JP5669417B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device using titanium as a part of a wiring layer, and more particularly to a method for manufacturing water by introducing water during film formation of titanium.

  In recent years, with the high integration of semiconductor devices, semiconductor elements and various wirings have been miniaturized. However, although miniaturization has progressed in the planar direction, it is difficult to ensure sufficient insulation between the wirings stacked vertically, as for the vertical direction, that is, in the film thickness direction, Since the semiconductor device surface needs to be sufficiently flattened, it has not progressed as much as in the planar direction.

The same is true for the interlayer insulating film that separates the semiconductor element and the wiring provided on the surface of the semiconductor device, and it is difficult to reduce the film thickness in order to ensure the insulation between the semiconductor element and the wiring.
The interlayer insulating film is provided with a connection hole (so-called contact hole) for connecting the semiconductor element and the wiring. As the semiconductor element and various wirings become finer, the diameter of the connection hole tends to be smaller, so the aspect ratio, which is the ratio of the diameter and depth of the connection hole, also tends to increase. As the aspect ratio increases, it becomes difficult to embed the wiring material up to the bottom of the connection hole.
In other words, as semiconductor elements and various wirings become finer, it becomes difficult to embed wiring materials using a sputtering method, which is a conventionally known wiring forming method, in connection between wirings and semiconductor elements. It will come.

As a technique for sufficiently filling a connection hole having a high aspect ratio with a wiring material, a high temperature sputtering method using aluminum as a wiring material is known.
The high-temperature sputtering method is a sputtering method in which the semiconductor substrate is heated to a high temperature during sputtering, and the aluminum that has reached the surface of the semiconductor substrate is surface-flowed and penetrates to the bottom of the connection hole. Even so, it is a technique that can embed wiring material.

In the high temperature sputtering method, a base layer is formed on the surface of the connection hole and the interlayer insulating film prior to filling of the connection hole with aluminum. In general, the underlayer has a structure in which a first titanium film, a titanium nitride film, and a second titanium film are laminated from the surface side of a semiconductor substrate.
Each membrane plays an important role. If the material of the semiconductor substrate is silicon, the first titanium layer stabilizes the contact resistance by forming titanium silicide (TiSi ₂ ) with silicon as the semiconductor substrate at the bottom of the connection hole. Have a role.
The titanium nitride film serves as a barrier layer that prevents aluminum formed by high-temperature sputtering from diffusing into the semiconductor substrate. Furthermore, since the second titanium film has wettability with respect to aluminum formed by a high temperature sputtering method, the second titanium film has a role of assisting aluminum to surface flow and bury the connection hole.

A typical wiring structure by high-temperature sputtering will be described with reference to FIG.
FIG. 7 is a cross-sectional view schematically showing the wiring structure in the connection hole. In FIG. 7, 51 is a semiconductor substrate, and 52 is an interlayer insulating film. The semiconductor substrate 51 is made of silicon, and the interlayer insulating film 52 is made of a silicon oxide film. Reference numeral 53 denotes a connection hole provided in the interlayer insulating film. This is a so-called contact hole. 54 is a first titanium film, 55 is a titanium nitride film, and 56 is a second titanium film. 57 is aluminum, which is laminated with a base layer 58 to form a wiring layer.

As shown in FIG. 7, the connection hole 53 is provided in the interlayer insulating film 52 provided on the semiconductor substrate 51 so that the surface of the semiconductor substrate 51 is exposed.
A first titanium film 54, a titanium nitride film 55, and a second titanium film 56 are sequentially formed, and a base layer 58 that is a laminated film is provided on the surface of the interlayer insulating film 52 and the connection hole 53. Then, aluminum 57 is provided on the surface of the base layer 58 so as to bury the connection holes 53.

  In general, aluminum used as a wiring material will be described. When considering wiring materials, resistance to electromigration becomes important. Electromigration is a phenomenon in which ions move and change the shape of the conductor because the momentum is exchanged between the electrons moving inside the conductor and the atoms forming the conductor. It is. Since defects occur in the wiring, the durability is important in order to ensure the reliability of the semiconductor device.

