JP2002105440A - Abrasive and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive and a polishing method permitting improvement in an abrasion speed and prevention of metallic contamination (improvement in qualities of a wafer) as well as polishing at a low cost. SOLUTION: The abrasive contains 0.1-30 wt.% of colloidal silica and with a 6C or higher amine bearing at least two amino groups (for example, 0.001-1 mol/L of 1,6-hexanediamine) added thereto. The polishing method of a wafer comprises pushing a wafer in a held state against the surface of a polishing cloth, supplying the abrasive on the polishing cloth at a specified flow rate and causing the surface to be polished of the wafer to be rubbed against the surface of the polishing cloth via the abrasive, where this abrasive is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an abrasive for polishing silicon wafers and similar materials, and a polishing method using the abrasive.

[0002]

2. Description of the Related Art In general, a method of manufacturing a semiconductor wafer such as silicon has a slicing step of slicing a single crystal ingot to obtain a thin disk-shaped wafer, and preventing a wafer obtained by the slicing step from cracking or chipping. A chamfering step for chamfering the outer periphery thereof, a lapping step for flattening the wafer, an etching step for removing processing distortion remaining on the chamfered and wrapped wafer, and polishing (polishing) for mirror-polishing the wafer surface. ) And a cleaning step of cleaning the polished wafer and removing abrasives and foreign matter adhering thereto.
The above steps show the main steps, and other steps such as a heat treatment step and a surface grinding step are added, or the order of the steps is changed.

In the polishing step, it is desired to mirror-polish the wafer to a high flatness and to improve the polishing ability. As an abrasive used in the polishing step of a silicon wafer, an abrasive mainly containing colloidal silica (SiO ₂ ) is often used. A suspension (slurry) abrasive obtained by diluting the colloidal silica (SiO ₂ ) with water and further adding an alkali is used.

As a method of improving the polishing ability, there is a method of devising an abrasive used for polishing. For example, a silica-based abrasive having a particle size of about 4 to 100 nm is used. If the particle size is increased, the polishing ability is improved. However, as the particle size increases, polishing damage and the like are more likely to occur on the wafer surface.

[0005] As another method, an additive may be added to the above-mentioned abrasive to improve the polishing rate. For example, N- (β-aminoethyl) ethanolamine, ammonia, methylamine, dimethylamine and the like, which are relatively lower alkyl groups having 5 or less carbon atoms, and cyclic compounds such as piperazine are used as additives. May be done.

[0006]

Additives such as N-(. Beta.-aminoethyl) ethanolamine used for improving the polishing rate cause metal contamination in the wafer, particularly Cu.
It has been found to promote pollution. This is because the additive N- (β-aminoethyl) ethanolamine itself is liable to be contaminated, and the contamination of the additive is brought into the slurry and brought into contact with the surface of the wafer for polishing. As a result, the wafer is contaminated. It is possible to do it. Therefore, while improving the polishing rate, a wafer with high flatness was obtained.
In addition, there has been a demand for an additive which is free of metal contamination and inexpensive.

An object of the present invention is to provide a polishing agent and a polishing method capable of improving the polishing rate (improving productivity) and preventing metal contamination (improving wafer quality) and polishing at low cost. And

[0008]

SUMMARY OF THE INVENTION The present invention is an improved abrasive for polishing silicon wafers and similar materials and a method of polishing using the abrasive, the abrasive comprising colloidal silica. And an amine having two or more amino groups and six or more carbon atoms.

It has been found that when an amine is added, the effect of capturing metals (chelating effect) disappears as the number of carbon atoms increases. When the number of carbon atoms is 6 or more, there is almost no chelating effect. Since it has no chelating effect, it can be added to the polishing agent without adsorbing unnecessary metal impurities, and can be polished without polluting the polishing agent. As a result, metal contamination on the wafer is also eliminated. Further, since the amine has two or more amino groups, the polishing rate is also improved. The amine is mainly an aliphatic, branched or linear diamine or polyamine.

In particular, the chemical formula of the amine is H ₂ N—R—N
Preferably diamine represented by H _2. It is preferred that the hydrocarbon chain in the R portion be a chain compound containing at least 6 or more carbon atoms.

As described above, it was found that the effect of capturing metals (chelating effect) disappears when the number of straight-chain carbon atoms in the R portion of the diamine represented by the chemical formula H ₂ N—R—NH ₂ increases. When the number of carbon atoms is 6 or more, there is almost no chelating effect. Since there is no chelating effect, it can be added to the polishing agent without adsorbing unnecessary metal impurities and can be polished without polluting the polishing agent.
It is a preferable additive without causing metal contamination on the wafer. Since the amine has two or more amines, the polishing rate is also improved.

