CN104183570B - Near-zero-eddy-current-loss interconnection line and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of radio frequency devices, and provides a near-zero-eddy-current-loss interconnection line and a preparation method of the near-zero-eddy-current-loss interconnection line. The near-zero-eddy-current-loss interconnection line comprises a substrate and an interconnection line body arranged on the surface of the substrate. The interconnection line body is a periodical composite superlattice film structure formed by stacking metallic copper thin film layers and ferromagnetic metal thin film layers alternately, wherein each metallic copper thin film layer is 50-1000 nm thick, each ferromagnetic metal thin film layer is 20-500 nm thick, ferromagnetic metal is alloy composed of magnetic metal and copper, and the periodicity of the periodical composite superlattice film structure is 5-200. The metallic copper is used as raw materials of the interconnection line body, so that the cost is low. The superlattice film structure is adopted, so that the interconnection line is simple in structure and easy to make, reduces stress caused by lattice mismatch and is low in resistivity. Near-zero effective magnetic conductivity is realized through frequency band selection, so that no obvious skin effect is caused when the thickness ranges from 10 micrometers to 100 micrometers. The interconnection line is prepared through a metal electrochemistry alternating deposit method in a multi-period and alternate electroplating mode, so that the difficulty and cost of the preparation process are reduced. The near-zero-eddy-current-loss interconnection line and the preparation method of the near-zero-eddy-current-loss interconnection line are suitable for the radio frequency devices.

Description

A kind of nearly zero eddy-current loss interconnection line and preparation method thereof

Technical field

The present invention relates to radio-frequency devices technical field, it is specifically related to a kind of ultralow eddy-current loss radio frequency interconnection line and its system Preparation Method, especially a kind of nearly zero eddy-current loss interconnection line for radio-frequency devices and preparation method thereof.

Background technology

In radio-frequency devices technical field, on piece, for example micro- inductance of integrated device, microstrip line, co-planar waveguide etc. are required for using figure Change thin film as interconnection line, and many in traditional devices material is prepared as interconnection line using copper.But due to there is skin effect Should, electromagnetic wave can cause vortex phenomenon inside copper conductor, and distribution in conductors cross for the electric current is no longer uniform, electric current Concentrate on the thin layer of adjacent conductors outer surface so that interconnection resistance increases, loss power increases.For the ease of describing skin effect Should, introducing a skin depth is critical depth δ, and the electric current density size of this depth is exactly the 1/e of surface current density Times:

$\mathrm{\δ}=\sqrt{\frac{\mathrm{\σ}}{{\mathrm{\πf\μ}}_0{\mathrm{\μ}}_r}}$

Wherein, f is frequency, μ₀μ_rFor pcrmeability (h/m), σ is electrical conductivity (s/m), comes for general metal material such as copper Say, its relative permeability μ_rFor 1, so pcrmeability is permeability of vacuum μ₀=4 π × 10^-7h/m.Therefore preparing high frequency device During part (especially radio-frequency devices), in order to increase skin depth, often adopt the bigger metal material of electrical conductivity such as silver as mutually Line, but because silver is noble metal, the cost of resulting devices can be greatly increased as interconnection line.Have not yet to see report cost Cheap and resistivity is low, or even nearly zero eddy-current loss interconnection line and its preparation side of nearly zero Effective permeability is realized in special frequency channel Method.

Content of the invention

The technical problem to be solved is to provide a kind of with low cost and realize nearly zero vortex damage in special frequency channel Interconnection line of consumption and preparation method thereof, can effectively eliminate the eddy-current loss when special frequency channel is as interconnection line for the metallic copper.

The technical solution adopted for the present invention to solve the technical problems is:

A kind of nearly zero eddy-current loss interconnection line, including the interconnection line of substrate base and substrate base surface；Described interconnection line It is that the periodicity being formed by the alternate stacking of metal copper film layer and ferromagnetic metal thin film layer is combined superlattice thin film structures；Its In, the thickness of every layer of metal copper film layer is 50～1000nm, and every layer of ferromagnetic metal thin film layer thickness is 20～500nm；Described Feeromagnetic metal is the alloy that magnetic metal is formed with copper；Described periodicity be combined superlattice thin film structures periodicity be 5～ 200.

