JPH10121234A - Sputtering device and collimator used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the asymmetry of formed coating by a long distant sputtering method. SOLUTION: The bulkhead 12a of the cell 10 of a collimator 4a is made oblique, and its angle is made wide as it closes from the center part to the circumferential part in the collimator 4a. The bulkhead 12a of the cell 10 of the collimator 4a is made slant in such a manner that the normal of the bulkhead on the circumferential side of the cell 10 orients not to the side of a substrate 2 but to the side of a target 6. In this way, since, in the circumferential part of a wafer 2, the effect of trapping the sputtered particles imparting asymmetry increases and the components at the shallow angles and the components having incident angles in the direction opposite to the gradient direction of the cell bulkhead 12a are hardly trapped, the effect of improving the asymmetry at the hall part is made higher than the case in which the cell bulkhead is vertical.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering apparatus used for manufacturing a semiconductor device, and more particularly, to a collimation sputtering apparatus having a collimator for giving directivity to sputtered particles between a target and a substrate on which a film is formed. It relates to the collimator used.

[0002]

2. Description of the Related Art With the miniaturization and multilayer wiring of semiconductor devices, a technique for filling fine holes has become important. Even in a contact hole for establishing conduction between the semiconductor substrate and the upper wiring, a Ti (titanium) film is generally formed on the bottom surface of the hole by a sputtering method in order to obtain a low contact resistance. In the conventional sputtering method, when an overhanging deposit is generated at the upper end of the hole, a fine hole having a hole diameter of 0.5 μm or less and a high aspect ratio is formed, a sufficiently thick Ti film is formed on the bottom of the hole. Would be difficult to do. In order to solve this problem, collimation sputtering, long-distance sputtering,
The CVD method of a metal film has been studied, and a part thereof has begun to be used for mass production.

In principle, the CVD method can form a metal film having the same thickness on all of the flat portion, the bottom portion and the side portion of the hole, and is advantageous for the process of fine holes.
Due to the problem of impurities from the source gas being taken into the film and the high cost of equipment and process gas, which is still in the development stage, an improved method of the conventional sputtering method is now the mainstream. .

In the collimation sputtering method, as shown in FIG. 1, a component called a collimator 4 having a structure that allows only a sputtered particle having a component almost perpendicular to the surface of a substrate 2 to be formed to pass through is formed. This is a method of performing sputtering film formation by setting the film between the target 6 and the substrate 2 (see Japanese Patent Publication No. Hei 7-116599). Compared with the conventional sputtering method, the ratio of sputter particles attached to the bottom of the hole (bottom coverage) Can be greatly increased. 8 is a sputtered particle.

In the ordinary collimation sputtering method, the distance between the target 6 and the substrate 2 is set to 100 mm or less. If, for example, a 6-inch wafer is used as a substrate on which a film is to be formed, the distance between the target 6 and the substrate 2 is usually smaller than the diameter of the substrate 2. In such a normal collimation sputtering method, the problem that the film formation rate is reduced by the proportion trapped by the collimator 4, the problem that the film formation rate changes over time due to clogging of the collimator opening, and the collimator 4 There is a problem that the film adhered to the substrate is peeled off and adheres to the substrate 2.

In the collimation sputtering method, a unit cell partition of a collimator is installed obliquely with respect to a normal direction of a substrate so that sputtered particles incident on the substrate have oblique directivity. It has been proposed (see JP-A-7-113172). This method aims at controlling the crystal orientation of the thin film, and all the inclined unit cell partition walls have the same inclination angle.

[0007] In the long-distance sputtering method, the distance between the target and the substrate is set to be larger than the diameter of the substrate, and the pressure at the time of film formation is reduced by about one digit compared with the conventional sputtering method. This is a technique of forming a film only of sputtered particles having a component close to the above (see Japanese Patent Application Laid-Open No. 6-220627). In the long distance sputtering method, the rate of deposition on the bottom surface of the fine hole increases, and the same effect as the collimation sputtering method can be obtained without installing another component between the target and the substrate.

