JP2001148360A - Chemical and mechanical grinding slurry and grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slurry with good quality and safety in a CMP method for reducing an added oxidant with a metal removing speed as fast as a conventional case and reducing the productive cost, and provide a CMP method for adjusting metal removing speed when the improved slurry is used. SOLUTION: A slurry for grinding a metallic layer in a semiconductor integrated circuit chemically and mechanically contains an aqueous agent made of many kinds of oxidants and a grinding agent. At least one of oxidant is a first oxidant for oxidizing the other oxidizing agents. At least another one is a second oxidant for oxidizing the metallic layer. Then, the second oxidant is reduced itself in a repeated cycle of the oxidation by the first oxidant. The slurry solution is made strong acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slurry used for chemical-mechanical polishing (hereinafter, referred to as CMP) and a CMP method using the slurry. The present invention relates to a CMP slurry capable of improving a polishing rate even with a small amount of an oxidizing agent by using a combination of an oxidizing agent having a high speed and an oxidizing agent having a high reduction potential, and a CMP method using the same.

[0002]

2. Description of the Related Art With the development of high integration, high speed, multi-function, etc. of a semiconductor device, a metal wiring layer for connecting a chip internal element and an external circuit has been multilayered. The vertical connection between the multi-layered metal wiring layers is a contact or via
Is done through Such contacts or vias
(via) indicates a contact hole or via (vi
a) After the hole is formed, the metal is deposited and the deposited metal is polished and removed by a CMP process to fill a contact hole or a via hole formed in an interlayer insulating film having a flat surface. It is formed by leaving only the deposited metal.

In the CMP process, a rotating polishing pad and a wafer are brought into direct pressure contact with each other, and a polishing slurry is provided at an interface between them. Therefore, the surface of the wafer is mechanically and chemically polished by the polishing pad coated with the slurry, and becomes flat. Depending on the composition of the slurry, polishing rate, polishing surface defects, defects, and properties such as corrosion and erosion can be changed.

[0004] CMP slurries contain an abrasive such as silica or alumina suspended in an oxidizing aqueous medium and an oxidizing agent. For example, U.S. Pat. No. 5,340,370 discloses potassium ferricyanide (potas) as an oxidizing agent.
Disclosed is a tungsten polishing slurry containing sium ferricyanide, silica as an abrasive, and potassium acetate (potassium acetate). In this patent, 0.1 mole potassium ferricyanide, containing 5% silica and a pH of 3.
It discloses that the removal rate of tungsten is 1600 to 2400 ° / min with the slurry composition adjusted to 4 to 3.6.

[0005] US Pat. No. 5,527,423 discloses a slurry for polishing tungsten containing a ferric nitrate as an oxidizing agent, alumina or silica as an abrasive, deionized water and the like. 5% in this patent
With a slurry composition containing ferric nitrate, 3% alumina or silica, the removal rate of tungsten is 3000
Or, it is disclosed that it is 2000 ° / min.

US Pat. No. 5,783,489 discloses a multi-metal polishing slurry containing an abrasive, a first oxidizing agent, a second oxidizing agent, an organic acid, and deionized water. This patent discloses a technique for effectively removing multiple metal layers composed of aluminum and copper alloys and titanium or an alloy thereof using one polishing slurry.

FIG. 1 shows tungsten (W) in a conductive metal.
FIG. 4 is a diagram for schematically illustrating two cases of an oxidation reaction proceeding on a tungsten surface by an oxidizing agent added to a slurry. Referring to FIG. 1, an oxidizing agent contained in tungsten undergoes an oxidation reaction with tungsten to remove electrons and is itself reduced. Meanwhile or tungsten that have lost electrons form a WO ₂ / WO ₃ form oxide film 12 of the bonded tungsten 10 surface with oxygen provided by oxidant, WO ₄ ^2-anion 1 like
Dissolved in the slurry in four forms. Since the oxide film formed by such an oxidizing agent is easier to remove than the metal itself, it is easily removed by the frictional force between the polishing agent and the polishing pad.

