JP2002246366A - Post-cleaning method for contact-hole etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an post-cleaning method for a contact-hole etching which uses dry cleaning instead of a wet cleaning. SOLUTION: A wafer has a tungsten metal layer, an oxide layer is formed on the surface of the tungsten metal layer, a photoresist layer is formed on the surface of the oxide layer, and a contact hole for so passing it through the photoresist and oxide layers, so as to expose to the outside a prescribed area of the surface of the tungsten metal layer. In a cleaning method of the wafer, there are performed a photoresist removing step for removing first the photoresist layer, a dry-cleaning applying step for removing thereafter the polymer residuals of the preceding step and for forming a water-soluble component, and water-washing step for so dipping finally the wafer in a pure water as to dissolve the water-soluble compound. As a result, the residuals present in the contact hole are completely removed therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a wafer, and more particularly to a method for cleaning a contact hole after etching.

[0002]

2. Description of the Related Art In the manufacture of semiconductors, which are constantly pursuing finer wiring and higher integration, fine particles (dust) greatly affect the yield of products. In particular, if the residue remaining in the contact hole is not completely removed during the manufacturing process of the contact hole between the metal layers, the quality of the electrical connection between the metal layers must be considerably adversely affected.

FIG. 1 is a sectional view showing the structure of a well-known contact hole, and FIG. 2 is a flowchart of a conventional post-contact cleaning method for contact etching. As shown in FIG. 1, a wafer 10 includes a substrate 12, a metal layer 14 formed on the surface of the substrate 12, an oxide layer 16 formed on the surface of the metal layer 14, and a photoresist layer 18 formed on the surface of the oxide layer 16. Consists of The contact hole 20 formed (defined) by the etching method penetrates through the photoresist layer 18 and the oxide layer 16 to expose a predetermined area on the surface of the metal layer 14.
After the contact holes are formed, post-cleaning is performed.
The post-cleaning method includes a photoresist removing step 22, a wet cleaning step 24, and a water cleaning step 26 as shown in FIG.

The photoresist removing step 22 removes the photoresist layer 18 by a dry etching method in a plasma reactor, that is, removes the photoresist layer 1 through a reaction between hydrocarbons in the photoresist layer 18 and oxygen plasma.
8 is removed by etching. CO, CO ₂ and H ₂ O generated during the reaction are exhausted by suction by a vacuum system.

However, a large amount of polymer residue generated during the removal of the photoresist 18 may be deposited in the contact hole 20 in a large amount. Therefore, it is necessary to perform a wet cleaning step 24 for completely removing the polymer residue by a wet cleaning method. In the conventional wet cleaning method, the wafer 10 is subjected to a predetermined etching solution, for example, ACT (a basic compound manufactured by ACT, USA, trade name: ACT935) under appropriate conditions such as time, temperature and concentration.
) Or EKC (a basic compound manufactured by EKC in the United States, trade name is EKC), and the residue is etched through the reaction between the polymer residue and the etching solution. That is, it is to be removed.

[0006] The last water washing step 26 is a washing with water for wafer 1.
This is for surely removing the etching solution remaining on the periphery of the zero. In this case, in order to completely remove the remaining etching solution, it is necessary to rotate the wafer 10 by 90 ° before immersing the wafer 10 in pure water.

[0007]

However, conventional post-cleaning methods using wet cleaning require certain chemicals, but such chemicals are not only very expensive, but also have scarce resources. For this reason, mass production costs cannot be reduced by the conventional post-process. On the other hand, when the wafer 10 is immersed in the etching solution, it takes time for the etching solution to completely react with the polymer residue. For this reason, the time for performing the cleaning method after the contact etching becomes longer.

An object of the present invention is to provide a post-contact-etch cleaning method using dry cleaning instead of conventional wet cleaning.

