KR101791685B1 - High Dose Implantation Strip (HDIS) In H2 Base Chemistry - Google Patents

Abstract

A plasma is generated using a hydrogen element, a weak oxidizing agent, and a fluorine-containing gas. An inert gas is injected into the plasma downstream of the plasma source and upstream of the showerhead, which directs the gas mixture into the reaction chamber, where the mixture reacts with the high dose implant photoresist. The treatment removes both the sheath and the layer of the layer of the resist at high strip speeds, which allows the workpiece surface to remove residues with little silicon loss.

Description

(High Dose Implantation Strip (HDIS) In H2 Base Chemistry < RTI ID = 0.0 >

The present invention is directed to a method and apparatus for photoresist material removal, and to a method and apparatus for removing associated residues from a workpiece surface. In particular, such applications are directed to a method and apparatus for removing photoresist material, i.e., a photoresist material (low or high dose implanted photoresist material) after ion implantation or plasma doping implantation.

A photoresist is a photosensitive material used in a constant manufacturing process to form a pattern coating on a workpiece, such as a semiconductor wafer. After exposing the photoresist-coated surface to a high-energy radiation pattern, a portion of the photoresist is removed, revealing the underlying surface, and the surface remaining surface is protected. Semiconductor processing such as etching, deposition and ion implantation is performed on the uncovered surface and the remaining photocurable resin. After performing one or more semiconductor treatments, the remaining photoresist is removed from the strip operation.

During ion implantation, boron ions, boron difluoride, indium, gallium, thallium, phosphorus, arsenic, antimony, bismuth, and germanium are accelerated as target ions. The ions are implanted in the exposed area of the workpiece and in the remaining photoresist surface. The process forms well regions (source / drain) and a lightly doped drain (LDD) and a double diffusion drain (DDD) region. The ion implants penetrate the photoresist and deplete the hydrogen surface. The shell of the outer layer or photoresist forms a layer of carbonized urea having a density higher than that of the underlying bulk photoresist layer. These two layers have different thermal expansion layers and respond to the removal process at different rates.

The difference between the outer layer and the bulk layer is very pronounced in the subsequent high dose ion implantation photoresist. In high dose implants, the ions are greater than 1 x 10 < ¹⁵ > ions / cm < ² >, and the energy is from 10 keV to greater than 100 keV. Conventional high-dose implantation (HDIS) processing uses oxygen chemistry, in which a monolayer oxygen plasma is formed away from the process chamber and then directed to the workpiece surface. The reactive oxygen is combined with the photoresist to form a gas byproduct removed by a vacuum pump. In the case of HDIS, an additional gas is used to remove the dopant introduced with oxygen.

Important HDIS considerations include strip speed, amount of residue, and film loss of exposed and underlying film layers. Residues are commonly found on the substrate surface after HDIS and removal. These arise from sputtering during high-energy implantation and are caused by incomplete removal of the sheath and / or oxidation of implanted atoms in the photoresist. After the removal, the surface should be free of residues, or substantially free of residues to ensure a high yield rate, and should not require additional residue removal treatment. The residue can be removed by overstripping, i. E. Continuing the stripping process beyond the point normally required for all photoresist removal. Unfortunately, in conventional HDIS operation, the over stripping sometimes removes a portion of the underlying functional device structure. In such an element layer, even very little silicon loss from the transistor source / drain region can have an undesirable effect on device performance, especially with ultra shallow junction devices < RTI ID = 0.0 > ). ≪ / RTI >

Therefore, there is a need to propose an improved method and apparatus for removing photoresist and residue associated with ion implantation, particularly during HDIS, which minimizes silicon losses and leaves no residue while maintaining acceptable strip speeds.

The present invention is directed to an improved method and apparatus for stripping photoresist and removing ion implantation-related residues from a workpiece surface. Plasma is generated using a hydrogen element, a weak oxidizing agent and a fluorine-containing gas. In certain embodiments, an inert gas is introduced into the plasma downstream of the plasma source and upstream of the showerhead, directing gas into the reaction chamber. The plasma-reactive gas flow with the inert gas reacts with a high-dose implant resist to remove both the shell and bulk resist layers and to remove residues with low silicon losses on the workpiece surface .

In one aspect of the invention, the method includes removing material from a workpiece in a processing chamber according to the following operations: A hydrogen element containing gas, a weak oxidizing agent, and a fluorine containing gas into a plasma source, generating a plasma from the gas injected into the plasma source, and inserting an inert gas into the plasma source and downstream of the workpiece. The plasma activated gas moves to a workpiece and is combined with an inert gas upstream of the showerhead in the reaction chamber. The electrically charged species in the plasma are discharged or partially discharged when they contact the showerhead.

The plasma activated gas comprising a hydrogen element, a weak oxidizing agent and a fluorine-containing gas flows into the workpiece along with an inert gas and reacts with the material from the workpiece. Examples of weak oxidizing agents include carbon dioxide, carbon monoxide, nitrogen dioxide, nitrogen oxides, water, hydrogen peroxide, or mixtures thereof. As the weak oxidizing agent, carbon dioxide is preferable. Examples of the fluorine-containing gas include other fluorocarbon including 4-fluorocarbon, fluorocarbon, fluorine, 3-fluorine, 6-fluorine, mixtures thereof and the like. The fluorine-containing gas is preferably 4 fluorocarbon. The inert gas may be argon, helium, nitrogen, a mixture thereof, or the like. A preferred inert gas is argon. The gas injected into the plasma source may be premixed or unmixed, and the volume is from about 1% to about 99%, or from about 0.1% to about 10%, or from about 3% to about 5% of the weak oxidizing agent. The inert gas is inserted at about 0.15 -10 times the hydrogen element volumetric flow rate, or about 2 times the gas flow rate. In this work, the gas may comprise up to 1% of the weak oxidizing agent species by volume and may comprise about 0.5% of the fluorine-containing gas species.

