Method for passivating parts of a workpiece

Abstract

An apparatus and method for processing a workpiece are disclosed, wherein a sacrificial capping layer is formed on the top surface of the workpiece. The workpiece is then exposed to an ion implantation process in which a selected material is used to passivate the workpiece. While the implantation process is underway, free radicals and stimulated material etch the sacrificial capping layer. This reduces the amount of etching experienced by the workpiece. In some embodiments, the thickness of the sacrificial capping layer is selected based on the total time used for the implantation process and the etching rate. The total time used for the implantation process may be a function of the desired dose, bias voltage, plasma power, and other parameters. In some embodiments, the sacrificial capping layer is applied prior to the implantation process. In other embodiments, material is added to the sacrificial capping layer during the implantation process.

Description

[0001] This application claims priority to U.S. Patent Application No. 16 / 935,774, filed on July 22, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] Embodiments of this disclosure relate to systems and methods for passivating workpieces using a plasma chamber, and more specifically, to passivating workpieces using implantation while minimizing etching of the workpiece. Background Technology

[0003] Dopant materials are often implanted into semiconductor workpieces to generate the desired conductivity. Plasma implantation is an effective method for doping or otherwise modifying the surface of semiconductor devices to form devices such as transistors.

[0004] As geometry continues to shrink, new challenges arise that impact the performance and reliability of these smaller transistors. For example, for advanced transistors, gate reliability (especially negative bias temperature instability, NBTI) is a critical parameter for device performance and reliability. As industry moves towards more advanced channel materials (such as high-germanium-concentration SiGe films), gate oxide reliability becomes even more critical.

[0005] The reliability of gate oxides is primarily related to defects and trapped states at the gate oxide interface, and performance can be improved by passivating these defects. For example, substances such as hydrogen, deuterium, and fluorine can be used to passivate these defects.

[0006] These materials can be introduced using a variety of different processes. In some embodiments, ion implantation is used to introduce these materials. This method has several advantages, including cost advantages due to the ability to achieve high doping levels at high dose rates, and especially at low implantation energies.

[0007] However, implanting workpieces using plasma-based processes can be challenging due to the presence of free radicals, excited substances, and ions during the implantation process. Free radicals and excited substances can lead to over-etching of the surface layer, thus adversely affecting device performance.

[0008] Therefore, equipment and methods capable of implanting materials to passivate a workpiece without etching its surface would be beneficial. Furthermore, this would be advantageous if the method did not significantly increase the time or cost of the overall semiconductor manufacturing process. Summary of the Invention

[0009] An apparatus and method for processing a workpiece are disclosed, wherein a sacrificial capping layer is formed on the top surface of the workpiece. The workpiece is then exposed to an ion implantation process in which a selected material is used to passivate the workpiece. While the implantation process is underway, free radicals and stimulated material etch the sacrificial capping layer. This reduces the amount of etching experienced by the workpiece. In some embodiments, the thickness of the sacrificial capping layer is selected based on the total time used for the implantation process and the etching rate. The total time used for the implantation process may be a function of the desired dose, bias voltage, plasma power, and other parameters. In some embodiments, the sacrificial capping layer is applied prior to the implantation process. In other embodiments, material is added to the sacrificial capping layer during the implantation process.

[0010] According to one embodiment, a method for passivating a portion of a workpiece is disclosed. The method includes: placing the workpiece in a plasma chamber; applying a sacrificial capping layer to the top surface of the workpiece; generating a plasma containing a passivating material in the plasma chamber, wherein the passivating material is selected from the group consisting of hydrogen, deuterium, fluorine, and gas mixtures containing hydrogen, deuterium, or fluorine as diluent or main processing gas, and wherein ions, free radicals, and excited molecules of the passivating material are generated therein; performing an implantation process in which the ions of the passivating material are implanted into the portion via the sacrificial capping layer by applying a bias voltage to the workpiece, and wherein during the implantation process, the free radicals and the excited molecules etch the sacrificial capping layer; and terminating the implantation process when a desired dose of passivating material has been implanted, wherein at the termination of the implantation process, the thickness of the sacrificial capping layer is less than 5 angstroms or the entire sacrificial capping layer has been completely removed and the workpiece has been etched by less than 10 angstroms. In some embodiments, the sacrificial capping layer is applied in the plasma chamber during a capping application period by introducing capping material and generating plasma containing the capping material while disabling the bias voltage. In some embodiments, the capping application period occurs before the implantation process. In some embodiments, an additional sacrificial capping layer is applied during the implantation process by allowing the capping material to flow into the plasma chamber. In some further embodiments, the flow of the capping material is continuous throughout the implantation process. In some further embodiments, the flow of the capping material is pulsed during the implantation process. In some further embodiments, the bias voltage is changed as the capping material flows into the plasma chamber during the implantation process. In some embodiments, the implantation process is terminated after a predetermined time, wherein the predetermined time is determined based on the passivation material and the desired dose of the passivation material. In some embodiments, an alarm is generated if the output of the metering system indicates that the workpiece is being etched. In some embodiments, the implantation process is terminated based on the output from the metering system indicating that the workpiece is being etched. In some embodiments, the initial thickness of the sacrificial cap layer is determined based on the etching rate of the sacrificial cap layer and the total duration of the implantation process. In some further embodiments, the initial thickness is adjusted based on chamber metrology, the number of workpieces processed, or the number of operating hours to compensate for varying etching rates. In some embodiments, the thickness of the sacrificial cap layer is between 5 angstroms and 100 angstroms. In some embodiments, the bias voltage applied is a pulsed direct current (DC) voltage between 0.1 kV and 10 kV.

