Patent Application
20060289795
1. Field of the Invention
Embodiments of the present invention generally relate to the fabrication of integrated circuits. More particularly, embodiments of the present invention relate to an apparatus and method for electron beam treatment of a substrate.
2. Description of the Related Art
Integrated circuit geometries have dramatically decreased in size since such devices were first introduced several decades ago. Since then, integrated circuits have generally followed the two year/half-size rule (often called Moore's Law), which means that the number of devices on a chip doubles every two years. Today's fabrication facilities are routinely producing devices having 0.13 μm and even 0.1 μm feature sizes, and tomorrow's facilities soon will be producing devices having even smaller feature sizes.
The continued reduction in device geometries has generated a demand for films having lower dielectric constant (k) values because the capacitive coupling between adjacent metal lines must be reduced to further reduce the size of devices on integrated circuits. In particular, insulators having low dielectric constants, less than about 4.0, are desirable. Examples of insulators having low dielectric constants include spin-on glass, fluorine-doped silicon glass (FSG), and polytetrafluoroethylene (PTFE), which are all commercially available.
More recently, organosilicon films having k values less than about 3.5 have been developed. One method that has been used to develop low dielectric constant organosilicon films has been to deposit the films from a gas mixture comprising one or more organosilicon compounds and then post-treat the deposited films to remove volatile or thermally labile species, such as organic groups, from the deposited films. The removal of the volatile or thermally labile species from the deposited films creates voids in the films, which lowers the dielectric constant of the films, as air has a dielectric constant of approximately 1.
Electron beam treatment has been successfully used to post-treat the deposited films and create voids in the films, while also improving the mechanical properties of the films. However, current electron beam chamber designs suffer from several major drawbacks. First, current electron beam chamber designs can have negative side effects on a substrate, such as damage or destruction of semiconductor devices on a substrate. For example, high gate oxide leakage and voltage threshold (VT) shift have been observed after electron beam treatment. It is believed that the electron beam treatment damages substrates by causing an excess negative charge build up on the substrates from the electrons bombarding the substrate. The excess negative charge build up during device manufacturing can create charge currents that form undesirable current paths in areas of the substrate that are normally insulating, and leakage current through the newly created current paths during operation of the devices can destroy the devices on the substrate. Second, current electron beam chamber designs have contributed to heavy metal contamination of wafers. Third, poor within wafer shrinkage due to a lack of temperature uniformity across the wafer surface has been exhibited. Shrinkage uniformity is an indication of film properties such as hardness.
Thus there remains a need for an improved apparatus and method of electron beam treatment of a deposited layer on a substrate.
Accordingly, the present invention provides an apparatus and method that solves the aforementioned problems.
Embodiments of the invention provide an electron beam apparatus for processing a substrate. In one embodiment, the electron beam apparatus for processing a substrate comprises a vacuum chamber, at least one thermocouple assembly in communication with the vacuum chamber, and a cross lamp heating device in communication with the vacuum chamber. In one aspect, the vacuum chamber may further provide a cathode, an anode, and a substrate support. In another aspect, the vacuum chamber comprises a grid located between the anode and the substrate support. In another aspect the vacuum chamber further comprises a plasma flood gun connected to the vacuum chamber, wherein the plasma flood gun is adapted to introduce low energy positive ions into the vacuum chamber. In another aspect the thermocouple assembly comprises a resilient member made of ceramic material. In another aspect the ceramic material is selected for a group consisting of silicon carbide, silicon nitride, aluminum nitride, synthetic diamond and combinations thereof.
In another embodiment, an apparatus for processing a substrate is provided. The apparatus comprises a tubular member with a first end and a second end, the first end having an opening and a temperature sensor disposed in the opening, wherein the temperature sensor comprises a resilient member attached to a surface made of a ceramic material wherein the surface made of ceramic material extends through the opening to provide a substrate contact surface. In one aspect the ceramic material is selected from the group consisting of silicon carbide, silicon nitride, aluminum nitride, synthetic diamond, and derivatives or combinations thereof. In another aspect the apparatus comprises a vacuum chamber and a heating device in communication with the vacuum chamber. In another aspect the vacuum chamber comprises a cathode, an anode, and a substrate support. In another aspect the heating device comprises an outer heating zone having cross lamps and an inner heating zone having parallel lamps. In another aspect, the temperature sensor and the heating device are in electronic communication with a controller configured to control the amount of heat emitted by the heating device. In another aspect, the outer heating zone has a circular light array that crosses the parallel lamps.
