JP2000031117A - Dry cleaning method after metal etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a metal-contaminated resist and sidewall polymer can be removed from a semiconductor device, particularly metallic conductors without using wet chemical solvents nor raising the temperature. SOLUTION: In a dry cleaning method, a resist is provided on a plurality of portions of a metal layer formed on a semiconductor device and the metal layer is etched, and after the remaining metal-contaminated resistor is ashed through reactive ion etching(RIE), downstream type microwave process is performed so as to make the remaining resist easily removable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor processing method and a manufacturing method.

[0002]

2. Description of the Related Art In a manufacturing process of an integrated circuit, metal conductors for electrical connection are formed. To form this metal wire, a metal layer is deposited, the resist is patterned to cover the area of the metal that is to be maintained to form the wire, and then plasma etched.
A plurality of uncoated portions of the metal layer are removed, leaving the metal lines. During plasma metal etching, the sidewall polymer (sidewal
l polymer) is formed. The sidewall polymer should be completely removed to ensure that there is no current leakage between adjacent metal conductors.

[0003] Sidewall polymers are typically cleaned using an active chemical solvent, such as an amine-based solvent, due to heavy metal contaminants. Some degree of alignment between metal leads and via plugs as design rules shrink and aggressive zeroing of metal leads to minimize die size Is inevitable. However, wet chemical based post-etch cleaning is problematic. This is because there may be misaligned metal conductors and the wet chemistry will erode the partially exposed via plugs. In addition, chemical solvents are very expensive to obtain and their disposal is expensive due to environmental regulations.

[0004]

SUMMARY OF THE INVENTION U.S. Pat. No. 5,174,856
Hwang discloses a process that includes a multi-step microwave plasma process at a high temperature (up to 245 ° C.), the process comprising using a fluorocarbon gas. At such high temperatures, stresses occur, erosion of the anti-reflective coating (ARC), such as a titanium nitride (TiN) layer, and additional time and power are required. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for removing metal-contaminated resist and sidewall polymers from semiconductor devices, particularly metal conductors, without using a wet chemical solvent and without raising the temperature. .

[0005]

According to the present invention, there is provided a method of cleaning a residue contaminated with heavy metals remaining after metal etching. This method combines a RIE (Reactive Ion Etching) plasma ashing process followed by a downstream microwave process to ash the contaminated photoresist and remove the residue (at this point, the residue is All are water soluble). No wet chemical stripper, ie no solvent, is required. This eliminates the high cost and environmental and safety issues associated with chemical solvents.

[0006] Following this process, the resulting compounds are usually rinsed off in deionized (DI) water. Since this method is performed at room temperature, the stress on the wafer is small.

[0007] The metal short circuit yield, metal conduction and electrical critical dimension (CD) were all equal to or better than the control wafers treated with wet chemical solvents. Therefore,
The method of the present invention avoids the problem of metal erosion associated with wet chemical cleaning, is less costly than wet cleaning methods, and is safer and more environmentally friendly.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method combining both an RIE plasma ashing process and a downstream type microwave ashing process, comprising a chemically modified and damaged photoresist and sidewall. Includes a method for stripping a polymer.

Referring to FIGS. 1 and 2, a metal layer 10 is formed on a substrate 12 and selected areas are covered with a resist 14 to protect areas of the metal which are to be left after metal etching. Have been done. For example, FIG. 1 shows a number of lines of resist defining a metal conductor. The metal is formed in a single layer or a multilayer, and is a pure metal, an alloy, or a metal compound.

Referring to FIGS. 2 and 3, the metal layer 10 not covered by the resist 14 is etched away using known metal etching techniques such as chlorine-based plasma etching. After this metal etching, the contaminated resist 18 and sidewall polymer 20 remain. The sidewall polymer controlling the contour of the metal wire has a composite form of metal residues such as Ti, W, Al and Cu, depending on the specific metal used and the etching process used.

