CN114113960A - Preparation method of GCPW calibration piece and GCPW calibration piece - Google Patents
Preparation method of GCPW calibration piece and GCPW calibration piece Download PDFInfo
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- 229910052751 metal Inorganic materials 0.000 claims abstract 7
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Abstract
The invention provides a preparation method of a GCPW calibration piece and the GCPW calibration piece. The method comprises the following steps: determining the cross-sectional dimension of the transmission line; determining the size of a via hole according to the cross section size and the theoretical highest frequency corresponding to the GCPW calibration piece, wherein a plurality of via holes are uniformly arranged on an upper floor and a lower floor on the front surface of a substrate, on the substrate and the grounding metal on the back surface of the substrate, and the positions of the upper floor or the lower floor, the substrate and the grounding metal correspond to each other to form a through hole; optimizing the size of the cross section to obtain the optimal size of the cross section; and carrying out semiconductor process machining according to the optimal cross section size and the via hole size, carrying out laser resistance trimming on the resistance of the load calibration piece in the machined calibration piece, and carrying out value setting on all the calibration pieces after resistance trimming to obtain the GCPW calibration piece. The invention can reduce the influence of the multimode transmission line and reduce the system calibration system error.
Description
Technical Field
The invention relates to the technical field of microwave characteristic measurement of primary crystal semiconductor devices, in particular to a preparation method of a GCPW calibration piece and the GCPW calibration piece.
Background
A large number of "on-chip S parameter test systems" equipped in the microelectronics industry require vector error correction using on-chip calibration before use. Therefore, the on-chip S parameter calibration is one of the main factors affecting the calibration accuracy of the on-chip vector network analyzer. The calibration piece has been widely used because of its high accuracy in the low frequency chip (below 50 GHz), coaxial and waveguide fields.
Currently, the collimating element is typically in the form of a Coplanar Waveguide (CPW), the substrate material is ceramic, and the thickness is typically 600 μm to 300 μm. However, as the on-chip test frequency gradually enters the terahertz frequency band, some system errors which can be ignored in the low frequency band become non-negligible: on the one hand, the leakage (which may also be referred to as cross-talk) from probe to probe becomes larger and larger; on the other hand, in the actual production test process, the substrate of the terahertz measured piece is generally GaAs, InP and the like with the thickness not more than 100 μm, and the back surface is provided with metal, while the substrate of the commercial calibration piece is ceramic with the thickness more than 200 μm, so that new system errors can be generated during calibration, and the test accuracy is limited.
Disclosure of Invention
The embodiment of the invention provides a preparation method of a GCPW calibration piece and the GCPW calibration piece, and aims to solve the problem of low test accuracy in calibration in the prior art.
In a first aspect, an embodiment of the present invention provides a method for preparing a GCPW calibrating material, including:
determining the cross-sectional dimension of the transmission line;
determining the size of a via hole according to the cross section size and the theoretical highest frequency corresponding to the GCPW calibration piece, wherein a plurality of via holes are uniformly arranged on an upper floor on the front surface of a substrate, a lower floor, the substrate and grounding metal on the back surface of the substrate, and the positions of the upper floor or the lower floor, the substrate and the grounding metal correspond to each other to form a through hole;
when the cross section size and the via hole size both meet the frequency requirement of a preset calibration piece, optimizing the cross section size to obtain the optimal cross section size;
and carrying out semiconductor process machining according to the optimal cross section size and the via hole size, carrying out laser resistance trimming on the resistance of the load calibration piece in the machined calibration piece, and carrying out value setting on all the calibration pieces after resistance trimming to obtain the GCPW calibration piece.
In one possible implementation, the substrate thickness is the same as the thickness of the piece under test;
the substrate is made of the same material as the tested piece.
In a possible implementation manner, the inner wall of the via hole is provided with metal;
the inner wall metal, the grounding metal, the upper floor and the lower floor are all made of gold with the purity of 99%.
In one possible implementation, the cross-sectional dimensions include a center conductor width of the transmission line and a spacing of the center conductor to the upper or lower floor;
determining the size of the via hole according to the cross section size and the theoretical highest frequency corresponding to the GCPW calibration piece, wherein the determining comprises the following steps:
determining the distance between the via holes at corresponding positions on the upper floor and the lower floor according to the width of the central conductor and the distance between the central conductor and the upper floor or the lower floor;
determining the distance between adjacent via holes on the upper floor or the lower floor according to the theoretical highest frequency;
the diameter of the via is set to a length less than or equal to 100 μm.
