Background Statement for SEMI Draft Document 4994
New Standard: GUIDE FOR HAFNIUM tert-BUTOXIDE
Note: 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.
Note: 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.
1 Introduction:
As the semi-conductor industry continues in its efforts to follow Moore’s Law many new materials have been introduced and continue to be introduced into electronic devices. The introduction of new materials being used covers all areas of the integrated circuit, including, but not limited to, high-k dielectric layers, barrier layers, metal interconnects, electrical contacts and low-k dielectric layers. Many of these new materials are deposited from liquid or solid chemicals by means of chemical vapour deposition or increasingly by atomic layer deposition. Therefore, there are now chemicals currently being used or could potentially be used in the future for which there are no SEMI guides or standards.
The Precursor Specification Task Force held its first meeting at SEMICON Europa in 2004 to identify new chemicals currently being used and to draft guides for these chemicals.
2 Steps taken:
With input from ITRS representatives The Precursor Specification Task Force initially examined which chemicals are currently being used or could potentially be used in the future for which there are no SEMI guides. The task force also examined the properties of these chemicals that are important for the deposition process and whether these could be included in a guideline. The Precursor Specification Task Force then selected a couple of chemicals to focus on initially with the aim of producing guides. In the case of hafnium several different classes of precursors could be used for the atomic layer deposition or chemical vapor deposition of hafnium oxide based materials. Alkoxides were one class of precursors to be considered, specifically hafnium tert-butoxide which has now been utilized in the semi-conductor industry. Therefore, it was decided to produce a guide for this chemical. An initial draft of the guide was produced based on task force discussions; this was then revised following comments from chemical manufactures, tool manufactures and end users.
3 Ballot Adjudication Information:
This ballot and all responses to it will be adjudicated at the next meeting of the Europe Gases and Liquid Chemicals Committee, tentatively scheduled for Thursday 26 May 2011 in Brussels, Belgium. The exact time, date, and location of the meeting will be announced when finalized.
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SEMI Draft Document 4994
New Standard: GUIDE FOR HAFNIUM tert-BUTOXIDE
1 Purpose
1.1 The purpose of this document is to provide a guide for hafnium tert-butoxide for which a need has been identified.
2 Scope
2.1 The scope of this document covers high purity hafnium tert-butoxide which is used in the semiconductor industry for the deposition of hafnium oxide based layers by atomic layer deposition or chemical vapor deposition.
3 Limitations
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the responsibility of the users of this standard to establish appropriate safety and health practices and determine the applicability of regulatory or other limitations prior to use.
4 Referenced Standards
4.1 SEMI Standards
SEMI C1 Guide for the Analysis of Liquid Chemicals
4.2 ASTM Standards[1]
ASTM D5127 — Standard Guide for Ultra Pure Water Used in the Electronics and Semiconductor Industry
NOTICE:As listed or revised, all documents cited shall be the latest publications of adopted standards.
5 Terminology
5.1 Acronyms
5.1.1 NMR – nuclear magnetic resonance
5.1.2 TMS – tetramethylsilane
6 Properties
Table 1Properties of hafnium tert-butoxide and CAS number
(for information only)
Molecular weight / 471.02 g/mol
CAS number / 2172-02-3
Boiling point / 90°C at 5mmHg
Vapor pressure
(P=mmHg, T=K) / log10P = 8.2277-2710.6/T
Solubility in water / Reacts
Appearance / Colorless liquid
7 Suggested values
7.1 The suggested values for hafnium tert-butoxide for Tier A are listed in Table 2.
8 Grade 1 Procedures
8.1 This section does not apply to this chemical.
9 Grade 2 Procedures
9.1 This section does not apply to this chemical.
10 Grade 3 Procedures
10.1 This section does not apply to this chemical.
11 Grade 4 Procedures
11.1 This section does not apply to this chemical.
12 Tier A Procedures
NOTE 1:Standardized test methods are being developed for all parameters at the purity level indicated. Until standardized test methods are published, test methodology shall be determined by user and producer.
12.1 Trace Metals Analysis The following method has given satisfactory results in determining trace metal impurities at the specified value for the elements listed in Table 2.
12.1.1 Mixed AcidPrepared by dilution of ultra pure 49% HF, ultrapure 70% HNO3and ultrapure 31 % H2O2 with ultrapure water in the following ratio : 25 mL of HF, 10 mL of HNO3 and 10 mL of H2O2 to 500 mL with water.
12.1.2 Standards Prepare multi-element standard solutions (calibration standards and quality control check standards) by diluting with mixed acid described in 12.1.1 of appropriate weights for ICP-MS.
12.1.3 Sample Preparation Dispense approximately 0.1 mL of the hafniumtert-butoxide sample into a dry and clean PFA sample bottle and record the weight to at least 3 decimal places. Under hood, add 49% HF dropwise into the sample aliquot. The sample will react vigorously with the HF; allow the reaction to proceed until it subsides before adding the next drop.Repeat until 2 mL of HF have been added.Dilute the sample with the acid mixture containing H2O2, HNO3 and HF (§12.1.1). The final dilution factor of the sample should be appropriate to minimize the space charge effects in the ICP-MS measurement of the sample. This dilution factor will be dependent on the type of ICP-MS used.
12.1.4 Analysis Analyze the samples by inductively couple plasma mass spectrometry (ICP-MS). High-resolution ICP-MS is suggested. It is recommended to run each sample in duplicate.In addition prepare a sample preparation blank for each analysis. It is also recommended to use an internal standard or a spiked sample solution to correct for the matrix effect.
12.2 Hydrocarbons Analysis The following method has provided satisfactory results in determining total hydrocarbons at the specified value using H-NMR.
12.2.1 Sample Preparation Under an inert atmosphere transfer 0.2ml of hafniumtert-butoxide into an NMR tube. Add 1ml of a solution of the internal standard (TMS) in deuterated benzene.
12.2.2 Analysis Calculate hydrocarbons from the integrations of peaks in the hydrocarbon region with that of the internal standard. For convenience hydrocarbons may be calculated as hexane.
12.2.3 Assayby NMR Ratio of the integration peaks from hafniumtert-butoxide to total integration of all peaks in the range -0.5 to 8ppm.
13 Tier B Procedures
13.1 This section does not apply to this chemical.
14 Tier C Procedures
14.1 This section does not apply to this chemical.
15 Tier D Procedures
15.1 This section does not apply to this chemical.
Table 2Impurity Limits and Other Suggested values for Hafnium tert-butoxide
Previous SEMI Reference # / --Tier A
(Guide)
Assay (1H NMR) / ≥99%
Hydrocarbons (1H NMR) / ≤1%
Aluminum (Al) / 500ppb
Antimony (Sb) / 200ppb
Arsenic (As) / 200ppb
Barium (Ba) / 200ppb
Boron (B) / 200ppb
Cadmium (Cd) / 200ppb
Calcium (Ca) / 200ppb
Chromium (Cr) / 200ppb
Copper (Cu) / 200ppb
Iron (Fe) / 200ppb
Lead (Pb) / 200ppb
Lithium (Li) / 200ppb
Magnesium (Mg) / 200ppb
Manganese (Mn) / 200ppb
Nickel (Ni) / 200ppb
Potassium (K) / 200ppb
Sodium (Na) / 200ppb
Tin (Sn) / 200ppb
Titanium (Ti) / 10ppm
Vanadium (V) / 200ppb
Zinc (Zn) / 200ppb
Zirconium (Zr) / 2000ppm
NOTICE: SEMI makes no warranties or representations as to the suitability of the standards set forth herein for any particular application. The determination of the suitability of the standard 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 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. 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
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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