In order to remove the resist 18 and the contaminated sidewall polymer 20 without oxidizing the metal residue, a low-temperature method is used, preferably at room temperature without applying heat. Generates heat). First, the outer layer hardened by the plasma is removed or at least decomposed using an RIE plasma ashing process. A downstream microwave ashing process is then performed using a small amount of halogen, for example, about 5% NF ₃ (or other halogen) to make the metal-containing compound volatile or water-soluble. The wafer is rinsed in deionized water to remove product compounds, thereby cleaning the wafer.

According to the scanning electron microscope (SEM) analysis,
It has been found that this dry process can remove all of the polymer residue from the metal conductor. It should also be noted that experiments have shown that performing only a downstream microwave process without performing the first RIE process does not normally remove the plasma-modified surface layer at low temperatures. It is. Though it is,
In some cases, residues can be sufficiently removed by simultaneously performing the RIE plasma ashing process and the downstream type microwave process.

The process includes TiN, Al or T
There is an advantage that it does not attack other layers including i. Temperature 5
Above 0 ° C., low temperature treatment is advantageous because fluorine radicals rapidly attack TiN.

Performing a steam passivation process at a high temperature before the ashing process and the cleaning process and after the metal etching, without performing a plasma process, in order to avoid metal corrosion; and / or
Alternatively, it is desirable to perform a deionized water rinse at ambient or elevated temperature. The passivation process and / or the deionized water rinse is performed in a separate chamber.

FIG. 4 illustrates the method of the present invention. The metal is deposited by a known technique such as physical vapor deposition or chemical vapor deposition (100). A resist is patterned on the metal surface by a known photolithography technique (1).
02). Metal parts not covered with resist are removed by a known chlorine-based etching process (10
4). The wafer is then passivated and / or
Alternatively, a rinsing process is performed (106). An RIE ashing process is performed at ambient temperature (108), followed by a downstream microwave ashing process at ambient temperature (110). An example of such a process is provided below.

[0016]

【Example】Example 1 Test behavior of two metal layers 0.25 mm thick
Vehicle is a deep ultraviolet (DUV) cash register for pattern formation
With TiN / AlCu / TiN / Ti
Metal laminated film. The metal is replaced with typical BCl
_Three/ Cl_TwoTCP (Trans-bonded Plas
B) Etching was performed in the reactor. Metal etching
After that, the resist and sidewall polymer are
Process, then downstream microwave process
Therefore, it was removed. Both processes are at ambient temperature
In other words, without applying heat to the wafer support
Done. RIE and microwave processes
The parameters are shown below. RIE plasma ashing Gas flow rate: O_Two, 1000sccm NF_Three, 140 sccm Ar, 120 sccm N_TwoH_Two, 50 sccm Pressure: 0.5 Torr Time: 30 to 90 seconds Power: 200 to 300 W (RF)Downstream microwave Gas flow rate: O_Two, 1000sccm NF_Three, 80sccm N_TwoH_Two, 50 sccm Pressure: 0.5 Torr Time: 15 to 60 seconds Power: 1500 W (μW: microwave) Each of these processes involves heating the wafer at ambient temperature
Made without additions.

The control wafer was a downstream O ₂
Stripped in a microwave ashing apparatus and then cleaned with a hydroxylamine based solvent.

After the metal dry process, the wafer was inspected using an optical microscope and a scanning electron microscope (SEM) to detect any corrosion and to inspect for residual sidewall polymer. Electrical tests for metal wire shorts and metal wire continuity were performed throughout the process steps for the dry treated devices as well as the control group treated with the wet solvent. The dry process is comparable to the solvent control group.