In a possible implementation manner, the determining, according to the width of the central conductor and the distance between the central conductor and the upper floor or the lower floor, the distance between the vias at corresponding positions on the upper floor and the lower floor includes:
according to L1Determining the distance between the via holes at corresponding positions on the upper floor and the lower floor as 2d +2g + w;
wherein L is1The distance between the via holes at the corresponding positions on the upper floor and the lower floor is represented, d represents the distance between the via holes and the edge of the floor where the via holes are located, the edge is the edge of the side closest to the central conductor, g represents the distance between the central conductor and the upper floor or the lower floor, and w represents the width of the central conductor.
In one possible implementation, the determining a distance between adjacent vias on the upper floor or the lower floor according to the theoretical highest frequency includes:
and determining that the distance between the centers of the adjacent through holes on the upper floor or the lower floor is 1/4 smaller than the wavelength corresponding to the theoretical highest frequency.
In a possible implementation manner, when both the cross-sectional size and the via size satisfy the frequency requirement of the preset calibration piece, optimizing the cross-sectional size to obtain an optimal cross-sectional size includes:
calculating a first theoretical maximum frequency of the transmission line according to the distance between the via holes at the corresponding positions on the upper floor and the lower floor;
calculating a second theoretical maximum frequency of the transmission line according to the cross-sectional dimension;
when the first theoretical maximum frequency and the second theoretical maximum frequency are both greater than or equal to the preset calibration piece frequency requirement, determining that the cross section size meets the requirement;
and optimizing the size of the cross section to obtain the optimal size of the cross section.
In a possible implementation manner, the calculating a first theoretical maximum frequency of the transmission line according to a distance between via holes at corresponding positions on the upper floor and the lower floor includes:
when the distance between the via holes at the corresponding positions on the upper floor and the lower floor is greater than the thickness of the substrate, the thickness is determined according to the
Calculating a first theoretical maximum frequency of the transmission line;
when the distance between the via holes at the corresponding positions on the upper floor and the lower floor is less than or equal to the thickness of the substrate, according to the method
Calculating a first theoretical maximum frequency of the transmission line;
wherein f is1And the first theoretical highest frequency of the transmission line is represented, mu represents the magnetic permeability of a medium in a waveguide cavity formed by the upper floor or the lower floor and the through hole, epsilon represents the dielectric constant of the medium in the waveguide cavity formed by the upper floor or the lower floor and the through hole, and h represents the thickness of the substrate.
In one possible implementation, the calculating the second theoretical maximum frequency of the transmission line according to the cross-sectional dimension includes:
according to
Calculating a second theoretical maximum frequency of the transmission line;
wherein f is2Represents the second theoretical maximum frequency, mu, of said transmission line0Denotes the air permeability, ∈0Denotes the dielectric constant of air,. epsilonrDenotes the substrate dielectric constant and h denotes the substrate thickness.
In a second aspect, embodiments of the present invention provide a device for preparing a GCPW calibrating material, including a calibrating material prepared by the steps of the method for preparing a GCPW calibrating material according to any one of the above embodiments.
The embodiment of the invention provides a preparation method of a GCPW calibration piece and the GCPW calibration piece. In the invention, through setting up the via hole, can reduce the influence of multimode transmission line, thus reduce the systematic error of calibration, in addition, the substrate of the calibration piece and measured piece are the same substrate and same boundary condition, thus can reduce the systematic error introduced by different boundary conditions of different substrates.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
FIG. 1 is a flow chart of an implementation of a method for preparing a GCPW calibration piece according to an embodiment of the present invention;
FIG. 2 is a side view of a transmission line provided by an embodiment of the present invention;
FIG. 3 is a top view of a transmission line provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a short circuit calibration assembly according to an embodiment of the present invention;
FIG. 5 is a schematic view of an open circuit calibration piece according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a resistance calibration piece according to an embodiment of the present invention;
FIG. 7 is a schematic illustration of a semiconductor process for manufacturing a calibration piece according to an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following description is made by way of specific embodiments with reference to the accompanying drawings.