In certain embodiments, the material removed from the workpiece is a high dose implant photoresist. The workpiece may be a 300 mm wafer. The plasma can be generated remotely using RF power between about 300 Watts and about 10 kilowatts. The temperature of the workpiece may be about 160-500 C when contacted with the gas. The process pressure may be about 300 mTorr to 2 Torr.

According to various embodiments, the high dose implant resist is removed from the workpiece at a rate greater than about 100 nm / min, and the silicon is removed from the workpiece surface at a total rate of up to about 4 nm / min. The resulting work piece is free of residues of the high-dose implanted resist after removal, and less than about 3 angstroms of silicon is lost from the underlying silicon layer.

Another aspect of the present invention is a multi-step method for removing a high dose implant resist from a workpiece surface in a reaction chamber. The method includes the steps of: inserting a plasma source into a plasma source with or without a hydrogen gas-containing first gas, a weak oxidizing agent and a fluorine-containing gas at a first overall flow rate, and introducing a first plasma from a first gas inserted into the plasma source And inserting a first inert gas downstream of the plasma source and upstream of the workpiece and reacting the first portion of material from the workpiece with the mixture, Lt; / RTI > The method may also include the step of inserting into the plasma source with or without a second gas comprising hydrogen, a weak oxidizing agent, and a fluorine-containing gas at a second overall flow rate, 2 plasma, and inserting a second inert gas downstream of the second plasma source and upstream of the workpiece, and reacting the second inert gas with the second material from the workpiece to remove the second material. . The first and second gas components are different. In certain embodiments, at least one of the first or second gases comprises a fluorine containing gas. In some embodiments, at the end of the removal process, no residue is present in the workpiece and less than about 3 angstroms of silicon is lost in the underlying silicon layer. The second partial removal operation occurs before the first partial removal operation. In certain embodiments, one or more of the removal operations are repeated one or more times. These removal operations occur at the same or different stations in the reaction chamber.

In accordance with another aspect of the present invention, the present invention is directed to an apparatus for removing resist material from a workpiece surface, the apparatus including a reaction chamber and a controller. The reaction chamber includes a plasma source, a gas inlet for inserting a hydrogen element containing gas mixture into the plasma source, a gas inlet for inserting an inert gas downstream of the plasma source and upstream of the workpiece, a showerhead located downstream of the gas inlet, And a workpiece support located downstream of the showerhead and supporting the workpiece to adjust the temperature of the workpiece including a pedestal and a temperature regulation mechanism. The controller is configured to perform a set of instructions including instructions to insert a hydrogen containing gas, a weak oxidizing agent, and a fluorine containing gas into the plasma source, a plasma from the gas injected into the plasma source, , Instructions to insert an inert gas downstream of the plasma source and upstream of the workpiece, and optionally instructions to insert a gas, generate a plasma, and to generate different flow rates and gas components And repeatedly inserting the inert gas by using the inert gas. The plasma source used in accordance with the method and apparatus of the present invention may be any of a number of plasma sources. For example, an RF ICP source may be used.

The processing chamber used in accordance with the method and apparatus of the present invention may be any suitable processing chamber. The processing chamber may be a chamber of a multi-chamber device or may be part of a single chamber device. In certain embodiments, the chamber may include a plurality of stations, and at least one station may include a plasma source, a plurality of gas inlets, a showerhead, and workpiece support.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, as will be appreciated by those skilled in the art, the present invention may be practiced without specific details, and may also be practiced using alternative embodiments or processes. In addition, well-known processing methods and the like will not be described in detail so as not to obscure the gist of the present invention.

In the present application, the terms "work piece", "semiconductor wafer", "wafer" and "partially fabricated integrated circuit" will be used interchangeably with the same meaning. Those skilled in the art will recognize that the term "partially fabricated integrated circuit" refers to a silicon wafer at any one of the various stages of integrated circuit fabrication. The following detailed description assumes that the present invention can be practiced on a wafer. However, the present invention is not limited thereto. The workpiece can be made in various shapes, sizes, and materials. In addition to semiconductor wafers, other workpieces that can utilize the present invention can be a variety of other materials such as displays, printed circuit boards, and the like.

As described above, the method and apparatus of the present invention can be used effectively and efficiently to remove photoresist material after high dose ion implantation. The present invention is not limited to high capacity injection strips (HDIS). The present invention is also not limited to specific doping categories implanted. For example, the described methods and apparatus can be effectively used with media or low-dose implanter stripping. Although specific dopant ions such as boron, arsenic, and phosphorus have been described, they can be effectively used to remove photoresists injected with other dopants such as nitrogen, oxygen, carbon, germanium, and aluminum.

Various methods and apparatus for photoresist stripping are filed on February 27, 2007 under the name " Enhanced Stripping of Low-K Films Using Downstream Gas Mixing " Quot; Low-K Films Using Downstream Gas Mixing ", which is incorporated herein by reference in its entirety for < RTI ID = 0.0 >Lt; RTI ID = 0.0 > U.S. Patent No. 7,202,176. ≪ / RTI > The contents of which are incorporated herein by reference.