[0011] According to another embodiment, a method for passivating a portion of a workpiece is disclosed. The method includes: applying a sacrificial capping layer to the top surface of the workpiece in a chamber, wherein the thickness of the sacrificial capping layer is between 5 angstroms and 100 angstroms; placing the workpiece in a plasma chamber, wherein the plasma chamber is different from the chamber described above; generating a plasma containing a passivating material in the plasma chamber, wherein the passivating material is selected from the group consisting of hydrogen, deuterium, fluorine, and gas mixtures containing hydrogen, deuterium, or fluorine as diluent or main processing gas, and wherein ions, free radicals, and excited molecules of the passivating material are generated therein; performing an implantation process in which the ions of the passivating material are implanted into the portion via the sacrificial capping layer by applying a bias voltage to the workpiece, and wherein during the implantation process, the free radicals and the excited molecules etch the sacrificial capping layer; and terminating the implantation process when a desired dose of passivating material has been implanted. In some embodiments, the chamber: heats the workpiece to a temperature close to the temperature of the implantation process; and grows the sacrificial cap layer by allowing gas to flow while the workpiece is being heated.

[0012] According to another embodiment, a method for passivating a portion of a workpiece is disclosed. The method includes: flowing a capping material into a plasma chamber, wherein the workpiece is disposed within the plasma chamber; stimulating the capping material to generate plasma, wherein during the capping application period, no bias voltage is applied to the workpiece to generate a sacrificial capping layer on the top surface of the workpiece; flowing a passivating material into the plasma chamber, wherein the passivating material is selected from the group consisting of hydrogen, deuterium, fluorine, and gas mixtures containing hydrogen, deuterium, or fluorine as diluent or main processing gas; performing an implantation process to implant passivating ions into the workpiece, wherein the implantation process is defined as a period of time during which a bias voltage is applied to the workpiece while plasma containing the passivating material is being generated; adding material to the sacrificial capping layer by flowing the capping material into the plasma chamber during the implantation process; and terminating the implantation process. In some embodiments, the implantation process is terminated when a desired dose of passivating ions has been implanted. In some embodiments, at the termination of the implantation process, the thickness of the sacrificial capping layer is less than 5 angstroms, or the entire sacrificial capping layer has been completely removed and the workpiece has been etched less than 10 angstroms. In some embodiments, the flow of the capping material is continuous throughout the implantation process. In some embodiments, the flow of the capping material is pulsed during the implantation process. In some further embodiments, the bias voltage is changed as the capping material flows into the plasma chamber during the implantation process. In some embodiments, the amount of material added is varied based on chamber metering, the number of workpieces processed, or the number of operating hours to compensate for varying etching rates. In some further embodiments, the capping material flows into the plasma chamber via a mass flow controller, and the amount of material is carried out by adjusting the flow rate of the capping material, the frequency at which the mass flow controller is actuated, or the load cycle of the mass flow controller. Attached Figure Description

[0013] For a better understanding of this disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference and in which:

[0014] Figure 1 An ion source according to one embodiment is shown.

[0015] Figure 2 The interaction between the sacrificial capping layer, ions, and free radicals is shown.

[0016] Figures 3A to 3C The timing diagrams show the application period of the cap and the implantation process according to different embodiments.

[0017] Figure 4 A flowchart is shown that can be used to determine the initial thickness of the sacrificial capping layer.

[0018] Figures 5A to 5B Two representative transistors that can use a sacrificial capping layer are shown.

[0019] Figure 6 A timing diagram of the implantation process for an embodiment in which a sacrificial capping layer is applied outside the plasma chamber is shown.

[0020] [Explanation of Symbols]

[0021] 10: Workpiece;

[0022] 100: Ion source;

[0023] 105: Plasma Chamber;

[0024] 107: Plasma chamber wall;

[0025] 120: Radio frequency (RF) antenna;

[0026] 121: RF power supply;

[0027] 125: Dielectric window;

[0028] 130: Pressure plate;

[0029] 135: Bias power supply;

[0030] 160: Controller;

[0031] 170a, 170b: Raw material gas containers;

[0032] 171a, 171b: Mass flow controllers;

[0033] 175: Gas baffle;

[0034] 180: Optical emission spectroscopy (OES) system;

[0035] 200: Excited molecules;

[0036] 210: Sacrificial top cover layer;

[0037] 220: Passivating ions;

[0038] 300, 301, 302, 303, 310, 311, 312, 313, 320, 321, 322, 323, 331, 332, 333: lines;

[0039] 400, 410, 420, 430, 440, 450, 460: Boxes;

[0040] 500, 530: Source pole;

[0041] 510, 540: Drain electrode;

[0042] 520, 550: Gate;

[0043] 521: Gate oxide;

[0044] 522, 554: Polycrystalline silicon layer;

[0045] 551: Interface layer;

[0046] 552: High K layer;

[0047] 553: Metal gate. Detailed Implementation

[0048] Figure 1 A cross-section is shown of an embodiment of a plasma chamber 105 that can be used in the ion source 100 of this disclosure. The ion source 100 includes a plasma chamber 105 defined by several plasma chamber walls 107, which may be made of aluminum, graphite, or another suitable material. This plasma chamber 105 may be supplied with one or more feed gases stored in one or more feed gas containers 170a, 170b, which enter the plasma chamber 105 via gas baffles 175. Mass flow controllers 171a, 171b are used to regulate the flow of feed gases from the feed gas containers 170a, 170b into the plasma chamber 105, respectively. This feed gas may be excited by a radio frequency (RF) antenna 120 or another plasma generation mechanism. The RF antenna 120 is in electrical communication with an RF power supply 121 that powers the RF antenna 120. A dielectric window 125 (e.g., a quartz or alumina window) may be provided between the RF antenna 120 and the interior of the plasma chamber 105.

