JP2002141352A - Method of heat treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform heat treatment without oxidizing a metal thin film. SOLUTION: The heat treatment method has first and second heating steps. In the first heating step, since a wafer 10 (an object to be treated) is heated to a first heating temperature in the range between 100 deg.C and 200 deg.C inclusive, moisture of the wafer 10 is completely removed while crystal grains of a copper thin film hardly grow. In the second step, not only moisture of the wafer 10 is removed, but the partial pressure of the moisture in an atmosphere in which the wafer 10 is placed is made 5×10-5 Pa or lower. Accordingly, even when the wafer 10 is heated to a second heating temperature, crystal grains grow without oxidizing the copper thin film. Thus, according to the heat treatment method, crystal grains sufficiently grow and a copper thin film whose mean grain size is uniform can be obtained.

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 thin film, and more particularly to a technique for heat-treating a metal thin film to be a wiring film of a semiconductor.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a semiconductor wiring film, an electrolytic plating method of forming a copper thin film serving as a wiring film on a substrate surface by electrolytic plating has been used. When a copper thin film formed by an electrolytic plating method is left at room temperature, a phenomenon in which copper crystal grains grow in the copper thin film over time (self-annealing phenomenon) is known, and the crystal grains grow. At the same time, the resistance of the copper thin film decreases,
When left at room temperature for about 00 hours, the resistance value of the wiring film becomes substantially equal to the original resistance value of copper. Such a wiring film has an advantage that the lifetime of electromigration is ten times or more longer than that of a wiring film made of aluminum.

However, it is not preferable that the crystal grains in the wiring film grow with time in manufacturing a semiconductor. Therefore, as is known in Japanese Patent Application Laid-Open No. 2000-77527, a heat treatment for forming a copper thin film on a substrate surface by an electrolytic plating method and then heating the whole to grow crystal grains in the copper thin film is generally performed ( JP-A-2000-7752
7).

[0004] Reference numeral 100 in FIG. 6 indicates a heat treatment apparatus used for heat treatment of such a copper thin film. The heat treatment apparatus 100 has a quartz tube 113, and a heating mechanism 115 for heating the quartz tube 113 is arranged around the quartz tube 113. A vacuum pump (not shown) is connected to the quartz tube 113, and the inside of the quartz tube 113 is evacuated by the vacuum pump.

In order to heat an object to be processed using such a heat treatment apparatus 100, first, the inside of the quartz tube 113 is heated to a predetermined temperature using a heating mechanism 115 while the inside of the quartz tube 113 is evacuated. . Next, a plurality of objects to be treated are mounted on a quartz boat, and a quartz tube 113 is mounted.
The quartz boat is carried into the quartz tube 113 while the vacuum atmosphere is maintained.

[0006] Reference numeral 110 in FIG. 6 indicates an object to be processed carried into the quartz tube 113 together with the quartz boat, and FIG. 111 shows the quartz boat. The processing object 110 has a copper thin film formed by an electrolytic plating method on its surface, and the growth rate of crystal grains is higher as the temperature is higher.
When heated to a predetermined temperature inside, the crystal grains of the copper thin film grow in a short time.

However, when the wafer 110 is heated, moisture adsorbed on the surface of the substrate and the wiring film of the wafer 110 and the inner wall of the vacuum chamber 113 evaporates, and the evaporated moisture oxidizes the wiring film.

If an inert gas such as nitrogen or argon is introduced into the vacuum chamber 113 before heating the wafer 110, oxidation of the wiring film can be suppressed to some extent. When the temperature is high (several hundred degrees Celsius), even if an inert gas is introduced, the surface of the wiring film is oxidized by the adsorbed moisture. In particular, when a copper thin film serving as a wiring film is formed by an electrolytic plating method, a large amount of moisture adheres to the surface of the wafer 110, so that oxidation of the copper thin film becomes more serious.

In order to prevent oxidation of the copper thin film, it is easy to introduce a highly reducing gas such as hydrogen into the vacuum chamber 113 and perform a heat treatment to reduce copper oxide generated on the surface of the copper thin film. Invented. However, the portion that has been oxidized and then reduced has a problem that the crystal grain size of the copper thin film is not constant because the growth of crystal grains is slower than that of the portion that is not oxidized.