Because the substrate of the terahertz measured piece in the prior art is generally GaAs, InP and the like with the thickness of not more than 100 μm and the back surface is provided with metal, while the substrate of the commercial calibration piece is ceramic with the thickness of more than 200 μm and the back surface is not provided with metal, a new system error can be generated during calibration, and the test accuracy is limited. If the calibration piece is designed to be the same substrate as the piece under test, the same boundary conditions, i.e. the same substrate thickness, substrate material, and substrate backside are provided with metal. Such an arrangement may be selected from two options: the microstrip transmission line structure has serious dispersion in a high frequency band, and the thickness of a substrate under 50 omega characteristic impedance is the same as the width of a microstrip transmission line conductor, so that the microstrip transmission line structure is not suitable for the design requirement of a millimeter wave calibration piece, because the transmission line width of the millimeter wave calibration piece is much smaller than that of the substrate; another option is a Grounded Coplanar Waveguide (GCPW) structure that reduces multi-mode transmission by reducing the width w of its center conductor and the distance g between the two sides of the ground, but also reduces calibration accuracy due to the severe parallel plate mode and surface wave mode between the upper and lower floors. In view of this, the implementation flowchart of the method for preparing a GCPW calibration material according to the embodiment of the present invention solves the problem of accuracy of the calibration material, and with reference to fig. 1, the following details are described:
Here, the cross-sectional dimensions of the transmission line include a center conductor width w, and a center conductor to upper or lower floor spacing g.
Fig. 2 shows a side view of the transmission line and fig. 3 shows a top view of the transmission line. Upper and lower floor widths w in fig. 2 and 3g，kg＝k1(2g+w)，k1Is any of 0.3 to 3. Thus, after the width w of the central conductor and the distance g between the central conductor and the corresponding floor are determined, the width w of the central conductor and the distance g between the central conductor and the corresponding floor can be determinedThe width of the floor is determined.
Optionally, the determining the cross-sectional dimension of the transmission line in this step may include:
acquiring the thickness of a substrate, the dielectric constant of the substrate, the conductivity of metal arranged on the substrate and the thickness of the metal; and obtaining the cross section dimension of the transmission line according to the substrate thickness, the substrate dielectric constant, the conductivity and the metal thickness.
The method adopts simulation software, and the thickness of the substrate, the dielectric constant of the substrate, the conductivity and the metal thickness are input, so that the corresponding cross section dimension of the transmission line can be obtained, and the width w of the central conductor and the distance g between the central conductor and the corresponding floor can be obtained. The emulation software may be EMPRO.
And 102, determining the size of the via hole according to the cross section size and the theoretical highest frequency corresponding to the GCPW calibration piece.
The through hole is arranged on the upper floor board, the lower floor board and the grounding metal on the back of the substrate on the front surface of the substrate, and the positions of the upper floor board or the lower floor board, the substrate and the grounding metal correspond to each other to form a through hole. See fig. 2 where 201 indicates a via is provided. The vias provided are denoted 301 in fig. 3.
It should be noted that the cross-sectional shape of the via may be a circle, an ellipse, a square, a rectangle, or an irregular shape, and the cross-sectional shape of the via is not limited in this embodiment.
Referring to fig. 2, in this embodiment, the thickness of the substrate is the same as that of the tested object, and the material of the substrate is the same as that of the tested object. The substrate thickness here may be set to be less than or equal to 200 μm. The back of the substrate is provided with metal, namely grounding metal, namely the designed GCPW calibrating piece and the tested piece have the same substrate and the same boundary condition, so that the on-chip S parameter testing system errors caused by different substrates and different boundary conditions are reduced. In addition, because metal is arranged above and below the substrate of the GCPW structure calibration piece, surface waves and multi-mode transmission such as a parallel plate mode can be excited, the design of reducing the geometric dimension of the GCPW calibration piece and increasing the through holes is adopted in the embodiment, the influence of the multi-mode transmission lines can be reduced, and the error of a system calibration system is reduced.
Optionally, the inner wall of the via hole is provided with metal, and the inner wall metal, the grounding metal, the upper floor and the lower floor are made of the same metal, for example, the inner wall metal, the grounding metal, the upper floor and the lower floor are made of gold with a purity of more than 90%. For example, the purity may be 90%, 95%, 99%, etc. Gold with a purity of 99% is preferred.
