JP2000218519A - Polishing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a high flatness at a high speed by composing a polishing material which performs polishing by way of scrubbing an object to be polished while free abrasive grains are supplied, of a soft resin and filler. SOLUTION: A polishing material 1 is composed of hard filler 2 and soft resin 3. The resin 3 has surface gaps such as pores 4 in which free abrasive grains 5 supplied is retained. Polishing work is carried out with the material 1 which scrubs a surface of an object to be polished 6. In the case where free abrasive grains 5 exist between the material 1 and the object 6, the grains 5 are not forcedly pushed into the object 6 because the pushing-in force is alleviated by the cushioning characteristic of the resin 3, while the filler 2 which is bound with the resin 3 so that there occurs no direct bonding therein, and in the case that there occurs generation of broken pieces due to wear of the material 1 during polishing operation the broken pieces are speedily crushed into separate fillers so that they do not act as big foreign matters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an abrasive. More specifically, the present invention relates to an abrasive material for polishing a semiconductor using free abrasive grains.

[0002]

2. Description of the Related Art Semiconductors tend to have higher performance year after year.
In order to manufacture a high-performance semiconductor, the most important issue is how to reduce the area and form as many circuits in the limited area.

As a method for solving this problem, a large number of circuits are formed in a limited area by narrowing circuit wirings, and a large number of circuits are formed without increasing the area by further layering the circuits. Means are used.

An insulating film for interrupting electricity is formed between each layer of the multilayer circuit, and an upper circuit is formed thereon. Of course, the formed insulating film has a lower circuit. The surface of the insulating film is not flat because of the irregularities remaining, but some irregularities remain. When a circuit is formed on the lower surface 41 having such irregularities,
As shown in FIG. 5, disconnection 43 is likely to occur in the upper wiring 42, which is not preferable. Further, regarding the exposure technique used in forming the wiring pattern, the use of a high-resolution technique to form a circuit pattern composed of fine wiring and the like inevitably narrows the focused range, but unevenness remains. If this is not the case, a part that is out of focus is generated, and a circuit pattern cannot be formed.

[0005] For these reasons, in the process of manufacturing a semiconductor, it is essential to have a step of eliminating irregularities on the surface on which a circuit is formed and flattening it. The planarization technology that has been conventionally used is a method of coating an interlayer insulating film made of an insulator between layers for forming a circuit so as to mitigate irregularities generated by the circuit and lower layers when forming the circuit. However, with the improvement in the precision of semiconductors, the flatness obtained by these conventional techniques became insufficient, and the wiring width was 0.3 μm,
The limit is about five layers. However, the production of a higher-performance semiconductor is essential, and accordingly, means for obtaining a better flatness has been required.

The method that has attracted attention is CMP (Chemical M).
The principle is the same as that of a so-called polishing process.
As shown in FIG. 1, a polishing material 31 made of a polishing pad or a polishing cloth is attached to a surface plate 32 made of a flat plate, etc. This is a method of removing irregularities by removing the surface of the object to be polished by rubbing the two while supplying the abrasive 34.

[0007] Since CMP is essentially a mechanical surface removal process, it has an excellent ability to preferentially remove and flatten surface protrusions as compared with other methods, and is currently used in many semiconductor manufacturing processes. Has been applied.

Although there are many factors affecting the CMP process, the most important factor is the characteristics of the abrasive. The polishing material used in the CMP process is generally a polishing pad made of a resin such as polyurethane.This is characterized by its higher hardness compared to polishing materials such as polishing pads and polishing cloths used for other purposes. Can be

The reason for this is to enhance the preferential removal capability of the projections. As shown in FIG. 2A, for example, when CMP is performed using a soft abrasive 11, the abrasive is soft. Therefore, it follows irregularities on the semiconductor surface 13. For this reason, the ability to preferentially remove the protrusions required for the CMP process cannot be obtained, and as a result, excellent flatness on the polished semiconductor surface 14 cannot be obtained. On the other hand, as shown in FIG. 2B, when the hard abrasive 12 is used, the ability to follow the unevenness is low, so that the convex portion is preferentially removed, and as a result, excellent flatness is obtained.

[0010]

As described above, the conventional CMP
The process uses a polishing pad made of, for example, a foamed polyurethane resin having a thickness of about 1.5 mm on a disk-shaped surface plate made of cast iron or ceramic, and uses a fine abrasive such as silicon dioxide as an abrasive having a surface removing action. A method of processing using a slurry in which particles are dispersed in a solution is used.

