central region 106-2. A second gas (etching gas or inactive gas) can be supplied to the central region 106-2 between the first baffle plate 115 and the second baffle plate 116 via the second gas supply port 150. Due to this feature, when plasma is generated in the upper region 106-1, the airflow can be controlled in the central region 106-2, and the distribution of free radicals can be controlled.

[0060] In this embodiment, when using ECR plasma, ions drift outwards, thus allowing for free setting of the through holes in the first shielding plate 115 and the second shielding plate 116 (see below). Figure 3 , 4 The position of ).

[0061] Next, regarding the plasma processing apparatus of this embodiment, the influence of the configuration of the through holes in the shielding plate on the performance of shielding ions will be explained.

[0062] First, the ion blocking effect will be explained. It is known that ions move along magnetic field lines in a plasma under a magnetic field. Figure 2 It is used for explanation Figure 1 A longitudinal sectional view of the state of the magnetic field lines 140 in the plasma processing apparatus shown. In the case of ECR ​​plasma, as... Figure 2 The magnetic field lines 140 shown travel along the longitudinal (up and down) direction, and the spacing between the magnetic field lines increases as they approach the sample.

[0063] Therefore, if the through holes 170 are evenly arranged across the entire surface of the first shielding plate 115, ions passing through the through holes 170 near the center will be incident on the sample 121 along the magnetic field lines 140. In contrast, the first shielding plate 115 of this embodiment has a plurality of through holes 170 in the area above the diameter of the sample 121 (outside the portion at a predetermined distance from the center). That is, by fabricating... Figure 3 The area 151 shown by the dashed line, which is equivalent to the sample diameter at the center of the first shielding plate 115 (the area obtained by projecting the sample 121 in the vertical direction), has no through-hole structure (free radical shielding region), and can completely block the incidence of ions generated on the dielectric window side (upper region 106-1) of the first shielding plate 115 onto the sample. It should be noted that the diameter of the through-hole 170 is preferably φ1 to 2 cm.

[0064] Furthermore, if the second shield 116 is not installed and only one is used, Figure 3 As shown, the first baffle plate 115, which lacks a through-hole near the center, supplies the processing gas to the central region 106-2 through a through-hole radially outwardly provided in the first baffle plate 115. Therefore, there is a tendency for the free radical distribution near sample 121 to become higher on the outer periphery. To address this issue, in this embodiment, a second baffle plate 116 is disposed below the first baffle plate 115, and this second baffle plate 116 is equipped with… Figure 4 The through hole 171 shown is shown.

[0065] Ions drift along magnetic field lines (deflecting radially outward as they approach sample 121), therefore the second shield 116 has through holes 171 within and outside a range 151 corresponding to the sample diameter. Figure 4In this example, the through-hole 171 is only arranged on the inner side of the range 151. Furthermore, if the size of the through-hole 171 is made uniform, there will be more free radicals near the sample stage on the outer side of the wafer. To eliminate this problem, it is preferable that the diameter of the through-hole 171 near the center of the second shielding plate 116 is larger than the diameter of the through-hole 171 near the outer periphery (or, the diameter of the through-hole 171 decreases as it moves away from the center). Ions drift along magnetic field lines, so if a shielding plate has through-holes in a range with a diameter equal to or greater than that of the wafer, ions can be blocked. Figure 4 In this design, multiple through holes 171 are disposed within a range 151 corresponding to the diameter of the sample 121, but it is also acceptable for them to be disposed in a range exceeding the diameter of the sample 121. Furthermore, it is also acceptable for the through holes 171 to be disposed in the shaded area of ​​the first shielding plate 115.

[0066] Figure 6A This is a simulated diagram showing the airflow of a plasma processing device with a single baffle structure, used as a comparative example, represented by streamlines. Figure 6B This is a graph showing the relationship between the radial position on sample 121 in the comparative example and the gas pressure and gas velocity.

[0067] In the comparative example, only one is configured inside the vacuum processing chamber 106. Figure 3 The first shielding plate 115 as shown. In the above case, as Figure 6A As shown, the gas flow lines pass through the outer edge of the sample (wafer radius) near the sample. Free radicals are supplied from the outer edge of the wafer towards the center, thus there is a tendency for radial excess on the outer edge and deficiency on the central edge. Therefore, the etching distribution tends to be higher on the outer periphery.

[0068] Figure 7A This is a graph showing the actual etching rate performed by a plasma processing device with a single-sheet shielding structure, used as a comparative example, represented by contour lines. Figure 7B This is a graph showing the ER (etch rate) distribution. Figure 7A When assigning directions using cardinal directions, the west is set to 0 degrees, the northwest to 45 degrees, the north to 90 degrees, and the northeast to 135 degrees. The relationship between radius and etching rate is shown for each direction. Figure 7A , 7B It can be seen that there is a tendency for radial excess on the outer side of the wafer, while there is a tendency for insufficient excess in the center.

[0069] Therefore, in this embodiment, by configuring below the first baffle plate 115 Figure 4The second baffle 116, as shown, alters the gas flow path. By altering the gas flow path, the required amount of free radicals is supplied from the center of the sample 121 outwards, and excess free radicals are discharged by the gas flow, thereby making the etching distribution nearly uniform. Furthermore, by supplying a sufficient amount of free radicals, the etching rate increases.

[0070] Figure 8A This is a simulated diagram showing the airflow of the plasma processing apparatus with a two-baffle structure, as described in this embodiment, represented by streamlines. Figure 8B This is a graph showing the relationship between the radial position on sample 121 and the gas pressure and gas velocity in this embodiment. (If compared with...) Figure 6A , 6B A comparison will make it clear, such as Figure 8A , 8B The flow path of the gas is changed, and the required amount of free radicals are supplied from the center of the wafer to the outside.

