JP3338470B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of cleaning a semiconductor substrate with an aqueous solution or pure water (cleaning step). The present invention relates to a method for manufacturing a semiconductor device capable of performing processing reliably and sufficiently. For example, according to the present invention, by allowing an aqueous solution or pure water to penetrate into the fine and high aspect ratio grooves formed in the semiconductor substrate, the inside of such fine and high aspect ratio grooves is reduced. And a method of dramatically improving the cleaning effect of the present invention.

[0002]

2. Description of the Related Art In recent years, the processing dimensions of semiconductor devices have been increasingly miniaturized, and the aspect ratio of grooves formed in a semiconductor substrate has been increasing. In particular, IEDM '
91 papers. In trench isolation as disclosed in 141, a groove having a pattern width of 1 μm or less and a depth of 10 μm or more may be formed. This groove is finally buried in a subsequent step, but it is necessary to clean the inside of the groove before the burying step. Hereinafter, the importance of cleaning will be described by taking a conventional method of forming a trench isolation as an example.

FIG. 4 is a sectional view of a semiconductor substrate in each step for forming a trench isolation. In the following description, a silicon (Si) substrate is used as an example of the semiconductor substrate 1.

[0004] A surface protection film 2 (resist) in which an isolation region is opened by a known patterning technique.
Is formed on the surface of the Si substrate 1, and the Si substrate 1 in the windowed area is etched to a desired depth using a plasma of a halon-based gas (for example, CF ₄ ). Thus, the structure shown in FIG. With the current processing technology,
It is easy to process the groove 1a having an aspect ratio of about 10.

In order to protect the inner wall of the groove 1a formed by the etching, the Si substrate 1 is oxidized to form silicon oxide 3 (SiO ₂ ) of about 50 nm on the surface of the Si substrate 1 including the inner wall of the groove. I do. Thus, the structure shown in FIG. By this step, the Si on the inner wall of the groove 1a is
-The interface of SiO ₂ becomes stable, and the leakage current flowing through this interface can be reduced to zero or minimized.

[0006] Poly-Si is deposited on the surface of the Si substrate 1 by using a known CVD technique, and then the entire surface is etched back, so that the trench 1a is buried.
4 to complete the trench isolation.

[0007] Of the trench isolation forming steps, the oxidizing step shown in FIG. 4 (b) is a crucial step that greatly affects the characteristics of elements formed on the Si substrate 1. More precisely, it is important to clean the surface of the Si substrate 1 immediately before the oxidation treatment. That is, in the oxidation step, if the by-product generated when the Si substrate 1 is etched remains inside the groove 1a,
During the oxidation step, the surface of the Si substrate 1 is contaminated and stable S
No i-SiO ₂ interface is formed, which causes leakage current. Therefore, cleaning using an aqueous ammonia solution (SC cleaning), cleaning using an aqueous acid solution (piranha cleaning), and the like have been conventionally performed before the oxidation treatment.

However, when the dimension of the groove 1a becomes 1 μm or less and the aspect ratio becomes large, as shown conceptually in FIG. 5, the cleaning aqueous solution 5 does not sufficiently enter the inside of the groove 1a, and the cavity 1b is formed. However, there is a problem that a portion 1c whose inner wall is not cleaned is formed inside the groove 1a, and the Si surface of the portion 1c cannot be cleaned. Such a problem is a known problem in the art, and has been conventionally examined by simulation evaluation and the like, and has been discussed at academic meetings, etc., but at present, no effective solution has yet been found. .

[0009]

SUMMARY OF THE INVENTION The present invention has been developed, for example, by developing a technique capable of reliably and sufficiently treating a semiconductor substrate when the semiconductor substrate is provided with an aqueous solution or pure water. The problem that the cleaning aqueous solution does not sufficiently enter the inside of the groove having a large aspect ratio and the surface of the Si substrate inside the groove cannot be cleaned can be solved. It is an object of the present invention to provide a semiconductor device having processing means which can be sufficiently penetrated and which can be applied to a cleaning technique in which a cleaning effect is enhanced.

[0010]

According to the present invention, there is provided a semiconductor device having a groove formed therein.
A method of treating a semiconductor substrate with an aqueous solution or pure water, the method comprising exposing the semiconductor substrate to an NH ₃ gas before treating the semiconductor substrate with the aqueous solution or pure water. Accordingly, the above object is achieved. Further, the present invention provides a method of manufacturing a semiconductor device having a step of treating a semiconductor substrate having a groove formed with an aqueous solution or pure water, wherein the semiconductor substrate is exposed to an NH ₃ gas before being treated with the aqueous solution or pure water.
Wherein the gas in the trench is replaced with NH ₃ gas, thereby achieving the above object.

According to the present invention, for example, before dipping a Si substrate in a cleaning solution, the Si substrate is exposed to a gas having a high solubility in water such as ammonia, and
After the inside of the groove formed in the i-substrate is replaced with the gas having high solubility, the Si substrate can be immersed in a cleaning liquid.

