JPH09312334A - Method of forming interlayer insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the breakdown resistance of insulation between conductive patterns. SOLUTION: In the first process, a silane coupling agent 14 is applied on the surface of a silicon oxide film 12 after formation of a conductive film 13 on a silicon oxide film 12 made on a substrate 11. In the second process, an organic film 15 is made in such condition that it covers the conductive pattern 13. In the third process, a space 17 is made between the conductive pattern 13 and the organic film 15 by cooling the above organic film 15 after annealing at a temperature higher than the glass transition temperature of the organic film 15 but lower than the thermal decomposition temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a method for forming an interlayer insulating film in a semiconductor device having a design rule of 0.25 μm or less.

[0002]

2. Description of the Related Art With the demand for finer semiconductor devices, lower power consumption and higher speed, it has been proposed to lower the dielectric constant of an interlayer insulating film. In one of them, a method of forming a conductive pattern (for example, wiring) on a substrate and then forming an organic film to be an interlayer insulating film in a state of covering the wiring is proposed. According to this method, when forming the organic film, a cavity may be formed between the organic film and the wiring.

[0003]

However, in the formation of the cavity by the conventional manufacturing method, there are a portion where the cavity is formed and a portion where the cavity is not formed on the wafer,
It was unstable with respect to the formation of cavities. Thus, although a wiring structure using a cavity has been proposed, its forming method is still under development and has not been established. Also,
If the wirings are formed as cavities, the withstand voltage between the wirings becomes insufficient and discharge occurs between the wirings.

[0004]

The present invention is a method for forming an interlayer insulating film, which has been made to solve the above problems. That is, in the first step, after forming a conductive pattern on a substrate having a silicon oxide based film, a silane coupling agent is applied to the silicon oxide based film. Then, in a second step, an organic film is formed on the substrate so as to cover the conductive pattern. Then, in a third step, the organic film is annealed at a temperature not lower than the glass transition temperature of the organic film and lower than the thermal decomposition temperature of the organic film, and then cooled to provide a space between the conductive pattern and the organic film. A method for forming an interlayer insulating film, which is characterized by forming a space.

Further, the conductive patterns are formed in parallel, a space is formed between the side wall of the conductive pattern and the organic film by the third step, and the wall made of the organic film is formed between the conductive patterns. Is a method of forming an interlayer insulating film.

In the above method for forming the interlayer insulating film, since the silane coupling agent is applied, the adhesiveness between the conductive pattern and the organic film is almost unchanged, and the adhesiveness between the silicon oxide film and the organic film is maintained. Since it becomes higher, the difference in adhesiveness between the two increases. As a result, the organic film can be reliably peeled off from the side wall of the conductive pattern. The organic film is annealed and expanded at a temperature not lower than the glass transition temperature of the organic film and lower than the thermal decomposition temperature, and then cooled to cause volume contraction of the organic film, resulting in relatively weak adhesion. A space is created between the side wall of the pattern and the organic film. As described above, the conductive pattern is more easily peeled off in the conductive pattern than the silicon oxide-based film, and the thermal expansion coefficient of the organic film is large. A space is surely formed on the side wall of the. Therefore, as a method of reducing the capacitance between the conductive patterns, a space having a relative dielectric constant of about 1.0 can be easily formed, which is theoretically most effective.

Further, conductive patterns are formed in parallel,
In the method of forming a space on the side wall of each conductive pattern, a space is formed between the side wall of the conductive pattern and the organic film for the reason described above. At that time, the organic film remains in the substantially central portion between the conductive patterns, and it becomes the wall of the organic film. By forming this wall, the conductive patterns do not face each other across the space, so that no discharge occurs between the conductive patterns through the space. Therefore, the dielectric strength between the conductive patterns is secured.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A first example of an embodiment of the present invention is shown in FIG.
It will be explained by.

As shown in (1) of FIG. 1, general chemical vapor deposition (hereinafter, referred to as CVD, CVD is Chemical V
The silicon oxide film 12 as a silicon oxide film is formed on the substrate (for example, a silicon substrate) 11 to a thickness of, for example, 500 nm by the apour deposition method. This C
In the VD method, monosilane (SiH ₄ ) and oxygen (O ₂ ) were used as the source gas. Alternatively, the above silicon oxide film 12
May be formed by a plasma CVD method. At that time, for example, tetraethoxysilane (TE
OS) and oxygen are used.

