FR2496985A1 - METHOD FOR MANUFACTURING ALLOWED CONTACTS POWER SEMICONDUCTOR COMPONENTS ON A LARGE SURFACE SILICON DISK - Google Patents

Abstract

A SILICON DISC IS FITTED BY AN ALLOY PROCESS ON A VERY HIGHLY DOPED SILICON SUPPORT DISC 6, WITH A THICKNESS OF APPROXIMATELY 1 MM AND WITH A SPECIFIC RESISTANCE R 1.5 MOHM PER CENTIMETER.

Description

The present invention relates to a method of manufacturing

  semiconductor components according to which in a disk-shaped silicon semiconductor body having a large surface, a large number of sets are created by doping with disturbing elements and after application of a mask. layered and of different types of conductivity of which

  the various layers have zones of conductivity

  The surfaces are also provided with an alloy metal layer on which branch electrodes are attached depending on the arrangement of the layers and areas of different conductivity and depending on the different conductivity type, the semiconductor disk. being then subdivided into a large number

of individual elements.

  Semiconductor components, such as, for example,

  diodes, transistors, thyristors or

  triacs, are manufactured according to methods known in

  trusting to a predetermined depth the characteristics

  electrical properties of all or part of the surface of homogeneously doped semiconductor disks by the incorporation of additional disturbing elements

  by means of alloying and / or diffusion processes of

  to obtain a set of different zone layers and conductivity types. The different areas on the surface are then provided with metal contacts

  reported by welding or alloying processes.

  Semiconductor components are connected to different

  circuits through these metal contacts.

  For economic reasons and with a view to

  rationing, it is advantageous not to realize

  components of small and medium size

  and carry out the usual operations, such as

  the application of masks, doping and metallizing

  on semiconductor disks with a relative surface area

  and then subdividing them, for example by acid etching, sawing, sanding, scaling, breaking or ultrasonic, into smaller elements of predetermined size, which are then connected to the

  current conductors by usual methods.

  For a silicon semiconductor body, it is

  usually as a contact and support material, molybdenum or, more rarely, tungsten because the thermal expansion coefficients of silicon and molybdenum or tungsten are very similar, which only creates constraints low temperatures during alternating operating temperatures, not too high, and during manufacturing operations by

  welding at temperatures not too high.

  When semiconductor components, especially semiconductor power components, are

  to exhibit great resistance to weather variations

  it is necessary to use allied contacts

  instead of welded contacts. Since the temperatures

  tures reach around 7000C during the process by

  bonding, the difference in the expansion coefficients between silicon and molybdenum or tungsten occurs to such an extent that it is no longer possible to use silicon and molybdenum large surface discs

  or tungsten. When using molybdenum disks,

  are relatively thin as support disks for silicon, these disks flex under the influence of

  different dilations resulting from high temperatures.

  The semiconductor disks can then either

  abruptly, support discs either have a crystalline structure deteriorated by the deflection, or the disc tears with inconvenience

  with regard to the stopping power of the component produced.

  Moreover, when increasing the thickness of the support disk, for example to 1 - 1.5 mm, so that it

  has a sufficient mechanical strength, the section-

  and the division into small partial disks of a molybdenum disk of such a thickness is very difficult and can only be performed by employing

  expensive. For these reasons it was not possible to use

  the process consisting in the subdivision into

  smaller ones of a large semiconductor disk

  surface and already equipped with all the contacts for

  of semiconductor power components whose

  contacts must be made by an alloying process.

  In the manufacture of semiconductor

  power providers it was necessary to proceed with division already after doping and proceed only

  then to the alloying operation on the various elements

  created. Consequently the realization of the contacts required additional and unavoidable operations, for example the precise implementation of the numerous elements

  which largely nullified the benefits of

  such as the establishment of a common mask and the

  doping of a large-area semiconductor disk.

  By the patent application DE 2 828 044 it is known

  a semiconductor component in which a silicon disc

  Cium serves as an active semiconductor element and on which a strongly silicon support disc is attached.

  dope. The subject of this application concerns only one

  rather than a process and relates exclusively to a single element of

  not be subdivided into several smaller elements.

  The object of the present invention is to create a

  assigned to manufacture semiconductor components of

  power with allied contacts, according to which all

  The usual rations, including the making of the contacts, are performed on a large silicon disk and in which the silicon disk is then only subdivided into a large number of partial elements so as to take full advantage of the advantage. consisting in the application of a single and common mask and in the

  doping alone and in the single operation of

  contacts. When making the contacts, taking place under an alloy temperature of about 7000C, the semiconductor disk must not detach from the support disk and it must not undergo any deterioration or modification of its crystalline structure; the division of the support disk connected to the semiconductor disk in order to

  to obtain partial elements must also be able to

  to do without great difficulty. The problems set out above are solved by a manufacturing method which is characterized in that the silicon disk is alloyed on a highly doped silicon support disk while providing for

  an aluminum-silicon interlayer.

