JP5250611B2 - Inductively coupled plasma reactor - Google Patents

Description

  The present invention relates generally to plasma processing techniques, and more particularly to inductively coupled radio frequency plasma systems and related etching and deposition methods.

  As semiconductor device technology becomes more complex, more and more device functions are incorporated into increasingly smaller device geometries. Equipment manufacturers require sophisticated processing equipment to meet the demand for the manufacture of high precision equipment ultra large scale integration (ULSI) equipment. However, the cost of processing increases as the processing device becomes more complex, and the purchase and maintenance of the device becomes more expensive. In order to cope with the increase in manufacturing cost, manufacturers increase the size of the semiconductor substrate on which the integrated circuit device is formed. By increasing the substrate size, the manufacturing cost per unit can be reduced. Today, semiconductor wafers with a diameter of 8 inches or more are common in state-of-the-art manufacturing facilities. Increasing the wafer diameter allows manufacturers to manufacture a large number of devices on a single substrate, but it is difficult to control the uniformity of the manufacturing process used for large diameter semiconductor wafers. There is a problem.

  In the plasma etching process, many factors can affect the uniformity of etching of the material layer deposited on the surface of the semiconductor wafer. These factors include plasma uniformity, ion flux uniformity on the wafer surface, supply of reactive gases to the etching system, and removal of reaction products across the wafer surface. Conventional plasma etch reactors are primarily designed with one power source for generating plasma and one injection point for introducing process gas. By limiting the system power and gas supply to one, the ability of the etching system to optimize process etch rate uniformity across large diameter wafers is greatly reduced. For example, there is virtually no method for spatially varying the etching process across the surface of a semiconductor wafer. In addition, plasma etching systems are usually equipped with a fixed processing chamber of component placement. Because the chamber design can affect the etching characteristics of certain thin film materials commonly used in semiconductor manufacturing, depending on chamber settings, the etching system can only etch one or a few materials. .

  Advanced etching techniques such as electron-cyclotron-resonance (ECR) etching and inductively-coupled-plasma (ICP) have been developed to etch semiconductor devices with extremely small features. These systems operate at a pressure much lower than the pressure at which the diode system can generate a high density plasma. Systems such as ECR and ICP etching systems also have advantages over conventional diode etching systems by not exposing the semiconductor substrate to high electric fields. By separating the substrate from the plasma generating element of the reactor, the ion transport efficiency and the anisotropy of ions can be enhanced, and more processing control can be performed.

Japanese Patent Laid-Open No. 03-094422 Japanese Patent Laid-Open No. 07-022322 JP 07-288259 A Japanese Patent Application Laid-Open No. 07-135093 Japanese Patent Laid-Open No. 01-184921

  In plasma deposition techniques, there are similar constraints on uniformity as the wafer diameter increases. Better adhesion uniformity is usually obtained at very low operating pressures. However, at low pressure, high density plasma is required to deposit a thin film layer on a large diameter substrate having a uniform thickness.

  At present, no means for spatially varying the plasma to uniformly etch and deposit on a large diameter semiconductor substrate is possible with either a plasma etching system or a plasma deposition system. Therefore, in order to etch a material layer uniformly on a large-diameter semiconductor wafer, further development of reactor design and etching processing technology is necessary.

  In carrying out the present invention, an inductively coupled radio frequency plasma reactor and a method for etching or depositing a material layer using the inductively coupled radio frequency plasma reactor are provided. The plasma reactor of the present invention comprises a coaxial multi-coil plasma source mounted in a reaction chamber. The plasma source is spaced apart from a chuck set to receive and support the semiconductor wafer thereon. The plasma source comprises a plurality of channels each having an independently controlled gas source and an independently controlled RF coil surrounding the channel.

  In operation, a semiconductor wafer is placed on the chuck and a gas control system is activated to fill the reactor with plasma forming gas. RF power is applied to the independent RF coil and the plasma is heated in the chamber. The material layer is etched while controlling etch uniformity by adjusting the RF power and frequency in the coil surrounding each channel and the flow rate and composition of the gas exiting each channel in the plasma source. Similarly, a material layer is deposited on the substrate while spatially controlling the plasma density and composition. By controlling the plasma density and composition independently according to the radial distance of the semiconductor wafer surface, uniform etching and adhesion can be performed with high accuracy.

  The present invention relates to an inductively coupled radio frequency plasma reactor capable of spatially varying the density and composition of plasma within the plasma reactor. To spatially vary the plasma density and composition, a coaxial multi-coil induction plasma source with a variable number of recessed channels is provided. Each channel has a process gas orifice surrounded by an independently powered RF coil. A gas control mechanism is provided so that the flow rate and composition of the processing gas can be individually varied for each channel in the plasma source.

