A passivation layer etching method of a HEMT device and a HEMT device

Abstract

The application discloses a passivation layer etching method of a HEMT device and the HEMT device. The method comprises the following steps: providing a functional layer with a passivation layer; forming a sacrifice layer on the surface of the passivation layer and forming an opening on the surface of the sacrifice layer; performing plasma dry etching on the exposed surface of the passivation layer in the opening at a gradually increased first temperature to form a first etching structure with a bottom in the passivation layer; performing default mask plasma dry etching on the sacrifice layer at a gradually increased second temperature to remove all the sacrifice layer; performing default mask chemical dry etching on the surface of the passivation layer and the first etching structure at a gradually increased third temperature to form a second etching structure with a bottom on the surface of the functional layer on the etched surface of the passivation layer, and completing annealing by using the third temperature. The application can effectively reduce etching damage and maintain etching morphology.

Description

Technical Field

[0001] This application relates to the field of semiconductor processing technology, and in particular to a passivation layer etching method for HEMT devices and the HEMT device itself. Background Technology

[0002] In the fabrication of gallium nitride (GaN) HEMT (high electron mobility transistor) devices, a surface passivation layer is typically deposited to suppress current collapse. Whether in ohmic contact or gate trench fabrication, the passivation layer must first be etched open before metal deposition. Passivation layer etching generally employs plasma etching, which allows for convenient control of etching uniformity and sidewall etching angles, and improves etching efficiency. However, the etching process touches the underlying GaN or AlGaN layer. If the etching damage to the GaN or AlGaN layer is significant, the two-dimensional electron gas is affected, resulting in a substantial decrease in device performance. Etching damage can include lattice damage, surface roughening, stoichiometric deviation, and surface contamination, primarily caused by the bombardment and chemical reactions of the GaN lattice by high-energy ions and active free radicals in the plasma. Therefore, it is necessary to investigate a process method that can significantly improve the reduction of underlying etching damage. Summary of the Invention

[0003] The purpose of this application is to overcome the above-mentioned problems existing in the prior art and to provide a passivation layer etching method for HEMT devices and HEMT devices.

[0004] To achieve the above objectives, the technical solution of this application is as follows:

[0005] According to a first aspect of this application, embodiments of this application provide a passivation layer etching method for a HEMT device, comprising:

[0006] Provides a functional layer with a passivation layer on its surface;

[0007] A sacrificial layer is formed on the surface of the passivation layer, and an opening is formed on the surface of the sacrificial layer;

[0008] Using a first etching process, and through the opening, the exposed surface of the passivation layer is etched at a first temperature to form a first etched structure on the surface of the passivation layer, wherein the bottom of the first etched structure is at a distance greater than zero from the surface of the functional layer.

[0009] Using a second etching process with a default mask, the sacrificial layer is etched at a second temperature to remove the sacrificial layer and expose the entire surface of the first etched structure and the surrounding passivation layer.

[0010] Using a third etching process with a default mask, the surface of the passivation layer and the first etched structure are etched at a third temperature, causing the surface of the passivation layer and the first etched structure to conformally move toward the surface of the functional layer until a second etched structure evolved from the first etched structure is formed on the etched surface of the passivation layer, exposing the surface of the functional layer located at the bottom of the second etched structure.

[0011] The first etching process and the second etching process include plasma dry etching process, and the third etching process includes chemical dry etching process. The first temperature, the second temperature and the third temperature are variable temperature that gradually increase and are sequentially connected.

[0012] In some embodiments, during the third etching, the third temperature is also used to perform a first treatment on the exposed surface of the functional layer to repair surface lattice damage.

[0013] In some embodiments, during the third etching, O2 is added to the etching gas to perform a second treatment on the surface of the exposed functional layer to reduce surface roughness.

[0014] In some embodiments, during the third etching, N2 is added to the etching gas to perform a third treatment on the surface of the exposed functional layer to stabilize the surface stoichiometry.

[0015] In some embodiments, the method further includes: after the third etching, using hydrogen radicals to perform a fourth treatment on the surface of the exposed functional layer to perform surface cleaning.

[0016] In some embodiments, the functional layer includes a GaN layer or an AlGaN layer.

[0017] In some embodiments, the passivation layer includes a dielectric layer.

[0018] In some embodiments, the sacrificial layer comprises an organic layer.

[0019] In some embodiments, the first etching is performed using a first plasma obtained by exciting a first gas, the first gas comprising a first fluorine-based gas.

[0020] In some embodiments, the second etching is performed using a second plasma obtained by exciting a second gas, the second gas including an oxygen gas.