In another embodiment an apparatus for processing a substrate comprising a tublular member with a first end and a second end is provided. The first end has an opening and a temperature sensor disposed in the opening. The temperature sensor has a resilient member attached to a surface made of a ceramic material. The surface made of a ceramic material extends through the opening to provide a substrate contact surface.
In another embodiment, the present invention comprises an apparatus for processing a substrate. The apparatus has a thermocouple tip having at least a first portion of a conductor. The thermocouple tip comprises a tubular member with a first end and a second end, the first end having an opening with a temperature sensor disposed in the opening. The temperature sensor comprises a resilient member attached to a surface made of a ceramic material. The surface made of ceramic material extends through the opening. The apparatus also has a connector having at least a second portion of the conductor, and a length of cable comprising an insulator and at least a third portion of the conductor coupling at least the first portion of the conductor with at least the second portion of the conductor.
Further embodiments include an apparatus for processing a substrate comprising a vacuum chamber, a cathode, an anode and a thermocouple. The thermocouple comprising a thermocouple tip having at least a first portion of a conductor wherein the thermocouple tip comprises a tubular member with a first end and second end, the first end having an opening with a temperature sensor disposed in the opening. The temperature sensor comprises a resilient member and a surface made of a ceramic material wherein the surface made of ceramic material extends throught the opening. The thermocouple assembly also has a connector having at least a second portion of a conductor. The thermocouple assembly futher comprises a length of cable comprising an insulator and at least a third portion of the conductor coupling at least the first portion of the conductor with the second portion of the conductor, the insulator encasing at least a portion of the conductor and a bushing disposed around the length of cable.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
Embodiments of the invention provide methods and apparatus for reducing charging damage to a substrate during electron beam treatment, reducing wafer contamination, and reducing wafer shrinkage. Generally, the methods and apparatus described herein increase the concentration of positive ions near the substrate during electron beam treatment and allow for greater temperature control across the surface of the wafer while reducing wafer contamination. The method and apparatus herein further provide an improved method and apparatus for temperature control.
Substrates that may be treated according to embodiments of the invention include silicon or silicon-containing substrates, patterned substrates, such as substrates having semiconductor devices thereon, and unpatterned or bare substrates. In one aspect, the substrate comprises a low dielectric constant film that is preferably post-treated with an electron beam to remove volatile species, thus forming pores and lowering the dielectric constant of the film. The low dielectric constant film may be deposited from a mixture comprising an organosilicon compound, a hydrocarbon compound, an optional oxidizer, and/or combinations thereof.
The Electron Beam Apparatus:
In one embodiment, a negative substrate bias is applied during the electron beam treatment to reduce or eliminate charging damage to the substrate during electron beam treatment. By applying a negative substrate bias, positive ions are accelerated towards the substrate. The positive ions neutralize the negative charges that may accumulate on the substrate during electron beam treatment and cause undesirable current paths during manufacturing of devices on the substrate.
In operation, according to an embodiment of the invention, a substrate is placed on the substrate support 114 in the vacuum chamber 102. The substrate support 114 is electrically isolated from ground. The chamber is then pumped down from atmospheric pressure to a pressure between about 1 mTorr and about 100 mTorr. A variable rate leak valve 112 is used in controlling the pressure.
The electron beam is typically generated at a high voltage, which is applied to the cathode 104 by the high voltage power supply 108. The high voltage may be between about −500 V to about 30,000 V, or higher. The variable low voltage power supply 110 applies a voltage to the anode 106 that is positive relative to the voltage applied to the cathode 104.
To initiate electron emission in the apparatus, gas in ionization region 120 between the anode 106 and the substrate support 114 must be ionized. The gas may include one or more of argon, helium, nitrogen, hydrogen, oxygen, ammonia, neon, krypton, and xenon, for example. In one embodiment, the gas includes argon. The ionization may be initiated by naturally occurring gamma rays or by a high voltage spark in the chamber 102. Following the initial ionization, the anode 106 is biased with a slightly negative voltage, e.g., between about 0 V and about −250 V to attract positive ions 122, e.g., argon ions, to the anode 106. The positive ions 122 pass into an accelerating field region 124 disposed between the cathode 104 and the anode 106 and are accelerated towards the cathode 104 as a result of the high voltage (e.g., form about −500 V to about 30,000 V applied to the cathode). Upon striking the cathode 104, the positive ions produce secondary electrons 126 that are accelerated back towards the anode 106. While some of the electrons strike the anode, many of the electrons continue on through the anode 106 to contact the substrate 117 on the substrate support 114.
An excess negative charge accumulation on the substrate 117 from the electrons 126 contacting the substrate is prevented by providing a negative bias to the substrate 117 during the electron beam treatment. The negative bias is provided to the substrate 117 by bias source 116 that is connected to the substrate support 114. The bias applied to the substrate may be a DC bias. Alternatively, the bias may be a RF bias, such as for applications involving electron beam treatment of SOI (silicon on insulator) substrates. The negative bias on the substrate 117 attracts some of the positive ions 128, e.g., positive argon ions, in the chamber and accelerates the positive ions 128 towards the substrate 117, resulting in a partial or total neutralization of the negative charges on the substrate 117. The remaining charge on the substrate may induce a charge current on the substrate of less than about 0.005 mA, such as less than about 0.002 mA, e.g., between about 0.001 mA and about 0.002 mA. In one embodiment, the remaining charge current on the substrate is 0 mA or about 0 mA. Without a substrate bias, the substrate charge current is generally approximately equivalent to the electron beam current, which is typically between about 0.5 mA and about 50 mA. Preferably, the negative bias on the substrate 117 is between about −10 and about −30 V, such as between about −20 and about −23 V. However, the optimal substrate bias, which results in a substrate charge current of 0 mA, may vary depending on the electron beam conditions used to treat the substrate.
Exemplary electron beam conditions that may be used include a chamber temperature of between about −200° C. and about 600° C., e.g. about 350° C. to about 400° C. The electron beam energy may be from about 0.5 keV to about 30 keV. The exposure dose may be between about 1 μC/cm2 and about 400 μC/cm2. The chamber pressure may be between about 1 mTorr and about 100 mTorr. The electron beam current may be between about 0.5 mA and about 50 mA. The electron beam conditions provided herein may be used with the apparatus of
The apparatus 400 of
Electron emission in the apparatus 400 is initiated and maintained as described above with respect to apparatus 100 of
The positive bias voltage that is applied to the grid 430 during the electron beam treatment of a substrate is provided at conditions sufficient to fully or partially neutralize the electron beam charge on the substrate. In one embodiment, the positive bias applied to the grid 430 is between about 3 V and about 30 V. However, it is recognized that the optimal grid bias voltage, which results in a substrate current charge of 0 mA, may vary depending on the electron beam conditions used to treat the substrate. For example, a higher grid bias voltage is required as the energy of the electron beam treatment is increased. The optimal grid bias voltage may also vary depending on the electrical field properties of the substrate itself, such as the substrate's tendency to accumulate negative charge.
Upon performing electron beam treatments of a substrate using a chamber according to
While
The following examples illustrate embodiments of the invention. The substrates in the examples were 300 mm substrates that were treated in an EBk™ electron beam chamber available from Applied Materials, Inc. of Santa Clara, Calif.
A bare silicon substrate was electron beam treated under the following conditions: an electron beam energy of 2 keV, an anode voltage of −125 V, an electron beam current of 1.5 mA, an argon flow of 100 sccm, and a substrate temperature of 353° C. The charge current on the substrate was measured at different substrate DC bias voltages.
A bare silicon substrate was electron beam treated under the following conditions: an electron beam energy of 3 keV, an anode voltage of −125 V, an electron beam current of 1.5 mA, an argon flow of 100 sccm, and a substrate temperature of 353° C. The charge current on the substrate was measured at different substrate DC bias voltages.
While the results described above with respect to Examples 1 and 2 were obtained using bare silicon substrates, similar results, i.e., a substrate charge current of approximately 0 mA at a substrate bias of −20 V, were obtained with patterned substrates containing semiconductor devices. It was also observed that applying negative bias to the substrate did not significantly affect the energy of the electron beam treatment. For example, using a 2 keV electron beam treatment and substrate bias of −20 V, a final electron beam energy of 1.98 keV was observed, illustrating that the substrate bias did not substantially reduce the electron beam energy.
It is also believed that applying a substrate bias as described herein may enhance sealing of pores that are located near the substrate surface and are created during electron beam treatment of substrates having low dielectric constant films thereon, as the substrate bias provides a very low energy ion bombardment to substrates.
