JP3203259B2 - Method and apparatus for preventing adhesion of active substance to inner wall surface of reaction tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for preventing an active substance from adhering to an inner wall surface of a reaction vessel.

[0002]

2. Description of the Related Art Various types of reactors are known in the art. In this reactor, for example, a target is opposed to a wafer on which a thin film of molecules or atoms ejected from the target is formed. It is known that a reaction system is formed by this. Various active substances are scattered around from the reaction system and adhere to the inner wall surface constituting the reaction tank. Conventionally, the inner wall surface is periodically cleaned by some means, or a gas for preventing adhesion is caused to flow along the inner wall surface.

However, even in the latter method, the mechanism for preventing the active substance from adhering to the inner wall surface has not been theoretically elucidated yet, and the mass flow rate of the gas is unduly increased or the active substance is not adhered. The situation is that they are not sufficiently prevented.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a gas for preventing adhesion is caused to flow in an internal space in an ideal state, and various active substances generated from a reaction system are generated in the reaction tank. A method for preventing the adhesion of active substances to the inner wall surface of a reaction tank that can prevent adhesion to the inner wall surface under ideal conditions
And an apparatus .

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a reaction vessel having a cylindrical internal space and having a reaction system disposed along and near the central axis thereof. A cylindrical gas ejection wall having a plurality of gas ejection ports formed at a first predetermined distance in a direction, and a second predetermined distance smaller than the first predetermined distance in a radial direction from the center axis; a gas for jetting means cyclic disposed on one end wall at a distance, the in the gas outlet of the gas ejection wall member
An inert first gas is ejected at a first predetermined speed in a direction toward a core axis, and an inert second gas is ejected at a second predetermined speed from the gas ejection means along the central axis. This is achieved by a method for preventing the active substance from adhering to the inner wall surface of the reaction tank, wherein Or cylindrical
A reaction vessel having an internal space having a shape, and a central axis of the reaction vessel
A reaction system disposed along and near the line;
A large number of gases at a first predetermined distance in the radial direction from the center axis
A cylindrical gas ejection wall having an ejection port formed therein;
More than the first predetermined distance in the radial direction from the center axis
An annular arrangement at one end wall at a small second predetermined distance
Means for ejecting gas, and
A first gas that is inert in a direction toward the central axis is moved to a first location.
The gas is ejected at a constant speed, and the center axis is
Injects an inert second gas at a second predetermined speed along the line
Active substance on the inner wall of the reaction tank characterized by having been discharged
Achieved by the anti-adhesion device.

[0006]

The first gas from the cylindrical gas ejection wall and the second gas from the annular gas ejection means are respectively centered.
Although the second gas is ejected in the direction toward the axis and in the direction of the central axis, the second gas serves to regulate the flow of the first gas and to prevent the reaction in the reaction system near the central axis from being adversely affected. In some cases, the gas may be the same as the gas used for the reaction, or may be a different gas.

When the jet velocity of these gases and the difference between the first predetermined distance and the second predetermined distance are appropriately taken, the reduction rate derived from the theoretical concentration equation described in detail below, The amount of the active substance attached to the inner wall surface when the first gas and the second gas flow into the internal space by the above method, and the amount of the active substance adhered to the inner wall surface when the first gas and the second gas are stationary. In the case of the present invention, the ratio to the amount of adhesion is the smallest in the case of the conventional reaction tank having any shape and the flow of the gas for preventing adhesion introduced into the reaction tank. That is, when the gas introduction amount per unit area of the wall is constant for a reaction tank having substantially the same dimensions, the minimum reduction rate is obtained. In addition, the adoption of the cylindrical container has a large effect of reducing the gas introduction amount since the wall area is minimized as a container for accommodating the reaction system which often becomes cylindrical.

Therefore, when any reaction system is provided in the reaction tank having the structure of the present invention, the amount of the scattered active substance generated from the reaction system and adhered to the inner wall surface is calculated as follows.
The effect of the reduction is remarkable as compared with the case where the same reaction system is incorporated in various conventional reaction tanks.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A reaction tank embodying the method and apparatus for preventing adhesion of the present invention will be described below with reference to the drawings.

In FIG. 1, the whole reaction tank is indicated by 1. The tank main body 2 has a cylindrical shape.
A ring-shaped opening 3a and a ring-shaped opening 3b are formed concentrically with the outer peripheral edge of the ring-shaped opening 3b. An annular tank 5 having a small diameter is provided.
Further, these have shapes as shown in FIG. 2, and gas supply pipes 6 and 7 are respectively connected to a part of the peripheral wall portion thereof so as to communicate with the inside thereof. As shown in FIG. 2, a number of small holes 13 and 14 are formed so as to communicate with the annular openings 3a and 3b of the lid member 3 so as to communicate therewith.

