Plasma Processing Equipment

Abstract

A plasma processing apparatus 100 comprises a discharge chamber 1, a processing chamber 2, and an exhaust chamber 3 which are provided inside of a vacuum container 101. A sample table 4 on which a wafer can be placed is disposed inside of 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 such that the processing chamber 2 and the discharge chamber 1 communicate. An exhaust plate 30 is provided between the processing chamber 2 and the exhaust chamber 3 so as to surround the sample table 4. A plurality of through holes 31 are formed in the exhaust plate 30 such that the processing chamber 2 and the exhaust chamber 3 communicate. A ring-shaped electrode EL1 is attached to the dispersion plate 20, and a ring-shaped 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 apparatus. [Background technology]

[0002] In the semiconductor device market, device structures are becoming finer and more three-dimensional in order to reduce power consumption or increase memory capacity. In the manufacture of three-dimensional device structures, since the structures are three-dimensional and complex, in addition to "anisotropic etching," which etches the wafer surface in the vertical direction, "isotropic etching," which also allows etching in the horizontal direction, is carried out.

[0003] For example, Patent Document 1 discloses a plasma processing apparatus capable of performing isotropic etching with high accuracy. In order to realize fine processing by isotropic etching, a reaction layer is formed by radical adsorption and then desorbed by heating. These manufacturing steps allow the amount of etching to be controlled to a level of several nm or less.

[0004] Specifically, first, a wafer, which is the object to be processed, is carried into a processing chamber in a vacuum vessel by a transport mechanism. Next, the wafer is placed on a sample stage equipped with an electrostatic adsorption function. Next, plasma is generated in a discharge chamber, and ions and electrons are reduced by a dispersion plate. In this way, relatively highly reactive particles such as neutral particles and radicals of gas are introduced into the processing chamber. Next, such particles are adsorbed onto the surface of the 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 desorbed from the surface of the film (desorption step). The adsorption step and the desorption step are alternately repeated at a predetermined cycle, whereby the film can be selectively etched.

[0006] Also, FIG. 4 of Patent Document 2 discloses a dispersion plate that separates the discharge chamber and the processing chamber, and through holes formed in the dispersion plate. In Patent Document 2, the through holes are arranged only on the outer periphery of the dispersion plate in order to suppress the intrusion of ions passing through the through holes into the wafer. The intrusion of ions into the processing chamber causes a decrease in the controllability of the etching amount and the accumulation of charge on the sample stage. During discharge, many ions are distributed near the center of the discharge chamber, and many radicals are distributed near the outer wall of the discharge chamber. Therefore, it is possible to efficiently pass radicals while greatly suppressing the intrusion of ions into the processing chamber. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-185594 A [Patent Document 2] International Publication No. 2021 / 124539 Summary of the Invention [Problem to be solved by the invention]

[0008] In the techniques disclosed in Patent Documents 1 and 2, the dispersion plate that separates the discharge chamber and the processing chamber can prevent most ions from entering the sample stage, but it cannot prevent ions from passing through the through holes in the dispersion plate. Therefore, ions are incident non-uniformly on the wafer placed on the sample stage, which is one of the causes of reduced uniformity of the etching process on the wafer.

[0009] For example, it is possible to use two dispersion plates to suppress the intrusion of ions from the through-holes, but in that case, the number of activated radicals supplied into the processing chamber will also decrease.

[0010] The main object of the present invention is to suppress ions from reaching the sample stage without affecting the distribution and supply amount of radicals. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0011] A brief outline of a representative embodiment of the present invention will be described below.

[0012] A plasma processing apparatus according to an embodiment includes a vacuum vessel, a processing chamber which is a part of the interior of the vacuum vessel, a discharge chamber which is a part of the interior of the vacuum vessel and is provided above the processing chamber and for generating plasma, an exhaust chamber which is a part of the interior of the vacuum vessel and is provided below the processing chamber and has an exhaust port, a sample stage which is arranged inside the processing chamber and on which a wafer can be placed, a dispersion plate provided between the processing chamber and the discharge chamber, a plurality of first through holes formed in the dispersion plate so that the processing chamber and the discharge chamber communicate with each other, an exhaust plate provided between the processing chamber and the exhaust chamber so as to surround the sample stage, and a plurality of second through holes formed in the exhaust plate so that the processing chamber and the exhaust chamber communicate with each other. A first ring-shaped electrode is attached to the dispersion plate, a second ring-shaped electrode is attached to 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. Effect of the Invention

[0013] According to one embodiment, it is possible to prevent ions from reaching the sample stage without affecting the distribution and supply amount of radicals. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic cross-sectional view showing a plasma processing apparatus in accordance with a first embodiment. [Diagram 2] FIG. 4 is a bottom view showing the dispersion plate in the first embodiment. [Diagram 3] FIG. 2 is a plan view showing an exhaust plate in the first embodiment. [Figure 4]4 is a schematic cross-sectional view showing the trajectories of ions that have passed through the dispersion plate in the first embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are used for the members having the same functions, and the repeated explanations are omitted. In the following embodiments, the explanations of the same or similar parts will not be repeated as a rule unless it is particularly necessary.

