JP2011202286A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device having a process of removing excessive deposite species which hinder a self-limiting surface reaction.SOLUTION: The method of manufacturing a semiconductor device includes a process of forming a thin film on a base body by alternately feeding a first raw material gas and a second raw material gas into a reaction furnace, wherein the surface of the base body is irradiated with plasma either after the first raw material gas is fed and before the second raw material gas is fed, or after the second raw material gas is fed and before the first raw material gas is fed.

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which an excessively adsorbed material removal step is provided when performing atomic layer vapor deposition.

  In manufacturing a semiconductor device, it is often necessary to deposit a thin film with a uniform thickness. This specific example will be described below.

  That is, in recent years, the delay of signal propagation in the wiring of the semiconductor device has limited the element operation. The delay constant in wiring is represented by the product of wiring resistance and wiring capacitance. Therefore, in order to speed up the device operation by lowering the wiring resistance, a material having a relative dielectric constant smaller than that of the conventional SiO2 is used for the wiring interlayer film and material, and Cu having a small specific resistance value is used for the wiring material. Used. In forming the Cu wiring, deterioration of element characteristics due to diffusion of Cu into Si, deterioration of workability due to poor adhesion to the insulating film, and oxidation proceeds to the inside without forming a passive oxide film. It is necessary to solve problems such as deterioration of the wiring characteristics due to things. As one means for solving these problems, a barrier metal is provided at the interface between Cu and the wiring interlayer film. Specifically, it is required to deposit thin films of various materials such as W, Al, Cu, Ta, TaN, SiO2, SiOC, SiN, HfOx, and HfAlO with good coverage.

  An atomic layer vapor deposition (hereinafter referred to as atomic layer deposition: “ALD”) method is known as a method suitable for such a purpose. ALD is performed by alternately supplying at least two kinds of raw materials to the substrate. At this time, the film forming conditions such as the substrate temperature, the raw material flow rate, and the raw material supply time are set to conditions under which these raw materials are saturated and adsorbed on the substrate. The deposition amount and composition are determined by the saturated adsorption amount, but in the ideal ALD, the saturated adsorption amount is constant on the wafer surface and the pattern, and it should be possible to form a uniform film on the wafer surface and the pattern. is there. If only a saturated amount of molecules is adsorbed by a single supply, the film thickness can be controlled on the atomic order.

  In order to facilitate the adsorption of the deposited species on the substrate surface and promote nucleation, a method of subjecting the substrate surface to plasma treatment has also been proposed (see, for example, Patent Document 1).

Japanese translation of PCT publication No. 2004-523885

  However, the conventional manufacturing method has a problem that the residue adsorbed on the substrate surface inhibits the self-limiting surface reaction and lowers the film quality.

  FIG. 8 is a flowchart for explaining a conventional method of manufacturing a semiconductor device. That is, FIG. 8 is a flowchart showing a method of forming a thin film using atomic layer vapor deposition (ALD).

First, the substrate to be treated is placed in a reaction furnace. Various types of substrates can be used as the substrate to be processed. Thereafter, the inside of the reaction furnace is purged. For purging the reactor, an inert gas such as Ar gas is used.
Next, as a first step 110, a first reactant is supplied onto a substrate disposed in the reaction furnace. For example, the first reactant is contained in an inert gas such as an Ar carrier gas and supplied into the reaction furnace. The gas flow rate can be appropriately changed depending on the substrate to be processed and the type of gas.

Next, as the second step 130, the inside of the reaction furnace is purged. An inert gas such as Ar gas is introduced into the reaction furnace, and the residual gas is removed.
Next, as the third step 140, a second reactant is supplied. For example, the second reactant is contained in an inert gas such as an Ar carrier gas and supplied into the reaction furnace.
Next, as the fourth step 150, the inside of the reaction furnace is purged. An inert gas such as Ar gas is introduced into the reaction furnace to remove unreacted substances.
The first to fourth steps are set as one cycle, and this cycle is repeated until the formed thin film reaches a desired thickness.

FIG. 9 is a timing chart showing a conventional method for manufacturing a semiconductor device.
FIG. 10 is a process cross-sectional view illustrating a main part of a conventional method for manufacturing a semiconductor device. That is, FIG. 10 is a schematic cross-sectional view showing a process of forming a thin film on the substrate 300.

  FIG. 10A shows a state in which the first reactant 310 is supplied into the reaction furnace in the first step 110 described above. As shown in the figure, the deposition species 310 (first reactant) comes on the substrate 300. A part 310a of the deposition species 310 is adsorbed on the surface of the substrate 300 by a relatively strong bond such as chemical adsorption. Further, the other part 310b of the deposited species 310 is adsorbed to the strongly coupled 310a or the like by a relatively weak bond such as physical adsorption. Further, the other part 310c of the deposited species 310 is not adsorbed and becomes a residual gas.

