DE1514668A1 - Method for producing metal contacts on semiconductor components - Google Patents

Description

Siemens & llalske Munich, 19JAN.1966

Aktiengesellschaft Wittelsbacherplatz 2

«6/2039

Process for making metal contacts on semiconductor components.

For the efficient manufacture of semiconductor components, in particular of semiconductor components, their manufacture based on planar technology, the attachment of the contacts to the electrodes is of great importance. In addition to the very expensive ball compression method, it is known to use metal contacts to evaporate through appropriate masks. These

VA 9 / 4-93 / 792 Edt / S - 2 -

909827/0 800 BAD OBJGtNAt.

Metal contacts mainly consist of aluminum and gold. The vapor-deposited metals in the previously usual processes must be heat-treated so that good and firmly adhering contacts are created. Through this annealing process become very often the blocking properties of the finished components worsened. In the case of planar diodes and transistors, diffusion layers with <? 1 / U thickness very lightly alloyed, whereby the normal production loss due to the attachment the number of contacts is still significantly increased. In addition, the formation of metal droplets can occasionally interfere, because the contact does not form a continuous metal layer.

The invention relates to a method of manufacture of contacts, in particular for semiconductor components, which are preferably manufactured according to planar technology and at which the applied metal layer is not tempered.

It is known that vapor-deposited chrome on glass surfaces gives good adhesive strength. The invention serves to The solution to the problem of these chromium layers by means of further vapor deposition layers to reinforce and to make it easy to solder.

The method based on the invention is characterized in that that cleaning by means of etching solutions is carried out on the surface to be contacted, that the to Koritaktiorende material heated up and then

BAO ORIGINAL "3 _

909827/0800

PA 9/493/792 - 3 -

a chrome layer is applied to the surface to be contacted, which is immediately followed by a second Metal layer, in particular consisting of silver, reinforced will. The advantage of the chrome layer is its good adhesive strength also on oxides and passivation layers and in the absence of blocking on low-resistance semiconductor material. Decisive for the adhesion of the second metal layer, for example silver, to chromium is the -defined continuous Transition of both metals. For this reason, both metals become simultaneously for a short time, for example by vapor deposition deposited.

Instead of silver, other metals such as gold, copper, tin, nickel, lead, indium, aluminum, zinc or cadmium can also be used or combined with one another. In this way * pressure and soldering contacts, especially for Kanunlötungen, can be made. On silicon, for example, the chrome silver contacts withstand temperatures of over 800 ° C. without damage and thus also survive the melting of passive glass layers and melting in hard glass. Be especially advantageous for the production of .zweiten metal layer has the combination of silver-lead be wlil Vr * t -.- '' · ■■ - ■■■

For an execution form based on the idea of the invention: The chroin layer is made by vapor deposition at a pressure < 10

90982 7/0800 _BAD

PA 9/493/792 - 4 -

Torr applied. As a vaporizer for chrome, a Tungsten tape, which is provided with a chromium layer, in particular galvanically applied, is very suitable proven.

However, such an arrangement can also be selected at the chrome is used in a powdery state. For better Adhesion of the chrome to the evaporator is expedient before heating a small addition of gold or a mixed with other metals that do not evaporate significantly at the chromium vapor deposition temperature.

The use of sintered or rolled chrome sheet as Vaporizer offers another way to do it of the method according to the invention.

In a further development of the inventive concept, provision is made for the evaporator temperature to be set to approximately 1200 ° C. and nine chrome layer in a layer thickness of <0.1 / U.

In principle, chromium can also be produced by cathode sputtering, e.g. I3. in hydrogen, at about 10 Torr. However, the steady transition to the second "metal" should be a little more difficult to manufacture. _Bä q ORIGINAL

_ 5 _ 909827/0800

-, EA- "9/493/792 - '' -" ./ - Ϊ ~ '

It is within the scope of the method according to the invention to produce the second metal layer, which preferably consists of silver, by vapor deposition at a pressure of < 10 ~ ^J Torr and to produce it in a layer thickness of approximately 5 / rev. These contacts can be connected to one another or to contact pads that are firmly adhered to a passivation layer by means of interconnects. Parts of the interconnects can possibly be reinforced by electroplating using photoresist, especially if small or complex geometries do not allow thicker vapor deposition through punched masks.

Around. the adhesive strength of the chromium layer on the semiconductor material To increase this, it is advantageous to carry out a surface cleaning by means of a buffered surface before the metal layers are deposited Carry out hydrofluoric acid solution and subsequent rinsing in distilled water and then the semiconductor material bake out at 350 - 400 ° C in 10 - 20 seconds.

