2. Non-parameterized Micromechanical Element Library

The non parameterized element library is a resource of working MEMS devices and structures. The intent is to provide the novice MEMS designer easy access to MEMS designs without having to extract information from references and reinvent the wheel. This chapter explains how to use the non parameterized cell library. Section 2.1 describes how to browse and retrieve cells from the library database. The browser allows the user to peruse a brief description of cells and select desired ones. Section 2.2 details how users can submit their own designs for addition to the library once they have been fabricated and tested. While this may be unimportant to the novice user, we hope that experienced MEMS designers will contribute generously to the library as it is paramount to the success of the library. Section 2.3 and Section 2.4 describe some of the cells currently available in the library. The programs used are written in the Practical Extraction and Report Language, perl. Thus, perl must be available on the machine on which the library programs are installed.


Table of Contents


2.1 Cell Retrieval

A simple perl script, DBRetrieve, is available for cell retrieval. It can be accessed electronically via ftp using the following steps:

ftp mcnc.org
Name: anonymous
Password: ident
cd pub/MEMS/NPCaMEL
get DBRetrieve
quit

This directory also includes a file named README.DBRead that provides further information about the installation procedure. To run the program type DBRetrieve and the rest should be self-explanatory. DBRetrieve is written in perl and utilizes a shell forms program called sf. The program will query the user for the cells desired then send mail to MCNC's cell library manager, which then extracts the design or designs and sends the layouts to the user. Designs are emailed to the user in either the CIF (CalTech Intermediate Form) or GDS II mask format.

DBRetrieve prompts the user for the mask format desired and browsing category. Designs may be browsed according to the process technology or the device design category. It is anticipated that the majority of designs will be for the MCNC MUMPs processes; however, the software is designed to include other processes as well. The design categories are currently test devices, motors, out-of-plane structures, linear actuators, and a miscellaneous category. Once these queries have been answered a sorted list will appear as shown in Figure 1.

1 (LIGA) [TEST] spiral, Allen Cowen
2 (UCB2poly) [TEST] 14v_220mA_fuse, G.K. Fedder/J.C. Chang/R.T. Howe
9 (MUMPS4) [TEST] Guckel_rings, Ramaswamy Mahadevan
3 (MUMPS3) [MOTORS] wobble_6_stator, Ramaswamy Mahadevan
4 (MUMPS3) [MOTORS] wobble_12_stator, Ramaswamy Mahadevan
6 (MUMPS3) [MOTORS] 12_stator_motor, Allen Cowen
8 (MUMPS3) [MOTORS] 12_stator_wobble_motor, Vijay Dhuler

If you would like to see more information on a cell, please enter
the number listed before the cell name. If no more information is
desired, just type `.'.

Figure 1. Window from DBRetrieve.

The user may then choose a cell and get further information about the device. An example of the information that will be available is shown in Figure 2. Finally, the user will be prompted for the desired designs, an appropriate email message will be sent automatically to MCNC, and the cell will be returned shortly to the user via email.

NAME: wobble_6_stator
Cell NAME:       wobble_6_stator, (MUMPS3)
SIZE:	Cell Width: 600 um
Cell Height: 600 um
DESCRIPTION:
6 stator wobble motor with a 50 micron radius. The motor was
designed with the parameterized library. The dimples may need
to be moved closer to the center.
SUBMISSION DATE: Wed Jun 1 9:17:00 1994
AUTHOR: Ramaswamy Mahadevan MCNC

Figure 2. Example of a manual entry for the 6 stator wobble motor.

2.2 Cell Entry

DBSubmit is a program used to automate the submission of MEMS cells to the MCNC - ARPA cell library. It is written in perl and is designed to be easy to use. The first time the program is run it prompts the user for information about the designer, fabrication process, and design and sets up a template file. This template file can then be edited and used for subsequent submissions. The program, DBSubmit, can be retrieved in the same manner as described in Section 2.1. It is also located in pub/MEMS/NPCaMELand the file README.DBSubmit provides installation information.

In order to use this program, the $DB_PROC variable in the script must be set correctly. It should be set to the directory containing the database of process information. An updated set of this information can be obtained via anonymous ftp as explained below. If the directory variable is not set correctly, a directory named./DB_PROC is created automatically. New processes can easily be added by the user within the framework of the program. To set up the process database directory, first create a directory $PATH/dir for the data. Then obtain the process information via ftp using:

cd $PATH/dir
ftp -i mcnc.org
Name: anonymous
Password: ident
cd pub/MEMS/NPCaMEL/DB_PROC
mget *
quit
cd ..

Before running the program DBSubmit, create a CIF or GDS II file with the mask layout of the design to be submitted. Do not forget to include definitions of any leaf cells that are called as instances within the main cell. DBSubmit is a forms based script that prompts the user for a number of items including name, address, cell descriptions, etc. Once the forms are filled out, the software will send the information to MCNC where the cell is entered in the library database and made available to domestic users. A file named cell_name.sbmt is saved in the user's directory and can be used for subsequent submissions by modifying the file and typing DBSubmit cell_name.sbmt. An example of a submission file is shown below with comments added after the pound (#) symbol.

