Patent ID: 12217936

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Embodiments described herein relate to plasma processes used in semiconductor processing. Embodiments specifically described herein are in the context of using a tunable direct current (DC) bias during a plasma process. A plasma etch process can include flowing a gas, igniting the gas to form a plasma, introducing the plasma in a chamber containing a substrate, and using the tunable DC bias to repel or attract ions to/from the substrate.

Those skilled in the art should recognize that a full process for forming a semiconductor device and the associated structures are not illustrated in the drawings or described herein. Although various operations are illustrated in the drawings and described herein, no limitation regarding the order of such steps or the presence or absence of intervening steps is implied. Operations depicted or described as sequential are, unless explicitly specified, merely done so for purposes of explanation without precluding the possibility that the respective steps are actually performed in concurrent or overlapping manner, at least partially, if not entirely.

Plasma processing can be performed in semiconductor processing. A plasma is an at least partially ionized gas with positive and negative particles including radicals, positively and/or negatively charged ions, and electrons (negatively charged). Some examples of plasma processing include plasma etching and plasma ashing.

Plasma ashing may be the process of removing a photoresist (e.g., a light sensitive coating) from an etched substrate. Using a plasma source, a monatomic (e.g., single atom) substance known as a reactive species can be generated. Some examples of reactive species include oxygen, hydrogen, fluorine, or combinations thereof. The reactive species can be combined with the photoresist to form ash which is removed, e.g., with a vacuum pump. High temperature ashing, or stripping, is performed to remove as much photoresist as possible, while a “descum” process is used to remove residual photo resist in, e.g., trenches. The two processes may use different temperatures that the substrate is exposed to while in the ashing chamber.

Plasma etching is a form of plasma processing that directs a plasma to etch a material. The plasma source uses an etch species of charged ions, radicals, and/or neutral atoms. Elements of the material and the reactive species in the plasma chemically react to etch the material.

While plasma ashing and plasma etching processes use radicals for the ashing or etching, respectively, ions and electrons are also generated. Some plasma processes use a remote plasma in which the plasma source is remote from a location where the plasma and material interaction occurs. Remote plasma tools can diminish energy of downstream (e.g., from the plasma source downstream to the where the material is located, such as the substrate) radicals and ions in the plasma. Some of the ions and electrons can recombine downstream while the radicals survive; however, some ions and electrons remain in the plasma. For example, monatomic oxygen is electrically neutral and, although it does recombine downstream during the channeling, it recombines at a slower rate than the positively or negatively charged free radicals, which attract one another. This means that when all of the free radicals have recombined, there is still a portion of the active species. Thus, after ashing the photoresist, the exposed metal film underneath can become oxidized by the oxygen ions. Hence, the remote plasma process can introduce ions that may penetrate the substrate surface. Surface modification can create halogen induced defects. As geometry sizes of semiconductor devices decrease, the effects of the surface modification can have a great impact on the performance.

FIG.1illustrates a simplified tool10in accordance with some embodiments. The tool10includes a plasma generator12. In some examples, the plasma generator12is an inductively coupled plasma (ICP) generator or other suitable plasma generator that is operable to generate a remote plasma14. The remote plasma14is remote from the low ion region36in which particle interaction occurs. The plasma generator12is powered by a power source16. In some examples, the power source16is a radio frequency (RF) power source (e.g., about 13.56 MHz or other suitable RF) or a microwave (MW) power source. The power source16is grounded to a ground18. In some examples, ultra-violet (UV) light (e.g., about 10 nm to 400 nm in wavelength) is generated in the remote plasma14. For example, the UV light is generated by interactions of the particles in the remote plasma14, resulting in photon emissions.

