Plasma processing apparatus

Abstract

A plasma processing apparatus (100) is provided with a discharge chamber (1), a processing chamber (2), and an exhaust chamber (3) provided inside a vacuum container (101). A sample stage (4) on which a wafer can be placed is disposed inside the processing chamber (2). A dispersion plate (20) is provided between the processing chamber (2) and the discharge chamber (1). A plurality of through-holes (21) are formed in the dispersion plate (20) so that the processing chamber (2) and the discharge chamber (1) communicate with each other. An exhaust plate (30) is provided between the processing chamber (2) and the exhaust chamber (3) so as to surround the sample stage (4). A plurality of through holes (31) are formed in the exhaust plate (30) so that the processing chamber (2) and the exhaust chamber (3) communicate with each other. An annular electrode (EL1) is attached to the dispersion plate (20), and an annular electrode (EL2) is attached to the exhaust plate (30). A variable DC power supply is electrically connected to each of the electrode (EL1) and the electrode (EL2).

Description

Technical Field

[0001] The present invention relates to a plasma processing device. Background Art

[0002] In the semiconductor device market, in order to reduce power consumption or increase storage capacity, the device structure is further miniaturized and three-dimensionalized. In the manufacture of three-dimensional device structures, the structure is three-dimensional and complex, so in addition to the "anisotropic etching process" that etches the surface of the wafer in the vertical direction, the "isotropic etching process" that can also etch in the horizontal direction is also implemented.

[0003] For example, Patent Document 1 discloses a plasma processing device capable of performing isotropic etching with high precision. In order to achieve microfabrication based on isotropic etching, formation of a reaction layer based on radical adsorption and detachment of the reaction layer based on heating are performed. Through these manufacturing processes, the etching amount can be controlled at a level of several nm or less.

[0004] Specifically, first, a wafer as a processed object is moved into a processing chamber in a vacuum container by a transport mechanism. Next, the wafer is placed on a sample stage having an electrostatic adsorption function. Next, plasma is generated in a discharge chamber, and ions and electrons are reduced by a dispersion plate. Thus, relatively highly reactive particles such as neutral particles and free radicals of a gas are introduced into the processing chamber. Next, such particles are adsorbed on the surface of a film to be etched, and a reaction layer is formed on the surface of the film through a chemical reaction between the two (adsorption process).

[0005] Next, heat or kinetic energy is applied to the reaction layer to cause the reaction layer to be detached from the surface of the film (detachment step). By alternately repeating the adsorption step and the detachment step at a predetermined cycle, the film can be selectively etched.

[0006] In addition, in Patent Document 2 Figure 4 In the patent document, a dispersion plate that cuts off a discharge chamber and a processing chamber and a through hole formed in the dispersion plate are disclosed. In patent document 2, in order to suppress the ions that pass through the through hole from invading the wafer, through holes are arranged only on the outer periphery of the dispersion plate. The entry of ions into the processing chamber causes a decrease in the controllability of the etching amount and the accumulation of charges on the sample stage. During discharge, more ions are distributed near the center of the discharge chamber, and more free radicals are distributed near the outer wall of the discharge chamber. Therefore, it is possible to greatly suppress the entry of ions into the processing chamber and allow free radicals to pass through effectively.

[0007] Prior Art Literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-185594

[0010] Patent Document 2: International Publication No. 2021 / 124539 Summary of the invention

[0011] -Problems to be solved by the invention-

[0012] In the technologies disclosed in Patent Documents 1 and 2, a dispersion plate that cuts off the discharge chamber and the processing chamber can prevent most ions from entering the sample stage, but it cannot prevent ions from entering through the through holes of the dispersion plate. Therefore, ions are unevenly incident on the wafer mounted on the sample stage, which is one of the reasons for the reduction of the uniformity of the wafer surface during etching.

[0013] For example, it is conceivable to suppress the entry of ions from the through-holes by using two dispersion plates. However, in this case, the radicals in the active state supplied into the processing chamber also decrease.

[0014] The main purpose of the present application is to suppress ions from reaching the sample stage without affecting the distribution and supply of radicals. Other issues and new features are apparent from the description of this specification and the accompanying drawings.

[0015] -Methods for solving the problem-

[0016] The outline of a typical embodiment among the embodiments disclosed in the present application will be briefly described as follows.

