Vacuum Processing Equipment

Abstract

To improve process stability by performing vacuum processing by desired pressure even in a space on the side to which a pressure gauge is not connected, in a vacuum processing apparatus having a shield plate.SOLUTION: A vacuum processing apparatus comprises a processing chamber that has two spaces generating differential pressure and in which a sample is vacuum-processed. The vacuum processing apparatus also comprises a control part in which conductance is determined by using an expression for a viscous flow region or an expression for a molecular flow region on the basis of a predetermined pressure threshold, in which the differential pressure is determined by using the determined conductance, and in which pressure in the processing chamber is controlled by using the differential pressure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vacuum processing apparatus. [Background technology]

[0002] 2. Description of the Related Art In the manufacturing process of semiconductor devices, there is a demand for miniaturization and integration of components included in semiconductor devices, for example, in integrated circuits and nanoelectromechanical systems, structures are increasingly being scaled down to the nanoscale.

[0003] Lithography techniques are typically used to create fine patterns in the manufacturing process of semiconductor devices. This technique involves applying a pattern of the device structure onto a layer of resist and selectively etching away the substrate exposed by the pattern in the resist layer. In subsequent processing steps, other materials can be deposited in the etched areas to form integrated circuits.

[0004] In particular, in recent years, the market has been demanding higher power consumption and speed for semiconductor devices, and there has been a clear trend toward more complex and highly integrated device structures. For example, in logic devices, the application of GAA (Gate All Around), in which channels are made of stacked nanowires, is being considered, and in the etching process for GAA, in addition to the conventional vertical processing by anisotropic etching, lateral processing by isotropic etching is required to form the nanowires.

[0005] Here, anisotropic etching is etching that utilizes ion-assisted reactions that promote radical reactions with ions, while isotropic etching is etching that is mainly based on surface reactions caused by radicals alone. Therefore, plasma etching equipment is becoming required to have both the function of etching by irradiating both ions and radicals, and the function of etching by irradiating only radicals.

[0006] For example, in atomic layer etching, which controls the etching depth with high precision, a method is being considered in which the etching depth is controlled by alternately repeating a first step in which only radicals are irradiated onto the sample, and a second step in which ions are irradiated onto the sample. In this etching method, radicals are adsorbed onto the sample surface in the first step, and then rare gas ions are irradiated onto the sample surface in the second step to activate the radicals adsorbed onto the surface, causing an etching reaction and controlling the etching depth with high precision.

[0007] Furthermore, for example, in a mass production factory producing a wide variety of products in small quantities, by installing an etching device that has both anisotropic etching functions, which irradiates both ions and radicals, and isotropic etching functions, which irradiates only radicals, it is possible to carry out multiple processes with a single etching device, thereby realizing space savings and significantly reducing equipment costs.

[0008] Thus, plasma etching apparatuses used in semiconductor device processing are required to have both the function of performing etching by irradiating both ions and radicals, and the function of performing etching by irradiating only radicals.

[0009] In response to such demands, Patent Document 1 proposes an apparatus that installs a shielding plate in a chamber to block the incidence of ions, and generates plasma below the shielding plate to perform plasma processing in which both ions and radicals are irradiated, or generates plasma above the shielding plate to perform processing using radicals only.

[0010] Furthermore, Patent Document 2 proposes a technology that selects an appropriate plasma molecule from among F, CF2, and CO, and measures the emission intensity at a specified wavelength to more precisely monitor than conventional techniques the true pressure inside an etching chamber during semiconductor processing that is isolated from a pressure sensor by a partition, thereby precisely controlling the etching process and significantly improving product yields. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2018-093226 A [Patent Document 2] JP 2000-133640 A Summary of the Invention [Problem to be solved by the invention]

[0012] Incidentally, in order to perform both a process of etching by irradiating both ions and radicals and a process of etching by irradiating only radicals in the same chamber with high precision, it is necessary to take into account the pressure difference due to the conductance of the shielding plate in the two spaces separated by the shielding plate.

[0013] However, in Patent Document 1, the pressure measuring device is only connected to the lower part of the shielding plate, and the pressure in the space above the shielding plate is not measured, which means that the pressure difference between above and below the shielding plate is not taken into consideration.

[0014] Furthermore, the technique of Patent Document 2 has a problem in that the change in emission intensity may be influenced by changes in the environment inside the chamber other than the pressure, and there is a risk that the pressure cannot be estimated accurately.

