Patent Application
20240194489
The present invention relates to a plasma processing method.
In the fabrication process steps of a semiconductor device, response to downscaling or integration of components included in the semiconductor device is requested. For example, in integrated circuits or nano-electromechanical systems, the shrinkage of a structure to nanoscale is further propelled.
Generally, in the fabrication process steps of the semiconductor device, in order to form fine patterns, a lithography technique is used. This technique is a technique in which patterns of a device structure are applied on a resist layer, and a substrate exposed from the patterns of the resist layer is selectively etched and removed. In the subsequent process steps, another material is deposited in an etching region, and then an integrated circuit can be formed.
More specifically, nowadays, requests for power saving and speedups to the semiconductor device are increased from the market, and the tendencies of sophistication and high integration of the device structure are noticeable. For example, in logic devices, the application of GAA (Gate All Around) in which channels are formed of stacked nanowires are studied. In the etching process steps of GAA, in addition to perpendicular processing by conventional anisotropic etching, lateral processing by isotropic etching is necessary in order to form nanowires.
Here, anisotropic etching means etching using the ion assist reaction that promotes the reaction to a radical with ions, and isotropic etching means etching mainly using the surface reaction. In the manufacture of next-generation three-dimensional devices such as GAA, there are a large number of process steps that request lateral etching by isotropic etching. For example, a technique is necessary, which highly selectively laterally etches hafnium oxide HfO2 of a high relative dielectric constant used for gate insulating films to silicon germanium SiGe.
To such a request, in PTL 1, a technique is proposed in which at least one kind of a non-reactive gas such as argon, an oxygen atom supply gas such as oxygen, and an oxidizing gas such as nitrogen oxide is activated in a remote plasma generator to form a gas containing an active species, and this gas is introduced into a chamber together with a halogen-based gas such as boron trichloride BCl3 to etch HfO2.
Moreover, in PTL 2, a technique is proposed in which HfO2 is etched with plasma generated from an etching gas mixture containing halogen-containing gas.
In order to laterally etch hafnium oxide HfO2 used for a gate insulating film, it is necessary to shield ions that advance etching in the vertical direction to perform etching with a radical alone. However, since the technique described in PTL 2 is not etching with the radical shielding ions, it is considered that etching in the vertical direction by ion injection proceeds.
Moreover, in the manufacture of next-generation three-dimensional devices such as GAA, highly selective etching of hafnium oxide HfO2 to silicon germanium SiGe is requested. However, neither PTL 1 nor PTL 2 refers to a technique of selectively etching hafnium oxide HfO2 to silicon germanium SiGe.
In order to manufacture of a device in a next generation three-dimensional structure such as GAA, a solution to the problems is to be achieved by a plasma processing method that laterally etches hafnium oxide HfO2 using a vacuum processing apparatus that is capable of perform radical etching in which a flow rate ratio is set such that a silicon tetrachloride SiCl4 gas is added to a boron trichloride BCl3 gas, and a flow rate ratio of the silicon tetrachloride SiCl4 gas at this time is lower than a flow rate ratio of the boron trichloride BCl3 gas and an SiClz deposition to be deposited on the silicon germanium SiGe larger than an SiClx deposition to be deposited on the hafnium oxide HfO2, and thus the hafnium oxide HfO2 is selectively etched to silicon germanium SiGe.
Moreover, a solution to the problems is to be achieved in the plasma processing method, the flow rate ratio of the silicon tetrachloride SiCl4 gas is set to 3 to 20%.
According to the present invention, it is possible to provide a plasma processing method that is capable of selectively laterally etching hafnium oxide HfO2 and to silicon germanium SiGe.
In the following, an embodiment of the present invention will be described with reference to the drawings.
The schematic cross-sectional view showing the overall structure of the vacuum processing apparatus according to the first embodiment of the present invention is shown in
Moreover, a radio frequency power supply 124 is connected to a sample 116 placed on a sample stage 115 through a matching box 123. The inside of the vacuum processing chamber 117 is connected to a pump 122 through a valve 121, and the internal pressure can be adjusted by the degree of opening of the valve 121.
