Back side metallization technology for eutectic welding
Technical field
The invention belongs to semiconductor device and integrated circuit processing technique, is silicon device back side metallization technology, particularly back side metallization technology for eutectic welding.
The back face metalization system is a transistorized important component part.It has two aspect functions, is bigger current path on the one hand, and it is again the path of a large amount of heat transferred heat radiations that transistor collector produced on the other hand, so the back face metalization system has very big influence to transistorized Performance And Reliability.It is little that good back face metalization system requirements has an ohmic contact resistance, the low and good reliability of contact heat resistance.From good electric property will be arranged,, require usually to select for use: the 1. lower metal material of schottky barrier height in order to form good Ohmic contact with silicon substrate; 2. the low metal of contact resistance; 3. high-dopant concentration backing material; 4. the substrate in high complex centre.In order to make the transistor back metal layer have good heat-conducting and reliability, reduce the thermal stress of silicon and back face metalization interlayer as far as possible.We know that when transistor was in the discontinuous operation state, device experienced periodic high temperature and chilling process, has formed thermal cycle.Because the coefficient of linear expansion difference between silicon, scolder and the base layers of material of transistor inside, in thermal cycle, internal system has produced thermal stress, and thermal resistance increases, and makes the transistor local overheating and loses efficacy.Because the difference of the coefficient of linear expansion between the stress of metal system and silicon substrate and each metal layer material is directly proportional.The back face metalization system that is used for practical devices at present, its structure generally are made up of three parts: ohmic contact layer, diffusion impervious layer and conductive layer (but this layer can be divided into layer and antioxidation coating again).
Summary of the invention
The purpose of this invention is to provide a kind of back side metallization technology for eutectic welding, solve common metal and be the problem of rectification characteristic, so that when lead-in wire, can obtain good Ohmic contact with the silicon contact.
The object of the present invention is achieved like this: back side metallization technology for eutectic welding.It is characterized in that it may further comprise the steps:
1, front protecting: be to stick layer protecting film in the front of silicon chip;
2, thinning back side: be to desired thickness with the silicon chip thinning back side;
3, polished backside: be that the affected layer that abrasive disc produces is removed;
4, clean: the silicon chip after will polishing cleans up;
5, evaporation: under vacuum condition, make and plate one deck arsenic gold on the burnishing surface.
The present invention can also adopt the alloy technique step, promptly makes the arsenic gold carry out alloy with chip under certain temperature and nitrogen atmosphere condition.
The present invention utilizes arsenic gold and the little characteristics of silicon contact resistance, at the back side of tube core evaporation last layer arsenic gold, has solved common metal and has been the problem of rectification characteristic with the silicon contact, so that can obtain good Ohmic contact when lead-in wire.The chip that utilizes this technology to make simultaneously is suitable for the solderless automatic soldering technique of tube cores such as 9000 serial small-signals.
Embodiment
Back side metallization technology for eutectic welding is characterized in that it may further comprise the steps:
1, front protecting: be to stick layer protecting film in the front of silicon chip;
2, thinning back side: be to desired thickness with the silicon chip thinning back side;
3, polished backside: be that the affected layer that abrasive disc produces is removed;
4, clean: the silicon chip after will polishing cleans up;
5, evaporation: under vacuum condition, make and plate one deck arsenic gold on the burnishing surface.
Present embodiment can also adopt the alloy technique step, promptly makes the arsenic gold carry out alloy with silicon chip under certain temperature and nitrogen atmosphere condition.