JPH07221055A - Method for forming wiring - Google Patents

Abstract

PURPOSE:To increase the polishing speed ratio for the insulation film of a metal film and easily control the film thickness of the metal film when the polishing is completed by a ground particle liquid where a surface-active agent with a higher polishing speed for the metal surface than the polishing speed for the insulation film is mixed on polishing. CONSTITUTION:A ground particle liquid where a surface-active agent with a higher polishing speed for a metal film 22 than the polishing speed for an insulation film 21 is mixed is used when polishing the metal film 22 on the projecting part of the insulation film 21. Then, the polishing speed for the metal film 22 becomes faster but that for the insulation film 21 does not change almost at all, thus polishing the metal film 22 faster than the insulation film 21. Further. since the surface of the metal film 22a inside a groove 21b cannot be etched easily, the film thickness of the metal film 22 when the polishing is completed can be easily controlled and at the same time the surface of the metal film 22a in the groove 21b and the surface 21c of the insulation film can be positively flattened, thus preventing a polishing device used for forming wiring from being corroded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring forming method,
More specifically, the present invention relates to a method for forming wiring in a semiconductor device by polishing.

[0002]

2. Description of the Related Art As a method of forming wiring by polishing, a groove is formed on an insulating film, and a metal material is embedded in the groove.
Further, after forming the film, there is a method of removing the upper portion of the metal film by polishing to form a wiring (Japanese Patent Laid-Open No. 62-102543).
Issue). FIG. 12 is a schematic cross-sectional view showing a method of forming a wiring by conventional polishing in the order of steps. (A) shows a state in which a groove is formed in an insulating film and a metal film is formed on the upper surface of the insulating film, (b) () Shows a state where the metal film is removed to the surface of the insulating film by polishing, and (c) shows a state where polishing is further continued. In this method, first, an insulating film 21 such as SiO ₂ is formed on a substrate (not shown) by sputtering, for example. The thickness t _a of the insulating film 21 is set to be equal to the sum of the thickness t _c of the insulating film 21a which is located below the metal film 22a as the wiring and the thickness t _b of the metal film 22a as the wiring ( t _a = t _b + t _c ). Next, using a photolithography technique, a patterning process is performed on the insulating film 21 to form a groove 21b. After that, a metal film 22 of an aluminum alloy (Al-Si or Al-Cu) is formed on the insulating film 21 (a). Next, the metal film 22 on the insulating film surface 21c is removed by polishing to planarize the entire surface and the groove 21b of the insulating film 21 is filled with the metal film 22a as a wiring. In this polishing, Al ₂ O ₃ particles or the like are used as abrasive grains, and an aqueous solution of sulfuric acid (pH 2.2), an aqueous solution of nitric acid (pH 2.2), an aqueous solution of acetic acid (pH 2.8) or the like is used as an abrasive grain liquid. When these abrasive liquids are used, the insulating film 2
A metal film 22 made of an aluminum alloy at a polishing rate of 1
The polishing rate is increased, and the thickness t _{b of the} metal film to be the wiring at the end of polishing is controlled (b).

Al ₂ O ₃ particles are used as abrasive grains, an aqueous surfactant solution is used as abrasive liquid, and brass and structural carbon steel (J
IS-S55C), a method of lapping and polishing a single metal of titanium and silver has been proposed (Tomoda et al .: 19
1993 Proceedings of Japan Society for Precision Engineering, Autumn Conference, Proceedings, p
723-p724).

[0004]

In the above method for forming a wiring, a sulfuric acid aqueous solution or an acetic acid aqueous solution is used as the abrasive liquid,
When polishing the insulating film 21 and the metal film 22, the metal film 22
The polishing rate ratio R _p to the insulating film 21 (R _p = polishing rate of metal film / polishing rate of insulating film) is relatively small. Therefore, as shown in FIG. 11C, after the polishing reaches the insulating film surface 21c, the insulating film 21 and the metal film 22a are further polished, and the thickness of the metal film 22a tends to be thin. Therefore, when the polishing is completed, the thickness of the metal film 22a to be the wiring is
There was a problem that it was difficult to control _b .