Specifically, the scope of the gross thickness of described interconnection line is 10～100 μm.

Specifically, described magnetic metal is one or more of ferrum, nickel or cobalt.

In order to prepare above-mentioned nearly zero eddy-current loss interconnection line, the technical scheme of employing is: a kind of nearly zero eddy-current loss interconnection The preparation method of line, comprises the following steps:

A. sputter barrier layer on silicon substrate substrate, and sputter copper seed layer over the barrier layer；

B. thick resist lithography is carried out on the seed layer using photoresist, expose interconnection line line pattern；

C. it is based on electrochemistry alternating deposit method, cross liquid alternatively plate week on interconnection line line pattern using electrochemical deposition The metal copper film layer of the alternate stacking of phase property and ferromagnetic metal thin film layer；D. rinse silicon substrate substrate, after being dried, remove photoresist；

E. the barrier layer beyond removal interconnection line line pattern and copper seed layer.

Specifically, step a is specially the method adopting magnetron sputtering, sputters the conduct of one layer of 50nm on silicon substrate substrate The layer of titanium metal on barrier layer, then in the copper seed layer sputtering 200nm in layer of titanium metal.

Preferably, the photoresist in step b is az4620 photoresist.

Preferably, also have step between step b and c:

B1. plasma cleaner bottoming film 50s is adopted to remove the Organic substance counterdie in interconnection line line pattern region and glue Dirty；

B2. the dilute sulfuric acid adopting 5% soaks silicon substrate substrate 1min.

Specifically, in step c, alternatively plate is carried out using many current potentials constant-voltage method.

Preferably, volume ratio is adopted to be 98%h in step e₂so₄: 30%h₂o₂:h₂The solution of o=5ml:1ml:100ml with The speed of 300nm/min removes layers of copper, and the hf solution using 5% removes titanium layer within 2～4s time.

The invention has the beneficial effects as follows: using metallic copper as interconnection line raw material, with low cost, using superlattice film Structure, structure is simple, it is easy to accomplish, reduce the stress that lattice mismatch leads to, there is low resistivity it is most important that can select Select frequency range and realize nearly zero Effective permeability, so thickness can be in 10～100 μm of no obvious Kelvin effects；Using metal electrification Learn alternating deposit fado cycle alternatively plate and prepare this interconnection line, reduce preparation technology difficulty and cost, increased design freedom. The present invention is applied to radio-frequency devices.

Brief description

Fig. 1 is that the periodicity in the interconnection line of the present invention is combined superlattice thin film structures schematic diagram；

Fig. 2 is the variation tendency with frequency for the square resistance under different cycles for the superlattice multilayer film；

Fig. 3 be different-thickness ratio in the case of superlattice film sheet resistance with frequency variation tendency；

Wherein, 1 is metal copper film layer, and 2 is ferromagnetic metal thin film layer, and 3 is substrate base.

Specific embodiment

Below in conjunction with the accompanying drawings, describe technical scheme in detail.

As shown in figure 1, the nearly zero eddy-current loss interconnection line of one kind of the present invention, including substrate base 3 and substrate base 3 surface Interconnection line, described interconnection line is that the periodicity that formed is answered by the alternate stacking of metal copper film layer 1 and ferromagnetic metal thin film layer 2 Close superlattice thin film structures；Wherein, the thickness of every layer of metal copper film layer 1 is 50～1000nm, every layer of ferromagnetic metal thin film layer 2 Thickness is 20～500nm；Described feeromagnetic metal is the alloy that magnetic metal is formed with copper；Described periodicity is combined superlattice film The periodicity of structure is 5～200.

Superlattice thin film structures are to interlaminate life with several nanometers to tens nanometers by two kinds of different materials Grow and keep the multilayer film of strict periodicity it is simply that the fine composite construction of the stratiform of particular form.The interconnection line of the present invention adopts Superlattice thin film structures, are to alternate the metal copper film layer 1 of superposition by multiple cycles and ferromagnetic metal thin film layer 2 is formed Structure.

