JP2001131737A - Sputtering target and method of grinding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target capable of effectively reducing or preventing cracking due to warp of a target itself in the process of manufacturing for a target, particularly a ceramic target, and also capable of effectively reducing or preventing cracking due to warp even during its transportation or attachment to equipment or at sputtering. SOLUTION: The sputtering target has <=0.57 μm surface roughness Ra and a directionality-free ground surface. In the method of grinding for the sputtering target having a directionality-free ground surface, grinding is performed using a face parallel to the direction of rotation of a rotating head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can effectively reduce or prevent chipping or cracking of a target which occurs during a bonding process of a target to a backing plate, during transport, during attachment to a film forming apparatus or during film formation. The present invention relates to a sputtering target and a grinding method thereof.

[0002]

2. Description of the Related Art In recent years, sputtering has been used to form thin films for semiconductor devices, various electronic devices, and the like. Sputtering has been performed at a higher speed to improve productivity. As is well known, the sputtering method irradiates charged particles toward a target, strikes out the particles from the target by the particle impact force, and comprises a target material on a substrate such as a wafer facing the target, for example, a wafer. This is a film forming method for forming a thin film having a substance as a central component.

Since the target receives a large amount of impact of charged particles during sputtering, the amount of heat input to the target gradually increases and accumulates. For this reason, it is necessary to cool the target, and in many cases, a material having good thermal conductivity (backing plate) such as pure copper or copper alloy is brazed to the back surface of the target, diffusion bonding, pressure bonding, bonding using the anchor effect, etc. The backing plate is cooled by external cooling means to absorb the heat of the target.

As described above, when joining a target to a backing plate, it is necessary to heat the target to an appropriate temperature in various joining methods, and after joining, the target is cooled. Due to the thermal effect in the heating and cooling process at the time of such bonding, there has been a problem that cracks due to warpage occur due to the difference in thermal expansion coefficient between the target and the backing plate. In addition, there is a problem that even when the target does not crack, the target is in a state in which strain is accumulated, and the probability of cracking in a subsequent process increases.

[0005] Even when the target is bonded to the backing plate with an adhesion rate of 90% or more without any problem, cracks may occur in the target due to thermal stress during sputtering. In the case of cracking during sputtering, a large amount of particles are generated at the moment when the target is cracked, resulting in a defective film or missing of the target, making it impossible to continue sputtering, and causing great damage to the sputtering equipment. Can be a big problem. From the viewpoint of the type of target material, a ceramic target is a brittle material having a small coefficient of thermal expansion and a large difference in the coefficient of thermal expansion from a backing plate material such as pure copper or a copper alloy. Cracks due to warpage are likely to occur.

In order to solve such a problem, it has been proposed to use a low melting point solder for bonding so that heat is not applied to the target and the backing plate at a high temperature. However, in this case, the joining force is weak, and when the target is heated to a high temperature by performing sputtering, there is a problem that the solder for joining melts out, and the solution has not been solved. It has also been proposed to form a plurality of bonding layers having different thermal expansions in a stepwise manner in order to alleviate the thermal expansion between the target and the backing plate (JP-A-61-250167). However, such means is not practical because the operation steps are complicated and the manufacturing cost is increased.

Further, in the step of joining the target and the backing plate, a method of mechanically applying a force in the opposite direction to the warped target to correct it, or before joining,
Proposal in which the target is given a reverse warp before joining in anticipation of the amount of warpage (Japanese Patent No. 2573653).
Was also made. However, in the case of brittle materials such as ceramics, cracks may be generated by applying mechanical stress higher than the material strength in the process of mechanical correction and deformation in this way, and these are also effective. It could not be said to be a means of solution.

[0008]

SUMMARY OF THE INVENTION The present inventors have found that in the production process of a target, in particular, a ceramic target,
The specific phenomenon that there is a direction in which cracks are likely to occur is specifically confirmed by a bending test, etc., and in the joining process between the target and the backing plate, cracks due to warping of the target itself are effectively reduced or prevented, It is an object to obtain a sputtering target that can effectively reduce or prevent cracking due to warpage during transportation, during attachment to an apparatus, or during sputtering.

[0009]

SUMMARY OF THE INVENTION The present invention focuses on ordinary processing steps such as grinding or polishing of a target, and improves this operation to prevent or reduce chipping or cracking of the target. 2. A sputtering target having a surface roughness Ra ≦ 0.5 μm and a ground surface having no directivity. 2) The surface roughness Ra ≦ 0.3 μm. The sputtering target according to any one of claims 1 to 3, wherein the sputtering target has a surface roughness Ra ≤ 0.1 µm. 4) The sputtering target is a ceramic target. I will provide a.