[0016] (Embodiment 1) <Configuration of Plasma Processing Apparatus> A plasma processing apparatus 100 according to the first embodiment will be described below with reference to FIG.

[0017] As shown in FIG. 1, the plasma processing apparatus 100 includes a vacuum vessel 101. A discharge chamber 1, a processing chamber 2, and an exhaust chamber 3 each constitute a part of the interior of the vacuum vessel 101. The discharge chamber 1 for generating plasma PZ is provided above the processing chamber 2. The exhaust chamber 3 is provided 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 each have a cylindrical shape, and their central axes are arranged coaxially or at positions that are close to each other so as to be regarded as coaxial. The discharge chamber 1 is formed of a cylindrical ceramic chamber 5.

[0018] A sample stage 4 on which a wafer, which is an object to be processed, can be placed is provided inside the processing chamber 2. The sample stage 4 has a function of fixing the wafer on its upper surface by electrostatic adsorption. The wafer is composed of a semiconductor substrate on which a p-type or n-type impurity region is formed, a semiconductor element such as a transistor formed on the semiconductor substrate, and a wiring layer formed on the semiconductor element. The wafer in the first embodiment is in the middle of being manufactured.

[0019] A dispersion plate 20 is provided between the processing chamber 2 and the discharge chamber 1. The dispersion plate 20 is made of, for example, a ceramic material. 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. The planar shape of each of the sample stage 4 and the dispersion plate 20 is circular. The central axes of each of the sample stage 4 and the dispersion plate 20 are arranged coaxially with the central axes of the discharge chamber 1, the processing chamber 2, and the exhaust chamber 3, or at positions close to the position that can be regarded as being coaxial.

[0020] An electrode EL1 is attached to the lower surface of the dispersion plate 20. The electrode EL1 is in the shape of a ring coaxial with the dispersion plate 20. The surface of the electrode EL1 is anodized to prevent the electrode EL1 from being directly exposed to the plasma PZ. The electrode EL1 may be built into the inside of the dispersion plate 20. In that case, the above-mentioned anodization may not be performed.

[0021] An ICP coil 6 is installed outside the discharge chamber 1. The ICP coil 6 is connected to a high-frequency power supply 8 via a matching box 7, and generates a plasma PZ by the ICP discharge method. The frequency of the high-frequency power used is in the frequency band of several tens of MHz, such as 13.56 MHz.

[0022] A top plate 10 is provided on the top of the discharge chamber 1. A gas dispersion plate 9 having a plurality of through holes is provided below the top plate 10. A processing gas supplied from a processing gas supply unit 11 is introduced into the inside of the discharge chamber 1 through the gas dispersion plate 9. A seal 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. This allows the inside of the discharge chamber 1 to be airtightly sealed.

[0023] The supply flow rate of the processing gas supplied from the processing gas supply unit 11 is adjusted by a mass flow controller 12 installed for each gas type. The processing gas is, for example, a combustible gas, a combustion supporting gas, or a mixed gas thereof. The mixed gas may be diluted with an inert gas.

[0024] An IR lamp unit 40 for heating the wafer and the inside of the processing chamber 2 is installed at the top of the processing chamber. The IR lamp unit 40 includes a lamp 41 for heating the wafer, a light-transmitting window 42 made of quartz, a lamp power supply 43, and a high-frequency cut filter 44.

[0025] The lamp 41 is provided above the sample stage 4 and is electrically connected to a lamp power supply 43 via a high-frequency cut filter 44. The high-frequency cut filter 44 is provided to prevent noise from the high-frequency power applied to the ICP coil 6 from flowing into the lamp power supply 43. The light emitted from the lamp 41 is light (IR light) mainly ranging from visible light to infrared light. Such IR light can pass through the light transmission window 42, and the wafer and the inside of the processing chamber 2 are heated by the IR light.

[0026] Here, a plurality of lamps 41 are provided (three in the figure). The plurality of lamps 41 are arranged on concentric circles. The magnitude of the power supplied to the arc-shaped portion of each lamp 41 can be adjusted independently, and the radial distribution of the amount of heat applied to the wafer can be adjusted.