For feeromagnetic metal, due to there is ferromagnetic resonance, when applying frequency is higher than resonant frequency, its pcrmeability is negative. For the superlattice structure thin film in the present invention, due to there is coupling, overall relative permeability can be expressed as:

${\mathrm{\μ}}_{rav}=\frac{1\·t_n+{\mathrm{\μ}}_{rf}\·t_f}{t_n+t_f}$

Wherein, t_nAnd t_fIt is respectively the thickness of metal copper film layer 1 and ferromagnetic metal thin film layer 2, μ_rfFor feeromagnetic metal Relative permeability.By above-mentioned formula as can be seen that due to μ_rfIt is negative under special frequency channel, by adjusting metal copper film layer 1 and ferromagnetic metal thin film layer 2 relative thickness it is possible to the relative permeability realizing superlattice film in special frequency channel tends to Zero, according to above-mentioned formula, when relative permeability is zero, its skin depth is infinity, and the eddy-current loss so causing is then Almost nil.

Using the m-cu alloy close with copper (cu) lattice paprmeter and lattice types, m is magnetic metal to feeromagnetic metal, specifically For ferrum (fe), nickel (ni) or cobalt (co).Its purpose is as follows: first, magnetic element alloy can provide high frequency negative magnetoconductivity；Its Secondary, m-cu alloy-layer is good with the lattice of cu layer, can reduce by interfacial stress, is that thick film is coated with and creates conditions；Again, The resistivity of m-cu alloy is close with cu, and lattice match is higher, and when electronics transmits at interface, energy loss is lower, favorably In the resistivity reducing superlattice film entirety；Finally, choose these three magnetic element and cu and form alloy, it is to avoid other yuan The introducing of element, just can adjust the performance of ferrimag only by the content changing cu, the technique reducing superlattices preparation Difficulty, is that the interconnection line that different frequency range uses provides bigger degree of freedom.

It is illustrated in figure 2 the variation tendency with frequency for the square resistance under different cycles for the superlattice multilayer film.Wherein, thin Film gross thickness is 6 μm, and ferromagnetic metal thin film layer is cocu layer herein, and cu layer and cocu layer are 3:1, and phase property is combined superlattice film The periodicity of structure is respectively 50,30,14 and 8.It can be seen that in frequency for 8.9ghz, square resistance goes out Show an obvious minimum, and now magnetic spectrum corresponding pcrmeability real part has been -3 it is contemplated that t_cu: t_cocu=3, according to above-mentioned Formula understands, the overall relative permeability μ of superlattices_av=0.Additionally, in figure understands that the cycle is bigger, each layer of thickness is thinner When, minimum is less, this show cycle bigger coupling stronger so that resistance is less.

In the case of different-thickness ratio, (cu layer is sequentially reduced 1 with the thickness of cocu layer than by 5) superlattices are thin as shown in Figure 3 The sheet resistance of film is with the variation tendency of frequency.It can be seen that metal copper film layer 1 ferromagnetic metal thin film layer relatively is thicker, The minimizing frequency of resistance occurs less.Therefore in actual applications, can be met not by change cycle and thickness ratio Same application demand.

In actual applications, can be obtained by gauging surface impedance on the basis of obtaining ferromagnetic metal magnetic film spectrum The square resistance of plural layers is with the variation tendency of frequency, and then perfect design is realized interconnection line and become in the pcrmeability of selected frequency range In zero, and skin depth is infinitely great.

Based on cost and realize effect and consider, the scope of the gross thickness of described interconnection line is 10～100 μm, with respect to identical The existing interconnection line of length, the resistance of the interconnection line of the present invention is greatly reduced, and eddy-current loss is close to zero.