The tool10includes a pedestal20by which a substrate22(e.g., a wafer) is supported during processing in the tool10. In some examples, the substrate22is or includes a bulk semiconductor substrate, a semiconductor-on-insulator (SOI) substrate, or the like, that can be doped (e.g., with a p-type or an n-type dopant) or can be undoped. In some embodiments, the semiconductor material of the substrate22includes an elemental semiconductor including silicon (Si) or germanium (Ge); a compound semiconductor; an alloy semiconductor; or combinations thereof. Various integrated circuits can be formed on and/or in the substrate22. The integrated circuits may include, for example, transistors (such as fin field effect transistors (FinFETs), planar FETs, or other transistors) and/or other devices on the substrate, metallizations on the substrate22to interconnect devices, etc. The pedestal20is electrically coupled to a bias source24. In some examples, the bias source24is a direct current (DC) voltage source that is grounded to the ground18. In some examples, the bias source24is a tunable bias source. In some examples, the bias source24is tunable to both negative DC biases and positive DC biases. For example, the bias source24is tunable from about −50 V to about +50 V. The DC bias source24includes a pulsing function for reducing the loading effect between an isolated and dense pattern. The pulsing function may be an on/off function for the DC bias source. For example, the pulsing function can be a square wave pulse function with any appropriate pulse duration and duty cycle. In some embodiments, the pedestal20includes a heating element28that is operable to heat the substrate22that is being supported by the pedestal20during processing in the tool10. For example, the heating element28causes the substrate22to be heated at or to a temperature in a range from about 90° C. to about 330° C. In some examples, the pressure may vary based on the particular process. For example, a higher temperature may be used for photoresist stripping due to a higher etch rate, and lower temperature (e.g., less than 100° C.) may be applied after the lithography process to remove the scum of photoresist in the bottom of trench pattern or hole pattern. Lower temperatures may be used in some surface treatment applications to avoid the collapse of small line pattern with high aspect ratio due to temperature induced thermal stress as the wafer is cooled from high temperature to room temperature.

A gas distribution plate (GDP)30is disposed in the tool10between the plasma generator12and the pedestal20. The GDP30is grounded to the ground18. In some examples, the GDP30is an aluminum plate or other suitable material. A gap34is between the GDP30and the pedestal20. In some examples, a size of the gap34is adjustable. For example, placement of the pedestal20relative to the GDP30is adjustable to increase or decrease the size of the gap34. In some examples, a translation mechanism can be mechanically coupled to the pedestal20to move the pedestal20farther away from or closer to the GDP30to increase or decrease the size of the gap34, respectively. In some examples, the size of the gap34between the pedestal20and the GDP30is in range from about 1 inch to about 3 inches. The GDP30distributes a gas, radicals, ions, etc. from the remote plasma14into a low ion region36. For example, the GDP30distributes the gas radicals, ions, etc. from the remote plasma14uniformly into the low ion region36. In some examples, the GDP30distributes, in the low ion region36, UV light from the remote plasma14, and the low ion region36may further be a low UV light region. The low ion region36may refer to a region having a lower energy relative to the plasma generator12region. For example, due to the GDP30, the UV light and/or the concentration of ions in the low ion region36may be lower than in the plasma generator12. The GDP30can have a number (e.g., a plurality) of through-holes. In some examples, the through-holes are of different or various sizes to suppress ions of the remote plasma14and/or UV light. Because the GDP30is grounded, most UV light is repelled from the surface of the GDP30.

During processing, a gas40is flowed into the plasma generator12. The gas may be delivered from a gas supply, such as a tank, to the plasma generator12. In some examples, the gas may be delivered via a pipe or tube, of a suitable material such as steel, from the supply to the plasma generator12. In some examples, the gas40is flowed into the plasma generator12at a flow rate in a range from about 200 sccm to about 9000 sccm. In some examples, the flow rate may vary depending on the plasma source and/or the particular process. For example, a lower flow rate may be used for a Toroidal plasma source (e.g., around 400 KHz) in a surface treatment application. A surface treatment application may remove a small amount of material, such as silicon, from a surface, similar to a gentle etch process. On the other hand, a higher flow rate may be used for an ICP plasma source, which may provide improved uniformity of photoresist stripping, or for a surface treatment. The higher flow rate may avoid failure of plasma ignition.

