JP3043053B2 - Magnetic field microwave plasma sputtering equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field microwave plasma sputtering apparatus used for forming wiring of a semiconductor integrated circuit.

[Conventional technology]

In a semiconductor manufacturing process, a wiring process for an integrated circuit is generally performed by a sputtering process using argon gas as a processing gas, aluminum as a target, and a silicon substrate as a sample to form a thin film of aluminum on the silicon substrate. ing. In this sputtering process, it is known that during sputtering, an impurity such as argon used as a processing gas is taken into the aluminum film to form a defect in the crystal lattice of the aluminum crystal.

The defects generated by impurities such as argon move in the crystal due to the thermal vibration of the crystal lattice, and the defects combine to become larger defects, or become trapped in already grown grain boundaries, resulting in aluminum. Nuclei of the crystal grain boundaries.

At the generated crystal grain boundaries, the movement of electrons concentrates at the grain boundaries when current is applied, causing aluminum atoms to move by the kinetic energy of the electrons, generating voids, and causing electromigration that breaks wiring. However, the concentration of tensile stress generated by the difference in the coefficient of thermal expansion between aluminum and the substrate material becomes a point of concentration of tensile stress, which causes stress migration that breaks. Therefore, in order to manufacture a high-quality semiconductor integrated circuit, impurities such as argon gas should be used as much as possible. It is required that contamination be reduced and crystal grain boundaries not grow.

Therefore, in order to reduce the contamination of impurities, it is necessary to perform sputtering under high vacuum with a small number of particles of argon gas to form a film.

However, when sputtering is performed using plasma generated by conventional RF discharge, high-density plasma cannot be obtained under a high vacuum. Sputtering has attracted attention.

Here, a magnetic field microwave plasma sputtering apparatus capable of generating high-density plasma under high vacuum will be described.

A sputtering apparatus using a magnetic field microwave plasma supplies an electromagnetic wave (microwave) synchronized with the angular frequency of a cyclotron-moving electron by a magnetic field, thereby causing the electron to resonate with the electromagnetic wave (microwave) (electron cyclotron resonance). The condition is hereinafter referred to as ECR condition), in which the energy of an electromagnetic wave is given to electrons, and the energy given to the electrons causes ionization of neutral atoms and molecules to generate plasma.

Generally, the cyclotron frequency of the microwave required to form the ECR condition is represented by the following equation.

Wc = − (e × B) / m (Wc is the cyclotron angular frequency, e is the charge of the electron, B is the magnetic flux density, m is the mass of the electron.) Since the mass m of the electron is a constant, from this equation, When an industrially used microwave power supply (2.45 GHz) is used, the magnetic flux density B forming the ECR condition is 875 Gauss.
s is calculated.

In sputtering, argon plasma is generated using plasma generated under ECR conditions, and the generated argon plasma collides with a target to which a negative potential is applied by electrostatic force, and a neutral target that pops out due to argon collision. Is formed by colliding the component particles with the sample. (1989 AMERICAN VACUUM SOC
IETY TECHNOL. A7 (4) JUL / AUG 2652, Applied Physics Vol. 57, No. 9, 1988 1301).

The configuration of this conventional magnetic field microwave plasma sputtering apparatus will be described with reference to FIG. FIG. 5 is a sectional view schematically showing a conventional magnetic field microwave plasma sputtering apparatus.

In FIG. 5, reference numeral (51) denotes a vacuum vessel. The vacuum vessel (51) is capable of introducing a processing gas such as an argon gas into the inside thereof, and the inside thereof is evacuated by a vacuum exhaust port (51a). The sample can be evacuated, and the sample (63) is placed on the sample table (62) in the vacuum vessel (51). In the vacuum vessel (51), a cylindrical target (59) made of aluminum or the like and an electrode (58) are arranged, and the target (59) is placed between the target (59) and the electrode (58). ) Is applied on the negative side so that DC current (60) is applied. A microwave irradiation window (52) made of quartz is incorporated in the vacuum vessel (51), and a waveguide (53) is connected to the microwave irradiation window (52), which is not shown. Microwaves from a microwave source (usually at 2.45 GHz) are introduced into the vacuum vessel (51) from the direction of the arrow (54) in FIG. (55) is a coil,
The coil (55) supplies a magnetic field having a magnetic flux density near 875 Gauss under the ECR condition (encircled by a dotted line (56) in FIG. 5) into the vacuum vessel (51).

