JPH08111420A - Method and equipment for fabricating semiconductor device - Google Patents

Abstract

PURPOSE: To form a highly reliable copper wiring pattern with high reproducibility by protecting a semiconductor substrate against corrosion when it is taken out to the atmosphere. CONSTITUTION: A Cu film 3 sandwiched by a barrier metal film 2 and a cover film 4 provided on a semiconductor substrate through an interlayer insulation film 1 is patterned by plasma etching using a chlorine based reaction gas in a first processing chamber. The semiconductor substrate is then carried into a second processing chamber without being exposed to the atmosphere and processed in a hydrogen plasma 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a semiconductor device, and more particularly to a method for preventing corrosion of a copper wiring used in a semiconductor integrated circuit device after a plasma etching process and a processing apparatus used therefor. It is about.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor integrated circuits has been improved, finer design rules have been required. Therefore, the wiring material has a lower volume resistivity than an alloy mainly containing aluminum, and A wiring structure using copper, which has high electromigration resistance and stress / migration resistance, is under study.

When copper is used as a wiring material, plasma etching is carried out using a gas containing chlorine or a chlorine atom, which has the highest vapor pressure among halogen compounds, or a mixed gas thereof. In addition, chlorine is adsorbed and remains on the surface of the substrate to be etched even after the etching is completed. This residual chlorine continues to corrode the surface of the substrate to be etched when the substrate to be etched is taken out into the atmosphere, which causes the problem of corrosion and collapse in which the pattern of the wiring layer patterned with high precision collapses. It will be.

Also, in the conventional plasma etching of aluminum-copper alloy, the occurrence of corrosion was observed, and in order to solve this, it has been proposed to perform hydrogen plasma treatment (Japanese Patent Publication No. 58-41766). Gazette). In this proposal, a 1 .mu.m thick aluminum / copper alloy layer containing 4% by weight of Cu is provided on a substrate at a pressure of 0.
1 Torr, etchant: BCl ₃ , high frequency power: 2
After plasma etching under the conditions of 00W and etching time: 20 minutes, the gas is switched and the pressure is 1 Tor.
The generation of corrosion is prevented by performing hydrogen plasma treatment under the conditions of r, high frequency power: 200 W, and treatment time: 5 minutes. Since the photoresist is used as a mask for the etching in this case, it is necessary to set the processing temperature to 150 ° C. or lower at which the photoresist is not deformed.

On the other hand, in order to solve the problem of corrosion in the copper wiring pattern, the etching temperature is raised to lower the adsorption coefficient of chlorine, which is an etching gas component, so that after the etching is completed, chlorine is left on the substrate surface to be etched. It is considered to prevent it from remaining.
However, in the case of a copper wiring pattern, unlike the case of an aluminum alloy, chlorine that causes corrosion exists not at the surface of the substrate to be processed but at the interface between the Cu film and the barrier metal film or the cover film. Therefore, it has been discovered that the means of lowering the adsorption coefficient at a high temperature is not effective, and corrosion is generated even if the temperature is increased.Therefore, it is proposed to prevent the occurrence of corrosion by combining wet treatment. There is.

The proposed corrosion prevention method will be described with reference to FIGS. 6 and 7. First, the plasma etching apparatus used in this manufacturing process will be described with reference to FIG. Referring to FIG. 7, the plasma etching apparatus 11 includes a high-frequency applying electrode 14 for mounting a semiconductor substrate 13 to be processed in a vacuum processing chamber 12.
And a parallel plate electrode composed of a ground electrode 15, a high-frequency power source 16 is connected to the high-frequency applying electrode 14, and a reaction gas introducing pipe 17 for introducing a reaction gas and an exhaust system for exhausting the gas after the reaction are connected. The exhaust pipe 18 is provided.

Next, a method of preventing corrosion at the time of patterning a copper wiring using this plasma etching apparatus will be described with reference to FIG. See FIG. 6A. First, a TiN film 2 serving as a barrier metal film, a Cu film 3, and a TiN film 4 serving as a cover film are sequentially deposited on an interlayer insulating film 1 provided on a semiconductor substrate. A SiO ₂ film serving as an etching mask is deposited and patterned to form an etching mask 5, and a semiconductor substrate 13 to be processed is prepared.

