CN111739870A - High polymer buffer layer copper coaxial TGV, adapter plate and preparation method thereof - Google Patents
High polymer buffer layer copper coaxial TGV, adapter plate and preparation method thereof Download PDFInfo
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 170
- 239000010949 copper Substances 0.000 title claims abstract description 159
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 157
- 229920000642 polymer Polymers 0.000 title claims abstract description 55
- 238000002360 preparation method Methods 0.000 title description 12
- UMIVXZPTRXBADB-UHFFFAOYSA-N benzocyclobutene Chemical compound C1=CC=C2CCC2=C1 UMIVXZPTRXBADB-UHFFFAOYSA-N 0.000 claims abstract description 49
- 238000000034 method Methods 0.000 claims abstract description 35
- 238000011049 filling Methods 0.000 claims abstract description 8
- 238000004519 manufacturing process Methods 0.000 claims abstract description 6
- 239000000758 substrate Substances 0.000 claims description 91
- 208000014903 transposition of the great arteries Diseases 0.000 claims description 56
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 29
- 239000004020 conductor Substances 0.000 claims description 24
- 238000000151 deposition Methods 0.000 claims description 19
- 238000005498 polishing Methods 0.000 claims description 19
- 239000011248 coating agent Substances 0.000 claims description 16
- 238000000576 coating method Methods 0.000 claims description 16
- 239000000377 silicon dioxide Substances 0.000 claims description 16
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 14
- 229910052710 silicon Inorganic materials 0.000 claims description 14
- 239000010703 silicon Substances 0.000 claims description 14
- 238000001259 photo etching Methods 0.000 claims description 12
- 229920002120 photoresistant polymer Polymers 0.000 claims description 12
- 238000005530 etching Methods 0.000 claims description 11
- 235000012239 silicon dioxide Nutrition 0.000 claims description 11
- 239000000853 adhesive Substances 0.000 claims description 10
- 230000001070 adhesive effect Effects 0.000 claims description 10
- 239000003292 glue Substances 0.000 claims description 10
- 238000000227 grinding Methods 0.000 claims description 9
- 238000000059 patterning Methods 0.000 claims description 9
- 238000009713 electroplating Methods 0.000 claims description 7
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- 239000008367 deionised water Substances 0.000 claims description 3
- 229910021641 deionized water Inorganic materials 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000004094 surface-active agent Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 2
- 239000002002 slurry Substances 0.000 claims 3
- -1 copper post (1) Chemical compound 0.000 claims 1
- 230000010354 integration Effects 0.000 abstract description 8
- 238000004806 packaging method and process Methods 0.000 abstract description 5
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 238000013461 design Methods 0.000 abstract description 2
- OUPZKGBUJRBPGC-UHFFFAOYSA-N 1,3,5-tris(oxiran-2-ylmethyl)-1,3,5-triazinane-2,4,6-trione Chemical compound O=C1N(CC2OC2)C(=O)N(CC2OC2)C(=O)N1CC1CO1 OUPZKGBUJRBPGC-UHFFFAOYSA-N 0.000 abstract 1
- 239000000463 material Substances 0.000 description 6
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- 229910052681 coesite Inorganic materials 0.000 description 4
- 229910052906 cristobalite Inorganic materials 0.000 description 4
- 238000000708 deep reactive-ion etching Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- 229910052682 stishovite Inorganic materials 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910052905 tridymite Inorganic materials 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 230000003139 buffering effect Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 2
- 238000004528 spin coating Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000013543 active substance Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
- H01L23/49827—Via connections through the substrates, e.g. pins going through the substrate, coaxial cables
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
- H01L21/4814—Conductive parts
- H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
- H01L21/486—Via connections through the substrate with or without pins
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
- H01L23/49866—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers characterised by the materials
- H01L23/49894—Materials of the insulating layers or coatings
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Abstract
The invention provides a copper coaxial TGV (triglycidyl isocyanurate) with a high polymer buffer layer, which comprises a copper column, an annular inner buffer layer, an annular copper layer and an annular outer buffer layer which are sequentially arranged, wherein the copper column, the inner buffer layer, the copper layer and the outer buffer layer are sequentially arranged from inside to outside, and the outer buffer layer and the inner buffer layer are high polymer benzocyclobutene layers. An interposer having the coaxial TGV and an interposer manufacturing method are also provided. The size of the high polymer buffer layer is flexible and variable, and coaxial TGV structures with different sizes can be designed conveniently according to a matching principle. A scheme for preparing a copper coaxial TGV structure of a high polymer buffer layer is given in detail, and the buffer layer is prepared by filling an annular groove with a high polymer. The process implementation scheme ensures impedance matching design, simultaneously ensures small overall structure size, improves thermal stability of packaging, and is beneficial to future high-density three-dimensional integration.