The conventional magnetic field microwave plasma sputtering apparatus efficiently converts the processing gas into plasma under the ECR condition (56) and converts positive ions (57) having a positive charge in the plasma into a DC power supply ( The target (59), to which a negative potential is applied by (60), is caused to collide with the target (59), thereby causing the component particles (61) of the target (59) to fly out. It is formed as.

[Problems to be solved by the invention]

However, in the conventional magnetic field microwave plasma apparatus, about 10 ⁻⁴ Torr is used as the pressure of the processing gas because ECR conditions are used. This is EC
When the R condition is used, the number of particles of the argon gas, which is the processing gas, itself decreases, so that high-density plasma cannot be obtained on the vacuum side higher than 10 ^-4 Torr, and the film formation rate decreases. Therefore, there is an essential problem that there is a practical limit in performing film formation with less contamination of impurities such as argon.

In a conventional magnetic field microwave plasma device, target component particles to be formed as a thin film on a sample float in a vacuum vessel, and the particles are made of quartz glass or the like that introduces microwaves into the vacuum vessel. The problem is that the film is not only attached to the microwave introduction window and shortens the life of the introduction window, but also the microwave introduction efficiency is reduced and the efficiency of plasma conversion is reduced, so that the film forming speed is reduced.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and provides a magnetic field microwave plasma sputtering apparatus capable of performing film formation with a small amount of impurities such as argon at a high film formation rate. The secondary object is to extend the life of the microwave introduction window of the magnetic field microwave plasma sputtering apparatus.

[Means for solving the problem]

According to the present invention, a processing gas is introduced into a vacuum vessel (21) in which a sample (28) and a target (29) are arranged, and a magnetic field is generated in the vacuum vessel (21) by magnetic field generating means (30). At the same time, the processing gas is turned into plasma by introducing microwaves by means of microwave introduction means (24), and the plasma is irradiated on the target (29) to put the components of the target (29) on the sample (28). In a magnetic field microwave plasma sputtering apparatus formed as a thin film, the following technical means have been taken in order to solve the above-mentioned problems of the prior art. That is, the magnetic field generated by the magnetic field generating means (30) is a diverging magnetic field diverging in the vicinity of the target (29), and the microwave introduction direction (27)
The microwave introducing means (24) is arranged so as to extend from the high magnetic field side to the low magnetic field side of the divergent magnetic field, and the intensity of the magnetic field formed by the magnetic field generating means (30) is adjusted to be close to the target (29) by electron cyclotron resonance. The strength is such that the conditions and the high magnetic field microwave absorption conditions can be formed.

The invention according to claim 2 provides, in addition to the above means,
The target gate (29) is arranged along a slope of a truncated cone whose top surface faces the direction (27) for introducing microwaves.

Further, the invention according to claim 3 is characterized in that, in addition to the above means, the degree of vacuum in the vacuum vessel (21) is 10 ^-5 Torr or less.

[Action]

The above-mentioned EC
It has been found by the present inventors that, apart from the R condition, in a diverging magnetic field including the ECR condition, under certain conditions, microwave absorption occurs in a high magnetic field that is 2-3 times the ECR condition,
A patent application has been filed as Japanese Patent Application No. Heisei 77318/1990.

This condition is referred to as a high magnetic field microwave absorption condition in the following description. However, it has been found that high density plasma can be obtained on the higher vacuum side than the ECR condition by using the high magnetic field microwave absorption condition.

This phenomenon will be described with reference to FIG. FIG. 6 is a graph showing the magnetic flux density on the horizontal axis and the plasma density on the vertical axis under a pressure of 5 × 10 ⁻⁵ Torr, and B ₁ in the figure is a peak indicating the ECR condition. of B ₂ is a peak indicating a high magnetic field microwave absorption conditions. As can be seen from this graph, high-density plasma can be obtained even on a higher vacuum side than ECR conditions by using these high-field microwave absorption conditions.

The present invention uses both of the plasmas obtained under the conditions capable of generating the two high-density plasmas described above, thereby forming a high-density plasma near the target under a high vacuum of 10 ⁻⁴ Torr or more. It is characterized in that high-purity film formation with little contamination of impurities such as argon, which is generated as a processing gas, can be performed at a high film-forming speed that can sufficiently withstand practical use.

