CN113517111A

CN113517111A - On-chip transformer and manufacturing process thereof

Info

Publication number: CN113517111A
Application number: CN202110873025.2A
Authority: CN
Inventors: 罗卫军; 王万礼; 张荣华; 张新玲; 张俊芳
Original assignee: Tianjin Huanxin Technology & Development Co ltd
Current assignee: Tianjin Huanxin Technology & Development Co ltd
Priority date: 2021-07-30
Filing date: 2021-07-30
Publication date: 2021-10-19

Abstract

A kind of on-chip transformer, including primary coil and secondary coil, primary coil and secondary coil include the multilayer metal layer; all the metal layers are stacked along the height direction of the primary coil and the secondary coil; each metal layer comprises a plurality of independent metal rings with the same structure; the metal ring is configured into a spiral structure which is arranged in a diffusion mode from inside to outside; the uppermost metal layer in the primary coil is provided with N input ends; the uppermost metal layer in the secondary coil has (N +1) output ends, wherein N is an integer; the signal enters through the input end and then is output from the output end. The invention also provides a manufacturing process for preparing the on-chip transformer. The invention has large coupling area and small occupied area, is simultaneously suitable for a half-bridge or full-bridge DC-DC converter, realizes output in any proportion by regulating voltage boosting, voltage reducing or equal pressure, balances resistance and reduces parasitic effect in a coil.

Description

On-chip transformer and manufacturing process thereof

Technical Field

The invention belongs to the technical field of Buck DCDC converters, and particularly relates to an on-chip transformer with three-terminal output and a manufacturing process thereof.

Background

With the development of electronic products, the demand of portable mobile devices is increasing, and the competition of various manufacturers is becoming more and more white, which promotes to reduce the volume and weight of electronic systems. In these electronic devices, the power supply part is a main factor affecting the volume and weight of the electronic equipment due to the presence of magnetic elements such as inductors and transformers. The on-chip transformer is widely used by people because the area and the weight of the transformer are greatly reduced. The half-bridge isolated DC-DC converter and the full-bridge isolated DC-DC converter are widely used in various power systems because they have the advantages of a bidirectional excitation transformer, few switches, large output power, wide output power range, low cost, high reliability, and the like.

In the prior art, GaN material is considered to meet the development requirements of novel power devices and is a research hotspot rapidly because of its excellent properties of large forbidden band width, high saturated electron mobility, small dielectric constant, good thermal conductivity, high temperature resistance, corrosion resistance and the like.

The existing on-chip transformer generally adopts a cross-coupling structure between metals in the same layer, that is, a primary coil and a secondary coil are both arranged in the same layer at intervals, for example, an on-chip transformer such as a balun in chinese patent publication CN107293393A and an on-chip transformer in CN104103636A, the on-chip transformer in such a structure not only has a small coupling area and a large occupied area, but also cannot be applied to a half-bridge or full-bridge DC-DC converter. Also, this type of structure is an asymmetric tapped transformer, and because the lengths of the secondary windings are different, a 1:1 turn ratio cannot be accurately achieved.

The transformer on the chip disclosed in the Chinese patent publication CN108269677A is an octagonal structure chip transformer, wherein each metal layer is formed by a plurality of circles of concentric octagonal rings with different diameters and closed, and lap joint circulation is carried out through connectors arranged on different circles; the structure not only causes a plurality of joints and influences signal transmission, but also cannot continuously and unimpededly transmit signals at one time. Moreover, the on-chip transformers of the structure are not completely overlapped in the direction vertical to the X axis, and the maximum coupling area cannot be achieved; meanwhile, the primary coil and the secondary coil have different structural lengths, and the turn ratio of the coil cannot be 1: 1.

Therefore, how to design an on-chip transformer, and combine with GaN base technology, obtain the DC-DC converter that is suitable for half bridge type or full bridge type, adjust through step-up, step-down or isobaric and realize the output of arbitrary proportion, balanced resistance and reduction parasitic effect in the coil, and realize accurately that the coil turns ratio is 1: the 1 output transformer is the key to improve the performance, conversion efficiency and working frequency of the power management system and obtain a power device with good performance, miniaturization and low consumption.

Disclosure of Invention

The invention provides an on-chip transformer and a manufacturing process thereof, which are particularly suitable for a half-bridge or full-bridge DC-DC converter and solve the technical problems of poor inductance storage capacity caused by poor coupling efficiency and high parasitic effect in the prior art.