Description
Technical Field
The invention relates to the technical field of manufacturing of three-dimensional integrated packaging adapter plates, in particular to a high polymer buffer layer copper coaxial TGV, an adapter plate and a preparation method thereof.
Background
3D packaging is currently the most mature category of integration in the industry, stacking bare chips or individually packaged chips together primarily by packaging, and currently involves many different technologies, most of which are extensions of the existing single chip packaging technologies in three dimensions. Interposer (Interposer), also known as Interposer or Interposer, is a new type of electronic substrate that enables interconnection between fine-pitch I/O at the top die level and larger-size, large-pitch I/O at the bottom package level. The adapter plate is provided with a plurality of Glass Through holes (TGVs) which penetrate Through the substrate to extend and be interconnected, so that the interconnection length is shortened while vertical integration is realized, the size, the weight and the power consumption are reduced, and the adapter plate is the foundation and the core of the current 2.5D/3D integration technology.
In order to meet the application of the three-dimensional integration technology in the high-frequency field such as microwave, the TGV structure is required to have the capability of transmitting high-frequency signals with the lowest loss possible. However, in the conventional TGV structure, the thermal expansion coefficient difference between copper and glass is large, which may cause cracks, affect the stability of the interposer, and affect the performance of the high-frequency system. The coaxial TGV structure can effectively utilize the buffering and shielding effects of the outer ring conductor, reduce the stress loss between copper and the substrate, and effectively reduce the noise of the substrate. At present, the research on coaxial TGV at home and abroad mostly focuses on the establishment and analysis of related electromechanical models, and the complete coaxial TGV process realization is rarely reported. The reported scheme for realizing coaxial TGV preparation is not beneficial to realizing future high-density three-dimensional integration due to the limitation of factors such as process and the like and large overall structure size.
Fig. 1 shows three typical excellent coaxial TGV structures provided by domestic and foreign research institutes to meet the requirements of high frequency fields on TGV signal transmission performance, wherein Cu is used as a conductive material, but different types of buffer dielectric layers are used. FIG. 1(a) shows the use of SiO2Coaxial TGV as a buffer material, however due to SiO2The thickness of the buffer layer is limited by the deposition process to only a few hundred nanometers, so the achievable radius ratio n (outer conductor to inner conductor) of the overall coaxial structure is very close to 1, resulting in a smaller characteristic impedance and a poorer impedance match. To solve the above problem, FIG. 1(b) proposes the use of mixed SiO between the inner and outer conductors of a coaxial TGV structure2a/Si buffer layer, which helps to increase the ratio n to achieve better impedance matching. But the transmission loss of such a coaxial TGV increases due to the insertion of a lossy silicon layer. In order to achieve low transmission loss and controllable characteristic impedance matching at the same time, a coaxial structure using a high polymer as a buffer layer is proposed as shown in fig. 1(c), but the overall structure size is large due to process limitations. The sizes of the coaxial structures of the polymer buffer layers in the related documents are compared as shown in the table:
| cushioning material | SU-8 | SU-8 | ABF |
| TGV (inner conductor) diameter/. mu.m | 65 | 100 | 70 |
| Buffer layer width/mum | 125/150 | 300 | 120 |
It can be seen that the size of the inner conductor of the three structures is large, and the size of the finally prepared integral coaxial TGV structure is also large, so that the three-dimensional integration of high density in the future is not facilitated.
Disclosure of Invention
The invention aims to solve the technical problem of providing a high polymer buffer layer copper coaxial TGV adapter plate with high stable transmission characteristic, controllable characteristic impedance matching and small overall structure size and a preparation method thereof.
The technical scheme adopted by the invention for solving the technical problems is as follows: high polymer buffer layer copper is coaxial TSV, including the copper post that sets gradually, annular interior buffer layer, annular copper layer and annular outer buffer layer, copper post, interior buffer layer, copper layer and outer buffer layer set gradually from interior to exterior, outer buffer layer is high polymer benzocyclobutene layer upon layer, interior buffer layer is high polymer benzocyclobutene layer.
