Plasma etching method

Abstract

A method for dry etching a compound comprising at least two metals involves injecting reactants and a carrier gas into an etch chamber containing the compound wherein each metal can be plasma etched by at least one reactant. The method includes stopping injection of one or more reactants to reduce its concentration during which the plasma is ignited within the chamber.

Description

Technical Field

[0001] The present invention relates to the field of metal etching methods, in particular to a method and system for dry etching a compound containing multiple metals. Background Art

[0002] Plasma-based dry etching is a key technology in the semiconductor industry, enabling the precise patterning of materials used in the manufacture of integrated circuits and other advanced electronic devices. The method involves using plasma to generate chemically reactive species that selectively remove material from a substrate (typically a semiconductor wafer). Plasma is rich in electrons, which play a key role in the dissociation of gas molecules into highly reactive free radicals and the ionization of some of these molecules. These free radicals are much more reactive than their stable molecular counterparts, making them very effective in etching applications.

[0003] Dry etching relies on neutral molecules in the plasma reacting with surface atoms of the material being etched to form volatile products.

[0004] Another synergistic effect of plasma dry etching is the high-energy ion bombardment of the surface, which breaks the material bonds and mixes the plasma and material atoms in an exchange layer that is typically a few nanometers thick.

[0005] Metallic compounds, by their very nature, contain multiple metals, sometimes exhibiting superior properties compared to their individual components. Consequently, there has been significant interest in the use and patterning of metallic compounds. However, each metal in the compound reacts at a different rate with the incoming species, which can cause the etching process to drastically slow down or even completely prevent further etching. Figures 1 to 4 This is reflected in the fact that the etching rate is usually limited by the slowest reacting component. For example, in a compound containing elements A, B, and C (see Figure 1 ), if element A is etched quickly, a surface consisting mainly of elements B and C will remain (see Figure 2 If element C does not form volatile products and must be sputtered off, it will accumulate on the wafer surface and hinder the etching process (see Figure 3 ).

[0006] For example, for InGaZnO compounds, chlorine can etch Ga but not In (at low temperatures); or for Mg x Zn 1-x O, chlorine can etch zinc, but MgO is not sensitive to chlorine; or for NiAl, CO can etch nickel but not aluminum. The introduction of other gases will cause deposition rather than etching (see Figure 4 ), thus making the process more complicated.

[0007] Despite advances in dry etching technology, further improvements are needed to address the challenges of etching compounds containing multiple metals with different reaction rates. Summary of the Invention

[0008] One object of embodiments of the present invention is to be able to well control the etching rate of compounds containing multiple metals. This object is achieved by the method and system for dry etching of compounds containing at least two metals according to the present invention.

[0009] In a first aspect, the present invention relates to a method for dry etching a compound containing at least two metals, the method comprising: a. injecting one or more reactants and a carrier gas into an etching chamber containing the compound, wherein each metal is etchable by a plasma of at least one of the reactants; b. ceasing the injection of at least one of the reactants, thereby causing the concentration of the reactant to decrease; and c. igniting a plasma in the etching chamber for a period of time such that the plasma is present during the concentration decrease. This provides the advantage of being able to control the etching rates of multiple metals simultaneously.

[0010] In embodiments, the method may include:

[0011] a. injecting two or more reactants (3) and a carrier gas into an etching chamber (5) containing a compound (1), wherein each metal (2) can be etched by the plasma of at least one of the reactants (3),

[0012] b. stopping the injection of at least one of the two or more reactants (3), thereby causing the concentration of the at least one reactant (3) to decrease, and

[0013] c. igniting a plasma in the etching chamber (5) for a period of time such that a plasma is present during said reduction,

[0014] Wherein, the carrier gas

[0015] - is different from any reactant and does not react with said compound,

[0016] or

[0017] - is one of the two or more reactants and is the main reactant responsible for etching the compound element having the slowest etching rate in the presence of its main reactant.

[0018] In an embodiment, step c may be represented as: igniting plasma in the etching chamber for a period of time such that plasma exists during the lowering period, thereby simultaneously controlling the etching rates of at least two metals.

[0019] In an embodiment, step c can be represented as: igniting plasma in the etching chamber (5) for a period of time, so that plasma exists during the lowering period and dry etching is performed.

[0020] In an embodiment, the one or more reactants may be two or more reactants.This embodiment provides the advantage of allowing more precise control of the etching process.

[0021] In an embodiment, if two or more reactants are injected in step a., step b. may include ceasing the injection of at least two of the reactants, thereby causing the concentrations of the at least two of the reactants to decrease, and wherein step c. may include igniting a plasma within the etching chamber for a period of time such that the plasma is present during the respective decreases in concentration. This embodiment provides the advantage of being able to more effectively control the etching rates of multiple metals.

[0022] In an embodiment, ignition of the plasma may be initiated within a time window of 500 ms before to 500 ms after, preferably 250 ms before to 250 ms after, and more preferably 100 ms before to 100 ms after, the cessation of injection of one of the reactants in step b. For example, injection of one of the reactants may be stopped simultaneously with the start of ignition of the plasma. Stopping injection of one of the reactants at approximately the same time as the start of the plasma generally yields good results.

[0023] In an embodiment, the gas injection of each reactant may be maintained for at least 10 ms, more preferably at least 50 ms, and even more preferably at least 100 ms. This is preferred because longer gas injection times are more repeatable and allow for better control of the etching process.

[0024] As used herein, unless otherwise specified, when contemplating the etch rate of a metal in the presence of its primary reactant, the etch rate may be the etch rate in the presence of the primary reactant alone, or the etch rate in the presence of all reactants (including the primary reactant).

[0025] In an embodiment, the flow rate of each of the two or more reactants during its injection may be determined based on the etch rate of each metal in the presence of its primary reactant (i.e., in the presence of the reactant that contributes most to its etch rate) when the plasma is ignited.

[0026] In an embodiment, the flow rate of each of the two or more reactants during its injection can be determined based on the etch rate of each metal in the presence of its primary reactant (i.e., in the presence of the reactant that has the greatest impact on its etching rate) when the plasma is ignited. Thus, the primary reactant for the metal with the highest etching rate is injected at the lowest flow rate, while the flow rates of the primary reactants for metals with successively lower etching rates are increased. When each reactant is the primary reactant for only one metal, this fine-tuning of the reactant flow rates is particularly effective in balancing the etching rates of different metals. In this way, the etching rates of different metals in the compound tend to be more balanced.

[0027] In an embodiment, in step a, the partial pressure achieved by each of the two or more reactants during the implantation may be determined based on the etch rate of each metal in the presence of its primary reactant when the plasma is ignited.

