JPH03133127A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a pattern from being corroded and to prevent a reduction in the electrical characteristics of the pattern from generating in a pattern formation process for removing a resist by an ashing by a method wherein prior to the ashing, a halogen compound remaining in a dry etching process is removed in such a way as to introduce nitrogen monoxide in a device. CONSTITUTION:A resist is applied on a semiconductor substrate with a thin film formed thereon, a window opening is formed in the resist by a selective exposure and a developing treatment, a dry etching is performed using halogen gas as an etchant and after the thin film on a part, in which the window opening is formed, is removed, the resist is removed by an ashing. Prior to this ashing, nitrogen monoxide is introduced in a device and a halogen compound remaining in a dry etching process is made to react with nitrogen gas monooxide and is removed as volatile halogenated nitrosyl. Thereby, the formation of a pattern, which is not accompanied by corrosion due to adsorbed gas, accordingly, is not reduced in electrical characteristics, becomes possible.

Description

[Detailed Description of the Invention] [Summary] In order to eliminate corrosion caused by adsorbed gas in the process of forming patterns on semiconductor substrates, a resist is coated on the semiconductor substrate on which a thin film has been formed, and then selective exposure and development are performed. In the pattern forming process in which a window is opened in the resist, dry etching is performed using a halogen-based gas as an etchant, and the thin film in the window-opened area is removed, the resist is removed by ashing. A method for manufacturing a semiconductor device is characterized in that nitrogen oxide is introduced.

[Industrial Field of Application] The present invention relates to a method for manufacturing a semiconductor device that is corroded by adsorbed gas.

Thin film formation technology and photolithography (photolithography or electron beam lithography) are frequently used in the manufacture of semiconductor devices.

That is, a physical method such as a vacuum evaporation method or a sputtering method, or a chemical vapor deposition method (chemical vapor deposition method) is applied to a single semiconductor such as silicon (St) or a compound semiconductor substrate such as gallium arsenic (GaAs).
A conductive film or an insulating film is formed on a semiconductor substrate (wafer) by a chemical method such as a chemical vapor deposition (CVD method).

Next, a resist is coated on this by a spin code method, and the resist is selectively exposed by exposing it to ultraviolet light through a mask or scanning with an electron beam,
When using a negative resist, the resist in the photosensitive area will cross-link and polymerize, making it difficult to dissolve in solvents, and when using a positive resist, the resist in the photosensitive area will decompose, making it easier to dissolve in solvents. A resist pattern is formed using

Next, using this resist pattern as a mask, dry etching or wet etching is performed to etch the thin film on the wafer and remove the remaining resist, thereby forming a fine thin film pattern.

Initially, thin film pattern formation was performed using wet etching, and resist removal was also performed using a solvent, but from the viewpoint of pattern accuracy, dry etching was used, and resist removal was also performed using oxygen. (0□) Ashing removed by sputter etching using gas (A
shing) has come to be widely used.

The present invention relates to dry etching and ashing processes.

[Conventional technology]

Conductive films formed on semiconductor wafers include aluminum (A) and polysilicon (polySt), which are used to form conductor lines, electrodes, and the like.

The insulating film is phosphosilicate glass (abbreviated as PSG).

Silicon dioxide (Sing), silicon nitride (5iJ4), etc. are used as the glabellar insulating film.

Here, the etching gas used to dry-etch these various thin films to form fine conductor lines, or to punch holes in insulating films to form contact holes and via-holes. Carbon tetrafluoride (C
Corrosive gases consisting of fluorides and chlorides such as carbon chloride fluoride (CF3C1, cpgct, methane trifluoride (CHF3), and boron trichloride (BCl2)) are used.

After dry etching the thin film on the wafer using the resist as a mask and reactive gas as an etchant using reactive ion etching (RIE), the wafer is transferred to a plasma etching device (plasma asher) and etched in a 0□ gas atmosphere. Perform plasma etching inside
The resist is oxidized and removed as carbon dioxide gas (CO2).

However, since dry-etched wafers are once exposed to the atmosphere before ashing, there is a problem in that the etchant adsorbed on the wafer reacts with moisture in the atmosphere and becomes acid, corroding the thin film.

In particular, A°C is used as a constituent material for conductor lines in semiconductor devices, but it is affected by its poor chemical resistance, which causes deterioration in characteristics such as a decrease in pattern accuracy and an increase in contact resistance. Met.

