JP2958467B2 - Method for manufacturing silicon oxide film of semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a silicon oxide film of a semiconductor device in which an SiO ₂ film is formed by a CVD method using a novel liquid material.

(Prior Art) The CVD method is a method of forming a desired thin film by sending one or more compound gases composed of elements constituting a thin film to a substrate surface and causing a chemical reaction on the substrate surface.

Conventionally, a SiH ₄ gaseous raw material has been used as a SiO ₂ -based CVD film forming material.

However, the pattern dimensions used for integrated circuits have continued to shrink with the increasing density of circuit patterns,
We are now in the submicron era. In addition, as LSIs become finer and more highly integrated, the area occupied by the wiring in the chip increases, and the number of wiring layers has further increased. Further, in the future multilayer wiring, the aspect ratio of the wiring has been increased due to the need to keep the wiring resistance small, and as a result, the unevenness of the substrate surface has become more and more severe. Therefore, planarization of an insulating film such as SiO ₂ is an indispensable technology.

In a conventional CVD process using a SiH ₄ gas source, steps and irregularities on a substrate cannot be flattened.

Further, in this CVD process, voids are formed between narrow electrodes or in a trench of a gate, and the film characteristics are remarkably deteriorated.

In addition, SiH ₄ is a self-igniting and extremely dangerous raw material.

In order to overcome the above drawbacks, recently, instead of SiH ₄ , a liquid raw material, tetraethoxysilane Si (OC
₂ H ₅₎ CVD method using ₄ are commercialized, it has become popular.

In this method, tetraethoxysilane is vaporized and introduced into a CVD reaction chamber.

The film grown by the CVD method using tetraethoxysilane has excellent step coverage, flattenability, etc., and tetraethoxysilane has no self-ignition property and is a very safe raw material in the manufacturing process of semiconductor devices. .

Further, as a feature of the flattening CVD film, even in a high-density pattern portion, a flattening film without voids can be achieved by reflow processing.

However, the film grown by the CVD method using tetraethoxysilane still has problems in the film quality such as its denseness, crack resistance, and insulating properties, and it is difficult to form a film so as to reduce this problem. Requires substrate heating of 600-700 ° C.

Therefore, when the SiO ₂ film is formed on the aluminum wiring by the CVD method using tetraethoxysilane, there is a disadvantage that the aluminum wiring is significantly deteriorated.

Therefore, a CVD liquid raw material that does not require high-temperature substrate heating and can form an SiO ₂ film at a lower temperature than tetraethoxysilane has been desired.

(Problems to be Solved) The present inventors have found that SiO _{2 can be used at a} lower temperature than tetraethoxysilane.
Manufacture of SiO ₂ film for semiconductor devices using a novel liquid raw material that can form a film, is excellent in step coverage, flatness, etc., and is also excellent in film quality such as denseness, crack resistance, insulation, etc. The law has applied for a patent. (Japanese Patent Application No. Hei 2-20121) The present invention relates to an improvement of this production method.

(Means for Solving the Problem) The present invention relates to a trialkoxy having one H group such as tripropoxysilane or tributoxysilane as a novel liquid material when an SiO ₂ film of a semiconductor device is manufactured by a CVD method. It is characterized by using silane or dialkoxysilane having two H groups such as dipropoxysilane or dibutoxysilane.

Tetraethoxysilane has a structure in which four ethoxy groups are attached to Si, whereas tripropoxysilane has a structure in which propoxy groups 3
And one hydrogen per Si, tributoxysilane has three butoxy groups and one hydrogen per Si, dipropoxysilane has two propoxy groups and two hydrogen per Si, and dibutoxysilane has two butoxy groups. It has a structure in which two hydrogen atoms are attached to Si, and is a colorless and transparent liquid at normal temperature.

Tripropoxysilane is n-HSi (OC ₃ H ₇ ) ₃ , i-HS
i (OC ₃ H ₇ ) ₃ etc., and tributoxysilane is n-HSi
(OC ₄ H ₉ ) ₃ , i-HSi (OC ₄ H ₉ ) ₃ , t-HSi (OC ₄ H ₉ )
₃ , sec-HSi (OC ₄ H ₉ ) _{3 and the} like.

Dipropoxy silane _{n-H 2 Si (OC 3} H 7) 2, i-H 2 S
i (OC ₃ H ₇ ) ₂ etc., and dibutoxysilane is n-H ₂ Si
_{(OC 4 H 9) 2,} i-H 2 Si (OC 4 H 9) 2, t-H 2 Si (OC
₄ including _{H 9) 2, sec-H} 2 Si (OC 4 H 9) 2 and the like.

The present invention is based on the following three facts obtained during the study of the decomposition of various alcoholates using pyrolysis gas chromatography and a plasma decomposition apparatus.

(1) The final thermal decomposition temperature of the metal alcoholate is determined by the side chain which is least likely to decompose among the side chains attached to the metal.

Taking Si as an example of a metal, methoxy group 700 ° C, ethoxy group 550 ° C, propoxy group 480 ° C, butoxy group 450
The higher the number of carbon atoms, such as ° C, the lower the final decomposition temperature.

(2) When the number of carbon atoms in the side chain increases, carbon tends to remain in the metal oxide film formed by decomposition.

(3) A low-viscosity liquid having a low vapor pressure can be formed on a silicon substrate by using an Si alkoxide and decreasing the plasma velocity.

