MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第118页

MIL-STD-883F METHOD 1019.6 7 March 2003 2 2.2 D osimetry system . An appropr iate dos imetr y syst em shall be provided whi ch is capable of carr ying out t he measurement s cal led for in 3.2. The f ollowing Amer ican S…

MIL-STD-883F

METHOD 1019.6

7 March 2003

METHOD 1019.6

IONIZING RADIATION (TOTAL DOSE) TEST PROCEDURE

1. PURPOSE

. This test procedure defines the requirements for testing packaged semiconductor integrated circuits for

ionizing radiation (total dose) effects from a cobalt-60 (

Co) gamma ray source. The testing includes both standard room

temperature irradiation as well as irradiation at elevated temperature. In addition this procedure provides an accelerated

annealing test for estimating low dose rate ionizing radiation effects on devices. This annealing test is important for low

dose-rate or certain other applications in which devices may exhibit significant time-dependent effects. This procedure

addresses only steady state irradiations, and is not applicable to pulse type irradiations. This test may produce severe

degradation of the electrical properties of irradiated devices and thus should be considered a destructive test.

1.1 Definitions

. Definitions of terms used in this procedure are given below:

a. Ionizing radiation effects

. The changes in the electrical parameters of a device or integrated circuit resulting from

radiation-induced charge. These are also referred to as total dose effects.

b. In-flux test

. Electrical measurements made on devices during irradiation exposure.

c. Not in-flux test

. Electrical measurements made on devices at any time other than during irradiation.

d. Remote tests

. Electrical measurements made on devices which are physically removed from the radiation

location.

e. Time dependent effects

. Significant degradation in electrical parameters caused by the growth or annealing or

both of radiation-induced trapped charge after irradiation. Similar effects also take place during irradiation.

f. Accelerated annealing test. A procedure utilizing elevated temperature to accelerate time-dependent effects.

g. Enhanced Low Dose Rate Sensitivity (ELDRS). Used to refer to a part that shows enhanced radiation induced

damage at dose rates below 50 rad(Si)/s.

h. Overtest. A factor that is applied to the specification dose to determine the test dose level that the samples must

pass to be acceptable at the specification level. An ovetest factor of 1.5 means that the parts must be tested at 1.5

times the specification dose.

i. Parameter Delta Design Margin (PDDM). A design margin that is applied to te radiation induced change in an

electrical parameter. For a PDDM of 2 the change in a parameter at a specified dose from the pre-irradiation value

is multiplied by two and added to the post-irradiation value to see if the sample exceeds the post-irradiation

parameter limit. For example, if the pre-irradiation value of Ib is 30 nA and the post-irradiation value at 20 krad(Si)

is 70 nA (change in Ib is 40 nA), then for a PDDM of 2 the post-irradiation value would be 110 nA (30 nA + 2 X 40

nA). If the allowable post-irradiation limit is 100 nA the part would fail.

2. APPARATUS

. The apparatus shall consist of the radiation source, electrical test instrumentation, test circuit board(s),

cabling, interconnect board or switching system, an appropriate dosimetry measurement system, and an environmental

chamber (if required for time-dependent effects measurements or elevated temperature irradiation). Adequate precautions

shall be observed to obtain an electrical measurement system with sufficient insulation, ample shielding, satisfactory

grounding, and suitable low noise characteristics.

2.1 Radiation source

. The radiation source used in the test shall be the uniform field of a

Co gamma ray source.

Uniformity of the radiation field in the volume where devices are irradiated shall be within ±10 percent as measured by the

dosimetry system, unless otherwise specified. The intensity of the gamma ray field of the

Co source shall be known with

an uncertainty of no more than ±5 percent. Field uniformity and intensity can be affected by changes in the location of the

device with respect to the radiation source and the presence of radiation absorption and scattering materials.

MIL-STD-883F

METHOD 1019.6

7 March 2003

2.2 Dosimetry system

. An appropriate dosimetry system shall be provided which is capable of carrying out the

measurements called for in 3.2. The following American Society for Testing and Materials (ASTM) standards and guidelines

or other appropriate standards and guidelines shall be used:

ASTM E 666 - Standard Method for Calculation of Absorbed Dose from Gamma or X Radiation.