[0009]

In order to achieve the above object, the present invention comprises a tungsten metal layer, an oxide layer formed on the surface of the tungsten metal layer, and a photoresist layer formed on the surface of the oxide layer. A method of cleaning a wafer having a contact hole that penetrates the photoresist layer and the oxide layer and exposes a predetermined area of the surface of the tungsten metal layer, wherein a photoresist removing step for removing the photoresist layer is performed first. And then performing a dry cleaning step to remove polymer residues and form a water-soluble compound, and finally immerse the wafer in pure water to dissolve the water-soluble compound. Perform a water wash step. As a result, the residue in the contact hole is completely removed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of an embodiment of the present invention which achieves the above-mentioned objects and solves the problems of the related art will be described in detail with reference to the accompanying drawings.

FIGS. 3 to 6 show a method for cleaning after contact hole etching according to an embodiment of the present invention, and FIG. 7 is a flowchart of a method for cleaning after contact etching according to an embodiment of the present invention.

The present invention provides a method for cleaning a wafer suitable for a post-contact etching cleaning step.
As shown in FIG. 3, the wafer 30 includes a substrate 32 and a substrate 32.
It has a tungsten metal layer 34 formed on the surface, an oxide layer 38 formed on the surface of the tungsten metal layer 34, a photoresist layer 40 formed on the surface of the oxide layer 38, and a contact hole 42. The contact hole 42 is formed by an etching method. In this etching method, the tungsten metal layer 34 is used as an etching stop layer to perform etching so as to penetrate the photoresist layer 40 and the oxide layer 38 to expose a predetermined area on the surface of the tungsten metal layer 34. In forming (depositing) the oxide layer 38, the reaction gas is TEOS.

As shown in FIG. 7, the post-cleaning method of the present invention includes a photoresist removing step 44, a dry cleaning step 46, and a water cleaning step 48.

The first photoresist removal step 44 removes the photoresist layer 40 by dry etching in a plasma reactor, ie, through the reaction of hydrocarbons in the photoresist layer 40 with oxygen plasma, the photoresist layer 4 is removed.
0 is removed by etching. As shown in FIG. 4, when removing the photoresist layer 40, a large amount of polymer residue 50 is generated and remains in the contact hole.

A subsequent dry cleaning step 46 is for removing such polymer residues by dry etching. The operating conditions for this stage are 10-20 seconds,
200-300 ° C, pressure 500mT, microwave about 800W, RF about 800-
100W. In the dry cleaning step of the present invention, CF ₄ and N ₂ H ₂ are used as main reaction gases and inert gas, N ₂ , H ₂
It is important to incorporate the reaction gas by the above method. here,
The ratio of CF ₄ gas to the total reaction gas may be 1 / 2−1 / 6, the flow rate of CF ₄ gas may be 40-200 sccm, and the flow rate of N ₂ H ₂ gas may be 100-500 sccm. As described above, at the same time as removing the polymer residue 50, CF ₄ can react with WO _x to generate volatile gases such as WF ₆ , WF _x , CO, and CO ₂ . On the other hand, N ₂ H ₂ can react with W to form a water-soluble residue 52 (FIG. 5) such as H ₂ O ₄ W, H ₄ H ₂ , H ₂ N ₂ O ₂ , NH _{3 and the} like. . The generated gas is exhausted by suction by a vacuum system.

Finally, a water washing step 48 is performed to remove water-soluble residues 52. In this method, the wafer 30 is directly immersed in pure water, and the water-soluble residue 52 is directly dissolved in pure water. Thus, all the residues in the contact hole 42 are completely removed as shown in FIG.

Although the present invention has been presented as in the above embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications within the spirit and scope of the present invention.

[0018]

As compared with the conventional post-cleaning method, the post-cleaning method of the present invention does not use a very expensive and rare basic solution such as ACT or EKC and can dry-clean a polymer. Since the residue 50 can be removed, the production cost can be significantly reduced. Further, by using the dry cleaning, the removal of the polymer residue 50 is promptly performed, and in the case of the water cleaning, the wafer 10 is not rotated by 90 °, so that the time for performing the post-cleaning method is considerably reduced. . Further, according to the method of the present invention, since the resist removal step and the dry cleaning step are performed in the same environment (in-situ), the photoresist layer 40 is sequentially formed only by adjusting the operating conditions of the plasma reactor. Polymer residue 50
Can be removed. This makes it more convenient to carry out the cleaning method after the contact hole etching.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a well-known contact hole.