[0010]

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 prevent the oxidation of the surface of a wiring film and to quickly perform a heat treatment. .

[0011]

Means for Solving the Problems The present inventors have paid attention to the partial pressure of water in a vacuum chamber and the heating temperature as heating conditions for heating a substrate, and conducted an experimental investigation on the relationship between these heating conditions and oxidation. Was. FIG. 3 shows the results, in which the vertical axis represents the water partial pressure (Pa) and the horizontal axis represents the temperature (° C.). The straight line L in FIG. 2 shows the boundary where the surface of the copper thin film is oxidized. When the substrate is heated to 200 ° C., the surface of the copper thin film is oxidized unless the water partial pressure is 5 × 10 ⁻⁵ Pa or less. It turned out to be.

Further, the present inventors have proposed that a 400 nm-thick copper thin film formed by an electrolytic plating method be treated at different heating temperatures.
After heating for 0 minutes, the growth of crystal grains after heating was observed. FIG.
Shows the results, and it was confirmed that under the conditions of a heating temperature of 200 ° C. or less and a heating time of 30 minutes, crystal grains hardly grow.

The present invention has been created based on the above findings, and the invention according to claim 1 is a heat treatment method for heating a processing object having a metal thin film on a surface, wherein the processing object is placed. A first heating step of elevating the temperature of the processing object to a first heating temperature in the range of 100 ° C. or more and 200 ° C. or less while evacuating or replacing the atmosphere, and placing the processing object. A measuring step of measuring the moisture partial pressure of the atmosphere, and measuring the moisture partial pressure of 5 × 10 ⁻⁵ P
a), and after the temperature has become equal to or less than a, a second heating step of raising the temperature of the object to be processed to a second heating temperature higher than the first heating temperature. The invention according to claim 2 is the heat treatment method according to claim 1, wherein the pressure of the atmosphere in which the object to be treated is placed is 1 Pa or less. The invention according to claim 3 is the invention according to claim 1, wherein the atmosphere in which the object to be treated is placed is filled with an inert gas, and the pressure of the atmosphere is reduced to 1 atm or less by the inert gas. This is the heat treatment method performed. The invention according to claim 4 is the heat treatment method according to any one of claims 1 to 3, wherein the first heating step is performed in a first processing chamber, and the second heating step is performed. Is performed in a second processing chamber separate from the first processing chamber, and the object to be processed is transported between the first processing chamber and the second processing chamber without being exposed to the atmosphere. Heat treatment method. The invention according to claim 5 is the heat treatment method according to claim 4, wherein
The first processing chamber is a heat treatment method in which the processing object is a loading / unloading chamber for loading / unloading the processing target from the air atmosphere. The invention according to claim 6 is the heat treatment method according to claim 5, wherein the first processing chamber is filled with nitrogen gas before carrying the processing object into the first processing chamber. This is a heat treatment method. The invention according to claim 7 is the invention according to claims 1 to 6.
4. The heat treatment method according to claim 1, wherein the metal thin film is a copper thin film formed by an electrolytic plating method.

According to the heat treatment method of the present invention, the object to be treated is first heated to the first heating temperature in the first heating step. The first heating temperature is in the range of 100 ° C. or more and 200 ° C. or less, and even when the atmosphere for treating the object to be treated in the first heating step is set to 1 atm, the evaporation of water occurs. Water can be removed from the processing object in the heating step.

Further, as shown in the graph of FIG.
At 200 ° C. or lower, the growth rate of copper crystal grains is extremely slow. Therefore, even when the oxidation-reduction reaction of the copper thin film occurs in the first heating step, the portion where the crystal grains have grown in the copper thin film and the portion where it is not, Will not occur.

In the first heating step, the atmosphere in which the object is placed is evacuated, and the moisture evaporated from the object is removed by evacuation, so that the partial pressure of the atmosphere increases. do not do.

Therefore, after the first heating step, the object to be treated has a sufficiently low water partial pressure (water partial pressure of 5 × 10 ⁻⁵ Pa or less).
In this state, if the object to be treated is heated to a temperature higher than the first heating temperature (second heating step), the copper thin film of the object to be treated is crystallized without being oxidized. Since the grains grow uniformly, a copper thin film having a uniform average grain size of crystal grains can be obtained.