The adapter plate comprises a substrate, wherein the substrate is provided with a plurality of the above high polymer buffer layer copper coaxial TGVs, one end of each copper column of the TGV is connected with the adjacent copper column of the TGV, and the other end of each copper column is connected with the other adjacent copper column of the TGV.
Furthermore, two adjacent copper columns are connected through copper wires, the copper wires on the front side of the substrate are embedded in the first photosensitive adhesive, and the second photosensitive adhesive is arranged between the copper wires on the back side of the substrate and the substrate.
The preparation method of the copper coaxial TGV adapter plate with the high polymer buffer layer is characterized by comprising the following steps of:
a. processing a plurality of annular grooves on the front surface of the substrate, wherein the depth of each annular groove is less than the thickness of the substrate;
b. depositing a copper layer on the outer ring layer;
c. filling high polymer benzocyclobutene in the annular groove to form an inner buffer layer;
d. coating photosensitive adhesive on the front surface of the substrate, exposing the column surface at the center of the annular groove through pattern exposure, depositing copper on the surface of the photosensitive adhesive, then coating the photoresist on the copper for photoetching and patterning, removing redundant copper, and forming a front copper wire between two adjacent silicon columns;
e. thinning the back of the substrate until the outer ring at the bottom of the annular groove is exposed;
f. coating photoresist on the back of the substrate, etching the glass column at the center of the annular groove to form a blind hole, and removing an outer annular layer on the side wall of the blind hole;
g. depositing copper on the back surface of the substrate and the side wall of the blind hole to be used as a seed layer for electroplating, and generating a copper column in the blind hole in an electroplating mode;
h. removing the redundant copper and photoresist on the back of the substrate, and polishing the back of the substrate after the inner buffer layer and the copper column are exposed;
i. depositing a BCB dielectric layer on the back of the substrate, forming a contact window of a copper column and a copper layer through photoetching, and then depositing copper, wherein the copper is connected with an external conductor;
j. coating photosensitive glue on the back of the substrate, and carrying out exposure patterning to expose the back of the copper pillar and connect with the window; depositing copper on the back of the substrate, and photoetching a back RDL wiring; and corroding the copper through a wet process to form a back copper wire.
Further, the step c specifically comprises:
c1, fixing the substrate on the turntable, wherein the center of the substrate is deviated from the rotation center of the turntable;
c2, dripping the AP-3000 solution on the front surface of the substrate, then integrally transferring the substrate to an environment of 50-150Pa, standing for 8-15min, controlling the turntable to rotate, and throwing off the redundant AP-3000 solution;
c3, heating the substrate to solidify the AP-3000 solution;
c4, dropwise coating the high polymer benzocyclobutene solution on the front surface of the substrate, then integrally transferring to an environment of 50-150Pa, standing for 8-15min, controlling the turntable to rotate, and throwing off the redundant high polymer benzocyclobutene solution;
c5, finally drying the high polymer benzocyclobutene solution to form the inner buffer layer.
Further, after step c, performing a planarization treatment on the front surface of the substrate:
the first step is as follows: removing the high polymer benzocyclobutene on the surface of the substrate by using the CMP polishing solution with high polymer grinding rate;
the second step is that: and (3) selecting the CMP polishing solution with the ratio of copper to high polymer being 1:1 to carry out flattening treatment on the surface of the copper layer.
Further, the CMP polishing solution of the first step comprises the following components by volume percent: 2 percent of nitric acid, 1.5 percent of surfactant, 5.0 percent of silicon dioxide particles and the balance of deionized water, wherein the diameter of the silicon dioxide particles is 1.3 mu m, and the pH value of the CMP polishing solution is 4.0.
Furthermore, the CMP polishing solution of the second step is a copper polishing solution, the pH value is 3.5, and the diameter of the silicon dioxide particles is 85 nm.
The invention has the beneficial effects that: 1. the size of the high polymer buffer layer is flexible and variable, and coaxial TGV structures with different sizes can be designed conveniently according to a matching principle. A scheme for preparing a copper coaxial TGV structure of a high polymer buffer layer is given in detail, and the buffer layer is prepared by filling an annular groove with a high polymer. The process implementation scheme ensures impedance matching design and simultaneously ensures that the overall structure is small in size, improves the thermal stability of packaging, avoids cracks caused by mismatching of thermal expansion coefficients, and is beneficial to future high-density three-dimensional integration.