[0049] A workpiece 10 is placed on a pressure plate 130 inside a plasma chamber 105. The pressure plate 130 is electrically connected to a bias power supply 135, which is used to negatively bias the pressure plate 130 during a specific time period, so that positive ions are attracted toward the workpiece 10.

[0050] In addition, the pressure plate 130 can also be heated. In one embodiment, heated fluid can flow through a channel embedded in the pressure plate 130. In another embodiment, a heating element (e.g., a resistive element) can be embedded in the pressure plate to heat it.

[0051] Controller 160 can communicate with bias power supply 135, RF power supply 121, and mass flow controllers 171a and 171b, which control the flow of feed gas into plasma chamber 105. Controller 160 may include a processing unit, such as a microcontroller, personal computer, dedicated controller, or other suitable processing unit. Controller 160 may also include a non-transitory computer-readable storage element, such as semiconductor memory, magnetic memory, or other suitable memory. This non-transitory storage element may contain instructions and other data that enable controller 160 to perform the functions set forth herein.

[0052] As mentioned above, when using, for example Figure 1 In the plasma chamber shown, the following situation may occur: when ions are implanted into workpiece 10, the surface of the workpiece is etched by free radicals and / or excited substances. This has the effect of removing material from the surface of workpiece 10, which may lead to performance degradation. When a feed gas is introduced into the plasma chamber and the RF antenna 120 is excited, some of the feed gas is ionized into plasma. These ions are acted upon by an electric field and can therefore be controlled and manipulated. However, some molecules of the feed gas are excited but not ionized. Other molecules are broken down into free radicals.

[0053] Both excited molecules and free radicals are highly reactive and tend to react with any surface. Therefore, if a free radical comes into contact with the surface of workpiece 10, it reacts with the material of workpiece 10 (typically silicon) and removes the material. Thus, while advantageously implanting ions into workpiece 10 to passivate it, free radicals and excited molecules disadvantageously etch the surface of the workpiece.

[0054] To retain the benefits of implanted passivation ions while resisting the etching effects of free radicals and excited molecules, a sacrificial capping layer can be provided on top of the workpiece, such as... Figure 2 As shown in the diagram, free radicals and excited molecules 200 can react with the sacrificial capping layer 210 disposed on the top of the workpiece 10. Simultaneously, passivating ions 220 pass through the sacrificial capping layer 210 and implant into the workpiece 10.

[0055] The sacrificial capping layer 210 contains a material that resists the etching effects of free radicals and excited molecules 200. In other words, the etching rate of the sacrificial capping layer 210 is lower than the etching rate of the underlying workpiece 10. In some embodiments, the etching rate of the sacrificial capping layer 210 may be 5 to 10 times slower than the etching rate of the underlying workpiece. In some embodiments, the etching rate of the sacrificial capping layer 210 may be more than 10 times slower than the etching rate of the underlying workpiece. In some embodiments, the sacrificial capping layer may be silicon dioxide (SiO2) or silicon nitride (SiO2). x N y) or silicon oxynitride (Si x O y N z ).

[0056] The thickness of the sacrificial capping layer 210 can be between 5 and 100 angstroms. In other embodiments, the sacrificial capping layer 210 can be between 10 and 100 angstroms. In other embodiments, the sacrificial capping layer 210 can be between 20 and 100 angstroms. This thickness is chosen such that passivation ions 220 can still penetrate the sacrificial capping layer 210. Furthermore, the thickness is chosen such that the sacrificial capping layer 210 can be completely or almost completely etched by free radicals and excited molecules 200 during the implantation of passivation ions 220. Therefore, the thickness of the sacrificial capping layer 210 can be determined based on the implantation time and the etching rate of the sacrificial capping layer 210.

[0057] This sacrificial capping layer 210 can be applied in a variety of different ways. For example, the sacrificial capping layer 210 can be applied in a plasma chamber used for ion implantation, or in a separate chamber.

[0058] Several different sequences can be used when the sacrificial capping layer is grown in the same plasma chamber used for passivating ion implantation.

[0059] Figure 3A The first embodiment is shown. In this figure, the vertical axis is used to represent process parameter values. Line 300 represents the flow rate of the capping material. The capping material includes any material that can be used to grow the sacrificial capping layer, including oxygen (O2) and nitrogen (N2). Other materials (such as nitric oxide (NO) or nitrogen dioxide (NO2)) can also be used to grow the sacrificial capping layer. All of these materials can be referred to as capping materials because they are used for the growth of the sacrificial capping layer. Line 301 represents the flow rate of the passivation material. Line 302 represents the flow rate of the passivation material from the bias power supply 135 (see...). Figure 1 The applied bias voltage. Line 303 shows the actuation of the RF power supply 121.