[0015] An object of the present invention is to provide a vacuum processing apparatus capable of performing vacuum processing at a desired pressure even in a space on the side of a shielding plate to which a pressure gauge is not connected, thereby improving process stability. [Means for solving the problem]

[0016] In order to solve the above problems, one representative vacuum processing apparatus according to the present invention comprises: The sample was placed on the stage. The sample is vacuum processed. It has two spaces where a pressure difference occurs In a vacuum processing apparatus having a processing chamber, A shielding plate is disposed between the two spaces to block the incidence of ions on the sample stage. The differential pressure is estimated based on an actual measured value of conductance; The average pressure of the two spaces is calculated using the estimated pressure difference; The shielding plate A formula for calculating the conductance in a viscous flow region or a formula for calculating the conductance in a molecular flow region is selected based on a predetermined formula; The differential pressure is calculated based on the conductance calculated using the selected formula for calculating the conductance in the viscous flow region or the selected formula for calculating the conductance in the molecular flow region; a control unit that controls the pressure in the processing chamber using the calculated differential pressure, The predetermined formula is a formula determined based on the viscosity of a gas used in the vacuum treatment, the molecular weight of the gas, the thickness of the shielding plate, the size of the through-hole of the shielding plate, and the temperature of the vacuum treatment; This is achieved by the equation being for judging whether or not the average pressure is greater than the pressure at the intersection of the equation for calculating the conductance in the viscous flow region and the equation for calculating the conductance in the molecular flow region. Effect of the Invention

[0017] According to the present invention, it is possible to provide a vacuum processing apparatus capable of performing vacuum processing at a desired pressure even in a space on the side of a shielding plate to which a pressure gauge is not connected, thereby improving process stability. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view of the overall configuration of a vacuum processing apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view showing a shielding plate according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a flowchart showing a vacuum processing method according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram illustrating details of step S103 in the flowchart showing the configuration according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The "vacuum processing" according to the present invention includes plasma processing.

[0020] [Embodiment] A schematic cross-sectional view of the overall configuration of a vacuum processing apparatus according to an embodiment of the present invention is shown in Fig. 1. In the vacuum processing apparatus of this embodiment, plasma can be generated in vacuum processing chamber 117 by electron cyclotron resonance (ECR) between a 2.45 GHz microwave supplied to vacuum processing chamber 117 through dielectric window 111 from magnetron 103, which is a high-frequency power source that supplies high-frequency microwave power, and a magnetic field created by solenoid coil 108, which is a magnetic field forming mechanism that forms a magnetic field in the processing chamber. Such a vacuum processing apparatus is called an ECR plasma processing apparatus.

[0021] Moreover, a high frequency power supply 124 is connected to a sample 116 placed on a sample stage 115 via a matching box 123. The inside of the vacuum processing chamber 117 is connected to a pump 122 via a valve 121, and the internal pressure can be adjusted by changing the opening degree of the valve 121.

[0022] The vacuum processing apparatus also has a dielectric shielding plate 113 shown in FIG. 2 inside the vacuum processing chamber 117. Through holes 131 of the same diameter are uniformly arranged on the outer periphery of the shielding plate 113. In this embodiment, "uniformly" means that when concentric circles (including the case where the radius is zero) with the same difference in diameter are drawn, the through holes 131 having their center points on the same circle are arranged at equal pitches in the circumferential direction. The shielding plate 113 divides (partitions) the inside of the vacuum processing chamber 117 into a first space 118 and a second space 119, and a pressure gauge 125 is connected only to the second space 119. Therefore, the pressure in the second space 119 can be measured, but the pressure in the first space 118 is not measured.

[0023] The vacuum processing apparatus used in this embodiment has the characteristic that, when the microwave frequency is 2.45 GHz, plasma can be generated near a surface with a magnetic field strength of 0.0875 T. Therefore, by adjusting the magnetic field so that the plasma generation region is located between the shielding plate 113 and the dielectric window 111 (first space 118), plasma can be generated on the dielectric window 111 side of the shielding plate 113, and since the generated ions can hardly pass through the shielding plate 113 (the shielding plate 113 blocks the ions), only radicals can be irradiated onto the sample 116. At this time, isotropic etching mainly caused by surface reactions by radicals alone proceeds on the sample 116.

[0024] On the other hand, if the magnetic field is adjusted so that the plasma generation region is located between the shielding plate 113 and the sample 116 (second space 119), plasma can be generated on the sample 116 side of the shielding plate 113, and both ions and radicals can be supplied to the sample 116. At this time, anisotropic etching progresses in the sample 116 using an ion-assisted reaction in which the reaction of radicals is promoted by ions.

