JP2003328111A - Thin film and method of deposition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film of arbitrary film thickness having decreased internal stress and also to provide its manufacturing method. <P>SOLUTION: The thin film consists of crystal groups of a material which is characterized in that internal stress of film changes from tensile stress into compressive stress or from compressive stress into tensile stress with respect to the increase of film thickness, and the internal stress is made to ≤100 MPa by the balance between the tensile stress and the compressive stress in the film deposition of prescribed film thickness under prescribed conditions. Further, the thin film is constituted of a plurality of thin films, and the part between the respective thin films is a region of discontinuous crystal growth. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thin film having a small internal stress and a film forming method thereof.

[0002]

2. Description of the Related Art When depositing a thin film on a substrate, the influence of the internal stress of the film on the production of the thin film element and its performance becomes a serious problem. Conventionally, various methods for reducing the internal stress of the film have been taken against this problem.

For example, in forming a metal film by sputtering, a film having a small internal stress can be formed by appropriately setting film forming conditions such as cathode current and argon pressure. However, even when the film forming conditions are the same, depending on the film thickness to be formed, the internal stress of the film cannot be reduced regardless of the film forming conditions.

FIG. 4 is a sectional view showing the structure of a conventional thin film. FIG. 4 shows a state after the step of forming a film composed of the crystal groups 2 and 3 on the substrate 1. When a titanium film is formed by sputtering under the conditions of a cathode current of 4 A and an argon pressure of about 0.5 Pa, the film thickness is 10
From 0 nm to about 200 nm, a crystal group 2 composed of hemispherical or conical crystals is formed by the growth of nuclei, and this crystal group generates compressive stress.

When the crystal formation due to the growth of nuclei reaches the limit by further increasing the film thickness, the crystal group 3 composed of columnar crystals is formed. The crystal group 3 composed of this columnar crystal generates a tensile stress. When a titanium film having a thickness of 1.0 μm is formed by sputtering, the crystal group 3 composed of columnar crystals grows greatly in the film thickness direction when the film thickness to be formed is larger than an appropriate value. Therefore, the tensile stress due to the crystal group 3 is excellent, and the internal stress of the entire thin film is large. Cathode current 4A, argon pressure 0.
When a titanium film thickness of 1.0 μm is formed by sputtering at around 5 Pa, the internal stress of the film is 200 MP.
It becomes a or more.

[0006]

However, when the internal stress of the thin film is large, the thin film may be deformed or damaged by its own internal stress at the same time when it is formed in a structure where the thin film is self-supporting.

Further, when it is desired to measure the mechanical properties of a thin film such as tensile strength, the value of the internal stress affects the stress data due to the load, and a correct measurement result cannot be obtained.

Further, as the internal stress of the thin film increases, the curvature of the substrate increases, and when the material strength of the substrate itself is exceeded, the substrate is damaged. Even if the material strength is not exceeded, the substrate is fragile and must be handled so as not to give an impact.

Generally used in the manufacturing process of thin film elements,
In the photofabrication process, it is necessary to adjust the relative position between the substrate and the mask before exposure. This adjustment is performed by using an aligner or stepper to align the alignment mark provided on the outer peripheral portion of the substrate with the alignment mark provided at the corresponding position on the mask side. When the substrate is curved, the distance between the substrate and the mask needs to be set larger than that when the substrate is not curved so that the substrate and the mask do not come into contact with each other. Normally, when there is no curvature, the distance between the substrate and the mask is about 5 to 30 μm, but when the curvature is large, it may be 50 μm or more. As a result, it is not possible to focus on the alignment marks on the substrate side and the mask side at the same time, so that the positioning accuracy is lowered and the dimensional accuracy of the product is lowered.

Further, at the time of exposure, due to the curvature of the substrate, the distance between the substrate and the mask cannot be made uniform over the entire surface of the substrate, and the distance between the substrate and the mask becomes larger than the set value depending on the place of the substrate. A place arises. There, the influence of the light diffraction phenomenon increases, so that the exposure accuracy decreases, and as a result, the dimensional accuracy of the product decreases.

When patterning a film having a large stress such that the substrate is curved, stress concentration occurs at the edge portion of the pattern, which may cause peeling or damage of the film.

