JPH11307484A - Polishing and cleaning method of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively polish and clean a desired salient part of a film to be polished without generating dishing, by polishing a film to be polished formed on a substrate having unevenness, using polishing liquid containing material in the state of polymer. SOLUTION: An Al film 3 formed on a silicon oxide film 1 as an insulating film in which a wiring trench 2 is formed is eliminated as far as the surface of the film 1 by polishing. In this case, material having the state of polymer of organic compound or the like is added to abrasive solution. On account of distance difference between the Al film 3 surface and an abrassive cloth 8, shearing stress is different. That is, viscosity of the abrassive solution having Bingham fluidity in a region β in which stress from the Al film 3 and the abrassive cloth 8 becomes lower than the viscosity in a region α, in which the stress from the Al film 3 and the abrassive cloth 8 is small. As a result, polishing amount of the Al film 3 per unit time is increased by that amount, thereby generating no dishing so that a buried metal wiring having a flat surface can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate polishing method and a cleaning method used in a semiconductor device manufacturing technique.
The present invention relates to a polishing method used in a step of flattening a substrate surface, in particular, a step of forming a buried metal wiring, a step of flattening an interlayer insulating film, or a step of forming a buried capacitor.
In addition, the present invention relates to a method for polishing a substrate and a method for removing abrasive particles after polishing.

[0002]

2. Description of the Related Art In recent ultra-large-scale integrated circuits and the like, there is a tendency that transistors and other semiconductor elements are reduced in size to increase the packaging density. For this reason, various microfabrication technologies have been researched and developed, and in the design rules,
It is on the order of submicron.

One of the technologies developed to satisfy such strict requirements for miniaturization is a chemical mechanical polishing (hereinafter referred to as CMP) technology. This technique is essential in the manufacturing process of a semiconductor device, for example, when forming a buried metal wiring, flattening an interlayer insulating film, forming a plug, separating a buried element, forming a buried capacitor, and the like.

FIGS. 20 to 24 show a conventional CMP technique by taking a process of forming a buried metal wiring as an example.
This will be described with reference to FIG.

As shown in FIG. 20, a silicon oxide film 101 is formed on a substrate 100 as an insulating film.

Next, as shown in FIG. 21, a wiring groove 102 is formed on the silicon oxide film 101 by ordinary photolithography and etching.

Further, as shown in FIG. 22, a metal film 103 is formed by a PVD method or a CVD method.

Next, as shown in FIG. 23, polishing is performed to form a buried metal wiring. FIG. 23 shows a cross-sectional shape in the case where the polishing process has been completed up to the oxide film.

FIG. 24 shows a surface state after polishing.

However, according to the conventional polishing technique, as shown in FIG. 23, when the width of the metal film 103 buried in the wiring groove 102 is large, the central portion of the metal film is polished preferentially. Then, there is a problem that dish-shaped recesses, so-called dishing, occur in the central portion (see FIGS. 23 and 24).

Further, as shown in FIG. 24, the abrasive particles 104 contained in the polishing liquid are adsorbed on the film to be polished, and remain on the film to be polished even if they are washed with pure water or the like. Therefore, there is a problem that a step of removing the polishing particles 104 remaining on the film to be polished is required in a subsequent step.

[0012]

In the conventional polishing technique, when the metal film embedded in the wiring groove is wide, there is a problem that the central portion of the metal film is polished preferentially and dishing occurs. . Further, the polishing particles contained in the polishing liquid are adsorbed on the film to be polished, and remain on the film to be polished even after the cleaning, and the polishing particles are washed after polishing.
It had to go through a removal step.

The present invention has been made in view of the above points, and provides a polishing method and a cleaning method capable of efficiently polishing and cleaning a desired convex portion of a film to be polished without causing dishing. With the purpose of
An object of the present invention is to provide a polishing method and a cleaning method for preventing adsorption of polishing particles contained in the polishing liquid on a film to be polished.

[0014]

According to the present invention, there is provided a process for forming a film to be polished on a substrate having irregularities, and polishing the film to be polished with a polishing liquid containing a polymer-state substance. And a step of flattening the substrate.

Further, in the method of polishing a substrate, the substance in a polymer state has a property of flowing Bingham, and the substance in a polymer state is a carboxyvinyl polymer of an organic compound. is there.

Further, the polishing target film is a metal film or an insulating film.

A step of forming a film to be polished on the substrate having irregularities; a step of polishing the film to be polished using a polishing liquid containing a substance in a polymer state to flatten the substrate;
Cleaning the flattened surface of the substrate.

