Improvement method of igbt negative resistance problem

Abstract

The invention discloses a method for improving the negative resistance problem of an IGBT (Insulated Gate Bipolar Transistor). The method comprises the following steps: selecting a substrate material and performing back thinning; filling the back surface with N-type heavily doped ions for the first time to form a second N-type field stop layer; performing thermal annealing; finishing a front graphic process of the IGBT; performing wet corrosion on the back surface of the substrate; filling the back surface with the N-type heavily doped ions for the second time to form a second N-type field stop layer; filling the back surface with P-type heavily doped ions to form a P-type filling layer; performing laser annealing activation; forming a back metal layer. According to the method, the relatively thick back field stop layer can be formed, the negative resistance reaction of the IGBT can be eliminated, the product reliability can be improved, the method is compatible with an existing semiconductor process, and the process cost is low.

Description

technical field [0001] The invention relates to a method for manufacturing a semiconductor integrated circuit, in particular to a method for improving the problem of IGBT negative resistance. Background technique [0002] Insulated Gate Bipolar Transistor (IGBT, Insulated Gate Bipolar Transistor) is a composite fully-controlled voltage-driven power semiconductor device composed of a bipolar transistor (BJT) and an insulated gate field effect transistor (MOSFET). The advantages of high input impedance and low conduction voltage drop of power transistor (GTR), that is, bipolar junction transistor with high voltage and high current resistance. It is very suitable for the conversion system with a DC voltage of 600V and above, such as AC motors, frequency converters, switching power supplies, lighting circuits, traction drives and other fields. [0003] For the high-voltage IGBT process, the ability to form a thicker N+ buffer layer on the back is of great significance for the p...

AI Technical Summary

Problems solved by technology

[0011] The disadvantage of the existing method is that during the front patterning process after the N-type field stop layer 110 is formed, impurities are easily introduced on the back side, resulting in uneven P-type implantation on the back side, that is, the doping of the P-type implanted layer 111 will be uneven. This will cause the product to have the problem of Vcesat negative resistance, Vcesat is the collector and emitter saturation voltage

figure 2 Yes figure 1 The Vcesat curve 201 of the IGBT shown; the abscissa is Vcesat, the ordinate is Ic, and Ic is the collector current; it can be seen that there is a negative resistance phenomenon in which the current increases and the voltage decreases in the area corresponding to the dotted line 202 of the curve 201, The reason is that when the doping of the P-type injection layer 111 will be uneven, after the IGBT is turned on, when Vce, that is, the voltage of the collector and the emitter is small, the hole efficiency of the P-type injection layer 111 injected into the drift region at each position will decrease. Inhomogeneous, with the increase of Vce, when the P-type injection layer 111 at each position starts to inject holes and turn on, the conductance of the drift region will be modulated, so that the on-resistance of the drift region will decrease, and the collector current will increase. output negative resistance effect

[0012] The appearance of the negative resistance effect will eventually lead to the shutdown failure of the dynamic test, such as image 3 shown, is figure 1 The dynamic curve of the shown IGBT; the curve 203 is the gate voltage, that is, the Vg curve, the curve 204 is the Ic curve, and the curve 205 is the Vce curve, and the area shown by the dotted line 206 corresponds to the process of turning off, and it can be seen that Vg is reduced to a low voltage After leveling off, Ic does not decrease and Vce does not rise, so the shutdown fails

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