[0027] 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 ring-shaped. The central axis of the exhaust plate 30 is coaxial with the central axis of the sample stage 4, or is located at a position close to the central axis so as to be considered as being coaxial.

[0028] The exhaust plate 30 has a plurality of through holes 31 formed therein so that the processing chamber 2 and the exhaust chamber 3 communicate with each other. An electrode EL2 is attached to the upper surface of the exhaust plate 30. The electrode EL2 is in the shape of a ring coaxial with the exhaust plate 30. The surface of the electrode EL2 is anodized to prevent the electrode EL2 from being directly exposed to the plasma PZ. The electrode EL2 may be built into the exhaust plate 30. In that case, the above-mentioned anodization may not be performed.

[0029] A vacuum pump 15 for reducing the pressure inside the vacuum vessel 101 is provided below the exhaust chamber 3 outside the vacuum vessel 101. 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 amount or exhaust speed.

[0030] The configuration of the dispersion plate 20 will be described in detail below with reference to FIG.

[0031] As shown in FIG. 2, the dispersion plate 20 has a plurality of through holes 21 arranged concentrically. The plasma PZ includes ions, electrons, neutral particles, and radicals. The dispersion plate 20 is provided mainly to reduce the number of ions and electrons introduced into the processing chamber 2. The radicals pass through the plurality of through holes 21 and are introduced into the processing chamber 2. The arrangement of the plurality of through holes 21 determines the distribution of the radicals introduced into the processing chamber 2, and adjusts the uniformity of the etching process within the wafer surface.

[0032] As will be described in detail later, not only radicals but also some of the ions contained in the plasma pass through the through-holes 21 .

[0033] The electrode EL1 has a ring-shaped structure coaxial with the dispersion plate 20, and is attached to the lower surface of the dispersion plate 20. The electrode EL1 is also electrically connected to a variable DC power supply 22 via a high-frequency cut filter 23. The high-frequency cut filter 23 is provided to prevent noise from 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 etching process conditions or the chamber structure, but is, for example, −1000 V or more and 2000 V or less.

[0034] The configuration of the exhaust plate 30 will be described in detail below with reference to FIG.

[0035] 2, the exhaust plate 30 is disposed between the outer circumferential side wall of the sample stage 4 and the inner circumferential side wall of the processing chamber 2. The exhaust plate 30 has a plurality of through holes 31 arranged concentrically. It is designed so that gas (ions, radicals, etc.) inside the processing chamber 2 is exhausted almost uniformly to the exhaust chamber 3 through the plurality of through holes 31.

[0036] The electrode EL2 has a ring-shaped structure coaxial with the exhaust plate 30, and is attached to the upper surface of the exhaust plate 30. The electrode EL2 is also electrically connected to a variable DC power supply 32 via a high-frequency cut filter 33. The high-frequency cut filter 33 is provided to prevent noise from 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, −1000V or more and 2000V or less.

[0037] Moreover, the multiple 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 multiple through-holes 31. With this arrangement, the trajectory of the ions that have passed through the multiple through-holes 21 is bent by the electric field lines generated from the electrode EL1 toward the electrode EL2. This makes it difficult for the ions to reach the sample stage 4, and the ions are guided to pass through the multiple through-holes 31.

[0038] A method for diverting the trajectory of the ions 50 that have passed through the dispersion plate 20 from within the wafer surface will be described below with reference to Fig. 4. For ease of understanding, the right side of Fig. 4 shows the lines of electric force generated between the electrodes EL1 and EL2 with dashed lines, and the left side of Fig. 4 shows the trajectory of the ions 50.

[0039] When a wafer is placed on the sample stage 4 and the wafer is irradiated with the plasma PZ, a process gas is supplied from the process gas supply unit 11 into the discharge chamber 1. By outputting microwaves from the high frequency power supply 8, a plasma PZ is generated inside the discharge chamber 1 by the ICP coil 6. The process gas is excited by the plasma PZ, and the inside of the discharge chamber 1 becomes filled with ions, electrons, neutral particles, and radicals.

[0040] Among the radicals contained in the plasma PZ, those that pass through the through holes 21 are adsorbed to the film on the surface of the wafer. A chemical reaction between the radicals and the material that constitutes the film forms a reaction layer on the surface of the film. The wafer is heated by the lamps 41 by applying a voltage from the lamp power supply 43 to the lamps 41. Thermal energy is applied to the surface of the wafer, heating the reaction layer, and the reaction layer is detached from the film. By periodically repeating such a process, selective isotropic etching can be performed on the film.