In terms of their electrical properties, chrome contacts are as ohmic contacts only on very low-ohmic silicon, d.lu essentially on diffusion layers with high surface concentration, and suitable on the usual epitaxial substrates. For example, while non-alloyed gold contacts' on p-doped silicon up to a few ohms cm (approx. 10 cm) are useful in the case of chromium contacts on p-silicon with

17 - 3 a surface concentration of 5 x 10 cm transition resistance

909827/0800 " ⁶ ~

BAD OHfGtNAL

• ΡΛ 9/493/792 - · -

levels of about 10 - 5 ohms with an area of 300yU 0 were found. On the other hand, the gold contact on n-silicon is only required as an ohmic contact ^{with high doping (> 10 ** cm ~ J).}

18 -3

bar, while chromium only starts below about 10 cm, rectifying To produce metal semiconductor contacts "

Another advantage of the method according to the invention is that Chromium is better than gold for making rectifying metal semiconductor contacts on »-silicon is suitable if from the course of the voltage dependency of the capacitance of a Aufdairpf layer the doping distribution, for example in epitaxial layers, is to be determined.

When germanium is used as a semiconductor material, the situation is similar.

Further advantages of the method according to the invention are y therein. see that the contacts may withstand the high temperatures associated with melting glass and adhere well to both semiconductor surfaces and passivation layers. This property can also be used for the production of interconnects on insulators ₀

The method according to the invention is therefore particularly suitable advantageously for the production of electrical, multi-pole components, such as resistors and capacitors.

909827/0800

PA-9 / 4.93 / 792 '. - 7 "

However, it can also be used advantageously in production of printed and integrated circuits.

With the aid of the method according to the invention, the production; of shark lead components, in particular of micro-semiconductor components, for example silicon planar transistors and diodes which are accommodated on a semiconductor wafer and before mounting on their base by dividing them accordingly can be obtained in the individual components, designed very efficiently and without great effort. Here is the Yield of good quality components significantly greater than this was possible according to the usual procedures.

In the following, the invention will be based on exemplary embodiments and FIGS. 1-6, from which further details and advantages emerge, are explained in more detail.

Has been in Fig. 1 in section, a p-doped Siliciumeinkristallscheibe 1 is shown, in which doped n-through diffusion by means of a substance such as phosphorus, a pn junction generates 2 * The semiconductor crystal wafer was erfinduni ^r> convention under provided with a chromium layer 3 , to which a further metal layer 4, for example consisting of silver, has been applied. This crystal disc is used to manufacture diodes in glass housings. .

. «Äsra-f -: - 90982t / 0800

BATH

ΡΛ 9/493/792. - 8th -

Before the metal vapor deposition process, the semiconductor crystal provided with the doping is subjected to a brief surface cleaning by etching off disturbed crystal material in buffered hydrofluoric acid and subsequent thorough rinsing in distilled water. After a short, about 10-20 seconds lance heating at 350-400 ° C., the crystal disks are immediately placed in a vapor deposition apparatus consisting of the recipient 11, as shown in FIG. An oil diffusion pump is connected to the vapor deposition apparatus at the arrow labeled 12. To shorten the pumping times and to reduce the oil vapor pressure, the recipient 11 is heated with hot water during evacuation, which is then replaced by tap water at normal temperature or by liquid nitrogen during the evaporation process. A boat 13 made of tungsten tape is used as an evaporator for chromium, into which chromium is poured in powder form. The chrome adheres better to the evaporator if a little gold has been added before heating. The boat with the chrome and the little added gold is now closed! ' Aperture ^ brought to a temperature of approx. 1200 ° C. by means of the power supply lines 10} a suitable vapor deposition rate is set by measuring the ionic current by means of an electrode 36 and a microamperometer. First, at a pressure <10 "* Torr, a very thin chrome layer 3, for example 0.1 / U thickness, is vapor-deposited, the layer thickness being controlled with a photocell 27, which is arranged behind a pane of glass 2 &

BAD ORJGWAi _ 9 _

909827/0800

VA 9 / ¥ J3 / 792 - 9 -. ·

and responds to the light from the glowing chrome boat 13. When the photo current drops to half after about 5 - 20 seconds Has dropped, the parts of the power supply lines 20 are operated Heating of the one charged with silver, next to the tungsten ship 13 arranged molybdenum boat 14 switched on, ■ so that both metals are vaporized at the same time for a short time » This is the good adhesive strength of the second metal layer guaranteed on the chrome layer. Finally, only the second metal, e.g. silver, is evaporated and down to the desired one Layer thickness, for example up to 5 / U? on that in the vapor deposition mask 9 clamped semiconductor material 1, 2, which is provided with a chromium film 3 · deposited. The deposition the silver layer 4 (see Fig. 1) lasts for one layer thickness from 5 / U about 30 seconds »