Next, a conductive layer was formed on the silicon oxide film 12 by sputtering, and then the conductive layer was patterned by a lithographic technique and etching to form a conductive pattern 13. The conductive layer is formed of aluminum containing silicon as an example here.

Subsequently, a plasma using a dinitrogen oxide (N ₂ O) gas is applied to the silicon oxide film 12 on the substrate 11.
The surface of is terminated with hydroxyl groups. This plasma irradiation is performed using a parallel plate type plasma generator, for example, at 13.56 MH
RF power of z was applied at 300W. At that time, a hydroxyl group (-
OH) is difficult to form, and hydroxyl groups are formed on the surface of the silicon oxide film 12 between the conductive patterns 13.

Next, as shown in FIG. 1B, nano-fluorohexytrichlorosilane [CF ₃ (CF ₂ ) _n CH 4 is used as a silane coupling agent 14 on the surface of the silicon oxide film 12 by a spin coating method. ₂ SiCl ₃ ; provided that n ≧ 2] or nanofluorohexytrimethoxysilane [CF ₃ (CF ₂ ) _n CH ₂ Si (OM
e) ₃ ; provided that n ≧ 2 and Me represents a methyl group]
Is applied. In this drawing, the silicon oxide film 12
The silane coupling agent 14 above is shown, and the silane coupling agent 14 applied to the surface of the conductive pattern 13 is not shown.

Next, as shown in (3) of FIG.
An organic film 15 is formed on the silicon oxide film 12 by the method D so as to cover the conductive pattern 13. Here, as the organic film 15, polyparaxylylene, which is one kind of fluorocarbon, is formed to a thickness of, for example, 500 nm. In this low pressure CVD method, for example, diparaxylylene (Di-Para-Xylylene) is used as a raw material gas, and at the time of CVD, the raw material gas is heated to 200 ° C. to be sublimated, decomposed into xylylene monomer at 650 ° C., and heated to 150 ° C. Board 11
Introduced above.

Next, as shown in (4) of FIG. 1, the silicon oxide film 1 is formed on the organic film 15 by a general CVD method.
6 is formed to a thickness of 500 nm, for example. In this CVD method, monosilane and oxygen were used as the source gas. Alternatively, the silicon oxide film 16 may be formed by a plasma CVD method using, for example, tetraethoxysilane and oxygen as source gases.

Then, annealing is performed in a nitrogen gas atmosphere as an inert atmosphere. In this annealing, the annealing temperature is a glass transition temperature of polyparaxylylene (250 ° C. as an example) or more and a thermal decomposition temperature (4 ° as an example).
The temperature was set lower than (00 ° C.), and here, as an example, it was set to 350 ° C. After that, for example, 50 ° C./min to 10
It was cooled at a cooling rate in the range of 0 ° C./minute. At this time, the organic film 15 is peeled off from the surface of the conductive pattern 13 due to the heat shrinkage of the organic film 15, but is not peeled off on the surface of the oxide silicide film 12 because of high adhesion. As a result, a space 17 was formed between the sidewall of the conductive pattern 13 and the organic film 15.

In the method of forming the interlayer insulating film, since the organic film 15 is formed after applying the silane coupling agent, the adhesiveness between the conductive pattern 13 and the organic film 15 is almost unchanged, and the oxidation is performed. Silicon film 12 and organic film 1
Adhesion with 5 is high. Therefore, the difference in adhesiveness between the two is widened. As a result, the organic film 15 can be reliably peeled off from the side wall of the conductive pattern 13.

Since the organic film 15 is annealed at a temperature higher than the glass transition temperature of the organic film 15 and lower than the thermal decomposition temperature, the organic film 15 expands. After that, the organic film 15 is cooled at a cooling rate such that the organic film 15 contracts, so that the organic film 15 contracts in volume, and the space 1 is formed between the side wall of the conductive pattern 13 having relatively weak adhesion and the organic film 15.
7 results.