FIG. 2 is a flowchart of a conventional post-contact cleaning method for contact etching.

FIG. 3 is a cross-sectional view illustrating a post-contact-hole etching cleaning method (before performing a photoresist removal step) according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a post-contact-hole etching cleaning method shown in FIG. 3 (a state after a photoresist removing step is performed).

FIG. 5 is a cross-sectional view showing a post-cleaning method (after a dry cleaning step is performed) of the contact hole etching shown in FIG. 3;

6 is a cross-sectional view showing a post-contact hole etching post-cleaning method shown in FIG. 3 (a state after performing a water cleaning step).

FIG. 7 is a flowchart of a post-contact etching cleaning method according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 30 wafer 32 substrate 34 tungsten metal layer 38 oxide layer 40 photoresist layer 42 contact hole 44 photoresist removal step 46 dry cleaning step 48 water cleaning step 50 polymer residue 52 water soluble residue

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) H01L 21/768 H01L 21/90 A (72) Inventor Hong-Long Chang Taiwan, Sinchu City, Gin-Quo Lo , Section 3, Number 67, 12 F-1 (72) Inventor Fan-Fai Liu Taiwan, Sing-Chu County, Chiung-Ling Country, Wen-Sun-Lord, Number 363 F-term (reference) 5F004 AA14 DA00 DA01 DA24 DA25 EA13 EB01 FA08 5F033 KK19 QQ07 QQ09 QQ11 QQ15 QQ24 QQ92 QQ96 RR03 SS04 XX09 5F043 AA02 CC16 GG02

Claims (13)

[Claims] A tungsten metal layer, an oxide layer formed on the surface of the tungsten metal layer, and a photoresist layer formed on the surface of the oxide layer, wherein the tungsten layer penetrates the photoresist layer and the oxide layer. A method for cleaning a wafer having a contact hole exposing a predetermined area of a surface of a metal layer, comprising: (a) removing a photoresist for removing the photoresist layer; and (b) reacting CF ₄ and N ₂ H ₂ . A post-contact hole etching post-cleaning method, comprising: a dry cleaning step of performing dry cleaning using gas; and (c) a water cleaning step. 2. The method of claim 1, wherein a flow rate of the CF ₄ gas used in the dry cleaning step is 40-200 sccm. 3. The method of claim 1, wherein the flow rate of the N ₂ H ₂ gas used in the dry cleaning step is 100-500 sccm. 4. The method according to claim 1, wherein the ratio of CF ₄ gas used in the dry cleaning step to the whole reaction gas is 1 / 2−1 / 6. Cleaning method. 5. The post-contact hole etching post-cleaning method according to claim 1, wherein the reactive gas used in the dry cleaning step further includes an inert gas. 6. The post-contact hole etching post-cleaning method according to claim 1, wherein two types of electric power are used in said dry cleaning step. 7. The method according to claim 6, wherein RF power and microwave power are used simultaneously in the dry cleaning step.
4. The method for cleaning after contact hole etching described in 1. 8. The method of claim 7, wherein the RF power is 80-120 watts. 9. The method of claim 7, wherein the microwave power is 700-900 watts. 10. The method as claimed in claim 1, wherein the water cleaning step is performed by immersing the wafer in pure water.
The post-contact hole etching post-cleaning method according to any one of the above. 11. A reaction gas for forming the oxide layer
11. The post-contact hole etching and cleaning method according to claim 1, wherein TEOS is used. 12. The method according to claim 1, wherein the step of removing the resist is a step of performing dry etching.
2. The method for cleaning after contact hole etching according to any one of 1. 13. The post-contact hole etching post-cleaning method according to claim 1, wherein the resist removing step and the dry cleaning step are performed in a similar environment.