JPH11204474A - Polishing of fluorine-containing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form stably an interlayer insulating film using a low-dielectric constant film consisting of a fluorine-containing film as the result that as polishing of the fluorine-containing film becomes possible, by a simple method without causing elosion of fluorine and a change in the skeleton construction of a silicon oxide film, an increase in the dielectric constant of the interlayer insulating film is inhibited and at the same time, the good flatness of the insulating film can be realized. SOLUTION: A polishing method is provided with a process for forming a fluorine-containing film (such as a fluorine-containing silicon oxide film or a fluorine-containing silicon nitrooxide film) 14 on a base body 10, and a process for polishing the surface of the film 14 while an abrasive slurry is fed to the surface of the film 14. In the polishing method, an ammonia aqueous solution, an organic amine aqueous solution, an organic fatty acid aqueous solution or an inorganic acid aqueous solution, for example, is used to a dispersion medium to disperse abrasive particles in the slurry, and at least one kind of an oxide out of a silicon oxide and a metallic oxide is used to abrasive grains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a film containing fluorine, and more particularly to a method for polishing a film containing fluorine for polishing an interlayer insulating film made of a film containing fluorine in a semiconductor device by polishing.

[0002]

2. Description of the Related Art As device rules have become finer, a problem of delay caused by interlayer capacitance of an interlayer insulating film has been pointed out, and it is necessary to lower the dielectric constant of the interlayer insulating film. Until now, low dielectric constant films have been used as tetraethoxysilane (TEO).
S) [Si (OC ₂ H ₅ ) ₄ ] with hexafluoroethane (C ₂ F ₆ ) or nitrogen trifluoride (NF
There has been proposed a method of forming a silicon fluorinated oxide (SiOF) film by adding ₃ ). For information on how to add hexafluoroethane, see Solid State Devices and Mat
erials, 25 (1993) Usami, Simokawa, Yoshimaru, p. 161-16
3 and the method of adding nitrogen trifluoride is described in the 40th Annual Meeting of the Japan Society of Applied Physics.
a-ZV-9.

[0003] In parallel with the lowering of the dielectric constant of these interlayer insulating films, the wiring technology is progressing in the direction of miniaturization and multi-layering as the density of devices increases. However, higher integration may cause a reduction in reliability. This is because the step of the interlayer insulating film becomes large and steep with the progress of miniaturization and multilayering of the wiring, and the processing accuracy and reliability of the wiring formed thereon are reduced. Therefore, it is necessary to improve the flatness of the interlayer insulating film at the present time when the step coverage of the aluminum wiring cannot be significantly improved.

As a planarization technique, a chemical mechanical polishing technique using fine particles of silicon oxide in a basic solution has recently been reported. In this polishing method, while the slurry is supplied onto a polishing cloth adhered to a rotating platen, the surface to be polished of the wafer on which the interlayer insulating film is formed is brought into sliding contact with the polishing cloth to flatten the wafer. . Note that, as the slurry, a dispersion of silicon oxide fine particles or metal oxide fine particles having a particle size of about 10 nm in an aqueous potassium hydroxide solution is usually used.

[0005]

However, the above-mentioned silicon oxide film containing fluorine is chemically and mechanically polished (hereinafter referred to as CMP) using a slurry in which ordinary silicon oxide fine particles are dispersed in an aqueous potassium hydroxide solution. Is Ch
When mechanical mechanical polishing is performed, the skeleton of the fluorine or silicon oxide film in the silicon oxide film containing fluorine and an alkali metal hydroxide such as potassium hydroxide contained in the polishing slurry used in the CMP process. Reacts to lower the fluorine concentration in the film, change the structure of the silicon oxide film, and increase the dielectric constant.

