JPH11224877A - Substrate processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the metallic pattern of an aluminum group from being corroded later, due to halogenicgas in dry-etching and ashing. SOLUTION: After dry-etching process or ashing processing of a metal layer M on a substrate 2, washing is perfumed by the weak acid and strong alkali salt solution 31 of sodium carbonate or potassium carbonate or the like, so that chlorine and the chloride of aluminum remaining after the dry-etching process are turned into a stable compound with a strong alkali component and washed away. Thus, a metallic paten is not corroded by cleaning, H<+> ions and Cl<-> ions act around the surface of the substrate at the time of other post- proceedings and handling thereafter, the corrosion of the metallic pattern by the aluminum or an aluminum alloy or the like is avoided by the combination and the quality and yield of a product are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a substrate after a metal dry etching step performed for manufacturing a semiconductor, forming a thin film circuit, or the like.

[0002]

2. Description of the Related Art One method of selectively etching a metal thin film layer made of aluminum or an aluminum alloy or a multilayer conductor including an aluminum alloy layer formed on a substrate to form a desired metal pattern is as follows. Cl ₂ ,
There is a dry etching method using a halogen gas such as BCl _3, which has been conventionally performed. There are various types of metal patterns to which this is applied, such as various wiring patterns of electric circuits formed on the surface of a semiconductor wafer, or high-density comb patterns for forming electronic components such as SAW filters.

In the etching, a metal thin film is selectively covered with a resist layer which is an etching-resistant layer so as to leave a desired metal pattern, so that a portion of the metal thin film which is not covered with the resist layer is selectively removed. Since the resist layer that selectively covers the metal thin film remains on the formed metal pattern even after the etching step and becomes unnecessary, a resist removing process for removing the unnecessary resist is also performed. This is a so-called ashing process.

The ashing process is generally performed by a method using plasma containing oxygen gas or fluorine gas.

[0005] Residues that are not removed after dry etching or ashing may remain, and chemical cleaning or cleaning with pure water is appropriately performed.

[0006]

However, in the above-described conventional post-treatment, the metal pattern sometimes corrodes later. This is so-called after-corrosion, and in some cases, the metal pattern may be disconnected. In this regard, the present inventors repeated various experiments and made repeated studies.

What has been found will be described with reference to a dry etching process showing one example of the embodiment of the present invention shown in FIG. The chlorine gas Cl ₂ or the aluminum chloride used in the dry etching step shown in FIG. 5A is formed by the metal pattern MP formed in the dry etching step or the resist thereon as shown in FIG. 5B. PR and remains on the surface of the wafer 2 or the like, which is an example of a substrate carrying the PR, which is exposed to the air during the above-mentioned post-processing operation procedure or after handling. To produce H ⁺ ions and Cl ⁻ ions, which act to melt the aluminum or aluminum alloy forming the metal pattern MP.

[0008] After-corrosion starts after a certain period of time in accordance with the environment in which the adhered and remaining chlorine or aluminum chloride comes into contact with the moisture in the atmosphere. Causes a decline.
FIG. 7 shows a state of the metal pattern MP when the wafer 2 from which the resist has been stripped after the dry etching step is left in the air for 52 hours without being subjected to a cleaning process. Metal pattern MP
Is a SAW filter pattern shown in FIG. 7A by multiplying 20 times, and by multiplying it by 400, the corrosion spreads over a wide area as shown in the wiring pattern MP shown in FIG. Seen in each part. After the resist is peeled off after the dry etching step, the wafer 2 is washed with pure water and then exposed to the air.
FIG. 8 shows the state of the metal pattern MP when left for a long time by 400 times. Again, corrosion is seen.

An object of the present invention is to provide a substrate processing method capable of preventing a metal pattern made of aluminum or an aluminum alloy from being corroded later due to halogen in dry etching for forming the metal pattern.