2. BCB is taken as a high polymer representative, and the feasibility of the process for filling the annular groove by the high polymer is researched and verified. Aiming at the preparation process of the coaxial structure, an optimization scheme of the sample surface BCB/Cu mixed material CMP process is provided, the finally obtained sample surface copper layer is smooth and has no obvious scratch, and the BCB layer is slightly lower than the copper layer by 90 nm. On the basis of the research of a key process, the preparation of a copper coaxial TGV structure with the diameter of an inner conductor of 20 mu m, the width of a BCB annular groove of 56 mu m, the width of an outer conductor of 5 mu m and the height of 70 mu m is realized.
Drawings
FIG. 1 is a schematic illustration of three prior art coaxial TGVs;
FIG. 2 is a schematic representation of a coaxial TGV of the present invention;
FIG. 3 is a schematic view of an adapter plate of the present invention;
FIGS. 4-13 are schematic illustrations of the preparation of an interposer of the present invention;
FIG. 14 is a schematic view of an interposer prepared in accordance with the present invention;
reference numerals: 1-copper column; 2-inner buffer layer; 3-a copper layer; 4-an outer buffer layer; 5, a substrate; 6-copper wire; 7-second photosensitive glue; 8-first photosensitive glue.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
As shown in fig. 2, the polymer buffer layer copper coaxial TGV of the present invention includes a copper pillar 1, an annular inner buffer layer 2, an annular copper layer 3, and an annular outer buffer layer 4, which are sequentially disposed, where the copper pillar 1, the inner buffer layer 2, the copper layer 3, and the outer buffer layer 4 are sequentially disposed from inside to outside, the outer buffer layer 4 is a polymer benzocyclobutene layer, and the inner buffer layer 2 is a polymer benzocyclobutene layer.
The high polymer benzocyclobutene (BCB) has the characteristics of low dielectric constant (2.65), good fluidity, excellent buffering performance and excellent thermal stability. The BCB material has the characteristic of easy filling, and can realize the preparation of copper coaxial TGV structures with different sizes and different depth-to-width ratios.
The adapter plate, as shown in fig. 3, includes a substrate 5, the substrate 5 has a plurality of above-mentioned high polymer buffer layer copper coaxial TGVs, one end of the copper column 1 of the TGV is connected with the copper column 1 of the adjacent TGV, and the other end of the copper column 1 is connected with the copper column 1 of another adjacent TGV.
Specifically, two adjacent copper columns 1 are connected through a copper wire 6, the copper wire on the front surface of the substrate 5 is embedded in a first photosensitive adhesive 8, and a second photosensitive adhesive 7 is arranged between the copper wire 6 on the back surface of the substrate 5 and the substrate 5.
The preparation method of the adapter plate comprises the following steps:
a. a plurality of annular grooves are formed in the front surface of the substrate 5, and the depth of the annular grooves is smaller than the thickness of the substrate 5. Specifically, a 4-inch p-type silicon substrate wafer with resistivity of 0-10 Ω -cm is selected and coated with photoresist or SiO2Defining an etching pattern by photoetching as a mask, and etching an annular groove with the depth of 80 mu m by using a DRIE (deep etching) process; the mask is then removed as shown in fig. 4. The front surface of the substrate 5 may be any one, and one surface is selected as the front surface, and the other surface is selected as the back surface.
b. And depositing an outer high polymer benzocyclobutene layer on the inner wall of the annular groove to serve as an outer buffer layer 4, and depositing a copper layer 3 on the outer buffer layer 4. Specifically, SiO with a thickness of 1 μm is deposited on the side wall of the annular groove by a high-temperature thermal oxidation process and a PECVD process2A dielectric layer; then in SiO2And sequentially sputtering Ti with the thickness of 100nm and copper with the thickness of 200nm on the surface of the buffer dielectric layer. And (3) growing copper with the thickness of 5 microns on the side wall of the annular groove by adopting a super conformal electroplating mode to serve as a seed layer of the outer conductor and the inner conductor of the coaxial structure, as shown in figure 5.
c. High polymer benzocyclobutene is filled in the annular groove to form the inner buffer layer 2, as shown in fig. 6.