In order to solve the technical problems, the invention adopts the technical scheme that:

the on-chip transformer comprises a primary coil and a secondary coil which are arranged on the same side of a substrate layer, wherein the primary coil and the secondary coil both comprise a plurality of metal layers;

all the metal layers are stacked along the height direction of the primary coil and the secondary coil;

each metal layer comprises a plurality of independent metal rings with the same structure;

the metal ring is configured into a spiral structure which is arranged in a diffusion mode from inside to outside;

the uppermost metal layer in the primary coil is provided with N input ends;

the metal layer of the uppermost layer in the secondary coil has (N +1) output terminals, where N is an integer;

and the signal enters through the input end and is output from the output end.

Furthermore, all the metal rings in all the metal layers and the metal rings which are adjacent up and down and correspond to the metal rings are stacked and arranged along the height direction of the primary coil and the secondary coil without dislocation;

and all the metal rings are annular spiral structures which are arranged in a diffusion mode from inside to outside.

Further, the number of the metal layers in the primary coil and the secondary coil is the same;

preferably, the number of the metal layers in the primary coil and the secondary coil is 2;

and all the metal rings in the metal layers on the same layer are arranged in the same row.

Furthermore, all the metal rings in the uppermost metal layers of the primary coil and the secondary coil are connected and arranged through a connecting bridge;

and all the metal rings in the metal layers of the other layers except the uppermost metal layer in the primary coil and the secondary coil are mutually disconnected.

Further, the number of turns of all the metal rings in the primary coil and the secondary coil is the same;

the width of each metal ring is the same;

and the width of the gap in each metal ring is the same;

the metal rings of different layers in the primary coil and the secondary coil are different in thickness.

Further, N is 2;

the input ends are arranged in the uppermost metal layer of the primary coil and are respectively arranged on the outer rings of the two outermost metal rings in the uppermost metal layer of the primary coil.

Furthermore, all the output ends are arranged in the uppermost metal layer of the secondary coil;

the two output ends are respectively arranged on the outer rings of the two outermost metal rings in the metal layer on the uppermost layer of the secondary coil;

the other output terminals are arranged on the connecting bridge in the metal ring.

Further characterized in that said primary coil is disposed adjacent to a side of said substrate layer;

between the primary coil and the substrate layer, and

between all adjacent metal layers in the primary coil and the secondary coil,

are all provided with Si₃N₄And forming dielectric layers with different structures for isolation.

Further, the thickness of the dielectric layer arranged between the primary coil and the substrate layer is larger than that of the dielectric layer arranged between the adjacent metal layers;

the thickness of the dielectric layer arranged between the primary coil and the substrate layer is 100-300 mu m; preferably, the thickness of the dielectric layer arranged between the primary coil and the substrate layer is 100 um.

Furthermore, the thicknesses of all the dielectric layers arranged between the adjacent metal layers are the same and are 60-200 nm;

preferably, the thickness of the dielectric layer arranged between the adjacent metal layers is 60 nm.

A manufacturing process for preparing an on-chip transformer as claimed in any preceding claim, comprising the steps of:

coating a dielectric layer on the substrate layer made of GaN;

sequentially growing the primary coil and the secondary coil which are formed by a plurality of metal layers on the dielectric layer, wherein each metal layer grows on the dielectric layer of different layers;

signals enter from N input ends arranged on the primary coil and are output through (N +1) output ends arranged in the secondary coil, wherein N is an integer.

Furthermore, all the metal rings in all the metal layers and the metal rings which are adjacent up and down and correspond to the metal rings are stacked and arranged along the height direction of the primary coil and the secondary coil without dislocation; and are

All the metal rings are annular spiral structures which are arranged in a diffusion mode from inside to outside.

Further, N is 2, and all the dielectric layers are Si₃N₄A dielectric layer;

the number of the metal layers in the primary coil and the secondary coil is the same and is 2.

The on-chip transformer and the manufacturing process thereof designed by the invention have the advantages of large coupling area and small occupied area, are simultaneously suitable for a half-bridge or full-bridge DC-DC converter, realize output in any proportion by regulating through boosting, reducing voltage or isobaric voltage, balance resistance and reduce parasitic effect in a coil.

