JPH1046342A - Formation of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart a consistency with etching in the subsequent process etching and to improve the yield of a device production in a method in which a target electrode having a rectangular planar shape is used and thin coating is formed by a sputtering method while a substrate with a large area is carried to a direction parallel to a short side of an electrode. SOLUTION: The carrying rate of a substrate holder 3 is controlled so as to make the distribution of coating thickness in the carrying direction of a substrate 4 to approximately coincide with the distribution of coating thickness in the direction vertical to the carrying direction to form thin coating having axial symmetry as for an axis vertical to a substrate face through the center of a substrate 4. Since, in an etching stage, a etching pregresses to the outer circumferential direction from the center part to a thin coating on the substrate 4, the possibility for over etching is eliminated, and a uniformity of a coating thickness after etching can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film, and more particularly to a method for forming a thin film on a large-area substrate using a target electrode having a rectangular planar shape by a sputtering method. Is made to have consistency in relation to the next etching step, so that the etching is completed in substantially the same time over the entire surface of the substrate to prevent the yield of elements formed on the substrate from being reduced by over-etching. Regarding membrane control

[0002]

2. Description of the Related Art Conventionally, when a thin film is formed on a large area substrate with a uniform distribution by a sputtering method, a target electrode having a rectangular planar shape is used, and the substrate opposed to the target electrode is used as a target electrode. A method is adopted in which a film is conveyed at a constant speed in a direction parallel to the short side to form a film.

FIG. 3 shows a schematic configuration of a thin film forming apparatus for that purpose. In the figure, 1 is 0.1 to 10P
a vacuum vessel for realizing an Ar gas pressure state of about a, a rectangular (long side: W × short side: B) target electrode (for example, the raw material is Al) fixed in the vacuum vessel 1, and 3 is a vacuum A substrate holder movable in a direction parallel to the short side of the target electrode 2 in the container 1, 4 is a large-area substrate mounted on the substrate holder 3, 5 is a transport driving device that drives the substrate holder 3 in the direction, Reference numeral 6 denotes a transfer controller for controlling the movement of the transfer drive device 5, 7 a power supply source for supplying high-frequency power to the target electrode 2, 8 a matching circuit, and 9 a capacitor.

The principle of the thin film forming operation is the same as that of the ordinary sputtering method. When high frequency power is supplied from the electrode supply source 7 to the target electrode 2 via the matching circuit 8 and the capacitor 9, the target electrode 2 and the vacuum container A glow discharge occurs during 1 and the high-energy A generated in the plasma
The r ions collide with the surface of the target electrode 2 and release atoms of the raw material, which adhere to the surface of the substrate 4 to form a thin film. On the other hand, in this apparatus, the transfer driving device 4 moves the substrate holder 3 in a direction parallel to the short side of the target electrode 2 based on the control of the transfer controller 6 in order to efficiently form a film on the substrate 4 having a large area. The substrate 4 is conveyed at a constant speed while facing the target electrode 2 in a sputtering state according to the above principle. That is, there is an advantage that uniform film formation can be performed over a large area of the substrate 4 using the target electrode 2 having a smaller plane area than when a target electrode having a circular planar shape is used.

[0005]

In the above-mentioned thin film forming apparatus, the length W of the long side of the target electrode 2 is
If the film thickness is sufficiently large with respect to the size, the film thickness distribution of the thin film formed on the substrate 4 can be made uniform over the entire surface; otherwise, even if the film thickness distribution in the transport direction is constant. In the direction perpendicular to the transport direction, the film has a film thickness distribution state in which the central region is thick and becomes thinner as the distance from the central region increases. This is because if the length W of the long side of the target electrode 2 is not large enough for the size of the substrate 4, the density of atoms emitted from the target electrode 2 is low on both sides of the substrate 4. To become

More specifically, as shown in FIG. 4, on a substrate 4 having a circular planar shape, an X axis is set in the transfer direction with the center thereof as an origin, a Y axis is set in a direction perpendicular to the transfer direction, and a Y axis is set. Taking a cross section parallel to and perpendicular to the substrate 4, the surface of the formed thin film 10 has a convex thickness distribution state that can be approximated by a quadratic function curve. In the figure, the distribution coefficient of the film thickness as viewed in the cross section is α (Y) = 1−aY ² (where a is a constant determined by sputtering conditions, the length of the long side W of the target electrode 2 and the like). An example is shown.