The RIE and microwave processes are preferably performed in a single chamber having a single or double cathode arrangement, as shown in FIGS. 1-4 of US patent application Ser. No. 08 / 731,612. The disclosure of this application is specifically incorporated by reference for all purposes. Example 2 In this example, the first RIE process is as in Example 1 above.
And the parameters of the microwave process are also essentially the same as those of Example 1, but during the downstream microwave process,
Applying RF bias with RF power of 50-200 W,
At the same time, an RF plasma / microwave process was performed. Thus, the microwave process was performed simultaneously in a single chamber in combination with the RF process. No heat was applied and the process could be performed at ambient temperature. Example 3 The process parameters in a further example are given below. RIE plasma ashing gas flow rate: O ₂ , 50 to 100 sccm Pressure: 0.05 to 0.2 Torr Time: 30 to 90 seconds Power: 300 to 650 W (RF) Downstream type microwave gas flow rate: O ₂ , 700 to 1500 sccm NF ₃ , 50 to 150 sccm N ₂ H ₂ , 0 to 100 sccm Pressure: 0.3 to 0.7 Torr Time: 15 to 60 seconds Power: 1500 W (μW: microwave) The microwave processing step is performed by applying an RF bias or It can be performed without multiplication, and the parameters are the same as those in the first and second embodiments. The RIE process, to lower the pressure, while increasing the power, please note that gas using only O _2.

The embodiment has been described above.
It can be done with parameters and gas flow rates within the following ranges: RIE plasma ashing gas flow rate: O ₂ , 700 to 1500 sccm NF ₃ , 100 to 200 sccm Ar, 0 to 200 sccm N ₂ H ₂ , 0 to 100 sccm Pressure: 0.3 to 0.7 Torr Power: 100 to 400 W (RF) downstream -Type microwave gas flow rate: O ₂ , 700 to 1500 sccm NF ₃ , 50 to 150 sccm N ₂ H ₂ , 0 to 100 sccm Pressure: 0.3 to 0.7 Torr Therefore, the present invention provides a metal-contaminated residue after plasma etching. A dry process that combines an RIE process with a downstream microwave process to clean the substrate. After this dry process, a wet stripper is no longer needed, thus eliminating the metal erosion problems associated with wet strippers. further,
Wafer processing costs are reduced because no expensive wet solvent processing steps are required.

[Brief description of the drawings]

FIG. 1 is a plan view of a metal layer having a patterned resist layer.

FIG. 2 is a cross-sectional view of a metal film provided with a patterned resist layer.

FIG. 3 is a cross-sectional view of a metal wire after etching in which a resist and a sidewall polymer remain.

FIG. 4 is a flowchart of the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal layer 12 Substrate 14, 18 Resist 20 Sidewall polymer

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Mohammed Boumerzog, New Hampshire, USA 03060 Nashua Atherton Avenue No. 4,11

Claims (14)

[Claims] A metal layer is formed on a semiconductor device, a resist is provided on a plurality of portions of the metal layer, and the metal is patterned such that the patterned metal and the metal-contaminated resist remain on the device. And performing a reactive ion etching (RIE) ashing process to ashing at least a portion of the metal-contaminated resist;
A method of processing a semiconductor device, wherein a downstream type microwave process is performed after the RIE ashing process to make any resist residue water-soluble. 2. The method according to claim 1, wherein the RIE process and the downstream microwave process are each performed without applying heat. 3. The method for processing a semiconductor device according to claim 1, wherein RF power is applied during the downstream type microwave process. 4. The method according to claim 2, wherein the RIE process is performed at an ambient temperature. 5. The method according to claim 2, wherein the RIE plasma ashing process is performed at room temperature. 6. The method of claim 2, wherein the downstream microwave ashing process is performed at room temperature.
The processing method of the semiconductor device according to the above. 7. The method according to claim 1, wherein said etching is a chlorine-based plasma etching. 8. The method according to claim 1, wherein the RIE process is performed using O ₂ but not using a halogen-containing gas. 9. The RIE process, together with O ₂ ,
2. The method for processing a semiconductor device according to claim 1, wherein the method is performed using a halogen-containing gas. 10. The method according to claim 9, wherein the halogen-containing gas is NF ₃ . 11. The method according to claim 8, wherein after said etching, said R
The method according to claim 1, further comprising performing steam passivation at a high temperature before performing the IE process. 12. After the etching, the R
2. The method according to claim 1, further comprising rinsing in deionized water before performing the IE process. 13. RIE at ambient temperature to remove metal-contaminated resist without using a wet solvent.
A stripping method after metal etching, comprising a step of performing a process and a downstream type microwave ashing process. 14. The method of claim 13, wherein the downstream microwave ashing process is performed using an RF power source to form a microwave / RF plasma combination. .