Further, in the above wiring forming method,
An acid such as a nitric acid aqueous solution is used as the abrasive liquid, and these abrasive liquids have the property of etching the metal film 22 itself. FIG. 13 is a schematic cross-sectional view showing a conventional wiring forming method in the order of steps when a nitric acid aqueous solution is used as the abrasive liquid.
(A) is a state before polishing, (b) is a state during polishing,
(C) shows a state in which the surface of the insulating film is polished. In the case of this method, if the concentration of the abrasive liquid is increased in order to increase the polishing rate ratio R _p , as the metal film 22 is polished, the grooves 21 are formed.
The surface of the metal film 22a in b is also etched (b), and when the polishing reaches the insulating film surface 21c, there is a problem that the thickness t _d of the metal film 22a to be the wiring tends to be thin (c). Further, since the surface of the metal film 22a is etched,
There is a problem that the surface of the metal film 22a and the surface 21c of the insulating film cannot be flattened so that they are flush with each other, and therefore it is difficult to increase the concentration of the abrasive liquid and increase the polishing rate ratio R _p. there were.

Further, in the above-mentioned wiring forming method,
Since an acid such as a nitric acid aqueous solution is used as the abrasive liquid, there is a problem that metal members (stainless steel, cast iron, etc.) constituting the polishing apparatus are likely to be corroded and practical application is difficult.

The present invention has been made in view of the above problems. The polishing rate ratio of a metal film to an insulating film can be increased, the thickness of the metal film can be easily controlled at the end of polishing, and the metal film can be easily controlled. It is an object of the present invention to provide a wiring forming method capable of flattening the surface of the substrate and the surface of the insulating film and preventing corrosion of a device used for forming the wiring.

[0008]

In order to achieve the above object, a method of forming a wiring according to the present invention is such that a metal film is formed on an insulating film having an uneven portion on the surface, and a metal film is formed on the convex portion of the insulating film. In the method of forming a wiring for removing the metal film by polishing, an abrasive liquid mixed with a surfactant having a polishing rate for the metal film that is higher than a polishing rate for the insulating film is used during polishing.

[0009]

FIG. 11 is a schematic cross-sectional view showing, in the order of steps, a method of forming a wiring when a predetermined surfactant is used as an abrasive liquid. (A) is a state before polishing and (b) is a polishing state. A state in the middle, (c) shows a state in which the surface of the insulating film is polished. In the case of this method, the dispersibility of the abrasive grains is enhanced by the surfactant, so that the polishing of the metal film 22 proceeds efficiently, while the etching action of the surfactant is extremely small, so that the groove 21b which does not hit the polishing pad is formed. Metal film 22a inside
The surface will not be etched (b). The present inventor has found that the addition of the surfactant increases the polishing rate for the metal film 22 but hardly changes the polishing rate for the insulating film 21. As a result, the insulating film 2
Therefore, the metal film 22 can be polished more quickly than in No. 1. Further, since the surface of the metal film 22a is difficult to be etched, the film thickness of the metal film 22 at the end of polishing can be easily controlled to t _b , and the surface of the metal film 22a in the groove 21b and the surface 21c of the insulating film are flattened. Can be reliably achieved (c).

According to the wiring forming method of the present invention, since the abrasive grain liquid mixed with the surfactant has a polishing rate for the metal film which is higher than the polishing rate for the insulating film during polishing, the insulating film of the metal film is used. The polishing rate ratio to On the other hand, since the metal film or the metal material constituting the polishing apparatus is difficult to be etched by the surfactant, it is possible to easily control the film thickness of the metal film as the wiring at the end of polishing by these combined actions, The surface of the metal film and the surface of the insulating film can be surely flattened, and further, corrosion of the polishing apparatus used for forming the wiring can be prevented.

