Review and adjudication information

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1 Background Statement for SEMI Draft Document 587 REVISION TO SEMI M77-, PRACTICE FOR DETERMINING WAFER NEAR-EDGE GEOMETRY USING ROLL-OFF AMOUNT, ROA With Title Change To: TEST METHOD FOR DETERMINING WAFER NEAR-EDGE GEOMETRY USING ROLL-OFF AMOUNT, ROA Notice: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this Document. Notice: Recipients of this Document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, patented technology is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided Background. Title change from Practice for determining wafer near-edge geometry using roll-off amount, ROA to Test method for determining wafer near-edge geometry using roll-off amount, ROA 2. Add test method for 45mm notched and 45mm notchless wafer. 3. Update description related with above item and 2. The additions are indicated by underline and deletions are indicated by strikethrough Review and adjudication information Task Force Review Committee Adjudication Group: Int l Advanced Wafer Geometry TF NA Silicon Wafer TC Chapter Date: Monday, July 3, 25 Tuesday, July 4, 25 Time & Timezone: 2: PM -5: PM PDT : PM -4: PM PDT Location: San Francisco Marriott Marquis San Francisco Marriott Marquis City, State/Country: San Francisco/California, US Leader(s): Noel Puduje (SMS), Jaydeep Sinha (KLA-Tencor), Yoshise (self) San Francisco/California, US Dinesh Gupta (dgupta@pacbell.net) Noel Poduje (n.poduje@comcast.net) Standards Staff: Kevin Nguyen, knguyen@semi.org Kevin Nguyen, knguyen@semi.org This meeting s details are subject to change, and additional review sessions may be scheduled if necessary. Contact the task force leaders or Standards staff for confirmation. Telephone and web information will be distributed to interested parties as the meeting date approaches. If you will not be able to attend these meetings in person but would like to participate by telephone/web, please contact Standards staff. Check on calendar of event for the latest meeting schedule.

2 F F ROA SEMI Draft Document 587 REVISION TO SEMI M77-, PRACTICE FOR DETERMINING WAFER NEAR-EDGE GEOMETRY USING ROLL-OFF AMOUNT, ROA With Title Change To: TEST METHOD FOR DETERMINING WAFER NEAR-EDGE GEOMETRY USING ROLL-OFF AMOUNT, ROA Purpose. Wafer near-edge geometry can significantly affect the yield of semiconductor device processing..2 Knowledge of near-edge geometrical properties can help the producer and consumer determine if the dimensional characteristics of a specimen wafer satisfy given geometrical requirements..3 The ROA metric is suitable for quantifying near-edge geometry of wafers used in semiconductor device processing..4 Consideration should be given to the use of this or other proposed edge geometry metrics as a process control tool rather than a material exchange specification. 2 Scope 2. This practice test method covers calculation of the near-edge geometry metric roll-off amount (ROA).F F 2.2 Calculation of ROA is based on height data that are representative of a height data profile associated with one or more of the front surface, the back surface, or thickness. 2.3 This practice test method covers selection of the point at which the ROA is determined and the reference line to be utilized for this determination. 2.4 The practice test method is applicable to notched 2 and 3 mm diameter wafers having dimensions in accordance with wafer categories.9.2,.9.3,.5, and.5. of SEMI M categories of wafers specified in SEMI M used in advanced IC manufacturing. 2.5 This practice test method has been shown to be suitable for quantifying near-edge geometry to improve CMP, 3 performance at wafer edge. values in that study were measured using an edge-referenced coordinate system. 2F On the other hand, measurement systems for high volume production geometry (e.g., whole-wafer flatness) use a center-referenced coordinate system. 2.6 This practice test method allows for the use of either an edge-referenced or a center-referenced coordinate system. 2.7 There are other metrics for near-edge geometrical properties, some of which quantify more specific aspects. These are outside the scope of this practice. 2.8 This practice test method does not cover acquisition of the height data array. However, it gives the required characteristics of the height data array. NOTICE: SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their use. It is the responsibility of the users of the documents to establish appropriate safety and health practices, and determine the applicability of regulatory or other limitations prior to use. Kimura, M., Saito, Y., Hiroshi, H., and Yakushiji, K., A New Method for the Precise Measurement of Wafer Roll off of Silicon Polished Wafer. Jpn. J. Appl. Phys. 38, (999): p Japan Electronics and Information Technology Industries Association (JEITA) Technical Report, The Impact of Edge Roll-off on CMP performance. JEITA EMR-3, The development of edge roll off measurement method for silicon wafers by JEITA Silicon Technologies Committee is hereby acknowledged. This method, Edge Roll-Off Measurement Method for Silicon Wafers, was published as a standard in the JEITA EMR series. Page Doc. 587 SEMI