Next, referring to FIG. 6B, the semiconductor substrate 13 to be processed is placed on the high-frequency applying electrode in the plasma etching apparatus, the inside of the processing chamber is evacuated, and the substrate temperature is set to 200 to 300 ° C. so,
A chlorine-based gas composed of a mixed gas of Cl ₂ , SiCl ₄ , N ₂ and NH ₃ was introduced through a reaction gas introduction pipe, and high-frequency power was applied to form a plasma.
Then, the TiN film 4, the Cu film 3, and the TiN film 2 are etched using the etching mask 5 made of a SiO ₂ film as a mask to form a wiring pattern.

Next, referring to FIG. 6 (c), the semiconductor substrate 13 to be processed is taken out into the atmosphere 7 in order to carry out other subsequent processing steps. At this time, it remains on the surface of the semiconductor substrate 13 to be processed. The reaction proceeds due to chlorine, and a corrosive substance 8 made of chloride of copper is generated on the exposed surface of the Cu film 3.

Next, in order to remove the corroded substance 8, the semiconductor substrate 13 to be processed is immersed in ammonia water 9 having a temperature of 20 ° C. and an ammonia concentration of 28% for 20 seconds. Then, the semiconductor substrate 13 to be processed is washed with pure water for 2 minutes to obtain a copper wiring pattern in which corrosive substances are completely removed and no subsequent corrosion occurs.

[0011]

However, since the conventional corrosion prevention method involves a wet etching process, an extra wet etching apparatus is required,
This will increase the cost. Ammonia water is Cu
It is not easy to secure dimensional accuracy because it dissolves a little, and in addition, corrosive substances are inevitably generated after plasma etching. However, there is a drawback that it is difficult to maintain the accuracy of the wiring pattern formed by plasma etching, and it is not a perfect corrosion prevention method.

When the corrosion prevention method for aluminum alloy is diverted as a corrosion prevention measure, the obtained wiring pattern is not perfect, and
Corrosion still occurs, and when a plurality of semiconductor substrates to be processed are continuously processed, the etching rate in the plasma etching process is lowered, and the etching time is not reproducible.

Therefore, according to the present invention, after the plasma etching step, chlorine is removed without exposing the semiconductor substrate to be processed to the atmosphere, thereby preventing the occurrence of corrosion when the semiconductor substrate to be processed is taken out into the atmosphere. However, the object is to form a highly reliable copper wiring pattern with good reproducibility.

[0014]

According to the present invention, in a method of manufacturing a semiconductor device, a barrier metal film (2 in FIG. 1) and a cover film provided on a semiconductor substrate via an interlayer insulating film (1 in FIG. 1). A Cu film sandwiched between the upper and lower parts by (4 in FIG. 1) (see FIG. 1).
3) is patterned in the first processing chamber by plasma etching using a chlorine-based reaction gas, and a semiconductor substrate is placed in the second processing chamber without being exposed to the atmosphere after the plasma etching process. And a hydrogen plasma treatment step of carrying and treating in hydrogen plasma (10 in FIG. 1).

Further, the present invention is characterized in that the substrate temperature of the semiconductor substrate to be processed in the plasma etching step is set to 150 ° C. to 300 ° C. Further, the present invention is characterized in that the substrate temperature of the semiconductor substrate to be processed in the hydrogen plasma processing step is set to 150 ° C. or higher.

Further, according to the present invention, a first processing chamber for performing a plasma etching process and a second processing chamber for performing a hydrogen plasma process are provided.
It is characterized in that it is connected to the processing chamber of (1) by a joint having a diameter capable of carrying the substrate.

Further, according to the present invention, a first processing chamber for carrying out a plasma etching process and a second processing chamber for carrying out a hydrogen plasma process are provided.
The processing chamber is connected to a processing chamber of 1 by a preliminary chamber having a diameter capable of transferring the substrate.

[0018]

[Function] By patterning by plasma etching and then treating in hydrogen plasma without exposing to the atmosphere, chlorine-based gas components can be removed without producing corrosive substances, which makes the wiring pattern high. The accuracy can be maintained, and since the processing chamber is separated, the residual hydrogen in the hydrogen plasma processing process does not affect the plasma etching process.
The reproducibility of etching is improved.

