JPS639121A - Dry etching - Google Patents

Abstract

PURPOSE:To enable a uniform and planar etching treatment (surface cleaning) of the inside of the groove at the post-treatment of RIE by utilizing, as a reaction gas, a gas which contains fluorine atoms but does not contain oxygen atoms, e.g., NF3 or NF6, thereby excluding the influence of the O2 gas which is a defect of CDE. CONSTITUTION:A substrate to be treated is prepared in which a mask 42 consisting of, for instance, thermally oxidized SiO2 film 42a, an Si3N4 film 42b and a CVD2-SiO2 film 42c is provided on a single crystal Si substrate 41, and it is etched with RIE to form a groove 43. Subsequently, after removing the organic materials on the surface by oxygen plasma, it is dipped in dilute hydrofluoric acid, rinsed and dried. The above structure is mounted on a sample stand 13 as substrate to be treated 12. After evacuating a cell 11, NF3 for instance is introduced as a reaction gas into a discharge tube 15, an active species is generated by microwave discharge, and this species is introduced into the cell 11. With this, the inside of the groove 43 is thinly etched.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a dry etching method used in a semiconductor device manufacturing process, and in particular, the present invention relates to a dry etching method used in a semiconductor device manufacturing process. The present invention relates to a dry etching method for etching.

(Prior Art) In recent years, with the miniaturization of pattern sizes in semiconductor integrated circuits, a technique of forming deep grooves in a 3i substrate, performing element isolation using the grooves, and forming capacitors within the grooves has been attracting attention. This type of groove is generally formed by reactive ion etching (RIE), but RIE involves ion bombardment, which damages the surface of the etched St coating.

Therefore, when a groove is formed in a 3i substrate by RIE, a surface cleaning treatment for removing the surface layer (damaged layer) is required as a subsequent treatment.

It is essential that the above surface cleaning treatment does not damage the substrate surface, but chemical dry etching (
CDE). This CDE is a method in which a reactive gas is dissociated by electric discharge in a region different from the substrate to be etched, and the active species generated by the discharge are transported to the substrate to be etched. Usually, in CDE such as gate polysilicon etching, CF4
A mixed gas of and 02 is used. However, when this was used in the V& treatment of RIE of single crystal Si, the following problems were caused due to the amount of o2 added. That is, when the amount of 02 added is small, the treated surface becomes rough. On the contrary, 0
It was found that when the amount of 2 added was large, etching slowed down near the mask, and the process did not proceed uniformly at the upper and lower parts of the groove.

In addition, with a multilayer resist process, spin-on glass (S
CDE is also used in the process of removing this SOG after patterning the resist with a mask of OG), but in a mixed gas system of CF4 and 02 similar to the above, the resist is corroded due to the oxygen contained. It will be done. In the case of submicron patterns, it has been found that the dimensional conversion difference due to this phenomenon becomes a serious problem.

(Problems to be Solved by the Invention) As described above, in the conventional method, it is difficult to uniformly remove the damaged layer without causing surface roughness in post-treatment (surface treatment) after forming grooves by RIE. there were.

Additionally, it has been difficult to etch spin-on glass in a multilayer resist structure without causing resist regression.

The present invention has been made in consideration of the above circumstances, and its purpose is to eliminate the influence of 02 gas, which is a disadvantage of CDE, and to achieve uniform and flat etching treatment ( It is an object of the present invention to provide a damage-free dry etching method that can perform a surface cleaning treatment.

Another object of the present invention is to provide a non-damaging dry etching method capable of etching a mask layer above a lower resist in a multilayer resist structure without damaging the resist.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to perform CDE using CF4+02 mixed gas.
In order to eliminate the influence of 02 gas, which is a drawback of CF4, a gas containing no carbon atoms is used instead of CF4 as a fluorine atom supply source.

In normal CDE using CF4 as a fluorine atom supply source, it is necessary to add 02 gas in an amount of several tens of percent to several times that of CF4. This removes the carbon generated by the CF4 discharge as a stable continuous substance bonded to oxygen during the transport of active species generated by the discharge or on the surface of the substrate to be treated, thereby effectively performing etching with fluorine atoms. This is to ensure that the

As shown in FIG. 2, the present inventors used CF4 to process a substrate in which a SiO2 mask 22 was formed on a single-crystal Si substrate 21.
Etching was performed with CDE of +02 mixed gas. As a result, when the amount of O2 added was large, a shape was obtained in which etching was slow near the mask 22, as shown in FIG. 3(a).

