Rf resistor calibration structure based on rdl process and method of manufacture

Abstract

The present application relates to the field of radio frequency integrated circuit and advanced semiconductor packaging technology, and particularly relates to a radio frequency resistor calibration structure and manufacturing method based on RDL process, comprising a main resistor module, a redundant resistor module, a laser trimming module, a shielding layer module and a temperature compensation module. The main resistor module is formed by sputtering of low-temperature coefficient metal alloy, and adopts a serpentine or interdigital geometry layout to reduce high-frequency skin effect; the redundant resistor module is driven by metal ion migration through a narrow neck structure and electromigration effect to compensate for photolithography line width deviation and sputtering thickness unevenness. The laser trimming module adjusts the conductive path through selective ablation or annealing by pulsed laser, and forms a closed-loop calibration combined with real-time feedback of the metal sensing electrode. The radio frequency circuit parameter consistency regulation at the packaging level is realized.

Description

Technical Field

[0001] This invention relates to the field of high-density semiconductor packaging and radio frequency component integrated calibration technology, and particularly to a radio frequency resistor calibration structure and manufacturing method based on RDL process. Background Technology

[0002] Redistribution Layer (RDL) technology is a micro-wiring technique used in semiconductor packaging. It constructs a multi-layered metal interconnect structure on the wafer surface through photolithography, metal deposition, and etching, enabling chip pad repositioning and signal path optimization to meet high-density integrated packaging requirements. The RF resistor calibration structure is a precision component designed for high-frequency signal characteristics. Through geometric topology optimization and material interface control, it maintains stable impedance characteristics within a specific frequency band. This structure integrates a temperature compensation layer and a shielding layer, effectively reducing the impact of parasitic capacitance and inductance on high-frequency signal integrity. Combined with the wiring precision of the RDL process, it enables consistent adjustment of RF circuit parameters at the packaging level, providing a reliable impedance matching reference for high-frequency applications such as millimeter-wave communication and radar systems.

[0003] In multilayer interconnect structures, linewidth deviations and etching rate variations during photolithography can cause resistor geometry to deviate from design values. Meanwhile, interface defects and thickness fluctuations in thin-film materials introduce additional resistance errors. The combined effect of these two factors directly impacts the impedance matching accuracy of RF circuits. For example, in high-frequency signal transmission scenarios, uncalibrated linewidth deviations can cause a systematic shift between the actual and theoretical resistance values ​​of RF resistors, leading to signal reflection or attenuation. Traditional single-point testing methods struggle to cover localized process fluctuations in mass production, resulting in yield losses. By employing laser fine-tuning and redundant structural design, the coupling effect of geometric parameters and material defects can be dynamically corrected at the packaging level, simultaneously improving the overall consistency of the resistor network. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a radio frequency resistor calibration structure and manufacturing method based on RDL process, which solves the problem of inaccurate resistance values ​​caused by limitations in photolithography precision and insufficient uniformity of thin film deposition in RDL process.

[0005] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0006] The first aspect is the RF resistor calibration structure based on RDL technology, including:

[0007] The main resistor module is made of a low temperature coefficient metal alloy material integrated onto the surface of the RDL interconnect layer by sputtering process. It adopts a serpentine or interdigitated geometric layout to reduce the high-frequency skin effect. The metal alloy material includes nickel-chromium alloy or tantalum nitride.

[0008] A redundant resistor module is connected in parallel or in series with the main resistor module through a metallized via. The metallized via penetrates the RDL interconnect layer and electrically connects the main resistor module and the redundant resistor module. The connection node of the redundant resistor module is provided with a narrow neck structure. By applying a directional current to induce an electromigration effect, metal ions are driven to migrate from the redundant resistor module to the main resistor module, compensating for the linewidth etching deviation caused by the photolithography process and the film thickness unevenness caused by the sputtering process.

[0009] The laser fine-tuning module covers the connection area of ​​the main resistor module and the redundant resistor module. It changes the conductive path by selectively ablation or annealing with pulsed laser. The laser fine-tuning module integrates a metal sensing electrode, which is embedded in the RDL interconnect layer and electrically connected to the main resistor module. It monitors the resistance change in real time and feeds it back to the laser parameter control system to dynamically adjust the laser energy density and scanning path.

[0010] A shielding layer module, covering the top of the main resistor module and the laser fine-tuning module, is composed of a silicon nitride or polyimide dielectric layer. The dielectric layer is formed by plasma-enhanced chemical vapor deposition process to suppress high-frequency electromagnetic coupling of adjacent metal wiring.

[0011] A temperature compensation module, located below the main resistor module, is composed of a titanium-tungsten composite layer. The titanium-tungsten composite layer is deposited between the RDL interconnect layer and the main resistor module by a sputtering process. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module, thereby reducing resistance drift caused by temperature changes.

[0012] Secondly, the method for fabricating an RF resistor calibration structure based on RDL technology provided by the present invention, applied to the RF resistor calibration structure, includes the following steps:

[0013] After the RDL bottom metal wiring is completed, a low temperature coefficient metal alloy thin film is deposited by magnetron sputtering. The metal alloy thin film is the nickel-chromium alloy or tantalum nitride. The substrate temperature is controlled at 200-300℃ and the sputtering power is 2-5kW to form the initial material layer of the main resistor module and the redundant resistor module.

[0014] The initial pattern of the main resistor and redundant resistor is defined by deep ultraviolet lithography. The metal alloy thin film area not protected by photoresist is removed by reactive ion etching process. The etching gas is a mixture of chlorine and argon with a volume ratio of 1:3 to 1:5 and an etching selectivity greater than 10:1, forming the resistor structure with a serpentine or interdigitated geometric layout.