The length of the primary coil and the length of the secondary coil are the same, the conversion of the coil turn ratio of 1:1 is accurately realized, the coupling efficiency is high, the parasitic effect in the coil is small, and therefore a transformer with a wider frequency range and a good parasitic effect can be obtained, and the inductance storage capacity is improved.

Drawings

FIG. 1 is a top view of an on-chip transformer in accordance with an embodiment of the present invention;

FIG. 2 is a cross-sectional view along the Y-axis of an on-chip transformer in accordance with an embodiment of the present invention;

FIG. 3 is a top view of a first embodiment of the present invention in fabricating a metal layer in a primary winding;

fig. 4 is a top view of a second metal layer in the primary coil according to an embodiment of the invention;

FIG. 5 is an equivalent circuit diagram of an on-chip transformer in accordance with an embodiment of the present invention;

FIG. 6 is a simulation of inductance values of different ports as a function of frequency according to one embodiment of the present invention;

FIG. 7 is a simulation of the coupling coefficient and quality factor as a function of frequency for one embodiment of the present invention.

In the figure:

10. substrate layer 20, dielectric layer one 30 and primary coil

31. First metal layer 32, second metal layer 40 and secondary coil

41. Metal layer three 42, metal layer four 50, dielectric layer two

60. Medium layer three 70, medium layer four 80, connecting bridge

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

The embodiment proposes an on-chip transformer, as shown in fig. 1, which includes a primary coil 30 and a secondary coil 40 disposed on the same side of a substrate 10, wherein the primary coil 30 is disposed near the substrate 10, and dielectric layers of different structures formed by Si3N4 are disposed between the primary coil 30 and the substrate 10 and between all adjacent metal layers in the primary coil 30 and the secondary coil 40 for isolation. The primary coil 30 and the secondary coil 40 both comprise a plurality of metal layers, all the metal layers are stacked along the height direction of the primary coil 30 and the secondary coil 40, and each metal layer comprises a plurality of independent metal rings with the same structure; all the metal rings are configured into a spiral structure which is arranged in a diffusion mode from inside to outside; and the uppermost metal layer in the primary coil 30 is provided with N input terminals; the uppermost metal layer in the secondary coil 40 has (N +1) output terminals, where N is an integer; one of the output ends is used as a ground wire of the bridge type isolation converter than the input end; the signal enters through the input end and then is output from the output end.

Specifically, for the on-chip transformer in fig. 1, the cross-sectional view along the Y axis is shown in fig. 2, and all metal loops in all metal layers and their corresponding metal loops are stacked without dislocation along the height direction of the primary coil 30 and the secondary coil 40; and the metal ring is in an annular spiral structure which is arranged by diffusion from inside to outside. That is, the primary coil 30 and the secondary coil 40 are both formed by connecting metal rings of annular spiral structures which are vertically corresponding and overlapped, the metal rings are overlapped, the coupling area of the primary coil 30 and the secondary coil 40 can be increased by the overlapped metal rings, the whole occupied area is small, and the transmission efficiency of magnetic flux can be increased on the structure vertical to each metal layer.

Further, the number of metal layers in the primary coil 30 and the secondary coil 40 is the same, and both are 2; that is, the primary coil 30 includes a first metal layer 31 and a second metal layer 32, the secondary coil 40 includes a third metal layer 41 and a fourth metal layer 42, each metal layer includes the same number of metal turns, and all the metal turns in the same metal layer are arranged in the same row. All the metal rings are in annular outward-diffusion continuous spiral structures, and the metal wires in arc structures are adopted at the joints of the spiral annular metal rings for connection. The connection position of the metal wires of the arc-shaped structure is an obtuse angle of 120-160 degrees as a connection angle of the inflection point, and preferably, the obtuse angle is 150 degrees. Compared with the metal coil of the multi-connection bridge connection mode of the existing polygonal structure, the connection mode of the arc structure has the advantages that the bending radian is gentle, the connection change amplitude is slow, the balance of the resistance is facilitated, the parasitic resistance can be consistent at the straight line and the inflection point as much as possible, and the parasitic effect of the metal coil of the transformer is reduced; especially, when the metal wire with the obtuse angle of 150 degrees is adopted to connect each spiral coil at the inflection point of the metal coil, the metal coil can be further ensured to be uniformly and annularly arranged outwards in a diffused mode.