In order to effectively perform such a metal CMP process, a removal rate (removal) of a metal, for example, tungsten is removed.
al rate) condition should be at least 2000 mm / min or more. However, when a slurry using a single oxidizing agent is manufactured as in the above-described conventional method, it takes 2,000 dollars.
In order to provide the above tungsten removal rate characteristics, a large amount of an oxidizing agent must be added.

However, when a slurry is manufactured by adding an excessive amount of an oxidizing agent as in the existing method to increase the metal removal rate, the metal removal rate can be increased, but the impurity concentration in the slurry increases and the slurry after the CMP step is increased. The electrical characteristics of the device may be degraded, or metal corrosion may be deepened, thereby adversely affecting the device yield. In addition, there is a problem that the quality of the slurry is reduced and the risk is increased, and the production cost of the slurry is increased, thereby lowering the competitiveness of the product.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the amount of oxidizing agent added to a slurry while maintaining the same or higher metal removal rate in order to solve the problems of the prior art. An object of the present invention is to provide a slurry for CMP that can reduce the manufacturing cost of the slurry and improve the quality and safety of the slurry. It is another object of the present invention to provide a CMP method capable of controlling a metal removal rate using an improved slurry.

[0011]

According to the present invention, there is provided a polishing slurry for chemically and mechanically polishing a metal layer used in a semiconductor integrated circuit.
(slurry), a plurality of oxidizing agents,
And an abrasive in an aqueous medium, wherein at least one of the plurality of oxidants is a first oxidant that oxidizes a reduced oxidant, and at least one other oxidizes the metal layer. In addition, the second oxidizing agent is reduced and oxidized by the first oxidizing agent, and the oxidizing power is restored to the second oxidizing agent. That is, in the present invention, the second oxidation reaction rate is high.
Since the oxidizing agent oxidizes the metal surface and is itself reduced, the reduced second oxidizing agent is oxidized again by the first oxidizing agent having a high reduction potential, so that the oxidizing power of the second oxidizing agent is reduced. Is restored. Therefore, such a second
The oxidant recycling mechanism is to maintain a high removal rate with only a small amount of oxidant.

The method of the present invention is a method for chemically and mechanically polishing a metal layer on a semiconductor wafer. The method comprises the steps of oxidizing an aqueous medium with an abrasive and a reduced oxidant.
Supplying a strongly acidic slurry containing a second oxidizing agent, which oxidizes the metal and oxidizes the metal itself to reduce the oxidizing power again by the first oxidizing agent, onto the semiconductor wafer; Removing a part of the metal layer while rotating a polishing pad in contact with the semiconductor wafer by using a slurry supplied on the semiconductor wafer to polish the surface of the semiconductor wafer to be flat; Is characterized by including.

Here, the metal layer is made of tungsten, titanium,
It has a single-layer or multi-layer structure made of titanium nitride, copper, aluminum or an alloy thereof. In particular, the slurry of the present invention is most suitable for tungsten. The first oxidizing agent is a peroxide compound having a large reduction potential to oxidize the reduced oxidizing agent, and the second oxidizing agent or the metal oxidizing agent is an iron compound having a high oxidation reaction rate with a metal.
The peroxide compound is hydrogen peroxide (H).
₂ O ₂ ), Benzoyl peroxide: (C ₆ H ₅
CO) ₂ O ₂ ), Calcium peroxide (C)
aO ₂ ), Barium peroxide (Ba)
O ₂ ) or sodium peroxide (Na)
₂ O ₂ ). Of these, hydrogen peroxide is most desirable. The hydrogen peroxide is present in the slurry composition at about 0.0
Most preferably, it is present in an amount in the range of 1 wt% to 10 wt%, particularly in an amount of about 0.5 wt% to 3 wt%. If it is less than 0.01%, the removal rate is too slow to apply the process, and if it is more than 10%, the removal rate is improved but the metal corrosion is deepened.