This phenomenon is due to the effect of O2, and when the amount of O2 added is reduced, an evenly etched shape is obtained as shown in FIG. 3(b). However, in this case, the etched surface becomes extremely rough because C is not sufficiently removed. Therefore, it is understood that in order to perform the ideal isotropic etching as shown in FIG. 3(C), it is sufficient to use a reaction gas that does not require the addition of 02, in other words, a reaction gas that does not contain carbon. .

The present invention has focused on these points, and a substrate to be processed in which grooves have been formed by reactive ion etching is housed in a vacuum container, and a reactive gas is dissociated by electric discharge in a region separated from the container. In a dry etching method in which active species generated by electric discharge are introduced into the container to etch the surface layer of the substrate to be processed, as the reactive gas,
A gas containing fluorine atoms and no oxygen atoms, such as N
This method uses F3 or SFs.

Further, the present invention provides a method in which a substrate to be processed, in which a multilayer resist structure consisting of an organic resist and an inorganic resist is formed on a base substrate and the multilayer resist structure is patterned, is housed in a vacuum container, and the substrate is separated from the container. In the dry etching method, the inorganic resist of the multilayer resist structure is etched by exciting a reactive gas in a region by electric discharge and introducing active species generated by the discharge into the container, wherein the reactive gas contains fluorine atoms. In addition, this method uses a gas that does not contain oxygen atoms, such as NF3 or SFs.

(Function) According to the above method, since the reaction gas does not contain carbon, there is no need to add oxygen. Therefore, the reaction gas is 3
Since it does not need to contain both oxygen and carbon, which are easily adsorbed by i, it is easier to obtain a clean etched surface compared to the conventional CF4+02 mixed gas system. Furthermore, since it is not necessary to include 02 in the reaction gas, there is less risk of damaging the resist, which is advantageous for microfabrication of substrates provided with resist masks such as multilayer resist structures.

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

FIG. 1 is a schematic diagram showing a dry etching apparatus used in an embodiment of the present invention. In the figure, reference numeral 11 denotes a vacuum container, and a sample stage 13 on which a substrate 12 to be processed is placed is accommodated within this container 11. A gas inlet 14 is provided in the container 11, and one end of a discharge tube 15 is connected to this gas inlet 14. The discharge tube 15 is coupled to a waveguide 17 connected to a microwave power source 16. A reactive gas or a mixed gas of a reactive gas and a diluent gas is introduced into the other end of the discharge tube 15 . Then, active species of the reactive gas are generated within the discharge tube 15, and these active species are introduced into the container 11 through the gas inlet 14. Furthermore, the gas introduced into the container 11 is exhausted from the gas exhaust port 18. Note that the diluent gas can also be introduced directly into the container 11 from a gas inlet 19 provided separately from the gas inlet 14 without passing through the discharge tube 15.

Next, the RIE post-processing method (surface cleaning process) using the above-mentioned apparatus will be explained with reference to FIG.

First, as shown in FIG. 4(a), a single crystal Si substrate 41 is thermally oxidized 3i02! 142a, S is I4! ! 4
2b, mask 42 consisting of CVD-81o2II42c
A substrate to be processed was prepared and etched by RIE to form a groove 43 having a depth of about 4.5 [μm] and an opening width of about 1 [μm]. Subsequently, after removing organic matter from the surface with oxygen plasma, it was immersed in dilute hydrofluoric acid, washed with water, and dried.

The above-described structure was used as a substrate 12 to be processed and placed on the sample stage 13 of the apparatus shown in FIG. After evacuating the inside of the container 11, discharge i! NF3 is introduced as a reactive gas into the reactor 15, active species are generated by microwave discharge, and the active species are introduced into the container 11.

As a result, as shown in FIG. 4(1)), the inside of the II43 was thinly etched, that is, cleaned. In this cleaning treatment, the surface layer could be etched uniformly and smoothly without causing surface roughness.