In some examples, the gas40includes O2, N2, H2, He, Ar, CF4, NF3, CxHyFz, or a mixture of some or all of these gases. In some particular examples, the gas40includes O2, H2, or a combination thereof. The gas40is ignited in the plasma generator12to generate the remote plasma14. In some examples, the gas40is ignited via radio frequency (RF) power (e.g., around 17.56 MHz). In some examples, the gas40is ignited by an inductively coupled plasma (ICP) plasma source in which the energy is supplied by electric currents produced by electromagnetic induction using time varying magnetic fields. The remote plasma14includes plasma effluents, such as ionized, excited, and/or neutral species of the gas40. In some examples, UV light is also generated in the remote plasma14. In some examples, a pressure in the low ion region36is in a range from 0.1 Torr to about 4 Torr. In some examples, the pressure may vary depending on the plasma source and/or the particular process. For example, a lower pressure may be used for a Toroidal plasma source in a surface treatment application. On the other hand, a higher pressure may be used for an ICP plasma source, in a photoresist stripping or surface treatment application. The higher pressure may avoid failure of plasma ignition. In some examples, ash rates and uniformity may be correlated to pressure, power, and flow rate. For example, 1 Torr pressure, 5000 W power, and 5000 sccm flow rate may provide high ash rates as compared to lower pressure, power, and/or flow rates.

Ionized, excited, and/or neutral species of the gas40from the remote plasma14diffuse through the GDP30to the low ion region36, where the substrate22is exposed to the ionized, excited, and/or neutral species of the gas40. In some examples, the ionized, excited, and/or neutral species of the gas40and/or other ions removed from the substrate22or material on the substrate22can be pumped out or removed from the tool10by an exhaust42.

During the exposure of the substrate22to the ionized, excited, and/or neutral species of the gas40, the bias source24can bias the pedestal20and hence, the substrate22, with a DC bias voltage, to achieve a desired effect. A polarity of the DC bias voltage, a magnitude of the DC bias voltage, a pulsing function (e.g., including a duty cycle), and/or combinations thereof may result in the desired effect, which can account for a loading effect between an isolated pattern and/or dense pattern. Some examples are described below to illustrate some desired effects.

FIG.1as described herein and illustrated in the figures is simplified to not obscure various aspects of the examples described herein. A person having ordinary skill in the art will readily understand various modifications of the simplified tool and/or other features that can be incorporated with the tool.

FIG.2is an example method for applying DC bias during a plasma process, for example, to attract or repel ions to/from the substrate22. The plasma process200is a general example of applying a DC bias during plasma processing, which may be performed as a part of a semiconductor device manufacturing process. More specific manufacturing processes and plasma processes are described below, for example, with respect toFIGS.3,5,7, and9. In block210, a gas is flowed into a remote plasma region of the tool10as the gas40. In some examples, the gas40is flowed into the plasma generator12at a flow rate in a range from about 200 sccm to about 9000 sccm. Various gases can be flowed depending on the plasma process being performed. As described in more detail below with respect toFIGS.3and4, the gas40could be oxygen for an oxidation process. As described in more detail below with respect toFIGS.3through9, the gas40could be oxygen, hydrogen, or a combination thereof, for a plasma ashing process. In some examples, the gas40is a fluorine-containing gas for a plasma etch process. Other gases or plasma processes can also be performed.

In block212, the pedestal20is biased with a DC bias voltage. For example, the bias source24is tunable from about −50 V to about +50 V. As described in further detail below, the DC bias voltage is applied to attract or repel ions to/from the substrate22. For example, the DC bias can be applied to oxidize, antioxidate, or defluorinate the substrate22. In some examples, the DC bias voltage is tunable, for example, to provide a stronger or weaker attraction or repulsion of the ions and/or to switch from a negative DC bias voltage to a positive DC bias voltage, or from a positive DC bias voltage to a negative DC bias voltage.