As a method of forming a thin film on a substrate by sputtering, not only a method in which the substrate 4 is opposed to the target electrode 2 as shown in FIG. 3 but also a method in which the substrate 4 is formed as shown in FIGS. The electrodes 2a, (2b, 2c) are opposed to the space in front of the target electrode 2a, (2b, 2c) in a perpendicular relationship with the short side of the target electrode 2a, (2b, 2c). There is also a method of forming a film while transporting the film in a direction perpendicular to the surface. Here, the configuration of FIG. 5 is a system using a single target electrode 2a, and the configuration of FIG.
b and 2c are opposed target systems which are arranged in such a manner that their electrode surfaces face each other. In any of these systems, when the substrate 4 is transported under the above conditions, the same as in the case of FIG. FIG. 4 shows the film formation state.

On the other hand, a device manufactured by making full use of thin film forming technology is generally completed by forming elements on a substrate while combining various film forming processes and etching processes. Therefore, in order to improve the production yield of the device, it is ideal that a uniform film is formed on the substrate and the film is uniformly etched.
In the case of a large-area substrate, uniformity of the film thickness may not be ensured in the film forming step as described above, and it is difficult to perform completely uniform etching also in the etching step,
For example, in an ion milling apparatus, generally, the etching of the central region of the substrate tends to proceed first and reach the periphery.

Now, assuming that a substrate 4 on which a thin film having a film thickness distribution as shown in FIG. 4 has been formed is etched by an ion milling device in the next step, FIG.
The etching state proceeds in the order shown in (1) to (5). However, the hatched area in the figure indicates an area where etching to a required depth has been completed, and the other areas indicate unfinished areas. As is apparent from FIG. 4, in the substrate 4 having the film thickness distribution shown in FIG. 4, the etching of both sides in the transport direction is delayed, and when the etching of the entire surface is completed, the central region may be over-etched. In addition, uniform etching over the entire surface cannot be guaranteed.

As described above, in a device process, it is extremely difficult to maintain a high yield while ensuring sufficient uniformity separately in a film forming step and an etching step. However, instead of a method of ensuring uniformity in the individual steps, based on the idea that the film thickness distribution is controlled in the film forming step so as to cancel the non-uniformity in the etching step, the non-uniformity in both steps is controlled. If the consistency is achieved in consideration of the tendency, it is possible to solve the above-mentioned problem and improve the yield.

Therefore, the present invention provides a method of forming a thin film capable of increasing the yield in the etching step based on the basic idea of achieving the consistency between the film forming step and the etching step as described above. Created for the purpose.

[0012]

The present invention relates to a method of forming a thin film by a sputtering method, wherein a target electrode having a rectangular planar shape is used, and a substrate is opposed to the target electrode, and a short side of the target electrode is formed. When the film is formed while being transported in a direction parallel to the target electrode, or the substrate is opposed to the space in front of the target electrode in a relationship perpendicular to the short side of the target electrode, and is perpendicular to the electrode surface of the target electrode. When forming a film while transporting it in different directions,
The present invention relates to a method for forming a thin film, wherein the transport speed of the substrate is controlled such that the thickness distribution of the substrate in the transport direction substantially coincides with the thickness distribution in the direction perpendicular to the transport direction.

According to the present invention, it is possible to realize a distribution state in which the film thickness formed on the substrate surface is substantially axially symmetric with respect to an axis passing through the center of the substrate surface and perpendicular to the substrate surface. As a result of the fact that the etching proceeds from the central region toward the outer periphery, it is possible to obtain an etching completed state in which the entire surface becomes uniform without over-etching.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the "thin film forming method" of the present invention will be described below in detail with reference to FIGS.
First, FIG. 1 is a schematic configuration diagram of a thin film forming apparatus for carrying out the method of the present invention, and those denoted by the same reference numerals as those in FIG. A thin film is formed on the surface of the substrate 4 while moving in a direction parallel to the short side of the target electrode 2.

