JP2022114542A - Vacuum processing apparatus - Google Patents

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

The present invention relates to a vacuum processing apparatus.

2. Description of the Related Art In the manufacturing process of semiconductor devices, it is required to cope with miniaturization and integration of components included in semiconductor devices. For example, in integrated circuits and nanoelectromechanical systems, structures are becoming more nanoscaled.

Lithographic technology is usually used to form fine patterns in the manufacturing process of semiconductor devices. This technique applies a pattern of device structures onto a resist layer and selectively etches away the substrate exposed by the pattern of the resist layer. Subsequent processing steps can deposit other materials in the etched regions to form an integrated circuit.

In particular, in recent years, there has been an increasing demand from the market for power saving and high speed semiconductor devices, and there has been a remarkable tendency for device structures to become more complicated and highly integrated. For example, in logic devices, the application of GAA (Gate All Around), in which channels are configured with stacked nanowires, is under consideration. Therefore, lateral processing by isotropic etching is required.

Here, anisotropic etching is etching that utilizes an ion-assisted reaction in which ions promote reactions of radicals, and isotropic etching is etching that mainly involves surface reactions only by radicals. Therefore, a plasma etching apparatus is required to have both a function of performing etching by irradiating both ions and radicals and a function of performing etching by irradiating only radicals.

For example, in atomic layer etching for controlling the etching depth with high accuracy, the etching depth is controlled by alternately repeating a first step of irradiating the sample with only radicals and a second step of irradiating the sample with ions. methods are being considered. In this etching method, radicals are adsorbed on the surface of the sample in the first step, and then, in the second step, ions of a rare gas are irradiated to activate the radicals adsorbed on the surface of the sample, thereby causing an etching reaction. It controls the etching depth with high accuracy.

Further, for example, in a mass production factory for high-mix low-volume production, by installing an etching apparatus having both functions of anisotropic etching that irradiates both ions and radicals and isotropic etching that irradiates only radicals, 1 A single etching system can perform multiple processes, thereby saving space and greatly reducing facility costs.

Thus, the plasma etching apparatus used in semiconductor device processing is 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. there is

In response to such a demand, in Patent Document 1, a shielding plate that shields the incidence of ions is installed in the chamber, and plasma is generated below the shielding plate to irradiate both ions and radicals. or by generating a plasma above the shielding plate, an apparatus capable of performing a treatment using only radicals has been proposed.

Moreover, in Patent Document 2, plasma molecules are appropriately selected from among F, CF ₂ and CO, and the emission intensity of a predetermined wavelength is measured, whereby an etching chamber in a semiconductor process is isolated from a pressure sensor by a partition plate. Techniques have been proposed to monitor the true internal pressure more precisely than before and precisely control the etching process to greatly improve product yield.

JP 2018-093226 A JP-A-2000-133640

By the way, in order to perform both the etching process by irradiating both ions and radicals and the etching process by irradiating only radicals in the same chamber with high accuracy, two chambers separated by a shielding plate are required. In space, it is necessary to consider the pressure difference due to the conductance of the shielding plate.

However, in Patent Document 1, the pressure measuring device is connected only to the lower part of the shielding plate, and the pressure in the upper space of the shielding plate is not measured. be.

Moreover, the technique of Patent Document 2 has a problem that the change in the emission intensity may be affected by the change in the environment inside the chamber other than the pressure, and the pressure may not be accurately estimated.

SUMMARY OF THE INVENTION 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.

In order to solve the above problems, one typical vacuum processing apparatus according to the present invention is
In a vacuum processing apparatus comprising a processing chamber having two spaces in which a differential pressure is generated and in which a sample is subjected to vacuum processing,
Conductance is determined using the viscous flow field equation or the molecular flow field equation based on a predetermined pressure threshold,
determining the differential pressure using the determined conductance;
This is achieved by further including a control unit that controls the pressure of the processing chamber using the differential pressure.

According to the present invention, it is possible to provide a vacuum processing apparatus that can perform vacuum processing at a desired pressure even in the space on the side of the shielding plate to which the pressure gauge is not connected, and that can improve process stability.
Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

FIG. 1 is a cross-sectional view of a schematic overall configuration of a vacuum processing apparatus according to an embodiment of the present invention. FIG. 2 is a plan view showing a shielding plate according to an embodiment of the invention. FIG. 3 is a flow chart illustrating a vacuum processing method according to an embodiment of the invention. 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.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. "Vacuum processing" according to the present invention includes plasma processing.