FIG. 10B shows a state in which purging is performed in the second step 130 described above. By purging the inside of the reaction furnace, the residual gas remaining in the reaction furnace is removed.
However, as shown in the figure, the deposition species 310c in the gas phase are removed, but the deposition species 310b that are relatively weakly bonded may remain adsorbed on the substrate 300 without being removed. That is, simply purging the inside of the reaction furnace may not be able to completely desorb the deposition species 310b by cutting relatively weak bonds such as physical adsorption. If the residual gas such as the deposition species 310b is not exhausted sufficiently, it reacts with other gas supplied thereafter.

  As a result, a thin film having a non-uniform film thickness or a low quality film quality is formed.

  In the conventional method for manufacturing a semiconductor device, the dispersion of the obtained thin film within the wafer surface of the film thickness is about 5%. Further, when purging was performed for a long time in order to improve the dispersion of the film thickness within the wafer surface to about 1%, it took 100% or more of the total film formation time.

  The present invention has been made based on the recognition of such a problem, and an object thereof is to provide a method for forming a stable thin film having high film quality without significantly increasing the film formation time.

In order to achieve the above object, according to the present invention,
A step of forming a thin film on a substrate by alternately supplying a first source gas and a second source gas into a reaction furnace,
After supplying the first source gas and before supplying the second source gas, after supplying the second source gas and before supplying the first source gas, In at least one of the above, there is provided a method of manufacturing a semiconductor device, wherein the surface of the substrate is irradiated with plasma.

Or according to the invention,
A first step of supplying a first source gas to the surface of the substrate;
A second step of irradiating the surface of the substrate with plasma;
A third step of flowing an inert gas over the surface of the substrate;
A fourth step of supplying a second source gas to the surface of the substrate;
A fifth step of flowing the inert gas over the surface of the substrate;
A method of manufacturing a semiconductor device is provided, which includes a step of forming a thin film on the substrate by repeating the steps in this order.

Or according to the invention,
A first step of supplying a first source gas to the surface of the substrate;
A second step of flowing an inert gas over the surface of the substrate;
A third step of irradiating the surface of the substrate with plasma;
A fourth step of supplying a second source gas to the surface of the substrate;
A fifth step of flowing the inert gas over the surface of the substrate;
A method of manufacturing a semiconductor device is provided, which includes a step of forming a thin film on the substrate by repeating the steps in this order.

  Here, performing the step of irradiating the surface of the substrate with the plasma between the fourth step and the fifth step, or between the fifth step and the first step. Can do.

The plasma may be generated from a mixed gas of helium gas and hydrogen gas.
Further, the first source gas may contain a metal element.

According to the present invention, the deposition species weakly bonded to the substrate or the like can be desorbed by adding a step of irradiating plasma after the deposition species are supplied into the reaction furnace. As a result, it is possible to proceed to the step of supplying another deposition species, leaving only the monomolecular layer of the deposition species on the substrate surface. That is, it is possible to remove excess deposition species that hindered the self-limiting surface reaction. As a result, the film quality is improved and a dense thin film can be formed without significantly increasing the film formation time.
As a result, it is possible to stably manufacture a high-performance and highly integrated semiconductor device and the like, and there are great industrial advantages.

3 is a flowchart for explaining a method for manufacturing the semiconductor device according to the first embodiment of the present invention; 3 is a timing chart for explaining the method for manufacturing the semiconductor device according to the first embodiment of the present invention; It is process sectional drawing for demonstrating the manufacturing method of the semiconductor device concerning the 1st Embodiment of this invention. It is a cross-sectional schematic diagram of the manufacturing apparatus which can be used in the manufacturing method of the semiconductor device concerning the 1st Embodiment of this invention. 3 is a flowchart for explaining a method of manufacturing a semiconductor device according to the first embodiment of the present invention; It is a flowchart for demonstrating the manufacturing method of the semiconductor device concerning 2nd Example. It is a flowchart for demonstrating the manufacturing method of the semiconductor device concerning 3rd Example of this invention. It is a flowchart for demonstrating the manufacturing method of the conventional semiconductor device. It is a timing chart for demonstrating the manufacturing method of the conventional semiconductor device. It is process sectional drawing for demonstrating the manufacturing method of the conventional semiconductor device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a flowchart for explaining a method of manufacturing a semiconductor device according to an embodiment of the present invention. That is, FIG. 1 is a flowchart showing a method of forming a thin film using atomic layer vapor deposition (ALD).

