Operating Instructions for the STS ICP Metal Etcher

Transcription

1 Operating Instructions for the STS ICP Metal Etcher Tool Owner: Pat Watson, x , cell: Backup: Joe Palmer, x , cell: Introduction The STS is a state of the art inductively coupled plasma etcher (Figure 1). The tool has been configured to enable users to etch Al, Cr, Ti, W, and Nb with a photoresist mask. The tool is plumbed with SF 6, CHF 3, Ar, O 2, Cl 2 and BCl 3 gases. It possesses a He mechanically clamped backside cooled chuck that is temperature controlled with a chilled water circulator. Specimens are loaded into the process chamber by a robot arm through a load lock to minimize contaminants entering the process chamber and to protect users from hazardous etch by-products. SEMI standard 100 mm diameter wafers can be processed in the system. Samples that are smaller than 100 mm in diameter must be mounted on a carrier wafer. There are 2 RF power sources to control the properties of the plasma. The first is a 1000W supply inductively coupled to the gas in the process chamber. It generates a high density of radicals and ions with only a small potential between the plasma and the wafer surface. An additional 500W source induces a potential between the chuck and the plasma just like a traditional RIE system. The advantage of this combination is that the plasma density and the substrate bias can be independently controlled. The system is controlled by a programmable controller mounted on the wall behind the tool. The user interface is a touchscreen mounted on the front of the electronics rack.

2 Electronics Rack Touch Screen Emergency Off Buttons Load Lock Chamber Main Unit Figure 1. The PRISM MNFL STS ICP etcher. The loadlock is in the foreground. The human interface touchscreen is the black screen behind it. Emergency Off buttons are marked. Overview of the System The etcher consists of the: main unit, which houses the turbopump and load lock and process chambers (Fig. 1); Electronics rack; Programmable controller, located on the wall behind the main unit; circulator, process dry pump and load lock dry pump, located behind the main unit in the service chase, J417;

3 Figure 2. The STS computer interface touch screen, displaying the Operator screen. There are 3 screen displays that are regularly used: The Operator screen, where the tool is controlled (Fig 2). The Main screen, where more information is shown while a recipe is running (Fig. 3). The Recipe screen, where the users may select and edit recipes (Fig. 4). Please see the staff before creating or modifying any recipes.

4 Figure 3. The Main screen. The status of the gas flows, RF generators, and other system components may be viewed here. Figure 4. The Recipe screen. Press the gray area to the left of a recipe to select it. Press Load to choose the selected recipe.

5 Start up and Login 1) To operate the etcher, the user must first log in to the tool through the MNFL reservation system. The load lock will not vent unless the user is logged in. 2) Sign in the logbook with user ID and start time. 3) The system should normally be left with the load lock pumped down. To bring the load lock to atmosphere: a. Select the Operator screen if it is not currently displayed on the touchscreen. b. Press Vent Loadlock and wait about 1 minute for the load lock to reach atmospheric pressure. Mounting and Loading a Sample Since the chuck must be protected at all times from the plasma, specimens that are not 100 mm diameter wafers must be bonded to a carrier wafer. 1) If a whole wafer is used, skip to step 3. A small sample (less than a 100mm wafer) must be mounted to a special carrier wafer. A 100 mm Si wafer covered with Kapton tape is typically used as the carrier, but an SiO2 coated wafer or a uncoated Si wafer may also be used. 2) Using a small cleanroom swab, coat the carrier (or the back of the specimen) with a thin layer of thermally conductive silicone grease. Make sure that as little grease is exposed as possible. Press the sample gently on the carrier to ensure good contact. Alternatively, thin strips of Kapton tape may be used to attach the sample to the carrier; however, thermal contact between the sample and the carrier wafer will be poor, possibly leading to uncontrolled etch rate and resist loss. 3) Check the back of the wafer to ensure it is free of any contaminants that could compromise the seal between the carrier and the He backside cooled chuck. 4) Open the load lock chamber door and place the carrier or wafer on the carrousel. Make sure it is properly centered. Up to two wafers may be loaded at a time. 5) Check to make sure that there are no obstructions or particles on the door o-ring and complementary surface, then lower the load lock door.

6 6) Press Pump and Map on the Operator screen to start the load lock pump down process. Etching The user will generally use established etch recipes. Please see the staff before modifying and recipe. Please notify the staff of any major new recipe changes before trying them to prevent hazardous or damaging situations. For instance, long runs using SF6 without some O2 can damage the turbopump. 1) From the Operator screen, press the Select Recipe button on the lower right. 2) Use the arrow keys on the lower right of the Recipe screen to view any recipes off-screen. Select a recipe by pressing on the entry on the left side of the recipe name. 3) Press the Load button on the lower right. 4) Return to the Operator screen by pressing the Close button on the lower left. 5) From the Operator screen, press the run recipe button on the upper left. 6) The user may switch between the operator and main screens throughout the process to view progress. The Operator screen will display Halt and Abort buttons to either halt the recipe at the current step, or cancel the run. Finishing Up 1) When the recipe is complete, the Operator screen will show text identifying that near the center of the screen. 2) From the Operator screen, select Unload 3) When this action is complete, press Vent Loadlock 4) When the load lock is at atmospheric pressure, open the door, remove the wafer(s). 5) Close the loadlock door and press Pump/Map. 6) Fill in the logbook with end time, recipe, type of chemistry, and any comments. 7) Log off the tool from the reservation system.

7 Appendix A: Chlorine Chemistry Etching The etch chamber is normally kept in a state ready for F chemistry etching. To use Cl2 and BCl3, it is prudent to prepare the chamber by loading a blank wafer and running the recipe Cl2 Prep. The preparation takes about 60 minutes. When complete, run the Cl2 recipe of interest with the same blank wafer. The chamber should now be ready. When etching is complete, load a blank wafer and pump down the load lock. From the Operator screen, press Start Purge to clear the Cl2 and BCl3 mass flow controllers. When this process is completed, load the blank wafer, then select and run the recipe F Prep. This recipe should take about 60 minutes to complete. Let other users know in that the chamber has been returned to the F chemistry state by noting it in the log book. Appendix B: STS Metal Etcher Short Operation Instructions 1) Log in with reservation system, write entry into log book, 2) Press vent loadlock on operator screen. 3) Load sample into loadlock and press pump/map 4) Press Load Wx to load appropriate sample into chamber 5) Press Select Recipe to access recipe page. Select recipe, load it and exit page. 6) Press Run from operator page 7) When etch is complete, press Unload sample 8) Vent load lock and remove sample, then press Pump/Map to evacuate load lock 9) Fill out rest of logbook and close reservation. Revised gpw 04/23/2012