[0025] In addition, adjustment or switching (upper or lower) of the height position of the plasma generation region relative to the height position of the shielding plate 113, adjustment of the period for which each height position is maintained, etc. can be performed using a control device 120 that controls the magnetic field of the solenoid coil 108.

[0026] 3 is a flowchart showing a vacuum processing method according to an embodiment of the present invention. The following description will be given with reference to this flowchart. The vacuum processing apparatus according to this embodiment includes a control device (not shown) that executes processing according to the flowchart shown in FIG.

[0027] In step S101, creation of a vacuum processing recipe begins. In step S102, a desired gas type, gas flow rate, and pressure p1 in the first space 118 to which no pressure gauge is connected are specified. In step S103, a pressure difference Δp occurring between the spaces above and below the shielding plate (first space 118 and second space 119) is estimated based on a database of actual measurements. Details of this step will be described with reference to FIG.

[0028] FIG. 4 is a schematic diagram illustrating details of the estimation in step S103 in the flowchart showing the configuration according to the embodiment of the present invention.

[0029] Figure 4 is a graph with pressure on the horizontal axis and conductance of the shielding plate on the vertical axis. The dotted line is the actual measured value of conductance for Ar gas, and the conductance for gas B entered into the recipe is estimated based on a database containing these measured values. Fluid flows can be broadly divided into three types: viscous flow, intermediate flow, and molecular flow. These are classified according to the relationship between the mean free path λ of the fluid and the diameter 2a of the through hole 131 in the shielding plate 113. In general, the mean free path λ is expressed by the following equation (Equation 1).

[0030]

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[0031] where R is the gas constant, T is the temperature, and N A is Avogadro's number, D is the molecular diameter of the fluid, and P is pressure. When 2a>>λ holds, it is a viscous flow, when 2a≒λ holds, it is an intermediate flow, and when 2a<<λ holds, it is a molecular flow. In the molecular flow and viscous flow regions, the conductance can be calculated from the conductance formula, but in the intermediate flow region, it is difficult to find an approximate formula.

[0032] Therefore, the conductance of gas B in the molecular flow region is estimated by multiplying the measured value of the conductance of the Ar gas by the following value (Equation 2).

[0033]

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[0034] In addition, the conductance of gas B in the viscous flow region is estimated by multiplying the measured value of the conductance of Ar gas by the following value (Equation 3).

[0035]

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[0036] Here, M in numbers 2 and 3 Ar is the molecular weight of argon, M B is the molecular weight of gas B, η Ar is the viscosity coefficient of argon, η B is the viscosity coefficient of gas B.

[0037] The estimated value for molecular flow is used on the lower pressure side than the intersection of the graphs of these estimated conductances, and the estimated value for viscous flow is used on the higher pressure side. This allows us to estimate the conductance C when gas B is used.

[0038] The differential pressure Δp is calculated by dividing the gas flow rate Q by the conductance C according to the following equation (Equation 4).

[0039]

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[0040] In addition, a single gas (including Ar) or a mixture of multiple gases may be used as gas B. For example, when using a mixture of two types of gases i and j, the molecular weight is calculated using formula (5), and the viscosity coefficient is calculated using formulas (6) and (8).

[0041]

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[0042]

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[0043]

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[0044]

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[0045] Here, M i , M j are the molecular weights of gas i and gas j, respectively, and y i , y j are the mole fractions of gas i and gas j, respectively, and η i , η j are the viscosity coefficients of gas i and gas j, respectively. Here, we have explained the case where two types of gas are used, but a mixed gas of three or more types may also be used. In the case of a mixed gas of three or more types, the third and subsequent terms are added to equation (5), and for equation (6), the parameters of the third and subsequent gases are added to the calculation results for a mixed gas of two gases, and this process is repeated.

[0046] 3, in step S104, the average pressure p in the spaces above and below the shielding plate (the first space 118 and the second space 119) is calculated from the pressure difference Δp estimated in step S103. Then, in step S201, it is determined whether the following formula (Math. 9) is satisfied.

[0047]

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[0048] Here, L is the thickness of the shielding plate, a is the radius of the through hole 131, and K is the Clausing coefficient described later.

[0049] Note that equation (9) is an equation that determines whether the average pressure is greater than the pressure at the intersection of the conductance calculation equation for the viscous flow region (described below) and the conductance calculation equation for the molecular flow region, and the right-hand side of equation 9 is a predetermined pressure threshold value.

[0050] If the formula (9) is satisfied, the conductance is calculated from the conductance calculation formula for the viscous flow region in step S105. The conductance calculation formula for the viscous flow region is expressed by the following formula (10).