As described above, the organic pattern 15 is more easily peeled off in the conductive pattern 13 as compared with the silicon oxide film 12, and the fact that the organic film 15 has a large coefficient of thermal expansion is utilized. Due to the heat shrinkage of 15, the space 17 is surely formed on the side wall of the conductive pattern 13. Therefore, as a method for reducing the capacitance between the conductive patterns 13, a space having a relative dielectric constant of about 1.0 is theoretically effective and is easily formed.

Further, as shown in FIG. 1, in the method of forming the conductive patterns 13 in parallel and forming the spaces 17 in the side walls of the respective conductive patterns 13, the side walls of the conductive patterns 13 are formed for the reasons described above. A space 17 is formed by heat contraction of the organic film 15. Therefore, the organic film 15 remains in the substantially central portion between the conductive patterns 13,
It becomes the wall 18 of the organic film 15. By forming the wall 18, the pressure resistance of the space 17 is ensured.

Next, as a second example of the embodiment, the organic film 15
A method of forming an interlayer insulating film using polytetrafluoroethylene, which is one of fluorocarbons, will be described below.
In this second example, the method of forming the organic film 15 and the organic film 1
The method is the same as the method described in the first example except for the annealing of No. 5. Therefore, only the method of forming the organic film 15 and its annealing will be described here.

After applying the silane coupling agent as described in the first example, the organic film 15 is formed on the silicon oxide film 12 by the spin coating method so as to cover the conductive pattern 13. Here, as the organic film 15, polytetrafluoroethylene represented by the formula (1) is formed to a thickness of, for example, 500 nm. As the polytetrafluoroethylene, for example, a substance called amorphous Teflon is known.

[0022]

Embedded image

In the above spin coating method, polytetrafluoroethylene is dissolved in a fluorocarbon-based solvent to obtain a viscosity of 3
It was adjusted to 0 cp. It was applied onto the substrate 11 by spin coating to form the organic film having a thickness of 500 nm. The rotation speed at that time was 3000 rpm. afterwards,
100 ° C in a nitrogen gas atmosphere as an inert atmosphere, 2
A minute baking was performed. As the fluorocarbon-based solvent, for example, a so-called Fluorinert is known.

Then, in the same manner as in the first example, a silicon oxide film 16 having a thickness of, for example, 500 nm was formed on the organic film 15 and then annealed in a nitrogen gas atmosphere as an inert atmosphere. In this annealing, the annealing temperature was set to a temperature not lower than the glass transition temperature of polytetrafluoroethylene (160 ° C. as an example) and lower than its thermal decomposition temperature (450 ° C. as an example), here 350 ° C. as an example. . Then, for example, 50 ℃
The cooling was performed at a cooling rate in the range of 1 / min to 100 ° C / min. At this time, the organic film 15 is peeled off from the surface of the conductive pattern 13 due to the heat shrinkage of the organic film 15, but is not peeled off on the surface of the oxide silicide film 12 because of high adhesion. as a result,
A space 1 is formed between the sidewall of the conductive pattern 13 and the organic film 15.
7 was formed.

In the second example, in addition to the operation described in the first example, the effect of applying the silane coupling agent to the surface of the silicon oxide film 12 is obtained by forming the organic film 15 by the spin coating method. It is fully demonstrated. That is,
This is because the silane coupling agent is less likely to evaporate when forming the organic film 15, as compared with the first example.

Next, as a third example of the embodiment, the organic film 15
A method for forming an interlayer insulating film using a cyclopolymerized fluorinated polymer which is one of fluorocarbons will be described below. In this third example, except for the method of forming the organic film 15 and the annealing of the organic film 15,
It is similar to the method described in the example. Therefore, only the method of forming the organic film 15 and its annealing will be described here.

After the silane coupling agent is applied as described in the first example, the organic film 15 is formed on the silicon oxide film 12 by the spin coating method so as to cover the conductive pattern 13. Here, as the organic film 15, a fluorocarbon-based cyclopolymerized fluorinated polymer represented by the formula (2) is used, and for example, 500 n
m was formed. As the cyclopolymerized fluorinated polymer, for example, a so-called CYTOP is known.

[0028]

Embedded image

In the spin coating method, the cyclopolymerized fluorinated polymer was dissolved in a fluorocarbon-based solvent to adjust the viscosity to 30 cp. It was applied onto the substrate 11 by spin coating to form the organic film having a thickness of 500 nm. The rotation speed at that time is 3000 rpm
And After that, baking was performed at 100 ° C. for 2 minutes in a nitrogen gas atmosphere as an inert atmosphere.