[0015] The connection area between the main resistor module and the redundant resistor module is located by a confocal optical system as the resistance fine-tuning area. The initial resistance value is measured by the four-probe method, and a laser scanning path is generated based on the resistance deviation.

[0016] Adjust the pulsed laser energy density to 0.5-2 J / cm² and the scanning speed to 10-50 mm / s, ablate the resistive material in stages or induce local annealing to change the length or cross-sectional area of ​​the conductive path, and calibrate the resistance value of the main resistor module to the target threshold.

[0017] The resistance change is monitored in real time by the metal sensing electrode integrated into the laser fine-tuning module. The monitoring data is fed back to the laser parameter control system to dynamically adjust the laser energy density and scanning path until the resistance reaches the target threshold.

[0018] Furthermore, the method for fabricating a radio frequency resistor calibration structure based on RDL process according to the present invention further includes: performing secondary photolithography correction on the laser-trimmed resistor pattern, and using negative photoresist to cover the edge of the trimmed area to protect the calibrated conductive path, wherein the trimmed area is the connection area of ​​the main resistor module and the redundant resistor module.

[0019] Residual photoresist is removed by oxygen plasma ashing, reducing the roughness of the metal-resistor contact interface to the required high-frequency signal transmission level.

[0020] A directional current is applied across the redundant resistor module to induce electromigration through the Joule heating effect, driving metal atoms to migrate from the narrow neck structure of the redundant resistor module to the area where the linewidth of the main resistor module is not sufficiently etched. The narrow neck structure is the area defined at the connection node of the redundant resistor module.

[0021] A silicon nitride or polyimide shielding layer is deposited on top of the resistor structure using plasma-enhanced chemical vapor deposition to cover the main resistor module and the laser fine-tuning module in order to suppress high-frequency electromagnetic coupling.

[0022] A titanium-tungsten composite layer is sputtered beneath the resistive thin film. The coefficient of thermal expansion of the titanium-tungsten composite layer is matched with the metal alloy material of the main resistive module to form the temperature compensation module to reduce the temperature drift effect.

[0023] Furthermore, the method for fabricating an RF resistor calibration structure based on RDL technology according to the present invention further includes:

[0024] The edges of the fine-tuning area of ​​the laser-trimmed resistor pattern are locally developed, and the fine-tuning area is covered with negative photoresist to prevent over-etching caused by the reactive ion etching process.

[0025] Photoresist residue is removed by oxygen plasma ashing, and the roughness of the metal-resistor contact interface is optimized to meet the requirements of high-frequency signal transmission.

[0026] Reactive ion etching is used to correct the linewidth deviation in the metal-resistor contact area. The ratio of the chlorine and argon gas mixture and the etching power parameters are adjusted to match the serpentine or interdigitated geometry of the main resistor module.

[0027] Furthermore, in the method for fabricating an RF resistor calibration structure based on RDL technology described in this invention, the electromigration effect compensation includes:

[0028] A controllable current density is applied across the redundant resistor module, and the temperature of the narrow neck structure region of the redundant resistor module is raised to the metal atom migration threshold through the Joule heating effect.

[0029] Drive metal atoms to migrate directionally from the narrow neck structure of the redundant resistor module to the area where the linewidth etching of the main resistor module is insufficient, filling the linewidth deviation caused by the photolithography process and the lack of conductive paths caused by the uneven film thickness caused by the sputtering process.

[0030] The resistance change of the main resistor module is monitored in real time, and the density and duration of the applied current are dynamically adjusted according to the resistance change until the resistance of the main resistor module reaches the target compensation threshold.

[0031] Furthermore, the method for fabricating an RF resistor calibration structure based on RDL technology according to the present invention further includes:

[0032] During the wafer-level packaging stage, the resistor network of the calibration structure is tested in parallel using a multi-probe array to excite all the main resistor modules and redundant resistor modules.

[0033] The impedance matching parameters of each resistor element in the target high-frequency band of the RF resistor calibration structure are measured using a vector network analyzer to generate an impedance distribution spectrum.

[0034] Based on the impedance distribution spectrum, abnormal units that still have impedance mismatch exceeding the tolerance range after laser calibration and electromigration compensation are screened.

[0035] For the selected abnormal units, the top metal interconnect of the RDL is completed by the electroplating copper filling process of the metallized vias, and the depth-to-width ratio of the vias is controlled to be less than the three to one ratio limited by the structure design, so as to reduce the impedance change of the signal transmission path.

[0036] Furthermore, in the method for fabricating an RF resistor calibration structure based on RDL technology described in this invention, the parallel testing includes:

[0037] The sixteen resistor units of the calibration structure are simultaneously excited by a four-by-four probe array, wherein the resistor units are the main resistor module and the redundant resistor module.

[0038] The scattering parameters of each unit are measured in the millimeter-wave communication band of the radio frequency resistor calibration structure, and the real and imaginary parts of the impedance corresponding to the high-frequency signal transmission requirements are extracted.

[0039] Calculate the matching deviation value based on the real and imaginary parts of the impedance data, and filter out abnormal units whose deviation values ​​exceed the target threshold tolerance range;

[0040] The abnormal unit is corrected by calling the laser fine-tuning module or the electromigration compensation process until the impedance matching parameters meet the consistency requirements of the RF circuit parameters.