The method and apparatus of the present invention use a plasma generated from a gas containing hydrogen. The gas comprises a weak oxidant and a fluorine-containing gas. The gas may also contain a weak oxidant and a fluorine-containing gas. It will be appreciated by those of ordinary skill in the art that the types of entities present in the plasma can be molecular mixtures generated from different ions, radicals, and hydrogen, weak oxidants, and fluorine containing gases. The reaction chamber may have other species, such as small amounts of hydrocarbons, carbon dioxide, water vapor and volatile components, because the plasma reacts to divide into organic photocurable resin and other residues. Those skilled in the art will recognize that the initial gases / gases inserted into the plasma are different from the gases present in the plasma as well as the gases contacting the workpiece during stripping.

1 is a schematic illustration of an apparatus 100 according to an embodiment of the present invention. The apparatus 100 has a processing chamber 103 separated by a plasma source 101 and a showerhead assembly 105. The plasma source 101 is connected to the gas inlet 111. The showerhead 109 forms the bottom of the showerhead assembly 105. The inert gas inlet 113 is downstream (downstream) of the plasma source 101 and upstream of the showerhead 109 and the wafer 123. Inside processing chamber 103 and wafer 123 with photoresist / dry etch byproducts are located on the platen (or stage) 117. The platen 117 is connected to a temperature control mechanism capable of heating or cooling the wafer on the platen as needed. In some embodiments, the platen 117 may be configured to apply a constant bias to the wafer 123. A low pressure can be reached in the reaction chamber 103 through the vacuum pump and conduit 119.

In operation, gas is introduced into the plasma source 101 through a gas inlet 111. The gas inserted into the plasma source includes chemically active species which will be ionized at the plasma source to form a plasma. The gas inlet 111 may be any kind of gas inlet, and may include multiple ports or jets. The plasma source 101 generates an active species of gas to be inserted into the source to form a plasma. In Figure 1, an RF plasma source is shown having an inductive coil 115 energized to form the plasma. An inert gas is introduced through the gas inlet 113 upstream of the showerhead and downstream of the plasma source. The inert gas is mixed with the plasma. The gas inlet 113 may be a type of gas inlet and may include multiple ports or jets to optimize the plasma mixture with the inert gas. The showerhead 109 allows the plasma / inert gas mixture to flow into the process chamber 103 through the showerhead hole 121. The number and arrangement of the showerhead holes 121 can be determined to maximize the plasma / gas mixture uniformity in the processing chamber 103. The showerhead assembly 105 may be grounded or have a constant applied voltage and may capture or discharge ions, thereby altering the gas flow composition into the processing chamber 103. That is, the gas comprises an increased neutral species. As mentioned above, the wav 123 is temperature controlled, and RF bias can be applied. The plasma / inert gas mixture removes photoresist / etch byproducts from the wafer.

In an embodiment of the claimed invention, the apparatus does not include a showerhead assembly 105 and a showerhead 109. In these embodiments, the inert gas inlet 113 inserts the inert gas directly into the process chamber, where it is mixed with the plasma upstream of the wafer. Various configurations and geometries of the plasma source 101 and the induction coil 115 may be used. For example, the induction coil 115 is wound annularly around the plasma source 101 in an interlaced pattern. In another embodiment, the plasma source 101 may be made in the form of a dome instead of a cylinder.

Suitable plasma devices include Gamma 2100, 2130 I ² CP (staggered and inductively coupled plasma) provided by Novellus Systems, Inc. of San Jose, CA, G400, and GxT. Other devices include Axcelis Technologies Inc. of Rockville, Maryland. , TERA21 supplied by PSK Tech Inc. of South Korea, and Mattson Technology Inc. of Fremont, CA. By the Aspen tool provided by the Aspen tool.

Figures 2A-2D illustrate various stages of semiconductor production before and after ion implantation and removal operations. 2A shows a semiconductor substrate 201 coated with a photoresist material 203. FIG. The substrate 201 may comprise one or more deposition film layers, such as an oxide film, a silicide contact, and / or a polysilicon film, or an exposed silicon substrate including a silicon-on- . Initially, the photoresist material covers the entire substrate surface. Such a photoresist is then exposed to pattern radiation generated through the mask, for example, to remove a portion of the original photoresist material, such as the opening 204 shown in FIG. 2A, between the remaining photoresist material 203.

The substrate is then exposed to an ion implantation process. During ion implantation, the surface of the workpiece or wafer is implanted with dopant ions. The treatment may be, for example, plasma-immersion ion implantation (PIII) or ion beam implantation. The ions are dropped onto the substrate surface including the exposed silicon layer 201 and the photoresist 203. With high energy ion implantation, a small amount of underlying material 207 is spread to the photoresist side walls. See FIG. 2B. The material includes other materials in the implanted species, plasma or ion beam, and some of the byproducts of the implant. These include other contact materials such as silicon, aluminum, carbon, fluorine, titanium, cobalt, and oxygen in the form of compounds. The actual species is determined by the composition of the substrate prior to ion implantation, the photoresist, and the implanted species.

In the exposed silicon layer 201, a doped region 209 is generated. The intensity of the ion energy or ion bombardment determines the depth or thickness of the doped region. The ion flux intensity determines the content of the doping.

The ions penetrate into the surface of the photoresist that generates the shell layer 205. The shell layer 205 may be carbonized and may be a polymer chain with a high degree of cross-linking. The shell layer is typically depleted of hydrogen and permeates into implant species. The outer skin layer 205 is denser than the bulk photoresist layer 203. The relative density depends on the ion flux, and the thickness of the shell layer is determined by the ion energy.

