Patent Application
20110064878
1. Field of the Invention
The present invention relates to an apparatus and a method for film deposition.
2. Background Art
A single-wafer deposition apparatus is often used to deposit a monocrystalline film, such as a silicon film or the like, on a substrate wafer, thereby forming an epitaxial wafer.
Attached to the upper and lower ends of the hollow columnar support 206 are, respectively, the wafer heating means 205 and an electrode securing unit 207, the latter of which serves as a lower lid for closing the lower end of the columnar support 206. Inside the columnar support 206 are two rounded rod electrodes 208 which extend through the electrode securing unit 207 and are thus secured to the columnar support 206. The two rod electrodes 208, typically formed of metallic molybdenum, penetrate the upper end of the columnar support 206, extending up to the wafer heating means 205 located inside the chamber 201.
The wafer heating means 205 comprises a heater 209 and two electrically-conductive busbars 210 for supporting the heater 209. Each of the busbars 210, typically formed of silicon carbide (SiC) or SiC-coated carbon, is secured to an electrically-conductive connector 211 that is connected to the upper end of the columnar support 206, which means that the heater 209 is connected to the columnar support 206 via the connectors 211 and the busbars 210. Further, the two rod electrodes 208 are each connected to one of the connectors 211.
Therefore, electricity can be conducted from the two rod electrodes 208 through the connectors 211 and the busbars 210 to the heater 209. The upper hollow end of the columnar support 206 is also closed by an upper lid 212.
A hollow rotary shaft 221 surrounds the columnar support 206. The rotary shaft 221 is attached to the base 202 such that the rotary shaft 221 can rotate around the hollow columnar support 206 via a bearing not illustrated. The rotation of the rotary shaft 221 is achieved by a motor 222.
A rotary drum 223 is installed on the upper end of the rotary shaft 221 that extends upwardly into the chamber 201. Installed on the top surface of the rotary drum 223 is a susceptor 220 on which to place the wafer 203. Therefore, the susceptor 220 inside the chamber 201 can be rotated above the wafer heating means 205 by the motor 222 rotating the rotary shaft 221 and the rotary drum 223.
Upon the deposition process by the above apparatus 200, the heater 209 of the wafer heating means 205, located below the susceptor 220, receives electricity from the rod electrodes 208 through the connectors 211 and the busbars 210, thereby heating the wafer 203 placed on the susceptor 220 while the wafer 203 is being rotated. The apparatus 200 then supplies the deposition gas 204 through the gas inlet port 215 to deposit an epitaxial film on the wafer 203.
During such vapor-phase deposition, the heating by the wafer heating means 205 may cause the temperature of the wafer 203 to become extremely high (e.g., higher than 1000 degrees Celsius).
JP-A-5-152207 also discloses a deposition apparatus similar to the above, in which a single wiring component penetrates a lower lid of a hollow columnar support and is secured to the columnar support at its upper and lower sections.
As stated above, the foregoing apparatus 200 supplies electricity from the rod electrodes 208 to the heater 209, with the electrically-conductive connectors 211, typically formed of metallic molybdenum, being connected to the electrically-conductive busbars 210 that supports the heater 209 and also to the rod electrodes 208. One problem with the apparatus 200 is that, in some cases, it has unwanted spaces at the joints between the connectors 211 and the busbars 210 and at the joints between the connectors 211 and the rod electrodes 208.
Such joint spaces are due primarily to the difference in the materials used for the busbars 210, the connectors 211, and the rod electrodes 208. Typically, the busbars 210 are formed of carbon, and the connectors 211 and the rod electrodes 208 are of metallic molybdenum. Because these materials have different rates of thermal expansion, wafer heating during vapor-phase deposition may cause unwanted tiny spaces at the joints between, for example, the busbars 210 and the connectors 211.
In such a case, the deposition gas 204 may flow into the tiny spaces, attaching by-products or causing corrosion. This may in turn increase the electric resistance of the joints, which necessitates more frequent maintenance of the wafer heating means 205, the rod electrodes 208, and the like and eventually shortens the mechanical life of the apparatus.
The present invention has been contrived to address the above issues. That is, one object of the invention is to provide a film deposition apparatus that prevents, at the time of film deposition onto a silicon wafer or the like, a deposition gas from flowing into the joint between a busbar for supporting a heater and a connector for supporting the busbar and into the joint between the connector and a rod electrode for conducting electricity to the heater.