[0028] In an embodiment, in step a, the partial pressure achieved by each of the two or more reactants during injection can be determined based on the etch rate of each metal in the presence of its primary reactant when the plasma is ignited. Thus, the primary reactant of the metal with the highest etching rate in the presence of its primary reactant is injected to achieve the lowest partial pressure among the reactants, while the primary reactants of metals with successively lower etching rates in the presence of their respective primary reactants are injected with increasing partial pressures. This fine-tuning of the reactant partial pressures is particularly effective in balancing the etching rates of different metals when each reactant is a primary reactant for only one metal. In this way, the etching rates of different metals in the compound tend to be more balanced.

[0029] In an embodiment, the time of step b may be determined based on the etch rate of each metal in the presence of its primary reactant when the plasma is ignited.

[0030] In one embodiment, the duration of step b can be determined based on the etch rate of each metal in the presence of its primary reactant when the plasma is ignited. Thus, the primary reactant of the metal with the highest etch rate is stopped first, while the primary reactants of metals with successively lower etch rates have increasingly longer stopping times. When each reactant is the primary reactant of only one metal, fine-tuning the stopping time of the reactants is particularly effective in balancing the etching of different metals during each cycle. This approach often results in a more balanced etching rate for different metals in the compound.

[0031] In an embodiment, the partial pressure of each of the two or more reactants during injection in step a and the time of step b may be determined based on the etch rate of each metal in the presence of its primary reactant when the plasma is ignited.

[0032] In an embodiment, the partial pressure of each of the two or more reactants during injection in step a and the duration of step b can be determined based on the etch rate of each metal in the presence of its primary reactant when the plasma is ignited. Thus, the primary reactant of the metal with the highest etching rate is injected to achieve the lowest partial pressure among the reactants, and the partial pressures of the primary reactants of metals with successively lower etching rates are increased accordingly. Consequently, the primary reactant of the metal with the highest etching rate is stopped earliest in step b, while the primary reactants of metals with successively lower etching rates in the presence of their respective primary reactants are stopped for successively longer periods of time. This fine-tuning is particularly effective for balancing the etching of different metals in each cycle when each reactant is the primary reactant of only one metal.

[0033] In an embodiment where at least one reactant is a primary reactant of two or more metals, the flow rate of each other reactant during its injection is preferably set to be lower than the flow rate of the at least one reactant that is the primary reactant of the two or more metals. The relative flow rates of the other reactants during their injection can be determined based on the etch rate of each metal for which the other reactants are the primary reactants when the plasma is ignited, whereby the primary reactant of the metal with the highest etch rate is injected at the lowest flow rate, while the flow rates of the primary reactants of the metals with successively lower etch rates are successively increased. When at least one reactant is a primary reactant of two or more metals, this fine-tuning of the reactant flow rates is particularly effective in balancing the etch rates of different metals. In this way, the etch rates of different metals in the compound tend to be more balanced.

[0034] In an embodiment where at least one reactant is a main reactant of two or more metals, the partial pressure reached by each other reactant during its injection is preferably set to a partial pressure lower than that reached by the at least one reactant as the main reactant of two or more metals. The relative size of the partial pressure of the other reactants during their injection can be determined based on the etch rate of each metal of the other reactants as the main reactant when igniting plasma, whereby the main reactant of the metal whose etch rate is the highest when its main reactant exists is injected to reach the lowest partial pressure in the reactant, while the partial pressure of the main reactant of the metal whose etch rate decreases in turn when its respective main reactant exists increases in turn. When at least one reactant is a main reactant of two or more metals, the fine adjustment of this reactant partial pressure is particularly effective to balancing the etching rates of different metals. By this method, the etching rates of different metals in the compound tend to be more balanced.

[0035] In an embodiment where at least one reactant is a main reactant of two or more metals, the time of step b of each other reactant is preferably set to be earlier than the time of the at least one reactant as the main reactant of two or more metals. The time of step b of each of the other reactants can be determined based on the etching rate of each metal with the other reactants as the main reactant when igniting plasma, whereby the main reactant of the metal with the highest etching rate stops earliest, while the stop time of the main reactant of the metal whose etching rate decreases in turn increases in turn. When at least one reactant is a main reactant of two or more metals, the fine adjustment of the reaction stop time is particularly effective for balancing the etching of each cycle of different metals. In this way, the etching rates of different metals in the compound tend to be more balanced.

[0036] In an embodiment where at least one reactant is a main reactant of two or more metals, the partial pressure of each reactant during injection in step a and the time of step b can be determined so that the partial pressure reached by each other reactant during injection in step a is set to be lower than the partial pressure of the at least one reactant as the main reactant of the two or more metals, and the time of step b of each other reactant is preferably set to be earlier than the time of the at least one reactant as the main reactant of the two or more metals. The determination of the partial pressure of the other reactants in step a and the time in step b can be based on the etching rate of each metal with the other reactants as the main reactant when the plasma is ignited, whereby the main reactant of the metal with the highest etching rate among the other reactants is injected to reach the lowest partial pressure, while the partial pressure of the main reactant of the metal whose etching rate decreases in turn increases accordingly, and thus, the main reactant of the metal with the highest etching rate stops earliest in step b, while the stop time of the main reactant of the metal whose etching rate decreases in turn in the presence of its respective main reactant increases in turn. When at least one reactant is a main reactant of two or more metals, this fine-tuning is particularly effective in balancing the etching of different metals in each cycle. With this approach, the etch rates of the different metals in the compound tend to be more balanced.

[0037] In an embodiment, the time of step b may be determined based on the etching rate of each metal (2) in the presence of its primary reactant (3) when the plasma is ignited, such that:

[0038] - if each main reactant is a main reactant of only one metal, the main reactant (3) of the metal with the highest etching rate stops first, and the main reactants (3) of the metals (2) with successively lower etching rates have successively longer stopping times, and

[0039] -If at least one reactant is a main reactant of two or more metals, the time of step b for each of the other reactants is preferably set to be earlier than the time for the at least one reactant that is the main reactant of the two or more metals, and the time of step b for each of the other reactants can be determined based on the etching rate of each metal with the other reactant as the main reactant when the plasma is ignited, thereby, the main reactant of the metal with the highest etching rate is stopped earliest, and the stopping time of the main reactant of the metals with successively lower etching rates is successively increased.

[0040] In an embodiment, the flow rates of the two or more reactants (3) during injection can be determined based on the etching rate of each metal (2) in the presence of the reactant (3) that contributes most to its etching rate when the plasma is ignited, such that:

[0041] - if each main reactant is a main reactant of only one metal, the reactant (3) having the greatest effect on the etching rate of the metal (2) having the highest etching rate is injected at the lowest flow rate, while the flow rates of the reactants (3) having the greatest effect on the etching rates of metals (2) having successively lower etching rates are successively increased, and

[0042] -If at least one reactant is a main reactant of two or more metals, the flow rate of each other reactant during injection is preferably set to be lower than the flow rate of the at least one reactant that is the main reactant of the two or more metals, and the relative flow rates of the other reactants during their injection can be determined based on the etching rate of each metal with the other reactant as the main reactant when the plasma is ignited, thereby, the main reactant of the metal with the highest etching rate is injected at the lowest flow rate, while the flow rates of the main reactants of the metals with successively lower etching rates are successively increased.

