Using IC-CAP with HP 4062UX and Prober/Matrix Drivers

This section describes how to use HP 4062UX instruments and the prober/matrix from IC-CAP for wafer device characterization. Also included in this section is information about writing a macro, controlling the prober, and conditions of which to be aware.

While the HP 4062UX is an ideal instrument for performing device characterization with IC-CAP, it is necessary to understand IC-CAP, probers, matrices, and the instruments under control. IC-CAP is an independent program from HP 4062UX TIS or VFP. It is not necessary, and can be damaging, to run the START program before running IC-CAP. To run IC-CAP after running the START program, the HP/Agilent 4142B must first be reset manually.

After running the HP 4062UX START program, the HP/Agilent 4142B is put into its binary mode. Because IC-CAP assumes that all the instruments to which IC-CAP is connected accept ASCII commands, IC-CAP cannot recognize the 4142B. Reset the 4142B by sending a Device Clear or by turning the instrument off and on again. To send a Device Clear to the 4142B, use the IC-CAP GPIB analyzer (Tools menu):

1	In the Instrument Setup Window, choose Tools > Send Byte.

2	Enter the default value 20 and choose OK.

Writing a Macro

While instruments like the HP/Agilent 4142B and the HP 4280A are controlled by IC-CAP with Setup tables, both the wafer prober and the switching matrix must be controlled through macro programs using the Pxxxxx() and Connect() functions. The Setup table defines which measurement unit is going to force certain output. Users must perform the following actions:

1	Determine which matrix port needs to be connected to which matrix pin.

2	Write several Connect() functions in a macro program that invokes this Setup measurement with a iccap_func() statement.

The example shown in the following figure involves 4 SMUs of an HP/Agilent 4142B and measures Id_vs_Vg characteristics of an NMOS device on a wafer.

Figure 4 Sample Wafer Test Program

! Prober and Matrix Test Program x = swm_init(19, 22, "HP4085B", "/dev/ice_raw_hpib") x = connect(fnport(1), 15) ! SMU1 - Drain x = connect(fnport(2), 7) ! SMU2 - Gate x = connect(fnport(3), 8) ! SMU3 - Source x = connect(fnport(4), 6) ! SMU4 - Bulk x = prober_init(2, 0, "EG2001X", "/dev/ice_raw_hpib") ! linput "Load Cassette and Press OK", msg status = prober_status() ! wait until Remote while (not status[0])    status = prober_status() endwhile iccap_func("/nmos2/large/idvg", "Display Plots") ! x = pscale(8200, 8200) ! test chip die size x = phome() ! goes to the first die while (x == 0)    x = porig(0, 0) ! first die coordinates    i = 0    while (i < 5) ! test diagonal 5 dies       x = pdown()       x = pmove(i, i)       x = pup()       print       print "Die Position X=";i;" Y=";i;       iccap_func("/nmos2/large/idvg", "Measure")       iccap_func("/nmos2/large/idvg", "Extract")       i = i + 1    endwhile    x = phome() ! load next wafer endwhile if (x == 1) then linput "Cassette Empty. Test End.", msg x = connect(0, 0) ! disconnect matrix pins

Prober Control

Prober control is determined by the number of test modules, which is either single or multiple per die.

With the Pxxxx functions, it is assumed that there is a single test module on each die and every test module exists in the same place relative to its die origin. In this case, it is easy to control the wafer prober.

The example in Figure 4 shows the size of each die to be 8200 m × 8200 m. The operator first indicates to the prober where the test module is on the first die. Once the prober is set to find this test module, Pmove() or Pimove() can step to any die and probe the same test module.

When there are multiple modules per die, every module position must be calculated in microns and Pscale(1,1) must be called. You must know each module position relative to its die origin, and each die position relative to its wafer origin. You must calculate these numbers to move the wafer chuck to its correct probing position.

Special Conditions

When using probers and matrices, be aware of the following conditions:

Interface File    A dedicated GPIB interface for a prober is recommended to avoid unknown effects on other instruments. However, if the given prober conforms to the IEEE 488 standard, it is possible to put the prober on the same GPIB with other instruments. Set the INST_START_ADDR system variable high enough to protect the prober from being accessed by the Rebuild (instrument list) operation.

Interrupt    Both prober and matrix functions are simple C functions called from the Macro interpreter of IC-CAP. It is possible to interrupt any one of these functions during its GPIB communication. Therefore, whenever you interrupt the execution of a Macro program that involves prober or matrix control, it might be necessary to reset the bus. Prober_init() resets its interface bus to clear any pending GPIB communications with the prober. However, SWM_init() only sends a Selected Device Clear to the matrix controller. If necessary, you can reset the measurement bus by choosing Tools > Interface > Reset.

Bus Lock    The HP 4062UX can lock the measurement bus even when a TIS program is not running. Be sure that the GPIB for measurement instruments is unlocked when IC-CAP starts up. The easiest way to ensure this unlocked condition is to exit the HP BASIC process from which any HP 4062UX program has been executed. IC-CAP also locks the measurement bus only during a measurement, which is similar to "Implicit Locking" of the HP 4062UX.

Measurement Accuracy    While the HP 4062UX performs certain error corrections for its 48- and 96-pin matrices, IC-CAP does not know about these internal parameters. Therefore the capacitance measurement accuracy is not specified when IC-CAP measures a capacitance through a switching matrix. However, performing a calibration at the matrix pins should reduce these errors introduced by the matrix.