JP3481613B2 - Semiconductor manufacturing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As shown in FIG. 10, in manufacturing a semiconductor device using a polysilicon electrode as a gate electrode, in cleaning before gate oxidation, the surface of a substrate is cleaned with ultrapure water to attach dust and dirt to the surface. After removing contaminants such as
In the gate oxidation, the substrate surface is oxidized by pyrogenic oxidation at about 850 ° C. to form a gate oxide film, then a gate electrode layer made of polysilicon is formed on the surface, and phosphorus is diffused into the gate electrode layer to form a P type. Then, the patterning is performed.

Generally, a gate electrode made of polysilicon is formed by a polysilicon electrode forming device (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.

FIGS. 12 and 13 show the wafer thermal desorption G of the organic substances attached to the surface of the substrate which has been contaminated with the organic substances.
The result measured by C-MS is shown. 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. 12 and 13, 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 kind of substance.

FIG. 12 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. 13 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. 12 and FIG. 13, although the amount of attached organic substances on the surface of the silicon substrate after the gate oxidation is smaller than that on the surface of the silicon substrate after cleaning with ultrapure water, the amount of organic matter adhered by the gate oxidation is smaller. 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, an object of the present invention is to obtain a semiconductor device in which organic substances adhering to the surface of a gate oxide film are efficiently removed to improve the dielectric strength characteristics of the gate oxide film.

[0010]

In order to achieve the above object, in the semiconductor manufacturing apparatus according to the invention of claim 1, silane gas is introduced into the reaction furnace to form a gate electrode made of polysilicon on the gate oxide film. A semiconductor manufacturing apparatus for
A means for inserting the semiconductor substrate on which the gate oxide film is formed into the reaction furnace, a means for holding the semiconductor substrate in the reaction furnace under an atmosphere of silane gas and oxygen-based gas for a certain time, and for a certain time After that, a means for sucking the inside of the reaction furnace and a means for forming the gate electrode on the gate oxide film after the suction are provided.

According to the first aspect of the present invention, the semiconductor substrate on which the gate oxide film is formed is held in the reaction furnace at a high temperature, preferably at the polysilicon film forming temperature in an atmosphere of silane gas and oxygen-based gas for a certain period of time. ing. Therefore, the organic matter adhering to the surface of the gate oxide film reacts with the silane gas due to the oxidizing power of oxygen contained in the oxygen-based gas to silylate,
The benzene ring is decomposed.

When the benzene ring is decomposed, the force of adhering to the surface of the gate oxide film is weakened, so that it can be easily removed from the surface of the gate oxide film by subsequent suction in the furnace. Therefore,
A semiconductor device in which the dielectric strength characteristics of the silicon oxide film are improved can be obtained.

According to a second aspect of the semiconductor manufacturing apparatus of the present invention, in the semiconductor manufacturing apparatus of the first aspect, the semiconductor substrate on which the gate oxide film is formed is held in the reaction furnace so that the gate is formed. It is characterized in that an organic substance having a benzene ring existing on the oxide film is decomposed into a linear ester.

According to the second aspect of the present invention, the organic matter attached to the surface of the gate oxide film reacts with silicon due to the oxidizing power of oxygen contained in the silane gas and the oxygen-based gas to be silylated, and the benzene ring has a straight chain ester. Is decomposed into. The linear ester is then sucked in the furnace,
It is easily removed from the surface of the gate oxide film.

A semiconductor manufacturing apparatus according to a third aspect of the present invention is the semiconductor manufacturing apparatus according to the first or second aspect,
It is characterized in that the oxygen-based gas is selected from the atmosphere, oxygen gas, and ozone gas.

A semiconductor manufacturing apparatus according to a fifth aspect of the present invention is the semiconductor manufacturing apparatus according to the first or second aspect,
The oxygen-based gas is oxygen in the atmosphere flowing into the reaction furnace when the semiconductor substrate is inserted into the reaction furnace.

