DE102006048586B4 - A method and apparatus for manufacturing a semiconductor device and semiconductor wafers having a metallization-facing front side - Google Patents

Abstract

method for manufacturing a semiconductor device comprising attaching a self-supporting, prefabricated metal structure (30) on a Front side (11) of a semiconductor wafer (10) and separating the Semiconductor device after applying the metal structure (30), wherein the metal structure (30) is a plurality of each a single Semiconductor device associated carrier elements (31), which are connected by webs (37).

Description

The The invention relates to a method for producing a semiconductor device, a semiconductor wafer and a manufacturing apparatus therefor.

at New generations of semiconductor devices are trying to do this Substrate so thin as possible to keep. Especially for vertical semiconductor devices, such as vertical DMOS power transistors, the thickness of the substrate is decisive for important Quality parameters of Semiconductor device. In particular, the on-resistance can be by a strong thinning of the back the semiconductor device, wherein the functional structures are obtained stay, decrease.

at a vertical semiconductor device or in a vertical component, where the electric current is not along the surface, but from the front side of the semiconductor device to the back of the semiconductor device guided is the volume adjacent to the front, depending on the voltage class only active to a depth of a few μm. This active volume has a thickness of, for example, 50 V blocking voltage less than 10 μm. Within this layer thickness, the voltage reduction occurs in the blocking case instead of. Also the authoritative ones Structures of the component are defined in this layer.

A vertical semiconductor device would then have an optimal on-resistance and optimum thermal properties, if at a given reverse voltage only this active volume of the semiconductor material used (eg silicon). The immediately adjoining areas should be possible provided with intermediate layers with low-resistance contact elements become.

manufacturing technology This means that semiconductor wafers are strong before completion thinned become. It is therefore necessary to handle semiconductor wafers having a thickness of a few microns. Smallest injuries, for example, of the wafer edge or too high mechanical stress can this to a destruction lead the wafer. The Wafers and also the later isolated semiconductor devices have such a small inherent stability on that a manufacturing or further processing without additional measures impossible is.

From the DE 1514893 A For example, a method for producing semiconductor devices is known in which a metal plate is applied to a surface side of the semiconductor wafer as a self-supporting metallic structure, and the semiconductor wafer is then divided into individual components.

It It is an object of the present invention to provide an efficient process for producing a high quality semiconductor device to provide in high yield. Furthermore, it is the task of present invention, a suitable semiconductor wafer as a process intermediate and a corresponding manufacturing device for a semiconductor device to provide with said properties.

According to the invention this Task by a method according to claim 1, a semiconductor wafer according to claim 5 and a manufacturing apparatus according to claim 10 solved.

According to the invention For example, there is provided a method of manufacturing a semiconductor device, comprising the application of a self-supporting, prefabricated metal structure on a front side of a semiconductor wafer and singulating the semiconductor device after the deposition of the metal structure.

One special thought here is that already in one relatively early Stage of the manufacturing process, a self-supporting metal structure applied to the front, which during further processing as a support structure for the entire semiconductor wafer is used. Thus, very thin semiconductor wafers without the Use additional support structures be transported and processed. As part of this metal structure in the further processing of the semiconductor device as a contact element, for example, as a leadframe or as part of it can, is a detachment of the handling carrier after the separation of the semiconductor chips no longer necessary.

With The proposed concept makes it possible, even in low-voltage applications on the use of highly doped silicon substrates as a carrier substrate to renounce and thus the physically smallest possible area specific Switch-on and threshold resistance to realize. The efficiency and thus added value The manufactured semiconductor devices can thus significantly increased become. In addition, this concept can be based on cheaper base material can be dispensed with by expensive epi layers. The used Wafer exists in realization of the invention exclusively of silicon material, which the doping and blocking ability the active layer corresponds to that in the finished semiconductor device anyway, only this layer remains. The step of applying the prefabricated support or support structure requires very little process time and is therefore highly cost effective.

According to the invention, the metal structure comprises a multiplicity of metal carrier elements which each associated with a single semiconductor device and connected by webs. Thus, the individual carrier elements can be matched exactly to the respective semiconductor device and form corresponding contacts for them. The structural strength and load capacity of the entire wafer is created by the combination of these support elements, for example by webs, which are removed or severed in a later process step. Specifically, the metallizing includes a soldering, in particular bonding, of the metal structure.