Since the aqueous potassium hydroxide solution is an aqueous solution of a strong base, it is subjected to a neutralization reaction (acid-base) with fluorine contained in an interlayer insulating film such as a silicon oxide film or hydrogen fluoride generated by hydrolysis. Reaction) occurs, and fluorine is eluted from the insulating film. It is generally known that in a solution of a strong base, the bond between silicon (silicon) and oxygen is decomposed by an alkali hydrolysis reaction. for that reason,
In an aqueous solution of potassium hydroxide, this reaction proceeds, the structure of the silicon oxide film changes, and the formation of silanol groups and the above-described fluorine extraction reaction are promoted. For this reason,
After the CMP, the relative dielectric constant of a film such as a silicon oxide film containing fluorine is increased.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a method for polishing a fluorine-containing film, which has been made to solve the above-mentioned problems, comprising the steps of: forming a fluorine-containing film on a substrate; A step of polishing the surface while supplying a polishing slurry to the surface of the surface, wherein an ammonia solution, an organic amine solution, and an organic fatty acid solution are dispersed in a dispersion medium for dispersing abrasive particles in the polishing slurry. , And an inorganic acid solution.

In the above method for polishing a film containing fluorine, an ammonia solution, an organic amine solution,
Since one of the organic fatty acid solution and the inorganic acid solution is used, for example, a neutralization reaction with fluorine contained in a film such as a silicon oxide film and hydrogen fluoride generated by hydrolysis (acid-base reaction) ) Is suppressed. Therefore, fluorine does not elute from the insulating film. Further, since the bond between silicon and oxygen is not broken, there is no change in the structure of the skeleton of the silicon oxide film. Therefore, desorption of fluorine from the film containing fluorine and deterioration of the film structure during polishing are suppressed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment relating to a method for polishing a fluorine-containing film of the present invention will be described with reference to the manufacturing process diagram of FIG.

As shown in FIG. 1A, a semiconductor substrate 1
1, an interlayer insulating film 12 is formed on the wiring layer 1.
3 are formed. As an example, such a substrate 10
Was prepared. The semiconductor substrate 11 is made of, for example, a silicon substrate, the interlayer insulating film 12 is made of an insulating film such as a silicon oxide film or a silicon oxyfluoride film, and the wiring layer 13 is made of a conductive material such as aluminum or an aluminum alloy. Consists of a body.

Next, as shown in FIG. 1 (2), for example, using a parallel plate type plasma CVD apparatus,
As the film 14 containing fluorine, for example, a silicon oxide film containing fluorine is formed. The conditions for the CVD are as follows: tetraethoxysilane (TEOS) [Si (O
C ₂ H ₅ ) ₄ ] [800 sccm] and hexafluoroethane (C ₂ F ₆ ) [800 sccm] as a fluorine source
And helium (He) as a carrier gas for tetraethoxysilane. The above sccm indicates a volume flow rate (cm ³ / min) in a standard state, and is hereinafter referred to as sccm. Also, when the pressure of the film formation atmosphere is set to 1.4 kPa, the substrate temperature is set to 400 ° C., and the RF power is set to 700 W, the fluorine-containing film 14 on the wiring layer 13 is polished when the fluorine-containing film 14 is polished in the next step. For example, a silicon oxide film containing fluorine is formed to have a predetermined thickness, for example.

Thereafter, as shown in FIG. 1C, CMP is performed on the fluorine-containing film 14 to flatten its surface. In this CMP, for example, fine particles of silicon oxide are used as abrasive particles, and an ammonia solution, an organic amine solution, an organic fatty acid solution, or an inorganic acid solution, for example, an aqueous ammonia solution is used as a dispersion medium for dispersing the abrasive particles. . Under such conditions, an interlayer insulating film 15 having a low dielectric constant and made of the film 14 containing fluorine is formed.

Thereafter, the relative dielectric constant and the fluorine content of the silicon oxide film containing fluorine after the above-mentioned CMP were measured. As a result, the relative dielectric constant before and after the CMP was 3.8, which was not changed, and the content of fluorine was not changed to 5 atoms%. Therefore, it was confirmed that desorption of fluorine and deterioration of the film structure in the polishing step can be suppressed by using silicon oxide for the abrasive particles and an aqueous ammonia solution for the dispersion medium.