Then, in the same manner as in the first example, a silicon oxide film 16 having a thickness of, for example, 500 nm was formed on the organic film 15, and then an inert gas atmosphere was annealed in a nitrogen gas atmosphere. In this annealing, the annealing temperature is higher than the glass transition temperature of the cyclopolymerized fluorinated polymer (120 ° C. as an example),
The temperature was set lower than the thermal decomposition temperature (420 ° C. as an example), and here, it was set to 350 ° C. as an example. Then, it cooled at the cooling rate of the range of 50 degree-C / min-100 degree C / min, for example. At this time, the organic film 15 is peeled off from the surface of the conductive pattern 13 due to the heat shrinkage of the organic film 15, but is not peeled off on the surface of the oxide silicide film 12 because of high adhesion. As a result, a space 17 was formed between the sidewall of the conductive pattern 13 and the organic film 15.

Next, as a fourth example of the embodiment, the organic film 15
A method of forming an interlayer insulating film using fluorinated polyallyl ether which is one of fluorocarbons will be described below. In the fourth example, the method of forming the organic film 15 and the organic film 15
The method is the same as the method described in the first example above, except for the annealing. Therefore, only the method of forming the organic film 15 and its annealing will be described here.

After applying the silane coupling agent as described in the first example, the organic film 15 is formed on the silicon oxide film 12 by the spin coating method so as to cover the conductive pattern 13. Here, as the organic film 15, a fluorinated polyallyl ether represented by the formula (3) is used, for example, 5
It was formed by forming a film with a thickness of 00 nm. As the above-mentioned fluorinated polyallyl ether, for example, a so-called flare is known.

[0033]

Embedded image

In the spin coating method, fluorinated polyallyl ether is dissolved in a fluorocarbon-based solvent to obtain a viscosity of 30.
Adjusted to cp. It was applied onto the substrate 11 by spin coating to form the organic film having a thickness of 500 nm.
The rotation speed at that time was 3000 rpm. After that, baking was performed at 100 ° C. for 2 minutes in a nitrogen gas atmosphere as an inert atmosphere.

Then, in the same manner as in the first example, a silicon oxide film 16 having a thickness of, for example, 500 nm was formed on the organic film 15, and then an inert gas atmosphere was annealed in a nitrogen gas atmosphere. In this annealing, the annealing temperature is set to a temperature not lower than the glass transition temperature (260 ° C. as an example) of the fluorinated polyallyl ether and lower than its thermal decomposition temperature (460 ° C. as an example), here 350 ° C. as an example. did. After that, for example, 50 ° C /
Cooling was performed at a cooling rate in the range of min-100 ° C / min. At this time, the organic film 15 is peeled off from the surface of the conductive pattern 13 due to the heat shrinkage of the organic film 15, but is not peeled off on the surface of the oxide silicide film 12 because of high adhesion. As a result, a space 17 is formed between the sidewall of the conductive pattern 13 and the organic film 15.
Was formed.

Next, as a fifth example of the embodiment, the organic film 15
A method of forming an interlayer insulating film using fluorinated polyimide, which is one of fluorocarbons, will be described below. The fourth example is the same as the method described in the first example except for the method of forming the organic film 15 and the annealing of the organic film 15. Therefore, only the method of forming the organic film 15 and its annealing will be described here.

After applying the silane coupling agent as described in the first example, the organic film 15 is formed on the silicon oxide film 12 by the spin coating method so as to cover the conductive pattern 13. Here, as the organic film 15, fluorinated polyimide is formed to a thickness of 500 nm, for example.
In the spin coating method, fluorinated polyimide was dissolved in a fluorocarbon-based solvent to adjust the viscosity to 30 cp. It is coated on the substrate 11 by spin coating to give a thickness of 50.
The above organic film having a thickness of 0 nm was formed. The number of rotations at that time is 30
It was set to 00 rpm. After that, baking was performed at 100 ° C. for 2 minutes in a nitrogen gas atmosphere as an inert atmosphere.