[0021] In some embodiments, the third etching is performed using a third plasma obtained by exciting a third gas and then filtering out charged particles from the third plasma to obtain neutral particles, wherein the third gas includes a second fluorine-based gas.

[0022] In some embodiments, the first fluorine-based gas includes CF4 and CHF3.

[0023] In some embodiments, the oxygen gas includes O2.

[0024] In some embodiments, the second fluorine-based gas includes CF4.

[0025] In some embodiments, the distance is 10% to 20% of the thickness of the passivation layer.

[0026] In some embodiments, the first temperature is a first variable temperature that gradually increases between 0°C and 150°C.

[0027] In some embodiments, the second temperature is a second variable temperature that gradually increases between 100°C and 250°C.

[0028] In some embodiments, the third temperature is a third variable temperature that gradually increases between 200°C and 300°C.

[0029] According to a second aspect of this application, embodiments of this application also provide a HEMT device, including a passivation layer, wherein the passivation layer is etched using the passivation layer etching method of the HEMT device provided in any of the embodiments of the first aspect described above.

[0030] The embodiments of this application may have, or at least have, the following advantages:

[0031] (1) By first using plasma dry etching (first etching process) and etching the passivation layer at a lower first temperature, the anisotropic etching characteristics can be utilized to accurately control the sidewall etching angle and etching uniformity. The high etching rate of plasma etching can be used to quickly remove most of the passivation layer thickness while avoiding direct contact with the functional layer. Then, by using a maskless chemical dry etching process (third etching process) and etching the remaining passivation layer at a higher third temperature, the mild nature of chemical dry etching can be used to gently remove a small amount of the remaining passivation layer, effectively reducing etching damage to the functional layer surface and maintaining the etching morphology formed after the first etching. Thus, by combining plasma dry etching and chemical dry etching, the problems of difficult damage control when using plasma dry etching alone and difficult morphology control when using chemical dry etching alone are well solved.

[0032] (2) By utilizing the annealing-like effect of a higher process temperature (third temperature) during the third etching process, the surface of the functional layer exposed after etching is treated first, which can repair any lattice damage that may exist on the surface of the functional layer after etching, thus ensuring the carrier transport efficiency. By adding O2 to the etching gas during the third etching process, oxygen free radicals are used to treat the surface of the functional layer exposed after etching second, which can "smooth out" any unevenness on the surface of the functional layer after etching, thereby further reducing the surface roughness. By adding N2 to the etching gas during the third etching process, nitrogen free radicals are used to treat the surface of the functional layer exposed after etching third, which can regulate the nitrogen content on the surface of the functional layer, thereby stabilizing the surface stoichiometry. By using hydrogen free radicals to treat the surface of the exposed functional layer after the third etching process fourth, surface contamination can be removed and surface activity can be improved, which is beneficial for the subsequent deposition of electrode metal. Thus, through one or more synergistic regulation methods, the two-dimensional electron gas can be avoided from being affected, significantly improving the device performance.

[0033] (3) By using a series of gradually increasing and sequentially connected variable temperatures for the first, second, and third etching processes—that is, by employing a gradual temperature increase method with sequentially connected temperatures—the waiting time for temperature switching between processes can be eliminated while ensuring continuous heating. This also shortens the necessary heating time before the first treatment, allowing annealing to be completed quickly and improving efficiency. Furthermore, since no separate dedicated heat treatment chamber is required for annealing, costs are saved. Simultaneously, the increased temperature also prepares the site for subsequent metal deposition.

[0034] Other advantages of this application will be described in the following detailed description. Attached Figure Description

[0035] Figure 1 This is a flowchart of a passivation layer etching method for a HEMT device according to a preferred embodiment of this application.

[0036] Figure 2 This is a schematic diagram of a structure in which a passivation layer has been applied to the surface of a functional layer, according to a preferred embodiment of this application.

[0037] Figure 3 This is a schematic diagram of a structure after a sacrificial layer is formed on the surface of a passivation layer, according to a preferred embodiment of this application.

[0038] Figure 4 This is a schematic diagram of a structure after an opening is formed on the surface of the sacrificial layer, which is a preferred embodiment of this application.

[0039] Figure 5 This is a schematic diagram of a structure after a first etched structure is formed on the exposed surface of the passivation layer at the bottom of the opening, according to a preferred embodiment of this application.

[0040] Figure 6 This is a schematic diagram of the structure after etching to remove the sacrificial layer, provided as a preferred embodiment of this application.

[0041] Figure 7 This is a schematic diagram of a structure formed on the surface of a passivation layer after etching, according to a preferred embodiment of this application.

