JP2006229221A - Coating solution for insulating film formation and method for forming insulating film for semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating solution for insulating film formation, which completely fills even a very small groove, enables thick coating for sufficiently flattening difference in a base level, achieves sufficient uniform flatness over the entire base pattern, contains no water to have a small dielectric constant, enables an insulating film with excellent film characteristics to be formed, and uses siloxanes etc., and a method for forming the insulating film for a semiconductor device. <P>SOLUTION: The coating solution for forming an insulating film used in production of a semiconductor devices includes siloxanes containing Si atoms bonded to at least one kind of organic substituent, and the content rate X found from an integral value of a signal of<SP>29</SP>Si-NMR spectrum of siloxanes satisfies a designated formula, the coating solution for forming the insulating film having a self-fluidization temperature of 150 to 300°C; and the method for forming the insulating film for the semiconductor device using the same is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides an insulating film that flattens and electrically insulates the substrate surface on which the unevenness is formed on the underlayer, particularly an interlayer insulation for flattening an electronic device wiring structure, for example, an LSI multilayer wiring structure and forming an insulating layer. In a solution containing siloxanes used as a film precursor, that is, a coating solution for forming an insulating film, in particular, determine the abundance ratio of unit structures of siloxanes that contain organic substituents directly bonded to Si atoms as part of their structures. Method for evaluating the insulating film forming siloxanes using this value, insulating film forming coating solution using siloxanes used for manufacturing a semiconductor device, manufacturing method thereof, and insulating film forming method The present invention also relates to a method of manufacturing a semiconductor device to which this is applied.

  2. Description of the Related Art Conventionally, as the integration of semiconductor devices increases, the step formed between the wirings becomes larger as the wiring of the elements becomes finer and multilayered. For this reason, the embedding property of the insulating material formed between the wirings and the flatness of the surface after forming the film are serious problems. As for the flatness tolerance, in order to follow the resolution in the photo process, the depth of focus of the resist is reduced. For example, in a line and space pattern of 0.7 μm, it is necessary to suppress the surface unevenness to 200 nm or less. There is also. Since suppression of this unevenness is required over the entire area of the chip or wafer, it is literally necessary to completely flatten a wide area.

In response to these problems, an insulating film is currently formed by chemical vapor deposition (O ₃ -TEOS AP-CVD) using ozone and tetraethoxysilane as raw materials as disclosed in, for example, Japanese Patent Laid-Open No. 61-77695. Thus, a method of embedding and mitigating the step of the base is known.
However, although O ³ -TEOS APCVD is characterized by good step coverage and excellent embeddability, since the film formation occurs conformally to the wiring, planarization over a wide range on the substrate is not possible. Impossible. O ₃ -TEOS APCVD has the disadvantage that the deposition rate on the wiring pattern densely spaced with a wide flat part and a narrow interval is different, so that it is difficult to flatten the pattern on the pattern where the wiring density varies depending on the location. is there.

  For example, LBVines and SKGupta, 1986 IEEE VLSI Multilevel Interconnect Conference, p.506, Santa Clara, CA (1986) or R. Chebi and S. Mittal, 1991 IEEE VLSI Multilevel Interconnect Conference, p.61, Santa, Clara, CA (1991) or BMSomero, RPChebi, EU Travis, HBHaver, and W. K. Morrow, 1992 IEEE VLSI Multilevel Interconnection Conf., P. 72, Santa Clara, CA (1992), etc. A method is also known in which an insulating film deposited thickly by chemical mechanical polishing (CMP) is polished from the surface and planarized. According to CMP, if the conditions are set appropriately, it is said that a flat shape with a wide area that is almost ideal can be obtained.

  However, prior to CMP, the trenches between the wirings must be filled separately. That is, it is necessary to combine other methods such as CVD for filling the grooves. There are a number of major problems with CMP itself, for example, it has been pointed out that the throughput is low, particle generation, metal / alkali contamination, instability of detection of the polishing end point, increase in equipment cost, etc. are still widely used. It has not reached.

If attention is paid only to the technique of filling the trench between the wirings, a high-density plasma CVD method (biased HDP CVD) in which a bias is applied to the substrate has attracted attention in recent years. S. Matsuo and M. Kiuchi, Jpn. J. Appl. Phys., 22, L210 (1983), or K. Machida and H. Oikawa, J. Vac. Sci. Technol., B4, 818 (1986) Unlike the normal CVD method, this is a method of depositing an oxide film while anisotropically sputter etching the substrate surface with argon ions. At this time, plasma sources with high plasma ion density such as ECR or ICP are used. Is done.
The formation of an interlayer insulating film by HDP is almost satisfactory as a trench filling technique, but since protrusions due to the remaining sputter etching are generated on the entire surface of the pattern, planarization must be performed by another method such as CMP. In addition, since the generation of particles and the deposition rate are small, problems such as a decrease in throughput have not yet been solved.

On the other hand, a method of forming an insulating film by coating by the spin-on-glass method (SPIN ON GLASS: SOG method) introduced in Applied Physics Vol. 57, No. 12 (1988) etc. It is widely used in the manufacture of semiconductor devices. For example, as an interlayer insulating film for LSI multilayer wiring, a SiO ₂ -based cured film by the SOG method is generally used.
SOG is a technology for applying a solution containing oligosilanol or oligosilicate onto a substrate by a spin coater and forming a cured film of SiO ₂ by thermal curing, or an insulating film formed by the method, or for forming an insulating film Refers to the coating solution. Since the SOG coating solution has a characteristic of flowing into the grooves between the narrow wirings, the formed film is well embedded in the grooves between the wirings and simultaneously flows into the wide flat recesses. It also has the feature of being able to flatten high steps. Since the SOG process is performed at a low temperature of about 400 ° C., it is used as an interlayer insulating film after Al wiring, which is easily damaged by heat.

Conventionally, an oligosilicate called inorganic SOG represented by the general formula Si (OR) _n (OH) _4-n that does not contain any organic substituent bonded to Si has been used as a material for SOG. Since inorganic SOG undergoes volume shrinkage of about 20% during heat curing, it has poor crack resistance and can only be applied to about 200 to 300 nm at a time. To alleviate the level difference due to the wiring having a wiring cross-sectional aspect ratio larger than about 1, thick coating of SOG at least about the wiring height is necessary. However, since inorganic SOG is cracked, such thick coating cannot be performed. That is, inorganic SOG could not be used for flattening a step pattern having a large cross-sectional aspect ratio.