The via size may include, for example, the distance between vias at corresponding locations on the upper and lower floors (as shown in fig. 3) and the diameter of the via. The distances between the via holes in this embodiment are distances between centers of the via holes. When the vias are in a pattern before rounding off, the distance between the centers of the vias is referred to.
Optionally, in this step, the distance between the via holes at corresponding positions on the upper floor and the lower floor is determined according to the width of the central conductor and the distance between the central conductor and the upper floor or the lower floor; determining the distance between adjacent via holes on the upper floor or the lower floor according to the theoretical highest frequency; the diameter of the via is set to a length less than or equal to 100 μm.
When determining the distance between the via holes at corresponding positions on the upper floor and the lower floor according to the width of the central conductor and the distance between the central conductor and the upper floor or the lower floor, the method may include: according to L1Determining the distance between the via holes at corresponding positions on the upper floor and the lower floor as 2d +2g + w;
wherein L is1The distance between the via holes at corresponding positions on the upper floor and the lower floor is represented, d represents the distance between the via holes and the edge of the floor where the via holes are located, the edge is the edge of the side closest to the central conductor, g represents the distance between the central conductor and the upper floor or the lower floor, and w represents the width of the central conductor.
Here, d is generally about 10 μm, and L is1Is less than or equal to 200 μm.
When determining the distance between adjacent vias on the upper floor or the lower floor according to the theoretical highest frequency, the method may include: the distance between the centers of adjacent vias on the upper or lower floor is determined to be 1/4 less than the wavelength corresponding to the theoretical highest frequency.
The theoretical maximum frequency is the maximum frequency that the calibration element is expected to cover, and the calibration element is able to transmit at a maximum frequency that does not cause large errors. The theoretical maximum frequency may be the theoretical maximum frequency of the transmission line calculated from the cross-sectional dimensions of the transmission line, see in particular the description of the calculation of the second theoretical maximum frequency in step 103. Typically, the pitch between adjacent vias is represented by c, which has a value in the range of 100 μm to 50 μm.
And 103, when the cross section size and the via hole size both meet the frequency requirement of a preset calibration piece, optimizing the cross section size to obtain the optimal cross section size.
Optionally, this step may include:
calculating a first theoretical maximum frequency of the transmission line according to the distance between the via holes at corresponding positions on the upper floor and the lower floor;
calculating a second theoretical maximum frequency of the transmission line according to the cross section size;
when the first theoretical maximum frequency and the second theoretical maximum frequency are both greater than or equal to the frequency requirement of a preset calibration piece, determining that the cross section size meets the requirement;
and optimizing the size of the cross section to obtain the optimal size of the cross section.
In this step, since the upper and lower floors and the via hole form a similar waveguide cavity, the size of the via hole needs to satisfy the cut-off frequency of the transmission mode of the waveguide cavity. According to the size relation between the distance between the through holes at the corresponding positions on the upper floor and the lower floor and the thickness of the substrate, different calculation modes can be adopted to calculate the cut-off frequency.
Specifically, when the distance between the via holes at corresponding positions on the upper and lower floor plates is greater than the thickness of the substrate, the distance is determined according to
Calculating a first theoretical maximum frequency of the transmission line;
when the distance between the via holes at corresponding positions on the upper floor and the lower floor is less than or equal to the thickness of the substrate according to
Calculating a first theoretical maximum frequency of the transmission line;
wherein f is1Denotes the first theoretical highest frequency of the transmission line, μ denotes the permeability of the medium in the waveguide cavity formed by the upper or lower floor and the via hole, e denotes the dielectric constant of the medium in the waveguide cavity formed by the upper or lower floor and the via hole, and h denotes the substrate thickness.
It should be noted that the size of the via hole can be considered to meet the requirement as long as the first theoretical maximum frequency corresponding to the designed size of the via hole is greater than or equal to the preset frequency of the calibration member.
Optionally, the condition for the GCPW etalon to maintain single mode TEM transmission is that the frequency corresponding to the cross-sectional dimension is greater than or equal to the preset etalon frequency, and thus, according to
Calculating a second theoretical maximum frequency of the transmission line;
wherein f is2Representing the second theoretical maximum frequency, mu, of the transmission line0Denotes the air permeability, ∈0Denotes the dielectric constant of air,. epsilonrDenotes the substrate dielectric constant and h denotes the substrate thickness.