ASTM E 668 - Standard Practice for the Application of Thermoluminescence Dosimetry (TLD) Systems

for Determining Absorbed Dose in Radiation-Hardness Testing of Electronic Devices.

ASTM E 1249 - Minimizing Dosimetry Errors in Radiation Hardness Testing of Silicon Electronic Devices.

ASTM E 1250 - Standard Method for Application of Ionization Chambers to Assess the Low Energy Gamma

Component of Cobalt 60 Irradiators Used in Radiation Hardness Testing of Silicon Electronic

Devices.

ASTM E 1275 - Standard Practice for Use of a Radiochromic Film Dosimetry System.

ASTM F 1892 - Standard Guide for Ionizing Radiation (Total Dose) Effects Testing of Semiconductor Devices.

These industry standards address the conversion of absorbed dose from one material to another, and the proper use of

various dosimetry systems. 1

2.3 Electrical test instruments

. All instrumentation used for electrical measurements shall have the stability, accuracy,

and resolution required for accurate measurement of the electrical parameters. Any instrumentation required to operate in a

radiation environment shall be appropriately shielded.

2.4 Test circuit board(s)

. Devices to be irradiated shall either be mounted on or connected to circuit boards together with any

associated circuitry necessary for device biasing during irradiation or for in-situ measurements. Unless otherwise specified, all

device input terminals and any others which may affect the radiation response shall be electrically connected during irradiation,

i.e., not left floating. The geometry and materials of the completed board shall allow uniform irradiation of the devices under test.

Good design and construction practices shall be used to prevent oscillations, minimize leakage currents, prevent electrical

damage, and obtain accurate measurements. Only sockets which are radiation resistant and do not exhibit significant leakages

(relative to the devices under test) shall be used to mount devices and associated circuitry to the test board(s). All apparatus

used repeatedly in radiation fields shall be checked periodically for physical or electrical degradation. Components which are

placed on the test circuit board, other than devices under test, shall be insensitive to the accumulated radiation or they shall be

shielded from the radiation. Test fixtures shall be made such that materials will not perturb the uniformity of the radiation field

intensity at the devices under test. Leakage current shall be measured out of the radiation field. With no devices installed in the

sockets, the test circuit board shall be connected to the test system such that all expected sources of noise and interference are

operative. With the maximum specified bias for the test device applied, the leakage current between any two terminals shall not

exceed ten percent of the lowest current limit value in the pre-irradiation device specification. Test circuit boards used to bias

devices during accelerated annealing must be capable of withstanding the temperature requirements of the accelerated

annealing test and shall be checked before and after testing for physical and electrical degradation.

2.5 Cabling

. Cables connecting the test circuit boards in the radiation field to the test instrumentation shall be as short as

possible. If long cables are necessary, line drivers may be required. The cables shall have low capacitance and low

leakage to ground, and low leakage between wires.

2.6 Interconnect or switching system

. This system shall be located external to the radiation environment location, and

provides the interface between the test instrumentation and the devices under test. It is part of the entire test system and

subject to the limitation specified in 2.4 for leakage between terminals.

2.7 The environmental chamber

. The environmental chamber for time-dependent effects testing, if required, shall be

capable of maintaining the selected accelerated annealing temperature within ±5°C.

/ Copies may be obtained from the American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103.

MIL-STD-883F

METHOD 1019.6

7 March 2003

2.8 The irradiation temperature chamber

. The irradiation temperature, if required for elevated temperature irradiation should

be capable of maintaining a circuit under test at 100 °C +

5 °C while it is being irradiated. The chamber should be capable of

raising the temperature of the circuit under test from room temperature to the irradiation temperature within a reasonable time

prior to irradiation and cooling the circuit under test from the irradiation temperature to room temperature in less than 20 minutes

following irradiation. The irradiation bias shall be maintained during the heating and cooling. The method for raising,

maintaining and lowering the temperature of the circuit under test may be by conduction through a heat sink using heating and

cooling fluids, by convection using forced hot and cool air, or other means that will achieve the proper results.

