Method for forming isolation layer of semiconductor device

1. A method for forming an isolation layer of a semiconductor device, the method comprising the steps of:

i) providing a semiconductor substrate having a predetermined isolation region;

ii) sequentially forming a pad oxide layer and a pad nitride layer exposing the predetermined isolatIon region on the semiconductor substrate;

iii) forming a trench through etching the semiconductor substrate by a predetermined thickness using the pad nitride layer as a mask;

iv) forming a wall oxide layer at a side wall of the trench;

v) sequentially forming a nitride layer and an oxide layer on a trench structure including the wall oxide layer;

vi) forming an Al 2 O 3 layer on an entire surface of a resultant structure, wherein the Al 2 O 3 layer has a wet etch rate less than 0.5 Å /sec in HF solution having a ratio of 50:1 to prevent damage to the Al 2 O 3 layer during a subsequent wet etching step;

vii) planarizing the Al 2 O 3 layer through polishing the Al 3 O 3 layer, and

viii) removing the pad nitride layer and the pad oxide layer by one or more wet etching processes without damaging the Al 2 O 3 layer.

2. The method as claimed in claim 1 , wherein the Al 2 O 3 layer is deposited under a temperature of about 300˜500° C.

3. The method as claimed in claim 1 , wherein the Al 2 O 3 layer is deposited under a pressure of about 0.1˜5 torr.

4. The method as claimed in claim 1 , wherein a deposition process for the Al 2 O 3 layer is carried out in single type equipment or batch type equipment.

5. The method as claimed in claim 1 , wherein the Al 2 O 3 layer is formed by using one of trimethyl-aluminum and triethyl-aluminum as a source.

6. The method as claimed in claim 1 , wherein the pad oxide layer is removed by dipping the substrate having the layers formed thereon in a fluoride acid solution.

7. The. method as claimed in claim 1 , wherein the Al 2 O 3 layer is formed through depositing triethyl-aluminum as a source gas at a temperature of 300 to 500 degree Celsius at a pressure of 0.1 to 5 torr.

8. The method as claimed in claim 1 , wherein the Al 2 O 3 layer is formed through depositing trimethyl-aluminum as a source gas at a temperature of 300 to 500 degree Celsius at a pressure of 0.1 to 5 torr.

9. The method as claimed in claim 7 further comprising the step of forming a gate oxide layer on the substrate and the isolation layer.

10. The method as claimed in claim 8 further comprising the step of forming a polycrystalline silicon layer on the gate oxide layer.