The atmosphere in the first and second heating steps is 1 Pa
When the evacuation speed of the vacuum evacuation is increased as described below, moisture desorbed from the processing object is quickly removed from the processing atmosphere without being re-adsorbed. Also, first,
Similar effects can be obtained when the atmosphere in which the second heating step is performed is filled with an inert gas.

In the present invention, a gas that inhibits a metal oxidation reaction is defined as an inert gas. That is, in the present invention, not only a rare gas generally called an inert gas but also a gas having a low reactivity such as a nitrogen gas or a gas having a high reducibility such as hydrogen can be used. In this case, it is preferable to use an inert gas containing almost no water,
For example, when the atmosphere in which the object to be treated is placed is filled with an inert gas, a material having a water partial pressure of 5 × 10 ⁻⁵ Pa or less is suitable.

The first processing chamber is used as a loading / unloading chamber. After the processing target is loaded into the first processing chamber, the processing target is evacuated to a predetermined degree of vacuum and then transferred to the second processing chamber. By doing so, the second processing chamber can always be maintained in a vacuum atmosphere. In this case, if the first heating step is performed in the first processing chamber, the object to be processed can be more efficiently heat-treated. The second heating temperature may be higher than the first heating temperature, but is preferably 200 ° C. or higher when the object to be processed has a copper thin film.

The upper limit of the second heating temperature is not particularly limited in the present invention. The second heating temperature differs depending on the purpose of the heat treatment. For example, when the titanium thin film formed on the silicon substrate surface is silicided by the heat treatment, the second heating temperature is 600 ° C. or more. Is preferred.

On the surface of a semiconductor wafer,
In some cases, an insulating layer made of a resin is formed, and such an insulating layer deteriorates when heated to 500 ° C. or higher. Is preferably less than 500 ° C.

Further, the moisture partial pressure of the atmosphere in which the object to be processed is heated is not limited to 5 × 10 ⁻⁵ Pa or less. The partial pressure only needs to be in the “region without oxidation” shown in the graph of FIG. 3 with respect to the heating temperature. However, the moisture partial pressure of the atmosphere in which the object to be treated is placed in the second heating step is 5 × 10 ⁻⁵ Pa or less, more preferably 1 × 10 ⁻⁵ Pa.
It is preferably in the range of 10 ⁻⁵ Pa or less.

[0024]

DETAILED DESCRIPTION OF THE INVENTION
A 400-nm thick copper thin film is formed on the surface of a disc-shaped silicon substrate by electrolytic plating, and impurities adsorbed on the wafer are analyzed by thermal desorption spectroscopy (Thermal Desorption Spectoroscopy). Was. Here, a 3 cm square sample piece cut out from the wafer was analyzed.

FIG. 5 is a diagram showing the results of the analysis. The vertical axis shows the measured temperature and the partial pressure of each gas, and the horizontal axis shows the heating time. Curves a, b, and c show partial pressures of water (steam), carbon monoxide, and hydrogen, respectively, and curve d shows the temperature of the sample piece.

As is clear from FIG.
When the temperature is raised from 20 ° C. (room temperature) to 200 ° C. in 0 seconds, the water partial pressure is 3 × 10 ⁻⁸ which is the maximum value of the curve a.
Pa, and the specimen was taken at 4000C for 20 seconds (room temperature).
The water partial pressure when the temperature is raised from
^-8 Pa.

Further, when the moisture partial pressure when 100 wafers are heated in the same vacuum chamber is determined from the moisture partial pressure when the sample piece is heated, the moisture partial pressure at 200 ° C. is 1 × 10 ^−. The water partial pressure at ⁴ Pa and 400 ° C. is 3 × 10
⁻⁵ Pa, and it was confirmed that a large amount of water was adsorbed on the wafer surface when the copper thin film was formed by the electrolytic plating method.

Referring to the drawings, a description will be given of a process of heat-treating the above-mentioned wafer as a processing object by the heat-treating method of the present invention. 1 indicates a first example of a vertical vacuum heat treatment apparatus used in the heat treatment method of the present invention.