If atmospheric air is used as the oxygen-based gas, it is not necessary to prepare a special device for introducing the gas, and therefore there is an advantage that facility cost and manufacturing cost are not required. Further, when oxygen gas is used as the oxygen-based gas, the efficiency of the reaction for silylating the benzene ring is improved, and the time of leaving it in the silane gas and the oxygen-based gas at the silicon film forming temperature can be shortened. Further, when ozone gas having a strong oxidizing power is used as the oxygen-based gas, the efficiency of the reaction for silylating the benzene ring is further improved, and the silicon film formation temperature when left in the silane gas and the oxygen-based gas is lowered. It can be done and the leaving time can be shortened.

A semiconductor manufacturing apparatus according to a fourth aspect of the present invention is the semiconductor manufacturing apparatus according to the third aspect, further comprising an injector for introducing the oxygen gas or the ozone gas into the reaction furnace. .

In the invention of claim 4, oxygen gas or ozone gas is introduced from the outside into the reaction furnace by an injector, and the inside of the furnace is kept under an atmosphere of silane gas and oxygen gas or ozone gas.

Further, in the semiconductor manufacturing apparatus according to the first aspect, it is preferable that the temperature in the reaction furnace is adjusted to 500 ° C. or more and 700 ° C. or less when holding the semiconductor substrate for a certain period. If the temperature is 500 ° C. or lower, the organic substances attached to the gate oxide film cannot be sufficiently silylated, and
When the temperature is higher than 00 ° C, another reaction of silicon proceeds, which is not preferable. From this, the holding temperature of the semiconductor substrate in the furnace is 500 ° C. or higher and 700 ° C. or lower, preferably 60 ° C.
When the temperature is 0 ° C. or higher and 700 ° C. or lower, more preferably about 620 ° C., organic substances can be efficiently removed.

[0021]

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 obtained plurality of silicon substrates are connected to the vertical LPC described above.
Charge the VD boat. After charging a plurality of silicon substrates into the boat, the boat is inserted into a polysilicon forming furnace whose furnace temperature is adjusted to about 620 ° C., and the inside of the polysilicon forming furnace is sealed and left for about 10 minutes.

At this time, organic substances adhering to the surface of the silicon substrate are removed by the oxygen in the air that has entered the polysilicon forming furnace as the boat is inserted and the SiH ₄ gas introduced in the previous treatment and remaining in the polysilicon forming furnace. Is silylated. By this silylation, the benzene ring is decomposed and the organic matter is converted into a linear silylated ester. For example, C ₆ H
_{7 SC (Si (CH 3)} 3) HC 2 H 3 is, (CH _3)
3 SiOCOC (Si (CH ₃ ) ₃ ) HCOOSi (C
H ₃ ) ₃ and (CH ₃ ) ₃ SiOCOSi (CH ₃ ) ₃
Be decomposed into.

Then, the inside of the polysilicon forming furnace is sucked by a suction device. FIG. 2 shows the result of measurement of the amount of organic substances attached to the surface of the silicon substrate at this time by wafer thermal desorption GC-MS. For comparison, the result of measuring the amount of organic substances on the surface of the silicon substrate when the boat was inserted into the polysilicon forming furnace in a state where the inside of the polysilicon forming furnace was filled with nitrogen and the silicon substrate was left in a nitrogen atmosphere FIG. 3 shows the amount of organic substances on the surface of a silicon substrate when the boat is inserted into the polysilicon forming furnace with the polysilicon forming furnace filled with nitrogen and the silicon substrate is left in a nitrogen atmosphere and vacuum suction is performed. The measurement results are shown in FIG. 4, and the results of measuring the amount of organic substances on the surface of the silicon substrate when the silicon substrate was left in the state where air was introduced while the boat was inserted into the polysilicon forming furnace are shown in FIG. 5, respectively.

As is clear from the comparison between FIG. 2 and FIGS. 3 to 5, the surface of the silicon substrate when the silicon substrate is left in a state where the boat is inserted into the polysilicon forming furnace and air is introduced and vacuum suction is performed. It can be said that almost no organic matter remains in the. That is, it can be said that the linear silylated ester formed by the silylation is easily removed from the surface of the silicon substrate by suction.

After that, SiH ₄ gas is introduced into the polysilicon forming furnace to start the formation of the polysilicon film, and when the silicon film is formed to a predetermined thickness, phosphorus is diffused to form P.
After forming the mold, patterning is performed to obtain a polysilicon electrode.