Although the problem described in the collimation sputtering method does not occur in the long-distance sputtering method, a problem occurs due to a principle cause. That is, the film thickness of the bottom and side surfaces of the fine hole becomes more asymmetric toward the periphery of the wafer. This is for the following reasons. In long-distance sputtering, the diameter of the target needs to be slightly larger than the diameter of the substrate in order to increase the bottom coverage. If the diameter of the target is too large, the number of particles obliquely incident on the substrate increases, and it becomes meaningless to separate the target from the substrate. When the target and the substrate are substantially the same size, the angle at which the target can be seen from the center of the wafer is represented by a cone having the axis of the normal to the substrate as an axis. Is represented by a cone whose axis is the line connecting the point and the center of the target. In low-pressure deposition such as long-distance sputtering, the probability that the sputtered particles are scattered between the target and the substrate is small, so the above-mentioned difference in the expected angle is directly reflected in the incident direction distribution of the sputtered particles on the wafer. As a result, the thickness of the side wall portion on the center side becomes thinner in the hole at the peripheral portion of the wafer, the thickness of the side wall portion on the peripheral side becomes thicker, and the film on the bottom portion also becomes an asymmetric distribution in which the film becomes thicker on the peripheral side. (See P.226 of the 1995 VMIC Conference).

When a Ti film or a TiN (titanium nitride) film formed in a contact hole is filled with a film such as W (tungsten) or Al (aluminum), the Si substrate is formed of W or Al or a source gas. Is used as a barrier layer for preventing the reaction with the barrier layer. Therefore, if there is a thin portion on the bottom surface of the contact hole, the function of the barrier layer may not be fulfilled. The problem of the asymmetry of the film thickness in the hole at the periphery of the wafer is remarkable in the long-distance sputtering method, but the same problem also occurs in the case of the collimation sputtering method depending on the relationship between the ratio of the diameter of the target to the substrate and the aspect ratio of the collimator. Will occur.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem of asymmetry.

[0011]

According to the present invention, in order to solve the problem of the asymmetry of the film thickness in a hole at the peripheral portion of a wafer, a sputtered particle is directed between a target and a substrate which are placed in parallel with each other. In a normal collimation sputtering apparatus in which a collimator giving the property is provided and the distance L between the target and the substrate is set smaller than the diameter of the substrate, the aspect ratio m of the collimator is set to m = L / (R−r). Set to. Here, R is the radius of the target, r is the radius of the substrate, and R> r. By setting the aspect ratio of the collimator in this way with a normal collimation sputtering apparatus, the maximum value in the incident direction of the sputtered particles becomes the same at all points of the substrate, and the fine hole in the peripheral portion of the substrate and the side wall portion of the hole. Asymmetry of the film thickness at the bottom portion does not occur.

In a long-distance sputtering apparatus in which the distance L between the target and the substrate is set to be equal to or greater than the diameter of the substrate, a collimator is provided between the target and the substrate, and the aspect ratio m of the collimator is set to L / R. ≦ m ≦ L / (R−r). The aspect ratio of such a collimator is suitably from 1.0 to 1.5. By setting the aspect ratio of the collimator provided in the long-distance sputtering device in this way, a large proportion of sputtered particles that cause asymmetry of the film thickness on the side wall and bottom of the hole in the fine hole around the substrate And the asymmetry of the film thickness can be improved.

Further, in order to improve the effect of improving the asymmetry, the collimator has been improved. A preferred example of such a collimator is such that when viewed in a cross-section passing through the center, the partition walls of the unit cell are parallel to the normal direction of the target and the substrate at the center, and the partition walls are inclined at the peripheral portion, and the inclination angle thereof Is increasing from the center to the periphery. By arranging the collimator so that the normal line of the partition wall of the unit cell inclined obliquely faces the target direction, sputter particles that cause asymmetry of the film thickness can be efficiently trapped.

By making the thickness of the collimator thinner from the center to the periphery,
The unevenness of the film thickness formed on the substrate due to the installation of the collimator can be corrected. Instead of making the thickness of the collimator thinner as going from the center to the periphery, at least one of the target side and the substrate side of the collimator having a constant thickness from the center to the periphery has a smaller diameter than the collimator. Processing is facilitated by integrating the collimator so that the centers are substantially aligned.