Further, if the substrate is curved, the automatic transfer device associated with the aligner, the resist coater, the film forming device, and the like may not be used in the manufacturing process, in which case the working efficiency is significantly reduced. The first reason why it cannot be used is that the substrate and the peripheral portion of the automatic carrier interfere with each other due to the curvature. The second reason is that the substrate gripping mechanism of the automatic carrier cannot accurately position on the deformed substrate, or in the case of the vacuum gripping mechanism, a leak occurs between the gripping mechanism and the deformed substrate. The reason is that the substrate cannot be gripped due to reasons such as

When visually inspecting using an optical microscope, an electron microscope or an atomic force microscope during the manufacturing process or after the completion of the manufacturing, if there is a curvature of the substrate, it may occur depending on the position of the substrate to be inspected. It is necessary to refocus the microscope, and when an electron microscope is used, it is also necessary to adjust astigmatism, which reduces the work efficiency of inspection. Also, when using an atomic force microscope, it is necessary to take a wide measurement range in the height direction due to the curvature of the substrate,
In this case, the resolution in the height direction is lower than that in the case where the substrate is not curved.

In general, if the internal stress is 100 MPa or less, the above problems do not occur. Therefore, the present invention improves the internal stress of the thin film to 100 MPa or less by improving the thin film with large internal stress and the manufacturing method thereof. Therefore, it is an object to eliminate the above problems.

[0015]

In order to solve the above-mentioned problems of the thin film, according to the present invention, the internal stress of the film changes from tensile stress to compressive stress or from compressive stress to tensile stress as the film thickness increases. A thin film made of a crystal group of materials having properties and having an internal stress of 100 MPa or less is obtained by balancing tensile stress and compressive stress in forming a film having a predetermined thickness under predetermined conditions.

Further, the thin film is composed of a plurality of thin films, and there are crystal growth discontinuities between the thin films. That is, by providing a crystal growth discontinuity in the film thickness direction of the thin film, the internal stress of the thin film having an arbitrary film thickness is reduced.

Further, it is assumed that the thin film is composed of a plurality of thin films having substantially the same film thickness, and a gap between the respective thin films is a discontinuous portion of crystal growth.

Further, a material different from the thin film is attached to the interface of the discontinuous crystal growth portion. Therefore, the crystal growth can be effectively discontinuous, and the internal stress can be reduced.

Further, the present invention provides a method for forming a thin film, which includes a crystal continuous growth inhibiting step for making the crystal growth of the thin film discontinuous in the film thickness direction.

Further, as a crystal continuous growth inhibiting step for forming a crystal growth discontinuous portion, the film formation is once stopped during the film formation and then the film formation is restarted.

Further, when the film formation is stopped in the crystal continuous growth inhibiting step, the substrate is cooled, the surface layer of the film whose film formation is stopped is removed, or the film formation of a different material is stopped. Adhering to the surface of the membrane is used individually or in any combination.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing the structure of a thin film according to Embodiment 1 of the present invention. FIG. 1 shows a state after the step of forming a film composed of the crystal groups 2 and 3 on the substrate 1. When a titanium film is formed by sputtering under the conditions of a cathode current of 4 A and an argon pressure of about 0.5 Pa, a crystal group 2 consisting of hemispherical or conical crystals due to nucleus growth is formed up to a film thickness of 100 μm to 200 μm. Are formed, and this crystal group generates compressive stress.

When the crystal formation due to the growth of nuclei reaches the limit by further increasing the film thickness, the crystal group 3 composed of columnar crystals is formed. The crystal group 3 composed of this columnar crystal generates a tensile stress. Cathode current 4
A, thickness about 0.5 at argon pressure around 0.5Pa
When μm is deposited, the stresses generated in the crystal groups 2 and 3 are balanced, and the internal stress of the entire titanium film can be suppressed to 100 MPa or less.

Generally, the internal stress of a thin film is 100 MPa.
It is possible to avoid the problem that the thin film is damaged by the internal stress of the thin film itself, to accurately measure the mechanical properties of the thin film, and to prevent the curvature of the substrate due to the internal stress of the thin film if Since the damage is reduced, the substrate is prevented from being damaged, the accuracy of the photofabrication process is improved, and the accuracy of the inspection process is improved, the above-mentioned problems can be sufficiently solved.

In the above description with reference to FIG. 1, the case where the target for reducing the film stress is the titanium film formed by sputtering has been described. Further, even for a material or a film forming method in which the internal stress of the film changes from tensile stress to compressive stress or from compressive stress to tensile stress as the film thickness increases, as in the above method, By forming a predetermined film thickness under the conditions, the film stress can be suppressed to 100 MPa or less. For example, the above effect can be obtained also in a niobium film formed by a sputtering method. (Embodiment 2) As shown in FIG.
A film having a small internal stress composed of 3 is formed, and the film formation is once stopped. When a titanium film is formed by sputtering under the conditions of a cathode current of 4 A and an argon pressure of about 0.5 Pa, the film thickness is 100 nm to 200 nm.
To a certain extent, a crystal group 2 consisting of hemispherical or conical crystals is formed by the growth of nuclei, and this crystal group generates compressive stress.