That is, the compressed gas supplied from the gas supply pipes 6 and 7 is once supplied to the intermediate tanks 4 and 5, from which the compressed gas is discharged at a uniform flow velocity into the tank body 2 in the axial direction as described later. It is supposed to be.

The reaction tank 1 has a cylindrical shape as a whole, but has a large number of small holes 8 concentrically around its central axis CC line.
a is formed at a predetermined interval from the gas ejection wall 8 to the tank body 2.
Are arranged at a slight distance h from the inner peripheral wall surface of the.

The compressed gas supplied to the intermediate tank 4 through the pipe 6 is homogenized here, and is provided with a number of small holes 13 formed in the bottom wall of the tank 4 and an annular opening of the lid member 3. 3a into an annular space H of thickness h, axis CC
The gas is jetted at a speed in the direction, and the jet speed is uniform over the entire circumferential direction.

Similarly, the compressed gas supplied to the intermediate tank 5 through the gas introduction pipe 7 is supplied to the small holes 14 formed in the bottom wall of the tank 5 and the annular opening 3 b of the lid member 3. Through the opening 3b, and is jetted into the tank main body 2 at a uniform flow rate in a direction parallel to the axis CC.

A sputtering apparatus 11 is provided in the tank main body 2 as a reaction system, and is configured in a known manner. The main configuration is illustrated. That is, a target member 9 is disposed above along the axis C-C, and a wafer 10 on which a thin film of atoms or molecules protruding from the target member is formed below and opposed thereto.
Are held by the mounting table 15 .

A gas outlet 1 is provided on the bottom wall of the tank body 2.
2 is formed, to which a known exhaust system is connected,
Thereby, the gas introduced from above the tank body 2 has a structure in which the gas flows toward the outlet 12 as a uniform flow. The reaction tank 1 according to the present invention is configured as described above. Next, this operation will be described.

According to the present embodiment, argon gas is used as the first gas and the second gas, which are supplied to the intermediate tanks 4 and 5 via the gas supply pipes 6 and 7, respectively. Here, through the annular openings 3a and 3b formed in the lid member 3 with a uniform velocity distribution, annular annular portions formed between the cylindrical gas ejection wall 8 and the inner wall of the tank body 2 are formed. It is jetted downward along the axial direction at a predetermined speed in the space H or near a second predetermined distance in the tank body 2.

FIG. 3 schematically shows the dimensions of each part of the reaction tank 1 shown in FIG. 1. As shown in FIG. 3, the argon gas flow a jetted into the H is a gas jet as shown in FIG. From the many small holes 8a formed in the wall body 8, an arrow v
_{Spouted in} the direction of ₁ , that is, the direction toward the central axis ,
Thereafter, while changing the direction, the direction becomes parallel to the argon gas flow b flowing in the axial direction through the above-described opening 3 b and is guided to the exhaust port 12. The following symbols are set in order to analytically examine how active molecules released from the reaction system 11 are prevented by this flow.

Now, using the cylindrical coordinates r, θ, and z with the direction of the axis CC being the z-axis direction, the distance r from the axis to the ejection wall 8 is defined as r = r ₁ (first predetermined distance). ), the outer end of the opening 3b provided in the lid member 3, i.e. the distance to the outer end of the gas stream b and r = r ₂ (second predetermined distance), should be further referred to as the width of the gas flow a r ₁ -r _2, i.e. gas stream b
Is a distance from the outer end of the gas ejection wall 8 to d.

The argon gas ejected from the gas ejection wall 8 has a velocity of r = r ₁ , that is, zero velocity in the z direction on the surface of the wall 8, but is directed toward the central axis CC. Or
Cormorant direction of the velocity is uniform, has a speed of v ₁ in the -r direction,
At r = r ₂ the flow is parallel to the axis, ie
The speed in the direction toward the central axis CC is set to zero.

As shown in FIG. 1 or FIG. 3, a reaction system 11 of a sputtering apparatus is provided inside the gas flow b, along the axis z and in the vicinity of the axis z. Scatters various active molecules p around, but this concentration n is at r = r ₁ , that is, n = 0 on the surface of the gas ejection wall 8, and r
= In r ₂ and n = n _1.