  The present invention also contemplates a method of depositing or etching a material layer. In the etching process, a semiconductor wafer is placed on a chuck mounted in a plasma reaction chamber. The chuck is mounted at a distance from the plasma source so that the center of the semiconductor wafer faces the central channel in the plasma source. By placing the semiconductor wafer relative to the channel structure of the plasma source, the density and composition of the plasma generated by the plasma source varies, so that the etching rate of the entire semiconductor wafer is locally controlled. Therefore, the etching rate of the material layer on the semiconductor wafer can be individually varied over the entire diameter of the semiconductor wafer.

  In the deposition process, the semiconductor wafer is placed on the chuck and the material layer is deposited on the semiconductor wafer. Due to the positional relative relationship with the plasma source, a material layer with a uniform thickness can be deposited by varying the plasma density and composition across the diameter of the semiconductor wafer.

  Through local control of process gas flow rate and composition, as well as local control of RF power density and frequency, the inductively coupled radio frequency plasma reactor of the present invention can increase the degree of process parameter control during the etching process. Furthermore, the reactor and method of the present invention provide a means for controlling the etching rate or thickness of a material layer on a large diameter substrate with high accuracy. Therefore, a large-diameter semiconductor wafer can be uniformly processed through local plasma density control performed by the present invention.

1 is a schematic diagram of an inductively coupled radio frequency plasma reactor arranged in accordance with an embodiment of the present invention. FIG. FIG. 3 is a cross-sectional view of a portion of a plasma source disposed in accordance with the present invention. 1 is a top view of a gas plenum suitable for delivering process gas to the plasma source of the present invention. FIG. FIG. 2 is a cross-sectional view of an alternative embodiment of a plasma source used in the inductively coupled radio frequency plasma reactor illustrated in FIG. FIG. 6 is a cross-sectional view of yet another embodiment of a plasma source suitable for use in the inductively coupled radio frequency plasma reactor illustrated in FIG. 1 is a top view of a general depiction of a semiconductor wafer. FIG. 1 is a cross-sectional view of a portion of a semiconductor wafer having an upper material layer that is etched in an inductively coupled radio frequency plasma reactor of the present invention. It should be understood that the elements shown in the drawings are not necessarily drawn to scale for simplicity and clarity of explanation. For example, the dimensions of some elements are exaggerated from each other. Further, where deemed appropriate, reference numerals are repeatedly used in the drawings to indicate corresponding elements.

  FIG. 1 illustrates an ICP reactor 10. The inductively coupled radio frequency plasma reactor 10 includes a processing chamber 12 that houses a chuck 14. The plasma source 16 is present on the upper portion of the processing chamber 12 at a position facing the chuck 14. The processing chamber 12 is supplied with RF power from an RF power supply system 18. As will be described below, the RF power system 18 includes a plurality of independent RF generators, each capable of operating at an individual power level and frequency. Processing gas from the gas supply system 20 is also supplied to the processing chamber 12. As will be described later, the gas supply system 20 can supply process gas to the process chamber 12 in a plurality of independent gas supply lines. The vacuum within the processing chamber 12 is controlled by a vacuum system 22. Reaction products and process gases are recovered from the process chamber 12 through the vacuum panel 24. The vacuum panel 24 is in a preferred arrangement below the chuck 14 in the processing chamber 12 and is coupled to a vacuum line 26. Those skilled in the art will appreciate that other processing chamber designs are possible and that different vacuum port configurations are possible. The temperature control of the chuck 14 can be performed by a cooling system (not shown). A liquid or gaseous refrigerant can be carried through a cooling channel embedded in the chuck 14.

  During operation, the semiconductor wafer 28 is placed on the chuck 14 and process gas is introduced into the process chamber 12 from the gas supply system 20. A desired vacuum pressure is obtained in the processing chamber 12 by the vacuum system 22 and RF power is applied from the RF power supply system 18 to ignite the plasma 30. In the case of plasma etching, the impact energy of the ionized species in the plasma 30 against the semiconductor wafer 28 is further controlled by applying an RF bias to the chuck 14 from an RF bias power supply 32.

