JP2005203602A - One set of polishing solution for cmp and method for polishing substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polishing solution for CMP and a polishing method for carrying out high planarization and for suppressing dishing or sinning without lowering a polishing speed at the time of forming the embedded wiring(pattern) of a metallic film by a CMP method. <P>SOLUTION: At the time of forming a conductor embedded wiring in a semiconductor integrated circuit, a first process (1) to polish the deposition film of a conductor to the middle by using first polishing solution containing abrasive grains, an oxidant for oxidizing a conductor, benzotriazol or its dielectric, and a second process (2) for polishing the residual deposition film of the conductor by using a second polishing solution containing the abrasive grains, an oxidant for oxidizing the conductor and a compound having an amino-triazole frame are sequentially performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a set of polishing liquid for chemical mechanical polishing (hereinafter referred to as CMP) and a method for polishing a substrate. More specifically, a conductor film is deposited on a substrate (substrate) in which grooves are formed in advance, and a set of conductor polishing liquids used in the wiring process of a semiconductor device in which conductors are embedded in the grooves, and the conductor polishing liquids are used. The present invention relates to a polishing method for a substrate.

  In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (hereinafter abbreviated as LSI). The CMP method is one of them, and is a technique that is frequently used in the LSI manufacturing process, in particular, the flattening of the interlayer insulating film, the formation of the metal plug, the formation of the embedded wiring in the multilayer wiring forming process (Patent Document 1). reference).

  Recently, copper alloys have begun to be used as wiring materials in place of conventional aluminum alloys in order to improve the performance of LSIs. However, since copper alloy is difficult to be finely processed by the dry etching method used in forming aluminum alloy wiring, a copper alloy thin film is deposited and embedded on a substrate on which a groove has been formed in advance, and the copper alloy thin film other than the groove is CMPed. A method (so-called damascene method) in which buried wiring is formed by removing by the above method is mainly employed. The damascene method is disclosed in Patent Document 2, for example.

A general method for planarizing metal by CMP is to apply a polishing pad on a circular polishing platen (platen), moisten the polishing pad surface with a metal polishing liquid, and press the metal film forming surface of the substrate. In this state, the polishing platen is turned with a predetermined pressure (hereinafter referred to as polishing pressure) applied from the back surface, and the convex portion of the metal film is removed by mechanical friction between the polishing liquid and the convex portion of the metal film. .
The metal polishing liquid used for CMP is usually composed of solid abrasive grains and an oxidizing agent. It is considered that the metal film surface is first oxidized by oxidation and the oxidized layer is scraped off by solid abrasive grains. Since the oxide layer in the concave portion on the metal surface does not touch the polishing pad so much and the effect of scraping with solid abrasive grains does not reach, the metal layer on the convex portion is removed with the progress of CMP, and the substrate surface is flattened (non-patent) Reference 1).

  As one method for increasing the polishing rate in the CMP method, a method is known in which a metal oxide solubilizer composed of aminoacetic acid or amide sulfuric acid such as glycine is blended in the polishing liquid (Patent Document 3). It is described that the metal oxide scraped by the solid abrasive grains is dissolved by the action of the metal oxide solubilizing agent, so that the effect of scraping by the abrasive grains is increased. However, when the oxide layer on the surface of the metal film in the recess is also dissolved (etched) and the surface of the metal film is exposed, the surface of the metal film is further oxidized by the oxidizing agent, and when this is repeated, the etching of the metal film in the recess proceeds. The flattening effect is impaired. In order to prevent this, an etching inhibitor (protective film forming agent) such as benzotriazole is further blended in the polishing liquid (similarly, Patent Document 3). However, in this method, it is not always easy to balance both the metal oxide dissolving agent and the protective film forming agent.

  Further, the applicant of the present invention provides a metal polishing liquid containing a metal oxide solubilizer, an oxidizer, and a compound having an amino-triazole skeleton, and polishing using the same, in order to keep the etching of the metal film low. The method was proposed previously (Patent Document 4).

U.S. Pat. 4944836 JP-A-2-278822 JP-A-8-83780 JP 2003-183628 A Journal of Electrochemical Society, Vol. 138, No. 11 (published in 1991), pages 3460-3464

When a buried wiring is formed by CMP using a conventional CMP polishing liquid, the following problems are likely to occur.
(1) A problem that the central portion of the surface of the embedded metal wiring is isotropically corroded to become a dish-like depression (hereinafter referred to as dishing).
(2) A problem that a decrease (hereinafter referred to as “thinning”) occurs in which the insulating film of the high-density wiring portion is reduced.

