JPH02152232A - Cleaning - Google Patents

Abstract

PURPOSE:To prevent impurity particles from adhering again without damaging an integrated circuit element by a method wherein, while a substrate to be treated is being held in a first liquid layer, the impurity particles are separated physically from the substrate to be treated and are dissolved in a second liquid layer. CONSTITUTION:A wafer is held inside an apparatus; a liquid of carbon tetrachloride is poured up to the upper part of the wafer; after that, an aqueous solution of HF-HNO3 is poured. Then, an ultrasonic cleaning operation is executed; N2 is blown from a gas introduction port 20; while the N2 is being bubbled, the water is treated for 10 minutes. Then, a drainage port 16 is opened; the aqueous solution of HF-HNO3 in an upper layer is drained; after that, pure water is introduced from a pipe 15; the remaining solution of HF-HNO3 is removed by a cleaning operation by running water; after that, the wafer 14 is taken out. When the number of dust particles on the taken-out wafer 14 are measured, an average of 10 pieces per wafer can be reduced, i.e. the number of fine impurity particles can be reduced to about 1/10 that before a treatment.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a cleaning method for removing impurity fine particles attached to the surface of a substrate to be processed, and for example, for cleaning electronic devices such as semiconductor integrated circuit elements. The present invention relates to a cleaning method effective in the Hakuzo process.

(Prior Art) In the manufacturing process of semiconductor integrated circuit elements, dust adhering to wafers causes a decrease in product performance and yield.

For this reason, the wafer must always be kept clean, but in actual manufacturing processes, it is difficult to completely prevent the attachment of impurity particles.

Among the commonly used cleaning methods, the currently effective method is to dissolve the impurities using a liquid, such as an acid, that is highly reactive or soluble with respect to the impurities. For example, when the impurity is an organic substance, an aqueous solution of hydrogen peroxide and sulfuric acid, an oxide impurity such as 8i0°, an aqueous hydrofluoric acid solution, and an impurity of Si or Al, an aqueous solution of hydrofluoric acid and nitric acid, etc. is a powerful cleaning solution.

However, the silicon wafer during the manufacturing process contains silicon, silicon dioxide, metals such as AI as a wiring material, etc. as constituent materials of the integrated circuit element itself. If these are directly exposed to acid, impurities are removed and at the same time the element itself is also corroded. In particular, since Al has extremely high reactivity with acids, treatment with acids is completely impossible after the wiring process.

In addition, ultrasonic cleaning or mechanical means such as bubbling are used to remove impurity particles from the substrate to be processed, but since the impurity particles that have been removed remain in the processing tank, the same There is a problem in that it re-adheres to the substrate to be processed in the processing tank.

(Problems to be Solved by the Invention) As described above, conventional cleaning methods have the problem that when chemical means such as acids are used, the element itself is corroded, and mechanical means cannot prevent particles from re-adhering. Ta.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a cleaning method that does not damage integrated circuit elements and prevents impurity particles from re-adhering.

[W4 of the invention] (Means for solving the problem) In order to achieve the above-mentioned object, the present invention does not corrode or dissolve the substrate to be treated to which impurity particles have adhered in the processing tank, and eliminates the impurity particles. Forming a separated state of two liquid layers consisting of a first liquid layer having a different specific gravity from the substrate to be treated and a second liquid layer that is difficult to dissolve in the first liquid layer and dissolves the impurity particles. , the impurity particles are physically released from the substrate to be treated while holding the substrate to be treated in the first liquid layer, and are dissolved in the second liquid layer. Provide a cleaning method.

(Function) According to the present invention, the first liquid layer in which the substrate to be treated is held has a specific gravity different from that of impurity particles, so it is in a state where it is easily released from the substrate, and furthermore, It can be completely released by applying a chemical action. The liberated impurity fine particles do not adhere to the substrate to be processed, which is dissolved by the second liquid layer. Moreover, the first liquid layer is
The substrate is not corroded or dissolved, and as mentioned above, there is almost no redeposition of impurity particles to the substrate to be treated.

(Example) The details of the present invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a schematic sectional view of a cleaning device f'ff used in an embodiment of the present invention. ■ is a Teflon cleaning tank,
A carbon tetrachloride liquid layer (12
, 10% HF and 10% HNO as the second liquid layer,
A mixed aqueous solution layer (13) is introduced.

A plurality of silicon wafers α as substrates to be processed are held in the lower carbon tetrachloride liquid layer (13).

The cleaning tank (11) is provided with an inlet α9 for introducing the first and second liquids, and an outlet (11αη) for discharging the first liquid and the second liquid, respectively. The entire cleaning tank α0 is provided inside the ultrasonic cleaning tank 0 seconds.The ultrasonic cleaning tank αe is filled with pure water in order to effectively transmit the ultrasonic waves to the carbon tetrachloride liquid layer (lz). is fulfilled.

In addition, the symbol (■) installed in the cleaning tank circle is a bubbling pipe, which can be used to flow gas such as N7 as needed into the cleaning tank.
ll) is capable of bubbling the liquid inside.

Using this cleaning device, we first attempted to remove impurity particles generated when a plasma CVD 5iO film was deposited on silicon.

These impurity particles are mainly generated during plasma CVD.
The 840° film attached to the inner wall of the chamber of device D has peeled off and adhered to the silicon wafer. In advance, use an optical dust counter to measure the size of 0.3μ.
When the number of impurity fine particles of m or more was measured, an average of 10i of particles were present per 5-inch wafer.