It is known that the electromigration resistance of a wiring material depends on its crystal orientation. Aluminum formed by high-temperature sputtering preferably has a high crystal orientation (111).
Furthermore, it is also known that the crystal orientation of aluminum is caused by the crystal orientation of the underlayer. For example, when the underlying layer is composed of the titanium film and the titanium nitride film described above, the higher the crystal orientation (002) of the first titanium film as the lowermost layer, the higher the (111) crystal orientation of the upper aluminum layer. It is known to be.

  For this reason, it has been proposed to increase the crystal orientation of the underlayer in order to improve the electromigration resistance of the aluminum wiring. As a measure for increasing the crystal orientation of the first titanium film, it is known to form the first titanium film in an atmosphere containing hydrogen (see, for example, Patent Documents 1 and 2).

  The conventional technique shown in Patent Document 1 uses a highly hygroscopic BPSG film as an interlayer insulating film, and the amount of moisture absorbed on the surface of the BPSG film, or the amount of moisture in the film formation chamber when forming a titanium film, It has been proposed to increase the crystal orientation (002) of the titanium film.

  The conventional technique shown in Patent Document 2 is an improvement over the technique shown in Patent Document 1. The factor affecting the crystal orientation (002) of the titanium film was found to be hydrogen rather than moisture, and the titanium film was introduced into the film formation chamber after introducing hydrogen gas or while introducing hydrogen gas. A method for forming a film is proposed.

  In the prior art disclosed in Patent Document 2, when a first titanium film is formed, a titanium film having high crystal orientation (002) can be obtained by introducing hydrogen. As a result, the crystal orientation of the titanium nitride film, the second titanium film, and aluminum that are subsequently formed is increased, and a wiring layer having high migration resistance can be formed.

Japanese Patent Laid-Open No. 10-41383 (page 10, FIG. 1) Japanese Patent Laid-Open No. 2008-300749 (page 14, FIG. 10)

The prior art shown in Patent Document 1 suggests that the crystal orientation (002) of the titanium film is stabilized by supplying water vapor into the film forming chamber. It was found that oxygen was generated by decomposing water, and this oxygen was mixed into the titanium film to become titanium oxide. The titanium film containing titanium oxide is disturbed in crystal orientation, and the crystal orientation of the subsequently sputtered titanium nitride film is also disturbed. As a result, the barrier property of the titanium nitride film is lowered.

  The conventional technique disclosed in Patent Document 2 introduces hydrogen gas into the film formation chamber. As a result, titanium oxide is not included in the titanium film, but hydrogen gas is a highly explosive gas, and it is necessary to take measures against ignition during work, etc., and handling of hydrogen gas is also necessary. If you try to use this technology, it will take a lot of work.

  As described above, in the conventional techniques shown in Patent Document 1 and Patent Document 2, it is difficult to safely obtain a titanium film having high crystal orientation (002), and as a result, aluminum having high migration resistance is reproducible. It was difficult to form well.

  The present invention has been made to solve such problems, and controls the hydrogen partial pressure that contributes to the crystal orientation (002) of the titanium film without using dangerous hydrogen gas, thereby migrating resistance. It provides a technique for forming aluminum that is superior to the above.

  In order to achieve the above object, a method for manufacturing a semiconductor device of the present invention employs the following method.

The surface of the semiconductor substrate, in the manufacturing method of a semiconductor device placing a titanium film,
The film forming chamber which arranged titanium sample, creating and water, and an inert gas comprising argon, the oxide formation gas consisting of nitrogen, the atmosphere due to the mixed gas, a mixed gas by entering guide comprising, mixed A gas introduction process;
The water is decomposed in the film formation chamber to generate hydrogen and oxygen, and the oxide generating gas and oxygen are combined to generate nitrogen oxide . The freeze-drying apparatus is used to bring the film formation chamber into a high vacuum atmosphere. In addition, the temperature is controlled in a temperature range in which hydrogen does not condense and inert gas and nitrogen oxides condense, so that the inert gas and nitrogen oxides are exhausted and only hydrogen is deposited in the deposition chamber. A dummy sputtering step of selectively leaving, introducing an inert gas to generate plasma, and exposing the surface of the titanium sample;
A substrate carrying-in step of carrying the semiconductor substrate into the film forming chamber with hydrogen remaining in the film forming chamber;
An inert gas introduction step of introducing an inert gas into the film formation chamber with hydrogen remaining in the film formation chamber;
A titanium film sputtering step, in which hydrogen is left in the film formation chamber, plasma is generated to perform sputtering, and a titanium film is formed on the surface of the semiconductor substrate ;
It is characterized by having .

