JPH0811050A - Polishing cloth and method of manufacturing semiconductor device using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] For polishing for flattening semiconductor wafers, etc., it is possible to follow the local film thickness variation of the material to be polished and to polish only the upper part of the step and to facilitate such structure. Provided is a technique relating to a polishing cloth that can be formed on a substrate. A polishing cloth used for flattening a flattened material 31 such as a semiconductor substrate wafer having a step, the polishing surface having a partially different surface hardness (soft portion 17,
The portion having the hard portion 18) and having a partially different surface hardness is formed by phase separation of the resin constituting the surface portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing cloth and a method for manufacturing a semiconductor device using the polishing cloth. The present invention is, for example,
It can be used for forming an interlayer insulating film applied to the field of manufacturing a semiconductor device, and particularly can be used for favorably forming a planarizing insulating film by so-called polishing.

[0002]

2. Description of the Related Art The field of application of polishing technology is wide, and it can be used, for example, to flatten the unevenness formed on a substrate such as a semiconductor substrate during the manufacture of a semiconductor device (see, for example, Japanese Patent Application Laid-Open No. 2000-242242). (See Sho 60-39835).

On the other hand, in the field of semiconductor devices, the capacity of devices is increasing, but in order to reduce the chip area as much as possible to increase the capacity, a multilayer wiring technique is required.
In this multilayer wiring technique, it is important to flatten the base in order to prevent disconnection of the multilayer wiring.

A polishing technique is known as a flattening technique. As this type, in recent years, a mechanochemical polishing technique using fine particles of silicon oxide in a basic solution has been reported.

[0005]

However, conventionally, a polishing cloth used for polishing is generally formed by using a polyurethane resin, and it is known that the shape after polishing greatly varies depending on the hardness of the resin. There is. For example, as shown in FIG. 2, a step in which a second interlayer insulating film 13 is formed on a wafer in which an Al wiring layer 12 is formed on a semiconductor substrate 11 in which an interlayer insulating film such as a silicon oxide film is formed is formed. Consider the case of polishing an existing wafer.

When a relatively soft polishing cloth is used, for example, as shown in FIG.
In the case where the soft pad is formed by arranging 5a, the local film thickness variation of the semiconductor substrate 11 is followed as shown in the figure,
The polishing cloth 15a is deformed by the pressing pressure and enters not only the upper part of the step but also the bottom part of the step, so that the polishing of the both proceeds and the flatness depends on the step shape.

On the other hand, when a hard polishing pad 15b is used to form a hard pad, as shown in FIG.
Since b is not deformed, the bottom of the step is not polished, but it cannot follow the local fluctuation of the film thickness of the semiconductor substrate 11, so that the flatness after polishing is deteriorated.

Further, in order to avoid the above-mentioned problem, as shown in FIG. 4, a soft material 15c is used for the lower layer, for example, an elastic substance such as soft polyurethane, and a hard polyurethane, which is the hard material 15d, is used for the upper layer. A polishing cloth has been proposed, but it is difficult to optimize the hardness of both layers, and even if it is optimized, the polishing rate at the upper part of the step is extremely high, and good flatness cannot be obtained.

Therefore, in order to follow the local film thickness fluctuation of the semiconductor substrate and to polish only the upper part of the step, as shown in FIG. 5, the elastic soft material 15c is formed in the lower layer.
By using a soft polyurethane or the like which is the above, and forming a polishing layer made of the hard material 15d in an island shape on this upper layer,
A method for improving the above problems has been proposed. This method has made it possible to solve the above problems.

However, in this technique, for example, a hard polyurethane is formed on a soft polyurethane and then processed into an island shape, so that the polishing cloth forming process is very complicated.
Therefore, a technique for easily forming the polishing cloth having the above structure is desired.

[0011]

The invention according to claim 1 of the present application is a polishing cloth used for flattening a material to be flattened having a step, the polishing surface having a partially different surface hardness. And a portion having a different surface hardness, which is formed by phase separation of a resin constituting a surface portion, which achieves the above object. Is.

The invention according to claim 2 of the present application is the polishing cloth according to claim 1, characterized in that a graft resin is used as the resin constituting the surface portion, and thereby the above object is achieved. is there.