In order to eliminate the above disadvantages of inorganic SOG and improve the shrinkage, flatness, etching rate, adhesion, and crack resistance of the film, it has an organic substituent directly bonded to Si, that is, in the chemical structure containing organic Si, general formula _{R m Si (OR) n (} OH) oligosiloxane called organic SOG represented by _4-nm has been studied and developed. As the organic substituent, a methyl group is mainly used because of thermal stability, degassing characteristics, plasma resistance, film yield value and film flexibility, but other types of substituents such as a phenyl group are used. May be used. Organic SOG is characterized by a smaller shrinkage rate of the film during heat curing than inorganic SOG, and therefore high crack resistance. Further, since the etching rate for the etching gas containing CHF ₃ is as low as that of the CVD film, the organic SOG is thickly applied on the CVD oxide film on the pattern and cured, and then the CVD film is etched by the etching gas containing CHF _3. At the same time, it is also characterized in that a flattening process can be easily configured by etching (constant-speed full surface etchback method).

However, even in the conventional organic SOG, curing by heating starts from about 100 ° C., and volume shrinkage occurs accordingly. Therefore, unevenness following the base shape appears on the surface once flattened by coating. There was a problem that the flatness was not so good.
In addition, the area range on the substrate where the effect of flattening by the flow of the coating solution is said to be a local one of the order of 10 μm at most, and the concave portion between the wirings wider than 10 μm and the convex portion on the wide wiring The film thickness on the top will be almost the same. That is, when viewed from a visual field on the order of 10 μm or more, the step between the concave portion and the convex portion is not relaxed at all. As described above, since the formed film thickness depends on the density of the wiring pattern, organic SOG is ineffective for flattening a wide area at the chip / wafer level.

Also, organic SOG has a volume shrinkage of at least about 7% during heat curing, and cracks due to shrinkage stress may occur due to coating formation with a thickness of 500 nm or more, similar to inorganic SOG.
Since organic SOG has poor film quality and easily contains or absorbs water, troubles due to degassing from SOG are likely to occur in a subsequent process. Further, the apparent dielectric constant is increased by water, so that the delay due to the capacitance between the lines is increased, and there are various difficult problems such as being disadvantageous as an insulating film for high-speed wiring.

のようになり、各Ｓｉに対し１つのメチル基（あるいはフェニル基）が結合し、さらに梯子状に規則正しい構造をとったものである。
ラダーシロキサンは、構造の規則性が高いため加熱により結晶のように溶融流動するという特徴があるものの、収縮率が大きく、クラック耐性が非常に悪いため、厚塗りが不可能であること、および構造上活性な水酸基（Ｓｉ−ＯＨ）に乏しく、下地との密着が悪く、剥がれを生じやすい、という致命的な欠点がある。 Several types of SOG have been reported that address the above drawbacks of organic SOG. One is a ladder siloxane oligomer. This can be expressed in the structural formula as

Thus, one methyl group (or phenyl group) is bonded to each Si, and a regular structure is formed like a ladder.
Ladder siloxane is characterized by high structural regularity and melt-flowing like a crystal when heated, but it has a large shrinkage ratio and very poor crack resistance, so that thick coating is impossible and There are fatal drawbacks in that the upper active hydroxyl group (Si—OH) is poor, adhesion to the base is poor, and peeling is likely to occur.

  As another countermeasure, inorganic SOG using hydrogen siloxane oligomer or perhydrosilazane oligomer as a raw material is also known. These new SOGs are characterized in that they do not have an organic group directly bonded to Si in the structure, but instead have hydrogen bonded directly to Si. In any case, after coating and drying, oxygen contained in the furnace atmosphere is absorbed during heat curing to cause volume expansion, so that the apparent shrinkage rate is small and the coating can be thickly applied. However, since there is a defect similar to that of organic SOG in which the uneven shape of the base is traced by shrinkage from application to drying, wide flatness is not desired. Furthermore, since free hydroxyl groups remain in the film even after heat curing, it also causes degassing and high dielectric constant.

To date, no material solution has been established for the problems listed above.
On the other hand, in order to improve the film characteristics of an insulating film of a semiconductor device, particularly an interlayer insulating film for LSI multilayer wiring, it is necessary to analyze siloxanes that form the insulating film.
In general, for analysis of siloxanes contained in various materials, siloxanes are extracted as they are or extracted into an appropriate organic solvent, and infrared spectrophotometry, nuclear magnetic resonance (NMR) method, plasma inductively coupled emission is used. A method of analyzing by a spectroscopic analysis method (see JP-A-4-40347) or the like is known. Also known is a method for detecting and quantifying decomposition products produced by chemically decomposing siloxanes (see Japanese Examined Patent Publication No. 62-8146). However, all of these methods are intended to measure the total amount of Si in the material.

  As described above, several methods for analyzing siloxanes are known, but an industrially useful method for analyzing the content ratio of organic substituents in organic SOG has not yet been established. An industrially useful method for accurately and simply analyzing and evaluating SOG, that is, siloxanes for forming an insulating film, is combined with the film characteristics of an insulating film of a semiconductor device, particularly an interlayer insulating film for LSI multilayer wiring, is still established. There was a problem that not. In addition, an insulating film forming coating solution capable of sufficiently improving the film characteristics of an insulating film of a semiconductor device, particularly an interlayer insulating film for LSI multilayer wiring, a manufacturing method thereof, and a method of forming an insulating film for a semiconductor device are desired. It was.

  The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to completely fill a fine groove, and it is possible to apply a thick coating sufficient to flatten a base step, and to form a base pattern. Achieving uniform (global) flatness as a whole, and forming an insulating film that does not contain water and has a low dielectric constant and is advantageous for high-speed wiring, that is, an insulating film with excellent film characteristics, particularly an interlayer insulating film for semiconductor devices An object of the present invention is to provide a coating liquid for forming an insulating film and a method for forming an insulating film for a semiconductor device using siloxanes.

As a result of diligent research on the characteristics of siloxanes and the interlayer insulating film for LSI multilayer wiring using the siloxanes, the present inventors have found that the content ratio of organic substituents in the siloxanes or the number of bonded organic substituents It has been found that the abundance ratio of different Si atoms, that is, the abundance ratio of the unit structure of siloxanes greatly affects the characteristics of the film, and as a result of intensive studies, the organic nature of SOG was determined from the signal integration value of the ²⁹ Si-NMR spectrum. It was found that an insulating film having excellent film characteristics can be formed by using the obtained organic SOG coating solution according to the evaluation, and the present invention has been achieved.

