JPH10270556A - Method for forming insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the insulating-film forming method, by which the flat insulating film having the excellent embedding property into a concave part can be formed and the cost reduction is achieved. SOLUTION: This is a device, wherein the inside is partitioned with nitrogen atmosphere after a wiring pattern 14 is washed. The film of SOG solution is formed by a rotary application method. By using a device for baking this film, the solution, whose main component is hydrogenated silsesquioxane class [(HSiO3/2 )n ] is dropped on a semiconductor substrate 1 wherein the wiring pattern 14 is formed. The semiconductor substrate 11 is horizontally rotated at 3000 rpm, and the film of the SOG solution is formed. Then, the semiconductor substrate 11 is baked, wherein the film of the SOG film is formed, and an SOG film 15 is formed. On the surface of the SOG film 15, an O3 -TEOS (tetraethyl ortho silicate) film 16 is formed. the O3 -TEOS film 16 is flatly polished so that the lower-layer in contact with the SOG film 15 remains in the thickness direction of the O3 -TEOS film 16 by the abrasive powder containing colloid silica particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an insulating film on a semiconductor substrate.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor devices, the spacing between wirings formed on a semiconductor substrate has been reduced, and the wiring formed on a semiconductor substrate has become a multilayer wiring. For this reason, when forming an insulating film on a semiconductor substrate, it is required to form an insulating film between adjacent wirings even if the wiring interval is small, and furthermore, a parasitic capacitance between the upper wiring and the lower wiring is required. It is required to form an insulating film having a low level.

On the other hand, conventionally, as a method of forming an insulating film on a semiconductor substrate, a method of applying a solution on a semiconductor substrate to form an insulating film, a method of forming an insulating film by a plasma CVD method, and a method of using an organic silane. A method of forming an insulating film by the used normal pressure CVD method or the like is employed.

[0004]

As a method of forming an insulating film by applying a solution on a semiconductor substrate, there are a method of forming an organic film having a low dielectric constant and a method of forming an SOG film having a Si-H bond. Although there is a method of forming the organic film, a method of forming an organic film having a low dielectric constant is effective in reducing the parasitic capacitance, but there is a problem that the organic film has poor adhesion to a base film. In addition, when the distance between the wirings formed on the semiconductor substrate becomes narrow, the solution dropped in forming the organic film becomes difficult to enter between the wirings, and there is a problem that it is difficult to form the organic film between the wirings. On the other hand, Si-H
As the thickness of the SOG film having a bond is increased, cracks are not easily formed when the thickness is increased. Therefore, in order to prevent cracks, it is necessary to suppress the thickness of the SOG film to about 3000 angstroms at most. Therefore, there is a problem that it becomes more difficult to use the SOG film as the insulating film as the height of the wiring increases.

As a method of forming an insulating film by a plasma CVD method, there is a method of forming a silicon oxide-based insulating film by a plasma CVD method using fluorine. When an insulating film is formed using fluorine, a low-dielectric insulating film can be formed; however, there is a problem in that wiring contained is deteriorated by fluorine contained in the insulating film. As a method of forming an insulating film by a plasma CVD method, there is a method of forming an insulating film by an ECR plasma CVD method.
There is a problem that particles are easily generated during the formation of the insulating film.

In addition, a normal pressure CVD method using an organic silane
As a method of forming an insulating film, Japanese Patent Application Laid-Open No.
No. 9, a silicon nitride film is formed on a semiconductor substrate
And then TEOS and O_Three And using silicon oxide film
(Hereafter O_Three -Called TEOS film) is disclosed
However, in this method, the shape of the silicon nitride film is
O _Three -The formation of the TEOS film is_Three −TE
It is said that the thickness of the OS film varies depending on the portion of this film.
There's a problem. Also, Japanese Patent Application Laid-Open No. 2-140957 discloses
Is O on the semiconductor substrate_Three -Forming a TEOS film;
_Three -Reactive ion etching (RIE) of TEOS film
Method of further etching back and then forming SOG film
Is disclosed, but O_Three −Erase the TEOS film by RIE.
There is a problem that dust is easy to be generated due to the backing.
Also, Japanese Patent Application Laid-Open No. 4-56323 discloses a semiconductor substrate.
Next, a TEOS film is formed by a plasma CVD method.
And O_Three -By forming a TEOS film,
Although the method of forming is disclosed, when the number of steps increases,
Problem and O_Three -The shape of the TEOS film is
It becomes a shape, O_Three -Form TEOS film flat
There is still a problem that it is difficult to do.