The features of this embodiment are as follows: (1) The transfer controller 6 has a program that does not move the substrate holder 3 at a constant speed as in the apparatus shown in FIG. And (2) a shielding plate 11 in which a slit 11a is formed between the target electrode 2 and the substrate 4 in a direction perpendicular to the direction in which the substrate 4 is transported. More specifically, the transport controller 6 controls the transport driving device 5 so that the moving speed of the substrate holder 3 is minimized when the center of the substrate 4 passes immediately below the center of the target electrode 2.
A function corresponding to the film thickness distribution in the direction perpendicular to the transport direction of the substrate 4 (the direction parallel to the short side of the target electrode 2) (the direction parallel to the long side of the target electrode 2). The shielding plate 11 is installed so that the slit 11a thereof is located immediately below the center of the target electrode 2 and in a direction perpendicular to the transport direction of the substrate 4. Here, the shielding plate 11 functions to more accurately control the film thickness distribution in the transport direction of the substrate 4, and the narrower the width of the slit 11a, the narrower the distance between the shielding plate 11 and the substrate 4. The more the control resolution can be improved. However, slit 11a
If the width is too narrow, the film forming speed will be reduced, so that it is determined in consideration of controllability and film forming efficiency. Furthermore, slit 11
The film thickness distribution can be controlled by changing the width of a without making it constant.

Meanwhile, in the apparatus shown in FIG. 3, the thickness distribution of the thin film 10 as shown in FIG. That is, the distribution coefficient in the Y-axis direction is α (Y) = 1.
−aY ² , and the X-axis direction has a constant film thickness determined by the distribution coefficient in the Y-axis direction. On the other hand, when the transport driving device 5 is controlled by the transport speed control program of the transport controller 6 of the present embodiment, as shown in FIG. 2, the distribution coefficient of the film thickness also in the transport direction of the substrate 4 (X-axis direction): α (X) =
1-aX ² is provided, each thicker central region with respect to the X-axis direction and the Y-axis direction, a thin film 12 of Al is formed by thinned manner with distance from the center.

Therefore, as shown in FIG. 4, when an arbitrary point P on the plane of the substrate 4 is represented by (X = rcos θ, Y = rsin θ), the film thickness distribution coefficient β at the point P is expressed by the following equation. You. β (X, Y) = α (X) · α (Y) = (1−aX ² ) · (1−aY ² ) = (1−ar ² ) + a ² r ⁴ sin ² θ · cos ² θ On the other hand, the distribution coefficient α of the film thickness in FIG. α (X, Y) = 1 -ar 2 sin 2 θ = (1-ar 2) + ar 2 cos 2 θ ...

Here, the first in the above equations and
The item (1-ar ² ) gives the distribution coefficient in the case of being axially symmetric with respect to a straight line passing through the center of the substrate 4 and perpendicular to the substrate 4, and the second item of each equation is based on the axial symmetry. Error is given. Then, comparing the two items of each equation, 1-
Under the condition that ar ² ≧ 0 and a is generally a very small constant, the following equation holds. a ² r ⁴ sin ² θ · cos ² θ≪ar ² cos ² θ (ar ² sin ² θ≪1) In other words, the distribution coefficient β (X, Y) of the equation is the distribution coefficient α (X, This gives a thin film distribution state that is much more axially symmetrical over the entire surface than Y). In particular, in the formula, the film thickness distribution is far away from the axial symmetry in both sides of the substrate 4 in the transport direction (| cos θ | is a range of θ near 1 and r is close to the maximum radius R of the substrate). In the formula based on this embodiment, it is possible to form a film thickness distribution very similar to the axially symmetric plane even in the region.

In the film thickness distribution according to this embodiment, the point where the axial symmetry is the worst is θ = (π / 4),
(3π / 4), (5π / 4), with (7 [pi] / 4), r is is the point of maximum radius R of the substrate 4, in this respect the left side in the expression a ² R ^4/4, the right side aR ^2/2 becomes, 1-aR ² = 0 left even assuming 1/4, and the right side becomes 1/2, more of this embodiment has a better axial symmetry. Moreover, 1-a is used as a distribution coefficient indicating more realistic axial symmetry.
In the case where R ² = 0.9, the ratio of the error of β (X, Y) at the point where the axial symmetry becomes the worst as described above is as follows: (a ² r ⁴ sin ² θ · cos ² θ) / 1−aR ² = (0.1) ² • {1 / sin (π / 4)} ² • {1 / cos (π / 4)} ² /0.9 = 0.0027 (≒ 0.3%), constant speed Since the error rate of 10% occurs in the film thickness distribution of FIG.

