Patent Application
20230057512
The present invention relates to a method for forming thin film, and more particularly, to a method for forming a thin film in which the thickness and the step coverage of the thin film can be easily controlled by forming a thin film having a very thin thickness.
DRAM devices continue to be miniaturized with the development of innovative technologies, reaching the 10 nm era. Accordingly, in order to improve performance and reliability, high capacitance and low leakage current characteristics must be sufficiently maintained even when the size of the capacitor is reduced, and a breakdown voltage must be high.
When a single zirconium oxide film is used as the dielectric film of the conventional MIM capacitor, the equivalent oxide film thickness characteristic (Toxeq) is good, but the leakage current characteristic is weak. To overcome this problem, a combined high dielectric layer such as ZrO2/Al2O3/ZrO2 is widely used.
However, since this dielectric layer is thicker than a single ZrO2 dielectric layer, Toxeq characteristics are not good. In addition, Al2O3 of the ZAZ structure prevents leakage current of the capacitor. If the thickness is too large, the capacitance decreases, and if the thickness is too small, the leakage current increases. Therefore, proper thickness control is required.
Therefore, in order to maintain constant capacitance and leakage characteristics, it is necessary to develop a material suitable for the characteristics as well as to make the capacitor dielectric film ultra-thin.
An object of the present invention is to provide a method for forming a very thin film.
Another object of the present invention is to provide a method for forming a thin film having good step coverage.
Other objects of the present invention will become more apparent from the following detailed description.
In accordance with an exemplary embodiment of the present invention, a method of forming a thin film using a surface protection material, the method comprising: supplying a metal precursor to the inside of a chamber in which a substrate is placed so that the metal precursor is adsorbed to the substrate; purging the interior of the chamber; and supplying a reaction material to the inside of the chamber so that the reaction material reacts with the adsorbed metal precursor to form the thin film, wherein before forming the thin film, the method further comprises: supplying the surface protection material to the inside of the chamber so that the surface protection material is adsorbed to the substrate; and purging the interior of the chamber.
The surface protection material may be represented by the following Chemical Formula 1:
in <Chemical Formula 1>, n is each independently an integer of 0 to 6, X is selected from O, S, R1 to R3 are independently an alkyl group having 1 to 6 carbon atoms, R4 is selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkylthio group having 1 to 6 carbon atoms.
The surface protection material may be represented by the following Chemical Formula 2:
in <Chemical Formula 2>, n is each independently an integer of 0 to 6, R1 to R6 are each independently an alkyl group having 1 to 6 carbon atoms, R7 is selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, and a dialkylamine having 1 to 6 carbon atoms.
The reaction material may be selected from O3, O2 and H2O.
The metal precursor may be a compound including at least one of a trivalent metal containing Al, a tetravalent metal containing Zr or Hf, and a pentavalent metal containing Nb or Ta.
The metal precursor may be represented by the following Chemical Formula 3:
in <Chemical Formula 3>, R1, R2 and R3 are different from each other and each independently selected from an alkyl group having 1 to 6 carbon atoms, a dialkylamine group having 1 to 6 carbon atoms, or a cycloamine group having 1 to 6 carbon atoms.
According to an embodiment of the present invention, it is possible to form a thin film with high purity without impurities and thinner than the thickness of one monolayer obtainable by the conventional ALD process. Since it has a very low thin film growth rate, it is easy to adjust the thickness of the thin film, and it is possible to control the step coverage, as well as to improve the electrical characteristics and reliability of the device.
Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to
In the conventional deposition process using a single precursor in a trench structure having a high aspect ratio (for example, 40:1 or more), a thin film deposited on an upper part (or an entrance) of the trench becomes thicker, and a thin film deposited on a lower part (or a bottom) of the trench becomes thinner. Therefore, the step coverage of the thin film is poor and not uniform.
However, the surface protection material described below behaves in the same manner as the metal precursor, and the surface protection material is adsorbed at a higher density in the upper part of the trench than in the lower part of the trench to impede the adsorption of the metal precursor in a subsequent process, therefore the metal precursor reacts with a reaction material to form the thin film having an uniform thickness in the trench.
The substrate is exposed to the surface protection material supplied to the interior of the chamber, and the surface protection material is adsorbed to the surface of the substrate. The surface protection material has a similar behavior to the metal precursor during the deposition process, in case of a trench structure having a high aspect ratio (for example, 40:1 or more), so that it is adsorbed at a high density in the entrance of the trench and at a low density in the bottom of the trench to impede the adsorption of the metal precursor in a subsequent process.
In accordance with an exemplary embodiment of the present invention, a method of forming a thin film using a surface protection material having a plurality of ether groups, the method comprising: supplying a metal precursor to the inside of a chamber in which a substrate is placed so that the metal precursor is adsorbed to the substrate; purging the interior of the chamber; and supplying a reaction material to the inside of the chamber so that the reaction material reacts with the adsorbed metal precursor to form the thin film, wherein before forming the thin film, the method further comprises: supplying the surface protection material to the inside of the chamber so that the surface protection material is adsorbed to the substrate; and purging the interior of the chamber.
A surface protection material is represented by the following Chemical Formula 1:
in <Chemical Formula 1>, n is each independently an integer of 0 to 6, X is selected from O, S, R1 to R3 are independently an alkyl group having 1 to 6 carbon atoms, R4 is selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkylthio group having 1 to 6 carbon atoms.
Also, the surface protection material may be represented by the following Chemical Formula 2:
in <Chemical Formula 2>, n is each independently an integer of 0 to 6, R1 to R6 are each independently an alkyl group having 1 to 6 carbon atoms, R7 is selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, and a dialkylamine having 1 to 6 carbon atoms.