[0041] Beneficial effects of this invention;

[0042] This invention utilizes the synergistic effect of redundant resistor modules and electromigration compensation mechanisms to dynamically correct linewidth deviations caused by photolithography and thin film thickness inhomogeneities caused by sputtering, achieving closed-loop compensation for resistance geometry parameters and material defects. A laser fine-tuning module, combined with a real-time feedback mechanism from a metal induction electrode, adjusts the conductive path through selective ablation or annealing, improving resistance calibration accuracy. A shielding layer and temperature compensation module suppress high-frequency electromagnetic coupling and temperature drift effects, enhancing the environmental stability of the RF resistor. Wafer-level parallel testing and electroplated copper filling processes synergistically optimize impedance matching consistency, making it suitable for impedance control requirements of RF circuits in high-density packaging scenarios. Attached Figure Description

[0043] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0044] Figure 1 A flowchart illustrating the manufacturing method of an RF resistor calibration structure based on RDL technology provided in an embodiment of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The technical solutions provided by various embodiments of this invention will be described in detail below with reference to the accompanying drawings. To better understand the objectives of this invention, it will be described in further detail below.

[0046] In a first aspect, the radio frequency resistor calibration structure based on RDL technology provided by the present invention includes:

[0047] The main resistor module is made of a low temperature coefficient metal alloy material integrated onto the surface of the RDL interconnect layer by sputtering process. It adopts a serpentine or interdigitated geometric layout to reduce the high-frequency skin effect. The metal alloy material includes nickel-chromium alloy or tantalum nitride.

[0048] A redundant resistor module is connected in parallel or in series with the main resistor module through a metallized via. The metallized via penetrates the RDL interconnect layer and electrically connects the main resistor module and the redundant resistor module. The connection node of the redundant resistor module is provided with a narrow neck structure. By applying a directional current to induce an electromigration effect, metal ions are driven to migrate from the redundant resistor module to the main resistor module, compensating for the linewidth etching deviation caused by the photolithography process and the film thickness unevenness caused by the sputtering process.

[0049] The laser fine-tuning module covers the connection area of ​​the main resistor module and the redundant resistor module. It changes the conductive path by selectively ablation or annealing with pulsed laser. The laser fine-tuning module integrates a metal sensing electrode, which is embedded in the RDL interconnect layer and electrically connected to the main resistor module. It monitors the resistance change in real time and feeds it back to the laser parameter control system to dynamically adjust the laser energy density and scanning path.

[0050] A shielding layer module, covering the top of the main resistor module and the laser fine-tuning module, is composed of a silicon nitride or polyimide dielectric layer. The dielectric layer is formed by plasma-enhanced chemical vapor deposition process to suppress high-frequency electromagnetic coupling of adjacent metal wiring.

[0051] A temperature compensation module, located below the main resistor module, is composed of a titanium-tungsten composite layer. The titanium-tungsten composite layer is deposited between the RDL interconnect layer and the main resistor module by a sputtering process. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module, thereby reducing resistance drift caused by temperature changes.

[0052] In the RF resistor calibration structure based on RDL technology, the main resistor module is integrated onto the surface of the RDL interconnect layer using a low-temperature-coefficient metal alloy sputtering process. Its serpentine or interdigitated geometry effectively reduces the impact of the high-frequency skin effect on impedance characteristics by increasing the current path length and cross-sectional area ratio. The metal alloy material is selected from nickel-chromium alloys or tantalum nitride. A uniform thin film is formed using magnetron sputtering under controlled substrate temperature and power. The initial pattern is defined by deep ultraviolet lithography and reactive ion etching processes. A mixture of chlorine and argon gas is used for etching to ensure steep sidewalls and reduce high-frequency losses.

[0053] The redundant resistor module is connected in parallel or series with the main resistor module through metallized vias. These vias penetrate the RDL interconnect layer and complete the electrical connection between the main and redundant resistors. A narrow neck structure is designed at the connection nodes of the redundant resistor module. By applying a directional current to induce electromigration, metal ions migrate from the redundant resistor region to the main resistor region, compensating for linewidth deviations caused by photolithography and uneven film thickness caused by sputtering. The narrow neck structure locally heats the metal atom migration threshold through Joule heating, allowing the directional migration of metal atoms to fill the conductive path gaps in the main resistor module. Combined with real-time resistance monitoring and dynamic adjustment of current density and duration, closed-loop correction of resistance deviations is achieved.

[0054] The laser fine-tuning module covers the connection area of ​​the main resistor and redundant resistor modules. It uses pulsed laser selective ablation or annealing to change the length or cross-sectional area of ​​the conductive path. A metal sensing electrode is embedded in the RDL interconnect layer and electrically connected to the main resistor module, monitoring resistance changes in real time and feeding them back to the laser parameter control system. The fine-tuning area is located using a confocal optical system, and the initial resistance is measured using a four-probe method to generate the laser scanning path. Resistance calibration is achieved through step-by-step ablation or annealing. The dynamic adjustment of laser energy density and scanning speed, linked with the feedback data from the metal sensing electrode, forms a closed-loop control mechanism for resistance calibration.

[0055] The shielding layer module deposits a silicon nitride or polyimide dielectric layer on top of the resistor structure using plasma-enhanced chemical vapor deposition (PECVD), covering the main resistor and laser trimming area to suppress high-frequency electromagnetic coupling between adjacent metal wirings. Interface defect control of the dielectric layer is achieved by optimizing deposition parameters, reducing the impact of parasitic capacitance and inductance on signal integrity. The temperature compensation module, located below the main resistor module, deposits a titanium-tungsten composite layer using sputtering. Its coefficient of thermal expansion matches the main resistor's metal alloy material, reducing resistance drift caused by temperature changes through thermal stress compensation. The interface bonding strength between the titanium-tungsten composite layer, the RDL interconnect layer, and the main resistor module is optimized through process parameters to achieve long-term stability.