Further, by setting the substrate temperature in the plasma etching step at 150 ° C. or higher, the reaction product can be prevented from adhering, and by setting it at 300 ° C. or lower, the etching shift amount can be reduced. By setting the substrate temperature in the hydrogen plasma treatment step to 150 ° C. or higher, the generation of corrosion can be completely suppressed.

Further, by making the processing chamber for performing the plasma etching process and the processing chamber for performing the hydrogen plasma treatment separate from each other, even if a large number of wafers are continuously processed, the processing of the previous wafer is affected. It is possible to realize a manufacturing apparatus capable of performing stable processing.

Further, by connecting the first processing chamber for performing the plasma etching processing and the second processing chamber for performing the hydrogen plasma processing with a preliminary chamber having a diameter capable of carrying the substrate, the processing chamber is formed. It is possible to realize a manufacturing apparatus that can prevent mutual influences and can perform stable processing.

[0022]

Embodiments of the present invention will be described with reference to FIGS. 1 is an explanatory diagram of the manufacturing process of the present invention, and FIG. 2 is an explanatory diagram of the correlation between the substrate temperature, the etching shift amount, and the reaction product attachment density when the plasma etching of the present invention is performed. FIG. 3 is an explanatory diagram of the correlation between the substrate temperature and the corrosion density when the hydrogen plasma treatment of the present invention is performed, and FIG. 4 is an explanatory diagram of the first manufacturing apparatus used for implementing the present invention. .

First, the structure of the first manufacturing apparatus will be described. Referring to FIG. 4, a manufacturing apparatus used for carrying out the present invention includes a plasma etching apparatus 11 and a hydrogen plasma processing apparatus 21, and a bonding portion 19 having a diameter capable of carrying a semiconductor substrate 13 to be processed which connects these apparatuses. The plasma etching apparatus 11 has the same configuration as the conventional etching apparatus shown in FIG.

The basic structure of the hydrogen plasma processing apparatus 21 is the same as that of the plasma etching apparatus, and a parallel plate including a high frequency applying electrode 23 and a ground electrode 24 for mounting the semiconductor substrate 13 to be processed in the vacuum processing chamber 22. Electrodes are arranged, a high-frequency power source 25 is connected to the high-frequency applying electrode 23, and a hydrogen gas introducing pipe 26 for introducing hydrogen gas and an exhaust pipe 27 connected to an exhaust system for exhausting the gas after the reaction.
Consists of

Then, this plasma etching apparatus 1
1 and the hydrogen plasma processing apparatus 21 are connected to the joint portion 19 having a diameter capable of carrying the semiconductor substrate 13 to be processed,
A gate valve 20 capable of completely blocking the two is provided, and a transfer device (not shown) for transferring the semiconductor substrate 13 to be processed is provided between the plasma etching device 11 and the hydrogen plasma processing device 21.

As described above, a single processing apparatus is not used for continuous processing as in the prior art, but a different processing apparatus is used for each processing.
The connection between them at the junction with the gate valve is
This is to prevent the etching rate from lowering when the next semiconductor substrate to be processed is subjected to plasma etching processing in the processing chamber exposed to hydrogen plasma.

That is, when the previous semiconductor substrate to be processed is finished and the next semiconductor substrate to be processed is processed, hydrogen is adsorbed on the surface of the wall of the vacuum processing chamber and is introduced from the reaction gas introducing pipe. Since the reaction gas is trapped by the adsorbed hydrogen, the etching rate is reduced to about 1/5.

Therefore, the plasma etching apparatus 1
1 to hydrogen plasma processing apparatus 21 semiconductor substrate 1 to be processed
In the case of carrying 3, the plasma etching apparatus 11
Hydrogen gas from the hydrogen plasma processing apparatus 21 to the hydrogen plasma processing apparatus 21, or the pressure inside the hydrogen plasma processing apparatus 21 is made lower than the atmospheric pressure inside the plasma etching apparatus 11 so that hydrogen gas or It is necessary to prevent hydrogen plasma from entering the plasma etching apparatus 11.