[0042] In the figure: 10. Functional layer; 11. Passivation layer; 111. Initial surface; 112. Post-etched surface; 12. Sacrificial layer; 13. Opening; 14. First etched structure; 15. Second etched structure. Detailed Implementation

[0043] When etching the passivation layer of HEMT devices, if the etching damage to the underlying GaN or AlGaN layer (functional layer) is large, the two-dimensional electron gas will be affected, which will significantly reduce the device performance. Therefore, it is crucial to select an appropriate etching method to reduce the underlying damage during passivation layer etching. Specifically, etching damage may manifest in the following forms: (1) Lattice damage: The momentum bombardment of high-energy ions will destroy the atomic arrangement of GaN crystals, resulting in defects such as displacement damage, vacancies, and interstitial atoms. These defects will introduce additional trap states, which will seriously affect the carrier transport efficiency. (2) Surface roughening: During the etching process, the material surface may become uneven, forming tiny pits or protrusions, increasing surface scattering and significantly reducing electron mobility. (3) Stoichiometric deviation: In plasma, N atoms are more volatile than Ga atoms, leading to the selective removal of N atoms from the GaN surface, forming a Ga-rich layer or a non-stoichiometric structure. This deviation will directly affect the electrical properties and interface quality of the material. (4) Surface contamination: Residual reaction products or sputtered materials in the etching cavity may be deposited on the GaN surface, introducing impurities and further deteriorating device performance.

[0044] To address the aforementioned problems, embodiments of this application provide a passivation layer etching method for HEMT devices, including:

[0045] Provides a functional layer with a passivation layer on its surface;

[0046] A sacrificial layer is formed on the surface of the passivation layer, and an opening is formed on the surface of the sacrificial layer;

[0047] Using a first etching process, and through the opening, the exposed surface of the passivation layer is etched at a first temperature to form a first etched structure on the surface of the passivation layer, wherein the bottom of the first etched structure is at a distance greater than zero from the surface of the functional layer.

[0048] Using a second etching process with a default mask, the sacrificial layer is etched at a second temperature to remove the sacrificial layer and expose the entire surface of the first etched structure and the surrounding passivation layer.

[0049] Using a third etching process with a default mask, the surface of the passivation layer and the first etched structure are etched at a third temperature, causing the surface of the passivation layer and the first etched structure to conformally move toward the surface of the functional layer until a second etched structure evolved from the first etched structure is formed on the etched surface of the passivation layer, exposing the surface of the functional layer located at the bottom of the second etched structure.

[0050] The first etching process and the second etching process include plasma dry etching process, and the third etching process includes chemical dry etching process. The first temperature, the second temperature and the third temperature are variable temperature that gradually increase and are sequentially connected.

[0051] This embodiment of the application first uses a plasma dry etching process (first etching process) to etch the passivation layer at a relatively low first temperature. This utilizes the anisotropic etching characteristics to accurately control the sidewall etching angle and etching uniformity, and leverages the high etching rate to rapidly remove most of the passivation layer thickness while avoiding direct contact with the functional layer. Then, a maskless chemical dry etching process (third etching process) is used at a higher third temperature to etch the remaining passivation layer thickness. This utilizes the gentle nature of chemical dry etching to achieve a gradual removal of the small amount of remaining passivation layer, effectively reducing etching damage to the functional layer surface and better preserving the etching morphology formed after the first etching. Therefore, by combining plasma dry etching and chemical dry etching, the problems of difficult damage control when using plasma dry etching alone, and difficult morphology control when using chemical dry etching alone, are effectively solved.

[0052] This application also provides a HEMT device, including a passivation layer, which is etched using the passivation layer etching method for HEMT devices described above.

[0053] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0054] refer to Figure 1According to a first aspect of this application, embodiments of this application provide a passivation layer etching method for a HEMT device, which may sequentially include the following steps:

[0055] Step S11: Provide a functional layer with a passivation layer on the surface.

[0056] refer to Figure 2 This diagram illustrates a structure with a passivation layer 11 on the surface of the functional layer 10. The functional layer 10 can be a GaN layer or an AlGaN layer in a HEMT device. The passivation layer 11 is disposed on the GaN or AlGaN layer to suppress current collapse effects. During HEMT device fabrication, the passivation layer 11 needs to be etched to form a through-etched structure (a second etched structure) to fill the etched structure with metal electrodes that connect to the surface of the functional layer 10.

[0057] In some embodiments, the functional layer 10 may be disposed on a substrate (e.g., a silicon substrate).

[0058] In some embodiments, the passivation layer 11 includes a dielectric layer. The dielectric layer may be an oxide layer (e.g., a silicon oxide layer, an aluminum oxide layer, a gallium oxide layer, an indium oxide layer, etc.) or a nitride layer (e.g., a silicon nitride layer).