Among them, (3) clarifies the reason why a flat oxide film can be formed by using tetraethoxysilane as a CVD material. That is, conventionally, it has been explained that a pseudo liquid is formed as the reason, but it is clarified that the pseudo liquid is not a liquid itself.

From this finding, it has been found that a CVD raw material that tends to become a low-viscosity liquid even when the liquid obtained in the decomposition process progresses is advantageous for flattening.

It is a well-known fact that polymetal alcoholate formed by decomposition has the lowest viscosity when it is a linear molecule, and solidifies or becomes highly viscous when it has a cyclic or three-dimensional structure. .

One gist of the present invention, one or two of the side chains of a metal, particularly silicon alkoxide, is a group that is particularly easily decomposed, and the remaining group is a group that is hardly decomposed. Is to make it small.

It is a well-known fact that the decomposition start temperature of silicon alkoxides is reduced to 200 to 300 ° C. by using active oxygen such as ozone.Under these conditions, alkoxides having a hydrogen group as a side chain are decomposed. Is easier to disassemble.

Another gist of the present invention is to select an alkoxide having a structure suitable for producing a linear molecule due to the ease of decomposition of the hydrogen group.

If the number of side-chain hydrogen groups is three or more, a three-dimensional steric structure is easily formed, which is not preferable.

An alkoxide having 5 or more carbon atoms in the side chain is not preferred because carbon tends to remain in the formed oxide film and tends to become a porous film.

As described above, the thermal decomposition temperature is, for example, HSi (OC
₂ H _{5) 3} than HSi (OC ₃ H _{7) 3} towards low, HSi (OC ₃ H _7)
3 from HSi (OC ₄ H _{9) 3} further lower the.

Therefore, when the SiO ₂ film of a semiconductor device is manufactured by the CVD method, HSi (OC ₃ H ₇ ) ₃ is used instead of HSi (OC ₂ H ₅ ) ₃ as a liquid material.
₃ or _{HSi (OC 4 H 9) 3} SiO 2 at lower temperatures is the law using
It was found that a film could be formed.

Process of tetraethoxysilane is SiO ₂ is once SiO ₂
Instead of (H ₅ C ₂ O) ₃ SiOSi (0C ₂ H ₅ ) ₃ , (H ₅ C ₂ O) ₃ SiOSi (0C
It is known that the intermediate condensate is converted to SiO ₂ via an intermediate condensate such as a dimer or trimer of tetraethoxysilane such as ₂ H ₅ ) ₂ OSi (OC ₂ H ₅ ) _3. Good step coverage,
It has a flattening property.

Tripropoxysilane or tributoxysilane,
Alternatively, dipropoxy silane or dibutoxy silane easily removes H in the molecule and enters O, and thus easily produces an intermediate condensate such as dimer or trimer than tetraethoxy silane. Excellent in chemical properties.

In addition, the decomposition product has an effect of converting the molecule into a linear molecule instead of a cyclic molecule.

Furthermore, it was found that the films grown by CVD using tripropoxysilane, tributoxysilane, or dipropoxysilane or dibutoxysilane also have extremely excellent film quality such as denseness, crack resistance, and insulating properties.

Further, these CVD raw materials are extremely safe raw materials in the manufacturing process of semiconductor devices, like tetraethoxysilane.

(Example 1) An Si substrate was placed in a plasma CVD apparatus, and the
Heated to ° C.

At 25 ° C., i-HSi (OC ₃ H ₇ ) ₃ was bubbled with a He carrier gas, introduced into a plasma CVD apparatus, mixed with oxygen in the apparatus, and a SiO ₂ film was formed on a Si substrate by plasma.

Plasma CVD using this film and tetraethoxysilane
As a result of comparing the film hardness with the film using a hardness meter, i-HS
It was found that the plasma CVD film using i (OC ₃ H ₇ ) ₃ had higher hardness and was sufficiently dense.

(Example 2) An Si substrate was set in a plasma CVD apparatus, and the substrate was
Heated to ° C.

At 25 ° C., n-HSi (OC ₄ H ₉ ) ₃ was bubbled with a He carrier gas, introduced into a plasma CVD apparatus, mixed with oxygen in the apparatus, and a SiO ₂ film was formed on a Si substrate by plasma.

Plasma CVD using this film and tetraethoxysilane
As a result of comparing the film hardness with the film using a hardness meter, it was found that the plasma CVD film using tributoxysilane had a higher hardness and was a sufficiently dense film.

(Effects of the Invention) According to the present invention, an SiO ₂ film can be formed at a lower temperature than tetraethoxysilane or triethoxysilane, and the film is excellent in step coverage and flattening property, hardness, and density. There is a feature that the film quality such as properties is also extremely excellent.

In addition, it has a feature that the film quality such as crack resistance and insulating property is extremely excellent.

Further, there is a feature that the safety is extremely high in the manufacturing process of the semiconductor device.

Claims (2)

(57) [Claims] An SiO ₂ film for a semiconductor device is formed by using a liquid material.
A method for producing a silicon oxide film for a semiconductor device, comprising using, as the liquid material, trialkoxysilane having one H group or dialkoxysilane having two H groups as the liquid material. 2. The trialkoxysilane having one H group is tripropoxysilane or tributoxysilane, and the dialkoxysilane having two H groups is dipropoxysilane or dibutoxysilane. 13. The method for producing a silicon oxide film of a semiconductor device according to claim 12.