Further, all the metal loops in the uppermost metal layer two 32 in the primary coil 30 and the uppermost metal layer four 42 in the secondary coil 40 are connected to each other by a connection bridge 80; and the uppermost metal layer is removed, and the other metal layers in the primary coil 30 and the secondary coil 40, that is, all the metal layers in the lowermost metal layer one 31 and the lowermost metal layer three 41 are disconnected from each other. And the metal rings on the same side in the primary coil 30 are communicated up and down through the via holes.

The number of turns of all the metal turns in the primary coil 30 and the secondary coil 40 is the same; the width of each metal ring is the same, and the width of the gap in each metal ring is the same. In this embodiment, the inner diameter of all the metal turns is 100 μm, the line width of the metal turns is 20 μm, the width of the gap in each turn of the metal wire is 10 μm, and the number of turns of each metal turn is 3.

The thickness of the primary coil 30 is the same as that of the secondary coil 40, and the thicknesses of the metal coils of different layers in the primary coil 30 and the secondary coil 40 are different, that is, the thickness of the metal layer one 31 in the primary coil 30 is smaller than that of the metal layer two 32, but is the same as that of the metal layer three 41 in the secondary coil 40; the thickness of metal layer three 41 in secondary coil 40 is less than the thickness of metal layer four 42; the thicknesses of the first metal layer 31 and the third metal layer 41 are the same, and the thicknesses of the second metal layer 32 and the fourth metal layer 42 are the same, that is, the thicknesses of all metal rings in the first metal layer 31 and the third metal layer 41 are the same, and the thicknesses of all metal rings in the second metal layer 32 and the fourth metal layer 42 are the same. This configuration allows the vertical distances between the primary winding 30 and the secondary winding 40 of the transformer to coincide, which effectively transfers the magnetic flux generated by the primary winding 30 directly to the secondary winding 40, while providing more area savings and higher output efficiency relative to other types of on-chip transformers.

In this embodiment, preferably N is 2, that is, there are 2 input terminals and 3 output terminals, where the 2 input terminals are the a terminal and the B terminal respectively, and are both disposed in the two uppermost metal layers 32 of the primary coil 30 and are separately disposed on the leads of the outer circles of the two outermost metal layers 32 in the two uppermost metal layers 32 of the primary coil 30. The 3 output ends are respectively a C end, a D end and an E end, and all the output ends are arranged in the metal layer IV 42 on the uppermost layer of the secondary coil 40, wherein the two output ends of the C end and the E end are respectively arranged on the outer rings of the two outermost metal rings in the metal layer IV 42 on the uppermost layer of the secondary coil 40 and are respectively aligned with the A end and the B end; the D terminal is provided on a connecting bridge 80 of the two metal rings, which is provided as a ground line of the bridge isolated converter.

Further, a first dielectric layer 20 is arranged between the primary coil 30 and the substrate layer 10, that is, a first dielectric layer 20 is arranged between the first metal layer 31 and the substrate layer 10; meanwhile, a second dielectric layer 50, a third dielectric layer 60 and a fourth dielectric layer 70 are respectively arranged between the first metal layer 31 and the second metal layer 32, between the second metal layer 32 and the third metal layer 41 and between the third metal layer and the fourth metal layer 42 as isolation layers, wherein all the dielectric layers adopt Si₃N₄A separation layer made of a material for separating the primary coil 30 and the substrate layer 10, and the primary coil 30 and the secondary coil 40The separation and isolation function is to allow only alternating current signals to pass between the primary coil 30 and the secondary coil 40, and no direct current signals to pass, so as to realize the function of a transformer, so that signals and power can be transmitted between the primary coil 30 and the secondary coil 40, and then the transmission from the electric signals to the magnetic signals to the electric signals is realized, namely, the on-chip transformer with the structure can be simultaneously suitable for a half-bridge or full-bridge DC-DC converter, and can be adjusted through boosting, reducing voltage or equalizing voltage, so as to realize output of any proportion, balance resistance and reduce parasitic effect in the coils.

Further, the thickness of the first dielectric layer 20 is larger than that of the dielectric layer arranged between the adjacent metal layers; this is because the first dielectric layer 20 on the substrate layer 10 can prevent the transformer from affecting the substrate layer 10, and reduce the parasitic effect between the transformer and the substrate layer 10. The thicker the dielectric layer one 20 is, the stronger the isolation capability is, the less the parasitic effect is; but the thickness of the first dielectric layer 20 cannot be too thick, which may affect the performance of other devices on the chip, wherein the thickness of the first dielectric layer 20 is in the range of 100-300um, and preferably, the thickness of the first dielectric layer 20 is 100 um.

