JP2008050610A - Silicaceous film forming composition, silicaceous film, method for producing the same, and electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicaceous film forming composition capable of forming a silicaceous film having low permittivity, excellent bondability, and sufficient mechanical strengths. <P>SOLUTION: The silicaceous film forming composition comprises a component (a): a siloxane resin prepared by hydrolytically condensing a compound represented by formula (1); R<SP>1</SP><SB>n</SB>SiX<SB>4-n</SB>(wherein R<SP>1</SP>is H, F, a group containing B, N, Al, P, Si, Ge, or Ti, or a 1-20C organic group; and X is a hydrolyzable group; and n is an integer of 0-2, provided that R<SP>1</SP>s may be the same or different from each other when n is 2; and Xs may be the same or different from each other when n is 0-2), a component (b): a solvent which can dissolve component (a), and a component (e): a polymer having hydroxyl-containing side chains, wherein the polymer satisfies the relationship represented by formula (2); 0<M<SB>OH</SB><0.4×10<SP>-2</SP>(wherein M<SB>OH</SB>is the concentration (mol/g) of the hydroxyl groups of the polymer). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composition for forming a silica-based film, a silica-based film, a method for producing a silica-based film, and an electronic component.

  Regarding electronic device parts such as semiconductor elements such as LSI, with the miniaturization of wiring due to high integration, an increase in signal delay time due to increase in inter-wiring capacitance has become a problem. In addition to heat resistance, mechanical properties, etc., further low dielectric constant and shortening of the heat treatment process are required.

In general, the signal propagation speed (v) of the wiring and the relative dielectric constant (ε) of the insulating material in contact with the wiring material show a relationship represented by the following formula (3) (k in the formula is a constant).
v = k / √ε (3),

That is, by increasing the frequency region to be used and reducing the relative dielectric constant (ε) of the insulating material, signal transmission speed can be increased. For example, a SiO ₂ film formed by a CVD method having a relative dielectric constant of about 4.2 has been used as a material for forming an interlayer insulating film. However, it reduces the capacitance between devices and reduces the operating speed of an LSI. From the viewpoint of improving the above, a material that exhibits a further low dielectric constant is desired.

  On the other hand, a low dielectric constant material that is currently in practical use includes a SiOF film formed by a CVD method having a relative dielectric constant of about 3.5. Examples of the insulating material having a relative dielectric constant of 2.5 to 3.0 include organic SOG (Spin On Glass) and organic polymers. Furthermore, as insulating materials having a relative dielectric constant of 2.5 or less, porous materials having voids in the film are considered to be promising, and studies and developments for application to LSI interlayer insulating films are actively conducted. ing.

As a method for forming such a porous material, Japanese Patent Application Laid-Open No. 11-3222992, Japanese Patent Application Laid-Open No. 11-310411, etc. propose a reduction in the dielectric constant of an organic SOG material. In this method, a film is formed from a composition containing a polymer having a property of volatilizing or decomposing by heating together with a hydrolyzed polycondensation product of a metal alkoxysilane, and pores are formed by heating the film. is there.
JP-A-11-322992 JP-A-11-310411

  However, the present inventors have examined the conventional method in detail, and in such a conventional method, in the condensation of the organic SOG in the final heating step, in addition to the stress due to heat, a rapid stress is applied to the film. In some cases, there is a possibility that a large effect may be caused to impair the functions of the underlying wiring and the like.

  Moreover, in such a conventional method, the heating temperature at the time of final curing of the coating film is as high as 450 ° C. or more, and the curing tends to require a long time of about 1 hour. When this happens, the amount of heat input (thermal budget) increases excessively, and there is a concern about deterioration of the wiring layer among the lower layers. Moreover, the problem that the curvature of a board | substrate becomes remarkable with the increase in the amount of heat inputs may also arise.

  Furthermore, as described above, miniaturization of wiring due to high integration is accelerating, and thinning / multilayering of each member layer constituting the device, and material change of wiring layers and the like are progressing. In order to cope with this, the influence of material deterioration of each layer due to heat input is expected to be greater than before, and there is an urgent need to improve the heat history by reducing the heat load in each process.

  Furthermore, when the above-described conventional method is used, the present inventors need to introduce a very large amount of voids (voids) into the film in order to achieve a desired low dielectric constant required for the insulating film. I found. In this case, when the mechanical film strength or film hardness of the SOG that is the base material of the film is inherently insufficient, the mechanical strength of the film tends to further decrease due to excessive increase in the porosity. It is in. In other words, such a conventional method has a problem that the film strength tends to decrease as the dielectric constant of the insulating film decreases, and there is a big problem from the viewpoint of process compatibility.

Furthermore, when a silica-based film is applied to an interlayer insulating film of a Cu-damascene process, a SiO ₂ film formed by a CVD method is used as a cap film. ) Weakens, interfacial debonding may occur in a Cu-CMP (Chemical Mechanical Polish) process for polishing an extra Cu film generated when the wiring metal is laminated.

  In addition, depending on the component added to the interlayer insulating film material, there is a risk of increasing the dielectric constant or increasing the desorption gas due to moisture absorption. When these situations occur, it is extremely inconvenient from the viewpoint of process compatibility.

  Therefore, the present invention has been made in view of such circumstances, and it is possible to obtain a silica-based film having excellent low dielectric properties and sufficient mechanical strength, and for forming the silica-based film at a low temperature or Silica-based coating that can be cured sufficiently in a short period of time, and that can suppress a sudden increase in stress of the coating, and that can improve adhesion to other layers (films) and electrical reliability It is an object of the present invention to provide a forming composition, a silica-based film obtained by using the composition, a method for producing the same, and an electronic component including the silica-based film.

  In order to solve the above-mentioned problems, the present inventors paid attention to the curing behavior when forming a silica-based film from a liquid composition, and repeated earnest research from the viewpoint of the material component of the composition and its composition, The present invention has been completed.

  The composition for forming a silica-based film according to the present invention comprises a siloxane resin, has fluidity, and is cured when heat is applied in the state of a film applied on a substrate. The stress of the silica-based film obtained when pre-cured by heating at 150 ° C. for 3 minutes is 10 MPa or more, and the relative dielectric constant of the silica-based film obtained by final curing is 3 It has the hardening characteristic which becomes less than 0.0.

That is,
(1) For forming a silica-based coating that contains a siloxane resin, has fluidity, and cures when a heat is applied in the state of a film applied on a substrate to form a silica-based coating. A composition comprising:
The silica-based coating obtained by heating at 150 ° C. for 3 minutes has a stress of 10 MPa or more, and has a curing characteristic such that the relative dielectric constant of the silica-based coating obtained by final curing is less than 3.0.
A composition for forming a silica-based film.

(2) For forming a silica-based film that contains a siloxane resin, has fluidity, and cures when a heat is applied in a film state applied on a substrate to form a silica-based film. A composition comprising:
When pre-cured at the first heating temperature in the film state and then finally cured at a second heating temperature higher than the first heating temperature, and finally cured at the second heating temperature The second stress of the silica-based coating is such that the second stress of the silica-based coating is smaller than the first stress of the silica-based coating when cured at the first heating temperature.
A composition for forming a silica-based film.

(3) The silica according to (2), wherein the first heating temperature is a temperature within a range of 100 ° C. or more and less than 350 ° C., and the second heating temperature is a temperature within a range of 350 or more and 500 ° C. or less. -Based film-forming composition.

(4) For forming a silica-based film that contains a siloxane resin, has fluidity, and cures when a heat is applied in a film state applied on a substrate to form a silica-based film. A composition comprising:
Modified-Edge Lift-OFF TEST ( m-ELT) parameters K ₁ obtained in the value is at least 0.20, and, as the dielectric constant of the silica-based coating film obtained by the final curing is less than 3.0 Have good curing properties,
A composition for forming a silica-based film.

(5) (a) component: following formula (1);
R ¹ _n SiX _4-n (1),
(In the formula, R ¹ represents an H atom or F atom, or a group containing B atom, N atom, Al atom, P atom, Si atom, Ge atom or Ti atom, or an organic group having 1 to 20 carbon atoms. , X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, each X is the same But it can be different)
A siloxane resin obtained by hydrolytic condensation of a compound represented by:
(B) component: a solvent capable of dissolving the component (a),
(C) component: onium salt,
(D) component: a pyrolysis volatile compound that pyrolyzes or volatilizes at a heating temperature of 250 to 500 ° C .;
The composition for forming a silica-based film according to any one of (1) to (4), comprising:

(6) (a) component: following formula (1);
R ¹ _n SiX _4-n (1),
(In the formula, R ¹ represents an H atom or F atom, or a group containing B atom, N atom, Al atom, P atom, Si atom, Ge atom or Ti atom, or an organic group having 1 to 20 carbon atoms. , X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, each X is the same But it can be different)
A siloxane resin obtained by hydrolytic condensation of a compound represented by:
(B) component: a solvent capable of dissolving the component (a),
(C) component: onium salt,
(E) component: a polymer having a side chain containing a hydroxyl group;
With
The polymer is represented by the following formula (2):
0 <M _OH <0.4 × 10 ⁻² (2),
M _OH : concentration of the hydroxyl group in the polymer (mol / g),
The composition for silica-type film formation which satisfy | fills the relationship represented by these.

(7) The component (b) includes a first solvent component composed of an alkylene glycol alkyl ether alkyl ester or an alkylene glycol alkyl ether acetate, and a second solvent component composed of an alkylene glycol monoalkyl ether. ) Or the composition for forming a silica-based film according to (6).

(8) The component (b) is for forming a silica-based film according to (7), wherein the mass content ratio of the first solvent component and the second solvent is from 1:99 to 60:40. Composition.

(9) The composition for forming a silica-based film according to (7) or (8), wherein the first solvent component is alkylene glycol methyl ether acetate.

(10) The composition for forming a silica-based film according to any one of (7) to (9), wherein the first solvent component is propylene glycol alkyl ether acetate.

(11) The composition for forming a silica-based film according to any one of (7) to (10), wherein the first solvent component is propylene glycol methyl ether acetate.

(12) The composition for forming a silica-based film according to any one of (7) to (11), wherein the second solvent component is propylene glycol monopropyl ether.

(13) The component (e) is for forming a silica-based coating film according to any one of (6) to (12), wherein the reduction rate in a nitrogen gas atmosphere at a temperature of 300 to 500 ° C. is 95% by mass or more. Composition.

(14) The composition for forming a silica-based film according to any one of (6) to (13), wherein the component (e) contains an ester bond in the molecule.

(15) The component (e) contains a (meth) acrylic acid derivative as a constituent component, and the content concentration of the (meth) acrylic acid derivative is 0.5 × 10 ⁻² (mol / g) or more. The composition for silica-type film formation in any one of (6)-(14) which is a thing.

(16) The composition for forming a silica-based film according to any one of (5) to (15), wherein the component (c) is an ammonium salt.

(17) The composition for forming a silica-based film according to any one of (5) to (16), further comprising nitric acid.

(18) The component (a) is composed of a group consisting of H atom, F atom, B atom, N atom, Al atom, P atom, Si atom, Ge atom, Ti atom, and C atom with respect to 1 mol of Si atom. The composition for forming a silica-based film according to any one of (5) to (17), wherein the total content of at least one selected atom is 0.65 mol or less.

(19) A silica-based film comprising a cured film formed by applying the composition for forming a silica-based film according to any one of (1) to (18) onto a substrate and heating the applied film.

(20) The silica-based film according to (19), wherein the relative dielectric constant is less than 3.0.

(21) The silica-based film according to (19), which has an elastic modulus of 2.5 GPa or more.

(22) A method for producing a silica-based film, wherein the composition for forming a silica-based film according to any one of (1) to (18) is applied onto a substrate, and the applied film is heated to cure the film.

(23) The composition for forming a silica-based film according to any one of (5) to (18) is applied on a substrate, the solvent contained in the applied film is removed, and then the film is formed to 250 to 500. A method for producing a silica-based film, which is baked at a heating temperature of ° C.

(24) An electronic component in which an insulating film is formed on a substrate on which an element structure is formed,
An electronic component, wherein the insulating film includes a silica-based film produced by the method for producing a silica-based film according to (22) or (23).

Here, “stress” refers to a value obtained by the following method.
[Stress evaluation method]
(1) Formation of silica-based coating for stress measurement First, a silica-based coating forming composition is applied on a predetermined Si wafer so as to have a certain thickness, thereby forming a coating. Specifically, with the orientation flat of a Si wafer (thickness: 625 ± 25 μm) having an outer diameter of 5 inches as a reference, the thin film stress measuring device (KLA Tencor device, model: FLX-2320) is placed at a predetermined position. The amount (initial value) of the “warp” of the Si wafer is measured in an atmosphere containing 23 ° C. ± 2 ° C. and a humidity of 40% ± 10%.

  Next, the Si wafer is taken out from this apparatus, and a silica-based film forming composition is applied thereon by spin coating to form a film. Then, this Si wafer is heat-processed on 150 degreeC / 3min hotplate conditions, the solvent etc. which are contained in a composition are removed, and it precures, and forms a silica-type film. After the heating is completed, the thickness of the silica-based film is measured. Next, the Si wafer is accommodated at a predetermined position in the apparatus (FLX-2320) with the orientation flat as a reference in the same manner as before the film formation, and the amount of ‘warping’ of the Si wafer is measured.

で表される関係から、シリカ系被膜の応力を算出する。 Using the initial value of the warp of the obtained Si wafer, the value of the warp after the heat treatment, and the film thickness of the silica-based coating, the following formula (4);

The stress of the silica-based film is calculated from the relationship represented by

In the formula, σ indicates the stress (MPa) of the silica-based coating, E indicates the Young's modulus (dyn / cm ² ) of the Si wafer, b indicates the thickness (μm) of the Si wafer, and ν indicates the Si wafer thickness. Poisson's ratio (-), l indicates the scanning distance (mm) of the surface roughness meter when calculating 'warp', d indicates the thickness of the silica-based coating (μm), and δ indicates the ' The amount of warp displacement (that is, the absolute value of the difference between the initial value of warp and the value after heat treatment) (μm) is shown.