In addition, the etching speed of 81 when using NF3 is approximately 1
000 [person/min], which is rather fast for cleaning processing. Therefore, when three times the amount of N2 was added together with NF3 through the discharge tube 15, the etching rate was approximately 20%.
The etching speed was moderately slow at 0 [people/1n], and the etched shape was still good.

Also, @e, Ne is used instead of N2 as a diluent gas.

The etching rate could be similarly controlled using a rare gas such as Ar. Furthermore, even if the diluent gas was directly introduced into the container 11 from the gas inlet 19 without passing through the discharge tube 15, the etching rate could be similarly controlled.

On the other hand, if CF4 with three times the amount of 02 added is used as the reaction gas, the etching speed of the openings 44 of the grooves 43 becomes slow, as shown in FIG. The damaged layer was not removed.

As described above, according to the method of this embodiment, when the surface of the groove 43 formed by RIE is cleaned by CDE,
By using NF3 as a reactive gas, the surface inside the groove 43 can be etched evenly and flatly,
Damaged layers can be reliably removed. Therefore, R
This method is extremely effective as a surface treatment method for removing damaged layers after IE.

Next, a method for mask etching a multilayer resist structure will be explained with reference to FIG.

First, as shown in FIG. 5(a), a thermal oxide film 52 with a thickness of 8,500 μm is formed on a single-crystal $1 substrate 51, and an Ag-5+ sputtered film with a thickness of 1 μm is formed on it. Form 53. On top of this, a multilayer resist structure of lower layer resist/SOG/upper layer resist is formed, and 0.8
A line pattern with a width of [μm] was formed. Subsequently, the 5OG 55 was etched using the upper resist (not shown) as a mask, and the lower resist 54 was roughly etched using the 5OG 55 as a mask. Here, an organic resist was used as the lower resist 54.

The substrate to be processed having the above structure was placed on the sample stage 13 of the apparatus shown in FIG.
When the resist 55 was etched, only the 5OG 55 could be removed without any regression of the resist 54, as shown in FIG. 5(b). This is because NF3, which does not contain carbon, is used as the reactive gas, so there is no need to add oxygen, and the resist is hardly attacked. Also, 2
Even under the condition of 0.00% coover etching, the width of the lower resist layer 54 decreased by 100% or less.

On the other hand, when 5OG55 was etched using a mixed gas of CF4 and O2 as in the past, 100[%
] Under the overetching condition, the lower resist 54 has a width of about 0.7 as shown in FIG. 5(C).
A decrease of =0.1 [μm] occurred. This retreat of the resist causes a difference in dimension conversion, which is a fatal drawback in submicron pattern formation.

As described above, according to the method of this embodiment, when 5OG55 is etched by CDE in a multilayer resist process, by using NF3 as a reactive gas, it is possible to remove 5OG55 by etching without causing regression of the lower resist 54. can. Therefore, it is extremely effective in forming submicron patterns.

Note that the present invention is not limited to the methods of each embodiment described above. For example, the same effect as in the example could be obtained by using SFs instead of NF3 as the reaction gas. In addition, in the multilayer resist structure,
By using a silicon-containing resist instead of SOG, it is also possible to apply a two-layer resist structure instead of a three-layer resist structure. Furthermore, as the lower layer resist, organic resist,
Any type resist can be used instead of SOG or silicon-containing resist. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, by using a gas containing fluorine atoms such as NF3 or SFs but not containing carbon atoms as a reaction gas when etching with CDE, etching by RIE can be performed. The damaged layer after etching can be removed (surface cleaning treatment) uniformly without causing surface roughness.