Another object of the present invention is to provide a film deposition apparatus that prevents, at the time of film deposition onto a silicon wafer or the like, a deposition gas from flowing into the joint between a busbar and a connector and into the joint between the connector and a rod electrode, thereby also preventing attachment of by-products or corrosion at the joints.
Still another object of the present invention is to provide a film deposition method that prevents, at the time of film deposition onto a silicon wafer or the like, a deposition gas from flowing into the joint between a busbar for supporting a heater and a connector for supporting the busbar and into the joint between the connector and a rod electrode for conducting electricity to the heater, thereby also preventing attachment of by-products or corrosion at the joints.
Other challenges and advantages of the present invention are apparent from the following description.
According to one aspect of the present invention, the film deposition apparatus comprises a chamber; a susceptor for placing thereon a substrate, the susceptor being located inside the chamber; a heater for heating the substrate;
an electrically-conductive busbar used to support the heater; a rotary drum for supporting the susceptor at an upper section thereof and for housing the heater and the busbar; a rotary shaft, located at a lower section of the chamber, for rotating the rotary drum.
The rotary shaft houses an electrode assembly for conducting electricity through the busbar to the heater; a columnar support for supporting the electrode assembly, wherein the electrode assembly includes: a hollow rod electrode having upper and lower openings; an electrically-conductive connector for securing an upper end section of the rod electrode, with the upper end section penetrating the connector and supporting the busbar, wherein a joint surface between the busbar and the connector is provided with: a clearance that is located around and communicates with the upper opening of the rod electrode; a groove that communicates with the clearance; and a plurality of gas outlet ports that extend outwardly from the groove, wherein a purge gas is fed from the lower opening of the rod electrode so that the purge gas can pass through the inside and the upper opening of the rod electrode and be discharged through the clearance, the groove, and the gas outlet ports into the rotary drum.
According to another aspect of the present invention, in a method of depositing a film on a surface of a substrate, the method comprising the steps of: placing the substrate on a susceptor installed on a rotary drum housed by a chamber; heating the substrate while rotating the rotary drum by a rotary shaft provided at a lower section of the chamber; and feeding a deposition gas into the chamber, wherein a heater is provided inside the rotary drum, wherein the heater includes:
an electrically-conductive busbar used to support the heater;
an electrically-conductive connector used to support the busbar; and a hollow rod electrode, having upper and lower openings, that penetrates the connector and extends up to a joint surface between the busbar and the connector, and wherein the substrate is heated by conducting electricity to the heater through the rod electrode, while feeding a purge gas from the lower opening of the rod electrode so that the purge gas can be discharged through the joint surface between the busbar and the connector.
The deposition apparatus 100 includes a deposition chamber 102 inside which a film is deposited on the wafer 101 and a base 104 on which to place the deposition chamber 102. Inside the base 104 is a non-electrically-conductive, hollow, columnar support 105 that extends upwardly into the chamber 102.
An upper portion of the chamber 102 is provided with a deposition gas inlet port 103. The inlet port 103 is designed to supply a deposition gas 115 after the wafer 101 is heated, so that a crystalline film can be deposited on the top surface of the wafer 101. In the present embodiment, trichlorosilane is used as the deposition gas 115. After mixed with a hydrogen gas, which acts as a carrier gas, the deposition gas 115 is fed through the gas inlet port 103 into the chamber 102.
Although not illustrated, a flow straightening vane with multiple through holes may be provided on the upstream side of the flow direction of the deposition gas 115 (the direction is illustrated by the topside arrows of
The chamber 102 houses a hollow rotary drum 111, and a susceptor 110 on which to place the wafer 101 is provided on the top surface of the rotary drum 111. The rotary drum 111 is supported by a hollow rotary shaft 112 and houses an upper portion of the columnar support 105, which protrudes from the base 104.
The rotary shaft 112 is attached to the base 104 such that the rotary shaft 112 can rotate around the columnar support 105 via a bearing not illustrated. The rotation of the rotary shaft 112 is achieved by a motor 113. When the motor 113 causes the rotary shaft 112 to rotate, the rotary drum 111 attached to the rotary shaft 112 also starts to rotate, and so does the susceptor 110 attached to the rotary drum 111.
The upper hollow end of the columnar support 105 is closed by an upper lid 106, and wafer heating means 120 is provided above the columnar support 105.