  As shown in FIG. 1, the plasma source 16 includes a number of channels, each of which is supplied with gas by separate gas supply lines 34, 35, 36. FIG. 2 is an exploded sectional view showing a part of the plasma source 16. A gas supply line 36 supplies a central channel 38 through an internal gas plenum 40. The gas orifice 42 provides conduction between the central channel 38 and the internal gas plenum 40. Similarly, the gas supply line 35 supplies process gas to the first channel 44 through an external gas plenum 46.

  Process gas is distributed to the central channel 38 and the first channel 44 through a circular plenum cap 50 shown in the top view of FIG. The plenum cap 50 houses an internal gas plenum 40 that distributes gas to the central channel 38. Correspondingly, the plenum cap 52 distributes gas to the external gas plenum 46. The gas supply line 36 is attached to the plenum cap 50 at its center. The gas supply line 35 can be attached to the plenum cap 52 at a number of locations as shown in FIG. Similarly, the gas orifice 43 is provided at a number of locations around the circular shape of the first channel 44.

  As shown in FIGS. 2 and 3, the first channel 44 is concentric with the central channel 38. In certain embodiments of the present invention, another channel within the plasma source 16 is also concentrically disposed with the central channel 38 and the first channel 44. For example, the outermost channel illustrated in FIG. 1 is concentric with the first channel 44. By arranging them concentrically continuously, many channels can be configured in the plasma source 16 depending on the desired degree of spatial control of the plasma 30.

  As shown in FIG. 2, the central RF coil 54 surrounds the central channel 38. Further, the first RF coil 56 surrounds the first channel 44. Both the central RF coil 54 and the first RF coil 56 are individually controlled by the RF power system 18. Each RF coil can supply individual power levels and RF frequencies to the process gas in the enclosed channel. The RF coils 54 and 56 are separated from the process gas in each channel by a dielectric housing 58. Current that travels in the RF coil is inductively coupled to the process gas species and ignites the plasma in each channel. Those skilled in the art will recognize that the plasma density and composition can be individually adjusted within each channel within the plasma source 16 by individually powering each RF coil and individually supplying each channel with a processing gas. Like.

  Although the concentric channel design of the plasma source 16 provides a significant degree of control over which the plasma density and composition can be locally varied, another embodiment of an ICP reactor designed in accordance with the present invention is illustrated. 4 and FIG. The plasma conditions applied to the semiconductor wafer 28 can be further controlled by varying the separation distance between the portion of the plasma source 16 and the surface of the semiconductor wafer 28. As shown in FIG. 4, the central channel 38 is adjacent to the semiconductor wafer 28, but the first channel 44 is separated from the semiconductor wafer 28 in the vertical direction.

  FIG. 5 shows an alternative structure. In this embodiment of the invention, the central channel 38 is longer than the first channel 44 and is vertically separated from the semiconductor wafer 28. By varying the longitudinal separation distance between the components of the plasma source 16 and the semiconductor wafer being etched, further control is provided to vary the plasma conditions across the surface of the semiconductor wafer. Furthermore, by combining the variable plasma conditions and the variable degree of RF bias applied to the chuck 14, ion collision with the semiconductor wafer 28 can be controlled with much higher accuracy.

  In yet another embodiment of the invention, an RF shield is placed outside each coil in the plasma source 16. As shown in FIG. 5, the central RF shield 60 surrounds the central RF coil 54, and the first RF shield 62 surrounds the first RF coil 56. The RF shields 60 and 62 minimize RF interference between coils that are individually powered within the plasma source 16. The RF shield can be constructed from a conductive material such as aluminum or from a highly permeable ferromagnetic material such as a ferrite material.

  By appropriately selecting the build material, the RF shields 60, 62 can enhance the magnetic field in each channel by keeping the magnetic field in the immediate region of the RF coil that the shield surrounds. Although the shield 60, 62 is illustrated in the particular ICP reactor embodiment of FIG. 5, those skilled in the art will appreciate that the shields 60, 62 may be similarly incorporated within any plasma source structure contemplated by the present invention. Will understand.

  The process control function of the ICP reactor of the present invention applied to the etching of the material layer on the semiconductor substrate will be described. In FIG. 6, a top view of a general depiction of a semiconductor wafer 28 is shown. The semiconductor wafer 28 has an overall circular geometry characterized by a radius “R” and a peripheral edge “P”. The semiconductor wafer 28 can be further characterized by a plurality of positions 64 disposed on the surface of the semiconductor wafer 28 and identified by a radial distance. The radial distance varies from zero to the radial distance of the peripheral edge P.

