JPH11181569A - Selective cvd method using gaseous fluorine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To selectively grow conductive thin film while cleaning the inside of a vacuum tank by a gas relatively weak in toxicity without using plasma by executing evacuation while gaseous fluorine is introduced into a vacuum tank before a substrate is carried therein and carrying the substrate after the passage of a prescribed time. SOLUTION: Before the formation of thin film of conductive substance, while the inside of a vacuum tank is evacuated, gaseous fluorine (gaseous F2 ) is introduced to fill the inside of the vacuum tank with the gaseous fluorine under certain pressure, the state is held for a certain time, and the precipitated conductive substance is removed. In the case a substrate is carried therein after the cleaning, and thermal CVD reaction is progressed, conductive thin film high in the film forming rate and small in particles can be obtd. In the case the introduction of the gaseous fluorine and the formation of the conductive thin film are repeated, cleaning effect is highest when the cleaning and the treatment of the substrate are alternately executed. It is possible that plural (e.g. <=10 pieces) substrates are treated per time of the cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CVD technique, and more particularly to a selective CVD method in which particles are small and the internal members of a vacuum chamber are not deteriorated.

[0002]

2. Description of the Related Art In recent years, conductive materials for filling a multilayer wiring film and micropores include tungsten metal and titanium metal.
A conductive material other than aluminum is used, and a sputtering device or a CVD device is used to form such a conductive thin film on a substrate surface.

In particular, when a conductive thin film is selectively grown on the surface of a silicon single crystal layer or a metal wiring layer exposed on the surface of a substrate, a selective CVD method is used.

[0004] Reference numeral 102 in FIG. 5 is a conventional CVD apparatus capable of performing a selective CVD method, and has a vacuum chamber 102. On the bottom wall of the vacuum chamber 102, an electrostatic chuck 10
3 and a gas distribution mechanism 110 on the ceiling side.
Is provided.

[0005] In the gas distribution mechanism 110, a first space 1 is provided.
11 and the second space 112 are provided independently,
The substrate on which a film is to be formed is placed on the electrostatic chucking device 103, the substrate is electrostatically sucked by the electrostatic chucking device 103, the heater inside the electrostatic chucking device 103 is heated, and the inside of the vacuum chamber 102 is heated. Is heated while evacuating.

After the substrate reaches a predetermined temperature, the gas introduction system 1
13, a tungsten fluoride (WF ₆ ) gas is introduced into the first space 111, a monosilane gas (SiH ₄ ) is introduced into the second space 112, and sprayed into the vacuum chamber 102 as a source gas for the CVD reaction. Then, the tungsten thin film selectively grows on the bottom surface of the fine hole formed in the insulating film on the substrate surface, but does not grow on the insulating film surface. At this time, the back surface of the deposition-preventing plate 105 is brought into contact with the edge portion of the substrate so that the tungsten thin film does not grow on the outer peripheral portion of the substrate.

When a tungsten thin film is selectively formed on a substrate surface by such a selective CVD method, a blanket CVD method in which a tungsten thin film is formed over the entire surface can be used.
There is an advantage that it is not necessary to remove the tungsten thin film on the insulator surface by etch back.

[0008] However, the tungsten thin film is slightly deposited in the vacuum chamber 102 in addition to the bottom surface of the fine holes of the substrate. Since the above-mentioned CVD reaction using a tungsten hexafluoride gas and a monosilane gas is a thermal CVD reaction, precipitation on a high-temperature member surface is remarkable.

The deposition-preventing plate 105 is made of quartz in which tungsten is unlikely to precipitate, but is in contact with the substrate, so that it is heated by a heater built in the electrostatic attraction device 103 and tungsten is deposited.

The tungsten thin film deposited on the members in the vacuum chamber 102 becomes particles when peeled,
The yield will be reduced.

Further, once the tungsten thin film is formed on the member, the deposition area on which tungsten can be deposited increases, so that the speed of forming the tungsten thin film on the substrate surface is reduced.

