JP5495478B2 - Trench filling composition - Google Patents

Description

  The present invention relates to a burying composition for trench isolation used for element isolation of a semiconductor device and a trench burying method using the same.

In a semiconductor device, it is necessary to form a region called element isolation in order to electrically isolate elements created in a substrate from each other. In the old days, a method called LOCOS (LOCal Oxidation of Silicon) that selectively oxidizes the element isolation region of the semiconductor substrate was used. However, as a method advantageous for further miniaturization, a trench is previously formed on the surface of the semiconductor substrate. After that, trench isolation in which an oxide is buried in the portion is widely used.
The most common method for embedding an oxide in a trench is a chemical vapor deposition method, but several methods have been proposed in which a liquid composition is applied and then sintered. Examples of such compositions include, for example, a perhydrogenated silazane polymer solution (Patent Document 1), a higher order silane-containing solution (Patent Document 2), a composition in which silicon oxide particles and a silicon-containing binder are mixed with an organic solvent. There is a thing (patent document 3).

  These methods have the advantage of being able to deal with finer trenches than the vapor phase chemical growth method, but they both require an organic solvent, so that carbon that has decomposed during the sintering process remains. It has the problem of being easy. As a method for solving this problem, a method of performing a sintering process at a high temperature of 900 ° C. (Patent Document 1) and a method of performing a sintering process in an oxidizing atmosphere (Patent Documents 2 and 3) have been proposed. However, since these methods decompose organic substances by heat or decompose them by oxidation to volatilize organic substances from the opening of the trench, there is a concern that carbon at the bottom of the trench cannot be sufficiently removed. In addition, the high temperature sintering process has the undesirable effect of thermally diffusing the dopant doped in the semiconductor substrate. The problem of thermal diffusion of dopants becomes more serious in advanced generations where coating-type compositions are required instead of vapor phase chemical growth.

JP-A-11-307626 JP 2003-31568 A JP 2006-310448 A

  The present invention can realize trench isolation comprising an oxide film having an amount of carbon atoms as an impurity of 0.1 mmol or less per cubic centimeter, without using an oxidizing atmosphere or an extremely high temperature environment. It is intended to provide a composition for use.

  An object of the present invention is to provide a trench filling composition containing silicon oxide particles and a solvent, wherein the solvent contains 90 parts by mass or more of water when the total amount of the solvent is 100 parts by mass. It can be solved by the composition.

  By performing trench burying using the composition of the present invention, the amount of carbon remaining as an impurity is 0.1 mmol or less per cubic centimeter in terms of carbon atoms without using an oxidizing atmosphere or an extremely high temperature environment. Trench isolation consisting of a film can be realized.

The trench filling composition of the present invention contains silicon oxide particles and a solvent for dispersing them, and when the total amount of the solvent is 100 parts by mass, it must contain 90 parts by mass or more of water. Hereinafter, the composition of the present invention will be described.
(1) Silicon oxide particles Silicon oxide particles and methods for producing the same are known. Examples include fumed silica obtained by oxidizing silicon halide and colloidal silica obtained by hydrolytic condensation of alkoxysilane. The latter colloidal silica is advantageous in realizing a low impurity concentration required for element isolation of a semiconductor device.
In general, since the silicon oxide particles have a certain size distribution, even if the average particle size is larger than the opening width of the trench, it does not necessarily hinder the achievement of the object of the present invention. A width smaller than the opening width of the trench is preferable because the trench can be embedded more efficiently.

(2) Solvent To achieve the object of the present invention, it is important that water is 90 parts by mass or more when the total amount of the solvent is 100 parts by mass. The ratio of water is more preferably 95 parts by mass or more.
Components other than water are less than 10 parts by weight, more preferably 3 parts by weight for the purpose of improving film thickness uniformity when applying the composition of the present invention and adjusting the viscosity to obtain a desired film thickness. It is also possible to add up to part of organic matter. Since the object of the present invention is to reduce the amount of residual carbon in the finally obtained silicon oxide, the organic substance to be added is selected from those that easily volatilize or decompose by heating in an inert atmosphere, and The addition amount is preferably as small as possible. Moreover, since the main component of the solvent is water, those having a high affinity for water are preferable. Examples of such organic substances include methanol, ethanol, isopropanol, polyvinyl alcohol, and polyethylene glycol. The preferred addition amount depends on the kind of the organic substance to be added, but for example, in the case of methanol and ethanol, it is less than 10 parts by mass relative to the whole solvent, in the case of polyvinyl alcohol and polyethylene glycol, 5 parts by mass or less, more preferably 3 parts by mass. Or less.

The ratio between the silicon oxide particles and the solvent is not particularly limited in achieving the object of the present invention, but the silicon oxide particles in the composition are stabilized and a film thickness usually used in a semiconductor device is easily formed. For this purpose, it is preferable to prepare the silicon oxide particles in a range of 0.5 to 30 parts by mass when the total composition is 100 parts by mass.
Next, a method for filling a trench using the composition of the present invention will be described.
A trench is formed in a substrate by a known method, for example, as described in Patent Document 1, a photoresist pattern is formed on a silicon nitride film formed on the substrate by vapor phase chemical growth in advance by dry etching. A method of transferring and dry etching the substrate using this silicon nitride film as a mask can be used.
The substrate to which the composition of the present invention can be applied is not particularly limited, but can be suitably used for a substrate made of, for example, silicon, gallium arsenide, or indium arsenide.