Specifically, step c includes:
c1, the substrate 5 is fixed to the turntable with the center of the substrate 5 offset from the center of rotation of the turntable. The substrate 5 is eccentrically arranged, and when the turntable rotates, the substrate 5 is subjected to larger centrifugal force, so that redundant waste on the substrate 5 can be thrown away. In addition, a plurality of substrates 5 can be arranged on one turntable, and the plurality of substrates 5 can be prepared at one time, so that the production efficiency is improved.
c2, dripping the AP-3000 solution on the front surface of the substrate 5, then integrally transferring the substrate to an environment with 50-150Pa, standing for 8-15min, controlling the rotating disc to rotate, homogenizing the glue for 5s at the linear speed of 600rpm/min, homogenizing the glue for 45s at the linear speed of 3000rpm/min, and throwing away the redundant AP-3000 solution.
c3, heating the substrate 5 to solidify the AP-3000 solution, specifically placing the substrate on a hot plate at 90 ℃ for 5 minutes to solidify. The AP-3000 solution is used as a tackifier, and can improve the stability of the inner buffer layer 2 after molding.
c4, dripping the high polymer benzocyclobutene solution on the front surface of the substrate 5, then integrally transferring to an environment with 50-150Pa, standing for 8-15min, controlling the turntable to rotate, and throwing away the redundant high polymer benzocyclobutene solution.
The pressure of the vacuum environment is 50-150Pa, and the air in the annular groove can quickly escape from the annular groove due to low air pressure, so that the solution is promoted to quickly enter the annular groove and fill the annular groove, the complete filling is realized, and the defects of bubbles, gaps and the like in the inner buffer layer 2 are prevented. The preferred embodiment is: standing for 10min in an environment of 100 Pa.
c5, finally drying the high polymer benzocyclobutene solution to form the inner buffer layer 2, and specifically, placing the substrate 5 in a vacuum chamber at 250 ℃ to heat for 60 minutes to complete permanent curing.
The inner and outer conductors of the copper coaxial TGV structure need to be electrically interconnected with the outside, so the polymer layer and the excessive copper layer on the surface must be removed and the surface is planarized for subsequent RDL preparation. The excess high polymer on the surface can be removed by CMP to expose the surface of the central conductor, and simultaneously, the copper layer in other areas of the wafer can be ensured not to be corroded, specifically:
the first step is as follows: and removing the high polymer benzocyclobutene on the surface of the substrate 5 by using the CMP polishing solution with high polymer grinding rate.
After BCB thermal curing, the chemical and physical properties are stable, and the corrosion rate in a CMP solution is low, so that the CMP solution and the process need to be reasonably configured and optimized: the CMP polishing solution comprises the following components in percentage by volume: 2 percent of nitric acid, 1.5 percent of surfactant, 5.0 percent of silicon dioxide particles and the balance of deionized water, wherein the diameter of the silicon dioxide particles is 1.3 mu m, and the pH value of the CMP polishing solution is 4.0. The active agent is capable of accelerating the rate of dissolution of the BCB in solution, and the nitric acid is used to enhance the chemical reaction of the BCB with the solution.
The second step is that: the CMP polishing solution with the ratio of copper to high polymer of 1:1 is selected to carry out the leveling treatment on the surface of the copper layer 3, the CMP polishing solution is the copper polishing solution, the pH value is 3.5, and the diameter of silicon dioxide particles is 85 nm.
Experiments show that the CMP solution with the particle size of the silicon dioxide particles being 1.3 mu m has the BCB grinding rate of about 80nm/min and the copper grinding rate of about 90 nm/min; the CMP solution with the particle size of 85nm has the BCB grinding rate of about 35nm/min and the copper grinding rate of about 50 nm/min. The CMP solution with large particle size has high grinding rate but poor surface flatness, and the grinding rate is too high to easily corrode the whole copper layer in a short time due to the thin thickness of the copper layer, thereby increasing the process difficulty. Therefore, in the experimental process, for a sample with a residual thickness of 5 μm of the BCB layer, the sample was first ground for 60 minutes by using the CMP solution having a large particle size, and then ground for 30 minutes by using the CMP solution having a small particle size.