When the substrate 4 on which the thin film 12 is formed as shown in FIG. 2 is subjected to an ion milling apparatus in the next step in the thin film forming apparatus according to this embodiment, the central processing is performed as described in the prior art. The etching proceeds axially symmetrically from the region toward the outer periphery. On the other hand, the thin film 12 has an axial symmetry given by the distribution coefficient β (X, Y) in the above equation, and is formed thick on the central region side. Therefore, the thickness distribution of the thin film 12 cancels the error of the etching depth occurring with time, and the state where the outermost portion is etched to a predetermined depth and the central region is just etched to that depth. Can be

In the above embodiment, the target electrode 2
The sputtering method in which the substrate and the substrate 4 are opposed to each other via the shielding plate 11 has been described. However, the film formation state shown in FIG. 4 can be obtained in the method shown in FIGS. If the transfer speed control program of this embodiment is given to the transfer controller 6, the film formation state shown in FIG. 2 is obtained, and the same effect can be obtained. Further, the shielding plate 11 has a function for more accurately controlling the film thickness distribution in the transport direction as described above, but it is an element for ensuring accuracy, and as a result, without it, almost no It is not an essential component if a film-formed state having axial symmetry can be obtained.

[0022]

The "thin film forming method" of the present invention has the following effects by having the above-described structure. The invention according to claim (1) is a method for forming a thin film by a sputtering method, wherein a target electrode having a rectangular planar shape is used, and a substrate is opposed to the target electrode and a direction parallel to a short side of the target electrode. When a film is formed while being transported, or when the substrate is opposed to the space in front of the target electrode in a relationship perpendicular to the short side of the target electrode, and is transported in a direction perpendicular to the electrode surface of the target electrode. When the film is formed while being formed, the distribution of the thin film can be made substantially axially symmetric with respect to an axis passing through the center of the substrate surface and perpendicular to the substrate surface. Eliminate the potential and increase device manufacturing yield. The invention of claim (2) is to increase the resolution of film formation control in the transport direction by providing a shielding plate having a slit perpendicular to the transport direction of the substrate, and by changing the width of the slit. It is possible to control the film thickness distribution in the slit direction.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a thin film manufacturing apparatus according to an embodiment of a thin film forming method of the present invention.

FIG. 2 is a plan view, a side view as viewed from a transfer direction, and a side view as viewed from a direction perpendicular to the transfer direction, showing a film formation mode in the thin film manufacturing apparatus according to the embodiment.

FIG. 3 is a schematic configuration diagram of a thin film manufacturing apparatus (a method in which a target electrode and a substrate are opposed to each other) according to a conventional technique.

FIG. 4 is a plan view of a substrate, a side view viewed from a transfer direction, and a side view viewed from a direction perpendicular to the transfer direction, showing a film formation mode in a thin film manufacturing apparatus according to a conventional technique.

FIG. 5 is a schematic configuration diagram of a thin film manufacturing apparatus (system in which a substrate is opposed to a space in front of a single target electrode) according to a conventional technique.

FIG. 6 is a schematic configuration diagram of a thin film manufacturing apparatus (opposite target method) according to a conventional technique.

FIG. 7 is a diagram showing the progress of etching when a substrate formed by a thin film manufacturing apparatus according to a conventional technique is etched.

[Explanation of symbols]

1 ... Vacuum container, 2,2a, 2b, 2c ... Target electrode, 3 ... Substrate holder, 4 ... Substrate, 5 ... Transport drive, 6 ... Transport controller, 7 ... Power supply source, 8 ... Matching circuit, 9 ... Capacitor , 10, 12: thin film, 11: shielding plate, 11a: slit, B: length of the short side of the target electrode, W: length of the long side of the target electrode.

Claims (2)

[Claims] 1. A method for forming a thin film by a sputtering method, wherein a target electrode having a rectangular planar shape is used, and a substrate is opposed to the target electrode while being conveyed in a direction parallel to a short side of the target electrode. When forming a film, or forming a film while facing the space in front of the target electrode in a direction perpendicular to the short side of the target electrode, and transporting the substrate in a direction perpendicular to the electrode surface of the target electrode. Wherein the transport speed of the substrate is controlled such that the film thickness distribution in the transport direction of the substrate substantially coincides with the film thickness distribution in the direction perpendicular to the transport direction. 2. When forming a film while transporting a substrate in a direction parallel to a short side of the target electrode while facing the target electrode, the substrate is placed in a space between the target electrode and the substrate. When forming a film while transporting in a direction perpendicular to the electrode surface of the target electrode, facing the front space with a relationship perpendicular to the short side of the target electrode, 2. The thin film forming method according to claim 1, wherein a thin film is formed between the substrates by interposing shielding plates each having a slit formed in a direction perpendicular to the transport direction of the substrate.