A step of forming a film to be polished on a substrate having irregularities; and pressing the substrate on which the film to be polished is formed on a polishing cloth on a polishing platen, and applying a polishing liquid containing a substance in a polymer state to the polishing pad. Polishing the film to be polished by relatively moving the substrate and the polishing platen while supplying the film between the film to be polished and the polishing cloth, the film to be polished formed on the concave portion. A polishing method for a substrate, characterized in that the removal amount per unit time of the film to be polished formed on the projections is higher than the removal amount per unit time, and the substrate is flattened.

Further, a step of forming a film to be polished on a substrate having irregularities, a step of polishing the film to be polished by using a polishing liquid to flatten the substrate, and a step of flattening the surface of the flattened substrate Cleaning the substrate with a substance having a high molecular state.

Further, the substance having a high molecular state is characterized in that it has a property of flowing Bingham, and the substance in a high molecular state is a carboxyvinyl polymer of an organic compound.

Further, in the method for cleaning a substrate, the film to be polished is a metal film or an insulating film.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments described here. The following embodiments can be variously modified without departing from the object of the invention.

An embodiment of the present invention will be described below with reference to FIGS.
8 will be described.

FIGS. 1 to 5 show changes in the cross-sectional shape when the sample W is polished using the polishing method of the present invention.

FIG. 1 is a sectional view for explaining a polishing method according to the first embodiment of the present invention. First, as shown in FIG. 1, a silicon oxide film 2 is formed on an Si substrate 1 as an insulating film.
To form Next, a width of 0.35 is formed on the silicon oxide film 2 by ordinary photolithography and etching.
A wiring groove 3 having a height of about 0.6 μm and a height of about 0.6 μm is formed.

Next, as shown in FIG. 2, a metal film having a thickness of 0.8 μm, for example, A
A sample W was formed by forming a 1 film. In the drawings, reference numeral 5 denotes a convex portion, and reference numeral 6 denotes a concave portion.

As shown in FIGS. 3 and 4, the Al film 4 is polished by performing CMP, and the Al film 4 is removed until it reaches the surface of the silicon oxide film 2.
As shown in the cross-sectional view of FIG. 5 and the perspective view of FIG.
Can be formed.

In FIG. 3, 7 represents abrasive particles, and 8 represents a polishing cloth.

When the conventional polishing method is used, dishing of the A1 film occurs in the wide A1 wiring portion. However, according to the polishing method of the present invention, the surface is flat without such dishing. Buried metal wiring can be formed.

Next, the polishing mechanism of the present invention will be described in more detail.

Next, FIG. 7 is a sectional view in which polishing is performed by the polishing cloth 8 (the substrate 1 is omitted). 7 is an abrasive. As shown in the figure, the difference in the distance between the surface of the Al film 4 and the polishing pad 8 causes a difference in shear stress. As a result, a high viscosity portion and a low viscosity portion of the abrasive are formed.

The portion α in the figure is the portion where the viscosity of the abrasive is high, where the abrasive particles do not move. Further, a portion β in the figure is a portion where the viscosity of the abrasive is low, where the movement of the abrasive particles is active.

That is, the Al film 4 on the Si substrate and the polishing pad 8
In the region where the stress from the Al film 4 and the polishing cloth 8 on the Si substrate is larger than the region where the stress from the substrate is small, the viscosity of the polishing liquid having Bingham fluidity is lower, and the polishing of the Al film 4 per unit time The amount will increase.

As described above, the portion where the viscosity of the abrasive is low is preferentially shaved.

FIG. 8 shows a state in which the convex portion of Al has been preferentially shaved as described above and flattening has been advanced.

As described above, according to the substrate polishing method of the present invention, only desired convex portions of the Al film 4 can be efficiently polished without generating dishing.

FIG. 9 shows a polishing apparatus used for polishing the sample W. The apparatus comprises a rotatable polishing table 21 and
A polishing cloth 22 stuck on a polishing platen 21 and a polishing platen 2
1 comprises a rotatable vacuum chuck holder 23 disposed above and a polishing liquid supply pipe 24 connected to the polishing liquid tank 25 and having a discharge portion extending to the vicinity of the polishing cloth 22.

The sample W is vacuum-chucked on the vacuum chuck holder 23 so that the surface to be polished faces the polishing pad 22. In addition, the polishing liquid supply pipe 24 includes means for controlling the supply amount of the polishing liquid. The polishing cloth 22 has a thickness of 1.2 mm and a hardness of 7 made of a suede type nonwoven fabric.
3.6 was used.