Through experiments, the following results are found: after the first step is finished, BCB is filled in the annular groove, the surface of the copper conductor is in a state that copper is mixed with BCB, and the surface is rough; after the second step is finished, the surface of the copper layer is smooth and has no obvious scratch. In order to ensure that no BCB residue exists on the surface of the copper layer and the copper layer is corroded as little as possible, the CMP rate is increased by adopting larger pressure in the second CMP process, the BCB is compressed into the deep groove due to the lower hardness of the BCB, the surface of the BCB in the annular groove is slightly lower than the surface of the surrounding copper layer, the height difference between the surface of the BCB and the surface of the surrounding copper layer is about 90nm, and the subsequent process requirements are met.
d. Coating photosensitive adhesive on the front surface of the substrate 5, exposing the surface of the silicon column at the center of the annular groove through pattern exposure, depositing copper on the surface of the photosensitive adhesive, then coating the photoresist on the copper for photoetching and patterning, removing redundant copper, and forming a front copper wire 6 between two adjacent silicon columns. Specifically, a layer of photosensitive PI with a thickness of 5 μm is coated on the front surface of the substrate 5, and exposure patterning is performed to expose the silicon pillar surface at the center of the annular groove. Sputtering and growing 1 mu m thick copper on the surface of the PI to be used as a front side interconnection RDL, wherein the PI is used as a buffer layer between the RDL and the outer conductor; then coating photoresist for photoetching patterning, corroding redundant copper by adopting a wet process, and keeping the width of the copper wire 6 in the pattern area to be 12 mu m; and finally, the PI with the same model is used as bonding glue to be bonded with the slide glass, as shown in figure 7.
e. The back side of the substrate 5 is thinned until the outer buffer layer 4 at the bottom of the annular groove is exposed. Specifically, adoptThinning and DRIE (direct drive etching) process are carried out on the back surface of the bonded substrate 5 until SiO (silicon dioxide) at the bottom of the annular groove is exposed2A surface; in the actual operation process, the thickness difference of the bonding sheet is considered, the thickness of the bonding sheet is reduced by adopting a thinning process, and the part of the wafer is exposed out of SiO (silicon dioxide) at the bottom of the annular groove2When the surface is coated, the DRIE process is used for continuously etching silicon, and finally, the silicon is over-etched until SiO at the bottom2Slightly above the Si surface as shown in fig. 8.
f. And coating photoresist on the back surface of the substrate 5, etching the silicon column at the center of the annular groove to form a blind hole, and removing the outer buffer layer 4 on the side wall of the blind hole. Specifically, the surface of a wafer is coated with photoresist, and an etching pattern of a central conductor is defined by photoetching; etching SiO by DRIE2Middle silicon pillar, SiO around the sidewall2As an etch stop layer; then wet etching is adopted to remove SiO in the blind hole2As shown in fig. 9.
g. Depositing copper on the back surface of the substrate 5 and the side wall of the blind hole, specifically depositing 20nm thick copper as a seed layer for electroplating by means of sputtering, and generating the copper pillar 1 in the blind hole by means of electroplating, as shown in fig. 10.
h. And thinning and removing the redundant copper and the photoresist on the back surface of the substrate 5 by adopting a CMP (chemical mechanical polishing) process, and polishing the back surface of the substrate 5 after the inner buffer layer 2 and the copper column 1 are exposed on the back surface of the substrate 5, as shown in FIG. 11.
i. A 300nm thick BCB dielectric layer is deposited on the back of the substrate 5 by a PECVD process at 250 ℃, contact windows of the copper pillar 1 and the copper layer 3 are formed by photolithography, and then copper is deposited, specifically, copper with a thickness of 1 μm can be sputtered, and the copper is connected with an external conductor, as shown in fig. 12.
j. Coating photosensitive glue on the back surface of the substrate 5 by adopting spin coating, and carrying out exposure patterning to expose the back surface of the copper pillar 1 and connect with a window; depositing copper on the back of the substrate 5, and photoetching to form back RDL wiring; the copper is etched by a wet process to form the back side copper line 6. Specifically, a layer of photosensitive PI with the thickness of 5 microns is coated on the surface of the wafer by a spin coating process, exposure patterning is carried out, and a contact window at the back of the copper pillar 1 is exposed; after the photosensitive PI is cured, sputtering copper with the thickness of 1 mu m on the back surface of the substrate 5, and photoetching to form back RDL wiring; the copper is etched by a wet process to form the back trace, as shown in fig. 13.
