JPH07252641A - Formation of thin film - Google Patents

Abstract

PURPOSE:To maintain a condition right after exchange of a target for a long time with a method for forming a thin film by irradiating the target with a laser beam and depositing the particles released from the target. CONSTITUTION:The device for this method has a rotating target 14, an excimer laser source 13 for emitting an excimer laser beam 17, a condenser lens 18 for condensing this excimer laser beam 17 onto the target 14, a perforated plate 42 arranged between this condenser lens 18 and the target 14 and a substrate 15 to be deposited with the particles released from the target 14. The perforated plate 14 applies an inclination to the energy density of the excimer laser beam by the distribution of hole. The annular spot scanning part of the target 14 is so constituted as to be consumed while maintaining a relation that its surface parallels with the initial surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming method, and more particularly to a thin film forming method in which a target is irradiated with a high energy beam and particles emitted from the target are used to form a thin film on a substrate.

A method of depositing particles emitted from a target to form a thin film is used in a process of manufacturing a semiconductor device.

Here, in order to improve the high speed, small power consumption, etc. of a semiconductor device, variations in various characteristics of the above thin film between different wafers and between different locations within one wafer are required. It is necessary that the variations in various characteristics of the above-mentioned thin film are suppressed to be small.

Therefore, it is desirable that the above-mentioned thin film forming method can form a thin film while suppressing variations in various characteristics.

[0005]

2. Description of the Related Art FIG. 11 shows a facility 10 used for a laser ablation method which is an example of a thin film forming method.

Reference numeral 11 is a vacuum container, 12 is an exhaust device, 13 is an excimer laser source, 14 is a disk-shaped target, and 15 is a disk-shaped substrate.

The substrate 14 is held so as to face the target 13 and is heated by the heater 16.

As shown by the arrow A, the target 14 is continuously rotated and the laser source 13 is operated.

As a result, the excimer laser light 17 emitted from the laser source 13 is obliquely applied to the rotating target 14 after being condensed through the condenser lens 18.

At this time, particles (plumes) are emitted from the position of the target 14 irradiated with the excimer laser beam 17 as indicated by reference numeral 19, and are deposited on the substrate 15 to form a thin film.

As shown enlarged in FIG. 12, a spot 20 of laser light 17 is formed on the target 14,
As the target 14 rotates in the direction of arrow A, the spot 20 scans the target 14 in a relatively circular shape.

Reference numeral 21 denotes an annular portion scanned by the spot 20. 22 is the center.

Target particles are emitted from the spot 20.

Here, the particles are emitted in an amount substantially proportional to the energy of the laser beam in the direction normal to the surface of the target 14 where the spot 20 is formed.

[0015]

The peripheral speed of the spot scanning portion 21 will be examined with reference to FIG. The peripheral speed is not constant for the entire spot scanning portion 21, and is higher toward the outer peripheral side. Circumferential speed V ₂ of the circumferential speed V ₁ and the inner circumferential side of the portion 21b of the outer peripheral near-side portion 21a are in a relation of V _1> V _2.

Therefore, of the targets 14, other than the above
The part 23 included in the part 21a near the circumference is the spot 2
The irradiation description time when repeatedly irradiated with 0 is t
₁, The portion 24 included in the portion 21b on the inner peripheral side is
Irradiation when repeated irradiation is performed by the tablet 20
Between t₂Then, t₁And t₂Is not the same as t ₁
<T₂Becomes

Therefore, regarding the spot scanning portion 21 of the target 14, as compared with the portion 21a on the outer peripheral side, more particles are emitted from the portion 21b on the inner peripheral side, and compared to the portion 21a on the outer peripheral side. Therefore, the portion 21b on the inner peripheral side is consumed more.

As a result, the surface of the spot scanning portion 21 of the target 14 was initially a surface 26 perpendicular to the rotation axis 25 of the target 14 as shown in FIG. While forming, as shown in FIG. 13B, the surface 27 is inclined so that the center side becomes lower. That is, the surface 27 changes to a surface that is not parallel to the surface 26.

