JP2003059291A - Test method for radiation of sdram - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a test method for radiation of a SDRAM (synchronized dynamic random access memory). SOLUTION: A radiation irradiation controller irradiates a SDRAM with radiation rays. A state of the SDRAM is calculated after a radiation test. The radiation test comprises Single Event Upset, Single Event Latch-up, Micro Latch-up, and Gate Rupture Test. A state of the SDRAM in before and after radiation test can be grasped.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a radiation test method,
In particular, SDRAM (synchronized dynamic random access)
memory) radiation test method.

[0002]

In the field of space engineering, electronic devices used in outer space are subject to anti-radiation tests.
n test) is performed. For example, electronic devices used in satellite communications must pass radiation tests. These electronic devices must have good resistance to radiation and good readability for use in outer space.

Under such circumstances, the radiation test of SDRAM is very important because SDRAM is an important device for data transmission. There are various methods for evaluating / detecting the damage of SDRAM by radiation and its reliability. Generally, in the single event upset (SEU) method, when the SDRAM is exposed to radiation, the write state of the SDRAM changes. However, if the state of the SDRAM is rewritten, the SDRAM can still function. Single event latch-up (SE
L: Single Event Latch-up) method, SDRAM
When exposed to radiation, SDRAM cannot function. However, if the SDRAM is restarted (restar
t), the SDRAM is functional again. The Micro Latch-up Test and the Gate Rupture Test are more reliable tests used to test SDRAM, to know the details of the tested device. You can
The microlatch-up test can detect the location of non-functional areas within the SDRAM after the SDRAM has been irradiated and tested, but the SDRAM does not need to restart its programming. The gate rupture test can tell if the SDRAM has been permanently damaged by the radiation test.

[0004]

With the improvement of semiconductor technology and the increasing demand for computer speed-up, SDRA
Development on the storage capacity of M devices is also in progress. However, since SDRAM belongs to a new device that is still in development, there is currently no publication on how it will be affected under radiation tests. Therefore, S exposed to the radiation test
The state of DRAM is still unknown.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a radiation test method for SDRAM. The method includes performing SEU, micro-latch-up, SEL, gate rupture-test in SDRAM. In this way, the state of the SDRAM after the radiation test can be determined, and the reliability of the SDRAM can be improved.

Another object of the present invention is to provide the following radiation test method for SDRAM. The method includes performing a self-test with the test equipment to ensure that all test equipment is functioning properly. The "start" signal is the irradiation controller (irradia
from the motion controller) to the radiation irradiation room, and periodic radiation is continuously generated. Each cycle of periodic radiation consists of an on / off region. Test equipment
Check if SDRAM is in off area.
When no radiation is detected in the SDRAM, the test pattern is written from the test equipment to the SDRAM. S
The readings taken from the DRAM are calculated to get the sum. When the SDRAM is in the ON region, that is, when radiation is detected in the SDRAM, the test device checks whether an abnormal current exists in the SDRAM. If there is an abnormal current in the SDRAM, the test equipment returns to the self-test step described above. However, if there is no abnormal current in the SDRAM, the test device checks if the SDRAM is in the off region. When the SDRAM is in the off region, the test pattern is written in the SDRAM from the test device. The readings taken from the SDRAM before and after the test are calculated and a sum is calculated which indicates the difference between the readings written in the test pattern and the readings obtained after testing these readings.

The test device checks whether a "stop" signal has been sent by the irradiation controller. If the radiation irradiation controller does not send the "stop" signal, the test process returns to the step of writing the test pattern from the test equipment to the SDRAM, the readings obtained from the SDRAM before and after the test are calculated, and then written to the test pattern. The difference between the reading taken and the reading taken after the test is obtained.

The above description and the following detailed description are intended to illustrate the present invention and not to limit the scope of the invention.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an SDRA according to the present invention.
It is a flowchart which shows the radiation test method of M. Figure 2
FIG. 3 is a schematic view of a radiation test apparatus according to the present invention. 1 and 2 show a radiation test method for an SDRAM. The radiation test is performed by generating radiation in the radiation irradiation room 204 by the radiation irradiation controller 206 arranged in the control room 202. Control room 20
The radiation irradiation controller 206 in the No. 2 is the SDRA placed on the test table 210 of the radiation irradiation room 204.
Irradiate M208 with radiation. Test device 212 is SD
SDRAM 208 to determine the state of RAM 208
Connected to.

As shown in FIG. 1, the test equipment 212 is
Before starting the radiation test, a self-test S102 is performed to confirm whether the test equipment normally functions when performing the SDRAM radiation test. If the test equipment is functioning normally, a "start" signal is sent from the radiation irradiation controller 206 to the control room 202 to start the radiation test. The irradiation controller 206 continuously generates periodic radiation in the irradiation room 204.