All the dielectric layers arranged between the adjacent metal layers have the same thickness, namely the thicknesses of the dielectric layer II 50, the dielectric layer III 60 and the dielectric layer IV 70 are all 60-200 nm; preferably, the thicknesses of the second dielectric layer 50, the third dielectric layer 60 and the fourth dielectric layer 70 are all 60 nm.

Wherein, the second dielectric layer 50 is grown on the first metal layer 31, and the thickness thereof is determined according to the magnitude of the applied voltage, in this embodiment, the input voltage is selected to be 48V, the thickness thereof is in the range of 60-200nm, and the Si is used as the basis₃N₄The dielectric material has the pressure-resistant characteristic, and the thickness of the dielectric material is selected to be 60nm, so that the metal ring can be led out conveniently.

The third dielectric layer 60 is grown on the second metal layer 32 in order to isolate the primary winding 30 from the secondary winding 40 and to allow only ac signals to pass through the primary winding 30, so that the transformer performs better without breakdown, and the thickness of the third dielectric layer 60nm is selected to facilitate the growth of the third metal layer 41 in the secondary winding 40.

Dielectric layer four 70 is used to isolate metal layer three 41 from metal layer four 42 in secondary coil 40 and facilitate the growth of metal layer four 42, and preferably, dielectric layer four 70 has a thickness of 60 nm.

The on-chip transformer which adopts a laminated structure without dislocation superposition and has each metal ring symmetrical relative to the X axis has the advantages that the efficiency of transmitting signals from the first metal layer 31 in the primary coil 30 to the fourth metal layer 42 in the secondary coil 40 is gradually increased, and the resistance and the signal loss are reduced; in addition, the on-chip transformer with the structure has small parasitic resistance in the use process, so that the resistance and the signal loss can be further reduced, and the output efficiency is improved.

The on-chip converter with the structure is mainly applied to the isolated DC-DC converters of a half bridge type and a full bridge type; compared with the on-chip transformer of the traditional DC-DC converter, the frequency and the efficiency can be improved, the occupied area can be greatly reduced, the coupling efficiency is improved, and the efficiency of the DC-DC converter is improved.

A manufacturing process for preparing the on-chip transformer as described above, comprising the steps of:

coating a first dielectric layer 20 on a substrate layer 10 made of GaN;

sequentially growing a primary coil 30 and a secondary coil 40 which are formed by a plurality of metal layers on the first dielectric layer 20, wherein each metal layer grows on the dielectric layers of different layers;

signals enter from N input terminals provided on the primary coil 30 and are output via (N +1) output terminals provided in the secondary coil 40, where N is an integer.

Furthermore, all the metal rings in all the metal layers and the metal rings which are adjacent up and down and correspond to the metal rings are stacked in a non-dislocation way along the height direction of the primary coil and the secondary coil; and are

Further, N is 2, and all dielectric layers are Si3N4 dielectric layers;

the number of metal layers in the primary coil 30 and the secondary coil 40 is the same, and is 2.

The method comprises the following specific steps:

s1, a first dielectric layer 20 is first applied on the GaN-based substrate layer 10.

The first dielectric layer 20 can prevent the transformer from influencing the substrate layer 10 and reduce the parasitic effect of the transformer and the substrate layer 10. The thicker the dielectric layer one 20 is, the stronger the isolation capability is, the less the parasitic effect is; but the thickness of the first dielectric layer 20 cannot be too thick, which may affect the performance of other devices on the chip, wherein the thickness of the first dielectric layer 20 is in the range of 100-300um, and preferably, the thickness of the first dielectric layer 20 is 100 um.

S2, growing the first metal layer 31 in the primary coil 30 on the first dielectric layer 20, and growing a second dielectric layer 50 on the first metal layer 31.