[0007] Materials in 1996
Research SocietyConference
e Proceedings ULSIXI Proceedings 1
On pages 21 to 125, after a wiring pattern is formed on a semiconductor substrate, tetraethylorthosilicate (TEOS)
And oxygen first silicon oxide film by a plasma CVD method using a raw material is formed, then dropwise a solution of hydrogenated silsesquioxanes the _{[(HSiO 3/2) n} ] as a main component and An SOG film is formed by a spin coating method, and then a plasma C
A second silicon oxide film is formed by the VD method.
Of the second silicon oxide film with S
There has been reported a method of forming an insulating film by polishing flat by a chemical mechanical polishing (CMP) method so as to leave a lower layer portion in contact with the OG film. In this method, however, the second silicon oxide film is Since the shape of the SOG film is easy to follow, when the step due to the unevenness of the surface of the SOG film is large,
If the thickness of the second silicon oxide film is small, it is not possible to sufficiently fill the recesses on the surface of the SOG film.
When the silicon oxide film is polished, the second silicon oxide film is exposed before the surface of the second silicon oxide film becomes flat. Therefore, in order to prevent the silicon oxide film from being exposed, a thick second silicon oxide film must be formed so as to fill the recesses of the SOG film. is there.

In Japanese Patent Application Laid-Open No. Hei 7-240460, hydrogenated silsesquioxanes [(H
A method is disclosed in which a solution containing SiO _3/2 ) _n ] as a main component is dropped, a SOG film is formed by a spin coating method, and the SOG film is polished by a CMP method. When the CMP method is adopted, the SOG film is easily polished.
Even if the G film is polished, the SOG film is polished so as to be thinner than a desired thickness. For example, if a SOG film is formed after forming a wiring pattern on a semiconductor substrate, and the SOG film is polished, There is a problem that the pattern is exposed.

Also, hydrogenated silsesquioxanes [(H
The SOG film formed by dropping a solution containing [SiO _3/2 ) _n ] as a main component has a low dielectric constant because of having Si—H bonds, but has poor heat resistance, and is baked. When the temperature reaches about 400 ° C., thermal decomposition of the Si—H bond causes a problem that it is difficult to increase the thickness of the SOG film. On the other hand, if the solid content of the solution containing hydrogenated silsesquioxanes [(HSiO _3/2 ) _n ] as the main component is increased, the thickness of the SOG film can be increased to some extent. Cracks easily occur, and the film is easily peeled off.

In view of the above circumstances, it is an object of the present invention to provide a method of forming an insulating film capable of forming a flat insulating film with good embedding into a concave portion and reducing cost.

[0011]

According to the present invention, there is provided an insulating film forming method for forming an insulating film on a semiconductor substrate, comprising: (1) forming a wiring pattern on the semiconductor substrate; First step (2) Second step of cleaning the wiring pattern with an organic solvent (3) Rotating the semiconductor substrate horizontally in a nitrogen atmosphere and using hydrogenated silsesquioxane as a main component A third step of dropping the solution and forming the solution into a film (4) a fourth step of baking the semiconductor substrate in a nitrogen atmosphere to form a film of the solution on the SOG film; Fifth step of forming a silicon oxide film on the surface of the SOG film by a CVD method using organic silane and ozone (6) Lowering the silicon oxide film in the thickness direction of the silicon oxide film in contact with the SOG film Leave Characterized by comprising a sixth step of polishing as.

The organic silane, which is a material of the silicon oxide film formed in the fifth step, has a property that when deposited on a hydrophobic film, it moves to fill the concave portion even if the film surface has irregularities. (Hereinafter, movement to fill such a concave portion is referred to as surface migration), so that the organic silane is deposited so as to be flat. When hydrophilic, surface migration is inhibited, and the organic silane is deposited to conform to the shape of the underlayer. Further, when the organic silane is directly deposited on the wiring, for example, the surface of the wiring is easily charged, and it is considered that the deposition of the organic silane directly on the charged portion is also a factor inhibiting the surface migration of the organic silane. . In the insulating film forming method of the present invention, the SOG film is formed from a solution containing hydrogenated silsesquioxanes [(HSiO _3/2 ) _n ] as a main component through the third and fourth steps. Therefore, this SOG film has a Si—H bond showing hydrophobicity. That is, the SOG film serving as a base film of the silicon oxide film formed in the fifth step is hydrophobic. In addition, since the SOG film is formed on the wiring pattern before the deposition of the organic silane, even if the wiring is charged, the influence of the charging can be reduced. Therefore, the silicon oxide film formed by performing the fifth step has a small thickness even if the thickness of the silicon oxide film is small.
It is formed so as to fill a concave portion on the surface of the G film. Therefore, even if a thin silicon oxide film is formed and the sixth step is performed, the silicon oxide film can be polished flat before the SOG film is exposed. That is, the thickness of the silicon oxide film formed by performing the fifth step may be small, and the manufacturing cost is reduced.