FIG. 6 shows the result of examining the insulation resistance of the gate oxide film in the obtained gate electrode. In FIG.
The horizontal axis shows voltage (V), and the vertical axis shows breakdown voltage failure rate (%). Similarly, in all of the below-described diagrams that examine insulation resistance, the horizontal axis shows voltage (V). The vertical axis represents the breakdown voltage defective rate (%), which suggests that the higher the breakdown voltage defective rate (%), the more current flows.

For comparison, a boat is inserted into the polysilicon forming furnace in a state where the inside of the polysilicon forming furnace is filled with nitrogen, the silicon substrate is left in a nitrogen atmosphere and vacuum suction is performed, and then the polysilicon film is removed. Fig. 7 shows the results of examining the insulation resistance of the gate oxide film in the formed gate electrode. Also, using a substrate with no organic substances attached to the substrate surface, insert the boat into a nitrogen-filled polysilicon forming furnace. Then, the silicon substrate is left to stand and vacuum insulation is performed, then a polysilicon film is formed, and the insulation resistance of the gate oxide film in the gate electrode obtained is examined. The results are shown in FIG. The gate electrode was obtained by forming a polysilicon film after leaving the silicon substrate in a state where air was introduced while the boat was inserted into the polysilicon forming furnace and vacuum suction was performed. The results of examining the dielectric strength of the gate oxide film are shown in FIG.

As shown in FIGS. 8 and 9, when a substrate having no organic substances attached to the substrate surface is used, good insulation resistance is obtained even if air or nitrogen is introduced into the polysilicon forming furnace. It has become. On the other hand, as shown in FIG. 7, when an organic substance adheres to the surface of the substrate, the boat is inserted into the polysilicon forming furnace in a state where the inside of the polysilicon forming furnace is filled with nitrogen, and the silicon substrate is placed in a nitrogen atmosphere. It can be seen that the insulation resistance of the gate oxide film in the gate electrode obtained by forming a polysilicon film after leaving it under vacuum suction is very poor.

That is, as shown in FIG. 6, the gate oxide film in the gate electrode obtained in the first embodiment is
As in FIGS. 8 and 9, it has a good insulation resistance, and nitrogen was introduced without introducing air when leaving a silicon substrate in which organic substances adhere to the substrate surface in a polysilicon forming furnace. It can be seen that the insulation resistance is improved even when compared with the case.

Furthermore, since the silicon substrate is left in the polysilicon forming furnace, it is not necessary to provide a special path for removing organic substances, and the processing can be relatively easy.
There are also advantages such as good manufacturing efficiency.

(Second Embodiment) In the second embodiment,
It is an application of the first embodiment described above, and in the method of the first embodiment, the air that has entered the polysilicon forming furnace together with the boat is not used for silylation of the organic substance, but is used from the injector to the polysilicon forming furnace. This is a method of utilizing oxygen introduced into the inside.

According to this method, the reaction of the organic substances adhering to the surface of the substrate with oxygen and SH ₄ gas becomes more efficient, so that the time for leaving the silicon substrate in the polysilicon forming furnace is about 620 ° C. At the internal temperature, it can be shortened to about 5 to 10 minutes.

Since the other points are the same as those in the first embodiment, the description thereof will be omitted. In the second embodiment, the amount of organic substances on the surface of the silicon substrate obtained by vacuum suction after leaving it in an oxygen atmosphere and the insulation resistance of the gate oxide film in the obtained gate electrode are the same as those described in the first embodiment. Since almost the same result as the embodiment was obtained, the illustration is omitted.

(Third Embodiment) In the third embodiment,
It is an application of the first embodiment described above, and in the method of the first embodiment, the air that has entered the polysilicon forming furnace together with the boat is not used for silylation of the organic substance, but is used from the injector to the polysilicon forming furnace. This is a method of utilizing ozone introduced into the interior.

According to this method, the reaction between the organic substances adhering to the surface of the substrate and ozone and SH ₄ gas becomes more efficient, so that the time for leaving the silicon substrate in the polysilicon forming furnace is about 620 ° C. At the internal temperature, it can be shortened to about 3 to 5 minutes.

