DE4237017A1 - Method of making a heating element - Google Patents

Abstract

In a process for producing a heating element, a working layer with contact areas is formed by plasma-chemical deposition on a substrate. A metal surface is used as substrate. First, an insulating layer is formed on the substrate through deposition from a first mixture consisting of a precursor mix of SiH4 and Ar, which contains 96-97 % Ar, and O, the ratio between precursor mix and O being 1:2.5-5. Then, a resistive layer of alloyed amorphous silicon is formed by deposition from a second mixture consisting of a precursor mix of SiH4 and Ar, which contains 96-97 % Ar, and BF3, the ratio between the precursor mix and BF3 being 100:5-10. Both deposition processes are carried at a substrate temperature of 250-500 DEG C, a pressure of 0.2-0.5 mmHg and a specific discharge output of 0.1-0.5 W/cm<2>.

Description

The invention relates to a method for producing a Heating element according to the preamble of the claim.

For the production of thin-layer resistance heating elements, it is made of Z.Ju. Gotra "Spravochnik po tekhnologii mikroelek tronnykh ustroistv" (manual of the technology of microelectronic devices), Lvov, 1986, page 257, the resistance alloys PC-4800, PC-3710, PC-3001, PC-1714, PC-1004, PC- 4206 to use, which contain 10, 30 or 50% silicon monoxide and 90, 70 or 50% chrome powder. The specific resistance of the layers produced from these resistance alloys is up to 20 kΩ / kV. The power loss is (1-5) W / cm ² . The layers are produced by "explosion" evaporation and thermal evaporation. The disadvantage of this method is that it is not possible to apply homogeneous layers to large areas, and in the low effectiveness of the method.

The invention has for its object a simple and reliable process for the production of large heating elements to create elements that have a high transmission coefficient to have.

This task is based on the generic method by the characterizing measures of claim ge solves.

The deposition from the first mixture forms an insulating layer made of SiO ₂ on the carrier. This can replace the ceramics (Sitall, Polykor, CHS-22) normally used on metals (aluminum, stainless steel). The SiO ₂ layer ensures good adhesion of the subsequently applied resistance alloy, since, for example, when using aluminum as the support, the anodization of the metal surface or when using stainless steel as the support, a secure adhesion of the growing oxide layer to the support is ensured. In addition, an almost ideal match of the thermal expansion coefficient can be achieved by using the SiO ₂ layer. The deposition of the resistance layer in the form of amorphous silicon ensures a controllable high specific resistance of (5 to 100 kΩ / kV).

The gases (SiH ₄ : Ar), O and BF ₃ introduced into a vacuum chamber are broken down and ionized in a high-frequency discharge field until they form an ion plasma. The ionized atoms are deposited on the heated support and, depending on which gas has been introduced, form either an insulating layer made of SiO ₂ or a resistance layer in the form of amorphous silicon, depending on the gas introduced. The layer thickness is determined depending on the duration of the deposition and on the desired output of the heating element.

The same starting mixture of SiH ₄ and Ar can be used for the insulating and resistance layers. It is only necessary to add either O or BF ₃ additionally.

If the argon content in the starting mixture with SiH _{4 is} less than 96%, no reliable adhesion of the growing layers to the support can be guaranteed. On the other hand, if the argon content is more than 97%, no stoichiometric layers of insulating material and resistance material with the required resistance temperature coefficient of (3 to 8) × 10 ^-4 K ^-1 can be formed.

If the ratio of the starting mixture to O is more than 1: 2.5, the oxide layer SiO ₂ cannot be formed. A ratio of less than 1: 5 is not appropriate since a reliable insulating layer cannot be formed.

If the ratio of the starting mixture to the alloy surcharge BF _{3 is} more than 100: 5, no layer with a specific resistance of less than 10 Ω / kV can be formed. If this ratio is less than 100:10, the resistance of the heating element drops significantly.

If the temperature of the carrier is below 250 ° C, no safe The adhesion of the growing layer to the carrier is achieved. A Temperature of the carrier above 500 ° C is uneconomical.

If the pressure is less than 0.2 mmHg, the manufacturing is fair layer growth rate not optimal. At a pressure of more than 0.5 mmHg will not completely shut off mixture of layers for the separation and deposition of the layers used.

Discharge powers of less than 0.1 W / cm ^{2 are not} sufficient for the deposition of uniform layers. Discharge powers of more than 0.5 W / cm ² are not practical for economic reasons.

example

A vacuum of 0.2 to 0.5 mmHg is generated in a deposition chamber for plasma chemical deposition. Then the plate-shaped carrier is heated to a temperature of 250-500 ° C. The starting mixture and O are then introduced into the deposition chamber in a ratio of 1: (2.5 to 5) and the insulating layer is deposited on the carrier at a discharge power of 0.1 to 0.5 W / cm ² . The starting mixture and BF _{3 are} then introduced into the deposition chamber in a ratio of 100: (5 to 10) and the resistance layer is deposited on the insulating layer at a discharge power of 0.1 to 0.5 W / cm ² . The respective deposition time is selected depending on the layer growth rate. This is 40 Å / min for the deposition of SiO ₂ and 60 Å / min for the deposition of Si: F.

Contact surfaces made of aluminum are placed on the structure obtained applied.

The heating element produced has a specific resistance of (5-100) kΩ / kV and a power loss of 8 to 10 W / cm ² .

Claims (1)

A method for producing a heating element, in which a working layer is formed by deposition in a plasma chemical process on a carrier with contact surfaces, characterized in that

• - that a metal surface is used as a carrier,
• - That first an insulating layer is formed by separation from a first mixture, which consists of a starting mixture of SiH ₄ and Ar, which contains 96-97% Ar, and O, the ratio between the starting mixture and O 1: (2.5 to 5),
• - That then a resistance layer of alloyed amor phem silicon is formed by deposition from a second mixture consisting of a starting mixture of SiH ₄ and Ar, which contains 96-97% Ar, and BF ₃ , the ratio between the starting mixture and BF ₃ 100: (5 to 10), and
• - That both deposition processes are carried out at a temperature of the carrier of 250 to 500 ° C, a pressure of 0.2 to 0.5 mmHg and a specific discharge power of 0.1 to 0.5 W / cm ² .