The interposer prepared by the above method is shown in fig. 14, in which a is the SEM scanning result of the overall structure, b is the SEM scanning result of the copper layer sidewall, and c is the surface optical map. The diameter of a copper column 1 of TGV on the adapter plate is 20 μm, the height is 70 μm, and the width of a middle BCB annular groove buffer layer is 56 μm. The size of the present invention is greatly reduced compared to prior art coaxial TGV structures. It can be seen from the figure that the BCB in the annular groove is completely filled without voids, and the inner conductor also realizes copper seamless filling. FIG. 14(b) is a cross-sectional view showing the buffer layer between the copper layer 3 and the substrate 5, the width of the copper layer 3 being 5 μm, and SiO being between the substrate2The thickness of the buffer layer was 1.12. mu.m. The optical diagram of the surface of the coaxial structure is shown in fig. 14(c), and it can be seen that the surface is flat after the CMP process, no obvious scratch is generated, and the boundary between Cu, BCB and the silicon substrate is clear.
And measuring the leakage value between the inner conductor and the outer conductor of the copper coaxial TGV interconnection structure by using B1500A, and judging the buffer performance of the dielectric layer and the feasibility of the process flow. The results show that: the leakage current of TGV increases with increasing voltage, and at an applied voltage of 20V, the leakage current value is about 950fA, indicating that the BCB buffer performance in the deep trench is good.
The resistance characteristic of the copper coaxial TGV is measured by adopting B1500A, and because the resistance value of a single copper TGV is small, a plurality of coaxial TGV interconnection structures which are connected in series are measured in order to improve the measurement accuracy. And in order to remove the connecting circuit and test the PAD resistor, a calibration structure only with an interconnecting wire and the PAD is designed, and finally the resistance value of the single copper coaxial TGV resistor is calculated by adopting a differential method. The diameters of the inner conductors of the tested copper coaxial TGV are respectively 20 mu m, 30 mu m and 40 mu m, and the heights of the inner conductors are all 70 mu m. The test result of the single copper coaxial TGV resistance is as follows: the average values of the direct current resistances of the three sizes are respectively 6.81, 3.05 and 1.83m omega. The measured values of resistance are slightly greater than the theoretical values because the electroplated copper equivalent resistivity is generally greater than the theoretical value of copper resistivity. The equivalent resistivity of TGV can be back-calculated according to ohm's law:
where ρ is the equivalent resistivity of copper and L, D is the length and diameter, respectively, of the copper TGV. Substituting three structural dimension values to obtain copper materials filled with TGV, wherein the equivalent resistivities of the copper materials are respectively 3.08, 3.1 and 3.28 mu omega cm. The average equivalent resistivity was about 3.15. mu. Ω. cm, which is larger than the theoretical resistivity value of copper (1.9. mu. Ω. cm), but was a lower value in the electrolytic copper plating. The resistivity range of the electrolytic copper obtained by the current relevant research is about 2.5-10 mu omega cm.
In order to evaluate the high-frequency characteristics of the copper coaxial TGV, the section adopts a vector network analyzer N5245A to perform S parameter test on the prepared copper coaxial TGV test structure. The result shows that the matching of the TGV before decoupling is slightly poor, but after decoupling, the single copper coaxial TGV is S within the frequency range of 0-20 GHz11(reverse transmission coefficient) and S21The (forward transmission coefficient) is respectively lower than-20 dB and-0.1 dB, and the performance is excellent, so that the application requirement in the high-frequency field can be met.
Claims (8)
1. Coaxial TGV of polymer buffer layer copper, including copper post (1), annular interior buffer layer (2), annular copper layer (3) and annular outer buffer layer (4) that set gradually, copper post (1), interior buffer layer (2), copper layer (3) and outer buffer layer (4) set gradually from inside to outside, its characterized in that, outer buffer layer (4) are the silica layer, interior buffer layer (2) are polymer benzocyclobutene layer.
2. Interposer, comprising a substrate (5), characterized in that: the substrate (5) has a plurality of polymer buffer copper coaxial TGVs according to claim 1, the TGVs having copper pillars (1) with one end connected to a copper pillar (1) of an adjacent TGV and the other end of a copper pillar (1) connected to a copper pillar (1) of another adjacent TGV.
