JPH10156707A - Machining method and its device, and flattening method in semiconductor process using this machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make dry machining possible so as to dispense with slurry waste disposal and chemical resistance treatment of a device by forming pellet of powder that is softer than a workpiece and can generate solid phase reaction to the workpiece, and sticking this pellet to a polishing base to polish the work piece with the powder as abrasive grains. SOLUTION: In the case of executing this method to a dry polishing wheel for a silicon wafer or the like, fine grain of SiO2 , CeO2 , or the like which is softer powder than silicon dioxide (SiO2 ) to be flattened is used as powder to be pellet. Pellet 1 formed of powder used as abrasive grains is arranged in segment shape on the polishing face of a polishing base 2, and the polishing base 2 is stuck to a wheel base metal 3. Accordingly, even though there is a large swell on the wafer face, the polished surface of a workpiece 10, this swell can be absorbed by deformation of the soft polishing base 2, so that uniform polishing force is applied to the wafer, and the whole surface can be flattened satistactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method and apparatus, and a flattening method in a semiconductor process using the processing method. INDUSTRIAL APPLICABILITY The present invention utilizes a novel polishing technique, and can be used for various processing methods using polishing, and can be used as a processing apparatus in that case. Further, it can be suitably used as a planarization method in manufacturing various semiconductor devices. The present invention typically uses, for example, in a semiconductor process, pellets formed by hot pressing together with a very small amount of a binder as fine particles that are softer than the workpiece and capable of causing a solid-phase reaction, using a base such as soft urethane. A wheel type tool for dry polishing is adhered in a segment shape, and using the tool, a global flattening method and its apparatus can be embodied as a technology enabling a dry process.

[0002]

2. Description of the Related Art Conventionally, processing techniques using polishing techniques have been used in various fields. For example, in a semiconductor process of manufacturing an electronic material such as a semiconductor device, it is used as a technique for eliminating a step and flattening a surface. 2. Description of the Related Art A planarization technique in a semiconductor process is indispensable for preventing the occurrence of a break in a pattern when forming a wiring or other patterns, and is an important technique for obtaining a highly reliable product.

Conventionally, various CMP (chemical mechanical polishing) techniques have been typically developed as a so-called global flattening technique for flattening the entire surface of a semiconductor substrate or the like (or the entire surface of a region of interest). The device is commercially available and in use.

However, the processing method (processing principle) of the conventional CMP (chemical mechanical polishing) technology is as follows.
Both are based on wet polishing. That is, polishing in a wet state is performed using colloidal silica or the like in an alkaline solution such as KOH as free abrasive grains (hereinafter referred to as “slurry”). As a tool, for example, a polishing pad made of foamed polyurethane or the like is used, and polishing is performed with this slurry.

[0005] For this reason, the apparatus must of course have a configuration based on wet processing. For example, it is necessary to address problems inevitable in a wet process, such as sticking and contamination of slurry during or after processing. As described above, in the prior art, measures against such sticking, contamination, and the like of the slurry have become a serious problem.

Further, the disadvantages of using a wet slurry include not only the problem that the slurry itself becomes a contamination source and dust in a semiconductor process, but also the following disadvantages. That is, the disadvantages of wet processing include the following problems. It sticks to the place by drying. Even if it is washed as a liquid, it will settle down or accumulate in the form of sludge in the flow. Generally, it is necessary to use a solution of a strong alkali, a strong acid, or the like, so that the liquid contact portion of the apparatus is corroded. If scattered, it adheres to everywhere as a mist-like atmosphere.

[0007] Further, there are the following problems regarding cleaning after processing. That is, in the wet process, as in other processes in a normal clean room in a semiconductor process, the following is required to dry-in / dry-out (to be carried in in a dry state and to be carried out in a dry state). It becomes complicated. (1) A wet type washer is required (2) A dryer for drying out is required

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the wet process, and is basically a processing method and apparatus capable of performing processing in a dry process, and the processing method. It is an object of the present invention to provide a planarization method in a semiconductor process using the method, and thereby to provide a technique using a polishing method which has solved various problems associated with the above-mentioned wet process.

[0009]

According to a working method of the present invention, a powder which is softer than a workpiece and can generate a solid phase reaction with the workpiece is formed into pellets, and the pellets are attached to a polishing base. At least, the workpiece is polished using the powder as abrasive grains.

The processing apparatus according to the present invention includes a polishing base that is in contact with a surface to be polished of a workpiece, and the polishing base is softer than the workpiece and can cause a solid-phase reaction with the workpiece. The present invention is characterized in that a pellet formed by molding powder into a pellet is adhered, and the surface to be polished of the workpiece is polished using the powder as abrasive grains.

