JP3487485B2 - Semiconductor wafer surface planarization method - Google Patents

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 the surface of an article, and more particularly, in the manufacturing process of a semiconductor element, eliminating steps on the surface of a semiconductor wafer in which components of the semiconductor element are incorporated. The present invention relates to a surface flattening method and apparatus suitable for flattening.

[0002]

2. Description of the Related Art A multilayer wiring structure is one of the techniques for making semiconductor devices such as IC circuits compact. In such a multilayer wiring structure, when a component part of a circuit is formed on a semiconductor wafer, an interlayer insulating film covering it is formed, and a new component part is formed on this interlayer insulating film. .

Photolithography technology is generally used to form the component parts. In this technique, since the surface of the interlayer insulating film, which is the required pattern baking surface, has a step corresponding to the shape of the constituent elements formed thereunder, the baking of the interlayer insulating film is performed before the pattern baking. It is necessary to smooth the surface and make it flat.

As a method of flattening the interlayer insulating film on this semiconductor wafer, conventionally, 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 metals or alkali metals contained in the slurry as a component of the chemical polishing agent remain on the surface to be polished, the residual metal causes Extremely rigorous washing with water is indispensable because pollution becomes a problem. Further, since silica contained in the slurry as a physical polishing agent causes dust, it is impossible to carry out the chemical mechanical polishing method in a clean room.

[0006]

The present invention adopts the following constitution in order to solve the above points. <Structure> The present invention relates to a semiconductor wafer in a semiconductor element manufacturing process.
In the surface flattening method, before the insulating film is formed on the upper surface
The step of preparing a semiconductor wafer and the step of preparing the upper surface of the insulating film.
The step of supplying water and the step of supplying water to the upper surface of the insulating film.
The water should be cooled and solidified in a nitrogen gas atmosphere.
Form an ice layer with a flat upper surface on the insulating film.
Forming step and etching for etching the insulating film
Press the frozen body of frozen liquid against the upper surface of the ice layer.
The frozen body relative to the top surface of the ice layer.
The ice layer and frozen body are melted by sliding.
A step of removing the ice and exposing the ice layer by melting
Before the insulating film is supplied by melting the frozen body
Etching with the above-mentioned etching solution, and
Characterized by have a planarizing the surface.

<Operation> In the surface flattening method according to the present invention, the ice layer obtained by coagulating water acts as a protective layer for protecting the surface of the insulating film from the etching action of the etching solution. for that reason,
As long as the surface is covered with the ice layer, the uneven surface of the insulating film is not affected by the etching action of the etching solution.
Then, the ice layer is cooled and solidified in a nitrogen gas atmosphere.
Therefore, be sure to prevent frost from attaching to the top surface of the ice layer.
Therefore, a flat top ice layer is formed on the insulating film.
it can. On the other hand, when the ice layer covering the uneven surface of the insulating film starts to melt uniformly from the surface and part of the insulating film is exposed from the ice layer, only the exposed part is etched by the etching solution. Therefore, with the melting of the flat ice layer on the top surface, successively, the convex portion of the insulating film exposed from the ice layer is subjected to etching, since the portion of the ice layer of the insulating film is always protected, the surface of the insulating film Are sequentially flattened, and the flattening ends when all ice layers have disappeared.

In the surface flattening method of the present invention, without using a slurry containing a component causing contamination and dust,
The etching liquid cooperates with the ice layer to sequentially remove the portions exposed from the ice layer by the etching action. Therefore, the problem of contamination of heavy metals or alkali metals contained in the slurry does not occur. Further, since it can be carried out on the production line in a clean room without causing the problem of dust, the production line can be made compact and the efficiency can be improved.

In the above structure, the ice layer is pushed onto the upper surface.
The surface of the frozen body to be pressed is flat .

In the above structure, the semiconductor wafer is
By rotating, it is supplied to the upper surface of the insulating film.
The step of flattening the upper surface of the water
And In this case, the rotation of the semiconductor wafer is 50
Characterized by being performed at a rotational speed of 0 to 3000 rpm
To do.

In the above structure, the water has a freezing temperature.
It is characterized in that it contains an organic solvent for adjustment.