[0059] Step S12: A sacrificial layer is formed on the surface of the passivation layer, and an opening is formed on the surface of the sacrificial layer.

[0060] refer to Figure 3 In some embodiments, a sacrificial layer 12 is formed on the surface of the passivation layer 11. The sacrificial layer 12 may include an organic layer, such as a photoresist layer.

[0061] In some embodiments, a spin-coating process is used to form a photoresist layer serving as a sacrificial layer 12 on the surface of the passivation layer 11. Then, a photolithography process is used to pattern the sacrificial layer 12, forming an opening 13 through the sacrificial layer 12 on its surface, exposing the surface of the passivation layer 11 located at the bottom of the opening 13, as shown below. Figure 4 As shown, opening 13 serves as the etching window for the first etching step (first etching) in the subsequent step etching process of the passivation layer 11.

[0062] Step S13: At a gradually increasing first temperature, plasma dry etching is performed on the surface of the passivation layer exposed in the opening to form a first etched structure with the bottom located in the passivation layer.

[0063] refer to Figure 5In some embodiments, a plasma dry etching process (first etching process) is used, and a first etching at a first temperature is performed on the surface (initial surface 111) of the passivation layer 11 exposed from the bottom of the opening 13 through the opening 13, forming a first etched structure 14 with its bottom located in the passivation layer 11 below the opening 13. The first temperature is a first variable temperature that gradually increases.

[0064] In some embodiments, an etching chamber may be used to etch the passivation layer 11. The etching chamber may include a hot stage for placing a substrate having the passivation layer 11 and the functional layer 10, and the substrate may be heated by the hot stage to perform the desired etching process at a set temperature. Specifically, by heating the hot stage, the substrate is gradually heated so that the passivation layer 11 on the substrate is brought to a gradually increasing first temperature for the first etching. The first temperature is the heating temperature of the hot stage (the same applies to the second and third temperatures mentioned below). A cooling device may be provided inside the hot stage for temperature regulation.

[0065] In some embodiments, the first temperature is a first variable temperature that gradually increases between 0°C and 150°C. For example, the passivation layer 11 can be heated to a temperature between 0°C and 150°C, or between 0°C and 140°C, or between 0°C and 130°C, or between 0°C and 120°C, or between 0°C and 110°C, or between 0°C and 100°C, or between 10°C and 150°C, or between 10°C and 140°C, or between 10°C and 130°C, or between 10°C and 120°C, or between 10°C and 110°C, or between 10°C and 100°C, or between 20°C and 150°C, or between 20°C and 140°C, or between 20°C and 130°C, or between 20°C and 120°C, or between 20°C and 110°C, or between 20°C and 100°C. The first etching is performed under a gradually increasing temperature range, such as between 30℃ and 150℃, or between 30℃ and 140℃, or between 30℃ and 130℃, or between 30℃ and 120℃, or between 30℃ and 110℃, or between 30℃ and 100℃, or between 50℃ and 150℃, or between 50℃ and 140℃, or between 50℃ and 130℃, or between 50℃ and 120℃, or between 50℃ and 110℃, or between 50℃ and 100℃, or between 40℃ and 100℃, or between 60℃ and 110℃, or between 70℃ and 120℃, or between 80℃ and 130℃, or between 90℃ and 140℃, or between 100℃ and 150℃.

[0066] In some embodiments, an anisotropic first etching is performed using a first plasma obtained by exciting a first gas. The first gas includes a first fluorine-based gas.

[0067] In some embodiments, the first fluorine-based gas includes CF4 and CHF3.

[0068] In some embodiments, the first gas includes CF4 and CHF3, and N2 or Ar may be used as an auxiliary gas.

[0069] In some embodiments, during the first etching, the flow rate of the first gas is 10 sccm to 50 sccm. For example, the flow rate of the first gas may be 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, 35 sccm, 40 sccm, 45 sccm, or 50 sccm, or any value between any two of the aforementioned flow rate values.

[0070] In some embodiments, the pressure during the first etching is 5 mTorr to 30 mTorr. For example, the pressure can be 5 mTorr, 6 mTorr, 7 mTorr, 8 mTorr, 9 mTorr, 10 mTorr, 15 mTorr, 20 mTorr, 25 mTorr, or 30 mTorr, or any value between any two of the aforementioned pressure values.

[0071] During the first etching, by employing the aforementioned first temperature, flow rate, and pressure, rapid etching of the passivation layer 11 can be achieved, forming a first etching structure 14 with a target depth and target sidewall etching angle on the surface of the passivation layer 11. The first etching structure 14 can be a trench or a slot, etc. The bottom of the first etching structure 14 is positioned such that there is a distance L greater than zero between it and the surface of the underlying functional layer 10, to prevent the high-energy plasma during the first etching from directly contacting the functional layer 10 and causing etching damage to its surface.

