Chemical Mechanical Planarization System Combined Synopsis - Questions and Answers 10 Feb 2020.pdf

Chemical Mechanical Planarization System Combined Synopsis/Solicitation

Questions and Answers

Notice ID: 80GSFC20Q0005

Date: February 7, 2020

Question 1: We want to bring to your attention that there are several types of wafer carriers.

Which style of wafer carrier would you prefer?

Government Response: As detailed in the Statement of Work (SOW) > Requirements >

Technical Requirements > 1. CMP Tool Specifications > l, m & n, the system shall include wafer carriers for 100 mm and 150 mm wafer diameters. Each wafer carrier shall have at least 3 separately adjustable pressure zones (i.e. at least two zones on the membrane contacting the back of the silicon wafer, plus one zone for the retaining ring surrounding the wafer). The vendor shall also include an option for a wafer carrier for 200 mm wafer diameter. (The SOW has been updated to clarify these requirements).

Question 2: What is the entire stack on the wafers? Please clarify the expected Pre-CMP uniformity and the across-wafer profile.

Government Response: The five silicon wafers to be supplied by GSFC will have 100 mm diameter and approximately 500 µm thickness. As stated in the SOW, the wafers will have been coated with 350 nm of aluminum oxide deposited by atomic layer deposition at GSFC. The aluminum oxide thickness will be highly uniform across the wafer, but in a few small locations

(0.1 mm in extent) it will have small bumps, 0.2 µm high, that will later provide indication of the degree of planarization achieved by the CMP process. The initial aluminum oxide will have been measured and mapped over each wafer surface prior to delivery to the vendor. The goal for the CMP process will be to remove 270 ± 27 nm of aluminum oxide uniformly and reproducibly across each wafer. The first requirement is that one standard deviation in amount of oxide removed is less than 10% of the mean value (i.e. 10% of 270 nm = 27nm). For each of the five wafers, the standard deviation in the amount removed, evaluated for samples distributed over that wafer, shall not exceed the 10% value. Furthermore, the mean amount removed, calculated for each wafer, shall not vary more than 10% from the mean amount removed on any other wafer. (The SOW has been updated to clarify these requirements).

Question 3: In the SOW it is listed that you want the following to be demonstrated:

• WIWU: Sigma/mu< 10% for each of the 5 wafers o Do you mean WIWU or WIWNU (within-wafer-non-uniformity)?

• WTWU: [max(mu)-min(mu]/men(mu) < 10% across the 5 wafers o Do you mean WTWU or do you mean WTWNU (wafer-to-wafer-non-uniformity)?

Government Response: The definition of Within-Wafer-Uniformity (WIWU) used in the SOW is as indicated by the formula given: the WIWU equals the standard deviation of within-wafer measurements of the amount of oxide removed, divided by the mean of those measurements. A

CMP process that results in a more uniform amount of oxide removed will therefore correspond to a smaller value for WIWU. A high degree of uniformity, and low value of WIWU, is desired.

Similarly, the definition given in the SOW for Wafer-To-Wafer-Uniformity (WTWU) is the spread in a set of measurements over the mean of those measurements. Consequently, a more uniform or repeatable process will correspond to a smaller value for WTWU. Some authors use the term Within-Wafer-Nonuniformity to refer to the same ratio of standard deviation divided by the mean. Irrespective of the convention used for the acronym used, the intent of the acceptance test components is that the CMP system and process recipe used should remove a uniform and reproduceable amount of material.