First, the substrate to be treated is placed in a reaction furnace. Various types of substrates can be used as the substrate to be processed. Thereafter, the inside of the reaction furnace is purged. For purging the reaction furnace, for example, an inert gas such as He gas or Ar gas is used.
Next, as a first step 11, a first reactant is supplied onto a substrate placed in the reaction furnace. For example, when a TaN film is formed as the first reactant, PDMAT (PentakisDiMethylAminoTantalum) can be used. However, it is not limited to PDMAT.
The thickness can be appropriately changed according to the case where various films such as W, Al, Cu, Ta, TaN, SiO2, SiOC, SiN, HfOx, and HfAlO are formed. For example, the first reactant is contained in an inert gas such as a He carrier gas and supplied at 100 to 5000 sccm.
The gas flow rate can be appropriately changed depending on the substrate to be processed and the type of gas.

Next, plasma irradiation is performed as the second step 12. The surface of the substrate is irradiated with plasma to remove the first reactant adhering to the surface of the substrate. Plasma irradiation can be performed, for example, with a He / H 2 mixed gas flow rate of 100 to 5000 sccm, a pressure of 0.6 to 130 Pa (pascal), and an RF power of 50 to 2000 W.
Next, as the third step 13, the inside of the reaction furnace is purged. For example, an inert gas such as He gas is introduced into a 100 to 5000 sccm reactor and the residual gas in the reactor is removed.

Next, as the fourth step 14, the second reactant is supplied. An example of the second reactant is NH3. For example, the second reactant is contained in an inert gas such as a He carrier gas and is supplied into a 100 to 5000 sccm reactor.
Finally, as the fifth step 15, the inside of the reactor is purged. For example, an inert gas such as He gas is introduced into a 100 to 5000 sccm reactor and the residual gas in the reactor is removed. The first to fifth steps are set as one cycle, and this cycle is repeated until the formed thin film reaches a desired thickness.

Next, the influence of the second step 12 described above on the film formation time will be described.
FIG. 2 is a timing chart showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.
As shown in the figure, according to the method of manufacturing a semiconductor device according to the embodiment of the present invention, even if the number of steps of plasma irradiation is increased, the total film formation time is about the conventional film formation time. It only increases about 20%.
When a film is formed by a conventional manufacturing method, it takes about 100% of the conventional film formation time to improve the dispersion of the formed thin film thickness within the wafer surface. In comparison, the film formation time can be greatly reduced.

Next, the effect of performing plasma irradiation in the above-described second step 12 will be described.
FIG. 3 is a process cross-sectional view illustrating the main part of the method of manufacturing a semiconductor device according to the embodiment of the present invention. That is, FIG. 3 is a schematic cross-sectional view showing a process of forming a thin film on the substrate 30.

  FIG. 3A shows a state in which the first reactant 31 is supplied into the reaction furnace in the first step 11 described above. As shown in the figure, the deposition species 31 (first reactant) comes on the substrate 30. A part 31 a of the deposited species 31 is adsorbed on the surface of the base 30 by a relatively strong bond such as chemical adsorption. In addition, the other part 31b of the deposited species 31 is adsorbed to the strongly bound 31a by a relatively weak bond such as physical adsorption. Further, the other part 31c of the deposited species 31 is not adsorbed and becomes a residual gas.

  FIG. 3B shows a state in which plasma irradiation is performed in the second step 12 described above. As shown in the figure, when the surface of the substrate 30 is irradiated with plasma, the deposited species 31b adsorbed by relatively weak bonds are broken. That is, it is possible to leave the deposited species 31a adsorbed by relatively strong bonds on the surface of the substrate 30, and to desorb only the accumulated species 31b adsorbed by relatively weak bonds from the substrate 30.

  That is, it is possible to leave only an adsorption layer (deposition species 31a) of a monomolecular layer or less on the surface of the substrate 30.

  FIG. 3C shows a state in which purging is performed in the third step 13 described above. As shown in the figure, by purging the inside of the reaction furnace, the gas remaining in the reaction furnace can be further removed.

Next, a semiconductor manufacturing apparatus that can be used in this embodiment will be described.
FIG. 4 is a schematic view illustrating a reaction furnace that can be used in the method for manufacturing a semiconductor device according to the embodiment of the invention.

  In the reaction furnace 40, the silicon wafer W can be placed on the wafer stage 41. An injector 42 for introducing gas and an exhaust port 44 connected to the vacuum pump 43 are provided on the side wall of the reaction furnace 40. Plasma is irradiated between the upper electrode 45 and the lower electrode 41 (wafer stage) using a high frequency power source.

As described above, in the method of manufacturing a semiconductor device according to the embodiment of the present invention, after supplying the deposition species into the reaction furnace, it is weakly bonded to the substrate or the like by adding a step of irradiating plasma. The deposited species can be desorbed. As a result, only the monomolecular layer of the deposited species is left on the substrate surface, and the process can proceed to the next step of supplying another deposited species.
That is, it is possible to remove excess deposition species that hindered the self-limiting surface reaction. As a result, the film quality is improved and a dense thin film can be formed.

