WO2005088699A1

WO2005088699A1 - Method of manufacturing an electronic device and a resulting device

Info

Publication number: WO2005088699A1
Application number: PCT/IB2005/050759
Authority: WO
Inventors: David D. R. Chevrie; Freddy Roozeboom; Antonius L. A. M. Kemmeren
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-03-10
Filing date: 2005-03-02
Publication date: 2005-09-22

Abstract

The method relates to the manufacturing of vertical interconnects extending from the first to the second side of a semiconductor substrate. Cavities are formed in the substrate by wet-chemical etching from the second side, and trenches are formed by etching from the first side of the substrate, said trenches and said cavities together forming through holes. Then the through-holes are given a conductive surface so as to form the vertical interconnect.

Description

Method of manufacturing an electronic device and a resulting device

The invention relates to a method of manufacturing an electronic device comprising a semiconductor substrate having a first and a second side and provided with a vertical interconnect extending from the first to the second side. The invention also relates to an electronic device comprising a semiconductor substrate having a first and a second side and provided with a vertical interconnect extending from the first to the second side, which is constructed as an electrically conductive connection in a through-hole.

Such an electronic device is known from EP-A 1154481. The known device is an interposer that is made of a heat-resistant insulator, which is preferably silicon, but alternatively glass or resin. Through-holes are made with a laser. Wiring patterns are then formed on both the first and the second side of the device, said wiring pattern extending at the side walls of the through-holes and thus forming the vertical interconnect. Gold or solder bumps may be applied on the second side for connection to a mounting board. It is a disadvantage that the through-holes in the device have a rather limited resolution. The diameter of the through-holes cannot be chosen as small as desired, because of the resolution of the applied technique. Moreover, for a proper functioning as interconnect, coverage of the side-walls of the through-holes with a conductive material is needed. Such coverage becomes problematic with small diameters. The limited resolution therewith hampers miniaturisation of the device.

It is therefore a first object of the invention to provide a method of the kind mentioned in the opening paragraph, which allows the provision of through-holes with a small diameter. This object is achieved in that the method comprises the steps of: (a) providing cavities in the substrate by wet-chemical etching from the second side; (b) forming trenches by etching from the first side of the substrate, said trenches and said cavities together forming through-holes, and (c) providing said through-holes with a conductive surface so as to form the vertical interconnect. The method of the invention uses a two-step etching process. With this process through-holes are obtained that comprise two parts that are complementary. The first part comprises one or more trenches and the second part is a cavity. Due to the trenches, the resolution of the through-hole, at least on the first side of the substrate, can be increased. Nevertheless, there is no danger of a failing electrical connection, as the length of the trench with a small diameter is reduced to part of the substrate thickness only. Besides, as a result of the wet-chemical etching, the cavity has an oblique angle to the second side of the substrate. This is very suitable from a rheological perspective. Any fluid needed for the provision of the conductive surface - whether a liquid, vapour or gas - is thus not hampered to enter the cavity and to make the surface in the first part of the through-hole conductive. It is an advantage that the process can be carried out at wafer-level. This reduces costs substantially. It is a further advantage that the first part of the through-holes may be completely filled. This allows the deposition of layers on the first side and on the second side of the substrate independently of each other. The first side of the substrate will generally be used for thin-film processing and for the assembly of separate electronic elements, such as integrated circuits. This includes fine patterns and different materials. A closed surface is then preferred for practical reasons and for a uniform construction of layers. Moreover, the filling will act as a protective layer against contamination for any layers and devices present on the first side of the substrate. If desired, the first part of the through-holes may be filled with a sacrificial material before etching or removing of the substrate from the second, opposed side thereof. This allows a good filling, and the sacrificial layer can be removed after opening of the through-holes from the second side. Suitable sacrificial materials are spin-on-glass materials, and CVD-deposited materials. Oxides and particularly TEOS are preferred. In a first embodiment, the cavities are provided first, and the trenches are formed thereafter, therewith opening the through-holes. This embodiment has the advantage that the patterning on the second side is limited to the first step of providing a cavity and then optionally a step of providing a wiring pattern. And this wiring pattern can be applied as the last step of the method. As a result, the method allows processing on the first side without the need to do any processing steps on the second side in the meantime. This reduces the risk of damage of any thin films applied to the first side. In a preferred implementation hereof, use is made of a single photolithographical mask for the provision of the cavities and the trenches, which mask is patterned on the second side before provision of the cavities, and is patterned on the first side after the provision of the cavities. This embodiment allows a further reduction of masks. Moreover, it is advantagous in that the first mask need not be replaced by a further mask. In another embodiment, the substrate is thinned from the second side after provision of the conductive surface, whereafter the substrate is provided on the second side with a desired pattern of electrically conductive material. In order to reduce masks, it is preferred that the conductive surface is provided in a maskless way, at least on the second side of the substrate. The presence of an unpattemed electrically conductive layer on this second side is not preferred for all applications, however. By thinning the substrate, for instance by grinding or (chemo-mechanical) polishing and/or by etching, the conductive ' surface is removed and can be replaced by a desired wiring pattern. Such a pattern for instance includes contact pads for connection to an external carrier with the help of bumps or solder or metal. It may also include a heatsink. Alternatively, an antenna or an inductor may be included.