  With such a structure, oxygen can be excluded from the deposition chamber, so that titanium oxide is not included in the titanium film. In addition, since hydrogen remains in the deposition chamber when titanium is formed, a titanium film with good crystal orientation can be formed.

In the mixed gas introducing step , water, an inert gas, and an oxide generating gas may be sequentially introduced into the film forming chamber to generate a mixed gas in the film forming chamber.

  With such a structure, a mixed gas can be generated in the deposition chamber even if the gas supply systems are independent of each other.

In the mixed gas introducing step , the first mixed gas in which water and an inert gas are mixed is introduced into the film forming chamber, and then the mixed gas is generated by introducing the oxide generating gas into the film forming chamber. It may be.

  With such a configuration, the inert gas becomes a carrier of water and can be efficiently introduced.

  The first mixed gas may be supplied from the same gas cylinder.

  With such a configuration, the inert gas and water can be managed in a unified manner, and the controllability of gas supply is improved.

The titanium film sputtering step may be performed while the semiconductor substrate is heated to a temperature of 200 ° C. to 250 ° C.

  With such a configuration, the crystal orientation (002) of the titanium film can be further increased.

According to the present invention, hydrogen is generated by plasma decomposition of water in the film forming chamber, and in addition to the conventional effect of improving the crystal orientation of the titanium film using this hydrogen, simultaneously generated oxygen is It can be removed from the film formation chamber by reacting with an oxide generating gas to form an oxide.
By removing the oxygen, the titanium oxide film is not included in the titanium film, and deterioration of the film quality of the titanium film can be suppressed.

It is a figure explaining the process flow of 1st Embodiment. It is a figure which shows typically the structure of the film-forming chamber of the semiconductor device used for 1st Embodiment. It is a figure explaining the process flow of 2nd Embodiment. It is a figure which shows typically the structure of the film-forming chamber of the semiconductor device used for 2nd Embodiment. It is a figure explaining the process flow of 3rd Embodiment. It is a figure which shows typically the structure of the film-forming chamber of the semiconductor device used for 3rd Embodiment. It is sectional drawing which shows typically the structure of the wiring in a connection hole.

[Description of First Embodiment: FIGS. 1 and 2]
A first embodiment of a semiconductor device manufacturing method will be described with reference to FIGS. FIG. 1 is a diagram illustrating a process flow. FIG. 2 is a diagram schematically showing the structure of the film forming chamber of the semiconductor manufacturing apparatus.

In FIG. 1, 1 is a dummy substrate carrying-in process, 2 is a mixed gas introducing process, 3 is a dummy sputtering process, 4 is a dummy substrate carrying-out process, 5 is a substrate carrying-in process, 6 is an inert gas introducing process, and 7 is a titanium film. It is a sputtering process.
After the titanium film sputtering process 7, the titanium nitride film formation, the second titanium film formation, the aluminum film formation, and the semiconductor device manufacturing process continue, but these manufacturing processes are the essential part of the present invention. Since there is no description, explanation is omitted.

In FIG. 2, 11 is a film forming chamber, 12 is a titanium sample, 13 is a substrate mounting table, 14 is a gas introduction port, 15 is a mixed gas cylinder, and 16 is an exhaust port.
In the sputtering in the first embodiment, the mixed gas 15 is introduced into the film forming chamber 11 through the gas introduction port 14 to generate plasma, thereby generating titanium particles from the titanium sample 12. A general DC sputtering method of forming a film on the arranged substrate can be used.