  FIG. 7 is a cross-sectional view of a part of the semiconductor wafer 28. A material layer 66 covers the surface of the semiconductor wafer 28. The method of the present invention contemplates the removal of many different types of materials commonly used in the manufacture of integrated circuit devices. For example, the material layer 66 can be a semiconductor material such as polycrystalline silicon or a refractory metal silicide. The material layer 66 can be made of a conductive material such as aluminum, an aluminum alloy with silicon, an aluminum alloy with silicon and copper, or elemental copper. Further, the material layer 66 may be a dielectric material such as silicon dioxide, silicon nitride, silicon oxynitride, or boron oxynitride.

  In realizing the present invention, when the material layer 66 is a semiconductor material, chlorine, hydrogen chloride, chlorinated halogen-containing carbon compound, fluorine and fluoride compound, chlorofluorocarbon, bromine, hydrogen bromide, iodine, hydrogen iodide, etc. Halogens and halogenated gases and mixtures thereof can be used for etching the material. When the material layer 66 is a dielectric material, fluorine, hydrogen fluoride, a fluorinated halogen-containing carbon compound, or a mixture thereof can be used. When the material layer 66 is a conductive material, the processing gas includes a fluorinated compound and chlorine and a chlorinated bromine compound.

  In order to perform the etching of the material layer 66, the semiconductor wafer 28 is ICP so that the center point shown as “C” in FIGS. 6 and 7 aligns substantially longitudinally with the central channel 38 in the plasma source 16. Located on the chuck 14 of the reactor 10. When the semiconductor wafer 28 is positionally aligned with the concentric channel of the plasma source 16, the local etch rate at the location 64 across the semiconductor substrate 28 is individualized by the spatially variable plasma conditions generated by the plasma source 16. Can be controlled. In this manner, radial control of the etching rate of the material layer 66 is performed, and the material layer 66 close to the peripheral edge portion P includes the material layer 66 portion at the center point C and the material layer at various points 64 of the entire semiconductor wafer 28. Etching is performed at the same time as 66 portion.

  In the case of plasma deposition, a material layer such as material layer 66 is deposited on the semiconductor wafer 28. In order to adhere, a processing gas is introduced from the gas supply system 20 into the processing chamber 12, which causes a plasma induced reaction to form a thin film layer on the semiconductor wafer 28. For example, when a semiconductor material such as polycrystalline silicon is to be deposited, a silicon-containing gas such as silane or a halogenated silane such as dichlorosilane is introduced. When a dielectric material such as silicon dioxide or silicon nitride is to be deposited, a processing gas such as tetraethylorthosilane (TEOS), halogenated silane and ammonia can be introduced. Furthermore, a refractory metal or a refractory metal silicide material can be deposited by introducing a refractory metal-containing gas.

  Those skilled in the art will appreciate that the above description is only representative of many different types of process gases that can be utilized in accordance with the present invention to etch or deposit material layers in ICP reactor 10. The present invention contemplates deposition and etching of any and all materials that can be formed in an ICP reactor.

  To perform the deposition of the material layer 66, the semiconductor wafer 28 is ICP so that the center point shown as “C” in FIGS. 6 and 7 is aligned substantially longitudinally with the central channel 38 in the plasma source 16. Located on the chuck 14 of the reactor 10. When the semiconductor wafer 28 is positionally aligned with the concentric channel of the plasma source 16, the local deposition rate at the location 64 across the semiconductor substrate 28 is independent of the spatially variable plasma conditions generated by the plasma source 16. Can be controlled. In this manner, radial control of the deposition rate of the material layer 66 is performed, and the material layer 66 close to the peripheral edge P includes the material layer 66 part at the center point C and the material layer at various points 64 of the entire semiconductor wafer 28. It is formed at the same time as 66 portion.