In a further and very suitable embodiment, an electrically insulating layer is provided at the surface of the substrate, both in the through-holes and on the first and second sides, before provision of the electrically conductive surface. With this electrically insulating layer the vertical interconnect is properly isolated from the substrate. This reduces parasitic interactions through the substrate of a capacitive and/or inductive nature. The electrically insulating layer may be a single layer such as an oxide; alternatively it may be a stack of layers, such as a stack of silicon oxide, silicon nitride and silicon oxide. The oxide layer is preferably applied as a thermal oxide layer, but could be applied otherwise, for instance by LPCVD deposition or by wet-chemical deposition of TEOS (tetraethoxyorthosilicate) and subsequent conversion into a dense oxide. It is an advantage of the known processing that the oxide layer can be applied maskless and on wafer level, such that all surfaces of the substrate are covered. In another embodiment, a first microelectronic element is defined in the substrate on the first side thereof, the definition including one or more substrate treatment.steps that are carried out before provision of the conductive surface. Substrate treatments can be carried out on the first side of the substrate in addition to thin-film processing. Such substrate treatments may be applied before or after the etching steps to create the through-hole. Suitable substrate treatments include etching of further structures, implantation steps, doping steps by means of diffusion. Microelectronic elements to be defined therewith include active devices such as transistors, diodes and lateral pin-diodes; and passive devices such as MOS-capacitors and vertical trench capacitors. Specifically, the microelectronic element is a vertical trench capacitor, and said substrate treatment steps comprising the etching of trenches and the doping of the surface with charge carriers. Such vertical trench capacitors have a large capacitance density, which makes them very suitable for use as decoupling capacitors. This function of decoupling is preferably integrated in a carrier substrate in addition to contact pads and means for heat dissipation. The manufacture of the trench capacitors and the opening of the vertical interconnect may be carried out in a single etching step, for instance with dry etching. It has been found, that the depth of the created trenches is dependent on the aperture in the etching mask. This allows the trenches for the capacitor and for the vertical interconnect to be of different depths. In a further embodiment, a metallisation is provided on the first side of the substrate, said metallisation includes a bond pad structure with an under bump metallisation. This makes the first side suitable for the assembly of semiconductor devices and other devices such as passive networks. The assembly can be carried out with bond wires, but also and preferably with a flip-chip technique. Although the substrate near the vertical interconnect is thinner in view of the cavity structure, still this area can be used for the metallisation and also for the bond pad structure. The metallisation may further contain inductors, and interconnects between individual devices. The invention also relates to an electronic device comprising a semiconductor substrate having a first and a second side and provided with a vertical interconnect extending from the first to the second side, which is constructed as an electrically conductive connection in a through-hole. It is a second object of the invention to provide such an electronic device with through-holes with an increased resolution, at least on the side on which further functionality is available. This object is achieved in that the through-hole comprises a first part and a second part, said second part being shaped as a truncated cone and said first part being shaped as at least one cylinder or block and extending from the first side to the top of the truncated cone of the second part. Due to this construction the through-hole has a diameter that is relatively small on the first side of the substrate. This small diameter can be understood as an increase in resolution on the first side. The increased resolution allows miniaturisation of the device, as well as a proper integration with the further functionality. In view of the reduced diameter, the dimension of the vertical interconnect can be of the same order of magnitude as that of other elements, instead of being an order of magnitude larger. This again has beneficial effects for design rules. A further advantage of the construction is that the resistance of the vertical interconnect is limited. The electrically conductive layer in the second part may be thicker than that in the first part, and can thus be substantially neglected in the determination of the resistance of the vertical interconnect. This makes