上記式〔１〕において、
ｋ、ｌ、ｎ：０〜１０００の整数を示す。
ｍ：１〜１０００の整数を示す。
Ｒ：飽和炭化水素基、不飽和炭化水素基、フェニル基から選ばれる少なくとも１種の有機置換基を示し、同一であっても異なっていてもよく、フェニル基としては、置換基を有するフェニル基でもよい。
酸素原子は、Ｓｉ、Ｒ、Ｈのいずれかと結合する。

上記式〔２〕において、
Ａ₀：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合をもたないＳｉに帰属されるＳｉシグナルの面積、
Ａ₁：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合を１本有するＳｉに帰属されるＳｉシグナルの面積、
Ａ₂：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合を２本有するＳｉに帰属されるＳｉシグナルの面積、
Ａ₃：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合を３本有するＳｉに帰属されるＳｉシグナルの面積を示す。 That is, the first aspect of the present invention is an insulating film forming coating solution used in the manufacture of a semiconductor device and is represented by the following formula [1] containing Si atoms bonded to at least one organic substituent. In addition, the content ratio X represented by the following formula [2] obtained from the integral value of the ²⁹ Si-NMR spectrum signal of the siloxane includes siloxanes satisfying the following formula [2]. Using an insulating film forming coating solution, the insulating film forming coating solution is applied and then dried, and fluidized while being held at a temperature of 150 ° C. or higher and 300 ° C. or lower, and further at a temperature of 350 ° C. or higher and 450 ° C. or lower. The present invention provides a method for forming an insulating film for a semiconductor device, including a curing step.

In the above formula [1],
k, l, n: An integer of 0 to 1000.
m: An integer of 1-1000.
R: represents at least one organic substituent selected from a saturated hydrocarbon group, an unsaturated hydrocarbon group, and a phenyl group, which may be the same or different. As the phenyl group, a phenyl group having a substituent But you can.
The oxygen atom is bonded to any one of Si, R, and H.

In the above formula [2],
A ₀ : The area of the Si signal attributed to Si having no Si—C bond, as determined from the ²⁹ Si-NMR spectrum,
A ₁ : Area of Si signal attributed to Si having one Si—C bond, determined from ²⁹ Si-NMR spectrum,
A ₂ : the area of the Si signal attributed to Si having two Si—C bonds, determined from the ²⁹ Si-NMR spectrum,
A ₃ : Indicates the area of the Si signal attributed to Si having three Si—C bonds, determined from the ²⁹ Si-NMR spectrum.

  Here, it is preferable to hold at a temperature of 150 ° C. or higher and 300 ° C. or lower for 30 seconds or longer. The curing is preferably performed in nitrogen.

By using a coating solution containing siloxanes, particularly methylsiloxane oligomers, provided in the present invention, it is possible to form an insulating film for semiconductor devices having excellent film characteristics, for example, an interlayer insulating film for LSI multilayer wiring.
That is, according to the coating liquid provided by the present invention and the method for forming an insulating film using the same, an insulating film having excellent film characteristics, that is, uniform flatness of the entire base pattern can be achieved, and fine grooves are completely formed. Insulating film that has excellent crack resistance, can be applied thick enough to flatten the base step, and does not contain water, has a low dielectric constant, and is advantageous for high-speed wiring. An interlayer insulating film for a semiconductor device can be formed.

The present invention is described in further detail below.
The evaluation method of siloxanes for forming an insulating film used in the present invention is an at least one kind of organic contained in an insulating film for semiconductor devices, for example, an insulating film forming coating solution used for forming an interlayer insulating film for LSI multilayer wiring. The siloxanes containing Si atoms bonded to substituents are analyzed for the presence of at least one Si atom with a different number of bonded organic substituents, and based on this, for example, in siloxanes In this method, the content ratio of the organic substituent is obtained, and thereby the siloxanes, for example, the organic property thereof is evaluated. In particular, in ²⁹ Si-NMR, the abundance ratio and content ratio are obtained from the area of the signal from organic silicon, and the organicity is evaluated.

  As a solution containing siloxanes used in the present invention, that is, a coating liquid for forming an insulating film (hereinafter simply referred to as a coating liquid), a precursor for forming an insulating film for a semiconductor device (hereinafter simply referred to as an insulating film). As long as it is a solution of siloxanes containing Si atoms bonded to at least one organic substituent or a solution in which such siloxanes are dissolved in an organic solvent, for example, usually An SOG solution for forming an SOG film or an organic SOG solution can be used. Here, the organic substituent may be any of a saturated hydrocarbon group, an unsaturated hydrocarbon group, and a phenyl group, or may contain two or more kinds. Further, the number of organic substituents bonded to one Si atom may be 1 to 3.

  Here, the siloxanes used in the present invention can be represented by the following formula [1], but the way of bonding of these unit structures is not particularly limited, and may be either linear or branched. . Moreover, you may mix and use these.

上記式〔１〕において、
ｋ、ｌ、ｍ、ｎ：０〜１０００の整数を示す。
Ｒ：飽和炭化水素基、不飽和炭化水素基、フェニル基から選ばれる少なくとも１種の有機置換基を示し、同一であっても異なっていてもよく、フェニル基としては、置換基を有するフェニル基でもよい。
酸素原子は、Ｓｉ、Ｒ、Ｈのいずれかと結合する。

In the above formula [1],
k, l, m, n: An integer of 0 to 1000 is shown.
R: represents at least one organic substituent selected from a saturated hydrocarbon group, an unsaturated hydrocarbon group, and a phenyl group, which may be the same or different. As the phenyl group, a phenyl group having a substituent But you can.
The oxygen atom is bonded to any one of Si, R, and H.

  Such siloxanes are preferably siloxane oligomers used for the purpose of forming an insulating film, and more preferably siloxane oligomers having a polymerization degree of 2 to 500. That is, the number of repeating units [k + l + m + n] of the following unit structures (a) to (d) of the siloxane oligomer represented by the above formula [1] is more preferably in the range of 2 to 500. Here, when the degree of polymerization (the number of repetitions) exceeds 500, the viscosity of the coating solution (SOG solution) composed of siloxane and a solvent becomes too high, and when it is less than 2, the siloxane easily evaporates in the insulating film forming step. In either case, it is difficult to form an insulating film.

上記単位構造（ａ）〜（ｄ）において、Ｒは飽和炭化水素基、不飽和炭化水素基、フェニル基から選ばれる少なくとも１種の有機置換基を示し、同一であっても異なっていてもよく、フェニル基としては、置換基を有するフェニル基でもよい。

In the unit structures (a) to (d), R represents at least one organic substituent selected from a saturated hydrocarbon group, an unsaturated hydrocarbon group, and a phenyl group, which may be the same or different. The phenyl group may be a phenyl group having a substituent.

In the present invention, when evaluating siloxanes for forming an insulating film, the content ratio of organic substituents in the siloxanes is analyzed, or Si atoms having different numbers of bonded organic substituents (the number of Si-C bonds is different). 0 to 4 Si atoms), that is, at least one of the unit structures (a) to (d) is analyzed, and the abundance ratio is measured. The method for analyzing the content ratio of the organic substituents of the siloxanes used in the present invention or the method for measuring the abundance ratio of the unit structures (a) to (d) is not limited, but the nuclear magnetic resonance (NMR) method is used. Is preferred. More preferably, such abundance ratio is determined from the integrated value of the ²⁹ Si-NMR spectrum signal.