Particularly, the amine is preferably 1,6-hexanediamine. This amine is preferable because it is inexpensive and easy to obtain, and because the amino group has a large amount of hydrogen, the polishing rate becomes higher. Further, since the number of carbon atoms is six or more between amino groups, metal contamination to the abrasive can be reduced.

The abrasive is prepared by adding colloidal silica to pure water at a concentration of 0.1 g.
A dispersion of 1 to 30 wt% is suitably used. The amine of the present invention is added to this abrasive, and the amount of the amine to be added is 1.000 per liter (liter) of the abrasive.
Molar amounts are sufficient. Particularly preferably 0.00
1 to 0.05 mol / L. When the amount is in this range, the polishing rate is improved and metal contamination can be sufficiently prevented.

This abrasive can be used in various polishing apparatuses. In other words, the wafer is pressed against the surface of the polishing cloth while holding the wafer, and at the same time, the abrasive is supplied onto the polishing cloth at a predetermined flow rate, and the polished surface of the wafer is rubbed with the surface of the polishing cloth via the abrasive. If the wafer is polished by polishing, the polishing agent can be suitably used, the polishing can be performed with high flatness, a high polishing rate, and prevention of metal contamination and the like.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Although there is no particular limitation on a polishing apparatus, for example, a polishing apparatus as shown in FIG. 3 is used. FIG. 3 shows an example of a batch-type polishing apparatus. The polishing apparatus A has a polishing platen 30 which is rotated at a predetermined rotation speed by a rotating shaft 37. A polishing cloth P is stuck on the upper surface of the polishing platen 30. 33
Is a work holding plate and a rotating shaft 3 via an upper load 35.
Rotated by 8. The plurality of wafers W are pressed against the surface of the polishing pad P while being held on the lower surface of the work holding plate 33 by bonding means, and are simultaneously passed through an abrasive supply pipe 34 by an abrasive supply device (not shown). The abrasive solution (slurry) 39 is supplied onto the polishing pad P at a flow rate of
Is rubbed against the surface of the polishing pad P, and the wafer W is polished. The basic polishing configuration of a single-wafer polishing apparatus is almost the same as that of a batch polishing apparatus. The major difference from the batch type polishing is that a single-wafer type head is provided at a portion for holding a wafer, and one wafer is held per head for polishing.

In order to improve the polishing ability (polishing speed), an amine having a large number of amino groups is preferable. From this viewpoint, an amine containing two or more amino groups is preferable.

Further, in order to reduce contamination by additives, chelating properties of diamines having different numbers of carbon atoms were confirmed. The confirmed amine was ethylenediamine, 1,3-
Propanediamine, 1,4-butanediamine, 1,5-
Confirmed with pentanediamine and 1,6-hexanediamine.

It was found that when the carbon number was increased to 1,6-hexanediamine, the chelating property was lost and the additive itself did not have metal contamination. If the number of carbon atoms is less than this, the polishing ability is high, but a chelating effect is obtained. If the chelating ability is strong and the metal is not released from the additive itself, there is no problem even if these amines having a small number of carbon atoms are added, but the metal may move to the wafer side during polishing,
If the additive contained metals before the addition, the wafer would be contaminated. When an additive having no chelating effect is used during polishing, that is, when 1,6-
When hexanediamine was polished, it was found that the polished wafer had almost no metal contamination. Thus, a linear amine having 6 or more connected carbon atoms is preferable.

Hereinafter, the present invention will be described with reference to specific examples. As an example of the present invention, 1,6-hexanediamine (Example 1) and, as a comparative example, N having a high polishing ability
-(Β-aminoethyl) ethanolamine (Comparative Example 1) and piperazine (Comparative Example 2) were added.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Colloidal silica (SiO₂) Containing
Polished using a polishing agent. The base abrasive is the entire abrasive
Colloidal silica having an average particle size of 50 nm (Si
O ₂) Is contained at about 2.5 wt% and the pH is adjusted to about 11.
It was done.

(Example 1) A polishing agent was prepared by adding 1,6-hexanediamine to the above-mentioned polishing agent as a base in an amount of 0.007 mol per liter of slurry. The pH at this time was 10.96.

(Comparative Example 1) N was added to the above-mentioned base abrasive.
-Slurry of (β-aminoethyl) ethanolamine 1
An abrasive to which 0.060 mol was added per liter was prepared. The pH at this time was 10.95.

(Comparative Example 2) Piperazine was added to the above base abrasive at 0.085 mol per liter of slurry.
An added abrasive was prepared. The pH at this time was 10.9
It was one.