Therefore, the mutual movement of the frozen body and the ice layer enables the appropriate supply of the etching solution and the uniform melting of the ice layer to be carried out at the same time, which makes the planarization method of the present invention relatively easy. And it can be implemented with high accuracy.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. <Specific Example> 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 the semiconductor wafer 10, for example, an interlayer insulating film 11 made of silicon oxide laminated by vapor phase epitaxy. The metal wiring 12 is formed via the. The metal wiring 12 is generally formed by using a technique of sputtering a metal material such as aluminum, lithography and dry etching.

To form a multi-layer wiring structure by forming an upper circuit such as another wiring on the metal wiring 12, an interlayer insulating film 1 is formed so as to cover the metal wiring 12.
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 13a of the interlayer insulating film 13 is formed corresponding 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 serves as 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 delicate pattern transfer.

In order to planarize the interlayer insulating film 13, FIG.
As shown in (B), the ice layer 14 is formed which fills the uneven surface 13a of the interlayer insulating film 13 and covers the uneven surface 13a. The ice layer 14 has a flat surface 14a. This ice layer 14 can be formed by freezing pure water. Further, in order to adjust the freezing point, which is the solidification temperature of 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 the surface 14a thereof while maintaining the flatness. Further, the surface 14a of the ice layer 14 is supplied with an etching solution such as a 0.1-10% hydrofluoric acid solution for chemically etching the interlayer insulating film 13 made of silicon oxide.

As the melting of the ice layer 14 progresses, FIG.
As shown in (C), when the convex portion of the uneven surface 13 a of the interlayer insulating film 13 is partially exposed from the surface 14 a of the ice layer 14, the exposed portion is the etching solution supplied to the surface 14 a of the ice layer 14. Are sequentially removed. On the other hand, the portion of the interlayer insulating film 13 below the ice layer 14 is prevented from coming into contact with the etching solution by the ice layer. Therefore,
The concave portion below 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 planarized.

In FIG. 1 (C), the frozen body 15 of the etching liquid is an ice layer for the purpose of uniform melting of the ice layer 14 and proper supply of the etching liquid to the surface 14a of the ice layer 14. An example of relatively sliding on the surface 14a of 14 is shown. 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.

Due to the frictional heat due to this mutual movement, the ice layer 1
The surface 14a of No. 4 and the lower surface 15a of the frozen body 15 are simultaneously melted. The melting of the frozen body 15 supplies the etching solution to the surface 14a, and the melting of the ice layer 14 exposes the convex portion of the interlayer insulating film 13 from the surface 14a of the ice layer, and the exposed portion is sequentially exposed by the etching solution. Receive etching. Therefore, due to the mutual movement of the ice layer 14 and the frozen body 15, as shown in FIG.
3a and the surface 14a of the ice layer 14 are kept in the same plane, while the thickness dimension is successively reduced. As a result, FIG. 1 (D)
As shown in FIG. 3, 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 is completed.

The surface 1 of the ice layer 14 is naturally melted or blown with warm air without using the frozen body 15.
4a, melting 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 1 of the interlayer insulating film 13 is melted.
As described above, it is desirable to use the frozen body 15 in forming a highly accurate flat surface on the 3a.

According to the flattening method of the present invention, as described above, the semiconductor wafer 10 containing the component causing the contamination and dust and without using the expensive slurry.
The surface 13a of the upper interlayer insulating film 13 can be appropriately flattened. Therefore, conventional washing for removing heavy metals, alkali metals, silica, etc. is not required, and it becomes possible to remove the residues involved in the flattening operation with a relatively simple water washing operation. Further, since the problem of dust due to silica is not caused, it becomes possible to carry out flattening in a clean room, and it is possible to make the entire production line compact and improve efficiency.

FIG. 2 is an explanatory view schematically showing the flattening device 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 planarization apparatus 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 rotating chuck 21, which is a rotating table, is operated around the rotating shaft 21b at a rotation speed of, for example, 500 to 3000 rpm while holding the semiconductor wafer 10 on the supporting surface 21a thereof.

The rotary chuck 21 is provided with a cooler 22 as cooling means. The cooler 22 has its pipeline 2
After 3, the cooling medium is supplied to the rotary chuck 21. Upon receiving the supply of this cooling medium, the support surface 21a of the rotary chuck 21 can be cooled to, for example, −15 ° C. to −150 ° C. A nozzle 24 is arranged above the rotary chuck 21 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 is located between the supply position shown by the solid line in FIG. 2 at the center of the rotary chuck 21 and the retracted position shown by the broken line at the side of the rotary chuck 21 in the direction indicated by the symbol A in the figure. Can be moved.