Here, in the method of forming an insulating film according to the present invention, after the execution of the fourth step and before the execution of the fifth step, the hydrogen content of the SOG film formed by the execution of the fourth step is reduced. It is preferable to include a seventh step of measuring the amount. The SOG film formed from a solution containing hydrogenated silsesquioxane as a main component mainly has Si—H bonds and Si—O—Si
Due to having a bond, when the hydrogen content is measured, Si—H
It is possible to check the amount of the bond, and it is possible to prevent the formation of the O ₃ -TEOS film on the surface of the SOG film where the amount of the Si—H bond is small in performing the fifth step.

Here, it is preferable that the seventh step is a step of measuring the hydrogen content on the surface of the SOG film by infrared absorption spectroscopy. With the use of infrared absorption spectroscopy, the amount of Si—H bonds can be easily checked. Here, it is preferable that the first step of the method of forming an insulating film of the present invention is a step of forming a wiring pattern using a material containing any one of aluminum, copper, gold, and silver as a main component.

When the above-mentioned material is used as the material of the wiring, a low-resistance wiring can be formed. Here, it is preferable that the sixth step of the insulating film forming method of the present invention is a step of polishing the silicon oxide film by a chemical mechanical polishing method. Polishing by chemical mechanical polishing method,
The film can be flattened with high accuracy.

Here, the fifth method of the insulating film forming method of the present invention is used.
Is preferably a step of forming a silicon oxide film by a CVD method using tetraethylorthosilicate and ozone. When a silicon oxide film is formed using tetraethyl orthosilicate and ozone, a silicon oxide film having a good filling property in the recess of the SOG film is formed.

[0017]

Embodiments of the present invention will be described below. 1 to 6 are cross-sectional views showing the steps of manufacturing an insulating film formed by using the insulating film forming method according to one embodiment of the present invention. First, as shown in FIG. 1, an interlayer insulating film 12 is formed on a surface of a silicon substrate 11 on which a semiconductor element is formed. In this embodiment, a BPSG film having a thickness of about 6000 Å is formed as the interlayer insulating film 12.

Next, a contact hole 13 is formed in the interlayer insulating film 12 as shown in FIG. Next, the surface of the interlayer insulating film 12 is made of a material containing Al as a main component and having a thickness of 8000.
A metal film having a thickness of about Å is formed, and the metal film is etched so that a desired pattern remains, and a wiring pattern 14 is formed as shown in FIG. In this embodiment, the wiring interval is 0.4 μm.

Next, the wiring pattern 14 is cleaned. In the present embodiment, EKC265 (2- (2
- aminoethoxy) ethanol H ₂ NOCH ₂ CH ₂ O
(H-containing organic solvent). When the wiring pattern 14 is washed with an organic solvent as described above, the O ₃ -TEOS film formed on the semiconductor substrate 11 becomes
_The phenomenon that is formed so as to follow the shape of the base film of the _3- TEOS film can be reduced.

Next, the semiconductor on which the wiring pattern 14 is formed is formed.
A hydrogenated silsesquioxane [(HS
iO_3/2 )_n ] With a low viscosity SOG solution
By dropping, an SOG film is formed. In the present embodiment, this S
As an apparatus for forming an OG film, the inside is partitioned in a nitrogen atmosphere
And forming a film of the SOG solution by a spin coating method.
Toray Dow using a device for firing the film as SOG solution
Corning FO _x Use −14. Distribute this solution
Drop on the semiconductor substrate 11 on which the line pattern 14 is formed
Then, the semiconductor substrate 11 is horizontally rotated at 3000 rpm.
To form a film of the solution, and the semiconductor on which the film of the solution is formed.
The body substrate 11 is heated in the order of 100 ° C., 200 ° C., and 300 ° C.
And calcined at each temperature for 60 seconds at a temperature of 400 ° C.
For 1 hour. Thus, as shown in FIG.
An SOG film 15 is formed.