[0071] It should be noted that in this plasma processing device, ions drift outward along magnetic field lines, so it is not necessary for the through holes of the first shielding plate 115 and the second shielding plate 116 to be configured not to overlap.

[0072] Next, regarding the plasma processing apparatus of this embodiment, the effect of the second gas flow disposed in the central region 106-2 on the distribution of free radicals will be explained.

[0073] As described above, an implementation using two baffles to alter the gas flow path has been explained. However, even if the through-hole 171 of the second baffle 116 is increased in the direction of the center, there is a possibility that the pressure difference on the outer side of the wafer within the vacuum processing chamber 106 may be too large, preventing airflow from being directed towards the center. In this case, by setting... Figure 1 , 2 The second gas supply port 150, as shown, supplies gas through the through hole 171 in the center of the second baffle plate 116.

[0074] Here, to ensure uniform gas pressure, it is preferable that the second gas supply port 150 is slit-shaped. For example... Figure 5 As shown, the flow of gas supplied from the first baffle plate 115 can be corrected using gas ejected from the second gas supply port 150. The gas supplied to the upper processing chamber is plasma-injected, and the resulting free radicals move towards the central region 106-2 through the first baffle plate 115. At this time, the gas flow is stripped from the upper surface of the second baffle plate 116 by a second airflow. Afterwards, the gas, now with corrected uniformity, enters the lower region 106-3 through the through-hole in the second baffle plate 116.

[0075] In particular, in this embodiment, gas is supplied via the second gas supply port 150 in order to correct the flow of free radicals.

[0076] Next, regarding the plasma processing apparatus of this embodiment, the effect of the second airflow supplied to the central region 106-2 on foreign matter in the processing chamber will be explained.

[0077] When the through-hole 170 of the first shielding plate 115 is positioned above the structural portion of the second shielding plate 116, it is assumed that the products generated in the upper region 106-1 accumulate above the structural portion of the second shielding plate 116 through the through-hole 170. In this case, it is assumed that the gas supplied from the first shielding plate 115 causes the aforementioned products to be dispersed and fall onto the wafer as foreign matter.

[0078] Therefore, through such Figure 1 , 2 As shown, by orienting the second gas supply port 150 upward (so that the axis of the second gas supply port 150 is oriented towards the first baffle plate 115 side relative to the horizontal direction, in other words, tilted at a predetermined angle relative to the vertical direction of the side of the vacuum processing chamber 106), it is possible to prevent gas from being ejected directly below the through hole 170 and to prevent the aforementioned products from flying.

[0079] Figure 9A This is a simulated diagram showing the airflow as gas is supplied upwards from the second gas supply port 150 in the plasma processing apparatus with a two-baffle structure, as described in this embodiment, represented by streamlines. Figure 9B This is a graph showing the relationship between the radial position on sample 121 and the gas pressure and gas velocity in this embodiment.

[0080] according to Figure 9A , 9B It was confirmed that by adding an upward airflow in the central region 106-2, the airflow path was lifted upward compared to the case where no airflow was added in the central region.

[0081] In particular, in this embodiment, the direction of airflow can be controlled to prevent foreign objects from entering.

[0082] The above-described embodiments have been presented in detail for ease of understanding and illustration of the present invention, but are not necessarily limited to possessing all the described structures. Furthermore, a portion of the structure of one embodiment can be replaced with a structure of another embodiment, and a structure of another embodiment can be added to the structure of one embodiment. Additionally, a portion of the structure of each embodiment can be added to, deleted from, or replaced with other structures.

Claims

1. A plasma processing apparatus comprising: a processing chamber for plasma processing of a sample; a high-frequency power supply for supplying high-frequency power for generating plasma; a sample stage for holding the sample; and a first plate disposed above the sample stage and having a plurality of through holes. The plasma processing device is characterized in that... The plasma processing apparatus further comprises: a second plate disposed between the first plate and the sample stage and facing the first plate; and a gas supply port disposed on the side of the processing chamber between the first plate and the second plate and supplying gas. The through holes are arranged concentrically only on the outer side of a portion at a predetermined distance from the center, and the spacing between adjacent through holes in the circumferential direction is smaller than the diameter of the through holes.

2. The plasma processing apparatus according to claim 1, characterized in that, The gas supply port is tilted at a predetermined angle relative to the vertical direction of the side of the processing chamber.

3. The plasma processing apparatus according to claim 1, characterized in that, The through holes in the second plate are configured such that their diameter decreases as they move away from the center.

4. The plasma processing apparatus according to claim 2, characterized in that, The through holes in the second plate are configured such that their diameter decreases as they move away from the center.

5. The plasma processing apparatus according to claim 1, characterized in that, The plasma processing apparatus also includes a magnetic field forming mechanism for generating a magnetic field within the processing chamber. The first plate and the second plate are made of dielectric material.

6. The plasma processing apparatus according to claim 2, characterized in that, The plasma processing apparatus also includes a magnetic field forming mechanism for generating a magnetic field within the processing chamber. The first plate and the second plate are made of dielectric material.

7. The plasma processing apparatus according to claim 3, characterized in that, The plasma processing apparatus also includes a magnetic field forming mechanism for generating a magnetic field within the processing chamber. The first plate and the second plate are made of dielectric material.

8. The plasma processing apparatus according to claim 4, characterized in that, The plasma processing apparatus also includes a magnetic field forming mechanism for generating a magnetic field within the processing chamber. The first plate and the second plate are made of dielectric material.

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