[0043] In embodiments, the method may further include a step p, prior to step a, of determining the relative etching rate of each metal in the presence of its primary reactant when the plasma is ignited. In other words, the method may further include a step p, prior to step a, of determining the relative etching rate of each metal in the presence of the reactant that contributes most to its etching when the plasma is ignited. This step is optional, as the behavior of each metal in the presence of its primary reactant when the plasma is ignited is known from scientific literature or past experience. However, this embodiment has the advantage that, by better understanding the etching rates upfront, a more informed approach to the etching process can be taken, resulting in better results.

[0044] In an embodiment, each reactant (3) whose injection is stopped in step b. may be injected in step a at a gas flow rate of 0.1 sccm to 1500 sccm, preferably 0.5 sccm to 500 sccm, more preferably 1 sccm to 200 sccm, and more preferably 2 sccm to 50 sccm. A maximum value of 50 sccm is advantageous in limiting the movement of the pressure regulating valve.

[0045] In embodiments, the compound can be amorphous. While the present invention is applicable to a variety of structures, including crystalline structures, amorphous compounds are advantageous, particularly when the material layer thickness is relatively low, such as less than 10 nm. The present invention is beneficial for all metal compounds and thicknesses. However, because the present invention is plasma-based, it can cause slight damage to the material's crystal lattice, on the order of a few angstroms or nanometers. This becomes more problematic when processing crystalline material layers only a few nanometers thick.

[0046] In embodiments, the compound may form a crystalline layer having a thickness of at least 10 nm.

[0047] In embodiments, the compound may form a conductive element of a semiconductor device. This is where the invention will find most application. However, it must be noted that the invention is equally applicable to semiconductor or dielectric compounds.

[0048] In an embodiment, the conductive element may be a metal interconnect, for example, for use in nodes smaller than 2 nm. The present invention is particularly applicable to advanced semiconductor technology nodes.

[0049] In an embodiment, the semiconductor device may be a memory (such as MRAM, FeRAM, RRAM, spin-torque, etc.) or a quantum computing device. The versatility of the present invention makes it suitable for a wide range of cutting-edge applications, including but not limited to these applications.

[0050] In embodiments, the conductive element may be a superconductor.This is another example of the versatility of the invention allowing it to be used at the forefront of technological trends.

[0051] In embodiments, the compound may be a metal alloy. While the present invention is applicable to non-metallic elements in the compound, such as in the case of Weyl semi-metals (e.g., TaAs), surprisingly, the present invention is particularly effective in the case of metals. Optimal results are achieved in the case of metal alloys.

[0052] However, the present invention is also applicable to compounds containing non-metallic elements. Non-limiting examples of compounds that can be advantageously etched by the present invention are Mg x Zn1-x O、In x Ga z Zn o O y , MAX phase materials (such as Cr x Al 1-x C) or superconductors (such as NbTiN).

[0053] In an embodiment, the etching process is performed in cycles, with each cycle comprising steps a through c. This embodiment allows for better control and more uniform etching. In fact, shorter, repetitive steps can achieve better results than a single, non-repetitive process with a longer etching time.

[0054] In an embodiment, less than 1 nm of compound can be removed per cycle. An advantage of this embodiment is that optimal etching performance can be achieved.

[0055] In a second aspect, the present invention relates to a system for dry etching a compound containing at least two metals, the system comprising: i. an etching chamber configured to receive the compound; ii. a gas delivery system configured to inject one or more reactants and a carrier gas into the etching chamber; iii. a plasma generation system configured to ignite and maintain a plasma in the etching chamber; iv. a controller configured (e.g., programmed) to: a. control the gas delivery system to stop injecting at least one of the one or more reactants, thereby causing a decrease in the concentration of the at least one reactant; and b. ignite the plasma in the etching chamber for a period of time such that the plasma exists during the period when the concentration of the at least one reactant decreases.

[0056] In an embodiment, the system may be configured (eg programmed) to perform the method steps according to any embodiment of the first aspect. An advantage of this embodiment is that it enables the system to perform the method accurately and reproducibly.

[0057] Any features of the second aspect may be as described correspondingly in any embodiment of the first aspect.

[0058] In a third aspect, the present invention relates to a computer program product comprising instructions for causing the system of the second aspect to perform the steps of the method of the first aspect.

[0059] Any features of the third aspect may be as described correspondingly in any embodiment of the first or second aspect.

[0060] In a fourth aspect, the invention relates to a computer readable medium having stored thereon the computer program product of the third aspect.

[0061] Any features of the fourth aspect may be as described correspondingly in the third aspect.

[0062] One advantage of embodiments of the present invention is that a method for dry etching a compound comprising at least two metals can be implemented in which the etch rates of the various metals are independently controlled by a new lever. Advantageously, this allows, for example, these etch rates to be brought closer together than would typically be achieved using classic plasma-based dry etching. Additionally, the method of the present invention can also be used to tailor the post-etch composition of the compound to individual needs. Another advantage of embodiments of the present invention is that the method can be applied to compounds of any degree of crystallinity, i.e., amorphous or crystalline, making the present invention applicable to a wide range of material types.

[0063] An advantage of embodiments of the present invention is that the method can be used for compounds of any conductivity, from dielectric materials to superconductors. An advantage of embodiments of the present invention is that the method can be used to form conductive elements of semiconductor devices, including metal interconnects for future nodes less than 2 nm, and can be applied to patterning of various types of memory, such as MRAM, FeRAM, RRAM, and devices used in quantum computing.

[0064] One advantage of embodiments of the present invention is that it helps prevent barrier formation and maintains a high etch rate.Another advantage of embodiments of the present invention is that the method allows for patterning of the metal compound layer.

[0065] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and with features of other dependent claims, and not only where explicitly set out in a claim.

[0066] The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate the principles of the present invention by way of example. This description is for illustrative purposes only and is not intended to limit the scope of the present invention. The reference figures cited below refer to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 is a schematic diagram of a ternary compound comprising at least two metals prior to exposure to a plasma according to the prior art or the present invention.

[0068] Figure 2 is a schematic diagram of the initial stages of etching a compound by exposure to a reactant according to the prior art.

[0069] Figure 3 is a schematic diagram of an etching process according to the prior art, in which predominantly one element is removed, leaving a surface comprising predominantly the remaining element and reactants.

[0070] Figure 4 Schematic diagram of the worst case scenario of deposition on the surface of the modifying compound during etching according to the prior art.