The purpose of this collimator is not to improve the bottom coverage of the fine holes, but to trap the sputtered particles causing the film thickness asymmetry by the collimator. The collimator has a function of limiting the incident angle of particles reaching the substrate to a certain range according to the aspect ratio. The non-symmetric property at the wafer periphery is caused by sputtered particles having oblique incident components flying from near the farthest position when the target is viewed from that point. If a collimator capable of trapping particles having an incident angle larger than the angle approaching perpendicular to a certain degree is installed, asymmetry can be improved. The present invention proposes an optimal collimator configuration for improving asymmetry without deteriorating other characteristics.

[0016]

【Example】

(Embodiment 1) FIG. 2 shows a geometric model used for calculation for obtaining an optimal collimator configuration. R and r are the radii of the target and the substrate, respectively, and L is the distance between the target and the substrate. The target 6 and the substrate 2 are installed in parallel with each other, and the partition 12 of the unit cell 10 of the collimator 4 is provided.
Is parallel to the normal line of the target 6 and the substrate 2.
The unit cell 10 of the collimator 4 has a hole diameter a and a depth b,
The aspect ratio is m (= b / a). Collimator 4
An incident particle having an angle ψ or more determined by tanψ = a / b is trapped. Considering the case where the collimator 4 is not installed, the angle range of the incident particle at the center of the substrate 2 is tan.
All fall within an angle θ determined by θ = R / L. However, the maximum value of the angle of the incident particle at the shortest part of the substrate 2 is tanφ1 = (R−r) from the near end of the target 6.
/ L, and tan from the far end
The angle φ2 is determined by φ2 = (R + r) / L.
The large difference between 1 and φ2 is the cause of the asymmetry.
Therefore, at least ψ
It is necessary that the relationship <φ2 be established. The highest improvement effect is obtained when the relationship of ψ ≦ φ1 is satisfied. In this case, the maximum value of the angles of the particles incident on all points on the substrate becomes the same value.

Table 1 shows that the target size is 8 inches (R =
100 mm) and the substrate size is 6 inches (r = 75 mm), the distance L between the target 6 and the substrate 2 is 50 to 25.
When it is changed to 0 mm, φ1 = と き に, θ = ψ, φ2
Here, a list of the aspect ratios m of the collimator satisfying the relationship of = ψ is shown.

[0018]

[Table 1]

For example, JP-A-6-220627 defines a case where L is 150 mm or more as long-distance sputtering, but when L is 150 mm, in order to completely eliminate asymmetry, an aspect ratio of 6. Zero or more collimators are required. However, the current mainstream aspect ratio is 1.
This is a very unrealistic value given that it is between 0 and 2.0. However, the values shown in the table are merely geometrical calculation results, and the angular distribution of sputtered particles radiated from the target is not taken into account. Therefore, when this effect is included in the model, φ1 = ψ, θ = ψ, The aspect ratio m of the collimator satisfying the relationship of φ2 = φ is about 30% smaller. Therefore, even in the case of long-distance sputtering, if a collimator having an aspect ratio of 1.0 to 1.5 is provided between the target and the substrate, it can be said that the asymmetry can be improved to a considerable extent, if not completely.

When a collimator is installed in a conventional sputtering apparatus, the film forming rate is reduced to about 1/5 to 1/10, but in a long-distance sputtering, only incident particles which are originally close to vertical reach the substrate. Therefore, even if a collimator is installed, the reduction in the film formation rate is reduced by 1/2 to 1/3.
Considered to be a degree, no problem.