Since the other points are the same as those in the first embodiment, the description thereof will be omitted. In addition, regarding the amount of organic substances on the surface of the silicon substrate obtained by vacuum suction after leaving in the ozone atmosphere and the insulation resistance of the gate oxide film in the obtained gate electrode in the third embodiment, the first embodiment described above is used. Since almost the same result as the embodiment was obtained, the illustration is omitted.

In the first to third embodiments described above, the atmosphere-based gas is oxygen, oxygen, or ozone. However, the oxygen-based gas is not limited to these, and any oxygen-based gas that does not etch the silicon substrate may be used. Can be used.

[0039]

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 gate oxide film can be removed, so that the dielectric strength characteristics of the gate oxide film are improved. The effect that a semiconductor 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 is a measurement diagram showing the amount of organic substances attached to the surface of the silicon substrate obtained in the first embodiment.

FIG. 3 is a measurement showing the amount of organic substances adhering to the surface of a silicon substrate when the boat is inserted into the polysilicon forming furnace with the polysilicon forming furnace filled with nitrogen and the silicon substrate is left in a nitrogen atmosphere. It is a figure.

FIG. 4 is an organic substance attached to the surface of a silicon substrate when the boat is inserted into the polysilicon forming furnace in a state where the inside of the polysilicon forming furnace is filled with nitrogen and the silicon substrate is left in a nitrogen atmosphere and vacuum suction is performed. It is a measurement figure showing quantity.

FIG. 5 is a measurement diagram showing the amount of organic substances adhering to the surface of a silicon substrate when the silicon substrate is left in a state where air is introduced while the boat is inserted into the polysilicon forming furnace.

FIG. 6 is a histogram showing the insulation resistance of the gate oxide film in the gate electrode obtained in the first embodiment.

FIG. 7 is a histogram showing insulation resistance of a gate oxide film in a gate electrode obtained by forming a polysilicon film after leaving a silicon substrate in a nitrogen atmosphere and performing vacuum suction.

FIG. 8 shows insulation resistance of a gate oxide film in a gate electrode obtained by forming a polysilicon film after leaving a silicon substrate in a nitrogen atmosphere and vacuum-suctioning the substrate without using organic substances on the substrate surface. It is a histogram.

FIG. 9 shows a gate electrode obtained by forming a polysilicon film after leaving the silicon substrate in a state where air has entered the polysilicon forming furnace and vacuum suctioning the substrate using a substrate having no organic substance attached to the surface of the substrate. 6 is a histogram showing the insulation resistance of a gate oxide film.

FIG. 10 is a flowchart schematically showing a conventional step of forming a gate electrode.

FIG. 11 is an explanatory view briefly showing the structure of a vertical LPCVD.

FIG. 12 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. 13 is a measurement diagram showing the amount of organic substances attached 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 (5)

(57) [Claims] 1. A semiconductor manufacturing apparatus in which a silane gas is flown into a reaction furnace to form a gate electrode made of polysilicon on a gate oxide film, and a semiconductor substrate having the gate oxide film is inserted into the reaction furnace. Means, a means for holding the semiconductor substrate in the reaction furnace in an atmosphere of silane gas and an oxygen-based gas for a certain time, a means for holding the semiconductor substrate for a certain time, and then sucking the inside of the reaction furnace, and the gate oxidation after the suction. A semiconductor manufacturing apparatus comprising: a unit for forming the gate electrode on a film. 2. By holding the semiconductor substrate having the gate oxide film formed therein in the reaction furnace, the organic substance having a benzene ring existing on the gate oxide film is decomposed into a linear ester. The semiconductor manufacturing apparatus according to claim 1, which is characterized in that. 3. The semiconductor manufacturing apparatus according to claim 1, wherein the oxygen-based gas is one selected from the atmosphere, oxygen gas, and ozone gas. 4. The semiconductor manufacturing apparatus according to claim 3, wherein an injector for introducing the oxygen gas or the ozone gas is provided in the reaction furnace. 5. The oxygen-based gas is oxygen in atmospheric air flowing into the reaction furnace when the semiconductor substrate is inserted into the reaction furnace, according to claim 1 or 2. Semiconductor manufacturing equipment.