However, a hard polishing pad has a disadvantage that the polishing rate is lower than that of a soft polishing material. As shown in FIG. 3, the processing principle of the polishing process using the abrasive and the free abrasive grains is such that the free abrasive grains 25 supplied between the abrasive 21 and the workpiece 26 have pores existing on the surface of the abrasive. Free abrasive grains 2 held in the gap by applying a motion such as rotation to the abrasive 21 or the object 26 to be polished,
Processing is performed by a mechanism 5 for removing the surface of the object to be polished by rubbing the surface of the object to be polished. However, when trying to increase the hardness of the conventional polishing pad, the porosity must be reduced because the content of the resin is increased, so that the number of voids holding fine abrasive grains contained in the slurry is reduced,
The removal rate of the surface by the free abrasive grains is reduced, resulting in a lower polishing rate. The main purpose of the CMP process is to obtain the above-mentioned flatness, so that a hard polishing pad is used.However, because it is hard, the porosity is low, and the process is time-consuming due to the above-described reasons, and productivity is low. Low is a disadvantage.

Furthermore, with the improvement in the performance of semiconductors, the required flatness is becoming severer year by year, and as a result, the polishing rate is further reduced as a result of using a harder polishing pad, and as a result, the productivity is further reduced. There is a problem. The present invention has been made under such circumstances, and it is an object of the present invention to have a high porosity, high hardness, excellent flatness of an object to be polished thereby, and a high polishing rate. An object of the present invention is to provide an abrasive material characterized by the following.

[0013]

According to a first aspect of the present invention, there is provided an abrasive material comprising a soft resin and a filler.

The second invention is an abrasive characterized by having a porosity of 30% or more and a compression modulus of 1000 kg / cm ² , and the third invention is characterized in that the filler is granular. The fourth invention is an abrasive characterized in that the filler is cerium oxide, and the fifth invention is an abrasive In the sixth aspect, the ratio of the volume occupied by the filler is 10% or more of the apparent volume of the abrasive, and the sixth invention divides the volume occupied by the filler in the abrasive by the volume occupied by the resin. The value is 0.2 or more, and the seventh invention is characterized in that the resin in the abrasive is a polyurethane resin alone or a resin containing a polyurethane resin as one of the components. Is the thing, the departure of the younger Akira is characterized in that the thickness of the abrasive is 10 mm or more.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The abrasive of the present invention comprises a resin and a filler. It has already been mentioned that the abrasive which is excellent in flatness obtained due to high hardness and the processing speed is excellent because of high porosity is an excellent abrasive, but the abrasive of the present invention is compared with soft resin and resin. Then, a method of using a filler having a high hardness as a component of the abrasive was used.

[0016] In the conventional abrasives made of resin alone, the method of increasing the hardness is to increase the hardness by increasing the amount of the resin, or to increase the hardness by using a harder resin. I have been. However, although the latter method of increasing the hardness of the resin itself does not reduce the porosity, the processing speed after the start of use provides excellent results, but often causes scratches on the semiconductor surface during polishing, It cannot be applied to the processing of a semiconductor which is an expensive object to be polished. It is considered that the reason for this is that the portion of the resin surface other than the pores existing on the surface of the polishing material, which is the portion in contact with the object to be polished, is excessively hard because the hard resin is used.

On the other hand, the former method of increasing the amount of the resin does not cause scratches during polishing because the hardness of the resin itself is low, but has the disadvantage that the porosity is reduced and the processing speed is reduced. .

In the abrasive of the present invention, the hardness is increased by using a soft resin and adding a filler. Since the hardness of the filler is significantly higher than that of the resin, it is possible to obtain a higher hardness as a whole than an abrasive made of the resin alone. Therefore, if the porosity is the same, a high hardness can be obtained, and if the porosity is the same, a high porosity can be obtained.

Occurrence of scratches which may be caused by abrasives having high hardness can be avoided for the following reasons. The following two points can be considered as causes of scratches during polishing.
In other words, when the surface of the polishing material that is in direct contact with the workpiece is excessively hard, free abrasive grains supplied between the polishing material and the workpiece are pushed into the workpiece with an extremely strong force. The first cause of scratches, and the abrasive itself wears during the polishing process, but some of the abrasive fragments generated at this time are significantly larger than free abrasive grains Therefore, when the abrasive is excessively hard, giant and hard fragments rub against the object to be polished, which is a second cause of scratches.

On the other hand, as shown in FIG. 1, the abrasive 1 of the present invention is composed of a hard filler 2 and a soft resin 3, and the soft resin 3 has voids such as pores 4. Then, the supplied loose abrasive grains 5 are held in gaps existing on the surface, and the processing is performed by rubbing the surface of the object 6 to be polished. Here, the oblique lines indicate a porous structure having a void portion. In order to explain the processing principle, the pores 4 are illustrated with greater emphasis. Regarding the first cause described above, when free abrasive grains are present between the abrasive and the object to be polished, the loose abrasive grains are softened by the strong cushioning property of the soft resin, so that the pushing force is reduced, and Even if loose abrasive grains are present between the workpiece and the filler, the loose abrasive grains are not pressed into the workpiece by the cushioning property of the resin around the filler. There is no pushing with strong force. Regarding the second cause, in the abrasive of the present invention, the hard filler is bonded by the soft resin and does not directly bond. For this reason, even when the abrasive is worn out during the polishing process and fragments are generated, the fragments are quickly crushed and decomposed into a single filler, so that they do not act as hard and huge foreign substances, resulting in scratches There is nothing.

As described above, the abrasive used in the present invention does not cause any damage to the object to be polished because the filler is quickly crushed into the respective fillers even when the fragments fall off. Therefore, it is highly preferable that the single filler does not cause even slight damage even after being broken down into individual fillers from fragments of the abrasive generated during the polishing process. For this reason, it is more preferable to use a filler which does not easily damage the filler, and more specifically, a filler having a granular shape and a small particle diameter is preferable. More specifically, the average particle size is preferably 1.5 μm or less, more preferably 1 μm or less. Further, if the filler itself has a high self-crushing property and one particle of the filler which is crushed after falling off and crushes into smaller particles, it is more preferable that the filler is less likely to be damaged. For this reason, for example, cerium oxide is preferably used as the filler.

As described above, the abrasive of the present invention can easily obtain a high hardness due to the characteristics of the hard filler, and thus easily obtain a sufficient porosity for obtaining a high processing speed while having a high hardness. The soft resin exhibits excellent cushioning properties on the surface in direct contact with the material to be polished and does not cause scratches. Specifically, it is extremely suitable for flattening a semiconductor.
The porosity, which indicates the ratio of voids to the apparent volume of the abrasive, is 30% or more, and the compression modulus is 1000 kg / cm ^2.
An abrasive having the above physical properties can be obtained. An abrasive having a porosity of 30% or more has an extremely excellent polishing rate because there are sufficient voids to hold the supplied free abrasive grains. Also, an abrasive having a compression modulus of 1000 kg / cm ² or more does not easily follow irregularities on the semiconductor surface during polishing, so that it has excellent preferential removal capability for convex portions and very good flatness can be obtained. This property, which was difficult to satisfy at the same time with the conventional abrasive, can be satisfied at the same time with the abrasive of the present invention. The compression modulus referred to herein is a ratio described in JIS K7220, which is a ratio of a compressive stress when a compression test is performed by applying an external force to a material and a strain of the material corresponding thereto. In summary, it is the force required to compress the material.

In the abrasive of the present invention, the volume occupied by the filler is preferably at least 10% of the apparent volume of the abrasive. If the volume occupied by the filler is 10% or more,
An abrasive having a high hardness and a high porosity can be easily obtained, and by selecting an appropriate filler and resin, and an appropriate compounding amount of both companies, for example, a porosity of 40% and a compression elasticity of 3000 kg / cm ² can be obtained. As described above, an extremely high porosity and hard abrasive can be obtained, and a large-scale and inexpensive production of an extremely high-performance semiconductor becomes possible.

In the abrasive of the present invention, the value obtained by dividing the volume occupied by the filler by the volume occupied by the resin is preferably 0.2 or more. The abrasive whose numerical value is 0.2 or more has an appropriate brittleness of the abrasive. For this reason, the surface of the abrasive material is worn little by little at the time of the polishing process, and a new surface appears from the inside. For this reason, it is possible to suppress the occurrence of a so-called clogging phenomenon that causes polishing debris generated during the polishing process to adhere to the surface of the abrasive material, lowering the porosity and significantly reducing the polishing rate. For this reason, there is a new advantage that processing for a long time can be stably performed.