[0071] Figure 5 is a flow chart of an etching process according to an embodiment of the present invention.

[0072] Figure 6 is a series of graphs plotting the relationship between gas concentration in a chamber and process time according to four embodiments of the present invention.

[0073] Figure 7 is a schematic diagram of a system for dry etching a compound according to an embodiment of the present invention.

[0074] In different drawings, the same reference numbers identify the same or similar elements. DETAILED DESCRIPTION

[0075] The present invention will be described with respect to specific embodiments and with reference to certain drawings, but the invention is not limited thereto but only by the claims. The drawings described are merely illustrative and non-limiting. In the drawings, the dimensions of some elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and relative dimensions do not correspond to actual reductions in practice of the invention.

[0076] The terms first, second, third, etc. in the specification and claims are used to distinguish similar elements and are not necessarily used to describe a sequence in time, space, hierarchy, or any other manner. It is understood that the terms so used are interchangeable under appropriate circumstances, and the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0077] Furthermore, in the specification and claims, the terms top and over, etc., are used for descriptive purposes and not necessarily for describing relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention are capable of operation in other orientations than those described or illustrated herein.

[0078] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the parts listed thereafter, and it does not exclude other elements or steps. Therefore, it should be understood as indicating the presence of the features, wholes, steps or components, but this does not exclude the presence or addition of one or more other features, wholes, steps or components or their combination. Therefore, the scope of the expression "a device comprising parts A and B" should not be understood as limiting the device to being composed only of parts A and B. It means that for the present invention, the relevant components of the device are only A and B. Therefore, the term "comprising" covers the case where only the features are present as well as the case where these features and one or more other features are present. Therefore, the word "comprising" as an embodiment according to the present invention also includes the case where no other components are present. When the word "comprising" is used to describe an embodiment in the present application, it should be understood that alternative versions of the same embodiment, in which the term "comprising" is replaced by "consisting of...", are also included in the scope of the present invention.

[0079] Likewise, it is important to note that the term "coupled" should not be interpreted as being limited to only direct connections. The terms "coupled" and "connected," as well as their derivatives, may be used. It should be understood that these terms are not intended to be synonymous with each other. Thus, the scope of the expression "device A is coupled to device B" should not be limited to devices or systems in which the output of device A is directly connected to the input of device B. This means that there is a path between the output of A and the input of B, which path may be a path that includes other devices or apparatuses. "Coupled" can mean that two or more elements are either in direct physical contact or in electrical contact, or that two or more elements are not in direct contact with each other, but still cooperate or interact with each other.

[0080] References in this specification to "one embodiment" or "an embodiment" mean that the specific features, structures, or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. Therefore, appearances of the phrases "in one embodiment" or "in an embodiment" throughout this specification do not necessarily all refer to the same embodiment, but may all refer to the same embodiment. Furthermore, it will be apparent to one of ordinary skill in the art that the specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0081] Similarly, it should be understood that in the description of illustrative embodiments of the invention, different features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof to simplify the disclosure and aid in understanding one or more different aspects of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Moreover, as reflected in the appended claims, inventive aspects may include fewer than all the features of a single embodiment disclosed above. Therefore, the appended claims are expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of the invention.

[0082] Furthermore, while some embodiments described herein include some features but not other features included in other embodiments, combinations of features from different embodiments are intended to be included within the scope of the present invention and to form different embodiments, as will be understood by those skilled in the art. For example, in the appended claims, any of the claimed embodiments may be used in any combination.

[0083] In addition, some embodiments are described herein as methods or combinations of method elements implemented by a processor of a computer system or by other means of implementing a function. Therefore, a processor having instructions required for implementing the method or method element forms a device for carrying out the method or method element. In addition, the elements of the device embodiments described herein are examples of devices for performing functions, and the functions are carried out by elements for implementing the purpose of the present invention.

[0084] Numerous specific details are set forth in the description herein. However, it should be understood that embodiments of the present invention may be practiced without these specific details. In other cases, well-known methods, structures, and techniques have not been described in detail in order not to obscure an understanding of this specification.

[0085] The present invention is now described in detail by describing several embodiments of the present invention. Obviously, other embodiments of the present invention can be constructed according to the knowledge of those skilled in the art without departing from the technical teachings of the present invention, and the present invention is limited only by the appended claims.

[0086] Aspects of the present invention relate to a method and system for dry etching a compound comprising at least two metals (2), as well as a computer program product and a computer readable medium for performing the method. The method is particularly advantageous for etching metal compounds in a controlled manner to fabricate semiconductor devices, including advanced memory technologies and quantum computing devices. We now refer to Figure 1 and 7 .

[0087] In a first aspect, the present invention relates to a method for dry etching a compound (1) comprising at least two metals (2), the method comprising the following steps:

[0088] a. injecting one or more reactants (3) and a carrier gas into an etching chamber (5) containing a compound (1), wherein each metal (2) can be etched by the plasma of at least one of the reactants (3),

[0089] b. Stopping the injection of at least one of the one or more reactants (3), thereby causing the concentration of the at least one reactant (3) to decrease.

[0090] c. Ignite a plasma in the etching chamber (5) for a period of time such that a plasma is present during said lowering.

[0091] As used herein, unless otherwise indicated, the term "compound comprising at least two metals" refers to a material comprising two or more different metallic elements, and ultimately other non-metallic elements, chemically bonded together. This includes, but is not limited to, mixed metal oxides, mixed metal nitrides, mixed metal oxynitrides, mixed metal carbides (such as Max phase materials), mixed metal oxycarbides, mixed metal carbonitrides, mixed metal oxycarbonitrides, metal alloys (such as high entropy alloys), intermetallic compounds, and metal matrix composites, wherein the metallic elements are present in any proportion. Preferably, the at least two metals together constitute at least 50 atomic %, preferably at least 75 atomic %, more preferably at least 90 atomic %, and most preferably 100 atomic % of the compound.

[0092] Preferably, each of the at least two metals forms an etching product having a boiling point below 600°C after reacting with its main reactant. Preferably, each of the at least two metals is selected from alkaline earth metals, transition metals and post-transition metals. Preferably, each of the at least two metals is not gold, silver, palladium or copper because their etching time is very long. Preferably, each of the at least two metals is selected from but not limited to Zn, Ga, In, Mg, Cr, Al, Mo, Ru, Ti, Ta, Zr, Hf, Sc, V, Nb, W, Co, Ni and Sn. Specific embodiments of such compounds may include intermetallic compounds (such as NiAl) and semiconductor metal oxides such as Mg x Zn 1-x O and IGZO (Indium Gallium Zinc Oxide). The number of metals in the compound is preferably 2 to 5. The number of chemical elements in the compound is preferably 2 to 5.