3. PROCEDURE

. The test devices shall be irradiated and subjected to accelerated annealing testing (if required for time-

dependent effects testing) as specified by a test plan. This plan shall specify the device description, irradiation conditions,

device bias conditions, dosimetry system, operating conditions, measurement parameters and conditions, and accelerated

annealing test conditions (if required).

3.1 Sample selection and handling

. Only devices which have passed the electrical specifications as defined in the test plan

shall be submitted to radiation testing. Unless otherwise specified, the test samples shall be randomly selected from the parent

population and identically packaged. Each part shall be individually identifiable to enable pre- and post-irradiation comparison.

For device types which are ESD-sensitive, proper handling techniques shall be used to prevent damage to the devices.

3.2 Burn-in

. For some devices, there are differences in the total dose radiation response before and after burn-in.

Unless it has been shown by prior characterization or by design that burn-in has negligible effect (parameters remain within

postirradiation specified electrical limits) on the total dose radiation response, then one of the following must be done:

3.2.1 The manufacturer shall subject the radiation samples to the specified burn-in conditions prior to conducting total

dose radiation testing or

3.2.2 The manufacturer shall develop a correction factor, (which is acceptable to the parties to the test) taking into

account the changes in total dose response resulting from subjecting product to burn-in. The correction factor shall then be

used to accept product for total dose response without subjecting the test samples to burn-in.

3.3 Dosimetry measurements

. The radiation field intensity at the location of the device under test shall be determined

prior to testing by dosimetry or by source decay correction calculations, as appropriate, to assure conformance to test level

and uniformity requirements. The dose to the device under test shall be determined one of two ways: (1) by measurement

during the irradiation with an appropriate dosimeter, or (2) by correcting a previous dosimetry value for the decay of the

source intensity in the intervening time. Appropriate correction shall be made to convert from the measured or calculated

dose in the dosimeter material to the dose in the device under test.

3.4 Lead/Aluminum (Pb/Al) container. Test specimens shall be enclosed in a Pb/Al container to minimize dose enhancement

effects caused by low-energy, scattered radiation. A minimum of 1.5 mm Pb, surrounding an inner shield of at least 0.7 mm Al, is

required. This Pb/Al container produces an approximate charged particle equilibrium for Si and for TLDs such as CaF

. The radiation

field intensity shall be measured inside the Pb/Al container (1) initially, (2) when the source is changed, or (3) when the orientation or

configuration of the source, container, or test-fixture is changed. This measurement shall be performed by placing a dosimeter (e.g., a

TLD) in the device-irradiation container at the approximate test-device position. If it can be demonstrated that low energy scattered

radiation is small enough that it will not cause dosimetry errors due to dose enhancement, the Pb/Al container may be omitted.

3.5 Radiation level(s)

. The test devices shall be irradiated to the dose level(s) specified in the test plan within ±10

percent. If multiple irradiations are required for a set of test devices, then the post-irradiation electrical parameter

measurements shall be performed after each irradiation.

3.6 Radiation dose rate

. The radiation dose rate for bipolar and BiCMOS linear or mixed-signal parts used in applications

where the maximum dose rate is below 50 rad(Si)/s shall be determined as described in paragraph 3.13 below. Parts used

in low dose rate applications, unless they have been demonstrated to not exhibit an ELDERS response shall use Condition

C, Condition D, or Condition E.

NOTE: Devices that contain both MOS and bipolar devices may require qualification to multiple subconditions to ensure that both

ELDRS and traditional MOS effects are evaluated.

3.6.1 Condition A.

For condition A (standard condition) the dose rate shall be between 50 and 300 rad(Si)/s [0.5 and 3

Gy(Si)/s]

Co 2/ The dose rates may be different for each radiation dose level in a series; however, the dose rate shall not

vary by more than ±10 percent during each irradiation.

2/ The SI unit for the quantity absorbed dose is the gray, symbol GY. 100 rad = 1 Gy.