Thereafter, a purge gas (for example, an inert gas such as Ar) is supplied to the interior of the chamber to discharge the unadsorbed surface protection material or by-products.
Thereafter, the substrate is exposed to a metal precursor supplied to the interior of the chamber, and the metal precursor is adsorbed on the surface of the substrate. The metal precursor may include a group III element such as Al, a group IV element such as Zr, Hf, or a group V element such as Nb or Ta.
Also, the metal precursor may be represented by the following Chemical Formula 3:
in <Chemical Formula 3>, R1, R2 and R3 are different from each other and each independently selected from an alkyl group having 1 to 6 carbon atoms, a dialkylamine group having 1 to 6 carbon atoms, or a cycloamine group having 1 to 6 carbon atoms.
For example, the surface protection material described above is adsorbed in the entrance of the trench more densely than in the bottom of the trench, and the metal precursor cannot be adsorbed at the position where the surface protection material is adsorbed. That is, in the conventional deposition process, the metal precursor is adsorbed in the entrance of the trench more densely than in the bottom of the trench to have a high density in the entrance of the trench. But, in the present invention, the surface protection material is adsorbed in the entrance of the trench more densely than in the bottom of the trench to impede the adsorption of the metal precursor in the entrance of the trench, therefore, the metal precursor can be uniformly adsorbed in the trench without over-adsorption on the entrance of the trench, and the step coverage of the thin film described below can be improved.
Thereafter, a purge gas (for example, an inert gas such as Ar) is supplied to the interior of the chamber to discharge the unadsorbed metal precursors or by-products.
Thereafter, the substrate is exposed to a reaction material supplied to the interior of the chamber, and a thin film is formed on the surface of the substrate. The reaction material reacts with the metal precursor to form the thin film, and the reaction material may be water vapor (H2O), oxygen (O2) and ozone (O3). A metal oxide film may be formed by the reaction. At this time, the reaction material oxidizes the adsorbed surface protection material, and the adsorbed surface protection material may be separated and removed from the surface of the substrate.
Thereafter, a purge gas (for example, an inert gas such as Ar) is supplied to the interior of the chamber to discharge the surface protective material/unreacted material or by-products.
On the other hand, it was previously described that the surface protection material is supplied before the metal precursor. Alternatively, the surface protection material may be supplied after the metal precursor or the metal precursor may be supplied both before and after the surface protection material.
An aluminium oxide film was formed on the silicon substrate without using the surface protection material described above. An aluminium oxide film was formed through the ALD process, the process temperature was 250 to 390° C., and the reaction material was ozone gas (O3).
The process of forming the aluminium oxide film through the ALD process is as follows, and the following process is performed as one cycle.
1) Ar is used as a carrier gas, the aluminium precursor TMA (Trimethylaluminium) is supplied to the reaction chamber at room temperature, and the aluminium precursor is adsorbed onto the substrate.
2) Ar gas is supplied into the reaction chamber to discharge unadsorbed aluminium precursors or byproducts.
3) Monolayer is formed by supplying ozone gas (O3) to the reaction chamber.
4) Ar gas is supplied into the reaction chamber to discharge unreacted substances or by-products.
As a result of measuring the thickness of the aluminium oxide film obtained by the above process, the thickness of the aluminium oxide film obtained for each cycle of the ALD process was about 1.0 Å/cycle at 300 to 350° C.
An aluminium oxide film was formed on the silicon substrate using a material having one ether group as a surface protection material. An aluminium oxide film was formed through the ALD process, the process temperature was 250 to 390° C., and the reaction material was ozone gas (O3).
The process of forming the aluminium oxide film through the ALD process is as follows, and the following process is performed as one cycle.
1) A surface protection material is supplied to the reaction chamber to be adsorbed onto the substrate.
2) Ar gas is supplied into the reaction chamber to discharge unadsorbed surface protection materials or by-products.
3) Ar is used as a carrier gas, the aluminium precursor TMA (Trimethylaluminium) is supplied to the reaction chamber at room temperature, and the aluminium precursor is adsorbed onto the substrate.
4) Ar gas is supplied into the reaction chamber to discharge unadsorbed aluminium precursors or byproducts.
5) Monolayer is formed by supplying ozone gas (O3) to the reaction chamber.
6) Ar gas is supplied into the reaction chamber to discharge unreacted substances or by-products.
As a result of using a material having one ether group as the surface protection material, the GPC reduction rates were 10.42% and 13.81% at 320° C. and 350° C., respectively. In conclusion, when a material having one ether group was used as a surface protection material, a low GPC reduction rate of about 10 to 13% was shown.
A aluminium oxide film was formed on a silicon substrate in the same manner as in Comparative Example 2, except that the surface protection material was changed from a material having one ether group to TMOA (Trimethyl Orthoacetate) having a plurality of ether groups.
In conclusion, the surface protection material shows a high GPC reduction effect through high adsorption performance, and through this, it is possible to form a thin film with high purity without impurities and thinner than the thickness of one monolayer obtainable by the conventional ALD process. In addition, since it has a very low growth rate of the thin film, it is easy to control the thickness of the thin film, it is possible to control step coverage, and it is possible to improve the electrical characteristics and reliability of the device.
Although the present invention is described in detail with reference to the exemplary embodiments, the invention may be embodied in many different forms. Thus, technical idea and scope of claims set forth below are not limited to the preferred embodiments.
The present invention may be applicable to a various method for manufacturing semiconductor.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2020-0003254 | Jan 2020 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2020/019426 | 12/30/2020 | WO |