This wafer was held in the apparatus shown in FIG. 1, and after a carbon tetrachloride solution was poured to the top of the wafer, an HF-HNo and aqueous solution was poured. Next, while performing ultrasonic cleaning and N2 bubbling by blowing Nt from the gas inlet 20,
Processed for minutes. Next, open the drain port (1e) and drain the upper layer of HF.
After draining the -HNo and aqueous solutions, pure water was introduced from 15, and the remaining Hl;' and HNO3 solutions were removed by washing with running water, and then the wafer 04 was taken out. As a result of measuring the number of dust on the wafer α side taken out, the number of impurity fine particles was reduced by an average xOM per wafer, that is, about 1710 fi before processing.

Next, an example will be described in which the present invention is applied to the removal of impurity particles attached during dry etching.

FIG. 2 is a cross-sectional view of a process in which an aluminum wiring is formed by dry etching and then an embodiment of the present invention is applied. First, as shown in FIG. 2(a), a 1 μm thick thin film made of Al-8i (1%) alloy was placed on a silicon wafer (not shown) on which a silicon oxide film Qυ was previously formed as an insulating layer. Form by sputter deposition.

Thereafter, as shown in FIG. 2(b), a mask (23) corresponding to the wiring pattern is formed on the Al-8i thin film using a photoresist.

Next, as shown in FIG. 2(C), the thin film is selectively etched by the RIE method. A parallel plate type dry etching device was used for this etching, the gas used for etching was chlorine, the pressure inside the container was 5 Pa, and the density of the high frequency power (13.56 MHz) applied to the cathode was IW.
/a/l. Next, the resist mask was removed by plasma ashing in oxygen gas and observed with a scanning electron microscope. As shown in Figure 2(d), the resist mask was removed perpendicularly from the end of the aluminum wiring (c). It is confirmed that there is a current remnant 241 standing on the ground.

This residual material (241) is made of an insulating material such as Al, O, etc.

Here, this sample was placed in the cleaning tank of the cleaning apparatus shown in FIG. 1, and treated in the same manner as in the previous example. As a result, when the cross section of the sample was observed, as shown in FIG. 2(e), it was confirmed that the residual material (3) had been removed. Also, the AI wiring width and underlying SiO, 7% $30, were not damaged at all.

In this embodiment, the removal of dust generated during plasma CVD and AJ etching has been described above. The impurities generated in these steps are mainly 8i0. and AltO,
or Si, A1, etc., a mixed aqueous solution of hydrofluoric acid and nitric acid is suitable as the second liquid that reacts with or dissolves these materials. When organic impurities are to be removed, a mixture of hydrogen peroxide and 1 sulfuric acid may be used instead of the mixture of hydrofluoric acid and nitric acid.

In addition, in the above embodiment, the first liquid layer is lower than the second liquid layer, that is, the specific gravity is higher, but the first liquid layer has a lower specific gravity than the second liquid layer. The second liquid layer may be used to settle impurity particles released from the substrate to be treated, and the second liquid layer may dissolve the impurity particles.

The present invention is not limited to the above embodiments,
An optimal combination of liquids may be used depending on the type of substrate to be treated and the nature of impurities.

〔Effect of the invention〕

According to the present invention, the substrate to be processed is not corroded by the cleaning liquid, and impurity particles do not re-deposit.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of the cleaning device used in the present invention, Fig. 2 is a schematic sectional view of the cleaning device used in the present invention;
Figures (a) to (d'5) are process cross-sectional views relating to an embodiment of the present invention. 11...Cleaning tank, 12...4 chloride rock liquid layer, 1
3...Aqueous solution layer of HP and HNO, 14...Silicon wafer 1 15...Treatment liquid inlet, 16~...17...Outlet, 18...Ultrasonic cleaning tank, 19. ...Pure water, 20...Gas inlet. Agent Patent Attorney Noriyuki Chika Yudo Hikaru Matsuyama 2 Figure 2, Old

Claims (7)

[Claims] (1) The substrate to be treated with impurity particles attached to it in the processing tank is not corroded or dissolved, and the impurity particles are dissolved in a first liquid layer having a specific gravity different from that of the substrate to be treated, and the first liquid layer. a second liquid layer that is difficult to dissolve and dissolves the impurity particles; and a second liquid layer that is difficult to dissolve and dissolves the impurity particles. A cleaning method characterized in that the substrate is physically separated from the substrate and dissolved in the second liquid layer. (2) The first liquid layer is located above the second liquid layer, and the specific gravity of the first liquid layer is smaller than the second liquid layer and impurity particles. (1) The cleaning method described. (3) The first liquid layer is located below the second liquid layer, and the specific gravity of the first liquid layer is greater than that of the second liquid layer and impurity particles. The cleaning method according to claim (1). (4) The cleaning method according to claim 1, wherein the impurity is silicon, a silicon compound, aluminum, an aluminum compound, or an organic compound. (5) A halogenated carbon liquid and an acid aqueous solution are used as the first and second liquids, respectively (
1) The cleaning method described. (6) The cleaning method according to claim (1), wherein a carbon tetrachloride liquid and a mixed aqueous solution of HF and HNO_3 are used as the first and second liquids, respectively. (7) The cleaning method according to claim (1), wherein the impurity particles are physically released from the substrate to be treated by ultrasonic vibration or bubbling of the first liquid layer.