[0056] Secondly, please refer to Figure 1 The present invention provides a method for fabricating an RF resistor calibration structure based on RDL technology, which is applied to the RF resistor calibration structure and includes the following steps:

[0057] Step 1: After the RDL bottom metal wiring is completed, a low temperature coefficient metal alloy thin film is deposited by magnetron sputtering. The metal alloy thin film is the nickel-chromium alloy or tantalum nitride. The substrate temperature is controlled at 200-300℃ and the sputtering power is 2-5 kW to form the initial material layer of the main resistor module and the redundant resistor module.

[0058] Step 2: Define the initial pattern of the main resistor and redundant resistor using deep ultraviolet lithography. Remove the metal alloy thin film area not protected by photoresist using reactive ion etching process. The etching gas is a mixture of chlorine and argon with a volume ratio of 1:3 to 1:5 and an etching selectivity greater than 10:1 to form the resistor structure with a serpentine or interdigitated geometric layout.

[0059] Step 3: Locate the connection area of ​​the main resistor module and the redundant resistor module as the resistance fine-tuning area using the confocal optical system, measure the initial resistance value using the four-probe method, and generate a laser scanning path based on the resistance deviation.

[0060] Step 4: Adjust the pulsed laser energy density to 0.5-2 J / cm² and the scanning speed to 10-50 mm / s, ablate the resistive material in stages or induce local annealing to change the conductive path length or cross-sectional area, and calibrate the resistance value of the main resistor module to the target threshold.

[0061] Step 5: The resistance change is monitored in real time by the metal sensing electrode integrated into the laser fine-tuning module, and the monitoring data is fed back to the laser parameter control system to dynamically adjust the laser energy density and scanning path until the resistance reaches the target threshold.

[0062] In the RDL-based method for fabricating RF resistor calibration structures, after completing the RDL bottom metal wiring, a low-temperature coefficient metal alloy thin film is deposited using magnetron sputtering. Nickel-chromium alloy or tantalum nitride is selected as the main material, and a uniform initial material layer is formed by controlling the substrate temperature and sputtering power. This process optimizes the film density by adjusting the magnetic field strength and the target distance, providing a stable electrical performance foundation for the subsequent resistor structure.

[0063] Subsequently, deep ultraviolet lithography was used to define the initial patterns of the main resistor and redundant resistors. A high-resolution mask was then used to expose and develop the photoresist, forming a precise pattern protection area. Unprotected metal alloy thin film areas were removed using reactive ion etching. The mixing ratio of chlorine and argon in the etching gas was adjusted to control the ion bombardment intensity and chemical reaction rate. Combined with etching selectivity, the sidewall steepness was controlled, forming a serpentine or interdigitated geometric resistor structure to reduce the impact of the high-frequency skin effect.

[0064] A confocal optical system is used to precisely locate the connection area between the main resistor module and the redundant resistor module, which is then used as the resistor fine-tuning area. The initial resistance value is measured using a four-probe method. A laser scanning path is generated based on the resistance deviation. The scanning path planning is based on the resistor geometry and resistance distribution differences, ensuring that the laser energy is focused on the conductive path area requiring correction. The pulsed laser energy density and scanning speed are adjusted, and the effective conductive path length or cross-sectional area of ​​the resistor is changed through selective ablation or local annealing. The resistance value is iteratively calibrated step-by-step to the target range.

[0065] The metal sensing electrode integrated into the laser fine-tuning module is embedded in the RDL interconnect layer and electrically connected to the main resistor module to monitor resistance changes in real time. The monitored data is transmitted to the laser parameter control system via a closed-loop feedback system to dynamically adjust laser output parameters, including energy density gradient adjustment and scan path optimization. The feedback mechanism triggers immediate correction of laser parameters by comparing the real-time resistance value with the target threshold, forming a closed-loop control link for resistance calibration.

[0066] Synergistic effects are achieved between each step through the linkage of process parameters: the thin film uniformity of the sputtering process provides the basis for photolithography and etching; the geometric accuracy of photolithography and etching directly affects the calibration efficiency of laser fine-tuning; the real-time feedback of the metal sensing electrode and the dynamic adjustment of laser parameters form a closed loop for process fluctuation compensation.

[0067] Specifically, the method for fabricating a radio frequency resistor calibration structure based on RDL process according to the present invention further includes: performing secondary photolithography correction on the laser-trimmed resistor pattern, and using negative photoresist to cover the edge of the trimmed area to protect the calibrated conductive path, wherein the trimmed area is the connection area of ​​the main resistor module and the redundant resistor module.

[0068] Residual photoresist is removed by oxygen plasma ashing, reducing the roughness of the metal-resistor contact interface to the required high-frequency signal transmission level.

[0069] A directional current is applied across the redundant resistor module to induce electromigration through the Joule heating effect, driving metal atoms to migrate from the narrow neck structure of the redundant resistor module to the area where the linewidth of the main resistor module is not sufficiently etched. The narrow neck structure is the area defined at the connection node of the redundant resistor module.

[0070] A silicon nitride or polyimide shielding layer is deposited on top of the resistor structure using plasma-enhanced chemical vapor deposition to cover the main resistor module and the laser fine-tuning module in order to suppress high-frequency electromagnetic coupling.

[0071] A titanium-tungsten composite layer is sputtered beneath the resistive thin film. The coefficient of thermal expansion of the titanium-tungsten composite layer is matched with the metal alloy material of the main resistive module to form the temperature compensation module to reduce the temperature drift effect.