The vertical vacuum heat treatment apparatus 1 has a first processing chamber 12 and a second processing chamber 13. A vacuum valve 28 is provided between the first processing chamber 12 and the second processing chamber 13. When the vacuum valve 28 is opened, the first processing chamber 13 and the second processing chamber 13 are connected. It is configured as follows. FIG. 1 shows a state in which the vacuum valve 28 is opened.

A door 14 is provided on the side of the first processing chamber 12. When the door 14 is opened, the first processing chamber 12
Are connected to the atmosphere. First and second processing chambers 12,
13 are connected to vacuum pumps 17 and 18, respectively, and when these vacuum pumps 17 and 18 are started with the door 14 and the vacuum valve 28 closed, the first and second processing chambers 12 and 13 are started. The inside is evacuated.

The first processing chamber 12 has a gas introduction system 2.
5 is connected, and when the gas introduction system 25 is started with the door 14 closed, the first processing chamber 12 is filled with nitrogen gas. The second processing chamber 13 is formed of an elongated quartz tube, one end of which is sealed, and the other end of which is connected to the second processing chamber via a vacuum valve 28. A heating mechanism 15 is provided around the second processing chamber 13.
The entire wall of No. 3 is heated and its inner wall is 100 ° C. or more and 500
It is configured to raise the temperature in the range of not more than ° C.

Outside the first and second processing chambers 12 and 13, pressure gauges 21 and 22 for measuring the total pressure inside them are provided, respectively. Further, a gas analyzer 24 is connected to the internal atmosphere of the second processing chamber 13, and the ratio of the gas species present in the second processing chamber 13 to the pressure of each gas species is controlled by the gas analyzer 24. Then, the partial pressure of each gas is determined from the measurement results and the total pressure measured by the pressure gauge 22.

In order to heat the wafer using the vertical vacuum heat treatment apparatus 1 having the above structure, first, the vacuum pumps 17 and 18 are started with the door 14 and the vacuum valve 28 closed, and the vacuum pumps 17 and 18 are activated. First, the second processing chambers 12 and 13 are evacuated to a predetermined degree of vacuum (here, 1 Pa or less), a heating mechanism 15 around the second processing chamber 13 is energized, and the inner wall of the second processing chamber 13 is cleaned. When the temperature is increased, the moisture adsorbed on the inner wall surface evaporates, and the evaporated moisture is removed by evacuation.

When the inner wall temperature of the second processing chamber 13 reaches the first heating temperature (here, the first heating temperature is 200 ° C.), the amount of electricity supplied to the heating mechanism 15 is adjusted, and the temperature is adjusted. If the vacuum evacuation is continued while maintaining the pressure, the pressure in the second processing chamber 13 becomes 1 Pa or less, and the water partial pressure is reduced to such a degree that the copper thin film is not oxidized (here, the water partial pressure is 5 × 10 ^-5 Pa or lower).

Next, the evacuation of the first processing chamber is stopped, and the inside of the first processing chamber 12 is filled with nitrogen gas by the gas introduction system 25. When the pressure in the first processing chamber 12 became 1 atm, the introduction of nitrogen gas was stopped and the door 14 was opened,
A quartz boat on which a plurality of wafers to be processed (here, a wafer immediately after a copper thin film is formed on a silicon substrate surface by an electrolytic plating method) is loaded is loaded. At this time, since the nitrogen gas is flowing in the first processing chamber 12, the air does not enter the first processing chamber.

After the quartz boat is loaded, the door 14 is closed, the evacuation of the first processing chamber 12 is resumed, the pressure in the first processing chamber 12 is set to 1 Pa, and then the vacuum valve 28 is opened.
The first and second processing chambers 12 and 13 are connected. At this time,
Since the pressure in the first processing chamber 12 is 1 Pa, which is the same as the pressure in the second processing chamber 13, the residual gas (nitrogen gas) in the first processing chamber 12 is supplied to the second processing chamber 13. Does not mix.

In this state, the quartz boat is moved to the first processing chamber 12 by a boat loader 29 which is a mechanism for moving the quartz boat between the first and second processing chambers 12 and 13.
Is transferred from the first processing chamber 13 to the second processing chamber 13, the bottom of the boat loader 29 abuts against the inner wall of the first processing chamber 12, and the first and second processing chambers 12 and 13 are shut off by the boat loader 29 itself. Is done.