[0072] In some embodiments, the distance L is 10% to 20% of the initial thickness (deposition thickness) of the passivation layer 11. For example, the distance L can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% of the initial thickness of the passivation layer 11, or any value between any two of the aforementioned percentage values.

[0073] In some embodiments, the target sidewall etching angle (the acute angle between the sidewall and the horizontal plane) of the first etching structure 14 can be 65 degrees to 85 degrees, forming an approximately inverted trapezoidal shape of the first etching structure 14 that is larger at the top and smaller at the bottom. For example, the target sidewall etching angle can be 65 degrees, 70 degrees, 75 degrees, 80 degrees or 85 degrees, or any value between any two of the aforementioned angle values.

[0074] Step S14: At a continuously increasing second temperature, perform plasma dry etching of the sacrificial layer using a default mask to remove all of the sacrificial layer.

[0075] refer to Figure 6 In some embodiments, a plasma dry etching process (second etching process) is used again, and with the default mask in place, the surface of the sacrificial layer 12 is completely exposed to the plasma. A second etching process is then performed on the sacrificial layer 12 at a second temperature to remove all of the sacrificial layer 12 on the passivation layer 11, thereby exposing the entire surface (initial surface 111) of the first etched structure 14 and the surrounding passivation layer 11. The second temperature is a gradually increasing temperature variation temperature with the temperature endpoint value of the first temperature variation temperature (first temperature) as the temperature starting point value. That is, the second temperature is achieved by continuously increasing the temperature based on the first temperature. The second temperature can be achieved through the continuous heating action of a hot stage.

[0076] In some embodiments, the second temperature is a second variable temperature that gradually increases between 100°C and 250°C. For example, the sacrificial layer 12 can be heated by heat conduction during the heating of the substrate using a hot stage, so that the sacrificial layer 12 is between 100℃ and 250℃, or between 100℃ and 240℃, or between 100℃ and 230℃, or between 100℃ and 220℃, or between 100℃ and 210℃, or between 100℃ and 200℃, or between 110℃ and 250℃, or between 110℃ and 240℃, or between 110℃ and 230℃, or between 110℃ and 220℃, or between 110℃ and 210℃, or between 110℃ and 200℃, or between 120℃ and 250℃, or between 120℃ and 240℃, or between 120℃ and 230℃, or between 120℃ and 220℃, or between 120℃ and 210℃, or The second etching is performed under a gradually increasing temperature range, such as between 120℃ and 200℃, or between 130℃ and 250℃, or between 130℃ and 240℃, or between 130℃ and 230℃, or between 130℃ and 220℃, or between 130℃ and 210℃, or between 130℃ and 200℃, or between 140℃ and 250℃, or between 140℃ and 240℃, or between 140℃ and 230℃, or between 140℃ and 220℃, or between 140℃ and 210℃, or between 140℃ and 200℃, or between 150℃ and 250℃, or between 150℃ and 240℃, or between 150℃ and 230℃, or between 150℃ and 220℃, or between 150℃ and 210℃, or between 150℃ and 200℃.

[0077] In some embodiments, a second plasma obtained by exciting a second gas is used to perform the second etching. The second gas includes an oxygen-based gas.

[0078] In some embodiments, the oxygen gas includes O2.

[0079] In some embodiments, the second gas includes O2, and N2 may be used as an auxiliary gas.

[0080] In some embodiments, during the second etching, the flow rate of the second gas is 100 sccm to 5000 sccm. For example, the flow rate of the second gas can be 100 sccm, 200 sccm, 500 sccm, 1000 sccm, 2000 sccm, 3000 sccm, 4000 sccm, or 5000 sccm, or any value between any two of the aforementioned flow rate values.

[0081] In some embodiments, the pressure during the second etching is 100 mTorr to 1000 mTorr. For example, the pressure can be 100 mTorr, 200 mTorr, 300 mTorr, 400 mTorr, 500 mTorr, 600 mTorr, 700 mTorr, 800 mTorr, 900 mTorr, or 1000 mTorr, or any value between any two of the aforementioned pressure values.

[0082] Step S15: At a continuously increasing third temperature, perform chemical dry etching with a default mask on the surface of the passivation layer and the first etched structure to form a second etched structure with its bottom located on the surface of the functional layer on the etched surface of the passivation layer, and complete the annealing using the third temperature.