Hereinafter, the process flow shown in FIG. 1 will be described in order. First, the dummy substrate carrying-in process 1 will be described.
Here, a dummy substrate (not shown) is carried into the film forming chamber 11 using a predetermined transport mechanism. The dummy substrate is installed on the upper part of the substrate mounting table 13. The dummy substrate is for covering the substrate mounting table 13 so that titanium particles do not fly when sputtering is performed, and the material is not particularly limited to the semiconductor substrate.

Next, the mixed gas introduction process 2 will be described.
Here, a mixed gas of water, an inert gas, and an oxide generating gas is introduced into the film forming chamber 11 from the mixed gas cylinder 15. For example, argon can be used as the inert gas. For example, nitrogen can be used as the oxide generating gas. In addition, water is in a state of water vapor inside the mixed gas cylinder 15, and when introduced into the film forming chamber 11 together with the inert gas and the oxide generating gas, the gas inlet 14 is already mixed. Supplied from

Next, the dummy sputtering step 3 will be described.
Here, a predetermined bias is applied between the titanium sample 12 and the substrate mounting table 13 to generate plasma and perform sputtering. Due to the generation of plasma, the mixed gas is decomposed into four types: hydrogen, oxygen, inert gas, and oxide generating gas.
Hydrogen is generated from water contained in the mixed gas in the film forming chamber 11, but oxygen is also generated at the same time. Since this oxygen oxidizes titanium as already explained, we want to remove it. For this reason, it is made to react with this oxygen using the oxide production gas. When nitrogen is used for the oxide generating gas, oxygen reacts with the oxide generating gas to become nitrogen oxides.

  And exhaust is performed. Thereby, nitrogen oxides are exhausted from the exhaust port 16. The inert gas is exhausted in the same manner. Hydrogen is not exhausted and remains in the film formation chamber 11. This eliminates unnecessary nitrogen oxides, leaving only hydrogen.

The oxide generating gas is originally used for the purpose of removing oxygen, but also reacts with the titanium sample 12 to generate a titanium compound on the surface of the titanium sample 12. When nitrogen is used for the oxide generating gas, the surface of the titanium sample 12 is covered with a titanium nitride compound.
If sputtering is performed in this state, a titanium nitride film is formed on the semiconductor substrate instead of a titanium film. In order to prevent this, dummy sputtering (surface exposure of the titanium sample) is further performed. This will be described later.

Here, a mechanism in which only hydrogen remains will be described.
In general, a sputtering apparatus uses a freeze-drying apparatus to form a high vacuum atmosphere. This is because the molecules scattered in the gas state are cooled, so that the molecules are condensed and adsorbed and excluded from the atmosphere.
Although the freezing point varies depending on the molecule, the freezing point of hydrogen is lower than that of an inert gas or an oxide. That is, by controlling the temperature of the freeze-drying apparatus within a temperature range in which hydrogen does not condense and inert gas and oxide condense, only hydrogen can be left selectively in the film forming chamber 11. It becomes.
Incidentally, although the freezing point of oxygen is higher than that of hydrogen, there is almost no difference, so that it is difficult to separate by freeze-drying device temperature control. In other words, oxygen can be selectively eliminated by reacting with the oxide-generating gas to form an oxide and raising the freezing point.

Next, the surface exposure of the titanium sample 12 will be described.
Since the surface of the titanium sample 12 is covered with the titanium nitride compound as described above, it is necessary to expose the titanium surface.
For example, an inert gas (not shown) is introduced into the film forming chamber 11, plasma is generated, and the surface of the titanium sample 12 is subjected to dummy sputtering. As a result, no titanium nitride compound remains on the surface of the titanium sample 12. For example, argon can be used as the inert gas.

Next, the dummy substrate carry-out process 4 and the main substrate carry-in process 5 will be described.
As described above, since the atmosphere in which only hydrogen remains in the film forming chamber 11 is formed, a titanium film is formed next on a production semiconductor substrate (hereinafter simply referred to as the present substrate) to be manufactured. The dummy substrate is unloaded using a predetermined transfer mechanism, and instead the main substrate is loaded and installed on the upper portion of the substrate setting table 13.