When the crystal formation due to the growth of nuclei reaches the limit by further increasing the film thickness, the crystal group 3 composed of columnar crystals is formed. The crystal group 3 composed of this columnar crystal generates a tensile stress. When the film is formed to a thickness of about 0.5 μm, the stresses generated in the crystal groups 2 and 3 are balanced, and the internal stress of the entire titanium film is 100%.
It can be suppressed to MPa or less.

Thereafter, as a crystal continuous growth inhibiting step, the film formation of the crystal groups 2 and 3 is once stopped at a film thickness at which the stresses generated in the crystal groups 2 and 3 are balanced, and then the crystal group 2 is formed. A film composed of the crystal groups 4 and 5 made of the same material as the crystal groups 2 and 3 is formed on the film composed of 3 in the same film thickness as the film composed of the crystal groups 2 and 3. As a result, a boundary between the crystal groups 3 and 4 can be generated as a crystal growth discontinuous portion. Here, the crystal group 4 is composed of hemispherical or conical crystals similarly to the crystal group 2, and generates compressive stress. Further, the crystal group 5 is composed of a columnar crystal similar to the aggregate group 3 and generates tensile stress. Crystal groups 2 and 3
, The stresses generated in each are balanced, and crystal groups 4 and 5
Since the stresses generated in the respective films are balanced, the conventional technique does not allow the internal stress of the film to be suppressed to 100 MPa or less, but in the present embodiment, it is composed of crystal groups 2, 3, 4, and 5. The internal stress of the film is 100
It can be kept below MPa.

In order to more effectively generate the crystal group 4 and suppress the film stress to be small, as a crystal continuous growth inhibiting step, when the film formation is stopped once after the films 2 and 3 are formed, the substrate is Wait for the film to cool to the temperature before film formation and then
Can also be formed into a film. Further, by removing the surface layer by performing reverse sputtering on the surfaces of the films 2 and 3, and then forming the films 4 and 5 thereon, the crystal group 4 is more effectively generated and the film stress is 100 MPa. It can be suppressed to the following.

Further, as shown in FIG. 2B, after the formation of the film composed of the crystal groups 2 and 3, the crystal groups 2 and 3,
The nucleation factor 6 made of a material different from that of 4, 5
The nucleation factor 6 is made to adhere to the film composed of 3, 4, and 5 so as not to affect the mechanical and electrical properties of the film, for example, with a thickness of several atoms to several tens of atoms. By forming a film composed of the crystal groups 4 and 5 on the above, the crystal group 4 is more effectively generated and the crystal groups 2, 3, 4, and 5 are generated.
The internal stress of the entire film composed of can be suppressed to 100 MPa or less. When the film composed of the crystal groups 2, 3, 4, and 5 is a titanium film formed by sputtering, gold is 1 at a cathode current of 0.4 A and an argon pressure of 1.1 Pa.
It can be formed as the nucleation factor 6 by sputtering for a second.

In the above description with reference to FIG. 2, the case where the target for reducing the film stress is the titanium film formed by sputtering has been described. Even for materials or film forming methods in which the internal stress of the film changes from tensile stress to compressive stress or from compressive stress to tensile stress as the film thickness increases, the film stress is suppressed to 100 MPa or less by the above method. be able to. For example, the above effect can be obtained also in a niobium film formed by a sputtering method.

According to the thin film having the above structure, the internal stress can be suppressed to 100 Pa or less even for the thin film having a relatively large film thickness, which cannot be suppressed by the conventional method. Accordingly, it is possible to avoid the problem that the thin film is damaged by the internal stress of the thin film itself in the thin film element, and it is possible to accurately measure the mechanical characteristics of the thin film. Further, there is an effect that the curvature of the substrate due to the internal stress of the thin film is reduced, the substrate is prevented from being damaged, the accuracy of the photofabrication process is improved, and the accuracy of the inspection process is improved. (Embodiment 3) FIG. 3 is a sectional view showing the structure of a thin film according to Embodiment 3 of the present invention.

