Patent Application
20220301837
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-043804, filed on Mar. 17, 2021; the entire contents of which are incorporated herein by reference.
Embodiments of the present invention relate to a film deposition apparatus, a sputtering target, and a manufacturing method for a semiconductor device.
As a film deposition apparatus, a plasma sputtering apparatus is known. In the plasma sputtering apparatus, plasma is generated between a semiconductor substrate and a target. The plasma ionizes a rare gas, and the resulting rare gas ions collide with the target. Consequently, atoms are sputtered from the surface of the target and thus deposit on the semiconductor substrate. Accordingly, a film is formed on the semiconductor substrate.
Embodiments will now be explained with reference to the accompanying drawings. The present invention is not limited to the embodiments.
A film deposition apparatus according to an embodiment includes a target including a film deposition material, a backing plate to which the target is to be joined, and a magnet disposed above the backing plate. The backing plate includes a first portion facing the magnet and a second portion in which the intensity of a magnetic field generated by the magnet is lower than in the first portion, the thermal conductivity of a first material included in the first portion is higher than that of a second material included in the second portion, and the Young's modulus of the second material is higher than that of the first material.
A semiconductor substrate 100, which is a deposition target, is placed on the stage 10. The stage 10 is connected to an AC power supply 201. The semiconductor substrate 100 is a silicon substrate, for example. The semiconductor substrate 100 has a film 101 formed thereon by sputtering. The film 101 is a conductive film or an insulating film. In the present embodiment, the film 101 is a silicon nitride (SiN) film.
The chamber 20 houses the semiconductor substrate 100 placed on the stage 10. The stage 10 is disposed at the bottom of the chamber 20. In addition, the sputtering target 30 is disposed above the chamber 20. Further, the chamber 20 has an air hole (not illustrated) through which a rare gas 202 is introduced. For the rare gas 202, an argon (Ar) gas or a nitrogen (N2) gas can be used, for example.
In the present embodiment, the chamber 20 is made of stainless steel. In addition, the inner face of the chamber 20 has an aluminum layer 21 formed thereon by spraying. The aluminum layer 21 can suppress generation of dust in the chamber 20.
The sputtering target 30 includes a target 31, a bonding material 32, and a backing plate 33.
The target 31 faces the stage 10. The target 31 includes a film deposition material to be deposited as the film 101 on the semiconductor substrate 100. The film deposition material is a silicon single crystal doped with boron (B), for example.
The bonding material 32 joins the target 31 to the backing plate 33. The bonding material 32 contains indium (In), for example.
The backing plate 33 holds the target 31 above the chamber 20. The backing plate 33 is connected to a direct-current power supply 203. Herein, the structure of the backing plate 33 will be described with reference to
The shape of the first portion 331 as seen in a plan view is annular, having the center of the backing plate 33 as the center of the first portion 331. The first portion 331 corresponds to the rotational trajectory of the magnet 50. Therefore, the intensity of a magnetic field in the first portion 331 is higher than that in the second portion 332.
Meanwhile, the second portion 332 is provided in an inscribed region inscribed in the first portion 331 and in a circumscribed region circumscribed about the first portion 331. The shape of the second portion 332 provided in the inscribed region as seen in a plan view is circular. The shape of the second portion 332 provided in the circumscribed region as seen in a plan view is annular, concentric with the first portion 331.
In the chamber 20, a region immediately below the magnet 50 has the highest magnetic field intensity. Therefore, the rare gas 202 is ionized most strongly in the region immediately below the magnet 50. Accordingly, the ionized rare gas 202 collides with a region of the target 31 immediately below the magnet 50, that is, a portion of the target 31 facing the first portion 331 most strongly. Consequently, the first portion 331 has the highest temperature in the backing plate 33 and thus is likely to warp.
To suppress a warp of the backing plate 33 due to heating, the thermal conductivity of a first material included in the first portion 331 is desirably higher than the thermal conductivity of a second material included in the second portion 332. Thus, in the present embodiment, the first material is a copper-chromium alloy (CuCr), and the second material is tungsten (W) or molybdenum (Mo).