The method preparing above-mentioned nearly zero eddy-current loss interconnection line, comprises the following steps:

A. sputter barrier layer on silicon substrate substrate, and sputter copper seed layer over the barrier layer；

The sputtering of Seed Layer can be realized using multiple existing methods, in order to effectively improve adhesive force, and stop copper Phase counterdiffusion between Seed Layer and the silicon of substrate base, can adopt the method for magnetron sputtering to grow one layer first on substrate Titanium (ti) layer of 50nm, simultaneously as copper is difficult to etch it is impossible to first deposit etched features again as traditional metallic aluminium, because This needs first to etch line pattern, then electroplates out circuit with deposition.But need during plating conductive it is therefore necessary on barrier layer Surface covers one layer of copper seed layer in order to conduction, when power supply is added in periodically compound superlattice thin film structures (anode) and silicon chip When between (negative electrode), the metallic element of anode reacts and changes into metal ion and electronics, and negative electrode also reacts simultaneously, cloudy Extremely nearby the copper ion of seed layer surface and electronics combine to form the copper being plated in seed layer surface.Ultimately form circuit, therefore need The copper wanting regrowth 200nm is as Seed Layer.B. thick resist lithography is carried out on the seed layer using thick glue az4620, expose interconnection line Line pattern；

Positive photoresist az4620 is widely used in microfabrication, uses, have resolution generally in the range of i line spectrum The advantages of rate is high, depth-to-width ratio is big, absorptance is little.

C. it is based on electrochemical metal alternating deposit method, cross liquid using electrochemical deposition alternately electric on interconnection line line pattern The metal copper film layer of the periodically alternate stacking of plating and ferromagnetic metal thin film layer, form superlattice thin film structures；

, the formula that electrochemical deposition crosses liquid includes taking the alloy that feeromagnetic metal is formed with copper for magnetic metal cobalt as a example coso₄.7h₂o、cuso₄.5h₂o、h₃bo₃, lft-930mu open cylinder agent, lft-930a brightener and lft-930b brightener.Electrification Learn deposition and cross the co in liquid²⁺With cu²⁺Ratio critically important, if cu²⁺Excessive so that when electroplating ferromagnetic metal thin film layer, co²⁺ Content can bad control；If co²⁺Content is excessive, it will makes during electro-coppering slowly or is difficult to plating up.The present invention Middle employing co²⁺: cu²⁺The formula of=25:1.H in liquid is crossed in chemical deposition₃bo₃Effect is to adjust ph value, using the ph of above-mentioned formula It is worth for 3.Lft-930mu open cylinder agent, lft-930a brightener and lft-930b brightener are the flatness in order to change scattered thin film And brightness, reduce defect so that quality is higher, resistivity is lower.In addition can also adopt and there is ni²⁺Or fe²⁺Plating Liquid.

The present invention adopts electrochemical metal alternating deposit method preparation metal copper film layer and ferromagnetic metal thin film layer alternately folded Plus the multilayer film being formed.Due to co²⁺Inertia be more than copper, there are different sedimentation states in volt-ampere curve.Work as voltage When sufficiently low, now cu²⁺Rate of reduction quickly, co²⁺Rate of reduction very slow, so that substantially all deposition is cu；And When voltage is larger, now for co²⁺Reduction potential maximal point, only there is co in such negative electrode²⁺Reduction.Therefore pass through to change Become current potential, the thin film of heterogeneity can be obtained；By changing electroplating time, the thin film of different-thickness can be obtained.

Below with deposit the feeromagnetic metal of co-cu and superlattice thin film structures that cu is constituted as an example, detailed description is adopted Process with many current potentials constant-voltage method alternatively plate.Using constant-voltage method, when deposition voltage is -1v, the composition of thin film is co_0.68cu_0.32, and the magnetic having had, can be used as required magnetosphere.Alternatively plate uses many current potentials constant-voltage method, Wherein current potential 1 is set as that -0.5v is set as -1v to deposit co to deposit cu layer, current potential 2_0.68cu_0.32Layer.By changing different electricity The time of staying of position can obtain the multilayer film of different-thickness ratio long.By programming Control time-interleaved change current potential, permissible Obtain multicycle structure.

D. rinse silicon substrate substrate, after being dried, remove photoresist；

Specifically, it is after plating completes, is dried up using deionized water rinsing and be dried, then with acetone by light Photoresist dissolving is removed photoresist.

E. the barrier layer beyond removal interconnection line line pattern and copper seed layer.

Volume ratio is specifically adopted to be 98%h₂so₄: 30%h₂o₂:h₂The solution of o=5ml:1ml:100ml with The speed of 300nm/min removes layers of copper, and the hf solution using 5% removes the titanium layer of 50nm within 2～4s time, and to cocu/ Cu multilayer film does not affect.