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

A high-frequency power supply 124 is connected via a matching device 123 to the sample 116 placed on the sample table 115 . 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 the opening of the valve 121. FIG.

This vacuum processing apparatus also has a dielectric shielding plate 113 shown in FIG. 2 inside the vacuum processing chamber 117 . Through-holes 131 having the same diameter are uniformly arranged in the shielding plate 113 along the outer peripheral portion thereof. In this embodiment, the term “uniform” means that when concentric circles having the same diameter difference (including cases where the radius is zero) are drawn, the through-holes 131 having center points on the same circle are arranged at equal pitches in the circumferential direction. It means that it is placed. A 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.

The vacuum processing apparatus used in this embodiment has the characteristic of being able to generate plasma in the vicinity of a plane with a magnetic field strength of 0.0875 T when the microwave frequency is 2.45 GHz. Therefore, by adjusting the magnetic field so that the plasma generation region is positioned between the shield plate 113 and the dielectric window 111 (first space 118), plasma can be generated on the dielectric window 111 side of the shield plate 113. Since the generated ions can hardly pass through the shield plate 113 (the ions are shielded), the sample 116 can be irradiated with only radicals. At this time, in the sample 116, isotropic etching mainly due to surface reaction only by radicals proceeds.

On the other hand, if the magnetic field is adjusted so that the plasma generation region is positioned between the shield plate 113 and the sample 116 (second space 119), plasma can be generated on the sample 116 side of the shield plate 113, and ions and radicals can be generated. can be supplied to the sample 116. At this time, the sample 116 undergoes anisotropic etching using an ion-assisted reaction, in which the ions accelerate the reaction of radicals.

The magnetic field of the solenoid coil 108 is controlled to adjust or switch the height position of the plasma generation region with respect to the height position of the shielding plate 113 (upper or lower), and to adjust the period for holding each height position. This can be done using the controller 120 .

FIG. 3 is a flow chart showing a vacuum processing method according to an embodiment of the invention. Hereinafter, description will be made along this flow chart. The vacuum processing apparatus according to this embodiment includes a control device (not shown) that executes processing according to the flowchart shown in FIG.

In step S101, vacuum processing recipe creation is started.
In step S102, a desired gas type, gas flow rate, and pressure p1 of the first space 118 to which the pressure gauge is not connected are designated.
In step S103, the differential pressure Δp generated between the space above and below the shielding plate (the first space 118 and the second space 119) is estimated based on the measured value database. Details of this step will be described with reference to FIG.

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.

FIG. 4 is a graph in which the horizontal axis represents the pressure and the vertical axis represents the conductance of the shield plate. The dotted line is the measured value of the conductance in Ar gas, and the conductance in gas B input to the recipe is estimated based on the database containing the measured values. Fluid flow can be roughly divided into three types: viscous flow, intermediate flow, and molecular flow. These are classified according to the size relationship between the mean free path λ of the fluid and the diameter 2a of the through-hole 131 of the shielding plate 113 . In general, the mean free path λ is represented by the following formula (Equation 1).

where _R is the gas constant, T is the temperature, NA is Avogadro's number, D is the molecular diameter of the fluid, and P is the pressure. When 2a>>λ holds, the flow is a viscous flow; when 2a≈λ, an intermediate flow; and when 2a<<λ, a molecular flow. The conductance can be calculated from the conductance calculation formula for the molecular flow and viscous flow regions, but it is difficult to obtain an approximation formula for the intermediate flow region.

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

Also, the conductance of the gas B in the viscous flow region is estimated by multiplying the measured value of the conductance in the Ar gas by the following value (Equation 3).

In Equations 2 and 3, M _Ar is the molecular weight of argon, M _B is the molecular weight of gas B, η _Ar is the viscosity coefficient of argon, and η _B is the viscosity coefficient of gas B.

On the low pressure side of the intersection of these estimated conductance graphs, the molecular flow estimate is used, and on the high pressure side, the viscous flow estimate is used. From this, the conductance C when the gas B is used is estimated.