According to the table illustrated in
It should be noted that the first material is not limited to a copper-chromium alloy (CuCr), and may be any material that satisfies the aforementioned condition, that is, any material with higher thermal conductivity than that of the second material. For example, an aluminum alloy can be used for the first material.
In addition, to suppress a warp of the backing plate 33, the rigidity of the backing plate 33 is desirably high. Thus, in the present embodiment, the Young's modulus of the second material included in the second portion 332 is higher than the Young's modulus of the first material included in the first portion 331. According to the table illustrated in
Further, in the present embodiment, the difference in the coefficient of thermal expansion between the second material (i.e., tungsten or molybdenum) and the material (i.e., silicon single crystal) of the target 31 is smaller than the difference in the coefficient of thermal expansion between the first material (i.e., a copper-chromium alloy) and the material of the target 31. Therefore, damage to the target 31 due to the difference in the coefficient of thermal expansion can be avoided.
Hereinafter, a part of a step of producing the backing plate 33 will be described with reference to
First, as illustrated in
Next, as illustrated in
Referring back to
The magnet 50 is provided in the cooling bath 40. The magnet 50 is a permanent magnet configured to rotate about the center of the backing plate 33. A magnetic field of the magnet 50 causes plasma to be generated in the chamber 20.
Described hereinafter is a step of forming a film of a semiconductor device using the aforementioned film deposition apparatus 1.
First, the semiconductor substrate 100 is placed on the stage 10. Next, the chamber 20 is evacuated to a vacuum. Next, alternating-current power is applied to the stage 10 from the AC power supply 201, and direct-current power is applied to the backing plate 33 from the direct-current power supply 203. Concurrently, the magnet 50 is rotated, and the rare gas 202 is introduced into the chamber 20.
The rare gas 202 is ionized by the plasma generated in the chamber 20, and collides with the target 31. Accordingly, silicon atoms are sputtered from the target 31. The sputtered silicon atoms deposit on the surface of the semiconductor substrate 100, and consequently, the film 101 is formed on the semiconductor substrate 100.
Hereinafter, a backing plate according to Comparative Example will be described with reference to
As illustrated in
When the film 101 is formed on the semiconductor substrate 100 by attaching the backing plate 330 according to Comparative Example to the film deposition apparatus 1 instead of the backing plate 33, direct-current power is applied to the backing plate 330.
When direct-current power is applied to the backing plate 330, the backing plate 330 is heated by sputtering. In such a case, the backing plate 330 warps downward as illustrated in
Parameters in the above expression are as follows.
When a film is formed with a plasma sputtering apparatus that includes the backing plate 330 according to Comparative Example, ionization of the rare gas 202 is promoted if the direct-current power applied to the backing plate 330 is high. Therefore, in such a case, the film formation time is shortened, and consequently, productivity of film formation improves.
However, as illustrated in the above expression and
Meanwhile, in the backing plate 33 according to the present embodiment, a material with high thermal conductivity is used for the first portion 331 that faces the rotational trajectory of the magnet 50 and thus is likely to have a high temperature as illustrated in
Therefore, as illustrated in
Therefore, according to the present embodiment, high direct-current power can be applied to the backing plate 33. Accordingly, the time required for forming the film 101 is shortened, and productivity of film formation can thus be improved. Although direct-current power is applied to the backing plate 33 in the present embodiment, alternating-current power may also be applied. In such a case, since high alternating-current power can be applied to the backing plate 33, the time required for forming the film 101 is shortened, and productivity of film formation can thus be improved as in the case where direct-current power is applied.
Further, in the present embodiment, the difference in the coefficient of thermal expansion between the backing plate 33 and the target 31 is also small. This can suppress fatigue fractures of the bonding material 32, and thus can avoid mixing of foreign matter into the film 101. Accordingly, the quality of film formation can also be improved.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-043804 | Mar 2021 | JP | national |