  The present invention further develops the CMP polishing liquid and polishing method previously proposed by the present applicant. The object of the present invention is to form a metal film embedded wiring (pattern) by the CMP method. It is to provide a polishing slurry for CMP that can suppress dishing and thinning as well as high flatness without reducing the polishing rate, and to provide a method for polishing a substrate using the same.

[Summary of the Invention]
In order to achieve the above object, the present inventors have made various studies and found the following (i) and subsequently (ii) to complete the present invention.
(I) Polishing copper or a copper alloy with a CMP polishing liquid containing either a compound having an amino-triazole skeleton, a compound having a triazole skeleton not having an amino group, or an imidazole compound in addition to the abrasive grains and the oxidizing agent Then, although the polishing rate was reduced, the occurrence of dishing and thinning was suppressed.
(Ii) Further advance the above knowledge and perform the CMP process.
a) a first step of polishing copper or a copper alloy halfway with a CMP polishing liquid containing benzotriazole or a derivative thereof; and b) a compound or imidazole having a triazole skeleton which may or may not have an amino group. A second step of polishing the remaining copper or copper alloy with a CMP polishing liquid containing the compound;
By dividing into these two steps, the occurrence of dishing and thinning could be suppressed without reducing the polishing rate.

That is, in the present invention, a polishing liquid containing abrasive grains, an oxidizing agent, and benzotriazole or a derivative thereof (protective film forming agent) is used as a first polishing liquid for CMP.
A polishing liquid containing abrasive grains, an oxidizing agent, and a compound having an amino-triazole skeleton is used as the second polishing liquid for CMP.
A set of polishing liquids for CMP in which the two liquids are combined.

Further, the present invention is a polishing method for forming a conductor embedded wiring in a semiconductor integrated circuit,
(1) First polishing a deposited film of a conductor halfway using a first polishing liquid containing abrasive grains, an oxidizing agent that oxidizes a conductor, and benzotriazole or a derivative thereof (protective film forming agent) Process;
(2) polishing the deposited film of the remaining conductor using a second polishing liquid containing abrasive grains, an oxidizing agent that oxidizes the conductor, and a compound having an amino-triazole skeleton (protective film forming agent). Two steps;
A substrate polishing method is also provided, characterized in that the steps are sequentially performed.

[Detailed description of the invention]
The present invention will be described in more detail.
In the present invention, the conductor to be scraped off is a metal film made of a deposited film having at least one metal layer of copper or a copper alloy (copper / chromium or the like).

In the present invention, the abrasive grains used in the first polishing liquid and the second polishing liquid are inorganic abrasive grains such as silica, alumina, ceria, titania, zirconia, germania, silicon carbide, polystyrene, polyacryl, polyvinyl chloride, etc. Although any organic abrasive can be used, colloidal silica and colloidal alumina having an average particle size of 100 nm or less are used in that the dispersion stability in the polishing liquid is good and the number of scratches generated by CMP is small. preferable. Colloidal silica can be produced by hydrolysis of silicon alkoxide or ion exchange of sodium silicate, and colloidal alumina can be produced by hydrolysis of aluminum nitrate.
Further, the concentration of the abrasive grains in the polishing liquid is preferably 0.01% by weight to 10% by weight in both the first polishing liquid and the second polishing liquid, and is in the range of 0.05% by weight to 5% by weight. Further preferred. If it is less than 0.01% by weight, there is no difference from the polishing rate when no abrasive grains are contained, and if it exceeds 10% by weight, the polishing rate is saturated, and adding more than that makes little sense.

In the present invention, the oxidizing agent used in the first polishing liquid and the second polishing liquid includes hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, hypochlorous acid, ozone water, and the like. Hydrogen peroxide is preferred. When the substrate is a silicon substrate including an integrated circuit element, an oxidizing agent that does not contain a nonvolatile component is preferable in order to avoid contamination with alkali metal, alkaline earth metal, halide, and the like. In addition, attention is required because ozone water has a severe compositional change over time. Note that when the substrate to be applied is a glass substrate that does not include a semiconductor element, an oxidizing agent that includes a nonvolatile component may be used.