# This is a completed template for the CaMEL DBSubmit program. To use
# simply copy it to another file and strip off all the comments which
# are anything after the # in a line.
#
*** CaMEL submission file *** 	# header
Replacement file: n 		# Is this replacing another design
Designer's name: Allen Cowen	# author of the design
Designer's affiliation: MCNC 	# author's affiliation
Submitter's name: Allen Cowen 	# submitter of design
Submitter's phone number: (919) 248-1424
Submitter's email address: cowen@mcnc.org
Submitter's address: 	# need a blank line after
MCNC 			# the address
PO Box 12889
3021 Cornwallis Road
Research Triangle Park, NC 27709-2889

Design name: octagon 	# name to describe design
Cell Width: 126.5 um
Cell Height: 126.5 um
Design description: 	# description should be
This is an octagon.	# followed by a blank line

Format of data: 1 	# [0-2] 0=CIF 1=GDSII 2=Tanner
Method of transfer: 2 	# [1-3] 1=ftp from your site
			# 2=ftp to our site
			# 3=email
Internet path: mcnc.org	# if method of transfer=1
File path: oct.gds 	# if method of transfer=1
File name: oct.gds 	# if method of transfer=2
File name: oct.gds 	# if method of transfer=3
Process Technology: LIGA 		# Name of technology used
Process Facility: MCNC 	# Name of processing facility
Device Tested: y 	# Was the device tested?
Device Performance: 	# If the device was tested
This device did not do very well. 	# give an explanation of
It went this fast; but it broke down very   # results followed by a blank
quickly.                                    # line. If not, take out Device
                                            # Performance line down to
                                            # blank line.
Device yield determined: y
Device yield: 			# Similar to device performance.
This device's yield was 95%. 	# Take out if not determined.

# The next line is the stream level for the only mask in the layout.
electroplated nickel STREAM layer: 49
end_of_file

2.3 Cell Index

This section lists the cells currently in the database. It will be augmented as contributions are received.

TABLE 1. Index of cells currently in the library.

----------------------------------------------------------------------------
Refnum	name			process categ.	author
----------------------------------------------------------------------------
1	spiral			LIGA	TEST	Allen Cowen
2	14v 220 mA fuse		UCB2polyTEST	GK Fedder, JC Chang RT Howe
3	wobble 6 stator		MUMPS3	MOTORS	Ramaswamy Mahadevan
4	wobble 12 stator	MUMPS3	MOTORS	Ramaswamy Mahadevan
5	simple hinge		MUMPS3	OUTPLANE	Kris Pister
6	12 stator motor		MUMPS3	MOTORS	Allen Cowen
7	linear actuator		MUMPS3	LINACT	Ramaswamy Mahadevan
8 	12 stator wobble motor	MUMPS3	MOTORS	Vijayakumar Dhuler
9	Guckel Rings		MUMPS4	TEST	Ramaswamy Mahadevan
10	pad			MUMPS4	OTHER	Ramaswamy Mahadevan
11	resonant comb drive 	MUMPS4	LINACT	Allen Cowen
----------------------------------------------------------------------------

Any of these cells may be obtained by sending mail to camel@mcnc.org with CaMEL retrieval file as the subject and the first line of the message body specifying the format desired [CIF/GDS] and subsequent lines the cell number corresponding to the designs listed above. The return email address is automatically extracted from the header. For instance, the following would return the 12 stator motor,

Please send the following designs in CIF format.
6

2.4 Cell Descriptions

The following subsections show sample manual entries for the various cells in the library.

2.4.1 Spiral

NAME: spiral
Cell NAME: spiral, (LIGA)
SIZE: 	Cell Width: 107.5 um 	Cell Height: 102.5
DESCRIPTION: This is a spiral spring with a 5 um beam width and 5 um
             spacing between turns.
SUBMISSION DATE: Mon Mar 7 16:55:26 1994
AUTHOR: Allen Cowen MCNC

2.4.2 Fuse

NAME: 14v_220mA_fuse
Cell NAME: 14v_220mA_fuse, (UCB2poly)
SIZE: 	Cell Width: unknown 	Cell Height: unknown
DESCRIPTION: This is a fuse designed to blow at ~ 14 v or ~ 220 mA pulse.
             It has 6um allowable displacement in x and no constraint in y.
SUBMISSION DATE: Tue Mar 8 13:51:54 1994
AUTHOR: G.K. Fedder, J.C. Chang, R.T. Howe Berkeley Sensors and Actuators
        Center

2.4.3 Wobble Motor with Six Stator Electrodes

NAME: wobble_6_stator
Cell NAME: wobble_6_stator, (MUMPS3)
SIZE: 	Cell Width: 250 um 	Cell Height: 600 um
DESCRIPTION: 6 stator wobble motor with a 50 micron radius. The motor was
             designed with the parameterized library. The dimples on the
             rotor could be moved closer to the center.
SUBMISSION DATE: Wed Jun 1 9:17:00 1994
AUTHOR: Ramaswamy Mahadevan MCNC