3 3 Limitations 3. Deficiencies of data such as inadequate spatial resolution, mispositioning, noise, etc. in the height data array used to calculate the ROA may lead to erroneous results. 3.2 The selection of the reference segment, the ROA measurement point, the measuring surface, and the type of the reference line is to be decided between the relevant parties. To make these conditions clear, a method for reporting ROA is provided in Because the diameter tolerance of 2 or 3 mm wafers is ±.2 mm (see SEMI M, Table 9 8) and of 45 mm wafer is ±.mm (see SEMI M, Table 9) the difference from nominal to real radius may be up to ±. mm for 2 mm and 3 mm and may be up to ±.5mm for 45 mm wafer. This difference may significantly affect the ROA calculation by shifting the positions of the measurement and reference segment points between the edgereferenced and center-referenced cases by the radius difference. Since the wafer surface height changes rapidly along the radius, the difference between ROA values determined with edge-referenced coordinates and center referenced coordinates can be significant. 3.4 Due to the existence of notch, the edge reference measurement is not applicable to the notch area, except 45 mm notchless wafer. 4 Referenced Standards and Documents 4. SEMI Standards SEMI M Specifications for Polished Single Crystal Silicon Wafers SEMI M2 Practice for Establishing a Wafer Coordinate System SEMI M59 Terminology for Silicon Technology SEMI M67 Practice for Determining Wafer Near-Edge Geometry from a Measured Thickness Data Array Using the ESFQR, ESFQD, and ESBIR Metrics SEMI M68 Practice for Determining Wafer Near-Edge Geometry from a Measured Height Data Array Using a Curvature Metric, ZDD SEMI M7 Practice For Determining Wafer-Near-Edge Geometry Using Partial Wafer Site Flatness NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions. 5 Terminology 5. General terms, acronyms, and symbols used in silicon wafer technology are listed and defined in SEMI M Other Terminology 5.2. Abbreviations and Acronyms ERO edge roll off L-ROA linear referenced ROA P-ROA polynomial referenced ROA ROA edge roll off amount Definitions center referenced property of a measurement or calculation with the radial measurement position established using the wafer center as the origin edge referenced property of a measurement or calculation with the radial measurement position established using the physical edge as the origin edge roll off (ERO) surface deviations of a large-diameter silicon wafer near the edge, but excluding effects due to wafer edge profiling, surface roughness, and global bending, such as warp, of the wafer. Page 2 Doc. 587 SEMI

4 edge roll off amount (ROA) the displacement from the reference line at the measurement point in the edge vicinity of an un-chucked wafer. ROA is defined as positive in the direction away from the reference line edge roll off measurement point the radial position where the edge roll off is measured. It is labeled x for an edge-referenced measurement or r for a center-referenced measurement linear-referenced ROA (L-ROA) the roll off value when a straight line is employed as the reference near edge geometry the topography of a surface of a large diameter silicon wafer in the outer region of the fixed quality area (FQA) physical edge the farthest extremity of the wafer. It is used as a reference point of an edge-referenced coordinate system when finding the profile of the edge region polynomial-referenced ROA (P-ROA) the roll off value when a cubic curve is employed as the reference reference line either a straight line or a cubic curve extrapolated by curve fitting from a section of an ideal surface that does not include edge roll off reference segment the section of the ideal surface that does not include edge roll off. 6 Summary of Practice Test Method 6. Measurement positions and measurement coordinate system are selected. 6.2 The ERO measurement point and the reference segments end points are selected and reported. 6.3 The type of reference line used is selected and reported. 6.4 Height data arrays of one or more of the front surface, the back surface, or thickness are acquired along the radial direction at the measurement positions. 6.5 The ROA is calculated for each measurement position. 6.6 ROA is reported for each measurement position and surface(s) analyzed. 6.7 Statistical quantities for ROA, as agreed upon by the parties to the test are calculated and reported for each wafer. 7 Apparatus 7. Measuring Equipment Suitable for acquiring the height data array over the entire FQA, except for instrument-dependent exclusion areas, and transferring it to the calculation equipment. NOTE : A test method for acquiring the height data array is outside the scope of this practice. 7.. The equipment shall perform all necessary calculations and corrections needed to produce the height data array internally and automatically, including instrument-dependent exclusion areas. The equipment shall be equipped with a means of detecting and either deleting or identifying invalid data (over-range signal) Height resolution shall to be nm or smaller Height data array data point spacing shall be. mm or less The acquisition spatial resolution shall be appropriate for the height data array data point spacing and shall be agreed upon between the parties to the test. 7.2 Calculation Software To perform the calculations of this practice and to provide outputs of the results, including statistical parameters as agreed upon by the parties to the test. 8 Procedure 8. Define recipe for calculation: 8.. Select edge-referenced or center-referenced coordinates (see X3.3X for cautionary warnings) Select the measurement position(s). Page 3 Doc. 587 SEMI