As shown in fig. 3, the first metal layer 31 includes two independent metal rings symmetrically arranged along the X axis and having a ring-shaped spiral structure diffused from inside to outside, the two metal rings are disconnected from each other, and the number of turns of each metal ring is 3. All the metal rings are of annular outward-diffused continuous spiral structures, and the connection part of each spiral annular metal ring is connected by adopting an obtuse-angle radian, wherein the obtuse angle is 120 degrees and 160 degrees, and preferably, the obtuse angle is 150 degrees. The reason is that the obtuse angle of 150 degrees is adopted to connect the annular connection parts of the outward diffusion of each spiral, compared with the metal coil of the connection mode of the multi-connection bridge with the polygonal structure, the bending radian is gentle, the connection change amplitude is slow, the resistance balance is facilitated, the parasitic resistance can be consistent at the straight line and the inflection point as much as possible, and the parasitic effect of the metal coil of the transformer is also reduced.

In order to ensure that the central metal wire of the metal ring in the first metal layer 31 is led out, a second dielectric layer 50 is arranged on the first metal layer 31, and the first metal layer 31 is separated from the second metal layer 32, so that the thickness of the second dielectric layer 50 is greater than that of the first metal layer 31. A second dielectric layer 50 is grown on the first metal layer 31, and its thickness is determined according to the magnitude of the applied voltage, in this embodiment, the input voltage is selected to be 48V, and its thickness is in the range of 60-200nm, and it is determined according to Si₃N₄The dielectric material has a dielectric characteristic of 60nm thicknessIs beneficial to leading out the metal ring.

And S3, growing a second metal layer 32 on the second dielectric layer 50, and growing a third dielectric layer 60 on the second metal layer 32.

As shown in fig. 4, etching and opening are sequentially performed on the second dielectric layer 50, and a second metal layer 32 is grown, wherein the second metal layer 32 also includes two metal rings having the same structure as the metal rings in the first metal layer 31, and the two metal rings are respectively overlapped with the metal rings in the first metal layer 31 in an up-and-down manner, and the metal liquid is connected with the metal rings in the first metal layer 31 through the opening and filled with the metal rings in the etched metal rings to form the second metal layer 32, and two adjacent metal rings are connected through a connecting bridge 80, and the connecting bridge 80 is also a structure formed by solidifying the same metal liquid. And input end leads are arranged at the outer ring end of the second metal layer 50, namely an end A and an end B.

And S4, growing a third metal layer 41 on the third dielectric layer 60, and growing a fourth dielectric layer 70 on the third metal layer 41.

The same as the process for manufacturing the primary coil 30, the third dielectric layer 60 is etched and holed in sequence, and a third metal layer 41 is grown, and the structure of the third metal layer 41 is the same as that of the first metal layer 31, and the structure is the same as that of fig. 3, and is omitted here, that is, the primary coil includes two metal rings which are independently arranged, and the metal ring in the third metal layer 41 and the metal ring in the second metal layer 32 are arranged in an up-and-down stacked manner.

And growing a dielectric layer IV 70 on the metal layer III 41, wherein the dielectric layer IV 70 is used for isolating the metal layer III 41 from the metal layer IV 42 in the secondary coil 40 and is beneficial to the growth of the metal layer IV 42, and the thickness of the dielectric layer IV 70 is preferably 60 nm.

And S5, growing a metal layer IV 42 on the dielectric layer IV 70, and arranging three output ends on the metal layer IV 42.

As shown in fig. 1, etching and opening are sequentially performed on the dielectric layer four 70, and a metal layer four 42 is grown, wherein the structure of the metal layer four 42 is the same as that of the metal layer two 32, and the metal layer four also includes two metal rings, the two metal rings of the metal layer four 42 are respectively overlapped and stacked with the two metal rings of the metal layer three 41, the manufacturing process is the same as that of the metal layer two 32, and the process is omitted here. Two metal rings in metal layer four 42 are connected by a connecting bridge 80. Output end leads, namely a C end and an E end, are arranged at the outer ends of the two metal rings in the metal layer IV 42, and an output lead of a D end is arranged on a connecting bridge 80 of the two metal rings in the metal layer IV 42.

For the equivalent circuit diagram of the on-chip transformer, as shown in fig. 5, where L1 is the inductance values of the terminals a and B in the primary coil 30, L2 is the inductance values of the terminals C and D in the secondary coil 40, and L3 is the inductance values of the terminals D and E in the secondary coil 40.