FIG. 3 shows the periodic cycle of radiation.
is a graph showing cycles). As shown in FIG. 3, the periodic cycle (i) has a first region, a second region and a third region. The first region is a region in the radiation irradiation room 204 during which no radiation is generated (S1).
06). The second region is a region in the radiation irradiation room 204 during which radiation is generated. The third region of the periodic cycle (i) is a region in the radiation irradiation room 204 where no radiation is generated during that period. As shown in FIGS. 1 and 3, in step S106, it is detected whether or not there is radiation in the radiation irradiation room 204. If the test apparatus detects radiation, the radiation irradiation controller 206 moves to step S108 for storing the read value from the radiation irradiation room 204. If the test device does not detect the radiation, the test device waits until the SDRAM is exposed to the radiation and then continues to step S108. In step S108, SDRA
An efficient algorithm of M is calculated.

In the test of the preferred embodiment of the present invention, the test is set up in a hexadecimal pattern with P = 0x5555 and Q = 0xaaa (16).
The decimal system may be set up with P = 0xaaaa, Q = 0x5555). The hexadecimal pattern example test is written to SDRAM 208 from tester 212 and readings from SDRAM 208 are recorded and calculated. The formula used for the calculation is shown below.

[0013]

[Equation 1]

FpSTK1 (i) has P = 0x5555
Are written in the SDRAM 208.
The SDRAM 208 is essentially "1" there. The test writes "0" to the SDRAM 208, but SDRA
The reading obtained from M208 is still "1". Based on the same principle, FpSTK0 (i) is P
= 0x5555 is written to the SDRAM 208. The SDRAM 208 is originally "
0 ". The test writes" 1 "to the SDRAM 208. However, the read value obtained from the SDRAM 208 is" 0 ". On the other hand, FqSTK1 (i) is
It indicates that Q = 0xaaaa is written to the SDRAM 208. The SDRAM 208 is essentially "1" there. The test writes "0" to SDRAM 208, but the read value obtained from SDRAM 208 is still "1". Based on the same principle, FqS
In TK0 (i), Q = 0xaaaa is SDRAM208
It is written to. There SDR
The AM 208 is originally “0”. The test is "1" SDR
Write to AM208. However, the SDRAM 20
The reading obtained from 8 is still "0".
STK1 (i) is a hypothetical test pattern (assumptive te
st pattern) Both P and Q are shown to be written to SDRAM 208, which is the initial reading (origi).
nal reading) Having “1”. However, during the test, "0" was written to SDRAM 208,
The final reading obtained from 208 is still "1". The same principle applies to STK0 (i). That is, STK0 (i) indicates that both hypothetical test patterns P, Q are written to SDRAM 208, which has an initial read value of "0". However, during the test, "1" is SDRAM20.
The final read value written to SDRAM 8 and obtained from SDRAM 208 is still "0".

In the first region of the cyclic cycle of radiation, the tests are written from the test equipment 212 to the SDRAM 208 and the test readings are SD.
Obtained from RAM 208. These readings obtained from the SDRAM 208 are S before and after irradiation with radiation.
It provides information about the state of DRAM 208. Based on these readings, the state change of the SDRAM during irradiation of radiation can be detected.

In step S110 of FIG. 1, the test apparatus detects whether radiation is present. In the presence of radiation, SDRAM 208 would be in the second area shown in FIG. During the period of the second region, step S1
12 is executed and the abnormal current is SD from the test device 212.
It is checked whether it has been sent to the RAM 208 [whether a single event latch-up (SEL) state has occurred]. If there is an abnormal current in SDRAM 208, the process returns to step S102. However, a predetermined amount is set by the gate rupture test to show how many times the SEL can occur. If SEL
Occurs over a predetermined amount, SDRAM 208 is considered to have been permanently damaged. Test equipment 212
Sends a "stop" signal to notify the irradiation controller that the radiation test is complete. However, SDR
If no abnormal current is present in AM 208, the process will be in the third region of FIG. 3, step S114 of FIG.

As shown in FIGS. 1 and 3, in step S114 of FIG. 1, if there is no radiation,
The test process is in the third area of the graph shown in FIG. The test device 212 has the SDRAM 2 after the radiation irradiation.
Read test readings from 08. Single Event Upset (SEU) test will be conducted. The calculation formula is shown below.

[0018]

[Equation 2]

In the RpSTK1 (i), a hypothetical test pattern "0" is written in the binary of the SDRAM 208, but some read values "after radiation test".
1 ”is obtained from the binary of the SDRAM 208. The amount of the reading changing from“ 0 ”to“ 1 ”is the binary amount after the radiation test. Based on the same principle, RqSTK0 (i) is , Hypothetical test pattern ”
1 "is written into the SDRAM 208 binary,
After the radiation test, some reading "0" is SDR
Obtained from AM208 binaries. "1" to "0"
The amount of reading that changes to is the binary amount before the radiation test. SEUar (i) is the S after radiation test.
The binary change amount in the DRAM 208 is shown. SE
Ubr (i) is the SDRAM 20 before the radiation test.
8 shows the binary change amount within 8. SEU (i) is
The binary change amount in the SDRAM 208 before and after the radiation test is shown.