A silicon wafer having a diameter of 150 mm, which has been subjected to an etching process in a general wafer manufacturing process, was polished using these abrasives. As the mirror polishing conditions,
Although not particularly limited, a silicon wafer is used under a polishing condition of a polishing load (250 g / cm ² ) and a polishing time (10 minutes) by using a polishing pad made of a foamed urethane resin, adding the above polishing agent at a rate of 10 L / min. Was polished.

The flatness of the wafer after being polished by the abrasive to which the above three types of additives were added was all good, and no polishing scratches or the like were generated.

The polishing rate and the state of contamination when these abrasives were used were confirmed. The polishing rate was calculated from the stock removal at the time of polishing for 10 minutes. As the contamination status, metal impurities adhering to the wafer surface after polishing were confirmed. This is VPD-AAS (Vapor Phase Decomposition and Atomic
Absorption spectroscopy). VPD-AAS is a technique in which a natural oxide film on the surface of a wafer is decomposed in gas phase with HF vapor, and at the same time, the decomposed impurities are recovered with a chemical solution such as HCl or HF and quantitatively analyzed by an atomic absorption spectrophotometer.

The results are shown in FIG. 1 and FIG. As shown in FIG. 1, when 1,6-hexanediamine of Example 1 was added, when the polishing rate of N- (β-aminoethyl) ethanolamine of Comparative Example 1 was 100,
There was about a 20% improvement in polishing performance. It can be seen that the polishing ability is improved even when N- (β-aminoethyl) ethanolamine is added as compared with the polishing agent to which nothing is added, but is further improved. Also in Comparative Example 2 to which piperazine was added, the polishing ability was improved by about 17% as compared with N- (β-aminoethyl) ethanolamine.

Regarding contamination (metal impurities) on the wafer surface, copper (Cu), which is particularly problematic when adhered, was observed. As shown in FIG. 2, this metal impurity concentration is about 0.77 × 10 ¹⁰ atoms / c in the first embodiment.
m ² , about 1.8 × 10 ¹⁰ atoms / c in Comparative Example 1.
m ² , about 0.38 × 10 ¹⁰ atoms /
cm ² .

As described above, the polishing rate of Example 1 to which 1,6-hexanediamine was added was 20% higher than that of Comparative Example 1.
It has improved. Further, the contamination of the wafer surface was suppressed to less than half of that in Comparative Example 1. That is, the polishing ability is improved as compared with the conventional additive, and the productivity is increased. In addition, since there is little contamination, it is possible to manufacture a wafer that is stable in quality.

The polishing rate can be improved to the same degree as in Example 1 and contamination of the wafer surface can be prevented by Comparative Example 2 in which piperazine is added. 1,6-hexanediamine provides a high polishing ability with a small addition amount of 0.01 mol / L or less, requires a small addition amount, and is inexpensive, so that the cost of the polishing agent per polishing can be reduced. it can.

[0031]

As described above, by using the abrasive of the present invention, it is possible to improve the polishing rate (improve productivity), prevent metal contamination (improve wafer quality), and perform polishing at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing a polishing rate of an abrasive to which each additive is added.

FIG. 2 is a view showing a metal contamination concentration on a wafer surface after polishing with an abrasive to which each additive is added.

FIG. 3 is a diagram illustrating an example of a polishing apparatus.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Norio Kashimura 150 Ohira, Odakura, Nishigo-mura, Nishishirakawa-gun, Fukushima Prefecture Inside the Shirakawa Plant, Shin-Etsu Semiconductor Co., Ltd. Address Shin-Etsu Semiconductor Shirakawa Plant F-term (reference) 3C058 AA09 AC04 CB03 CB05 CB06 CB10 DA02 DA17

Claims (5)

[Claims] 1. A polishing agent containing colloidal silica, wherein an amine having 2 or more amino groups and 6 or more carbon atoms is added. 2. The abrasive according to claim 1, wherein the amine is a chain compound having a carbon chain containing at least 6 or more carbon atoms. 3. The abrasive according to claim 1, wherein the amine is 1,6-hexanediamine. 4. A colloidal silica of 0.1 to 30.0 w
%, 1,6-hexanediamine 0.001 to 0.001%
The abrasive according to any one of claims 1 to 3, wherein 1.000 mol / L is added. 5. A wafer is pressed against the surface of the polishing cloth while holding the wafer, and at the same time, an abrasive is supplied onto the polishing cloth at a predetermined flow rate. A method for polishing a wafer by rubbing with a polishing agent, wherein the polishing is performed using the polishing agent according to claim 1.