{"id":17878,"date":"2026-04-19T16:52:41","date_gmt":"2026-04-19T11:22:41","guid":{"rendered":"https:\/\/aluminiummagazine.com\/mag\/?p=17878"},"modified":"2026-04-19T16:53:35","modified_gmt":"2026-04-19T11:23:35","slug":"trimethylaluminum-tma-pyrophoric-ald-guide","status":"publish","type":"post","link":"https:\/\/aluminiummagazine.com\/mag\/aluminium\/compounds\/trimethylaluminum-tma-pyrophoric-ald-guide.html","title":{"rendered":"Trimethylaluminum (TMA): Technical Guide to a Pyrophoric Semiconductor Precursor"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Trimethylaluminum, globally shortened to TMA, is a violently reactive organometallic compound. It is a clear, colorless liquid that is <strong>pyrophoric<\/strong> \u2013 it spontaneously ignites on contact with air. Despite its extreme danger, it is the premier aluminium precursor for semiconductor manufacturing, used in Atomic Layer Deposition (ALD) and as a Ziegler\u2011Natta co\u2011catalyst.<\/p>\n\n\n\n<div style=\"height:50px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">1. <strong>Basic Identification<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Chemical Formula:<\/strong> Al\u2082(CH\u2083)\u2086 (exists as a dimer; monomer Al(CH\u2083)\u2083 is not stable at room temperature)<\/li>\n\n\n\n<li><strong>Alternative Names:<\/strong> TMA, aluminum trimethyl<\/li>\n\n\n\n<li><strong>Molecular Weight:<\/strong> 144.18\u202fg\/mol (dimer)<\/li>\n\n\n\n<li><strong>CAS Number:<\/strong> 75-24-1<\/li>\n\n\n\n<li><strong>Appearance:<\/strong> Clear, colorless liquid<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">2. <strong>Physical Properties<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">Property<\/th><th class=\"has-text-align-center\" data-align=\"center\">Trimethylaluminum (Dimer)<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Melting Point<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">15\u202f\u00b0C (59\u202f\u00b0F) \u2013 freezes in cold weather<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Boiling Point<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">126\u202f\u00b0C (258\u202f\u00b0F)<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Density<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">0.752\u202fg\/cm\u00b3<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Vapor Pressure<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">~12\u202fmmHg at 25\u202f\u00b0C (volatile)<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Solubility<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Reacts violently with water; soluble in dry non\u2011polar hydrocarbons (hexane, toluene)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">In a sealed, argon\u2011filled container, TMA looks like pure water \u2013 but it sits on a razor edge of reactivity. The aluminum core is so electron\u2011deficient that methyl groups bridge to form the dimer.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">3. <strong>Chemical Behavior &amp; Reactions<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">3.1 Spontaneous Pyrophoricity<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">TMA ignites instantly on contact with air:<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Al\u2082(CH\u2083)\u2086 + 12 O\u2082 \u2192 Al\u2082O\u2083 + 6 CO\u2082 + 9 H\u2082O<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The flame is intensely hot, blinding white, and produces thick white smoke (aluminium oxide dust).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3.2 Water Reactivity<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Contact with water causes explosive decomposition, releasing methane gas that also ignites.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">4. <strong>Industrial Applications<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">4.1 Atomic Layer Deposition (ALD) and MOCVD<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">TMA is the standard aluminium precursor for depositing ultra\u2011thin <strong>aluminium oxide (Al\u2082O\u2083)<\/strong> layers in semiconductor fabrication:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>A silicon chip sits in a vacuum chamber.<\/li>\n\n\n\n<li>A pulse of TMA vapor adsorbs as a single atomic layer.<\/li>\n\n\n\n<li>A pulse of water vapor reacts with the TMA, stripping methyl groups and leaving one atom\u2011thick layer of Al\u2082O\u2083.<\/li>\n\n\n\n<li>The cycle repeats to build flawless dielectric insulators for advanced CPUs.<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">4.2 Ziegler\u2011Natta Co\u2011Catalyst<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">In polyethylene production, TMA activates titanium\u2011based catalysts, enabling high\u2011density plastic manufacturing.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">5. <strong>Safety &amp; Hazard Management<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">GHS Symbol<\/th><th>Meaning<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\">\ud83d\udd25 GHS02<\/td><td>Pyrophoric liquid<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\">\u26a0\ufe0f GHS05<\/td><td>Corrosive<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Critical Warning:<\/strong> TMA is one of the most dangerous chemicals handled industrially. Containment failure leads to instantaneous, unstoppable fire.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<h3 class=\"wp-block-heading\">5.1 Health Effects<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Route of Exposure<\/th><th>Effect<\/th><\/tr><\/thead><tbody><tr><td><strong>Inhalation<\/strong><\/td><td>Vapors react with lung moisture, causing auto\u2011ignition and fatal thermal\/chemical burns.<\/td><\/tr><tr><td><strong>Skin Contact<\/strong><\/td><td>Splashes ignite instantly, causing third\u2011degree burns and corrosive damage.<\/td><\/tr><tr><td><strong>Eye Contact<\/strong><\/td><td>Instant ignition, permanent destruction of corneal tissue.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">5.2 PPE &amp; Handling<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Open manipulation is strictly banned.<\/strong> Handle only in argon\u2011flooded gloveboxes or stainless steel Schlenk lines.<\/li>\n\n\n\n<li><strong>Body:<\/strong> Flame\u2011retardant Nomex suit, face shield.<\/li>\n\n\n\n<li><strong>No synthetics<\/strong> \u2013 they melt into skin.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">5.3 Firefighting<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Use:<\/strong> Dry sand, vermiculite, or Met\u2011L\u2011X Class D powder to smother oxygen.