[0093] The compound may be present in any shape, but is typically present in the form of a layer. The present invention is applicable to any thickness. The thickness of the compound, such as the thickness of the layer, is preferably 0.1 nm to 1000 nm.

[0094] As used herein, unless otherwise specified, the term "reactant" refers to a chemical species introduced into the etching chamber and capable of reacting with the compound under plasma conditions. These reactants may be gaseous and include, but are not limited to: H2; CH4; O2; CO; CO2; SO2; CH4; N2; N2O; NH3; halogen-containing gases such as: Cl2, Br2, F2, BCl3, SF6, SiF4, NF3, C x F y (such as CF4 or C4F8) and CH x F y (eg CH3F). The number of reactants injected is usually 1 to 8, preferably 2 to 5.

[0095] The one or more reactants (3) may be two or more reactants (3), thereby allowing for more precise control of the etching process.

[0096] In an embodiment, the method may include, for example:

[0097] a. injecting two or more reactants (3) and a carrier gas into an etching chamber (5) containing a compound (1), wherein each metal (2) can be etched by the plasma of at least one of the reactants (3),

[0098] b. stopping the injection of at least one of the two or more reactants (3), thereby causing the concentration of the at least one reactant (3) to decrease, and

[0099] c. igniting a plasma in the etching chamber (5) for a period of time such that a plasma is present during said reduction,

[0100] Wherein, the carrier gas

[0101] - is different from any reactant and does not react with said compound,

[0102] or

[0103] - is one of the two or more reactants and is the main reactant responsible for etching the compound element having the slowest etching rate in the presence of its main reactant.

[0104] In an embodiment, the time of step b can be determined based on the etching rate of each metal in the presence of its main reactant when the plasma is ignited. For example, one or more reactants (3) can be two or more reactants (3), thereby allowing the etching process to be more accurately controlled. In an embodiment, the time of step b can be determined based on the etching rate of each metal in the presence of its main reactant when the plasma is ignited, whereby the main reactant of the metal with the highest etching rate stops earliest, while the stop time of the main reactant of the metal whose etching rate decreases in turn increases in turn. This determines the priority of etching the metal based on the reactivity of the metal. In order to determine which metal has the highest reactivity with the reactant, one or both of Experiment 1 and Experiment 2 can be performed. In an embodiment in which at least one reactant is the main reactant of two or more metals, the time of step b of each other reactant is preferably set to be earlier than the time of the at least one reactant as the main reactant of two or more metals. The time of step b of each reactant in the other reactants can be determined based on the etching rate of each metal with the other reactants as the main reactant when the plasma is ignited, whereby the main reactant of the metal with the highest etching rate stops earliest, while the stop time of the main reactant of the metal whose etching rate decreases in turn increases in turn.

[0105] In an embodiment, the carrier gas may include one or more of Ar, He, Xe, N2, and O2. In a preferred embodiment, the carrier gas may include one or more of Ar, He, and Xe because they are not chemically reactive. Preferably, the carrier gas is non-reactive toward the compound. If the carrier gas is also one of the reactive gases, it is preferably the primary reactant responsible for etching the element whose etching rate is slowest in the presence of its primary reactant. Preferably, the carrier gas is different from any of the reactants. Preferably, the carrier gas is more electropositive than any of the reactants.

[0106] As used herein, unless otherwise specified, the term "etching chamber (5)" refers to a sealed environment, typically located within an etching system (4), in which the etching process is performed. The etching chamber is designed to contain the compound (1) to be etched and to allow for the controlled introduction of reactants (3), carrier gases, and the generation of a plasma. The etching chamber may include various components, such as a gas inlet, an exhaust system, and electrodes for generating the plasma. It is typically constructed of materials that are resistant to the corrosive effects of the etching process.

[0107] During the implementation of the method, the injection of at least one reactant (3) is stopped in step b. Figure 6In each embodiment shown, it can be seen that in an embodiment, two or more reactants are injected in step a, and the injection of at least two of these reactants is stopped in step b. In other words, step b may include stopping the injection of at least two of the reactants (3), thereby causing the concentrations of at least two of the reactants (3) to decrease, respectively, and wherein step c. includes igniting a plasma in the etching chamber (5) for a period of time such that the plasma is present during the period when the concentrations are respectively reduced. This is also Figure 6 Typically, when more than one reactant is stopped in step b, they are not stopped simultaneously. In an embodiment, all reactants injected in step a are stopped in step b. This is reflected in Figure 6 d). In other embodiments, all reactants injected in step a are stopped in step b except one reactant. This is reflected in Figure 6 a) to 6c).

[0108] In a plasma etching system, a vacuum pump is used to maintain the low pressure required for plasma generation. Once the injection of reactants is stopped, the existing reactant molecules in the chamber are gradually removed by the vacuum system, resulting in a decrease in concentration.

[0109] In step c, a plasma is ignited. As used herein, unless otherwise specified, the term "igniting a plasma" refers to the process of initiating a plasma state within an etching chamber (5) by applying energy to a gas mixture containing reactants (3) and a carrier gas. The energy can be provided by various means, such as radio frequency (RF) power, microwave power, or direct current (DC) discharge. Plasma is composed of a collection of particles including electrons, ions, and neutral species that can interact with compound (1) to produce an etching effect.

[0110] The plasma is ignited for a period of time such that the plasma exists during a period during which the concentration of at least one reactant decreases. Preferably, the plasma is ignited for a period of time such that the plasma exists during a period during which the concentration of all reactants whose injection has been stopped in step b decreases. Figure 6 This is reflected in all embodiments of the present invention. The plasma does not necessarily have to be in the on state, i.e. ignited, during the entire process of reducing the concentration of at least one reactant. It is sufficient that the plasma is ignited during at least a portion of the process of reducing the concentration of at least one reactant (3). Figure 6 This is not reflected in the above. Preferably, the plasma exists during the entire period during which the concentration of at least one reactant (3) is reduced. The plasma is usually ignited before or at the same time as the injection of at least one reactant (3) is stopped, such as Figure 6 However, the plasma can also be ignited after being stopped (not shown in the figure). Figure 5The time of plasma ignition start in an embodiment of the first aspect is shown. As shown, the plasma can be started at any time as long as the plasma is present during the reduction of the reactant (3).

[0111] In an embodiment, step c can be represented as: igniting plasma in the etching chamber (5) for a period of time so that plasma exists during the reduction period, thereby simultaneously controlling the etching rates of at least two metals (2).

[0112] In an embodiment, step c can be expressed as: igniting plasma in the etching chamber (5) for a period of time, so that plasma exists during the lowering period and dry etching is performed.