By using two congruent punched molybdenum noses, between which the crystal disc is held during the vapor deposition and which on both sides only the later Dividing the systems provided, corresponding to the scoring tracks, cover about 10OyU wide strips, it is possible that To separate systems in such a way that they do not adhere to one another at the motor contacts after breaking. The ones covered on both sides Silicon crystal wafers are then made using a commercially available Adhesive cemented onto a glass plate and broken down into the individual systems by ticking along the kita lanes, which are then built into the tilas housing.

90982770800 - 10 -

BATH ORIGINAL

PA 9/493/792 - 10 -

Another arrangement, the production of which is also based on the method on which the invention is based, is shown in FIG. The arrangement represents a process step of a silicon planar diode, which is to be installed in a miniature glass housing. "In a p-doped silicon single crystal disk 1, an η-doped zone 2 was produced by diffusion from the gas phase by means of phosphorus in the area of an oxide window 7 and the semi-conductor crystal surface with provided a vitreous phosphorus oxide layer, in which a smaller window 17 was etched concentrically to the first window 7 for attaching the contact using again the known photoresist technology, so that the parts of the phosphorus oxide glass layer and the silicon dioxide layer remained on the semiconductor crystal surface, which in the figure with 15 and 5. The vapor deposition process for producing the metal contact on the etched-free η-doped zone 2 takes place as described in the embodiment according to FIG The chrome-silver layer (3 and 4) can easily be freed again by etching in a suitable solvent. During vapor deposition through this tantalum mask 6, a pile-shaped deposit 4 (height at least 70 / ^u ) of the material (3j 4) provided for late contacting is formed on η-doped zone 2, which can be clearly seen in FIG. 3. After removing the masks, the planar systems can be used after dividing the crystal disk into the individual

909827/0800 bad original -11-

ΡΛ 9/493/792 '- 11 -

Systems can be built into * the glass housing immediately. Included prevents the pile-like deposition of the ear-silver contacts (3, 4) on del? η-doped zone 2 that between Contact clips and scratches short circuits occur.

FIG. A shows an enlargement of the arrangement shown in FIG. 3 after removal of the double mask, the layer sequence of the silicon dioxide layer 5 applied to the dome with the η-doped zone 2, the phosphorus oxide glass layer 15 and the chromium-silver produced according to the inventive method -Layer 3 and 4 can be seen very clearly.

In Figures 5 and 6 it is shown how it is done with the help of the teaching of the invention based method is possible, To produce contact patches for semiconductor components with the smallest of geometries. In a p-doped silicon single crystal wafer 1 were made by diffusion from the gas phase by means of phosphorus. Using known photoresist techniques and Diffusion masking is generated at certain points provided for this purpose η-doped zones.2. The areas marked 8 on the semi-conductor crystal surface are the areas which are at the free etching were masked for the phosphorus diffusion and consist of a passivating silicon dioxide layer. before the pedamping of the crystal disc with the metal contacts the one created over tier n-doped zone 2 during diffusion

909827/0800

BAD OBIGlNAt

ΡΛ 9- / '«93/792 - 1?« ~'

Phosphorus oxide glass layer etched off and the semiconductor wafer also on the passivation layer as in the exemplary embodiment steamed described in Fig. 1. In well-known Way are the contacts, loit tracks and contact patches with covered with a photoresist and the rest of the vapor-deposited chrome and silver layer with one or two different solvents to which the photoresist used is resistant j is replaced. This creates the one designated by 3 in FIG Chromium layer and the silver layer labeled A. In Fig. is the same arrangement in plan view as in Fig. 5 in section The same reference numerals as in FIG. 5 apply. This type of steaming is used when pressure and temperature when contacting are not acceptable for the system geometry or if due to the very small geometric distances direct contact is not feasible.

The metal contacts produced by the method according to the invention can, if necessary, galvanically be reinforced. If pn-silver transitions switched in the reverse direction hinder the galvanic deposition, then the last application of the photographic technique described above can be applied essentially in the opposite way, i.e. that only the contacts, interconnects and contact surfaces to be reinforced remain free of photoresist and are galvanically reinforced, so that after removal of the lacquer by a simple Etching without cover for the electroplating as bridges

- 13 909827/0800

BADORlQiNAL

ΡΛ 9A9J / 792 ■. - 13 -

required parts of the 'on vapor layer can be removed, with the galvanically reinforced Tolle only insignificant attacked wex'den.