The invention according to claim 3 of the present application is the polishing cloth according to claim 1, characterized in that an incompatible resin is used as the resin constituting the surface portion, thereby achieving the above object. It is a thing.

The invention according to claim 4 of the present application is characterized in that a soft material is used for at least the lower layer and a resin partially having a layer having a hardness higher than that of the lower layer is used for the upper layer. The polishing cloth according to any one of 3 above, which achieves the above object.

According to a fifth aspect of the present invention, in a method of manufacturing a semiconductor device, which comprises a flattening insulating film forming step of forming a flattening insulating film on a substrate having a step, the polishing surface partially has surface hardness. Characterized in that the portion having a different surface hardness is subjected to polishing using a polishing cloth that is formed by phase separation of the resin that constitutes the surface portion, and planarized. A method of manufacturing a semiconductor device, which achieves the above object.

The invention according to claim 6 of the present application is the method for manufacturing a semiconductor device according to claim 5, characterized in that a polishing cloth using a graft resin is used as the resin constituting the surface portion. This achieves the above object.

The invention according to claim 7 of the present application is the method for manufacturing a semiconductor device according to claim 5, characterized in that a polishing cloth using an incompatible resin as a resin constituting the surface portion is used. This achieves the above-mentioned object.

The invention of claim 8 of the present application is characterized in that a soft material is used for at least the lower layer, and an abrasive cloth using a resin partially having a layer having a hardness higher than that of the lower layer is used for the upper layer. A method of manufacturing a semiconductor device according to any one of claims 5 to 7, wherein the above object is achieved.

In order to achieve the above-mentioned object, the present inventor has
In the process of earnestly studying, a method of partially forming a hard resin layer on a soft resin was found, and the present invention was completed. This method is a method of forming a part having a different hardness (for example, a hard part) by phase separation.

In the present invention, for example, in the step of polishing an Al wiring interlayer insulating film, a resin having a two-layer structure in which an upper resin layer is formed by using a graft block polymer such as a styrene-butadiene block polymer on a lower soft polyurethane resin. By carrying out the method using the cloth, it is possible to polish the film thickness variation of the semiconductor substrate and only the convex portion of the underlying step.

[0021]

The polishing cloth proposed by the present invention follows the film thickness variation of the step base due to the lower soft layer, and the resin layer formed on the upper layer has a hard portion, whereby only the upper part of the step can be polished. Since the portions having different hardnesses (hard portions in the soft material) are formed by phase separation of the surface portion (polishing portion) resin, this structure can be easily obtained. For example, in the graft block polymer formed in the upper layer, two or more kinds of monomers form a long chain length of each structural unit, which has a structure in which they are linked by a chemical bond and each polymer component is independently aggregated. , Phase-separation is performed to form a multilayer structure, and a portion having a different surface hardness is partially formed by itself.

Therefore, for example, when a styrene-butadiene resin is selected as the upper layer resin, a styrene phase having high hardness can be formed in the butadiene phase of the soft layer by optimizing the mixing ratio. Therefore, this styrene phase makes it possible to polish only the upper part of the step, and by using this, it is possible to provide a good polishing process for the interlayer insulating film.

[0023]

Embodiments of the present invention will be described below. However, as a matter of course, the present invention is not limited to the following examples.

Prior to the description of the specific polishing process, an example of the structure of the polishing apparatus used in each of the following examples for carrying out the present invention will be described with reference to FIG.

Although a single-wafer polishing apparatus is taken as the polishing apparatus here, the configuration of the wafer mounting and the devising method of use are not particularly limited. In FIG. 6, a wafer 25 is fixed to a wafer holding sample table (carrier) 26 by a vacuum chuck method. On the other hand, a pad 28 is fixed on the polishing plate (platen) 23, and the slurry 22 is supplied thereto from the slurry introducing pipe 21. During the polishing (polishing) process, by rotating the upper wafer holding sample stage rotating shaft 27 and the polishing plate rotating shaft 24, the uniformity of the polishing within the wafer surface is ensured.

The pressing pressure of the wafer during polishing is controlled by controlling the force applied to the wafer holding sample table (carrier) 26.

Next, a method of forming a polishing pad used for carrying out the present invention will be described in each example. For example, for the polyurethane prepared by adding ethylene glycol as the diol component and adipic acid as the dicarboxylic acid as the lower resin layer, 4,4-methylenediphenyl diisocyanate and ethylene glycol as the chain extender, A desired resin can be produced by adding trifunctional or trifunctional triisocyanate obtained by reacting glycerne with hexamethylene diisocyanate and the like to carry out a crosslinking reaction.

Thereafter, a styrene-butadiene resin was used as the upper layer resin. By optimizing the mixing ratio to 2: 8, since the upper layer resin is incompatible with the lower layer resin, it is possible to form a styrene phase having high hardness in the butadiene phase of the soft layer by phase separation. Therefore, a desired polishing cloth can be prepared.

Embodiment 1 This embodiment is an implementation of the invention of claim 1, particularly claim 2 of the present application. In this embodiment, a polishing cloth is prepared by using a graft resin as the phase separation resin and is applied to the polishing process of the Al wiring interlayer insulating film.

As shown in FIG. 7A, after forming an interlayer insulating film 32 and an Al wiring layer 33 on a semiconductor substrate 31 made of silicon or the like, the Al wiring layer 33 is processed by etching using a resist process. . After that, a wafer having an interlayer insulating film 34 formed thereon was prepared.

Then, as shown in FIG. 7B, an excessive silicon oxide film on the step difference such as SiO ₂ which is the interlayer insulating film 34 is removed by polishing. The polishing conditions were as described above.

The polishing cloth used in this example was formed as follows. Polyurethane prepared by adding ethylene glycol as a diol component and adipic acid as a dicarboxylic acid as a lower resin layer and ethylene glycol as a chain extender with 4,4-methylenediphenyldiisocyanate was used as a lower resin layer. Glycerin and hexamethylene The cross-linking reaction was performed by adding tri- or more-functional triisocyanate obtained by reacting diisocyanate or the like to produce a desired lower layer resin.

Thereafter, a styrene-butadiene resin was used as the upper layer resin. Since the styrene phase can make the butadiene phase incompatible, it is possible to form a styrene phase having high hardness in the butadiene phase of the soft layer by optimizing the mixing ratio, for example, 2: 8. A desired polishing cloth can be prepared. That is, as schematically shown in FIG. 1, a polishing cloth having a form in which a butadiene phase which is a soft part 17 which is phase-separated and a hard part 18 which is phase-separated are formed on a urethane resin which is a lower layer resin 16 is formed. can get.

Using this polishing cloth, the insulating film 3 was formed under the following conditions.
4 (SiO ₂ ) was polished.

SiO ₂ Polish Condition Rotational Speed of Polishing Plate 23: 37 rpm Rotational Speed of Wafer Holding Sample Table 26: 17 rpm Polishing Pressure: 5.5 × 10 ³ Pa Slurry Flow Rate: 225 ml / l Slurry Component: Polishing Fine Particles KOH Water

After the polishing is completed, the slurry is removed by washing with water to complete the formation of the interlayer insulating film.

The formation of the interlayer film was carried out here by using a means using an organic silicon compound as a Si source gas, particularly tetraethoxysilane was used as a Si raw material, but here, for example, another organic metal alkoxide is used. Can be changed appropriately. Examples thereof include tetramethoxysilane and tetraisopropoxysilane.

Here, a styrene-butadiene resin is used as the graft polymer, but any other suitable graft polymer can be used. For example, styrene-
Isoprene type, polybutadiene-acrylonitrile type,
Examples thereof include propylene-ethylene type and ethylene-nylon type.

According to the present embodiment, in the step of polishing the interlayer insulating film using the above-mentioned polishing cloth, after forming the soft phase in the lower layer and using the phase separation resin in the upper layer, a local film on the semiconductor substrate is formed. It was possible to provide a polishing cloth which can follow the thickness variation and can satisfactorily polish only the upper part of the step. Further, as a result, it is possible to provide a method for manufacturing a semiconductor device capable of flattening an excellent interlayer insulating film.

Embodiment 2 This embodiment is an implementation of the invention of claim 1, particularly claim 3 of the present application. This example is a case where a polishing cloth is made of an incompatible resin as a phase separation resin and applied to a polishing process of an Al wiring interlayer insulating film.

As shown in FIG. 7A, after forming an interlayer insulating film 32 and an Al wiring layer 33 on a semiconductor substrate 31 made of silicon or the like, the Al wiring layer 33 is processed by etching using a resist process. . After that, a wafer having an interlayer insulating film 34 formed thereon was prepared.

Then, as shown in FIG. 7B, an excess silicon oxide film on the step such as SiO ₂ which is the interlayer insulating film 34 is removed by polishing. The polishing conditions were as described above.

The polishing cloth used in this example was formed as follows. That is, as the lower resin layer, as in Example 1,
A polyol formed by using ethylene glycol as a diol component and adipic acid as a dicarboxylic acid is
Regarding polyurethane prepared by adding 4-methylenediphenyl diisocyanate and ethylene glycol as a chain extender, trifunctional or more triisocyanate obtained by reacting glycerin and hexamethylene diisocyanate or the like is added to the polyurethane, thereby performing a crosslinking reaction, A desired lower layer resin was prepared.

Then, in this example, polyvinyl chloride and polybutadiene resin were used as the upper layer resin. Since polyvinyl chloride and polybutadiene-based resin are mutually incompatible resins, the mixing ratio is optimized, for example, 8: 2 here.
By optimizing this, it becomes possible to form a polyvinyl chloride phase having a high hardness in the polybutadiene phase of the soft layer, and a desired polishing cloth can be produced.

Using this polishing cloth, the insulating film 3 was formed under the following conditions.
1 (SiO ₂ ) was polished.

SiO ₂ Polish Condition Rotational Speed of Polishing Plate 23: 37 rpm Rotational Speed of Wafer Holding Sample Stage 26: 17 rpm Polishing Pressure: 5.5 × 10 ³ Pa Slurry Flow Rate: 225 ml / l Slurry Component: Polishing Fine Particles KOH Water

After the polishing is completed, the slurry is removed by washing with water to complete the formation of the interlayer insulating film.

Here, the polyvinyl chloride-butadiene resin was used as the incompatible polymer, but any incompatible polymer can be appropriately changed. For example, polystyrene-polymethylmethacrylate, polystyrene-polyethylene, etc. may be mentioned.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a conceptual diagram of prior art (a).

FIG. 3 is a conceptual diagram of a conventional technique (b).

FIG. 4 is a conceptual diagram of prior art (c).

FIG. 5 is a conceptual diagram of prior art (d).

FIG. 6 is a conceptual diagram of an experimental device of an example.

FIG. 7 is a cross-sectional view of an object to be polished of an example.

[Explanation of symbols]

 10, 31 Semiconductor substrate 11, 32 Silicon oxide film 12, 33 Al wiring layer 13, 34 Silicon oxide film 21 Slurry introducing pipe 22 Slurry 23 Polishing plate 24 Polishing plate rotating shaft 25 Wafer 26 Wafer holding table 27 Wafer holding table Rotating shaft 28 Polishing cloth (pad)

Claims (8)

[Claims] 1. A polishing cloth used for flattening a material to be flattened having a step, wherein a polishing surface has a part having a different surface hardness, and the part having a different surface hardness is A polishing cloth formed by phase separation of a resin forming a surface portion. 2. The polishing cloth according to claim 1, wherein a graft resin is used as the resin constituting the surface portion. 3. The polishing cloth according to claim 1, wherein an incompatible resin is used as the resin forming the surface portion. 4. The polishing according to claim 1, wherein at least the lower layer is made of a soft material and the upper layer is made of a resin partially having a layer having a hardness higher than that of the lower layer. cloth. 5. A method of manufacturing a semiconductor device, comprising a flattening insulating film forming step of forming a flattening insulating film on a substrate having steps, wherein a polished surface partially has a portion having a different surface hardness. A method of manufacturing a semiconductor device, characterized in that a portion having a partially different surface hardness is polished and flattened by using a polishing cloth formed by phase separation of a resin forming a surface portion. 6. The method for manufacturing a semiconductor device according to claim 5, wherein a polishing cloth using a graft resin is used as the resin forming the surface portion. 7. The method of manufacturing a semiconductor device according to claim 5, wherein a polishing cloth using an incompatible resin as a resin forming the surface portion is used. 8. A polishing cloth using a soft material for at least the lower layer and a resin for the upper layer which partially has a layer having a hardness higher than that of the lower layer.
A method for manufacturing a semiconductor device according to any one of 1.