According to the present invention, the insulating film and the metal film formed on the substrate are polished, and the polishing rate ratio of the metal film to the insulating film is increased, while the surfaces of the insulating film and the metal film are polished. This is a flattening method, which is a technique different from the above-described single metal lapping and polishing method.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wiring forming method according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an embodiment of a wiring forming method according to the present invention in the order of steps. FIG. 1A shows a state in which a groove is formed in an insulating film and a metal film is formed on the upper surface of the insulating film. , (B) show a state where the metal film is removed to the surface of the insulating film by polishing. First, ECR-
CVD (Electron Cyclotron Resonance Chemical Vapo
The insulating film 11 made of SiO ₂ or the like is formed on a substrate (not shown) having a substantially flat shape by the r Deposition method. Next, using a photolithography technique, a patterning process is performed on a predetermined portion of the insulating film 11 to form a groove 11b. After that, Al-C is formed on the insulating film 11 by the ECR sputtering method.
A metal film 12 of u alloy or Cu is formed (a). Next, the metal film 12 on the insulating film surface 11c is removed by polishing to planarize the entire surface and the groove 11b of the insulating film 11 is removed.
A metal film 12a as a wiring is embedded and formed. In this polishing, a mixture of a surfactant having a large polishing rate ratio R _p of the metal film 12 to the insulating film 11 is used as the abrasive liquid (b).

Below, Si having an average particle size of about 0.05 μm is used.
Using an abrasive liquid in which a surfactant is added to and mixed with a mixture of O ₂ particles in pure water of about 15%, the concentration of the surfactant in the abrasive liquid and the polishing rate of the metal film 12 with respect to the insulating film 11 are used. Ratio R _p (hereinafter, simply referred to as polishing rate ratio R _p ) and metal film 1
Etch rate ratio for the two polishing rate R _e (hereinafter, simply polishing rate of the etching rate / metal film .R _e = metal film, referred to as the etch rate ratio R _e) described the results of investigating the relationship between. As a sample, 6 inch Si
A substrate on which an insulating film of SiO ₂ is formed by the ECR-CVD method (A) and Al-by the ECR sputtering method
A Cu alloy or a Cu metal film (B) was used. As the surfactant, stearylamine acetate, polyethylene glycol, sodium laurate and sodium oleate shown in Table 1 below were used.

[0014]

[Table 1]

The polishing apparatus used is one normally used for polishing silicon wafers, and the polishing pressure is 100 g / cm ² ,
The relative speed between the substrate and the polishing platen in the polishing apparatus was set to 60 cm / sec. The polishing rate ratio R _p was measured by polishing the sample (A) and the sample (B) under the same conditions, and polishing the metal film (depth) / insulating film (depth) per single time. . Etching rate ratio R
_e was measured by etching the metal film of the sample (B) at room temperature with an abrasive liquid and etching the metal film per unit time (depth) / polishing amount of the metal film (depth).
As a comparative example, SiO ₂ having an average particle size of about 0.05 μm
A metal film of an Al—Cu alloy and an insulating film of SiO ₂ were prepared by using the abrasive liquids in which sulfuric acid, acetic acid, and nitric acid shown in Table 1 were added and mixed in a mixture of particles in pure water of about 15%. The case of polishing or etching will be described together.

FIGS. 8 and 9 show the weight% concentration, the polishing rate ratio R _p and the etching rate ratio R _e in the case of using the abrasive liquids in which sulfuric acid and acetic acid were added and mixed in Comparative Examples 1 and 2, respectively. It is a curve figure showing the relation with. As is clear from FIG. 8 and FIG. 9, in the case of using an abrasive grain liquid to which sulfuric acid and acetic acid are added and mixed, the polishing rate ratio R _p increases as the concentration of sulfuric acid and acetic acid in the abrasive grain liquid increases, and etching is performed. The speed ratio R _e also increases. Therefore, the polishing stop effect of the metal film 12a (both in FIG. 1) by the insulating film surface 11c becomes large, but the metal film 12a is easily etched, and the surface of the metal film 12a and the insulating film surface 11c (both in FIG. 1) are flattened. It becomes difficult to obtain the desired film thickness of the metal film 12a (FIG. 1) which will be the wiring.

FIG. 10 is a curve diagram showing the relationship between the weight% concentration and the polishing rate ratio R _p and the etching rate ratio R _e in the case of using the abrasive liquid in which nitric acid was added and mixed in Comparative Example 3. is there. As is clear from FIG. 10, nitric acid was added.
When a mixed abrasive liquid is used, the polishing rate ratio R _p is relatively high and the etching rate ratio R _e is small when nitric acid is at a low concentration, facilitating the flattening and achieving a predetermined metal film thickness. Is relatively easy to obtain. However, as the nitric acid concentration in the abrasive liquid increases, the polishing rate ratio R _p further increases and the etching rate ratio R _e also increases, so that the polishing stop effect of the insulating film becomes larger, but the planarization is difficult. Therefore, it becomes difficult to obtain the desired film thickness of the metal film.

