Improved radio frequency chip of on-chip integrated RC circuit
By integrating RC circuits inside the RF chip, and optimizing the resistance and capacitance combination using the parallel connected metal layer structure and passivation layer, the oscillation problem of RF chips in the current technology and the high coupling loss of resistor and capacitance combination structure in the resistor and capacitance combination structure in the prior art is solved. Problem, improving the gain and robustness of RF power devices.
Patent Information
- Application Number
- CN202310801239.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-03
- Publication Date
- 2025-01-03
AI Technical Summary
When used in low frequency applications, existing RF chips are prone to oscillation of the amplifier tube due to excessive gain of the device. Although external damping structures such as resistors and capacitors can stabilize the circuit, the structure is far away from the active area of the RF chip, and it is impossible to effectively suppress the inside of the chip. Loop oscillation and the coupling loss of the resistor and capacitor combination structure is high, resulting in insufficient gain and robustness of RF power devices at low and high frequencies.
The RC circuit is integrated inside the chip, and connected in parallel with the first metal layer and the third metal layer to form a shielding structure, reduce parasitic capacitance, increase the capacitance value of the capacitance, and optimize the resistor and capacitance combination structure through the passivation layer and the multi-layer metal structure , reduce coupling loss.
It effectively suppresses chip gain, prevents oscillation, improves the gain and robustness of RF power devices at low and high frequencies, and reduces coupling loss.
Smart Images
Figure CN119252831A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of radio frequency device chips, and in particular to an improved radio frequency chip with an on-chip integrated RC circuit. Background Art
[0002] In existing RF chips, such as LDMOS chips, the gate of the chip is directly connected to the input metal pad through a low-resistance metal (such as gold). When this type of chip is used at low frequencies, it often causes problems such as power amplifier tube oscillation due to excessive device gain. Usually, a damping structure such as resistors and capacitors is added to the outside of the power amplifier device to stabilize the circuit. This circuit is generally implemented on a PCB board. Although adding a damping structure to the outside of the device can play a certain stabilizing role, since the external damping structure is far away from the active area of the RF chip in the circuit matching structure, the role of the external damping structure is not obvious when a loop oscillation occurs inside the chip.
[0003] The invention patent with application number 202011189666.8 applied by the applicant in 2020 discloses a radio frequency chip with an on-chip integrated RC circuit, including a substrate and an epitaxial layer, an active area arranged on the epitaxial layer, and multiple groups of resistor-capacitor combination structures are arranged on the epitaxial layer between the gate of the active area and the input metal pad, the resistors and capacitors of the resistor-capacitor combination structure are connected in parallel, and the gate of the active area is connected to the input metal pad after passing through the resistor-capacitor combination structure. Its capacitor includes a two-layer structure of a lower metal layer and an upper metal layer arranged on the epitaxial layer. Although it can prevent loop oscillation from occurring inside the chip and avoid the problem of resistor power overload due to too low gain when inputting high-frequency applications, the coupling loss between the resistor-capacitor combination structure and the substrate is high, so that the gain and robustness of the radio frequency power device at low and high frequencies need to be further improved. Summary of the invention
[0004] In view of the above-mentioned technical problems, the purpose of the present invention is to provide an improved radio frequency chip with an on-chip integrated RC circuit, by integrating the RC circuit inside the chip, further improving the structure of the capacitor of the resistor-capacitor combination structure, the first metal layer and the third metal layer are connected in parallel, and the middle metal layer is shielded by the first metal layer and the third metal layer, thereby reducing the parasitic capacitance between the capacitor plate connected to the active area and the ground, reducing the coupling loss, and improving the gain and robustness of the radio frequency power device at low and high frequencies.
[0005] In order to solve these problems in the prior art, the technical solution provided by the present invention is: An improved radio frequency chip with an on-chip integrated RC circuit comprises a substrate, an epitaxial layer, and an active region arranged on the epitaxial layer. A plurality of groups of resistor-capacitor combination structures are arranged on the epitaxial layer between the gate of the active region and an input metal pad. The resistors and capacitors of the resistor-capacitor combination structures are connected in parallel. The gate of the active region is connected to the input metal pad through the resistor-capacitor combination structure. The capacitor of the resistor-capacitor combination structure comprises a first metal layer, a second metal layer, and a third metal layer arranged on the epitaxial layer from bottom to top in sequence. A passivation layer is arranged between the first metal layer, the second metal layer, and the third metal layer. The first metal layer and the third metal layer are connected in parallel as a first plate of a capacitor connected to the input metal pad, and the second metal layer is connected to the gate as a second plate of the capacitor.