In the method of polishing a film containing fluorine according to the first embodiment, since an aqueous ammonia solution is used as a dispersion medium of the polishing slurry, for example, fluorine contained in the interlayer insulating film 15 having a low dielectric constant, Neutralization reaction (acid-base reaction) with hydrogen fluoride generated by decomposition is suppressed. Therefore, fluorine does not elute from the interlayer insulating film 15. Also, since the bond between silicon and oxygen is not broken, no change in the structure of the skeleton of the silicon oxide film occurs.
Therefore, elimination of fluorine from the interlayer insulating film 15 containing fluorine during polishing and deterioration of the film structure are suppressed.

Next, a second embodiment relating to a method of polishing a film containing fluorine will be described. In the second embodiment, in the first embodiment, the film containing fluorine is replaced by electron cyclotron resonance (ECR).
A silicon oxide film containing fluorine is formed using a plasma CVD apparatus. In CMP, cerium oxide is used as abrasive particles, and an aqueous ammonia solution is used as a dispersion medium.

First, the ECR plasma CVD apparatus will be described with reference to the schematic diagram of FIG. As shown in FIG. 2, a plasma generation chamber 22 communicating with the reaction chamber 21 is provided above the reaction chamber 21. A magnet 23 for satisfying the ECR condition is provided on the outer periphery of the plasma generation chamber 22. In addition, in the upper part of the plasma generation chamber 22,
A microwave waveguide 24 for introducing microwaves is provided in the plasma generation chamber 22.

The reaction chamber 21 is provided with a gas introduction pipe (not shown) through which a film forming gas (source gas) is introduced, and a reaction is performed to maintain the inside of the reaction chamber 21 at a predetermined pressure. An exhaust pipe 25 from which the gas in the chamber 21 is exhausted is provided.

Further, a lower electrode 26 for mounting the substrate 10 on which a film is to be formed is provided inside the reaction chamber 21. The lower electrode 26 is provided inside the lower electrode 26.
A heater 27 for heating the heater is provided. A power supply 29 is connected to the lower electrode 26 via a capacitor 28.
Is connected. ECR plasma CVD as described above
The device 20 is configured.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, in the first embodiment, the fluorine-containing film 14 is replaced with the ECR plasma C.
It is formed using a VD apparatus. In CMP, cerium oxide is used as abrasive particles, and an aqueous ammonia solution is used as a dispersion medium.
At this time, the same components as those in the first embodiment will be described with the same reference numerals. .

As shown in FIG. 1A, a semiconductor substrate 1
1, an interlayer insulating film 12 is formed, and a wiring layer 13 is further formed. As an example, such a substrate 10 was prepared. The semiconductor substrate 11 is made of, for example, a silicon substrate, the interlayer insulating film 12 is made of an insulating film such as a silicon oxide film or a silicon oxyfluoride film, and the wiring layer 13 is made of a conductive material such as aluminum or an aluminum alloy. Consists of a body.

Next, as shown in FIG. 1B, for example, a fluorine-containing silicon oxide film is formed as the fluorine-containing film 14 using, for example, the ECR plasma CVD apparatus described with reference to FIG. As the CVD conditions, tetrafluorosilane (SiF ₄ ) [80 sccm], monosilane (Si
H ₄ ) [40 sccm], oxygen (O ₂ ) [100 scc]
m] and argon (Ar) [50 scc] as a carrier gas
m] was used. In addition, the pressure of the film formation atmosphere is 1 Pa, the substrate temperature is 200 ° C., the microwave power is 2.0 kW, the RF power is
The power is set to 2.0 kW, and the fluorine-containing film 14 on the wiring layer 13 is polished so as to have a predetermined film thickness when the film 14 is polished in the next step. The film 14 is formed.

Thereafter, as shown in FIG. 1C, the film 14 containing fluorine is subjected to CMP to flatten its surface. In this CMP, for example, fine particles of cerium oxide are used as abrasive particles, and an ammonia solution, an organic amine solution, an organic fatty acid solution, or an inorganic acid solution, for example, an aqueous ammonia solution is used as a dispersion medium for dispersing the abrasive particles. . Under such conditions, a low dielectric constant interlayer insulating film 15 made of a silicon oxide film containing fluorine is formed.