Next, the manufacturing process of the present invention will be described. See FIG. 1 (a). First, the substrate temperature is set to 200 ° C. and the temperature is set to 10 mT on the interlayer insulating film 1 made of SiO ₂ provided on the silicon semiconductor substrate.
Discharge power is 1k in an orr argon gas atmosphere
With the dc power of W applied, a TiN film 2 serving as a barrier metal film is deposited to a thickness of 50 nm by a sputtering method using TiN as a target, and then heat-treated at 450 ° C. for 30 minutes to enhance the barrier property of the TiN film 2. .

Next, under the same film forming conditions as the TiN film 2, C
The u film 3 is formed by a sputtering method using Cu as a target.
After being deposited to a thickness of 00 nm, the TiN film 4 serving as a cover film is also deposited to a thickness of 50 nm by a sputtering method under the same film forming conditions as the TiN film 2 in another sputtering apparatus while being transported in a vacuum container.

Next, a SiO ₂ film serving as an etching mask is deposited by the CVD method, a photoresist having a thickness of 1 μm is applied thereon, exposed, and then developed with an alkali developing solution to form a photoresist pattern. To do.
Then, using this photoresist pattern as a mask, the SiO ₂ film is etched by reactive ion etching using CF ₄ / CHF ₃ plasma until the underlying TiN film 4 is exposed to form an etching mask 5 made of SiO ₂ . A semiconductor substrate 13 to be processed is prepared.

The various conditions in the film forming step are not limited to the above numerical values, and the substrate temperature of the silicon semiconductor substrate may be 150 ° C. to 300 ° C. The reason for this will be described with reference to FIG. .

See FIG. 2. FIG. 2 is an explanatory view of the correlation between the substrate temperature of the semiconductor substrate to be processed, the etching shift amount, and the reaction product attachment density.
The etching shift amount represents the difference between the width of the etching mask and the width of the wiring pattern that is the member to be etched, that is, the amount of shift in the dimension of the wiring pattern due to side etching, and the reaction product adhesion density is It represents the area ratio of the region where the reaction product adheres to the entire surface of the substrate to be processed.

As shown in FIG. 2, when the substrate temperature is lower than 150 ° C., the reaction product is attached and the etching rate is lowered, which is not a practical condition, and the wiring pattern is incomplete and corrosion is likely to occur. Become. Further, when the substrate temperature is higher than 300 ° C., the etching shift amount becomes large and the pattern shape deteriorates, which is not a condition for practical use.

The gas pressure in the processing chamber is 9 to 11 mTorr.
r may be set, and the film thickness is appropriately set according to the aspect ratio (= step height / distance between step) of the semiconductor device to be manufactured, and the discharge power can be obtained as the throughput. It is appropriately determined depending on the correlation with the film quality, and the temperature in the annealing process of the TiN film 2 may be 400 ° C. to 500 ° C.

Next, referring to FIG. 1B, the semiconductor substrate 13 to be processed is placed on the high frequency applying electrode in the plasma etching apparatus, the inside of the processing chamber is evacuated, and the substrate temperature is set to 260 ° C. Cl ₂ ,
A chlorine-based gas composed of a mixed gas of SiCl ₄ , N ₂ , and NH ₃ was introduced through a reaction gas introduction pipe to obtain 1.6 W / c.
A high frequency power of m ² is applied to generate plasma, and the chlorine-based plasma 6 is used to mask the TiN film 4, the Cu film 3, and the Ti film with the etching mask 5 made of the SiO ₂ film as a mask.
The N film 2 is etched to form a wiring pattern. The volume flow rate of the reaction gas is Cl ₂ : 20 cc / min, Si
Cl ₄ : 20 cc / min, N ₂ : 80 cc / min, and N
H ₃ : 10 cc / min, gas pressure is 30 mTorr, and etching time is 5 minutes.

Next, after the etching is completed, the introduction of the chlorine-based reaction gas is stopped immediately, and the processing chamber is evacuated for a while. In this case, although the time required for evacuation depends on the exhaust system capacity, evacuation was performed for about 1 minute in this example.