(Embodiment 2) The results shown in Table 1 are for the case where the partition 10 of the cell of the collimator 4 is parallel to the normal direction of the substrate 2 and the target 6, but in order to improve the asymmetry efficiently. In addition, the partition wall of the collimator cell is made oblique, and the angle is increased as the distance from the center of the collimator to the peripheral portion increases. FIG. 3 shows the cross-sectional shape. The partition wall 12a of the cell 10a of the collimator 4a is inclined such that the normal line of the partition wall on the peripheral side of the collimator cell 10a faces the target 6 side instead of the substrate 2 side. With such a configuration, the efficiency of trapping sputter particles (components near the angle φ2 in FIG. 2) causing asymmetry at the peripheral portion of the wafer is increased, and the components at a shallow angle and the inclination direction of the cell partition 12a are increased. A component having an incident angle in the opposite direction is hardly trapped, so that the effect of improving the asymmetry of the hole is greater than when the cell partition is vertical. Since the asymmetry of the film formed in the hole is originally small near the center of the substrate 2, the degree of the inclination of the cell partition wall 12a is small, and it is not necessary to incline in the center.

The external view of such a collimator 4a has a shape as shown in FIG. 4, for example, in which a large number of metal cones having the same height and different bottom areas are cut out at the same height so that their centers coincide. Can be created by welding to each other.

(Embodiment 3) The sputtering apparatus including the long-distance sputtering apparatus is designed so that the uniformity of the film thickness formed on the substrate is improved when no collimator is provided. When the proportion of particles trapped by the collimator increases in the peripheral portion, the uniformity of the film thickness deteriorates due to the installation of the collimator. In order to solve such non-uniformity, optimizing the design of a magnet or the like installed on the back side of the target is an essential solution, but it is a major modification.
Therefore, as a simple solution, as shown in FIG. 5, the shape of the collimator 4a of the second embodiment is changed to a configuration 4a-1 in which the thickness is increased toward the center and the aspect ratio is increased, so that the vicinity of the center is increased. The film forming rate can be adjusted to the film forming rate in the peripheral portion.

(Embodiment 4) The collimator 4a of Embodiment 3
1 has a considerably complicated shape, and when processing is difficult, the diameter of the collimator 4a of Example 2 is reduced to one or both sides near the center as shown in FIG. A collimator 4a having a smaller aspect ratio than the collimator 4a may be added. This collimator 4b is
A configuration parallel to the normal direction of the substrate 2 and the target 6 or a configuration in which the diameter of the collimator 4a in FIG. 4 is reduced may be used.

(Embodiment 5) Although all of the above embodiments are directed to the long-distance sputtering method, the collimation sputtering method is not as extreme as the long-distance sputtering method as described in the object of the invention. There is a problem of thickness asymmetry in the peripheral holes. The configuration of the collimator for improving the asymmetry can be determined by the same method as the calculation in the first embodiment.

Tables 2 and 3 show that when the substrate size is 6 inches and the target sizes are 10 inches and 12 inches, respectively, when the distance L between the target and the substrate is changed from 50 to 250 mm, φ1 = ψ, A list of aspect ratios m of the collimator satisfying the relationship of θ = ψ, φ2 = ψ is shown.

[0027]

(Equation 2)

[0028]

(Equation 3)

In a normal collimation sputtering method, the distance between the target and the substrate is usually set to 100 mm or less, and the aspect ratio of a collimator satisfying φ1 = ψ is 2.0 at the maximum, and is now available. It can be seen that the collimator used can be used as it is. That is, when the radii of the target and the substrate are R and r, respectively, the distance L between the target and the substrate and the aspect ratio m of the collimator satisfy φ1 = φ, that is, m = L
If it is set so as to satisfy / (R-r), the problem of asymmetry can be efficiently solved.

As described in the description of the first embodiment, in the case of the long-distance sputtering method, since the aspect ratio of the collimator satisfying the above relationship is extremely large, the rate of film formation is drastically reduced, which is an unrealistic value. Is θ = ψ, that is, m = L / R
Even if a collimator that satisfies the relationship is established, a sufficient effect can be obtained without drastically reducing the film forming rate if the angular distribution of sputter particles emitted from the target is taken into consideration.

On the other hand, when m ≦ L / R, the effect of improving the asymmetry is reduced although the decrease in the film formation rate is small. Therefore, in the case of the long-distance sputtering method, the problem of asymmetry can be solved by setting the aspect ratio m of the collimator to a value satisfying the relationship of L / R ≦ m ≦ L / (R−r). It can be solved.