The calibration piece frequency is preset as a required calibration piece frequency, such as the requirement of a customer.
In the step, the cross section size is optimized to obtain the optimal cross section size, which is S in S parameter11And judging for the simulation target. Optionally, optimizing the cross-sectional dimension to obtain the optimal cross-sectional dimension includes:
changing the cross section size within a first preset stepping range to obtain a plurality of groups of cross section sizes;
simulating a plurality of groups of transmission lines with cross section sizes and preset lengths, and carrying out S transformation on all the transmission lines11The cross-sectional dimension corresponding to the minimum value is determined as the optimum cross-sectional dimension.
Optionally, the first preset step range is 1 μm to 5 μm. That is, w and g are both stepped from 1 μm to 5 μm, the values are (w-5 to w +5) μm and (g-5 to g +5) μm respectively. For example, the sets of cross-sectional dimensions may be (w-1) μm and (g-1) μm, (w-2) μm and (g-2) μm, (w +3) μm and (g +3) μm, respectively, and so forth.
The predetermined length may be any value between 100 μm and 500 μm, for example, the transmission line may be a transmission line of 100 μm, a transmission line of 200 μm, or the like.
Inputting the determined cross section sizes and preset lengths of the transmission lines into simulation software to obtain S corresponding to each transmission line11Selecting S11The cross-sectional dimension corresponding to the minimum value is determined as the optimum cross-sectional dimension.
When the cross section size is optimized in the step, multiple groups of stepping sizes are adopted for simulation verification according to the cross section size, so that the optimal cross section size can be obtained, the design success rate and efficiency are improved, and the deviation caused by process errors is effectively overcome.
After optimizing the cross-sectional dimensions of the transmission line, it is also possible to optimize again based on the characteristic impedance.
Optionally, multiple groups of transmission lines are set based on the optimal cross-sectional dimension, and a target transmission line with characteristic impedance closest to a preset impedance value in the multiple groups of transmission lines is determined. After the optimal cross section size is determined, the layout is processed to determine the size of the transmission line with the characteristic impedance closest to 50 omega. The preset impedance value is therefore 50 Ω here.
In particular, when the cross-sectional dimension is optimized again,
changing the optimal cross section size within a second preset stepping range to obtain multiple groups of optimal cross section sizes, and processing different transmission line layouts based on the multiple groups of optimal cross section sizes and at least three lengths corresponding to each group of optimal cross section sizes;
calibrating the characteristic impedance of the transmission line by adopting a preset resistor;
and measuring the characteristic impedance of each transmission line based on the transmission line layout and the preset resistor, and determining the transmission line corresponding to the characteristic impedance closest to the impedance value of the preset resistor as a target transmission line.
Here, the second preset step range is different from the first preset step range. The second predetermined step range may be 0.5 μm to 1 μm. The optimum cross-sectional dimensions of the sets thus obtained may be (w-0.5) μm and (g-0.5) μm, (w-1) μm and (g-1) μm, (w +1) μm and (g +1) μm, and so on.
The preset resistance may be a resistance of 50 Ω.
In the step, the target transmission line adopts multiple groups of stepping sizes according to the cross section size of the transmission line and adopts different transmission line lengths for simulation verification, so that the target transmission line closest to the preset impedance value can be obtained, the design success rate and efficiency are improved, and the deviation caused by process errors is effectively overcome.
Terahertz calibration piece types include transmission line standards, reflection standards and crosstalk standards. The transmission line standard needs to select the number and the length of transmission lines aiming at a coverage frequency band; the reflection standard comprises an open circuit, a short circuit or only one of the open circuit and the short circuit; the crosstalk standard comprises open circuit, short circuit, resistance, resistance open circuit, resistance short circuit, open circuit short circuit or reciprocity of the standard components, and only at least one of the standards can be selected.
The determined transmission line is equivalent to a through calibration piece, and an open calibration piece, a short calibration piece and a load calibration piece can be obtained according to the through calibration piece. And the open circuit in the crosstalk standard is composed of two open circuit calibration pieces, and the short circuit is composed of two short circuit calibration pieces, etc.
In the embodiment, the crosstalk standard component is added in the high-frequency band, so that the system error caused by the crosstalk error in the terahertz frequency band is solved.