The present invention further provides: 5) a method for grinding a sputtering target, characterized in that, when grinding using a rotating body, grinding is performed using a surface parallel to the rotating direction of the rotating body. When grinding using a body, grinding using a surface parallel to the rotation direction of the rotating body, surface roughness Ra ≦ 0.5 μm
7. A method for grinding a sputtering target, characterized in that the surface roughness Ra ≦ 0.3 μm. 8) A method for grinding a sputtering target according to claim 6, wherein the surface roughness Ra ≦ 0.1 μm. 7. The method for grinding a sputtering target according to claim 6, wherein: 9) grinding without directivity is performed.
The sputtering method according to any one of claims 5 to 9, wherein the sputtering is performed over a part or the entire surface of the target by relative movement of the rotating body or the target. And a method of grinding a target.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, a ceramic target has a small coefficient of thermal expansion and a large difference from the coefficient of thermal expansion of a backing plate made of copper or the like. For this reason, warpage and cracks occur more frequently than metal-based targets, but it is known that cracks are particularly affected by surface defects. Surface grinding is performed in the stage of manufacturing the target, and the present inventor has found a specific phenomenon in joining with the backing plate depending on the direction of the grinding. It was specifically confirmed by a bending test and the like that cracks frequently occurred in a direction parallel to the grinding direction and, conversely, cracks decreased in a direction perpendicular to the grinding direction. That is, the fact that materials of the same quality have directionality depending on the grinding direction.

In general, in particular, in the case of a ceramic target, surface defects tend to cause cracks as described above. Therefore, it is ideal to perform mirror polishing or finish processing similar thereto. However, in order to perform such processing, the process time is increased and the manufacturing cost is increased. Conventionally, no particular consideration has been given to the arrangement of targets for preventing cracking due to warpage in the joining step. Also, it has been difficult to predict in advance the warping direction for various forces (deformations) in each step. The present invention is intended to easily and effectively reduce or prevent chipping or cracking of a target during a joining step of a target and a backing plate, a transfer step, attachment to an apparatus, or a sputtering operation. This will increase target productivity, improve product yield and reduce cracking,
This has the effect of improving the yield of products such as electronic devices, such as reducing defects and troubles in the sputtering process of the sputtered film.

In order to prevent or reduce cracking or chipping of the target, it is extremely effective not to give directionality to the grinding. It is also more effective to make the surface roughness as small as possible, and the surface roughness Ra ≦ 0.5 μm,
Preferably Ra ≦ 0.3 μm, more preferably Ra ≦
It is effective to set it to 0.1 μm. In particular, in the case of a rectangular ceramic target, cracks in the width direction are likely to occur due to warpage in the long plate direction, but this isotropic grinding can effectively prevent or reduce cracks in the width direction.

In the isotropic grinding according to the present invention, as shown in FIG. 1, it is effective to grind the target 1 using a rotating body 2 having abrasive grains for grinding on the lower surface parallel to the rotation direction 3.
That is, grinding is performed using a surface parallel to the rotation direction 3 of the rotating body 2. Fixed abrasive grains are mounted on the lower surface of the rotating body 2 for grinding, but it is also possible to mount a sponge for loose abrasive grains and perform grinding with the loose abrasive grains. Thereby, the surface roughness Ra ≦
It can be adjusted to 0.5 μm, preferably Ra ≦ 0.3 μm, more preferably Ra ≦ 0.1 μm.

In grinding, the target 1 to be ground is
May be fixed and the position of the rotating body 2 provided with the abrasive grains for grinding may be moved to grind a part or the entire surface of the target 1,
Conversely, the position of the rotating body 2 may be fixed, and the target 1 which is the object to be ground may be moved in the X-axis direction and the Y-axis direction to perform grinding. Alternatively, the target 1 and the rotating body 2 which are the objects to be ground may be simultaneously moved to grind a part or the entire surface of the target 1. In addition, a plurality of rotating bodies 2 provided with abrasive grains for grinding are mounted or exchangeably installed, and these are gradually (for example) shifted (replaced) gradually from coarser grains to finer ones as the grinding proceeds. However, grinding may be performed semi-continuously.

As described above, by grinding the part or the entire surface of the target 1 by the relative movement of the rotating body 2 and / or the target 1, a ground surface having no directivity is obtained, and chipping or cracking of the target 1 is achieved. Can be effectively prevented or reduced. Since the ceramic target is a brittle material having a small coefficient of thermal expansion and a large difference in coefficient of thermal expansion from a backing plate material such as pure copper or copper alloy, the probability of cracking due to warpage is high. Preventing the generation of cracks in the target is extremely effective.

[0017]

Examples and comparative examples are described below based on examples and comparative examples. This embodiment is merely an example, and the present invention is not limited to this example. That is,
It is intended to include other aspects or modifications included in the technical concept of the present invention.

Examples 1 to 6 and Comparative Examples 1 to 4 ITO
For a target material (sintered body) of (In ₂ O ₃ -10 wt% SnO ₂ ), a rotating body having abrasive grains for grinding on the lower surface shown in FIG. 2 was used, and a surface parallel to the rotating direction of the rotating body was used. And ground. Diamond was used for the abrasive grains.
The speed of the rotating body is 300 rpm, and the pressing pressure is 3
kg / cm ² . The surface roughness Ra is 0.5
Grinding was performed on a plurality of targets so as to be not more than μm, not more than 0.3 μm, and not more than 0.1 μm. All are examples of the present invention which are isotropically ground. As a comparative example, the target is ground in parallel to the longitudinal direction and Ra is 0.5 μm or less and Ra is 0.5 μm or more, and the target is ground in the width direction and Ra is 0.5 μm or less. Shows those of 0.5 μm or more. FIG. 2 shows the concept of measuring the roughness of the target surface according to the embodiment. Code 5
Denotes a measurement in the longitudinal direction, and reference numeral 6 denotes a measurement in the width direction. FIG.
The conceptual diagram of the target surface roughness measurement of the comparative example is shown in FIG.
Reference numeral 7 indicates a grinding direction. A roughness measurement was performed in the longitudinal direction of reference numeral 8.