A flattening method in a semiconductor process according to the present invention is a flattening method in which a flattened surface is flattened by polishing in a semiconductor process. The flattening method is softer than the material of the flattened surface and is flattened. Forming a powder capable of causing a solid phase reaction with the surface material into pellets, attaching the pellets to a polishing base, and polishing the surface to be flattened using the powder as abrasive grains to perform flattening. It is characterized by the following.

[0012]

According to the above construction of the present invention, the powder is polished as abrasive grains by using a pellet formed by molding a powder that is softer than the workpiece and can cause a solid phase reaction with the workpiece. In this case, polishing is achieved by a dry solid phase reaction instead of a wet state. Since the powder used as the abrasive grains is in the form of pellets, the powder is repeatedly dropped off due to the friction during polishing, and the action as the abrasive grains is continued, so that good polishing is performed. Therefore, processing that solves problems associated with a wet process using a slurry can be realized. Since the processing is performed by directly contacting the solid abrasive particles having a high solid phase reactivity with the workpiece without intervening another liquid or the like, the processing efficiency can be increased. The dry process has its advantages, for example, the ability to maintain the cleanliness of the apparatus by performing air blowing in consideration of airflow and suction from the exhaust duct. And, because of the dry type and high processing efficiency, it is possible to reduce the size of tools and the like, and also possible to reduce the size of the entire apparatus. Contamination, and the post-processing washing load can be greatly reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, and specific embodiments will be described with reference to the drawings.

In the present invention, a powder which is softer than the workpiece and is capable of causing a solid phase reaction with the workpiece is used as the abrasive. The present invention allows the surface to be polished in a processing form substantially similar to conventional lapping and polishing, but is softer than the workpiece (equivalent softness or lower than the workpiece). The processing principle is completely different from that of the prior art in that abrasives are used, as long as they have softness, which may be, for example, mechanically soft. It is a method based on. This is an application of mechanochemical polishing known as a polishing method for sapphire, silicon or the like, but is completely different from the prior art in that it can be configured in a dry manner.

According to the present invention, for example, preferably, pellets formed by hot pressing together with an extremely small amount of a binder are used as abrasive grains, which powder is mechanically softer than the workpiece and can generate a solid phase reaction with the workpiece. By using a wheel-type tool adhered to a base such as soft urethane in a segment shape, the surface of the workpiece can be polished. For example, this embodiment can be suitably applied as a processing technique for globally removing a step of a wafer in a semiconductor process.

The basic working mechanism of the present invention will be described below. Here, with reference to FIG. 3, polishing of a typical example of silicon dioxide (SiO ₂ ) as an interlayer insulating film material of a semiconductor device will be described. FIG. 3 shows a workpiece 10A (S
i, SiO _{2 and} other workpieces. Here, SiO ₂ )
And abrasive grains (SiO ₂ or CeO) that can cause a solid-phase reaction with it.
_2nd class soft particles. Here, it is a diagram showing a contact model with CeO ₂ ).

As a powder softer than silicon dioxide (SiO ₂ ) forming an interlayer insulating film as the workpiece 10A, S
Fine particles such as iO ₂ and CeO ₂ are prepared. In any of these, the Vickers hardness of the bulk material is equal to or less than that of the interlayer insulating film material. Here, CeO ₂ fine particles are taken as an example of the abrasive grains 1A. When such a powder (abrasive 1A) is supplied in a dry manner, a high temperature and a high pressure are generated due to frictional energy at a local portion of the contact point, and a solid-phase reaction between the two occurs within a minute contact time, so that the minute reaction portion is subjected to friction. Polishing proceeds by being removed by the force. In FIG. 3, this small reaction portion is indicated by reference numeral B. This minute reaction portion B is removed, and polishing proceeds. Since the powder (abrasive 1A) is in the form of pellets, even if it falls off after exhibiting a polishing action, new powder (abrasive 1A) continues to be polished one after another and polishing continues. .

That is, in the present invention, since the powder formed into a pellet is used in this case, the fine powder particles fall off the pellet due to the frictional force, and new particles come into contact with each other one after another, thereby making the powder continuous. The polishing process proceeds.

First Embodiment FIG. 1 shows a processing apparatus according to a first embodiment. FIG. 1 particularly shows a dry polishing wheel used in the present embodiment. FIG. 1 (a) is a side sectional view, and FIG. 1 (b) is a lower surface (a surface in contact with a surface to be polished).