Although not illustrated, a radiation thermometer is provided at an upper section outside the chamber 102 to measure the surface temperature of the wafer 101 while the wafer 101 is being heated. It is preferred that the chamber 102 and the flow straightening vane (not illustrated) be formed of quartz because, as known in the art, the use of quartz prevents the chamber 102 and the flow straightening vane from affecting the temperature measurement by the radiation thermometer. After the temperature measurement, its data is sent to a control device not illustrated.
The control device controls the operation of a three-way valve (not illustrated) installed inside a path through which the hydrogen gas flows. Specifically, when the temperature of the wafer 101 reaches or exceeds a particular value, the control device activates the three-way valve to control the supply of the hydrogen gas to the chamber 102. The control device also controls the output of a heater 121.
The main components of the film deposition apparatus 100 will now be described more in detail.
As illustrated in
The height of the rim is set in such a way as not to prevent the discharge of a purge gas from a groove 132 and gas outlet ports 133, both described later, which are provided at the joint surface between a connector 124 and a busbar 123. Shaping the upper portion of the columnar support 105 as above allows reliable attachment of the wafer heating means 120, which will also be described later in detail.
Installed inside the hollow columnar support 105 are two electrode assemblies 107. Each of the electrode assemblies 107 includes a hollow rod electrode 108 formed of metallic molybdenum (Mo) and also includes an electrically-conductive connector 124, fixed to the upper end of the rod electrode 108, for supporting an electrically-conductive busbar 123.
The rod electrodes 108 are each shaped like a hollow cylinder (although square, hexagonal, triangle are also acceptable) having upper and lower openings as stated above, and the lower hollow end of each of the rod electrodes 108 communicates with a purge gas supply port 116 from which to supply a purge gas 117.
In the present embodiment, we set the outer diameter of each of the rod electrodes 108 to 8 mm and the inner diameter of each (i.e., the diameter of the hollow portion of each) to 4 mm. The outer diameter is set to a value that allows the columnar support 105 to house the rod electrodes 108. The inner diameter is determined such that the purge gas 117 can flow smoothly inside the rod electrodes 108 and such that the rod electrodes 108 can maintain sufficient electrical conductivity. It is preferred in the present embodiment that the outer diameter of each of the rod electrodes 108 be from 6 mm to 10 mm and the inner diameter of each from 2 mm to 6 mm.
The busbar 123 is secured to a connector 124 via bolts 135 that penetrate the busbar 123 and the connector 124 and via nuts 136. As illustrated in
The clearance 131 can be provided at the lower joint section of the busbar 123 as stated above or instead provided at the upper joint section of the connector 124 by cutting away some upper portion of the connector 124 around the rod electrode 108. Alternatively, both the busbar 123 and the connector 124 can be machined to provide the clearance 131.
The clearances 131 of
As illustrated in
Note that the groove 132 that communicates with the clearance 131 can instead be provided at the upper joint section of the associated connector 124. Alternatively, the groove 132 can be provided at both the lower joint section of the busbar 123 and the upper joint section of the connector 124.
The two left-side circles of
Note also that, as is similar to the groove 132, the gas outlet ports 133 can instead be provided at the upper joint section of the connector 124 such that they communicate with the clearance 131. Alternatively, the gas outlet ports 133 can also be provided at both the lower joint section of the busbar 123 and the upper joint section of the connector 124.
When the clearance 131 is to be provided at the upper joint section of the connector 124 as stated above, it is preferred that the groove 132 and the gas outlet ports 133 be provided there, too. Instead, it is of course possible to provide the groove 132 and the gas outlet ports 133 at the lower joint section of the busbar 123 or at both the lower joint section of the busbar 123 and the upper joint section of the connector 124.
With the above configuration of the deposition apparatus 100, the upper openings 118 of the hollow rod electrodes 108 act as outlet ports through which to supply the purge gas 117 from the lower openings of the rod electrodes 108. Specifically, when the purge gas 117 is fed through the lower openings of the rod electrodes 108 from the purge gas supply ports 116, the purge gas 117 moves upward through the rod electrodes 118, passing through the openings 118 of the rod electrodes 108. The purge gas 117 further passes through the clearances 131, the grooves 132, and the gas outlet ports 133, all located at the joint surfaces between the busbars 123 and the connectors 124, and is eventually discharged into the rotary drum 111 located inside the chamber 102.
