JP3426597B1 - Method for manufacturing semiconductor device - Google Patents

Abstract

An object of the present invention is to provide a method of manufacturing a semiconductor device in which an organic substance adhering to a substrate surface is efficiently removed to improve a withstand voltage characteristic of a silicon oxide film. SOLUTION: In a method of manufacturing a semiconductor device in which a polysilicon film is formed on a silicon oxide film, the semiconductor substrate on which the silicon oxide film is formed is treated with ozone in a cleaning solution containing sulfuric acid and hydrogen peroxide or ultrapure water. A method of manufacturing a semiconductor device, comprising: immersing in an added ozone-added cleaning water, and then forming a polysilicon film on the silicon oxide film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device using a polysilicon electrode as a gate electrode.

[0002]

2. Description of the Related Art As shown in FIG. 7, a semiconductor device using a polysilicon electrode as a gate electrode is manufactured by cleaning the surface of a substrate with ultrapure water in cleaning before gate oxidation to attach dust or dirt to the surface. After removing contaminants such as gate oxide, the substrate surface is oxidized by pyrogenic oxidation at about 850 ° C. to form a gate oxide film, and then a gate electrode layer made of polysilicon is formed on the surface. This is done by diffusing phosphorus into the layer to make it P-type and then patterning.

Generally, a gate electrode made of polysilicon is formed by a polysilicon electrode forming apparatus (vertical LPCVD) having a structure as shown in FIG. This polysilicon electrode forming apparatus forms a polysilicon when a polysilicon forming furnace 12 whose internal temperature is adjusted by a heater 10 and a plurality of wafers are charged and a wafer charging portion is loaded into the polysilicon forming furnace 12. A boat 14 for sealing the inside of the furnace 12 and an atmosphere adjusting means 16 for introducing a gas of a predetermined type into the polysilicon forming furnace 12 are provided.

A substrate having a gate oxide film formed on its surface is
Charged to the boat 14 while maintaining cleanliness, N
It is inserted into the polysilicon forming furnace 12 filled with ₂ gas. When the boat 14 is completely inserted into the polysilicon forming furnace 12 and the inside of the furnace 12 is sealed, the atmosphere adjusting means 16
Vacuum suction of about 1.0 × 10 ^-3 Torr
After adjusting the temperature to about 600 ℃ -700 ℃, SiH ₄
A gas is introduced to deposit polysilicon on the gate oxide film to form a polysilicon film. Then boat 14
Is taken out of the furnace 12 and conveyed into a diffusion furnace (not shown). After diffusing phosphorus in the diffusion furnace, patterning is performed by a patterning device (not shown) to form a gate electrode.

[0005]

All of the above steps are carried out in a clean room in which the cleanliness is adjusted to a high level. Phthalate ester, which is an aeration test agent for air, and DBP (dibutylph), which is a type of plasticizer that constitutes equipment, cassettes, boxes, etc.
or BHT (Butyl Hydroxytolu), which is a type of plasticizer that constitutes the wafer case.
Organic substances such as ene) may adhere to the surface of the substrate.

FIG. 9 and FIG. 10 show a wafer thermal desorption GC for organic substances adhering to the surface of a substrate that has been contaminated with organic substances.
-Shows the result measured by MS. The wafer thermal desorption GC-MS is an apparatus configured to subject the gas desorbed from the substrate surface to chromatography when the substrate is heated. In each of FIGS. 9 and 10, the vertical axis represents relative intensity and the horizontal axis represents The time is shown, and the higher the relative intensity, the larger the amount of organic substances attached, indicating that the substances detected at the same time are the same type of substance.

FIG. 9 shows the result of measuring the amount of organic substances adhering to the surface of the silicon substrate after cleaning with ultrapure water before forming the gate oxide film, and FIG. 10 shows the result of adhering to the surface of the silicon substrate after forming the gate oxide film. It is the result of measuring the amount of organic matter. Comparing FIG. 9 and FIG. 10, although the amount of organic substances adhering to the surface of the silicon substrate after gate oxidation is smaller than that of the surface of the silicon substrate after cleaning with ultrapure water, It can be seen that the organic substances attached to the surface of the silicon substrate are not completely removed.

Many of the organic substances attached to the surface of the silicon substrate by washing with ultrapure water with deteriorated water quality and the organic substances attached to the surface of the silicon substrate during the transportation of the substrate between the devices have a benzene ring. Of the organic substances having a benzene ring, those that react with the silicon oxide film during gate oxidation become difficult to burn, and remain on the surface of the silicon substrate even after gate oxidation. Such organic substances remaining on the surface of the silicon substrate cause deterioration of the dielectric strength characteristics of the gate oxide film.