Therefore, conventionally, the inside of the vacuum chamber 102 is cleaned every time a predetermined number of substrates are processed. In the CVD apparatus 101, RF electrode 121, the vacuum chamber 102 and the gas distribution mechanism 110 is provided in an electrically insulated state, NF ₃ from the gas distribution mechanism 110
A cleaning gas such as a gas (nitrogen trifluoride gas) or a C ₂ F ₆ gas (ethylene hexafluoride gas) is introduced into the vacuum chamber 102, a high-frequency voltage is applied to the RF electrode 121, and
2 generates a cleaning gas plasma inside the CV
The tungsten thin film is gasified by the reverse reaction of the D reaction,
It was removed by evacuating.

However, in the above-described cleaning method using plasma, a high-frequency power source is required, and the RF electrode 121 must be provided in the vacuum chamber 102, so that the CVD apparatus 101 becomes complicated and the cost increases.

In the vacuum chamber 102, the surface of the component exposed to the plasma is rapidly cleaned, whereas the plasma cannot enter a narrow space or a closed space. There is a problem that the speed is low. For example, in the above-described CVD apparatus 101, the front surface of the deposition-preventing plate 105 is easily cleaned, but tungsten is deposited on the rear surface, but the portion is not exposed to plasma, so that there is a problem that cleaning is difficult.

In this case, when chlorine trifluoride (ClF ₃ ) gas having extremely strong oxidizing power is used as the cleaning gas,
Since the tungsten thin film can be removed without generating plasma, the back surface of the deposition-preventing plate 105 can also be cleaned.

However, chlorine trifluoride gas corrodes almost all organic substances, metals other than nickel and aluminum, and alloys thereof at high temperatures, so that the synthetic resin sealing member 109 such as an O-ring or the like is used. Parts will deteriorate.

Further, chlorine trifluoride gas is more corrosive than other cleaning gases, so strict control is required and handling is troublesome.

[0018]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages of the prior art, and has as its object to clean the inside of a vacuum chamber with a relatively toxic gas without using plasma. Another object of the present invention is to provide a technique capable of selectively growing a conductive thin film while growing.

[0019]

According to a first aspect of the present invention, a substrate carried into a vacuum chamber is heated, and a source gas for a CVD reaction is introduced into the vacuum chamber. A selective CVD method of a conductive thin film for selectively growing a conductive thin film on the substrate, wherein the fluorine gas (F ₂ gas) is introduced into the vacuum chamber before the substrate is carried into the vacuum chamber. Evacuate while introducing and after a predetermined time,
The substrate is loaded.

According to a second aspect of the present invention, there is provided the selective CVD method according to the first aspect, wherein the introduction of the fluorine gas and the formation of the conductive thin film are repeated. The method is performed every time a predetermined number of substrates are formed.

In this case, as in the third aspect of the present invention,
When the predetermined number is 1 to 10 sheets, the cleaning effect is high.

In the selective CVD method according to any one of claims 1 to 3, the conductive thin film is made of a metal silicide thin film, a tungsten thin film, or a titanium thin film. Thin film, tantalum thin film,
Any one of a tungsten nitride thin film and a titanium nitride thin film can be used.

The present invention is configured as described above, and heats a substrate carried into a vacuum chamber and, by a thermal CVD reaction, deposits a conductive material contained in a raw material gas on a conductive material exposed on the substrate surface. Deposits a thin film of material.

Such a thermal CVD reaction proceeds not only on the substrate surface but also on the surface of a component heated to a high temperature in a vacuum chamber.
This causes the generation of particles, and once the conductive thin film adheres to the component surface, the deposition area of the conductive thin film to be formed increases, and the deposition rate on the substrate surface decreases.

In the selective CVD method of the present invention, before forming a thin film of a conductive material, fluorine gas is introduced while evacuating the vacuum chamber, and the vacuum chamber is filled with fluorine gas at a constant pressure. The state is maintained for a certain period of time to remove the deposited conductive material.After such cleaning, when the substrate is carried in and the thermal CVD reaction is allowed to proceed, a film forming rate is high, and a conductive thin film with few particles is formed. Obtainable.