  When performing a nuclear magnetic resonance (NMR) method, first, a sample siloxane, for example, an SOG solution is dissolved in a deuterium solvent. The deuterium solvent used here is not particularly limited as long as the components in the SOG solution are not separated from the solution by adding the deuterium solvent. For example, deuterated chloroform, deuterated acetone, deuterated methanol and the like can be used. . If the concentration of the sample is too low, sufficient detection sensitivity cannot be obtained, and if it is too high, the ratio of the deuterium solvent is lowered, and the frequency stability of the NMR apparatus is not good, so 10 to 90% is preferable.

^The sample tube used for ²⁹ Si-NMR measurement is preferably made of Teflon (registered trademark). This is to avoid the appearance of a ²⁹ Si signal due to silicate glass in a normal glass NMR sample tube.
In the ²⁹ Si-NMR measurement performed for the purpose of the present invention, it is desirable not to decouple hydrogen nuclei. This is because the sign of the ²⁹ Si-NMR nuclear Overhauser effect factor is negative, so that the intensity of the ²⁹ Si-NMR signal may be attenuated depending on the sample. This is to ensure.
It is also preferable to add a relaxation reagent such as tris (acetylacetonato) chromium (III), tris (acetylacetonato) iron (III) in order to shorten the measurement time.

Assigning each signal of the ²⁹ Si-NMR spectrum obtained by the measurement, the abundance ratio of the unit structures (a), (b), (c), (d) from each signal area, or further an organic substituent The ratio of bonded Si atoms is determined. The content ratio of the organic substituent can be defined in several different ways depending on the purpose, and may be properly used according to the purpose or necessity. For example, the area of the Si signal attributed to Si having no Si—C bond is A ₀ , the area of the Si signal attributed to Si having one Si—C bond is A ₁ , and the Si—C bond is When the area of the Si signal attributed to Si having A is represented by A ₂ and the area of the Si signal attributed to Si having three Si—C bonds represented by A ₃ , as an organic scale (represented by X), For example, the following formula [3] or formula [4] can be defined.

式〔３〕はシロキサン中のＳｉ原子数に対する有機置換基の数の比を表わす式であり、式〔４〕はシロキサン中のＳｉ原子数に対する有機Ｓｉ原子数の比を表わす式である。有機性を評価する式の形は分析の目的によって上記式〔３〕、〔４〕に限ることなく定義できる。

Formula [3] is a formula representing the ratio of the number of organic substituents to the number of Si atoms in the siloxane, and Formula [4] is a formula representing the ratio of the number of organic Si atoms to the number of Si atoms in siloxane. The form of the formula for evaluating the organicity can be defined without being limited to the above formulas [3] and [4] depending on the purpose of analysis.

According to the evaluation method used in the present invention, in the analysis of the content ratio of organic substituents of organosiloxanes, the abundance ratio for each unit structure, which was impossible with the conventional method, can be obtained. The organic substituent content ratio can be easily determined.
Therefore, this evaluation method can be used, for example, for organic evaluation of siloxanes in a solution containing an organic siloxane used for forming an insulating film of a semiconductor device, particularly an interlayer insulating film for LSI multilayer wiring. Depending on the evaluation method used, film properties such as chemical resistance and water resistance of the insulating film can be predicted in advance. In addition, according to the present invention, there is an effect that quality control at the time of manufacturing SOG used for the insulating film is appropriately performed.

  According to a third aspect of the present invention, an insulation using a coating solution for forming an insulating film for a semiconductor device using siloxanes, for example, an interlayer insulating film for LSI multilayer wiring (hereinafter simply referred to as an insulating film), based on the above evaluation method. This is a film forming method.

The insulating film forming coating solution used in the method for forming an insulating film according to the third aspect of the present invention will be described below.
Here, the present inventors have found that there is a close relationship between the chemical structure of siloxanes and the characteristics of the SOG film.
That is, a coating solution containing a siloxane, preferably a siloxane oligomer, in which the following abundance ratio X obtained from the integral value of the ²⁹ Si-NMR spectrum signal of the siloxane represented by the formula [1] satisfies the following formula [2]: It was found that the characteristics of the insulating film to be formed are excellent.

上記式〔２〕において、
Ａ₀：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合をもたない
Ｓｉに帰属されるＳｉシグナルの面積
Ａ₁：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合を一本有す
るＳｉに帰属されるＳｉシグナルの面積
Ａ₂：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合を二本有す
るＳｉに帰属されるＳｉシグナルの面積
Ａ₃：²⁹Ｓｉ−ＮＭＲスペクトルから求められる、Ｓｉ−Ｃ結合を三本有す
るＳｉに帰属されるＳｉシグナルの面積

In the above formula [2],
A ₀ : No Si—C bond determined from ²⁹ Si-NMR spectrum
Area of Si signal attributed to Si A ₁ : One Si—C bond determined from ²⁹ Si-NMR spectrum
Area of Si signal attributed to Si A ₂ : ^{29 There} are two Si-C bonds determined from the Si-NMR spectrum.
Area of Si signal attributed to Si A ₃ : ^{29 It} has three Si-C bonds determined from the Si-NMR spectrum.
Area of Si signal attributed to Si

  Here, the reason why the properties of the insulating film are excellent when a coating solution containing siloxanes having a content ratio X represented by the above formula [2] of 80% or more is (1) water absorption Therefore, the degassing amount and dielectric constant can be kept low, (2) the crack resistance is improved and thick coating is possible, and (3) the dry etching rate is low, so the etch back margin is wide. It can be taken.

Next, the insulating film forming coating solution provided in the present invention will be described.
It can be said that the coating liquid provided in the present invention is an evaluation of the above-mentioned organic scale according to the above formula [3].
In the present invention, an irregular structure having a weight average molecular weight of 1500 or more and 6000 or less represented by a composition formula (CH ₃ ) _y SiO _{2 -y / 2} (wherein y is 0.8 or more and 1.3 or less). The present invention provides a coating liquid characterized by dissolving a methylsiloxane oligomer having a boiling point in an organic compound having an organic compound having a boiling point of 120 ° C. or higher and 200 ° C. or lower as a main component. Unlike the conventional organic SOG (the range of y is 0.3 to 0.6), this coating solution is characterized in that the value of y in the composition formula is 0.8 or more and 1.3 or less, The ladder siloxane having an ordered structure has an irregular structure.