Next, the inert gas introduction process 6 will be described.
An inert gas is introduced into the film forming chamber 11. The introduction of the inert gas is for forming a titanium film on the substrate. Argon can be used as the inert gas. This inert gas is introduced into the film forming chamber 11 from a gas cylinder (not shown) different from the mixed gas cylinder 15 through a gas introduction port (not shown).

Next, the titanium film sputtering step 7 will be described.
Here, a predetermined bias is applied between the titanium sample 12 and the substrate mounting table 13 to generate plasma and perform sputtering. As described above, since the film formation chamber 11 is filled with hydrogen, a titanium film having high crystal orientation (002) is formed on this substrate.

  In forming the film, it is desirable to control the temperature of the substrate mounting table 13 in the range of 200 to 250 ° C. In general, the crystal orientation of a thin film is influenced by the lattice vibration of the deposition surface and thus has temperature dependence. However, according to experiments, the crystal orientation of the titanium film (002) indicates that the substrate temperature is 200 to 250 ° C. It has been found that the highest value is obtained by controlling the range.

[Description of Second Embodiment: FIGS. 3 and 4]
A second embodiment of the semiconductor device manufacturing method will be described with reference to FIGS. FIG. 3 is a diagram for explaining the process flow. FIG. 4 is a diagram schematically showing the structure of the film forming chamber of the semiconductor manufacturing apparatus. Note that the same number is assigned to the same process already described, and the description thereof is omitted.

  In FIG. 3, 2a is a water introduction step, 2b is an inert gas introduction step, 2c is an oxide generation gas introduction step, and 20 is a generic name for these 2a to 2c. The difference from the first embodiment already described is that water, an inert gas, and an oxide generating gas are sequentially introduced into the film forming chamber 11 to form a mixed gas in the film forming chamber. Moreover, about the gas introduction process 20, the order which introduce | transduces each gas does not have limitation in particular, It can select freely. Of course, you may introduce simultaneously.

  In FIG. 4, 15a is a water cylinder, 15b is an inert gas cylinder, and 15c is an oxide generation gas cylinder. In the water cylinder 15a, the water is in a steam state. 14a is a gas inlet for the water cylinder 15a, 14b is a gas inlet for the inert gas cylinder 15b, and 14c is a gas inlet for the oxide generating gas cylinder 15c. Thus, by providing a gas cylinder and a gas inlet for each gas, each can be introduced individually.

  Even in this case, the gas atmosphere in the film forming chamber 11 in the dummy sputtering step 3 can be made the same as in the first embodiment. The second embodiment also has the advantage that the mixing ratio of each gas can be set freely.

[Explanation of Third Embodiment: FIGS. 5 and 6]
A third embodiment of a method for manufacturing a semiconductor device will be described with reference to FIGS. FIG. 5 is a diagram for explaining the process flow. FIG. 6 is a diagram schematically showing the structure of the film forming chamber of the semiconductor manufacturing apparatus. Note that the same number is assigned to the same process already described, and the description thereof is omitted.

  In FIG. 5, 2d is a process of introducing a mixed gas of water and inert gas. The gas introduction step 21 is a generic name for the oxide generation gas introduction step 2c and the mixed gas introduction step 2d already described. The difference from the already described second embodiment is that water and inert gas use the same cylinder. About the gas introduction process 21, the order which introduce | transduces each gas does not have limitation in particular, It can select freely. Of course, you may introduce simultaneously.

  In FIG. 6, 15d is a mixing cylinder of water and inert gas. 14d is a gas inlet for the mixing cylinder 15d. The oxide generating gas cylinder 15c and the gas inlet for the oxide generating gas cylinder 15c are the same as those already described.

  By introducing water and an inert gas from the gas inlet 14d and an oxide generating gas from the gas inlet 14c, a mixed gas atmosphere of water, an inert gas, and an oxide generating gas is formed in the film forming chamber 11. Can be formed.