[0020]

[Equation 3]

From the above, after the radiation test is completed, the binary read values changed in the SDRAM 208 before and after the radiation test are accumulated. The total is obtained from the radiation test and how much radiation the device can be exposed to in space, ie the SDRAM2
08 is used to determine if it can be used as a device in outer space. In another state:

[0022]

[Equation 4]

From the above, after the radiation test is completed, the binary read values changed in the SDRAM 208 before and after the radiation test are accumulated. Totals are obtained from radiation tests. If the value of microlatchup is greater than a certain threshold, then a SEL has occurred in SDRAM 208. From FIG. 1, when the SEL occurs in SDRAM 208, the flow process returns to step S102. However, when the number of generated SELs reaches a predetermined number in the gate rupture test, the SDRAM 208 is considered to have been permanently damaged. The test device 212 sends a signal to the irradiation controller to stop the radiation test.

In step S118, the test device checks whether or not the "stop" signal is transmitted from the radiation irradiation controller 206. Radiation irradiation controller 206
Does not send a "stop" signal, the flow process returns to step S108. On the other hand, when the "stop" signal is transmitted, the radiation test in the SDRAM 208 ends.

[0025]

The main feature of the present invention resides in that radiation tests such as SEU, micro latch-up, SEL and gate rupture tests are carried out in SDRAM. From this radiation test, the state of the SDRAM 208 before and after the radiation test can be grasped. SD
Based on the readings obtained from the RAM, errors are determined and corrections and improvements are made to the SDRAM. On the other hand, the present invention provides a sophisticated test method that can determine the state of SDRAM after radiation test by calculating those readings. Therefore, the SDRAM
Improvements can be made to 208, reducing errors and improving reliability in outer space.

Other forms of the invention will be apparent to those skilled in the art based on the discussion of the invention within this specification and the actual form of the invention described herein. The specification and the embodiments should be understood only as an explanation for understanding the present invention, and the scope of the technical idea of the present invention is shown by the claims.

[Brief description of drawings]

FIG. 1 is a flowchart showing a radiation test method for an SDRAM according to the present invention.

FIG. 2 is a schematic diagram of a radiation test apparatus according to the present invention.

FIG. 3 is a graph showing a periodic cycle of a radiation test according to the present invention.

[Explanation of symbols]

202 control room 204 Radiation irradiation room 206 Radiation irradiation controller 208 SDRAM 210 test table 212 test equipment

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeo Hayashi             Taiwan Taoyuan 縣 中 ▲ ri ▼ city ▲ ri ▼ village success road             No. 156, No. 13 F term (reference) 2G132 AA08 AB04 AD01 AH07                 5L106 AA01 DD21

Claims (3)

[Claims] 1. SDR with a test device
A method of irradiating AM (synchronized dynamic random access memory) with SDRA after a radiation test.
The method is characterized in that the status of M is determined and calculated, the method comprising the following steps:
Performing a self-test in the test device; waiting for a "start" signal from the irradiation controller, the irradiation controller
Continuing to generate periodic radiation, each cycle of said periodic radiation comprises an on / off region; checking whether the SDRAM is in an off region, where the SDRAM irradiates the radiation Instead, the test pattern is written from the test device to the SDRAM; the read value obtained from the SDRAM (rea
dings) to obtain the difference in readings; SDRAM
Check whether the radiation is in the on-region where the radiation is applied to the SDRAM, and check whether the abnormal current exists in the SDRAM. However, if the abnormal current exists in the SDRAM, the test device is Return to the self-test step; if there is no abnormal current in the SDRAM, check whether the SDRAM is in the off region; make sure that the SDRAM is in the off region, where the SDRAM is not exposed to radiation,
A test pattern is written from the test equipment to the SDRAM; calculate the readings obtained from the SDRAM before and after the radiation test and obtain the difference between these readings; see if a "stop" signal was sent from the radiation controller. Check; if the radiation irradiation controller does not send a "stop" signal, the test equipment sends an S
Returning to the step of writing the test pattern in the DRAM, the readings obtained from the SDRAM before and after the radiation test are calculated to obtain the difference between these readings. 2. The test pattern transmitted from the test device to the SDRAM is two sets of complementary readings.
(complementary readings), the differences between the periodic radiations in the SDRAM are accumulated to obtain a total, and if the accumulated total of the differences causes an abnormal current in the SDRAM, the test apparatus returns to the self-test step. The method of claim 1 wherein: 3. If the SDRAM is in the ON region and the abnormal current is present in the SDRAM, the test device is
The DRAM is recorded as damaged, and when the number of damages reaches a predetermined number of gate rupture tests, it is considered that the SDRAM has been permanently damaged, and the test device is the radiation irradiation controller. The method of claim 1, further comprising informing the end of the radiation test.