CN102570018B

CN102570018B - Method for manufacturing integrated radio frequency patch microstrip antenna based on BCB/Au

Info

Publication number: CN102570018B
Application number: CN201110434081.2A
Authority: CN
Inventors: 王天喜; 罗乐; 徐高卫; 汤佳杰; 宋恩亮
Original assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Current assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Priority date: 2011-12-21
Filing date: 2011-12-21
Publication date: 2014-02-26
Anticipated expiration: 2031-12-21
Also published as: CN102570018A

Abstract

The invention relates to a method for manufacturing an integrated patch antenna on silicon substrate based on BCB (benzocyclobutene)/Au (aurum). The method is characterized in that a deep notch is etched on substrate silicon to increase the thickness of dielectric material, so that the bandwidth of the antenna is increased; and material filled in the notch and the dielectric material of a transmission line are the same and both are BCB with low dielectric constant. The manufacture process is as follows: a deep notch is etched on the silicon substrate to increase the thickness of dielectric material, a seed layer is formed through splashing, Au is plated to serve as the ground plane of the antenna; the dielectric material is filled in the groove and temperature is controlled for solidification; an Au pillar is manufactured to serve as a through hole that allows a ground wire to be led out; a layer of BCB dielectric material is applied, CMP(chemical mechanical planarization), namely, thinning and polishing, are carried out after solidification so as to improve the surface finish, and the through hole is exposed; and the pattern of the antenna is formed on the BCB through photoetching and plating. After the manufacturing method is adopted, the antenna and an integrated circuit are manufactured as a whole, so that the size is reduced, the reliability is improved, simultaneously, the transmission distance between a transmitter module and the antenna is reduced, and transmission loss is decreased.

Description

A kind of method of making integrated RF paster microstrip antenna based on BCB/Au

Technical field

The invention provides a kind of microwave radio antenna method that adopts microelectronic technique to make, for wafer level packaging, belong to wafer level radio frequency encapsulation technology field.

Background technology

Antenna is indispensable in less radio-frequency field.Microstrip antenna is a kind of new antenna of succeeding in developing phase early 1970s.Compare with conventional microwave antenna, it has the following advantage: volume is little, lightweight, and low section can be conformal with carrier, manufactures simply, and cost is low; Feature on electrical equipment is to obtain unidirectional wide lobe directional diagram, and greatest irradiation direction is in the normal direction of plane, is easy to microstripline integratedly, is easy to realize linear polarization or circular polarization.The microstrip antenna of same structure can form microstrip antenna array, to obtain higher gain and larger bandwidth.Therefore microstrip antenna obtains paying attention to more and more widely.It is upper that traditional RF patch antenna is generally made in PCB (printed circuit board (PCB)), by coaxial cable, is connected with radiating circuit.Although this kind of method has above-mentioned plurality of advantages, but the dielectric constant of baseplate material, thickness, and the dimensional uniformity of antenna is poor, particularly at higher frequency band, these errors can make a big impact to antenna parameter, often after making, need further debugging to use, production efficiency is reduced, increased cost.In addition, traditional paster antenna and integrated circuit separate, and can be subject to the restriction of connector while connecting together, and produce some problems: as impedance matching, and stray inductance, parasitic capacitance etc.

Due to above shortcoming, the antenna being produced on silicon chip arises at the historic moment, and it is together with integrated circuit, and this antenna manufacture craft is accurate, and high conformity, is widely used.But this antenna has a kind of shortcoming, substrate is thinner, generally only has tens μ m even less than 1 μ m, and bandwidth is reduced greatly.Improve substrate thickness h realizes more difficult on silicon, in bibliographical information, conventional way is etching groove on silicon, in groove, filling solid dielectric material makes with highly consistent around, then of liquid, antenna pattern is made thereon, this method makes antenna substrate material have at least two kinds, and aerial loss increases, and the baseplate material of antenna pattern and feeder line is different, easily produce impedance mismatch, emulation simultaneously and technique are made trouble; Another kind be in groove, fill and other regions just as dielectric material (being generally liquid), then solidify, this method can also be used when the degree of depth of groove is more shallow, but in the time of the large degree of depth, often cause the planarization of antenna surface bad, antenna is caused to harmful effect.

Summary of the invention

Shortcoming for conventional patch antenna, the object of the invention is to propose a kind of method of making integrated RF paster microstrip antenna based on BCB/Au, particularly the method for above-mentioned etching tank is improved, make in large degree of depth situation, can and make the evenness of groove top and around be consistent with same material.The method and embedded type wafer level radio frequency packaging technology are completely compatible, can make together with MMIC (monolithic integrated microwave circuit Monolithic Microwave Integrated Circuit) packaging technology, do not need to increase extra step.