5 NOTE 2: Recommended positions are the following eight angular ones,, 45, 9º, 35º, 8º, 225º, 275º, and 35º for 2 mm, 3 mm and notched 45 mm wafer (see Figure a) and, 45, 9º, 35º, 8º, 225º, 27 and 35 for 45 mm notchless wafers (see Figure b) as defined in the R-θ coordinate system of SEMI M2 (see Figure ). This practice test method does not define the measuring method for the notch portion of the wafer and its neighborhood Y X a Figure Recommended Measurement Positions on the Front Surface of the Specimen notched and notchless Wafer b 8..3 Select the reference line as a straight line (L-ROA) or a third order polynomial (cubic) curve (P-ROA) Select the locations of the measurement point and reference segment end points. Designate these as x, x, and x 2, respectively, (x 2 > x ) when using edge-referenced coordinates or r, r, and r 2, respectively (r > r 2) when using center-referenced coordinates (see Figure 2). ROA () x: Distance from the edge (mm) x [mm] r [mm] ROA (49) 49 r: Distance from Center the center (mm) Figure 2 Recommended Measurement Positions on the Front Surface of the Specimen Wafer The default location of the reference segment for L-ROA is between x = 3 mm and x 2 = 6 mm for the edge referenced case, or between r = (R 3) mm and r 2 = (R 6) mm for the center referenced case, where R is the nominal wafer radius. The default edge roll off measurement point for L-ROA is taken as x = mm for the edge referenced case, or r = (R ) mm for the center referenced case. See Appendix for a discussion of the reasons why these default values are selected for the reference segment end points The default location of the reference segment for P-ROA is between x = 5 mm and x 2 = 2 mm for the edge referenced case or between r = (R 5) mm and r 2 = (R 2) mm for the center referenced case. The default edge roll off measurement point for L-ROA is r = mm for the edge referenced case or r = (R ) mm for the center referenced case. See Appendix for a discussion of the reasons why these default values are selected for the reference segment end points Select the surface or surfaces to obtain the height data array as one or more of the following: front surface, back surface, or thickness Determine statistics to be reported for each wafer. As a minimum, these shall include maximum, average, range, and standard deviation. 8.2 Acquire the height data array in accordance with a method agreed upon by all parties to the practice. Page 4 Doc. 587 SEMI