Thereafter, in the same manner as in the first example, the organic film 1
After forming the silicon oxide film 16 on the substrate 5 to a thickness of 500 nm, for example, annealing was performed in a nitrogen gas atmosphere as an inert atmosphere. In this annealing, the annealing temperature is equal to or higher than the glass transition temperature of the fluorinated polyimide (200 ° C. as an example) and its thermal decomposition temperature (42 ° C. as an example).
0 ° C), and here, as an example,
The temperature was set at 50 ° C. Then, for example, 50 ° C./min to 100
Cooled at a cooling rate in the range of ° C / min. At this time, the organic film 15 is peeled off from the surface of the conductive pattern 13 due to the heat shrinkage of the organic film 15, but is not peeled off on the surface of the oxide silicide film 12 because of high adhesion. As a result, a space 17 was formed between the sidewall of the conductive pattern 13 and the organic film 15.

Also in the third to fifth examples, the second
The same effect as the example is obtained. It is also possible to use organic SOG (Spin on glass) as the organic film 15.

The glass transition temperature and the thermal decomposition temperature of each of the above materials are changed by adding an additive to each material. Therefore, when the additive is added, the annealing temperature condition is appropriately changed.

The organic film 15 described above contains carbon atoms and fluorine atoms to reduce the dielectric constant. With such a material, a material having a dielectric constant of about 1.5 to 2.5 is being realized. As the above-mentioned material, in addition to the fluorocarbon polymer, polyimide, polyparaxylylene described in the above embodiment, organic SOG and the like are known. It is said that these materials have a low dielectric constant by containing a carbon atom as an alkyl group to reduce the density of the material and reduce the polarizability of the molecule itself. Further, the above-mentioned materials not only have a low dielectric constant but also have heat resistance which is indispensable as a material for forming a semiconductor device. For example, polyimide has an imide bond, polyparaxylylene, a fluorocarbon polymer, and the like have a benzene ring, and organic SOG has a siloxane structure, so that each has heat resistance.

The demand for reduction of the dielectric constant of the low dielectric constant film has become stronger and stronger as the miniaturization of ULSI progresses. Among them, the low dielectric constant film that is likely to be put into practical use at present is an organic fluorocarbon film that is expected as a next-generation film, and its dielectric constant is about 2.0.

[0043]

As described above, according to the present invention,
Since the silane coupling agent is applied to the silicon oxide based film, the adhesiveness between the conductive pattern and the organic film hardly changes, and the adhesiveness between the silicon oxide based film and the organic film can be increased. Therefore, when the organic film is annealed and then cooled, the organic film is easily peeled off from the sidewall of the conductive pattern, so that a space can be reliably formed on the sidewall of the conductive pattern. Further, when a space is formed on the side wall of the conductive pattern, the organic film remains in a substantially central portion between the conductive patterns, which serves as a wall of the organic film. Since this wall is formed, it becomes possible to secure a dielectric strength voltage between the conductive patterns.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment according to the present invention.

[Explanation of symbols]

11 substrate 12 silicon oxide film 13 conductive pattern 14 silane coupling agent 15 organic film 17
space

Claims (4)

[Claims] 1. A first step of applying a silane coupling agent to the surface of the silicon oxide based film after forming a conductive pattern on the substrate of which the surface is a silicon oxide based film, and the conductive step on the substrate. A second step of forming an organic film so as to cover the organic pattern, and annealing the organic film at a temperature not lower than the glass transition temperature of the organic film and lower than the thermal decomposition temperature of the organic film, and then cooled, A method of forming an interlayer insulating film, comprising a third step of forming a space between the conductive pattern and the organic film. 2. The method for forming an interlayer insulating film according to claim 1, wherein after forming the conductive pattern and before applying the silane coupling agent, the surface of the silicon oxide based film is terminated with a hydroxyl group. A method for forming an interlayer insulating film, comprising: 3. The method for forming an interlayer insulating film according to claim 1, wherein the conductive patterns are formed in parallel, and a space is formed between a sidewall of the conductive pattern and the organic film by the third step. And a wall made of the organic film between the conductive patterns is formed. 4. The method for forming an interlayer insulating film according to claim 2, wherein the conductive patterns are formed in parallel, and a space is formed between a sidewall of the conductive pattern and the organic film by the third step. And a wall made of the organic film between the conductive patterns is formed.