[0083] refer to Figure 7 In some embodiments, a chemical dry etching process (third etching process) is used, and under the default mask state, a third etching is performed on the surface of the passivation layer 11 (initial surface 111) and the inner wall of the first etched structure 14 at a third temperature. This causes the surface of the passivation layer 11 and the first etched structure 14 to dynamically and conformally move towards the surface of the functional layer 10 during etching, until a second etched structure 15, evolved from the first etched structure 14, is formed on the etched surface 112 of the passivation layer 11 (i.e., the first etched structure 14 is etched into the second etched structure 15), exposing the surface of the functional layer 10 located at the bottom of the second etched structure 15. The third temperature is a gradually increasing third temperature variation temperature with the temperature endpoint value of the second temperature variation temperature as the temperature starting value. That is, the third temperature is achieved by continuously increasing the temperature based on the second temperature. The third temperature can also be achieved by continuous heating using a hot stage.

[0084] In some embodiments, the third temperature is a third variable temperature that gradually increases between 200°C and 300°C. For example, the passivation layer 11 can be heated by heating the substrate using a hot plate, so that the passivation layer 11 is between 200°C and 300°C, or between 210°C and 300°C, or between 220°C and 300°C, or between 230°C and 300°C, or between 240°C and 300°C, or between 250°C and 300°C, or between 210°C and 250°C, or between 220°C and 260°C, or between 230°C and 270°C, or between 240°C and 280°C. The third etching is performed under a gradually increasing temperature range, such as between 250℃ and 290℃, or between 200℃ and 250℃, or between 210℃ and 290℃, or between 220℃ and 280℃, or between 230℃ and 270℃, or between 240℃ and 260℃, or between 210℃ and 280℃, or between 220℃ and 280℃, or between 230℃ and 280℃, or between 240℃ and 280℃, or between 250℃ and 280℃.

[0085] In some embodiments, the first temperature, the second temperature, and the third temperature are variable temperatures that gradually increase and are sequentially connected. For example, by the continuous heating effect of the hot stage, the first etching can be performed at a first temperature that gradually increases between room temperature (20°C) and 100°C, the second etching can be performed at a second temperature that continuously increases between 100°C and 200°C, and the third etching can be performed at a third temperature that continuously increases between 200°C and 300°C.

[0086] In some embodiments, when switching between the first etching, the second etching, and the third etching processes, the process can be carried out under continuous heating without a transition time. Alternatively, a transition holding time can be set between the starting temperature of the second temperature and the ending temperature of the first temperature, and between the starting temperature of the third temperature and the ending temperature of the second temperature.

[0087] In some embodiments, isotropic third etching is performed using a third plasma obtained by exciting a third gas, and neutral particles obtained after filtering out charged particles from the third plasma. The third gas includes a second fluorine-based gas.

[0088] In some embodiments, the second fluorine-based gas includes CF4.

[0089] In some embodiments, the third gas includes CF4, and O2 and / or N2 may be added as auxiliary gases.

[0090] In some embodiments, during the third etching, the flow rate of the third gas is 50 sccm to 300 sccm. For example, the flow rate of the third gas may be 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 100 sccm, 150 sccm, 200 sccm, 250 sccm, or 300 sccm, or any value between any two of the aforementioned flow rate values.

[0091] In some embodiments, the pressure during the third etching is 300 mTorr to 800 mTorr. For example, the pressure can be 300 mTorr, 350 mTorr, 400 mTorr, 450 mTorr, 500 mTorr, 550 mTorr, 600 mTorr, 650 mTorr, 700 mTorr, 750 mTorr, or 800 mTorr, or any value between any two of the aforementioned pressure values.

[0092] Specifically, the bias power is turned on during the first and second etching processes, and turned off during the third etching process. Furthermore, the pressure during the third etching process is made greater than the pressure during the first etching process, and the flow rates of O2 and N2 in the third gas are made greater than the flow rates of CF4, respectively, in order to further reduce the etching damage to the surface of the functional layer 10 and avoid damaging the etching morphology.

[0093] Through the third etching, the surface of the passivation layer 11 and the first etched structure 14 are dynamically and conformally moved towards the surface of the functional layer 10. This transforms the initial surface 111 of the passivation layer 11 into the etched surface 112 after the third etching. Simultaneously, the first etched structure 14, originally formed on the initial surface 111 of the passivation layer 11, transforms into a second etched structure 15 formed on the etched surface 112 of the passivation layer 11 after the third etching. Compared to the first etched structure 14, the critical dimension of the second etched structure 15 is increased (the sidewalls of the first etched structure 14 are etched in the third etching, resulting in an increase in the critical dimension after etching), but the sidewall etching angle is maintained, thus controlling the overall etching morphology. Furthermore, by accumulating empirical data, variables such as the initial thickness of the passivation layer 11, the critical dimension of the first etched structure 14, and the distance L can be controlled to ensure that the critical dimension and etching angle of the final second etched structure 15 meet the design requirements.