In block214, the gas40is ignited to generate the remote plasma14. The gas40can be ignited before the pedestal20is biased with the DC bias voltage in block212, after the pedestal20is biased with the DC bias voltage in block212, or at the same time that the pedestal20is biased with the DC bias voltage in block212. In block216, the remote plasma14is then introduced to expose the substrate22to the plasma. For example, the remote plasma14is diffused through the GDP30to the low ion region36where the substrate22is exposed. In some examples, a pressure in the low ion region36is in a range from 0.1 Torr to about 4 Torr. In some examples, the heating element28causes the substrate22to be heated at or to a temperature in a range from about 90° C. to about 330° C.

In a first example of the method for applying DC bias during a plasma process, a remote plasma process is implemented to oxidize a material of the substrate22.FIG.3is an example of the method for oxidizing a material on the substrate22. In block302, a layer is formed on a substrate22. In block304, a process is formed to oxidize at least a portion of the layer. In other examples, the substrate22may be oxidized, for example, without first forming the layer at302. In block306, an oxygen-containing gas, such as O2, is flowed into a remote plasma region in the tool10as the gas40. In some examples, the oxygen-containing gas is flowed into the plasma generator12at a flow rate in a range from about 200 sccm to about 9000 sccm. In block308, the pedestal20is biased with a positive DC bias voltage applied to the pedestal20to attract negative oxygen ions. In some examples, the DC bias is tunable. For example, the bias source24is tunable from about +1 V to about +50 V. A larger positive bias can be used to form a thicker oxide layer and a smaller positive bias can be used to form a thinner oxide layer. In block310, the oxygen-containing gas is ignited to form the remote plasma14. The ignition of the oxygen-containing gas at block310to generate the remote plasma14can be before the pedestal20is biased with the DC bias voltage at block308, after the pedestal20is biased with the DC bias voltage at block308, or at the same time that the pedestal20is biased with the DC bias voltage at block308. Next, in block312, the remote plasma14is introduced to the substrate22to expose the substrate22to the plasma. For example, the remote plasma14is diffused through the GDP30to the low ion region36where the substrate22is exposed. In some examples, a pressure in the low ion region36is in a range from 0.1 Torr to about 4 Torr. In some examples, the heating element28causes the substrate22to be heated at or to a temperature in a range from about 90° C. to about 330° C. For example, for an oxidation process, temperatures higher than 200° C. may be preferred.

Further processing steps may be included in the manufacturing process of the semiconductor device. In block314, a photoresist may be deposited on the oxidized layer. In block316, the photoresist is patterned. The patterning may depend on the lithography process and type of photoresist being used. The patterning may include masking and exposure to light for example. In block318, additional processing of the substrate22may be performed, such as an etch process using the patterned photoresist.

FIG.4illustrates the oxidation mechanism for silicon (Si) to form silicon oxide (SiO2) as an example. In other examples silicon germanium (SiGe) or other materials can be oxidized with the process ofFIG.3. Oxidation mechanisms include thermal oxidation and plasma oxidation. Thermal oxidation can involve a high activity energy (e.g., around 2 eV) and a neutral oxygen species. Plasma oxidation can involve a low activation energy (e.g., around 0.15 eV) and negative oxygen ions. The remote plasma generated by igniting the oxygen-containing gas at block310contains negative oxygen ions (e.g., O2−and O−). The negative oxygen ions then become exposed to the substrate22in the low ion region36. The positive DC bias voltage from the bias source24that is applied at block308causes a positive electrical charge to accumulate on the pedestal20at the surface that supports the substrate22. The positive electrical charge on the surface of the pedestal20can cause a positive charge to accumulate on the surface of the substrate22distal from the pedestal20. Because the oxygen ions are negatively charged and the surface of the substrate22distal from the pedestal20is positively charged, an electrostatic force (e.g., attraction) exists between the negative oxygen ions and the substrate22. The electrostatic force (e.g., attraction) between the negative oxygen ions and the positive charge on the pedestal20can cause the oxygen ions to penetrate into the substrate22, which permits the oxygen ions to react with a material, e.g., silicon, of the substrate22to oxidize the material. A larger positive DC bias voltage and/or larger duty cycle can result in a higher oxidation rate, more oxidation, and a thicker oxide layer. In some examples, more oxidation is implemented, such as for a nitride film oxidation, to improve photoresist adhesion and profile, control fin width, increase metal oxidation of isolation, etc. In some examples, the rate of oxidation is a function of the oxygen flow rate, the amplitude of the positive DC bias applied, a duration of the process, electron density in the plasma, and/or other factors such as temperature. In some examples, the DC bias voltage is applied to control a uniformity of the oxidation of the substrate22material.