The blending amount of the oxidizing agent is preferably 0.003 mol to 0.7 mol, more preferably 0.03 mol to 0.5 mol, with respect to the total amount of polishing liquid 100 g in the first polishing liquid. It is especially preferable to set it as 0.1 mol-0.3 mol.
In the second polishing liquid, the amount of the oxidizing agent is preferably 0.003 mol to 0.7 mol, more preferably 0.03 mol to 0.5 mol, with respect to 100 g of the total amount of the polishing liquid. It is especially preferable to set it as 0.05 mol-0.3 mol.
In both cases of the first polishing liquid and the second polishing liquid, if the amount is less than 0.003 mol, the metal oxidation is insufficient and the polishing rate tends to be low, and if the amount exceeds 0.7 mol, the polished surface tends to be rough. become.

In the present invention, the benzotriazole or benzotriazole derivative used in the first polishing liquid has hitherto been widely used in CMP polishing liquids and has a function as a protective film forming agent.
Here, as the benzotriazole derivative, for example, one in which one hydrogen atom of the benzene ring of benzotriazole is substituted with a methyl group (tolyltriazole), one substituted with a carboxyl group (benzotriazole-4-carboxylic acid), There are those in which the hydrogen atom of the carboxyl group is substituted with an ethyl group, a propyl group, a butyl group or an octyl group, or naphthotriazole, naphthotriazole derivatives, and the like.
The blending amount of benzotriazole or benzotriazole derivative (protective film forming agent) in the first polishing liquid is preferably 0.0001 mol to 0.05 mol, and 0.0003 mol to 0 mol with respect to 100 g of the total amount of the first polishing liquid. More preferably, the amount is 0.005 mol, and particularly preferably 0.0005 mol to 0.0035 mol. If it is less than 0.0001 mol, it tends to be difficult to suppress etching, and if it exceeds 0.05 mol, the polishing rate tends to decrease.

In the present invention, the compound (protective film forming agent) having an amino-triazole skeleton used in the second polishing liquid is a compound in which an amino group is bonded to nitrogen of a triazole ring, and preferable ones are 1-amino-1,2, 4-triazole.
The compounding amount of the compound having an amino-triazole skeleton is preferably 0.0001 mol to 0.010 mol, more preferably 0.0003 mol to 0.0050 mol with respect to 100 g of the total amount of the second polishing liquid, It is especially preferable to set it as 0.0005 mol-0.0030 mol. If it is less than 0.0001 mol, it tends to be difficult to suppress etching, and if it exceeds 0.010 mol, the polishing rate tends to be low.

  Here, it is preferable that a compound having a triazole skeleton other than a compound having an amino-triazole skeleton or an imidazole compound is further added to the second polishing liquid as a protective film forming agent.

Examples of the compound having a triazole skeleton other than the compound having an amino-triazole skeleton include 1,2,3-triazole, 1,2,4-triazole, benzotriazole, 1-hydroxybenzotriazole and the like. There is.
Examples of imidazole compounds include 2-methylimidazole, 2-ethylimidazole, 2- (isopropyl) imidazole, 2-propylimidazole, 2-butylimidazole, 4-methylimidazole, 4-ethylimidazole, and 2,4-dimethylimidazole. Or 2-ethyl-4-methylimidazole.

An acid, a water-soluble polymer, or water can be added to the first polishing liquid and the second polishing liquid as necessary.
Examples of acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2 -Methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, Examples thereof include phthalic acid, malic acid, tartaric acid, citric acid and the like, or salts such as ammonium salts of these organic acids, sulfuric acid, nitric acid, ammonia, ammonium salts such as ammonium persulfate, ammonium nitrate, ammonium chloride, and chromic acid. Among these, malic acid, tartaric acid, citric acid or glycolic acid is preferably used in that a practical polishing rate can be obtained.

The amount of acid used in the first polishing liquid is preferably 0 to 0.005 mol, more preferably 0.00005 mol to 0.0025 mol, and more preferably 0.0005 mol with respect to 100 g of the total amount of the first polishing liquid. It is especially preferable to set it to -0.0020 mol.
The amount of acid used in the second polishing liquid is preferably 0 to 0.005 mol, more preferably 0.00005 mol to 0.0025 mol, and more preferably 0.0001 mol with respect to 100 g of the total amount of the second polishing liquid. It is especially preferable to set it to -0.0020 mol. In both cases of the first polishing liquid and the second polishing liquid, if the amount of the acid exceeds 0.005 mol, it becomes difficult to suppress etching.