  Then, the formation treatment of the silica-based coating and the stress evaluation are performed on the five Si wafers, and the average value of the stress of the silica-based coating in the heat treatment at 150 ° C./3 minutes is obtained. Note that “stress” in the present invention means its absolute value.

  Such a composition for forming a silica-based film of the present invention is applied on a substrate such as a wafer and then cured by heating to form a silica-based film (low-k film) that exhibits a low dielectric constant. . At this time, since the stress when the composition is pre-cured for 3 minutes at 150 ° C. is 10 MPa or more, even in such a low-temperature heat treatment, bonds that form a siloxane skeleton tend to be formed to some extent. Accordingly, the silica-based coating can be cured by heat treatment at a low temperature and in a short time as compared with the conventional case. On the other hand, when the stress is less than 10 MPa, the formation of the siloxane skeleton in the low-temperature heat treatment becomes insufficient, and it becomes difficult to significantly lower the pre-curing treatment temperature.

As such a composition for forming a silica-based film, specifically, (a) component: the following formula (1);
R ¹ _n SiX _4-n (1),
(In the formula, R ¹ represents an H atom or F atom, or a group containing B atom, N atom, Al atom, P atom, Si atom, Ge atom or Ti atom, or an organic group having 1 to 20 carbon atoms. , X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, each X is the same However, it may be different), a siloxane resin obtained by hydrolytic condensation of a compound represented by (a), a component (b): a solvent capable of dissolving the component (a), a component (c): an onium salt, d) Component: It is preferable to contain a pyrolytic volatile compound that thermally decomposes or volatilizes at a heating temperature of 250 to 500 ° C.

  With such a composition, when curing proceeds by heating, fine pores are gradually formed in the film due to thermal decomposition or volatilization of component (d), and refinement and homogenization of the shape during final curing Can be achieved. Furthermore, due to the presence of the onium salt as component (c), the dehydration condensation reaction of the compound represented by formula (1) proceeds, and the density of siloxane bonds is increased by reducing the Si—OH bonds. In addition, the stress relaxation of the film can be caused by the combined action of the vacancy formation process and the densification of the siloxane bonds and the annealing effect during the final heating. However, the action is not limited to this.

  In general, a silica-based film cured by such a heat treatment has a disadvantage in terms of device characteristics due to an increase in stress generated as described above. On the other hand, according to the composition of the present invention, it is caused by heat application. Since the stress of the silica-based coating is relieved by the curing history, the influence of the stress can be reduced.

  The component (a) is selected from the group consisting of H atom, F atom, B atom, N atom, Al atom, P atom, Si atom, Ge atom, Ti atom, and C atom with respect to 1 mol of Si atom. The total content of at least one kind of atoms is preferably 0.65 mol or less, more preferably 0.55 or less, still more preferably 0.50 or less, and particularly preferably 0.45 or less. Moreover, it is desirable that the lower limit value of the total content ratio is about 0.20. If it does in this way, the fall to the adhesiveness to other films | membranes (layers) of a silica-type film and mechanical strength will be suppressed.

  Alternatively, the composition for forming a silica-based film according to the present invention comprises a siloxane resin, has fluidity, and is cured when heat is applied in the state of a film coated on a substrate, thereby forming silica. When the system coating is formed and pre-cured at the first heating temperature in the film state, and then finally cured at the second heating temperature higher than the first heating temperature, the second The second stress of the silica-based coating when it is finally cured at the heating temperature is less than the first stress of the silica-based coating when cured at the first heating temperature. It is characterized by.

Specifically, the first heating temperature _{T 1} is preferably less than 100 or 350 ° C., more preferably 150 to 300 ° C., particularly preferably at a temperature in the range of 150 to 250 ° C., the second heating temperature T _{When 2} is preferably at a temperature in the range of 350 to 500 ° C., it preferably has the curing characteristics as described above. Here, “stress” in “first stress” and “second stress” refers to a value obtained by the following method.

[Stress evaluation method]
(1) Formation of silica-based coating for stress measurement First, a silica-based coating forming composition is applied on a predetermined Si wafer so as to have a certain thickness, thereby forming a coating. Specifically, with the orientation flat of a Si wafer (thickness: 625 ± 25 μm) having an outer diameter of 5 inches as a reference, the thin film stress measuring device (KLA Tencor device, model: FLX-2320) is placed at a predetermined position. The amount (initial value) of the “warp” of the Si wafer is measured in an atmosphere containing 23 ° C. ± 2 ° C. and a humidity of 40% ± 10%.

Next, the Si wafer is taken out from this apparatus, and a silica-based film forming composition is applied thereon by spin coating to form a film. Thereafter, this Si wafer is heated under a hot plate condition of a predetermined first heating temperature T ₁ ° C. (for example, 150 ° C./1 minute + 250 ° C./1 minute) to remove the solvent and the like contained in the composition. Pre-curing to form a silica-based film (pre-curing step). After the heating is completed, the thickness of the silica-based film is measured. Next, the Si wafer is accommodated at a predetermined position in the apparatus (FLX-2320) with the orientation flat as a reference in the same manner as before the film formation, and the amount of warpage of the Si wafer is measured.

Then, the Si wafer having undergone the preliminary curing step is heat-treated at a _second heating temperature T ₂ ° C. (for example, 400 ° C./30 minutes) in a nitrogen (N ₂ ) gas atmosphere to be finally cured (final curing step). . And while measuring the film thickness of the obtained silica-type coating film, the amount of "warp" of Si wafer is measured like other Si wafers mentioned above.

で表される関係から応力を算出する。 Using the initial value of the warp of the obtained Si wafer, the warp value after heat treatment of both Si wafers, and the thickness of the silica-based coating on both Si wafers, the following formula (4);

The stress is calculated from the relationship represented by

In the formula, σ indicates the stress (MPa) of the silica-based coating, E indicates the Young's modulus (dyn / cm ² ) of the Si wafer, b indicates the thickness (μm) of the Si wafer, and ν indicates the Si wafer thickness. Poisson's ratio (-), l indicates the scanning distance (mm) of the surface roughness meter when calculating 'warp', d indicates the thickness of the silica-based coating (μm), and δ indicates the ' The amount of warp displacement (that is, the absolute value of the difference between the initial value of warp and the value after heat treatment) (μm) is shown.

And the formation process of such a silica type coating and stress evaluation are performed with respect to five Si wafers, and the average value of the stress of a silica type coating in each heating temperature is calculated | required. The stress value calculated for the silica-based film on the Si wafer pre-cured at the first heating temperature T ₁ ° C is the “first stress”, while the final value is the second heating temperature T ₂ ° C. The stress value calculated for the silica-based coating on the cured Si wafer is the “second stress”. Note that “stress” in the present invention means its absolute value.

  Such a composition for forming a silica-based film is applied onto a substrate such as a wafer and then cured by heating to form a silica-based film (Low-k film) that exhibits a low dielectric constant. At this time, in the heat treatment step at the first heating temperature, the composition is gradually cured from the initial stage of heating to the latter stage, and the stress increases accordingly. Next, when a heat treatment at the second heating temperature, that is, a final curing treatment is performed, the stress of the silica-based coating obtained is reduced to a second stress that is smaller than the first stress.

  In general, a silica-based film cured by such a heat treatment has a disadvantage in terms of device characteristics due to an increase in stress generated as described above. On the other hand, according to the composition of the present invention, it is caused by heat application. Since the stress of the silica-based coating is relieved by the curing history, the influence of the stress can be reduced.

As such a composition for forming a silica-based film, specifically, (a) component: the following formula (1);
R ¹ _n SiX _4-n (1),
(In the formula, R ¹ represents an H atom or F atom, or a group containing B atom, N atom, Al atom, P atom, Si atom, Ge atom or Ti atom, or an organic group having 1 to 20 carbon atoms. , X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, each X is the same However, it may be different), a siloxane resin obtained by hydrolytic condensation of a compound represented by (a), a component (b): a solvent capable of dissolving the component (a), a component (c): an onium salt, d) Component: It is preferable to contain a pyrolytic volatile compound that thermally decomposes or volatilizes at a heating temperature of 250 to 500 ° C.

  With such a composition, when curing proceeds by heating, fine pores are gradually formed in the film due to thermal decomposition or volatilization of component (d), and refinement and homogenization of the shape during final curing Can be achieved.

  Furthermore, due to the presence of the onium salt as component (c), the dehydration condensation reaction of the compound represented by formula (1) proceeds, and the density of siloxane bonds is increased by reducing the Si—OH bonds. In addition, the stress relaxation of the film can be caused by the combined action of the vacancy formation process and the densification of the siloxane bonds and the annealing effect during the final heating. However, the action is not limited to this.

  The component (a) is selected from the group consisting of H atom, F atom, B atom, N atom, Al atom, P atom, Si atom, Ge atom, Ti atom, and C atom with respect to 1 mol of Si atom. The total content of at least one kind of atoms is preferably 0.65 mol or less, more preferably 0.55 or less, still more preferably 0.50 or less, and particularly preferably 0.45 or less. Moreover, it is desirable that the lower limit value of the total content ratio is about 0.20. If it does in this way, the fall to the adhesiveness to other films | membranes (layers) of a silica-type film and mechanical strength will be suppressed.

Furthermore, the composition for forming a silica-based film according to the present invention comprises a siloxane resin, has fluidity, and is cured when heat is applied in the state of a film coated on a substrate. be one system coating is formed, Modified-Edge Lift-OFF TEST (m-ELT) value of the parameter _{K 1} obtained in 0.20 or more, preferably 0.25 or more, more preferably 0.27 As described above, it is particularly preferably 0.29 or more, and the silica-based coating obtained by final curing has a curing characteristic such that the relative dielectric constant is less than 3.0.

The upper limit of _{K 1,} preferably about 0.6. Here, “m-ELT” is a test method shown below, and K ₁ is a physical property parameter obtained as a result of this test.

[Modified-Edge Lift-OFF TEST (m-ELT) method]
(1) K ₁ forming a silica-based coating film for evaluation First, on a predetermined Si wafer, a silica-based coating composition was coated to a predetermined thickness to form a film. Specifically, a silica-based film forming composition is applied onto an 8-inch Si wafer (thickness: 725 ± 25 μm) by spin coating so that the thickness is 0.5 to 0.6 μm. Form. Thereafter, this Si wafer is heat-treated at 150 ° C./1 minute + 250 ° C./1 minute to remove the solvent and the like contained in the composition and pre-cured, and further, 400 ° C. under nitrogen (N ₂ ) gas atmosphere. Heat treatment is performed at / 30 minutes for final curing to form a silica-based film.

(2) Evaluation of parameter K ₁ value For the following measurement, a 3.5 cm × 7 cm central portion of the 8-inch Si wafer on which the silica-based film is formed in the above (1) is used as a test piece. First, the thickness h1 of the test piece is measured with a micro fine made by Union Tool.

  Next, the surface of the test piece was treated for 150 seconds using a UV-zone processing apparatus (manufactured by Oak Manufacturing; UV dry processor VUM-3073-B), and then Omega99Epoxy manufactured by Frontier Semiconductor was used, and BYK-Gardner Film Casting Kife. To a thickness of about 200 μm. Subsequently, the test piece is dried for 1 hour by a dangerous material type high-temperature drier (manufactured by Enomoto Kasei; EHT-H02 ETAC) maintained at 177 ° C.

Thereafter, the test piece is cut into a 1 cm square with a diamond cutter, and the thicknesses h2 of the four corners (top portions) are measured by the above-described apparatus used for the measurement of h1. Furthermore, the test piece cut into 1 cm square was placed on the stage in the chamber of the m-ELT apparatus (manufactured by Modern Metalcraft), and the following temperature program;
・ Cooling start temperature: 100 ° C
-Temperature drop end temperature: -175 ° C
・ Cooling rate: 3 ℃ / min,
The temperature T (° C.) at which the attached epoxy resin is peeled when the temperature is lowered is read.

Using the obtained thicknesses h1, h2 and temperature T, the following formulas (5) and (6):
K ₁ = σ × {(h1-h2) / 2} ^1/2 (5),
σ = −0.00002 × T ² −0.192 × T + 24.0 (6),
K ₁ value is calculated from the relationship expressed by:

Parameter K ₁ in the m-ELT obtained in this manner, adhesion between the silica film and the underlying layer, and is an index showing the strength of the film itself, adhesion between the silica film and the underlying layer larger the K ₁ value It shows that the force (adhesion) is high and the film strength is excellent.

This K ₁ value is less than 0.2, in the case of applying a silica-based coating film as an interlayer insulating film in Cu- damascene process, it is attenuated adversely adhesion between the SiO ₂ film of the coating and the base, the wiring metal In the Cu-CMP process for polishing excess Cu wiring generated when the layers are laminated, there is a possibility that a major problem such as peeling or cohesive failure of the film itself may occur.

As such a composition for forming a silica-based film, specifically, (a) component: the following formula (1);
R ¹ _n SiX _4-n (1),
(In the formula, R ¹ represents an H atom or F atom, or a group containing B atom, N atom, Al atom, P atom, Si atom, Ge atom or Ti atom, or an organic group having 1 to 20 carbon atoms. , X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, each X is the same However, it may be different), a siloxane resin obtained by hydrolytic condensation of a compound represented by (a), a component (b): a solvent capable of dissolving the component (a), a component (c): an onium salt, d) Component: It is preferable to contain a pyrolytic volatile compound that thermally decomposes or volatilizes at a heating temperature of 250 to 500 ° C.

  With such a composition, when curing proceeds by heating, fine pores are gradually formed in the film due to thermal decomposition or volatilization of component (d), and refinement and homogenization of the shape during final curing Can be achieved. Furthermore, due to the presence of the onium salt as component (c), the dehydration condensation reaction of the compound represented by formula (1) proceeds, and the density of siloxane bonds is increased by reducing the Si—OH bonds. In addition, the stress relaxation of the film can be caused by the combined action of the vacancy formation process and the densification of the siloxane bonds and the annealing effect during the final heating. However, the action is not limited to this.