[0072] In the RDL-based method for fabricating RF resistor calibration structures, during the secondary photolithography correction of the laser-trimmed resistor pattern, negative photoresist is used to cover the edges of the trimmed area. A protective layer is formed through exposure and development processes to prevent subsequent processes from damaging the calibrated conductive path. The trimmed area is defined as the connection region between the main resistor module and the redundant resistor module, which has undergone laser ablation or annealing. The photoresist coverage is limited by mask design to avoid over-etching that could cause offsets in the resistor's geometric parameters.

[0073] When residual photoresist is removed via oxygen plasma ashing, oxygen free radicals react with the photoresist residue to generate volatile gases. The ashing time and power parameters are matched to the interface roughness control requirements. Roughness optimization of the metal-resistor interface is achieved by adjusting the ion bombardment intensity of the ashing process, reducing interface contact resistance and meeting the surface flatness requirements for high-frequency signal transmission.

[0074] When a directional current is applied across the redundant resistor module, a Joule heating effect is induced by a controllable current density, causing the narrow neck region of the redundant resistor module to locally heat up to the metal atom migration threshold. The narrow neck structure, through geometric constraints, concentrates the current density, driving metal atoms to migrate along the electric field gradient from the redundant resistor region to areas where the main resistor module's linewidth etching is insufficient, filling the gaps in conductive paths caused by photolithography deviations or sputtering thickness fluctuations. The migration path and the conductive path of the main resistor module are electrically connected through metallized vias. Resistance changes are monitored in real time using a four-probe method and fed back to the current parameter adjustment system.

[0075] When a silicon nitride or polyimide shielding layer is deposited on top of a resistive structure using plasma-enhanced chemical vapor deposition (PECVD), the reactive gas ionizes under a high-frequency electric field to generate active groups. During deposition, the gas ratio and substrate temperature are controlled to form a low-defect dielectric layer. The shielding layer covers the main resistor module and the laser-trimmed area, reducing parasitic effects in high-frequency signal transmission by suppressing capacitive coupling and inductive crosstalk between adjacent metal wirings. The uniformity of the dielectric layer thickness is achieved through the coordinated control of plasma power and deposition rate, ensuring electromagnetic shielding performance and structural reliability.

[0076] When sputtering a titanium-tungsten composite layer beneath the resistive thin film, the titanium layer acts as an adhesion layer to enhance interfacial bonding strength, while the tungsten layer matches the metal alloy material of the main resistor module through its low coefficient of thermal expansion. During the composite layer deposition process, the crystal structure is optimized by gradient control of the substrate temperature and sputtering power to offset the thermal stress differences caused by temperature variations. The interface between the titanium-tungsten composite layer, the RDL interconnect layer, and the main resistor module is annealed to reduce lattice defects and mitigate the resistance temperature drift effect.

[0077] Specifically, the method for fabricating an RF resistor calibration structure based on RDL technology according to the present invention further includes:

[0078] The edges of the fine-tuning area of ​​the laser-trimmed resistor pattern are locally developed, and the fine-tuning area is covered with negative photoresist to prevent over-etching caused by the reactive ion etching process.

[0079] Photoresist residue is removed by oxygen plasma ashing, and the roughness of the metal-resistor contact interface is optimized to meet the requirements of high-frequency signal transmission.

[0080] Reactive ion etching is used to correct the linewidth deviation in the metal-resistor contact area. The ratio of the chlorine and argon gas mixture and the etching power parameters are adjusted to match the serpentine or interdigitated geometry of the main resistor module.

[0081] In the RDL-based method for fabricating RF resistor calibration structures, when locally developing the edges of the fine-tuning area of ​​the laser-trimmed resistor pattern, a negative photoresist is used to cover the fine-tuning area. The photoresist coverage is limited by mask design to avoid over-etching of the calibrated conductive path by reactive ion etching. The exposure and development process of the negative photoresist selectively cures the non-fine-tuning area using an ultraviolet light source, retaining a protective layer in the fine-tuning area, precisely controlling the etched area boundaries, and maintaining the geometric accuracy of the resistor structure.

[0082] When residual photoresist is removed by oxygen plasma ashing, oxygen free radicals react with the organic matter in the photoresist to generate carbon dioxide and water vapor. The ion bombardment intensity and time parameters of the ashing process are matched to the interface roughness optimization requirements. The roughness of the metal-resistor contact interface is reduced by adjusting the plasma power and gas flow rate, thereby reducing the uneven current distribution caused by surface irregularities and meeting the interface flatness requirements for high-frequency signal transmission.

[0083] When using reactive ion etching (RIE) to correct linewidth deviations in the metal-resistor contact area, the ratio of chlorine to argon gas is adjusted to balance the etching rate and selectivity. Chlorine removes the metal alloy material through a chemical reaction, while argon enhances the anisotropy of the sidewalls through physical bombardment. The etching power parameters are optimized by matching the serpentine or interdigitated geometry of the main resistor module to control the sidewall steepness and linewidth uniformity. The etched conductive path's geometric parameters are verified using a confocal optics system to ensure consistency with the laser-trimmed resistance calibration target.

[0084] Specifically, the method for fabricating a radio frequency resistor calibration structure based on RDL technology according to the present invention includes electromigration effect compensation comprising:

[0085] A controllable current density is applied across the redundant resistor module, and the temperature of the narrow neck structure region of the redundant resistor module is raised to the metal atom migration threshold through the Joule heating effect.

[0086] Drive metal atoms to migrate directionally from the narrow neck structure of the redundant resistor module to the area where the linewidth etching of the main resistor module is insufficient, filling the linewidth deviation caused by the photolithography process and the lack of conductive paths caused by the uneven film thickness caused by the sputtering process.

[0087] The resistance change of the main resistor module is monitored in real time, and the density and duration of the applied current are dynamically adjusted according to the resistance change until the resistance of the main resistor module reaches the target compensation threshold.

[0088] In the RDL-based method for fabricating RF resistor calibration structures, electromigration compensation is achieved by applying a controllable current density across the redundant resistor module. This, through the Joule heating effect, raises the temperature of the narrow-neck structure region to the metal atom migration threshold. The narrow-neck structure concentrates the current density through geometric constraints, and the local temperature increase activates the directional migration ability of metal atoms. The migration direction is driven by the electric field gradient, and the metal atoms move along the connection path between the redundant resistor module and the main resistor module.

[0089] During the migration of metal atoms, the migration path forms an electrical connection with the main resistor module through metallized vias, filling the gaps caused by linewidth etching deviations in the main resistor module due to photolithography and uneven film thickness caused by sputtering. During migration, metal atoms diffuse from the narrow neck region of the redundant resistor module to the areas lacking conductive paths in the main resistor module, supplementing volume defects in the conductive material and restoring the continuity and cross-sectional area uniformity of the conductive paths. The migration rate is adjusted by a gradient in the current density to match the process deviation compensation requirements.

[0090] When monitoring the resistance changes of the main resistor module in real time, resistance data is collected using a four-probe method or a metal sensing electrode integrated into the interconnect layer, and the resistance changes are fed back to the current control system. Based on a preset target compensation threshold, the density and duration of the applied current are dynamically adjusted to form a closed-loop correction mechanism. When the resistance reaches the threshold, the current is terminated to avoid excessive migration that could damage the structure of the redundant resistor module.

[0091] Specifically, the method for fabricating an RF resistor calibration structure based on RDL technology according to the present invention further includes:

[0092] During the wafer-level packaging stage, the resistor network of the calibration structure is tested in parallel using a multi-probe array to excite all the main resistor modules and redundant resistor modules.

[0093] The impedance matching parameters of each resistor element in the target high-frequency band of the RF resistor calibration structure are measured using a vector network analyzer to generate an impedance distribution spectrum.

[0094] Based on the impedance distribution spectrum, abnormal units that still have impedance mismatch exceeding the tolerance range after laser calibration and electromigration compensation are screened.

[0095] For the selected abnormal units, the top metal interconnect of the RDL is completed by the electroplating copper filling process of the metallized vias, and the depth-to-width ratio of the vias is controlled to be less than the three to one ratio limited by the structure design, so as to reduce the impedance change of the signal transmission path.

[0096] In the RDL-based method for fabricating RF resistor calibration structures, during the wafer-level packaging stage, when testing the resistor network in parallel using a multi-probe array, the probe array layout matches the physical positions of the main resistor module and redundant resistor modules of the calibration structure. Test signals are synchronously applied to all modules via multiple signal excitations. The test signal frequency range covers the target high-frequency band, and signal reflection is reduced through probe impedance matching circuits to obtain the steady-state response data of each resistor unit.

[0097] When measuring impedance matching parameters using a vector network analyzer, the analyzer is calibrated to a wafer-level testing environment. Based on scattering parameters, the real and imaginary parts of the impedance of each resistive element in the target frequency band are extracted. The data processing algorithm integrates the multi-point measurement results into an impedance distribution map. The map visually reflects the impedance matching deviation through color gradients or numerical distributions, identifying local high-loss or abnormal reflection areas.

[0098] When screening abnormal cells based on impedance distribution patterns, the preset tolerance range is set based on RF circuit design specifications. The algorithm marks cells that exceed the tolerance range by comparing the impedance values ​​of each cell with the theoretical model. The abnormal cell screening logic combines spatial distribution characteristics to distinguish between random deviations caused by process fluctuations and systematic design defects, focusing on target areas that require secondary correction.

[0099] For the identified anomalous units, when correcting impedance abrupt changes through a copper plating filling process with metallized vias, the via location and the conductive path of the anomalous unit are correlated through design rules. The copper plating filling process controls the current density and plating solution flow rate, optimizes the copper layer density to reduce resistivity, and controls the via aspect ratio by adjusting plating time and voltage parameters. The via aspect ratio limits the signal transmission path optimization requirements based on the structural design, reducing impedance discontinuities of high-frequency signals at the via interface.

[0100] Specifically, the method for fabricating an RF resistor calibration structure based on RDL technology according to the present invention includes the following parallel testing:

[0101] The sixteen resistor units of the calibration structure are simultaneously excited by a four-by-four probe array, wherein the resistor units are the main resistor module and the redundant resistor module.

[0102] The scattering parameters of each unit are measured in the millimeter-wave communication band of the radio frequency resistor calibration structure, and the real and imaginary parts of the impedance corresponding to the high-frequency signal transmission requirements are extracted.

[0103] Calculate the matching deviation value based on the real and imaginary parts of the impedance data, and filter out abnormal units whose deviation values ​​exceed the target threshold tolerance range;

[0104] The abnormal unit is corrected by calling the laser fine-tuning module or the electromigration compensation process until the impedance matching parameters meet the consistency requirements of the RF circuit parameters.

[0105] In the RDL-based method for fabricating RF resistor calibration structures, a parallel testing step simultaneously excites sixteen resistor units in both the main resistor module and the redundant resistor module using a four-by-four probe array. The probe array layout matches the physical arrangement of the calibration structure. High-frequency excitation signals are applied synchronously through multiple signal sources, covering the millimeter-wave communication frequency band. The contact impedance between the probes and the resistor units is compensated using a calibration algorithm, reducing errors introduced by the testing system and improving the signal-to-noise ratio of the measurement signal.

[0106] When measuring scattering parameters in the millimeter-wave band, the vector network analyzer and probe array are connected via a coaxial cable. Before testing, the system is calibrated using a standard impedance calibrator to eliminate phase shifts and amplitude distortions in the test path. The extraction of scattering parameters is based on the amplitude and phase information of the incident and reflected waves, which are converted into impedance real and imaginary part data through Fourier transform or equivalent circuit model to generate impedance distribution maps for each unit.

[0107] The matching deviation value is calculated by comparing the real and imaginary parts of the impedance with a preset theoretical model. The deviation value is defined as the Euclidean distance or normalized difference between the measured impedance and the theoretical value. The screening logic is based on a tolerance range threshold, marking abnormal units that exceed the threshold, and combining spatial distribution characteristics to distinguish between local process deviations and systemic design defects, prioritizing the correction of critical units on the high-frequency signal path.

[0108] When the laser fine-tuning module is invoked for the screened abnormal units, the conductive path ablation or local annealing mode is selected according to the impedance deviation type. The target area is located through a confocal optical system, and the laser parameters are adjusted for secondary fine-tuning. If the deviation is caused by uneven material thickness, a directional current is applied to the redundant resistor module through an electromigration compensation process to drive metal atoms to migrate and fill the defects. The corrected units need to undergo impedance testing again until the matching parameters meet the consistency requirements of the RF circuit.

[0109] This invention addresses the linewidth deviation problem caused by insufficient photolithography precision through redundant resistor modules and an electromigration effect compensation mechanism. The redundant resistor modules form a parallel or series structure with the main resistor module via metallized vias. A narrow neck structure is set at the connection node, and a directional current is applied to induce metal atom migration. During migration, metal ions fill the missing conductive paths of the main resistor module from the redundant region, correcting linewidth etching deviations during the photolithography development stage and uneven film thickness caused by the sputtering process, thus achieving dynamic compensation for geometric parameters and material defects.

[0110] The laser fine-tuning module covers the connection area between the main resistor and redundant resistors, using pulsed laser selective ablation or annealing to alter the length and cross-sectional area of ​​the conductive path. An integrated metal sensing electrode monitors resistance changes in real time, feeding back to the laser parameter control system to dynamically adjust the energy density and scanning path, forming a closed-loop control for resistance calibration. This mechanism, combined with a secondary photolithography correction process, optimizes the contact interface roughness, reduces high-frequency signal transmission loss, and improves resistance calibration accuracy.

[0111] The shielding module forms a silicon nitride or polyimide dielectric layer on top of the resistor structure using plasma-enhanced chemical vapor deposition (PECVD) to suppress high-frequency electromagnetic coupling between adjacent metal wirings. The temperature compensation module sputters a titanium-tungsten composite layer beneath the resistor film; its coefficient of thermal expansion matches that of the main resistor material, offsetting resistance drift caused by temperature changes. Combined with wafer-level parallel testing and copper plating filling processes to correct impedance abrupt changes, consistent control of RF circuit parameters at the package level is ultimately achieved.

Claims

1. A radio frequency resistor calibration structure based on a RDL process, characterized in that, Comprising: a main resistance module, integrated on the surface of the RDL interconnection layer by sputtering process with low-temperature coefficient metal alloy material, adopting a serpentine or interdigital geometric layout to reduce high-frequency skin effect, the metal alloy material including nickel-chromium alloy or tantalum nitride; a redundant resistance module, connected in parallel or series with the main resistance module through a metallized via, the metallized via penetrating through the RDL interconnection layer and electrically connecting the main resistance module and the redundant resistance module, a narrow neck structure being provided at the connection node of the redundant resistance module, and a directed current being applied to induce electromigration effect to drive metal ions to migrate from the redundant resistance module to the main resistance module, thereby compensating for the line width etching deviation caused by the photolithography process and the film thickness unevenness caused by the sputtering process; a laser fine-tuning module, covering the connection area of the main resistance module and the redundant resistance module, and changing the conductive path by selective ablation or annealing of pulsed laser, the laser fine-tuning module integrating a metal sensing electrode embedded in the RDL interconnection layer and electrically connected with the main resistance module, real-time monitoring of resistance value change and feedback to the laser parameter control system, dynamic adjustment of laser energy density and scanning path; a shielding layer module, covering the top of the main resistance module and the laser fine-tuning module, composed of silicon nitride or polyimide dielectric layer, the dielectric layer being formed by plasma enhanced chemical vapor deposition process, and inhibiting high-frequency electromagnetic coupling of adjacent metal wiring; a temperature compensation module, provided below the main resistance module, composed of titanium-tungsten composite layer, the titanium-tungsten composite layer being deposited between the RDL interconnection layer and the main resistance module by sputtering process, the thermal expansion coefficient of the titanium-tungsten composite layer matching the metal alloy material of the main resistance module, and reducing resistance drift caused by temperature change.