Silicon substrates having a film of Black Diamond IIx (process conditions available from Applied Materials, Inc. of Santa Clara, Calif.) deposited thereon were electron beam treated in an apparatus as shown in
The Thermocouple:
Embodiments of the present invention also provide a thermocouple assembly comprising a ceramic tip. Although primarily discussed with processing chamber 600, the thermocouple assembly 160 may also be used with the aforementioned chambers as well as other processing chambers including but not limited to CVD, PVD, PECVD or any other processing or manufacturing chambers requiring temperature monitoring.
Other details of the e-beam chamber 600 are described in U.S. Pat. No. 5,003,178, entitled “Large-Area Uniform Electron Source,” issued Mar. 26, 1991, and herein incorporated by reference to the extent not inconsistent with the invention.
The contact surface 830 can be any shape but preferably has a low mass with a smooth surface. The contact surface 830 is preferably made of a ceramic material selected from the group consisting of silicon carbide, silicon nitride, aluminum nitride, synthetic diamond and derivatives thereof. Other materials possessing fast response time and excellent thermal conductivity that do not react with process chemistries are also acceptable. The choice between these materials is process dependent.
The resilient member 820 is preferably a spring loaded device like a leaf spring, compression spring, flat spring, or conical spring but can also be any resilient or bendable wire providing the desired characteristics. The resilient member 820 is of such length and shape so that in both the resilient member's 820 compressed and uncompressed state the resilient member 820 extends past the opening 816 of the first end 812 of the tubular member 810. Full contact between the thermocouple junction and the substrate surface is assured by the over travel allowance of the thermocouple tip 710. Further, full contact with the substrate surface is assured by the gimbal action of the thermocouple tip 710. The resilient member 820 comprises any suitable spring type material such as aluminum, stainless steel (e.g. INCONEL®) and other high strength, corrosion resistant metal alloys that do not react with process chemistries.
The conductor 910 is attached by brazing or other attachment methods known in the art to the opposite surface of the contact surface 830 to form the thermocouple junction attached to the resilient member 820. If the conductor 910 is soldered to the contact surface 830, care must be taken to use a minimal amount of solder because a large mass of solder will decrease the rate of response by conducting heat away from the junction and will also interfere with the proper flexure of the resilient member 820.
The thermocouple is inserted into the hole 634 of the e-beam chamber 600 of
In operation, the substrate with the low dielectric constant film thereon to be exposed with the electron beam is placed on the target plane 630.
During processing, a voltage is developed between the two wires of the conductor attached at the thermocouple junction and the unattached end of the wires or reference junction which is maintained at a known temperature. The difference in temperature between the thermocouple junction and the reference junction generates an electromotive force that is proportional to the temperature difference. This measured voltage is transmitted through the conductor 910 to the controller 150 and used to determine the temperature of the substrate.
Aspects of the processing chamber 600 are operated by a control system. The control system may include any number of controllers, such as controller 150, processors and input/output devices. In one embodiment, the control system is a component of a closed loop feedback system which monitors various parameters within the process chamber 600 while processing a substrate, and then issues one or more control signals to make necessary adjustments according to various setpoints. In general, the parameters being monitored include temperature, pressure, and gas flow rates.
The X Lamp Heater:
Embodiments of the present invention also provide a heating device or heater 113; preferably, the heater 113 is a cross lamp heating assembly. Although discussed with reference to electron beam chambers, the heater 113 may also be used with other processing chambers including but not limited to CVD, PVD, PECVD chambers.
If needed, the wafer pin lift mechanism (not shown) can be modified by changing the slide/servo units to a motor wrap version for packaging clearance along with changing the wafer pin lift to quartz to eliminate shadowing. If converting between 200 and 300 mm wafers a SiC coated graphite preheat ring (not shown) can be used to convert between 200 mm and 300 mm wafers. The preheat ring eliminates wafer edge loss by running at a higher temperature.
To verify the lamp module design, Lamp Irradiance Simulation was performed. The modeling demonstrated both the inner and outer zone irradiance patterns and was also able to verify the patterns controllability. Changing inner and outer zone power settings demonstrated the capability of producing a flat, concave or convex irradiation pattern along with a smooth transition between zones.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/143,270 (APPM/009914), filed Jun. 2, 2005. This application also claims benefit of U.S. provisional patent application Ser. No. 60/717,386 (APPM/010221L), filed Sep. 15, 2005; and benefit of U.S. provisional patent application Ser. No. 60/781,908 (APPM/010221L02), filed Mar. 13, 2006. Each of the aforementioned related patent applications is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60717386 | Sep 2005 | US | |
| 60781908 | Mar 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11143270 | Jun 2005 | US |
| Child | 11383383 | May 2006 | US |