Here, the main firing temperature is set to 400 ° C.
The reasons are as follows. Hydrogenated silsesquioxanes
When a SOG film is formed by dropping a solution containing
Due to the formation of i-H bonds, this SOG film becomes hydrophobic.
Show. After forming the SOG film, the surface of the SOG film is
Is made from TEOS as a raw material, as described later. _Three -TEO
An S film is formed. Thus, TEO is applied to the hydrophobic film surface.
O using an organosilane such as S_Three -Form TEOS film
Then this O_Three -The TEOS film is SOG which serves as a base film.
It is formed so as to fill the concave portion of the film. By the way, this
O_Three The firing temperature of the SOG film serving as the base film of the TEOS film is
Decomposes due to thermal decomposition of Si-H bonds
Hydrogen to be released increases, which may cause the SOG film to show hydrophobicity.
Si—H bonds are reduced. Below, the change in firing temperature
The change in the number of desorbed hydrogens will be described.

FIG. 7 is a graph showing a change in thermal history of an SOG film formed by dropping a solution containing hydrogenated silsesquioxane as a main component on a semiconductor substrate. This graph shows the SOG when the temperature of the SOG film is raised from the room temperature point (a) to 500 ° C. and then cooled to 50 ° C. (point b).
4 is a graph showing a change in tensile stress of a film.

As can be seen from this graph, in the process of raising the temperature of the SOG film, the tensile stress of the SOG film is almost the same when the temperature of the SOG film is in the range from room temperature to about 400 ° C. It can be seen that when the temperature of the film becomes higher than 400 ° C., the tensile stress of the SOG film sharply increases. It is considered that the reason why the tensile stress of the SOG film rapidly increases is that when the temperature of the SOG film exceeds 400 ° C., the thermal decomposition of the Si—H bond rapidly proceeds and hydrogen is desorbed. When desorption proceeds rapidly, Si-H
Bonding is reduced, and TEOS, which is the material of the O ₃ -TEOS film formed on the surface of the SOG film, is less likely to cause surface migration. When the surface migration hardly occurs as described above, the O ₃ -TEOS film is formed so as to follow the shape of the SOG film serving as the base film, and the SOG film is formed.
The film has a poor embedding property in the concave portions of the film, and a film having a large step due to surface irregularities is formed. For this reason, the main firing temperature of the SOG film is set to 400 ° C.

Next, the hydrogen content of the SOG film formed by firing under the above-described firing conditions is examined. Here, the purpose of examining the hydrogen content is to examine the abundance of Si—H bonds. By examining the abundance of Si—H bonds, O Prevents formation of a _3- TEOS film. In the present embodiment, when examining the hydrogen content, the SOG film formed from a solution containing hydrogenated silsesquioxane as a main component mainly forms Si—H bonds and Si—O—Si bonds. Therefore, the hydrogen content is determined by examining the ratio between the Si—H bond and the Si—O—Si bond of the SOG film by FT-IR.

FIG. 8 is an example of a spectrum obtained by analyzing the SOG film surface by FT-IR. The horizontal axis of the graph shown in FIG. 8 is the wave number, and the vertical axis is the light absorption intensity. An absorption peak whose wave number appears near 800 cm ⁻¹ is an absorption peak of Si—H (hereinafter referred to as a first peak),
The absorption peak that appears near cm ⁻¹ is the Si—O—Si absorption peak (hereinafter, referred to as a second peak).

Only when the ratio of the light absorption intensity of the first peak to the light absorption intensity of the second peak (hereinafter referred to as peak ratio) is 0.7 or more, an O ₃ -TEOS film is formed on the surface of the SOG film. Form. Here, O ₃ only when the peak ratio is 0.7 or more
The reason for forming the -TEOS film is that if the peak ratio is less than 0.7, the film is likely to crack in a later step or the film is easily peeled.

Next, on the surface of the SOG film having a peak ratio of 0.7 or more, tetraethylorthosilicate (TEOS) and ozone (O ₃ ) are used as raw materials using an atmospheric pressure CVD apparatus.
As shown in FIG. 5, an O ₃ -TEOS film 16 is formed. In the present embodiment, the film is formed under the conditions of a temperature of 420 ° C. in the apparatus and an O ₃ concentration of 120 g / m ³ in the apparatus.
An O ₃ -TEOS film 16 of about 0 Å is formed. In the present embodiment, as described above, O ₃ -TE
Prior to the formation of the OS layer 16, for forming the SOG layer 15 from a solution composed mainly of hydrogenated silsesquioxanes, SOG film 15 serving as a base film of O ₃ -TEOS film 16
Is hydrophobic, and the SOG film 15 is formed on the wiring pattern 14 even if the wiring pattern 14 is charged.
Less susceptible to charging. Therefore, the O ₃ -TEOS film 16 is formed so that the concave portion of the SOG film 15 is buried.