The shape of the trench to which the composition of the present invention is applied is not particularly limited, but a trench having an opening width of 20 nm to 300 nm and an aspect ratio of 5 to 30 can be particularly preferably used.
In the step of applying the composition of the present invention to a substrate having a trench to form a trench-coated composition-coated substrate, any of known methods such as spin coating and dip coating may be used. The spin coating method is preferably used for manufacturing the apparatus.
Next, in order to remove a solvent, the process of heating the composition application | coating base material for trench embedding of this invention is passed. Specifically, the composition-applying base material for trench embedding is heated in a process usually called pre-baking. In the present invention, since the solvent is mainly water, it is preferably heated at 100 ° C. or higher and 150 ° C. or lower. In addition, since the diffusion of the dopant in the semiconductor substrate does not become a problem at a temperature in this range, the atmosphere during heating may be an inert atmosphere or in the air.

  Finally, the semiconductor substrate is sintered to form a desired trench isolation region. Sintering is performed using a heating device such as a furnace or an oven. The heating temperature is 200 ° C to 900 ° C, more preferably 200 ° C to 500 ° C, still more preferably 200 ° C to 400 ° C. The atmosphere at that time is preferably an inert atmosphere such as nitrogen or argon having an oxygen concentration of 1000 ppm or less, more preferably 500 ppm or less. In the case where an organic substance as described above is added to the solvent, a step of heating in an oxygen or air atmosphere may be added for the purpose of more completely removing carbon contained therein. 550 ° C. or lower, more preferably 250 ° C. or lower, is preferable in that the diffusion of the dopant can be suppressed. In addition, after this step, when further sintering is performed at a higher temperature, it is preferable to replace the atmosphere with an inert atmosphere and then raise the temperature to a desired temperature.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1]
A composition for filling trenches is prepared by adding polyvinyl alcohol “Kuraray Poval 205C” manufactured by Kuraray Co., Ltd. to colloidal silica “Quartron PL-06L” manufactured by Fuso Chemical Co., Ltd. (average particle size 6 nm, using water and methanol as solvents). It was. The composition was prepared such that silicon oxide particles were 4.7 parts by mass, polyvinyl alcohol 2.0 parts by mass, water 91.3 parts by mass, and methanol 2.0 parts by mass with respect to 100 parts by mass of the composition (application of this). Called Liquid A). In the coating liquid A, the amount of water with respect to 100 parts by mass of the solvent is 95.8 parts by mass.

The obtained composition was applied to a 150 mm diameter silicon wafer having no trench formed at a rotation speed of 1000 rpm, and then heated in air at 140 ° C. for 2 minutes using a hot plate. This operation was repeated four times to obtain a thin film having a thickness of 1 μm.
This silicon wafer with a thin film was sintered in a nitrogen atmosphere at 800 ° C. for 2 hours using a vertical furnace. The amount of carbon remaining in the obtained thin film was analyzed with a secondary ion mass spectrometer (SIMS). For determination of carbon, a standard sample (MB-f1702 manufactured by Toray Research Center, Inc.) in which carbon was ion-implanted into silicon dioxide was used. The result was 0.08 mmol in terms of carbon atoms per cubic centimeter.

[Example 2]
The coating liquid A was applied and baked under the same conditions as in Example 1 using a 150 mm silicon wafer in which a trench having a width of 300 nm and a depth of 5000 nm was previously formed. When the obtained sample was cleaved and observed with a scanning electron microscope, an oxide film free from cracks and voids was formed in the trench.
[Comparative Example 1]
Colloidal silica “OSCAL1421” (average particle diameter: 7 nm, using isopropanol as a solvent) manufactured by Catalyst Chemical Co., Ltd. was directly used as a trench filling composition (referred to as coating solution B). Silicon oxide particles are 20.5 parts by mass, isopropanol is 79.5 parts by mass, and water is not contained, relative to 100 parts by mass of the composition. After coating and baking the coating liquid B under the same conditions as in Example 1, the amount of residual carbon was measured by the same method as in Example 1. The amount of carbon atoms per cubic centimeter was 0.8 mmol.

INDUSTRIAL APPLICABILITY The present invention can be suitably used for an oxide film forming application for trench isolation used for element isolation of various memory devices and logic devices.

Claims (2)

In the trench embedding composition containing silicon oxide particles and a solvent, when the whole composition is 100 parts by mass, the silicon oxide particles are contained in an amount of 0.5 to 30 parts by mass , and the solvent is 100 parts by mass. A trench filling composition comprising: 90 parts by mass or more of water, and further containing 5 parts by mass or less of polyvinyl alcohol with respect to the total solvent . A trench comprising a step of applying the trench filling composition according to claim 1 to a substrate having a trench to form a trench coating composition coating substrate, and a step of heating the trench filling composition coating substrate. A trenching method , wherein the heating step includes a step of heating at 200 ° C. to 550 ° C. in an oxygen atmosphere and a step of heating at 200 ° C. to 900 ° C. in an inert atmosphere. Embed method .