FIG. 1 shows this state. Since the inner wall of the second processing chamber 13 is heated to the first heating temperature by the heating mechanism 15, the quartz carried into the second processing chamber 13 is The boat 11 and the wafer 10 are heated to the first heating temperature by the radiant heat from the inner wall of the second processing chamber 13.

At this time, the quartz boat 11 and the wafer 10
Since the water adsorbed on the surface of the second processing chamber evaporates and the evaporated water is removed by vacuum evacuation, the water partial pressure in the second processing chamber 13 does not increase. Therefore, here, not only do the crystal grains not grow in the copper thin film of the wafer, but also little oxidation of the copper thin film occurs.

In this state, heating is continued for 30 minutes (first heating step), and the partial pressure of water in the second processing chamber 13 is sufficiently low by the gas analyzer (here, 5 × 10 ⁻⁵ Pa or less).
After confirming that, the amount of electricity to the heating mechanism 15 is increased to further raise the temperature of the inner wall of the second processing chamber 13, and the temperature of the inner wall is raised to the second heating temperature (here, the second heating temperature). Was set to 500 ° C.).

As the temperature of the inner wall of the second processing chamber 13 rises, the temperature of the wafer 10 also rises. When the temperature of the wafer 10 becomes higher than the first heating temperature, crystal grains grow in the copper thin film of the wafer 10. I do. At this time, the inside of the second processing chamber 13 is continuously evacuated, and the partial pressure of water in the second processing chamber 13 is sufficiently reduced, so that the copper thin film is not oxidized.

Heating is continued for 30 minutes while the temperature of the wafer 10 is raised to 500 ° C. When the crystal grains of the copper thin film have sufficiently grown (the average particle diameter is about 1.8 μm), the heating is terminated ( Second heating step).

Next, when the quartz boat 11 is returned to the first processing chamber 12 using the boat loader 29, the bottom of the boat loader 29 is separated from the inner wall of the first processing chamber 12. Next, the vacuum valve 28 is closed, the first processing chamber 12 and the second processing chamber 13 are shut off again, and then the chamber is filled with an argon gas or a nitrogen gas until the pressure becomes the same as the atmospheric pressure. Next, if the door 14 is opened, the wafer 10 after the first and second heating steps can be taken out of the vertical vacuum heat treatment apparatus 1 together with the quartz boat 11.

The method of performing the first and second heating steps in the second processing chamber 13 in which the degree of vacuum is set to a predetermined degree of vacuum (1 Pa) or less has been described above, but the present invention is not limited to this. . Reference numeral 51 in FIG. 2 indicates a second example of a vertical vacuum heat treatment apparatus used in the heat treatment method of the present invention.

The vertical vacuum heat treatment apparatus 51 has first and second processing chambers 12 and 13 connected via a vacuum valve 28, similarly to the vertical vacuum heat treatment apparatus 1 of the first example. . Among these, a gas analyzer 23 similar to that connected to the second processing chamber 13 is connected to the first processing chamber 12 separately from the vacuum pump 18, the gas introduction system 25, and the pressure gauge 21. The gas analyzer 23 and the pressure gauge 21 are configured to measure the type of gas existing in the second processing chamber 13 and the partial pressure of each gas. Further, a heating mechanism 19 is provided in the first processing chamber 12.

In order to heat-treat a wafer (object to be processed) using such a vertical vacuum heat treatment apparatus 51, first,
With the door 14 and the vacuum valve 28 closed, the inside of the first and second processing chambers 12 and 13 is evacuated to a predetermined degree of vacuum (here, 1 Pa or less) and then heated around the second processing chamber 13. The mechanism 15 is energized to raise the temperature of the inner wall of the second processing chamber 13. At this time, the moisture adsorbed on the inner wall surface of the second processing chamber 13 evaporates, and the evaporated moisture is removed by evacuation.

When the temperature of the inner wall of the second processing chamber 13 reaches the second heating temperature (here, the second heating temperature is set to 500 ° C.), the amount of electricity supplied to the heating mechanism 15 is adjusted. If the evacuation is continued while maintaining the inner wall temperature of the processing chamber 13 at that temperature, the pressure in the second processing chamber 13 becomes 1 Pa
And the water partial pressure is sufficiently reduced. Here, the water partial pressure in the second processing chamber 13 was set to 5 × 10 ⁻⁵ Pa or less.

