TWI428434B - Chemical mechanical polishing slurry for polysilicon - Google Patents

Description

Application of chemical mechanical polishing liquid in polishing polycrystalline germanium

This invention relates to a chemical mechanical polishing fluid, and more particularly to a chemical mechanical polishing fluid for polishing polycrystalline germanium.

In the fabrication of integrated circuits, the standard of interconnect technology continues to increase, and a layer is deposited on top of one layer, resulting in an irregular topography on the surface of the ruthenium. One method of planarization used in the prior art is Chemical Mechanical Polishing (CMP), which uses an abrasive-containing mixture and a polishing pad to polish a batt surface. In a typical chemical mechanical polishing process, the cymbal is placed in direct contact with a rotating polishing pad to apply pressure on the back of the cymbal. During polishing, the bake and the polishing table/polishing pad are rotated while maintaining a downward force on the back of the batt, applying an abrasive and a chemically active solution (commonly referred to as a polishing or polishing slurry) to the polishing pad. The polishing solution chemically reacts with the film being polished to begin the polishing process.

For the polishing of polysilicon, it is mainly applied to two types of wafers, one is DRAM and the other is Flash. In the latter application, polishing of cerium oxide is often involved in the polishing of polycrystalline germanium. There are two technical problems in this polishing process:

First, in the prior art, an alkaline slurry using cerium oxide as abrasive particles is mainly used to polish the polycrystalline germanium layer and the cerium oxide layer. During the polishing process, the removal rate of polycrystalline germanium is often much higher than that of cerium oxide. It is easy to cause excessive removal of polycrystalline germanium to cause depression, which affects the subsequent process.

At present, some technical solutions for solving this problem have been disclosed in the literature.

A method of manufacturing a Flash is disclosed, for example, in US Patent Publication Nos. 2003/0216003 A1 and US 2004/0163324 A1. The invention comprises a polishing liquid for polishing polycrystalline germanium, the polishing crucible comprising at least one compound containing a -N(OH), -NH(OH) or -NH ₂ (OH) group, and the polycrystalline germanium and cerium oxide using the slurry The polishing selection ratio is 50:1~300:1, but the selection ratio is still higher.

A slurry for polycrystalline germanium chemical mechanical polishing comprising one or more nonionic surfactants forming a passivation layer on a polycrystalline germanium layer, and a paste is disclosed, for example, in US Pat. No. 2005/0130428 A1 and Chinese Patent No. CN 1637102 A. An amine or imine surfactant for adjusting the relative removal rate of tantalum nitride and ruthenium oxide. The nonionic surfactant is at least one ethylene oxide-propylene oxide block copolymer alcohol and/or ethylene oxide-propylene oxide triblock polymer. The slurry can reduce the depth of depression of the polysilicon.

Second, in a conventional polycrystalline cerium alkaline slurry polishing liquid, an inorganic base such as KOH or an organic amine such as ammonia water, tetramethylammonium hydroxide (TMAH) or tetrabutylammonium hydroxide (TBAH) is usually used to adjust the pH. U.S. Patent Document US2005 / 0130428A1 and mainland China patent CN1637102A discloses a slurry for chemical mechanical polishing of polysilicon, using _{KOH, NH 4 OH, TMA,} TMAH and TEA composed of a combination of pH control agents. However, inorganic alkali will introduce metal ion pollution into the slurry, and metal ions have potential hidden dangers to the yield of the wafer. Ammonia water is very polluting to the environment. Hydroxylamine compounds inhibit the dielectric such as cerium oxide under alkaline conditions. Material removal rate

One aspect of the present invention is to provide a chemical mechanical polishing liquid for polishing polycrystalline germanium having a suitable polycrystalline germanium/cerium oxide selectivity ratio and no pollution, to solve the above polycrystalline germanium/cerium oxide selectivity ratio, and a conventional alkali Metal ion pollution and environmental pollution caused by pH regulators.

The polishing liquid of the present invention contains a polyol type nonionic surfactant, an anthraquinone compound, abrasive particles, and water.

In the present invention, the polyol type nonionic surfactant is preferably an ester surfactant and/or polyethylene glycol surface active formed by esterification of a polyol with a fatty acid. Agent. The weight percentage of the polyol type nonionic surfactant is preferably from 0.0001% to 20%, more preferably from 0.001% to 10%. In the polishing liquid of the present invention, the polyol type nonionic surfactant can significantly reduce the removal rate of polycrystalline germanium without lowering the removal rate of germanium dioxide, thereby significantly reducing the selection ratio of polycrystalline germanium to germanium dioxide, and avoiding polycrystalline germanium. Depression caused by excessive removal.