  The component (a) is selected from the group consisting of H atom, F atom, B atom, N atom, Al atom, P atom, Si atom, Ge atom, Ti atom, and C atom with respect to 1 mol of Si atom. The total content of at least one kind of atoms is preferably 0.65 mol or less, more preferably 0.55 or less, still more preferably 0.50 or less, and particularly preferably 0.45 or less. Moreover, it is desirable that the lower limit value of the total content ratio is about 0.20. If it does in this way, the fall to the adhesiveness to other films | membranes (layers) of a silica-type film and mechanical strength will be suppressed.

  Furthermore, the present inventors have conducted extensive research from the viewpoint of the material component for obtaining a silica-based film as an insulating film and its composition, and a composition containing a specific component has various conventional problems. It has been found that the problem can be solved, and the present invention has been completed.

That is, the composition for forming a silica-based film according to the present invention comprises (a) component: the following formula (1);
R ¹ _n SiX _4-n (1),
A siloxane resin obtained by hydrolytic condensation of a compound represented by formula (b): a component (b): a first solvent component comprising an alkylene glycol alkyl ether alkyl ester or an alkylene glycol alkyl ether acetate, and an alkylene glycol monoalkyl ether A solvent containing a second solvent component, (e) component: a polymer having a side chain containing a hydroxyl group, and (c) component: an onium salt (onium compound), A polymer has the following formula (2);
0 <M _OH <0.4 × 10 ⁻² (2),
It satisfies the relationship expressed by

Note that in formula (1), R ¹ represents an H atom or an F atom, or a group containing a B atom, an N atom, an Al atom, a P atom, a Si atom, a Ge atom, or a Ti atom, or a group having 1 to 20 carbon atoms. Represents an organic group, X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, Each X may be the same or different. Moreover, in Formula (2), _MOH shows the density | concentration (mol / g) of the hydroxyl group in the polymer which is (e) component.

  The composition having such a structure is applied onto a substrate such as a wafer and then cured by heating to form a silica-based film (Low-k film) that exhibits a low dielectric constant. At this time, it was confirmed that the finally obtained silica-based film achieves sufficient mechanical strength when the solvent as the component (b) contains the first solvent component and the second solvent component.

  In addition, by containing a hydroxyl group in the side chain of the polymer as the component (e), the phase separation between the siloxane resin of the component (a) and the polymer is prevented when the solvent of the component (b) is volatilized. As a result, the pores formed inside the film are made finer and the shape is made uniform. Not only that, the decomposition of the component (e) during heating is suppressed and its volatilization is promoted.

  Further, when the onium salt as the component (c) is present, the dehydration condensation reaction of the compound represented by the formula (1) proceeds, and the density of the siloxane bond is increased by decreasing the Si—OH bond. Strength is further improved. However, the action is not limited to this.

  The component (a) is selected from the group consisting of H atom, F atom, B atom, N atom, Al atom, P atom, Si atom, Ge atom, Ti atom, and C atom with respect to 1 mol of Si atom. The total content of at least one kind of atoms is preferably 0.65 mol or less, more preferably 0.55 or less, still more preferably 0.50 or less, and particularly preferably 0.45 or less. Moreover, it is desirable that the lower limit value of the total content ratio is about 0.20. If it does in this way, the fall to the adhesiveness to other films | membranes (layers) of a silica-type film and mechanical strength will be suppressed.

  In addition, the component (b) preferably has a mass content ratio of the first solvent component and the second solvent of 1:99 to 60:40. If it carries out like this, while the fall of the mechanical strength of a silica-type film can fully be suppressed, deterioration of physical properties, such as the uniformity of the film thickness, is suppressed.

  Specifically, it is useful that the first solvent component is alkylene glycol methyl ether acetate or propylene glycol alkyl ether acetate, particularly propylene glycol methyl ether acetate. Alternatively, the second solvent component is preferably propylene glycol monopropyl ether.

  Furthermore, the component (e) is preferably a polymer having a reduction rate in a nitrogen gas atmosphere at a temperature of 300 to 500 ° C. of preferably 95% by mass or more, more preferably 97% by mass or more, and further preferably 99% by mass or more. It is. When such a component (e) is used, when the composition is heated, it is sufficiently suppressed that the polymer or the polymer-derived reaction product remains in the finally obtained silica-based film. Is done.

  Furthermore, it is more preferable that the component (e) contains an ester bond in the molecule. In this case, decomposition or volatilization of the polymer when the composition is heated is further promoted.

Furthermore, the component (e) contains a (meth) acrylic acid derivative as a constituent component, and the content concentration of the (meth) acrylic acid derivative is 0.5 × 10 ⁻² (mol / g) or more. It is useful to be. In this way, there is an advantage that the decomposition or volatilization of the polymer when the composition is heated is further accelerated.

  In addition, although the onium salt as component (c) is not particularly limited, it can be further improved in the electrical properties and mechanical properties of the resulting silica-based coating, and moreover is an ammonium salt from the viewpoint of enhancing the stability of the composition. Useful.

  More preferably, the composition for forming a silica-based film of the present invention further contains nitric acid. In this case, nitric acid functions as a catalyst for promoting the hydrolysis-condensation reaction in the hydrolysis-condensation of the compound represented by the formula (1). A substance exhibiting such a catalytic function is present in addition to nitric acid, but the use of nitric acid in particular increases the hardness of the silica-based coating obtained by heat curing. In addition, it is suitable from the viewpoint of further lowering the dielectric constant.

  The silica-based coating according to the present invention comprises a cured film formed by applying the silica-based coating forming composition of the present invention onto a substrate such as a Si wafer and heating the applied coating. .

  Further, the silica-based film of the present invention obtained from the composition for forming a silica-based film of the present invention has a relative dielectric constant of less than 3.0 and preferably 2.7 or less, as described above. Or less, more preferably 2.2 or less. As described above, the relative dielectric constant of the silica-based film is preferably as small as possible from the viewpoint of using an interlayer insulating film or the like, but the lower limit is desirably about 1.5 in order to prevent the mechanical strength of the film from being lowered. .

[Measurement method of relative permittivity]
Here, the “relative dielectric constant” of the silica-based coating in the present invention refers to a value measured in an atmosphere of 23 ° C. ± 2 ° C. and humidity of 40 ± 10%, and includes Al metal and an N-type low resistivity substrate ( It is obtained from the measurement of the charge capacity between the Si wafers). Specifically, first, a silica-based film for measuring relative permittivity is formed.

For example, a silica-based film forming composition is applied onto an N-type low resistivity Si wafer (resistivity <10 Ωcm) by spin coating so that the film thickness becomes 0.5 to 0.6 μm to form a film. To do. Next, the solvent in the composition is removed with a hot plate heated to 200 ° C., and further heated at 400 ° C. for 30 minutes in a nitrogen (N ₂ ) gas atmosphere to be finally cured to form a silica-based film.

  Next, Al metal is vacuum-deposited on this silica-based film in a circle having a diameter of 2 mm and a thickness of about 0.1 μm using a vacuum deposition apparatus. Thereby, a structure in which the insulating film is disposed between the Al metal and the low resistivity substrate is formed. Next, the charge capacity of this structure was measured using a device in which a dielectric test fixture (Yokogawa Electric: HP16451B) was connected to an LF impedance analyzer (Yokogawa Electric: HP4192A) at a use frequency of 1 MHz. taking measurement.

And the measured value of the charge capacity is expressed by the following formula (7);
Dielectric constant of silica-based film = 3.597 × 10 ⁻² × charge capacity (pF) × film thickness (μm) (7),
And the relative dielectric constant of the silica-based film is calculated.

  By the way, as described above, the silica-based coating according to the present invention is excellent in low dielectric constant, but in order to achieve further reduction in dielectric constant, for example, the content of the component (d) in the composition is reduced. It is effective to increase the amount of fine pores introduced into the film by adjusting.

  However, it should be noted that if the amount of micropores introduced is excessively increased in this way, the mechanical strength of the coating may be reduced. In this respect, it is preferable to form a silica-based film using a composition for forming a silica-based film having a composition that inherently provides a film having a low relative dielectric constant as much as possible without introducing micropores.

  Furthermore, the elastic modulus of the silica-based film is preferably 2.5 GPa or more, more preferably 3.0 GPa or more, further preferably 3.5 GPa or more, particularly preferably 4.0 GPa or more. It is very preferable that it is 5 GPa or more.

  The upper limit is not particularly limited, but is usually about 30 GPa. When this elastic modulus is less than 2.5 GPa, for example, when this silica-based film is used as a semiconductor insulating film, there is a possibility that inconvenience such as difficulty in processing occurs.

  In order to increase the elastic modulus, for example, it is effective to reduce the ratio of the pores contained in the siloxane resin, but as described above, from the viewpoint of reducing the relative dielectric constant, It is advantageous to increase the amount of pores inside, and it is desirable to consider the balance between the two.

[Measurement method of elastic modulus]
Here, the “elastic modulus” of the silica-based coating in the present invention is an elastic modulus in the vicinity of the surface of the coating, and is a value measured using a nanoindenter DCM manufactured by MTS. As the silica-based film for measurement, a silica-based film prepared in the same manner as described in [Method of measuring relative dielectric constant] is used. At this time, if the thickness of the silica-based coating is thin, it is affected by the base, and as described above, the initial coating thickness is preferably 0.5 to 0.6 μm.

Further, the vicinity of the surface means a depth within 1/10 of the film thickness, more specifically, a position at a depth of 15 nm to 50 nm from the film surface. Furthermore, in the measurement, the load and the load speed are expressed by the following equation (8);
dL / dt × 1 / L = 0.05 (sec ⁻¹ ) (8)
Vary to satisfy the relationship expressed by.

  In the formula, L represents a load, and t represents time. Furthermore, a Barkovic indenter (material: diamond) is used as the indenter for pushing, and the amplitude frequency of the indenter is set to 45 Hz for measurement.

  Furthermore, the silica-based coating according to the present invention is one in which (a large number of) pores having an average pore diameter of preferably 4.0 nm or less, more preferably 3.0 nm or less, and particularly preferably 2.2 nm or less are formed. More preferably. As a result, a satisfactory low dielectric constant can be reliably achieved while having sufficient mechanical strength such as CMP resistance. In this case, the average pore diameter is preferably such that formation of the pores is not difficult. Also, if the average pore diameter is extremely small, it may be difficult to achieve the required low dielectric constant.

  Alternatively, it is desirable that the highest frequency hole diameter of the holes formed in the silica-based film is 2.0 nm or less, more preferably 1.5 nm or less. Even if it does in this way, it will become easy to achieve both sufficient mechanical strength and a low dielectric constant.

  The “average pore diameter” in the present invention is obtained from pore distribution measured by X-ray diffuse scattering analysis using a commonly used X-ray diffractometer for a silica-based thin film. It shows the average value of the pore diameters. Further, the “maximum frequency hole diameter” in the present invention indicates a hole diameter having the highest appearance frequency in the hole distribution measured in the same manner.

  In addition, it is preferable that there are substantially no holes having a diameter of 10 nm or more, in other words, the maximum value of the formed hole diameter is less than 10 nm. Specifically, the maximum pore diameter in the pore distribution measured as described above is preferably less than 10 nm. As a result, the generation and progress of cracks in the film starting from the pores, and the film breakage are sufficiently prevented. Here, “substantially does not exist” includes not only the case where the frequency is zero in the pore distribution but also the case where it is statistically determined to be below the detection limit of the measuring device.

  The method for producing a silica-based film according to the present invention is characterized in that the composition for forming a silica-based film of the present invention is applied on a substrate, and the applied film is heated to cure the film. More specifically, in the method for producing a silica-based film according to the present invention, the composition for forming a silica-based film of the present invention is applied on a substrate, the solvent contained in the applied film is removed, and then the film is applied. Baking is performed at a heating temperature of 250 to 500 ° C.

  Furthermore, an electronic component (device) according to the present invention has an insulating film formed on a substrate on which an element structure is formed, and the insulating film is manufactured by the silica-based film manufacturing method of the present invention. Or a silica-based coating thereof.

  Hereinafter, embodiments of the present invention will be described in detail. As described above, the composition for forming a silica-based film according to the present invention comprises a siloxane resin, has fluidity, and is cured when heat is applied in the state of a film applied on a substrate. A silica-based film is formed, the stress of the silica-based film obtained when heated at 150 ° C. for 3 minutes is 10 MPa or more, and the relative dielectric constant of the silica-based film obtained by final curing is 3 It has a curing characteristic that becomes less than 0.0.

  Therefore, formation of a siloxane skeleton in the film is started by heat treatment at a low temperature of about 150 ° C. and for a short time of about several minutes, and a certain degree of curing, that is, preliminary curing can be achieved. Thus, since the curing is performed in a low temperature region and in a short time as compared with the conventional case, the amount of heat input to a substrate such as a wafer to which the composition is applied can be reduced. Therefore, it is possible to reduce the thermal influence on the underlying wiring layer and the like. Moreover, since the final curing process at a higher temperature can be performed in a short time, the amount of heat input can be further reduced.

  The composition for forming a silica-based film according to the present invention comprises a siloxane resin as described above, has fluidity, and when heat is applied in a film state applied on a substrate. When it is cured to form a silica-based film, cured at the first heating temperature in the film state, and then finally cured at a second heating temperature higher than the first heating temperature, Curing characteristics such that the second stress of the silica-based coating when finally cured at the second heating temperature is smaller than the first stress of the silica-based coating when cured at the first heating temperature. I have it.

  Therefore, such a composition for forming a silica-based film reduces the stress when the film formed by the heat treatment at the first heating temperature before the final curing is finally cured at the second heating temperature. . Accordingly, it is possible to prevent a sudden stress from acting on the obtained silica-based film.