One of ordinary skill in the art will be able to practice the present invention with little effort and be fully aware of the operational advantages of the present invention. Accordingly, the following examples are merely illustrative of the invention and are not intended to limit the invention in any way.
Example I
The semiconductor substrate 28 is first subjected to a chemical vapor deposition process, and a material layer 66 is deposited thereon. The semiconductor substrate 28 is then placed on the chuck 14 in the ICP reactor 10. The processing gas is selected according to the composition of the material layer to be etched. For example, when the material layer 66 is polycrystalline silicon, a halogen gas such as chlorine and a hydrogen halide gas such as hydrogen chloride and hydrogen bromide are introduced together with an inert gas diluent. The total gas flow from the gas supply system 20 is adjusted to a value of 40 to 200 sccm, and the vacuum system 22 is adjusted to obtain a processing pressure in the processing chamber 12 of about 1 to 10 millitorr. Next, RF power is applied from the RF power supply system 18 to the RF coils 54 and 56 in the plasma source 16. Preferably, about 100 to 5000 watts of RF power is applied to the RF coils 54,56. In addition, approximately 0 to 5000 watts of RF power is applied to the chuck 14 from the RF bias power supply 32. Thereafter, plasma etching of the material layer is performed and completed.
Example II
A semiconductor substrate 28 is placed on the chuck 14 in the ICP reactor 10. The processing gas is selected according to the composition of the material layer to be deposited. For example, if material layer 66 is epitaxial silicon, hydrogen and silane are introduced into processing chamber 12 at a flow ratio of about 3: 1. The total gas flow from the gas supply system 20 is adjusted to a value of 40 sccm, and the vacuum system 22 is adjusted to obtain a processing pressure in the processing chamber 12 of about 1 to 25 millitorr. Next, RF power is applied from the RF power supply system 18 to the RF coils 54 and 56 in the plasma source 16. Preferably, about 500 to 1500 watts of RF power is applied to the RF coils 54 and 56 at a frequency of about 13.56 MHz. Further, a direct current of about 0 to −60 volts is applied to the chuck 14 while maintaining the chuck 14 at a temperature of about 400 to 700 degrees Celsius. Thereafter, plasma deposition of the material layer is performed and completed.

  Thus, it is apparent that the present invention provides an inductively coupled high frequency plasma reactor and material layer etching method that fully satisfies the above advantages. Although the invention has been described and illustrated with reference to specific illustrative examples, it is not intended that the invention be limited to these illustrative examples. Those skilled in the art will recognize that variations and modifications can be made without departing from the spirit of the invention. For example, the present invention contemplates etching a layer of material having a predefined lithographic pattern for the purpose of creating various device structures such as gate electrodes, electrical contacts, electrical interconnects, and the like. In addition, the present invention uses many different types of chemicals to deposit or etch a wide range of materials used to form thin film layers in semiconductor devices. Accordingly, the present invention is intended to embrace all such alterations and modifications that fall within the scope of the appended claims and their equivalents.

  The present invention can be used in the field of manufacturing semiconductor devices such as semiconductor integrated circuit devices.

DESCRIPTION OF SYMBOLS 10 Inductively coupled high-frequency plasma reactor 12 Processing chamber 14 Chuck 16 Plasma source 18 RF power supply system 20 Gas supply system 22 Vacuum system 24 Vacuum panel 26 Vacuum line 28 Semiconductor wafer 30 Plasma 32 RF bias power supply 34, 35, 36 Gas supply line

Claims (4)

An inductively coupled plasma reactor (10) comprising:
Processing chamber (12);
A chuck (14) housed in the processing chamber (12);
A plasma source (16) comprising a first channel (38) and a second channel (44) disposed concentrically with the first channel (38), wherein the second channel is a first channel Surrounding the channel;
A first gas supply line (36) for supplying process gas to the first channel (38) and a second gas supply line (supply for supplying process gas to the second channel (44)). 35);
A first RF coil (54) surrounding the first channel (38) and a second RF coil (56) surrounding the second channel (44), the first RF coil (54) And the RF power supplied to the second RF coil (56) are independently controllable;
Comprising
Process gas supplied to the first channel (38) by the first gas supply line (36) and process supplied to the second channel (44) by the second gas supply line (35). Inductively coupled plasma reactor (10) characterized in that the gas can be controlled independently. Inductively coupled plasma reactor (10) according to claim 1,
Said first channel (38) and a second channel (44) each have a gas orifice (42, 43), said second channel to said gas orifices Le (44) (43) is the first Two channels (44) at a plurality of positions,
The first gas supply line (36) supplies process gas to the first channel (38) through a gas plenum (40) communicating with a gas orifice (42) of the first channel (38);
The second gas supply line (35) supplies process gas to the second channel (44) through a gas plenum (46) communicating with a gas orifice (43) of the second channel (44). Inductively coupled plasma reactor (10) featuring. Inductively coupled plasma reactor (10) according to claim 1 or 2,
Regarding the distance between the first and second channels (38, 44) and the chuck (14), the first channel (38) is more in contact with the chuck (14) than the second channel (44). ) Inductively coupled plasma reactor (10), characterized in that Inductively coupled plasma reactor (10) according to claim 1 or 2 ,
Regarding the distance between the first and second channels (38, 44) and the chuck (14), the first channel (38) is more in contact with the chuck (14) than the second channel (44). An inductively coupled plasma reactor (10) characterized in that it is spaced apart from ).

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