As illustrated in
The supply of the purge gas 117 from the purge gas supply ports 116 is also controlled by the above-mentioned control device (not illustrated), which, as stated above, controls the supply of the hydrogen gas to the chamber 102. Thus, the hydrogen gas can be used both as the purge gas 117 and as the carrier gas for the deposition gas 115. It is also possible for the control device to use another purge gas source (not illustrated) to supply an inert gas, such as nitrogen gas and argon gas, as the purge gas 117.
To deposit a silicon crystalline film on a wafer, it is preferred to use a hydrogen gas or a nitrogen gas as the purge gas 117. To deposit a silicon carbide (SiC) crystalline film at 1600 degrees Celsius, it is preferred to use a less reactive argon gas as the purge gas 117. When depositing a film of gallium nitride (GaN), on the other hand, it is preferred to use a hydrogen gas as the purge gas 117.
As stated above, the purge gas 117 is fed from the lower openings of the hollow rod electrodes 108 to let it pass through the rod electrodes 108. The purge gas 117 further passes through the clearances 131, the grooves 132, and the gas outlet ports 133, all located at the joint surfaces between the busbars 123 and the connectors 124, and is eventually discharged into the rotary drum 111 located inside the chamber 102.
Consequently, even if unwanted spaces are present in the joints between the connectors 124 and the busbars 123 and in the joints between the connectors 124 and the rod electrodes 108, the deposition apparatus 100 of the present embodiment is capable of preventing the deposition gas 115 from flowing into those spaces during film deposition onto a silicon wafer.
Moreover, by achieving the above, the deposition apparatus 100 is also capable of preventing attachment of by-products to and corrosion of those joints.
The rod electrodes 108 housed by the hollow columnar support 105, though subject to lower temperatures than the heater 121 and its nearby components, are sometimes exposed to high temperatures (e.g., 700 to 800 degrees Celsius or higher) within the chamber 102. In such a case, impurities may be released from the metallic molybdenum that constitutes the rod electrodes 108, or the molybdenum may thermally decompose itself; in either case, the wafer 101 is likely to be contaminated.
To prevent such contamination of the wafer 101 as well, the purge gas 117 is fed through the rod electrodes 108. This makes it possible to cool the rod electrodes 108 so that the rod electrodes 108 cannot be heated to a high temperature during wafer heating and also to control the temperatures of the rod electrodes 108 such that the temperatures do not reach the range of 700 to 800 degrees Celsius, in which contaminants are likely to be released from the rod electrodes 108 formed of molybdenum.
As stated above, when the purge gas 117 flows out of the gas outlet ports 133 located at the joints between the busbars 123 and the connectors 124, the purge gas 117 is discharged from the outlet ports 119 of the rotary drum 111 and then from the exhaust port (not illustrated) of the chamber 102. Thus, the purge gas 117 that has flowed through the rod electrodes 108 is prevented from being directed toward the vicinity of the wafer 101 located at an upper section of the rotary drum 111. Note also that the reason the purge gas 117 is discharged from the outlet ports 119 of the bottom section of the rotary drum 111 into the chamber 102 is to prevent the purge gas 117 from moving upward inside the rotary drum 111, so that the purge gas 117 cannot contaminate the silicon wafer 101.
The connectors 124 of the electrode assemblies 107 are shaped such that the connectors 124 extend toward the outer circumference of the columnar support 105 from the upper ends of the rod electrodes 108. Thus, the electrode assemblies 107, each comprising a connector 124 and a rod electrode 108, are L-shaped. Each of the connectors 124 is also formed of metallic molybdenum, meaning the entire electrode assemblies 107 are formed of metallic molybdenum.
As stated above, the connectors 124 can be provided with the clearance 131, the groove 132, and the gas outlet ports 133, through which to pass the purge gas 117 discharged from the upper openings 118 of the rod electrodes 108.
With reference again to
The wafer heating means 120 comprises the following components: the heater 121 for heating the silicon wafer 101; and the two arm-like busbars 123 for supporting the heater 121. The lower ends of the busbars 123 are attached to the connectors 124 via bolts or the like, as illustrated in
The heater 121 is formed of silicon carbide (SiC), and the two busbars 123 for supporting the heater 121 are electrically conductive and formed of a SiC-coated carbon material, for example. Since both the connectors 124 and the rod electrodes 108 are formed of molybdenum as stated above, electricity can be conducted from the electrode assemblies 107 through the busbars 123 to the heater 121.