[0010]

In order to achieve the above-mentioned object, a substrate processing method of the present invention comprises etching a metal layer made of aluminum or an aluminum alloy on a substrate with a halogen gas to form a desired metal pattern. The main feature is that after the dry etching or ashing step to be formed, washing is performed with an aqueous solution of a weakly acidic strong alkali salt such as sodium carbonate or potassium carbonate.

In such a configuration, the weak acid strong alkali salt becomes weakly alkaline in the aqueous solution, but aluminum or aluminum alloy formed in the dry etching step,
Alternatively, it hardly reacts with the metal pattern composed of other metals, and therefore does not dissolve it.While acting as washing water in the entire aqueous solution, the metal pattern, the resist thereon, and the surface of the substrate carrying them are exposed. Stable sodium chloride (NaCl) and potassium chloride (KC) are formed by combining strong alkali components such as sodium and potassium in the weak acid strong alkali salt aqueous solution with respect to the remaining chlorine.
It dissociates as 1 and is washed away as a mixture in an aqueous solution. Therefore, this cleaning does not corrode the metal pattern, and does not cause chlorine or aluminum chloride to be combined with atmospheric moisture around the surface of the substrate during other post-processing and handling. H ⁺ ions and Cl ⁻ ions due to such a compound can be prevented from corroding a metal pattern made of aluminum or an aluminum alloy, and the quality and yield of a product are improved.

The resist removal treatment for removing unnecessary resist remaining in the dry etching process by using a plasma containing an oxygen gas or a fluorine gas may be performed before or after the cleaning. Generally, the cleaning is performed after the ashing process. It is preferable that the cleaning process is performed promptly, and after the ashing process, it is ideal to proceed to the cleaning process without exposure to the air.

After washing with an aqueous solution of a weakly acidic strong alkali salt, it is preferable to further wash with pure water to remove residues.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the substrate processing method according to the present invention will be described below with reference to the drawings.

The substrate processing method according to the present embodiment uses
This is an example of a case where a metal pattern, particularly, a high-density wiring pattern of an electric circuit or a high-density comb pattern of an electronic component such as a SAW filter is formed on a semiconductor wafer. The metal pattern is a metal layer made of aluminum or an aluminum alloy, or a metal multilayer film containing aluminum. Aluminum alloy is, for example, AlSi,
AlCu, AlSiCu and the like.

The dry etching step for forming a metal pattern is performed, for example, in the reaction chamber 1 of the dry etching apparatus shown in FIGS. A well-known load lock chamber 3 for loading and unloading the wafer 2 while blocking the wafer 2 from the outside is arranged adjacent to the reaction chamber 1. Prior to dry etching, the reaction chamber 1 is evacuated through a vacuum exhaust line 4. The wafer 2 in the load lock chamber 3 is carried into the reaction chamber 1 after evacuation.

In this state, the reaction chamber 1 is supplied with the halogen gas Cl ₂ through the gas supply line 5 and the high frequency is applied through the first and second electrodes 6 and 7. Thus, the halogen gas C supplied into the reaction chamber 1
l ₂ is turned into plasma and acts as shown in FIG. 5A on the metal layer M shown in FIG. 5 which is a schematic diagram of the dry etching and post-processing of FIG. A portion selected by PR is etched as shown in FIG. 5B to form a predetermined metal pattern MP.

After the dry etching step, the metal pattern MP and the resist PR, and the wafer 2 carrying these
As shown in FIG. 5B, the surface of a substrate such as
₂ and aluminum chloride adhere and remain. For this reason, if post-treatments such as ashing and various cleanings after the dry etching process and various handlings are performed in the conventional manner, the chlorine Cl ₂ or aluminum chloride may be removed during the subsequent processing procedure or by the subsequent handling. When an object comes into contact with the atmosphere, it reacts with the moisture in the atmosphere to react with H ⁺
Ions or Cl 2 ^- ions are generated, and this is the metal pattern M
After-corrosion occurs in which aluminum or an aluminum alloy forming P is melted, and in some cases, a disconnection state is caused.