[0051]

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[0052] On the other hand, if formula (9) does not hold, the conductance is calculated from the conductance calculation formula for the molecular flow region in step S106. The conductance calculation formula for the molecular flow region is expressed by the following formula (11).

[0053]

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[0054] Here, C1 is called the conductance of the orifice in the molecular flow region and is expressed by the following equation (Equation 12).

[0055]

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[0056] Here, A is the total area of ​​the through holes 131. Moreover, K in the equation (11) is called the Clausing coefficient, and is expressed by the following equation (13).

[0057]

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[0058] Here, x is the ratio of the shielding plate thickness L to the diameter 2a of the through hole 131, as shown in the following equation (Equation 14).

[0059]

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[0060] Equation (9) is obtained by joining the right-hand side of equation (10) and the right-hand side of equation (11) with an equal sign and solving for the average pressure p.

[0061] In step S107, a pressure difference Δp' between the first space 118 and the second space 119 is calculated from the conductance C' calculated in step S105 or step S106. The pressure difference Δp' is calculated by dividing the flow rate Q by the conductance C' according to the following equation (Equation 15).

[0062]

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[0063] In step S108, the pressure value in the recipe is replaced with a value p2 obtained by subtracting or adding the differential pressure Δp' calculated in step S107 from the desired pressure p1 in the first space 118 to which no pressure gauge is connected. At this time, if the first space 118 is located upstream of the second space 119 in the gas flow, the pressure value in the recipe is replaced with a value obtained by subtracting the differential pressure Δp' from the desired pressure in the first space 118, and if it is located downstream, the pressure value is replaced with the added value.

[0064] In step S109, a vacuum processing sequence is started. In step S110, the value of the pressure gauge 125 connected to the second space 119 is read.

[0065] Then, in step S202, it is determined whether the value of pressure gauge 125 has reached value p2 replaced in step S108. If it is determined that the value of pressure gauge 125 has not reached value p2, in step S111, the difference between the actual measurement value of pressure gauge 125 and value p2 replaced in step S108 is calculated, and the opening of the pressure control valve is feedback-controlled according to the difference (pressure control is performed in the space containing sample 116), and the process returns to step S110.

[0066] On the other hand, if it is determined that the value of the pressure gauge 125 has reached the value p2, the process proceeds to step S112, where a vacuum process is started, and after a predetermined vacuum process time has elapsed, the process proceeds to step S113, where the vacuum process is ended. The above is an explanation of the flowchart showing the configuration according to the embodiment of the present invention.

[0067] The above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to the embodiment having all of the configurations described. [Explanation of symbols]

[0068] 103... magnetron, 108... solenoid coil, 111... dielectric window, 113... shielding plate, 115... sample stage, 116... sample, 117... vacuum processing chamber, 118... first space, 119... second space, 120... control device, 121... valve, 122... pump, 123... matching box, 124... high frequency power source, 125... pressure gauge, 131... through hole of shielding plate 113

Claims

1. A vacuum processing apparatus having a processing chamber having two spaces in which a sample placed on a sample stage is vacuum-processed to generate a pressure difference, the pressure difference is estimated based on an actual measurement value of a conductance of a shielding plate that is disposed between the two spaces and shields the ions from being incident on the sample stage; The average pressure of the two spaces is calculated using the estimated pressure difference; a formula for calculating the conductance of the shielding plate in a viscous flow region or a formula for calculating the conductance of the shielding plate in a molecular flow region is selected based on a predetermined formula; The differential pressure is calculated based on the conductance calculated using the selected formula for calculating the conductance in a viscous flow region or the selected formula for calculating the conductance in a molecular flow region; a control unit that controls the pressure in the processing chamber using the calculated differential pressure, a molecular weight of the gas used in the vacuum processing, a thickness of the shielding plate, a size of the through hole of the shielding plate, and a temperature of the vacuum processing, the predetermined formula being an equation for determining whether the average pressure is greater than the pressure at the intersection of an equation for calculating the conductance in the viscous flow region and an equation for calculating the conductance in the molecular flow region.

2. 2. The vacuum processing apparatus according to claim 1, A vacuum processing apparatus, characterized in that the pressure of the space containing the sample is controlled by the control unit.

3. 3. The vacuum processing apparatus according to claim 2, 1. A vacuum processing apparatus further comprising: a high-frequency power source for supplying high-frequency microwave power; and a magnetic field forming mechanism for forming a magnetic field within the processing chamber.

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