[0060] In this embodiment, the RF power supply 121 is actuated approximately simultaneously with the introduction of the capping material. The capping material may be stored in the feed gas container 170a. Therefore, to introduce the capping material, the controller 160 may actuate the mass flow controller 171a so that the capping material can enter the plasma chamber 105 at a desired flow rate. Actuation of the RF power supply 121 ionizes the capping material, which allows the sacrificial capping layer 210 to grow on the top surface of the workpiece. The bias voltage is not enabled at this time so that the ionized capping material is not implanted into the workpiece. The period during which the RF power supply 121 is actuated, the mass flow controller 171a is actuated, and the bias voltage is disabled may be referred to as the capping application period. While the sacrificial capping layer is growing during the capping application period, the flow of the passivation material may begin, as shown in line 301. The passivation material may be hydrogen, deuterium, fluorine, or a gas mixture containing hydrogen, deuterium, or fluorine as a diluent or primary process gas. The passivating material can be stored in the feed gas container 170b, and the controller 160 can actuate the mass flow controller 171b, allowing the passivating material to flow into the plasma chamber 105. Of course, the rate at which the passivating material is introduced can differ from... Figure 3A The rate shown. After the flow of the top material has stopped (e.g., by disabling the mass flow controller 171a), the bias power supply 135 can apply a bias voltage, as shown in line 302. Although Figures 3A to 3C The bias voltage is shown (positive), but it should be understood that a negative bias voltage is used to attract positive ions. The bias voltage can be a pulsed DC voltage with an amplitude between 0.1 kV and 10 kV (depending on the passivation material). For example, a heavier passivation material (e.g., fluorine) can use a larger bias voltage than a lighter passivation material (e.g., hydrogen). The amplitude of the bias voltage is selected so that passivation ions can pass through the sacrificial capping layer and stop in the portion of workpiece 10 to be passivated.

[0061] In some embodiments, this portion may be an interface between polysilicon and another material, such as in the gate of a transistor. Examples of two different semiconductor structures using a sacrificial capping layer during the passivation process are found in […]. Figures 5A to 5B In. Figure 5A The image shows a transistor having a source 500 and a drain 510 formed in a silicon substrate. A gate 520 is then formed on the silicon substrate between the source 500 and the drain 510. The gate 520 may include a gate oxide 521 and a polycrystalline silicon / poly-silicon layer 522 disposed on the gate oxide 521. A sacrificial capping layer 210 is placed on top of the polycrystalline silicon layer.

[0062] exist Figure 5BThe image shows a transistor with a metal gate. The transistor has a source 530 and a drain 540 formed in a silicon substrate. A gate 550 is then formed on the silicon substrate between the source 530 and the drain 540. The gate 550 includes an interface layer 551, a high-k layer 552, a metal gate 553, and a polysilicon layer 554. A sacrificial capping layer 210 is placed on top of the polysilicon layer.

[0063] While the passivating material flows into the plasma chamber 105, the RF power supply 121 remains actuated. Workpiece implantation occurs when the bias power supply 135, RF power supply 121, and mass flow controller 171b are all actuated. Therefore, this period can be referred to as the implantation process. The implantation process continues until the desired dose is implanted into the workpiece. The desired dose can be between 1E15 and 3E17 / cm². 3 between.

[0064] During the implantation process, free radicals and excited molecules 200 etch the sacrificial capping layer 210. The thickness of the sacrificial capping layer 210 is such that it is completely or substantially etched away during the implantation process. For example, in one embodiment, when the implantation process is complete, the dose within the implanted portion of the workpiece 10 is within a desired range and no more than 5 angstroms of the sacrificial capping layer 210 remains. In another embodiment, when the implantation process is complete, the dose within the implanted portion of the workpiece 10 is within a desired range, the sacrificial capping layer 210 is completely etched, and the workpiece 10 has been etched by no more than 10 angstroms.

[0065] Therefore, the thickness of the sacrificial cap layer 210 is determined by the implantation time and the etching rate of the sacrificial cap layer 210, which is applied during the capping phase prior to the implantation process. The etching rate of the sacrificial cap layer 210 can be determined based on the material used to generate the sacrificial cap layer 210, the passivation material, and other process parameters. The implantation time can be determined by the power supplied by the RF power supply 121, the bias voltage, and the desired dose.

[0066] In other words, in one embodiment, the implantation time is calculated based on the parameters described above. Once this is determined, the initial thickness of the sacrificial capping layer 210 can be determined based on this implantation time and the etching rate. Note that in some embodiments, the etching rate of the sacrificial capping layer 210 can vary as a function of the number of operating hours since the last cleaning. For example, the etching rate may change when the walls of the plasma chamber are coated with material generated during earlier processes. Therefore, in some embodiments, the controller 160 may monitor the number of operating hours since the last cleaning and adjust the etching rate based on this monitoring value. In some embodiments, the controller 160 may monitor the number of workpieces processed since the last cleaning and adjust the etching rate based on this monitoring value. In another embodiment, the controller 160 may rely on a metrology system to determine the actual etching rate of the sacrificial capping layer. Therefore, in these embodiments, the controller monitors parameters (e.g., operating hours, number of workpieces processed, or output from a metrology system) to compensate for the etching rate changes over time.