When the introduction of the fluorine gas and the formation of the conductive thin film are repeatedly performed, the cleaning effect is highest when the cleaning and the processing of the substrate are alternately performed (single wafer cleaning). A plurality of substrates may be processed per cleaning, and according to an experiment, when the number of substrates is 10 or less, adhesion of the conductive thin film to the component surface and generation of particles were not observed.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described together with a CVD apparatus used in the present invention. Reference numeral 1 in FIG.
The CVD apparatus has a vacuum chamber 2. A disk-shaped electrostatic adsorption device 3 is fixed on the bottom wall of the vacuum chamber 2, and a gas distribution mechanism 10 is provided on the ceiling side.

A plurality of holes are provided on the bottom wall of the vacuum chamber 2 at the back surface of the electrostatic attraction device 3, and in these holes, the attraction electrode terminals 21a and the heater electrode terminals 21b are provided. Is inserted.

In the electrostatic chuck 3, an electrostatic chuck pattern (not shown) and a resistance heater are provided, and the electrostatic chuck pattern is connected to the electrode terminals 21a for electrostatic chuck.
The resistance heater is connected to the heater electrode terminal 21b. In FIG. 1 (and FIGS. 2 to 4), the electrode terminal 21a for electrostatic attraction and the electrode terminal 21b for the heater appear to be overlapped only at one place, but each terminal is provided two by two, and a vacuum chamber is provided. It is connected to two external power supplies, respectively, and is configured to be capable of independently applying voltages to the resistance heater and the electrostatic attraction pattern.

A ring-shaped protection plate 5 is mounted on the edge of the electrostatic attraction device 3. A hole is provided in the bottom wall of the vacuum chamber 2 at a position on the back surface of the deposition-preventing plate 5, in which a lifting rod 22 is vertically inserted, and the upper end portion is formed of the deposition-preventing plate 5.
It is attached to the bottom of.

The lifting lot 22 is inserted through a bellows 25 on the outside of the vacuum tank 2 and has a lower end attached to a lifting mechanism (not shown), and can be moved up and down while maintaining the vacuum atmosphere in the vacuum tank 2. It is configured as follows.

When a tungsten thin film is selectively formed on the substrate surface by using such a CVD apparatus 1, first, the inside of the vacuum chamber 2 is evacuated, and as shown in FIG. Lift the protection plate 5.

In the transfer chamber adjacent to the vacuum chamber 2, a substrate transfer robot is provided.
On the hand 32 at the leading end of the substrate 4, a substrate 4 as a film formation target is placed.
Is placed (FIG. 2).

The gate valve provided on the side wall between the vacuum chamber 2 and the transfer chamber is opened, the arm 30 and the hand 32 of the transfer robot are inserted into the vacuum tank 2 from the carry-in / out port 15, and the substrate 4 on the hand 32 is moved. Is stopped between the adhesion-preventing plate 32 and the electrostatic attraction device 3.

Holes communicating with each other are provided on the bottom walls of the electrostatic chuck 3 and the vacuum chamber 2, and a plurality of lifting pins 30 are inserted into these holes.

The lifting pin 30 is located outside the vacuum chamber 2
It is inserted into the bellows 26, and the lower end is attached to the lifting support 24. Therefore, the lifting pin 30 is
When the lifting support 24 moves up and down, it can move up and down while maintaining the vacuum atmosphere.

When the lifting support 24 is lowered, the lifting pins 30 are housed in the holes, and the upper ends thereof are hidden in the holes. On the other hand, when the elevator 24 is raised, as shown in FIG. 3, the upper end of the elevating pin 22 is in contact with the back surface of the substrate 4, and
Can be lifted.

When the substrate 4 is lifted, the substrate 4 is placed horizontally on the elevating pins 30 and the electrostatic chuck 3
When the hand 32 is pulled out from the space between the base plate 4 and the deposition prevention plate 5, the arm 30 of the transfer robot is returned to the transfer room, the gate valve is closed, and the elevating pin 22 is lowered, and the substrate 4 is placed on the electrostatic suction device 3. You.

A voltage is applied to the electrostatic attraction pattern by the attraction electrode terminal 21 to electrostatically attract the substrate 4 to the surface of the electrostatic attraction device 3. The resistance heater built in the electrostatic attraction device 3 is energized in advance, and the electrostatically attracted substrate 4 is quickly heated to a predetermined temperature. At this time, as shown in FIG. 4, the deposition-preventing plate 5 is lowered and brought into close contact with the surface of the substrate 4 so that the conductive thin film does not grow around the substrate 4.

After the substrate 4 is stabilized at 300 ° C., when tungsten hexafluoride gas and monosilane gas are introduced into the first space 11 and the second space 12 in the gas distribution mechanism 10, respectively, both gases are selected. It becomes a source gas for the CVD reaction and is sprayed into the vacuum chamber 2.

Here, the flow rate of the tungsten hexafluoride gas is set at 50 sccm, and the flow rate of the monosilane gas is set at 35 sccm. did.

The raw material gas in the vacuum chamber 2 is supplied to the electrostatic adsorption device 3
The gas is exhausted from an exhaust port 16 provided around the
Since a uniform flow of the source gas is formed on the surface,
The VD reaction is performed uniformly on the surface of the substrate 4.

A selective CVD reaction is performed for a predetermined time to
When a 1 μm-thick tungsten thin film is selectively grown on the surface, the introduction and dispersion of the source gas are stopped.

The elevating rod 22 and the elevating pins 23 are lifted to raise the deposition-preventing plate 5 and the substrate 4 (the state shown in FIG. 3), and the arm 30 of the substrate transfer robot is inserted between the substrate 4 and the electrostatic suction device 3. Then, the lifting pins 23 are lowered, and the substrate 4 is transferred onto the hand 32.

In this state, the arm 30 is stored in the transfer chamber,
The substrate 4 on which the tungsten thin film is formed is carried out of the vacuum chamber 2.

After the gate valve is closed and the inside of the vacuum chamber 2 is shielded from the transfer chamber, a gas obtained by adding 5% fluorine gas (F ₂ gas) to argon gas is introduced into the vacuum chamber 2 by the gas introduction system 13. When introduced, the tungsten thin film deposited on the deposition-preventing plate 5 and other components in the vacuum chamber 2 reacts with fluorine gas to be gasified. At this time, no other gas such as a monosilane gas is introduced.

At this time, the flow rate of argon gas to which 5% of fluorine gas was added was set to 100 sccm, the exhaust speed was adjusted with a variable valve, and the vacuum in the vacuum chamber 2 was adjusted so that the pressure in the vacuum chamber 2 became 50 Pa. Evacuation was performed to remove reaction products.

As described above, components such as the deposition-preventing plate 5 on which tungsten is easily deposited are placed in a fluorine gas atmosphere while being heated, and a selective CVD reaction is performed between the deposited tungsten and the fluorine gas. The reverse reaction occurs, and the tungsten thin film is gasified and removed by evacuation.

The introduction of the fluorine gas into the vacuum chamber 2 is performed by a substrate transport robot, which controls the substrate 4 on which the tungsten thin film is formed.
For 30 seconds while exchanging with an untreated substrate. After that period has elapsed and the inside of the vacuum chamber 2 has been cleaned,
Stop the introduction and spraying of the fluorine gas, open the gate valve, and remove the undeposited substrate from the vacuum
Carry in. Then, the substrate is placed on the electrostatic attraction device 3 and heated to 300 ° C. in the same manner as the substrate 4 to selectively grow a tungsten thin film. Selective CVD can be performed.

Further, after a tungsten thin film is formed on the substrate, cleaning with fluorine gas is performed. As described above, cleaning is performed each time a thin film is formed on one substrate, and when a predetermined number of substrates are processed, the selection CV
Since the D reaction is always performed in the vacuum chamber 2 that has been cleaned (single wafer cleaning), a high quality tungsten thin film can be obtained without generating particles or lowering the film formation speed.