Moreover, the present vacuum processing apparatus has a shield plate 113 that is made of silica shown in
The plasma processing apparatus used in the present embodiment has characteristics that in the case where the frequency of a microwave is 2.45 GHz, plasma can be generated near the surface of a magnetic field strength of 0.0875 T. Therefore, when the magnetic field is adjusted such that a plasma generation region is located between the shield plate 113 and the dielectric window 111 (the first space 118), plasma can be generated on the dielectric window 111 side of the shield plate 113, and most of the generated ions fail to pass the shield plate 113, and thus it is possible to apply a radical alone to the sample 116. At this time, in the sample 116, isotropic etching mainly using a surface reaction with the radical alone proceeds.
To this, when the magnetic field is adjusted such that the plasma generation region is located between the shield plate 113 and the sample 116 (the second space 119), plasma can be generated on the sample 116 side from the shield plate 113, and both of ions and a radical can be supplied to the sample 116. At this time, in the sample 116, anisotropic etching using an ion assist reaction that promotes the reaction to a radical with ions proceeds.
Note that the adjustment or switching (upward or downward) of the height position of the plasma generation region to the height position of the shield plate 113, the adjustment of the period for which the height positions are retained, or the like can be performed using a controller 120.
In the first embodiment of the present invention, the magnetic field is adjusted such that the plasma generation region is located between the shield plate 113 and the dielectric window 111 (the first space 118), and the sample 116 is laterally etched by isotropic etching mainly using the surface reaction with the radical alone. Into the inside of the vacuum processing chamber 117, a mixed gas of a boron trichloride BCl3 gas and a silicon tetrachloride SiCl4 gas is introduced to generate plasma, a radical generated from the plasma generated in the first space 118 passes the through holes 131 disposed on the shield plate 113 and reaches the sample 116, and thus etching proceeds. At this time, the flow rate ratios of the BCl3 gas and the SiCl4 gas are adjusted such that the etching rate at which the sample 116 is hafnium oxide HfO2 is higher than the etching rate at which the sample 116 is silicon germanium SiGe, i.e., HfO2 is selectively etched to SiGe. The sample 116 is a substrate for manufacturing a semiconductor used for the manufacture of next-generation three-dimensional devices such as GAA (Gate All Around). In the manufacture of next-generation three-dimensional devices such as GAA, there are a large number of process steps that request lateral etching by isotropic etching. For example, HfO2 of a high relative dielectric constant used for a gate insulating film is highly selectively laterally etched to SiGe. In the sample 116, HfO2 is to be etched in the perpendicular direction to a direction in which SiGe is stacked. Consequently, in the case where a plurality of layers of SiGe is stacked in the vertical direction that is a perpendicular direction to the surface in the horizontal direction of the semiconductor substrate as the sample 116, HfO2 is to be etched in the lateral direction that is the perpendicular direction to the vertical direction (i.e., the horizontal direction).
When etching is performed in which the flow rate ratio of the SiCl4 gas is 0%, i.e., with the BCl3 gas alone, the etching rate of SiGe is higher than the etching rate of HfO2, which leads to no selective etching of HfO2 to SiGe. Hence, the SiCl4 gas is added to increase the flow rate ratio of the SiCl4 gas to 3% or more, the etching rate of HfO2 becomes higher than the etching rate of SiGe, which allows selective etching of HfO2 to SiGe. In other words, HfO2 is etched using a mixed gas of the BCl3 gas and the SiCl4 gas. A configuration may be provided in which the flow rate of the SiCl4 gas is smaller than the flow rate of the BCl3 gas. Furthermore, since the flow rate ratio of the SiCl4 gas is increased to deposit a SiClx deposition, which inhibits etching, both of the etching rates of HfO2 and SiGe are reduced.
The present invention is usable for a plasma processing method that selectively etches HfO2, which is a gate insulating film in a Gate All Around structure, to SiGe, with plasma, and a plasma processing method that selectively etches HfO2 to SiGe with plasma.
The foregoing embodiment describes the present invention in detail for easy understanding, which does not necessarily limit the present invention to ones having all the configurations having been described.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/039032 | 10/22/2021 | WO |