The CMP polishing liquid according to the embodiment of the present invention is obtained by dispersing alumina particles having an average particle diameter of 0.04 μm in pure water at a ratio of 1.5%, and adding the dispersed particles to a Bingham (B)
ingham) a highly viscous organic compound having fluidity;
For example, a product obtained by adding 0.1% by weight of a carboxyvinyl polymer was used. The polishing conditions were such that the polishing pressure was 300 g.
f / cm ² , and the rotation speeds of the polishing platen and the vacuum chuck holder were each 60 rpm (hereinafter, these conditions are referred to as standard conditions for polishing). The sample W
The pressure when the abutment with the polishing pad 22 can be arbitrarily controlled by compressed air.

In the present invention, the standard conditions for polishing as described above are used. However, it goes without saying that the standard conditions for polishing can be flexibly changed according to other conditions.

Next, a cleaning mechanism will be described with reference to FIG.

As shown in FIG. 10A, a substance exhibiting the property of Bingham flow forms a fibrous aggregate by connecting particles when left standing. The aggregates further overlap to form a pseudostructure called a mesh structure. Therefore, assuming that the stress is σ, the structure is maintained when the stress σ is small, so that the resistance to the flow is large and the viscosity is high.

From the above state (a), when the stress σ increases, the aggregate structure is destroyed and the viscosity decreases.
The structure shown in FIG.

Generally, the abrasive particles adhere to the surface of the Al film 4 due to an electric force, but the abrasive particles of the Bingham flow form a stronger aggregate. Therefore, it is considered that the cleaning mechanism is because the abrasive particles exhibiting the Bingham flow wrap the abrasive particles on the surface of the Al film 4 and strip them off.

[0045] As described above, tends to remain abrasive particles such as SiO ₂ sticks on Al wiring film, conventionally, it was necessary steps to remove it at the end, the Bingham fluid abrasive particles of the Al film surface Since the abrasive shown is wrapped and separated from the Al film, the abrasive particles can be easily and effectively washed and removed using pure water or the like.

Next, a second embodiment of the present invention will be described.
This will be described with reference to FIGS. Second embodiment of the present invention
The polishing method according to this embodiment will be described for a case where the polishing method is applied to an interlayer insulating film.

First, as shown in FIG.
m, and a silicon oxide having a thickness of about 1.6 μm to be an interlayer insulating film on a Si-based 1 plate 1 having a protrusion having a width of about 100, 200 or 500 μm and occupying about 50% of the entire substrate area. The film 2 was formed to prepare a sample.

Next, using the polishing apparatus shown in FIG. 9, the sample W ′ was subjected to CMP to flatten the interlayer insulating film. In CMP, the polishing liquid has an average particle size of 0.1.
Cerium oxide particles of 6 μm are dispersed in pure water at a ratio of 1.0% by weight, and a high-viscosity organic compound having bingham fluidity, for example, a carboxyl vinyl polymer is dispersed in 0.1% by weight.
What added 1 weight% was used.

The polishing conditions employed were the standard conditions described in the first embodiment of the present invention. By performing such polishing, through the cross-sectional shape shown in FIG.
As shown in FIG. 3, the convex portion of the silicon oxide film 2 was polished, and a flat interlayer insulating film was formed without generating a dish-shaped concave portion.

Next, a third embodiment of the present invention will be described.
This will be described with reference to FIGS.

In the third embodiment of the present invention, the sample W polished by the polishing method according to the first embodiment of the present invention is cleaned in the following order.

First, the cleaning apparatus shown in FIGS. 14 and 15 will be described.

FIG. 14 is a side view of the present cleaning apparatus, and FIG. 15 is a top view.

The apparatus shown in FIGS. 14 and 15 is provided with a rotatable chuck holder 31 installed horizontally and a pair of rotatable roll sponges 32 which are vertically sandwiched between central portions of the chuck holder. , 33 and a pure water pipe 34 whose discharge section is installed near the upper and lower roll sponges 32, 33. The sample W is chucked by the chuck holder 31, and the sample W is held by a pair of roll sponges from above and below. 32 and 33 are sandwiched while rotating.

As described above, cleaning was performed using the cleaning apparatus shown in FIGS.

Another embodiment will be described using the cleaning apparatus shown in FIGS.

FIG. 16 is a side view of the present cleaning apparatus, and FIG. 17 is a top view.