[0017] A plasma processing device according to one embodiment includes: a vacuum container; a processing chamber, which is a part of the interior of the vacuum container; a discharge chamber, which is a part of the interior of the vacuum container, is disposed above the processing chamber and is used to generate plasma; an exhaust chamber, which is a part of the interior of the vacuum container, is disposed below the processing chamber and is formed with an exhaust port; a sample stage, which is arranged inside the processing chamber and can carry a wafer; a dispersion plate, which is disposed between the processing chamber and the discharge chamber; a plurality of first through holes, which are formed in the dispersion plate, so that the processing chamber and the discharge chamber are connected; an exhaust plate, which is disposed between the processing chamber and the exhaust chamber so as to surround the sample stage; and a plurality of second through holes, which are formed in the exhaust plate, so that the processing chamber and the exhaust chamber are connected. A first annular electrode is mounted on the dispersion plate, a second annular electrode is mounted on the exhaust plate, a first variable DC power supply is electrically connected to the first electrode, and a second variable DC power supply is electrically connected to the second electrode.

[0018] -Effects of the Invention-

[0019] According to one embodiment, it is possible to suppress ions from reaching the sample stage without affecting the distribution and supply amount of radicals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a schematic cross-sectional view showing the plasma processing apparatus in the first embodiment.

[0021] Figure 2 This is a bottom view showing the dispersion plate in the first embodiment.

[0022] Figure 3 It is a top view showing the exhaust plate in Embodiment 1.

[0023] Figure 4 This is a schematic cross-sectional view for illustrating the trajectory of ions that have passed through the dispersion plate in the first embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, the embodiments are described in detail based on the accompanying drawings. In addition, in all the figures used in the embodiments of the specification, the components having the same functions are marked with the same reference numerals, and their repeated descriptions are omitted. In addition, in the following embodiments, the description of the same or identical parts is not repeated in principle except when particularly necessary.

[0025] (Implementation Method 1)

[0026] <Structure of Plasma Processing Device>

[0027] Below, use Figure 1 , the plasma processing apparatus 100 in Embodiment 1 is described.

[0028] like Figure 1 As shown, the plasma processing apparatus 100 includes a vacuum container 101. The discharge chamber 1, the processing chamber 2, and the exhaust chamber 3 respectively constitute a part of the interior of the vacuum container 101. The discharge chamber 1 for generating plasma PZ is arranged above the processing chamber 2. The exhaust chamber 3 is arranged below the processing chamber 2. An exhaust port 13 is formed at the bottom of the exhaust chamber 3. The discharge chamber 1, the processing chamber 2, and the exhaust chamber 3 are respectively cylindrical, and their central axes are arranged on the same axis or at positions that can be regarded as being approximately on the same axis. In addition, the discharge chamber 1 is composed of a cylindrical ceramic chamber 5.

[0029] Inside the processing chamber 2, a sample stage 4 is provided on which a wafer as a processed object can be placed. The sample stage 4 has a function of fixing the wafer by electrostatic adsorption on its upper surface. In addition, the wafer is composed of a semiconductor substrate having a p-type or n-type impurity region, a semiconductor element such as a transistor formed on the semiconductor substrate, and a wiring layer formed on the semiconductor element. The wafer of the first embodiment is a wafer in the middle of its manufacturing.

[0030] A dispersion plate 20 is provided between the processing chamber 2 and the discharge chamber 1. The dispersion plate 20 contains, for example, a ceramic material. A plurality of through holes 21 are formed in the dispersion plate 20 so as to communicate with the processing chamber 2 and the discharge chamber 1. The planar shape of each of the sample stage 4 and the dispersion plate 20 is a circle. The central axis of each of the sample stage 4 and the dispersion plate 20 is arranged on the same axis as the central axis of each of the discharge chamber 1, the processing chamber 2, and the exhaust chamber 3, or at a position close to the degree that it can be regarded as being on the same axis.

[0031] The electrode EL1 is mounted on the lower surface of the dispersion plate 20. The electrode EL1 is formed in a ring shape coaxial with the dispersion plate 20. The surface of the electrode EL1 is subjected to aluminum anodizing treatment to prevent the electrode EL1 from being directly exposed to the plasma PZ. The electrode EL1 is sometimes built into the dispersion plate 20. In this case, the aluminum anodizing treatment may not be performed.