  By limiting the value of y to 0.8 or more in the composition formula of the methylsiloxane oligomer, the shrinkage during the heat polymerization curing of the methylsiloxane oligomer can be almost eliminated. Therefore, thick coating can be achieved, which is advantageous for flatness. This limitation also allows the water absorption rate of the methylsiloxane oligomer to be almost zero, and further to lower the dielectric constant to 3.5 or less, so that it does not contain water and has a low dielectric constant and high-speed wiring. It is possible to provide a feature of forming an SOG film advantageous to the above. When the value of y is less than 0.8, it shows similar characteristics to normal organic SOG, and shrinkage rate, water absorption rate, flattening performance, and dielectric constant can be obtained only within the range of the prior art. . On the other hand, if y exceeds 1.3, heat polymerization becomes difficult, and no film is formed, resulting in a rubbery material. Therefore, the upper limit of y is set to 1.3.

  In the prior art, the higher the value of y, the lower the adhesion to the substrate, making it impossible to put it to practical use. Ladder methylsiloxane is also represented by the same composition formula as in the present invention, and is in the range of y of the present invention (y = 1 is necessary to form a ladder structure). As described in the prior art, it is difficult to use because there is a problem that it is poor and the shrinkage is large.

  In the present invention, the problem of adhesion reduction due to an increase in y is solved by making the siloxane skeleton an irregular structure, defining the molecular weight, and defining the solvent. Due to the introduction of the irregular structure, a large amount of Si-OH termination that contributes to adhesion is incorporated in the oligomer structure and the Si-O-Si network structure becomes sparse, so the ability to soften the film and absorb stress Is considered to contribute to the improvement of adhesion. Although an appropriate parameter for defining the irregular structure has not yet been found, it is presumed that the conventional organic SOG is easy to take an ordered structure even if y is increased, and has poor adhesion. If the molecular weight is less than 1500, volume shrinkage during polymerization is remarkable, so that internal stress is likely to occur, causing cracking and peeling. Further, when a solvent having a boiling point of less than 120 ° C. is used, not only coating unevenness is likely to occur due to an in-plane difference in drying speed, but also stress due to drying is remarkably generated, which adversely affects adhesion.

  The reason why the weight average molecular weight of the methylsiloxane oligomer is limited to 1500 to 6000 is that, in addition to solving the above-mentioned adhesion problem, if it is less than 1500, a continuous coating film is not formed, and if it exceeds 6000, This is because since the viscosity becomes too high, radial coating unevenness called striation occurs. The weight average molecular weight is most preferably 1500-3500.

  As the solvent for dissolving the methylsiloxane oligomer, a solvent mainly composed of an organic compound having a boiling point of 120 ° C. or higher and 200 ° C. or lower is used. When the boiling point is less than 120 ° C., most of the solvent is volatilized by rotation during coating, and thus flattening by sufficient flow of the coating solution cannot be achieved. In addition, as described above, a decrease in adhesion due to stress generated by drying becomes a problem. On the other hand, if the boiling point exceeds 200 ° C., drying is remarkably slowed, throughput is reduced, defects are generated during substrate transportation, foaming or carbon residue is generated during the heating process, and thus cannot be used. A more preferred solvent boiling range is between 130-160 ° C.

  It should be noted that the viscosity of the solvent greatly affects the filling performance of fine grooves and the uniformity of the coating film. Preferably, a solvent having a viscosity of 2.0 cP or less at 25 ° C. is used. In other words, when the viscosity of the solvent is larger than 2.0 cP, the embedding of the groove of 0.2 μm or less becomes incomplete, and at the time of coating, a radial stripe pattern from the center of the substrate to the periphery is generated. The frequency of occurrence of uneven film thickness increases significantly.

  Solvents satisfying the requirements of the present invention include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol dimethyl ether, di-n-butyl ether, diisobutyl ether, di-n-amyl ether. Methyl n-amyl ketone, methyl isoamyl ketone, n-amyl acetate, isoamyl acetate, n-hexyl acetate and the like can be used.

  These solvents can be used alone or in combination of two or more. In addition, other low boiling point solvents such as methanol, ethanol, isopropyl alcohol, acetone, methyl ethyl ketone, water, and butyl acetate can be added to lower the viscosity and improve the coating performance. However, the proportion of the solvent whose boiling point is other than 120 ° C. or more and 200 ° C. or less is preferably such that the volume proportion does not exceed 50% of the whole solvent. In the coating liquid of the first aspect of the present invention described later and the coating liquid used in the second or third aspect of the present invention, the above-described solvent may be used to dissolve siloxanes. Needless to say.

  If a coating solution that satisfies the above requirements is used, the detailed reason is not clear, but once dried and solidified, the film softens when heated, reflows and becomes even more flat. A phenomenon called self-fluidization occurs. Planarization due to self-fluidization occurs in the lower temperature range of 150-200 ° C., where condensation cure of the methylsiloxane oligomer occurs. Due to this phenomenon, it is possible to achieve flattening over a wider area than conventional SOG.

  For the reasons described above, by using one or both of the coating solutions provided in the present invention, uniform flatness of the entire base pattern can be achieved, and fine grooves are completely embedded. In addition, it is possible to form an insulating film that is thick enough to flatten the base step, and that does not contain water, has a low dielectric constant, is excellent in insulation, and is advantageous for high-speed wiring.

An organic SOG coating liquid having such characteristics can be produced by a coating liquid manufacturing method described later. That is, a compound such as alkoxysilane or alkylalkoxysilane, in particular, one compound selected from the group consisting of tetraalkoxysilane, methyltrialkoxysilane and dimethyldialkoxysilane, or a mixture of two or more thereof, is used as a raw material. Formulated so that the molar concentration of CH ₃ is not less than 80% and not more than 130% of the molar concentration of Si in the entire raw material, and water in an amount of 2 to 4 times the molar concentration of Si in the entire raw material is added to the organic carboxylic acid. As a catalyst, it is polymerized by heating to a temperature of 40 ° C. or higher and 80 ° C. or lower, and the polymerization product is diluted by adding a solvent containing an organic compound having a boiling point of 120 ° C. or higher and 200 ° C. or lower as a main component. Water and alcohol, which are by-products of the polymerization reaction, are distilled off under reduced pressure or reduced pressure.

As the tetraalkoxysilane, tetramethoxysilane (Si (OCH ₃ ) ₄ ) or tetraethoxysilane (Si (OC ² H ₅ ) ₄ ) is generally used. As methyltrialkoxysilane, methyltrimethoxysilane (CH ₃ Si (OCH ₃ ) ₃ ) or methyltriethoxysilane (CH ₃ Si (OC ₂ H ₅ ) ₃ ) is generally used. As dimethyldialkoxysilane, dimethyldimethoxysilane ((CH ₃ ) ₂ Si (OCH ₃ ) ₂ ) or dimethyldiethoxysilane ((CH ₃ ) ₂ Si (OC ₂ H ₅ ) ₂ ) is used. These raw materials are mixed alone or in advance so that the molar concentration of Si—CH 3 is 80% or more and 130% or less of the molar concentration of Si in the whole raw material. This value is equal to the value of y when the composition formula of the methylsiloxane oligomer is expressed as (CH ₃ ) _y SiO _{2−y / 2} in the coating solution provided in the present invention. That is, y in the formula needs to be 0.8 or more and 1.3 or less.