3. The interposer as recited in claim 2, wherein: two adjacent copper columns (1) are connected through a copper wire (6), the copper wire on the front surface of the substrate (5) is buried in the first photosensitive adhesive (8), and a second photosensitive adhesive (7) is arranged between the copper wire (6) on the back surface of the substrate (5) and the substrate (5).
4. A method of manufacturing an interposer as recited in claim 2 or 3, comprising the steps of:
a. processing a plurality of annular grooves on the front surface of the substrate (5), wherein the depth of each annular groove is less than the thickness of the substrate (5);
b. depositing an outer high polymer benzocyclobutene layer on the inner wall of the annular groove to serve as an outer buffer layer (4), and depositing a copper layer (3) on the outer buffer layer (4);
c. filling high polymer benzocyclobutene in the annular groove to form an inner buffer layer (2);
d. coating photosensitive glue on the front surface of a substrate (5), exposing the surface of a silicon column at the center of an annular groove through pattern exposure, depositing copper on the surface of the photosensitive glue, then coating the photoresist on the copper for photoetching and patterning, removing redundant copper, and forming a front copper wire (6) between two adjacent silicon columns;
e. thinning the back surface of the substrate (5) until the outer buffer layer (4) at the bottom of the annular groove is exposed;
f. coating photoresist on the back surface of the substrate (5), etching the silicon column at the center of the annular groove to form a blind hole, and removing the outer buffer layer (4) on the side wall of the blind hole;
g. depositing copper on the back surface of the substrate (5) and the side wall of the blind hole to be used as a seed layer for electroplating, and generating a copper column (1) in the blind hole in an electroplating mode;
h. removing redundant copper and photoresist on the back surface of the substrate (5), exposing the inner buffer layer (2) and the copper column (1), and polishing the back surface of the substrate (5);
i. depositing a high polymer benzocyclobutene layer dielectric layer on the back of the substrate (5), forming a contact window of the copper column (1) and the copper layer (3) through photoetching, and then depositing copper, wherein the copper is connected with an external conductor;
j. coating photosensitive glue on the back surface of the substrate (5), and carrying out exposure patterning to expose the back surface of the copper pillar (1) and connect with a window; depositing copper on the back of the substrate (5), and photoetching to form back RDL wiring; and etching the copper by a wet process to form a back copper wire (6).
5. The method for preparing the interposer as claimed in claim 4, wherein the step c comprises:
c1, fixing the substrate (5) on the turntable, wherein the center of the substrate (5) is deviated from the rotation center of the turntable;
c2, dropwisely coating the AP-3000 solution on the front surface of the substrate (5), then integrally transferring to an environment of 50-150Pa, standing for 8-15min, controlling the turntable to rotate, and throwing off the redundant AP-3000 solution;
c3, heating the substrate (5) to solidify the AP-3000 solution;
c4, dropwise coating the high polymer benzocyclobutene solution on the front surface of the substrate (5), then integrally transferring to an environment with 50-150Pa, standing for 8-15min, controlling the turntable to rotate, and throwing off the redundant high polymer benzocyclobutene solution;
c5, finally drying the high polymer benzocyclobutene solution to form the inner buffer layer (2).
6. Method for the production of an interposer as claimed in claim 4, characterized in that, after step c, the front side of the substrate (5) is subjected to a planarization treatment:
the first step is as follows: removing the high polymer benzocyclobutene on the surface of the substrate (5) by using CMP polishing solution with high polymer grinding rate;
the second step is that: and (3) selecting the CMP polishing solution with the ratio of copper to the high polymer of 1:1 to carry out flattening treatment on the surface of the copper layer (3).
7. The method of preparing an interposer as recited in claim 6, wherein the CMP slurry of the first step has a composition and volume percent of: 2 percent of nitric acid, 1.5 percent of surfactant, 5.0 percent of silicon dioxide particles and the balance of deionized water, wherein the diameter of the silicon dioxide particles is 1.3 mu m, and the pH value of the CMP polishing solution is 4.0.
8. The method of manufacturing an interposer as recited in claim 6, wherein the CMP slurry of the second step is a copper slurry, the pH is 3.5, and the diameter of the silica particles is 85 nm.
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| CN113066758A (en) * | 2021-03-23 | 2021-07-02 | 成都迈科科技有限公司 | TGV deep hole filling method |
| CN116722093A (en) * | 2023-08-04 | 2023-09-08 | 季华实验室 | Display substrate and manufacturing method thereof |
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