Here, the shape of the target for simultaneously generating the two plasmas near the target will be described. It is difficult to continuously change the frequency of microwaves in a vacuum vessel in order to achieve both ECR conditions and high magnetic field microwave absorption conditions. It is necessary to make the divergent magnetic field gradually decrease according to the position.

In addition, since the ECR plasma reflects microwaves, the microwave introduction means is arranged so that the direction of introduction of the microwaves extends from the high magnetic field side to the low magnetic field side of the diverging magnetic field, and the microwave is introduced from the high magnetic field microwave absorption condition side. Waves need to be incident.

The position where the target is placed will be described with reference to FIG.

FIG. 2a is a graph with the magnetic flux density taken along the vertical axis and the position along the microwave introduction direction taken along the horizontal axis, and FIGS. 2b and 2c show the plasma density taken along the vertical axis and the horizontal axis. 7 is a graph showing the magnetic flux density.

Here, FIG. 2B is a graph under a pressure of 10 ⁻⁴ Torr, and FIG. 2C is a graph under a pressure of 10 ⁻⁵ Torr. As shown in the graph of Figure 2 b and Figure 2 c, the plasma density in the high-field microwave absorption condition (shown graphically in B _2), the plasma density in the ECR condition (shown graphically in B ₁₎ which 10 ^It can be seen that the plasma density under the high magnetic field microwave absorption condition does not decrease much as compared with that under the high vacuum of ^-5 Torr. Further, as shown in FIG. 2A, the magnetic field of the present invention is a divergent magnetic field, and the magnetic flux density decreases as shown by the curve (b) in FIG. 2A. In order to carry out the present invention, it is necessary to form both of these two conditions in the vicinity of the target. Therefore, the target may be arranged at the position indicated by (a) in FIG. 2A.

Next, the movement of the particles of the sputtering of the present invention is described as the third.
This will be described with reference to the drawings.

FIGS. 3a to 3c illustrate the movement of particles under high magnetic field microwave absorption conditions, and FIGS.
FIG. F illustrates the movement of particles under ECR conditions. In FIG. 3, (01) is a cylindrical aluminum target, (02) is a silicon sample, (03) is a plasma region under ECR conditions, (04) is a plasma region under high magnetic field microwave absorption conditions, (05) is a DC power supply, (0
6) (06 ') is the cation of argon, and (07) and (07') are the component particles of the target that jumped out of the target. The cations (06) and (06 ') of argon are attracted by the DC power supply (05) and collide with the target (01) (third).
Fig. A, Fig. 3b). This collision causes the component particles (07) and (07 ') to fly out of the target (01) (FIG. 3b,
Fig. 3e). Component particles that jumped out by this collision (07)
(07 ') forms a thin film on the surface of the sample (02). (FIGS. 3c and 3f).

As described above, the present invention exerts its effects particularly in a high vacuum state of 10 ⁻⁴ Torr or more, but is not particularly limited thereto. That is, even if the degree of vacuum is 10 ⁻⁴ Torr or less, the film formation rate can be obtained because the plasma density is higher than that of the conventional magnetic field microwave plasma sputtering apparatus.

FIG. 4 is a schematic diagram showing the operation of the invention of claim 2.
This will be described with reference to the drawings.

The incident energy of the argon ions depends on the electrostatic force of the negatively charged target, and during sputtering, the argon atoms are incident almost perpendicular to the target. The direction of aluminum sputtered out by the incident argon ions has a certain probability distribution with respect to the incident argon ions. This probability distribution varies depending on the atom to be sputtered, the material of the target, and the like. The probability becomes lower as it approaches the target in parallel.

This probability distribution is shown in FIG. In FIG. 4a,
Reference numeral (10) denotes a target. When a cation (11) such as an argon gas collides with the target (10) in a direction indicated by an arrow, component particles (12) of the target (10) fly out. The dotted line (13) indicates the probability distribution in the popping-out direction.

Then, by arranging the target along the slope of the truncated cone with its top surface facing the microwave introduction direction,
The fact that component particles of the sputtered target are not adhered to the quartz window will be described with reference to FIG. 4B.

In FIG. 4b, (10) is a conical target,
(15) shows a quartz window, (16) shows a sample, (14a) shows a plasma region established under ECR conditions, and (14b) shows a plasma region established under high magnetic field microwave absorption conditions. As shown in the figure, the target component particles (13a) and (13b) ejected by the collision of the positive ions (11a) and (11b) of the plasma established under either condition also head toward the sample (16),
It does not go to the quartz window (15) side. Therefore,
The component particles of the target sputtered by the plasma generated under both conditions do not fly out in the direction of microwave introduction by forming a conical target, and aluminum is introduced into the introduction window such as quartz glass for microwave introduction. This can prevent the adherence of the particles.