  The support disc advantageously has a specific resistance of S <1.5 mohm per centimeter and a thickness of about 1 mm. Both monocrystalline silicon and polycrystalline silicon can be used

  which is usually grown in a crucible.

  Thanks to the process according to the invention the material of

  semiconductor body and that of the support disk pre-

  have the same coefficient of expansion, which has the effect that there are no thermal stresses even for temperatures varying within a wide range and for large areas. Therefore, during the manufacturing process, it is possible to carry out alloying operations under

  higher temperatures even for a silicon disc

  large area and not yet subdivided without risk

  abrupt detachment of the semiconductor disk by

  relative to the support disc or deterioration of the disc

  than semiconductor. As a result, in addition to mask and doping, it is also possible to perform

  the formation of contacts by alloying semi-components

  Power conductors on the large area disk not yet subdivided which allows by a single operation the formation of contacts of a large number of individual elements. The division into individual elements of the large support disk connected to the silicon disk can be performed relatively simply, for example by an ultrasonic method, because it is easier to cut a silicon support disk that a molybdenum support disc, especially when the latter has a layer of molybdenum of greater thickness. The following process

  the invention also has an economic advantage

  the fact that a silicon support disk, which does not require excessive purity, is priced at

  returns lower than a corresponding molybdenum disc.

  Since the thermal conductivity of the

  lybdenum and silicon are virtually identical, the dissipation of lost heat is as good for a silicon support disk as for a

molybdenum support.

  The slightly lower electrical conductivity of silicon over that of molybdenum is largely offset by the lower transfer resistances of

  silicon. Volumetric resistance and the fall of

  inside the semiconductor disk play only a minor role in relation to the role

by the transfer resistors.

  Various other features of the present invention

  come out from the following detailed description.

  An embodiment of the object of the invention

  is shown, by way of non-limiting example, to the

annexed.

  Figs. 1 to 6 show in section the various stages

  of manufacturing a semiconductor component

the process of the invention.

  Fig. 1 shows a silicon disk 1 made of n-type base material and having a diameter of about 7.6 cm and a thickness of about 280pum. The n-type layer 3 is transformed into a surface and by one of the known diffusion processes into a n-type layer 2 and a n-type layer 4

  As is apparent from FIG. 2 an inner layer

  mediate 5 in a eutectic aluminum-silicon system and

  thickness between 10 and 30) um is all

  edge reported on layer 4 of type + Disk 1 is

  then connected by alloy and by means of the

  mediator 5 to a support disc 6 made of very strong silicon.

  doped. The thickness of the support disk 6 is

  viron 1 mm and its specific resistance is f <1.5 mOhm per centimeter. Fig. 3 shows that aluminum layers 7 and 8 with a thickness of between 10 and 30 um are then

  reported by evaporation on both surfaces of

  2 and 6. Layers 7 and 8 are structured according to

  the intended shape and they are annealed.

  The set of layers thus produced is then bonded to a glass or steel plate 9, as shown in FIG. 4, and is subdivided into individual elements for example using an ultrasonic piercing device 10. FIG. 5 shows one of the elements obtained. As is apparent from FIG. 6, this element is rectified in the usual way on these edges and it is provided with a passivation

  marginal 11 and a copper contact 12.

Claims (6)

  1 - Process for manufacturing semi-finished components   conductive conductors in which a disk-shaped silicon semiconductor body having a large surface is generated, by doping with disturbing elements and after application of a mask, a large number of   layered assemblies and types of conductive   different surfaces, the surfaces being provided with an alloy metal layer on which branching electrodes are reported according to the arrangement of the layers and the zones of   different conductivity and depending on the type of   different, the semiconductor disk being   subdivided into a large number of individual elements,   characterized in that the silicon disk is reported by alloy on a silicon support disk very strongly   doped by providing an intermediate layer of aluminum-   silicon. 2 - Process according to claim 1, characterized in that the support disk has a resistance   specific of 5 <1.5 mohm per centimeter.   3 - Process according to one of claims 1 and 2,   characterized in that the support disk has a thickness of about 1 mm.   4 - Process according to one of claims 1 to 3,   characterized in that aluminum layers having a thickness of between 10 and 30pum are reported   by evaporation on the surfaces of the layers (2) and (6).   5 - Process according to one of claims 1 to 4,   characterized in that all the layers (2, 3, 4, 5, 6, 7, 8) are glued to a glass or steel plate and   is subdivided into individual elements using a   Drilling equipment including ultrasounds.   6 - Process according to one of claims 1 to 5,   characterized in that the individual elements are   on their edges and are passivated   marginal (11) and a copper contact (12).