Such an outer layer 205 is more difficult to remove than the bulk photoresist 203 below. The removal rate of the shell layer is 50% or 75% slower than the underlying bulk photoresist. The bulk photoresist includes a relatively high level of chemical bonding nitrogen and a portion of the original casting solvent. At elevated wafer temperatures, such as from 150 to 200 < ⁰ > C or higher, the bulk photoresist removes gas or expands in relation to the shell layer. The entire photoresist then "pops" as the following bulk photoresist raises the pressure below the shell. Since it is particularly difficult to remove residues from the wafer surface and interior portions of the chamber, the photoresist popping becomes a source of particles and causes processing defects. The greater the doping ion implantation, the greater the density difference between the shell and the underlying bulk photoresist layer. The outer skin becomes thicker.

FIG. 2C shows the substrate after the strip, showing the failure to completely remove the photoresist 205 and the sidewall sputter residue 207. The sidewall sputter residues 207 include particles that do not form volatile compounds in conventional strip chemistries. These particles may remain after conventional strip operations. The residues may also include implanted species of oxides formed from reactive oxygen used in conventional strip chemistry, such as boron oxide and arsenic oxide. A portion of the sheath 205 will remain on the substrate. The shell sidewalls and photoresist bias bottom corners are not easy to remove due to their geometry.

These residual particles can in some instances be removed by fluorochemical reaction, or wet cleaning overstripping of the wafer. Over-stripping in conventional oxygen chemical reactions results in unwanted silicon oxidation, which nevertheless fails to remove the existing boron oxide residues and arsenic oxide residues. Fluorinated chemical compounds are used in the plasma generated in accordance with the present invention to generate fluoride radicals that form volatile boron fluoride and arsenic fluoride. In this way, residues can be removed, but silicon and silicon oxide underlying the substrate can also be etched.

The silicon loss has a functional relationship of photoresist thickness, sheath thickness, and overstrip percent. Longer, more aggressive stripping can be used to remove more silicon to remove thicker sheaths. In the case of a photoresist with a thinner shell, the difference between the shell layer and the bulk photoresist layer becomes more noticeable. Said thicker outer sidewalls and corners are more difficult to peel off. Thus, strip processing designed to remove thick envelopes tends to remove more silicon. Overstrips are used to adjust photoresist uniformity and geometry in addition to residue removal. If the photoresist is completely removed in the wafer region and not in the other regions, the stripping continuation will cause additional material such as silicon and silicon oxide to be removed from the stripped (stripped) region. The overstrip is about 100%.

Figure 2D shows a substrate from which all residues have been removed. Preferably, the residue is removed with no additional silicon loss or oxidation and with minimal delay. More preferably, the stripping leaves no residue, thus reducing the number of processing steps.

The above-described processes and apparatus of the present invention use hydrogen-using plasma chemistry as a weak oxidant and fluorine-containing gas to achieve strip-free strip treatment with minimal silicon loss. The silicon loss causes the fluorine radicals in the plasma to combine with hydrogen in the process gas to remain fluorine radicals and to form hydrogen fluoride (HF) instead of etching the underlying silicon. The combination of carbon dioxide in the plasma and carbon tetrafluoride is stripped of the post high dose implant photoresist and exposed to SEM radiation or to the substrate in accordance with a defect illuminator provided by KLA-Tencor, Milpitas, It was described as leaving no residue or leaving almost no residue. This is achieved with a minimum overstrip (e.g., about 100% overstrip). According to various implementations, less than 3% of the conditions without residues, as detected by the defect inspection apparatus, are marked as having an examined die, polymer defect.

The minimum acceptable silicon loss is about 3 angstroms, preferably about 1 angstrom. Regardless of the factors that can affect the photoresist thickness and other silicon losses, semiconductor device requirements require this minimum silicon loss. To reduce the measurement error, the silicon loss is measured by treating the wafer through the same strip process several times, for example, five times, before measuring the silicon loss in the device structure using an electron microscope such as a transmission electron microscope. The average silicon loss thus obtained is used to compare various treatments.

PROCESS PARAMETERS

Upstream Inlet Gas

A hydrogen-containing gas comprising urea hydrogen is inserted into the plasma source. The gas inserted into the plasma source includes a chemically active species to be ionized in the plasma source to form a plasma. The gas inserted into the plasma source comprises a fluorine-containing gas such as other fluorocarbons including carbon tetrafluoride, C ₂ F ₆ and hydrogen fluoride, nitrogen trifluoride, and 6 fluorinated sulfur. In certain embodiments, the fluorine containing gas is carbon tetrafluoride. In certain embodiments, the gas injected into the plasma source is comprised of a tetrafluorinated material having a volume of from about 0.1% to about 3%. The gas inserted into the plasma source comprises a weak oxide such as carbon dioxide, carbon monoxide, nitrogen dioxide, nitrogen oxides or water. In certain embodiments, the weak oxide is carbon dioxide.

According to various embodiments, the inlet gas has a volume of about 1-99 percent, about 80-99.9 percent, or about 95 percent molecular hydrogen, about 0-99 percent, or about 0-10 percent of a weak oxidizing agent, 10 percent fluorine compound. In certain embodiments, the inlet gas comprises about 95-99 percent by volume of molecular hydrogen, about 0.1-3 percent of a weak oxidizing agent, and 0.1-1 percent of a fluorine compound. In certain embodiments, the gas introduced into the plasma source comprises about 95-99 percent hydrogen atoms, about 1-3 percent carbon dioxide, and 1 percent or less tetrafluorinated materials.

The gases introduced into the plasma source are pre-mixed, partially mixed, or not mixed. The individual gas sources flow into the mixing space before being inserted into the plasma source. In another embodiment, the different gases are separated into the plasma source. The gas inserted into the plasma source has different components when used in different reaction stations of the multi-station chamber. For example, in a six-station chamber, station 1 or station 6 may use a relatively large amount of blanched gas as the process gas to remove the envelope and residue, respectively. One or two or more other stations may use a small amount of gas or no fluorine-containing gas as the process gas. A process gas having no carbon dioxide or a weak oxidizing agent may be used.