[0006] In a preferred technical solution, two ends of the first metal layer and the third metal layer are connected via through holes to form a longitudinal parallel structure.
[0007] In the preferred technical solution, the third metal layer is divided into a first third metal layer and a second third metal layer by a fracture, a passivation layer is arranged in the fracture, the first third metal layer is a U-shaped structure, the second third metal layer is a mountain-shaped structure, the U-shaped structure is inverted in the middle of the mountain-shaped structure, the first third metal layer is connected to the second metal layer through a first through hole, and the second third metal layer is connected to the first metal layer through a second through hole.
[0008] In a preferred technical solution, the second metal layer extends from the second end portion to a certain distance from the second through hole.
[0009] In a preferred technical solution, the first metal layer extends from the first end to a certain distance from the second end.
[0010] In a preferred technical solution, the resistor of the resistor-capacitor combination structure includes at least one double field plate structure, and the double field plate structure includes a first metal field plate and a second metal field plate arranged on the epitaxial layer, the second metal field plate is arranged above the first metal field plate, and a passivation layer is arranged between the first metal field plate and the second metal field plate, and the two ends of the first metal field plate and the second metal field plate are respectively connected to an upper metal connection layer arranged above through through holes, the upper metal connection layer and the second metal field plate connection end are connected to the gate, the upper metal connection layer and the first metal field plate connection end are connected to the input metal pad, and the thickness of the upper metal connection layer is greater than the thickness of the metal field plate.
[0011] In a preferred technical solution, a plurality of double field plate structures are connected in series via an upper metal connection layer.
[0012] Compared with the solutions in the prior art, the advantages of the present invention are: An RC circuit is integrated inside the chip to further improve the structure of the capacitor of the resistor-capacitor combination structure. The first metal layer and the third metal layer are connected in parallel, and the middle metal layer is shielded by the first metal layer and the third metal layer, thereby increasing the capacitance of the capacitor. The metal layer position of the capacitor plate connected to the gate of the active area is raised, thereby reducing the parasitic capacitance between the capacitor plate connected to the active area and the ground, reducing coupling losses, and improving the gain and robustness of the RF power device at low and high frequencies. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 An input layout of the input part of the radio frequency chip of the improved on-chip integrated RC circuit of the present invention; Figure 2 A schematic diagram of a resistor structure according to an embodiment of the present invention; Figure 3 for Figure 2 AA' section view; Figure 4 A schematic diagram of a capacitor structure according to an embodiment of the present invention; Figure 5 for Figure 4 AA' section view; Figure 6 is another schematic diagram of a capacitor structure according to an embodiment of the present invention; Figure 7 for Figure 6 AA' section view. Implementation
[0014] The above scheme is further described below in conjunction with specific examples. It should be understood that these examples are used to illustrate the present invention and are not limited to the scope of the present invention. The implementation conditions adopted in the examples can be further adjusted according to the conditions of the specific manufacturer, and the unspecified implementation conditions are usually the conditions in conventional experiments.
[0015] Example
[0016] like Figure 1 As shown, a radio frequency chip with an on-chip integrated RC circuit includes a substrate 100, an epitaxial layer 101, and an active area arranged on the epitaxial layer 101. A plurality of resistor and capacitor combination structures 60 are arranged on the epitaxial layer 101 between the gate 40 of the active area and the input metal pad 50. The resistors and capacitors of the resistor and capacitor combination structures 60 are connected in parallel, and the gate 40 of the active area is connected to the input metal pad 50 through the resistor and capacitor combination structure.
[0017] By designing an RC structure with a certain combination of resistance and capacitance, when the chip is used at low frequencies, the RF signal will pass through the series resistor to effectively suppress the chip gain and prevent device oscillation. When the chip is used at high frequencies, the RF signal will pass through the series capacitor to reduce the RF power borne by the resistance structure, thereby achieving high-gain and high-efficiency working goals.
[0018] The RF chip with on-chip integrated RC circuit is applicable to GaAs, Si-based LDMOS, and GaN processes.