For this reason, the flow of particles emitted from the target 14 is initially parallel to the rotation axis 25, as indicated by reference numeral 28, but gradually changes toward the rotation axis 25 side, and the reference numeral 28 As indicated by 29, it is considerably inclined toward the rotation axis 25 side.

That is, as the thin film formation is continued, the state of the discharged particle flow, that is, the state of forming the thin film changes.

With respect to the substrate on which the thin film is formed, the particle flow is initially supplied from the front and is gradually supplied obliquely.

As a result, the characteristics of the thin film formed on the first substrate after setting a new target and the thin film formed on the tenth and tenth substrates are not the same.

In addition, regarding the tenth and subsequent substrates, the film thickness distribution of the thin film becomes worse even within the same substrate. This tendency becomes more remarkable as the diameter of the substrate increases.

Therefore, an object of the present invention is to provide a thin film forming method that solves the above problems.

[0025]

According to a first aspect of the present invention, a target is irradiated with a high energy beam, the relative position of the high energy beam spot on the target and the target is changed, and the spot is the target. In a thin film forming method of forming a thin film on a substrate by depositing particles emitted from a site of the spot on the target in a circular shape on the target, the energy of the high energy beam at the spot A structure configured to irradiate the high-energy beam in a state where the density distribution is adjusted so that the energy density on the side closer to the center of the circle is lower than the energy density on the side farther from the center of the circle. Is.

According to a second aspect of the present invention, the target is irradiated with a high energy beam, the relative position of the high energy beam spot on the target and the target is changed, and the spot draws a circle on the target. In the thin film forming method of depositing particles emitted from the spot on the target on the substrate to form a thin film on the substrate, the shape of the spot is a fan centered on the center of the circle. It is configured to irradiate the high energy beam in a state of being adjusted to the shape.

[0027]

According to the first aspect of the present invention, the distribution of the energy density of the high energy beam on the spot is adjusted by adjusting the amount of energy received by a portion of the annular spot scanning portion on the inner peripheral side, and the energy density distribution. It acts to suppress it compared to when it is not done.

By adjusting the spot shape to a fan shape in claim 2, the amount of energy received by a portion of the annular spot scanning portion closer to the inner peripheral side is suppressed as compared with the case where the spot shape is not adjusted. Act as you do.

[0029]

EXAMPLES Examples of the thin film forming method of the present invention will be described below.

[First Embodiment] In this embodiment, the energy density in the spot is inclined. Figure 2
Shows the equipment 40 used in the present embodiment.

The basic structure of the equipment 40 is the same as that of the equipment 10 shown in FIG. 2, parts corresponding to the parts shown in FIG. 11 are designated by the same reference numerals, and the description thereof will be omitted.

Reference numeral 41 is a perforated plate, which is provided at a position between the condenser lens 18 and the target 14.

As shown in FIG.
After passing through the lens 18, passes through the perforated plate 41, reaches the target 14, and spots 20 on the target 14.
A is formed.

The porous plate 41 has a large number of holes 42 in a matrix. The diameter of the hole 42a in the upper row is d ₁ , the diameter of the hole 42b in the middle row is d ₂ , and the diameter of the hole 42c in the lower row is d _3.
Then, there is a relationship of d ₁ > d ₂ > d ₃ . That is, the sizes of the holes are made different gradually in the direction of the line 43 (vertical direction in FIG. 1).

Therefore, the aperture ratio of the perforated plate 41 is large at the upper side and gradually becomes smaller at the lower side.
The aperture ratio is gradually different along the direction of the line 43.

A line passing through the center 22 of the target 14 and the center of the spot 20A is indicated by reference numeral 44.

The porous plate 41 is provided so that the line 44 and the line 43 are included in the same plane S ₁ .