[0113] As used herein, unless otherwise specified, the term "time window of 500 ms before to 500 ms after" refers to a specific time period relative to the cessation of injection of one of the reactants (3) to initiate plasma ignition. This time window defines an acceptable time range for initiating plasma ignition, where "500 ms before" means that the plasma can ignite within half a second before the cessation of reactant injection, and "500 ms after" means that the plasma can ignite within half a second after the cessation of reactant injection. Preferred embodiments provide for narrower time windows, such as 250 ms before and after, or 100 ms before and after. For example, injection can be stopped at the same time as the start of plasma ignition. Stopping injection of one of the reactants at approximately the same time as the start of the plasma generally produces good results. However, depending on the specific circumstances, the injection of the reactant can also be stopped before or after, or even more than 500 ms before or after.

[0114] In an embodiment, the gas injection of each reactant (3) is maintained for at least 10 ms, more preferably at least 50 ms, and even more preferably at least 100 ms. This is preferred because longer gas injection times are more reproducible and allow for better control of the etching process.

[0115] The flow rate of two or more reactants (3) during injection can be determined based on the etching rate of each metal (2) in the presence of the reactant (3) that has the greatest effect on its etching rate when the plasma is ignited (for example, in the presence of the two or more reactants (3) when the plasma is turned on). In an embodiment in which at least one reactant is the main reactant of two or more metals, the flow rate of each other reactant during its injection is preferably set to be lower than the flow rate of the at least one reactant that is the main reactant of the two or more metals. The relative flow rates of the other reactants during their injection can be determined based on the etching rate of each metal of the other reactants that are the main reactants when the plasma is ignited, whereby the main reactant of the metal with the highest etching rate is injected with the lowest flow rate, while the flow rate of the main reactant of the metal with the etching rate decreasing in turn increases in turn. Each reactant (3) that stops being injected in step b can be injected with a gas flow rate of 0.1 sccm to 1500 sccm, providing a preferred range for more precise control. As used herein, unless otherwise specified, the term "gas flow rate of 0.1 sccm to 1500 sccm" refers to the flow rate range for introducing the reactant (3) into the etching chamber (5). The unit "sccm" stands for standard cubic centimeters per minute, which is the volumetric flow rate of gas standardized according to a set of reference conditions of temperature and pressure. Preferred embodiments provide for narrower ranges, such as 0.5 sccm to 500 sccm, 1 sccm to 200 sccm, or 2 sccm to 50 sccm. Typically, a gas flow rate of 0.1 to 50 sccm is most suitable for most reactants. In an embodiment, if the metal (2) has the lowest etching rate in the presence of its main reactant (3) when the plasma is ignited, its main reactant (3) can be injected continuously, that is, step b is not performed. It is particularly useful if the lowest etching rate is at least two times, for example at least four times, less than the etching rate of the metal with the second lowest etching rate in the presence of its main reactant (3) when the plasma is ignited. In an embodiment, if the etching rate of the primary reactant is at least two times, for example, at least four times, lower than the etching rate of the metal with the second lowest etching rate in the presence of the primary reactant when the plasma is ignited, then it is preferred to continuously inject the primary reactant of the metal with the lowest etching rate at a gas flow rate of 100 to 1500 sccm. In an embodiment, when a reactant is the primary reactant for two or more metals, the reactant may be continuously injected at a higher flow rate than the other reactants.

[0116] The method may further comprise a step p, prior to step a, of determining the relative etching rate of each metal (2) in the presence of the reactant (3) that contributes most to its etching rate when the plasma is ignited, for example, the relative etching rate in the presence of the two or more reactants (3) when the plasma is ignited. This step is optional, as the behavior of each metal in the presence of its primary reactant when the plasma is ignited is known from scientific literature or past experience. However, an advantage of this embodiment is that by having a better understanding of the etching rates in advance, a more informed approach to the etching process can be taken, resulting in better results.

[0117] In embodiments, the compound can be amorphous. While the present invention is applicable to a variety of structures, including crystalline structures, amorphous compounds are advantageous, particularly when the material layer thickness is relatively low, such as less than 10 nm. The present invention is beneficial for all metal compounds and thicknesses. However, because the present invention is plasma-based, it can cause slight damage to the material's crystal lattice, on the order of a few angstroms or nanometers. This becomes more problematic when processing crystalline material layers only a few nanometers thick.

[0118] In embodiments, the compound may form a crystalline layer having a thickness of at least 10 nm.

[0119] Compounds can form conductive elements of semiconductor devices, such as metal interconnects, or become part of memory devices or quantum computing devices. As used herein, unless otherwise specified, the term "conductive elements of semiconductor devices" refers to components in semiconductor devices that are designed to conduct electrical current. This includes, but is not limited to, metal interconnects, electrodes, gates, and contacts. These conductive elements can be made of a variety of conductive materials, including metals and metal alloys, and are integral to the functioning of semiconductor devices (such as transistors, diodes, and integrated circuits). As used herein, unless otherwise specified, the term "metal (2) interconnect" refers to conductive pathways within a semiconductor device that electrically connect different components or regions of the device. These interconnects are typically made of metals or metal alloys and are used to establish electrical continuity within the device. The term "<2nm node" refers to a semiconductor technology node with a feature size less than 2nm, representing an advanced semiconductor manufacturing process that can produce devices with extremely fine geometries.

[0120] As used herein, unless otherwise specified, the term "memory" includes various types of data storage technologies used in semiconductor devices, including but not limited to magnetoresistive random access memory (MRAM), ferroelectric RAM (FeRAM), resistive RAM (RRAM), and spin-torque memory devices. The term "quantum computing device" refers to a computing system that uses the principles of quantum mechanics, such as superposition and entanglement, to perform operations on data.

[0121] The conductive element may also be a superconductor. As used herein, unless otherwise specified, the term "superconductor" refers to a material that can conduct electricity without resistance below a certain critical temperature. Superconductors can be used in various applications, including as conductive elements in semiconductor devices, where they can achieve high efficiency electrical conduction. Non-limiting examples of compound (1) include Mg x Zn 1-x O, IGZO or NiAl. The compound is not necessarily a conductor, but can also be a semiconductor compound (such as IGZO) or a dielectric.

[0122] In an embodiment, the etching process can be performed in a cyclic manner, each cycle comprising steps a. to c., for example, each cycle can remove less than 1 nm of compound (1). This enables precise removal of material with a minimal etching amount per cycle.

[0123] As used herein, unless otherwise specified, the term "removing less than 1 nm of compound (1) per cycle" means that the thickness of material etched away from compound (1) in a single cycle of the etching process is less than one nanometer. This level of control allows for very fine tuning of etched features, which is particularly advantageous in advanced semiconductor manufacturing where feature sizes can reach nanometers.

[0124] In embodiments, the method can be used to pattern compound (1).

[0125] As used herein, unless otherwise specified, the term "patterning compound (1)" refers to the process of creating a specific geometric pattern on the surface of compound (1) by selectively removing material by etching.