In order to prevent this, in the present embodiment, after the dry etching step and the ashing step, the wafer 2 is subjected to a weak acid strong alkali salt aqueous solution 31 such as sodium carbonate or potassium carbonate as shown in FIG. Wash with For this cleaning, for example, if a conventionally used spin rinser 8 is used, a special device is not required, and the cleaning can be performed uniformly and in a short time by rotating the wafer 2 by the spinner 8a.

For this purpose, the wafer 2 after the dry etching step and the ashing step is carried out through the load lock chamber 3 and transferred to the spin rinser 8 in the rinser chamber 19, and is supplied through the rinse liquid supply line 9 as shown in FIG. , An aqueous solution 31 of a weakly acidic and strongly alkaline salt is supplied onto the wafer 2. However, the spin of the wafer 2 is not indispensable. Basically, with respect to the substrate on which various metal patterns MP such as the wafer 2 are formed by dry etching using a halogen gas and ashing processing by a plasma containing an oxygen gas, and carried. Any cleaning means other than the spin rinser 8 may be used as long as it can supply and wash the weak acid strong alkali salt aqueous solution 31. In the spin rinser 8, first, the substrate is washed with the above-mentioned weakly acidic strong alkali salt aqueous solution 31, and then the supply liquid is switched to pure water W to remove the residue. Then, the supply of the pure water W is stopped and the substrate is rotated at high speed. Allow to dry.

The weakly acidic strong alkaline salt aqueous solution 31 becomes weakly alkaline and hardly reacts with the metal pattern MP formed of aluminum or an aluminum alloy formed in the dry etching step, so that it does not dissolve and is washed with the entire aqueous solution. Work as water. On the other hand, in the washing process with the weakly acidic strong alkaline salt aqueous solution 31, the strong alkaline components such as sodium and potassium in the weakly acidic strong alkaline salt aqueous solution 31 are removed by the metal pattern MP and the resist P thereon.
R and the remaining chlorine Cl ₂ adhering to the surface of the wafer 2 carrying them are combined to form stable sodium chloride NaCl or potassium chloride KCl, which is represented by NaCl in FIG. And is washed away as a mixture in the aqueous solution 31.

Accordingly, the metal pattern M
P does not corrode, and chlorine Cl ₂ and aluminum chloride do not combine around the surface of the wafer 2 with atmospheric moisture during other subsequent processing and handling. H ⁺ ions and Cl ⁻ ions due to the metal pattern MP made of aluminum or an aluminum alloy can be avoided, and the quality and yield of products can be improved. CO ₂ generated by the dissociation of the sodium chloride NaCl and the potassium chloride KCl is diverged and does not cause any particular problem.

In one embodiment, an aqueous solution containing about 1% by weight of sodium carbonate or potassium carbonate was used as the weakly acidic strong alkali salt aqueous solution 31, and the above-mentioned washing was performed. The pH value of this aqueous solution is around 11.5 even if the concentration is variously changed to 50: 1 or 100: 1.

FIG. 6 shows a 400 times magnification of the state of the metal pattern MP when the wafer 2 after the cleaning with the weakly acidic and strongly alkaline aqueous solution 31 is left in the air for 52 hours. As can be seen from FIG. 6, no corrosion is observed in the wiring pattern MP.

The weak acid strong alkali substance is not limited to sodium carbonate or potassium carbonate, but may be any combination of a weak acid component and a strong alkali component as long as they have the same function. Alternatively, the strong alkali component may not necessarily act alone to dissociate by being combined with chlorine, and the case where the strong alkali component is achieved with the aid of another component is also included in the scope of the present invention.