(Problems to be Solved by the Invention) As described above, since dry etching is performed using a halogen compound, at the end of etching,
This gas is adsorbed on the wafer.

For this reason, when the resist is transferred to a plasma asher for resist removal, it reacts with moisture in the atmosphere and becomes an acid, which causes metals with weak chemical resistance such as ^i to suffer corrosion, resulting in poor pattern accuracy and electrical characteristics. The problem is that this decrease occurs, and the challenge is to solve this problem.

[Means to solve the problem]

The above problem is to cover a semiconductor substrate on which a thin film has been formed with a resist, open a window in the resist through selective exposure and development, and perform dry etching using a halogen gas as an etchant to remove the thin film in the open area. This problem can be solved by configuring a semiconductor device manufacturing method characterized by introducing nitrogen monoxide into the device prior to ashing in a pattern forming step in which the resist is removed by ashing.

[Effect]

In the present invention, the halogen compound remaining in the dry etching process is removed as a volatile nitrosyl halide (NOx, where X is a halogen group) by reacting with nitrogen monoxide (NO) gas.

Table 1 shows the physical properties of the etchant and the resulting nitrosyl halide.

Table 1 The present invention deals with CF adsorbed on wafers and resists.

Since it is difficult to remove etchants such as BCl3 and BCl3, the etchant is made to float above the adsorption position by reacting with No gas, which easily reacts with it, and is converted into nitrosyl halide, which is removed by being carried on the No gas supplied into the device. It is.

By employing such a method, the side surfaces of thin film patterns formed by dry etching have often been corroded, but this corrosion can be eliminated.

〔Example〕

PSG is formed to a thickness of approximately 1 μm on the St wafer by CVD to form an insulating film, and A is deposited on this by sputtering.
f was formed to a thickness of approximately 7,000 people.

Next, a resist was applied to a thickness of approximately 1 μm using a spin code method, selectively irradiated with ultraviolet light using a photomask, and developed to open a test circuit containing 100,000 1 μm square pads. A sample was prepared.

FIG. 1 shows the configuration of a dry etching apparatus for carrying out the present invention. It consists of an etching chamber 2 and a processing chamber 3, each of which is load-locked and provided with transport devices 4, 4' and 4#.

Further, the etching chamber 2 is provided with an RIE device.

First, the sample 5 enters the preparation chamber 1 through the inlet 6, is evacuated under reduced pressure, and is then transferred to the etching chamber 2 by the transport device 4.4'.
to go into.

BCl3, which is an etching gas, is supplied into the room from an etching gas introduction lower through a hole provided in a discharge electric scraper 8, and is exhausted from an exhaust port 9 connected to a vacuum system, thereby creating a vacuum of approximately 2 x 10-'' torr. While maintaining the temperature, perform RIE to remove the exposed 82.

Next, the sample 5' is transferred to the processing chamber 3, and after thorough evacuation, the BCh adsorbed on the etched surface of the sample 5# is removed by evacuation while supplying No gas from the No gas inlet 10. After removing the gas, sample 5# is taken out from the take-out port 11.

Thereafter, the sample is transferred to a plasma asher in the same way as before.
A test circuit pattern consisting of 8 liters was formed by ashing.

Pad of test circuit formed in this way (1 μm square)
When the contact resistance value was measured, it decreased to 1.3Ω or less, whereas in the past it fluctuated from infinity to 2Ω due to the attachment of etching products.

〔Effect of the invention〕

Conventionally, the side surfaces of conductive patterns were easily corroded by dry etching, and the minimum width of conductive patterns was now sub-μm, which affected the characteristics of products, but with the implementation of the present invention, patterns can be formed without corrosion. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a dry etching apparatus used in carrying out the present invention. In the figure, 1 is a preparation chamber, 2 is an etching chamber, 3 is a processing chamber, 5° 5' is a sample, 7 is an etching gas inlet, and 10 is an NO gas inlet.

Claims (1)

[Claims] A semiconductor substrate on which a thin film has been formed is coated with a resist,
In the pattern forming process, in which the resist is opened by selective exposure and development, dry etching is performed using a halogen-based gas as an etchant, the thin film in the opened part is removed, and the resist is removed by ashing. A method for manufacturing a semiconductor device, comprising first introducing nitrogen monoxide into the device.