Multi-chip module homogeneity bonding system quality conformance is improved one's methodsTechnical field
The invention relates to multi-chip module (being called for short MCM), specifically, relates to ceramic thick film type multi-chip module (being called for short MCM-C), further, relates to homogeneity bonding system ceramic thick film type multi-chip module.
Background technology
In original multi-chip module integrated technology, on thick film low temperature multilayer co-firing ceramic substrate (being called for short LTCC substrate), adopt the mode of silk screen printing, by conductor paste, ruthenium system resistance slurries such as gold paste, silver slurry or palladium-silver pastes, by the requirement of top layer layout-design, LTCC substrate forms conduction band, stopband figure, through high temperature sintering aftershaping.In the termination of conduction band or the place of specifying, form bond area, semiconductor chip assembling region or other chip components and parts assembling region, surface protection is carried out with glass uranium insulating barrier in all the other regions (comprising thick film stopband).Substrate carries out the assembling of semiconductor chip, other chip components and parts, spun gold or silicon-aluminium wire is adopted to carry out bonding connection between chip (being generally aluminium bonding region), conduction band (being generally gold or silver-colored bonding region), pin (being generally gold or nickel bonding region), form complete circuit to connect, the bonding system formed thus is gold-aluminium (Au-Al), silver-aluminium (Ag-Al) or nickel-aluminium (Ni-Al) heterogeneous bonding system.
The subject matter that original technology exists is: 1. in silver-colored conduction band, palladium-silver conduction band, silver is easily oxidized, and in long-term energising situation, easily produces ELECTROMIGRATION PHENOMENON, has a strong impact on the reliability of device, is usually expressed as the decline of bond strength; 2. golden conduction band is in big current situation, and in Au-Al bonding system, bond contact region layer gold ELECTROMIGRATION PHENOMENON is obvious, and between Au-Al, easily form " purple plague purpura ", its product composition is AuAl2, cause the alloy point formed during Au-Al bonding loose and Voiding, final bonding force declines to a great extent; 3. at high temperature, because gold spreads in aluminium, form " hickie " between Au-Al, its product is Au to gold-aluminium bonding system2al, Au5al2, Au5al, formed one deck crisp and insulation intermetallic compound (i.e. golden aluminium compound), this product can make alloy point conductivity significantly reduce, and can form open circuit time serious; 4., between chip (surface metal-layer is aluminium lamination), conduction band (golden conduction band or silver-colored conduction band), stem (gold-plated or nickel plating), lead-in wire (spun gold or Si-Al wire), in bonding technology, compatible respective requirement is difficult to; 5. the roughness on thick film conduction band, surface, thick film bonding region is comparatively large, the problem that the quality conformances such as bonding system bond-pull and long-term reliability are poor.
Through retrieval, the patent application relating to multi-chip module has more than 20 parts, but does not improve the application part of multi-chip module homogeneity bonding system quality conformance.
Summary of the invention
The object of this invention is to provide a kind of multi-chip module homogeneity bonding system quality conformance to improve one's methods, to overcome the defect of original multi-chip module integrated technology, solve the uniform quality sex chromosome mosaicism of multi-chip module homogeneity bonding system, improve reliability, can high-end product be widely used in.
Inventor studies and finds because the surface of LTCC substrate own is comparatively coarse, add that the large and silk screen printing mesh of thick film ink particle has certain thickness, thick film conduction band/bonding region surface ratio is more coarse, surface smoothness is poor, its roughness is usually at 2 ~ 5 μm, and film thickness controls at 1 ~ 5 μm usually, therefore, the film gauge uniformity directly directly formed on its surface, film quality uniformity are poor, the consistency of aluminium-aluminium (Al-Al) bonding quality can be caused poor, thus cause the comparison of coherence of each homogeneity bonding system bond-pull, reliability poor.Therefore the evenness problem on surface, bond area must be solved.
To achieve the above object of the invention, inventor is the angle from improving each homogeneity bonding system quality conformance, employing realizes the method for each bonding region topochemistry mechanical polishing one by one (CMP), specific practice is: select suitable noble metal polishing fluid, by local polishing machine specialized, polishing is carried out to each bonding region, make its surface smoothness≤0.1 μm, adopt the method for Mechanical masks afterwards, in high vacuum sputtering unit or evaporator, form one deck aluminium film, nickel-chromium-aluminium or chromium-copper-aluminium laminated film on surface, the bonding region of polishing; Finally, hybrid integrated circuit integrated technique routinely, by on semiconductor chip and the integrated thick film substrate after treatment of chip components and parts, the bonding of semiconductor chip adopts silicon-aluminium wire bonding, adopt gold wire bonding between pin and substrate, quality conformance is good, reliability is high Jin-Jin (Au-Au), aluminium-aluminium (Al-Al) homogeneity bonding can be realized.
The hardness of the abrasive grain of above-mentioned noble metal polishing fluid is at 5GPa ~ 50GPa, particle diameter≤100nm.
The thickness of above-mentioned aluminium film or nickel-chromium-aluminium laminated film or chromium-copper-aluminium laminated film controls usually at 1 ~ 5 μm.
Above-mentioned chip components and parts do not comprise semiconductor chip.
The inventive method has following characteristics: 1. by topochemistry mechanical polishing, the evenness on surface, LTCC on-chip all bonding regions is made to control at≤0.1 μm, improve consistency, the uniformity of preparing aluminium film thickness and quality on surface, bonding region, improve the quality conformance of homogeneity bonding system, thus improve reliability and the rate of finished products of multi-chip module; 2. improve the bonding performance of thick film gold conduction band bonding region and silicon-aluminium wire, form highly reliable homogeneity bonding system.Improve the ability of the long-term fully reliably working of multi-chip module; 3. by changing the size of metal mask clear size of opening, local aluminum bonding region can be formed on same golden conduction band bonding region, can simultaneously compatible gold wire bonding (between bonding region and gold plated pins), silicon-aluminium wire bonding (between substrate bonding region and chip bonding district), form highly reliable perfect bonding system.Such devices is widely used in the fields such as space flight, aviation, boats and ships, precision instrument, communication, Industry Control, is specially adapted to the applications such as high-power, highly reliable, aerospace level, has wide market prospects and application space.