[0067] Therefore, controller 160 can perform the following sequence. First, as Figure 4 As shown in block 400, the passivation material and its desired dose can be determined or provided to controller 160. Based on this information, controller 160 can determine the implantation time available for delivering the desired dose, as shown in block 410. The selected capping material can then be determined or provided to controller 160, as shown in block 420. Next, the controller can optionally determine the amount of time the plasma chamber 105 has been operated since the last cleaning, as shown in block 430. Alternatively, controller 160 can determine the number of workpieces processed since the last cleaning. Controller 160 then determines an estimated etching rate for the sacrificial capping layer 210 based on the passivation material, the capping material, the power applied by the RF power supply, and optionally the number of hours the plasma chamber has been operated or the number of workpieces processed, as shown in block 440. In another embodiment, controller 160 can use metrology to determine changes in the etching rate as a result of chamber utilization. Based on the etching rate and implantation time, controller 160 calculates the desired initial thickness of the sacrificial capping layer 210, as shown in block 450. The initial thickness can be calculated as the product of the etching rate and the total implantation time. Using this information, the controller 160 can calculate the duration of the capping application period, during which the mass flow controller 171a is actuated to form the sacrificial capping layer, as shown in block 460. In other words, the initial thickness of the sacrificial capping layer 210 is calculated as a function of the subsequent implantation time, which in turn is a function of the passivation material and the desired dose.

[0068] If desired, then it can be Figure 3A The sequence shown is repeated multiple times. Figure 3AThe sequence in which the sacrificial capping layer 210 is generated and then the implantation process is performed until the sacrificial capping layer 210 is etched away is shown.

[0069] Therefore, in some embodiments, a thinner sacrificial cap layer can be grown, and a shorter implantation process can be performed. After the thin sacrificial cap layer has been etched away, the implantation process can be repeated. Figure 3A The sequence shown is correct. Therefore, the sequence of applying the cap after the implantation process can be repeated multiple times. Although this may increase the overall fabrication time, it is preferable to perform it only once. Figure 4 Compared to the sequence shown, this allows for the use of a thinner initial sacrificial capping layer. This enables the passivation ions 220 to travel to greater depths, especially at the start of the implantation process.

[0070] Figure 3B Another embodiment is shown. In this figure, the vertical axis is used to represent process parameter values. Line 310 represents the flow rate of the capping material. The capping material includes any material that can be used to grow the sacrificial capping layer, including oxygen (O2) and nitrogen (N2). Other materials (such as nitric oxide (NO) or nitrogen dioxide (NO2)) can also be used to grow the sacrificial capping layer. All of these materials can be referred to as capping materials because they are used for the growth of the sacrificial capping layer. Line 311 represents the flow rate of the passivation material. Line 312 represents the flow rate of the passivation material from the bias power supply 135 (see...). Figure 1 The applied bias voltage. As mentioned above, the bias voltage is positive; however, it should be understood that a negative bias voltage is used to attract positive ions. Line 313 illustrates the actuation of the RF power supply 121.

[0071] In this embodiment, the mass flow controller 171a is actuated to allow the capping material to flow. As described above, during the capping period, the bias voltage is disabled to prevent the implantation of ions into the capping material. After a predetermined amount of time, the flow of the passivation material can begin, as shown in line 311. The passivation material can be hydrogen, deuterium, fluorine, or a gas mixture containing hydrogen, deuterium, or fluorine as a diluent or primary process gas. The passivation material can be stored in the feed gas container 170b, and the controller 160 can actuate the mass flow controller 171b to allow the passivation material to flow into the plasma chamber 105. Of course, the rate at which the passivation material is introduced can differ from... Figure 3B The flow rate is shown in the figure. After the flow of the capping material has stopped (e.g., by disabling the mass flow controller 171a), the bias power supply 135 can apply a bias voltage, as shown in line 312. The bias voltage can be a pulsed DC voltage with an amplitude between 0.1 kV and 10 kV (depending on the passivation material). The amplitude of the bias voltage is selected such that the passivation ions 220 can pass through the sacrificial capping layer 210 and stop in the passivation portion of the workpiece. In some embodiments, this portion can be the interface between polysilicon and another material, such as... Figures 5A to 5B As shown in the diagram, the RF power supply 121 can be kept actuated while the passivating material flows into the plasma chamber 105. When the bias power supply 135, RF power supply 121, and mass flow controller 171b are all actuated, the implantation process occurs. The implantation process continues until the desired dose is implanted into the workpiece 10. The desired dose can be between 1E15 and 3E17 / cm². 3 Between. However, with Figure 3A Unlike the embodiments shown, controller 160 periodically actuates mass flow controller 171a to allow capping material to flow during the implantation process. In some embodiments, the capping material is much heavier than the passivation material. For example, the capping material may be oxygen or nitrogen, while the passivation material is hydrogen or deuterium. Therefore, even if ions of the implanted capping material are present, they will still travel to a much shallower depth than the passivation ions 220. Furthermore, the presence of the sacrificial capping layer 210 can further slow down these ions of the capping material. In some embodiments (although not shown), the bias voltage may be reduced during the time the capping material flows into plasma chamber 105 during the implantation process. This can also be used to reduce the number of ions of the implanted capping material and the depth at which these ions are implanted.

[0072] In this embodiment, the sacrificial capping layer 210 can be etched by free radicals of the passivating material and excited molecules 200 during the implantation process, but the sacrificial capping layer 210 also grows during the implantation process. This effectively reduces the etching rate of the sacrificial capping layer 210. Figure 3A Compared to the illustrated embodiment, this allows for the growth of a thinner initial sacrificial capping layer prior to the implantation process. This enables passivating ions to migrate to greater depths, especially at the start of the implantation process.