that the vertical interconnect is shortened effectively. In a first embodiment the first part of the through-hole is filled with electrically conductive material. This filling of the first part leads to a further reduction of the impedance of the vertical interconnect. It is noted that such filling is not foreseen in the prior art EP-A 1154481. The reason thereof must be found in the actual diameter of the through- holes. Due to the high resolution in the first part of the through-hole, the conductive material will first cover side walls but thereafter fill the first part of the through-hole. In an even further embodiment, the first part of the vertical interconnect comprises a plurality of parallel trenches, each of which is filled with electrically conductive material. This construction allows the provision of a very low impedance. Not only does the resistance decrease due to the parallel circuitry, but also are circular currents within the vertical interconnect minimized, which would otherwise give rise to parasitic inductance. Another advantage is that polycrystalline silicon may be used as single filling material, although this material does not have a very low resistivity. Its advantage lies in its easy application and good adhesion, particularly to an oxide layer, and in the reduction of the number of process steps. In another suitable embodiment, a first vertical interconnect is used for grounding and a second interconnect is used for signal transmission. Grounding and signal transmission are important aspects of the function of an interposing substrate, if the device is used for RF applications. With the vertical interconnects, these functions can be fulfilled excellently. Further embodiments are suitable to improve the characteristics of the electronic device. It may first of all comprise microelectronic elements on its first side, both in the substrate and on top of the substrate, such as inductors and resistors. Moreover, an electrically insulating layer may be present on the side- walls of the through-holes to limit parasitic interaction between substrate and vertical interconnect. This is particularly important in the case where the vertical interconnect is used for signal transmission and not only for provision of a thermal path. Beyond that, the substrate may comprise a high-ohmic zone which is present adjacent to the vertical capacitors and acts as a protection against parasitic currents. Such high-ohmic zone could circumfere the vertical capacitors and preferably extends from the first to the second side of the substrate. 'High- ohmic' is usually understood to be a zone of more than 500 Ω/cm, preferably more than 1500 Ω/cm. Such a zone acts as a barrier against any kind of interaction through the substrate. This is particularly advantageous for the reduction of inductive interaction. Protective layers or specific packages may be provided. In order to cope with differences in thermal expansion between the device and any carrier such as a printed circuit board, an underfill or protective layer such as benzocyclobutene could be provided at the side to be attached to the carrier. It is a further option that certain semiconductor devices are assembled in a cavity in the substrate. Their rearside could be exposed to a heatsink by local removal of the substrate. Such local removal of the substrate can be realized in the same step as the etching from the second side to provide or open the vertical interconnect. A more detailed description of such a process is given in the non-prepublished patent application EP03101729.6 (PHNL030659), which is herein included by reference. This allows that devices with different substrate materials can be combined with a single interconnect structure that does not need the provision of any bond wires or solder balls. This has a functional advantage for RF applications in addition to the practical advantage of reduced assembly activities. The device of the invention is desirably assembled together with a semiconductor device into one assembly. The semiconductor device will be attached to either the first side or the second side of the substrate. In order to contact the device, use can be made of a flip-chip process or of wirebonding. A flip-chip process is herein preferred in view of the lower impedance. The solder or metal bumps for the flip-chip process can be chosen corresponding to available processes as well as the desired pitch. The semiconductor device can thereafter be overmoulded with a protective layer. Alternatively, a heat-spreader could be provided on the side facing away from the substrate. Instead, one more semiconductor and other electronic devices can be provided on the chosen side of the substrate. The further electronic devices may be devices that cooperate with the semiconductor device to provide a functional subsystem. Examples hereof are ESD/EMI protection devices, bandpass filters, such as BAW filters, impedance matching circuits.