Furthermore, the mask layer above the lower resist in a multilayer resist structure can be removed without causing the lower resist to retreat. Therefore, it can be applied to various semiconductor integrated circuit manufacturing processes to obtain effective effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a dry etching apparatus used in a method according to an embodiment of the present invention, FIGS. 2 and 3 are schematic diagrams for explaining the present invention in detail, and FIG. FIG. 5 is a cross-sectional view for explaining one embodiment and shows the groove surface cleaning process, and FIG. 5 is a cross-sectional view for explaining another example, showing the SOG etching process of a multilayer resist structure. . 11... Vacuum container, 12... Substrate to be processed, 13...
・Sample stand, '14.19...Gas inlet, 15...
Discharge tube, 16... Microwave NN, 17... Waveguide, 18... Gas exhaust port, 41.51... Single crystal 81
Substrate, 42... Mask, 43... Groove, 54... Lower layer resist, 55... SOG. Applicant's agent Patent attorney Takehiko Suzue No. 1117 Figure 2 Figure 3 Figure 4 Procedural amendments October 24, 1985 Commissioner of the Patent Office Kuro 1) Akio Tono 1, Indication of Case Patent Application 151587, 1988 No. 2, Name of the invention Dry etching method 3, Relationship with the person making the amendment Patent applicant (307) Toshiba Corporation 4, Agent 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo UBE Building 1
00 Telephone 03 (502) 3181 (main representative)
(1) Correct the statement of the scope of claims as shown in the attached sheet. (2) From line 15 on page 6 of the specification to line 16 on the same page, the phrase "substrate to be processed" is corrected to read "substrate to be processed with rRIE damage." (3) On page 9, line 15 of the specification, the phrase ``It has become a thing.'' has been corrected to ``It has become a thing.'' (1) The substrate subjected to ion bombardment by reactive ion etching is housed in a vacuum container, and the reaction gas containing fluorine atoms but not carbon atoms is dissociated by electric discharge in a region separated from the second container. A dry etching method characterized in that the surface layer of the substrate to be processed is etched by introducing active species generated by the discharge into the container. method. (3) The dry etching method according to claim 1, wherein NF3 or SF6 is used as the reaction gas. (4) The dry etching method according to claim 1 or 3, wherein the reaction gas is diluted with N2 or a rare gas. (5) The dry etching method as set forth in claim 1, wherein a single crystal silicon substrate is used as the substrate to be processed. (6) A substrate to be processed in which a multilayer resist structure consisting of an organic resist and an inorganic resist is formed on a base substrate and this multilayer resist structure is patterned is housed in a vacuum container, and a region separated from the container is A reactive gas containing fluorine atoms but not containing carbon atoms is excited by electric discharge, and active species generated by this electric discharge are introduced into the container,
A dry etching method characterized by etching an inorganic resist having the above multilayer resist structure. (7) The dry etching method according to claim 6, characterized in that NF3 or SF6 is used as the reaction gas. (8) The dry etching method according to claim 6 or 7, wherein the reaction gas is diluted with N2 or a rare gas. (9) The dry etching method according to claim 6, wherein a spin-on glass or silicon-containing resist is used as the inorganic resist.

Claims (8)

[Claims] (1) A substrate to be processed with grooves formed by reactive ion etching is housed in a vacuum container, and a reactive gas containing fluorine atoms but not containing carbon atoms is dissociated by electric discharge in a region separated from the container. . A dry etching method, characterized in that active species generated by this discharge are introduced into the container to etch the surface layer of the substrate to be processed. (2) The dry etching method according to claim 1, wherein NF_3 or SF_6 is used as the reaction gas. (3) The dry etching method according to claim 1 or 2, wherein the reaction gas is diluted with N_2 or a rare gas. (4) The dry etching method according to claim 1, wherein a single crystal silicon substrate is used as the substrate to be processed. (5) A substrate to be processed in which a multilayer resist structure consisting of an organic resist and an inorganic resist is formed on a base substrate and patterned with this multilayer resist structure is housed in a vacuum container, and a region separated from the container is exposed to fluorine. A reactive gas containing atoms but not containing carbon atoms is excited by electric discharge, and active species generated by this electric discharge are introduced into the container,
A dry etching method characterized by etching an inorganic resist having the above multilayer resist structure. (6) The dry etching method according to claim 5, wherein NF_3 or SF_6 is used as the reaction gas. (7) The dry etching method according to claim 5 or 6, wherein the reaction gas is diluted with N_2 or a rare gas. (8) The dry etching method according to claim 5, wherein a spin-on glass or silicon-containing resist is used as the inorganic resist.