See FIG. 4. After the exhausting is completed, the gate valve 20 provided at the joint 19 is provided.
To open the semiconductor substrate 13 to be processed after etching
Is loaded into the hydrogen plasma processing apparatus 21, placed on the high frequency application electrode 23, and the gate valve 20 is closed. in this case,
It is necessary to consider the pressure in the vacuum processing chambers 12 and 22 so that the hydrogen gas in the hydrogen plasma processing apparatus 21 does not mix into the plasma etching apparatus 11 via the joint portion 19.

Then, referring to FIG. 1 (c), hydrogen gas having a flow rate of 100 cc / min is introduced into the processing chamber through the hydrogen gas introducing pipe to adjust the substrate temperature to 220 ° C.
With the gas pressure set to 100 mTorr and the high frequency discharge power density set to 0.4 W / cm ² , hydrogen plasma 10 is generated, and the semiconductor substrate 13 to be processed is irradiated with hydrogen radicals and hydrogen ions, and the hydrogen plasma is supplied for 1 minute. Perform processing.

Next, as shown in FIG. 1D, the etching mask 5 is removed by an appropriate means to obtain a copper wiring pattern free from corrosion.

The various conditions in the above hydrogen plasma processing step are not limited to the above numerical values, the substrate temperature of the semiconductor substrate 13 to be processed may be 150 ° C. or higher, and the gas pressure may be 100 mTorr to 300 mTorr. I wish I had it.

Here, the reason why the substrate temperature of the semiconductor substrate 13 to be processed is set to 150 ° C. or higher will be described with reference to FIG. See FIG. 3. FIG. 3 is an explanatory diagram of the correlation between the substrate temperature and the corrosion density of the semiconductor substrate to be processed. When the substrate temperature is 150 ° C. or lower, corrosion occurs and the hydrogen plasma treatment effect is lost. The corrosion density represents the area ratio of the region where corrosion has occurred to the entire surface of the semiconductor substrate to be processed.

In this case, the reason why the upper limit temperature of the substrate temperature should be limited is not so much from the viewpoint of preventing the occurrence of corrosion, but if it is too high, the hydrogen adsorption effect decreases,
Along with this, the hydrogen plasma treatment effect may decrease, and plasma treatment at high temperature may damage the semiconductor substrate to be treated, so 300 ° C. or lower is preferable.

Next, with reference to FIG. 5, a second embodiment of the manufacturing apparatus used for carrying out the present invention will be described. 5, the configurations of the plasma etching apparatus 11 and the hydrogen plasma processing apparatus 21 in the manufacturing apparatus of the second embodiment are similar to those of the manufacturing apparatus of the first embodiment of FIG.
The difference is in the configuration of the connecting portion.

That is, in the manufacturing apparatus of the second embodiment, a spare chamber 28 is provided between the plasma etching apparatus 11 and the hydrogen plasma processing apparatus 21, and the spare chamber 28 and the plasma etching apparatus 11 are connected to each other. The first gate valve 29, the auxiliary chamber 28 and the hydrogen plasma processing apparatus 21.
A second gate valve 30 is provided between the first and second valves, and a purge gas introducing pipe 31 for introducing a gas for purging the gas that has entered the spare chamber and an exhaust pipe 32 for connecting to an exhaust system are provided. Also in this case, a transfer device (not shown) for transferring the semiconductor substrate 13 to be processed is provided between the plasma etching apparatus 11 and the hydrogen plasma processing apparatus 21.

In this case, after the plasma etching process is completed, the first gate valve 29 is opened and the semiconductor substrate 13 to be processed is loaded into the preliminary chamber 28, and the first gate valve 29 is opened.
After closing, the purge gas introducing pipe 31 introduces a purge gas made of an inert gas such as nitrogen gas or argon gas into the spare chamber and exhausts the gas.

Next, the second gate valve 30 is opened, the semiconductor substrate 13 to be processed is loaded into the hydrogen plasma processing apparatus 21, placed on the high frequency applying electrode 23, and the second gate valve 30 is closed. After that, the hydrogen plasma treatment is started. In this case, since the vacuum processing chambers 12 and 22 do not interfere with each other, it is possible to perform highly accurate processing with good reproducibility even if such processing steps are repeated many times.