[0126] In a second aspect, a system (4) for dry etching a compound (1) includes an etching chamber (5), a gas delivery system (6), a plasma generation system (7), and a controller (8). The controller (8) is configured to control the gas delivery system (6) to stop injecting at least one reactant (3) and ignite plasma in the etching chamber (5) for a period of time, so that the plasma exists during a period when the concentration of the at least one reactant (3) decreases.

[0127] As used herein, unless otherwise specified, the term "system for dry etching (4)" refers to an apparatus or device designed for performing a dry etching process on a compound (1) comprising at least two metals (2). The system includes various components, such as an etching chamber (5), a gas delivery system (6), a plasma generation system (7), and a controller (8), which work together to facilitate the etching process. Figure 7 A schematic diagram of the system (4) is provided showing the components and their arrangement in the etching system.

[0128] The system (4) may be configured to perform the method steps according to any embodiment of the first aspect, such that the system (4) is able to perform the method accurately and reproducibly.

[0129] In a third aspect, the present invention relates to a computer program product comprising instructions for causing the system of the second aspect to perform (4) the steps of the method of the first aspect. As used herein, and unless otherwise specified, the term "computer program product" refers to a software product comprising instructions which, when executed by a computer or controller (8), cause the system (4) to perform specific operations. For example, the product may be distributed on a physical medium such as a CD-ROM or as a digital download.

[0130] In a fourth aspect, the present invention relates to a computer-readable medium having stored thereon the computer program product of the third aspect. As used herein, and unless otherwise specified, the term "computer-readable medium" refers to any data storage device that can store data that can thereafter be read by a computer system. This includes, but is not limited to, hard drives, solid-state drives, CDs, DVDs, USB flash drives, and memory cards. The computer-readable medium may store the computer program product of claim 21, the program product comprising instructions for executing the method steps of claim 1 when the dry etching system (4) is in operation.

[0131] Example: Etching of metal compounds with uniform composition.

[0132] In the prior art, etching of metal compounds is often uneven, with some elements etching faster than others. The etching method provided by the present invention can reduce or even eliminate this tendency. The inventors recognized that each element in the metal compound has different requirements in terms of ion assistance or neutral species supply, and therefore, each element requires a different neutral species to ion flux ratio (for each neutral species and ion type).

[0133] In this non-limiting example, a method for implementing this method will be described, assuming that the etching rates of the various components of the metal compound cannot be predicted. We will consider an alloy having components (A, B, C), each of which has different etching requirements (chemical reactants, ion assist, etc.). R1, R2, and R3 are reactants injected to etch the various components of the alloy. For the sake of clarity and simplicity, we will assume that R1 is primarily responsible for etching A, R2 is primarily responsible for etching B, and R3 is primarily responsible for etching C. In other words, R1, R2, and R3 are the primary reactants for A, B, and C, respectively.

[0134] The challenge is that different metals in a metal compound have different requirements in terms of neutrals and ions in order to achieve optimal etch rates.

[0135] The inventors realized that different etching requirements translate in process terms as follows:

[0136]

[0137] Table 1: Etching requirements and Figure 6 The correspondence between the injection schemes shown

[0138] The inventors have realized that the flux ratio of neutral species to ions can be controlled by allowing the concentration of one or more reactants in the plasma phase to decay, thereby controlling the relative etching rate of each metal. During a decay process, since the neutral species are consumed by the reaction or pumped out, the flux of the neutral species decreases after the injection of gas is stopped. Therefore, the time of cessation relative to the ignition period of the plasma will determine the etching effect achieved on the metal with the stopped reactant as the main reactant during the cycle. Therefore, by maintaining the plasma ignition state during the decay period of the reactants, the etching rates of A, B and C can be adjusted using a new control lever. Therefore, in an embodiment, step c can be expressed as: igniting a plasma in the etching chamber (5) for a period of time so that the plasma is present during the decay period, thereby simultaneously controlling the etching rates of at least two metals (2).

[0139] The most typical use of this new control lever is to achieve more equal etch rates for A, B, and C than would otherwise be the case. This is the use we will discuss in this example. Of course, other uses are also contemplated.

[0140] In this example, we assume that the carrier gas is more electropositive than R1, R2, and R3. As the flux of neutral species decreases, the flux of ions will increase. The inventors speculate that in this case, the etching rates of A, B, and C can be made closer to equal by considering the following factors:

[0141] If a low neutral species / ion ratio is preferred, the injection of the corresponding gas is preferably stopped before (or simultaneously with) ignition of the plasma.

[0142] If a high neutral species / ion ratio is preferred, the injection of the corresponding gas is preferably continued throughout the entire plasma step (or stopped slightly before the end).

[0143] If a moderate neutrals / ions ratio is preferred, gas injection can be maintained as needed during the plasma step for a sufficient time to ensure demand for reactive neutrals before concentration decay, while the remaining plasma time ensures demand for energetic ions. If both demands are low, gas injection can be started during the plasma step, thus shortening both the neutrals injection time and the ion bombardment time of the reactant-saturated surface.

[0144] like Figure 6As shown in R1 in b, in order to adapt to the excessive reactivity of the reactant with a certain component of the alloy, a very short pulse of low concentration can be injected.

[0145] Figure 6 The four most common cases are represented by a, b, c, and d. Other less common cases are not shown here because the functionality they provide is often redundant when another adjustment parameter (such as gas flow or RF source power) is available.

[0146] Now we refer to Figure 6 , which embodies four typical scenarios. In order to determine whether a specific process will occur in Figure 6 Under which of the four schemes shown in , the following method can be applied as an illustrative embodiment.

[0147] 1) Experiment 1: Determine the respective etching rates.

[0148] In this example, we assume that the etching rates of A, B, and C in the presence of R1, R2, and R3, respectively, are unknown. This is the worst-case scenario. To determine the etching rates of each, follow these steps.

[0149] - inject one reactant at any flow rate (but it is recommended to keep it in a low flow range, such as 2-50 sccm, to limit the movement of the pressure regulating valve),

[0150] - igniting the plasma while stopping the injection (as an example), and

[0151] - Keep the plasma on for an arbitrary time (e.g. 3 seconds).

[0152] By measuring the composition of the alloy before and after etching, it is possible to see how much the proportions of each component have changed (accumulation of certain elements, depletion of others). This allows one to determine which metal is most etched by the reactant. Furthermore, it provides an indication of the etch rate of each metal in the presence of that reactant.

[0153] The experiment was repeated for each reactant.

[0154] 2) Experiment 2: Improve the respective etching rates.

[0155] To more precisely understand the relative etch rates of A, B, and C during etching in the presence of all three reactants, the following experiment can be performed.

[0156] - inject all three reactants simultaneously at the same arbitrary flow rate (e.g. 2-50 sccm),

[0157] - igniting the plasma while stopping the injection of all three reactants (as an example),

[0158] - Keep the plasma on for an arbitrary time (e.g. 3 seconds).