Concrete production program of the present invention: a) take silica as mask, with the anisotropic etchant KOH deep trouth that degree of depth of etching is 200-400 μ m on silicon chip;

B) in the deep trouth forming at step a, fill the BCB material of relative dielectric constant < 3.5, utilize the surface tension of liquid, make BCB (benzocyclobutene benzocyclobutene) liquid surface exceed the plane of silicon chip, the contraction when BCB that the volume compensation exceeding is filled solidifies;

C) silicon chip that step b is filled with to BCB in deep trouth is placed on minute second-stage solidification in hot reflux stove, and first stage curing temperature is 170-190 ℃; Second stage curing temperature is 210-250 ℃, is then down to normal temperature; To guarantee that the BCB dielectric material of filling in follow-up high temperature no longer shrinks; Meanwhile, the BCB air spots of filling after solidifying, intermediate recess surrounding projection;

D) after step c solidifies, plant ball and form Au soldered ball, draw the ground wire of described antenna;

E) on glue spreader, apply one deck BCB, static 2-4 hour after applying, then solidifies, and by normal temperature, is warmed up to 210-230 ℃ again, and the time is 20-40min, insulation 40-60min, and last linear cooling, temperature fall time is 20-40min; Surperficial evenness is further improved;

F) after step e completes, carry out CMP (chemico-mechanical polishing Chemical Mechanical Planarization) technique, make surface more smooth, Au soldered ball exposes;

G) photoetching electric plating method is made the figure of antenna above deep trouth, the steps include:

1. first at BCB surface sputtering one deck Seed Layer TiW/Au, thickness is respectively

2. then apply photoresist, photoetching, develops, and exposes antenna pattern window above groove, then electroplates Au;

3. finally remove photoresist, remove Seed Layer, leave antenna pattern.

Its further feature is:

(1) in described step e, applying one deck BCB thickness of dielectric layers is 20-50 μ m again.

(2) in described step c, first stage curing temperature is 180 ℃, and second stage curing temperature is 230 ℃.

(3) the Au ball height described in steps d is 20-50 μ m.

(4) the Au ball height described in steps d is 30-40 μ m.

(5) in described step e, applying one deck BCB thickness of dielectric layers is 25-40 μ m again.

(6) in described step g, 2. described plating Au thickness is 2-5 μ m.

(7) described method, is characterized in that:

1. in step c, from room temperature, to be warmed up to 170-190 ℃ of time be 60 minutes the first stage, and BCB is slowly solidified, and BCB is fully mobile, shrinks little that the depression that causes tries one's best;

2. be then warmed up to 210-250 ℃, make BCB completely curing, the whole process control of first stage and second stage is at 120min.

(8) dielectric constant < 3.5 materials described in step b are PI, also use heating means to solidify.

The sectional view of the antenna finally completing and vertical view are respectively as f in Fig. 1 (a) and f (b), and antenna is integrated in silica-based upper, and has increased dielectric substrate thickness by digging the way of deep trouth.

This kind of antenna overcome the thinner shortcoming of silicon base integrated antenna medium substrate, compares with traditional silicon base integrated antenna, can obviously increase the bandwidth of antenna, improved the performance of antenna.From manufacturing process, can find out, this kind of fabrication processing and embedded type chip package are compatible, the compatible microelectronic technique of its manufacture craft process, can carry out together with MMCM (Microwave Multichip Module Microwave multichip module) packaging technology, and complete on the basis of wafer level packaging.Without increasing additional technical steps.So the antenna that this kind of method made can encapsulate together with chip, compares with traditional external antenna method, has reduced the transmission range between antenna transmission module and antenna, thereby has reduced loss.Meanwhile, antenna, together with integrated chip, has improved reliability, has reduced volume, meets the trend of modern integrated circuits encapsulation.

Accompanying drawing explanation

Fig. 1: micro-strip paster antenna fabrication processing.

A) with KOH corrosive liquid deep trouth of etching on silica-based;

B) in groove, fill excessive BCB;

C) solidify BCB, and on substrate, plant ball;

D) with spin-coating method, at silicon substrate surface, apply one deck BCB;

E) carry out CMP, Au soldered ball is exposed, BCB reaches suitable thickness and surfacing;

F) use galvanoplastic to make antenna pattern at BCB upper surface, the sectional view that wherein f (a) is the antenna that completes, f (b) is vertical view, in figure, 102 is silicon substrate surface stratum; 103 is the dielectric material of filling in groove; 104 is the via hole on the dielectric material of top layer, i.e. soldered ball; 105 is the antenna pattern of groove upside.