Examples of water-soluble polymers include polyacrylic acid, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyacrylamide and other monomers having a carboxyl group. And a salt thereof, a polymer having a vinyl group monomer such as polyvinyl alcohol and polyvinylpyrrolidone as a basic structural unit. However, when the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, the water-soluble polymer is preferably polyacrylic acid or ammonium polyacrylate in order to avoid contamination by alkali metal, alkaline earth metal, halide, etc. . Note that this is not the case when the substrate is a glass substrate or the like. The weight average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 1500 or more, and particularly preferably 5000 or more. The upper limit of the weight average molecular weight is not particularly specified, but is preferably 5 million or less from the viewpoint of solubility.
These water-soluble polymers have the effect of forming a protective film that protects the surface of the metal, and in combination with the action of the protective film forming agent (benzotriazole or its derivative), it has flattening properties such as suppression of dishing. It is to improve.

The blending amount of the water-soluble polymer used in the first polishing liquid is preferably 0 to 3% by weight and preferably 0.03% to 1% by weight with respect to 100 g of the total amount of the first polishing liquid. More preferred is 0.1 to 0.8% by weight.
The blending amount of the water-soluble polymer in the polishing liquid used in the second polishing liquid is preferably 0 to 1% by weight with respect to the total amount of the second polishing liquid, and is 0.003% to 0.5% by weight. More preferably, it is particularly preferably 0.01% to 0.1% by weight. In both cases of the first polishing liquid and the second polishing liquid, the polishing rate tends to decrease when the amount of the water-soluble polymer exceeds 1% by weight.

As described above, the substrate polishing method of the present invention is as follows.
(1) First polishing a deposited film of a conductor halfway using a first polishing liquid containing abrasive grains, an oxidizing agent that oxidizes a conductor, and benzotriazole or a derivative thereof (protective film forming agent) Process;
(2) a second step of polishing the deposited film of the remaining conductor using a second polishing liquid containing abrasive grains, an oxidizing agent that oxidizes the conductor, and a compound having an amino-triazole skeleton;
Are performed in order.

  On the substrate side, a recess is provided on the surface, and a metal film containing copper or a copper alloy (copper / chromium or the like) is formed and filled thereon. When this is polished by the polishing method of the present invention, the metal film on the convex portion of the substrate is scraped off, leaving the metal film in the concave portion, and a desired conductor pattern is obtained.

  The polishing of the substrate is performed by supplying the polishing liquid according to the present invention onto the polishing cloth of the polishing surface plate, while pressing the substrate (substrate) having the conductor deposition film against the polishing cloth, relative to the polishing surface plate and the substrate. This can be done by moving the target position.

  In the first step of polishing the copper or copper alloy film halfway in the substrate polishing method of the present invention, the polishing time of the copper or copper alloy film is such that the copper or copper alloy film is removed and the base film or substrate It is preferable to set it as 75 to 95% of the time which a part exposes to the wafer surface, It is more preferable to set it as 80 to 93%, It is especially preferable to set it as 85 to 92%. If the polishing time is less than 75%, the polishing time of the copper or copper alloy film tends to be long in the second step. On the other hand, if it exceeds 95%, dishing and thinning after copper or copper alloy is completely removed in the subsequent second step tends to be large.

  According to the present invention, dishing and thinning as well as high planarization can be suppressed without decreasing the polishing rate when forming a metal film embedded wiring (pattern) by CMP.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
(1) Preparation of first polishing liquid 0.3 parts by weight of colloidal silica (abrasive grains) having an average particle diameter of 20 nm produced by hydrolysis of tetraethoxysilane in an aqueous ammonia solution and benzotriazole (protective film forming agent) 0.29 parts by weight, 0.21 parts by weight of malic acid, 0.57 parts by weight of ammonium polyacrylate (water-soluble polymer), 0.71 parts by weight of methanol, 97.92 parts by weight of water, Stir and mix well. Next, this liquid mixture and hydrogen peroxide (special grade reagent, 30% aqueous solution) were mixed at a weight ratio of 7: 3 to obtain a first polishing liquid.

(2) Preparation of Second Polishing Liquid Similarly, 0.56 parts by weight of colloidal silica (abrasive grains) having an average particle diameter of 20 nm, 0.06 parts by weight of 1-amino-1,2,4-triazole, 2-methyl- 0.22 parts by weight of 4-methylimidazole (protective film forming agent), 0.07 parts by weight of malic acid, 0.02 parts by weight of ammonium polyacrylate (water-soluble polymer), 99.07 parts by weight of water Weighed and stirred and mixed well. Next, this liquid mixture and hydrogen peroxide (special grade reagent, 30% aqueous solution) were mixed at a weight ratio of 9: 1 to obtain a second polishing liquid.