[0032] An ICP coil 6 is provided outside the discharge chamber 1. The ICP coil 6 is connected to a high frequency power supply 8 via a matching device 7, and generates plasma PZ by an ICP discharge method. The frequency of the high frequency power is a frequency band of several tens of MHz such as 13.56 MHz.

[0033] A top plate 10 is provided at the top of the discharge chamber 1. A gas distribution plate 9 having a plurality of through holes is provided at the bottom of the top plate 10. The processing gas supplied from the processing gas supply unit 11 is introduced into the inside of the discharge chamber 1 through the gas distribution plate 9. A sealing member such as an O-ring is sandwiched between the top plate 10 and the upper end of the side wall of the discharge chamber 1. Thus, the inside of the discharge chamber 1 is hermetically sealed.

[0034] The processing gas supplied from the processing gas supply unit 11 is adjusted in supply flow rate by a mass flow controller 12 provided for each gas type. The processing gas is, for example, a combustible gas, an oxidizing gas, or a mixed gas thereof. The mixed gas may be diluted with an inert gas.

[0035] An IR lamp unit 40 for heating the wafer and the interior of the processing chamber 2 is provided at the upper portion of the processing chamber. The IR lamp unit 40 includes a lamp 41 for heating the wafer, a quartz light-transmitting window 42, a lamp power supply 43, and a high-frequency cutoff filter 44.

[0036] The lamp 41 is disposed above the sample stage 4 and is electrically connected to the lamp power supply 43 via a high-frequency cutoff filter 44. The high-frequency cutoff filter 44 is provided to prevent the noise of the high-frequency power applied to the ICP coil 6 from flowing into the lamp power supply 43. The light radiated from the lamp 41 is mainly light (IR light) in the visible to infrared region. Such IR light can pass through the light-transmitting window 42, and heat the wafer and the interior of the processing chamber 2 through the IR light.

[0037] Here, a plurality of lamps 41 (three in the figure) are provided. The plurality of lamps 41 are arranged on concentric circles. The magnitude of the electric power supplied to the arc-shaped portion of each lamp 41 can be adjusted independently, and the radial distribution of the heating amount of the wafer can be adjusted.

[0038] An exhaust plate 30 is provided between the processing chamber 2 and the exhaust chamber 3 so as to surround the sample stage 4. The exhaust plate 30 is made of, for example, a ceramic material. The exhaust plate 30 is annular. The central axis of the exhaust plate 30 is arranged coaxially with the central axis of the sample stage 4 or at a position close to the coaxial axis.

[0039] A plurality of through holes 31 are formed in the exhaust plate 30 so as to communicate with the processing chamber 2 and the exhaust chamber 3. An electrode EL2 is mounted on the upper surface of the exhaust plate 30. The electrode EL2 is in a ring shape coaxial with the exhaust plate 30. In order to prevent the electrode EL2 from being directly exposed to the plasma PZ, the surface of the electrode EL2 is subjected to an aluminum anodizing treatment. The electrode EL2 is sometimes built into the exhaust plate 30. In this case, the above-mentioned aluminum anodizing treatment may not be performed.

[0040] A vacuum pump 15 for decompressing the interior of the vacuum container 101 is provided outside the vacuum container 101 and below the exhaust chamber 3. The vacuum pump 15 is connected to the exhaust port 13 via a pressure regulating valve 14. The pressure regulating valve 14 increases or decreases the cross-sectional area of ​​the exhaust path to adjust the exhaust volume or exhaust speed.

[0041] Below, use Figure 2 The structure of the dispersion plate 20 will be described in detail.

[0042] like Figure 2 As shown, a plurality of through holes 21 arranged in a concentric circle are formed in the dispersion plate 20. The plasma PZ contains ions, electrons, neutral particles and free radicals. The dispersion plate 20 is mainly provided to reduce the ions and electrons introduced into the processing chamber 2. The free radicals pass through the plurality of through holes 21 and are introduced into the processing chamber 2. The distribution of the free radicals introduced into the processing chamber 2 is determined by the arrangement of the plurality of through holes 21, and the uniformity of the etching process in the wafer surface is adjusted.

[0043] As will be described in detail later, not only radicals but also some of the ions included in plasma pass through the plurality of through holes 21 .

[0044] The electrode EL1 has a ring-shaped structure coaxial with the dispersion plate 20 and is mounted on the lower surface of the dispersion plate 20. In addition, the electrode EL1 is electrically connected to the variable DC power supply 22 via the high-frequency cutoff filter 23. The high-frequency cutoff filter 23 is provided to prevent the noise of the high-frequency power applied to the ICP coil 6 from flowing into the electrode EL1. The voltage range of the variable DC power supply 22 varies depending on the conditions of the etching process or the chamber structure, for example, from -1000V to 2000V.