A method of stripping photoresist and a hydrogen-using plasma etchant with a weak oxidizing agent are disclosed in U.S. Patent No. 7,288,484, which is incorporated herein by reference.

Plasma Generation

Various types of plasma sources may be used in accordance with the present invention and include RF, DC, and microwave use plasma sources. In a preferred embodiment, a downstream RF plasma source is used. Typically, the RF plasma power for a 300 mm wafer is between about 300 watts and 10 kilowatts. In certain embodiments, the RF plasma power is between about 1000 Watts and 2000 Watts.

Inert gas

Various inert gases are used in the stripping process. As described, these gases are inserted downstream of the plasma source and upstream of the showerhead to mix with the plasma. In certain embodiments, the inert gas is argon or helium. In certain embodiments, the inert gas is argon. However, an inert gas containing nitrogen and helium may be used. In certain embodiments, the inert gas flow rate is about 0.15-10.0 times the hydrogen flow rate. In certain embodiments, the inert gas flow rate is about 1 - 3 times or about 2 times the hydrogen flow rate.

Inert gas inlet

The inert gas inlet may be any one of various types of gas inlets and may include multiple ports or jets to facilitate mixing with the plasma. The inlet jet angle may also be optimized to maximize mixing. In one embodiment, there are four or more unallowable gas inlet jets. In another embodiment, the angle of the inlet jets measured at the bottom of the plasma source is zero such that the inlet gas is directed perpendicular to the plasma flow direction from the plasma source into the showerhead assembly (or the process chamber if no shower assembly is present) . In many embodiments, the angles may be parallel to the workpiece surface, although other inlet angles may of course be used.

Showerhead Assembly

According to various embodiments of the present invention, the plasma gas is dispersed through the showerhead assembly to the work surface. The showerhead assembly may be grounded or may have a constant applied voltage so as to draw a constant charge species with a wattage bias of, for example, 0-1000, without affecting the neutral species flow to the wafer. Many electrical charge species in the plasma are recombined in the showerhead. The assembly includes a showerhead, which may be a metal plate having holes to direct the plasma and inert gas mixture to the reaction chamber. The showerhead causes the active hydrogen from the plasma source to be redispersed over a large area, allowing a smaller plasma source to be used. The number and arrangement of showerhead holes are set to maximize strip speed and strip speed uniformity. When the plasma source is centered in the wafer, the showerhead apertures become smaller and smaller in the center of the showerhead, so that the active gas can be directed to the outer region. The showerhead may have at least 100 holes. A preferred showerhead is available from Novellus Systems, Inc. of San Jose, CA, USA. Of a gamma xPR showerhead or a GxT drop-in showerhead.

In embodiments without a showerhead assembly, the plasma and inert gas mixture enters the processing chamber directly.

Process Chamber

The processing chamber may be any suitable reaction chamber for stripping operations. It may be a chamber of a multi-chamber device, or it may be a single chamber device. The chamber may include multiple stations where multiple wafers may be processed simultaneously. The process chamber may be the same chamber in which an implant (implant), etch, or other photoresist-related process occurs. In another embodiment a separate chamber is used separately for the strip. The process chamber pressure may be 300 mTorr -2 Torr. In another embodiment, the pressure range is 0.9 Torr to 1.1 Torr.

The processing chamber may include one or more processing stations where a strip operation is performed. In certain embodiments, the one or more processing stations include a preheating station, at least one strip station, and an over-ash station. The various features of the processing chamber and processing station are described in connection with FIG. The wafer support is configured to support the wafer during processing. The wafer support also transfers heat to the wafer during processing and receives heat from the wafer to adjust the required wafer temperature. In certain embodiments, the wafer is supported at a plurality of minimal contacts and is not physically in contact with the wafer support surface planes. The spindle picks up the wafer and transfers it from one station to another.

Suitable plasma chambers and systems include Novellus Systems, Inc. of San Jose, CA. Gamma 2100, 2130 I ² CP (Interlaced Inductively Coupled Plasma), G400, and GxT, all of which are provided by the company. Other systems include Axcelis Technologies Inc. of Rockville, Maryland, USA. Fusion line from PSK Tech Inc., South Korea ≪ / RTI > In addition, the various strip chambers may be constructed with cluster tools. For example, the strip chamber may be added to a Centura cluster from Applied Materials, Santa Clara, CA.

Work piece

In a preferred embodiment, the workpiece used in accordance with the method and apparatus of the present invention is a semiconductor wafer. Any wafer size can be used. Most modern wafer production equipment uses 200 mm or 300 mm wafers. As described above, the process and apparatus strip photoresist after a processing operation such as etching, ion implantation, or deposition. The present invention is suitable for wafers having very small features or critical dimensions of 100 nm or less, 65 nm, or 45 nm or less. The low silicon loss feature of HDIS is suitable for very shallow junctions of advanced logic devices. The present invention is also suitable for wafers that are subjected to line (FEOL, substrate processing) ion implantation, especially high dose ion implantation front ends.

The plasma-active species interacts with the photoresist and sputteres the residue on the wafer. In the wafer, the reaction gas may comprise a number of plasma activated species, the inert gas, radicals, charged species, and gas byproducts. The volumetric concentration of the various hydrogen species accounts for about 20-80% of the wafer gas. The volumetric concentration of the various fluorine species is between 0.01% and about 2% or less than 1% of the wafer gas. The concentration of the various species of weak oxidizing agent is from 0.05 to about 5% or about 1.2%. These species are _{^{H 2 *, H 2 +,}} H +, H *, e -, OH, O *, CO, CO 2, H 2 O, HF, F *, F -, CF, CF 2, and CF ₃ .