[0159] By measuring the composition of the alloy before and after etching, it is possible to see how much the proportions of each component have changed (accumulation of certain elements, depletion of others).

[0160] 3) Experiment 3: Relationship between etching rate and neutral species and ion flux.

[0161] This experiment provides a deeper understanding of the sensitivity of metals to neutral substances. In fact, the more sensitive the metal's etching rate is to neutral substances, the more the increase in pressure will increase its etching rate.

[0162] For this experiment, the same experiment as above can be performed at a higher pressure (such as 20-40 mTorr) without changing the gas flow or power settings, and the composition of the alloy after etching can be measured to refine the pressure range required for this process.

[0163] 4) Experiment 4: Interaction between gases in the plasma step.

[0164] Further experiments could be performed to explore how the presence of multiple reactants affects etching during the plasma step. For example, a gas injection scheme similar to Figures c or d could be implemented to ensure that at least two gases are present in the reactor simultaneously. The composition could then be measured after etching.

[0165] 5) Experiment 5: Determine the gas concentration and injection stop point.

[0166] To maintain the same composition as much as possible during etching, it is preferable to set the reactant flow rate of the element with the slowest etching rate higher than that of the other elements. In addition, their injection lasts longer than that of the other elements (again, more gas is required to achieve an etching rate comparable to that of the other elements). Based on this logic and the results of previous experiments on composition and etching rate, the gas injection time and relative concentrations can be adjusted.

[0167] Combining one or more of the above experiments, based on prior knowledge of the behavior of A, B, and C in the presence of R1, R2, and R3, will help to Figure 6 The most relevant solution is selected from the solutions to perform the etching process.

[0168] 6) Experiment 6: Effect of ion fluence on alloy composition.

[0169] For this experiment, a longer plasma duration (e.g., 5 to 10 seconds instead of the initial 3 seconds) can be used in the selected protocol to evaluate whether more ions are needed for a certain element.

[0170] It is not intended to experimentally determine the optimal power, as the pressure in Experiment 3 also indicates whether the molecules of each reactant should dissociate heavily (high power) or not (low power), and Experiment 6 will indicate whether more ions are needed. If power optimization is intended, a good time to do it would be after Experiment 3 and while conducting Experiment 4.

[0171] It is recommended to keep the gas flow rate of each reactant at a level lower than the carrier gas flow rate. In fact, when the injection is stopped, the total gas flow rate is not conserved during the process, causing the pressure regulating valve to move (close more). When the plasma ignites, the density of the species (and the overall pressure) increases (the molecules dissociate into multiple fragments), and the same valve will also move (open more). By keeping the injection gas flow rate relatively lower than the carrier gas flow rate, these movements can be minimized and even compensated by dedicated optimization. Going for larger reactant gas flows will lead to larger valve movements, which will affect the reproducibility of the results. If a large flow ratio is used, the delay of the injection will be the most appropriate parameter to set the relative concentrations of these gases.

[0172] It should be understood that although preferred embodiments, specific configurations and constructions, and materials for the devices of the present invention have been discussed herein, various changes or modifications may be made to the form and details without departing from the scope of the present invention. For example, any schemes presented above are merely representative of processes that may be used. Functions may be added or deleted from the block diagrams, and operations may be interchanged between functional blocks. Steps may be added or subtracted from the methods described within the scope of the present invention.

Claims

1. A method for dry etching a compound (1) containing at least two metals (2), the method comprising: a. injecting two or more reactants (3) and a carrier gas into an etching chamber (5) containing a compound (1), wherein each metal (2) can be etched by the plasma of at least one of the reactants (3), b. stopping the injection of at least one of the two or more reactants (3), thereby causing the concentration of the at least one reactant (3) to decrease, and c. igniting a plasma in the etching chamber (5) for a period of time such that a plasma is present during said reduction, Wherein, the carrier gas - is different from any reactant and does not react with said compound, or - is one of the two or more reactants and is the main reactant responsible for etching the compound element having the slowest etching rate in the presence of its main reactant.

2. The method of claim 1 , wherein step b. comprises ceasing the injection of at least two of the reactants (3), thereby causing the concentrations of at least two of the reactants (3) to decrease, respectively, and wherein step c. comprises igniting a plasma within the etching chamber (5) for a period of time such that a plasma is present during the respective decreases in concentration.

3. The method according to claim 1 , wherein the ignition of the plasma is started within a time window of 500 ms before to 500 ms after the cessation of the injection of one of the reactants (3) in step b), preferably 250 ms before to 250 ms after, more preferably 100 ms before to 100 ms after.

4. The method according to any one of claims 1 to 3, wherein the time of step b is determined based on the etching rate of each metal (2) in the presence of its main reactant (3) when the plasma is ignited.

5. The method of claim 1 , wherein the flow rates of the two or more reactants (3) during injection are determined based on the etching rate of each metal (2) in the presence of the reactant (3) that has the greatest effect on its etching rate when the plasma is ignited.

6. The method of claim 4 or 5 further comprising a step p before step a of determining the relative etching rate of each metal (2) in the presence of the reactant (3) that has the greatest effect on its etching rate when the plasma is ignited.

7. A method as claimed in any one of the preceding claims, wherein each reactant (3) whose injection is stopped in step b. is injected in step a. at a gas flow rate of 0.1 sccm to 1500 sccm, preferably 0.5 sccm to 500 sccm, more preferably 1 sccm to 200 sccm, and even more preferably 2 sccm to 50 sccm.

8. A method as claimed in any one of the preceding claims, wherein compound (1) is amorphous.

9. A method as claimed in any one of the preceding claims, wherein compound (1) forms a crystalline layer at least 10 nanometres thick.

10. A method as claimed in any one of claims 1 to 9, wherein the compound (1) forms a conductive element of a semiconductor device.

11. The method according to any one of the preceding claims, wherein the etching process is performed in cycles, each cycle comprising steps a. to c.

12. A system (4) for dry etching a compound (1) comprising at least two metals (2), the system (4) comprising: i. an etching chamber (5) configured to receive a compound (1); ii. a gas delivery system (6) configured to inject one or more reactants (3) and a carrier gas into the etching chamber (5); iii. a plasma generating system (7) configured to ignite and maintain a plasma within the etching chamber (5); iv. Controller (8), configured to a. controlling the gas delivery system (6) to stop injecting at least one of the one or more reactants (3), thereby reducing the concentration of the at least one reactant (3); as well as b. Ignite a plasma within the etching chamber (5) for a period of time such that the plasma exists during the period in which the concentration of the at least one reactant (3) decreases.

13. A computer program product comprising instructions for causing the system (4) of claim 12 to perform the steps of the method of claim 1.

14. A computer-readable medium having stored thereon the computer program product of claim 13.

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