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SEMI M40-0200 © SE MI 2000 12 NOTICE: SEMI makes no w arranties or representations as to the sui tability of the guide set forth herein for any particular application. The determ ination of the suitability of the guide i…

SEMI M40-0200 © SEMI 200011

APPENDIX 1

NOTE: The material in this appendix is an official part of SEMI M40 and was approved by full letter ballot procedures on

December 15, 1999 by the North American Regional Standards Committee.

A1-1 Examples of Roughness Measurement Specifications and Related Output

The construction of typical measurement specifications and reported results are shown below. These could be the

input to and output from a suitably equipped metrology tool, or directions for manual execution and reporting of the

measurement and calculation sequence. The elements and codes are listed only in the first example. The

quantitative data below is presented for illustration only, it does not represent actual instrument or sample

measurements.

1. Mechanical Profiler

The Mechanical profiler measurement was specified as MPR,5,L,A,A,A,250/10. This corresponds to

measuring a 5-point pattern with a local line-scan and with pattern orientation A, and reporting Ra average

value over a bandwidth from 250 to 10 µm.

Elements Profiler, Mechanical; 5-point; line-scan; orient A; Ra; average; 250/10 µm

Codes MPR 5 L A A A 250/10

Output Example MPR,5,L,A,A,A,250/10 = 0.53 nm

2. Angle-Resolved Light Scattering

The Angle-resolved light scattering instrument measurement was specified as ARLS,9,B,P,Q,A,40/2.0. This

corresponds to measuring a 9-point pattern with a single spot and with pattern orientation B, reporting rms (Rq)

average value over a bandwidth from 40 to 2 µm.

Output Example ARLS,9,B,P,Q,A,40/2.0 = 0.15 nm

3. Interference Microscope

The Interference microscope measurement was specified as IM,5,A,A,T,D,250/10. This corresponds to

measuring a 5-point pattern with a local area and with pattern orientation A, reporting peak-to-valley (Rt)

standard deviation over a bandwidth from 250 to 10 µm.

Output Example IM,5,A,A,T,D,250/10 = 0.05 nm

4. Total Integrated Scattering

The Total Integrated Scattering system (TIS) measurement was specified as TIS,S,P,A,Q,D,38/0.50. This

corresponds to measuring a full FQA/spiral scan with a local spot and with pattern orientation A, reporting rms

(Rq) standard deviation over a bandwidth from 38 to 0.5 µm.

Output Example TIS,S,P,A,Q,D,38/0.50 = 0.02 nm

5. Optical Profiler

The Optical Profiler measurement was specified as OPR,9,L,B,A,AD,80/0.50. This corresponds to measuring a

9 point pattern with a local line-scan and with pattern orientation B, reporting Ra average value and standard

deviation over a bandwidth from 80 to 0.5 µm.

Output Example OPR,9,L,B,A,AD,80/0.50 = 0.17nm (Ra average), 0.02 nm (Ra, standard

deviation)

6. AFM

The AFM measurement was specified as AFM,5,A,A,Z,A,20/0.04. This corresponds to measuring a 5 point

pattern with local area and with pattern orientation A, reporting Rz average value over a bandwidth from 20 to

0.040 µm.

Output Example AFM,5,A,A,Z,A,20/0.04 = 0.43 nm

SEMI M40-0200 © SEMI 2000 12

NOTICE: SEMI makes no warranties or representations as to the suitability of the guide set forth herein for any

particular application. The determination of the suitability of the guide is solely the responsibility of the user. Users

are cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other relevant literature

respecting any materials mentioned herein. These guides are subject to change without notice.

The user’s attention is called to the possibility that compliance with this guide may require use of copyrighted

material or of an invention covered by patent rights. By publication of this guide, SEMI takes no position respecting

the validity of any patent rights or copyrights asserted in connection with any item mentioned in this guide. Users of

this guide are expressly advised that determination of any such patent rights or copyrights, and the risk of

infringement of such rights, are entirely their own responsibility.

SEMI M40-0200 © SEMI 200013

RELATED INFORMATION 1

EXPERIMENTS AND MODELS RELATING TO ROUGHNESS

DISTRIBUTION OF SILICON WAFERS

NOTE: This related information is not an official part of

SEMI M40 but was approved for publication by full letter

ballot procedures.