On the other hand, FIG. 2 is a curve diagram showing the relationship between the weight% concentration and the polishing rate ratio R _p and the etching rate ratio R _e in the case of using the abrasive liquid mixed with stearylamine acetate in Example 1. Is. As is clear from FIG. 2, when the abrasive liquid containing stearylamine acetate was used, the concentration of stearylamine acetate in the abrasive liquid was 0.01% to 20%.
The polishing rate ratio R _p increases from approximately 2 to approximately 20 as the percentage increases, while the etching rate ratio R _e is maintained at approximately 0.

As is clear from the above description and measurement results, the polishing rate ratio R _p can be increased by the method of forming a wiring according to the first embodiment. On the other hand, since the metal film 12 and the metal material constituting the polishing apparatus are difficult to be etched by stearylamine acetate, the combined effect of these effects makes it possible to easily control the film thickness of the metal film 12a as wiring at the end of polishing. Therefore, the surface of the metal film 12a and the surface 11c of the insulating film can be surely flattened, and corrosion of the polishing apparatus used for forming the wiring can be prevented. In particular, when an abrasive grain liquid containing 0.1% or more of stearylamine acetate is used, the polishing rate ratio R _p can be greatly increased, and flattening and wiring film thickness control can be realized more reliably. .

FIG. 3 is a curve diagram showing the relationship between the weight% concentration and the polishing rate ratio R _p and the etching rate ratio R _e in the case of using the abrasive liquid mixed with polyethylene glycol of Example 2. . As is clear from FIG. 3, when the abrasive grain liquid mixed with polyethylene glycol is used, the polishing rate ratio R _p is approximately 2 to approximately as the polyethylene glycol concentration in the abrasive grain liquid increases from 0.01% to 20%. 1
Although it increases to 0, the etching rate ratio R _e is maintained at about 0.

As is clear from the above description and measurement results, according to the wiring forming method of the second embodiment, since the abrasive grain liquid contains polyethylene glycol, the polishing rate ratio R _p can be increased. it can. On the other hand, since the metal film 12 and the metal material forming the polishing apparatus are difficult to be etched by polyethylene glycol, the effect similar to that of the first embodiment can be obtained due to the combined effect of these.

FIG. 4 is a curve diagram showing the relationship between the weight% concentration and the polishing rate ratio R _p and the etching rate ratio R _e in the case of using the abrasive liquid containing sodium laurate of Example 3. is there. As is clear from FIG. 4, when the abrasive liquid containing sodium laurate is used, the concentration of sodium laurate in the abrasive liquid is 0.01% to 20%.
As the polishing rate ratio R _p increases, the polishing rate ratio R _p increases from about 2 to about 12, but the etching rate ratio R _e is maintained at about 0.

As is clear from the above description and measurement results, according to the wiring forming method of Example 3, the polishing rate ratio R _p should be increased because sodium laurate is mixed in the abrasive grain liquid. You can On the other hand, since the metal film 12 and the metal material forming the polishing apparatus are difficult to be etched by sodium laurate, the effects similar to those of the first embodiment can be obtained due to the combined effects thereof.

FIG. 5 is a curve diagram showing the relationship between the weight% concentration, the polishing rate ratio R _p, and the etching rate ratio R _e in the case of using the abrasive liquid containing sodium oleate of Example 4. is there. As is clear from FIG. 5, when the abrasive liquid containing sodium oleate was used, the concentration of sodium oleate in the abrasive liquid was 0.01% to 20%.
The polishing rate ratio R _p increases from approximately 2 to approximately 18 as the percentage increases, while the etching rate ratio R _e is maintained at approximately 0.

As is clear from the above description and measurement results, according to the wiring forming method of Example 4, the polishing rate ratio R _p is increased because sodium oleate is mixed in the abrasive grain liquid. You can On the other hand, since the metal film 12 and the metal material forming the polishing apparatus are difficult to be etched by sodium oleate, it is possible to obtain substantially the same effect as that of the first embodiment due to the combined effect of these.