The iron compounds include ferric nitrate and ferric phosphate (fer
ric phosphate), ferric sulfate or potassium ferricyanide, of which ferric nitrate is most desirable. Ferric nitrate is present in the slurry composition in an amount ranging from about 0.025 wt% to 5 wt%. In particular, it is desirable to be present in an amount in the range of about 0.025 wt% to 1 wt%, most preferably in an amount of about 0.05 wt% to 0.5 wt%. When the content is 0.025 wt% or less, the removal rate is too slow to apply the process, and when the content is 5 wt% or more, the dispersibility of the slurry itself is reduced, and a phenomenon that the slurry clumps occurs.

The slurry of the present invention may have a pH within the range of 2 to 3, preferably 2 to 2.
Within 5 ranges is good. That is, it is effective not to exceed a maximum of 3 from the aspect of slurry dispersion stability. To adjust the pH of the slurry, sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO
₃ ), hydrochloric acid (HCl), or phosphoric acid (H ₃ PO ₄ ).

The abrasive is alumina, silica or ceria (c
eria) is desirably used. In particular, colloidal silica is desirably present in the slurry composition in an amount ranging from about 3 wt% to 25 wt%. In particular, it is most desirable to be present in an amount of about 3-10 wt%. It is desirable that the slurry of the present invention further contains an additive such as a surfactant.

[0017]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 2A to 2D show a process sequence of forming a metal wiring layer using a general CMP process. Referring to FIG. 2A, an interlayer insulating film 102, which is a low dielectric film, is deposited on a semiconductor wafer or a substrate 100, and a trench 104 is formed in the deposited interlayer insulating film 102 by a photo-etching process.

In FIG. 2B, a barrier layer, for example, a barrier layer 106 composed of a composite layer of titanium and titanium nitride is wrapped over the interlayer insulating film 102 in which the trench 104 is formed with a uniform thickness. A metal layer 108 is then formed by depositing thick tungsten over barrier layer 106 to sufficiently fill trench 104.

Referring to FIG. 2C, the semiconductor wafer 100 on which the metal layer 108 is formed is provided with a polishing pad 11 formed on a rotary table 114 by a carrier 116 equipped with CMP.
2 is pressure-bonded. At this time, since the slurry 118 is provided on the polishing pad 112, the semiconductor wafer 1
Slurry is supplied to the interface between 00 and the polishing pad 112. The supplied slurry 118 is an improved slurry according to the present invention.

Referring to FIG. 2D, the surface of the semiconductor wafer 100 is polished by the above-described CMP process to form an interlayer insulating film 102.
The overlying metal layer and the barrier layer are completely removed, and the barrier layer 106 and the metal layer 11 filled in the trench 104 are removed.
Only 0 remains. The remaining barrier layer 106 and metal layer 110 are provided as a wiring layer.

FIG. 3 illustrates a reaction mechanism of a metal chemical and mechanical polishing process using a slurry to which a plurality of oxidizing agents are added according to the present invention. That is, Fe provided from ferric nitrate which is a second oxidizing agent having a high reaction rate
^{The +3} ions 122 ^remove electrons from tungsten (W) and are reduced to Fe ⁺² ions 120. Meanwhile, the tungsten is oxidized loses electrons W ^- become anionic.

[0022] Fe ⁺² ions 120 are reduced, the reduction potential is deprived of electrons by high hydrogen peroxide 124 Fe ⁺³
The hydrogen peroxide 124 is restored to the ions 122,
It becomes 6. Therefore, the second oxidizing agent, which directly oxidizes tungsten, oxidizes the metal and can reuse the reduced and oxidized recycling reduced by oxidizing the metal, so that a high removal rate can be obtained even in a small amount. become able to. Meanwhile, the oxidized metal anions combine with oxygen contained in the slurry to form an oxide film 120. The oxide film 120 is easily removed by frictional force with the solid silica 418 as an abrasive or the polishing pad.

That is, in the present invention, when the second oxidizing agent for oxidizing the metal is reduced by the oxidation reaction, the first oxidizing agent oxidizes the reduced second oxidizing agent again to restore the oxidizing power, Since a process in which the restored second oxidant again participates in the oxidation reaction occurs cyclically during the CMP process, the metal removal rate can be improved with a smaller amount of the oxidant. Thus, an embodiment of the improved slurry of the present invention comprising two oxidizing agents is as follows.