FIG. 3A shows a state after the step of forming a film composed of the crystal groups 2 and 3 on the substrate 1.
In forming a titanium film by sputtering, first, a crystal group 2 consisting of hemispherical or conical crystals formed by the growth of nuclei
Are formed, and the film composed of this crystal group generates compressive stress. When the crystal formation due to the growth of nuclei reaches the limit by further increasing the film thickness, the crystal group 3 composed of columnar crystals is formed. The crystal group 3 composed of this columnar crystal generates a tensile stress. By selecting appropriate film forming conditions and film thicknesses, the stresses generated in the crystal groups 2 and 3 are balanced, and the internal stress of the entire titanium film can be suppressed to 100 MPa or less.

FIG. 3B shows a state after the step of forming a film composed of the crystal groups 4, 5, 7, and 8 on the crystal group 3 of FIG. 3A. As a continuous crystal growth inhibition process,
After temporarily stopping the formation of the film composed of the crystal groups 2 and 3 at a film thickness at which the stresses generated in the crystal groups 2 and 3 are balanced,
A film composed of the crystal groups 4 and 5 made of the same material as the crystal groups 2 and 3 is formed on the film composed of the crystal groups 2 and 3 in the same film thickness as the film composed of the crystal groups 2 and 3. To do. This allows
A boundary between the crystal groups 3 and 4 can be generated as a crystal growth discontinuous portion. Here, the crystal group 4 is composed of hemispherical or conical crystals similarly to the crystal group 2, and generates compressive stress. Further, the crystal group 5 is composed of a columnar crystal similar to the aggregate group 3 and generates tensile stress. The stresses generated in the crystal groups 2 and 3 are balanced, and the crystal group 4 and
The stresses generated at 5 are balanced.

Further, as the crystal continuous growth inhibiting step, the film formation of the crystal groups 4 and 5 is once stopped at a film thickness at which the generated stresses of the crystal groups 4 and 5 are balanced, and then the crystal groups are formed. Crystal group 2, on a film composed of 2, 3, 4, 5
A film composed of crystal groups 7 and 8 made of the same material as 3, 4 and 5 is formed with the same film thickness as the film composed of crystal groups 2 and 3. As a result, the crystal group 5 is regarded as a crystal growth discontinuous portion.
And the boundary of the crystal group 7 can be generated. Here, the crystal group 7 is composed of hemispherical or conical crystals similarly to the crystal group 2, and generates compressive stress. Further, the crystal group 8 is composed of a columnar crystal similar to the aggregate group 3 and generates tensile stress. The stresses generated in the crystal groups 2 and 3 are balanced, the stresses generated in the crystal groups 4 and 5 are balanced,
Furthermore, the stresses generated in the crystal groups 7 and 8 are balanced. After all, the internal stress of the entire film composed of the crystal groups 2, 3, 4, 5, 7, and 8 can be suppressed to 100 MPa or less.

In the above description, the case where the target for reducing the film stress is the titanium film formed by sputtering has been described. Even for materials or film forming methods in which the internal stress of the film changes from tensile stress to compressive stress or from compressive stress to tensile stress as the film thickness increases, the film stress is suppressed to 100 MPa or less by the above method. be able to. For example, the above effect can be obtained also in a niobium film formed by a sputtering method.

Further, in the above description with reference to FIG. 3, the case where the continuous crystal growth inhibiting step is performed twice has been described. Furthermore, by performing the crystal continuous growth inhibiting step three times or more, the same action and effect as in the present embodiment can be obtained even in a film having a large film thickness.

According to the thin film having the above structure, the internal stress can be suppressed to 100 MPa or less even if the thin film having a relatively large film thickness cannot be suppressed to 100 MPa or less by the conventional method. You can Accordingly, it is possible to avoid the problem that the thin film is damaged by the internal stress of the thin film itself in the thin film element, and it is possible to accurately measure the mechanical characteristics of the thin film. In addition, the curvature of the substrate due to the internal stress of the thin film is reduced, the damage of the substrate is prevented,
There is an effect that the precision of the photofabrication process and the precision of the inspection process can be improved.

[0038]

As described above, according to the thin film having the above-mentioned structure, the internal stress is suppressed to 100 MPa or less even for the thin film having a relatively large film thickness which cannot be suppressed by the conventional method. be able to. Accordingly, it is possible to avoid the problem that the thin film is damaged by the internal stress of the thin film itself in the thin film element, and it is possible to accurately measure the mechanical characteristics of the thin film. In addition, the curvature of the substrate due to the internal stress of the thin film is reduced, the damage of the substrate is prevented,
There is an effect that the precision of the photofabrication process and the precision of the inspection process can be improved.