Preferably, before electrochemical deposition, also need to carry out two step Seed Layer pretreatment, therefore, in step b and step c Between also have step:

B1. adopt plasma cleaner, such as using oxygen gas plasma o₂Plasma bottoming film 50s removes interconnection line circuit Organic substance counterdie in graphics field and pickup；

B2. the dilute sulfuric acid adopting 5% soaks silicon substrate substrate 1min, removes layers of copper in oxygen gas plasma and in the air shape The oxide-film becoming.

The nearly zero eddy-current loss interconnection line for radio-frequency devices that said method generates can effectively eliminate using copper in spy Determine frequency range as eddy-current loss during interconnection line.Easily and accurately control the thickness of each layer in multilayer film by changing different potentials Degree and composition, are made being facilitated using frequency range of interconnection line adjustable, greatly reduce preparation time and cost, in radio-frequency devices and collection Become in circuit and there is very big application prospect.

Claims (9)

1. a kind of nearly zero eddy-current loss interconnection line, including the interconnection line of substrate base (3) and substrate base (3) surface, its feature It is, described interconnection line is that the periodicity being formed by the alternate stacking of metal copper film layer (1) and ferromagnetic metal thin film layer (2) is multiple Close superlattice thin film structures；Wherein, the thickness of every layer of metal copper film layer (1) is 50～1000nm, every layer of iron magnetic metal film Layer (2) thickness is 20～500nm；Described feeromagnetic metal is the alloy that magnetic metal is formed with copper；Described periodicity is combined super brilliant The periodicity of lattice membrane structure is 5～200.

2. as claimed in claim 1 a kind of nearly zero eddy-current loss interconnection line it is characterised in that the gross thickness of described interconnection line Scope is 10～100 μm.

3. the nearly zero eddy-current loss interconnection line of one kind as claimed in claim 1 is it is characterised in that described magnetic metal is ferrum, nickel One or more of or cobalt.

4. a kind of preparation method of nearly zero eddy-current loss interconnection line is it is characterised in that comprise the following steps:

A. sputter barrier layer on silicon substrate substrate, and sputter copper seed layer over the barrier layer；

B. thick resist lithography is carried out on the seed layer using photoresist, expose interconnection line line pattern；

C. it is based on electrochemistry alternating deposit method, cross liquid using electrochemical deposition and plate cycle is replaced on interconnection line line pattern The metal copper film layer of alternate stacking and ferromagnetic metal thin film layer；

D. rinse silicon substrate substrate, after being dried, remove photoresist；

E. the barrier layer beyond removal interconnection line line pattern and copper seed layer.

5. as claimed in claim 4 a kind of preparation method of nearly zero eddy-current loss interconnection line it is characterised in that step a is concrete It is the method using magnetron sputtering, the layer of titanium metal as barrier layer of one layer of 50nm is sputtered on silicon substrate substrate, then exists The copper seed layer of 200nm is sputtered on layer of titanium metal.

6. as claimed in claim 5 a kind of preparation method of nearly zero eddy-current loss interconnection line it is characterised in that in step b Photoresist is az4620 photoresist.

7. as claimed in claim 6 a kind of preparation method of nearly zero eddy-current loss interconnection line it is characterised in that step b and c it Between also have step:

B1. plasma cleaner bottoming film 50s is adopted to remove Organic substance counterdie and pickup in interconnection line line pattern region；

B2. the dilute sulfuric acid adopting 5% soaks silicon substrate substrate 1min.

8. as claimed in claim 6 a kind of preparation method of nearly zero eddy-current loss interconnection line it is characterised in that in step c Alternatively plate is carried out using many current potentials constant-voltage method.

9. as claimed in claim 8 a kind of preparation method of nearly zero eddy-current loss interconnection line it is characterised in that adopting in step e It is 98%h with volume ratio₂so₄: 30%h₂o₂:h₂The solution of o=5ml:1ml:100ml goes copper removal kind with the speed of 300nm/min Sublayer, the hf solution using 5% removes layer of titanium metal within 2～4s time.