In further embodiments the method comprises a step of thinning the semiconductor wafer, the thinning after metallizing takes place. For easy transport and further processing and positioning of the semiconductor wafer to enable, it is advantageous that the self-supporting metal structure before thin is applied.

In further embodiments The metal structure is essentially planar to the front of the semiconductor wafer applied. In further embodiments be hollowed and / or interspaces on the front of the semiconductor wafer to form a planar Backfilled.

There different contact areas of the semiconductor device electrically must be separated from each other and the subsequent Removing connections in the functional area sometimes very expensive or impossible is, the metal structure is at least within the functional range the semiconductor device thus provided with separating sections, that in these areas electrical insulation between the Contact areas already during application of the metallization is provided.

hereby can interspaces arise, which according to a Embodiment of this method or this arrangement with insulating Material filled up can be. this makes possible when thinning the wafer a homogeneous distribution of contact pressure to the grinding / polishing wheel and ensures a high quality result. The filling material can be chosen like that be that they in a further processing of the semiconductor device does not have to be removed again, but at the same time as a housing component serves.

In further embodiments the metal structure is designed to act as a contact element the semiconductor device to be manufactured, in particular as a source metal contact and / or serves as a gate metal contact. For vertical components points the front side of the semiconductor wafer usually has a source and gate contact area. The semiconductor structure can each include separate sections that correspond to the respective contact areas applied, in particular bonded, are.

According to the invention becomes a semiconductor wafer having a metallization Front and one back provided comprising a self-supporting prefabricated metal structure the mounted at least on portions of the front of the semiconductor wafer is.

One important thought exists here, analogous to the already described Procedure, in it, early on prior to singulating the semiconductor wafer by means of a soldered or otherwise stabilized metal structure to stabilize formed in such a way is that she has a lot of the semiconductor wafer spans and this stiffened. In this way, a safe handling of the semiconductor wafer ensured.

According to the invention the metal structure has a plurality of support elements, respectively assigned to a single semiconductor device and formed and deposited on the semiconductor wafer by the metallization device are that each a support element a source electrode and / or a gate electrode of the plurality of Semiconductor elements at least partially covered. As the source electrode usually a relatively large area of single semiconductor devices occupies, can here a large-area support structure soldered become.

In a further embodiment For example, the metal structure includes a support frame that is continuous soldered onto an edge region of the semiconductor wafer. The proposed metal structure has in these areas a carrier edge or a carrier ring auf, which is soldered onto the semiconductor wafer.

The z. B. grid-shaped Support structure the semiconductor wafer with mutually perpendicular sections stability can be optimized, since the support edge a cross-bracing between sections. In primarily non-metallized areas The wafer can solder to seal the spaces between the self-supporting Metal structure and the semiconductor wafer are provided to the Construction, especially in the edge area, to be sealed throughout. Dirt, for example, in the chemical thinning process occur so are kept away from the front of the semiconductor wafer.

system end With the invention, a manufacturing device is provided with a metallization device for applying a self-supporting, prefabricated metal structure on a front side of a semiconductor wafer.

Of Furthermore, the manufacturing device has a thinning device on after the application of the self-supporting metal structure the backside of the semiconductor wafer thins. This can be a thinning device act that performs a chemical and / or mechanical thinning.

The Manufacturing device also has a filling device and they is preferably a separating device, wherein the Separating device for separating the plurality of semiconductor devices Sections of the self-supporting metal structure severed. Both that Silicon as well as the metal structure can thus be split simultaneously become. In one embodiment the electrical insulation of carrier elements takes place at the same time, which are soldered on the source and the gate electrode.

In a further embodiment is the soldering device formed so that they in the metallization a continuous Carrier frame on solder a peripheral region of the semiconductor wafer. This requires an additional Stabilization of the metal structure and provides protection of the front of the Semiconductor opposite contamination in further processing steps.

Further Embodiments of the invention will become apparent from the respective dependent claims or embodiments, the closer by means of pictures explained become. Hereby show:

1 a top view of a semiconductor wafer with a self-supporting metal structure,

2 the semiconductor wafer 1 , with saw frame,

3 a section of the semiconductor wafer from 1 .