<\/li>\n\n\n\n<li><strong>Do NOT use:<\/strong> Water (explosive accelerant), CO\u2082, or Halon (TMA re\u2011ignites after gas disperses).<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">6. <strong>Storage &amp; Handling<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Container:<\/strong> Double\u2011walled stainless steel \u201cbubblers\u201d with VCR metal\u2011gasket valves<\/li>\n\n\n\n<li><strong>Atmosphere:<\/strong> Pressurized ultra\u2011high purity argon<\/li>\n\n\n\n<li><strong>Location:<\/strong> Outdoor gas bunkers or flame\u2011isolated cabinets<\/li>\n\n\n\n<li><strong>Disposal:<\/strong> Dilute in dry hexane inside glovebox, then slowly quench with isopropanol over days.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">7. <strong>Environmental Impact<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">TMA does not persist in the environment. Upon release, it instantly ignites and burns to CO\u2082, water, and aluminum oxide dust \u2013 no water contamination. However, the fire will destroy nearby organic material.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">8. <strong>Comparison with Other Reactive Aluminum Compounds<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">Compound<\/th><th class=\"has-text-align-center\" data-align=\"center\">Formula<\/th><th>Primary Nature<\/th><th>Primary Danger<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Trimethylaluminum<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Al\u2082(CH\u2083)\u2086<\/td><td>Pyrophoric liquid<\/td><td>Spontaneous ignition in air<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Lithium Aluminum Hydride<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">LiAlH\u2084<\/td><td>Water\u2011reactive solid<\/td><td>Ignites on contact with moisture<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Aluminum Chloride<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">AlCl\u2083<\/td><td>Corrosive Lewis acid<\/td><td>Fumes HCl; does not auto\u2011ignite<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">9. <strong>Frequently Asked Questions<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Q: Why not transport TMA as a solid powder?<\/strong><br>A: TMA freezes at 15\u202f\u00b0C. It is often transported refrigerated to keep it solid, which slows reaction in case of a leak.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Q: What happens if a syringe of TMA drops?<\/strong><br>A: The syringe becomes a flaming flamethrower, igniting the workbench and potentially the chemist. This is why syringing TMA is considered one of the most dangerous operations in synthetic chemistry.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Q: Could TMA be used as jet fuel?<\/strong><br>A: No. It ignites instantly on contact with air \u2013 any crack in a fuel tank would cause mid\u2011air explosion.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">10. <strong>Summary Data Sheet<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">Property<\/th><th class=\"has-text-align-center\" data-align=\"center\">Value<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Chemical Name<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Trimethylaluminum<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Acronym<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">TMA<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Formula<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Al\u2082(CH\u2083)\u2086 (dimer)<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Appearance<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Clear, volatile liquid<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Density<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">0.752\u202fg\/cm\u00b3<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Primary Utility<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">ALD precursor, Ziegler\u2011Natta co\u2011catalyst<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Defining Hazard<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Pyrophoric \u2013 spontaneously ignites in air<\/td><\/tr><\/tbody><\/table><\/figure>\n<\/p><script>document.addEventListener(\"DOMContentLoaded\",function(){\n        if(window.innerWidth <= 768){\n            if (\"immediate\" === \"delay\") {\n                setTimeout(function(){document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\")},0);\n            } else if (\"immediate\" === \"scroll\") {\n                window.addEventListener(\"scroll\",function(){\n                    let s=window.scrollY\/(document.body.scrollHeight-window.innerHeight);\n                    if(s>0.1){\n                        document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\");\n                    }\n                });\n            } else {\n                document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\");\n            }\n        } else {\n            document.querySelectorAll(\".pai-ad\").forEach(el=>el.remove());\n        }\n    });<\/script>","protected":false},"excerpt":{"rendered":"<p>Trimethylaluminum, globally shortened to TMA, is a violently reactive organometallic compound. It is a clear, colorless liquid that is pyrophoric \u2013 it spontaneously ignites on contact with air. Despite its extreme danger, it is the premier aluminium precursor for semiconductor manufacturing, used in Atomic Layer Deposition (ALD) and as a Ziegler\u2011Natta co\u2011catalyst. 1. Basic Identification &#8230; <a title=\"Trimethylaluminum (TMA): Technical Guide to a Pyrophoric Semiconductor Precursor\" class=\"read-more\" href=\"https:\/\/aluminiummagazine.com\/mag\/aluminium\/compounds\/trimethylaluminum-tma-pyrophoric-ald-guide.html\" aria-label=\"Read more about Trimethylaluminum (TMA): Technical Guide to a Pyrophoric Semiconductor Precursor\">Read more<\/a><\/p>\n","protected":false},"author":12,"featured_media":18028,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4155],"tags":[4141,4142],"class_list":["post-17878","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-compounds","tag-aluminium-compounds","tag-aluminum-formula"],"_links":{"self":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts\/17878","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/comments?post=17878"}],"version-history":[{"count":0,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts\/17878\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/media\/18028"}],"wp:attachment":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/media?parent=17878"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/categories?post=17878"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/tags?post=17878"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}