The lower surfaces of the connectors 124 are at least partially in contact with the top surface of the upper portion of the columnar support 105, which portion protrudes from the main cylindrical structure of the support 105. Further, at least one of each of the busbars 123 and each of the connectors 124 is in contact with the upwardly extending rim of the upper portion of the columnar support 105 at two points at least.
Since the electrode securing unit 109 is attached to the lower end of the columnar support 105, that is, located outside the chamber 102, it is less exposed to high temperatures. Thus, the material for the electrode securing unit 109 can be selected from among a relatively wide range of materials. It is preferred to use a material which is moderate in thermal resistance and flexibility. An example of such a material is resin, and a fluorine resin is particularly preferred because it is less subject to degradation under the above temperature environment.
Described next is a method for film deposition of the present invention. Deposition of a silicon epitaxial film on the silicon wafer 101 takes the following steps.
The wafer 101 is first loaded into the chamber 102. The wafer 101 is placed on the susceptor 110, and the rotary drum 111 then starts rotation to rotate the wafer 101 at 50 rpm or thereabout.
Next, the heater 121 is activated to heat the wafer 101 gradually up to, for example, 1150 degrees Celsius, a film deposition temperature. After the radiation thermometer (not illustrated) registers 1150 degrees Celsius, meaning that the temperature of the wafer 101 has reached that value, then, the rotational speed of the wafer 101 is increased gradually. Thereafter, the deposition gas 115 is fed from the deposition gas inlet port 103 via the flow straightening vane (not illustrated) and directed toward the top surface of the wafer 101.
When the heater 121 starts heating the wafer 101, the purge gas 117 (hydrogen gas) is introduced into the hollow rod electrodes 108 through the purge gas supply ports 116 as instructed by the control device (not illustrated), so that the hydrogen gas can cool the rod electrodes 108. As stated above, the purge gas 117 flows through the inside of the rod electrodes 108, then passing through the upper openings 118 of the rod electrodes 108, the clearances 131, the grooves 132, and the gas outlet ports 133.
As a result, even if unwanted spaces are present in the joints between the connectors 124 and the busbars 123 and in the joints between the connectors 124 and the rod electrodes 108, the deposition gas 115 is prevented from flowing into those spaces due to the flow of the purge gas 117.
Even after the supply of the deposition gas 115, the radiation thermometer continues to measure the temperature of the wafer 101, and after the temperature reaches a particular value, the control device activates the three-way valve (not illustrated) to control the supply of the carrier gas (hydrogen gas) into the chamber 102.
After an epitaxial film of a particular thickness is deposited on the wafer 101, the supply of the deposition gas 115 is stopped. The supply of the carrier gas can also be stopped at the same time; alternatively, it can also be stopped after the temperature of the wafer 101, as measured by the radiation thermometer, becomes lower than a particular value. After the deposition process, the supply of the purge gas 117 to the rod electrodes 108 is also stopped when the temperature of the wafer 101 becomes lower than a particular value.
Finally, the wafer 101 is transferred out of the chamber 102 after the temperature of the wafer 101 is reduced to a particular value.
The features and advantages of the present invention may be summarized as follows:
In accordance with the first aspect of the invention, it is possible to provide a film deposition apparatus that prevents, at the time of wafer heating, a deposition gas from flowing into the joint between the busbar used for supporting the heater and the connector used for supporting the busbar and also into the joint between the connector and the rod electrode used for conducting electricity to the heater, thereby also preventing attachment of by-products to and corrosion of these joints.
In accordance with the second aspect of the invention, it is possible to provide a film deposition method that prevents, at the time of wafer heating, a deposition gas from flowing into the joint between the busbar used for supporting the heater and the connector used for supporting the busbar and also into the joint between the connector and the rod electrode used for conducting electricity to the heater, thereby also preventing attachment of by-products to and corrosion of those joints.
The present invention is not limited to the above-described embodiments but can be embodied in various forms without departing from the scope of the invention. The epitaxial deposition apparatus employed in the present embodiment is only meant to be an example of a film deposition apparatus, and the invention is not limited thereto. Any other apparatus can be used as long as it is capable of depositing a film on the surface of a substrate by feeding a deposition gas into the chamber and heating the substrate inside the chamber.
Obviously many modifications and variations of apparatus and/or methods are possible in light of the present invention. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
The entire disclosure of a Japanese Patent Application No. 2009-216288, filed on Sep. 17, 2009 including specification, claims, drawings and summary, on which the Convention priority of the present application is based, are incorporated herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-216288 | Sep 2009 | JP | national |