  In addition, since preliminary curing can be performed in a low temperature region before final curing, heat treatment at a higher temperature in the final curing process can be performed in a short time. Therefore, the amount of heat input to a substrate such as a wafer to which the composition is applied can be reduced. Therefore, it is possible to reduce the thermal influence on the underlying wiring layer and the like. Furthermore, since the stress of the silica-based coating is relieved, it becomes possible to improve the adhesion with other layers (films).

Furthermore, as described above, the composition for forming a silica-based film according to the present invention contains a siloxane resin, has fluidity, and when heat is applied in a film state applied on a substrate. cure to be those silica-based film is formed, the value of the parameter _{K 1} obtained in m-ELT is 0.20 or more, preferably 0.25 or more, more preferably 0.27 or more, particularly preferably It is 0.29 or more and has a curing characteristic that the relative dielectric constant of the silica-based film obtained by final curing is less than 3.0. The upper limit value of _{K 1,} preferably about 0.6.

When a silica-based film obtained from such a composition is used as an interlayer insulating film or the like of an electronic component such as a semiconductor device, the adhesiveness with the underlying layer or the upper layer (other film) and the strength of the film itself are conventional. Compared to, it will be much improved. Therefore, for example, at the interface with the SiC film used as a cap film and the interface with the SiO ₂ film that is the underlayer, the resistance to peeling during polishing and the resistance to cohesive failure are enhanced. Lamination) and cohesive failure can be suppressed.

[First embodiment]
Specific examples of the composition for forming a silica-based film according to the present invention include, for example, the following components (a), (b), (c), and (d) as essential components. Things.

<(A) component>
(A) component is the following formula (1);
R ¹ _n SiX _4-n (1),
A siloxane resin obtained by hydrolytic condensation of a compound represented by the formula:

Here, in the formula, R ¹ is an H atom or F atom, or a group containing a B atom, an N atom, an Al atom, a P atom, a Si atom, a Ge atom, or a Ti atom, or an organic group having 1 to 20 carbon atoms. X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, May be the same or different.

  Examples of the hydrolyzable group X include an alkoxy group, a halogen atom, an acetoxy group, an isocyanate group, and a hydroxyl group. Among these, an alkoxy group is preferable from the viewpoint of the liquid stability of the composition itself and the coating property.

  Examples of the compound (alkoxysilane) of the formula (1) in which the hydrolyzable group X is an alkoxy group include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-iso-propoxysilane, tetra- n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, tetraalkoxysilane such as tetraphenoxysilane, trimethoxysilane, triethoxysilane, tripropoxysilane, fluorotrimethoxysilane, fluorotriethoxysilane, Methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltri-iso-propoxysilane, methyltri-n-butoxysilane, methyltri-iso-butoxysilane, methyltri-t rt-butoxysilane, methyltriphenoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltri-iso-propoxysilane, ethyltri-n-butoxysilane, ethyltri-iso-butoxysilane, ethyltri- tert-butoxysilane, ethyltriphenoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltri-n-propoxysilane, n-propyltri-iso-propoxysilane, n-propyltri-n -Butoxysilane, n-propyltri-iso-butoxysilane, n-propyltri-tert-butoxysilane, n-propyltriphenoxysilane, iso-propyltrimethoxysilane, iso-propi Triethoxysilane, iso-propyltri-n-propoxysilane, iso-propyltri-iso-propoxysilane, iso-propyltri-n-butoxysilane, iso-propyltri-iso-butoxysilane, iso-propyltri-tert -Butoxysilane, iso-propyltriphenoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-butyltri-n-propoxysilane, n-butyltri-iso-propoxysilane, n-butyltri-n-butoxy Silane, n-butyltri-iso-butoxysilane, n-butyltri-tert-butoxysilane, n-butyltriphenoxysilane, sec-butyltrimethoxysilane, sec-butyltriethoxysilane, sec-butyltri-n -Propoxysilane, sec-butyltri-iso-propoxysilane, sec-butyltri-n-butoxysilane, sec-butyltri-iso-butoxysilane, sec-butyltri-tert-butoxysilane, sec-butyltriphenoxysilane, t-butyl Trimethoxysilane, t-butyltriethoxysilane, t-butyltri-n-propoxysilane, t-butyltri-iso-propoxysilane, t-butyltri-n-butoxysilane, t-butyltri-iso-butoxysilane, t-butyltri -Tert-butoxysilane, t-butyltriphenoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyltri-iso-propoxysilane, phenyltri n-butoxysilane, phenyltri-iso-butoxysilane, phenyltri-tert-butoxysilane, phenyltriphenoxysilane, trifluoromethyltrimethoxysilane, pentafluoroethyltrimethoxysilane, 3,3,3-trifluoropropyltri Trialkoxysilane such as methoxysilane, 3,3,3-trifluoropropyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-propoxysilane, dimethyldi-iso-propoxysilane, dimethyldi-n-butoxysilane Dimethyldi-sec-butoxysilane, dimethyldi-tert-butoxysilane, dimethyldiphenoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldi-n-pro Xysilane, diethyldi-iso-propoxysilane, diethyldi-n-butoxysilane, diethyldi-sec-butoxysilane, diethyldi-tert-butoxysilane, diethyldiphenoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethoxy Silane, di-n-propyldi-n-propoxysilane, di-n-propyldi-iso-propoxysilane, di-n-propyldi-n-butoxysilane, di-n-propyldi-sec-butoxysilane, di-n- Propyl di-tert-butoxysilane, di-n-propyldiphenoxysilane, di-iso-propyldimethoxysilane, di-iso-propyldiethoxysilane, di-iso-propyldi-n-propoxysilane, di-iso-propyldi- iso-propo Xysilane, di-iso-propyldi-n-butoxysilane, di-iso-propyldi-sec-butoxysilane, di-iso-propyldi-tert-butoxysilane, di-iso-propyldiphenoxysilane, di-n-butyldimethoxy Silane, di-n-butyldiethoxysilane, di-n-butyldi-n-propoxysilane, di-n-butyldi-iso-propoxysilane, di-n-butyldi-n-butoxysilane, di-n-butyldi- sec-butoxysilane, di-n-butyldi-tert-butoxysilane, di-n-butyldiphenoxysilane, di-sec-butyldimethoxysilane, di-sec-butyldiethoxysilane, di-sec-butyldi-n- Propoxysilane, di-sec-butyldi-iso-propoxysilane, di sec-butyldi-n-butoxysilane, di-sec-butyldi-sec-butoxysilane, di-sec-butyldi-tert-butoxysilane, di-sec-butyldiphenoxysilane, di-tert-butyldimethoxysilane, di- tert-butyldiethoxysilane, di-tert-butyldi-n-propoxysilane, di-tert-butyldi-iso-propoxysilane, di-tert-butyldi-n-butoxysilane, di-tert-butyldi-sec-butoxysilane , Di-tert-butyldi-tert-butoxysilane, di-tert-butyldiphenoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldi-n-propoxysilane, diphenyldi-iso-propoxysilane, dipheni Di-n-butoxysilane, diphenyldi-sec-butoxysilane, diphenyldi-tert-butoxysilane, diphenyldiphenoxysilane, bis (3,3,3-trifluoropropyl) dimethoxysilane, methyl (3,3,3) -Diorganodialkoxysilane such as (trifluoropropyl) dimethoxysilane.

  Moreover, as the compound (halogenated silane) of the formula (1) in which the hydrolyzable group X is a halogen atom (halogen group), a compound in which the alkoxy group in each alkoxysilane molecule is substituted with a halogen atom. Can be mentioned.

  Further, examples of the compound of formula (1) (acetoxysilane) in which the hydrolyzable group X is an acetoxy group include those in which the alkoxy group in each of the above alkoxysilane molecules is substituted with an acetoxy group.

  Furthermore, examples of the compound (isocyanate silane) of the formula (1) in which the hydrolyzable group X is an isocyanate group include those in which the alkoxy group in each alkoxysilane molecule is substituted with an isocyanate group.

  Furthermore, examples of the compound of formula (1) (hydroxysilane) in which the hydrolyzable group X is a hydroxyl group include those in which the alkoxy group in each alkoxysilane molecule is substituted with a hydroxyl group.

  These compounds represented by the formula (1) are used alone or in combination of two or more.

  Further, as a catalyst for promoting the hydrolysis condensation reaction in the hydrolysis condensation of the compound represented by the formula (1), formic acid, maleic acid, fumaric acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid , Octanoic acid, nonanoic acid, decanoic acid, oxalic acid, adipic acid, sebacic acid, butyric acid, oleic acid, stearic acid, linoleic acid, linolenic acid, salicylic acid, benzoic acid, p-aminobenzoic acid, p-toluenesulfonic acid, Organic acids such as phthalic acid, sulfonic acid, tartaric acid, and trifluoromethanesulfonic acid, and inorganic acids such as hydrochloric acid, phosphoric acid, nitric acid, boric acid, sulfuric acid, and hydrofluoric acid can be used.

  The amount of the catalyst used is preferably in the range of 0.0001 to 1 mol with respect to 1 mol of the compound represented by the formula (1). When the amount used exceeds 1 mol, gelation tends to be promoted at the time of hydrolysis condensation, and when it is less than 0.0001 mol, the reaction does not substantially proceed.

  Furthermore, in this reaction, alcohol produced as a by-product by hydrolysis may be removed using an evaporator or the like, if necessary. Furthermore, the amount of water to be present in the hydrolysis-condensation reaction system can be appropriately determined. The amount of this water is 0.5 to 20 with respect to 1 mol of the compound represented by the formula (1). A value within the molar range is preferred. When the amount of water is less than 0.5 mol or more than 20 mol, the film-formability of the silica-based film is deteriorated and the storage stability of the composition itself may be lowered.

  The siloxane resin as the component (a) is measured by gel permeation chromatography (hereinafter referred to as “GPC”) from the viewpoint of solubility in a solvent, mechanical properties, moldability, and the like, and a standard polystyrene calibration curve. Is preferably 500 to 20,000, and more preferably 1,000 to 10,000. When the mass average molecular weight is less than 500, the film formability of the silica-based film tends to be inferior. On the other hand, when the mass average molecular weight exceeds 20,000, the compatibility with the solvent tends to decrease.

  Further, at least selected from the group consisting of H atom, F atom, B atom, N atom, Al atom, P atom, Si atom, Ge atom, Ti atom and C atom bonded per silicon atom of the siloxane resin. The total number (M) of one kind of atom (hereinafter referred to as “specific bond atom”) is preferably 0.65 or less, more preferably 0.55 or less, and particularly preferably 0.50 or less, It is very preferable that it is 0.45 or less. Further, the lower limit is preferably about 0.20.

  When the total number (M) of the specific bonding atoms exceeds 0.65, there is a tendency that adhesiveness with other films (layers) of the finally obtained silica-based film, mechanical strength, and the like are inferior. On the other hand, when the total number (M) is less than 0.20, the dielectric characteristics when used as an insulating film tend to be inferior.

  Further, among these specific bonding atoms, the siloxane resin is at least one of H atom, F atom, N atom, Si atom, Ti atom, and C atom in terms of film-formability of the silica-based film. Among these, it is more preferable that at least one of H atom, F atom, N atom, Si atom and C atom is included in terms of dielectric properties and mechanical strength.

In addition, this total number (M) can be calculated | required from the preparation amount of the siloxane resin which is (a) component, for example, following formula (6);
M = (M1 + (M2 / 2) + (M3 / 3)) / Msi (6)
It can be calculated using the relationship represented by

  In the formula, M1 represents the total number of atoms bonded to a single (only one) Si atom among specific bond atoms, and M2 is shared by two silicon atoms among the specific bond atoms. M3 represents the total number of atoms shared by three silicon atoms among the specific bonded atoms, and Msi represents the total number of Si atoms.

<(B) component>
The component (b) is a solvent capable of dissolving the component (a), that is, the aforementioned siloxane resin. For example, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, t -Butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethyl Butanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, Enol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and other alcohol solvents, acetone, Methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl-iso-butyl ketone, methyl-n-pentyl ketone, methyl-n-hexyl ketone, diethyl ketone, di-iso-butyl ketone, trimethylnonanone, cyclohexanone, Such as cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, diacetone alcohol, acetophenone, γ-butyrolactone, etc. Ketone solvents, ethyl ether, iso-propyl ether, n-butyl ether, n-hexyl ether, 2-ethylhexyl ether, ethylene oxide, 1,2-propylene oxide, dioxolane, 4-methyldioxolane, dioxane, dimethyldioxane, ethylene glycol monomethyl Ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol mono-n-hexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, ethylene glycol dibutyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether , Diethylene glycol diethyl ether, diethylene glycol mono n-butyl ether, diethylene glycol di-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol di-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, di Ether solvents such as propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, methyl acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate I-butyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methyl acetate Xylbutyl, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, γ-butyrolactone, γ-valerolactone, methyl acetoacetate, ethyl acetoacetate, ethylene glycol monomethyl acetate Ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, diacetate acetate Propylene glycol monomethyl ether, dipropylene glycol monoethyl acetate Tellurium, diacetate glycol, methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, Examples thereof include ester solvents such as n-amyl lactate, and solvents such as acetonitrile, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide and the like. These may be used alone or in combination of two or more.

  The amount of the solvent (that is, the component (b)) is preferably such that the amount of the component (a) (siloxane resin) is 3 to 25% by mass. When the amount of the solvent is too small and the concentration of the component (a) exceeds 25% by mass, the film formability of the silica-based film is deteriorated and the stability of the composition itself tends to be lowered. On the other hand, when the amount of the solvent is excessive and the concentration of the component (a) is less than 3% by mass, it tends to be difficult to form a silica-based film having a desired film thickness.

<(C) component>
The component (c) is an onium salt, and examples thereof include ammonium salts, phosphonium salts, arsonium salts, stibonium salts, oxonium salts, sulfonium salts, selenonium salts, stannonium salts, iodonium salts, and the like.