In the abrasive of the present invention, the resin preferably contains a polyurethane resin alone or a polyurethane resin as one of the components. Since the polyurethane resin is a resin having excellent elasticity, the abrasive of the present invention containing the polyurethane resin exhibits excellent cushioning properties on the surface directly in contact with the material to be polished, so that the object to be polished is scratched. It is much easier to prevent such a situation.

Further, since the conventional abrasive has a low hardness and easily undergoes elastic deformation, an extremely thin abrasive having a thickness of about 1 to 2 mm has been used. This is because if the hardness of the material is constant, the larger the thickness, the greater the amount of deformation when pressing the object to be polished, making it difficult to obtain flatness. However, when the thickness is at most 1 to 2 mm, the usable period is extremely short, and there is a problem that the replacement frequency is extremely high. However, since the abrasive of the present invention has a high hardness and a small deformation when pressing an object to be polished, it can be used in a thicker size than a conventional abrasive. Specifically, since a sufficient flatness can be obtained even with a thickness of 10 mm or more, there is a new advantage that the abrasive can be used for a long time several times longer than that of a conventional abrasive.

[0027]

EXAMPLES Table 1 shows the physical properties of the abrasive of the present invention and the conventionally used abrasive and the results of flattening the semiconductor by polishing.

[Table 1] The compression modulus was measured by the method described in JIS K7220. However, since it was difficult to prepare a test piece having the dimensions described, the height, width, and length of the dimensions were changed to 30 mm, 10 mm, and 10 mm, respectively. Regarding the flatness, processing speed, presence / absence of scratches, and usable period, excellent, good, and acceptable were indicated by symbols ◎, ○, and Δ, respectively.

As is clear from Table 1, the abrasive of the present invention can simultaneously obtain high hardness and porosity as compared with the conventional abrasive, so that the semiconductor is flattened by polishing to obtain an excellent flatness and high porosity. Processing speed can be obtained.

[0029]

According to the present invention, it is possible to obtain a high flatness at a high processing speed, which could not be achieved conventionally in a semiconductor manufacturing process. For this reason, a high-performance semiconductor can be manufactured in large quantities at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a polishing material of the present invention and a polishing process using the polishing material.

FIG. 2 is an explanatory diagram of a flattening operation of a semiconductor surface using polishing.

FIG. 3 is an explanatory diagram of the principle of polishing using an abrasive and loose abrasive grains.

FIG. 4 is an explanatory diagram of a semiconductor polishing method using CMP.

FIG. 5 is an explanatory diagram of disconnection in circuit wiring.

[Explanation of symbols]

 1: abrasive material 2: filler material 3: soft resin 4: pores 5: loose abrasive 6: polished object 11: soft abrasive material 12: hard abrasive material 13: semiconductor surface 14: semiconductor surface after polishing 21 : Abrasive 24: Pores 25: Free abrasive 26: Polished object 31: Abrasive 32: Surface plate 33: Semiconductor wafer 34: Abrasive 35: Wafer holder 41: Lower surface 42: Upper layer wiring 43: Disconnection

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/304 622 H01L 21/304 622A F term (Reference) 3C058 AA07 AA09 AC04 CB01 CB03 CB10 DA17 3C063 AA02 AB07 BA02 BB01 BB07 BC03 BC09 EE10 4F071 AA53 AB18 AD02 AE17 AF14 DA08 DA17 4J002 CK021 DE096 FD016 GT00

Claims (8)

[Claims] 1. A polishing material which is polished by rubbing the surface of an object to be polished while supplying free abrasive grains, wherein the polishing material comprises a soft resin and a filler. 2. The abrasive according to claim 1, wherein the porosity is 30% or more, and the compression modulus is 1000 kg / cm ² or more. 3. The filler is granular and has an average particle diameter of 1.
3. The abrasive according to claim 1, wherein said abrasive is 5 μm or less. 4. The abrasive according to claim 1, wherein the filler is cerium oxide. 5. The abrasive according to claim 1, wherein the proportion of the volume occupied by the filler in the abrasive is at least 10% of the apparent volume of the abrasive. 6. The abrasive according to claim 1, wherein the value obtained by dividing the volume occupied by the filler in the abrasive by the volume occupied by the resin is 0.2 or more. 7. The abrasive according to claim 1, wherein the resin is a polyurethane resin alone or a resin containing a polyurethane resin as one of the components.
7. The abrasive according to 5 or 6. 8. A polishing material, wherein the thickness of the polishing material is 10 mm.
Claims 1, 2, 3, 4,
The abrasive according to 5, 6, and 7.