Fig. 4 shows a short circuit calibration piece, fig. 5 shows an open circuit calibration piece, and fig. 6 shows a resistance calibration piece.
And 104, carrying out semiconductor process machining according to the optimal cross section size and the via hole size, carrying out laser resistance trimming on the resistance of the load calibration piece in the machined calibration piece, and carrying out value setting on all the calibration pieces after resistance trimming to obtain the GCPW calibration piece.
Semiconductor processing of the calibration piece is performed based on the GCPW calibration piece determined above, and other calibration piece types defined below. As shown in fig. 7.
And 701, preparing a mask plate corresponding to the strip line and the resistor and a via hole mask plate according to the determined optimal cross section size and via hole size of the GCPW calibration piece.
The calibration piece adopts two processes of strip line and resistance, so that the corresponding mask plate is prepared according to the determined size of the calibration piece. There are patterns with lines and resistors on the reticle, and other patterns need to be cleaned.
At step 702, the substrate is cleaned and dried.
Alternatively, the substrate is made of the same material as the tested piece, and is generally made of GaAs, InP, or the like, and the thickness is generally less than or equal to 100 μm.
In this step, the cleaning and drying of the substrate may include:
in a first cleaning solution, boiling the substrate within a preset temperature range for a first preset time, taking out, and washing with water until the pH of the substrate is neutral; soaking the substrate subjected to the first step in hydrofluoric acid for a second preset time, and washing the substrate with water until the pH value of the substrate is neutral; in a second cleaning solution, boiling the substrate treated in the second step at a preset temperature for a first preset time, taking out, and washing with water until the pH of the substrate is neutral; the substrate was blow-dried using dry filtered nitrogen.
Wherein, first washing liquid is mixed for water, aqueous ammonia and hydrogen peroxide and forms, and its volume ratio is 4 in proper order: 1: 1;
the second cleaning liquid is formed by mixing water, hydrochloric acid and hydrogen peroxide, and the volume ratio of the second cleaning liquid is 4: 1: 1;
the predetermined temperature range is a range of 80 ℃ to 90 ℃. It should be noted that, when cooking in the first cleaning solution or the second cleaning solution, the temperature is only required to be kept between 80 ℃ and 90 ℃, and it is not required to keep a constant temperature all the time during cooking.
The first preset time is any time from 10min to 15 min;
the second preset time is 2 min.
And cleaning and drying the substrate, and sputtering a resistance layer on any surface of the substrate by adopting a magnetron sputtering device.
Optionally, the resistance layer is made of NiC or TaN; the thickness of the resistive layer is any value of 40nm to 100 nm.
When the calibration piece is prepared, a resistor with low resistivity is designed under the transmission line, so that attenuation can be increased, and the frequency response of the transmission line is smoother.
And sputtering an alloy layer on the resistance layer by adopting magnetron sputtering equipment.
Optionally, the alloy layer is made of Ti/W, where the ratio of Ti to W may be 3: 1; the thickness of the alloy layer is any value of 50nm to 1 μm. The thickness of the alloy layer may be 50nm, 100nm, or 1 μm.
Electroplating 99% of gold on the strip line in the mask plate pattern on the surface of the Ti/W alloy by adopting electroplating equipment.
Optionally, the strip line is made of gold with a purity of more than 90%, for example, the purity of gold may be 90%, 95%, 99%, etc. Preferably, 99% gold is used. The thickness of the strip line plating is any value of 1 μm to 10 μm, for example, the thickness of the strip line plating may be 1 μm, 4.7 μm, 6 μm, 10 μm, or the like.
After the plating, washing and drying are required.
After the electroplating is finished, the alloy layer and the resistance layer outside the mask pattern need to be etched away, and only the alloy layer and the resistance layer corresponding to the pattern area are left. A completed through-via calibration piece was prepared as shown in FIG. 7, where 701 is the substrate, 702 is the NiCr resistor, 703 is the Ti/W alloy, and 704 is gold.
And 707, thinning the substrate to a preset thickness, coating photoresist on the back surface of the calibration piece sample, and corroding via holes communicated with the upper surface and the lower surface of the calibration piece sample by using a via hole mask.
Optionally, after the substrate is thinned, the thickness of the substrate is the same as that of the tested piece.