6 9 Calculations NOTE 3: The following calculations are performed automatically within the equipment. An outline of the calculation structures is provided here to indicate the nature of the procedure. 9. For each profile, determine reference line as: 9.. The least square line in case L-ROA is selected, or 9..2 The least square cubic order polynomial curve in case P-ROA is selected. 9.2 Calculate the distance between the measured profile and reference line at the ERO measurement point (see Figure 2). 9.3 Record ROA as the distance between the measured profile and the reference line at the edge roll off measurement point (see Figure 3). P-ROA Profile L-ROA Measured profile Linear reference line Profile Measured profile Cubic polynomial reference line x = x =3 x 2 =6 x = x =5 x 2 =2 Location (mm) Location (mm) Figure 3 L-ROA Measurement Method (left hand) and P-ROA Measurement Method (right hand) 9.4 Calculate statistics (see X8..6X) for each wafer for each surface (front surface, back surface, and thickness) for which ROA was calculated. 9.5 For multi-measurement tests, calculate the standard deviations of each set of wafer measurements and such other statistical parameters as agreed to by the parties to the test. Report. Report the following information:.. Date, time of test,..2 Identification of operator,..3 Location (laboratory) of test,..4 Identification of measuring instruments, including measuring equipment and calculation equipment (identification of make, model, software version, etc.),..5 Acquisition spatial resolution and data point spacing,..6 Lot identification and wafer identification,..7 Description of sampling plans, if any, and..8 Measurement conditions, as follows:..8. Surface measured (front surface, back surface, or thickness),..8.2 Type of the reference line (a linear reference line or a polynomial cubic reference curve), Page 5 Doc. 587 SEMI

7 ..8.3 Origin of coordinate (center-reference or edge reference),..8.4 Edge roll off measurement point,..8.5 The reference segment end points, and..9 ROA data and its angular position of the measurement (in degrees, in accordance with the R-θ coordinate system of SEMI M2) for each wafer measured for each position..2 In addition, report all statistical quantities (e.g., average, range, standard deviation, other) as agreed to by the parties to the test for each wafer measured (see X8..6X). NOTE 4: In reporting statistical properties of measurements on a wafer surface, the name of the statistical quantity should be substituted for the angular position..3 For multi-measurement tests, also report the standard deviation of each set of wafer measurements and such other statistical parameters as have been agreed to by the parties to the test. Keywords. ERO; ROA; near-edge geometry; semiconductor; silicon; wafers Page 6 Doc. 587 SEMI

8 X As F APPENDIX REFERENCE SEGMENT LOCATIONS NOTICE: The material in this appendix is an official part of SEMI M77 and was approved by full letter ballot procedures on August 27, 2. A- Edge roll off is the displacement of un-chucked wafer surface profile in the edge vicinity from a reference line (virtual ideal surface) and ROA (roll off amount) is defined as the vertical (z direction) distance from the reference line to the surface at a specific point on the radius. The reference line represents a virtual ideal straight line or curve without the edge roll off and is determined from the surface profile of the edge vicinity and inner (toward the wafer center) part of the wafer in order to avoid any influence of the edge roll off. If sori, bow, and warp (hereinafter called global bending) do not exist, the reference line is determined by extrapolating a line from the inner surface profile. However, in case that global bending exists, it is necessary to eliminate its effect. A-2 In general, the global bending of the wafer surface has a relatively small spatial frequency compared to the edge roll off so that this practice includes a choice between two kinds of reference lines. One is a reference line (linear reference) by fitting a straight line to a short segment that is hardly biased by the global bending, and the other is a reference line (curved reference) by fitting a third order polynomial line to the wafer global bending. As for the short segment, the 3 mm segment that is from 3 6 mm is employed according to the literature of Kimura et al.x for the third order polynomial line, the 5 mm segment that is from 5 2 mm is employed as a recommended segment based on the following reason. A-3 As shown in Figure A-, assuming that the edge roll off is independent of the global bending, the amount of the edge roll off should not be changed by the existence of the global bending. On the other hand, the global bending does not exist in the thickness profile so that straight line can be fitted to it as a reference line. From these points of view, if the curved reference line reflects the global bending well, the sum of the front surface ROA and back surface ROA calculated using each reference line must be exactly the same as thickness ROA calculated separately using the linear reference line. If it is not, the global bending influences the front surface ROA and back surface ROA, and it means that roll off is not correctly evaluated. A-4 Then, measuring real wafers (JEITA obtained 9 wafers in 23), the thickness ROA is compared to the sum of the front surface ROA and the back surface ROA calculated using various reference segments. For all 9 wafers, 8 points along every 45 orientation on each wafers were measured. As for the front surface ROA and the back surface ROA, the curve reference line ROA is calculated using 8 kinds of curved reference segment, [3,6], [5,], [5,2], [5,25], [, 5], [.2], [, 25]. As for thickness ROA, it is calculated by the straight line of the recommended segment. Figure A-2 is 8 graphs in which the sum of the front surface ROA and the back surface ROA is plotted against the thickness ROA for each reference segment. To evaluate the ROA calculation error caused by global bending, the mean square of the difference between the thickness ROA and sum of the front surface ROA and the back surface ROA is calculated by the following equation: [ROAt (ROAf + ROAb )] Calculated error = (A-) N where ROA t, ROA f and ROA b are the thickness ROA, the front surface ROA and the back surface ROA respectively. Table A- shows the calculated results and that the minimum error was obtained in 5 2 mm segment. It is concluded from this that the 5 mm segment from 5 2 mm is the most appropriate one. Of course, these results were tested for limited wafers and it is quite possible to choose another segment by agreement among users, since, 4 for example, there is another proposal by Riedel et al.f 2 4 F. Riedel, H. -A. Gerber, and P. Wagner, Metrics for Wafer Edge Roll-Off Measurement. SEMI Standards Silicon Wafer Workshop (SEMICON Europa 25, Munich, Germany, April 4, 25). Page 7 Doc. 587 SEMI