The surface roughness Ra and the average strength of the ground surface obtained by employing the above-described grinding examples and adjusting the surface roughness are shown below.
The strength is a bending test by a three-point bending test (JISR1601). Then, the resistance to cracking of the target was evaluated based on the strength of the bending test. The bending test conditions of the target (sintered body) are as follows. Target material: ITO (In ₂ O ₃ -10 wt% S
nO ₂ ) Target density: 7.12 g / cm ³ Grinding whetstone used: # 400, # 800, and # 4000 diamond fixed abrasive whetstone Distance between fulcrum points: 70 mm Plate thickness: 6 mm Board width: 20 mm Test speed: 0.5 mm / Min

The above results are shown in Tables 1 and 2. In Table 1, Examples 1 to 3 show Ra in the longitudinal direction of the test piece.
And the results of the bending test, and Comparative Example 1, which was ground in the longitudinal direction,
2 shows the results of the Ra and bending test in the length direction of No. 2. Further, in Table 2, Examples 4 to 6 show the results of Ra and bending test in the width direction of the test piece, and Comparative Examples 3 and 4 in which the test piece was ground in the width direction. The results of the folding test are shown. As is clear from Tables 1 and 2, in Examples 1 to 6, # 400 and # 80 were used.
As a result of the roughness measurement performed at 0 and # 4000, there was almost no difference between the longitudinal direction and the width direction. Also, there was no difference in bending strength. On the other hand, as shown in Comparative Examples 1 to 4, as for the ones subjected to unidirectional grinding at # 400 and # 80, the results of the roughness measurement show that the cases of longitudinal grinding and widthwise grinding were performed. And a clear difference was also found in the bending strength.

[0021]

[Table 1]

[0022]

[Table 2]

As described above, when the surface roughness is rough, the strength is greatly reduced. In the case of directional polishing, particularly in the case of grinding in a direction perpendicular to the bending direction, the strength is extremely reduced. However, when the target was ground isotropically, it was confirmed that the strength was uniformly improved in all directions of the target.

[0024]

According to the present invention, a target, especially a ceramic, can be obtained by grinding using a surface parallel to the rotation direction of the rotating body and performing non-directional grinding, and by appropriately adjusting the surface roughness Ra if necessary. In the target manufacturing process, an excellent effect of effectively reducing or preventing cracks and chips due to warpage of the target itself, and also reducing or preventing cracks and chips due to warpage during transportation, during mounting to an apparatus, or during sputtering. Having.

[Brief description of the drawings]

FIG. 1 is an explanatory view (A: front sectional view, B: plan view) showing the concept of grinding of the present invention.

FIG. 2 is an explanatory diagram showing a position for measuring the roughness of a target surface.

FIG. 3 is an explanatory view showing a relationship between a warp direction and a grinding direction (C:
Grinding in the longitudinal direction, D: grinding in the width direction).

[Explanation of symbols]

 Reference Signs List 1 target 2 rotating body 3 rotating direction 4 moving direction of target or rotating body 5 maximum warping direction of target 6 grinding direction of target 7 longitudinal direction 8 width direction

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 3C058 AA07 AA11 AB01 BA07 CA01 CB02 CB10 4K029 BA45 BA47 BC09 BD02 CA05 DC01 DC05 DC09 DC12

Claims (10)

[Claims] 1. A sputtering target having a surface roughness Ra ≦ 0.5 μm and a ground surface having no directivity. 2. The sputtering target according to claim 1, wherein a surface roughness Ra ≦ 0.3 μm. 3. The sputtering target according to claim 1, wherein a surface roughness Ra ≦ 0.1 μm. 4. The sputtering target according to claim 1, wherein the sputtering target is a ceramic target. 5. A method for grinding a sputtering target, wherein when grinding using a rotating body, grinding is performed using a surface parallel to the rotating direction of the rotating body. 6. When grinding using a rotating body, grinding is performed using a surface parallel to the rotating direction of the rotating body, and the surface roughness Ra ≦
A method for grinding a sputtering target, characterized by grinding to 0.5 μm. 7. The method for grinding a sputtering target according to claim 6, wherein the surface roughness Ra ≦ 0.3 μm. 8. The method for grinding a sputtering target according to claim 6, wherein the surface roughness Ra ≦ 0.1 μm. 9. The method for grinding a sputtering target according to claim 5, wherein grinding without directionality is performed. 10. The method for grinding a sputtering target according to claim 5, wherein grinding is performed on a part or the entire surface of the target by relative movement of the rotating body or the target.