2.4.4 Wobble Motor with Twelve Stator Electrodes

NAME: wobble_12_stator
Cell NAME: wobble_12_stator, (MUMPS3)
SIZE: 	Cell Width: 250 um 	Cell Height: 600 um
DESCRIPTION: 12 stator wobble motor with a 50 micron radius. The motor was
             designed with the parameterized library. The dimples on the
             rotor could be moved closer to the center.
SUBMISSION DATE: Wed Jun 1 15:45:07 1994
AUTHOR: Ramaswamy Mahadevan MCNC

2.4.5 Simple Hinge

NAME: simple_hinge
Cell NAME: simple_hinge, (MUMPS3)
SIZE: 	Cell Width: 30 	Cell Height: 33
DESCRIPTION: This is the standard hinge that we use to rotate structures
             out of the plane of fabrication. Hinge pin is 2um wide poly1.

Yield: Device yield is probably better than 99%. Structure yield can be
       substantially lower (e.g. 0%) depending upon the complexity of the
       structure. In some cases it _is_ the hinges that actually fail,
       but this is typically due to a bad structure design.

Device Performance: In general the hinge performance in MUMPS3 is
       acceptable, with some caveats. Due to undercut of poly1, a wider
       hinge pin may be desirable (3 um drawn seems to work ok). The poly 1
       thickness is comparable to the ox1+ox2 thicknesses, leading to
       potential problems with the hinge pin sliding under the edges of
       the staple and breaking during assembly. If a bit of caution is
       used during assembly, these problems can be avoided.

SUBMISSION DATE: Thu Jun 2 21:46:35 1994
AUTHOR: Kris Pister UCLA

2.4.6 Rotary Side Drive Motor with Twelve Stator Electrodes

NAME: 12_stator_motor
Cell NAME: 12_stator_motor, (MUMPS3)
SIZE: 	Cell Width: 710 um 	Cell Height: 710 um
DESCRIPTION: This is a 12/8 stator/rotor salient pole motor with a 50
             micron rotor radius.
Device Performance: They worked successfully with excitation under 100 volts.
SUBMISSION DATE: Wed Jun 8 10:13:57 1994
AUTHOR: Allen Cowen MCNC

2.4.7 Linear Comb Drive

NAME: linear_comb
Cell NAME: linear_comb, (MUMPS3)
SIZE: 	Cell Width: 144 	Cell Height: 118
DESCRIPTION: This is a linear comb drive with 8 fingers on the moveable
             part. It has a 4 micron finger width, a 3 micron gap, and
             stator-rotor finger overlap of 30 microns. It was designed
             with the parameterized cell library.
SUBMISSION DATE: Mon Jun 13 16:59:29 1994
AUTHOR: Ramaswamy Mahadevan MCNC

2.4.8 Wobble Motor with Twelve Stator Electrodes

NAME: 12_stator_wobble_motor
Cell NAME: 12_stator_wobble_motor, (MUMPS3)
SIZE: 	Cell Width: 710 um 	Cell Height: 710 um
DESCRIPTION: This is a 12 stator wobble motor with a 50 micron rotor
             radius. The bearing has a 10 micron radius.
Device Performance: They worked successfully with excitation under 100
                    volts.
SUBMISSION DATE: Mon Jun 13 17:04:36 1994
AUTHOR: Vijay Dhuler MCNC

2.4.9 Guckel Rings

NAME: Guckel_rings
Cell NAME: Guckel_rings, (MUMPS4)
SIZE: 	Cell Width: unknown 	Cell Height: unknown
DESCRIPTION: This is a set of Guckel rings used to measure stress in
             the MUMPS wafers. They were generated using the parameterized
             element library. They have a 20 micron ring width and 10 micron
             beam width. The smallest ring has a diameter of 98 microns and
             the largest has a diameter of 718 microns.
SUBMISSION DATE: Tue Jun 14 10:48:46 1994
AUTHOR: Ramaswamy Mahadevan MCNC

2.4.10 Pad

NAME: pad
Cell NAME: pad, (MUMPS4)
SIZE: 	Cell Width: 118 	Cell Height: 118
DESCRIPTION: This is a pad to connect from the top metal level to both
             levels of structural poly and the lowest poly0 layer.
SUBMISSION DATE: Mon Jun 27 9:49:24 1994
AUTHOR: Ramaswamy Mahadevan MCNC

2.4.11 Linear Comb Resonator

NAME: resonant_comb_drive
Cell NAME: resonant_comb_drive, (MUMPS4)
SIZE: 	Cell Width: 330 	Cell Height: 316
DESCRIPTION: This is a comb drive resonator with a folded beam suspension.
             There are two comb drives with 15 fingers on the rotor. The
             finger length is 40 um, width 3 um, air gap 3 um, and overlap
             is 20 um. The folded beam suspension has beams 150 microns
             long and 2 microns wide.
SUBMISSION DATE: Wed Jul 13 9:34:46 1994
AUTHOR: Allen Cowen MCNC