4 to 6 Cross sections through the neckline 3 .

7 a section of a semiconductor wafer without a self-supporting metal structure,

8th the cutout 7 with a self-supporting metal structure,

9 a section of a semiconductor wafer with a self-supporting metal structure,

10 a cross section through the neck 9 and

11 a block diagram of the manufacturing stations of a semiconductor manufacturing device.

Semiconductor wafers serve as the starting material in the manufacture of semiconductor devices. 1 shows a schematic representation of a semiconductor wafer 10 in the plan view. For example, to keep the semiconductor substrate thickness and the semiconductor wafer thickness as small as possible, after forming functional regions 20 in a wafer front 11 the semiconductor wafer 10 so thinned that only a very small part of its original thickness remains.

In the step of thinning the semiconductor wafer 10 For example, a grinding process, in particular using an ablation-supporting chemical, is used. This is from a wafer backside 13 (see. 4 ) Removed material in a manufacturing device. A description of the manufacturing device will be given below with reference to the block diagram of 11 given.

To the heavily thinned semiconductor wafer 10 stabilize is at the wafer front 11 a self-supporting metal structure 30 soldered. This metal structure 30 spans, for example, the wafer front 11 in a grid shape. The grating causes a deflection-stabilization of the semiconductor wafer 10 , To enhance the stabilizing effect, the metal structure comprises 30 further, for example, a support ring 39 which is circular over an edge region of the semiconductor wafer 10 runs. The longitudinal and transverse sections of the metal structure are through this support ring 39 stiffened against each other.

In a later manufacturing step, the individual functional areas 20 from the semiconductor wafer 10 cut out, so the semiconductor devices are isolated. For this example, a precision saw can be used along one or more saw frame 15 (see. 2 ) the semiconductor wafer 10 severed. The 2 shows this saw frame 15 which is designed so that simultaneously with the severing of the semiconductor wafer 10 the metal structure 30 also isolated. There remain individual semiconductor devices together with soldered portions of the metal structure 30 ,

In 3 schematically is a section of the semiconductor wafer 10 out 1 and 2 shown. The individual sections showing the metal structure 30 form a plurality of support elements 31 and jetties 37 , The carrier elements 31 are over the jetties 37 connected with each other. The carrier elements 31 are with a lot 35 each on a functional area 20 Soldered and cover this largely. More specifically, the functional area includes 20 a gate area 21 and a much larger source area 23 , During the Gate area even after the application of the metal structure 30 freely contactable from above becomes the essential part of the source region 23 from the carrier element 31 which later forms part of the metal terminal of the respective semiconductor device.

As 4 to 6 show has the metal structure 30 no flat surface. While the support elements 31 essentially parallel to the wafer front 11 run, form the webs 37 a bridge-like connection extending from the wafer front 11 wegwölbt. This bent portion may form a clip for contacting the corresponding semiconductor device. It is conceivable to bend this clip right after the separation. Alternatively, other metal sections on specially provided sections of the webs 37 can be soldered to form the clip or corresponding source pins, or a wire bond can be made. The gate area 21 is connected via a wire bond with a corresponding gate pin.

7 and 8th show an alternative embodiment of the self-supporting metal structure 30 , In 7 are six functional areas 20 a semiconductor wafer 10 shown. The semiconductor wafer 10 does not have any metal structure here 30 for stabilization. The individual functional areas 20 comprise mutually isolated source regions 23 and gate areas 21 , In this embodiment, a substantially planar metal structure 30 on the gate areas 21 and source areas 23 bonded on. 8th shows the corresponding plan view of the semiconductor wafer 10 with the metallised metal structure 30 ,

In a later method step, the semiconductor devices become out of the semiconductor wafer 10 sporadically. This is done by the individual functional areas 20 along the cutting edges 17 from the semiconductor wafer 10 be cut out. The cut edges 17 thus define the saw frame 15 , The in 8th shown section of the metal structure 30 for example, has six recesses 33 , each with a functional area 20 correspond. The recesses 33 are each arranged so that after a separation in each functional area 20 a section of the metal structure 30 remains that the source area 23 covered, and another section that covers the gate area 21 covered.