These and other aspects of the electronic device, the assembly and the method of the invention will be further elucidated with reference to the figures, in which: Fig. 1 shows diagramatically a cross-sectional view of the electronic device; Figs. 2a-d show cross-sectional views of four stages in a first embodiment of the method. Figs. 3a-e show cross-sectional views of five stages in a second embodiment of the method; Figs. 4-6 show different embodiments of the assembly including the device of the invention.

The Figures are not drawn to scale and purely diagrammatical. Identical reference numbers in different figures refer to identical parts. Fig. 1 shows in cross-sectional view a first embodiment of the electronic device 100 of the invention. The device 100 comprises a substrate 10 with a first side 1 and an opposed second side 2. A vertical trench capacitor 20 is present, and exposed at the first side 1, in addition to a vertical interconnect 30. In this embodiment both the vertical interconnect 30 and the capacitor 20 comprise a plurality of trenches, 21, 311, 312, 313. However, although very much preferred, this is in principle not necessary. The vertical interconnect 30 comprises a first part 31 and a second part 32 of wider dimensions. As will become clear from the further discussion, the first part 31 is made by anisotropic etching from the first side 1, and the second part 32 is made by etching from the second side 2, and particulary wet-chemical etching. The device 100 comprises a couple of layers on its surfaces on the first and second side 1,2 as well as in the trenches 21, 31, 32. Not shown here are first conductive surfaces 22 that constitute the bottom electrode of the vertical trench capacitor 20. Shown is a layer 11 of dielectric material which is present at nearly the complete surface. On top of the layer 11 of dielectric material, a layer 12 of electrically conductive material is present. This layer is for instance polysilicon, but may alternatively be another material such as copper, sol-gel deposited silver, aluminum, TiN. On the first side 1 the capacitor 20 and the interconnect 30 are provided with a further metallisation of AlCu in this case. The layers 12 and 13 can be used as interconnect layers, and may be mutually separated by an insulating layer at certain positions. The second part 32 of the interconnect has its surface covered with a layer 14, in this case of electroplated copper. The copper extends on the second side 2 of the substrate and forms the wiring pattern. The layer 14 may fill the second part of the interconnect 30. Fig. 2 shows in cross-sectional view four stages in a first embodiment of the method. This first embodiment leads to a device 100 of the first embodiment, with minor variations. Fig. 2a shows the first stage of the method, after etching from the first side has taken place. Dry etching is used for this purpose. A mask was used with circular opening of 1.5 μm diameter and 3.5 μm spacing in the area of the capacitors, and openings of 10 μm diameter and 14 μm spacing in the area of the vertical interconnect. The mask contained a stack of 1 μm thermal oxide and 1.3 μm photoresist. The dry etching was executed at wafer level, using substrates 150 mm in diameter. The resistivity of the wafers was in the order of 1 to 5 mΩ.cm, with the exception of high-ohmic zones 18,19 in the substrate, that had a resistivity of 1000-1500 Ωcm. The wafers were etched at room temperature in an ASE™ Inductively Coupled Plasma (ICP) reactor of STS. Typical etching conditions were 12 to 16 mTorr pressure and 20 °C chuck temperature, yielding etch rates of around 0.6 μm/min. With this process the macropore structures are characterized by a smooth pore wall with a rounded bottom and a pore depth uniformity of more than 97%. The trenches 21 with a mask opening of 1.5 μm diameter led to a depth of 40 μm and a diameter of 2 μm. The trenches 311,312,313 with a mask opening of 10 μm diameter led to a depth of 200 μm and a diameter of 12 μm. The pore depth is slightly larger than the mask opening due to underetch. Hence, the difference in openings in the mask led to differences in the pore depth, which phenomenon was exploited effectively in the invention. Fig 2b shows a second stage in this first embodiment of the method. After the etching, the etch mask was removed, and another mask was deposited. Through this mask, for instance a nitride, an implantation step was carried out. This implantation step provided a first conductive surface 22 in the trenches 21. The mask layout was such that also a conductive surface 42 was provided, to be used as bottom electrode of a planar capacitor.