The differential pressure Δp is obtained by dividing the gas flow rate Q by the conductance C as shown in the following equation (Equation 4).

As the gas B, a single gas (including Ar) may be used, or a mixed gas of a plurality of gases may be used. For example, when a mixed gas of two types of gas i and gas j is used, the molecular weight is calculated by equation (5), and the viscosity coefficient is calculated by equations (6) to (8).

Here, M _i and M _j are molecular weights of gas i and gas j respectively, y _i and y _j are molar fractions of gas i and gas j respectively, and η _i and η _j are viscosity coefficients of gas i and gas j respectively. be. Although the case where two types of gases are used has been described here, a mixed gas of three or more types may be used. In the case of a mixed gas of three or more types, the third term and subsequent terms are added to the formula (Equation 5). Repeat adding parameters.

In the flowchart of FIG. 3, in step S104, the average pressure p of the spaces above and below the shield plate (the first space 118 and the second space 119) is calculated from the differential pressure Δp estimated in step S103. After that, in step S201, it is determined whether or not the following equation (Equation 9) holds.

Here, L is the thickness of the shielding plate, a is the radius of the through hole 131, and K is the Clausing coefficient, which will be described later.

The formula (9) is a formula for determining whether or not the average pressure is greater than the pressure at the intersection of the conductance calculation formula for the viscous flow region and the conductance calculation formula for the molecular flow region, which will be described later. is the predetermined pressure threshold.

If the formula (Formula 9) holds, the conductance is calculated from the conductance calculation formula for the viscous flow region in step S105. The formula for calculating the conductance in the viscous flow region is expressed by the following formula (Equation 10).

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

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

Here, A is the total area of the through holes 131 .
Also, K in the equation (11) is called a Clausing coefficient and is represented by the following equation (13).

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

Equation (9) is obtained by connecting the right side of Equation (10) and the right side of Equation (11) with an equal sign and solving for the average pressure p.

In step S107, the differential pressure Δp' between the first space 118 and the second space 119 is calculated from the conductance C' calculated in step S105 or S106. The differential pressure .DELTA.p' is obtained by dividing the flow rate Q by the conductance C' as shown in the following equation (Equation 15).

In step S108, the recipe pressure value is replaced with a value p2 obtained by subtracting or adding the differential pressure Δp' calculated in step S107 from the desired pressure p1 of the first space 118 to which the pressure gauge is not connected. At this time, when the first space 118 is positioned upstream of the gas flow with respect to the second space 119, the pressure value in the recipe is the desired pressure in the first space 118 minus the differential pressure Δp′. , and if it is located downstream, replace it with the added value.

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

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

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 to start vacuum processing, and after a predetermined vacuum processing time has elapsed, proceeds to step S113 to end the vacuum processing. The above is the description of the flowchart showing the configuration according to the embodiment of the present invention.

The above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations.

DESCRIPTION OF SYMBOLS 103... Magnetron, 108... Solenoid coil, 111... Dielectric window, 113... Shielding plate, 115... Sample table, 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 supply 125 Pressure gauge 131 Through hole of shield plate 113

Claims (5)

In a vacuum processing apparatus comprising a processing chamber having two spaces in which a differential pressure is generated and in which a sample is subjected to vacuum processing,
Conductance is determined using the viscous flow field equation or the molecular flow field equation based on a predetermined pressure threshold,
determining the differential pressure using the determined conductance;
A vacuum processing apparatus according to claim 1, further comprising a controller that controls the pressure of the processing chamber using the differential pressure. In the vacuum processing apparatus according to claim 1,
A vacuum processing apparatus, wherein the space is partitioned by a shielding plate that shields ions. In the vacuum processing apparatus according to claim 1,
A vacuum processing apparatus, wherein the pressure of the space containing the sample is controlled by the controller. In the vacuum processing apparatus according to claim 2,
A vacuum processing apparatus, wherein the pressure of the space containing the sample is controlled by the controller. In the vacuum processing apparatus according to claim 4,
A vacuum processing apparatus, further comprising: a high-frequency power source for supplying microwave high-frequency power; and a magnetic field forming mechanism for forming a magnetic field in the processing chamber.

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