Although the manufacturing apparatus of the first and second embodiments of the present invention is constructed by combining the parallel plate electrode type reactive ion etching apparatus, it is not limited to such a construction. Instead, an etching apparatus using high-density plasma such as ECR plasma or inductively coupled plasma may be used, and etching apparatuses having different configurations may be combined.

[0049]

According to the present invention, after the plasma etching step using the chlorine-based reaction gas, the hydrogen plasma treatment is performed without exposing the semiconductor substrate to be treated to the atmosphere,
Since it is possible to completely prevent the occurrence of corrosion due to chlorine remaining on the surface of the copper wiring pattern, it is possible to use copper having a low volume resistivity and high electromigration resistance and stress / migration resistance as a wiring layer, and therefore a semiconductor integrated circuit. Further miniaturization of the device becomes possible.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of a manufacturing method of the present invention.

FIG. 2 is an explanatory diagram of a correlation between a substrate temperature, an etching shift amount, and a reaction product attachment density in an example of the manufacturing method of the present invention.

FIG. 3 is an explanatory diagram of the correlation between the substrate temperature and the corrosion density in the example of the manufacturing method of the present invention.

FIG. 4 is an explanatory diagram of the first embodiment of the manufacturing apparatus of the present invention.

FIG. 5 is an explanatory diagram of a second embodiment of the manufacturing apparatus of the present invention.

FIG. 6 is an explanatory diagram of a conventional corrosion prevention method.

FIG. 7 is an explanatory diagram of a conventional manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Interlayer insulating film 2 Barrier metal film 3 Cu film 4 Cover film 5 Etching mask 6 Chlorine-based plasma 7 Atmosphere 8 Corrosion product 9 Ammonia water 10 Hydrogen plasma 11 Plasma etching equipment 12 Vacuum processing chamber 13 Processed semiconductor substrate 14 High frequency application electrode 15 ground electrode 16 high frequency power supply 17 reaction gas introduction pipe 18 exhaust pipe 19 junction 20 gate valve 21 hydrogen plasma device 22 vacuum processing chamber 23 high frequency application electrode 24 ground electrode 25 high frequency power supply 26 hydrogen gas introduction pipe 27 exhaust pipe 28 preparatory chamber 29 First gate valve 30 Second gate valve 31 Purge gas introduction pipe 32 Exhaust pipe

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Claims (8)

[Claims] 1. A Cu film sandwiched above and below by a barrier metal film and a cover film provided on a semiconductor substrate with an interlayer insulating film interposed therebetween by plasma etching using a chlorine-based reaction gas in a first processing chamber. A plasma etching step of patterning, and a hydrogen plasma processing step of carrying the semiconductor substrate to the second processing chamber without exposing it to the atmosphere after the plasma etching step and processing it in hydrogen plasma. And a method for manufacturing a semiconductor device. 2. The barrier metal film and the cover film are made of Ti.
The method of manufacturing a semiconductor device according to claim 1, wherein the method comprises a N film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein a silicon oxide film is used as an etching mask in the plasma etching step. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the temperature of the semiconductor substrate in the plasma etching step is set to 150 ° C. to 300 ° C. 5. The method of manufacturing a semiconductor device according to claim 3, wherein the temperature of the semiconductor substrate in the hydrogen plasma treatment step is set to 150 ° C. or higher. 6. The first processing chamber for performing the plasma etching processing and the second processing chamber for performing the hydrogen plasma processing are connected by a joint having a diameter capable of carrying the semiconductor substrate. A manufacturing apparatus used in the method of manufacturing a semiconductor device according to claim 1. 7. A first processing chamber for performing the plasma etching processing and a second processing chamber for performing the hydrogen plasma processing are connected by a preliminary chamber having a diameter capable of carrying the semiconductor substrate, and 2. The manufacturing apparatus used in the method of manufacturing a semiconductor device according to claim 1, wherein first and second gate valves are provided between the preliminary chamber and the first and second processing chambers, respectively. 8. The manufacturing apparatus according to claim 7, wherein a purge gas introducing pipe and an exhaust pipe are provided in the preliminary chamber.