Between the conductive surface 22 and 42 the high-ohmic zone 18 is present so as to prevent any parasitic currents as much as possible. Furthermore, a pad 23 was defined in connection with the conductive surface 22, so as to enable electrical connection of the first conductive surface 22. Use was made of a P indiffusion from a pre-deposited phosphorous silicate glass layer. The silicate layer was then removed by wet etching in 1% (v/v) HF. Fig. 2c shows a third stage in this first embodiment of the method. In a first step hereof, the vertical interconnects 30 were opened from the second side 2 of the substrate 10 by wet-chemical etching. This led to the second parts 32 of the interconnects 30. Use was made herein of a KOH etch. A photolithographical mask was provided in this purpose on the second side of the substrate. It is observed that in the same step saw lanes can be defined on the second side 2 of the substrate 10. This will simplify the separation of the substrate into individual devices, such that other methods than sawing can be used. Alternative methods for the interconnect opening include powder blasting or lasering . After the provision of the second parts 32 a dielectric layer 11 was deposited. The dielectric layer 11 was in this example a nominally 30 nm 'ONO' dielectric layer stack consisting of a thermal oxide (5 nm), LPCVD nitride (20 nm) and an oxide layer (5 nm) deposited by LPCVD TEOS. The layer was deposited without a mask, such that the complete surface of the device was covered with the dielectric layer 11. Fig. 2d shows the device 100 after the dielectric layer 11 is partially etched away in the following steps, and a layer of electrically conductive matrial is provided to define a top electrode 44 of the planar capacitor 40, the second conductive surface 24 of the vertical capacitor 20, the contact 25 to the first conductive surface 23, and the filling of the first part 31 of the vertical interconnect 30. In this example, use is made of a 0.5 μm thick conductive layer of n-type in situ doped polysilicon. It was deposited by LPCVD from SiH and diluted PH₃. After a furnace annealing step of 30 minutes at 1000 °C the conductivity of the polysilicon is in the order of 1 mΩ.cm. Due to the use of parallel trenches 311, 312, 313 for the first part 31 of the vertical interconnect 30, this conductivity does not lead to an impedance that is too high. The trenches 311 , 312, 313 are filled. In this filling process the polysilicon is first deposited on the side-walls, because it grows in the kinetic regime. Although not explicitly shown, the polysilicon layer 11 is also used as seed layer for the wiring pattern on the second side 2 of the substrate. This wiring pattern is grown by electroplating thereafter. Alternatively, use can be made of the polysilicon as seed layer also in the first part 31 of the interconnect 30. The trenches 311, 312, 313 in the first part will be completely filled, even if the seed material is present only at their ends. Instead of the stack of oxide, nitride and oxide, other materials or combinations thereof may be applied as the dielectric material. Such a material can be any single layer of oxide, nitride or the like; any material with a higher dielectric constant, such as tantalum oxide or hafnium oxide, or the like. These layers can be suitably applied with (low pressure) chemical vapour deposition. With this technique, the complete surface as far as uncovered with a mask, is provided with the desired material. An alternative is the use of wet-chemical deposition techniques, including sol-gel processing. It is preferred to apply an oxide layer, such as a thermal oxide, onto the substrate, in order to improve the adhesion. Another alternative is the use of a single nitride layer of about 15 nm - instead of the stack with 30 nm thickness. This increases the capacitance density from 30 to 90 nF/mm², but reduces the breakdown voltage from 25 to 7 V. Figs. 3 show in cross-sectional view five stages in a second embodiment of the method of the invention. Contrary to the first embodiment, the first step of the method is herein the provision of the second parts 32 of the interconnects 30 from the second side of the substrate 10. This has the major advantage that after this first step no photolithographical step on the second side 2 of the substrate is needed anymore, until the provision of the wiring pattern 14 in the last step of the method. Fig. 3a shows the obtained structure after providing the second parts 32 of the interconnect 30 from the second side 2 of the substrate 10. In this case, this was carried out by first providing a mask 51 of oxide and nitride on all sides of the substrates 10, then patterning the mask 51 according to the desired pattern on the second side 2 of the substrate 10 and finally wet-chemical etching of the silicon substrate 10 with KOH. Fig. 3b shows the result at a second stage of the method. In this method, the the mask 51, or at least the nitride layer thereof, is patterned from the first side 1 of the substrate 10, and used for definition of high-ohmic substrate zones (not shown). Thereafter, a hard mask 52 is deposited and patterned on the first side 1 of the substrate 10 to define the first part 31 of the interconnect 30. Fig. 3c shows the result at a third stage of the method. First the substrate 10 is etched from the first side 1 through the deposited mask. This etching can be done both with dry-etching and with wet-chemical etching. The etching is preferably carried out in the same step as the etching of trenches 21 to define a vertical capacitor. However, this is not essential. Thereafter, a conductive surface is provided in the manner described earlier with respect to the first embodiment of the method. Only hereafter the mask 51 is removed and the dielectric layer 11 is provided without a mask. Thereafter, a layer 12 of electrically conductive material, in this example polysilicon, is deposited and etched in accordance with any desired pattern. Fig. 3d shows the result at a fourth stage of the method. Contact windows have been etched in the dielectric layer 11 on the first side 1 of the substrate 10. A thick dielectric layer 15, in this case TEOS, was deposited in part of the windows. Afterwards, a patterned layer 13 