The back side of the calibration piece sample here is the opposite side from which the resistive layer was prepared.
The through holes are uniformly formed in the upper floor, the lower floor and the substrate on the front surface of the substrate, and the positions of the upper floor or the lower floor and the substrate correspond to each other to form through holes.
And 708, gold plating is carried out on the inner wall of the through hole, and gold plating is carried out on the back surface of the substrate, so that the GCPW calibration piece is obtained.
Alternatively, gold having a purity of 99% may be used for gold plating.
In the embodiment, the substrate of the calibration piece is made of the same material and the same thickness as the measured piece, and the back surface of the substrate is provided with the metal, so that systematic errors caused by different substrates and different boundary conditions can be reduced.
Because the upper surface and the lower surface of the substrate of the calibration piece are both provided with metal, the metal can generate surface waves and multi-mode transmission such as a parallel plate mode, and the like, and the through hole is arranged in the embodiment, so that the influence of the multi-mode transmission line can be reduced, and the error of a system calibration system can be reduced.
It should be noted that, when different calibration pieces are prepared, only different reticles need to be processed, and the subsequent processes from step 701 to step 708 are not changed.
After step 708 is performed, the prepared calibration piece needs to be cleaned and dried, and then microscopic examination is adopted to detect whether the calibration piece is qualified. The microscopic examination means that whether the calibration piece meets the conditions or not is observed under a microscope, if the calibration piece meets the conditions, the calibration piece is qualified, and if the calibration piece does not meet the conditions, the calibration piece is rejected. The object of the microscopic examination can be whether the gold on the calibration piece is obviously too thick or too thin, whether the redundant photoresist exists, and the like.
After the calibration piece is machined, laser trimming is performed on the resistance of the load calibration piece in the calibration piece, which can be performed by using a trimming system in the prior art and is not described in detail herein.
After the resistance repairing is finished, all calibration pieces are subjected to value fixing, and the calibration pieces are applicable to the types of calibration methods: (Short Open-Load, SOL), (Short Open-Load-Thru, SOLT), (Short-Open-Load-Reflect, SOLR), (Line-Reflect-Match, LRRM), (Line-Reflect-Match, LRM), (Thru-Reflect-Line, TRL) or multiline TRL, 16-term, etc., and the prepared calibration piece can be subjected to value fixing by adopting the above mode.
According to the preparation method of the GCPW calibration piece, the size of the through hole is determined according to the cross section size and the theoretical highest frequency corresponding to the GCPW calibration piece by determining the cross section size of the transmission line, and then the calibration piece is prepared according to the size of the transmission line through a process, so that the calibration piece is obtained. In the invention, through setting up the via hole, can reduce the influence of multimode transmission line, thus reduce the systematic error of calibration, in addition, the substrate of the calibration piece and measured piece are the same substrate and same boundary condition, thus can reduce the systematic error introduced by different boundary conditions of different substrates. When the size of the calibration piece is designed, the cross section size is calculated, and then the multi-group stepping sizes are adopted to carry out verification twice according to the cross section size, so that the design success rate and efficiency can be improved, and the deviation caused by process errors can be effectively overcome. When the calibration piece is prepared, the resistor with low resistivity is designed, so that attenuation can be increased, and the frequency response of the transmission line is smoother.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
The embodiment of the invention also provides a GCPW calibration piece, which is prepared by adopting the preparation method of the GCPW calibration piece described in any one of the embodiments and has the beneficial effects generated in the preparation process of the calibration piece in any one of the embodiments.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.
Claims (10)
1. A preparation method of a GCPW calibration piece is characterized by comprising the following steps:
determining the cross-sectional dimension of the transmission line;
determining the size of a via hole according to the cross section size and the theoretical highest frequency corresponding to the GCPW calibration piece, wherein a plurality of via holes are uniformly arranged on an upper floor on the front surface of a substrate, a lower floor, the substrate and grounding metal on the back surface of the substrate, and the positions of the upper floor or the lower floor, the substrate and the grounding metal correspond to each other to form a through hole;
when the cross section size and the via hole size both meet the frequency requirement of a preset calibration piece, optimizing the cross section size to obtain the optimal cross section size;
and carrying out semiconductor process machining according to the optimal cross section size and the via hole size, carrying out laser resistance trimming on the resistance of the load calibration piece in the machined calibration piece, and carrying out value setting on all the calibration pieces after resistance trimming to obtain the GCPW calibration piece.