Accompanying drawing explanation
The following drawings in order to compare the difference of the present invention and original technology, and further illustrates the inventive method.
Fig. 1 is original integrated technology schematic diagram, Fig. 2 is the golden conduction band/gold bonding district enlarged diagram of original technology, Fig. 3 is local of the present invention (bonding region) chemico-mechanical polishing enlarged diagram, Fig. 4 is deposit aluminium film enlarged diagram after local of the present invention (bonding region) polishing, Fig. 5 is integrated technology schematic diagram of the present invention, Fig. 6 is original process chart, and Fig. 7 is process chart of the present invention.
In figure, 1 is base, and 2 is pin nickel plating end face, 3 is golden conduction band/gold bonding district, and 4 is semiconductor chip, and 5 is Si-Al wire lead, 6 is stopband, and 7 is chip components and parts, and 8 is LTCC substrate, 9 is pin, 10 is internal layer through hole, and 11 is internal layer conduction band, and 12 is the gold-plated end face of pin, 13 is spun gold lead, and 14 is the aluminium film of deposit.
Potsherd in LTCC substrate is multilayer, at least two layers.
Embodiment
Embodiment is used for comparing original integrated technology and the present invention, better the present invention to be described.
Embodiment 1:
As shown in Figure 6, process description is as follows in original technological process:
(1) material prepares: get out ceramic chips, gold conductive paste, ruthenium system resistance slurry, semiconductor chip etc.;
(2) cut-parts: the size according to specific product LTCC substrate carries out cut-parts on request;
(3) punching: each interlayer is interconnected by through hole and conduction band.Adopt mechanical punch pattern, make the interconnected path between LTCC substrate each layer potsherd by the figure of product design and aperture;
(4) filling perforation and conduction band printing: by the method for silk screen printing on potsherd, metal paste is filled in via hole, prints out conduction band figure by compulsory figure, and dry (150 DEG C, 10min);
(5) stopband printing: by the method for silk screen printing on potsherd, prints out stopband figure by resistance slurry by compulsory figure, and dries (150 DEG C, 10min);
(6) lamination: each layer potsherd is accurately stacked according to design sequence.For making the mutual close adhesion of potsherd, substrate film preset during curtain coating need be removed;
(7) isostatic pressed: the multi-layer ceramics accurately stacked is fitted under mechanical high pressure, realizes close contact;
(8) cut: by the potsherd after static pressure, carry out cutting and separating according to module alignment;
(9) sinter: after potsherd cutting and separating, in sintering furnace, carry out binder removal and sintering, porcelain material hardening structure is stablized;
(10) by the method for silk screen printing, LTCC substrate surface printing conduction band figure after sintering and stopband figure, and dry (150 DEG C, 10min).Binder removal and sintering (850 DEG C, 10min, total time 35min) is carried out in sintering furnace;
(11) laser resistor trimming: use power laser to carry out meticulous adjustment to the resistance made by silk screen printing, to reach designing requirement;
(12) detect: become film substrate to carry out visual inspection and electric test to the LTCC after resistance trimming;
(13) being become by LTCC film substrate to adopt the mode of alloy welding to fill is attached on Guan Ji, and integrated circuit packaging technology routinely, carries out the assembling of semiconductor chip, other SMD components, complete leading wire bonding;
(14) function and outward appearance are tested by product requirement;
(15) under the protection of High Purity Nitrogen, in the stove of about 150 DEG C, carry out the high-temperature baking of more than 8h, steam is thoroughly dried;
(16) sealing cap: carry out sealing cap in specific environment, completes the integrated of whole device and production;
(17) by Product Process file and checking file, complete the test of device, screening, printing and packaging and put in storage.
As shown in Figure 1, bonding system is the heterogeneous bonding system of gold-aluminium to result.
Embodiment 2
Technological process of the present invention as shown in Figure 7, is the technique of improvement in dotted line frame in figure:
After trimming at thick-film resistor, being completed, increase surface, golden thick film bonding region topochemistry mechanical polishing process, just can complete the making that LTCC becomes film substrate, the technique of increase part is described below:
(1) carry out the bonding region figure of aluminium-aluminium (Al-Al) bonding as required, adopt stainless steel substrates or slope Mo alloy sheet, utilize the method for photoetching to carry out the preparation of bonding region Mechanical masks;
(2) the golden polishing fluid that hardness of the abrasive grain is 25GPa ± 5GPa, particle diameter is 50nm ± 10nm is prepared;
(3) carry out chemico-mechanical polishing by local polishing machine specialized to needing the gold bonding district carrying out aluminium-aluminium bonding, surface smoothness controls at≤0.1 μm;
(4) washed with de-ionized water, oven dry;
(5) in high vacuum magnetic control platform, utilize Mechanical masks to carry out the preparation of nickel-chromium-aluminium laminated film, mask alignment precision is less than 10 μm, composite film thickness: Ni-Cr:0.6 μm, Al:3.0 μm;
(6) deposited film inspection;
(7) examination of materials operation is entered.
Except the operation increased, all the other operations are with embodiment 1.
Result as shown in Figure 7, realizes Jin-Jin (Au-Au), aluminium-aluminium (Al-Al) homogeneity bonding, by local mechanical chemical polishing, reaches the requirement of bonding system quality conformance.