9 ERO Actual shape of a wafer Component of ERO Component of global bending Figure A- Components of ERO and global bending Table A- Calculated Results Using Equation A- for Each Set of Reference Segments for Front and Back Surface P-ROA Reference Segment Calculated Error 3 6 mm mm.2 5 5mm mm mm.56 5 mm 42 2 mm mm.2 Page 8 Doc. 587 SEMI

10 Front Surface P-ROA(.) + Back Surface P-ROA(.) (µm) Front Surface P-ROA(.) + Back Surface P-ROA(.) (µm) Thickness L -ROA(.) [ 3, 6] (µm) (a) Reference Segment 3 6 mm.25 - Front Surface P-ROA(.) + Front Back Surface P-ROA(.) + (µ Back Surface P-ROA(.) m) (µm) Front Surface P-ROA(.) + Back Surface P-ROA(.) (µm) Th ickn ess L -RO A(.) [ 3, 6] (µ m) (b) Reference Segment 5 mm Thickness L-ROA(.) [ 3, 6] (µm) Thickness L-ROA(.) [ 3, 6] (µm) (c) Reference Segment 5 5 mm (d) Reference Segment 5 2 mm Front Surface P-ROA(.) + Back Surface P-ROA(.) (µm) Front Surface P-ROA(.) + Back Surface P-ROA(.) (µm) Thickness L-ROA(.) [ 3, 6] (µm) (e) Reference Segment 5 25 mm -.25 Thickness L-ROA(.) [ 3, 6] (µm) (g) Reference Segment 2 mm Front Surface P-ROA(.) + Back Surface P-ROA(.) (µm) Front Surface P-ROA(.) + Back Surface P-ROA(.) (µm) Thickness L-ROA(.) [ 3, 6] (µm) (f) Reference Segment 5 mm -.25 Thickness L-ROA(.) [ 3, 6] (µm) (h) Reference Segment 25 mm Figure A-2 Comparison of the Thickness L-ROA with reference segment [3,6] with the sum of the Front Surface P-ROA and the Back Surface P-ROA for Each Reference Segment. The description (*) and [*, *] in each axis title are indicated as the measurement point and reference segment, respectively. Page 9 Doc. 587 SEMI

11 NOTICE: SEMI makes no warranties or representations as to the suitability of the standard(s) set forth herein for any particular application. The determination of the suitability of the standard(s) 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 or equipment mentioned herein. These standards are subject to change without notice. The user s attention is called to the possibility that compliance with this standard may require use of copyrighted material or of an invention covered by patent rights. Shin-Etsu Handotai has filed a statement with SEMI asserting that licenses will be made available to applicants throughout the world for the purpose of implementing this standard without unfair discrimination. Attention is also drawn to the possibility that some elements of this standard may be subject to patented technology or copyrighted items other than those identified above. Semiconductor Equipment and Materials International (SEMI) shall not be held responsible for identifying any or all such patented technology or copyrighted items. By publication of this standard, SEMI takes no position respecting the validity of any patent rights or copyrights asserted in connection with any item mentioned in this standard. Users of this standard 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. Page Doc. 587 SEMI