Next, the operation of the perforated plate 41 will be described.

In FIG. 1, reference numeral 45 denotes a laser beam which has passed through a portion of the porous plate 41 on the upper side, that is, a portion having a large aperture ratio.

Reference numeral 46 denotes a laser beam which has passed through a portion of the perforated plate 41 on the lower side, that is, a portion having a small aperture ratio.

The laser light 17 is shielded by the perforated plate 41 according to the reciprocal of the aperture ratio. That is, the laser beam transmission efficiency of the porous plate 41 is large on the upper side and small on the lower side,
It is inclined along the line 43.

Therefore, the energy of the laser light 46 is smaller than the energy of the laser light 45.

The laser light 45 and the laser light 46 form a spot 20A.

The laser beams 45 and 46 are in a state of a bundle of laser beams corresponding to the holes 42 immediately after passing through the perforated plate 41, but thereafter, the laser beams are spread and the laser beams are focused again. As a result, the laser beams corresponding to the holes are mixed and integrated to reach the target 14.

Laser light 1 in the radial direction (direction of the line 44) of the target 14 at the spot 20A.
As shown by the line I in FIG. 3, the distribution of the energy density of _No. 7 is such that the center of the target 14 (P ₁ ) is the target 14
It is slanted so as to be smaller than the outer peripheral side (P ₂ ).

Next, the operation of forming a thin film by the laser ablation method using the above equipment 40 will be described.

The target 14 is irradiated with the laser beam passing through the perforated plate 41 while rotating in the direction of arrow A. The substrate 15 is MgO and is heated to about 800 ° C. The inside of the vacuum container 11 is an oxygen atmosphere of 100 mTorr. The average energy density on the target 14 is ² J / cm ² . A CeO thin film is formed on the substrate 15 at a deposition rate of 0.05 nm / s.

FIG. 4A shows a state in which a new target 14 is set and thin film formation is started.

The target 14 emits particles from the spot 20 by the laser beams 45 and 46.

Initially, there is a stream of emitted particles indicated by the reference numeral 28.

Here, as in the case shown in FIG. 12, V ₁
Corresponding to> V ₂ and t ₁ <t ₂ , the energy density distribution is inclined so that the inner peripheral side is smaller, as shown in FIG.

As a result, the spot scanning portion 21 of the target 14 is in a state in which the consumption amount of the inner peripheral side portion 21b is suppressed as compared with the conventional case.

As a result, in the spot scanning portion 21 of the target 14, the outer peripheral side portion 21a and the inner peripheral side portion 21b are consumed substantially uniformly.

As a result, even after the thin film formation is completed on ten or more substrates, the surface 4 of the spot scanning portion is
6 is kept parallel to the initial surface 27 and the orientation of the emitted particle stream 47 is the same as the orientation of the initial emitted particle stream 28.

As described above, even if the consumption of the target 14 progresses, the direction of the discharged particle flow is maintained in the initial state.

As a result, even for several tenth substrate,
A thin film having the same characteristics as the thin film formed on the first substrate is formed.

A thin film having the same film thickness distribution as that formed on the first substrate is also formed on the tens of substrates.

Second Embodiment In this embodiment, the shape of the spot is fan-shaped by using a mask without changing the energy density distribution.

FIG. 6 shows the equipment 60 used in this embodiment.

The basic configuration of the equipment 60 is the same as the equipment 40 shown in FIG. 6, parts corresponding to the parts shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

Reference numeral 61 is a mask, which is provided at a position between the condenser lens 18 and the target 14.

As shown in FIG. 5, the mask 61 is
It has a fan-shaped opening 62.

The laser beam 17 passes through the lens 18 and then
Reach the mask 61. At the location of the mask 61, the laser light 1
7 has a circular cross section 63 indicated by a chain double-dashed line. The fan-shaped opening 62 has a size included in the cross section 63.