[0019] The structure of the resistor 61 of the resistor-capacitor combination structure 60 is as follows: Figure 2 , 3 As shown, it is implemented by stacking and connecting two layers of thin film metal in parallel, including at least one double field plate structure 63, the double field plate structure 63 includes a first metal field plate 611 and a second metal field plate 612 arranged on the epitaxial layer 101, the second metal field plate 612 is arranged above the first metal field plate 611, a passivation layer 613 is arranged between the first metal field plate 611 and the second metal field plate 612, the first metal field plate 611 and the second metal field plate 612 are connected at both ends to an upper metal connection layer 615 arranged above through a through hole 614, one end of the upper metal connection layer 615 is connected to the gate 40, and the other end is connected to the input metal pad 50.
[0020] In a preferred embodiment, the thickness of the first metal field plate 611 and the second metal field plate 612 is very thin, about tens of nm to hundreds of nm, and is composed of metal or a combination of metal and metal nitride, and has a relatively large resistance. The upper metal connection layer 615 is made of a relatively thick metal and has a relatively small resistance. It is preferred that the thickness of the first metal field plate 611, the second metal field plate 612 and the upper metal connection layer 615 differ by more than 10 times.
[0021] The resistance required for the application is achieved by designing the aspect ratio of the metal field plate. Taking into account the metal current capacity, the use of double-layer field plate metal stacking can significantly improve the heat dissipation of the resistor and increase the overall power capacity of the resistor.
[0022] A passivation layer 616 may be further disposed above the second metal field plate 612 .
[0023] In a preferred embodiment, multiple groups of the above-mentioned double field plate structures 63 can be connected in series through the upper metal connection layer 615, which can improve the resistor power capacity, reduce the length of each group of resistor unit field plate metal, further optimize the resistor reliability, and effectively prevent the resistor burning problem.
[0024] The structure of the capacitor 62 of the resistor-capacitor combination structure 60 is as follows: Figure 4 , 5As shown, it includes a first metal layer 620, a second metal layer 621 and a third metal layer 622 which are arranged on the epitaxial layer 101 from bottom to top, the third metal layer 622 is arranged above the second metal layer 621, and the second metal layer 621 is arranged above the first metal layer 620. The passivation layer 625 of the first metal layer 620 and the second metal layer 621 serves as a dielectric layer of the capacitor, and the passivation layer 624 of the second metal layer 622 also serves as a dielectric layer of the capacitor. The first metal layer 620 and the third metal layer 622 are connected in parallel as a first plate of the capacitor connected to the input metal pad 50, and the second metal layer 621 serves as a second plate of the capacitor connected to the gate 40.
[0025] The first metal layer 620 and the third metal layer 622 form a shield for the middle metal layer (the second metal layer 621), which increases the capacitance of the capacitor and increases the design flexibility. The metal layer position of the capacitor plate connected to the gate of the active area becomes higher, which reduces the parasitic capacitance between the capacitor plate connected to the active area and the ground, and reduces the coupling loss. The gain and robustness of the RF power device at low and high frequencies are further improved.
[0026] In a preferred embodiment, the first metal layer 620 and the third metal layer 622 are connected through the second through hole 6232 and then connected to the input metal pad 50 through the third metal layer 622 .
[0027] Specifically, the third metal layer 622 is divided into a first third metal layer 6222 and a second third metal layer 6223 by a fracture 6221, and a passivation layer is disposed in the fracture 6221, such as Figure 4 In an example shown, a fracture 6221 is set around the third metal layer 622, so that the divided first and third metal layers 6222 surround the second and third metal layers 6223, and both ends of the first metal layer 620 extend to the outside of the epitaxial layer 101. The second through hole 6232 is set on the extended first metal layer 620, the first and third metal layers 6222 are a U-shaped structure, and the second and third metal layers 6223 are a mountain-shaped structure, and the U-shaped structure is inverted in the middle of the mountain.
[0028] The first and third metal layers 6222 are connected to the second metal layer 621 through the first through hole 6231, and a passivation layer 624 is provided between the second metal layer 621 and the third metal layer 622. The second metal layer 621 serves as a plate of the capacitor, and the first metal layer 620 is further provided below the second metal layer, and a passivation layer 625 is provided between the second metal layer 621 and the first metal layer 620. The second and third metal layers 6223 and the first metal layer 620 are connected to serve as another plate of the capacitor through the second through hole 6232, and the passivation layer 624 between the second metal layer 621 and the third metal layer 622 and the passivation layer 625 between the first metal layer 620 and the second metal layer 621 serve as dielectric layers of the capacitor, forming a parallel plate capacitor.
