JPS60143633A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable to perform a dry etching on silicon or silicon compounds sticking on the surface of a semiconductor substrate while preventing a hindrance due to carbons to the dry etching by a method wherein a plasma etching or a sputter etching is performed on the surface thereof using fluorine-containing hydrocarbon having the carbons as etching gas. CONSTITUTION:When fluorine-containing hydrocarbon is used as etching gas, C ions and radicals generate, but H ions and radicals are also produced simultaneously and both are easily polymerized by the energy of plasma. For example, the two are polymerized into a compound in the form of -(CH2)- and the compound adheres on a material to be etched or the sidewall surface of a reaction vessel or is exhausted to the exterior. Fluorine-containing hydrocarbon having a small number of Cs is desirable as etching gas, because the less the number of Cs is, the less the hindrance due to the Cs to a dry etching is. In particular, fluorine- containing hydrocarbon having the number of Cs of less than two is desirable as etching gas. When gas containing at least one selected from among methyl fluoride fluoroform, trifluoroethylen, vinyl fluoride, ethyl fluoride or diofluoroethane is used as etching gas, a more favorable result is obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and more specifically to a semiconductor device in which silicon or a silicon compound on the surface of a semiconductor substrate can be dry etched while preventing damage caused by carbon. Relating to a manufacturing method.

[Background of the invention]

As is well known, plasma etching and high frequency sputter etching have come to be used as etching methods used in the manufacturing process of semiconductor devices.

Plasma etching is performed using CF4. CCQ4. A gas such as oxygen is turned into plasma in a reaction chamber under a pressure of several 10 to 0.0 ITorr, and this plasma is brought into contact with a semiconductor paper board to perform etching by reaction with the plasma-turned gas.

In addition, sputter etching involves accelerating an inert gas such as Ar into plasma under a pressure of about 0.1 to 10' Torr and colliding it with the surface of the semiconductor substrate, causing etching by the ion bombardment. This is the way to do it. In this sputter etching, if a reactive gas such as CF4, C, or CRA4 is used, etching is performed by both ion bombardment and chemical reaction.

However, when plasma etching or sputter etching is performed using a gas consisting of carbon and halogen elements such as CF4 or CCl24, carbon separated from fluorine and chlorine adheres to the surface of the semiconductor substrate and the wall of the reaction vessel. Often causes blackening and contamination of the surface.

In particular, carbon adhering to the surface of a semiconductor substrate hinders highly accurate microfabrication and is one of the causes of lower yields in semiconductor device manufacturing.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device, which solves the above-mentioned conventional problems and allows silicon or silicon compounds to be dry-etched without being seriously hindered by carbon.

[Summary of the invention]

In order to achieve the above object, the present invention etches silicon or a silicon compound with high precision by plasma etching or nupatta etching using a fluorine-containing hydrocarbon as an etching gas.

When fluorinated carbon, which has been used in large amounts in the past, is used as an etching gas, the carbon causes problems as described above.

That is, it is said that fluorine ions F- and fluorine radicals F0 are mainly effective in etching silicon, and ions and radicals in the form of CFn are effective in etching silicon oxide and the like.

However, the C generated when separated from F does not have the chemical action of etching silicon or its compounds, and is implanted into the surface of the object to be etched during reactive sputter etching, causing contamination. Cause.

When wiring is formed on a silicon substrate whose surface is contaminated with such C, the contact resistance between the two increases,
It becomes difficult to get good contacts.

The contaminated layer cannot be removed even by using an etchant containing hydrofluoric acid. After performing the above reactive sputtering blue, etching, etc., irradiation with acid ionizing,
It is possible to remove the contamination layer by setting Sj to 5in2 and removing this oxide layer using hydrofluoric acid treatment, but this not only requires a complicated process of irradiation with oxygen ions, but also requires the irradiation. A problem arises in that the substrate and the like are damaged by the oxygen ions released.

3- On the other hand, when a fluorine-containing hydrocarbon such as CH2F2 is used as an etching gas, C ions and radicals are generated as in the case of fluorocarbon, but I-
1 ions and radicals are also generated at the same time.