  Among these, ammonium salts are preferable because they are superior in stability of the composition. For example, tetramethylammonium oxide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium fluoride, tetrabutylammonium oxide, tetrabutylammonium. Examples include chloride, tetrabutylammonium bromide, tetrabutylammonium fluoride, tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate, and tetramethylammonium sulfate.

  Furthermore, among these, from the viewpoint of improving the electrical properties of the silica-based coating, tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate, tetramethylammonium sulfate, etc. The ammonium salt is particularly preferred.

  The amount of onium salt used as component (c) is preferably 0.001 ppm to 5%, more preferably 0.01 ppm to 1%, based on the total amount of the composition for forming a silica-based film. 0.1 ppm to 0.5% is more preferable.

  If the amount used is less than 0.001 ppm, the electrical properties and mechanical properties of the finally obtained silica-based coating tend to be inferior. On the other hand, when the amount used exceeds 5%, the stability of the composition and the film formability tend to be inferior, and the electrical characteristics and process suitability of the silica-based coating tend to be lowered. In addition, these onium salts can be added so that it may become a desired density | concentration, after melt | dissolving or diluting in water or a solvent as needed.

  Moreover, when an onium salt is used as an aqueous solution, the pH is preferably 1.5 to 10, more preferably 2 to 8, and particularly preferably 3 to 6. When this pH is less than 1.5 or when the pH exceeds 10, the stability of the composition, the film formability, etc. tend to be inferior.

<(D) component>
The component (d) is a pyrolytic volatile compound that thermally decomposes or volatilizes at a heating temperature of 250 to 500 ° C., for example, a polymer having a polyalkylene oxide structure, a (meth) acrylate polymer, a polyester polymer, Examples include polycarbonate polymers, polyanhydride polymers, tetrakissilanes, and the like.

  Examples of the polyalkylene oxide structure include a polyethylene oxide structure, a polypropylene oxide structure, a polytetramethylene oxide structure, and a polybutylene oxide structure.

  More specifically, polyoxyethylene alkyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, ethylene oxide derivative of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropylene alkyl ether Ether type compounds such as polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene fatty acid alkanolamide sulfate and other ether ester type compounds, polyethylene glycol fatty acid ester, ethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin Fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester And the like of the ester-type compound.

  Moreover, as acrylic acid ester and methacrylic acid ester constituting the (meth) acrylate polymer, acrylic acid alkyl ester, methacrylic acid alkyl ester, acrylic acid alkoxyalkyl ester, methacrylic acid alkyl ester, methacrylic acid alkoxyalkyl ester, etc. Can be mentioned.

  Examples of the alkyl acrylate ester include 1 to 6 carbon atoms such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, pentyl acrylate, and hexyl acrylate. An alkyl ester etc. can be illustrated.

  Moreover, as alkyl methacrylate, it is C1-C1 such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate. 6 alkyl esters and the like.

  Further, examples of the alkoxyalkyl acrylate include methoxymethyl acrylate and ethoxyethyl acrylate, and examples of the methacrylic acid alkoxyalkyl ester include methoxymethyl methacrylate and ethoxyethyl methacrylate.

  Examples of acrylic acid and methacrylic acid having a hydroxyl group include 2-hydroxylethyl acrylate, 2-hydroxylpropyl acrylate, 2-hydroxylethyl methacrylate, 2-hydroxylmethacrylic acid, and the like. The (meth) acrylic acid, the (meth) acrylic acid alkyl ester, the (meth) acrylic acid alkoxyalkyl ester, and the hydroxyl group-containing (meth) acrylic acid constituting the (meth) acrylate polymer may be used alone or in combination of two or more. Are used in combination.

  Furthermore, examples of the polycarbonate include polycondensates of carbonic acid and alkylene glycols such as polyethylene carbonate, polypropylene carbonate, polytrimethylene carbonate, polytetramethylene carbonate, polypentamethylene carbonate, and polyhexamethylene carbonate.

  Furthermore, polyanhydrides include polycondensates of dicarboxylic acids such as polymalonyl oxide, polyadipoyl oxide, polypimeyl oxide, polysuberoyl oxide, polyazelayl oxide, and polysebacoyl oxide. it can.

  In addition, examples of tetrakissilanes include tetrakis (trimethylsiloxy) silane, tetrakis (trimethylsilyl) silane, tetrakis (methoxyethoxy) silane, tetrakis (methoxyethoxyethoxy) silane, and tetrakis (methoxypropoxy) silane.

  Here, if the pyrolytic volatile compound as the component (d) is pyrolyzed or volatilized at a temperature lower than 250 ° C., it will be pyrolyzed and volatilized before the siloxane skeleton is formed, so that desired dielectric properties can be obtained. There is a risk of not being able to. On the other hand, if the pyrolytic volatile compound is pyrolyzed or volatilized at a temperature exceeding 500 ° C., the wiring metal may be deteriorated. Therefore, if it decomposes or volatilizes in such a temperature range, there is an advantage that it is easy to adjust the dielectric characteristics of the insulating film while suppressing the deterioration of the wiring metal.

  In addition, it is desirable that the composition for forming a silica-based film of the present invention does not contain an alkali metal or an alkaline earth metal, and even when it is contained, the metal ion concentration in the composition is preferably 100 ppb or less, and 20 ppb The following is more preferable.

  When the concentration of these metal ions exceeds 100 ppb, the metal ions are liable to flow into a semiconductor element having a silica-based film obtained from the composition, which may adversely affect the device performance itself. Therefore, it is effective to remove alkali metal or alkaline earth metal from the composition using an ion exchange filter or the like as necessary.

  Such a composition for forming a silica-based film is applied onto a substrate such as a wafer as described later, and then cured by heating and baking, whereby a silica-based film (Low-k) that exhibits a low dielectric constant. Film) is formed. At this time, fine pores (voids, vacancies) are gradually formed in the film by pyrolysis or volatilization of the component (d), and the pores can be further refined and uniform in shape at the time of final curing. .

  Furthermore, since the onium salt that is the component (c) is contained as an essential component, the mechanical strength and electrical reliability of the silica-based coating can be improved. Therefore, for example, when CMP is performed in a later step, it is possible to prevent peeling at the interface between the silica-based film and another layer (film). Although the details of the mechanism of action that exerts such effects are still unclear, the onium salt promotes the dehydration condensation reaction, increasing the density of siloxane bonds, and further reducing the remaining silanol groups. It is estimated that this is due to the improvement of dielectric properties.

  And it is thought that the stress relaxation of the whole film | membrane is caused by combining the annealing effect which can be show | played at the time of final heating in addition to the above void | hole formation processes and the densification of a siloxane bond. However, the action is not limited to these.

  Furthermore, when the total number of bonded atoms in the siloxane resin is 0.65 or less, a sufficient mechanical strength can be realized, and sufficient adhesiveness with other films (layers) can be secured. Therefore, it is possible to further prevent the occurrence of interfacial peeling in the Cu-CMP process for polishing an extra Cu film generated when the wiring metal is laminated.

  A method for forming a silica-based film on a substrate using such a composition for forming a silica-based film according to the present invention will be described with reference to a spin coating method that is generally excellent in film formability and film uniformity of a silica-based film. To do. In this method, a liquid silica-based film-forming composition is applied onto a substrate such as a Si wafer to form a film, and a pre-curing step and a subsequent final curing step are performed on the film, thereby the present invention. This is a method of forming a silica-based film.

  First, the composition for forming a silica-based film is spin-coated on a substrate such as an Si wafer, preferably at 500 to 5000 rotations / minute, more preferably 1000 to 3000 rotations / minute, to form a film. At this time, if the rotational speed is less than 500 revolutions / minute, the film uniformity tends to be deteriorated. On the other hand, if it exceeds 5000 revolutions / minute, the film formability may be deteriorated.

Next, a preliminary curing step is performed on the coating. This process is a step for drying the solvent in the composition and increasing the degree of cure of the siloxane resin, and is preferably 100 to 350 ° C, more preferably 150 to 300 ° C, and particularly preferably 150 to 250 ° C. Heat treatment is performed at the first heating temperature T ₁ ). Note that the pre-curing step may be multi-stage heating at different temperatures as necessary.

When the heating temperature T ₁ is less than 100 ° C., it tends to dry the solvent is not sufficiently performed. On the other hand, if the heating temperature T ₁ is greater than 350 ° C., pyrolysis volatile compounds for porous formation ((d) component) it will thermally decompose volatile before the siloxane skeleton is formed in the film, desired mechanical strength In addition, it may be difficult to obtain a silica-based film having low dielectric properties.

  The heating time in this preliminary curing step is preferably 1 second to 1 hour, more preferably 2 seconds to 10 minutes, still more preferably 10 seconds to 5 minutes, and particularly preferably 30 seconds to 3 minutes. When the heating time is less than 1 second, the solvent is not sufficiently dried and the curing of the resin does not proceed sufficiently. On the other hand, when the heating time exceeds 1 hour, the throughput is lowered and it becomes difficult to keep the heat input sufficiently low.

  Comparing these viewpoints, the optimum conditions in the pre-curing step are, for example, 150 ° C./1 minute + 250 ° C./1 minute, depending on the thickness of the coated film and the required physical properties of the silica-based film. Multi-stage heating.

Next, the film from which the solvent has been removed and the preliminary curing has been performed is baked at, for example, a temperature of 350 to 500 ° C. (second heating temperature T ₂ ) to perform final curing (final curing step). However, it may be 350 ° C. or lower, for example, about 300 ° C., but if it is lower than 300 ° C., it tends to be difficult to achieve sufficient curing. Moreover, when this heating temperature is less than 350 degreeC, decomposition | disassembly and volatilization of (d) component may not fully be accelerated | stimulated.

On the other hand, when the heating temperature exceeds 500 ° C., when there is a metal wiring layer, the amount of heat input may increase and the wiring metal may be deteriorated. Considering the viewpoint of further reducing the amount of heat input to the Si wafer and the viewpoint of carrying out sufficient curing in a short time, it is particularly preferably 400 ° C. or less, more preferably 375 ° C. or less, and further about 350 ° C. preferable. The final curing is preferably performed in an inert atmosphere such as N ₂ , Ar, and He. In this case, the oxygen concentration is preferably 1000 ppm or less.

  Furthermore, the heating time in this case is preferably 2 to 60 minutes, more preferably 2 to 30 minutes. If this heating time exceeds 60 minutes, the amount of heat input may increase excessively and the wiring metal may deteriorate. Furthermore, it is preferable to use a heat treatment apparatus such as a quartz tube furnace or other furnace, a hot plate, or rapid thermal annealing (RTA) as the heating apparatus.

  Further, the thickness of the silica-based film formed in this manner is preferably 0.01 to 40 μm, and more preferably 0.1 μm to 2.0 μm. When such a film thickness exceeds 40 μm, cracks are likely to occur due to stress, while when it is less than 0.01 μm, when metal wiring layers exist above and below the silica-based coating, the leakage characteristics between the upper and lower wirings are reduced. There is a tendency to get worse.

  Furthermore, according to the production method using the silica-based composition of the present invention, the elastic modulus is preferably 2.5 GPa or more, more preferably 3.0 GPa or more, still more preferably 3.5 GPa or more, and particularly preferably 4.0 GPa. A silica-based film having the above high elasticity can be obtained. When this elastic modulus is less than 2.5 GPa, for example, when a silica-based coating is used as a semiconductor insulating film, there is a possibility that inconveniences such as difficulty in processing occur.

  In addition, the silica-based coating according to the present invention is one in which (a large number of) pores having an average pore diameter of preferably 4.0 nm or less, more preferably 3.0 nm or less, and particularly preferably 2.2 nm or less are formed. . If this average pore diameter exceeds 4.0 nm, the CMP resistance may be insufficient depending on the film thickness. On the other hand, when the average pore diameter is extremely small (for example, 0.1 nm or less), it is difficult to form pores and it may be difficult to achieve a required low dielectric constant.

  Further, it is more useful that the maximum frequency pore diameter is preferably 2.0 nm or less, more preferably 1.5 nm or less. If the maximum frequency pore diameter exceeds 2.0 nm, depending on the film thickness, it tends to be difficult to achieve sufficient mechanical strength.

  Furthermore, it is preferable that pores having a diameter of 10 nm or more are not substantially present in the silica-based coating (the maximum value of the pore diameter is less than 10 nm). If there is an average pore diameter of 10 nm or more, even if other pores are finer, when an unnecessary force such as some stress acts on the film, the film cracks starting from the large diameter pore There is a concern that this may occur and progress, and as a result, the film may break.

[Second form]
Moreover, as a composition for silica-type film formation by this invention, (a) component, (b) component, and the (e) component shown below as an essential component may be included. Hereinafter, the composition for forming a silica-based film will be described.

<(A) component>
This is the same as described in [First Embodiment].

<(B) component>
The component (b) in this embodiment is a solvent capable of dissolving the component (a), that is, the aforementioned siloxane resin, in particular, a first solvent component comprising an alkylene glycol alkyl ether alkyl ester or an alkylene glycol alkyl ether acetate, and The solvent preferably contains a second solvent component composed of an alkylene glycol monoalkyl ether as an essential component.

  Moreover, the mass content ratio of the first solvent component and the second solvent is preferably 1:99 to 60:40, more preferably 5; 95 to 50:50, and still more preferably 10:90 to 40:60. It is said. When the mass content ratio is less than 1:99 (that is, the mass ratio of the first solvent / second solvent is less than 1/99), the mechanical strength of the finally obtained silica-based coating is significantly deteriorated. It tends to be. On the other hand, when the mass content ratio exceeds 60:40 (that is, the mass ratio of the first solvent / second solvent exceeds 60/40), the physical properties such as the film thickness uniformity of the silica-based coating deteriorate. Tends to be prominent.

  Examples of the first solvent component include ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, acetate ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, diethylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, and diethylene glycol. -N-butyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate and the like. Of these, alkylene glycol methyl ether acetate or propylene glycol alkyl ether acetate is preferred from the viewpoint of mechanical strength of the silica-based coating obtained as a cured film, and propylene glycol methyl ether acetate is particularly preferred.