In a second example of the method for applying DC bias during a plasma process, a remote plasma process can be implemented to reduce or prevent oxidization of a material of the substrate, such as during an ashing process.FIG.5is an example method for reducing or preventing oxidization of a material of the substrate during a plasma process. In block502a layer may be formed on a substrate, such as the substrate22. In block504, a photoresist may be deposited on the layer. In block506, the photoresist is patterned. In some examples, the photoresist may be deposited on the substrate22, for example, rather than forming the layer in block502. In block507, additional processing may be performed after patterning the photoresist, for example, an etch process could be performed. In block508, a process is performed to remove the photoresist, including the blocks512-517. In block512, an oxygen-containing gas (and/or a nitrogen-containing gas), such as O2, is flowed into a remote plasma region of the tool10as the gas40. In some examples, the oxygen-containing gas is flowed into the plasma generator12at a flow rate in a range from about 200 sccm to about 9000 sccm. The oxygen-containing gas can be used in an ashing process to remove various layers, such as the photoresist or a bi-layer or tri-layer structure used for patterning the deposited layer and/or substrate22. In block514, the pedestal20is biased with a negative DC bias voltage to repel the negative oxygen ions. In block516, the oxygen-containing gas is ignited to generate the remote plasma14for the plasma process. In some examples, the DC bias voltage is tunable. For example, the bias source24is tunable from about −1 V to about −50 V. A larger negative DC bias can be used to further reduce or eliminate oxidation during the plasma process. The ignition of the oxygen-containing gas at block516to generate the remote plasma14can be before the pedestal20is biased with the negative DC bias voltage at block514, after the pedestal20is biased with the negative DC bias voltage at block514, or at the same time that the pedestal20is biased with the negative DC bias voltage at block514. Next, in block517, the remote plasma14is introduced to the substrate22to expose the substrate22to the plasma. For example, the remote plasma14is diffused through the GDP30to the low ion region36where the substrate22is exposed. In some examples, a pressure in the low ion region36is in a range from 0.1 Torr to about 4 Torr. In some examples, the heating element28causes the substrate22to be heated at or to a temperature in a range from about 90° C. to about 330° C. In a process to remove photoresist, a higher temperature (e.g., higher than 200° C.) may be used for a higher ash rate; but, the higher temperature may increase oxidation and, in turn, substrate loss. However, by using the negative DC bias to repel oxygen ions, the higher ash rate can still be achieved without increased oxidation. In block518, additional processing may be performed, such as depositing additional layers or material and etching.