of metal has been deposited, while leaving the area of the TEOS layer free. Fig. 3e shows the result at a fifth stage, after further steps. After provision of a patterned layer 16 of electrically insulating material, a patterned layer 17 of electrically conductive material was provided. This second patterned layer 17, for instance of AlSiCu, has a sufficient thickness, for instance in the order of 1 -4 microns, for definition of high- quality inductors. The pattern of electrically insulating material of the layers 15,16 functions as a mechanical support, such that the overlying area in the second metal layer 13 can be used as bond pad 28. The complete structure is then covered with a passivation layer 29, for instance of silicon nitride, which will be locally removed at the area of the bond pad 28. The substrate 10 is thereafter thinned by grinding from the second side 2 thereof. This is of course by no means a necessary step. Figs. 4, 5 and 6 show in diagrammatical and cross-sectional views examples of the assembly according to the invention. Fig. 4 shows an assembly 300 including the device 100, a leadframe 310 and a semiconductor device 200. The assembly makes use of a double flip chip construction, in which the semiconductor device 200 is electrically connected to the leadframe 310 via the electronic device 100. Herein the bumps 201 between devices 100 and 200 are for instance gold bumps, and the bumps 301 between leads 311 of the leadframe 310 and the device 100 are for instance solder bumps of SAC (tin-silver-copper alloy). Thermally, the semiconductor device 200 is directly coupled to the heatsink 312 of the leadframe 310. This system is assembled in the following manner. Metal has been applied at the bond pad areas of both the device 100 and the active device 200. The device 100 is thereto provided with an underfill metal, such as a Ni or TiW layer on top of the bond pads. The metal is joined in a thermal compression treatment. Thereafter an underfill material is provided so as to fill the area between the device 100 and the active device 200. This underfill acts as a protective layer against moisture and other chemical contamination, layer, which layer is known per se. The leadframe 210 comprises a first and a second electrically conductive layer of Cu. The lead frame 210 is formed by skillfully etching it with a semi- etching technique, first from the first side and then from the second side or the other way around. This results in a heat sink 312 and in leads 311 , while the heat sink 312 is also a contact surface. The heat sink 312 is customarily connected to the rest of the lead frame 310 by means of four wires. There is an open space under the leads 311, which is filled with a moulding material. This provides a mechanical anchoring of the leadframe in the moulding material. On the heatsink 312 a conductive adhesive is applied i.e. a silver containing glass epoxy adhesive. Solder dots are provided on the leads 311, for example, by printing with a stencil. The solder is here a low-melting SAC solder which contains over 96% Sn, 3% Ag and about 0.5% Cu. In an example, the active device 200 together with the bumps 201 has a thickness of 150 ± 15 μm. The layers of the lead frame 310 have a thickness of 70 ± 20 μm while in the location of the heat sink 312 relative to the device 100 there is a play of about 20 μm. The maximum spreading is thus about 55 μm. This spreading can be eliminated by remelting the solder balls and the solder dots, and slightly in the adhesive layer which, however, is chosen to be thin, for example of a thickness of about 20 μm. After the curing of the conductive adhesive, as a result of a heat treatment of 100-150 °C, the heat sink 312 of the lead frame 310 is then pulled up when the adhesive layer shrinks. The result is a downward pressure. The resulting stress is relaxated by taking the bumps 201, 301 to beyond their reflow temperature. In this manner the bumps 201,301 are able to distort, and are particularly flattened. Contrary to the other embodiments, the second side 2 of the device 100 is not provided with contact pads for coupling to an external carrier. In this construction the vertical interconnects 30 provide a thermal path to the second side 2 of the electronic device 100. This improves the heat-spreading function of the device 100. Although not indicated, it is preferable to provide a connection from the second side 2 of the device 100 to the leadframe 310. Alternatively or additionally, the vertical interconnects 30 are used for grounding. Although two vertical interconnects 30 provide an additional resistance to ground, this construction of the grounding has the advantage that ground can be assumed to have the same potential everywhere in the device. Such well-defined ground is particularly preferred if the assembly 300 comprises more than a single element. The vertical capacitors (not-shown) are herein provided on the side 1 of the device 100 facing the semiconductor device 200. Fig. 5 shows an alternative embodiment of the assembly 300. This embodiment has practical advantages for multichip modules, in which more than one device 200 is assembled to the electronic device 100. This electronic device 100 acts here as the carrier of the assembly 300. The advantages are that devices 200 of different height can be included, and that there is no need for a simultaneous attachment of the devices 200 to an individual heatsink 312 or one common heatsink 312. In addition, the assembly 300 of this embodiment is a chip-scale package without a leadframe, which can be provided at wafer level instead of at die level. Herewith a substantial cost reduction is achieved. A disadvantage of the embodiment are, however, the reduced possibilities for thermal dissipation. Although not shown, that the heatsink 180 on the second side of the device 100 is preferably provided with solder balls or other means for thermal coupling to an external carrier. Fig. 6 shows a further embodiment of the assembly 300. This embodiment is a more advanced version of the embodiment of figure 5. It has the further feature that devices 200 are attached to both the first side 1 and the second side 2 of the device 100. If desired, a leadframe with heatsink could be used as shown in Fig. 4.