[0073] therefore, Figure 3B The following sequence is shown: a sacrificial cap layer 210 is generated during the cap application period, and then an implantation process is performed, wherein the sacrificial cap layer is periodically grown by actuating a mass flow controller 171a during the implantation process. Note that... Figure 3B Line 310 is shown as a periodic function during the implantation process because it has a constant amplitude, frequency, and load cycle. However, other embodiments are also possible. For example, the load cycle actuated by the mass flow controller 171a may decrease or increase as the implantation process proceeds. Additionally, the frequency at which the mass flow controller 171a is actuated may decrease or increase as the implantation process proceeds.

[0074] In addition, Figure 3B In this embodiment, the flow rate of the capping material is shown as constant whenever the mass flow controller 171a is actuated. However, in some embodiments, the flow rate of the capping material may be lower during the implantation process than during the capping application period.

[0075] In this embodiment, the controller calculates the initial thickness of the sacrificial cap layer 210. However, unlike previous embodiments, the controller 160 also considers that material will be added to the sacrificial cap layer during the implantation process. The amount of material added to the sacrificial cap layer is a function of the flow rate of the mass flow controller 171a during the implantation process, as well as the load cycles and frequency of the mass flow controller 171a. The etching rate can be calculated as described above. Additionally, the total amount of etched sacrificial cap layer can be determined as described above. Furthermore, the controller 160 can use information such as the number of operating hours since the last cleaning, the number of workpieces processed since the last cleaning, or the output of the metering system to determine the change in etching rate over time. Based on this modified etching rate, the controller 160 can change the flow rate of the mass flow controller 171a, or change the frequency or load cycles of the mass flow controller 171a, to compensate for the changing etching rate.

[0076] Therefore, in this embodiment, the initial thickness of the sacrificial cap layer 210 can be calculated as the product of the etching rate of the sacrificial cap layer and the total implantation time, minus the amount of material added to the sacrificial cap layer during the implantation process. Therefore, in Figure 3B In the embodiment shown, the initial thickness of the sacrificial cap layer is greater than that in Figure 3A The embodiment shown is thin. This allows passivating ions to travel to greater depths, especially at the beginning of the implantation process.

[0077] Figure 3C A third embodiment is shown, which is similar to... Figure 3B In this figure, the vertical axis represents process parameter values. Line 320 represents the flow rate of the capping material. The capping material includes any material that can be used to grow the sacrificial capping layer, including oxygen (O2) and nitrogen (N2). Other materials (such as nitric oxide (NO) or nitrogen dioxide (NO2)) can also be used to grow the sacrificial capping layer. All of these materials can be called capping materials because they are used for the growth of the sacrificial capping layer. Line 321 represents the flow rate of the passivation material. Line 322 represents the flow rate of the passivation material from bias power supply 135 (see...). Figure 1 The bias voltage applied. Similarly, the bias voltage is positive; however, it should be understood that a negative bias voltage is used to attract positive ions. Line 323 illustrates the actuation of the RF power supply 121.

[0078] In this embodiment, instead of pulses being generated by the mass flow controller 171a during the implantation process, flow of the capping material is always enabled during the implantation process. In some embodiments (e.g.) Figure 3CAs shown in the illustration, the flow rate of the capping material can be constant throughout the implantation process. However, in other embodiments, the flow rate may increase or decrease throughout the implantation process. Additionally, the flow rate of the capping material may be lower during the implantation process than during the capping application period.

[0079] Furthermore, the controller 160 can use information such as the number of operating hours since the last cleaning, the number of workpieces processed since the last cleaning, or the output of the metering system to determine the change in etching rate over time. Based on this modified etching rate, the controller 160 can change the flow rate of the mass flow controller 171a, or change the frequency or load cycle of the mass flow controller 171a, to compensate for the changing etching rate.

[0080] Therefore, in some embodiments, a semiconductor processing apparatus is disclosed. The apparatus includes a plasma chamber 105. The apparatus also includes a feed gas container 170a containing a top cover material, a mass flow controller 171a that adjusts the flow of the top cover material from the feed gas container 170a to the plasma chamber 105, a feed gas container 170b containing a passivating material, and a mass flow controller 171b that adjusts the flow of the passivating material from the feed gas container 170b to the plasma chamber 105. Additionally, the apparatus includes an RF power supply 121 that powers an RF antenna 120. A pressure plate 130 is disposed within the plasma chamber 105. The pressure plate 130 is electrically connected to a bias power supply 135. The apparatus also includes a controller 160 that communicates with the RF power supply 121, the bias power supply 135, and the mass flow controllers 171a and 171b. The controller 160 includes features that enable it to perform the above-described... Figures 3A to 3C The instructions for the functions shown are as follows. Therefore, controller 160 controls the device to generate the cap application period and implantation process. As described above, controller 160 can implement the cap application period before and / or during the implantation process. Furthermore, in some embodiments, controller 160 communicates with a metering system. Controller 160 can terminate the implantation process based on the output of the metering system. In other embodiments, controller 160 can issue an alarm based on the output of the metering system.

[0081] although Figures 3A to 3C An embodiment is shown in which the sacrificial capping layer is applied in the same plasma chamber as the implantation process; however, in other embodiments, the sacrificial capping layer is applied outside the plasma chamber used to perform the implantation process. For example, in one embodiment, the workpiece may be placed in a heated chamber (e.g., above 600°C), and capping material may be introduced. Due to the presence of these materials in the heated chamber, the capping layer will be grown under conditions in this environment without the use of any bias voltage.