[0012]

According to the present invention, the semiconductor substrate to be processed is exposed to a gas having a high solubility in water before the processing, and then treated with an aqueous solution or pure water. With sufficient penetration and contact, sufficient aqueous treatment can be achieved. For this reason, for example, cleaning with an aqueous solution inside a groove having a high aspect ratio, which has not been conventionally solved,
It is possible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. Needless to say, the present invention is not limited by the embodiments.

Embodiment 1 In this embodiment, as shown in FIG. 1, for a semiconductor substrate 1 which has been subjected to various processes I such as formation of fine grooves 1a, this substrate 1 is converted into a gas having a high solubility, A step II of exposing to ammonia gas (NH ₃ ) is performed, and then a treatment step III with an aqueous solution or pure water, here, a cleaning step is performed.

In this embodiment, the following steps are performed in more detail.

The Si substrate 1 (see FIG. 4A) on which the groove 1a is formed by using the conventional technique is left in an ammonia (NH ₃ ) atmosphere, and the inside of the groove 1a is replaced with air by NH ₃ gas. . At this time, in order to increase the replacement efficiency, FIG.
In the apparatus shown in (1), the Si substrate 1 is set in a vacuum apparatus 6, and once evacuated (low pressure) by a vacuum pump 6a and then filled with NH ₃ gas, so that the inside of the fine and high-aspect-ratio groove can be formed. , Can be sufficiently replaced with NH ₃ gas. In FIG. 2, 6b is an NH ₃ gas supply source, 1 is S
i-substrate.

Next, the Si substrate 1 is immersed in an SC cleaning solution, that is, an aqueous ammonia solution (NH ₄ OH) mixed with a hydrogen peroxide solution (H ₂ O ₂ ). As schematically shown in FIG. 3, the NH ₃ gas, which is a gas 7 having high solubility, is positively dissolved in the aqueous solution, so that the inside of the groove 1a becomes a negative pressure with respect to the atmospheric pressure, and the cleaning solution is removed. It is positively sucked into the groove. At this time, NH dissolved in the cleaning solution
₃ is combined with water (H ₂ O) in the solution to form NH ₄ OH and becomes a component of the cleaning solution, so that it has no effect on the cleaning effect, and has no special effect on the Si substrate 1. It has no effect. Since the cleaning effect of the SC cleaning solution is clear in the art, the description is omitted here.

In this embodiment, ammonia gas is used as a gas having a high solubility. It is clear from the data (according to the scientific chronological table) shown in Table 1 that the ammonia gas has a high solubility in water.

Table 1 Solubility: A value obtained by converting the volume of a gas at 1 atm. Dissolved in 1 cm ³ of water into the volume at 0 ° C. and 1 atm.

As described in detail above, according to this embodiment, the SC cleaning solution for purifying the surface of the Si substrate 1 can penetrate into the fine and high aspect ratio grooves 1a. It is also possible to sufficiently clean the inner wall of a fine groove having a high aspect ratio, which has been impossible in the past.

In the above description, a silicon substrate is taken as an example of a semiconductor substrate, ammonia gas is taken as a gas having high solubility, and an SC solution is taken as an example of a cleaning solution. This patent does not limit these materials.

[0021]

According to the present invention, when a process for treating a semiconductor substrate with an aqueous solution or pure water is provided, it is possible to provide a technique capable of performing the treatment reliably and sufficiently. Thus, for example, even when cleaning a semiconductor substrate having a groove having a large aspect ratio, a cleaning aqueous solution can sufficiently penetrate into the groove, and effective cleaning can be performed.

[Brief description of the drawings]

FIG. 1 is a flowchart of a first embodiment.

FIG. 2 is a system diagram of an NH ₃ gas replacement device used in Embodiment 1.

FIG. 3 is a conceptual diagram illustrating an effect of the first embodiment.

FIG. 4 is a cross-sectional view in each step for forming a trench isolation.

FIG. 5 is a diagram showing a problem of the related art.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate (Si substrate) 1a groove 7 gas having high solubility (ammonia gas) II process of exposing to gas having high solubility III treatment process with aqueous solution or pure water (cleaning process)

Claims (2)

(57) [Claims] In a method of manufacturing a semiconductor device, the method includes a step of treating a semiconductor substrate with a groove formed therein with an aqueous solution or pure water.
A method for manufacturing a semiconductor device , comprising exposing to a NH ₃ gas . 2. A method for manufacturing a semiconductor device, comprising the step of treating a semiconductor substrate with a groove formed therein with an aqueous solution or pure water, prior to treating the semiconductor substrate with an aqueous solution or pure water.
The gas in the groove is exposed to NH ₃ gas by exposing it to NH ₃ gas.
A method for manufacturing a semiconductor device, comprising: