Radio frequency resistor calibration structure based on RDL process and manufacturing method

Abstract

The invention relates to the technical field of radio frequency integrated circuits and advanced semiconductor packaging, in particular to a radio frequency resistor calibration structure based on an RDL process and a manufacturing method, and the radio frequency resistor calibration structure comprises a main resistor module, a redundant resistor module, a laser fine tuning module, a shielding layer module and a temperature compensation module. The main resistor module is sputtered into a film through a low-temperature coefficient metal alloy, and the high-frequency skin effect is reduced by adopting a snakelike or interdigital geometric layout; and the redundant resistor module drives metal ions to migrate through a narrow-neck structure and an electromigration effect, and compensates photoetching line width deviation and uneven sputtering thickness. The laser fine tuning module adjusts a conductive path through selective ablation or annealing of pulse laser, and forms closed-loop calibration in combination with real-time feedback of the metal induction electrode. And the consistency regulation and control of radio frequency circuit parameters of a packaging level are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of high-density semiconductor packaging and radio frequency component integrated calibration, and in particular to a radio frequency resistor calibration structure and a manufacturing method based on an RDL process. Background Art

[0002] The RDL (Redistribution Layer) process is a micro-wiring technology used in semiconductor packaging. It constructs a multi-layer metal interconnect structure on the wafer surface through steps such as photolithography, metal deposition, and etching. This allows for the rearrangement of chip pad positions and optimization of signal paths, thereby adapting to the needs of high-density integrated packaging. 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 temperature compensation layers and shielding layers to effectively reduce the impact of parasitic capacitance and inductance on high-frequency signal integrity. Combined with the routing accuracy of the RDL process, it enables consistent adjustment of RF circuit parameters at the packaging level, providing a reliable impedance matching benchmark for high-frequency applications such as millimeter-wave communications and radar systems.

[0003] In multi-layer interconnect structures, line width deviations and etching rate differences during the photolithography and development stages will cause the resistor geometry to deviate from the design value, while interface defects and thickness fluctuations in thin film materials will introduce additional resistance errors. The combination of the two will directly affect the impedance matching accuracy of the RF circuit. For example, in high-frequency signal transmission scenarios, uncalibrated line width deviations may cause a systematic shift between the actual resistance and theoretical value of the RF resistor, resulting in signal reflection or attenuation, while traditional single-point testing methods are difficult to cover local process fluctuations in batch manufacturing, resulting in yield loss. Through laser fine-tuning and redundant structure design, the coupling effect of geometric parameters and material defects can be dynamically corrected at the packaging level, and the overall consistency of the resistor network can be simultaneously improved. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides an RF resistor calibration structure and manufacturing method based on the RDL process to solve the problem of resistance value inaccuracy caused by photolithography precision limitations and insufficient thin film deposition uniformity in the RDL process.

[0005] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows: First, the RF resistor calibration structure based on the RDL process includes: The main resistor module is integrated on the surface of the RDL interconnect layer through a sputtering process using a low temperature coefficient metal alloy material, and adopts a serpentine or interdigitated geometric layout to reduce high-frequency skin effect. The metal alloy material includes nickel-chromium alloy or tantalum nitride; A redundant resistor module is connected in parallel or in series with the main resistor module via a metallized through-hole. The metallized through-hole penetrates the RDL interconnect layer and electrically connects the main resistor module and the redundant resistor module. A narrow neck structure is provided at the connection node of the redundant resistor module. 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, thereby compensating for line width etching deviation caused by the photolithography process and uneven film thickness caused by the sputtering process. A laser trimming module covers the connection area between the main resistor module and the redundant resistor module, and changes the conductive path through pulsed laser selective ablation or annealing. The laser trimming module integrates metal sensing electrodes, which are embedded in the RDL interconnect layer and electrically connected to the main resistor module. The module monitors resistance changes in real time and feeds back to the laser parameter control system to dynamically adjust the laser energy density and scanning path. A shielding layer module, covering the top of the main resistance module and the laser trimming module, is composed of a silicon nitride or polyimide dielectric layer formed by a plasma-enhanced chemical vapor deposition process to suppress high-frequency electromagnetic coupling between adjacent metal wirings; The temperature compensation module is arranged below the main resistor module and 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 through a sputtering process. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module, reducing resistance drift caused by temperature changes.

[0006] In a second aspect, the present invention provides a method for preparing a radio frequency resistor calibration structure based on an RDL process, which is applied to the radio frequency resistor calibration structure and includes the following steps: After the RDL bottom metal wiring is completed, a low temperature coefficient metal alloy film is deposited by a magnetron sputtering process. The metal alloy film is the nickel-chromium alloy or tantalum nitride. The substrate temperature is controlled at 200-300°C and the sputtering power is controlled at 2-5kW to form the initial material layer of the main resistor module and the redundant resistor module. Deep ultraviolet lithography is used to define the initial patterns of the main resistor and the redundant resistor, and a reactive ion etching process is used to remove the metal alloy film area not protected by the photoresist. The etching gas is a mixture of chlorine and argon with a volume ratio of 1:3 to 1:5 and an etching selectivity ratio greater than 10:1, thereby forming the resistor structure having the serpentine or interdigitated geometric layout; Locating the connection area between the main resistor module and the redundant resistor module as a resistance fine-tuning area using a confocal optical system, measuring the initial resistance value using a four-probe method, and generating a laser scanning path based on the resistance deviation; Adjust the pulsed laser energy density to 0.5-2 J / cm² and the scanning speed to 10-50 mm / s, ablating the resistor material step by step or inducing local annealing to change the conductive path length or cross-sectional area, and calibrating the resistance value of the main resistor module to the target threshold; The metal sensing electrode integrated in the laser fine-tuning module monitors the resistance change in real time, feeds the monitoring data back to the laser parameter control system, and dynamically adjusts the laser energy density and scanning path until the resistance reaches the target threshold.

[0007] Furthermore, the method for preparing a radio frequency resistor calibration structure based on an RDL process according to the present invention further includes: performing secondary photolithography correction on the resistor pattern after laser trimming, using a negative photoresist to cover the edge of the trimming area to protect the calibrated conductive path, wherein the trimming area is the connection area between the main resistor module and the redundant resistor module; Removing residual photoresist by oxygen plasma ashing to reduce the roughness of the metal and resistor contact interface to the high-frequency signal transmission requirement; Applying a directional current 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 under-etched area of ​​the main resistor module. The narrow neck structure is a defined area at the connection node of the redundant resistor module. Depositing a silicon nitride or polyimide shielding layer on top of the resistor structure by a plasma enhanced chemical vapor deposition process, covering the main resistor module and the laser trimming module to suppress high-frequency electromagnetic coupling; A titanium-tungsten composite layer is sputtered below the resistor film. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module to form the temperature compensation module to reduce the temperature drift effect.

[0008] Furthermore, the method for preparing the radio frequency resistor calibration structure based on the RDL process of the present invention further includes: Partially developing the edge of the trimming region of the resistor pattern after laser trimming, and covering the trimming region with a negative photoresist to prevent over-etching caused by the reactive ion etching process; Removing photoresist residues by oxygen plasma ashing, and optimizing the roughness of the metal and resistor contact interface to meet the high-frequency signal transmission requirements; A reactive ion etching process is used to correct the line width deviation of the metal and resistor contact area, and the ratio of the chlorine and argon mixed gas and the etching power parameters are adjusted to match the serpentine or interdigitated geometric design of the main resistor module.

[0009] Furthermore, in the method for preparing a radio frequency resistor calibration structure based on an RDL process according to the present invention, the electromigration effect compensation includes: Applying a controllable current density at both ends of the redundant resistor module to increase the temperature of the narrow neck structure region of the redundant resistor module to a metal atom migration threshold through Joule heating effect; Driving metal atoms to migrate directionally from the narrow neck structure of the redundant resistor module to the insufficiently etched line width area of ​​the main resistor module to fill the conductive path loss caused by the line width deviation caused by the photolithography process and the uneven film thickness caused by the sputtering process; The resistance change 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 change until the resistance of the main resistance module reaches the target compensation threshold.

[0010] Furthermore, the method for preparing the radio frequency resistor calibration structure based on the RDL process of the present invention further includes: During the wafer-level packaging phase, the resistor network of the calibration structure is tested in parallel by a multi-probe array to stimulate all the main resistor modules and redundant resistor modules; measuring the impedance matching parameters of each resistor unit within the target high frequency band of the RF resistor calibration structure using a vector network analyzer to generate an impedance distribution map; screening abnormal cells having impedance mismatches exceeding a tolerance range after the laser calibration and the electromigration compensation according to the impedance distribution map; For the abnormal cells screened out, the RDL top layer metal interconnection is completed through the electroplated copper filling process of the metallized through hole, and the through hole aspect ratio is controlled to be less than three to one specified by the structural design to reduce the impedance mutation of the signal transmission path.

[0011] Furthermore, in the method for preparing a radio frequency resistor calibration structure based on an RDL process according to the present invention, the parallel testing includes: Simultaneously stimulating sixteen resistance units of the calibration structure through a four-by-four probe array, the resistance units being the main resistance module and the redundant resistance module; Measuring the scattering parameters of each unit in the millimeter wave communication frequency band of the radio frequency resistor calibration structure, and extracting the real and imaginary impedance data corresponding to the high-frequency signal transmission requirements; Calculating a matching deviation value based on the real and imaginary impedance data, and screening abnormal units whose deviation values ​​exceed the target threshold tolerance range; The laser trimming module or the electromigration compensation process is called to perform secondary correction on the abnormal unit until the impedance matching parameters meet the consistency requirements of the radio frequency circuit parameters.

[0012] Beneficial effects of the present invention: The present invention dynamically corrects the line width deviation caused by the photolithography process and the uneven film thickness caused by the sputtering process through the synergistic effect of the redundant resistor module and the electromigration compensation mechanism, thereby achieving closed-loop compensation of the resistor geometric parameters and material defects. The laser fine-tuning module, combined with the real-time feedback mechanism of the metal sensing electrode, adjusts the conductive path through selective ablation or annealing to improve the resistance calibration accuracy; the shielding layer and temperature compensation module respectively suppress high-frequency electromagnetic coupling and temperature drift effects, thereby enhancing the environmental stability of the RF resistor. Wafer-level parallel testing and electroplating copper filling processes synergistically optimize impedance matching consistency, which is suitable for the impedance control requirements of RF circuits in high-density packaging scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on the drawings without paying any creative labor.

[0014] Figure 1 This is a flow chart of a method for manufacturing a radio frequency resistor calibration structure based on an RDL process provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The technical solutions provided by each embodiment of the present invention are described in detail below in conjunction with the drawings. In order to better understand the purpose of the present invention, the present invention is further described in detail below.

[0016] In a first aspect, the present invention provides a radio frequency resistor calibration structure based on an RDL process, comprising: The main resistor module is integrated on the surface of the RDL interconnect layer through a sputtering process using a low temperature coefficient metal alloy material, and adopts a serpentine or interdigitated geometric layout to reduce high-frequency skin effect. The metal alloy material includes nickel-chromium alloy or tantalum nitride; A redundant resistor module is connected in parallel or in series with the main resistor module via a metallized through-hole. The metallized through-hole penetrates the RDL interconnect layer and electrically connects the main resistor module and the redundant resistor module. A narrow neck structure is provided at the connection node of the redundant resistor module. 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, thereby compensating for line width etching deviation caused by the photolithography process and uneven film thickness caused by the sputtering process. A laser trimming module covers the connection area between the main resistor module and the redundant resistor module, and changes the conductive path through pulsed laser selective ablation or annealing. The laser trimming module integrates metal sensing electrodes, which are embedded in the RDL interconnect layer and electrically connected to the main resistor module. The module monitors resistance changes in real time and feeds back to the laser parameter control system to dynamically adjust the laser energy density and scanning path. A shielding layer module, covering the top of the main resistance module and the laser trimming module, is composed of a silicon nitride or polyimide dielectric layer formed by a plasma-enhanced chemical vapor deposition process to suppress high-frequency electromagnetic coupling between adjacent metal wirings; The temperature compensation module is arranged below the main resistor module and 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 through a sputtering process. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module, reducing resistance drift caused by temperature changes.

[0017] In the RDL-based RF resistor calibration structure, the main resistor module is integrated onto the surface of the RDL interconnect layer via a sputtering process using a low-temperature-coefficient metal alloy. Its serpentine or interdigitated geometry effectively reduces the impact of high-frequency skin effect on impedance characteristics by increasing the current path length to cross-sectional area ratio. The metal alloy is made of nickel-chromium alloy or tantalum nitride. A uniform thin film is formed through magnetron sputtering under substrate temperature and power control. Deep ultraviolet lithography and reactive ion etching are combined to define the initial pattern. A mixture of chlorine and argon is used as the etching gas to ensure sidewall straightness and reduce high-frequency losses.

[0018] The redundant resistor module forms a parallel or series structure with the main resistor module via metallized through-holes (MTHs). The MTHs 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 node of the redundant resistor module. By applying a directional current to induce an electromigration effect, metal ions migrate from the redundant resistor area to the main resistor area, compensating for line width deviations caused by the photolithography process and uneven film thickness caused by the sputtering process. The narrow neck structure locally heats up to the metal atom migration threshold through the Joule heating effect. The metal atoms migrate in a directional manner to fill the missing conductive path of the main resistor module. Combined with real-time resistance monitoring, the current density and duration are dynamically adjusted to achieve closed-loop correction of resistance deviations.

[0019] The laser trimming module covers the connection area between the main resistor and redundant resistor modules, using pulsed laser selective ablation or annealing to change the length or cross-sectional area of ​​the conductive path. Metal sensing electrodes are embedded in the RDL interconnect layer and electrically connected to the main resistor module, monitoring resistance changes in real time and providing feedback to the laser parameter control system. A confocal optical system locates the trimming area, and the laser scanning path is generated using the four-probe method to measure the initial resistance. Resistance calibration is achieved through step-by-step ablation or annealing. Dynamic adjustment of laser energy density and scanning speed is linked to feedback data from the metal sensing electrodes, forming a closed-loop control mechanism for resistance calibration.

[0020] The shielding layer module uses a plasma-enhanced chemical vapor deposition process to deposit a silicon nitride or polyimide dielectric layer on top of the resistor structure, covering the main resistor and laser trimming area, thereby suppressing high-frequency electromagnetic coupling from adjacent metal wiring. Interface defects in the dielectric layer are controlled by optimizing deposition parameters, reducing the impact of parasitic capacitance and inductance on signal integrity. The temperature compensation module is located below the main resistor module and uses a sputtering process to deposit a titanium-tungsten composite layer. Its thermal expansion coefficient matches that of the main resistor metal alloy, offsetting thermal stress and reducing resistance drift caused by temperature changes. The interface bonding strength between the titanium-tungsten composite layer, the RDL interconnect layer, and the main resistor module is optimized through process parameter optimization to achieve long-term stability.

[0021] Second, see Figure 1 The method for preparing a radio frequency resistor calibration structure based on an RDL process provided by the present invention is applied to the radio frequency resistor calibration structure, and comprises the following steps: Step 1: After the RDL bottom metal wiring is completed, a low temperature coefficient metal alloy film is deposited by a magnetron sputtering process. The metal alloy film is the nickel-chromium alloy or tantalum nitride. The substrate temperature is controlled at 200-300°C and the sputtering power is controlled at 2-5 kW to form the initial material layer of the main resistor module and the redundant resistor module. Step 2: using deep ultraviolet lithography to define the initial patterns of the main resistor and the redundant resistor, and removing the metal alloy film area not protected by the photoresist by reactive ion etching, wherein the etching gas is a mixture of chlorine and argon with a volume ratio of 1:3 to 1:5 and an etching selectivity ratio greater than 10:1, to form the resistor structure having the serpentine or interdigitated geometric layout; Step 3: Using a confocal optical system, locate the connection area between the main resistor module and the redundant resistor module as a resistance fine-tuning area, measure the initial resistance value using a four-probe method, and generate a laser scanning path based on the resistance deviation; Step 4: Adjust the pulse laser energy density to 0.5-2 J / cm² and the scanning speed to 10-50 mm / s, ablating the resistor material step by step or inducing local annealing to change the length or cross-sectional area of ​​the conductive path, and calibrating the resistance value of the main resistor module to the target threshold; Step 5: Monitor the resistance change in real time through the metal sensing electrode integrated in the laser fine-tuning module, feed the monitoring data back to the laser parameter control system, and dynamically adjust the laser energy density and scanning path until the resistance reaches the target threshold.

[0022] The RDL-based method for fabricating RF resistor calibration structures begins with the completion of the RDL underlying metal routing. A low-temperature-coefficient metal alloy film, made of nickel-chromium alloy or tantalum nitride, is deposited via magnetron sputtering. A uniform initial layer of material is formed by controlling the substrate temperature and sputtering power. This process optimizes film density by adjusting the magnetic field intensity and target distance, providing a stable electrical performance foundation for the subsequent resistor structure.

[0023] Deep ultraviolet lithography is then used to define the initial patterns of the main and redundant resistors. A high-resolution mask is used to expose and develop the photoresist, creating precise pattern protection areas. Reactive ion etching (RIE) is then used to remove unprotected areas of the metal alloy film. The chlorine-argon ratio in the etching gas is adjusted to regulate the ion bombardment intensity and chemical reaction rate. The etch selectivity is combined with the control of sidewall steepness to form a resistor structure with a serpentine or interdigitated geometry, minimizing the impact of the high-frequency skin effect.

[0024] A confocal optical system precisely locates the connection area between the main and redundant resistor modules, defining this as the resistor fine-tuning area. A four-probe method is used to measure the initial resistance value, and a laser scanning path is generated based on the resistance deviation. Scan 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. By adjusting the pulsed laser energy density and scanning speed, selective ablation or localized annealing is used to alter the effective conductive path length or cross-sectional area of ​​the resistor body, allowing for a step-by-step, iterative calibration of the resistance to the target range.

[0025] The metal sensing electrodes integrated into the laser trimming module are embedded in the RDL interconnect layer, forming an electrical connection with the main resistor module and monitoring resistance changes in real time. This data is transmitted to the laser parameter control system via a closed-loop feedback system, dynamically adjusting laser output parameters, including energy density gradient adjustment and scanning path optimization. This feedback mechanism compares the real-time resistance value with the target threshold, triggering immediate correction of laser parameters and forming a closed-loop control link for resistance calibration.

[0026] 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 etching; the geometric accuracy of photolithography etching directly affects the calibration efficiency of laser fine-tuning; the real-time feedback of the metal sensing electrode and the dynamic adjustment of the laser parameters form a closed loop for process fluctuation compensation.

[0027] Specifically, the method for preparing an RF resistor calibration structure based on an RDL process according to the present invention further includes: performing secondary photolithography correction on the resistor pattern after laser trimming, using negative photoresist to cover the edge of the trimming area to protect the calibrated conductive path, wherein the trimming area is the connection area between the main resistor module and the redundant resistor module; Removing residual photoresist by oxygen plasma ashing to reduce the roughness of the metal and resistor contact interface to the high-frequency signal transmission requirement; Applying a directional current 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 under-etched area of ​​the main resistor module. The narrow neck structure is a defined area at the connection node of the redundant resistor module. Depositing a silicon nitride or polyimide shielding layer on top of the resistor structure by a plasma enhanced chemical vapor deposition process, covering the main resistor module and the laser trimming module to suppress high-frequency electromagnetic coupling; A titanium-tungsten composite layer is sputtered below the resistor film. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module to form the temperature compensation module to reduce the temperature drift effect.

[0028] In the RDL process, the fabrication method for RF resistor calibration structures involves secondary photolithography correction of the laser-trimmed resistor pattern. A negative photoresist is used to cover the edges of the trimming area. Exposure and development processes form a protective layer to prevent subsequent damage to the calibrated conductive path. The trimming area is defined as the connection between the main resistor module and the redundant resistor module, which is laser ablated or annealed. The photoresist coverage is limited by mask design to prevent excessive etching that could cause geometric parameter deviations in the resistor body.

[0029] When removing residual photoresist through an oxygen plasma ashing process, oxygen free radicals react with the photoresist residue to produce volatile gases. The ashing time and power parameters are tailored to the interface roughness control requirements. Optimizing the roughness of the metal-resistor interface is achieved by adjusting the ion bombardment intensity during the ashing process, reducing the interface contact resistance and meeting the surface flatness requirements for high-frequency signal transmission.

[0030] When a directional current is applied across the redundant resistor module, the Joule heating effect is induced by controllable current density, causing the narrow neck structure of the redundant resistor module to heat up locally to the metal atom migration threshold. The narrow neck structure concentrates the current density through geometric constraints, driving metal atoms to migrate along the electric field gradient from the redundant resistor region to the underetched area of ​​the main resistor module, thereby filling the gap in the conductive path caused by photolithography development deviations or sputtering thickness fluctuations. This migration path is electrically connected to the conductive path of the main resistor module via metallized through-holes. Resistance changes are monitored in real time using a four-probe method and fed back to the current parameter adjustment system.

[0031] When a silicon nitride or polyimide shielding layer is deposited on top of the resistor structure via a plasma-enhanced chemical vapor deposition process, the reactive gases are ionized in a high-frequency electric field to generate active radicals. The gas ratio and substrate temperature are controlled during the deposition process to form a low-defect dielectric layer. The shielding layer covers the main resistor module and the laser trimming area, suppressing capacitive coupling and inductive crosstalk between adjacent metal traces, thereby reducing parasitic effects in high-frequency signal transmission. Dielectric layer thickness uniformity is achieved through coordinated control of plasma power and deposition rate, ensuring electromagnetic shielding performance and structural reliability.

[0032] When sputtering a titanium-tungsten composite layer beneath the resistor film, the titanium layer acts as an adhesion layer to enhance interfacial bonding strength, while the tungsten layer's low thermal expansion coefficient matches the metal alloy material of the main resistor module. During composite layer deposition, gradient control of substrate temperature and sputtering power optimizes the crystal structure, offsetting thermal stress differences caused by temperature variations. Annealing is performed at the interface between the titanium-tungsten composite layer, the RDL interconnect layer, and the main resistor module to reduce lattice defects and mitigate temperature drift effects.

[0033] Specifically, the method for preparing a radio frequency resistor calibration structure based on an RDL process according to the present invention further includes: Partially developing the edge of the trimming region of the resistor pattern after laser trimming, and covering the trimming region with a negative photoresist to prevent over-etching caused by the reactive ion etching process; Removing photoresist residues by oxygen plasma ashing, and optimizing the roughness of the metal and resistor contact interface to meet the high-frequency signal transmission requirements; A reactive ion etching process is used to correct the line width deviation of the metal and resistor contact area, and the ratio of the chlorine and argon mixed gas and the etching power parameters are adjusted to match the serpentine or interdigitated geometric design of the main resistor module.

[0034] In the RDL process, the fabrication method for RF resistor calibration structures uses a negative photoresist to cover the trimming area during local development of the edges of the laser-trimmed resistor pattern. Mask design limits the photoresist's coverage to prevent over-etching of the calibrated conductive path during reactive ion etching. The negative photoresist exposure and development process selectively cures the non-trimmed areas using a UV light source, preserving the protective layer in the trimming areas. This precisely controls the boundaries of the etched areas and maintains the geometric accuracy of the resistor structure.

[0035] When oxygen plasma ashing is used to remove residual photoresist, oxygen free radicals react with organic matter in the photoresist to produce carbon dioxide and water vapor. The ion bombardment intensity and duration parameters of the ashing process are matched to the requirements for optimizing interface roughness. The roughness of the metal-resistor contact interface is reduced by adjusting the plasma power and gas flow rate, reducing the uneven current distribution caused by surface irregularities and meeting the interface flatness requirements for high-frequency signal transmission.

[0036] When using reactive ion etching (RIE) to correct linewidth deviations in the metal-resistor contact area, the ratio of the chlorine and argon gas mixture is adjusted to balance the etch rate and selectivity. Chlorine removes the metal alloy material through chemical reaction, while argon enhances sidewall anisotropy through physical bombardment. Etch power parameters are optimized to control sidewall steepness and linewidth uniformity by matching the serpentine or interdigitated geometry of the main resistor module. The geometric parameters of the etched conductive path are verified using a confocal optical system to ensure consistency with the resistance calibration target after laser trimming.

[0037] Specifically, the method for preparing a radio frequency resistor calibration structure based on an RDL process of the present invention, wherein the electromigration effect compensation includes: Applying a controllable current density at both ends of the redundant resistor module to increase the temperature of the narrow neck structure region of the redundant resistor module to a metal atom migration threshold through Joule heating effect; Driving metal atoms to migrate directionally from the narrow neck structure of the redundant resistor module to the insufficiently etched line width area of ​​the main resistor module to fill the conductive path loss caused by the line width deviation caused by the photolithography process and the uneven film thickness caused by the sputtering process; The resistance change 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 change until the resistance of the main resistance module reaches the target compensation threshold.

[0038] In the RDL-based fabrication method for RF resistor calibration structures, electromigration effects are compensated by applying a controlled current density across the redundant resistor module. This Joule heating effect heats the narrow neck region to the metal atom migration threshold. The narrow neck structure concentrates the current density through geometric constraints. This localized temperature increase activates the directional migration of metal atoms, driven by the electric field gradient. The metal atoms move along the path connecting the redundant resistor module to the main resistor module.

[0039] When metal atoms are driven to migrate, they form an electrical connection with the main resistor module through the metallized vias, compensating for linewidth etching variations caused by the photolithography process and uneven film thickness caused by the sputtering process. During this migration process, metal atoms diffuse from the narrow neck structure of the redundant resistor module to the missing conductive path area of ​​the main resistor module, filling the volume defects of the conductive material and restoring the continuity and cross-sectional uniformity of the conductive path. The migration rate is adjusted by the current density gradient to match the process deviation compensation requirements.

[0040] When monitoring the resistance changes of the main resistor module in real time, resistance data is collected using a four-probe method or metal sensing electrodes integrated into the interconnect layer. Resistance changes are then 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, forming a closed-loop correction mechanism. When the resistance reaches the threshold, the current is terminated to prevent structural damage to the redundant resistor module caused by excessive migration.

[0041] Specifically, the method for preparing a radio frequency resistor calibration structure based on an RDL process according to the present invention further includes: During the wafer-level packaging phase, the resistor network of the calibration structure is tested in parallel by a multi-probe array to stimulate all the main resistor modules and redundant resistor modules; measuring the impedance matching parameters of each resistor unit within the target high frequency band of the RF resistor calibration structure using a vector network analyzer to generate an impedance distribution map; screening abnormal cells having impedance mismatches exceeding a tolerance range after the laser calibration and the electromigration compensation according to the impedance distribution map; For the abnormal cells screened out, the RDL top layer metal interconnection is completed through the electroplated copper filling process of the metallized through hole, and the through hole aspect ratio is controlled to be less than three to one specified by the structural design to reduce the impedance mutation of the signal transmission path.

[0042] In the RDL process-based RF resistor calibration structure fabrication method, during the wafer-level packaging stage, a multi-probe array is used to parallelly test the resistor network. The probe array layout matches the physical locations of the calibration structure's primary and redundant resistor modules. Test signals are then applied synchronously to all modules using multiple signal excitations. The test signal frequency range covers the target high-frequency band, and the probe impedance matching circuitry reduces signal reflections to obtain steady-state response data for each resistor unit.

[0043] When measuring impedance matching parameters using a vector network analyzer, the analyzer is calibrated to a wafer-level test environment and extracts the real and imaginary impedance components of each resistor unit within the target frequency band based on scattering parameters. A data processing algorithm integrates the multi-point measurement results into an impedance distribution map. This map visually reflects impedance matching deviations through color gradients or numerical distributions, identifying areas of localized high loss or abnormal reflections.

[0044] When screening for abnormal cells based on the impedance distribution map, a preset tolerance range is set based on RF circuit design specifications. The algorithm compares each cell's impedance value with the theoretical model and flags cells that fall outside the tolerance range. The abnormal cell screening logic incorporates spatial distribution characteristics to distinguish random deviations caused by process fluctuations from systematic design flaws, focusing on target areas requiring secondary corrections.

[0045] For identified abnormal cells, the impedance jump is corrected through the copper electroplating filling process of the metalized through-holes. The through-hole location and the conductive path of the abnormal cell are linked through design rules. The copper electroplating filling process controls the current density and plating solution flow rate to optimize the density of the copper layer to reduce resistivity. The through-hole aspect ratio is also controlled by adjusting the electroplating time and voltage parameters. The through-hole aspect ratio limits the optimization requirements of the signal transmission path based on the structural design, reducing the impedance discontinuity of high-frequency signals at the through-hole interface.

[0046] Specifically, the method for preparing a radio frequency resistor calibration structure based on an RDL process according to the present invention, wherein the parallel testing includes: Simultaneously stimulating sixteen resistance units of the calibration structure through a four-by-four probe array, the resistance units being the main resistance module and the redundant resistance module; Measuring the scattering parameters of each unit in the millimeter wave communication frequency band of the radio frequency resistor calibration structure, and extracting the real and imaginary impedance data corresponding to the high-frequency signal transmission requirements; Calculating a matching deviation value based on the real and imaginary impedance data, and screening abnormal units whose deviation values ​​exceed the target threshold tolerance range; The laser trimming module or the electromigration compensation process is called to perform secondary correction on the abnormal unit until the impedance matching parameters meet the consistency requirements of the radio frequency circuit parameters.

[0047] In the RDL-based RF resistor calibration structure fabrication method, a parallel test step uses a four-by-four probe array to simultaneously excite the sixteen resistor elements of the main and redundant resistor modules. The probe array layout matches the physical arrangement of the calibration structure, and multiple signal sources are used to synchronously apply high-frequency excitation signals, covering the millimeter-wave communication frequency band. The contact impedance between the probes and the resistor elements is compensated using a calibration algorithm, reducing errors introduced by the test system and improving the signal-to-noise ratio of the measured signal.

[0048] When measuring scattering parameters in the millimeter-wave frequency band, the vector network analyzer and probe array are connected via a coaxial cable. Before testing, the system is calibrated using standard impedance calibration kits to eliminate phase offset and amplitude distortion in the test path. Scattering parameters are extracted based on the amplitude and phase information of the incident and reflected waves. These are converted into real and imaginary impedance data using Fourier transform or equivalent circuit models, generating an impedance distribution map for each element.

[0049] Matching deviation is calculated by comparing the real and imaginary impedance data with a pre-set theoretical model. The deviation is defined as the Euclidean distance or normalized difference between the measured impedance and the theoretical value. The screening logic, based on tolerance thresholds, flags abnormal cells that exceed the threshold. It also uses spatial distribution characteristics to distinguish between local process deviations and systemic design defects, prioritizing correction of critical cells in the high-frequency signal path.

[0050] When the laser trimming module is invoked for identified abnormal cells, either conductive path ablation or local annealing is selected based on the type of impedance deviation. The confocal optical system locates the target area, and laser parameters are adjusted for secondary fine-tuning. If the deviation is caused by uneven material thickness, an electromigration compensation process applies a directed current to the redundant resistor module, driving metal atoms to migrate and fill the defect. After correction, the cell undergoes impedance retesting until the matching parameters meet the consistency requirements of the RF circuit.

[0051] This invention addresses line width deviation issues caused by insufficient photolithography precision through the use of redundant resistor modules and an electromigration compensation mechanism. The redundant resistor modules are connected in parallel or series with the main resistor modules via metallized through-holes. Narrow neck structures are provided at the connection nodes, and a directional current is applied to induce metal atom migration. During this migration, metal ions from the redundant regions fill the gaps in the conductive path of the main resistor modules, correcting line width deviations during the photolithography development phase and uneven film thickness caused by the sputtering process, thereby achieving dynamic compensation for geometric parameters and material defects.

[0052] The laser trimming module covers the connection area between the main resistor and the redundant resistor, changing the length and cross-sectional area of ​​the conductive path through pulsed laser selective ablation or annealing. An integrated metal sensing electrode monitors resistance changes in real time, providing feedback to the laser parameter control system to dynamically adjust the energy density and scanning path, forming a closed-loop control loop for resistance calibration. This mechanism, combined with a secondary lithography correction process, optimizes the contact interface roughness, reduces high-frequency signal transmission loss, and improves resistance calibration accuracy.

[0053] The shielding module uses plasma-enhanced chemical vapor deposition to form a silicon nitride or polyimide dielectric layer on top of the resistor structure, suppressing high-frequency electromagnetic coupling from adjacent metal traces. The temperature compensation module sputters a titanium-tungsten composite layer beneath the resistor film. Its thermal expansion coefficient matches that of the main resistor material, offsetting resistance drift caused by temperature changes. This combination of wafer-level parallel testing and copper electroplating fill processes corrects for impedance fluctuations, ultimately achieving consistent control of RF circuit parameters at the package level.

Claims

1. The RF resistor calibration structure based on RDL process is characterized by: include: The main resistor module is integrated on the surface of the RDL interconnect layer through a sputtering process using a low temperature coefficient metal alloy material, and adopts a serpentine or interdigitated geometric layout to reduce high-frequency skin effect. The metal alloy material includes nickel-chromium alloy or tantalum nitride; A redundant resistor module is connected in parallel or in series with the main resistor module via a metallized through-hole. The metallized through-hole penetrates the RDL interconnect layer and electrically connects the main resistor module and the redundant resistor module. A narrow neck structure is provided at the connection node of the redundant resistor module. 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, thereby compensating for line width etching deviation caused by the photolithography process and uneven film thickness caused by the sputtering process. A laser trimming module covers the connection area between the main resistor module and the redundant resistor module, and changes the conductive path through pulsed laser selective ablation or annealing. The laser trimming module integrates metal sensing electrodes, which are embedded in the RDL interconnect layer and electrically connected to the main resistor module. The module monitors resistance changes in real time and feeds back to the laser parameter control system to dynamically adjust the laser energy density and scanning path. A shielding layer module, covering the top of the main resistance module and the laser trimming module, is composed of a silicon nitride or polyimide dielectric layer formed by a plasma-enhanced chemical vapor deposition process to suppress high-frequency electromagnetic coupling between adjacent metal wirings; The temperature compensation module is arranged below the main resistor module and 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 through a sputtering process. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module, reducing resistance drift caused by temperature changes.

2. A method for preparing a radio frequency resistor calibration structure based on an RDL process, applied to the radio frequency resistor calibration structure according to claim 1, characterized in that: The following steps are involved: After the RDL bottom metal wiring is completed, a low temperature coefficient metal alloy film is deposited by a magnetron sputtering process. The metal alloy film is the nickel-chromium alloy or tantalum nitride. The substrate temperature is controlled at 200-300°C and the sputtering power is controlled at 2-5 kW to form the initial material layer of the main resistor module and the redundant resistor module. Deep ultraviolet lithography is used to define the initial patterns of the main resistor and the redundant resistor, and a reactive ion etching process is used to remove the metal alloy film area not protected by the photoresist. The etching gas is a mixture of chlorine and argon with a volume ratio of 1:3 to 1:5 and an etching selectivity ratio greater than 10:1, thereby forming the resistor structure having the serpentine or interdigitated geometric layout; Locating the connection area between the main resistor module and the redundant resistor module as a resistance fine-tuning area using a confocal optical system, measuring the initial resistance value using a four-probe method, and generating a laser scanning path based on the resistance deviation; Adjust the pulsed laser energy density to 0.5-2 J / cm² and the scanning speed to 10-50 mm / s, ablating the resistor material step by step or inducing local annealing to change the conductive path length or cross-sectional area, and calibrating the resistance value of the main resistor module to the target threshold; The metal sensing electrode integrated in the laser fine-tuning module monitors the resistance change in real time, feeds the monitoring data back to the laser parameter control system, and dynamically adjusts the laser energy density and scanning path until the resistance reaches the target threshold.

3. The method for preparing a radio frequency resistor calibration structure based on an RDL process according to claim 2, wherein: Also includes: Performing secondary photolithography correction on the resistor pattern after laser trimming, using negative photoresist to cover the edge of the trimming area to protect the calibrated conductive path. The trimming area is the connection area between the main resistor module and the redundant resistor module. Removing residual photoresist by oxygen plasma ashing to reduce the roughness of the metal and resistor contact interface to the high-frequency signal transmission requirement; Applying a directional current 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 under-etched area of ​​the main resistor module. The narrow neck structure is a defined area at the connection node of the redundant resistor module. Depositing a silicon nitride or polyimide shielding layer on top of the resistor structure by a plasma enhanced chemical vapor deposition process, covering the main resistor module and the laser trimming module to suppress high-frequency electromagnetic coupling; A titanium-tungsten composite layer is sputtered below the resistor film. The thermal expansion coefficient of the titanium-tungsten composite layer matches the metal alloy material of the main resistor module to form the temperature compensation module to reduce the temperature drift effect.

4. The method for preparing a radio frequency resistor calibration structure based on an RDL process according to claim 3, wherein: Also includes: Partially developing the edge of the trimming region of the resistor pattern after laser trimming, and covering the trimming region with a negative photoresist to prevent over-etching caused by the reactive ion etching process; Removing photoresist residues by oxygen plasma ashing, and optimizing the roughness of the metal and resistor contact interface to meet the high-frequency signal transmission requirements; A reactive ion etching process is used to correct the line width deviation of the metal and resistor contact area, and the ratio of the chlorine and argon mixed gas and the etching power parameters are adjusted to match the serpentine or interdigitated geometric design of the main resistor module.

5. The method for preparing a radio frequency resistor calibration structure based on an RDL process according to claim 4, wherein: The electromigration effect compensation includes: Applying a controllable current density at both ends of the redundant resistor module to increase the temperature of the narrow neck structure region of the redundant resistor module to a metal atom migration threshold through Joule heating effect; Driving metal atoms to migrate directionally from the narrow neck structure of the redundant resistor module to the insufficiently etched line width area of ​​the main resistor module to fill the conductive path loss caused by the line width deviation caused by the photolithography process and the uneven film thickness caused by the sputtering process; The resistance change 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 change until the resistance of the main resistance module reaches the target compensation threshold.

6. The method for preparing a radio frequency resistor calibration structure based on an RDL process according to claim 5, wherein: Also includes: During the wafer-level packaging phase, the resistor network of the calibration structure is tested in parallel by a multi-probe array to stimulate all the main resistor modules and redundant resistor modules; measuring the impedance matching parameters of each resistor unit within the target high frequency band of the RF resistor calibration structure using a vector network analyzer to generate an impedance distribution map; screening abnormal cells having impedance mismatches exceeding a tolerance range after the laser calibration and the electromigration compensation according to the impedance distribution map; For the abnormal cells screened out, the RDL top metal interconnection is completed through the electroplated copper filling process of the metallized through-hole, and the through-hole aspect ratio is controlled to be less than three to one specified by the structural design to reduce the impedance mutation of the signal transmission path.

7. The method for preparing a radio frequency resistor calibration structure based on an RDL process according to claim 6, wherein: The parallel testing includes: Simultaneously stimulating sixteen resistance units of the calibration structure by a four-by-four probe array, the resistance units being the main resistance module and the redundant resistance module; Measuring the scattering parameters of each unit in the millimeter wave communication frequency band of the radio frequency resistor calibration structure, and extracting the real and imaginary impedance data corresponding to the high-frequency signal transmission requirements; Calculating a matching deviation value based on the real and imaginary impedance data, and screening abnormal units whose deviation values ​​exceed the target threshold tolerance range; The laser trimming module or the electromigration compensation process is called to perform secondary correction on the abnormal unit until the impedance matching parameters meet the consistency requirements of the radio frequency circuit parameters.

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