Embodiment 1 In this embodiment, the amount of the second oxidizing agent is 0.5 to evaluate the change in the characteristics of the slurry due to the amount of the first oxidizing agent.
wt%, and the amount of the first oxidizing agent added was 0.01 wt%.
% Of the sample slurry was changed from 3% to 3% by weight. The prepared slurry is composed of colloidal silica, acid, and deionized water in addition to the oxidizing agent, and the sample is a low dielectric film such as a thermal oxide film (HT) on a polysilicon substrate.
O) was deposited at about 1000 °, and a TiN barrier layer and a W metal layer were deposited to a thickness of about 1000 ° and 10,000 °, respectively.

Polishing is performed using 6 inch PRESI equipment (“PR
The pad and carrier film used were a Rodel IC1000 stack pad and R200 carrier film. Also,
Polishing conditions: load pressure = 9 psi, table speed = 30 r
pm, spindle speed = 30 rpm, and slurry flow rate = 250 ml / min.
Table 1 below shows such CMP conditions and evaluation results for each slurry.

[0026]

[Table 1]

As can be seen from the results shown in Table 1, the removal rate of the interlayer insulating film is almost negligible as the addition amount of the hydrogen peroxide as the first oxidizing agent is increased.
It can be seen that the tungsten removal rate gradually increases. However, as the amount of the first oxidizing agent increases, the removal rate of tungsten gradually becomes saturated.

Embodiment 2 In Embodiment 2 of the present invention, in order to evaluate the change in the characteristics of the slurry due to the amount of ferric nitrate as the second oxidizing agent of the present invention, hydrogen peroxide as the first oxidizing agent was used. 1 wt%
%, And the addition amount of the second oxidizing agent is 0.01 to 1 wt.
Four sample slurries varying in% range were prepared. Each condition was given in the same manner as in the first embodiment. The polishing conditions were the same as in Example 1. Such a C
Table 1 below shows the MP conditions and the evaluation results for each slurry.

[0029]

[Table 2]

As can be seen from the results shown in Table 2, as the amount of ferric nitrate as the second oxidizing agent increases, the removal rate of the oxide film hardly changes, but the removal rate of tungsten greatly increases. Showed the result. FIG. 4 is a graph showing the relationship between the polishing rate of the metal layer and the species of the oxidizing agent. In FIG. 4, A shows a case where a slurry to which only about 1 wt% of hydrogen peroxide (H ₂ O ₂ ) was added alone as an oxidizing agent was used, and B shows about 0.5 wt% of ferric nitrate as an oxidizing agent. This shows a case where a slurry to which is added alone is used. C is 1wt
₂ shows a case where a slurry to which hydrogen peroxide (H ₂ O ₂ ) of 0.05% and ferric nitrate of 0.05 wt% are simultaneously added is used. Therefore, as shown in the graph, in the case of A and B, the tungsten removal rate is less than about 500 ° / min, while in the case of C using the slurry according to the present invention, the tungsten removal rate is about 2200 °. / Mi
It can be seen that the removal rate is about 6 to 7 times as high as that obtained when a single oxidizing agent is used at about n.

If only a single oxidizing agent was used and 2000
It is expected that a large amount of oxidizing agent must be added in order to have the removal rate characteristics of Å or more. In fact, when only ferric nitrate is used, approximately 7 to 8 wt% is required to have a tungsten removal rate of about 2000 °.
When the above addition amount is necessary and only hydrogen peroxide is used, even if 10 wt% or more is added, about 400 Å / m
Removal rates results as low as in.

Therefore, when the slurry according to the present invention is used, the second oxidizing agent is recycled by the first oxidizing agent due to the difference between the different oxidation reaction rates and the reduction potentials between the two oxidizing agents. It has the advantage that the same effect as when a large amount is added can be obtained with a small amount. When the pH of the slurry solution of the present invention is changed, the removal ratio and selectivity of tungsten and oxide film are shown in Tables 3 and 4 below.