The above-described tungsten thin film forming process is performed on 50 lots (25 lots per lot) of substrates.
The film forming speed on the substrate surface, the number of particles on the surface, the state of deterioration of the seal member 9, and the state of adhesion of the tungsten thin film to the components in the vacuum chamber 2 were observed.

As comparative examples, no cleaning was performed, cleaning was performed for each lot by introducing chlorine trifluoride gas, and plasma cleaning was performed for each lot using nitrogen trifluoride gas. When,
Similarly, when performing single-wafer plasma cleaning with nitrogen trifluoride gas, the film forming speed, the number of particles on the surface, the deterioration state of the seal member, and the adhesion state of the tungsten thin film to the components in the vacuum chamber 2 were observed. . The conditions for forming the tungsten thin film were the same as in the above embodiment. The results are shown in Table 1 below.

[0053]

[Table 1]

As can be seen from Table 1 above, the selective CVD method of the present invention using fluorine gas has the same cleaning effect as the case of performing single-wafer plasma cleaning using nitrogen trifluoride gas. I understand.

Next, the above-described CVD apparatus 1 was used to perform cleaning each time a plurality of substrates were processed, instead of performing cleaning for each substrate. When cleaning was performed every time one lot of substrates was processed, adhesion of a tungsten thin film to the surface of the component was observed. However, when the number of processed substrates after one cleaning was reduced to ten, the component was cleaned. No attachment of a tungsten thin film to the surface was observed, and no increase in particles was observed.

The number of processed wafers per cleaning is affected by the thickness of the tungsten thin film to be formed, the cleaning time, and the like. In the selective CVD method of the present invention, cleaning is performed in units of 1 to 10 wafers. It turns out that it is good.

In the above embodiment, the argon gas to which 5% fluorine gas is added is used, but it may be added at another ratio. Generally, a 3% to 20% fluorine-added argon gas is easily available. Further, instead of the argon gas, a gas obtained by adding a fluorine gas to another inert gas may be used. Further, it is also possible to use only fluorine gas.

The present invention is not limited to the CVD method for forming a tungsten thin film, but can be widely used for conductive materials other than a copper thin film and an aluminum thin film. Removal has not been confirmed).

[0059]

According to the present invention, the selective CVD reaction can be carried out in a vacuum chamber in which no conductive thin film is deposited, so that the deposition rate is stable and no particles adhere.

[Brief description of the drawings]

FIG. 1 shows an example of a CVD apparatus that can be used in the present invention.

FIG. 2 is a view showing a state in which an unprocessed substrate is loaded into the CVD apparatus or a state in which a processed substrate is unloaded.

FIG. 3 is a diagram showing a state in which an unprocessed substrate is placed on elevating pins of the CVD apparatus, or a state in which the processed substrate is lifted.

FIG. 4 is a view for explaining a state in which a substrate is placed on an electrostatic chuck of the CVD apparatus.

FIG. 5 is a view for explaining a conventional CVD apparatus.

[Explanation of symbols]

 1 CVD apparatus 2 Vacuum chamber 4 Substrate

Claims (4)

[Claims] 1. The method of claim 1, wherein the temperature of the substrate carried into the vacuum chamber is increased, a source gas for a CVD reaction is introduced into the vacuum chamber, and a conductive thin film is selectively grown on the substrate by selective CVD. The method, before carrying the substrate into the vacuum chamber, evacuating while introducing a fluorine gas (F ₂ gas) into the vacuum chamber, and carrying the substrate after a predetermined time has elapsed. A selective CVD method characterized by the above-mentioned. 2. The selective CVD method according to claim 1, wherein the introduction of the fluorine gas and the formation of the conductive thin film are repeatedly performed, wherein the introduction of the fluorine gas forms the predetermined number of the conductive thin films on the substrate. Selective CVD characterized by being performed every time
Method. 3. The selective CVD method according to claim 2, wherein the predetermined number is one or more and ten or less. 4. The conductive thin film is one of a metal silicide thin film, a tungsten thin film, a titanium thin film, a tantalum thin film, a tungsten nitride thin film, and a titanium nitride thin film.
The selective CVD method according to claim 1, wherein the selective CVD method is a seed.