The laser beam 17a having a fan-shaped cross section goes toward the target 14 side of the mask 61 through the fan-shaped opening 62.

As shown in FIG. 7, a fan-shaped spot 64 centered on the center 22 of the target 14 is formed on the target 14.

The energy density distribution of the laser light in the spot 64 is substantially constant.

The circumferential size of the spot 64 is the center 22
Is proportional to the distance from, and a ₂ <a ₁ .

[0068] Thisゝa, the peripheral velocity V ₂ of the peripheral velocity V ₁ and the inner peripheral portion close 21b of the outer peripheral portion close 21a of the spot scanning portion 21, as in the case of FIG. 12, the relation of V _1> V ₂ is there.

Corresponding to the relationship of V ₁ > V ₂ , a ₂ <a ₁
There is.

Since the shape of the spot 64 is fan-shaped, the portion 2 of the target 14 on the outer peripheral side is located.
Irradiation statement time t ₃ when the portion 23 included in 1a is repeatedly irradiated by the spot 64 and irradiation statement time t ₄ when the portion 24 included in the portion 21b on the inner peripheral side is repeatedly irradiated by the spot 64. And are equal, and t ₃ = t ₄ .

As a result, as shown in FIGS. 8A and 8B, in the spot scanning portion 21 of the target 14, the outer peripheral side portion 21a and the inner peripheral side portion 21b are consumed substantially uniformly. The surface 65 of the spot scanning portion 21 is kept parallel to the surface 26 in the initial state.

Therefore, even if the consumption of the target 14 progresses, the direction of the emitted particle stream 66 is maintained in the same direction as that of the initially emitted particle stream 28.

As a result, even for several tenth substrate,
A thin film having the same characteristics as the thin film formed on the first substrate is formed.

Further, even if it corresponds to several tens of substrates, 1
A thin film having the same film thickness distribution as the good film thickness distribution formed on the first substrate is formed.

[Third Embodiment] This embodiment is a modification of the second embodiment, in which the spot shape is fan-shaped by the lens without changing the energy density distribution.

FIG. 10 shows the equipment 70 used in this embodiment.

The basic structure of the equipment 70 is the same as that of the equipment 60 shown in FIG. In FIG. 10, those parts corresponding to the parts shown in FIG. 6 are designated by the same reference numerals, and a description thereof will be omitted.

The mask 61 in FIG. 6 is removed, and instead of this, a special condenser lens 71 is provided instead of the general condenser lens 18.

The laser light 17 is condensed by the condenser lens 71.
It is refracted nonuniformly, and a fan-shaped spot 72 centered on the center 22 of the target 14 is formed on the target 14 as shown in FIG.

The spot 72 has a substantially constant energy density distribution, and has the same shape as the spot 64 of the second embodiment.

Therefore, as in the case of the second embodiment described above, the spot scanning portion 21 of the target 14 is uniformly consumed, its surface is kept parallel to the surface in the initial state, and the emitted particles are The direction of flow is kept the same as in the beginning. As a result, the same effect as in the second embodiment can be obtained.

[Modification] The target may be fixed and the excimer laser light may be rotated so that the spot of the laser light scans the target in a circular shape.

Further, an electron beam or an ion beam can be used instead of the excimer laser light.

[0084]

As described above, according to the invention of claim 1, the distribution of the energy density of the high-energy beam on the spot is adjusted so that the inner portion of the annular spot scanning portion is closer to the inner peripheral side. The amount of energy that the part receives
Suppressed more than without adjusting the distribution of energy density,
As a result, the amount of energy received by the portion closer to the inner circumference side of the annular spot scanning portion becomes equal to the amount of energy received by the portion closer to the outer circumference side. It can be consumed while keeping parallel to the plane. This makes it possible to maintain the direction in which the particles are emitted from the target in the initial direction for a long period of time, and after replacing the target, the first substrate is also used for several tens of substrates. A thin film having the same characteristics and the same film thickness distribution as the thin film formed on the target can be formed. Further, the present invention is effective especially when the substrate has a large diameter. Therefore, according to the present invention, a large-diameter wafer can be used to manufacture a high-performance semiconductor device having high speed and low power consumption with high yield.

According to the invention of claim 2, by adjusting the distribution of the energy density of the high-energy beam on the spot, the amount of energy received by the portion of the annular spot scanning portion on the inner peripheral side is It is suppressed as compared with the case where the shape of the spot is not adjusted, whereby the amount of energy received by the portion closer to the inner peripheral side and the amount of energy received by the portion closer to the outer peripheral side of the annular spot scanning portion become equal, The spot scan portion can be consumed while the surface remains parallel to the original surface. This makes it possible to maintain the direction in which the particles are emitted from the target in the initial direction for a long period of time, and after replacing the target, the first substrate is also used for several tens of substrates. A thin film having the same characteristics and the same film thickness distribution as the thin film formed on the target can be formed. Further, the present invention is effective especially when the substrate has a large diameter. Therefore, according to the present invention, a large-diameter wafer can be used to manufacture a high-performance semiconductor device having high speed and low power consumption with high yield.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a thin film forming method according to a first embodiment of the present invention.

FIG. 2 is a diagram showing equipment used in the thin film forming method according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a distribution of energy density of laser light at a spot portion in FIG.

FIG. 4 is a diagram showing a target consumption state and a particle emission state during thin film formation.

FIG. 5 is a diagram illustrating a thin film forming method according to a second embodiment of the present invention.

FIG. 6 is a diagram showing equipment used in a thin film forming method according to a second embodiment of the present invention.

FIG. 7 is a diagram showing the shapes of spots in FIG.

FIG. 8 is a diagram showing a target consumption state and a particle emission state during thin film formation.

FIG. 9 is a diagram illustrating a thin film forming method according to a third embodiment of the present invention.

FIG. 10 is a diagram showing equipment used in a thin film forming method according to a third embodiment of the present invention.

FIG. 11 is a diagram showing a conventional thin film forming method.

FIG. 12 is an enlarged view showing a main part in FIG. 11.

FIG. 13 is a diagram showing a target consumption state and a particle emission state during thin film formation.

[Explanation of symbols]

 11 Vacuum Container 13 Excimer Laser Source 15 Substrate 16 Heater 17 Excimer Laser Light 18 Condensing Lens 19 Emitted Particle Flow 20A Spot 21 Spot Scanning Part 21a Outer Side Part 21b Inner Outer Side Part 22 Center 23 Outer Part Included in part 24 Part included in the part on the inner peripheral side 25 Rotation axis 26 Surface 28 Emitted particle flow 40, 60, 70 Equipment 41 Perforated plate 42 Hole 43 Line 44, 45 Laser light 46, 65 Surface 47, 66 Emission Particle flow 61 Mask 62 Fan-shaped opening 63 Cross section of laser light at mask 64, 72 Fan-shaped spot 71 Special condensing lens

Claims (2)

[Claims] 1. A target is irradiated with a high-energy beam, the relative position of the spot of the high-energy beam on the target and the target is changed, and the spot draws a circle on the target. In the thin film forming method of depositing particles emitted from the spot portion on a substrate to form a thin film on the substrate, the energy density distribution of the high energy beam at the spot is close to the center of the circle. A thin film forming method, characterized in that the high energy beam is irradiated in a state where the energy density on the side is adjusted to be lower than the energy density on the side farther from the center of the circle. 2. A target is irradiated with a high-energy beam, the relative position of the high-energy beam spot on the target and the target is changed, and the spot draws a circle on the target. In the thin film forming method of depositing particles emitted from the spot portion on a substrate to form a thin film on the substrate, the shape of the spot is adjusted to a fan shape centered on the center of the circle. Then, the thin film forming method is characterized in that the high energy beam is irradiated.