Further, FIG. 6 shows the weight% concentration of stearylamine acetate, the polishing rate ratio R _p, and the etching rate ratio in the case of using the abrasive liquid in which stearylamine acetate was mixed with 0.05% sulfuric acid in Example 5. is a curve diagram showing the relationship between R _e. As is clear from FIG. 6, when an abrasive grain liquid in which stearylamine acetate and 0.05% sulfuric acid are mixed is used, the stearylamine acetate concentration in the abrasive grain liquid is 0.01%.
The polishing rate ratio R _p increases from approximately 3 to approximately 22 as the etching rate ratio increases from 20% to 20%, but the etching rate ratio R _e increases to approximately 0.0.
Maintained at 2.

As is clear from the above description and measurement results, according to the wiring forming method of Example 5, since stearylamine acetate and 0.05% sulfuric acid are mixed in the abrasive liquid, polishing is performed. The speed ratio R _p can be increased. On the other hand, the metal material constituting the metal film 12 and the polishing apparatus is difficult to be etched by stearylamine acetate and 0.05% sulfuric acid, and therefore, the combined effect of these can obtain substantially the same effect as that of the first embodiment. .

Further, FIG. 7 shows a case in which the substrate having the Cu metal film 12 (FIG. 1) instead of the Al—Cu metal film formed thereon was polished by using the abrasive liquid mixed with stearylamine acetate in Example 6. FIG. 6 is a curve diagram showing the relationship between the weight% concentration of stearylamine acetate and the polishing rate ratio R _p and etching rate ratio R _e . As is clear from FIG. 7, in the case of using the abrasive liquid mixed with stearylamine acetate, the polishing rate ratio R _p is approximately 2 as the stearylamine acetate concentration in the abrasive liquid increases from 0.01% to 20%. However, the etching rate ratio R _e is maintained at about 0.

As is clear from the above description and measurement results, according to the wiring forming method of the sixth embodiment, since stearylamine acetate is mixed in the abrasive liquid, the metal film 12 is made of Cu. However, the polishing rate ratio R _p can be increased. On the other hand, since the metal film 12 and the metal material forming the polishing apparatus are difficult to be etched by stearylamine acetate, it is possible to obtain substantially the same effect as in the case of the first embodiment due to these combined effects.

Although the Al--Cu alloy or Cu is used as the metal film 12 in the above-described embodiment, in another embodiment, Al, W, Ag, Au, Al--Si alloy, Al--Si is used.
It is also possible to use a Cu alloy or the like.

Although the SiO ₂ film formed by ECR-CVD or ECR sputtering is used as the insulating film 11 in the above-mentioned embodiment, TEOS is used in another embodiment.
-CVD, p-CVD, thermal CVD, thermal oxidation, it is also possible to use a SiO ₂ film formed by a method such as sputtering.

Further, although the SiO ₂ film is used as the insulating film 11 in the above-mentioned embodiment, SiN, Si are used in another embodiment.
It is also possible to use ON, SiOF, PSG, BPSG, SOG films and the like.

Although SiO ₂ particles having an average particle size of approximately 0.05 μm were used as the abrasive grains in the above-mentioned examples, Al ₂ O ₃ particles having an average particle size of approximately 0.05 μm were used in another example. It is also possible to use.

Further, in the above-mentioned embodiment, the abrasive grains having an average particle diameter of about 0.05 μm are used, but in another embodiment, it is possible to use the abrasive grains having an average particle diameter of not 0.05 μm.

Although stearylamine acetate, polyethylene glycol, sodium laurate, and sodium oleate were used as surfactants in the above-described examples, in another example, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, and butylnaphthalene were used. It is also possible to use surfactants such as sodium sulfonate, trimethylstearyl ammonium chloride, laurylamine acetate, polyethylene glycol monolauryl ether, sorbitan monolaurate.