Further, since the solution containing dropped hydrogenated silsesquioxane SOG as a main component has a low viscosity, the solution accumulates thinly on the wiring and thickens in the concave portion between the wirings. Therefore, comparing the portion of the SOG film formed on the wiring with the portion of the SOG film formed between the wirings, the wiring between the wirings has more Si—H bonds and therefore has a higher hydrophobicity. As described above, the fact that the hydrophobicity is higher between the wirings than on the wirings also effectively acts to form the O ₃ -TEOS film so as to fill the concave portions.

After forming the O ₃ -TEOS film 16 as shown in FIG. 5, an abrasive containing colloidal silica particles is used.
The O ₃ -TEOS film 16 is polished flat in the thickness direction of the O ₃ -TEOS film 16 so as to leave a lower layer portion in contact with the SOG film as shown in FIG. After polishing, pure water 0.0
O ₃ − with an aqueous solution of hydrofluoric acid diluted to a concentration of 5% to 0.1%
After the surface of the TEOS film is washed for several seconds, it is washed with an IPA aqueous solution and then spin-dried.

Next, the O ₃ -TEOS film 16 and the SOG
By forming a contact hole in a portion of the film 16 formed on the wiring pattern 14 and forming a wiring pattern so as to fill the contact hole, a wiring pattern formed on the wiring pattern 14 is obtained. When a wiring pattern is further formed, an SOG film and an O ₃ -TEOS film are formed in the same manner as described above. When the insulating film is formed in this manner, an insulating film having excellent filling and flatness between wirings is formed.

In the present embodiment, the FT-IR method is used to check the hydrogen content of the SOG film. However, the hydrogen content may be checked by another method. In the present embodiment, the hydrogen content of the SOG film is checked. However, without checking the hydrogen content, the SOG film is formed from a solution containing a silsesquioxane hydride as a main component, and then the OSG film is formed. ₃ -TE
By forming the OS film, an insulating film with excellent filling between wirings and excellent flatness can be formed.

In this embodiment, TEOS is used as the organic silane as the raw material of the O ₃ -TEOS film, but another organic silane may be used.

[0033]

As described above, according to the method of forming an insulating film of the present invention, the manufacturing cost can be reduced, and a flat insulating film having good embedding into recesses can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of an insulating film formed by using an insulating film forming method according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a process of manufacturing an insulating film formed by using the insulating film forming method according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a process of manufacturing an insulating film formed by using the insulating film forming method according to one embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of an insulating film formed by using the insulating film forming method according to one embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a process of manufacturing an insulating film formed by using the insulating film forming method according to one embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a process of manufacturing an insulating film formed by using the insulating film forming method according to one embodiment of the present invention.

FIG. 7 is a graph showing a change in thermal history of an SOG film.

FIG. 8 is an infrared absorption spectrum of the SOG film.

[Explanation of symbols]

Reference Signs List 11 silicon substrate 12 interlayer insulating film 13 contact hole 14 wiring 15 SOG film 16 O ₃ -TEOS film

Claims (6)

[Claims] 1. An insulating film forming method for forming an insulating film on a semiconductor substrate, comprising: a first step of forming a wiring pattern on the semiconductor substrate; and a second step of cleaning the wiring pattern with an organic solvent. A third step of horizontally rotating the semiconductor substrate in a nitrogen atmosphere and dropping a solution containing hydrogenated silsesquioxane as a main component to form the solution into a film, A fourth step of baking the semiconductor substrate to form a film of the solution on the SOG film, and forming a CV on the surface of the SOG film using organic silane and ozone.
A fifth step of forming a silicon oxide film by the method D; and forming the silicon oxide film in a thickness direction of the silicon oxide film.
A polishing step so as to leave a lower layer portion in contact with the SOG film. 2. After the execution of the fourth step and before the execution of the fifth step, the S formed by the execution of the fourth step is formed.
The method according to claim 1, further comprising a seventh step of measuring a hydrogen content of the OG film. 3. The method according to claim 2, wherein the seventh step is a step of measuring the hydrogen content on the surface of the SOG film by infrared absorption spectroscopy. 4. The method according to claim 1, wherein the first step is performed using aluminum, copper,
2. The method according to claim 1, wherein the step of forming a wiring pattern is performed using a material containing at least one of gold and silver. 5. The method according to claim 1, wherein the sixth step is a step of polishing the silicon nitride film by a chemical mechanical polishing method. 6. The method according to claim 1, wherein the fifth step is a step of forming a silicon oxide film by a CVD method using tetraethyl orthosilicate and ozone.
4. The method for forming an insulating film according to any one of items 1 to 3.