Therefore, it is an object of the present invention to obtain a semiconductor device in which organic substances adhering to the surface of a substrate are efficiently removed to improve the dielectric strength characteristics of a silicon oxide film.

[0010]

In order to achieve the above object, in the method of manufacturing a semiconductor device according to the invention of claim 1, when the polysilicon film is formed on the silicon oxide film, the silicon oxide film is formed. The semiconductor substrate is immersed in a cleaning liquid containing sulfuric acid and hydrogen peroxide or ozone-added cleaning water in which ozone is added to ultrapure water, and then a polysilicon film is formed on the silicon oxide film. .

According to the first aspect of the present invention, after the silicon oxide film for the polysilicon electrode layer is formed on the semiconductor substrate, the semiconductor substrate is immersed in a cleaning solution containing sulfuric acid and hydrogen peroxide or ozone-added cleaning water. Since the polysilicon film is formed in a state where the organic substances adhering to the surface of the silicon oxide film have been removed by the immersion, a semiconductor device in which the dielectric strength characteristics of the silicon oxide film are improved can be obtained.

As described above, in the method for manufacturing a semiconductor device according to a second aspect of the present invention, in the method for manufacturing a semiconductor device according to the first aspect, the cleaning removes organic substances existing on the silicon oxide film by oxidation. It is characterized by being

Further, as in the method for manufacturing a semiconductor device according to the third aspect of the present invention, the cleaning liquid containing the sulfuric acid and the hydrogen peroxide is obtained by mixing the sulfuric acid and the hydrogen peroxide in a ratio of 9: 1. It is good to be

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
~ It demonstrates with reference to FIG. Wafer thermal desorption GC
-In all the diagrams showing the results measured by MS, the vertical axis represents relative intensity and the horizontal axis represents time. The higher the relative intensity, the greater the amount of organic substances attached, and those detected at the same time are of the same type. It is a substance.

(First Embodiment) The first embodiment will be described with reference to FIGS. First, as shown in FIG.
A silicon substrate having a pattern formed on its surface is washed with ultrapure water (cleaning before gate oxidation), and then a gate oxide film is formed by pyrogenic oxidation (gate oxidation). Next, the temperature of the obtained plurality of silicon substrates was adjusted to 125 ° C., and SPM (Surfic Peroxide mixture) in which sulfuric acid and hydrogen peroxide were mixed at a ratio of 9: 1.
e) Immerse in the cleaning liquid for about 5 minutes. At this time, the organic substances attached to the surface of the silicon substrate are oxidized and removed by the SPM cleaning liquid.

After that, a plurality of silicon substrates are charged in the vertical LPCVD boat described above, and then inserted into a polysilicon forming furnace in which the temperature inside the furnace is adjusted to about 620 ° C., and SiH ₄ gas is introduced into the polysilicon forming furnace. Is started to form a polysilicon film, and when a silicon film is formed to a predetermined thickness, phosphorus is diffused to form a P type, and then patterning is performed to obtain a polysilicon electrode.

FIG. 2 shows the results of measuring the amount of organic substances in the silicon substrate by the wafer thermal desorption GC-MS. Figure 2
In Table 1, Sample 1 is the result of measuring the amount of organic substances on the silicon substrate surface after cleaning with ultrapure water, Sample 2 is the amount of organic substances on the silicon substrate surface after gate oxidation, and Sample 3 is the result of measuring the amount of organic substances on the silicon substrate surface after SPM cleaning. Is. As is apparent from FIG. 2, it is found that most of the organic substances strongly adhered to the surface of the silicon substrate are removed by performing the SPM cleaning.

The results of examining the insulation resistance of the gate oxide film in the obtained gate electrode are shown in FIG. For comparison, FIG. 4 shows the results of examining the insulation resistance of the gate oxide film in the gate electrode obtained by forming the polysilicon film without performing SPM cleaning after the gate oxidation, and also shows the adhesion of organic substances to the substrate surface. FIG. 5 shows the results of examining the insulation resistance of the gate oxide film in the gate electrode obtained by forming a polysilicon film by performing SPM cleaning after gate oxidation using a substrate without a substrate. FIG. 6 shows the results of examining the insulation resistance of the gate oxide film in the gate electrode obtained by forming a polysilicon film without performing SPM cleaning after the gate oxidation using.