The processing conditions may vary depending on the wafer size. In another embodiment of the present invention, it is desirable to maintain the workpiece at a certain temperature during application of the plasma to the workpiece surface. The wafer temperature may be between about 110 and 500 degrees Celsius. In order to reduce the possibility of the photoresist popping described above, the wafer temperature may be gradually increased until sufficient shells are removed and photoresist popping is not a concern. The initial station temperature is between about 110 degrees Celsius and about 200 degrees Celsius, for example, about 180 degrees Celsius. Later stations can maintain good strip speeds using temperatures as high as between 285 degrees Celsius and 350 degrees Celsius.

Process Flow

3 is a process flow diagram illustrating various operations in accordance with certain embodiments of the present invention. One wafer is located in the reaction chamber on the wafer support. In operation 301, a hydrogen containing gas is inserted into the plasma source. Plasma is generated from the gas in operation 303. As more gas is applied to the plasma source, the plasma flows downstream and is mixed with the inert gas injected in operation 305. [ Some of the charged species in the plasma are mixed to form neutrals despite being active species. The active species and the inert gas flow through the showerhead front plate and react with the photoresist at the wafer surface at operation 307. The reaction generates volatile fumes from work 309 that are removed by the treatment area with a vacuum pump. The process can be repeated one or more times using different process parameters. For example, the wafer may be heated or cooled during the repetition of the process. In another example, different initial hydrogen containing gas and inert gas components and flow rates may be used. Preferably, at least one of the repetitions comprises a hydrogen-using gas comprising hydrogen atoms, carbon dioxide and tetrafluorocarbon. Containing gas that does not contain carbon dioxide or tetrafluorocarbon at least one or more times during the repetition.

According to various embodiments, the various repetitions are designed to target a high-dose ion implantation photoresist having different portions of the photoresist, such as the shell and bulk photoresist discussed above. A first strip repetition in the first strip station is designed to strip the envelope layer. The first strip repetition may include generating a plasma with or without hydrogen atoms, carbon dioxide (or other weak oxidizing agent), and tetrafluorocarbon (or other fluorine containing gas) do. When the sheath layer is sufficiently thin or completely removed, the second strip repetition often causes the bulk photoresist to strip with the residue and the remaining sheath layer at a higher wafer temperature.

 The second strip process may be performed at a different processing station than the first strip process. The second strip treatment may use a plasma generated without a weak oxidizing agent or a fluorine-containing gas, or both. After the bulk photoresist is removed, another strip treatment using other gas components is designed to strip the copper residue if the residue is still present. Such a residue stripping process makes it possible to remove any oxidation implant species using a fluorine-containing gas. The above-described strip repetition can be performed in any order or frequency depending on the number of photoresist components to be stripped and the number of processing stations. Those skilled in the art will be able to strip a thicker or thinner shell having a higher or lower resistance for the strip chemical reaction, using the concepts described herein. The concepts described herein may also be applied to other stations to target different photoresist layers as two or more photoresist layers with different properties are stripped using different strip chemistries.

Example 1

In this embodiment, the carbon dioxide and carbon tetrafluoride for the residue can be examined. A 300mm wafer is patterned with a 45nm structure and is implanted with LDD (doped drain) in the P + region. The resulting post high dose implant resist has a sheath of 680 angstroms and a thickness of about 2000 angstroms.

The wafers are stripped in a strip chamber having five plasma stations. The plasma is generated with RF power at 2000 watts. The wafer is exposed to the plasma-activated reaction gas for about 97 seconds for about 20 seconds at each station. The wafer support temperature is 350 degrees Celsius. The chamber pressure is 900 mTorr. The hydrogen flow rate is 6 slm (standard liters per minute). And the downstream argon flow rate is 14 slm. The carbon dioxide flow rate is 0 to 150 sccm. 4 The fluorocarbon flow rate is 20-40 sccm. These flow rates are the total flow rate for the entire chamber with five plasma stations. Each station accommodates about 1/5 of the total flow rate.

SEM ports for the wafer before and after stripping with various plasma-active reactive gases are shown in Figures 4A-4D. Figure 4A shows a small portion of the wafer prior to stripping. Structure 401 is the post high dose implant photoresist. Pad 405 includes structure 403 thereon, and the photoresist is removed during the patterning process. The HDIS processing thus removes structure 401.

In the first wafer as shown in FIG. 4B, 20 sccms of 4 Pullulan carbon and 150 sccms of carbon dioxide are added to the hydrogen to form the plasma. "Remnant 407, such as a worm, remains after the treatment. [0053] In a second wafer as shown in Figure 4C, 40 sccms of 4 fluorocarbons and 150 sccms of carbon dioxide are added to the hydrogen As shown in Figure C, the strip leaves no residue. 40 sccms of 4 fluorocarbon in another wafer, shown in Figure 4D, is added to the hydrogen to form the plasma without carbon dioxide Remnant formation such as worms was again observed. This result shows that the addition of carbon dioxide with 4 fluorocarbon generates a residue-free film in hydrogen-using HDIS.

Example 2

In this example, carbon dioxide flow rate and 4 fluorocarbon flow rate effects with silicon loss are independently tested. Under HDIS under the same processing conditions as in Example 1, the silicon loss is measured for carbon dioxide flow rates of 0, 50, 100, and 150 sccm, and the 4 fluorocarbon flow rates remain constant at 40 sccm. The results are shown in Figure 5A. The silicon loss is lowest at a carbon dioxide flow rate of 150 sccm and is highest when carbon dioxide is not added. This result shows that the presence of some carbon dioxide in the plasma reduces silicon loss.