FIG.6illustrates the mechanism for reducing or preventing oxidation (e.g., antioxidation) of silicon (Si) as an example. The remote plasma14contains negative oxygen ions (e.g., O2−and O−) that then become exposed to the substrate22in the low ion region36. If the oxygen ions penetrate the silicon layer63of the substrate22, the silicon layer63can oxidize to form the SiO2layer61. The negative DC bias voltage from the bias source24causes a negative electrical charge to accumulate on the pedestal20at the surface that supports the substrate22. The negative electrical charge on the surface of the pedestal20can cause a negative charge to accumulate on the surface of the substrate22distal from the pedestal20. An electrostatic force (e.g., repulsive) is created by the negatively charged oxygen ions and the negative charge accumulated on the surface of the substrate22distal from the pedestal. The electrostatic force (e.g., repulsive) between the negative oxygen ions and the negative charge on the surface of the substrate22distal from pedestal20can cause the oxygen ions to be repelled from the substrate22to thereby reduce or prevent the oxygen ions from penetrating or coming into contact with a material, e.g., silicon layer63, of the substrate22, which can reduce or prevent oxidization of the material. Substrate loss can thereby be mitigated. Thus, the ashing process shown inFIG.5can simultaneously achieve both ashing of the photoresist with the remaining radicals (O*) and antioxidation of the material of the substrate22by repelling the negative oxygen ions (e.g., O2−and O−).

In some examples, the oxygen ashing process and the oxidation process are performed sequentially. For example, the oxygen ashing process as described with respect toFIGS.5and6can be performed to strip a photoresist from the substrate22using the negative DC bias voltage to prevent or reduce oxidation during the ashing process. Next, the positive DC bias voltage could be applied to perform the oxidation process as described with respect toFIGS.3and4if an oxide layer is desired.

In a third example of the method for applying DC bias during a plasma process, a remote plasma process can be implemented to reduce fluorination (e.g., defluorinate) of a material of the substrate, such as during an ashing process. In some examples, fluorination of the material occurs during a process prior to the ashing process and can be removed during the ashing process. In some examples, the fluorination of the material occurs during an etch process. For example, an etching process can implement fluorine-based gases and plasmas. In those examples, negative fluorine ions can penetrate (e.g., diffuse into) a material of the substrate22causing fluorination of the material, which can cause defects. For example, presence of fluorine in the material of the substrate22can induce outgassing in subsequent processing of the substrate22. The outgassing can lead to defects such as condensation defects, film voids, and/or fluorinated pads leading to corrosion of the pad. In some examples, after such an etch process, an ashing process and/or an additional treatment process implementing a remote plasma is performed. As described inFIG.7, the plasma process can be implemented to reduce the fluorination of the material.

FIG.7is an example method for reducing fluorination of a material of the substrate during a plasma process. The manufacturing process illustrated inFIG.7involves a process that uses fluorine, such as an etch process prior to the ashing process. As shown inFIG.7, in block702a layer may be formed on a substrate, such as the substrate22. In block704, a photoresist may be deposited on the layer. In block706, the photoresist is patterned. In some examples, the photoresist may be deposited on the substrate22, for example, rather than forming the layer in block702. Additional processing may be performed after patterning the photoresist, for example, in block707a fluorine etch process is performed on the layer. In block708, a process is performed to remove the photoresist, including the blocks712-717. In block712, a hydrogen-containing gas, such as H2, is flowed into a remote plasma region in the tool10as the gas40. In some examples, the hydrogen-containing gas (and sometimes also a nitrogen-containing gas) is flowed into the plasma generator12at a flow rate in a range from about 200 sccm to about 9000 sccm. The hydrogen-containing gas can be used in an ashing process to remove various layers, such as the photoresist or a bi-layer or tri-layer structure used for patterning the deposited layer and/or substrate22. In block714, the pedestal20is biased with a negative DC bias voltage to repel negative fluorine ions. In some examples, the DC bias is tunable. For example, the bias source24is tunable from about −1 V to about −50 V. A larger negative DC bias voltage can be used to further reduce or eliminate fluoridation during the plasma process. In block716, the hydrogen-containing gas is ignited to generate the remote plasma14for the plasma process. The ignition of the hydrogen-containing gas at block716to generate the remote plasma14can be before the pedestal20is biased with the negative DC bias voltage at block714, after the pedestal20is biased with the negative DC bias voltage at block714, or at the same time that the pedestal20is biased with the negative DC bias voltage at block714. Next, in block717, the remote plasma14is introduced to the substrate22to expose the substrate22to the plasma. For example, the remote plasma14is diffused through the GDP30to the low ion region36where the substrate22is exposed. In some examples, a pressure in the low ion region36is in a range from 0.1 Torr to about 4 Torr. In some examples, the heating element28causes the substrate22to be heated at or to a temperature in a range from about 90° C. to about 330° C. In a process to remove photoresist, a higher temperature (e.g., higher than 200° C.) may be used for a higher ash rate as well as better removal of the fluorine. In block718, additional processing may be performed, such as depositing additional layers or material and etching.