Next, the relative dielectric constant and the fluorine content of the silicon oxide film containing fluorine before and after the CMP were measured.
As a result, the relative dielectric constant before and after CMP was 3.5 and remained unchanged, and the fluorine content was unchanged at 9 atoms%. Therefore, it was confirmed that the desorption of fluorine and the deterioration of the film structure in the polishing step were suppressed by using silicon oxide as the abrasive particles and an aqueous ammonia solution as the dispersion medium.

In the method for polishing a fluorine-containing film according to the second embodiment, an aqueous ammonia solution is used as a dispersion medium for the polishing slurry. Therefore, as described in the first embodiment, the interlayer insulating film 15 Since the neutralization reaction (acid-base reaction) with the contained fluorine or hydrogen fluoride generated by hydrolysis is suppressed, fluorine does not elute from the interlayer insulating film 15. Also, since the bond between silicon and oxygen is not broken, no change in the structure of the skeleton of the silicon oxide film occurs. Therefore, desorption of fluorine from the interlayer insulating film 15 containing fluorine during polishing and deterioration of the film structure are suppressed.

Next, a third embodiment will be described with reference to FIG. In the third embodiment, in the first embodiment, the film 14 containing fluorine is formed using an inductively coupled plasma (ICP) CVD apparatus, and aluminum oxide is used for polishing particles in CMP. An acetic acid aqueous solution is used as a dispersion medium. At this time, the same components as those in the first embodiment will be described with the same reference numerals. .

As shown in FIG. 1A, the semiconductor substrate 1
1, an interlayer insulating film 12 is formed, and a wiring layer 13 is further formed. As an example, such a substrate 10 was prepared. The semiconductor substrate 11 is made of, for example, a silicon substrate, the interlayer insulating film 12 is made of an insulating film such as a silicon oxide film or a fluorine silicon oxide film, and the wiring layer 13 is made of a conductor such as aluminum or an aluminum alloy. Consists of

Next, as shown in FIG. 1B, for example, a silicon oxynitride film containing fluorine is formed as the film 14 containing fluorine by using, for example, an ICP-CVD apparatus.
As the CVD conditions, monosilane (SiH ₄ ) [80 sccm], tetrafluorosilane (SiF ₄ ) [40 sccm], and dinitrogen monoxide (N ₂ O) [100 sccm] were used as a film forming gas (source gas). Argon (Ar) [100 sccm] was used as a carrier gas. Further, the pressure of the film formation atmosphere was set to 1 Pa, the substrate temperature was set to 400 ° C., the ICP power was set to 2.0 kW, and the RF power was set to 1.8 kW.
A silicon oxynitride film containing fluorine is formed such that the film containing fluorine on the wiring layer 13 has a predetermined thickness when the film containing fluorine 14 is polished in the next step.

Thereafter, as shown in FIG. 1C, the film 14 containing fluorine is subjected to CMP to flatten its surface. In this CMP, for example, fine particles of aluminum oxide are used as abrasive particles, and an ammonia solution, an organic amine solution, an organic fatty acid solution, or an inorganic acid solution, for example, an acetic acid aqueous solution is used as a dispersion medium for dispersing the abrasive particles. . Under such conditions, a low dielectric constant interlayer insulating film 15 made of the film 14 containing fluorine is formed.

The relative dielectric constant and the fluorine content of the silicon oxynitride film containing fluorine before and after the CMP were measured. As a result, the relative dielectric constant before and after the CMP was unchanged at 5.0 and the fluorine content was not changed to 4 atom%. By using aluminum oxide for the abrasive particles and acetic acid aqueous solution for the dispersion medium, the polishing process was improved. It was confirmed that desorption of fluorine and deterioration of the film structure could be suppressed.

In the method for polishing a fluorine-containing film according to the third embodiment, since an aqueous acetic acid solution is used as a dispersion medium of the polishing slurry, fluorine contained in the interlayer insulating film 15 or fluorine generated by hydrolysis is used. Since a neutralization reaction (acid-base reaction) with hydrogen chloride does not occur, fluorine does not elute from the interlayer insulating film 15. Also, since the bond between silicon and oxygen is not broken, no change in the structure of the skeleton of the silicon oxide film occurs. Therefore, desorption of fluorine from the interlayer insulating film 15 containing fluorine during polishing and deterioration of the film structure are suppressed.