Further, above the rotary chuck 21, there is provided a 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, for example, a chuck, and the lower surface 15 a of the frozen body 15 is attached to the support surface 21 of the rotary chuck 21.
Hold so as to be parallel to a. Also, the pressing means 25
Holds the frozen body 15 to the semiconductor wafer 1 on the rotary chuck 21.
It is movable in the direction indicated by the symbol B between the pressing position toward 0 and the retracted position shown in the figure which is separated from the pressing position.
A rotary shaft 25a is provided on the chuck of the pressing means 25, and the rotary chuck 21 can be rotated in the direction opposite to the rotating direction.

In the flattening apparatus 20, as described above, the semiconductor wafer 10 is placed on the supporting surface 21a of the rotary chuck 21.
However, the uneven surface 13a of the interlayer insulating film 13 is positioned and held above. The rotation chuck 21 is, for example, 500
When rotated at ˜3000 rpm, pure water at room temperature passes through the supply port 24a of the nozzle 24 at the supply position, 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 supporting 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 its retracted position. After a few seconds have passed since the water supply was stopped, the uneven surface 13a of the interlayer insulating film 13
When the upper surface of the water layer covering the
Rotation 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 water layer on 3a is not lost by evaporation, the cooling device 22 quenches the support surface 21a of the rotary chuck 21 to, for example, -15 ° C to -150 ° C. By this rapid cooling, the water covering the uneven surface 13a of the interlayer insulating film 13 is frozen. Due to this freezing, the uneven surface 13a of the interlayer insulating film 13 is formed.
Is formed and covers the uneven surface 13a, and an ice layer 14 having a flat surface 14a is formed.

As described above, the freezing temperature adjusting agent can be added to pure water. Moreover, in order to prevent frost from adhering to the surface 14a of the ice layer 14 during freezing of water, 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, this ice layer 1
4, the frozen body 15 has its lower surface 15a.
Can be pressed. At this time, the rotary chuck 21 is rotated at 1000 to 3000 rpm, for example. As described with reference to FIG. 1C, the ice layer 14 and the frozen body 15 are simultaneously moved by the frictional heat due to the relative sliding motion of the ice layer 14 and the frozen body 15 accompanying the rotation of the rotary chuck 21. Since it melts, the convex portion of the interlayer insulating film 13 exposed from the ice layer 14 is subjected to the etching action of the etching liquid due to the melting of the frozen body 15 under the protection action of the ice layer 14.

As a result, the surface 13a of the interlayer insulating film 13 is formed.
And the surface 14a of the ice layer 14 maintains the same surface,
The thickness dimension is successively 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 planarization work of the interlayer insulating film 13 on the semiconductor wafer 10 is completed.

As a post-treatment, when the frozen body 15 is pulled up to the retracted position, the rotary chuck 21 is moved to, for example, 1000 to
Pure water is again supplied from the nozzle 24 at a flow rate of, for example, 100 cc / min onto the flat interlayer insulating film 13 of the semiconductor wafer 10 while rotating at 3000 rpm. By supplying the pure water, the etching liquid is removed from the interlayer insulating film 13 and the interlayer insulating film 13 is cleaned, and the semiconductor wafer 10 including the interlayer insulating film 13 is dried by the subsequent rotation of the rotary chuck 21. Then, the flattening work is completed.

Thus, the flattening apparatus 20 according to the present invention
According to this, the flattening method according to the present invention can be carried out properly and efficiently, and processing with extremely high accuracy becomes possible.

FIG. 3 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 having a polysilicon film. Such a semiconductor structure is used 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, interlayer insulation made of silicon oxide containing boron and phosphorus (BPSG) or the like, which is laminated by, for example, a vapor phase epitaxy method. Through the membrane 11
An interlayer film 12 * such as a silicon oxide film is formed by using vapor phase growth method, lithography and dry etching techniques. An insulating film 13 made of polysilicon is formed on the interlayer film 12 *. This insulating film 13 is
Corresponding to the lower interlayer film 12 *, its surface 13a has an uneven shape.