Under the same processing conditions as in Example 1, the silicon loss for HDIS is measured for 4 fluorocarbon flow rates of 0, 40, 60, 80, and 100 sccm, and the carbon dioxide flow rate is kept constant at 150 sccm . The result is shown in Figure 5B. The silicon loss is highest at a 4 fluorocarbon flow rate of 60-80 sccm.

These results show that the silicon loss is affected by carbon dioxide and 4 fluorocarbon flow rates. For certain films, those skilled in the art will be able to design a HDIS process that minimizes silicon loss and leaves no residue on the film.

Example 3

In yet another embodiment, the effect of using different gas compositions at different stations has been investigated in connection with silicon losses and strip residues. The treatment conditions are the same as those in Example 1. However, the wafer support temperature is 250 degrees Celsius. In the first method, 4 fluorocarbon was used at a total speed of 40 sccm at all stations. In the second method, 4 fluorocarbon was delivered to RF stations 1 and 2 at a total speed of 20 sccm (10 sccm / station). The carbon dioxide flow rate was kept constant at 150 sccm.

In both cases, residue free substrate was obtained after HDIS treatment. The average loss of silicon lost was 8.1 angstroms per cycle in the first method and 17% in 6.7 angstroms in the second method. One cycle is to completely pass the device, including processing at all stations. This result shows that sequential stripping using different gas components can reduce silicon loss while maintaining a residue free substrate.

Example 4

In such an embodiment, short processing times per station and low 4 fluorocarbon flow rate effects were investigated. In the first method, 4 fluorocarbon was not added and the treatment time was 20 seconds per station. In the second method, 4 fluorocarbons were added to lie at 10 sccm and the strip handling time was only 10 seconds for the station. In both methods, the wafer support temperature was 285 degrees Celsius.

In the first method, if there is no 4 fluorocarbon in the plasma, residues after the strip have been found. The average silicon loss per cycle was 1.93 angstroms (A). In a second method in which the 4 fluorocarbon flow was reduced and the process reduced, the substrate had no residue and the average silicon loss per cycle was 3.12 angstroms (A). This results in a 4 fluorocarbon flow rate reduction and a shorter treatment time to make the substrate free of residues.

Example 5

In this embodiment, 4 fluorocarbon was inserted into the plasma source at different stations. In the first method, 5 sccm of 4 fluorocarbon was inserted into the RF station 1. In the second method, 5 sccm of 4 fluorocarbon was inserted into the RF station 3. Silicon losses were measured after the first cycle and after the fifth cycle and averaged. The other process parameters are the same as in the first embodiment.

The first method produced a substrate free of residues. The silicon loss after the first cycle with 4 fluorocarbon was 14.4 Angstroms (A). The silicon loss after the fifth cycle was 18.6 Angstroms (A). The average silicon loss per cycle was reduced from 14.4 Angstroms to 3.7 Angstroms.

A small amount of residue was observed on the substrate after HDIS as the second method. The silicon loss after the first period was 6.9 angstroms (A), which was less than the silicon loss in the first method. The silicon loss after the fifth cycle was 10.3 Angstroms (A). The average silicon loss per cycle was reduced from 6.9 angstroms (A) to 2.1 angstroms (A).

This result shows that the silicon loss using this chemical reaction is a self-limiting reaction, with most of the silicon loss occurring in the first cycle. Further processing does not remove more silicon. This is advantageous over conventional oxygen with a fluorine stripping chemical reaction, where the total silicon loss is proportional to the treatment time. When overstripping is required, for example when the photoresist thickness is not uniform, the oxygen chemistry will cause more silicon loss than the hydrogen chemistry, as described.

This result shows that if the 4 fluorocarbon is not used, the first periodic silicon loss is reduced. Those skilled in the art will appreciate that the insertion of 4 fluorocarbon can be delayed to reduce the total silicon loss.

While specific embodiments have been presented for purposes of illustration, it is to be understood that the invention is not intended to be limited to the specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram illustrating an apparatus according to certain embodiments for carrying out the method of the present invention.

Figures 2A-2D are diagrams illustrating the various stages of semiconductor fabrication before and after ion implantation and removal operations.

Figure 3 is a process flow diagram illustrating various operations in accordance with certain implementations of the present invention.

Figures 4A-4D show SEM photographs before and after strip stripping of the photoresist pattern under various conditions according to various embodiments of the present invention.

Figure 5A is a plot of silicon loss for HDIS using various carbon monoxide in accordance with various embodiments of the present invention.

Figure 5B is a plot of silicon loss for HDIS using 4 fluorocarbon flow rates in accordance with various embodiments of the present invention.