2. The method for preparing the radio frequency resistor calibration structure based on the RDL process, applied to the radio frequency resistor calibration structure of claim 1, characterized in that, Comprising the following steps: after the completion of the RDL bottom layer metal wiring, depositing a low-temperature coefficient metal alloy thin film by magnetron sputtering process, the metal alloy thin film being the nickel-chromium alloy or tantalum nitride, and controlling the substrate temperature to be 200-300℃ and the sputtering power to be 2-5 kW to form the initial material layer of the main resistance module and the redundant resistance module; defining the initial pattern of the main resistance and the redundant resistance by deep ultraviolet lithography technology, removing the metal alloy thin film area not protected by photoresist by reactive ion etching process, the etching gas being chlorine and argon mixed gas with a volume ratio of 1:3 to 1:5, the etching selectivity being greater than 10:1, and forming the resistance structure with serpentine or interdigital geometric layout; positioning the connection area of the main resistance module and the redundant resistance module as the resistance fine-tuning area by confocal optical system, measuring the initial resistance value by four-probe method, and generating laser scanning path based on resistance value deviation; adjusting the pulsed laser energy density to be 0.5-2 J / cm² and the scanning speed to be 10-50 mm / s, step-by-step ablation of resistance material or induction of local annealing to change the length or cross-sectional area of the conductive path, and calibrating the resistance value of the main resistance module to the target threshold value; real-time monitoring of resistance value change by the metal sensing electrode integrated in the laser fine-tuning module, feedback of the monitoring data to the laser parameter control system, and dynamic adjustment of laser energy density and scanning path until the resistance value reaches the target threshold value.

3. The method of claim 2, wherein the RDL process based radio frequency resistor calibration structure preparation method further comprises: Also included are: Secondary photoetching correction is performed on the laser fine-tuned resistance pattern, and negative photoresist is used to cover the edge of the fine-tuning area to protect the calibrated conductive path. The fine-tuning area is the connection area of the main resistance module and the redundant resistance module. Oxygen plasma ashing is used to remove residual photoresist, and the roughness of the metal-resistance contact interface is reduced to meet the high-frequency signal transmission requirements. A controllable current density is applied across the redundant resistance module, and the temperature of the narrow neck structure area of the redundant resistance module is raised to the metal atom migration threshold value through the Joule heating effect. Metal atoms are driven to migrate from the narrow neck structure of the redundant resistance module to the line width etching insufficient area of the main resistance module, filling the line width deviation caused by the photoetching process and the missing conductive path caused by the uneven film thickness of the sputtering process. A silicon nitride or polyimide shielding layer is deposited on the top of the resistance structure through a plasma-enhanced chemical vapor deposition process to cover the main resistance module and the laser fine-tuning module to suppress high-frequency electromagnetic coupling.

4. The method of claim 3, wherein the RDL process based radio frequency resistor calibration structure fabrication method further comprises: A titanium-tungsten composite layer is sputtered below the resistance film, and the thermal expansion coefficient of the titanium-tungsten composite layer matches that of the metal alloy material of the main resistance module to form the temperature compensation module to reduce the temperature drift effect. Also included are: Local development is performed on the edge of the fine-tuning area of the laser fine-tuned resistance pattern, and negative photoresist is used to cover the fine-tuning area to prevent excessive etching caused by the reactive ion etching process. Oxygen plasma ashing is used to remove photoresist residues, and the roughness of the metal-resistance contact interface is optimized to meet the high-frequency signal transmission requirements.

5. The method of claim 4, wherein the RDL process based radio frequency resistor calibration structure fabrication method further comprises: The reactive ion etching process is used to correct the line width deviation of the metal-resistance contact area, and the proportion of chlorine gas and argon gas and the etching power parameters are adjusted to match the serpentine or interdigital geometry of the main resistance module. The electromigration effect compensation includes: A controllable current density is applied across the redundant resistance module, and the temperature of the narrow neck structure area of the redundant resistance module is raised to the metal atom migration threshold value through the Joule heating effect. Metal atoms are driven to migrate from the narrow neck structure of the redundant resistance module to the line width etching insufficient area of the main resistance module, filling the line width deviation caused by the photoetching process and the missing conductive path caused by the uneven film thickness of the sputtering process.

6. The method of claim 5, wherein the RDL process based radio frequency resistor calibration structure fabrication method further comprises: The resistance value of the main resistance module is monitored in real time, and the density and duration of the applied current are dynamically adjusted according to the resistance value change until the resistance value of the main resistance module reaches the target compensation threshold. Also included are: During the wafer-level packaging stage, the resistance network of the calibration structure is tested in parallel through a multi-probe array, and all the main resistance modules and redundant resistance modules are excited. The impedance matching parameters of each resistance unit in the target high-frequency band of the RF resistor calibration structure are measured by a vector network analyzer to generate an impedance distribution map. According to the impedance distribution map, abnormal units that still have impedance mismatch beyond the tolerance range after laser calibration and electromigration compensation are screened out.

7. The method of claim 6, wherein the RDL process based radio frequency resistor calibration structure fabrication method further comprises: For the screened abnormal units, the RDL top layer metal interconnection is completed through the copper plating filling process of the metallized via, and the via aspect ratio is controlled to be less than three to one as limited by the structure design to reduce the impedance discontinuity of the signal transmission path. The parallel test includes: The sixteen resistance units of the calibration structure are simultaneously excited by a four-by-four probe array, the resistance units being the main resistance module and the redundant resistance module; The scattering parameters of each unit are measured in the millimeter wave communication frequency band of the radio frequency resistor calibration structure, and the impedance real part and imaginary part data corresponding to the high frequency signal transmission requirement are extracted; The matching deviation value is calculated according to the impedance real part and imaginary part data, and the abnormal unit whose deviation value exceeds the target threshold tolerance range is screened out; The laser fine tuning module or the electromigration compensation process is called for secondary correction of the abnormal unit until the impedance matching parameters meet the consistency requirements of the radio frequency circuit parameters.

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