The apparatus shown in FIGS. 16 and 17 includes a rotatable chuck holder 41 installed horizontally, a rotatable sponge 42 disposed above the chuck holder, and a discharge unit disposed above the chuck holder 41. Pure water piping 4 arranged
And 3.

The sample W is chucked to the chuck holder 41 such that the surface to be polished faces upward. The arm supporting the sponge 42 presses the sample W while rotating the sponge 42, and swings while drawing an arc on the sample W.

Next, the liquid viscosity will be described with reference to FIG.

As shown in FIG. 18, it is assumed that a force F is applied to the upper plate so that the upper plate moves at a speed u relative to the lower plate between two flat plates having an area A sandwiched between liquids having a viscosity η. Here, h is the distance between the upper plate and the lower plate, and the force causing the flow is τ
(Shear stress), the velocity gradient in the fluid is Δ, the area A of the slip is F, and the force applied to the area A is F.

At this time, the force F applied to the upper plate is expressed by the following equation.

F = k · A · (u / h) (1) F / A = k (du / dh) (2) г = du / dh (3) τ = ηг (3) 4) At this time, k is a proportional constant, which is generally represented by viscosity (coefficient) η. If η is large, τ naturally becomes large. As can be seen from this, η is the flow resistance, and it is understood that the greater the resistance, the more force is required.

Next, the types of flow will be described with reference to FIG.

The fluids are divided as shown from A ′ to E ′ in FIG. 19, and each fluid has the properties shown in FIG. 19 in the relation between the shear stress τ and the shear rate г.

A ′ is called Newtonian flow, and the relationship between shear stress τ and shear rate г is proportional. B 'is dilatant flow, C' is quasi-viscous flow, D 'is Bingham flow, and E' is pseudo-viscous flow. Here, τ ₀ is a yield value.

As shown in FIG. 19, a fluid exhibiting such a Bingham flow has a yield value τ ₀ , which indicates that the fluid does not move unless a force greater than this value is applied to the fluid. .

As described above, the sample W was polished by the polishing apparatus shown in FIG. 9 using the polishing method of the present invention.
4, cleaning was performed with the cleaning apparatus shown in FIGS. By performing such polishing, FIG.
As shown in FIG. 3, a flat and clean surface state could be obtained without the abrasive particles contained in the polishing liquid remaining adsorbed on the surface of the A1 film.

Further, the present invention is not limited to the above-described first to third embodiments, and various changes are possible. For example, as abrasive particles, SiO ₂ particles, Fe ₂ O ₃ particles, SiC particles, SiN particles, ZO ₂
The same effects as described above can be obtained by using particles and TiO ₂ particles. The same effect as described above can be obtained by adding an alkali such as KOH, NaOH, NH ₄ OH or an acid such as HCl to the polishing liquid in order to increase the polishing rate. Further, the same effect as described above can be obtained even when the temperature of the polishing liquid is changed in the range of 0 to 90 ° C.

In the first and second embodiments of the present invention, the case where the film to be polished is an A1 film and a silicon oxide film (SiO ₂ ) is described.
The film to be polished is an Ag film, Cu film, Si film, Si ₃ N ₄ film, α
-Si, poly-Si, SiON, SiOF, BPS
G, (Boron-Phospho-Silicate
Glass), PSG (Phospho-Silic)
ate Glass), SiN, Si ₃ N ₄ , Si,
The same effects as described above can be obtained when W, Ag, Cu, Ti, TiN, Au, Pt, or Ru are used.

In the third embodiment of the present invention, the case where a high molecular weight organic compound carboxyvinyl polymer having the property of Bingham flow is added to the polishing liquid has been described. FIG. 1 shows a solution containing an organic compound carboxyvinyl polymer having
4 can be used as a cleaning liquid while being dropped onto the surface of the Si substrate from the pure water pipe 34 of the cleaning apparatus. In this case, since the surface of the Si substrate is cleaned with a cleaning liquid to which a substance in a polymer state is added, the cleanliness of the surface of the Si substrate is further increased.

Other examples having the property of flowing Bingham include a solution obtained by dissolving iron oxide and aluminum oxide particles in water. Depending on the conditions, it can be used, and the same effect can be obtained.

[0073]

As described above, the polishing method and the cleaning method according to the present invention are characterized in that a material having a high molecular state such as an organic compound is added to a polishing liquid to thereby provide a polishing solution between a concave surface of a film to be polished and a polishing cloth surface. And the viscosity of the polishing liquid existing between the surface of the convex portion of the film to be polished and the surface of the polishing cloth become different, so that only the desired convex portion can be efficiently used without generating a dishing shape. Can be polished and cleaned well.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a polishing method according to a first embodiment of the present invention.