Now, when considering a concentration equation for a concentration n that satisfies the boundary condition, it is shown that the gas flow a may be treated as a continuum flow.
Since the width d of the gas flow a is considered to be larger than the mean free path λ), the velocity components of the gas flow a in the r and z directions are represented by v _r ,
v _z , the diffusion coefficient of active molecules diffusing in this stream
Then, Equation 1 below is obtained.

[0023]

(Equation 1)

Here, when considering the above-described behavior at the boundary of the gas flow a, the boundary condition for v _r and v _z is r = r ₁
And v _r = v ₁ , R = r ₂ and v _r = 0. Since this boundary condition is a non-viscous flow boundary condition, it is expected that a good approximation solution can be obtained by treating it as a non-viscous flow. By substituting the thus obtained v _r and v _z into the concentration equation, a solution of the concentration equation satisfying the boundary condition of the concentration n described above is obtained. From this solution, the unit area of the gas ejection wall 8 is calculated. The number of active molecules arriving per unit time, that is, the flux J can be determined. Now, especially zero velocity of the gas stream a, i.e. the flux when v ₁ = 0 and J _0, when defining the reduction rate at α = J / J _0, α is a value smaller than 1, the wall when the flow rate of gas converted per unit area of the body is constant, alpha is, the more smaller, is believed to have a high ability to prevent adhesion to the wall surface of the active molecule.

In the present case, the reduction rate α is obtained from the obtained flux, and when this is α ₁ , the following equation 2 is obtained.

[0026]

(Equation 2)

Here, the symbol used in Equation 2 is Equation 3
Is described in.

[0028]

(Equation 3)

The decrease rate α obtained as described above is r
_1, r _2, is a function of p _e, in particular, p _e = v ₁ d /
D greatly changes depending on D, and the reduction rate decreases as p _e increases. That is, the smaller the diffusion coefficient D, the greater the ejection velocity v ₁ of the gas flow a,
Also, the larger the d = (r ₁ -r ₂ ), which is also the width of the gas flow a, the smaller the reduction rate α.

Here, in order to clarify the effect of the present invention, a reduction ratio in a reaction vessel having another shape and a flow rate of a gas flow with respect to the reaction vessel are compared.

FIG. 4 shows an example of a conventional reaction tank. In this case, the reaction tank has a substantially linear shape as a whole, and a space Q for accommodating the reaction system is defined therein. From this, the active molecules indicated by N are scattered around. For example, in order to prevent
It is assumed that the argon gas flows at a uniform flow rate U in parallel with the wall surface of the wall 50 with a width d.

Now, as a coordinate system, x along this wall surface
The y-axis is provided vertically to the axis, and as a boundary condition for the concentration n of the active molecule, as in the case of FIG.
0, and n = n ₁ in y = d. In this case, the concentration equation with respect to the concentration n of the active molecule is given by the following Expression 4 when the diffusion coefficient of the active molecule in the argon gas is D.

[0033]

(Equation 4)

By using the above boundary condition for n and solving it, the reduction rate is calculated in the same manner as in the present invention. When the reduction rate in this case is α ₂ , α ₂ = 1−1
_{^{exp (-π 2 x / p e}} d) next, where p _e = Ud
/ D.

FIG. 5 shows a gas flow in another conventional reaction tank. In this conventional example, the reaction tank also has a rectangular shape, and a gas ejection plate 52 is provided along the wall 51. And a large number of gas ejection ports 52a formed therein,
A gas (for example, argon) is ejected to the wall at a speed of v ₃ in the vertical direction, and a gas ejection nozzle port 53 is formed at a position separated by d from the ejection body 52, and a reaction gas necessary for film formation is formed therefrom. (For example, S _i H ₄ ) is ejected in parallel to the wall surface 51. Also in this case, the gas ejected perpendicularly to the ejection plate from the gas ejection holes 52a thereafter changes the flow direction,
Let y = d and flow in the direction parallel to the x-axis.

As shown in FIG. 5, the direction parallel or perpendicular to the wall surface 51 is x or y, respectively, and the boundary condition for the concentration n of the active molecule is n = 0 when y = 0 and n when y = d.
= Take n _1. Assuming that u and v are flow velocities in the x and y axis directions, the concentration equation in this case is as follows, where D is the diffusion coefficient of active molecules.

[0037]

(Equation 5)

[0038] u, v just as substitutes solution of inviscid flow precedent for, by solving the original boundary conditions described above, reduction rate alpha ₃ of the conventional example as Equation 6 below can get.