(3) Polishing conditions / Substrate: A groove having a depth of 0.5 μm was formed on the surface of silicon dioxide, and a tantalum nitride film (barrier layer) having a thickness of 50 nm was formed by a known sputtering method. Similarly, a silicon substrate in which a copper film was formed by sputtering and embedded by a known heat treatment was used.
Polishing pad: A foamed polyurethane resin having closed cells was used.
Polishing pressure: 140 gf / cm ²
・ Relative speed between substrate and polishing platen: 100 m / min

(4) Polishing product evaluation method and dishing amount: Polishing using the above-mentioned substrate, and the surface shape of the striped pattern part in which the wiring metal part width of 100 μm and the insulating film part width of 100 μm are alternately arranged by a stylus type step gauge From this, the amount of reduction of the wiring metal part relative to the insulating film part was determined.
Thinning amount: The surface shape of the striped pattern portion having a total width of 2.5 mm in which the wiring metal portion width of 45 μm and the insulating film portion width of 5 μm are alternately formed on the dishing amount evaluation base is measured with a stylus type step meter. The amount of film reduction of the insulating film portion near the center of the pattern with respect to the insulating film field portion around the stripe pattern was determined.

(5) Polishing and results of substrate As a preliminary test, first, the first polishing liquid was used to polish the preliminary substrate until a part of the underlying copper layer was exposed. The polishing time was 82 seconds.
Then, next, the substrate for this test is polished for 74 seconds (90% of 82 seconds in the preliminary test) using the first polishing liquid, and then the remaining copper is completely removed using the second polishing liquid. Polished until The polishing time with the second polishing liquid was 126 seconds. The dishing of this substrate was 50 nm and the thinning was 30 nm. The total polishing time with the first polishing liquid and the second polishing liquid was 200 seconds (3 minutes and 20 seconds).

  For comparison, when polishing was performed using only the first polishing liquid until copper was exhausted, the dishing of the wafer was 120 nm, the thinning was 80 nm, and the polishing time was 160 seconds (Comparative 1).

  Further, when polishing was performed using only the second polishing liquid until copper was exhausted, the dishing of the wafer was 50 nm, the thinning was 40 nm, and the polishing time was 600 seconds (Comparative 2).

  It can be seen that the substrate polishing method of the present invention has better dishing than the polishing method of Comparative Example 1. Further, it can be seen that, compared with the polishing method of Comparative Example 2, both dishing and thinning have the same value, but the polishing time is short.

Claims (6)

A polishing liquid containing abrasive grains, an oxidizing agent, and benzotriazole or a derivative thereof is used as a first polishing liquid for CMP.
A polishing liquid containing abrasive grains, an oxidizing agent, and a compound having an amino-triazole skeleton is used as the second polishing liquid for CMP.
A set of polishing liquids for CMP in which both liquids are combined. The polishing slurry for CMP according to claim 1, wherein the compound having an amino-triazole skeleton is a compound in which an amino group is bonded to nitrogen of a triazole ring. The polishing slurry for CMP according to claim 2, wherein the compound in which an amino group is bonded to nitrogen of the triazole ring is 1-amino-1,2,4-triazole. The polishing slurry for CMP according to any one of claims 1 to 3, further comprising a compound having a triazole skeleton other than a compound having an amino-triazole skeleton, or an imidazole compound. The compound having a triazole skeleton other than the compound having an amino-triazole skeleton is 1,2,3-triazole, 1,2,4-triazole, benzotriazole, or 1-hydroxybenzotriazole. ,
The imidazole compound is 2-methylimidazole, 2-ethylimidazole, 2- (isopropyl) imidazole, 2-propylimidazole, 2-butylimidazole, 4-methylimidazole, 4-methylimidazole, 2,4-dimethylimidazole or 2- The polishing slurry for CMP according to claim 4, which is ethyl-4-methylimidazole. A method of polishing a substrate for forming a conductor-embedded wiring in a semiconductor integrated circuit,
A first step of polishing the deposited film of the conductor halfway using a first polishing liquid containing abrasive grains, an oxidizing agent, and benzotriazole or a derivative thereof;
A second step of polishing the remaining conductor deposited film using a second polishing liquid containing abrasive grains, an oxidizing agent, and a compound having an amino-triazole skeleton;
A method for polishing a substrate, comprising sequentially performing steps.