FIG. 2 shows a polishing method according to a first embodiment of the present invention,
FIG. 4 is a cross-sectional view showing a state after the formation of an l film.

FIG. 3 shows a polishing method according to a first embodiment of the present invention,
Sectional drawing which shows the l film after flattening.

FIG. 4 is a sectional view showing a change in a polishing step according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing a change in a polishing step according to the first embodiment of the present invention.

FIG. 6 is a perspective view showing a change in a polishing process according to the first embodiment of the present invention.

FIG. 7 is a sectional view showing a polishing mechanism of the present invention.

FIG. 8 is a sectional view showing a polishing mechanism of the present invention.

FIG. 9 is a side view showing the polishing apparatus according to the first embodiment of the present invention.

FIG. 10 is a view showing a cleaning mechanism of the present invention.

FIG. 11 is a sectional view showing a polishing method according to a second embodiment of the present invention.

FIG. 12 is a sectional view showing a polishing method according to a second embodiment of the present invention.

FIG. 13 is a sectional view showing a polishing method according to a second embodiment of the present invention.

FIG. 14 is a side view showing a cleaning method according to a third embodiment of the present invention.

FIG. 15 is a top view showing a cleaning method according to a third embodiment of the present invention.

FIG. 16 is a side view showing a cleaning method according to a third embodiment of the present invention.

FIG. 17 is a top view showing a cleaning method according to the third embodiment of the present invention.

FIG. 18 is a conceptual diagram showing the definition of viscosity.

FIG. 19 is a comparative diagram showing characteristics of flow.

FIG. 20 is a sectional view showing a polishing method according to a conventional technique.

FIG. 21 is a cross-sectional view after a wiring groove is formed by a polishing method according to a conventional technique.

FIG. 22 is a cross-sectional view after a metal film is formed by a polishing method according to a conventional technique.

FIG. 23 is a cross-sectional view after a metal wiring is formed by a polishing method according to a conventional technique.

FIG. 24 is a cross-sectional view showing a state after polishing by a polishing method according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 100 ... Substrate 2, 101 ... Silicon oxide film 3, 102 ... Wiring groove 4, 103 ... Al film 5 ... Al film convex part 6 ... Al film concave part 7, 104 ... Abrasive particles 8, 22 ... Polishing Cloth 9 Electrode 21 Polishing plate 22 Polishing cloth 23 Vacuum chuck holder 24 Polishing liquid supply pipe 25 Polishing liquid tank 31, 41 Chuck holder 32, 33 Roll sponge 34, 43 Pure water pipe 42 ... Sponge W, W '... Sample α: High viscosity abrasive β: Low abrasive viscosity

Claims (10)

[Claims] A step of forming a film to be polished on a substrate having irregularities; and a step of polishing the film to be polished using a polishing liquid containing a substance in a polymer state to flatten the substrate. A method for polishing a substrate, comprising: 2. The substrate polishing method according to claim 1, wherein the high molecular substance has a Bingham flow property. 3. The method for polishing a substrate according to claim 1, wherein the substance in a polymer state is a carboxyvinyl polymer of an organic compound. 4. The method according to claim 1, wherein the film to be polished is a metal film or an insulating film. 5. A step of forming a film to be polished on a substrate having irregularities, a step of polishing the film to be polished by using a polishing liquid containing a substance in a polymer state, and a step of flattening the substrate; Cleaning the flattened surface of the substrate. 6. A step of forming a film to be polished on a substrate having irregularities, and pressing the substrate on which the film to be polished is formed against a polishing cloth on a polishing platen to form a polishing liquid containing a substance in a polymer state. Polishing the film to be polished by relatively moving the substrate and the polishing platen while supplying the film between the film to be polished and the polishing cloth; A method of polishing a substrate, comprising: removing a polishing target film formed on a convex portion per unit time from the removal amount per unit time of a polishing film; and planarizing the substrate. 7. A step of forming a film to be polished on a substrate having irregularities, a step of polishing the film to be polished by using a polishing liquid to flatten the substrate, and a step of flattening the surface of the substrate. Washing the substrate with a substance having a high molecular state. 8. The method for cleaning a substrate according to claim 7, wherein the substance having a high molecular state has a property of flowing Bingham. 9. The method according to claim 7, wherein the high-molecular substance is a carboxyvinyl polymer of an organic compound.
Or the method for cleaning a substrate according to 8. 10. The method according to claim 7, wherein the film to be polished is a metal film or an insulating film.