FIG.8illustrates the mechanism for reducing fluorination of a material (e.g., a metallization such as AlCu) on the substrate22as an example. A bi-layer or tri-layer structure, such as oxide layer83, SiN layer81, and hardmask layer85, is implemented for masking and patterning a metallization (e.g., AlCu) layer87and a dielectric layer89. The patterning uses a fluorine-based plasma that causes negative fluorine ions (F−) to diffuse into the metallization layer87. The plasma includes positive hydrogen ions (e.g., H+) that then become exposed to the substrate22in the low ion region36. The negative DC bias voltage from the bias source24causes a negative electrical charge to accumulate on the pedestal20at the surface that supports the substrate22. An electrostatic force (e.g., repulsive) is created between the negative fluorine ions and the negative charge on the pedestal20. The electrostatic force between the negative fluorine ions and the negative charge on the pedestal20can cause the fluorine ions to be repelled and removed from the substrate22to thereby reduce fluorination of the metallization layer87. An electrostatic force (e.g., attractive) exists between the positive hydrogen ions and the negative fluorine ions. The electrostatic force between the positive hydrogen ions and the negative fluorine ions can also further cause the negative fluorine ions to be removed from the substrate22thereby reducing fluorination of the metallization layer87. The removed fluorine atoms can be attracted to and react with the hydrogen ions to form volatile hydrofluoric acid (HF) (e.g., F−+H+→HFgas), which can be pumped or exhausted42out of the tool10. Thus, the ashing process shown inFIG.7can simultaneously achieve both ashing of the photoresist and defluorination of the material of the substrate22.

In a fourth example of the method for applying DC bias during a plasma process, a remote plasma process is implemented for anti-oxidizing and de-fluorinating a material of the substrate22.FIG.9is an example method that includes removing a photoresist in block908that further reduces oxidization and fluorination of a material on the substrate22. For example, the plasma process ofFIG.9can be implemented in the manufacturing process illustrated inFIG.7in which a fluorine etch is performed in the process. In block912, an oxygen-containing gas, such as O2, is flowed into a remote plasma region in the tool10as the gas40. In block914, the pedestal20is biased with a negative DC bias voltage. In block916, the oxygen-containing gas is ignited to form the remote plasma14. The ignition of the oxygen-containing gas at block916to generate the remote plasma14can be before the pedestal20is biased with the negative DC bias voltage at block914, after the pedestal20is biased with the negative DC bias voltage at block914, or at the same time that the pedestal20is biased with the negative DC bias voltage at block914. Next, in block918, the remote plasma14is introduced to the substrate22to expose the substrate22to the plasma. For example, the remote plasma14is diffused through the GDP30to the low ion region36where the substrate22is exposed. The blocks912-918can be implemented as an ashing process to remove photoresist from the substrate22. Use of the negative DC bias during the ashing process reduces or prevents oxidation of the material of the substrate, for example, as described above with respect toFIG.6for the example of the mechanism of reducing or preventing oxidation of silicon by repelling the negative oxygen ions.

