Flash memory device and method for manufacturing the same
View Patent ↗A flash memory device, and a manufacturing method thereof, having advantages of protecting sidewalls of a floating gate and a control gate and preventing a recess of an active area of a source region are provided. The method includes forming a tunneling oxide layer on an active region of a semiconductor substrate, forming a floating gate, a gate insulation layer, and a control gate on the tunneling oxide layer, forming insulation sidewall spacers on sides of the floating gate and the control gate, and removing at least portions of the tunneling oxide layer and the device isolation layer so as to expose the active region.
1. A method for manufacturing a flash memory device, comprising:
forming a tunneling oxide layer in an active region of a semiconductor substrate further including a device isolation region having an isolation layer therein;
forming a floating gate, a gate insulation layer, and a control gate on the tunneling oxide layer;
forming insulation sidewall spacers on sides of the floating gate and the control gate, wherein a first insulation sidewall spacer is over the active region and a second insulation sidewall spacer is over the device isolation region in a cross-section of the floating gate, the gate insulation layer, the control gate, and the insulation sidewall spacers;
forming a photoresist pattern over the first insulation sidewall spacer and part of the floating gate, the gate insulation layer, and the control gate exposing the second insulation sidewall spacer and the device isolation layer;
exposing a source region by selectively removing portions of the device isolation layer using the photoresist pattern and the second insulation sidewall spacer as an etching mask, wherein a portion of the device isolation layer remains below the second insulation sidewall in the device isolation region; and
implanting impurity ions into the source region.
2. The method of claim 1 , wherein the insulation sidewall spacers comprise a single layer or a combination of layers.
3. The method of claim 2 , wherein the insulation sidewall spacers comprise an oxide layer and a silicon nitride layer.
4. The method of claim 2 , wherein forming the insulation sidewall spacers comprise sequentially forming an oxide layer and a silicon nitride layer on an entire surface of the semiconductor substrate, including the floating gate and the control gate and anisotropically etching the oxide layer and the silicon nitride layer.
5. The method of claim 3 , wherein each of the oxide layer and the silicon nitride layer has a thickness of 180-220Å.
6. The method of claim 1 , wherein forming the photoresist pattern comprises coating a photoresist on the semiconductor substrate, including the insulation sidewall spacers, and patterning the photoresist.
7. The method of claim 6 , wherein the photoresist pattern is formed before portions of the tunneling oxide layer and the device isolation layer are removed.
8. The method of claim 6 , wherein, the tunneling oxide layer and the device isolation layer are selectively removed by a plasma etching process using the patterned photoresist as an etching mask.
9. The method of claim 1 , wherein implanting the impurity ions into the source region uses the photoresist pattern as a mask.
10. The method of claim 1 , further comprising forming the isolation layer in the device isolation region of the semiconductor substrate.
11. The method of claim 1 , wherein the tunneling oxide layer has a greater width than corresponding widths of the floating gate and the control gate.