Finally, the operation of the invention according to claim 3 will be described. When the inside of the vacuum chamber is set to a high vacuum of about 10 ⁻⁵ Torr, the plasma densities under the conditions for generating two high-density plasmas are different. That is, the plasma density under high magnetic field microwave absorption conditions is higher. By arranging the target along the slope of the truncated cone with the top surface facing the microwave introduction direction, the volume of the part where both conditions are satisfied is set according to the ratio of both plasma densities, The target particles sputtered from both plasmas can equally collide with the sample.

〔Example〕

An embodiment of the magnetic field microwave plasma sputtering apparatus of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view schematically showing an embodiment of a magnetic field microwave plasma sputtering apparatus according to the present invention.
In FIG. 1, (21) is a vacuum vessel, and this vacuum vessel (21) has a funnel-shaped microwave introduction section (21a);
A cylindrical main body (21b) connected to the large-diameter side opening of the microwave introduction section (21a), and the inside thereof can be evacuated by a vacuum deaerator (not shown). . The main body (21b) and the microwave introduction part (2
An insulator (22) made of a material such as Teflon that electrically insulates the two, and an O-ring (23) that secures airtightness between the two are provided between the two. I have.
A disk-shaped sample (28) is arranged at the center of the main body (21b) in the vacuum vessel (21), and a target is formed along the inner surface of the conical part of the funnel-shaped microwave introduction part (21a). (29) is arranged.

In addition, a cylindrical waveguide (24) is connected to the opening on the small diameter side of the microwave introduction part (21a) of the vacuum vessel (21) through a disk-shaped quartz window (25). Microwaves generated by a microwave source not shown are introduced into the vacuum vessel (21) through the waveguide (24) and the quartz window (25) from the direction of the arrow (27) in the figure.

Further, a donut-shaped electromagnetic coil (30) is arranged around the microwave introduction part (21a) of the vacuum vessel (21), and the coil (30) is provided with a funnel-shaped microwave introduction part (21).
A divergent magnetic field diverging toward the large diameter side is formed in the conical portion of a).

(31) is a DC power supply, and this DC power supply (31)
The main unit (21b) of the vacuum vessel (21) and the microwave introduction unit (2
1a), and applies a negative voltage (approximately 600 V to 1 KV) to the microwave introduction section (21a) to set the target (29)
The surface is at a negative potential. In addition, in order to prevent the component particles from adhering to the target (29), the insulator (22) is located in a recessed position between the main body (21b) and the microwave introduction part (21a) of the vacuum vessel (21). Are located.

The operation of the apparatus shown in FIG. 1 will be described. First, a silicon substrate is placed as a sample (28) in a vacuum vessel (21), and an aluminum plate is placed as a target (29). Thereafter, an argon gas is introduced into the vacuum vessel (21) as a processing gas, and further evacuated to create a vacuum vessel (2).
1) The inside is set to a pressure of, for example, about 10 ⁻⁵ Torr. In this state, microwaves are applied to the vacuum container (2
When introduced into 1), argon gas as a processing gas is turned into plasma by the cooperative action with the magnetic field formed by the coil (30).

At this time, particularly high-density plasma is generated in a portion where the ECR resonance condition and the high magnetic field microwave absorption condition are satisfied. The positive ions in the plasma are attracted to the negative potential applied by the DC power supply (31) and collide with the target (29), and the collision causes aluminum particles, which are components of the target (29), to fly out. Adheres to the surface of the sample (28) to form a thin film on the surface of the sample (28).

The angle α formed by the conical portion of the funnel-shaped microwave introduction portion (21a) is desirably about 45 degrees according to experiments performed by the present inventors, but the angle α can be appropriately selected according to the material and the working pressure. . In other words, as described in the operation of the third aspect of the present invention, the thin film is uniformly formed on the sample according to the ratio between the plasma density under the ECR condition and the plasma density under the high magnetic field microwave absorption condition. Angle α so that
And design so as not to disturb the microwave mode.