[0082] In another embodiment, the workpiece may be placed in a preheating chamber with a temperature between 200°C and 600°C. A capping material may be introduced into the preheating chamber. A sacrificial capping layer may be grown under these conditions. In a variation of this embodiment, a remote plasma generator is used to generate plasma using one or more capping materials. This plasma is then introduced into the preheating chamber.

[0083] In another embodiment, a plasma deposition process (PVD) can be used to grow the sacrificial capping layer. In PVD, plasma is generated in a chamber containing the workpiece using one or more capping materials. Ions or molecules from the plasma are then deposited on the workpiece to form the sacrificial capping layer.

[0084] It should also be noted that other methods and apparatus exist for generating the sacrificial capping layer, and this disclosure is not limited to the embodiments disclosed above. Furthermore, in some embodiments, the chamber used to apply the sacrificial capping layer may also be used to heat the workpiece, for example, to the temperature utilized during the passivation process.

[0085] In each of these embodiments in which a sacrificial cap layer is applied outside the plasma chamber, the following can be used: Figure 4 The flowchart shown determines the initial thickness of the sacrificial capping layer. Furthermore, in Figure 6 The figure shows the sequence in plasma chamber 105 used in these embodiments. In this figure, the vertical axis is used to represent process parameter values. Line 331 represents the flow rate of the passivation material. Line 332 represents the flow rate of the bias power supply 135 (see Figure 105). Figure 1 The applied bias voltage. Similarly, the bias voltage is positive; however, it should be understood that a negative bias voltage is used to attract positive ions. Line 333 illustrates the actuation of the RF power supply 121. The flow rate of the passivation material may differ from... Figure 6 The flow rate is shown. Note that, except for the period during which the top cover is applied outside the plasma chamber 105, Figure 6 Similar to Figure 3A .

[0086] Furthermore, although the above disclosure describes an implantation process based on a predetermined termination time, other embodiments are also possible. For example, in one instance, such as... Figure 1 As shown, a metrology system (e.g., an optical emission spectroscopy (OES) system 180) may be located in the plasma chamber 105.

[0087] In some embodiments, the OES system 180 can be used to terminate the implantation process. Specifically, as the sacrificial capping layer 210 is etched, the spectrum detected by the OES system 180 will show the presence of oxygen or nitrogen (depending on the composition of the sacrificial capping layer). The spectrum may also show peaks indicating the presence of silicon. However, once the sacrificial capping layer 210 has been completely etched away, the spectrum will show much larger peaks for silicon, and the peaks associated with oxygen and / or nitrogen will disappear. Therefore, in one embodiment, instead of utilizing a predetermined time for the implantation process, the OES system 180 is used to detect when the sacrificial capping layer disappears. Once this detection is performed, the implantation process is then terminated. This approach can be advantageous when the final device parameters are relatively insensitive to dose but highly sensitive to any etching of the surface.

[0088] In some embodiments, the OES system 180 may be used as an alarm system. For example, the implantation process may be a timed process for a predetermined duration. However, if the OES system 180 detects an increase in silicon emission before the predetermined duration expires, the controller 160 may prematurely terminate the implantation process.

[0089] In addition to the OES system, other metrology systems can be used. For example, absorption spectroscopy can be used to monitor the plasma. Alternatively, Fourier-transform infrared spectroscopy (FTIR), reflectance spectroscopy, or ellipsometrics can be used to monitor the sacrificial top cover.

[0090] The embodiments described in this disclosure can have many advantages. For example, it is advantageous to implant ions into a semiconductor substrate to passivate the semiconductor substrate. Compared to what can be done using other processes, the use of implantation allows the passivating ions to be delivered deeper into the substrate. The formation of a sacrificial capping layer makes it possible to perform this passivation implantation without the harmful etching that sometimes accompanies the implantation process. Therefore, these embodiments expand the available processing space for a given configuration, thereby enabling the use of greater energy and / or dose.

[0091] While the above disclosure describes implants for passivating workpieces, this disclosure is not limited to these embodiments. For example, implants can be used to alter the conductivity of a workpiece or to dope the workpiece for bulk modification. For example, the implant can be a dopant material, such as a group 3, 4, or 5 material. Therefore, in some embodiments, the implant material can be a passivating material. In other embodiments, the implant material can be a dopant material.

[0092] The scope of this disclosure is not limited to the specific embodiments described herein. In fact, from the foregoing description and accompanying drawings, it will be apparent to those skilled in the art that various other embodiments and modifications of this disclosure, in addition to those described herein, are also possible. Therefore, these other embodiments and modifications are all intended to fall within the scope of this disclosure. Furthermore, although this disclosure has been set forth herein for a specific purpose, in a specific setting, and in the context of a specific implementation, those skilled in the art will recognize that the utility of this disclosure is not limited thereto and that it can be advantageously practiced for any number of purposes and in any number of settings. Therefore, the foregoing claims should be understood in light of the full scope and spirit of this disclosure as described herein.