[0094] By first using a plasma dry etching process (first etching process) and performing the first etching of the passivation layer 11 at a relatively low first temperature, the anisotropic etching characteristics can be utilized to accurately control the sidewall etching angle and etching uniformity. The high etching rate of plasma etching can be used to achieve rapid removal of most of the passivation layer 11, while avoiding direct contact with the functional layer 10. Then, by using a maskless chemical dry etching process (third etching process) and performing the third etching of the remaining passivation layer 11 at a relatively high third temperature, the mild nature of chemical dry etching can be utilized to achieve gentle removal of a small amount of the remaining passivation layer 11, which can effectively reduce the etching damage to the surface of the functional layer 10 and better maintain the etching morphology formed after the first etching. Thus, by combining plasma dry etching and chemical dry etching in a two-step etching method, the problem of difficulty in controlling damage when using plasma dry etching alone and difficulty in controlling morphology when using chemical dry etching alone is well solved. A second etched structure 15 with target key dimensions and target sidewall etching angle is formed on the etched surface 112 of the passivation layer 11.

[0095] In some embodiments, during the third etching, the surface of the functional layer 10 exposed after etching can be annealed (first treatment) by utilizing the similar annealing effect of the continuously rising higher third temperature. This can repair any lattice damage that may exist on the surface of the functional layer 10 after etching, thus ensuring the carrier transport efficiency.

[0096] In some embodiments, during the third etching, O2 can be added to the etching gas (third gas) and the resulting oxygen free radicals can be used to perform a second treatment on the surface of the functional layer 10 exposed by etching. This can have a "peak-shaving and valley-filling" effect on the unevenness that may exist on the surface of the functional layer 10 after etching, thereby further reducing the surface roughness.

[0097] In some embodiments, during the third etching, N2 can be added to the etching gas (third gas) to perform a third treatment on the surface of the functional layer 10 exposed by etching using nitrogen free radicals, thereby regulating the nitrogen content on the surface of the functional layer 10 and stabilizing the surface stoichiometry.

[0098] In some embodiments, after the third etching, the surface of the exposed functional layer 10 can be subjected to a fourth treatment to clean the surface by using hydrogen radicals obtained after exciting hydrogen gas and filtering out charged particles. This not only removes surface contaminants but also improves surface activity, which is beneficial for the subsequent deposition of electrode metals.

[0099] Thus, by employing one or more synergistic control methods, the two-dimensional electron gas can be prevented from being affected, significantly improving device performance.

[0100] Furthermore, by using gradually increasing and sequentially connected variable temperatures for the first, second, and third etching processes—that is, by employing a gradual temperature increase method for the first, second, and third etching processes—the waiting time for temperature switching between different etching processes can be eliminated while ensuring continuous heating. This also shortens the necessary heating time before the first treatment, allowing annealing to be completed quickly and improving efficiency. Moreover, since a separate dedicated heat treatment chamber is not required for annealing, costs are saved. Simultaneously, the increased temperature also prepares the site for subsequent metal deposition.

[0101] According to a second aspect of this application, embodiments of this application also provide a HEMT device, the HEMT device including a passivation layer, the passivation layer being etched using the passivation layer etching method of the HEMT device provided in any of the embodiments of the first aspect above.

[0102] refer to Figure 7 In some embodiments, the HEMT device includes a functional layer 10 and a passivation layer 11 disposed on the surface of the functional layer 10. The functional layer 10 may be further disposed on a substrate (not shown). The functional layer 10 may be a GaN layer or an AlGaN layer. The passivation layer 11 is disposed on the GaN layer or the AlGaN layer and is used to suppress current collapse effects. The passivation layer 11 is etched using the passivation layer etching method of the HEMT device provided in any of the embodiments of the first aspect described above, and a second etched structure 15 is formed on the etched surface 112 of the passivation layer 11, with its bottom communicating with the surface of the functional layer 10. The second etched structure 15 may be a trench or a via for filling electrode metal to form a metal electrode connecting the surface of the functional layer 10. The passivation layer 11 includes a dielectric layer; the dielectric layer may be, for example, a silicon nitride layer.

[0103] In a third aspect, embodiments of this application also provide a plasma processing apparatus for performing a passivation layer etching method for the HEMT device corresponding to the above embodiments to form the HEMT device containing a second etched structure corresponding to the above embodiments. The plasma processing apparatus includes inductively coupled plasma (ICP) etching equipment or capacitively coupled plasma (CCP) etching equipment, etc.