In a plasma where C and 14 radicals and ions coexist, they are easily polymerized by the energy of the plasma, forming a compound in the form of -(CH□)-, for example, and are deposited on the object to be etched or the wall surface of the reaction vessel. or adhere to
Or it may be discharged outside.

Polymers such as -(CH2)- are neutralized and stable, so they are hardly implanted into the object to be etched and are simply adsorbed onto the surface.

-(CH2)- attached to such a surface can be easily removed by oxidation using oxygen plasma, which is performed to remove the resist film, so the above-mentioned problem that occurs when using carbon fluoride such as CF4 occurs. There is very little fear.

5-4- The smaller the number of C atoms in the above fluorine-containing hydrocarbon, the less the hindrance caused by C is, which is preferable.

In particular, methyl fluoride (C:H,F), which is a fluorine-containing hydrocarbon in which the number of C atoms is 2 or less, and fluoroform (CHF)
, I-lifluoroethylene (C2HF, ), vinyl fluoride (C2H, 1F), ethyl fluoride (c2H5F), or difluoroethane (C2H4F2) is used as an etching gas without adding 02 or irradiating oxygen ions. However, very favorable results can be obtained.

That is, when selectively etching a desired portion of a SiO2 film formed on a silicon substrate by dry etching using a photoresist film as a mask, if CF4 or the like is used as an etching gas, the silicon exposed by the removal of the SiO2 film will be etched. The substrate surface is contaminated with C.

If electrodes or wiring are formed on this contaminated substrate, the contact resistance between the two increases as described above, making it impossible to obtain good contact.

The above contamination is not removed when the photoresist film is removed using oxygen plasma, which is performed after the selective etching of the SiO□ film, and it is necessary to further irradiate the film with oxygen ions.

However, when the above-mentioned fluorine-containing hydrocarbon in which the number of C atoms is 2 or less is used as an etching gas, the contamination layer due to C is A good contact with low contact resistance can be formed without irradiation with oxygen ions.

The above-mentioned fluorine-containing hydrocarbons such as CH and F, in which the number of C atoms is 2 or less, are used as an etching gas, and the gas pressure is 0.2-0.
3Torr, output 200-300W/400KHz
Under these conditions, using the photoresist film as a mask, SiO2
Table 1 shows the results when the film was selectively etched. In addition,
The apparatus used was a parallel plate type reactive sputter etching apparatus.

Table 1 As is clear from Table 1, according to the present invention, carbon can be removed by simply contacting with oxygen plasma without adding oxygen to etching gas or irradiating oxygen ions. The contamination layer caused by this is removed.

Therefore, when the photoresist film is removed using oxygen plasma following the selective etching of the 5102 film, the C contamination layer is also removed at the same time, and the film can be used as it is for forming electrodes and wiring.

Furthermore, when CF4 is used as an etching gas, the etching rate of Si is much higher than the etching rate of SiO2, so it is difficult to selectively remove a desired portion of the SiO2 film to form a contact hole. If H2 is added to CF4 and etching is performed, Si and SiO
Although the etching speed ratio of □ can be reversed, I]2 is explosive and dangerous and requires special care in handling.

However, as shown in Table 1, according to the present invention, S
Since 5 in2 can be etched at a sufficiently large etching speed ratio to i, and no dangerous H2 is added, no special precautions are required.

It goes without saying that each of the above-mentioned fluorine-containing hydrocarbons may be used alone or in combination.

〔Effect of the invention〕

As is clear from the above description, the present invention has the following advantages: 8- It is possible to prevent damage to the object to be etched by C, and there is no need to add hydrogen, resulting in high safety and ease of implementation. It is extremely useful in practice.

Claims (1)

[Claims] Plasma etching or sputter etching of silicon or a silicon compound on the surface of a semiconductor substrate using a gas containing at least one selected from methyl fluoride, fluoroform, trifluoroethylene, vinyl fluoride, ethyl fluoride, or difluoroethane. A method for manufacturing a semiconductor device, characterized in that: