JPH10144652A - Method and apparatus for planarizing surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for planarizing a work, instead of a chemical mechanical polishing method which uses a slurry contg. metals causing the pollution or silica producing dusts. SOLUTION: An ice layer having a flat surface 14a is formed to fill up and cover a rough surface 13a of a work 10 and molten uniformly from its surface 14a while an etching liq. for chemically polishing the work 10 is fed on the surface 14a of the layer 14 such that the ice layer 14 melts to result in exposed parts which are removed one after another by the etching liq. until the surface 13a is made flat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for flattening a surface of an article, and more particularly, to a method for manufacturing a semiconductor device by eliminating a step on a surface of a semiconductor wafer in which components of the semiconductor device are incorporated. The present invention relates to a surface flattening method and apparatus suitable for flattening.

[0002]

2. Description of the Related Art One of the techniques for downsizing a semiconductor device such as an IC circuit is a multilayer wiring structure. In such a multilayer wiring structure, when a component part of a circuit is formed on a semiconductor wafer, an interlayer insulating film covering the component part is formed, and a new component part is formed on the interlayer insulating film. .

[0003] Photolithography technology is generally used to form the components. In this technique, the surface of the interlayer insulating film, which is the required pattern baking surface, has a step corresponding to the shape of the component formed thereunder. Therefore, the baking of the interlayer insulating film is performed prior to the pattern baking. It is necessary to make the surface smooth and to make it flat.

Conventionally, as a method of planarizing an interlayer insulating film on a semiconductor wafer, a slurry containing a chemical polishing agent and a physical polishing agent is supplied between a puff and a polishing surface, and mechanical polishing by puff polishing is performed. So-called chemical-mechanical polishing method (ch
emical mechanical polishing) was adopted.

[0005]

However, in this chemical mechanical polishing method, if any heavy metal or alkali metal contained as a component of the chemical polishing agent in the slurry remains on the surface to be polished, the residual metal Due to the problem of contamination, extremely rigorous washing is essential. Further, silica contained as a physical abrasive in the slurry causes dust, so that the chemical mechanical polishing method cannot be performed in a clean room.

[0006]

The present invention adopts the following constitution in order to solve the above points. <Structure> The surface flattening method according to the present invention is a surface flattening method for flattening an uneven surface of an article, after forming an ice layer having a flat surface that embeds the uneven surface and covers the uneven surface. While uniformly dissolving the ice layer from the surface, an etchant for chemically polishing the article is supplied to the surface of the ice layer, and a portion exposed from the ice layer as the ice layer melts is formed on the uneven surface. Are sequentially removed with an etchant until the surface becomes flat.

<Function> In the surface flattening method according to the present invention, for example, an ice layer obtained by solidifying a fluid such as water,
It acts as a protective layer for protecting the article surface from the etching action of the etchant. Therefore, as long as the surface is covered with the ice layer, the uneven surface of the article is not subjected to the etching action by the etchant. However, when the ice layer covering the uneven surface of the article is uniformly melted from the surface and a part of the article is exposed from the ice layer, only the exposed portion is etched by the etchant.
Therefore, with the melting of the ice layer, the convex portion of the article exposed from the ice layer is sequentially etched, and the part under the ice layer of the article is always protected, so that the surface of the article is sequentially flattened, The flattening ends when all the ice layers disappear.

[0008] In the surface flattening method of the present invention, without using a slurry containing components causing contamination and dust,
The etchant, in cooperation with the ice layer, sequentially removes portions exposed from the ice layer by its etching action. Therefore, there is no problem of polluting heavy metals or alkali metals contained in the slurry. In addition, since it is possible to carry out the process on a production line in a clean room without causing the problem of dust, the production line can be made more compact and more efficient.

<Structure> A flattening device according to the present invention is a device for flattening an uneven surface of an article, comprising: a turntable for holding the article on a surface opposite to the uneven surface of the article; Means for supplying water to the uneven surface of the article, and a flat surface that embeds the uneven surface and covers the uneven surface by freezing the water while being uniformly spread on the uneven surface by rotating the turntable. Cooling means for forming an ice layer;
Means for pressing a frozen body of an etchant for chemically polishing the uneven surface while rotating the turntable against the surface of the ice layer.

<Operation> In the flattening device according to the present invention, when the means for supplying water supplies water onto the uneven surface of the article while the article is rotated on the turntable, the water on the uneven surface is Due to the centrifugal force caused by the rotation, the article is uniformly spread on the uneven surface of the article so that the surface becomes flat. The water layer forms an ice layer that buries the uneven surface by being cooled by the cooling means.

[0011] When a frozen body of the etching solution is pressed against the surface of the ice layer by a pressing means in a state where the turntable is rotated, the frozen body and the ice layer are uniformly formed by frictional heat caused by mutual sliding. Start to melt. Due to the thawing of the frozen body, the etching solution as the thawing solution is appropriately supplied to the surface of the ice layer. On the other hand, the melting of the ice layer partially exposes the protrusions of the article from the surface of the ice layer, and since the exposed portion is not protected by the ice layer from being etched,
It is sequentially etched.

Therefore, by the mutual movement of the frozen body and the ice layer, the appropriate supply of the etching solution and the uniform melting of the ice layer can be simultaneously performed, thereby making the flattening method of the present invention relatively easy. And it can be implemented with high accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a process diagram showing an example in which the planarization method according to the present invention is applied to the planarization of a semiconductor wafer provided with a silicon oxide film.

FIG. 1A shows a semiconductor wafer 10 made of, for example, a silicon substrate. On this semiconductor wafer 10, an interlayer insulating film 11 made of, for example, silicon oxide laminated by a vapor phase growth method is shown. , A metal wiring 12 is formed. The metal wiring 12 is generally formed using a technique of sputtering, lithography, and dry etching of a metal material such as aluminum.

For example, an upper circuit such as another wiring is formed on the metal wiring 12 to realize a multilayer wiring structure.
3 is formed. As the interlayer insulating film 13, an insulating material such as silicon oxide (BPSG) containing boron and phosphorus, which exhibits fluidity by heat treatment and easily causes smoothing, is used. However, as shown in the figure, the surface 13 a of the interlayer insulating film 13 corresponds to the lower metal wiring 12.
Indicates a wavy shape.

The surface of the interlayer insulating film 13, that is, the uneven surface 1
Since 3a is a pattern transfer surface in lithography for forming an upper layer circuit, the surface 13a of the interlayer insulating film 13 is flattened in order to enable precise pattern transfer.

To planarize the interlayer insulating film 13, FIG.
As shown in (B), an ice layer 14 is formed to fill the uneven surface 13a of the interlayer insulating film 13 and to cover the uneven surface 13a. The ice layer 14 has a flat surface 14a. This ice layer 14 can be formed by freezing pure water. In addition, for adjusting the freezing point, which is the solidification temperature of the pure water, the pure water may contain, for example, an organic solvent. As the organic solvent, a material that does not cause contamination of the semiconductor is appropriately selected.

Next, the ice layer 14 is uniformly melted from its surface 14a while maintaining the flatness. Further, an etching solution such as a 0.1 to 10% hydrofluoric acid solution for chemically etching the interlayer insulating film 13 made of silicon oxide is supplied to the surface 14 a of the ice layer 14.

As the melting of the ice layer 14 progresses, FIG.
As shown in FIG. 2C, when the convex portion of the uneven surface 13a of the interlayer insulating film 13 is partially exposed from the surface 14a of the ice layer 14, the exposed portion is supplied to the surface 14a of the ice layer 14 by the etching solution. Are sequentially removed. On the other hand, the portion of the interlayer insulating film 13 below the ice layer 14 is prevented from being in contact with the etchant by the ice layer. Therefore,
The concave portion under the ice layer 14 on the uneven surface 13a of the interlayer insulating film 13 is protected from the etching solution by the ice layer 14,
Since the convex portions of the uneven surface 13a are sequentially etched, the surface 13a of the interlayer insulating film 13 is flattened.

FIG. 1 (C) shows that a frozen body 15 of the etching solution is used to uniformly melt the ice layer 14 and supply an appropriate etching solution to the surface 14a of the ice layer 14. 14 shows an example of sliding relatively on the surface 14a of the surface 14a. The frozen body 15 is relatively slid on the flat lower surface 15 a on the flat surface 14 a of the ice layer 14.

The ice layer 1 is generated by the frictional heat generated by the mutual movement.
4 and the lower surface 15a of the frozen body 15 are simultaneously melted. By the melting of the frozen body 15, the etching solution is supplied to the surface 14a, and by the melting of the ice layer 14, the convex portion of the interlayer insulating film 13 is exposed from the surface 14a of the ice layer. Receive etching. Therefore, due to the reciprocal movement between the ice layer 14 and the frozen body 15, as shown in FIG.
The thickness dimension is sequentially reduced while the surface 3a and the surface 14a of the ice layer 14 keep the same surface. As a result, FIG. 1 (D)
As shown in (2), when the ice layer 14 is completely melted, the uneven surface of the interlayer insulating film 13 becomes flat, and the work of flattening the interlayer insulating film 13 ends.

Without using the frozen body 15, the surface of the ice layer 14 is melted by spontaneous thawing or blowing hot air.
4a to be melted sequentially, and independently of this melting,
An etching solution can be supplied to the surface 14a of the ice layer 14. However, the surface 14a of the ice layer 14 is uniformly melted with high accuracy, and finally the surface 1a of the interlayer insulating film 13 is melted.
In order to form a high-precision flat surface on 3a, it is desirable to use the frozen body 15 as described above.

According to the flattening method according to the present invention, as described above, the semiconductor wafer 10 contains components causing contamination and dust and does not use expensive slurry.
The surface 13a of the upper interlayer insulating film 13 can be appropriately planarized. Therefore, the conventional cleaning for removing heavy metals, alkali metals, silica, and the like is not required, and it is possible to remove the residues related to the flattening operation by a relatively simple washing operation. Further, since the problem of dust due to silica does not occur, it is possible to perform flattening in a clean room, and it is possible to improve the overall compactness and efficiency of the production line.

FIG. 2 is an explanatory view schematically showing a flattening apparatus according to the present invention. The flattening device 20 is used for flattening the semiconductor wafer 10 provided with the interlayer insulating film 13 having the uneven surface 13a as shown in FIG. The planarizing device 20 includes a rotary chuck 21 that holds the semiconductor wafer 10 provided with the interlayer insulating film 13 such that the uneven surface 13a of the interlayer insulating film 13 is located above. The rotary chuck 21, which is a rotary table, is driven around the rotary shaft 21b at a rotation speed of, for example, 500 to 3000 rpm while the semiconductor wafer 10 is held on the support surface 21a.

The rotary chuck 21 is provided with a cooler 22 as a cooling means. The cooler 22 is connected to the pipe 2
After 3, the cooling medium is supplied to the rotary chuck 21. Upon receiving the supply of the cooling medium, the support surface 21a of the rotary chuck 21 can be cooled to, for example, −15 ° C. to −150 ° C. Above the rotary chuck 21, a nozzle 24 is disposed as a means for supplying pure water onto the semiconductor wafer 10 held on the rotary chuck 21. The nozzle 24 is arranged with its supply port 24a facing downward. The nozzle 24 moves between the supply position indicated by the solid line in FIG. 2 at the center of the rotary chuck 21 and the retracted position indicated by the broken line on the side of the rotary chuck 21 in the direction indicated by the symbol A in the figure. Can be moved.

Above the rotary chuck 21, there is provided means 25 for pressing the frozen body 15 of the etching solution (for example, −50 to −150 ° C.) toward the semiconductor wafer 10. The pressing means 25 is formed of, for example, a chuck, and the lower surface 15 a of the frozen body 15 is
Hold so as to be parallel to a. Further, pressing means 25
Moves the frozen body 15 to the semiconductor wafer 1 on the rotary chuck 21.
It is possible to move in the direction shown by the symbol B between the pressed position toward 0 and the retracted position shown in the figure, which is separated from the pressed position.
A rotary shaft 25 a is provided on the chuck of the pressing means 25, and the rotary shaft 21 can be rotated in a direction opposite to the rotation direction.

In the flattening apparatus 20, the semiconductor wafer 10 is placed on the support surface 21a of the rotary chuck 21 as described above.
Is held with the uneven surface 13a of the interlayer insulating film 13 positioned upward. The rotating chuck 21 is, for example, 500
When rotated at 3000 rpm, pure water at normal temperature is supplied from the supply port 24a of the nozzle 24 at the supply position to, for example, 10
It is supplied onto the uneven surface 13a of the interlayer insulating film 13 at a flow rate of 0 cc / min. At this time, the support surface 21a of the rotary chuck 21 is cooled to about 2 to 5 ° C. by the cooler 22.

When the temperature of the support surface 21a of the rotary chuck 21 reaches a predetermined temperature, the supply of water from the nozzle 24 is stopped.
The nozzle 24 is moved to the retracted position. Several seconds have elapsed since the supply of water was stopped, and the uneven surface 13a of the interlayer insulating film 13
When the upper surface of the water layer covering
Is stopped. The thickness of the water layer at this time is
For example, it is 1 to 10 μm. Then, this uneven surface 1
Before the layer of water on 3a is not lost by evaporation, the cooling surface of the rotating chuck 21 is rapidly cooled to, for example, −15 ° C. to −150 ° C. by the cooler 22. This rapid cooling freezes the water covering the uneven surface 13a of the interlayer insulating film 13. Due to this freezing, the uneven surface 13a of the interlayer insulating film 13 is formed.
And an ice layer 14 covering the uneven surface 13a and having a flat surface 14a is formed.

As described above, a freezing temperature regulator can be added to pure water. In order to prevent frost from adhering to the surface 14a of the ice layer 14 when the water is frozen, it is desirable to freeze the water under a gas atmosphere such as nitrogen gas.

When the formation of the ice layer 14 is completed, the ice layer 1
4 toward the front surface 14a, and the frozen body 15
Is pressed. At this time, the rotary chuck 21 is rotated at, for example, 1000 to 3000 rpm. As described with reference to FIG. 1 (C), the ice layer 14 and the frozen body 15 are simultaneously caused by the frictional heat generated by the relative sliding movement of the ice layer 14 and the frozen body 15 accompanying the rotation of the rotary chuck 21. Because of the melting, the convex portion of the interlayer insulating film 13 exposed from the ice layer 14 is subjected to the etching action of the etching solution due to the melting of the frozen body 15 under the protection action of the ice layer 14.

Thus, the surface 13a of the interlayer insulating film 13
And while the surface 14a of the ice layer 14 keeps the same surface,
The thickness is sequentially reduced, and as a result, when the ice layer 14 is completely melted, the uneven surface of the interlayer insulating film 13 becomes flat,
The flattening operation of the interlayer insulating film 13 on the semiconductor wafer 10 ends.

As a post-processing, when the frozen body 15 is raised to the retracted position, the rotary chuck 21
While rotating at 3000 rpm, pure water is again supplied from the nozzle 24 onto the flat interlayer insulating film 13 of the semiconductor wafer 10 at a flow rate of, for example, 100 cc / min. With the supply of the pure water, the etchant is removed from above the interlayer insulating film 13 and the surface of the interlayer insulating film 13 is purified. When the rotation of the rotary chuck 21 continues, the semiconductor wafer 10 including the interlayer insulating film 13 is dried. Thereby, the flattening operation is completed.

As described above, the flattening apparatus 20 according to the present invention
According to the method, the flattening method according to the present invention can be appropriately and efficiently performed, and processing with extremely high accuracy can be performed.

FIG. 3 is a process chart showing an example in which the planarizing method according to the present invention is applied to planarizing a semiconductor wafer having a polysilicon film. Such a semiconductor structure is employed for a cell plate of a memory or the like.

As shown in FIG. 3A, on a semiconductor wafer 10 made of, for example, a silicon substrate, an interlayer insulating film made of silicon oxide containing boron and phosphorus (BPSG) or the like laminated by, for example, a vapor growth method. Through the membrane 11,
An interlayer film 12 * such as a silicon oxide film is formed by using a technique of vapor phase growth, lithography and dry etching. An insulating film 13 made of polysilicon is formed on the interlayer film 12 *. This insulating film 13
The surface 13a has an uneven shape corresponding to the lower interlayer film 12 *.

On the insulating film 13 made of polysilicon,
As shown in FIG. 3B, an ice layer 14 is formed to fill the uneven surface 13a of the insulating film 13 and cover the uneven surface 13a. This ice layer 14 has a flat surface 14a.
Having. Prior to the formation of the ice layer 14, it is desirable to treat the uneven surface 13a of the insulating film 13 with hydrochloric acid / hydrogen peroxide or the like in order to increase the hydrophilicity of the polysilicon.

The surface 14a of the ice layer 14 is relatively slid using, for example, a frozen body 15, as shown in FIG. When the insulating film 13 to be etched is made of polysilicon, for example, a hydrofluoric nitric acid solution (1 to 50%) or the like can be used for the etching.
As 5, the ice of the etchant is used.

As shown in FIG. 3C, the ice layer 14 and the frozen body 15 are simultaneously melted by the frictional heat generated by the relative sliding motion of the ice layer 14 and the frozen body 15, so that
Under the protection effect of the ice layer 14, the convex portion of the insulating film 13 exposed from the ice layer 14 is subjected to the etching action of the etching solution due to the melting of the frozen body 15.

Thus, as in the example shown in FIG. 1, the surface 13a of the insulating film 13 and the surface 1a of the ice layer 14 are formed.
4a, while maintaining the same surface, the thickness dimension is sequentially reduced. As a result, when the entire ice layer 14 is melted, the uneven surface of the interlayer insulating film 13 becomes flat, and the interlayer insulating film on the semiconductor wafer 10 becomes flat. 13 is finished.

In the above description, an example of a semiconductor wafer provided with an insulating film having an uneven surface as an article to be planarized has been described. However, the planarizing method according to the present invention is not limited to this. Can be applied to various articles subjected to chemical etching.

Further, as the etching solution, a liquid which does not cause a residue problem such as dilute hydrofluoric acid, dilute hydrofluoric nitric acid and hydrofluoric acid peroxide can be appropriately selected according to the material of the article to be etched. . This etching solution can be supplied in the form of sherbet, instead of a liquid or a frozen body, on an ice layer that has a masking action, that is, a protective action for etching. Furthermore, as the ice that acts as a mask for the etching, various liquids suitable for coagulation can be selected in addition to water, and the coagulated body can be used.

[0042]

According to the method of the present invention, as described above, the etching solution can be formed in cooperation with the ice layer without using a slurry containing components causing contamination and dust.
Since the portions exposed from the ice layer are sequentially removed by the etching action, the flattening of the articles can be achieved without causing a problem of contamination of heavy metals or alkali metals and a problem of dust. Therefore, the present invention can be implemented on a production line in a clean room, so that the production line can be made more compact and more efficient.

Further, according to the apparatus of the present invention, as described above, the proper supply of the etching solution is achieved by the frictional heat caused by the mutual motion between the frozen body of the etching solution and the ice layer functioning as a protective layer against the etching solution. Since uniform melting of the ice layer can be performed simultaneously, the planarization method of the present invention can be performed relatively easily and with high accuracy.

[Brief description of the drawings]

FIG. 1 is a process diagram showing an example in which a planarization method according to the present invention is applied to planarization of a semiconductor wafer having a silicon oxide film.

FIG. 2 is an explanatory view schematically showing a flattening device according to the present invention.

FIG. 3 is a process chart showing an example in which the planarization method according to the present invention is applied to planarization of a semiconductor wafer having a polysilicon film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Article (semiconductor wafer) 13a Irregular surface 14 Ice layer 14a Surface of ice layer 15 Frozen body 20 Flattening device 21 Turntable (rotary chuck) 24 Means for supplying water (nozzle) 22 Cooling means (cooling machine) 25 Pressing means

Claims (7)

[Claims] 1. A surface flattening method for flattening an uneven surface of an article, comprising: forming an ice layer having a flat surface that embeds the uneven surface and covers the uneven surface; An etchant for chemically polishing the article is supplied to the surface of the ice layer while being uniformly melted from the surface of the ice layer, and the portion exposed from the ice layer as the ice layer melts is flattened. A method of planarizing the surface, which comprises sequentially removing the surface with the etching solution. 2. The method according to claim 1, wherein the article is a semiconductor wafer having an insulating film formed on a surface. 3. The supply of the etching solution is performed by relatively sliding a frozen body of the etching solution on the ice layer and melting the frozen body and the ice layer by frictional heat. Item 4. The method for flattening a surface according to Item 1. 4. An apparatus for flattening an uneven surface of an article, comprising: a turntable for holding the article on a surface opposite to the uneven surface of the article; and water on the uneven surface of the article on the turntable. An ice layer having a flat surface that embeds the uneven surface and covers the uneven surface by freezing the water in a state where the water is uniformly spread on the uneven surface by the rotation of the turntable. A flattening apparatus comprising: a cooling unit for rotating the turntable, and a unit for pressing a frozen body of an etching solution for chemically polishing the uneven surface while rotating the turntable against the surface of the ice layer. 5. The surface flattening apparatus according to claim 4, wherein the water contains an organic solvent for adjusting a freezing temperature. 6. The surface flattening apparatus according to claim 4, wherein the article is a semiconductor wafer on which an insulating film having irregularities is formed on a surface, and the flattening apparatus is a step flattening apparatus for a semiconductor wafer. . 7. The surface flattening apparatus according to claim 6, wherein said cooling means is incorporated in said turntable.