Fig. 2: the curing temperature curve of BCB in etching tank.

Fig. 3: the temperature curve that surperficial BCB is curing.

Embodiment

Below in conjunction with reference to accompanying drawing, embodiments of the invention further being specifically described.Scope of the present invention is not limited to the following examples.

Embodiment:

(1) use KOH at deep trouth of silicon (101) surface etch, the degree of depth is that 200 these examples of μ m-400 μ m are 300 μ m, sputter one deck TiW/Au, and thickness is respectively

as Seed Layer, electroplate the about 3 μ m of Au, as the ground level (102) of antenna.

(2) advanced low-k materials of excessive filling liquid in groove, this example is BCB (103), in the situation that not overflowing groove edge, injection dielectric material as far as possible, then in hot reflux stove, solidify, curing temperature curve as shown in Figure 2, first 60 minutes under lower temperature (180 ℃) (being room temperature or normal temperature～180 ℃) BCB is slowly solidified, BCB can be fully mobile simultaneously, the depression that less contraction causes as far as possible, then rises to 230 ℃, makes BCB completely curing, be down to again room temperature, whole process 120 minutes.Described room temperature or normal temperature are 18-25 ℃.

(3) after solidifying, plant ball (104), draw ground wire, the about 30-40 μ of the height m of Au soldered ball.

(4) on glue spreader, apply again BCB (103), thickness is 30 μ m, after coating, standing more than 2 hours, make surface more smooth, then solidify, curing time curve as shown in Figure 3, in the present embodiment, the curing temperature of surperficial BCB is 205 ℃, BCB is solidified still substantially and not exclusively, be beneficial to CMP technique below.

(5) carry out CMP technique, make surface more smooth, Au soldered ball (104) exposes, and makes top layer BCB thickness at 25-40 μ m.

(6) by galvanoplastic, on surface, make antenna pattern (105), finally complete the manufacture craft of antenna.

Claims

1. make a method for the microstrip antenna of radio frequency paster, it is characterized in that the step of making is:

A) take silica as mask, with the anisotropic etchant KOH deep trouth that degree of depth of etching is 200-400 μ m on silicon chip;

B) in the deep trouth that step a forms, fill the BCB material of relative dielectric constant <3.5, utilize the surface tension of liquid, make BCB liquid surface exceed the plane of silicon chip, the contraction when BCB that the volume compensation exceeding is filled solidifies;

C) silicon chip that step b is filled with to BCB in deep trouth is placed in hot reflux stove and solidifies, within first 60 minutes, at lower temperature BCB, slowly solidify, BCB can be fully mobile simultaneously, the depression that less contraction causes as far as possible, then rise to 230 ℃, make BCB completely curing, then be down to room temperature, whole process 120 minutes, to guarantee that the BCB dielectric material of filling in follow-up high temperature no longer shrinks; Meanwhile, the BCB air spots of filling after solidifying, intermediate recess surrounding projection;

F) after step e completes, carry out CMP technique, make surface more smooth, Au soldered ball exposes;

3. finally remove photoresist, remove Seed Layer, leave antenna pattern.

2. by method claimed in claim 1, it is characterized in that in step e, applying one deck BCB thickness of dielectric layers is 20-50 μ m again.

3. by method claimed in claim 1, it is characterized in that in step c, first stage curing temperature is 180 ℃, second stage curing temperature is 230 ℃.

4. by method claimed in claim 1, it is characterized in that the Au ball height described in steps d is 20-50 μ m.

5. by the method described in claim 1 or 4, it is characterized in that the Au ball height described in steps d is 30-40 μ m.

6. by the method described in claim 1 or 2, it is characterized in that in step e, applying one deck BCB thickness of dielectric layers is 25-40 μ m again.

7. by method claimed in claim 1, it is characterized in that in step g that 2. described plating Au thickness is 2-5 μ m.

8. by method claimed in claim 1, it is characterized in that:

9. by method claimed in claim 1, it is characterized in that the dielectric constant <3.5 material described in step b is PI, use heating means to solidify.

10. by the method described in any one in claim 1-4, it is characterized in that:

1. described method is also carried out with microelectronic technique compatibility together with MMCM packaging technology, and completes on the basis of wafer level packaging;

The beamwidth of antenna of 2. making obviously increases.