[0045] Below, use Figure 3 The structure of the exhaust plate 30 will be described in detail.

[0046] like Figure 2 As shown, the exhaust plate 30 is arranged between the outer peripheral side wall of the sample stage 4 and the inner peripheral side wall of the processing chamber 2. A plurality of through holes 31 arranged in a concentric circle are formed in the exhaust plate 30. The gas (ions, free radicals, etc.) inside the processing chamber 2 is designed to be exhausted roughly uniformly to the exhaust chamber 3 through the plurality of through holes 31.

[0047] The electrode EL2 is an annular structure coaxial with the exhaust plate 30 and is mounted on the upper surface of the exhaust plate 30. In addition, the electrode EL2 is electrically connected to the variable DC power supply 32 via the high-frequency cutoff filter 33. The high-frequency cutoff filter 33 is provided to prevent the noise of the high-frequency power applied to the ICP coil 6 from flowing into the electrode EL2. The voltage range of the variable DC power supply 32 is, for example, not less than -1000V and not more than 2000V.

[0048] In addition, the plurality of through holes 21 are located closer to the outer periphery of the dispersion plate 20 than the electrode EL1, and the electrode EL2 is located closer to the outer periphery of the exhaust plate 30 than the plurality of through holes 31. With such a configuration, the ions that have passed through the plurality of through holes 21 are bent by the electric lines of force generated from the electrode EL1 toward the electrode EL2. As a result, the ions are difficult to reach the sample stage 4 and are guided to pass through the plurality of through holes 31.

[0049] Below, use Figure 4 A method for deviating the trajectory of the ions 50 that have passed through the dispersion plate 20 from the wafer surface will be described. Figure 4 In order to make it easier to understand, Figure 4 The dashed lines on the right side of FIG. 1 represent the electric lines of force generated between the electrode EL1 and the electrode EL2. Figure 4 The left side of represents the orbit of ion 50.

[0050] When the wafer is placed on the sample stage 4 and the plasma PZ is irradiated to the wafer, the processing gas is supplied from the processing gas supply unit 11 to the inside of the discharge chamber 1. The microwave is output from the high frequency power supply 8, and the plasma PZ is generated inside the discharge chamber 1 through the ICP coil 6. The processing gas is excited by the plasma PZ, and the inside of the discharge chamber 1 is filled with ions, electrons, neutral particles, and radicals.

[0051] The free radicals that have passed through the plurality of through holes 21 among the plurality of free radicals included in the plasma PZ are adsorbed to the film on the surface of the wafer. A reaction layer is formed on the surface of the film by a chemical reaction between the material constituting the film and the free radicals. The lamp 41 heats the wafer by applying a voltage to the lamp 41 from the lamp power supply 43. The reaction layer is heated by applying thermal energy to the surface of the wafer, and the reaction layer is separated from the film. By periodically repeating such a process, the film can be selectively subjected to isotropic etching.

[0052] Most of the ions included in the plasma PZ are blocked by the dispersion plate 20 , but they cannot be completely blocked by the dispersion plate 20 alone. Some of the ions 50 pass through the plurality of through holes 21 and enter the interior of the processing chamber 2 .

[0053] However, in the first embodiment, when the wafer is irradiated with plasma PZ, electric lines of force are generated between the electrode EL1 and the electrode EL2. The electric lines of force are formed symmetrically around the central axis of the sample stage 4, gradually expanding from the lower surface of the dispersion plate 20 toward the sample stage 4, and are formed with a distribution of intensity that is uniform in the circumferential direction or can be regarded as being approximately uniform in the axial direction. The trajectory of the ions 50 incident into the processing chamber 2 also expands symmetrically around the central axis of the sample stage 4.

[0054] That is, the ions 50 passing through the plurality of through holes 21 have their trajectories bent by the electric lines, pass through the plurality of through holes 31, enter the exhaust chamber 3, and are exhausted from the exhaust port 13 to the outside of the vacuum container 101. Thus, the ions 50 passing through the plurality of through holes 21 do not reach the wafer.