As shown in FIGS. 5 and 6, when a substrate having no organic substance adhered to the substrate surface is used, it has good insulation resistance whether SPM cleaning is performed or not. Has become. On the other hand, as shown in FIG. 4, when an organic substance is attached to the surface of the substrate, the insulation resistance of the gate oxide film in the gate electrode obtained by forming the polysilicon film without SPM cleaning is very poor. I understand.

That is, as shown in FIG. 3, the gate oxide film in the gate electrode obtained in the first embodiment is
Similar to FIGS. 5 and 6, it has a good insulation resistance, and the insulation resistance is better than that of the case where a gate electrode without SPM cleaning is formed on a silicon substrate on which organic substances adhere to the substrate surface. You can see that it is improving.

In the above-described first embodiment, the case where the SPM cleaning liquid in which sulfuric acid and hydrogen peroxide are mixed at a ratio of 9: 1 is used is described. However, if it is used as the SPM cleaning liquid, sulfuric acid is used. The ratio with hydrogen peroxide may be any ratio.

Further, instead of the SPM cleaning liquid, ozone-added cleaning water which is ultrapure water to which ozone is added to enhance the oxidizing property may be used. Also in this case, the amount of organic substances on the surface of the silicon substrate after cleaning and the insulation resistance of the gate oxide film in the obtained gate electrode are almost the same as those in the above-described first embodiment, and therefore the illustration is omitted. .

Although the SPM cleaning liquid and the ozone-added cleaning water have been described as the cleaning liquid after the gate cleaning in the first embodiment, the cleaning liquid is not limited to these and any cleaning liquid that does not etch the silicon substrate may be used. it can.

In the first embodiment described above, the case of improving the insulation resistance of the gate oxide film in the gate electrode has been described. However, the present invention improves the insulation resistance of other silicon oxide films. Can also be applied to.

[0025]

As described above, according to the first to fourth aspects of the present invention, most of the organic substances strongly adhered to the surface of the silicon substrate can be removed, so that the semiconductor having improved dielectric strength characteristics of the silicon oxide film. The effect that a device can be manufactured is achieved.

[Brief description of drawings]

FIG. 1 is a flow chart briefly showing a first embodiment of the present invention.

FIG. 2 shows the amount of organic substances adhering to the surface of a silicon substrate during pre-gate oxidation cleaning, the amount of organic substances adhering to the surface of a silicon substrate after gate oxidation, and the amount of organic substances adhering to the surface of a silicon substrate after SPM cleaning. FIG.

FIG. 3 is a histogram showing insulation resistance of a gate oxide film in a gate electrode obtained in the second embodiment.

FIG. 4 is a histogram showing insulation resistance of a gate oxide film in a gate electrode obtained by forming a polysilicon film without performing SPM cleaning after gate oxidation.

FIG. 5 is a histogram showing the insulation resistance of a gate oxide film in a gate electrode obtained by forming a polysilicon film by performing SPM cleaning after gate oxidation using a substrate on the surface of which no organic substance is attached.

FIG. 6 is a histogram showing the insulation resistance of the gate oxide film in a gate electrode obtained by forming a polysilicon film without performing SPM cleaning after gate oxidation using a substrate on the surface of which no organic substance is attached.

FIG. 7 is a flow chart briefly showing a step of forming a conventional gate electrode.

FIG. 8 is an explanatory view briefly showing the configuration of vertical LPCVD.

FIG. 9 is a measurement diagram showing the amount of organic substances attached to the surface of a silicon substrate after cleaning with ultrapure water before forming a gate oxide film.

FIG. 10 is a measurement diagram showing the amount of organic substances adhering to the surface of a silicon substrate after forming a gate oxide film.

[Explanation of symbols]

10 heater 12 Polysilicon forming furnace 14 boats 16 Atmosphere adjusting means

Claims (3)

(57) [Claims] 1. A method of manufacturing a semiconductor device in which a polysilicon film is formed on a silicon oxide film, wherein the semiconductor substrate on which the silicon oxide film is formed is cleaned with a cleaning liquid containing sulfuric acid and hydrogen peroxide or ultrapure water and ozone. A method of manufacturing a semiconductor device, comprising: forming a polysilicon film on the silicon oxide film after immersing the cleaning film in ozone-added cleaning water. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the cleaning removes organic substances existing on the silicon oxide film by oxidation. 3. The semiconductor according to claim 1, wherein the cleaning liquid containing the sulfuric acid and the hydrogen peroxide contains the sulfuric acid and the hydrogen peroxide mixed in a ratio of 9: 1. Device manufacturing method.