In the embodiment of FIG. 5, as shown in FIG. 5D, unnecessary portions of FIG.
An ashing process for removing the resist PR shown by the phantom line by the oxygen gas O ₂ plasma as shown by the solid line in FIG. 5D is performed after the cleaning shown in FIG. 5C. However, the order of these operations may be reversed as performed in the above-described steps, and in any case, washing with the weakly acidic strong alkali salt aqueous solution 31 is effective, and almost the same operation and effect are exhibited.

The cleaning with the weakly acidic strong alkaline salt aqueous solution 31 is performed after the dry etching step and the metal pattern MP.
The time during which the corrosion of the steel does not start or the conditions under which the corrosion does not start may be set as appropriate depending on post-treatment conditions, environmental conditions, and the like.

The above-described dry etching step and post-processing operation may be performed by any apparatus.
In the example of the dry etching apparatus shown in FIGS. 1 to 4 of the present embodiment, the inert gas is inactive before and after the dry etching in the reaction chamber 1 and the weakly acidic strong alkaline salt aqueous solution 31 in the spin rinser 8 provided in the rinser chamber 19. Since the rinser chamber 19 is purged with nitrogen through the load lock chamber 3 purged with nitrogen as a gas, the wafer 2 is prevented from coming into contact with the atmosphere.
Corrosion of the metal pattern MP due to oxygen is also eliminated. This dry etching apparatus handles wafers 2 stored in a wafer cassette 21. In order to supply the wafer 2 before the dry etching process or to store the wafer 2 after the dry etching process and the post-processing, the wafer vertically moving table 24 is
The wafers 2 are transferred to and from the load lock chamber 3 via the interface, and the wafers 2 before dry etching are supplied to the load lock chamber 3 and the wafers 2 after the dry etching and post-processing are removed from the load lock chamber 3. Perform storage.

Each of the reaction chamber 1 and the load lock chamber 3 has vacuum evacuation lines 4 and 10 for evacuating, and each of the load lock chamber 3 and the rinser chamber 19 has a nitrogen purge for purging nitrogen as an inert gas. Lines 25, 26
Is connected, and a drain pipe 19 is provided at the bottom of the rinser chamber 19.
a is connected. The rinsing liquid supply line 9 is connected to the rinsing nozzle 8b of the spin rinser 8, so that the weakly acidic and strongly alkaline aqueous solution 31 can be supplied.

The first and second electrodes 6 and 7 of the reaction chamber 1 are provided above and below the reaction chamber 1 as an example. However, the arrangement relation can be freely set. The first electrode 6 arranged at the lower part is used as a mounting table for the wafer 2, and is provided with a push-up pin 11 inserted from below. The push-up pin 11 is connected to a vertical shaft 12 below the first electrode 6.

An elevating fork 14 is supported by a support 13 provided alongside the vertical shaft 12 so that the fork 14 can be rotated halfway by a shaft 15. The lifting fork 14 is driven by an arm drive mechanism 46 to move the vertical shaft 12 up and down via the groove fitting 15. The arm driving mechanism 46 also vertically moves the wafer vertical moving table 24 via a lifting and lowering fork 37 supported on a column 35 so as to be rotatable in the middle by a shaft 36 and a vertical moving shaft 38.

The structure of the ashing chamber 50 will be described with reference to FIG. The lower structure of the ashing chamber 50 has a configuration similar to that of the reaction chamber 1 in the dry etching process. The difference is that a heater 54 is arranged in the mounting table 53 for the wafer 2 and the mounting table 5
No high frequency is applied to 3. A quartz cylinder 55 is provided above the ashing chamber 50, and a gas supply line 51 is connected to an upper end thereof, and an ashing gas mainly composed of oxygen is supplied. A pair of electrodes 56 and 57 are arranged on the outer periphery of the quartz cylinder 55, and a structure is used in which a high frequency is applied between them.

In the load lock chamber 3, there are provided a double arm having an upper arm 16 and a lower arm 17, and joint mechanisms 16a and 17a for moving them forward and backward in a specific horizontal direction. The upper and lower arms 16 and 17 are individually mounted on upper ends of shafts 32 and 33 penetrating the vacuum seal bearing 18 and are connected to the arm driving mechanism 46 located below the vacuum bearing 18. The arm driving mechanism 46 includes the arm turning mechanism 3
4 to perform various arm operations.

The spinner 8a of the spin rinser 8 sucks and holds the wafer 2 by evacuation, is driven to rotate by a motor 41, and is supported by a shaft 42 attached to the spinner 8a so as to be rotatable halfway by a shaft 43. The arm drive mechanism 4 is moved via the lifting fork 44
6 to move up and down. Thereby, the wafer 2
While rotating and moving up and down, the weakly acidic strong alkali salt aqueous solution 31 is supplied from above from the rinsing nozzle 8b so as to be more effectively cleaned than in the stationary state.

The operation of the thus-configured apparatus for performing dry etching, ashing, and cleaning will now be described. In FIG. 1, first, the wafer 2 taken out of the wafer cassette 21 of the cassette elevating device 22 is loaded into the double arms 16 and 17 after the load lock chamber 3 is brought into the atmospheric pressure state.
Is carried into the load lock chamber 3. Thereafter, evacuation of the load lock chamber 3 is started through the evacuation line 10. After evacuation of the load lock chamber 3, the wafer 2 in the load lock chamber 3 is carried into the reaction chamber 1 by the double arms 16 and 17. Then, an etching gas of a chlorine-based gas is injected into the reaction chamber 1 through the gas supply line 5, and a high frequency is applied to the first and second electrodes 6, 7 to start plasma etching. The wafer 2 after the completion of the etching is returned to the load lock chamber 3 by the double arms 16 and 17.

Subsequently, the wafer 2 is placed on the double arms 16, 1
7 and carried into the ashing chamber 50 shown in FIGS. After the interior of the ashing chamber 50 is evacuated by the vacuum exhaust line 52,
A gas containing oxygen and fluorine as main components is introduced from the gas line 51 into the inside thereof, a high frequency is applied to the electrodes 56 and 57, and the assembling of the resist PR is started by the downflow gas. After the ashing, the wafer 2 is moved to the double arm 1
The load lock chamber 3 is returned to the body pressure by returning to the load lock chamber 3 through steps 6 and 17, and then the inside of the load lock chamber 3 is purged with nitrogen through a nitrogen purge line 26. During continuous processing, replacement of the wafer 2 after the completion of etching in the reaction chamber 1 is performed simultaneously by the double arms 16 and 17.

The wafer 2 after the ashing step is carried into the rinser chamber 19 by the double arms 16 and 17. Further, nitrogen is blown through the nitrogen purge line 25 so that moisture does not flow into the load lock chamber 3 through the gate when the wafer 2 is transferred. Then, if there is a wafer 2 in the rinser chamber 19, the wafer 2 is replaced by the double arms 16 and 17. The arm on which the wafer 2 before cleaning is mounted stops in the rinser chamber 19, the spinner 8a rises, and the wafer 2 is mounted on the spinner 8a, leaves the arm, and returns to the load lock chamber 3. And spinner 8
a descends and sucks the wafer 2 while evacuating the wafer 2. In this state, while the spinner 8a rotates to supply the weakly acidic strong alkali salt aqueous solution 31 to the rinse nozzle 8b through the rinse liquid supply line 9, the rinse nozzle 8b swings left and right, and the wafer 2 that rotates and moves up and down moves from above to below. The cleaning is performed by pouring the weakly acidic strong alkali salt aqueous solution 31, and the chlorine and aluminum chloride on the surface of the wafer 2 are dissolved by chemical cleaning, that is, by the chemical mechanism as described above. After the cleaning, the wafer 2 is rotated at a high speed, and dried by a nitrogen purge through a nitrogen purge line 26 while shaking off a weakly acidic strong alkali aqueous solution 31 containing HCl or the like generated by the chemical cleaning. In the rinser chamber 19 after the cleaning, the wafer 2 after the cleaning and the wafer 2 before the cleaning are exchanged between the load lock chamber 3 and the wafer 2 by the double arms 16 and 17. The washed wafer 2 is placed in a cassette elevating device 23.
In the wafer cassette 21.

Further, in the cleaning step, the final cleaning is performed by supplying pure water W from the branch line 9a to the rinsing nozzle 8b through the rinsing liquid supply line 9, and the drying step is performed. Can be washed away, which can contribute to stabilization of characteristics of a semiconductor manufactured by the wafer 2.

[0039]

According to the substrate processing method of the present invention, the weakly acidic strong alkali salt aqueous solution is chemically and chemically bonded to a metal pattern formed of aluminum, an aluminum alloy, or a multilayer conductor containing aluminum formed in the dry etching step and the ashing step. The metal solution and the resist on it, and the remaining halogen and aluminum chloride adhering to the surface of the substrate carrying them, while acting as washing water in the entire aqueous solution without dissolving the metal by reacting with Since the strong alkali component dissociates into a stable compound and is washed away as a mixture in an aqueous solution, the metal pattern is not corroded by washing, and H is formed around the surface of the substrate during other post-processing and handling.
⁺ Ions and Cl ⁻ ions can be activated to prevent the combination thereof from corroding a metal pattern made of aluminum or an aluminum alloy, thereby improving product quality and yield.

[Brief description of the drawings]

FIG. 1 is a plan view showing a dry etching apparatus for realizing a dry etching method according to an embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a reaction chamber and a load lock chamber of the apparatus of FIG.

FIG. 3 is a longitudinal sectional view of a load lock chamber and a rinser chamber of the apparatus of FIG. 1;

FIG. 4 is a longitudinal sectional view of an ashing chamber of the apparatus of FIG.

FIG. 5 is a schematic diagram sequentially showing a series of steps of dry etching and post-processing in the embodiment of the present invention.

FIG. 6 is a plan view showing a result of an after-corrosion test according to one embodiment of the present invention, which is a metal pattern enlarged by 400 times.

FIG. 7 is a plan view of a metal pattern showing an after-corrosion test result in a case where the metal pattern is left without washing after completion of the dry etching step, in which (a) is a figure magnified 20 times and (b) is a figure magnified 400 times. is there.

FIG. 8 is a plan view showing a result of an after-corrosion test in a case where the metal pattern is washed with pure water and allowed to stand after completion of the dry etching step, which is 400 times as large as a metal pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Wafer 5 Gas supply line 6, 7, 56, 57 Electrode 8 Spin rinser 8b Rinse nozzle 9 Rinse liquid supply line 9a Branch line 19 Rincer chamber 26 Nitrogen purge line 31 Weak acid strong alkali salt aqueous solution 50 Ashing chamber M Metal layer MP metal pattern PR resist W pure water

Continued on the front page (72) Inventor Ichiro Nakayama 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A method according to claim 1, wherein the metal layer on the substrate is etched with a halogen gas to form a desired metal pattern, followed by washing with a weakly acidic aqueous solution of a strong acid such as sodium carbonate or potassium carbonate. Substrate processing method. 2. The method for processing a substrate according to claim 1, wherein the substrate is washed with a weak acid strong alkali salt aqueous solution and then with pure water. 3. After a dry etching step of etching a metal layer made of aluminum or an aluminum alloy on a substrate with a chlorine-based gas to form a desired metal pattern, an aqueous solution of a weak acid strong alkali salt such as sodium carbonate or potassium carbonate is added. A substrate processing method characterized by sequentially cleaning with pure water. 4. The substrate processing method according to claim 1, wherein before or after the cleaning, a resist removing process of removing unnecessary resist remaining in the dry etching step by using a plasma containing oxygen gas. . 5. The substrate processing method according to claim 1, wherein the cleaning is performed in a cleaning chamber filled with an inert gas.