On the insulating film 13 made of polysilicon,
As shown in FIG. 3B, the ice layer 14 that fills the uneven surface 13a of the insulating film 13 and covers the uneven surface 13a is formed. This ice layer 14 has a flat surface 14a.
Have. 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 by using, for example, a frozen body 15, as shown in FIG. 3 (C). When the insulating film 13 to be etched is made of polysilicon, a hydrofluoric nitric acid solution (1 to 50%) or the like can be used for the etching.
As for 5, the ice of the etching solution is used.

As shown in FIG. 3C, the ice layer 14 and the frozen body 15 are melted at the same time by the frictional heat due to the relative sliding motion of the ice layer 14 and the frozen body 15.
Under the protective action 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 liquid due to the melting of the frozen body 15.

As a result, similarly to the example shown in FIG. 1, the surface 13a of the insulating film 13 and the surface 1 of the ice layer 14 are formed.
4a keeps the same surface, and the thickness is sequentially reduced. As a result, when the ice layer 14 is completely melted, the uneven surface of the interlayer insulating film 13 becomes flat, and the interlayer insulating film on the semiconductor wafer 10 is flattened. The flattening work of 13 is completed.

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

Further, as the etching liquid, a liquid which does not cause a residue problem such as dilute hydrofluoric acid, dilute hydrofluoric nitric acid and hydrofluoric acid / hydrogen peroxide can be appropriately selected according to the material of the article to be etched. . This etching liquid can be supplied in the form of a sherbet, instead of a liquid or a frozen body, on an ice layer that acts as a mask or a protection against etching. Further, in addition to water, various liquids suitable for solidification can be selected and used as the solidified body as ice that acts as a mask for etching.

[0042]

According to the method of the present invention, as described above, the etching solution is used in cooperation with the flat ice layer on the upper surface without using a slurry containing a component causing contamination and dust. Since the part exposed from the ice layer is sequentially removed by its etching action, without causing the problem of heavy metal or alkali metal contamination,
Further, the insulating film can be flattened without causing the problem of dust, and therefore, the production line can be implemented in a clean room. Therefore, the production line can be made compact and the efficiency can be improved. Can be planned.

[0043]

[Brief description of drawings]

FIG. 1 is a process chart showing an example in which a planarizing method according to the present invention is applied to planarizing 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 planarizing method according to the present invention is applied to planarizing a semiconductor wafer having a polysilicon film.

[Explanation of symbols]

10 Articles (semiconductor wafers) 13a Uneven surface 14 Ice layer 14a Ice layer surface 15 Frozen body 20 Flattening device 21 Rotary table (rotary chuck) 24 Means for supplying water (nozzle) 22 Cooling means (cooler) 25 Pressing means

Continuation of the front page (56) Reference JP-A-8-255773 (JP, A) JP-A-6-302583 (JP, A) JP-A-9-7986 (JP, A) JP-A-8-222536 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21 / 308,21 / 306

Claims (5)

(57) [Claims] 1. A method of flattening a surface of a semiconductor wafer in a semiconductor device manufacturing process, the step of preparing the semiconductor wafer having an insulating film formed on the upper surface, the step of supplying water to the upper surface of the insulating film, Forming an ice layer having a flat upper surface on the insulating film by cooling and solidifying the water supplied to the upper surface of the insulating film in a nitrogen gas atmosphere; and etching the insulating film. The frozen body in which the etching liquid is frozen is pressed against the upper surface of the ice layer, and the frozen body is slid relative to the upper surface of the ice layer, thereby melting the ice layer and the frozen body. And a step of etching the insulating film exposed by melting the ice layer with the etching solution supplied by melting the frozen body to flatten the upper surface of the insulating film. Surface planarization method for semiconductor wafers, characterized by a step. 2. The surface flattening method for a semiconductor wafer according to claim 1, wherein a surface of the frozen body pressed against the upper surface of the ice layer is flat. 3. The semiconductor wafer according to claim 1, further comprising the step of flattening an upper surface of the water supplied to the upper surface of the insulating film by rotating the semiconductor wafer. Surface flattening method. 4. The rotation of the semiconductor wafer is 500 to
The method for planarizing a surface of a semiconductor wafer according to claim 3, wherein the method is performed at a rotation speed of 3000 rpm. 5. The surface flattening method for a semiconductor wafer according to claim 1, wherein the water contains an organic solvent for adjusting a freezing temperature.