[0029] The second metal layer 621 extends from the second end portion to a certain distance from the second through hole 6232 .
[0030] All of the above passivation layers are generally oxides or nitrides, and the capacitance required for the application can be achieved by adjusting the thickness of the passivation layer and the parallel plate metal area.
[0031] Of course, in order to achieve special requirements, the first metal layer 620 and the second metal layer 621 of the capacitor may be implemented by metal field plates.
[0032] In a preferred embodiment, for the convenience of design, Figure 1 As shown, the third metal layer 622 of the capacitor and the upper metal connection layer 615 of the resistor are the same metal layer, and the metal layers can respectively connect the gate 40 and the input metal pad 50. The above RC circuit and active area are packaged as a whole into a radio frequency chip.
[0033] In a preferred embodiment, the first third metal layer 6222 and the second third metal layer 6223 are made of relatively thick metal, with a thickness of about 1 um, and have relatively small resistance.
[0034] In another embodiment, if Figure 6 , 7 As shown, the first metal layer 620 extends from the first end to a certain distance from the second end, which can make the capacitance value more accurate and facilitate the process implementation. The second metal layer 621 is formed with a shoulder 6211 near the first metal layer 620. The metal layer of the capacitor plate connected to the gate of the active area is located at a higher position, which reduces the parasitic capacitance between the capacitor plate connected to the active area and the ground, and reduces the coupling loss.
[0035] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.
Claims
1. An improved radio frequency chip with an on-chip integrated RC circuit, comprising a substrate, an epitaxial layer, and an active region arranged on the epitaxial layer, wherein a plurality of resistor and capacitor combination structures are arranged on the epitaxial layer between the gate of the active region and an input metal pad, wherein the resistor and capacitor of the resistor and capacitor combination structures are connected in parallel, and the gate of the active region is connected to the input metal pad via the resistor and capacitor combination structures, characterized in that: The capacitor of the resistor-capacitor combination structure includes a first metal layer, a second metal layer and a third metal layer which are arranged on the epitaxial layer from bottom to top in sequence, and a passivation layer is arranged between the first metal layer, the second metal layer and the third metal layer. The first metal layer and the third metal layer are connected in parallel as the first plate of the capacitor connected to the input metal pad, and the second metal layer is connected to the gate as the second plate of the capacitor.
2. The improved radio frequency chip with on-chip integrated RC circuit according to claim 1, characterized in that: The two ends of the first metal layer and the third metal layer are respectively connected through through holes to form a longitudinal parallel structure.
3. The improved radio frequency chip with on-chip integrated RC circuit according to claim 1, characterized in that: The third metal layer is divided into a first third metal layer and a second third metal layer by a fracture, a passivation layer is arranged in the fracture, the first third metal layer is a U-shaped structure, the second third metal layer is a mountain-shaped structure, the U-shaped structure is inverted in the middle of the mountain-shaped structure, the first third metal layer is connected to the second metal layer through a first through hole, and the second third metal layer is connected to the first metal layer through a second through hole.
4. The improved radio frequency chip with on-chip integrated RC circuit according to claim 3, characterized in that: The second metal layer extends from the second end portion to a certain distance from the second through hole.
5. The improved radio frequency chip with on-chip integrated RC circuit according to claim 3, characterized in that: The first metal layer extends from the first end to a distance from the second end.
6. The improved radio frequency chip with on-chip integrated RC circuit according to claim 1, characterized in that: The resistor of the resistor-capacitor combination structure includes at least one double field plate structure, and the double field plate structure includes a first metal field plate and a second metal field plate arranged on the epitaxial layer, the second metal field plate is arranged above the first metal field plate, and a passivation layer is arranged between the first metal field plate and the second metal field plate, and the two ends of the first metal field plate and the second metal field plate are respectively connected to an upper metal connection layer arranged above through through holes, the upper metal connection layer and the second metal field plate connection end are connected to the gate, the upper metal connection layer and the first metal field plate connection end are connected to the input metal pad, and the thickness of the upper metal connection layer is greater than the thickness of the metal field plate.
7. The improved radio frequency chip with on-chip integrated RC circuit according to claim 6, characterized in that: A plurality of double field plate structures are connected in series through an upper metal connection layer.