  Examples of the second solvent component include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-hexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, propylene glycol monomethyl. Ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, etc. Among these, from the viewpoint of improving the film thickness uniformity of the silica-based coating, Propylene glycol monopropyl ether is particularly preferred.

  Furthermore, the solvent which is (b) component may contain the other solvent component as needed. Examples of such other solvent components include various solvents that can be used as the component (b) described above. They can be used alone or in combination of two or more with the first solvent and the second solvent.

  The amount of component (b) used is preferably such that the amount of component (a) (siloxane resin) is 3 to 25% by mass, as described above. When the amount of the solvent is too small and the concentration of the component (a) exceeds 25% by mass, the film formability of the silica-based film is deteriorated and the stability of the composition itself tends to be lowered. On the other hand, when the amount of the solvent is excessive and the concentration of the component (a) is less than 3% by mass, it tends to be difficult to form a silica-based film having a desired film thickness.

<(E) component>
The component (e) has a side chain containing a hydroxyl group, and the hydroxyl group concentration M _OH (mol / g) in the side chain is represented by the following formula (9);
0 <M _OH <0.4 × 10 ⁻² (9),
It is a polymer satisfying the relationship represented by

When the hydroxyl group concentration _MOH is 0 (zero) mol / g, that is, when no hydroxyl group is contained in the side chain, when the solvent is removed from the composition by volatilization or the like, the siloxane of component (a) There is a possibility that the resin and the polymer are phase-separated. In this case, the pore diameter of the finally obtained silica-based coating film becomes excessively large, the diameter distribution is widened, and the uniformity of the fine pores tends to be deteriorated, and the mechanical strength may be lowered. On the other hand, when the hydroxyl group concentration M _OH exceeds 0.4 × 10 ⁻² mol / g, the polymer is difficult to decompose or volatilize during heating, and the heat treatment requires a high temperature or a long time. Arise.

Here, the hydroxyl group concentration M _OH (mol / g) can be determined from the charged amount of the polymer. For example, the following formula (10);
M _OH = (Ma × Mb / Mb) / Mh × 100 (10),
It can be calculated using the relationship represented by

  In formula, Ma shows the molar ratio of the minimum repeating unit in which a hydroxyl group is contained, Mb shows the molecular weight of a hydroxyl group (OH group), Mh shows the average molecular weight of a polymer.

  The polymer as the component (e) preferably has a reduction rate in a nitrogen gas atmosphere at a temperature of 300 to 500 ° C. of 95% by mass or more, more preferably 97% by mass or more, and still more preferably 99% by mass. % Or more. When the reduction rate is less than 95% by mass, the polymer tends to be insufficiently decomposed or volatilized when the composition is heated, and the polymer or polymer is finally contained in the silica-based film finally obtained. There is a risk that a reaction product derived from a part of the polymer or from the polymer may remain. In this case, the electrical characteristics of the silica-based film may be deteriorated such as an increase in relative dielectric constant.

In addition, the “decrease rate” of the polymer as the component (e) in the present invention is a value determined by the following apparatus and conditions.
-Equipment used: TG / DTA6300 (manufactured by Seiko Instruments Inc.)
-Temperature rise start temperature: 50 ° C
・ Temperature increase rate: 10 ℃ / min
-Sample amount: 10mg
Atmosphere: nitrogen _{(N 2)} gas 200ml / min
Reference: α-Alumina (Seiko Instruments)
・ Sample container: Open sample pan φ5 aluminum (manufactured by Seiko Instruments Inc.)

  Moreover, let the reference | standard mass before the decomposition | disassembly start of the polymer which is (e) component be the mass in 150 degreeC which is in the middle of temperature rising. This is because the decrease in mass at 150 ° C. or less is due to the removal of adsorbed moisture and the like, and it is estimated that the polymer itself as the component (e) is not substantially decomposed.

  Further, in the measurement of the “decrease rate”, when the polymer as the component (e) cannot be directly weighed because the polymer is dissolved in the solution, the solution containing the polymer For example, a residue obtained by taking about 2 g in a metal petri dish and drying at 150 ° C. for 3 hours in air at normal pressure is used as a sample.

  The polymer as the component (e) has a mass average molecular weight measured by GPC and converted using a standard polystyrene calibration curve from the viewpoint of compatibility with the siloxane resin as the component (a). 500 to 100,000, and more preferably 1,000 to 50,000. When the mass average molecular weight is less than 500, the film formability of the silica-based film tends to be inferior. On the other hand, when the mass average molecular weight exceeds 100,000, the compatibility with the siloxane resin tends to decrease.

  Specific examples of the compound (monomer component) having a hydroxyl group constituting the polymer of the component (e) include acrylic acid, 2-hydroxyethyl acrylate, diethylene glycol acrylate, 2-hydroxypropyl acrylate, and dipropylene. Examples include (meth) acrylic acid derivatives such as glycol acrylate, methacrylic acid, 2-hydroxyethyl methacrylate, diethylene glycol methacrylate, 2-hydroxypropyl methacrylate, and dipropylene glycol methacrylate, vinyl alcohol, and allyl alcohol.

Further, the polymer of component (e), for the purpose of adjusting the concentration M _OH of the hydroxyl groups in the side chain may contain a compound having no hydroxyl group as a constituent component.

  Examples of such compounds having no hydroxyl group include vinyl ether compounds, vinyl compounds having a polyethylene oxide structure, vinyl compounds having a polypropylene oxide structure, vinyl pyridine compounds, styrene compounds, and alkyl ester vinyl compounds. Examples thereof include compounds and (meth) acrylate acid compounds. Among these, a compound having an ester bond is preferable from the viewpoint of excellent decomposition characteristics or volatilization characteristics of the polymer, and a (meth) acrylate acid compound ((meth) acrylate) as mentioned in the description of the component (d) above. Acid derivatives) are particularly preferred.

  Examples of the (meth) acrylate acid derivatives include acrylic acid esters, methacrylic acid alkyl esters, acrylic acid alkyl esters, acrylic acid alkoxyalkyl esters, methacrylic acid alkyl esters, and methacrylic acid alkoxyalkyl esters.

  In addition, as alkyl acrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, etc. Alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, and the like. Examples thereof include alkyl esters having 1 to 6 carbon atoms.

  Further, examples of the alkoxyalkyl acrylate ester include methoxymethyl acrylate and ethoxyethyl acrylate, and examples of the methacrylic acid alkoxyalkyl ester include methoxymethyl methacrylate and ethoxyethyl methacrylate.

  In addition, the composition for forming a silica-based film according to the [second embodiment] (including the components (a), (b) and (e) as essential components) is also the one according to the [first embodiment]. Similarly, it is desirable that no alkali metal or alkaline earth metal is contained, and even when it is contained, the concentration of those metal ions in the composition is preferably 100 ppb or less, and more preferably 20 ppb or less.

  When the concentration of these metal ions exceeds 100 ppb, the metal ions are liable to flow into a semiconductor element having a silica-based film obtained from the composition, which may adversely affect the device performance itself. Therefore, it is effective to remove alkali metal or alkaline earth metal from the composition using an ion exchange filter or the like as necessary.

  Moreover, the composition for forming a silica-based film of this embodiment is also cured by heating and baking after being applied onto a substrate such as a wafer, as described later, in the same manner as in the first embodiment. A silica-based film (Low-k film) that exhibits a low dielectric constant is formed. At this time, since the solvent containing the first solvent component and the second solvent component is used as the solvent of the component (b), the mechanical strength of the silica-based coating can be sufficiently increased and the film thickness uniformity can be improved. Can be made.

  Moreover, when the hydroxyl group is contained in the side chain of the polymer as the essential component (e), when the solvent of the component (b) is removed by volatilization or the like, the siloxane resin of the component (a) and the above Phase separation from the polymer is prevented, and the pores formed inside the membrane are made finer and the shape is made uniform. Therefore, it is possible to further suppress the decrease in mechanical strength of the finally obtained silica-based coating.

  In addition, since the onium salt which is the component (c) is contained as an essential component, the mechanical strength and electrical reliability of the silica-based coating can be improved. Therefore, it is possible to prevent peeling at the interface between the silica-based film and another layer (film) in the CMP process.

  Although the details of the mechanism of action that exerts such effects are still unclear, the onium salt promotes the dehydration condensation reaction, increasing the density of siloxane bonds, and further reducing the remaining silanol groups. It is estimated that this is due to the improvement of dielectric properties. However, the action is not limited to this.

  Furthermore, when the total number of bonded atoms in the siloxane resin is 0.65 or less, a sufficient mechanical strength can be realized, and sufficient adhesiveness with other films (layers) can be secured. Therefore, in the process of CMP (Chemical Mechanical Polish) on the wiring metal such as Cu deposited on the silica-based film, the occurrence of interface peeling can be further prevented.

  Furthermore, since the concentration of the hydroxyl group in the side chain of the polymer as the component (e) is set to the upper limit value or less, the decomposition of the component (e) is suppressed during heating and the volatilization thereof is promoted. Therefore, the composition can be cured at a low temperature or in a short time as compared with the prior art without excessively high temperature. As a result, the amount of heat input to the substrate can be remarkably reduced, the deterioration of the characteristics of other films (layers) and, in turn, the device can be suppressed, and the throughput can be improved by shortening the process time.

  A method for forming a silica-based film on a substrate using such a composition for forming a silica-based film of the present invention will be described by taking a spin coating method as an example, as described above.

  First, the composition for forming a silica-based film is spin-coated on a substrate such as a silicon wafer, preferably at 500 to 5000 rotations / minute, more preferably 1000 to 3000 rotations / minute, to form a film. At this time, if the rotational speed is less than 500 revolutions / minute, the film uniformity tends to be deteriorated. On the other hand, if it exceeds 5000 revolutions / minute, the film formability may be deteriorated.

  Next, the solvent in the coating is dried on a hot plate or the like preferably at 50 to 350 ° C., more preferably at 100 to 250 ° C. If this drying temperature is less than 50 ° C., the solvent tends not to be sufficiently dried. On the other hand, if the drying temperature exceeds 350 ° C., the polymer for porous formation (component (e)) is thermally decomposed before the siloxane skeleton is formed in the coating, and the volatilization amount increases undesirably. It may be difficult to obtain a silica-based film having desired mechanical strength and low dielectric properties.

Next, the film from which the solvent has been removed is baked at a heating temperature of 250 to 500 ° C. to perform final curing. The final curing is preferably performed in an inert atmosphere such as N ₂ , Ar, or He. In this case, the oxygen concentration is preferably 1000 ppm or less. When this heating temperature is less than 250 ° C., sufficient curing tends not to be achieved, and decomposition and volatilization of the component (e) tend not to be promoted sufficiently. On the other hand, when the heating temperature exceeds 500 ° C., when there is a metal wiring layer, the amount of heat input may increase and the wiring metal may be deteriorated.

  Further, the heating time at this time is preferably 2 to 60 minutes, and more preferably 2 to 30 minutes, as in the above-described final curing step. If this heating time exceeds 60 minutes, the amount of heat input may increase excessively and the wiring metal may deteriorate. Furthermore, it is preferable to use a heat treatment apparatus such as a quartz tube furnace or other furnace, a hot plate, or rapid thermal annealing (RTA) as the heating apparatus.

  Further, the film thickness of the silica-based film thus formed is preferably 0.01 to 40 μm, more preferably 0.1 μm to 2.0 μm, as described above. When such a film thickness exceeds 40 μm, cracks are likely to occur due to stress, while when it is less than 0.01 μm, when metal wiring layers exist above and below the silica-based coating, the leakage characteristics between the upper and lower wirings are reduced. There is a tendency to get worse.

[Electronic parts]
Examples of the electronic component having a silica-based film formed by using the composition for forming a silica-based film of the present invention include devices having an insulating film such as a semiconductor element and a multilayer wiring board.

  Specifically, in a semiconductor element, it can be used as a surface protective film (passivation film), a buffer coat film, an interlayer insulating film, and the like. On the other hand, in a multilayer wiring board, it can be suitably used as an interlayer insulating film.

  More specifically, as semiconductor elements, individual semiconductors such as diodes, transistors, compound semiconductors, thermistors, varistors, thyristors, DRAMs (dynamic random access memories), SRAMs (static random access memories), EPROMs. (Eraseable Programmable Read Only Memory), Mask ROM (Mask Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), Flash Memory and Other Memory Elements, Microprocessor, DSP , Theoretical circuit elements such as ASIC, integrated circuit elements such as compound semiconductors represented by MMIC (monolithic microwave integrated circuit), hybrid integrated circuits (hybrid IC), light emission Diode, etc. The photoelectric conversion element such as a charge coupled device and the like. Examples of the multilayer wiring board include a high-density wiring board such as MCM.

  By providing the silica-based coating of the present invention that exhibits a low dielectric constant, such an electronic component can achieve high performance such as a reduction in signal propagation delay time and at the same time can achieve high reliability.

  Specific examples according to the present invention will be described below, but the present invention is not limited thereto.

<Synthesis Example 1-1>
The pyrolytic volatile compound as component (d) was synthesized by the following procedure. First, 300 g of propylene glycol monomethyl ether acetate (PGMEA) was charged in a 1000 ml flask, and 100 g of methyl methacrylate in which 2.0 g of azobisisobutyronitrile (AIBN) was dissolved in a 200 ml dropping funnel. After substituting with the gas, the solution in the dropping funnel was dropped into the flask over 2 hours while stirring and heating in an oil bath at 130 ° C. in a nitrogen gas atmosphere.

  Next, after stirring for 30 minutes, 97.8 g of PGMEA in which 0.2 g of AIBN was dissolved was charged in the dropping funnel and dropped into the flask over 1 hour. After the dropwise addition, the mixture was further stirred for 2 hours, and returned to room temperature to obtain a pyrolytic volatile compound as a component (d).