Next, the evacuation of the first processing chamber 12 is stopped, and nitrogen gas is introduced into the first processing chamber 12 by the gas introduction system 25. When the pressure in the first processing chamber 12 becomes 1 atm, the door 14 is opened while flowing nitrogen gas,
As in the case of the vertical vacuum heat treatment apparatus 1 of the first example, the wafer placed on the quartz boat is carried into the first processing chamber 12 and the door 14 is closed. At this time, since the inside of the first processing chamber 12 is filled with the nitrogen gas, the atmosphere hardly enters the first processing chamber 12.

Next, the vacuum evacuation is resumed, and when the decrease in the pressure in the first processing chamber 12 decreases to a predetermined degree of vacuum, the heating mechanism 19 is energized, and the wafer is raised by the radiant heat from the heating mechanism 19. Let warm.

At this time, the temperature of the quartz boat and the inner wall of the first processing chamber 12 rises together with the wafer, and the water adsorbed on the surface of the wafer and the quartz boat and the inner wall of the first processing chamber 12 evaporates. The evaporated water is removed by evacuation.

When the inner wall temperature of the first processing chamber 12 reaches a first heating temperature lower than the second heating temperature (here, the first heating temperature is set to 200 ° C.), power is supplied to the heating mechanism 19. If the evacuation is continued while adjusting the amount and maintaining the temperature, the pressure in the first processing chamber 12 becomes 1 Pa or less, and the water partial pressure is reduced to such an extent that the copper thin film is not oxidized. Here, the water partial pressure was reduced to 5 × 10 ⁻⁵ Pa or less. In this state, crystal grains hardly grow in the copper thin film.

After completely removing the moisture from the wafer and the quartz boat, the first processing chamber 12 and the second processing chamber 13 are connected by opening the vacuum valve 28, and the quartz boat is moved using the boat loader 29. It is transported from one processing chamber 12 to a second processing chamber 13.

FIG. 2 shows this state. Wafer 1
The water adsorbed on the surfaces of the quartz boat 11 and the quartz boat 11 has been completely removed in the first heating step.
Since the water partial pressure is also set to 5 × 10 ⁻⁵ Pa or less in advance, the wafer 10 is heated to the second heating temperature in the second processing chamber 13 without oxidizing the copper thin film on the surface. And
Copper crystal grains grow in the copper thin film (second heating step). After the crystal grains of the copper thin film are sufficiently grown, the wafer 10 can be taken out of the vertical vacuum heat treatment apparatus 51 in the same process as in the case of the vertical vacuum heat treatment apparatus 1 of the first example.

The case where the heat treatment is carried out while evacuating the first and second processing chambers 12 and 13 to 1 Pa or less has been described above, but the present invention is not limited to this. . For example, an inert gas having a water partial pressure of 5 × 10 ⁻⁵ Pa or less is introduced into the first and second processing chambers, and heat treatment is performed in a state where the first and second processing chambers are filled with the inert gas. May be performed.

In this case, if the evacuation is performed while continuously introducing the inert gas in the heat treatment step, the first and second processing chambers are replaced with an inert gas having a water partial pressure of 5 × 10 ⁻⁵ Pa or less. Therefore, the copper thin film is not oxidized. As the inert gas, for example, a rare gas such as argon or a gas having low reactivity such as nitrogen can be used. Further, in the present invention, a highly reducing gas such as hydrogen can be used as the inert gas.

When the above-mentioned inert gas is used,
The first and second processing chambers 12 and 13 do not need to be in a vacuum atmosphere, and the internal pressure is equal to or lower than the atmospheric pressure (including the atmospheric pressure).
Is fine. However, when a combustible gas such as hydrogen is used as the inert gas, or when moisture in the wafer is removed in a short time in the first heating step,
It is desirable to perform the heat treatment while reducing the pressure.

Further, the case where the copper thin film formed by the electrolytic plating method is heat-treated to grow the crystal grains of the copper thin film has been described above. However, the present invention is not limited to this, and various metal The thin film can be heat treated for various purposes. For example, when a copper thin film is formed on a wafer by CVD or sputtering, heat treatment such as reflow of the copper thin film can be performed by the heat treatment method of the present invention.