[0033]

[Table 3]

[0034]

[Table 4]

Accordingly, it can be seen that, in the slurry of the present invention, the etching selectivity between the tungsten and the oxide film is increased depending on the pH of the solution, that is, from a strong alkali to a strongly acidic. Therefore, if the pH value of the slurry solution is adjusted to a strong acidity of about pH 2 to 3 where the etching selectivity between tungsten and the oxide film is large, only the desired tungsten can be removed while the removal amount of the oxide film is minimized.

The present invention may be embodied in various different forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely a simple example in every respect, and should not be construed as limiting. Also, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

[0037]

As described above, according to the present invention, 2
According to the slurry containing the kind of oxidizing agent, the following effects are exhibited. First, the use of the two oxidizing agents can greatly reduce the total amount of the oxidizing agents to be added, thereby greatly reducing the cost of the slurry. Second, the quality and safety of the slurry are ensured by adding a small amount of the oxidizing agent. Third, not only can the metal polishing rate be greatly improved, but also the removal rate of the metal can be easily controlled.

[Brief description of the drawings]

FIG. 1 is a view for explaining two kinds of oxidation reactions occurring on a metal surface by an oxidizing agent of a slurry for metal CMP according to the related art.

FIG. 2 is a process sectional view sequentially illustrating a method of forming a metal wiring using a general CMP process.

FIG. 3 is a view illustrating a mechanism of a chemical and mechanical polishing process of a metal using a slurry to which a plurality of oxidizing agents are added according to the present invention;

FIG. 4 is a graph showing a relationship between a polishing rate of a metal layer and a kind of an oxidizing agent.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 semiconductor wafer or substrate 102 interlayer insulating film 104 trench 106 barrier layer 108, 110 metal layer 112 polishing pad 114 turntable 116 carrier 118 slurry 120 reduced iron ions 122 oxidized iron ion restored 124 hydrogen peroxide 126 water 128 oxide film 130 abrasive

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 13/04 C09K 13/04 101 101 102 102 H01L 21/306 H01L 21/306 M

Claims (32)