For example, when methyltrimethoxysilane is used alone, it can be used as it is because Si—CH3 / total Si = 100% and y = 1 when used alone as a raw material. When tetramethoxysilane and methyltrimethoxysilane are mixed, if the mixing ratio r is r = [Si (OCH ₃ ) ₄ ] / [CH ₃ Si (OCH ₃ ) ₃ ], 0 <r ≦ If 0.25, 0.8 ≦ y <1.0 can be obtained. When tetramethoxysilane and dimethyldimethoxysilane are mixed, if the mixing ratio r is r = [Si (OCH ₃ ) ₄ ] / [(CH ₃ ) ₂ Si (OCH ₃ ) ₂ ], 7/13 ≦ If r ≦ 1.5, then 0.8 ≦ y ≦ 1.3. Thus, the raw materials can be used in combination of two or three kinds.

When the molar concentration of Si—CH ₃ contained in the blend or the single raw material is less than 80% of the molar concentration of Si in the whole raw material, the resulting methylsiloxane oligomer is represented by the composition formula: (CH ₃ ) _y SiO _{2 -y / 2} When y is less than 0.8, desired characteristics cannot be exhibited for the reasons described above. Further, when the molar concentration of Si—CH ₃ contained in the blend or the single raw material exceeds 130%, y of the methylsiloxane oligomer similarly produced exceeds 1.3, so that a cured film is not formed for the reason described above. .

  When 2 to 4 times the molar concentration of Si in the raw material is added to this raw material, and an organic carboxylic acid such as formic acid, acetic acid, or succinic acid is added, the condensation reaction starts immediately, and a polymer is formed. Is called. When the amount of water is less than twice the molar amount of the raw material, not only the reaction rate is remarkably lowered, but also the residual ratio of alkoxyl groups in the polymer increases, so that carbon in the formed film tends to remain. In addition, when the amount of water exceeds 4 times the amount of the raw material, the production reaction occurs too rapidly, which makes control difficult and increases the proportion of free hydroxyl groups (Si—OH) in the methylsiloxane oligomer. Therefore, the storage stability is lacking.

  The concentration of the organic acid as a catalyst is not particularly limited because it does not affect the structure and state of the product so much. However, if the concentration is too high, the solution tends to be acidic, which may affect the stability of the coating solution. The concentration is as low as possible, preferably about 1/1000 mol to 1/100 mol of the raw material. Inorganic acids other than organic acids, such as hydrochloric acid and phosphoric acid, are not used because they affect the metal on the coated substrate.

After the addition of water, the mixed solution is generally incompatible, so it is necessary to continue mixing vigorously using a stirrer or the like. Within a few minutes to several hours, an alcohol which is a double product of the hydrolysis reaction is produced, and the hydrophilicity of the polymer is increased, so that they become compatible.
Prior to this polymerization reaction, a solvent such as alcohol can be added to dilute in advance. For example, by adding 0.5 moles of methanol relative to the raw material, it is possible to reduce heat generation at the initial stage of reaction, increase compatibility, improve the stability of the reaction, and delay the polymerization reaction. As a solvent to be added for this purpose, methanol, ethanol, dioxane or the like of about 0.2 to 3 moles of the raw material is used.

In order to polymerize the methylsiloxane oligomer to a weight average molecular weight of 1500 to 6000, the mixture is heated to a temperature of 30 ° C. or higher and 80 ° C. or lower. Polymerization is preferably carried out at a low temperature when the ratio y of the molar concentration of Si—CH ₃ contained in a single raw material to the molar concentration of Si in the whole raw material is relatively small, and at a high temperature when y is relatively large. . When the heating temperature is less than 30 ° C., the polymerization rate is extremely lowered, and a desired molecular weight cannot be obtained. On the other hand, when the heating temperature exceeds 80 ° C., boiling of the by-product alcohol occurs or polymerization occurs very rapidly, which is difficult to control. In general, the reaction is preferably carried out at a temperature of around 50 ° C. and sealed in a thermostatic chamber. The time required for the reaction depends on the temperature, but is not particularly limited, and an appropriate time may be selected from about 4 to 120 hours while measuring the molecular weight.

  In the polymerization product thus obtained, water added as a raw material, alcohol as a by-product, and a solvent for dilution coexist with the solvent. It is necessary to remove this, but if it is distilled or dried as it is, the concentration of the methylsiloxane oligomer increases rapidly, so the polymerization reaction rate increases at an accelerated rate, resulting in a gel body with a molecular weight of several hundred thousand or more. In removing water, alcohol, and solvent, it is necessary to devise a technique that does not increase the concentration of the methylsiloxane oligomer. For this purpose, a main solvent used for dilution, that is, a solvent mainly composed of an organic compound having a boiling point of 120 ° C. or higher and 200 ° C. or lower is added in advance and diluted, and the diluted solution is distilled as it is under normal pressure or reduced pressure. It is necessary to. As distillation conditions, water, alcohol, and solvent are distilled off, but it is important to select a temperature and pressure at which the main solvent is not distilled.

Needless to say, the same main solvent as that used in the coating solution provided in the present invention can be used.
Thus, the solution of the methylsiloxane oligomer from which water, alcohol, and solvent have been removed can be used as it is, or after adding an appropriate solvent and performing operations such as filtration and aging as necessary.

The method for forming an insulating film for a semiconductor device according to the third aspect of the present invention uses the coating liquid for forming an insulating film provided in the present invention. It includes a step of fluidizing by holding at a temperature of 300 ° C. or lower, preferably 30 seconds or longer.
After the fluidizing step, the insulating film is preferably formed by further curing in nitrogen at a temperature of 350 ° C. or higher and 450 ° C. or lower.
Thus, a semiconductor device having an insulating film excellent in film characteristics, particularly an interlayer insulating film, can be manufactured in the present invention.

  This is largely the same as the conventional organic SOG film coating and forming method, but paying attention to the fact that the self-fluidization temperature of the SOG of the present invention is 150 ° C. or higher and 300 ° C. or lower. The greatest feature is that the self-flow flattening is completed by holding at a temperature of ℃ or lower, preferably for 30 seconds or longer. That is, the coated and dried film is fluidized again within this temperature range, and high flatness can be obtained. The subsequent process is nothing but a process called normal SOG curing.

