MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第609页

MIL-STD-883F METHOD 5004.11 18 June 2004 19 APPENDIX A Screens - 100% of a popul ation ( dice or wafers ) is inspec ted or t ested and al l mater ial c ontaining t argeted def ects are reject ed. Sub-proc ess - Any numbe…

MIL-STD-883F

METHOD 5004.11

18 June 2004

APPENDIX A

Excursion containment

- Efforts undertaken to find, limit and segregate discrepant material.

Homogeneous

- The state in which every wafer in a lot has received the exact same processing, including: correlated

equipment (as specified in appendix A of MIL-PRF-38535), same recipes, same operations and same materials. This

does not include metrology or inspection steps.

ILD - Inter-layer dielectric

. Typically refers to the layer separating different conductor material layers but is occasionally

used to describe the layer between first metal and the underlying layers.

In-line

- The process steps that comprise wafer fabrication from initial starting material through and including initial test

(electrical test and sort).

Inspection

- Any procedure designed to detect or measure defects. Depending on the equipment or procedure, the

quantity or types of defects may or may not be measurable; depending on the inspection, defects may or may not be

removed. These procedures may utilize visual detection (human or automated), laser surface scatter, in-situ particle

detectors, etc.

Interconnects

- Any structures on the wafer surface used for electrical connection from one device (or portion of a device)

to another. These structures are typically made of polysilicon or metal.

Killer defect

- A defect that has a high probability of causing failure, under any condition, at some given point in a products

intended life.

Letter of suitability

- A formal written document from the qualifying activity stating the manufacturer has sufficient capability

and competency to implement/execute the subject procedure.

Look-back inspection

- An inspection that is capable of detecting defects not only at the current process layer but also at

some number of preceding process layers. Ideally, this inspection allows for differentiation between defects at the current

process layer and those of preceding ones.

LPCVD

- Low-pressure chemical vapor deposition.

LTO

- Low-temperature oxidation or low-temperature oxide.

LYA

- Low-yield analysis. A method for determining the reason for yield loss by analyzing low-yielding material.

Mask level

- A structure (electrical, physical and/or chemical) on, in, above or below a wafer substrate, achieved or

modified by various sequential physical or chemical processes, such as: oxidation, diffusion, etch, film deposition, implant,

etc.

Material review board (MRB)

- A group of individuals who have sufficient expertise and are duly authorized by the facility

to disposition discrepant or non-conforming material.

Monitor

- Inspections or tests performed on a sampled population.

Non-critical defect

- A defect that has been demonstrated not to cause premature failure, regardless of defect density,

defect placement on the die or defect size.

- Preventive maintenance procedure.

Poly

- Polycrystalline silicon.

Process baseline

- An approved set of instructions, conditions and procedures for wafer fabrication.

Product

- Material resulting from the output of a wafer fab process that is ultimately destined for delivery to a customer.

MIL-STD-883F

METHOD 5004.11

18 June 2004

APPENDIX A

Screens

- 100% of a population (dice or wafers) is inspected or tested and all material containing targeted defects are

rejected.

Sub-process

- Any number of related process steps leading to an outcome on the wafer. Examples would include poly

interconnect formation (comprised of poly deposition, poly layer lithography, poly etch and resist strip) and contact

formation (dielectric deposition, contact layer lithography, contact etch and resist strip).

Telescoping defects

- Defects which increase in visibility, due to an apparent increase in size, as wafers are processed

through subsequent operations. The increase is a function of the defect being decorated by etches or films, the defect

acting as a nucleation site for subsequent depositions or by the defect creating non-uniform regions in a film or oxide.

Test

- 1) Evaluate (ie: stress and measure) reliability, quality and performance; 2) ensure the defects present do not

affect reliability, quality or performance.

Unexpected failures

- Failures that are not detected, or cannot be predicted, using the manufacturer's standard in-line

inspection and containment plans.

Wafer process

- The materials, equipment, operations and environment necessary to manufacture a product or family of

products. This includes all potential sources of defect generation.

Yield analysis

- The analysis of die yields to determine failure modes and defect mechanisms. This can entail analyzing

low yielding material, average yielding material or high yielding material or combinations of these items. This type of

analysis can be used to validate in-line monitors.

MIL-STD-883F

METHOD 5004.11

18 June 2004

APPENDIX A

ATTACHMENT 1

Example 1 - Quality Scenario

A defect characterization has been performed on an LPCVD operation. The primary defect mechanism was found to be

particles. These particles were quantified using a laser surface-scanning tool. The results show that the particles fell into

three size distributions: 1) <0.3 microns randomly distributed from wafer to wafer and within a wafer, 2) about 1.0 microns

with a higher density near the pump end of the deposition tube, and 3) greater than 6.0 microns that appeared heavily on

some wafers but did not appear at all on others. The defects in the 1.0 micron or less categories were found to be relatively

small, dark particles when viewed with an optical microscope. The larger particles (>6 microns) appeared as large, black

particles that appeared to be on the wafer surface. A compositional analysis of particles from the three distributions showed

that the first two types (<0.3 microns and about 1.0 microns) were composed of Si and O, essentially the same composition

as the deposited film. The large particles were composed of primarily Fe and Ni.

Wafers containing defects from the smaller size distributions were processed through the subsequent patterning

operations. The 1.0 micron particles were observed to have an affect on the subsequent pattern when they occurred

adjacent to the patterned lines. The <0.3 micron particles had no observable effect. Both defects were characterized using

optical microscopes and an automated pattern inspection system. After resist strip, the 1.0 micron particles were gone, with

only their effects on the patterning operation being visible. The <0.3 micron defects were still observable after resist strip.

After a subsequent LTO deposition, the <0.3 micron particles appeared to "telescope" in size to about 1 micron due to the

conformal nature of the LTO film. The "telescoped" particles had a noticeable effect on the next patterning operation.

Observation of both particle types using an SEM (scanning electron microscope) showed that the 1.0 micron particles

appeared to be incorporated into the film, whereas the <0.3 micron particles appeared to be under the film. This was

consistent with the defect behavior observed during subsequent processing.

The signal from the large particles suggested contamination from a stainless steel source. Observation of the defect with

an SEM showed that the defects were on top of the deposited film. The defects were found to be coming from the unload

arm of the LPCVD system. The unload arm was occasionally striking another piece of the load/unload assembly, generating

metal particles each time it did this.

The characterization of particle defects from this LPCVD operation resulted in the following monitoring plan: 1) The

alignment of the unload arm was found to be most affected by the preventive maintenance procedure performed on the

load/unload assembly once each week. As a result, a bare silicon particle monitor is run after each PM, before any product

wafers can be run on the system. The monitor is set to look for 6 micron and larger particles with the expectation that no

such particles should be present if the unloader is working properly. 2) The source of the 1.0 micron particles is unknown.

What is known is that these defects are always worse near the pump-end of the tube. As a result, the monitor for this

particle source is run at the pump end of the tube, with a door end monitor run simultaneously as a "control". Different

action limits exist for each monitor. 3) The small particles were found to be very difficult to monitor at the LPCVD operation

since they fell into the "noise" caused by limitations in the particle detection equipment. However, they are easily monitored

in a "look-back" fashion after the subsequent patterning operation using the automated pattern inspection system. As a

result, this defect is monitored at the post-patterning inspection step with action limits initiating feedback to the LPCVD

operation.