[0041] Most of the ions contained in the plasma PZ are blocked by the dispersion plate 20, but the dispersion plate 20 alone cannot completely block the ions. Some of the ions 50 pass through the through holes 21 and enter the inside of the processing chamber 2.

[0042] However, in the first embodiment, when the plasma PZ is irradiated to the wafer, electric field lines are generated between the electrodes EL1 and EL2. The electric field lines are formed symmetrically around the central axis of the sample stage 4, widening from the lower surface of the dispersion plate 20 toward the sample stage 4, and are formed with a distribution of strength that is uniform or approximately equal in the circumferential direction. The trajectory of the ions 50 entering the inside of the processing chamber 2 also widens symmetrically around the central axis of the sample stage 4.

[0043] That is, the ions 50 that have passed through the multiple through-holes 21 have their trajectories bent by the electric field lines, pass through the multiple through-holes 31, enter the inside of the exhaust chamber 3, and are exhausted from the exhaust port 13 to the outside of the vacuum vessel 101. In this way, the ions 50 that have passed through the multiple through-holes 21 do not reach the wafer.

[0044] The radicals present inside the processing chamber 2 are not affected by the electric field lines, and therefore the etching process is not affected by the radicals. In addition, the wafer misalignment caused by the accumulation of electric charges, which was described in Patent Document 1, can also be eliminated.

[0045] In this way, according to the first embodiment, it is possible to prevent ions from reaching the sample stage without affecting the distribution and supply amount of radicals, and therefore it is possible to solve the problem that ions are non-uniformly incident on the wafer placed on the sample stage 4, resulting in a decrease in the uniformity of the etching process within the wafer surface.

[0046] Although the present invention has been specifically described based on the above embodiment, the present invention is not limited to the above embodiment and can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0047] 100 Plasma treatment device 101 Vacuum container 1 Discharge chamber 2. Processing Room 3 Exhaust chamber 4 Sample stage 5 Ceramic Chamber 6 ICP coil 7 Matching box 8 High frequency power supply 9 Gas Dispersion Plate 10. Top plate 11 Processing gas supply section 12 Mass flow controller 13 Exhaust port 14 Pressure Regulating Valve 15 Vacuum Pump 20 Dispersion plate 21 Through hole 22 Variable DC power supply 23 High frequency cut filter 30 Exhaust plate 31 Through hole 32 Variable DC power supply 33 High frequency cut filter 40 IR lamp unit 41 Lamp 42 Light-transmitting window 43 Lamp power supply 44 High frequency cut filter 50 Aeon EL1, EL2 electrode PZ Plasma

Claims

1. A vacuum vessel; a processing chamber that is a part of the interior of the vacuum vessel; a discharge chamber which is a part of the inside of the vacuum vessel and is provided above the processing chamber and which generates plasma; an exhaust chamber which is a part of the inside of the vacuum vessel and is provided below the processing chamber and has an exhaust port; a sample stage disposed inside the processing chamber and capable of supporting a wafer; a dispersion plate provided between the processing chamber and the discharge chamber; a plurality of first through holes formed in the dispersion plate so that the processing chamber and the discharge chamber communicate with each other; an exhaust plate provided between the processing chamber and the exhaust chamber so as to surround the sample stage; a plurality of second through holes formed in the exhaust plate so that the processing chamber and the exhaust chamber communicate with each other; Equipped with A ring-shaped first electrode is attached to the dispersion plate, A ring-shaped second electrode is attached to the exhaust plate, a first variable DC power source is electrically connected to the first electrode; A second variable DC power supply is electrically connected to the second electrode.

2. 2. The plasma processing apparatus according to claim 1, The first electrode is attached to a lower surface of the dispersion plate, The second electrode is attached to an upper surface of the exhaust plate.

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

4. 4. The plasma processing apparatus according to claim 3, The plasma processing apparatus comprises: a wafer placed on the sample stage; and when the wafer is irradiated with the plasma, electric lines of force are generated between the first electrode and the second electrode.

5. 5. The plasma processing apparatus according to claim 4, A plasma processing apparatus, wherein, of the plurality of ions contained in the plasma, the ions that pass through the plurality of first through holes have their trajectories bent by the electric field lines, pass through the plurality of second through holes, and enter the interior of the exhaust chamber.

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

7. 6. The plasma processing apparatus according to claim 5, a lamp disposed above the sample stage for heating the wafer; Among the plurality of radicals contained in the plasma, the radicals that have passed through the plurality of first through holes are adsorbed onto a 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 radicals, The plasma processing apparatus heats the reaction layer, thereby causing the reaction layer to separate from the film.

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