The chrome filin under the silver layer can be inserted into very advantageous because of its resistance to Use hydrofluoric acid-nitric acid mixtures as an etching mask

If individual parts, a group or all contacts of a Disk are not sufficiently heavily doped on the surface, so that on them Ghrom does not give sufficient-lock-froion contact, E.g. base contacts made of p-silicon, then initially these contacts are etched free with photoresist technology. then the entire surface of the semiconductor wafer is vapor-deposited with a suitable metal, on the one hand with or without alloying has a desired contact character and adheres firmly to the semiconductor, but on the other hand adheres so loosely to the oxide glass layer that the parts vapor-deposited on it e.g., without using a cover in an ultrasonic bath can be removed. Contacting then follows ex ' and the application of interconnects and / or contact pads in in the manner described above according to the method according to the invention.

21 claims,

9 09827/0800

BATH -

Claims (21)

Claims' I. A method of making contacts, in particular for llalblei terbauelemente, which are preferably made according to the planar technology ', without heat treatment of the applied metal layers, _v characterized in that cleaning is carried out on the surface to be contacted by means of etching solutions that then the Material is baked out and then a chromium layer is applied to the surface to be contacted, which chromium layer is then immediately reinforced by a second metal layer, in particular consisting of silver. 2. The method according to claim 1, characterized in that the second metal layer made of at least one of the metals Silver, gold, copper, tin, nickel, lead, indium, aluminum, zinc or cadmium. 3- The method according to claim 2, characterized in that the combination of silver and lead is preferably selected for producing the second metal layer. 4. The method according to at least one of claims 1 - 3 » vapor at <10 Torr is applied. characterized in that the chromium layer is BAD ORiQiNAL - 15 - 909827/0800 FA 9/493/792 -15- 1S1 4668 5. Method according to at least one of Claims 1 - A, characterized in that a tungsten strip is used as an evaporator for chromium, which with one, in particular galvanically applied chrome layer is provided 6. The method according to at least one of claims 1 - 5, characterized in that chromium is in powder form State evaporated wii'd. 7 · method according to at least one of claims 1-6, characterized in that additions of gold are added to the evaporator. 8. The method according to at least one of claims 1 - 7 » characterized in that a sintered evaporator is used or rolled chrome sheet is used. 9. The method according to at least one of claims 1 - 8, cUulurch characterized that the evaporator temperature on about 1200 C is set. 10. The method according to at least one of claims 1-9 »thereby characterized that the chronic layer by cathodes.- ' atomization in hydrogen at 10 torr. 11 »Method according to at least one of claims 1 - 10, - 16 909827/0800 IAD ORIGINAL pa 9A93 / 792 - a - characterized in that the chromium layer in one Layer thickness C 0.1 / U is produced. . 12. The method according to at least one of claims 1-11, characterized in that the second metal layer, preferably consisting of silver, by vapor deposition is generated at <10 Torr. 13 · Method according to at least one of Claims 1-11, characterized in that the second metal layer is made in a strength of about 5 / U. 14. The method according to at least one of claims I - 13, characterized in that the second metal layer is reinforced by electrodeposition. 15 · method according to at least one of claims 1 - 14, characterized in that the applied metal layers at certain locations provided for this purpose be galvanically reinforced by means of known photo techniques. 16. The method according to at least one of claims 1-15 »characterized in that the prior to the deposition of the Surface cleaning of the metal layers Semiconductor material takes place by means of buffered hydrofluoric acid and subsequent rinsing in distilled water. '- ^: \ 909827/0800 bad original " PA .9 / 493/792 - - Λ7 - 17 · method according to at least one of claims 1 - 16, characterized in that the heating of the semiconductor materials before the metal layers are deposited at ^- "4GO C is made in 10 - 20 seconds» 18. Electrical multi-pole components, such as, for example, resistors and capacitors, produced by a method according to claims 1-17. 19 »Printed circuits, manufactured according to a process according to claim 1 -17 · 20. Integrated circuits, produced by a method according to claims 1-17 · 21. Semiconductor components, in particular micro-semiconductor components, for example silicon planar transistors and diodes housed on a semiconductor wafer and before mounting on their base by corresponding Dividing into the individual components are obtained, produced according to a method Claim 1-17 909827/0800 Blank page