  The mass average molecular weight measured by GPC method was 12,800. Furthermore, the concentration of the pyrolytic volatile compound obtained by weighing 2 g of the solution in a metal petri dish and drying for 3 hours with a dryer at 150 ° C. was 18.5% by mass.

<Synthesis Example 1-2>
In a solution prepared by dissolving 116.7 g of tetraethoxysilane and 78.5 g of methyltriethoxysilane in 339.8 g of propylene glycol monopropyl ether (PGP), 64.2 g of water in which 0.92 g of 70% nitric acid was dissolved was added. The solution was added dropwise over 30 minutes with stirring. After completion of dropping, the reaction was allowed to proceed for 5 hours to obtain a polysiloxane solution.

<Example 1-1>
200 g of the polysiloxane solution obtained in Synthesis Example 1-2 and 48.7 g of the liquid pyrolysis volatile compound obtained in Synthesis Example 1-1 were placed in a 300 ml eggplant flask and stirred for 2 hours. Next, ethanol and low-boiling substances were distilled off in a warm bath under reduced pressure using a rotary evaporator to obtain 180.0 g of a polysiloxane / pyrolytic volatile compound in a liquid form. Next, 13.5 g of a 2.4% tetramethylammonium nitrate aqueous solution was added to this solution to prepare a silica-based film forming composition of the present invention.

<Synthesis Example 1-3>
The pyrolytic volatile compound as component (d) was synthesized by the following procedure. First, 300 g of PGMEA was charged into a 1000 ml flask, 95 g of methyl methacrylate in which 2.0 g of AIBN was dissolved and 5 g of 2-hydroxyethyl methacrylate were charged into a 200 ml dropping funnel, and the system was replaced with nitrogen gas. The solution in the dropping funnel was dropped into the flask over 2 hours while heating and stirring in an oil bath at 130 ° C. in an atmosphere.

  Next, after stirring for 30 minutes, 97.8 g of PGMEA in which 0.2 g of AIBN was dissolved was charged in the dropping funnel and dropped into the flask over 1 hour. After the dropwise addition, the mixture was further stirred for 2 hours, and returned to room temperature to obtain a pyrolytic volatile compound as a component (d).

  When this mass average molecular weight was measured by GPC method, it was 10,700. Furthermore, the concentration of the pyrolytic volatile compound obtained by weighing 2 g of the solution in a metal petri dish and drying it for 3 hours with a dryer at 150 ° C. was 16.8% by mass.

<Example 1-2>
200 g of the polysiloxane solution obtained in Synthesis Example 1-2 and 47.5 g of the liquid pyrolysis volatile compound obtained in Synthesis Example 1-3 were placed in a 300 ml eggplant flask and stirred for 2 hours. Next, ethanol and low-boiling substances were distilled off in a warm bath under reduced pressure using a rotary evaporator to obtain 180.0 g of a polysiloxane / pyrolytic volatile compound in a liquid form. Next, 13.5 g of a 2.4% tetramethylammonium nitrate aqueous solution was added to this solution to prepare a silica-based film forming composition of the present invention.

<Comparative Example 1-1>
200 g of the polysiloxane solution obtained in Synthesis Example 1-2 and 48.7 g of the liquid pyrolysis volatile compound obtained in Synthesis Example 1-1 were placed in a 300 ml eggplant flask and stirred for 2 hours. Next, under reduced pressure using a rotary evaporator, the produced ethanol and low-boiling substances are distilled off in a warm bath to prepare a silica-based film-forming composition comprising 180.0 g of a polysiloxane / pyrolytic volatile compound. did.

<Stress evaluation 1>
(1) Formation of silica-based film and measurement of film thickness, etc. The compositions for forming a silica-based film obtained in Examples 1-1 and 1-2 and Comparative Example 1-1 were subjected to a plurality of Si at a rotation speed of 1250 rpm / 30 seconds. A film was formed by spin coating on each wafer. After spin coating, each Si wafer was subjected to a heat treatment at 150 ° C./3 minutes to remove the solvent in the coating to form a silica-based coating.

  And the film thickness of this film was measured with an ellipsometer (manufactured by Gartner; ellipsometer L116B, wavelength used: 633 nm). Specifically, He—Ne laser light was irradiated on the interlayer insulating film, and the film thickness obtained from the phase difference generated by irradiation at a specified wavelength was measured. Next, the amount of “warp” of the Si wafer was measured according to the method and procedure described in [Stress Evaluation Method] described above.

Further, the Si wafer, whose film thickness and amount of warpage were measured, was heat-treated in a quartz tube furnace in which the O ₂ concentration was controlled to around 100 ppm for 400 ° C./30 minutes, and the silica-based coating was finally cured. The film thickness and the amount of “warp” were measured in the same manner as described above for this film.

(2) Stress evaluation The displacement amount of the obtained “warp”, the above measured film thickness value, and other parameter values were substituted into the equation (4), and the stress of each silica-based coating was calculated. The results are shown in Table 1-1 together with the film thickness.

<Relative permittivity measurement 1>
The relative dielectric constant of the silica-based film formed in the above <Stress Evaluation 1> was measured according to the above-mentioned [Measurement method of relative dielectric constant]. The results are also shown in Table 1-1.

<Elastic modulus measurement 1>
The elastic modulus of the silica-based film formed in <Stress Evaluation 1> was measured according to the above-mentioned [Measuring Method of Elastic Modulus]. The results are also shown in Table 1-1.
Table 1-1

<Void distribution measurement 1>
X-ray diffractometer ATX-G manufactured by Rigaku Denki Kogyo Co., Ltd. as a measuring device for the silica-based coating formed in Example 1-2 and the silica-based coating formed using the conventional composition (conventional product). The pore distribution of each film was measured by analyzing the X-ray diffuse scattering data. FIG. 1 is a graph showing the obtained pore distribution (standardized by pore diameter), and the curves L1 and L2 in the figure are obtained for Example 1-2 and the conventional silica-based coating, respectively. The obtained frequency distribution is smoothed and shown. Moreover, the result of the average hole diameter and the highest frequency hole diameter obtained from these hole distributions is shown in Table 1-2.
Table 1-2

<Synthesis Example 2-1>
The pyrolytic volatile compound as component (d) was synthesized by the following procedure. First, 300 g of propylene glycol monomethyl ether acetate (PGMEA) is charged in a 1000 ml flask, and 95 g of methyl methacrylate and 5 g of 2-hydroxyethyl methacrylate in which 2.0 g of azobisisobutyronitrile (AIBN) is dissolved in a 200 ml dropping funnel. Then, the system was replaced with nitrogen gas, and then the solution in the dropping funnel was dropped into the flask over 2 hours while stirring and heating in an oil bath at 130 ° C. in a nitrogen gas atmosphere.

  Next, after stirring for 30 minutes, 97.8 g of PGMEA in which 0.2 g of AIBN was dissolved was charged in the dropping funnel and dropped into the flask over 1 hour. After the dropwise addition, the mixture was further stirred for 2 hours, and returned to room temperature to obtain a pyrolytic volatile compound as a component (d).

  When this mass average molecular weight was measured by GPC method, it was 10,700. Furthermore, the concentration of the pyrolytic volatile compound obtained by weighing 2 g of the solution in a metal petri dish and drying it for 3 hours with a dryer at 150 ° C. was 16.8% by mass.

<Synthesis Example 2-2>
In a solution prepared by dissolving 116.7 g of tetraethoxysilane and 78.5 g of methyltriethoxysilane in 339.8 g of propylene glycol monopropyl ether (PGP), 64.2 g of water in which 0.92 g of 70% nitric acid was dissolved was added. The solution was added dropwise over 30 minutes with stirring. After completion of dropping, the reaction was allowed to proceed for 5 hours to obtain a polysiloxane solution.

<Example 2-1>
200 g of the polysiloxane solution obtained in Synthesis Example 2-2 and 47.5 g of the liquid pyrolysis volatile compound obtained in Synthesis Example 2-1 were placed in a 300 ml eggplant flask and stirred for 2 hours. Next, ethanol and low-boiling substances were distilled off in a warm bath under reduced pressure using a rotary evaporator to obtain 180.0 g of a polysiloxane / pyrolytic volatile compound in a liquid form. Next, 13.5 g of a 2.4% tetramethylammonium nitrate aqueous solution was added to this solution to prepare a silica-based film forming composition of the present invention.

<Stress evaluation 2>
(1) Formation of silica-based film and measurement of film thickness, etc. The silica-based film forming composition obtained in Example 1 was spin-coated on a plurality of Si wafers at a rotation speed of 1390 rpm / 30 seconds, respectively, to form a film. . After spin coating, each Si wafer is subjected to a heat treatment at 150 ° C./1 minute + 250 ° C./1 minute (pre-curing step at the first heating temperature) to remove the solvent in the coating to form a silica-based coating. did.

  And the film thickness of this film was measured with an ellipsometer (manufactured by Gartner; ellipsometer L116B, wavelength used: 633 nm). Specifically, He—Ne laser light was irradiated on the interlayer insulating film, and the film thickness obtained from the phase difference generated by irradiation at a specified wavelength was measured. Next, the amount of “warp” of the Si wafer was measured according to the method and procedure described in [Stress Evaluation Method] described above.

Further, the Si wafer whose thickness and the amount of “warp” were measured was heat-treated at 400 ° C./30 minutes in a quartz tube furnace in which the O ₂ concentration was controlled to around 100 ppm to finally cure the silica-based coating (first Final curing step at a heating temperature of 2). The film thickness and the amount of “warp” were measured in the same manner as described above for this film.

(2) Stress evaluation The displacement amount of the obtained “warp”, the above-mentioned measured film thickness value, and other parameter values are substituted into the equation (3), and the silica-based coating in the preliminary curing at the first heating temperature is substituted. The stress (first stress) and the stress of the silica-based coating film (second stress) in the final curing at the second heating temperature were calculated. The results are shown in Table 2-1 together with the film thickness.

<Relative permittivity measurement 2>
The relative dielectric constant of the silica-based film formed in the above <Stress Evaluation 2> was measured according to the above-mentioned [Measurement method of relative dielectric constant]. The results are also shown in Table 2-1.

<Elastic modulus measurement 2>
The elastic modulus of the silica-based film formed in the above <Stress Evaluation 2> was measured according to the above-mentioned [Measuring Method of Elastic Modulus]. The results are also shown in Table 2-1.
Table 2-1.

<Synthesis Example 3-1>
The pyrolytic volatile compound as component (d) was synthesized by the following procedure. First, 300 g of PGMEA was charged into a 1000 ml flask, 95 g of methyl methacrylate in which 2.0 g of AIBN was dissolved and 5 g of 2-hydroxyethyl methacrylate were charged into a 200 ml dropping funnel, and the system was replaced with nitrogen gas. The solution in the dropping funnel was dropped into the flask over 2 hours while heating and stirring in an oil bath at 130 ° C. in an atmosphere.

  Next, after stirring for 30 minutes, 97.8 g of PGMEA in which 0.2 g of AIBN was dissolved was charged in the dropping funnel and dropped into the flask over 1 hour. After the dropwise addition, the mixture was further stirred for 2 hours, and returned to room temperature to obtain a pyrolytic volatile compound as a component (d).

  When this mass average molecular weight was measured by GPC method, it was 10,700. Furthermore, the concentration of the pyrolytic volatile compound obtained by weighing 2 g of the solution in a metal petri dish and drying it for 3 hours with a dryer at 150 ° C. was 16.8% by mass.

<Synthesis Example 3-2>
65.8 g of water in which 0.92 g of 70% nitric acid was dissolved in a solution in which 132.3 g of tetraethoxysilane and 65.1 g of methyltriethoxysilane were dissolved in 335.94 g of propylene glycol monopropyl ether (PGP). The solution was added dropwise over 30 minutes with stirring. After completion of dropping, the reaction was allowed to proceed for 5 hours to obtain a polysiloxane solution.

<Example 3-1>
200 g of the polysiloxane solution obtained in Synthesis Example 3-2 and 53.2 g of the liquid pyrolysis volatile compound obtained in Synthesis Example 3-1 were placed in a 300 ml eggplant flask and stirred for 2 hours. Next, ethanol and low-boiling substances were distilled off in a warm bath under reduced pressure using a rotary evaporator to obtain 180.0 g of a polysiloxane / pyrolytic volatile compound in a liquid form. Next, 13.5 g of a 2.4% tetramethylammonium nitrate aqueous solution was added to this solution to prepare a silica-based film forming composition of the present invention.

<Comparative Example 3-1>
200 g of the polysiloxane solution obtained in Synthesis Example 3-2 and 44.7 g of a 20 wt% PGP solution of polyethylene glycol monooleyl ether (n≈7, manufactured by Tokyo Chemical Industry Co., Ltd.) were placed in a 300 ml eggplant flask and stirred for 2 hours. Next, ethanol and low-boiling substances were distilled off in a warm bath under reduced pressure using a rotary evaporator to obtain 180.0 g of a polysiloxane / pyrolytic volatile compound in a liquid form. Then, 13.5 g of 2.4% tetramethylammonium nitrate aqueous solution was added to this solution to prepare a composition for forming a silica-based film.

<Manufacture of interlayer insulating film 1>
The composition for forming a silica-based film obtained in Example 3-1 and Comparative Example 3-1 was spin-coated on a plurality of Si wafers at a rotation speed of 1500 rpm / 30 seconds to form a film. After spin coating, each Si wafer was subjected to a heat treatment at 150 ° C./1 minute + 250 ° C./1 minute to remove the solvent in the coating to form a silica-based coating. Next, heat treatment was performed at 400 ° C./30 minutes in a quartz tube furnace in which the O ₂ concentration was controlled to around 100 ppm, and the silica-based film as an interlayer insulating film was finally cured.

<Evaluation of interlayer insulating film 1>
Film thickness, relative dielectric constant, elastic modulus, adhesiveness, and film strength evaluation were performed on the obtained interlayer insulating films by the following methods. The results are summarized in Table 3-1.