Claims (29)

A gas containing at least one hydrogen molecule selected from the group consisting of carbon dioxide, carbon monoxide, nitrogen dioxide, nitrogen oxides, water, hydrogen peroxide and combinations thereof, a fluorine-containing gas and hydrogen molecules different from the weak oxidizing agent, Generating a plasma from the gas injected into the plasma source, and Inserting an inert gas downstream of the plasma source and upstream of the workpiece, Wherein the hydrogen molecule containing gas, the weak oxidizing agent, and the fluorine containing gas flow along with the inert gas to the workpiece to react with the photoresist material from the workpiece, Wherein the gas introduced into the plasma source comprises a gas comprising hydrogen molecules in an amount of from 80 to 99.9 vol% Wherein the volumetric flow rate of the inert gas is between 0.15 and 10 times the hydrogen molecule volumetric flow rate. The method of claim 1, wherein the inert gas is selected from the group consisting of argon, helium, nitrogen, and combinations thereof. 2. The method of claim 1, wherein inserting the inert gas comprises inserting the gas upstream of the showerhead in the reaction chamber. 4. The method of claim 3, wherein electrically discharged species in the plasma are discharged when in contact with the showerhead. delete The method of claim 1, wherein the weak oxidizing agent is carbon dioxide. The method according to any one of claims 1 to 4, wherein the gas volume inserted into the plasma source is between 0.1% and 10% of the weak oxidizer. The method according to any one of claims 1 to 4 and 6, wherein the fluorine-containing gas is at least one selected from the group consisting of 4 fluorocarbon, fluorine element, 3 fluorine nitrogen, 6 fluorine sulfur, fluorocarbon, fluorocarbon, RTI ID = 0.0 > 1, < / RTI > The method according to any one of claims 1 to 4 and 6, wherein the fluorine-containing gas is tetrafluorocarbon. The fluorine-containing gas according to any one of claims 1 to ₄ , wherein the fluorine-containing gas is CF ₄ , C ₂ F ₆ , CHF ₃ , CH ₂ F ₂ , C ₃ F ₈ or NF ₃ How to. The method according to any one of claims 1 to 4 and 6, wherein the gas volume inserted into the plasma source is from 0.1% to 3% of the fluorine-containing gas. The method according to any one of claims 1 to 4 and 6, wherein the gas volume inserted into the plasma source is from 0.1% to 3% of the fluorine-containing gas. delete The method according to any one of claims 1 to 4, wherein the volume flow rate of the inert gas is the hydrogen molecule volumetric flow rate of 2 times. 7. A method according to any one of claims 1 to 4 and 6, wherein the gas introduced into the plasma source is pre-mixed. The method of any one of claims 1 to 4 and 6 wherein the plasma is generated with RF power between 300 and 10 kilowatts. 7. Process according to any one of claims 1 to 4 and characterized in that the temperature of the workpiece is between 160 DEG C and 400 DEG C when brought into contact with a hydrogen-containing gas, a weak oxidizing agent and a fluorine-containing gas Way. The method according to any one of claims 1 to 4, wherein the pressure in the reaction chamber is between 300 mTorr and 2 Torr. 7. The method of any one of claims 1 to 4, wherein the high dose implantation photoresist is removed from the workpiece at a rate of at least 100 nm / min and the silicon is removed at a rate of up to 4 nm / min Is removed from the workpiece surface. 20. The method of claim 19, wherein after the workpiece removal operation, there is no high dose implant photoresist residue and no more than 3 angstroms of silicon is lost from the underlying silicon layer. Inserting a first gas containing hydrogen molecules, a weak oxidizing agent and a fluorine-containing gas into the plasma source at a first overall flow rate, Generating a first plasma from a first gas inserted into the plasma source, and Inserting a first inert gas downstream of the plasma source and upstream of the workpiece to form a first mixture, And removing the first portion of material from the workpiece, comprising reacting a first portion of the material from the workpiece with the first mixture, A second gas comprising hydrogen at a second overall flow rate, and a weak oxidizing agent, into the plasma source, wherein the second gas composition is different from the first gas, Generating a second plasma from a second gas inserted into the plasma source, Inserting a second inert gas into the plasma source downstream and upstream of the workpiece to form a second mixture, And removing the second portion of material from the workpiece, comprising reacting a second portion of the material from the workpiece with the second mixture. A method for removing a high dose implant photoresist material from a workpiece surface in a reaction chamber. 22. The method of claim 21, wherein the second partial removal operation occurs prior to the first partial removal operation. 22. The method of claim 21, wherein the operation of removing the first or second portion is repeated once or twice. 22. The method of claim 21, wherein the first partial removal operation and the second partial removal operation occur in different reaction stations in the reaction chamber. 22. The method of claim 21, wherein the first partial removal operation and the second partial removal operation occur at different reaction stations at different temperatures in the reaction chamber. 22. The method of claim 21, wherein the second gas is free of any fluorine-containing gas. Plasma source, A gas inlet for inserting the hydrogen molecule containing gas mixture into the plasma source, A gas inlet for inserting an inert gas downstream of the plasma source and upstream of the workpiece, A showerhead located downstream of the gas inlet and a workpiece support located downstream of the showerhead for supporting the workpiece to adjust the temperature of the workpiece including a fiducial and temperature regulation mechanism And a reaction chamber To incorporate into the plasma source a gas comprising a weak oxidizing agent selected from the group consisting of carbon dioxide, carbon monoxide, nitrogen dioxide, nitrogen oxides, water, hydrogen peroxide and combinations thereof, a fluorine containing gas and hydrogen molecules different from the weak oxidizing agent Instructions, An instruction to generate a plasma from the gas injected into the plasma source, and A controller for executing a set of instructions including an instruction to insert an inert gas downstream of the plasma source and upstream of the workpiece, Wherein the gas introduced into the plasma source comprises a gas comprising hydrogen molecules in an amount of from 80 to 99.9 vol% Wherein the volumetric flow rate of the inert gas is between 0.15 and 10 times the hydrogen molecule volumetric flow rate. 28. The apparatus of claim 27, wherein the instructions further include repeating inserting a gas, generating a plasma, and inserting an inert gas at a different flow rate. 28. The apparatus of claim 27, wherein the reaction chamber comprises multiple stations, each station including a plasma source, a plurality of gas inlets, a showerhead, and a workpiece support.

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