Among them, the ester surfactant may preferably be a polyol fatty acid ester R ₁ O _m H _mn (OCR ₂ ) _n , a polyethylene glycol fatty acid ester R ₂ COO(CH ₂ CH ₂ O) _p H or R ₂ COO(CH ₂ CH ₂ O) _p OCR ₂ , polyoxyethylene polyol fatty acid ester R ₁ O _m H _mn (CH ₂ CH ₂ O) _p (OCR ₂ ) _n , wherein R ₁ (OH) _m is 2 m 8 polyols, 4 p 120 (corresponding (CH ₂ CH ₂ O) _p H ₂ O is a polyethylene glycol having a molecular weight of 200 to 6000), R ₂ COOH is a fatty acid having 8 to 22 carbon atoms, n=1 to 4 and m n. Wherein, the polyhydric alcohol is preferably ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin, polyglycerin, polyoxyethylene glycerin, pentaerythritol, xylitol, poly Oxyethylene dehydrated xylitol, sorbitol, polyoxyethylene sorbitol, sorbitan, polyoxyethylene sorbitol, sucrose or polyethylene glycol.

Among them, the polyethylene glycol surfactant is preferably polyethylene glycol (PEG) having a molecular weight of 200 to 20,000.

In the present invention, the quinone compound may preferably be hydrazine, cesium carbonate, cesium acetate, cesium hydrogen phosphate, cesium hydrochloride, cesium nitrate, cesium sulfate, aminoguanidine, aminoguanidine hydrogencarbonate, aminoguanidine sulfonate, amino group.胍Nitrate or aminoguanidine hydrochloride. The concentration by weight of the quinone compound is preferably from 0.001% to 3%, more preferably from 0.01% to 2%. The quinone compound has a function of adjusting the selectivity ratio of polycrystalline germanium to cerium oxide in the polishing liquid of the present invention. In the case where the other components and their contents are the same, the higher the content of the terpene compound, the higher the selection ratio of polycrystalline germanium to ceria. However, the degree of regulation of the selectivity of the terpenoids is much less than that of the polyol-type nonionic surfactants, and thus can be used as a finely tuned component. A polishing liquid having a suitable polycrystalline germanium/cerium oxide selectivity ratio can be obtained by a simple experiment. At the same time, terpenoids also have a pH-adjusting effect. Therefore, the polishing liquid of the present invention It is not necessary to add a general pH adjusting agent, such as an inorganic base such as KOH or an organic amine such as ammonia water, etc., so that the polishing liquid of the present invention has a low metal ion content and less environmental pollution.

In the present invention, the abrasive particles are abrasive particles commonly used in the art, among which cerium oxide, aluminum oxide, aluminum-doped cerium oxide, aluminum-coated cerium oxide, cerium oxide, titanium oxide and/or high are preferred. Molecular abrasive particles. The particle diameter of the abrasive particles is preferably from 20 nm to 150 nm. The content of the abrasive particles is preferably from 0.5% to 30% by weight.

The pH of the polishing liquid of the present invention is preferably from 8 to 12.

The polishing liquid of the present invention may further contain an acidic pH adjuster such as HCl, H ₂ SO ₄ or HNO ₃ , a viscosity modifier and/or an antifoaming agent, etc., by which characteristics such as pH and viscosity of the polishing liquid are controlled.

The polishing liquid of the present invention is obtained by simply mixing and mixing the above components.

Thereby, the polishing liquid of the present invention can better polish the polycrystalline silicon film under alkaline conditions. Among them, the polyol type nonionic surfactant can significantly reduce the removal rate of polycrystalline germanium without reducing the removal rate of cerium oxide, thereby significantly reducing the selectivity ratio of polycrystalline germanium to cerium oxide; the cerium compound can also regulate polycrystalline germanium and dioxide. The selection ratio of hydrazine is selected to obtain a suitable selection ratio, and the quinone compound also has a pH adjusting effect, so that the polishing liquid of the present invention does not need to add a general pH adjusting agent (organic alkali such as KOH or an organic amine such as ammonia water, etc.). Metal ion pollution and environmental pollution are greatly reduced.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

The invention is further illustrated by the following examples, which are not intended to limit the invention.

Example 1 : Polycrystalline germanium chemical mechanical polishing liquid

Table 1 lists the formulations of the polycrystalline germanium chemical mechanical polishing liquids 1 to 6 of the present invention, and the polishing liquids of the respective examples are obtained by uniformly mixing the components and their contents given in the table, and the water is the balance.

Effect Example 1 :

Table 2 lists the formulation and polishing effect data of the comparative polishing liquid 1 and the polishing liquid 7 to 36. The polishing liquids of the respective examples are obtained by uniformly mixing the components and their contents in the table, and the water is the balance.

The polishing process parameters were: 3 psi under pressure, 70 rpm for polishing disc (14 inches in diameter), 80 rpm for polishing head, 200 ml/min for polishing fluid, PPG fast pad CS7, and Logitech LP50 polishing machine.

As can be seen from the data in Table 2, compared with the comparative polishing liquid 1, the polishing liquids 7 to 36 of the present invention significantly reduce the removal rate of polycrystalline germanium without lowering the removal rate of cerium oxide, thereby reducing the selection ratio of polycrystalline germanium to cerium oxide. .