In the present embodiment, an interlayer insulating film (silicon dioxide film) of a semiconductor wafer, especially a silicon wafer
This shows polishing when flattening is performed. As the powder to be pelletized, silicon dioxide to be planarized (Si
Fine particles such as SiO ₂ and CeO ₂ which are softer than O ₂ ) can be employed. Here, fine particles of CeO ₂ which is a preferable abrasive powder are employed as pellets as described later. In FIG. 1, a pellet 1 formed of a powder (fine particle powder) used as an abrasive is arranged in a segment on the polishing surface of a polishing base 2 (see FIG. 1B). The pellets 1 are clearly shown in FIG. The polishing base 2 of this example is formed of urethane. The polishing base 2 in which the pellets 1 are arranged in a segment shape is attached to a wheel base 3 as shown in FIG.

The wheel base 3 has an opening forming a nozzle 4 at the center. The wheel base 3 is driven to rotate by being fixed to the main shaft 5. From the nozzle 4, dry air for cleaning or the like is jetted.

The size of the pellet 1 is adjusted to the size of the wafer-shaped chip to be flattened by polishing. As shown in FIG. 2, if the size of one chip on the surface to be polished is S,
The size of the pellet 1 is also substantially S. For example, 20
When a 20 mm chip is polished, a pellet 1 having a size of 20 mm is used.

In this embodiment, since the polishing base 2 made of flexible urethane is used, as shown in FIG. 2, large undulations occur on the wafer surface of the workpiece 10 during polishing, as shown in FIG. Even if there is, the undulation can be absorbed by the deformation of the soft polishing base 2. Therefore, a uniform polishing force is applied to the flattened wafer, which is the workpiece 10, and the entire surface can be satisfactorily flattened.

The hardness of the molded pellet 1 is softer than the wafer to be polished (equivalent to or softer than the silicon dioxide to be polished. Here, fine particles of CeO ₂ softer than silicon dioxide are employed). ), But is much harder in nature than the polishing base 2 made of urethane. For this reason, compared with the conventional wet polishing using a urethane foam polishing pad, the ability to remove the minute steps, that is, the flatness obtained by the polishing can be dramatically improved.

Next, the formation of the pellets 1 in this embodiment will be described. Here, the pellet 1 is manufactured by a hot press method.

The hot pressing method is to put powder in a mold,
This is a method of applying pressure simultaneously with heating and sintering, and this method itself has been conventionally used. With reference to FIG. 4, formation of the pellet 1 by the hot press method in the present embodiment will be described. FIG. 4 shows the configuration of the hot press apparatus used here. In FIG. 4, reference numeral 51 denotes a pellet forming die, 52 denotes a powder to be formed, 53 denotes an induction coil, which constitutes a heater, and 54 denotes a refractory.

Here, pellet molding by the hot press method is performed as follows. In molding, as a binder or a matrix necessary for solidifying the fine powder, for example, a resin material, for example,
Mix at 10% and perform molding at relatively low temperature and low pressure.

Here, since it is required that the formed pellets fall off due to friction and new particles appear one after another, the amount of the binder mixed is as low as possible, but the strength is such that the pellet is not broken by rotation or processing pressure. Required to have. As a preferred example, CeO having a high solid phase reactivity with SiO ₂ is used for polishing an interlayer insulating film as in this example.
₂ etc. are suitable.

For example, when a 0.5 μm CeO ₂ powder is formed into pellets, a phenol resin is used as a binder at 5% (by weight) and about 1 kgf / c.
It can be formed by hot pressing at about 300 ° C. and m ² . The pressure is indicated by an arrow in FIG.
This is performed by an induction coil 53 serving as a heater. The obtained pellet is adhered to the urethane base with, for example, an epoxy-based adhesive having the same hardness as that of the urethane base, whereby a polishing base with pellets can be manufactured.

At the time of processing, in order to stabilize the contact area contributing to the polishing, it is necessary to face the formed pellets once on a polishing machine as shown in FIG. It is preferred that That is, the facing of the molded pellet is performed, as shown in FIG. 5, by attaching the pellet 1 to the base 2 attached to the wheel base 3, and using the diamond cup wheel 6 on the wafer chuck table 7, Z
Facing is performed by operating the axis, the main axis and the table axis.

Next, the polishing in this embodiment will be described with reference to FIG. Here, polishing for planarizing an interlayer insulating film of a semiconductor wafer is shown. In the present embodiment, the processing is performed by a dry process to which the present invention is applied, so that the processing fluid flow path and the chemical resistant treatment as in the related art are unnecessary.

Referring to FIG. The polished wafer 10 is
The wafer is loaded onto the wafer chuck table 86 on the X-axis slide table 85 at the loading / unloading position 84 by the loader 82, the opening / closing shutter 87 is closed, and the processing chamber 88 is sealed.

The wafer 10 to be polished, which has been moved to the processing position 89 by the movement of the X axis 81, is rotated by the rotation of the wafer chuck table 86. At this time, a polishing wheel 12 (carrying the pellet 1 via the base 2) at a position opposed to the wafer 10 and attached to a rotating main spindle 11 is polished by the lowering of the Z-axis 13. The wafer is brought into contact with the wafer 10 and pressurized to perform polishing. During processing, a constant pressure mechanism (not shown) of the Z-axis 13 is applied so that the processing pressure becomes constant. Further, dry air is injected into the processing chamber 88 sealed by the nozzle 14 and the air blow nozzle 15, and is suctioned / discharged and removed from the exhaust duct 16 as an atmosphere containing fine reaction substances, fine particle powder, and the like generated by processing. . Reference numeral 17 denotes a bellows.

After the processing is completed, the wafer returns to the loading / unloading position 84 again, and after the opening / closing shutter 87 is opened, the unloader 83 unloads the wafer 10 to be polished.

The entire wafer chuck table 86 and the base 3 of the polishing wheel 12 have a structure in which cooling water whose temperature has been adjusted can be supplied from the outside in order to suppress the influence of heat generated by processing. Has become.

The number of rotations of the wafer 10 to be polished and the polishing wheel 12 during the processing and polishing is, for example, about 5 to 1 respectively.
At about 00 rpm and about 100 to 500 rpm, it is determined to be an appropriate value together with the pressurized pressure in consideration of the influence of heat.

According to the present embodiment, since dry processing is used, it is not necessary to dispose of the slurry or perform chemical treatment of the apparatus as in the case of wet processing. In addition, because of processing with a molded pellet having high hardness, the ability to remove steps is high. That is, processing with good flatness can be performed. Further, since the polishing base uses a flexible urethane base, there is little processing unevenness due to variations in the thickness of the wafer. In other words, by adopting a soft urethane base, the pellets are much harder than urethane,
The step can be efficiently removed. Therefore, processing with good uniformity is efficiently achieved.

Further, according to the present embodiment, since the solid abrasive particles having high solid phase reactivity directly contact the workpiece without intervening other liquids or the like, the processing efficiency is high. And,
Because of the dry type and high processing efficiency, the size of tools and the like can be reduced, and the size of the entire apparatus can be reduced. Furthermore, because of the dry processing, there is little contamination of the workpiece (in this case, the wafer), and the cleaning load in post-processing can be greatly reduced. Since it is a dry type, there is also an advantage that the cleanliness of the apparatus can be favorably maintained by air blowing and suction taking into account the air flow.

[0039]

According to the present invention, since dry processing is used, it is not necessary to dispose of the slurry or treat the equipment chemically, and since the processing is carried out using molded pellets having a high hardness, the ability to remove steps is high and good. It can perform smooth flattening. Since the solid abrasive particles having high solid phase reactivity are used to directly contact the workpiece without intervening other liquids, the processing efficiency is high. It is also possible to reduce the size of tools and the like and the size of the entire apparatus. Due to the dry processing, the contamination of the workpiece is small, and the washing load in the post-processing is small. Cleanliness can be maintained easily and well. In addition, it is easy to reduce the processing unevenness due to the thickness variation of the workpiece by making the polishing base a flexible base.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a processing apparatus according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory view at the time of processing according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating the principle of the processing technique of the present invention.

FIG. 4 is a diagram showing an apparatus for manufacturing pellets by a hot press method in Embodiment 1 of the present invention.

FIG. 5 is a diagram illustrating on-machine facing according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating a processing apparatus according to the first embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pellet, 2 ... Polishing base, 3 ... Wheel base, 4 ... Nozzle, 10 ... Workpiece (wafer).

Claims (3)

[Claims] 1. A powder, which is softer than a workpiece and is capable of causing a solid-phase reaction with the workpiece, is formed into pellets, and the pellets are adhered to a polishing base. A processing method characterized by polishing an object. 2. A polishing base, which is in contact with a surface to be polished of a workpiece, and a powder, which is softer than the workpiece and capable of causing a solid-phase reaction with the workpiece, is formed into pellets on the polishing base. A processing apparatus characterized in that the pellets thus formed are adhered and the surface to be polished of the workpiece is polished using the powder as abrasive grains. 3. A planarization method for planarizing a surface to be planarized by polishing in a semiconductor process, wherein the material is softer than the material of the surface to be planarized and can cause a solid-phase reaction with the material of the surface to be planarized. Flattening a semiconductor process by forming the powder into pellets, attaching the pellets to a polishing base, and polishing the surface to be flattened using the powder as abrasive grains. .