SCR electrostatic discharge protection for integrated circuits

A protection device for an integrated circuit comprising:

• a substrate of a semiconductor material of one conductivity type having a surface;
• a well region of a conductivity type opposite that of the substrate in the substrate at said surface, said well region having a junction with the substrate;
• a first region of the one conductivity type in the well region at the surface, said first region having a pair of opposed sides;
• a second region of the opposite conductivity type in the substrate at the surface and spaced from the well region;
• a third region of the opposite conductivity type in the substrate at the surface, the third region having a pair of opposed sides with one side contacting the first region;
• a fourth region of the opposite conductivity type in the substrate at the surface and electrically connected to the well region, said fourth region having a pair of opposed sides;
• and
• a fifth region in the substrate at the surface and contacting the fourth region;
• the first region, well region, substrate and second region forming an SCR, the first region and third region forming a zener diode in series with the SCR, and the fourth region and fifth region forming a zener diode in parallel with the SCR.

A structure comprising:

• an integrated circuit having first and second terminals;
• a protection circuit having first and second electrodes, each electrode being connected to one of said terminals;
• the protection circuit comprising:
• a silicon controlled rectifier (SCR) having a clamping voltage;
• an electric triggering means for triggering the SCR to its on-state electrically connected in parallel with said SCR;
• and
• a first zener diode electrically connected in series with the SCR to control the clamping voltage of the SCR.