[0104] In summary, this embodiment of the application first uses a plasma dry etching process (first etching process) and performs a first etching of the passivation layer 11 at a relatively low first temperature. This utilizes the anisotropic etching characteristics to accurately control the sidewall etching angle and etching uniformity. Furthermore, the high etching rate of plasma etching allows for rapid removal of most of the passivation layer 11 while avoiding direct contact with the functional layer 10. Then, a maskless chemical dry etching process (third etching process) is used to perform a third etching of the remaining passivation layer 11 at a higher third temperature. This utilizes the gentle nature of chemical dry etching to achieve a gradual removal of the small amount of remaining passivation layer 11, effectively reducing etching damage to the surface of the functional layer 10 and better preserving the etching morphology formed after the first etching. Therefore, by combining plasma dry etching and chemical dry etching, the problems of difficult damage control when using plasma dry etching alone, and difficult morphology control when using chemical dry etching alone, are effectively solved.

[0105] The above are merely preferred embodiments of this application. These embodiments are not intended to limit the scope of protection of this application. Therefore, any equivalent changes made based on the description and drawings of this application should also be included within the scope of protection of this application.

Claims

1. A method for etching the passivation layer of a HEMT device, characterized in that, include: Provides a functional layer with a passivation layer on its surface; A sacrificial layer is formed on the surface of the passivation layer, and an opening is formed on the surface of the sacrificial layer; Using a first etching process, and through the opening, the exposed surface of the passivation layer is etched at a first temperature to form a first etched structure on the surface of the passivation layer, wherein the bottom of the first etched structure is at a distance greater than zero from the surface of the functional layer. Using a second etching process with a default mask, the sacrificial layer is etched at a second temperature to remove the sacrificial layer and expose the entire surface of the first etched structure and the surrounding passivation layer. Using a third etching process with a default mask, the surface of the passivation layer and the first etched structure are etched at a third temperature, causing the surface of the passivation layer and the first etched structure to conformally move toward the surface of the functional layer until a second etched structure evolved from the first etched structure is formed on the etched surface of the passivation layer, exposing the surface of the functional layer located at the bottom of the second etched structure. The first etching process and the second etching process include plasma dry etching process, and the third etching process includes chemical dry etching process. The first temperature, the second temperature and the third temperature are variable temperature that gradually increase and are sequentially connected.

2. The passivation layer etching method for HEMT devices according to claim 1, characterized in that, During the third etching, the third temperature is also used to perform a first treatment on the exposed surface of the functional layer to repair surface lattice damage.

3. The passivation layer etching method for HEMT devices according to claim 1, characterized in that, During the third etching, O2 is added to the etching gas to perform a second treatment on the surface of the exposed functional layer to reduce surface roughness.

4. The passivation layer etching method for HEMT devices according to claim 1, characterized in that, During the third etching process, N2 is added to the etching gas to perform a third treatment on the surface of the exposed functional layer in order to stabilize the surface stoichiometry.

5. The passivation layer etching method for HEMT devices according to claim 1, characterized in that, Also includes: After the third etching, hydrogen radicals are used to perform a fourth treatment on the exposed surface of the functional layer to clean the surface.

6. The passivation layer etching method for HEMT devices according to claim 1, characterized in that, The functional layer includes a GaN layer or an AlGaN layer; and / or, the passivation layer includes a dielectric layer; and / or, the sacrificial layer includes an organic layer.

7. The passivation layer etching method for HEMT devices according to claim 1, characterized in that, The first etching is performed using a first plasma obtained by exciting a first gas, the first gas including a first fluorine-based gas; the second etching is performed using a second plasma obtained by exciting a second gas, the second gas including an oxygen-based gas; the third etching is performed using a third plasma obtained by exciting a third gas, and neutral particles obtained after filtering out charged particles from the third plasma, the third gas including a second fluorine-based gas.

8. The passivation layer etching method for HEMT devices according to claim 7, characterized in that, The first fluorine-based gas includes CF4 and CHF3; and / or, the oxygen-based gas includes O2; and / or, the second fluorine-based gas includes CF4; and / or, the distance is 10% to 20% of the thickness of the passivation layer.

9. The passivation layer etching method for HEMT devices according to claim 1, characterized in that, The first temperature is a first variable temperature that gradually increases between 0°C and 150°C; and / or, the second temperature is a second variable temperature that gradually increases between 100°C and 250°C; and / or, the third temperature is a third variable temperature that gradually increases between 200°C and 300°C.

10. A HEMT device, comprising a passivation layer, characterized in that, The passivation layer is etched using the passivation layer etching method for HEMT devices as described in any one of claims 1-9.

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