Further, the dispersion of the film thickness in the wafer surface can be improved to about 1% according to the method of manufacturing a semiconductor device according to the embodiment of the present invention, compared to about 5% in the past. Conventionally, it has been necessary to increase the film formation time by 100% or more in order to obtain the same degree of improvement. However, according to the method of manufacturing a semiconductor device according to the embodiment of the present invention, the film formation time is approximately 20%. It was improved by increasing. Therefore, a stable film can be formed without greatly reducing the throughput.
That is, according to the method for manufacturing a semiconductor device according to the embodiment of the present invention, a dense thin film having a uniform film thickness can be formed.

Next, the first embodiment will be described. That is, in this embodiment, a case where plasma irradiation is performed even after the second reactant is supplied will be described.
FIG. 5 is a flowchart for explaining a method of manufacturing a semiconductor device according to the first embodiment of the present invention. That is, FIG. 5 is a flowchart showing a method of forming a thin film using atomic layer vapor deposition.
That is, in this embodiment, plasma irradiation is performed not only after supplying the first reactant but also after supplying the second reactant. According to the present embodiment, it is possible to efficiently desorb the deposited species that were weakly bound to the second reactant. Also in this embodiment, the same effect as described above can be obtained.

Next, a second embodiment will be described. That is, in this embodiment, a case will be described in which a purging step is inserted before the plasma irradiation step.
FIG. 6 is a flowchart for explaining a method of manufacturing a semiconductor device according to the second embodiment of the present invention. That is, FIG. 6 is a flowchart showing a method of forming a thin film using atomic layer vapor deposition. The step of irradiating the plasma and the step of purging are in random order, and the purge step may be performed first. It can be appropriately changed depending on the kind of the deposition species and the kind of the substrate.
Also in this example, the same effect as that obtained in the above-described embodiment can be obtained.

Next, a third embodiment will be described. That is, in this embodiment, a case where the purging step is omitted will be described.
FIG. 7 is a flowchart for explaining a method of manufacturing a semiconductor device according to the third embodiment of the present invention. That is, FIG. 7 is a flowchart showing a method of forming a thin film using atomic layer vapor deposition.

Depending on the type of deposition and the type of substrate, there are cases where the residual gas can be almost removed simply by omitting the purge step and performing plasma irradiation. In that case, as shown in the figure, the purging step can be omitted and the film formation time can be shortened.
Also in this example, the same effect as that obtained in the above-described embodiment can be obtained.

The embodiments of the present invention have been described above with reference to specific examples.
However, the present invention is not limited to these specific examples. For example, even if those skilled in the art have changed the design of the elements constituting the semiconductor device manufactured using the manufacturing method of the present invention, the scope of the present invention is within the scope of the present invention as long as it has the gist of the present invention. Is included.

11 First Step 12 Second Step 13 Third Step 14 Fourth Step 15 Fifth Step 16 Sixth Step 30 Substrate 31 Deposition Species 31a Deposition Species 31b Strongly Bonded Deposition Binds Weakly Species 31c Unattached deposition seed 40 Reactor 41 Lower electrode 42 Injector 43 Vacuum pump 44 Exhaust port 45 Upper electrode

Claims (6)

A step of forming a thin film on a substrate by alternately supplying a first source gas and a second source gas into a reaction furnace,
After supplying the first source gas and before supplying the second source gas, after supplying the second source gas and before supplying the first source gas, In at least one of the above, a method of manufacturing a semiconductor device, wherein the surface of the substrate is irradiated with plasma. A first step of supplying a first source gas to the surface of the substrate;
A second step of irradiating the surface of the substrate with plasma;
A third step of flowing an inert gas over the surface of the substrate;
A fourth step of supplying a second source gas to the surface of the substrate;
A fifth step of flowing the inert gas over the surface of the substrate;
A method of manufacturing a semiconductor device, comprising: forming a thin film on the substrate by repeating the steps in this order. A first step of supplying a first source gas to the surface of the substrate;
A second step of flowing an inert gas over the surface of the substrate;
A third step of irradiating the surface of the substrate with plasma;
A fourth step of supplying a second source gas to the surface of the substrate;
A fifth step of flowing the inert gas over the surface of the substrate;
A method of manufacturing a semiconductor device, comprising: forming a thin film on the substrate by repeating the steps in this order.   The step of irradiating the surface of the substrate with the plasma is performed between the fourth step and the fifth step or between the fifth step and the first step. A method of manufacturing a semiconductor device according to claim 2 or 3.   The method of manufacturing a semiconductor device according to claim 1, wherein the plasma is generated from a mixed gas of helium gas and hydrogen gas.   6. The method of manufacturing a semiconductor device according to claim 1, wherein the first source gas contains a metal element.

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