Further, for the above reason, the coating liquid for forming an insulating film according to the first aspect of the present invention can be self-flow planarized by holding at a temperature of 150 ° C. or higher and 300 ° C. or lower when forming the insulating film. It is a coating solution.
That is, the coating solution for forming an insulating film according to this embodiment is obtained by dissolving a methylsiloxane oligomer in a solvent containing an organic compound as a main component, and the molar concentration of Si-CH3 in the methylsiloxane oligomer is a methylsiloxane oligomer. It is characterized by having a self-flowing temperature of 80 ° C. or higher and 130% or lower and 150 ° C. or higher and 300 ° C. or lower of the total Si molar concentration.
In this embodiment, the solvent mainly composed of a methylsiloxane oligomer and an organic compound includes all those described in the coating liquid for forming an insulating film provided in the present invention.

The method for forming an insulating film for a semiconductor device according to the second aspect of the present invention uses the coating liquid for forming an insulating film according to the first aspect of the present invention.
In this aspect, it is preferable to include a step of drying after coating the coating liquid for forming an insulating film according to the first aspect of the present invention, and holding and fluidizing at a temperature of 150 ° C. or higher and 300 ° C. or lower. More preferably, the temperature is maintained at a temperature of 300 ° C. or lower for 30 seconds or longer.
Further, after the fluidizing step, it is preferable that the insulating film is formed by further curing in nitrogen at a temperature of 350 ° C. or higher and 450 ° C. or lower.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
The abundance ratio of the unit structures (a), (b), (c), and (d) in the siloxane oligomer contained in the commercial organic SOG and the organic substituent content ratio were analyzed. Here, two types of organic SOGs, Sample A (SF1014 manufactured by Sumitomo Chemical) and Sample B (Type 12000T manufactured by Tokyo Ohka), were analyzed.
An organic SOG (each of sample A and sample B) 1.5 ml and about 40 mg of tris (acetylacetonato) chromium (III) were added to 1.5 ml of heavy acetone and dissolved to obtain a uniform solution. This solution was put into a Teflon (registered trademark) NMR sample tube having an inner diameter of 10 mm, and ²⁹ Si-NMR was measured with a Fourier transform NMR spectrometer (GX270 manufactured by JEOL). Observation center frequency 53.67 MHz, observation frequency range 16 kHz, data point 16 k or 32 k, integration number 10,000-45000, and tetramethylsilane was used as an internal standard for chemical shift.

An example of the obtained ²⁹ Si-NMR spectrum is shown in FIG. The relative ratio of A ₀ , A ₁ , A ₂ , A ₃ was determined from the area of each signal shown in the figure. The peak area in FIG. 1 is proportional to the number of Si atoms in the corresponding unit structure. Here, in the case of the unit structures (a) and (c), it is the total value of a plurality of peak areas shown in the figure.
Table 1 shows the results of calculating the organic substituent content ratio defined by the formula [3].
In this example, R is a methyl group.

As described above, by using the evaluation method used in the present invention, by analyzing ²⁹ Si-NMR in the analysis of the content ratio of organic substituents of organosiloxanes, a unit that was impossible with the conventional method The abundance ratio for each structure can be determined, and for example, the abundance ratio and organic substituent content ratio of the unit structures (a), (b), (c) and (d) in the organic SOG can be easily determined.

(Example 2)
As raw materials, methyltrimethoxysilane and tetramethoxysilane were dissolved in methanol in the proportions shown in Table 2, and water and formic acid 0.002 mol in the proportions shown in Table 1 were added thereto and stirred at 30 to 60 ° C. for 24 hours. A polymerization reaction was performed. 650 ml of a 1: 1 mixture of benzene and ethylene glycol monoethyl ether was added to the product, and distilled under reduced pressure to remove excess methanol and water to prepare a coating solution having a solid content concentration of about 20% by weight. When the weight average molecular weight of the siloxane oligomer contained in the coating solution was measured by gel permeation chromatography, it was about 3,000, which corresponds to a degree of polymerization of 40-50.

This coating solution is spin-coated on a 6-inch diameter silicon wafer at a rotation speed of 3,000 rpm, baked at 150 ° C., 200 ° C. and 250 ° C. for 60 seconds each, and then heated at 400 ° C. for 30 minutes in a nitrogen stream. An insulating film was produced.
The results of measuring the shrinkage rate, dielectric constant, and water absorption of this film are shown in Table 2 and FIG. 2 together with the value of X in Formula [2].

Here, as the shrinkage rate evaluation method, coating films having different film thicknesses were formed on the cleaned semiconductor substrate by controlling the number of rotations, and the shrinkage rate was obtained from the following equation [5].
Shrinkage rate (%) = {(t _b −t _a ) / t _b } × 100 [5]
However, t _a is the thickness after curing, t _b is the thickness after pre-baking.

  The dielectric constant is obtained by forming an Al film on the entire surface of the cleaned semiconductor substrate by sputtering, and forming a coating film having a thickness of about 300 nm on this by controlling the number of rotations by the above method. After the treatment, an approximately 3mm square Al electrode is deposited using a metal mask, and the edge of the film is etched with dilute hydrofluoric acid to measure the capacitance between the entire lower surface Al and the deposited Al film. And obtained from the electrode area and film thickness.

In addition, the water absorption is generated by leaving the cured film for 24 hours in a clean room, and water contained in the film is generated up to 400 ° C with an electrolytic cell moisture meter (MEA (Moisture Evaluation Analyzer) manufactured by DuPont). It was measured by measuring the amount of water.
As is clear from Table 2 and FIG. 2, there is a clear correlation between X and film properties, and when X ≧ 80%, the shrinkage, dielectric constant, and water absorption are all small and excellent. It was found that film characteristics can be obtained.

(Example 3)
First, a coating solution for forming SOG provided in the present invention was manufactured according to the following procedure based on the method for manufacturing a coating solution provided in the present invention. The raw material blending ratio, synthesis conditions, typical film properties, etc. are listed in Tables 3 and 4. Table 3 shows a combination of three kinds of raw materials, and Table 4 shows data obtained when various synthesis conditions are changed. Tables 3 and 4 also show the measured data. A detailed description of the measurement method is described below. The measured film physical properties are the same in Tables 3 and 4. Except for the scope of the present invention, an asterisk (*) was added in front of the number to provide a control comparative example.