A device having the same configuration as the device shown in FIG. 1, wherein the inner diameter of the vacuum vessel (21) is φ250-φ100 mm, and the cone α of the conical portion of the funnel-shaped microwave introduction part (21a) is 45 degrees. ECR near the target of the device with the target (29)
The coil (30) was installed so that the conditions and the high magnetic field microwave absorption conditions were satisfied. At this time, the inner diameter of the coil (30) is φ
180 mm, when a coil current of 300 A is passed, high-field microwave absorption conditions near the microwave waveguide (24),
The ECR condition was satisfied at the exit of the conical targate (29). Under these conditions, when aluminum was formed by sputtering on a silicon substrate, the results shown in Table 1 below were obtained.

It goes without saying that the present invention can be applied to target materials other than aluminum, and can also be applied to reactive sputtering such as formation of a thin film of SiO ₂ or TaO ₂ .

Furthermore, in order to change the position where the plasma collides with the target and make the target wear evenly, the amount of current applied to the coil is changed to change the magnetic field strength, and the position where the ECR condition and the high magnetic field microwave absorption condition are formed is changed. You may make it change.

Also, the position of the target may be freely changed instead of changing the strength of the magnetic field, or the position of the coil may be changed.

〔The invention's effect〕

In the magnetic field microwave plasma sputtering apparatus of the present invention, high-density plasma is generated near the target by using both plasmas obtained under the two plasma generation conditions of the ECR plasma and the high magnetic field microwave absorbing plasma. Sputtering at a high film speed can be performed.

Further, with the magnetic field microwave plasma sputtering apparatus of the present invention, high-purity film formation with less contamination of impurities such as argon can be performed at a sufficiently practical film formation rate even under a high vacuum.

According to the second aspect of the present invention, it is possible to prevent the component particles of the target from adhering to the microwave irradiation window for vacuum sealing of quartz glass or the like, and to prolong the life of expensive quartz glass or the like member. In addition to this, it is possible to prevent a decrease in the film formation rate due to a decrease in the microwave transmittance, and to further reduce the time required for maintenance.

Furthermore, according to the third aspect of the present invention, even in the case of a high vacuum of about 10 ^-5 Torr at which high-purity film formation can be performed, the component particles of the sputtered target can equally collide with the sample. Therefore, there is an effect that unevenness of the thin film can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment of a magnetic field microwave plasma sputtering apparatus according to the present invention, FIG. 2a is a graph showing an arrangement position of a target in the present invention, and FIG.
2 and 3 are graphs showing high magnetic field microwave absorption conditions, FIG. 3 is a schematic diagram showing the principle of magnetic field microwave plasma sputtering of the present invention, and FIG. FIG. 5 is a cross-sectional view schematically showing an example of a conventional magnetic field microwave plasma sputtering apparatus, and FIG. 6 is a graph showing high magnetic field microwave absorption conditions. (21) ... vacuum vessel, (24) ... waveguide, (27) ... microwave introduction direction, (28) ... sample, (29) ... target, (3
0)… Electromagnetic coil.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-277775 (JP, A) JP-A-61-194174 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 14/00-14/58 C23C 16/00-16/56 H01L 21 / 205,21 / 31,21 / 203

Claims (3)

(57) [Claims] A process gas is introduced into a vacuum vessel (21) in which a sample (28) and a target (29) are arranged, and a magnetic field is generated in the vacuum vessel (21) by magnetic field generating means (30). The process gas is turned into plasma by being formed and microwaves are introduced by a microwave introduction means (24), and the plasma is irradiated on the target (29), and the components of the target (29) are placed on the sample (28). The magnetic field generated by the magnetic field generating means (30) is a diverging magnetic field diverging near the target (29) in the magnetic field microwave plasma sputtering apparatus formed as a thin film on the
The microwave introduction means (24) is arranged so that the microwave introduction direction (27) extends from the high magnetic field side to the low magnetic field side of the divergent magnetic field, and furthermore, the intensity of the magnetic field generated by the magnetic field generation means (30) is set to the target. (29) A magnetic field microwave plasma sputtering apparatus characterized in that the intensity is such that electron cyclotron resonance conditions and high magnetic field microwave absorption conditions can be formed in the vicinity. 2. The magnetic field micro-device according to claim 1, wherein the target is arranged along a slope of a truncated cone whose top surface faces the direction of introduction of the microwave. Wave plasma sputtering equipment. 3. The magnetic field microwave plasma sputtering apparatus according to claim 2, wherein the degree of vacuum in the vacuum vessel (21) is 10 ^-5 Torr or less.