Effect Example 2 :

Table 3 lists the formulation and polishing effect data of the polishing liquids 37 to 40. The polishing liquids of the respective examples are obtained by uniformly mixing the components and their contents given in Table 3, and the water is the balance.

Polishing process parameters are: 3psi under pressure, rotating disc (14 inches in diameter) 70 rpm, polishing head speed 80 rpm, polishing liquid flow rate 200 ml/min, polishing pad is PPG fast pad CS7, Logitech LP50 polishing machine.

It can be seen from the data of the polishing liquids 37 to 39 in Table 3 that, in the case where the other components and their contents are the same, the higher the content of the terpene compound, the slightly higher the selection ratio of the polycrystalline germanium to the ceria. It can be seen from the polishing liquid 40 that although the effect of the quinone compound on the selectivity ratio has the opposite effect on the selectivity ratio of the polyol type nonionic surfactant, the degree of influence is much smaller than that of the polyol type nonionic surfactant. The extent of the impact on the selection ratio. Therefore, the polycrystalline cerium/cerium oxide selectivity of the polishing liquid can be adjusted by the content of the polyol type nonionic surfactant and the quinone compound.

Effect Example 3 :

Table 4 lists the composition and polishing effect of the comparative polishing liquid 2~4 and the polishing liquid 41. According to the ingredients and their contents uniformly mixed in the table, each polishing liquid can be obtained, and the water is the balance.

The process parameters during polishing were: 3 psi under pressure, 70 rpm for polishing disc (14 inches in diameter), 80 rpm for polishing head, 200 ml/min for polishing fluid, PPG fast pad CS7, and Logitech LP50 polishing machine.

It can be seen from the data in Table 4 that the polishing liquid 41 has a good polishing effect and reduces metal ion pollution and environmental pollution with respect to the comparative polishing liquid 2 to 4.

Further, the reagents used in the present invention are all commercially available products.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed. Therefore, the scope of the patented scope of the invention should be construed as broadly construed in the

Claims (11)

A chemical mechanical polishing liquid for use in polishing a polycrystalline silicon, characterized in that the chemical mechanical polishing liquid comprises: a polyhydric alcohol type nonionic surfactant; a terpenoid compound; an abrasive particle; and a water, wherein the poly The alcohol type nonionic surfactant is an ester surfactant and/or a polyethylene glycol surfactant formed by esterification of a polyol with a fatty acid, wherein the content of the polyol type nonionic surfactant is 0.0001% by weight. %~20%, wherein the content of the quinone compound is 0.001% to 3% by weight. The use according to claim 1, wherein the ester surfactant is selected from the group consisting of polyol fatty acid ester R ₁ O _m H _mn (OCR ₂ ) _n , polyethylene glycol Fatty acid ester R ₂ COO(CH ₂ CH ₂ O) _p H or R ₂ COO(CH ₂ CH ₂ O) _p OCR ₂ , polyoxyethylene polyol fatty acid ester R ₁ O _m H _mn (CH ₂ CH ₂ O ) _p (OCR ₂ ) _n , where R ₁ (OH) _m is 2 m 8 polyols, 4 p 120, R ₂ COOH is a fatty acid having 8 to 22 carbon atoms, n=1~4 and m n. The application of claim 1, wherein the polyol is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin, polyglycerol. , polyoxyethylene glycerol, pentaerythritol, xylitol, polyoxyethylene xylitol, sorbitol, polyoxyethylene sorbitol, sorbitan, polyoxyethylene sorbitol, sucrose, and polyethylene glycol. The application of claim 1, wherein the polyethylene glycol surfactant has a molecular weight of 200 to 20,000. The application of claim 1, wherein the polyol type nonionic surfactant is present in an amount of from 0.001% to 10% by weight. The application of claim 1, wherein the terpenoid is selected from the group consisting of hydrazine, cesium carbonate, cesium acetate, cesium hydrogen phosphate, guanidine hydrochloride, cesium nitrate, cesium sulfate, and amino groups. Anthracene, aminoguanidine hydrogencarbonate, aminoguanidine sulfonate, aminoguanidine nitrate, and aminoguanidine hydrochloride. The application according to claim 1, wherein the content of the anthraquinone compound is 0.01% to 2% by weight. The application of claim 1, wherein the abrasive particles are selected from the group consisting of cerium oxide, aluminum oxide, aluminum-doped cerium oxide, aluminum-coated cerium oxide, Ceria, titanium dioxide and/or polymer abrasive particles. The application of claim 1, wherein the abrasive particles have a particle diameter of 20 nm to 150 nm. The application of claim 1, wherein the abrasive particles are present in an amount of from 0.5% to 30% by weight. The application of claim 1, wherein the chemical mechanical polishing liquid has a pH of 8 to 12.