R1-1 Executive Summary

R1-1.1 Roughness is measured traditionally only on

selected spots on a surface and only a few methods,

such as light scattering, are practical for a complete

surface scan. Therefore a systematic, standardized

approach is required for defining the roughness of the

entire surface of a silicon wafer. This can be done by

defining one or several patterns of measurement spots

which represent the entire surface so that the deviation

of the average roughness and its standard deviation

from the “true” values are small. The task of finding

such patterns and verifying that they represent the entire

surface was approached in two steps: 1. by

investigating various patterns on various wafer surfaces

experimentally, and 2. by simulating the roughness map

of surfaces and by applying the selected patterns to

them.

R1-1.2 Five different site patterns were used for the

experimental investigation of silicon wafer surfaces

which were final polished, stock removal polished and

acid etched. The patterns consist of one, five, nine, ten

and thirteen points (thirteen being the sum of a five and

nine point pattern), respectively, and the measurements

were performed with 10, 30, 80 and 250 µm filter

lengths. Therefore 20 average roughness values and

corresponding standard deviations were obtained for

every wafer investigated, five for any filter length.

R1-1.3 Haze maps of these surfaces either displayed no

variation, variations with an approximately rotational

symmetry or a gradient across the surface, respectively.

The average roughness of the surfaces measured with

the various site patterns varied over four and a half

orders of magnitude for the set of wafers used and the

filter settings selected. The corresponding standard

deviations were found to be <10% of the average

roughness with the exception of four 200 mm final

polished wafers where standard deviations up to 50-

60% occurred. The 5-, 9- and 10-point site patterns

were compared with respect to the average roughness

and the corresponding standard deviation for every

wafer. The variation (standard deviation) of the

average roughness and the standard deviations as

measured were found to be smaller than or

approximately 10% in any case when normalized to the

total average roughness of the corresponding wafer

(average over all points of all patterns for a wafer).

R1-1.4 Roughness maps were generated for the

simulation according to three different models: maps

with a roughness pattern with rotational symmetry, with

a linear gradient and with mirror symmetry. Two maps

with a pixel size of 1 mm

were generated for each

surface to take into account any anisotropy of the

roughness, and center roughness and edge roughness,

respectively, were used as free parameters for both

maps. These parameters were varied between two level

(0.1 and 0.2) for both maps resulting in a 2

factorial

design of “experiment” where the symmetry was

considered as 5

parameter. The 1-, 5- and 9-point site

patterns were applied to the various maps and the

average roughness and standard deviation of roughness

were calculated as well as the true values using all

points of a map. Strong effects were observed for the

1-point pattern. As expected one point in the wafer

center does in general not represent the average

roughness of the entire surface reasonably well. The 5-

point measurement provides the correct average ± 6%,

the 9-point measurement is ± 2.5%. Similarly, the 5-

point standard deviation is correct ± 1.6% and the 9-

point one is ± 1%. Second order effects were found to

be smaller than the main effects. Therefore it is

concluded that the suggested five and nine point

measurement patterns provide a good estimate of the

roughness of an entire surface and its variations for

reasonably homogeneous Si wafer surfaces.

R1-2 Introduction

R1-2.1 Roughness measurement of surfaces is

performed with a variety of techniques, the most

common ones being mechanical or optical profiling in

real space or light scattering in reciprocal space (1,2,3).

The numerical result of a roughness measurement

process depends significantly on several parameters

such as spatial bandwidth of the response function of

the tool used including filtering, scan length, probe

diameter, scanning speed etc. These parameters are not

independent of each other and have been standardized

only for mechanical profilers (e.g.4,5). The roughness

values reported by different types of tools usually do

not agree but they correlate provided their parameters

were set up not too differently (6). The standardized

roughness metrics such as average roughness R

root-mean-square roughness R

refer mainly to line

scans as performed by profiling techniques (e.g. 7).

Area scans performed by profiling tools by aligning a

series of line scans are usually very slow. Scanning the

entire surface of a Si wafer with a profiler therefore