[0039]

(Equation 6)

As described above, the reduction ratios for the three cases (FIGS. 3, 4, and 5) of the blocking flow for protecting the side wall were obtained. Examine how the rate of reduction in each case is different when the same mass flow is applied to protect the wall. In FIGS. 4 and 5, a wall having the same area has an area designated by a unit length in the z direction and a length L = 10 cm in the x direction, and a circumferential surface of r ₁ = 40 cm in FIG. 3 of the present invention. Above, consider the area specified by the unit length in the circumferential direction and L = 10 cm in the z direction,
D is 5 cm in each case.

Now, the flow rate of the blocking flow is such that p _e = 10 in FIG. 5, ie, 145 SCCM, and the diffusion coefficient D is the same value (D = 0.12 at atmospheric pressure) in each case.
cm ² / sec), the reduction rates α in the three cases are 0.013 in the reactor of the present invention and 0.351 and 0.017 in the reactors of FIGS. 4 and 5 (FIG. 4). In the case of (1), an average value is taken), and α of the present invention is the smallest. This means that in the present invention, the amount of active molecules attached to the wall surface is the smallest. In addition, when the (i) wafer or the like is considered to be circular, the reaction system is often cylindrical. Therefore, when the vessel wall is formed in a cylindrical shape, the area for the vessel containing the same size reaction system is minimized. This has the effect of reducing the flow of the blocking flow. (Ii) In consideration of the advantage that the symmetry of the flow necessary for obtaining a uniform film is easily obtained when the wall is formed into a cylindrical shape, the method of the invention of the present application is intended to prevent the adhesion of active molecules to the wall. It can be seen that the effect is greatest.

The above is a comparison of the reduction rate, required flow rate, and the like between the reaction tank of the embodiment of the present invention and the conventional reaction tank. Next, effects unique to the embodiment of the present invention will be described.

In the embodiment of the present invention, assuming that the jet velocity of the gas ejected from each ejection hole 8a of the gas ejection wall 8 is constant over the entire range from the upper end portion to the lower end portion of the reaction tank 2, the reduction rate is assumed to be constant. However, when h is small, the gas ejection speed at the upper end portion is higher. Therefore, in order to make this uniform over the entire area, h must be increased to a certain degree or more. However, according to the present invention, the gas jetting wall 8 has a distance from the wall surface of the reaction tank main body 2, that is, h, which can be adjusted (the inner diameter of the main body 2 may be changed). Adjust,
Since the difference between the gas ejection speeds of the upper wall portion and the lower wall portion can be appropriately reduced, the above-described reduction rate can be effectively used.
In some cases, the arrival of active molecules is higher in the upper wall portion, and when the adhesion of the active molecules is higher, the gas ejection speed in the upper wall portion is reduced by decreasing h instead of
Larger values are more effective.

Further, in this embodiment, intermediate tanks 4 and 5 having a large number of small holes 13 and 14 are provided at the bottom thereof, and argon gas is introduced into the internal space of the reaction tank main body 2 through this. Therefore, gas is introduced into the annular space at a uniform ejection speed and is devised so as to flow downward in a substantially uniform state in the circumferential direction. It is considered to be realized. Incidentally, the reduction rate of the present invention is a function of _{r 1, r 2, p e} (= v 1 d / D), greatly influenced by p _e number becomes smaller The larger this value Thus, the smaller the diffusion coefficient D, the larger the jet velocity v ₁ of the gas flow, and the larger the width d of the blocking flow, the smaller the diffusion coefficient. Using this reduction rate, the size of the reaction tank and the gas flow rate for preventing adhesion can be determined as follows. First, the value of the diffusion coefficient D is determined depending on the type of gas used, and the value of r ₂ is determined from the size of the reaction system disposed near the center axis of the reaction vessel body. Here, when setting the reduction rate to a desired value,
From this theoretical formula, the relationship between the values of r ₁ and v ₁ required to determine the size of the reaction tank and the gas flow rate can be understood, so that the space for installing this reaction tank and the capacity of the vacuum pump required to reduce the pressure In consideration of the above, it is possible to determine r ₁ and v ₁ , that is, the size of the reaction tank and the flow rate of the gas used.

If the temperature of the gas is cooled, the diffusion coefficient D becomes smaller, which helps to reduce the size of the reaction tank or the flow rate of the gas used. It is desirable to use the gas after cooling.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiments, the sputtering apparatus 11 was described as a reaction system. However, the present invention is not limited to this, and the present invention can be applied to a general CVD apparatus or any chemical vapor deposition apparatus. is there. In the above embodiment, the gas flowing to prevent the adhesion is described as argon gas. However, the gas is not limited to this, and may be another inert gas (for example, xenon Xe). Alternatively, the gas may not be an active gas as an element in the so-called periodic table of elements, and in the present specification, any gas that does not react with an active molecule generated from a reaction system built in a reaction tank is referred to as an inert gas. Define.