The performance parameters of the on-chip transformer obtained by the manufacturing process can be calculated through Z parameter simulation, parasitic parameters of the primary coil 30 are calculated, wherein imag represents an imaginary part of the Z parameter, real represents a real part of the Z parameter, w represents an angular frequency of an output transformer signal, f represents a frequency of the output signal, M represents mutual inductance of a primary coil and a secondary coil of the transformer, and the calculating method comprises the following steps:

parasitic resistance of the transformer: r1 ═ real (Z)₁₁)

The transformer inductance is:

transformer mutual inductance: the mutual inductance is as follows:

coupling coefficient:

quality factor:

through simulation, various parameters of the on-chip transformer of 5-100MHz can be obtained, that is, a simulation graph of inductance values of three different ports with frequency variation is obtained, as shown in fig. 6, where L1 is the inductance values of the a terminal and the B terminal in the primary coil 30, L2 is the inductance values of the C terminal and the D terminal in the secondary coil 40, and L3 is the inductance values of the D terminal and the E terminal in the secondary coil 40. Meanwhile, as shown in fig. 7, a is a simulation diagram of the on-chip voltage transformation with frequency variation of the coupling coefficient and the quality factor, where a is the coupling coefficient K and b is the quality factor Q.

The on-chip transformer with the structure adopts an isolation type laminated on-chip transformer which is formed in an up-down symmetrical mode, so that the turn ratio can be 1; the quality factor can be 1.9 at most. The quality factor of the inductor represents the inductor energy storage capacity. The higher the quality factor of the inductor, the greater the energy stored by the inductor.

As can be seen from fig. 6 and 7, the on-chip transformer can be used in a relatively wide range, and the higher the frequency, the smaller the parasitic resistance, indicating that the power consumption is also smaller. When the frequency is relatively small, the parasitic inductance is relatively large, indicating that the energy transfer of the primary coil 30 and the secondary coil 40 is increased more. The requirements can be completely met for a general isolation DC-DC converter.

The embodiments of the present invention have been described in detail, and the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.

Claims

1. The on-chip transformer comprises a primary coil and a secondary coil which are arranged on the same side of a substrate layer, and is characterized in that the primary coil and the secondary coil both comprise a plurality of metal layers;

the uppermost metal layer in the primary coil is provided with N input ends;

and the signal enters through the input end and is output from the output end.

2. The on-chip transformer of claim 1, wherein all the metal rings in all the metal layers and the metal rings adjacent to the metal rings at the upper and lower sides of the metal rings are stacked without dislocation along the height direction of the primary coil and the secondary coil;

3. An on-chip transformer according to claim 1 or 2, characterized in that the number of said metal layers in said primary coil and said secondary coil is the same;

4. The on-chip transformer of claim 3, wherein all the metal loops in the uppermost metal layers of the primary coil and the secondary coil are connected to each other via a connecting bridge;

5. The on-chip transformer of claim 4, wherein the number of turns of all the metal turns in the primary coil and the secondary coil are the same;

the width of each metal ring is the same;

and the width of the gap in each metal ring is the same;

6. The on-chip transformer according to any of claims 1-2, 4-5, wherein N is 2;

7. The on-chip transformer of claim 6, wherein all of the output terminals are disposed in the uppermost metal layer of the secondary winding;

8. A transformer on a chip according to any of claims 1-2, 4-5, 7, wherein said primary winding is arranged adjacent to a side of said substrate layer;

between the primary coil and the substrate layer, and

si is arranged between all adjacent metal layers in the primary coil and the secondary coil₃N₄And forming dielectric layers with different structures for isolation.

9. The on-chip transformer of claim 8, wherein a thickness of the dielectric layer disposed between the primary coil and the substrate layer is greater than a thickness of the dielectric layer disposed between adjacent ones of the metal layers;

10. The on-chip transformer of claim 9, wherein all of the dielectric layers disposed between adjacent metal layers have the same thickness of 60-200 nm;

11. A manufacturing process for preparing an on-chip transformer according to any of claims 1-10, characterized in that the steps comprise:

coating a dielectric layer on the substrate layer made of GaN;

12. The manufacturing process of the on-chip transformer according to claim 11, wherein all the metal rings in all the metal layers and the metal rings which are adjacent to each other up and down and correspond to each other are stacked and arranged along the height direction of the primary coil and the secondary coil without dislocation; and are

13. All the metal rings are annular spiral structures which are arranged in a diffusion mode from inside to outside. The process of claim 12, wherein N is 2 and all the dielectric layers are Si₃N₄A dielectric layer;