This system boasts the following features.
| (1) |
Capacity for simultaneous burn-in of 64 die
Contact can be made with 64 die at once for burn-in, so a typical 8-inch wafer can be completely tested with only 6 scans, providing high-speed management. |
| (2) |
8-Channel clock driver
An 8-channel clock driver provides burn-in control for high-capacity DRAM. This driver provides fine control through the ability to individually set VIH and VIL. The driver also provides the capacity to drive a 2mF load at 200mS Tr/Tf. This equipment also gives the ability to add super drivers that can driver high-capacity loads such as word line.
|
| (3) |
Capacity for contact checking
The clock driver prober can automatically determine whether proper contact is made with the wafer pad. This solves the problem of burn-in not being made due to defective contact. As shown in Fig. 4, proper contact can be determined if Vf voltage can be detected within normal range when constant current incidentally generated by the diode is applied to the signal input pad. The unit determines a short in the input pad when 0 V is detected, and determines that a circuit is open in the input pad when limit voltage is detected. Multiple pads are generally used for power application pads and grand pads, so contact checking such as that used for signal pads cannot be used. Because of this, determination of proper contact is made when the power source is measured and found to be within the expected range. If the value is outside the expected range, defective contact (including test device problems) is determined. |
|
|
|
Fig. 4 Contact checking circuit
|
| |
 |
|
|
| |
|
| (4) |
Mask functions for each die
This system drives each die individually using 64 driver substrates. This provides individual control of each die.
When defective contact and abnormal current are detected, the die in which they are detected is not tested.
During the test, the system routinely for each die performs voltage OVP and source current OCP, and monitors the clock with the window comparator. If an error is detected, the hardware control immediately interrupts the current and the clock for that die only. As seen in Fig. 5, in a power line interrupt, the grand line can also be cut off by the relay. This function prevents the defective die from affecting the normal die, and at the same time works to protect the system.
|
|
|
|
Fig. 5 Power circuits
|
| |
 |
|
|
| |
(5) Fail data indicator function
As seen in Fig. 6, abnormal source current of OCP and OVP, defective contact, and clock monitoring failure can be displayed as bit information in the indicated shape of the wafer map. In this way, a defective die on the wafer can easily be recognized.
As Fig. 7 shows, the values for the measured source current can be displayed in the indicated shape of the wafer map.
|
| |
|
Fig. 6 Fail indication
|
| |
 |
|
| |
|
Fig. 7 Source cirrent indication
|
| |
 |
|
| |
|
| (6) |
Testing based on test sequence
As Fig.8 shows, burn-in can be carried out based on test sequence, in the form Test 1 to Test n. Sequences such as DC stress and dynamic testing can be carried out automatically for a fixed number of tests or for a specified time period. Fig. 9 shows a sequence setting screen.
|
|
| |
|
Fig. 8 Test sequence
|
Fig. 9 Test sequence setting screen
|
| |
 |
|
 |
|
|
|
|
|
(7)
|
Ease of operation using a touch panel
Photo 2 shows a touch panel. The color LCD display sports a touch panel using the dialog method and the menu method for ease of operation. The control software runs as a Windows* application. (*Windows is a registered trademark of the Microsoft Corporation.) |
|
|
|
Photo 2 Touch panel
|
| |
 |
|
|
| |
|