[0048]

As described above, according to the method and the apparatus for preventing the adhesion of the active substance to the inner wall surface of the reaction tank according to the present invention, the inner wall surface of the reaction tank due to each gas flow in the conventional reaction tank of each structure. It has a much better effect of preventing the adhesion of the active substance to the wall surface than the method of preventing the adhesion of the active substance to the wall, and it is possible to obtain this effect by minimizing the gas flow for preventing the adhesion of the active substance. it can. Although it has a cylindrical internal space, the size in the radial direction and the speed of the gas flow for preventing adhesion can be adjusted so that the reduction rate is constant, so that there is great freedom in designing the device. Can give degree and guidance.

[Brief description of the drawings]

FIG. 1 is a partially broken side view of a reaction vessel according to an embodiment of the present invention.

FIG. 2 is a partially broken plan view of the same.

FIG. 3 is a schematic view of a main part for explaining the operation of the embodiment.

FIG. 4 is a schematic view showing a part of a conventional reaction vessel and a gas flow for comparison with the operation shown in FIG.

FIG. 5 is a schematic diagram showing a main part and a gas flow of another conventional reaction tank.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction tank 8 Gas ejection wall body 11 Sputtering apparatus V ₁ gas flow V ₂ gas flow

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C30B 25/14 C23C 14/00-14/58 C23C 16/00-16/56 H01L 21/203-21/205 H01L 21 / 302 H01L 21/31

Claims (9)

(57) [Claims] 1. A reaction vessel having a cylindrical internal space and having a reaction system disposed along and near a central axis thereof, a large number of which are arranged at a first predetermined distance in the radial direction from the central axis of the reaction tank. A cylindrical gas ejection wall having a gas ejection port formed therein is provided, and the first gas ejection wall is formed in a radial direction from the center axis.
An annular gas ejection means is disposed at one end wall portion at a second predetermined distance smaller than the predetermined distance, and is inert in a direction from the gas ejection port of the gas ejection wall toward the central axis. A reaction in which the first gas is jetted at a first predetermined speed, and the inert gas is jetted from the gas jetting means at a second predetermined speed along the central axis. A method for preventing the adhesion of active substances to the inner wall surface of the tank. 2. The method according to claim 1, wherein the first gas and / or the second gas are cooled and jetted into the internal space. Method. 3. The method according to claim 1, wherein the first predetermined speed is adjustable. 4. The method according to claim 1, wherein the difference between the first predetermined distance and the second predetermined distance is made as large as possible to reduce the adhesion of the active molecule to the wall surface. 2. The method for preventing an active substance from adhering to an inner wall surface of a reaction vessel according to claim 1. 5. A relatively large volume outside said end wall.
First and second volume forming means having an annular internal space;
And the first and second gas are respectively provided in the volume forming means.
The body is introduced from the outside, and then the gas ejection wall side and
4. The method according to claim 1, wherein the guide is directed to the gas ejection means.
The activity on the inner wall surface of the reaction tank according to any one of claim 4
How to prevent substance adhesion. 6. A reaction vessel having a cylindrical internal space;
Disposed along and near the central axis of the reaction vessel
And a first point in the radial direction from the central axis.
Cylindrical gas with multiple gas outlets formed at a fixed distance
A wall for ejection, and the second wall in a radial direction from the center axis.
One end wall at a second predetermined distance smaller than the first predetermined distance
Means for ejecting an annular gas provided in the section,
Inactive in the direction from the body ejection outlet toward the central axis
1 gas at a first predetermined speed Let out the gas
Displacing an inert second gas along said central axis from the means
2. The reaction tank characterized in that it is jetted at a predetermined speed.
A device to prevent active substances from adhering to the inner wall. 7. The first gas and / or the second gas.
Claims to cool the body and squirt into said interior space
Item 6. A device for preventing adhesion of an active substance to an inner wall surface of a reaction vessel according to Item 6.
Place. 8. A contractor for adjusting said first predetermined speed.
An active substance on the inner wall surface of the reaction vessel according to claim 6 or 7.
Quality anti-adhesion device. 9. A relatively large volume outside said end wall.
First and second volume forming means having an annular internal space;
And the first and second gas are respectively provided in the volume forming means.
The body is introduced from the outside, and then the gas ejection wall side and
7. The gas injection means according to claim 6, wherein said gas ejection means is guided to said gas ejection means.
Item 9. Activity on the inner wall surface of the reaction vessel according to any one of claim 8
Substance adhesion prevention device.