[0036]

As described above in detail, in the method of forming a wiring according to the present invention, the abrasive liquid containing a surfactant having a polishing rate for the metal film which is higher than the polishing rate for the insulating film during polishing. Therefore, the polishing rate ratio of the metal film to the insulating film can be increased. on the other hand,
Since the metal material constituting the metal film or the polishing apparatus is difficult to be etched by the surfactant, it is possible to easily control the film thickness of the metal film as the wiring at the end of polishing by these combined actions, It is possible to surely flatten the surface of the metal film and the surface of the insulating film, and further to prevent corrosion of the polishing apparatus used for forming the wiring.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a wiring forming method according to the present invention in the order of steps. FIG. 1A shows a groove formed in an insulating film and a metal film formed on the upper surface of the insulating film. Status,
(B) shows a state where the metal film is removed to the surface of the insulating film by polishing.

FIG. 2 is a weight% concentration and a polishing rate ratio R in the case of using an abrasive liquid mixed with stearylamine acetate in Example 1.
FIG. 7 is a curve diagram showing the relationship between _p and the etching rate ratio R _e .

FIG. 3 is a curve diagram showing a relationship between a weight% concentration and a polishing rate ratio R _p and an etching rate ratio R _e in the case of using an abrasive grain liquid mixed with polyethylene glycol of Example 2.

FIG. 4 is a weight% concentration and a polishing rate ratio R in the case of using an abrasive liquid mixed with sodium laurate of Example 3.
FIG. 7 is a curve diagram showing the relationship between _p and the etching rate ratio R _e .

5 is a weight% concentration and a polishing rate ratio R in the case of using an abrasive liquid mixed with sodium oleate of Example 4. FIG.
FIG. 7 is a curve diagram showing the relationship between _p and the etching rate ratio R _e .

FIG. 6 Stearylamine acetate and sulfuric acid of Example 5 0.0
FIG. 5 is a curve diagram showing the relationship between the weight% concentration of stearylamine acetate and the polishing rate ratio R _p and the etching rate ratio R _e in the case of using an abrasive liquid mixed with 5%.

FIG. 7 is a graph showing a stearylamine acetate weight% concentration and a polishing rate ratio R in the case of a substrate on which a Cu metal film is formed, using the abrasive liquid mixed with stearylamine acetate in Example 6.
FIG. 7 is a curve diagram showing the relationship between _p and the etching rate ratio R _e .

FIG. 8 is a curve diagram showing the relationship between the weight% concentration, the polishing rate ratio R _p, and the etching rate ratio R _e in the case of using the abrasive liquid in which sulfuric acid was mixed in Comparative Example 1.

FIG. 9 is a curve diagram showing the relationship between the weight% concentration and the polishing rate ratio R _p and the etching rate ratio R _e in the case of using an acetic acid liquid mixed with acetic acid of Comparative Example 2.

FIG. 10 is a curve diagram showing the relationship between the weight% concentration and the polishing rate ratio R _p and the etching rate ratio R _e in the case of using the abrasive grain liquid in which nitric acid was mixed in Comparative Example 3.

FIG. 11 is a cross-sectional view schematically showing a step of forming a wiring when a predetermined surfactant is used as an abrasive liquid, (a) showing a state before polishing and (b) showing a state during polishing. Status,
(C) shows a state in which the surface of the insulating film is polished.

FIG. 12 is a schematic cross-sectional view showing a conventional wiring forming method in the order of steps, FIG. 12A shows a state in which a groove is formed in an insulating film and a metal film is formed on the upper surface of the insulating film, and FIG. Shows a state where the metal film is removed to the surface of the insulating film by polishing, and (c) shows a state where the polishing is further continued.

13A and 13B are schematic cross-sectional views showing, in the order of steps, a conventional method of forming a wiring when a nitric acid aqueous solution is used as an abrasive liquid, (a) showing a state before polishing and (b) showing a state during polishing. ,
(C) shows a state in which the surface of the insulating film is polished.

[Explanation of symbols]

 11 Insulating film 12, 12a Metal film

Claims (1)

[Claims] 1. A method for forming a wiring in which a metal film is formed on an insulating film having an uneven portion on the surface and the metal film on the convex portion of the insulating film is removed by polishing. A method for forming a wiring, which comprises using an abrasive liquid containing a surfactant having a polishing rate for the metal film higher than the polishing rate.