Even in this case, the gas atmosphere in the film forming chamber 11 in the dummy sputtering step 3 can be made the same as in the first and second embodiments.
Water is highly adsorbable, and a single gas cylinder is adsorbed on the inner wall of the gas cylinder or the inner wall of the gas introduction path, so that the introduction efficiency is poor. However, by supplying from the same cylinder as the inert gas, the inert gas becomes a carrier of water, and the introduction efficiency is improved.
Compared to the second embodiment, the third embodiment cannot select the mixing ratio of water and inert gas, but can improve the water introduction efficiency. It can be appropriately selected according to convenience.

  By the method for manufacturing a semiconductor device of the present invention, a titanium film having high crystal orientation (002) can be obtained. Thereby, aluminum having high electromigration resistance can be provided, and the reliability of the semiconductor device can be improved. For this reason, it can be used for the manufacturing method of the semiconductor device mounted in the electronic device which requires high reliability.

DESCRIPTION OF SYMBOLS 1 Dummy substrate carrying-in process 2 Mixed gas introduction process 2a Water introduction process 2b Inert gas introduction process 2c Oxide production gas introduction process 2d Introduction process of mixed gas of water and inert gas 3 Dummy sputtering process 4 Dummy substrate carry-out process 5 This substrate carrying-in process 6 Inert gas introduction process 7 Titanium film sputtering process 11 Deposition chamber 12 Titanium sample 13 Substrate mounting table 14 Gas introduction port for mixed gas 14a Gas introduction port for water cylinder 14b Gas introduction port for inert gas cylinder 14c Gas introduction port for oxide generation gas cylinder 14d Gas introduction port for mixing cylinder of water and inert gas 15 Mixed gas cylinder 15a Water cylinder 15b Inert gas cylinder 15c Oxide generation gas cylinder 15d Water and inert gas Mixing cylinder 16 Exhaust port 51 Semiconductor substrate 52 Interlayer insulating film 53 Connection port 54 First titanium film 55 Titanium nitride film 56 Second titanium film 57 Aluminum 58 Underlayer

Claims (5)

The surface of the semiconductor substrate, in the manufacturing method of a semiconductor device placing a titanium film,
The film forming chamber which arranged titanium sample, creating and water, and an inert gas comprising argon, the oxide formation gas consisting of nitrogen, the atmosphere due to the mixed gas, a mixed gas by entering guide comprising, mixed A gas introduction process;
Wherein at the film forming chamber to decompose the water to produce hydrogen and oxygen to generate the oxides generated gas is bound to said oxygen nitrogen oxides, by freeze-drying apparatus, the film forming chamber While controlling the temperature within a high vacuum atmosphere and controlling the temperature within such a range that the hydrogen does not condense and the inert gas and nitrogen oxides condense, the inert gas and nitrogen oxides are controlled. A dummy sputtering step of evacuating and selectively leaving only the hydrogen in the film formation chamber, introducing the inert gas to generate plasma, and exposing the surface of the titanium sample;
A substrate carrying-in step of carrying the semiconductor substrate into the film forming chamber in a state where the hydrogen remains in the film forming chamber;
An inert gas introduction step of introducing the inert gas into the film formation chamber while leaving the hydrogen in the film formation chamber;
A titanium film sputtering step, in which the hydrogen is left in the film formation chamber to generate plasma and perform sputtering to form the titanium film on the surface of the semiconductor substrate ;
A method for manufacturing a semiconductor device, comprising: In the mixed gas introducing step , the water, the inert gas, and the oxide generating gas are sequentially introduced into the film forming chamber to generate the mixed gas in the film forming chamber. A method for manufacturing a semiconductor device according to claim 1. In the mixed gas introducing step , the first mixed gas obtained by mixing the water and the inert gas is introduced into the film forming chamber, and then the oxide generating gas is introduced into the film forming chamber. The method of manufacturing a semiconductor device according to claim 1, wherein the mixed gas is generated.   The method of manufacturing a semiconductor device according to claim 3, wherein the first mixed gas is supplied from the same gas cylinder. The titanium film sputtering process, a method of manufacturing a semiconductor device according to claim 1, any one of 4, characterized in that deposition while heating the semiconductor substrate to a temperature of 250 ° C. from 200 ° C..

Images