[0032]

According to the present invention, since the aspect ratio m of the collimator is set to a predetermined value in a normal collimation sputtering apparatus, the maximum value in the incident direction of sputtered particles becomes the same at all points of the substrate, and In the peripheral fine hole, asymmetry of the film thickness between the hole side wall portion and the bottom portion does not occur. A collimator is also provided in the long-distance sputtering device, and the aspect ratio of the collimator is set within a predetermined range. A significant proportion of the particles can be trapped and the asymmetry of the film thickness can be improved. In addition, by improving the collimator, it is possible to efficiently trap sputter particles that cause asymmetry of the film thickness, and to correct the nonuniformity of the film thickness formed on the substrate due to the installation of the collimator. .

[Brief description of the drawings]

FIG. 1 is a front sectional view schematically showing a collimation sputtering apparatus.

FIG. 2 is a schematic front sectional view of a collimation sputtering apparatus showing a geometric model used for calculation for obtaining an optimal collimator configuration.

FIG. 3 is a front sectional view schematically showing an embodiment of a collimation sputtering apparatus provided with a preferable collimator.

FIG. 4 is a schematic perspective view showing a collimator in the embodiment.

FIG. 5 is a front sectional view schematically showing an embodiment of a collimation sputtering apparatus provided with another preferred collimator.

FIG. 6 is a front sectional view schematically showing an embodiment of a collimation sputtering apparatus provided with still another preferred collimator.

[Explanation of symbols]

 2 Substrate 4, 4a, 4a-1, 4b Collimator 6 Target 8 Sputtered particle 10, 10a Unit cell 12, 12a Partition wall of unit cell

Claims (8)

[Claims] In a collimation sputtering apparatus in which a collimator for giving directivity to sputtered particles is provided between a target placed in parallel with a target and a substrate on which a film is formed, a distance L between the target and the substrate is equal to a diameter of the substrate. When the radius of the target is R and the radius of the substrate is r (R> r), the aspect ratio m of the collimator is set to be m = L / (R−r). A collimation sputtering apparatus. 2. A collimation sputtering apparatus in which a collimator for giving directivity to sputter particles is provided between a target placed in parallel with a substrate and a substrate on which a film is formed, wherein a distance L between the target and the substrate is equal to a diameter of the substrate. In the long-distance sputtering apparatus set as above, where the radius of the target is R and the radius of the substrate is r (R> r), the aspect ratio m of the collimator is L / R ≦ m ≦ L / (R− r) A collimation sputtering apparatus characterized in that: 3. The collimator according to claim 1, wherein a partition wall of the unit cell is parallel to a normal direction of the target and the substrate at the center when viewed in a cross section passing through the center, and the partition wall is inclined at a peripheral portion.
2. The collimator according to claim 1, wherein the inclination angle increases from the center to the periphery, and the collimator is installed such that a normal line of a partition wall of the unit cell inclined obliquely faces the target direction. Or the collimation sputtering apparatus according to 2. 4. The collimation sputtering apparatus according to claim 3, wherein the thickness of the collimator decreases from the center to the periphery. 5. The collimator according to claim 1, wherein a collimator having a smaller diameter is integrated with at least one of a target side and a substrate side of the collimator having a constant thickness from the center to the peripheral portion so that the center of the collimator is substantially aligned with the center. The collimation sputtering apparatus according to claim 3. 6. A collimator used in a collimation sputtering apparatus, wherein a partition wall of a unit cell is parallel to a normal direction of a target and a substrate at the center when viewed in a cross section passing through the center, and the partition wall is inclined at a peripheral portion. A collimator characterized in that the inclination angle increases from the center to the periphery. 7. The collimator according to claim 6, wherein the thickness decreases from the center to the periphery. 8. The method according to claim 6, wherein a collimator having a diameter smaller than that of the collimator is integrated with at least one of the surfaces having the opening of the collimator having a constant thickness from the center to the periphery with the center substantially coincident with the center. The collimator described.