Because of the recesses 33 these two areas are separated spatially and electrically after separation from each other. The part of the metal structure remaining after singulation 30 is used for further processing of the semiconductor device, in particular for contacting during packaging. A detachment of serving as a stabilizing structure metal structure 30 is not necessary.

To a regular, full-surface pressing of the semiconductor wafer 10 To ensure the step of thinning, all the bumps and the recesses 33 filled with insulating compound (mold compound). The emergence of bumps when grinding from the wafer back 13 by a locally irregular contact pressure against the corresponding grinding or polishing wheel is avoided.

Another alternative embodiment of the metal structure 30 will be in the 9 and 10 shown. Should the metal structure 30 are used as connecting means (clip) for a special housing, the clip is generally larger than the associated silicon chip or functional area 20 , In this case, a working clip by a special spatial form ("folding") of the metal structure 30 be generated. 9 and 10 shows such a metal structure 30 , In 9 are a total of eight functional areas with corresponding gate areas 21 and source areas 23 shown. On every source area 23 is a carrier element 31 soldered. The individual carrier elements 31 are by longitudinal and transverse webs 37 connected with each other.

In cross section (see. 10 ) shows the special spatial form of the present metal structure 30 , The substantially square shaped support elements 31 each comprise on one side a folding portion which is perpendicular to the respective carrier element 31 protrudes upward. The longitudinally oriented webs 37 take up an upper portion of these folding sections and thus stabilize the entire semiconductor wafer 10 , In addition, each folding sections of adjacent support elements 31 connected to form a bridge structure and stabilized so the semiconductor wafer 10 further.

The connections between the folding sections are so parallel to the functional areas 20 , above the sawing frame 15 arranged that after singling each have a functional area 20 with a carrier element 31 and a cross-section perpendicular to the carrier element 31 standing folding section remains. To form the clip of the semiconductor device, this folding section can be bent down so as to be substantially a planar continuation of the carrier element 31 forms. In this position, the folding section protrudes beyond the isolated semiconductor device (formerly functional area 20 ) and can be installed in a special housing. Alternatively, the folding section can be bent so that in cross-section a zigzag shape, comprising the folding portion and the support element 31 , results.

In a further embodiment, the folding section may be dimensioned so tight that it only a solder pad parallel to the base surface of the functional area 20 to which a special pin clop (pin clip) is soldered to pins (source pins). The connection to a gate terminal (gate pin) can be made by means of a bonding wire.

The method described for contacting the pins (source pins and gate pins) comprises attaching additional solder joints. This can be circumvented by performing another process step when soldering the leadframe to the back of the chip. Since the usual soldering (Solder Die Bonding) or a coupled reflow process causes temperatures that also affect the solder 35 below the carrier element 31 can melt the metal structure 30 or the corresponding carrier element 31 be lifted and in the same soldering all the necessary connections realizing clip (a so-called. "Full clip") are placed. This full clip can provide corresponding contacts, ie gate pins and source pins, in curved or unbent form, as required.

In known semiconductor device fabrication processes, the functional areas are 20 comprising gate areas 21 and source areas 23 , on a semiconductor wafer 10 always aligned the same. So is the gate area 21 for example, in a plan view in each row and each column of functional areas 20 each in the upper left corner. For the design of the described metal structure 30 it may be advantageous to break this conventional type of arrangement. Thus, the functional areas can be arranged in pairs or groups, each with a special orientation to each other. So it is possible the functional areas 20 one line to align with each other while the functional areas 20 an adjacent line are rotated by 180 °. Alternatively, four adjacent functional areas each 20 a group in the semiconductor wafer 10 be aligned so that the four associated source areas 23 located in the immediate vicinity.

An embodiment of the manufacturing apparatus for manufacturing semiconductor devices according to the invention comprises, as in 11 shown very simplified, two metallization devices 41 , a filling device 43 , a thinning device 45 and a separating device 47 , For further process steps, other devices known in the manufacture of semiconductor devices may be added to said manufacturing device.

After the completion of the functional areas are in the first metallization 41 Contact areas on the wafer front 11 educated. This can be done for example by sputtering a diffusion barrier and a thin copper layer. After completing the contact areas, in the first metallization device 41 the semiconductor wafer 10 spanning metal structure 16 soldered.