Claims

CLAIMS:

1. A method of manufacturing an electronic device comprising a semiconductor substrate having a first and a second side and provided with a vertical interconnect extending from the first to the second side, comprising the steps of: providing cavities in the substrate by wet-chemical etching from the second side; forming trenches by etching from the first side of the substrate, said trenches and said cavities together forming through-holes, and providing said through-holes with a conductive surface so as to form the vertical interconnect.

2. A method as claimed in Claim 1, wherein the cavities are provided first and the trenches are formed thereafter, therewith opening the through-holes.

3. A method as claimed in Claim 2, wherein use is made of a single photolithographical mask for the provision of the cavities and the trenches, which mask is patterned on the second side before provision of the cavities, and is patterned on the first side after the provision of the cavities

4. A method as claimed in Claim 1, wherein the substrate is thinned from the second side after provision of the conductive surface, whereafter the substrate is provided on the second side with a desired pattern of electrically conductive material

5. A method as claimed in Claim 1, wherein an electrically insulating layer is provided on the surface of the substrate, both in the through-holes and on the first and second sides, before provision of the electrically conductive surface.

6. A method as claimed in Claim 1, wherein a first microelectronic element is defined in the substrate on the first side thereof, the definition including one or more substrate treatment steps that are carried out before provision of the conductive surface.

7. A method as claimed in Claim 6, wherein the first microelectronic element is a vertical trench capacitor, and said substrate treatment steps comprise the etching of trenches and the doping of the surface with charge carriers.

8. A method as claimed in Claim 1, wherein a metallisation is provided on the first side of the substrate, said metallisation including a bond pad structure with an under bump metallisation.

9. An electronic device comprising a semiconductor substrate having a first and a second side and provided with a vertical interconnect extending from the first to the second side, which is constructed as an electrically conductive connection in a through-hole, said through-hole comprising a first part and a second part, said second part being shaped as a truncated cone and said first part being shaped as at least one cylinder or block and extending from the first side to the top of the truncated cone of the second part.

10. An electronic device as claimed in Claim 9, wherein the first part of the through-hole is filled with electrically conductive material.