[Claims] 1. A slurry for chemically and mechanically polishing a metal layer used in a semiconductor integrated circuit, wherein a plurality of oxidizing agents and a polishing agent are provided in an aqueous medium, and at least one of the plurality of oxidizing agents is provided. Is a first oxidizing agent for reducing another oxidizing agent, and at least another one oxidizes the metal layer and is itself reduced to form the first oxidizing agent.
A slurry comprising a second oxidizing agent which is oxidized by the oxidizing agent to restore its oxidizing power and is recycled, and wherein the slurry solution is strongly acidic. 2. The slurry according to claim 1, wherein the metal layer is one of tungsten, titanium, titanium nitride, copper, aluminum or a combination thereof. 3. The method according to claim 2, wherein the first oxidizing agent is a peroxide compound.
The second oxidizing agent is an iron compound.
The slurry according to 1. 4. The method according to claim 1, wherein the peroxide compound is hydrogen peroxide (H).
₂ O ₂ ), benzoyl peroxide ((C ₆ H ₅ CO) ₂ O ₂ ), calcium peroxide (CaO ₂ ), barium peroxide (Ba)
4. The slurry according to claim 3, wherein the slurry is any one of O ₂ ) and sodium peroxide (Na ₂ O ₂ ). 5. 5. The slurry of claim 4, wherein said hydrogen peroxide is present in said slurry composition in an amount ranging from about 0.01% to 10% by weight. 6. The slurry of claim 4, wherein said hydrogen peroxide is present in said slurry composition in an amount ranging from about 0.5 wt% to 3 wt%. 7. The slurry according to claim 3, wherein the iron compound is one of iron compounds such as ferric nitrate, ferric phosphate, ferric sulfate, potassium ferricyanide and the like. . 8. The slurry of claim 7, wherein said ferric nitrate is present in said slurry composition in an amount ranging from about 0.025 wt% to 5 wt%. 9. The slurry of claim 7, wherein said ferric nitrate is present in said slurry composition in an amount ranging from about 0.025 wt% to 1 wt%. 10. The slurry of claim 7, wherein said ferric nitrate is present in said slurry composition in an amount ranging from about 0.05 wt% to 0.5 wt%. 11. The pH of the slurry solution is 2 to 3
The slurry according to claim 1, which is within the range. 12. A method for controlling the pH of the slurry solution, comprising sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ), and hydrochloric acid (HC).
l), and phosphoric acid (H ₃ PO ₄₎ slurry of claim 11, further comprising any one of the acid therein. 13. The slurry according to claim 1, wherein the abrasive uses one of alumina, silica, and ceria. 14. The slurry of claim 13, wherein the abrasive is present in the slurry composition in an amount ranging from about 3 wt% to 25 wt%. 15. The slurry according to claim 13, wherein the abrasive is present in the slurry composition in an amount of about 5-10 wt%. 16. The slurry according to claim 1, wherein the slurry further comprises a surfactant. 17. A method for chemically and mechanically polishing a metal layer on a semiconductor wafer, comprising: a) a first polishing agent for oxidizing a reduced oxidizing agent.
Supplying a slurry comprising an oxidizing agent and a second oxidizing agent, which is oxidized and reduced by the metal layer and is oxidized again by the first oxidizing agent to restore oxidizing power, in a strongly acidic aqueous medium onto a semiconductor wafer; And b) removing a part of the metal layer while rotating a polishing pad in contact with the semiconductor wafer using the slurry supplied on the semiconductor wafer to make the surface of the semiconductor wafer flat. A chemical and mechanical polishing method comprising the steps of: 18. The method according to claim 18, wherein the metal layer is tungsten, titanium,
The method according to claim 17, wherein the method is one of titanium nitride, copper, aluminum or a combination thereof. 19. The chemical and mechanical polishing method according to claim 18, wherein the first oxidizing agent is a peroxide compound and the second oxidizing agent is an iron compound. 20. The method according to claim 1, wherein the peroxide compound is hydrogen peroxide (H ₂
O ₂ ), benzoyl peroxide ((C ₆ H ₅ CO) ₂ O ₂ ), calcium peroxide (CaO ₂ ), barium peroxide (Ba)
O _2), and chemical and mechanical polishing method according to claim 19, characterized in that the one of sodium peroxide (Na ₂ O _2). 21. The method of claim 20, wherein the hydrogen peroxide is present in the slurry composition in an amount ranging from about 0.01 wt% to 10 wt%. 22. The method of claim 20, wherein the hydrogen peroxide is present in the slurry composition in an amount ranging from about 0.5% to 3% by weight. 23. The method according to claim 1, wherein the iron compound is one of iron compounds such as ferric nitrate, ferric phosphate, ferric sulfate, and potassium ferricyanide.
10. The chemical and mechanical polishing method according to item 9. 24. The method of claim 23, wherein said ferric nitrate is present in said slurry composition in an amount ranging from about 0.025 wt% to 5 wt%. 25. The method of claim 23, wherein the ferric nitrate is present in the slurry composition in an amount in a range from about 0.025 wt% to 1 wt%. 26. The chemical and mechanical polishing of claim 23, wherein the ferric nitrate is present in the slurry composition in an amount ranging from about 0.05 wt% to 0.5 wt%. Method. 27. The method of claim 17, wherein the pH of the slurry is within a range of 2 to 3. 28. Sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ), hydrochloric acid (HC
l), and phosphoric acid (H ₃ PO ₄₎ chemical and mechanical polishing method according to claim 27, further comprising any one of the acid therein. 29. The chemical and mechanical polishing method according to claim 17, wherein the polishing agent uses one of alumina, silica and ceria. 30. The method of claim 29, wherein the abrasive is present in the slurry composition in an amount ranging from about 3 wt% to 25 wt%. 31. The method of claim 29, wherein the abrasive is present in the slurry composition in an amount of about 5 wt%. 32. The method of claim 17, wherein the slurry further comprises a surfactant.