CS201379B1 - Method of amplifiing the thin conductive layers of hybrid integrated circuits - Google Patents

Description

CZECHOSLOVAK SOCIALIST REPUBLIC DESCRIPTION 201379 (11) (Bl) (19) TO COPYRIGHT CERTIFICATE (51) Int. Cl.3 H 05 K 3/24 (22) Registered 30 11 78 (21) (PV 7874-78) (40) Published 29 02 80 OFFICE AND DISCOVERY OFFICE (45) Published 15 06 82 (75)

Author of vylálzu SMlD LUDĚK ing and BADAL JAN ing., CSc., PRAGUE (54) Method of strengthening thin conductive layers in hybrid integrated circuits

BACKGROUND OF THE INVENTION The present invention relates to a method for strengthening thin conductive layers in hybrid integrated circuits by a galvanic method.

In order to increase the electrical conductivity of some conductive paths in thin layers of hybrid integrated circuits, it is preferred to use these thin-film layers in a galvanic manner. Appropriate motifs are obtained by applying galvanic layers to the windows in a preformed photoresist mask. However, this method creates grape-like clusters, mainly at the edges of the centrefold patterns. These increases deteriorate the visual acuity and the accuracy of the conductors so produced. The increases also cause increased stress in the applied galvanic layer and generally reduce the surface quality of the deposited layers. This results in a deterioration of the adhesion of these layers to the backing and peeling away from the backing layers, in particular due to the long-term exposure to temperature and temperature changes.

These disadvantages are eliminated by the method of amplifying thin conductive layers in hybrid integrated circuits by galvanic method into the photoresist mask openings, the principle of which according to the invention is to connect the source of the thin current conductive layers in the plating bath with a source of galvanic current supplied by alternating current pulses, wherein the ratio of the duration of the negative and positive pulses varies depending on the type of metallization bath used, from 4: 1 to 25: 1 with a repetition rate of 0.1 to 1 Hz and a mean current density given by the galvanic bath used. The advantage of this method of cross-linking thin-film layers in hybrid integrated circuits is the limited formation of undesirable racemates and better adhesion to other layers or substrates. The surface of the deposited layers is smoother and more homogeneous, as well as the accuracy of the motifs produced.

The invention will now be explained in more detail by the following examples, wherein in the first example the galvanically deposited layer of copper on the anchor layer of the vacuum-welded nickel, and in the second example, the layer of gold. EXAMPLE 1 In the formation of golden air bridges when crossing conductive paths in hybrid integrated circuits, the layers are galvanically applied to the anchoring layer by vacuum vapor deposition into the resist mask apertures. It is desirable that the copper interlayer has a homogeneous surface, a defined thickness over the entire surface of the substrate, good adhesion, and good edge sharpness without grape-like growths. 20 1 37 9

Claims (1)

2 Prepare a galvanic bath and make up: 120 g cuprous cyanide, 175 g potassium cyanide, 60 g potassium carbonate and make up to 1 liter with water. The bath is heated to a working temperature of 55 ° C. The mean current density of the copper-anode and the thin-walled substrate was 4 A / dm 2. A bath with an anchored layer of steamed nickel of 50 to 100 nm thickness is immersed in the bath. A source of galvanic current with a current pulse of 1: 10 and a repetition of the frequency of 1 Hz is connected. It is plated for 50 minutes to remove a copper layer of about 35 μτη. EXAMPLE 2 To increase the conductivity of thin layers of steam-baked titanium-palladium-gold sandwich, it is necessary to galvanically apply these motifs. a substrate with thin conductive layers immersed in the bath is connected to a galvanic source to apply a layer of gold to the holes of the resist mask. The surface of the deposited gold layer needs to be smooth so that the shapes of the edges produced by the motifs are accurate and the dimensional tolerance of 5 μτη. A gold bath containing 10 g of gold-potassium cyanide, 60 g of potassium phosphate, 60 g of phosphoric acid and 60 g of water per liter of bath is prepared. The bath is heated to a working temperature of 50 ° C. The current density is 2 A / dm 2. Plates with thin conductive motifs are immersed in a plating bath and a pulsed source of galvanic current is coupled, with a negative and positive current duration ratio of 15: 1 with a repetition rate of 0.5 Hz. Plating for 20 minutes. The deposited gold layer has a thickness of about 10 μτη and meets the above requirements. the current which supplies alternating current pulses, the ratio of the duration of the negative to positive pulses varies depending on the 4: 1 to 25: 1 plating bath used with a repetition rate of 0.1 to 1 Hz and the mean current density of the used galvanic bath.