[Film thickness measurement]
The film thickness of each interlayer insulating film was measured with an ellipsometer (manufactured by Gartner; ellipsometer L116B, wavelength used: 633 nm). Specifically, He—Ne laser light was irradiated on the interlayer insulating film, and the film thickness obtained from the phase difference generated by irradiation at a specified wavelength was measured.

[Specific permittivity measurement]
The measurement was performed according to the above-mentioned [Method of measuring relative permittivity].

(Elastic modulus measurement)
It measured according to the above-mentioned [Measuring method of elastic modulus].

[Adhesion evaluation]
Was determined parameter K ₁ according to the above-described as an index of adhesion Method of Modified-Edge Lift-OFF TEST ( m-ELT)].

[Single-film CMP resistance]
CMP polishing was performed on each interlayer insulating film under the condition that the interlayer insulating film was not polished. Specifically, the Si wafer is cut into 2 cm squares, and HS-C430 manufactured by Hitachi Chemical Co., Ltd. is used as the slurry, and polishing is performed at an applied load of 400 gf / cm ² for 1 minute to determine whether the insulating film remains. Examined.

When the insulating film remains, it indicates that the film strength is sufficient. In Table 1, “○” indicates that there is no problem at all, and the case where cohesive failure of the insulating film is observed. Was determined to be '×'.
Table 3-1.

<Synthesis Example 4-1>
A polymer as component (e) was synthesized by the following procedure. First, 300 g of propylene glycol monomethyl ether acetate (PGMEA) is charged in a 1000 ml flask, and 95 g of methyl methacrylate and 5 g of 2-hydroxyethyl methacrylate in which 2.0 g of azobisisobutyronitrile (AIBN) is dissolved in a 200 ml dropping funnel. Then, the system was replaced with nitrogen gas, and then the solution in the dropping funnel was dropped into the flask over 2 hours while stirring and heating in an oil bath at 130 ° C. in a nitrogen gas atmosphere.

  Next, after stirring for 30 minutes, 97.8 g of PGMEA in which 0.2 g of AIBN was dissolved was charged in the dropping funnel and dropped into the flask over 1 hour. After the dropping, the mixture was further stirred for 2 hours and returned to room temperature to obtain a polymer solution.

From these charges, the hydroxyl group concentration M _OH of the side chain calculated using the above formula (10) was 0.038 × 10 ⁻² mol / g. Moreover, it was 9,950 when the mass mean molecular weight was measured by GPC method. Furthermore, the polymer concentration obtained by weighing 2 g of the polymer solution in a metal petri dish and drying for 3 hours with a dryer at 150 ° C. was 16.7% by mass. Furthermore, the mass reduction rate at 500 ° C. measured using the obtained polymer dried product was 99%.

<Example 4-1>
65.8 g of water in which 0.92 g of 70% nitric acid was dissolved in a solution in which 132.3 g of tetraethoxysilane and 65.1 g of methyltriethoxysilane were dissolved in 335.94 g of propylene glycol monopropyl ether (PGP). The solution was added dropwise over 30 minutes under stirring. After completion of dropping, the reaction was allowed to proceed for 5 hours to obtain a polysiloxane solution.

  To this solution, 229.6 g of the polymer solution obtained in Synthesis Example 1 was added, and the ethanol produced was distilled off in a warm bath under reduced pressure, so that the mass content ratio of PGMEA and PGP (ratio of PGMEA: PGP) was 36. : A polysiloxane / polymer solution of 64 was obtained. Next, 26.47 g of a 2.38% tetramethylammonium nitrate aqueous solution (pH 3.6) was added to the polysiloxane / polymer solution to prepare a silica-based film forming composition of the present invention.

<Synthesis Example 4-2>
A polymer as component (e) was synthesized by the following procedure. First, 300 g of PGP was charged into a 1000 ml flask, 45 g of methyl methacrylate and 55 g of 2-hydroxyethyl methacrylate in which 1.7 g of AIBN was dissolved were charged into a 200 ml dropping funnel, and the system was replaced with nitrogen gas. The solution in the dropping funnel was dropped into the flask over 2 hours while heating and stirring in an oil bath at 130 ° C. in an atmosphere.

  Next, after stirring for 30 minutes, 97.8 g of PGP in which 0.17 g of AIBN was dissolved was charged into the dropping funnel and dropped into the flask over 1 hour. After the dropping, the mixture was further stirred for 2 hours and returned to room temperature to obtain a polymer solution.

These charged amounts, hydroxyl group concentration _{M OH} calculations side chain using the preceding equation (10) was 0.48 mol / g. Moreover, it was 10,700 when the mass mean molecular weight was measured by GPC method. Furthermore, the polymer concentration obtained by weighing 2 g of the polymer solution in a metal petri dish and drying it for 3 hours with a dryer at 150 ° C. was 15.0% by mass. Furthermore, the mass reduction rate at 500 ° C. measured using the obtained polymer dried product was 95%.

<Comparative Example 4-1>
To the polysiloxane solution prepared in the same manner as in Example 4-1, 255.6 g of the polymer solution obtained in Synthesis Example 4-2 was added, and the produced ethanol was distilled off in a warm bath under reduced pressure to remove 650 g of polysiloxane. A composition for forming a silica-based film comprising a siloxane / polymer solution was prepared.

<Manufacture of interlayer insulation film 2>
Each of the silica-based film forming compositions obtained in Example 4-1 and Comparative Example 4-1 was spin-coated on a silicon wafer at a rotation speed of 1500 rpm / 30 seconds to form a film. After spin coating, the solvent in the film is removed over 150 ° C / 1 minute + 250 ° C / 1 minute, and the film is finally cured in 400 ° C / 30 minutes in a quartz tube furnace in which the O ₂ concentration is controlled to around 100 ppm. A silica-based film as an interlayer insulating film was manufactured.

<Evaluation of interlayer insulating film 2>
The film thickness, electrical characteristics, and film strength were evaluated for each obtained interlayer insulating film by the following method.

[Film thickness measurement]
The thickness of each interlayer insulating film was measured in the same manner as <Evaluation 1 of interlayer insulating film>.

[Specific permittivity measurement]
The measurement was performed according to the above-mentioned [Method of measuring relative permittivity].

(Elastic modulus measurement)
It measured according to the above-mentioned [Measuring method of elastic modulus].

The above measurement results are summarized in Table 4-1.
Table 4-1

  As described above, according to the composition for forming a silica-based film, the silica-based film, and the method for producing the same according to the present invention, it has excellent dielectric strength and sufficient mechanical strength, and has a uniform film thickness. In addition, it is possible to obtain a silica-based coating film that is excellent in properties and has improved adhesion to other films (layers), thereby improving CMP resistance and preventing occurrence of interfacial peeling. Further, since the curing proceeds in a low temperature region as compared with the conventional case, the amount of heat input to the substrate on which the silica-based coating is formed can be reduced. Accordingly, it is possible to prevent the function of the underlying wiring from being impaired.

  Further, since the curing proceeds in a low temperature region, the high temperature heat treatment for performing the final curing can be shortened. Therefore, the heat history can be further improved. In addition, since the stress of the film is reduced in the final curing, a rapid increase in the stress of the film can be suppressed when forming the silica-based film. Accordingly, it is possible to prevent the function of the underlying wiring from being impaired.

  Moreover, since the electronic component according to the present invention has such a silica-based film, it is possible to improve the electrical reliability of the entire device, and to improve the yield of product production and the process margin. Furthermore, due to the excellent characteristics of the silica-based coating, it is possible to provide an electronic component with high density, high quality and excellent reliability.

FIG. 1 is a graph showing the pore distribution of Example 1-2 and the conventional silica-based coating.

Claims (28)

(A) component: following formula (1);
R ¹ _n SiX _4-n (1),
(In the formula, R ¹ represents an H atom or F atom, or a group containing B atom, N atom, Al atom, P atom, Si atom, Ge atom or Ti atom, or an organic group having 1 to 20 carbon atoms. , X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, each X is the same But it can be different)
A siloxane resin obtained by hydrolytic condensation of a compound represented by:
(B) component: a solvent capable of dissolving the component (a),
(E) component: a polymer having a side chain containing a hydroxyl group;
With
The polymer is represented by the following formula (2):
0 <M _OH <0.4 × 10 ⁻² (2),
M _OH : concentration of the hydroxyl group in the polymer (mol / g),
The composition for silica-type film formation which satisfy | fills the relationship represented by these. The component (a) is at least selected from the group consisting of H atom, F atom, B atom, N atom, Al atom, P atom, Si atom, Ge atom, Ti atom, and C atom with respect to 1 mol of Si atom. The total content of one kind of atoms is 0.65 mol or less,
The composition for forming a silica-based film according to claim 1. The component (b) includes a first solvent component composed of an alkylene glycol alkyl ether alkyl ester or an alkylene glycol alkyl ether acetate, and a second solvent component composed of an alkylene glycol monoalkyl ether.
The composition for forming a silica-based film according to claim 1 or 2. The component (b) has a mass content ratio of the first solvent component and the second solvent component of 1:99 to 60:40.
The composition for forming a silica-based film according to claim 3. The first solvent component is alkylene glycol methyl ether acetate;
The composition for forming a silica-based film according to claim 3 or 4. The first solvent component is propylene glycol alkyl ether acetate;
The composition for forming a silica-based film according to claim 3 or 4. The first solvent component is propylene glycol methyl ether acetate;
The composition for silica-type film formation as described in any one of Claims 3-6. The second solvent component is propylene glycol monopropyl ether;
The composition for silica-type film formation as described in any one of Claims 3-7.   (C) Component: The composition for silica-type film formation as described in any one of Claims 1-8 further equipped with onium salt. The component (c) is an ammonium salt.
The composition for forming a silica-based film according to claim 9. The component (e) has a reduction rate of 95% by mass or more in a nitrogen gas atmosphere at a temperature of 300 to 500 ° C.
The composition for silica-type film formation as described in any one of Claims 1-10. The component (e) contains an ester bond in the molecule.
The composition for silica-type film formation as described in any one of Claims 1-11. The component (e) contains a (meth) acrylic acid derivative as a constituent component, and the concentration of the (meth) acrylic acid derivative is 0.5 × 10 ⁻² (mol / g) or more. is there,
The composition for silica-type film formation as described in any one of Claims 1-12.   Nitric acid is further included, The composition for silica-type film formation as described in any one of Claims 1-13 characterized by the above-mentioned. The silica-based coating is such that the stress of the silica-based coating obtained when heated at 150 ° C. for 3 minutes is 10 MPa or more, and the relative dielectric constant of the silica-based coating obtained by final curing is less than 3.0. It is a silica-based film having curing characteristics,
The composition for silica-type film formation as described in any one of Claims 1-14. When preliminarily cured at a first heating temperature in the state of a film applied on a substrate, and then finally cured at a second heating temperature higher than the first heating temperature, the second heating temperature The second stress of the silica-based coating when finally cured has a curing characteristic such that the second stress of the silica-based coating is smaller than the first stress of the silica-based coating when cured at the first heating temperature.
The composition for silica-type film formation as described in any one of Claims 1-14.   The silica-based coating film according to claim 16, wherein the first heating temperature is a temperature within a range of 100 ° C or higher and lower than 350 ° C, and the second heating temperature is a temperature within a range of 350 or higher and 500 ° C or lower. Forming composition. The silica film is a Modified-Edge Lift-OFF TEST ( m-ELT) value of the parameter K ₁ obtained 0.20 or more in, and relative dielectric constant of the silica-based coating film obtained by the final curing 3 It is a silica-based film having curing characteristics such that it is less than 0.0.
The composition for silica-type film formation as described in any one of Claims 1-17.   A silica-based film comprising a cured film formed by applying the composition for forming a silica-based film according to any one of claims 1 to 18 onto a substrate and heating the applied film.   The silica-based film according to claim 19, wherein the relative dielectric constant is less than 3.0.   The silica-based film according to claim 19, having an elastic modulus of 2.5 GPa or more.   The manufacturing method of the silica type coating which apply | coats the composition for silica-type film formation as described in any one of Claims 1-18 on a base | substrate, and hardens this coating film by heating the apply | coated film.   The composition for forming a silica-based film according to any one of claims 1 to 18 is applied on a substrate, the solvent contained in the applied film is removed, and then the film is heated at 250 to 500 ° C. A method for producing a silica-based film, which is fired at a temperature. An electronic component having an insulating film formed on a substrate on which an element structure is formed,
24. An electronic component, wherein the insulating film includes a silica-based film produced by the method for producing a silica-based film according to claim 22 or 23. A composition for forming a silica-based film comprising a siloxane resin, having fluidity, and being cured when heat is applied in a film state coated on a substrate to form a silica-based film. There,
The silica-based coating obtained by heating at 150 ° C. for 3 minutes has a stress of 10 MPa or more, and has a curing characteristic such that the relative dielectric constant of the silica-based coating obtained by final curing is less than 3.0.
A composition for forming a silica-based film. A composition for forming a silica-based film comprising a siloxane resin, having fluidity, and being cured when heat is applied in a film state coated on a substrate to form a silica-based film. There,
When pre-cured at the first heating temperature in the film state and then finally cured at a second heating temperature higher than the first heating temperature, and finally cured at the second heating temperature The second stress of the silica-based coating is such that the second stress of the silica-based coating is smaller than the first stress of the silica-based coating when cured at the first heating temperature.
A composition for forming a silica-based film.   27. The silica-based film according to claim 26, wherein the first heating temperature is a temperature within a range of 100 ° C. or more and less than 350 ° C., and the second heating temperature is a temperature within a range of 350 or more and 500 ° C. or less. Forming composition. A composition for forming a silica-based film comprising a siloxane resin, having fluidity, and being cured when heat is applied in a film state coated on a substrate to form a silica-based film. There,
Modified-Edge Lift-OFF TEST ( m-ELT) parameters K ₁ obtained in the value is at least 0.20, and, as the dielectric constant of the silica-based coating film obtained by the final curing is less than 3.0 Have good curing properties,
A composition for forming a silica-based film.

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