Claims

1. A method for passivating a portion of a workpiece, comprising: The workpiece is placed in the plasma chamber; A sacrificial capping layer is applied to the top surface of the workpiece; A plasma containing a passivating material is generated in the plasma chamber, wherein the passivating material is selected from the group consisting of hydrogen, deuterium, fluorine and gas mixtures containing hydrogen, deuterium or fluorine as diluent gas or main processing gas, and wherein ions, free radicals and excited molecules of the passivating material are generated therein. An implantation process is performed in which the ions of the passivation material are implanted into the portion via the sacrificial capping layer by applying a bias voltage to the workpiece, and wherein the free radicals and the excited molecules etch the sacrificial capping layer during the implantation process. as well as When the desired dose of the passivating material has been implanted, the implantation process is terminated, wherein at the termination of the implantation process, the thickness of the sacrificial capping layer is less than 5 angstroms, or the entire sacrificial capping layer has been completely removed and the workpiece has been etched to less than 10 angstroms. The initial thickness of the sacrificial capping layer is determined based on the etching rate of the sacrificial capping layer and the total duration of the implantation process.

2. The method of claim 1, wherein the sacrificial cap layer is applied in the plasma chamber during the cap application period by introducing cap material and generating plasma containing the cap material while disabling the bias voltage.

3. The method of claim 2, wherein the application of the cap occurs before the implantation process.

4. The method of claim 3, wherein an additional sacrificial cap layer is applied during the implantation process by flowing the cap material into the plasma chamber.

5. The method of claim 4, wherein the flow of the capping material is continuous throughout the implantation process.

6. The method of claim 4, wherein the flow of the capping material is pulsed during the implantation process.

7. The method of claim 6, wherein the bias voltage is changed during the implantation process when the capping material flows into the plasma chamber.

8. The method of claim 1, wherein the implantation process is terminated after a predetermined time, wherein the predetermined time is determined based on the passivating material and the desired dose of the passivating material.

9. The method of claim 8, wherein an alarm is generated if the output of the metering system indicates that the workpiece is being etched.

10. The method of claim 1, wherein the implantation process is terminated based on an output from a metering system indicating that the workpiece is being etched.

11. The method of claim 1, wherein the initial thickness is adjusted based on chamber metering, the number of workpieces processed, or the number of operating hours to compensate for varying etching rates.

12. The method of claim 1, wherein the thickness of the sacrificial cap layer is between 5 angstroms and 100 angstroms.

13. The method of claim 1, wherein when the bias voltage is applied, the bias voltage is a pulsed DC voltage having an amplitude between 0.1 kV and 10 kV.

14. A method for passivating a portion of a workpiece, comprising: A sacrificial capping layer is applied to the top surface of the workpiece in a chamber, wherein the thickness of the sacrificial capping layer is determined based on the etching rate of the sacrificial capping layer and the total duration of the implantation process; The workpiece is placed in a plasma chamber, wherein the plasma chamber is different from the chamber described above; A plasma containing a passivating material is generated in the plasma chamber, wherein the passivating material is selected from the group consisting of hydrogen, deuterium, fluorine and gas mixtures containing hydrogen, deuterium or fluorine as diluent gas or main processing gas, and wherein ions, free radicals and excited molecules of the passivating material are generated therein. The implantation process is performed in which the ions of the passivation material are implanted into the portion via the sacrificial capping layer by applying a bias voltage to the workpiece, and wherein the free radicals and the excited molecules etch the sacrificial capping layer during the implantation process. as well as The implantation process is terminated once the desired dose of the passivating material has been implanted.

15. The method of claim 14, wherein the chamber: Heating the workpiece to a temperature close to the temperature of the implantation process; and The sacrificial cap layer is grown by allowing gas to flow while the workpiece is being heated.

16. A method for passivating a portion of a workpiece, comprising: The material on the top cover flows into the plasma chamber, where the workpiece is placed; The capping material is excited to generate plasma, wherein during the capping application period, no bias voltage is applied to the workpiece to generate a sacrificial capping layer on the top surface of the workpiece. The passivating material is flowed into the plasma chamber, wherein the passivating material is selected from the group consisting of hydrogen, deuterium, fluorine and gas mixtures containing hydrogen, deuterium or fluorine as diluent gas or main processing gas; An implantation process is performed to implant passivating ions into the workpiece, wherein the implantation process is defined as a period of time during which the bias voltage is applied to the workpiece while a plasma containing the passivating material is being generated. Material is added to the sacrificial cap layer by allowing the cap material to flow into the plasma chamber during the implantation process; as well as Terminating the implantation process, The initial thickness of the sacrificial cap layer is determined based on the etching rate of the sacrificial cap layer, the total duration of the implantation process, and the amount of material added to the sacrificial cap layer during the implantation process.

17. The method of claim 16, wherein the implantation process is terminated when a desired dose of the passivating ions has been implanted.

18. The method of claim 16, wherein at the termination of the implantation process, the thickness of the sacrificial cap layer is less than 5 angstroms or all of the sacrificial cap layer has been completely removed and the workpiece has been etched less than 10 angstroms.

19. The method of claim 16, wherein the flow of the capping material is continuous throughout the implantation process.

20. The method of claim 16, wherein the flow of the capping material is pulsed during the implantation process.

21. The method of claim 20, wherein the bias voltage is changed during the implantation process when the capping material flows into the plasma chamber.

22. The method of claim 16, wherein the amount of material added is varied to compensate for the varying etching rate based on chamber metering, the number of workpieces processed, or the number of operating hours.

23. The method of claim 22, wherein the top cover material flows into the plasma chamber via a mass flow controller, and the amount of material is delivered by adjusting the flow rate of the top cover material, the frequency at which the mass flow controller is actuated, or the load cycle of the mass flow controller.

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