Further, according to the present invention, even when the internal stress of the film is increased by the conventional method, the internal stress is reduced to 10%.
The film formation is temporarily stopped at a certain film thickness of 0 MPa or less, or when the film formation is once stopped, the substrate is cooled, the film surface layer is removed, or a nucleation factor is attached to the film surface, and then the film is again formed. By performing film formation with a film thickness equal to the thickness, the internal stress of the film can be suppressed to 100 MPa or less.

Further, according to the present invention, even when the internal stress of the film is increased by the conventional method, when the film formation is once stopped or once the film formation is stopped at a certain film thickness where the internal stress becomes small. Substrate cooling, removal of the film surface layer, or a crystal continuous growth inhibition step of attaching a nucleation factor to the film surface is performed, and then film formation is again performed, and film formation is stopped at a film thickness equal to the above film thickness.
Further, the continuous crystal growth inhibiting step is performed to form a film having a film thickness equal to the above-mentioned film thickness, which has an effect of suppressing the internal stress of the film. By repeating the continuous crystal growth inhibiting step a plurality of times, the internal stress of a film having an arbitrary film thickness can be suppressed.

Further, the present invention, as explained above,
The internal stress of the thin film can be suppressed to 100 MPa or less. Accordingly, it is possible to avoid the problem that the thin film is damaged by the internal stress of the thin film itself in the thin film element, and it is possible to accurately measure the mechanical characteristics of the thin film. Further, it is possible to reduce the curvature of the substrate due to the internal stress of the thin film, prevent the substrate from being damaged, improve the accuracy of the photofabrication process, and improve the accuracy of the inspection process.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a thin film according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of a thin film according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a thin film according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a conventional thin film in the present invention.

[Explanation of symbols]

1 ... Substrate 2 ... Crystal group 3 ... Crystal group 4 ... Crystal group 5 ... Crystal group 6 ... Nucleation factor 7 ... Crystal group 8 ... Crystal group

Continued front page    (72) Inventor Tokuo Chiba             1-8 Nakase, Nakase, Mihama-ku, Chiba City, Chiba Prefecture             Ico Instruments Co., Ltd. F-term (reference) 4K029 BB02 BC00 CA00 CA05 EA02                       EA08

Claims (10)

[Claims] 1. A film comprising a crystal group of materials having a property that the internal stress of the film changes from tensile stress to compressive stress or from compressive stress to tensile stress as the film thickness increases. The internal stress is 100 due to the balance between the tensile stress and the compressive stress in thick film formation.
A thin film having a pressure of MPa or less. 2. A plurality of thin films according to claim 1,
A thin film in which the crystal growth discontinuity is between each thin film. 3. A thin film comprising a plurality of thin films according to claim 1, which have substantially the same film thickness, and the discontinuity of crystal growth is between the thin films. 4. The thin film according to claim 2, wherein a material different from the material of the thin film is formed at the interface of the crystal growth discontinuity in a thickness of several atoms to several tens of atoms. A thin film deposited on all or part of a thin film. 5. The film formation of the thin film according to any one of claims 2 to 4, comprising a crystal continuous growth inhibiting step of making the crystal growth of the thin film discontinuous in the film thickness direction. Membrane method. 6. The step of inhibiting continuous crystal growth is a step of temporarily stopping the film formation during the film formation and then performing the operation of forming the same material as the film formation once or a plurality of times. A method for forming a thin film as described. 7. The continuous crystal growth inhibiting step is a step in which film formation is temporarily stopped during film formation, the substrate is cooled, and then the same material as in the film formation is formed once or a plurality of times. The method for forming a thin film according to claim 5, wherein 8. The crystal continuous growth inhibiting step stops the film formation during film formation, removes the surface layer of the film to an extent enough to prevent continuous crystal growth, and thereafter removes the same material as the film formation. The thin film forming method according to claim 5, which is a step of performing the film forming operation once or a plurality of times. 9. The continuous crystal growth inhibiting step comprises a step of temporarily stopping film formation during film formation, depositing a material different from that during the film formation, and then forming the same material as during the film formation. The method for forming a thin film according to claim 5, wherein the method is performed once or a plurality of times. 10. The method of forming a thin film according to claim 5, wherein the step of inhibiting continuous crystal growth comprises steps 6 to 9.
A method for forming a thin film, which is a combination of the operations described above.