2. The method of claim 1, wherein the GCPW calibration piece is prepared from a base material,
the thickness of the substrate is the same as that of the tested piece;
the substrate is made of the same material as the tested piece.
3. The method of claim 1, wherein the GCPW calibration piece is prepared from a base material,
the inner wall of the via hole is provided with metal;
the inner wall metal, the grounding metal, the upper floor and the lower floor are all made of gold with the purity of more than 90%.
4. The method of claim 2, wherein the cross-sectional dimensions comprise a center conductor width of the transmission line and a spacing of the center conductor from the upper or lower floor;
determining the size of the via hole according to the cross section size and the theoretical highest frequency corresponding to the GCPW calibration piece, wherein the determining comprises the following steps:
determining the distance between the via holes at corresponding positions on the upper floor and the lower floor according to the width of the central conductor and the distance between the central conductor and the upper floor or the lower floor;
determining the distance between adjacent via holes on the upper floor or the lower floor according to the theoretical highest frequency;
the diameter of the via is set to a length less than or equal to 100 μm.
5. The method of claim 4, wherein the determining the distance between the vias at corresponding locations on the upper and lower floors according to the width of the center conductor and the distance from the center conductor to the upper or lower floor comprises:
according to L1Determining the distance between the via holes at corresponding positions on the upper floor and the lower floor as 2d +2g + w;
wherein L is1The distance between the via holes at the corresponding positions on the upper floor and the lower floor is represented, d represents the distance between the via holes and the edge of the floor where the via holes are located, the edge is the edge of the side closest to the central conductor, g represents the distance between the central conductor and the upper floor or the lower floor, and w represents the width of the central conductor.
6. The method of claim 4, wherein the determining the distance between adjacent vias on the upper floor or the lower floor based on the theoretical maximum frequency comprises:
and determining that the distance between the centers of the adjacent through holes on the upper floor or the lower floor is 1/4 smaller than the wavelength corresponding to the theoretical highest frequency.
7. The method of claim 5, wherein optimizing the cross-sectional dimension to obtain an optimal cross-sectional dimension when the cross-sectional dimension and the via dimension both meet the pre-determined calibrator frequency requirement comprises:
calculating a first theoretical maximum frequency of the transmission line according to the distance between the via holes at the corresponding positions on the upper floor and the lower floor;
calculating a second theoretical maximum frequency of the transmission line according to the cross-sectional dimension;
when the first theoretical maximum frequency and the second theoretical maximum frequency are both greater than or equal to the preset calibration piece frequency requirement, determining that the cross section size meets the requirement;
and optimizing the size of the cross section to obtain the optimal size of the cross section.
8. The method of claim 7, wherein the calculating the first theoretical maximum frequency of the transmission line according to the distance between the vias at corresponding positions on the upper floor and the lower floor comprises:
when the distance between the via holes at the corresponding positions on the upper floor and the lower floor is greater than the thickness of the substrate, the thickness is determined according to the
Calculating a first theoretical maximum frequency of the transmission line;
when the distance between the via holes at the corresponding positions on the upper floor and the lower floor is less than or equal to the thickness of the substrate, according to the method
Calculating a first theoretical maximum frequency of the transmission line；
Wherein f is1And the first theoretical highest frequency of the transmission line is represented, mu represents the magnetic permeability of a medium in a waveguide cavity formed by the upper floor or the lower floor and the through hole, epsilon represents the dielectric constant of the medium in the waveguide cavity formed by the upper floor or the lower floor and the through hole, and h represents the thickness of the substrate.
9. The method of claim 7, wherein the calculating a second theoretical maximum frequency of the transmission line from the cross-sectional dimension comprises:
according to
Calculating a second theoretical maximum frequency of the transmission line;
wherein f is2Represents the second theoretical maximum frequency, mu, of said transmission line0Denotes the air permeability, ∈0Denotes the dielectric constant of air,. epsilonrDenotes the substrate dielectric constant and h denotes the substrate thickness.
10. A GCPW calibration member, comprising a calibration member prepared by the steps of the GCPW calibration member preparation method as claimed in any one of claims 1 to 9.
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