The method can further be used to defluorinate the substrate22. For example, prior to the ashing process ofFIG.9, the process707using fluorine can be performed, such as a plasma etch process using fluorine. The process using fluorine results in fluorination of a material on the substrate22, such as a metallization. Thus, in block920, the method stops flowing the oxygen-containing gas, and in block922, a hydrogen-containing gas, such as H2, is flowed into a remote plasma region of the tool10as the gas40. In some examples, the pedestal20may remain biased with the negative DC bias voltage used during the oxygen ashing in block914. In some examples, the negative DC bias voltage could be turned off, and is turned back on. In some examples, the negative DC bias voltage can be tuned to a different negative DC bias voltage. For example, a first negative DC bias voltage may be used during the oxygen ashing and a different negative DC bias voltage is used during the defluorination. In block924, the hydrogen-containing gas is ignited to form a second remote plasma14. The second remote plasma14is then introduced to the substrate22to expose the substrate22to the plasma in block926. For example, the second remote plasma14is diffused through the GDP30to the low ion region36where the substrate22is exposed. The negative DC bias voltage causes fluorine ions to leave material of the substrate22, thereby defluorinating the material of the substrate22, for example, as described above with respect toFIG.8for the example of the mechanism of reducing or preventing fluorination of AlCu. Thus, the method ofFIG.9can provide an efficient technique to achieve simultaneous defluorination and photoresist removal, with minimal oxidation, in a single dry ash process.

In a fifth example of the method for applying DC bias during a plasma process, a remote plasma process is implemented for anti-oxidizing and de-fluorinating a material of the substrate22. An oxygen-containing gas and hydrogen-containing gas are flowed into the tool10as the gas40and ignited to form the remote plasma14. The pedestal20is biased with a negative DC bias voltage. The oxygen and/or hydrogen plasma can be used to ash the photoresist, while the negative DC bias voltage applied to the pedestal20reduces or prevents oxidation and also cause fluoride to be released. The fluoride can combine with the hydrogen ions and be removed from the tool10by the exhaust42.

The example methods described herein are to illustrate aspects of various embodiments. Embodiments may be implemented in and/or for other processes that would be readily understood by a person having ordinary skill in the art. Further, some aspects of the example methods described above can be implemented together and/or in combination with other features not described herein. For example, an ash process can implement O2and H2gas to achieve various benefits described herein. The example methods may also be performed in any logical order, and any order described herein or illustrated in the figures is merely for convenience in describing the examples. Various embodiment methods may be performed in other orders.

Embodiments can have benefits. For example, some embodiments can reduce or avoid oxidation of a substrate during an ashing process. Further, substrate loss from the ashing process can be reduced or avoided. Penetration of halogenic ions into a substrate can be reduced or avoided, which can reduce or avoid defects in the substrate. Some embodiments can reduce or eliminate fluorination of a substrate during an ashing process, which can avoid defects in the substrate. Some embodiments can reduce or avoid oxidation of a substrate and also reduce or eliminate fluorination of the substrate during a single ashing process. Some embodiments can increase oxidation during a plasma process.

In an embodiment, a method is provided. The method includes generating a plasma containing negatively charged oxygen ions. The method includes exposing a substrate to the plasma. The substrate is disposed on a pedestal while being exposed to the plasma. The method includes applying a negative direct current (DC) bias voltage to the pedestal while exposing the substrate to the plasma to repel the negatively charged oxygen ions from the substrate.

In another embodiment, a method is provided. The method includes generating a plasma comprising positively charged hydrogen ions. The method includes exposing a substrate to the plasma. The substrate contains negatively charged fluorine ions and is disposed on a pedestal while being exposed to the plasma. The method includes applying a negative direct current (DC) bias voltage to the pedestal to repel the negatively charged fluorine ions from the substrate while exposing the substrate to the plasma.

In yet another embodiment, a method is provided. The method includes generating a plasma containing negatively charged oxygen ions. The method exposing a substrate to the plasma. The substrate is disposed on a pedestal while being exposed to the plasma. The method includes applying a positive direct current (DC) bias voltage to the pedestal to attract the negatively charged oxygen ions to the substrate while exposing the substrate to the plasma.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.