[0055] In addition, the radicals existing in the processing chamber 2 are not affected by the electric lines of force, and thus have no influence on the etching process by the radicals. In addition, the wafer shift due to the accumulation of electric charges described in Patent Document 1 can also be eliminated.

[0056] Thus, according to Embodiment 1, ions can be prevented from reaching the sample stage without affecting the distribution and supply amount of radicals. Therefore, it is possible to solve the problem that ions are unevenly incident on the wafer mounted on the sample stage 4 and the uniformity of the etching process in the wafer surface is reduced.

[0057] As mentioned above, although this invention was specifically described based on the said embodiment, this invention is not limited to the said embodiment, Various changes are possible within the range which does not deviate from the summary.

[0058] -Description of Reference Numerals-

[0059] 100 Plasma treatment device

[0060] 101 Vacuum Container

[0061] 1 Discharge chamber

[0062] 2 Processing Chamber

[0063] 3 Exhaust chamber

[0064] 4 Sample stage

[0065] 5 Ceramic Chamber

[0066] 6 ICP Coil

[0067] 7 Matchers

[0068] 8 High frequency power supply

[0069] 9 Gas dispersion plate

[0070] 10 Top Plate

[0071] 11 Processing gas supply unit

[0072] 12 Mass Flow Controller

[0073] 13 Exhaust port

[0074] 14 Pressure regulating valve

[0075] 15 Vacuum Pump

[0076] 20 Dispersion Plate

[0077] 21 Through hole

[0078] 22 Variable DC Power Supply

[0079] 23 High frequency cutoff filter

[0080] 30 Exhaust plate

[0081] 31 Through hole

[0082] 32 Variable DC Power Supply

[0083] 33 High frequency cutoff filter

[0084] 40 IR light units

[0085] 41 Lights

[0086] 42 Light-transmitting window

[0087] 43 Lighting power supply

[0088] 44 High frequency cutoff filter

[0089] 50 ions

[0090] EL1, EL2 electrodes

[0091] PZ Plasma.

Claims

1. A plasma processing device, characterized in that: have: Vacuum container; A processing chamber is a part of the interior of the vacuum container; A discharge chamber, which is a part of the interior of the vacuum container, is disposed above the processing chamber and is used to generate plasma; The exhaust chamber is a part of the interior of the vacuum container, is disposed below the processing chamber, and is formed with an exhaust port; A sample stage, disposed inside the processing chamber and capable of mounting a wafer; a dispersion plate, disposed between the processing chamber and the discharge chamber; A plurality of first through holes are formed in the dispersion plate so as to allow the processing chamber and the discharge chamber to communicate with each other; An exhaust plate, disposed between the processing chamber and the exhaust chamber so as to surround the sample stage; as well as A plurality of second through holes are formed in the exhaust plate so as to allow the processing chamber and the exhaust chamber to communicate with each other. A first annular electrode is mounted on the dispersion plate. A second annular electrode is mounted on the exhaust plate. The first electrode is electrically connected to a first variable DC power supply, The second electrode is electrically connected to a second variable DC power supply.

2. The plasma processing device according to claim 1, wherein: The first electrode is mounted on the lower surface of the dispersion plate, The second electrode is mounted on the upper surface of the exhaust plate.

3. The plasma processing device according to claim 2, wherein: The plurality of first through holes are located closer to the outer periphery of the dispersion plate than the first electrode. The second electrode is located closer to the outer peripheral side of the exhaust plate than the plurality of second through holes.

4. The plasma processing device according to claim 3, wherein: When the wafer is placed on the sample stage and the plasma is irradiated onto the wafer, electric lines of force are generated between the first electrode and the second electrode.

5. The plasma processing apparatus according to claim 4, wherein: Among the plurality of ions included in the plasma, the ions that have passed through the plurality of first through holes have their trajectories bent by the electric lines of force, pass through the plurality of second through holes, and enter the exhaust chamber.

6. The plasma processing apparatus according to claim 5, wherein: The ions that have passed through the plurality of first through holes do not reach the wafer.

7. The plasma processing apparatus according to claim 5, wherein: The plasma processing device further comprises: a lamp, which is arranged above the sample stage and is used to heat the wafer; Among the plurality of radicals included in the plasma, the radicals that have passed through the plurality of first through holes are adsorbed on the film on the surface of the wafer, A reaction layer is formed on the surface of the film by chemical reaction between the material constituting the film and the free radicals. By heating the reaction layer, the reaction layer is detached from the membrane.

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