Method and system for sculpting spacer sidewall mask

Abstract

Provided is a method of forming a spacer sidewall mask, the method comprising: providing a substrate in a process chamber, the substrate having a carbon mandrel pattern and an underlying layer, the underlying layer comprising an amorphous silicon layer above a silicon nitride layer; performing a breakthrough etch process including growth of a conformal native silicon oxide layer, creating an ALD patterned structure; performing a spacer sidewall sculpting process on the ALD patterned structure; performing an amorphous silicon main etch (ME) process on the ALD patterned structure, the ME process causing a spacer oxide open and carbon mandrel removal; and performing an amorphous silicon ME over etch (OE) process on the ALD spacer oxide pattern, the ME OE process transferring the ALD spacer oxide pattern into the amorphous silicon layer, generating a first sculpted pattern comprising a first sculpted sub-structure with a trapezoidal shape.

What is claimed is: 
     
         1 . A method of forming a spacer sidewall mask, the method comprising:
 providing a substrate in a process chamber, the substrate having a carbon mandrel pattern and an underlying layer, the underlying layer comprising an amorphous silicon layer above a silicon nitride layer;   performing a breakthrough process involving growth of a conformal native silicon oxide layer by exposing the substrate to oxygen in an atomic layer deposition (ALD) step, creating an ALD patterned structure;   performing a spacer sidewall sculpting process on the ALD patterned structure;   performing an amorphous silicon main etch (ME) process on the ALD patterned structure, the ME process causing a spacer oxide open and carbon mandrel removal, the process creating an ALD spacer oxide pattern, the ALD spacer oxide pattern comprising a first spacer sub-structure having a parallelogram shape leaning to the right and a second spacer sub-structure having a parallelogram shape leaning to the left; and   performing an amorphous silicon ME over etch (OE) process on the ALD spacer oxide pattern, the ME OE process transferring the ALD spacer oxide pattern into the amorphous silicon layer, generating a first sculpted pattern comprising a first sculpted sub-structure with a right angle trapezoidal shape and a second sculpted sub-structure with a left angle trapezoidal shape.   
     
     
         2 . The method of  claim 1  wherein the spacer sidewall sculpting process utilizes HBr/CH 3 F/Ar chemicals. 
     
     
         3 . The method of  claim 2  wherein the silicon nitrate layer comprises Si 3 N 4 . 
     
     
         4 . The method of  claim 3  wherein a glancing angle of the first sculpted pattern is changed by the spacer sculpting process such that subsequent patterning of the amorphous silicon layer only requires HBr to get etch selectivity to the Si 3 N 4  layer of the substrate. 
     
     
         5 . The method of  claim 4  wherein the spacer sidewall sculpting process is performed using a high frequency power in a range from 0 to 1,500 watts in a range from 50 to 70 MHz, a low frequency power in a range from 0 to 900 watts in a range from 11 to 15 MHz, and an active control chuck in a range from −10 to 80 degree C. 
     
     
         6 . The method of  claim 5  wherein the HBr flow rate is in a range from 0 to 583 sccm, CH 3 F flow rate is in a range from 0 to 232 sccm, and the Ar flow rate is in a range from 0 to 1,775 sccm. 
     
     
         7 . The method of  claim 6  wherein a radical distribution control (RDC) of the process chamber is in a range from 5 to 95%, a temperature of an upper electrode is in a range from 40 to 80 degrees C., a temperature of a wall of the process chamber is in a range from 40 to 80 degrees C., and a temperature of a chiller in the process chamber is in a range from −10 to 80 degrees C. 
     
     
         8 . The method of  claim 7  wherein the spacer sidewall sculpting process is performed with a pressure in a range from 7 to 900 mTorr, for a time in a range of 10 to 30 seconds. 
     
     
         9 . The method of  claim 8  wherein an optimal result of the spacer sidewall sculpting process was obtained at low pressure, low power, and high electrostatic chuck (ESC) temperature. 
     
     
         10 . The method of  claim 9  wherein a pitch imbalance metric is used to assess improvement of the sidewall sculpting process. 
     
     
         11 . The method of  claim 11  wherein the pitch imbalance is a sum of an absolute value of a first pitch less a second pitch, the second pitch less a third pitch, the third pitch less a fourth pitch, and the fourth pitch less the first pitch. 
     
     
         12 . The method of  claim 11  wherein the pitch imbalance is substantially zero. 
     
     
         13 . The method of  claim 12  wherein performing the spacer sidewall sculpting process comprises a spacer sculpting stability step and a spacer sculpting etch step. 
     
     
         14 . The method of  claim 13  wherein the OE process did not cause a recess in the silicon nitrate layer. 
     
     
         15 . The method of  claim 14  wherein the OE process did not cause an undercut in amorphous silicon portion of the sculpted pattern. 
     
     
         16 . The method of  claim 15  wherein a ratio of a top critical dimension (CD) to a bottom CD of the first sculpted pattern is in a range from 0.92 to 1.00. 
     
     
         17 . The method of  claim 16  wherein a ratio of a middle CD to the bottom CD of the first sculpted pattern is in a range from 0.90 to 1.00. 
     
     
         18 . The method of  claim 17  wherein operating variables of the spacer sidewall sculpting process include process time, pressure, high frequency energy, low frequency energy, control chuck temperature, flow rates of etch gases, percentage radical distribution control, temperature of the upper electrode, temperature of the wall in the process chamber, and temperature of the chiller in the process chamber. 
     
     
         19 . The method of  claim 18  wherein selected two or more integration operating variables in two or more steps involving the breakthrough process, spacer sidewall sculpting process, the amorphous silicon ME process, and the amorphous silicon ME over etch (OE) process are concurrently controlled in order to achieve integration process objectives. 
     
     
         20 . The method of  claim 19  the integration objectives include fabricating the profile of the structures without an undercut and without a recess in the underlying layer, minimizing pitch imbalance, improving etch uniformity, and reducing processing time. 
     
     
         21 . A system for forming a spacer sidewall mask, the system comprising:
 a process chamber configured to perform a breakthrough process involving growth of a conformal native silicon oxide layer by exposing the substrate to oxygen in an atomic layer deposition (ALD) step, creating an ALD patterned structure, perform a spacer sidewall sculpting process on the ALD patterned structure, perform an amorphous silicon main etch (ME) process on the ALD patterned structure, the ME process causing a spacer oxide open and carbon mandrel removal, the process creating an ALD spacer oxide pattern, and perform an amorphous silicon ME over etch (OE) process on the ALD spacer oxide pattern, the ME OE process transferring the ALD spacer oxide pattern into the amorphous silicon layer, generating a first sculpted pattern comprising a first sculpted sub-structure with a right angle trapezoidal shape and a second sculpted sub-structure with a left angle trapezoidal shape; and   a controller coupled to the process chamber, the controller configured to control selected two or more operating variables in order to achieve spacer sidewall sculpting objectives.