After that, bumps and recesses are created 33 on the surface of the metal structure 30 in the filling device 43 filled with molding compound. Thanks to the metal structure 30 is a simple transport of the semiconductor wafer 10 between the stations or devices possible.

In the thinning device 45 then becomes the semiconductor wafer 10 thinned. This is done by a grinding process, in particular using an ablation-supporting chemical, in the substrate from the wafer back 13 Will get removed.

In another metallization device 41 becomes the thinned semiconductor wafer 10 (after cleaning) with further contact areas on the back of the wafer 13 Mistake. In the separating device 47 becomes the semiconductor wafer 10 severed by a precision saw. The here sawed saw frame 15 runs so that the metal structure 16 is severed such that an immediate further processing of the resulting semiconductor device is possible.

The execution The invention is not limited to the embodiments shown above limited, but also in any combination of the features of the dependent claims and a variety of modifications possible in the context of expert Acting are.

Claims (14)

A method of manufacturing a semiconductor device comprising mounting a self-supporting prefabricated metal structure ( 30 ) on a front side ( 11 ) of a semiconductor wafer ( 10 ) and singulation of the semiconductor device after application of the metal structure ( 30 ), wherein the metal structure ( 30 ) a plurality of each of a single semiconductor device associated carrier elements ( 31 ), which is supported by webs ( 37 ) are connected. The method of claim 1, wherein attaching the metal structure ( 30 ) a Auflöten or Aufsin tern of the prefabricated metal structure ( 30 ). Method according to Claim 2, which comprises filling hollow spaces and / or gaps ( 33 ) on the front side ( 11 ) of the semiconductor wafer ( 10 ). Method according to one of claims 1 to 3, which is a thinning of the semiconductor wafer ( 10 ) after attaching the metal structure. Semiconductor wafer having a metallization front side ( 11 ) and a back ( 13 ), comprising: a self-supporting prefabricated metal structure ( 30 ), which comprise a multiplicity of carrier elements each assigned to a single semiconductor device ( 31 ), which are interconnected by webs, and which at least on portions of the front side of the semiconductor wafer ( 10 ) is attached. A semiconductor wafer according to claim 5, comprising: a filling layer adapted to form a planar surface on the front side ( 11 ) in interspaces of the metal structure ( 30 ) is introduced. A semiconductor wafer according to claim 5 or 6, wherein the metal structure ( 30 ) is formed to form contact elements of semiconductor devices in the semiconductor wafer. Semiconductor wafer according to one of claims 5 to 7, comprising: a variety of recesses for the formation of electric isolated contact elements. A semiconductor wafer according to any one of claims 5 to 8, wherein the metal structure ( 30 ) a support edge ( 39 ) which extends continuously to a peripheral area ( 19 ) of the semiconductor wafer ( 10 ) is attached. Manufacturing device ( 40 ) for semiconductor devices ( 10 ) for carrying out the method according to one of claims 1 to 4, with a metallization device ( 41 ) for mounting a self-supporting prefabricated metal structure ( 30 ) on a front side ( 11 ) of a semiconductor wafer ( 10 ), wherein after the metallization device ( 41 ) a filling device ( 43 ) arranged to form a substantially planar surface on the metal structure ( 30 ) by filling cavities and / or gaps ( 33 ) on the front side ( 11 ) of a semiconductor wafer ( 10 ) after application of the metal structure ( 30 ) serves. Manufacturing apparatus according to claim 10, wherein the Metallization device comprises a soldering device. Manufacturing apparatus according to claim 10 or 11, having a post-metallization device ( 41 ) arranged thinning device ( 45 ) for thinning the semiconductor wafer ( 10 ) on the back ( 13 ) after application of the self-supporting metal structure ( 30 ). Manufacturing device according to one of claims 10 to 12, with a separating device ( 47 ) for separating the plurality of semiconductor devices, wherein the separating device ( 47 ) for cutting through sections of the self-supporting metal structure ( 30 ) is trained. Manufacturing device according to one of claims 10 to 13, wherein the metallization device ( 41 ) is formed such that when attaching the metal structure, a continuous support edge ( 39 ) of the metal structure ( 30 ) on a border area ( 19 ) of the semiconductor wafer ( 10 ) is fixed.