As another example, if a thin film made of titanium is formed on a silicon substrate and the wafer is subjected to a heat treatment by the heat treatment method of the present invention, the titanium thin film can be silicided without being oxidized. Also, the material of the substrate is not limited to silicon,
Various substances can be used as long as they have heat resistance. Further, an insulating layer can be provided on the surface of the wafer on which the copper thin film is formed. In this case, the material of the insulating layer is preferably a heat-resistant resin.

Although the case where the first heating temperature is set to 200 ° C. has been described above, the present invention is not limited to this, and may be in the range of 100 ° C. to 200 ° C. When the object to be treated has a copper thin film formed by the electroplating method, the partial pressure of water at which the object to be treated is placed in the first heating step is in the region without oxidation shown in the graph of FIG. For example, when the first heating temperature is 100 ° C., it may be 6 × 10 ⁻⁵ Pa or less.

Also in the second heating step, the moisture partial pressure of the atmosphere in which the object to be treated is placed is not limited to 5 × 10 ⁻⁵ Pa or less. The water partial pressure in the second heating step is preferably lower than the water partial pressure in the first heating step. As shown in the graph of FIG. 3, for example, when the second heating temperature is 500 ° C. , Moisture partial pressure is 2
When it is in the range of × 10 ⁻⁵ Pa or less, more preferably 2 × 10 ⁻⁶ Pa or less, the oxidation of the metal thin film to be processed can be sufficiently prevented.

[0061]

According to the present invention, a plurality of processing objects can be heat-treated efficiently in a short time. Even when the object to be treated contains a large amount of water, it is not oxidized during heating.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a first example of a vertical vacuum heat treatment apparatus used in an embodiment of the present invention.

FIG. 2 is a view for explaining a second example of a vertical vacuum heat treatment apparatus used in the embodiment of the present invention.

FIG. 3 is a graph for explaining a relationship among oxidation of a copper thin film, a partial pressure of water in a heating atmosphere, and a heating temperature.

FIG. 4 is a graph for explaining the relationship between the growth of crystal grains in a copper thin film and the heating temperature.

FIG. 5 is a graph showing measurement results of a thermal desorption gas analysis performed on a wafer.

FIG. 6 is a diagram for explaining a wafer heat treatment process according to the related art.

[Explanation of symbols]

 10: processing object (wafer) 12: first processing chamber (load-in / out chamber) 13: second processing chamber

Continued on the front page (72) Inventor Takashi Komatsu 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Semiconductor Technology Laboratory (72) Inventor Kazuyuki Koizumi 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Pref. F-term (reference) in Semiconductor Technology Laboratory Co., Ltd.

Claims (7)

[Claims] 1. A heat treatment method for heating a processing object having a metal thin film on its surface, wherein the processing object is heated to 100 ° C. or higher while evacuating or replacing an atmosphere in which the processing object is placed. A first heating step of raising the temperature to a first heating temperature in a range of 200 ° C. or less, a measuring step of measuring a moisture partial pressure of an atmosphere in which the object to be treated is placed, and a measured value of the moisture partial pressure A heating step of raising the temperature of the object to be processed to a second heating temperature higher than the first heating temperature after the pressure becomes 5 × 10 ⁻⁵ Pa or less. 2. The heat treatment method according to claim 1, wherein the pressure of the atmosphere in which the object to be treated is placed is 1 Pa or less. 3. The heat treatment method according to claim 1, wherein the atmosphere in which the processing object is placed is filled with an inert gas, and the pressure of the atmosphere is reduced to 1 atm or less by the inert gas. 4. The first heating step is performed in a first processing chamber, and the second heating step is performed in a second processing chamber separate from the first processing chamber. The heat treatment method according to any one of claims 1 to 3, wherein the object is transported between the first processing chamber and the second processing chamber without being exposed to the atmosphere. 5. The heat treatment method according to claim 4, wherein the first processing chamber is a loading / unloading chamber for loading the object to be processed from the atmosphere. 6. The heat treatment method according to claim 5, wherein the first processing chamber is filled with nitrogen gas before the object to be processed is carried into the first processing chamber. 7. The heat treatment method according to claim 1, wherein the metal thin film comprises a copper thin film formed by an electrolytic plating method.