In the abrasive grains used in each of the above embodiments, in addition to the above-described silicon oxide, cerium oxide, and aluminum oxide, metal oxides such as titanium oxide and manganese oxide , Vanadium oxide, molybdenum oxide, tungsten oxide, copper oxide,
And cobalt oxides, and a plurality of these oxides can be used in combination.

The dispersion medium used in each of the above embodiments includes:
As described above, other than the aqueous ammonia solution and the aqueous acetic acid solution
In addition, as an organic amine solution, for example, an organic amine aqueous solution,
For example, organic fatty acid aqueous solution, inorganic acid solution
As the liquid, for example, an aqueous solution of an inorganic acid can be used.
Examples of the organic amine include, for example, methylamine (CH
_ThreeNH_Two), Ethylamine (C_TwoH_FiveNH_Two), Isop
Ropylamine [(CH _Three)_TwoCHNH_Two], Dimethyla
Min [(CH_Three)_TwoNH], diethylamine [(C_TwoH
_Five)_TwoNH], diisopropylamine [[(CH_Three)_Two
CH]_TwoNH], trimethylamine [(CH_Three)
_ThreeN], triethylamine [(C_TwoH_Five)_ThreeN], bird
Isopropylamine [[(CH_Three)_TwoCH]_ThreeN]
Nirin (C₆H _FiveNH_Two). Also the above organic fat
Examples of the acid include formic acid (HCOOH), acetic acid (CH
_ThreeCOOH), propionic acid (C_TwoH_FiveCOOH), dairy
Acid (C_FourH_FiveO_Two), Succinic acid (HOOC (CH_Two)_Two
COOH). Further, as the inorganic acid, nitric acid
(NH_Three), Sulfuric acid (H_TwoSO_Four) Etc. can be used
It is. It should be noted that water-insoluble substances such as aniline
It is desirable to dissolve in basic organic solvent
No. As the organic solvent, for example, triethylamine,
Xylene, toluene and the like can be used.

The addition amount of the organic or inorganic base is effective when the pH of the slurry is greater than 7 and 14 or less, and preferably the pH is 8 to 11. The amount of the organic or inorganic acid added is effective when the pH of the slurry is 1 or more and less than 7, and preferably the pH is 3 to 6.

[0034]

As described above, according to the present invention,
Polishing of a film containing fluorine can be performed by a simple method without causing elution of fluorine or a change in the skeletal structure of the silicon oxide film, so that an increase in the dielectric constant can be suppressed and good flatness can be realized. As a result, it is possible to stably form the interlayer insulating film with a low dielectric constant film made of a film containing fluorine. Therefore, an increase in interlayer capacitance due to a decrease in the dielectric constant of the interlayer insulating film can be suppressed, and a delay time and power consumption of the semiconductor device can be reduced.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram illustrating each embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an ECR-CVD apparatus.

[Explanation of symbols]

 10: substrate, 14: film containing fluorine

Claims (4)

[Claims] 1. A fluorine-containing film comprising: a step of forming a film containing fluorine on a substrate; and a step of polishing the surface of the film containing fluorine while supplying a polishing slurry to the surface of the film containing fluorine. In the polishing method, a method of polishing a fluorine-containing film, characterized in that any one of an ammonia solution, an organic amine solution, an organic fatty acid solution and an inorganic acid solution is used as a dispersion medium for dispersing abrasive particles in the polishing slurry. . 2. The method for polishing a fluorine-containing film according to claim 1, wherein said polishing abrasive grains use at least one of silicon oxide and metal oxide. Polishing method of the film. 3. The method for polishing a film containing fluorine according to claim 1, wherein the film containing fluorine is made of a silicon oxide film containing fluorine or a silicon oxynitride film containing fluorine. Polishing method of the film. 4. The method for polishing a film containing fluorine according to claim 2, wherein the film containing fluorine is made of a silicon oxide film containing fluorine or a silicon oxynitride film containing fluorine. Polishing method of the film.