(Synthesis of coating solution)
As raw materials, tetramethoxysilane, methyltrimethoxysilane, and dimethyldimethoxysilane having a purity of 99% or more were mixed in the proportions shown in Tables 3 and 4, and water in the proportions shown in Tables 3 and 4 was added thereto. After adding 0.002 mol of formic acid aqueous solution as formic acid and stirring to make a uniform solution, it was sealed and immersed in a constant temperature water bath at the temperature shown in Tables 3 and 4, and held for the time shown in Tables 3 and 4 A polymerization reaction was performed. Methyl n-amyl ketone (2-heptanone, boiling point 151 ° C.) was added to the polymerization product as a solvent, and distilled using a rotary evaporator at 50 ° C. under a reduced pressure of 50 Torr to remove excess methanol and water. Thereafter, it was further diluted with methyl n-amyl ketone (2-heptanone) to prepare a coating solution having a solid content concentration of 20% by weight. Table 4 lists the results obtained by measuring the weight average molecular weight of the siloxane oligomer contained in the coating solution by gel permeation chromatography. It can be seen that all of the coating liquids synthesized in the examples of Table 4 satisfy the conditions of the coating liquid provided by the present invention. However, the irregularity of the Si-O-Si network is excluded because there is no method that can be measured, but it does not take a regular structure such as a ladder structure in anticipation of the shrinkage rate described later being very small. Is naturally known.

This coating solution is spin-coated on a 6-inch diameter silicon wafer at a rotation speed of 3000 rpm, baked at 150 ° C., 200 ° C., and 250 ° C. for 60 seconds each, and then heated at 400 ° C. for 30 minutes in a nitrogen stream to form a coating film. Was made.
The results of measuring the shrinkage rate, dielectric constant, and water absorption rate of this film are shown in Table 3 together with the y value in the following composition formula 1.
(CH ₃ ) _y SiO _{2-y / 2} (Composition Formula 1)
Here, the shrinkage rate, dielectric constant and water absorption were measured and evaluated in the same manner as in Example 2.

  As is clear from Tables 3 and 4, there is a clear correlation between y and the film properties, and the shrinkage is small when 0.8 ≦ y ≦ 1.3, the dielectric constant is small, It was found that excellent film characteristics of a small amount can be obtained.

Next, a method for forming an insulating film in the present invention will be described with reference to the drawings.
FIG. 3 is a partial cross-sectional view showing the manufacturing process of the insulating film according to the present invention. In the step shown in FIG. 3A, after a wiring layer having a thickness of 1.2 μm is formed on the semiconductor substrate 1 subjected to a desired process, this is patterned, and wirings 2a, 2b having a wiring width = 1 μm and 2c (interval between wirings 2a and 2b = interval between wirings 2b and 2c = 1 μm), and wirings 3a, 3b and 3c (intervals between wirings 3a and 3b) having wiring width = 0.5 μm = Line-and-space wiring pattern 3 having a distance between wiring 3b and wiring 3c = 0.5 μm) was formed. The interval between the wiring pattern 2 and the wiring pattern 3 was 3 μm. By this process, a step was generated between the semiconductor substrate 1 and the wiring patterns 2 and 3.

Next, in the step shown in FIG. 3 (2), a plasma CVD method based on tetraethoxysilane (TEOS) is applied to the entire surface of the semiconductor substrate 1 and the wiring patterns 2 and 3 obtained in the step shown in FIG. 3 (1). Thus, the SiO ₂ layer 4 was formed with a thickness of 300 nm. Although the CVD oxide film 4 has good step coverage, the film formation is performed along the shape (step) of the base, so that the trench between the wirings cannot be buried.

Next, in the step shown in FIG. 3 (3), various coating liquids listed in Tables 3 and 4 synthesized by the above method are used as the raw material of the insulating film, and 0.7 to 1. The insulating film 5 was applied to a thickness of 1 μm, and prebaking treatment was performed in a nitrogen atmosphere at 80 ° C., 150 ° C., and 230 ° C. for 60 seconds. Thereafter, a curing (curing) treatment in nitrogen was performed at 400 ° C. for 30 minutes to form an insulating film 5. Thus, the semiconductor device 6 provided by the present invention was manufactured. The cross section of the insulating film 5 of the obtained semiconductor device 6 was observed. The flatness was evaluated by using a flatness scale (DOP) shown in FIG. The DOP (%), which is a measure of flatness, was determined by the following formula.
DOP (%) = {1− (θ / 90) (d ₀ / d _m )} × 100
Here, theta is the slope of the step of the insulating film 8 caused by the wiring 7, as shown in FIG. 4, d ₀ is the height difference between the insulating film 8, the thickness of d _m wiring 7.

The results of the flatness measurement are shown in Tables 3 and 4.
It can be seen that excellent flatness was achieved by using the SOG according to the present invention.

It is a ²⁹ Si-NMR spectrum of sample A (see Table 1) used in Example 1. It is a graph which shows the relationship between X defined by Formula [2] in Example 2, and the shrinkage | contraction rate of a dielectric film, a dielectric constant, and a water absorption. (1), (2), and (3) are partial cross-sectional schematic diagrams showing respective steps of a wiring layer pattern forming step, a CVD oxide film forming step, and an insulating film forming step in the manufacture of an insulating film for a semiconductor device according to the present invention. FIG. 10 is a schematic cross-sectional view of a step portion of an insulating film showing a method for obtaining DOP which is a measure of flatness measured in Example 3. FIG.

Claims (3)

A coating solution for forming an insulating film used for manufacturing a semiconductor device, comprising a siloxane represented by the following formula [1] containing a Si atom bonded to at least one organic substituent, and the siloxane Using the coating solution for forming an insulating film containing a siloxane in which the content ratio X represented by the following formula [2] obtained from the integral value of the ²⁹ Si-NMR spectrum of the above satisfies the following formula [2]: A semiconductor comprising a step of drying after coating a film-forming coating solution, holding the fluid at 150 ° C. to 300 ° C., and further curing at 350 ° C. to 450 ° C. A method for forming an insulating film for a device.

In the above formula [1],
k, l, n: An integer of 0 to 1000.
m: An integer of 1-1000.
R: represents at least one organic substituent selected from a saturated hydrocarbon group, an unsaturated hydrocarbon group, and a phenyl group, which may be the same or different. As the phenyl group, a phenyl group having a substituent But you can.
The oxygen atom is bonded to any one of Si, R, and H.

In the above formula [2],
A ₀ : The area of the Si signal attributed to Si having no Si—C bond, as determined from the ²⁹ Si-NMR spectrum,
A ₁ : Area of Si signal attributed to Si having one Si—C bond, determined from ²⁹ Si-NMR spectrum,
A ₂ : the area of the Si signal attributed to Si having two Si—C bonds, determined from the ²⁹ Si-NMR spectrum,
A ₃ : Indicates the area of the Si signal attributed to Si having three Si—C bonds, determined from the ²⁹ Si-NMR spectrum.   The method for forming an insulating film for a semiconductor device according to claim 1, wherein the holding at a temperature of 150 ° C. or higher and 300 ° C. or lower is performed for 30 seconds or longer.   The method for forming an insulating film for a semiconductor device according to claim 1, wherein the curing is performed in nitrogen.

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