JPS6231124A - Surface processing method - Google Patents

Abstract

PURPOSE:To perform suitable surface processing by a method wherein, after the surface of an object to be processed has been etched with active species generated by exciting a gas containing fluorine, etching is performed with the active species that is generated by exciting the gas containing harogen elements other fluorine than. CONSTITUTION:An object to be processed 12 is placed on a sample stand 13, CF4+O2 gas is introduced from a electric discharge pipe 14a to generate the F radical with electric discharge, which is active species of the fluorine gas, and the F radical, is introduced into a container 11. The natural oxide film 24 formed on the surface of an Si substrate 21 of the object to be processed 12 is etched with the F radical. Then, a Cl2 gas is introduced into an electric discharge pipe 14, and the surface of the substrate 21 is etched by introducing the Cl2 radical, which is active species of chlorine gas generated by electric discharge, into the electric discharge pipe 14b. Then, Cl+O2 gas is introduced into the electric discharge pipe 14b, and the active species generated by electric discharge so as to form a thin oxide film 25 for protection on the surface of the substrate 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a surface treatment method in a semiconductor manufacturing process.

[Technical background of the invention and its problems]

In the semiconductor device manufacturing process, a so-called surface treatment process, which is a post-processing process for cleaning the wafer surface, stabilizing the surface of the molding 2, etc., is performed between each process.

Currently, y! of LSI etc. On the surface of a wafer to which im processing is performed, grooves and the like that are deeper than the opening diameter are formed, and it is necessary to perform surface treatment even to the inside of such grooves.

Conventionally, techniques using liquid chemicals have mainly been used to perform surface treatment on substrates to be processed, such as Si wafers. However, a substrate to be treated having deep grooves as described above has the drawback that the liquid chemical may not be able to enter the inside of the grooves, and thus cannot be treated satisfactorily.

Dry processing that does not use liquid is also being considered. For example, there are methods of exposing to a gas atmosphere at high temperatures, using active species generated by electric discharge, and the like. Processing at high temperatures is undesirable when producing fine elements because it may cause spreading of the diffusion layer and generation of defects due to thermal distortion, and it is better to perform such processing at low temperatures. A method using active species generated by electric discharge is advantageous for this type of surface treatment because it is a low-temperature treatment and can treat the inside of a fine structure in a low gas pressure region. However, in the method of placing the substrate to be processed in the discharge region, the substrate to be processed may be damaged by particles having kinetic energy such as charged particles from the discharge region, which adversely affects device characteristics.

There is a method called chemical dry etching (CDE) to eliminate the influence of particles with kinetic energy. CF4 is mainly used in CDE.
This method uses active species (especially F radicals) generated by +02 gas discharge, but since this active species has strong reactivity with Si and etching progresses rapidly, when processing the fine II structure as described above, There is a problem that the shape changes due to etching. Therefore, it is possible to use a gas containing a halogen element other than fluorine, which has weak reactivity with 3i, but it has not been possible to surface-treat the 3i surface with this type of gas.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to perform surface treatments such as cleaning and molding in detail on the surface of a substrate to be treated having a fine structure;
Another object of the present invention is to provide a surface treatment method that has a slow etching rate compared to F radicals and has good controllability of the etching rate.

[Summary of the invention]

The gist of the present invention is to thinly etch the surface of a substrate to be processed such as Si using F radicals, and then to etch the surface of the substrate to be processed using active species of a gas containing a halogen element other than F (for example, Cβ radicals). .

That is, the present invention provides a surface treatment method in which the surface of a substrate to be treated is etched into a thin layer for surface treatment, in which the surface of the substrate to be treated is first etched by active species generated by exciting a fluorine-containing gas, and then etched by an active species other than fluorine. This is a method in which the surface of a substrate to be processed is etched using active species generated by exciting a gas containing a halogen element.

Si by active species containing halogen elements such as CQ other than F
In the etching of Si, the reaction is not as exothermic as in the etching of the F radical, and it is extremely easy to control the etching rate of Si. However, the active species containing Ca are Si
If there is a native oxide film on the surface of 81, etching of Si is hindered because it hardly reacts with O2. This made it impossible to treat the surface of Si with halogen elements other than F. On the other hand, SiO2 due to F radical
The etching progresses at a rate of about 100 to 200 people/1n, which is a practical rate for removing the native oxide film.

Therefore, by first removing the natural oxide film using F radicals and then treating the surface with an active species containing a halogen element other than F, such as 02, it becomes possible to perform etching treatment on the 3i surface with good controllability.

Note that generation of active species containing F can be obtained by many methods such as discharge of CF4 or CF4, discharge of SF2, and photolysis of SFH. In addition, active species containing Ca include CD2. C
CM+, Cl-1cL3゜CH2C(12, CCRH
It can be generated by discharging or photodecomposing a gas containing at least CI2, such as CI2.

The active species containing F and the active species containing C are generated in a separate chamber from the processing chamber. This is because the charged particles generated by the discharge for generating active species do not damage or otherwise affect the substrate to be processed. Since the substrate to be processed is placed in a chamber with relatively low pressure, if the sample has fine grooves or the like on its surface, gas particles may enter the inside of the fine grooves and clean the surface. I can do it.

〔Effect of the invention〕

According to the present invention, the surface of the substrate to be processed can be thinly etched without damaging the substrate, and contaminants and the like on the surface can be removed and cleaned. In addition, the etching speed is extremely slow compared to the surface treatment method using only F radicals, so the etching controllability is good.
Appropriate surface treatment can be easily performed. Furthermore, it is particularly effective when the surface has fine grooves, and it
Extremely effective in manufacturing processes.

In the present invention, since active species are generated in a region separate from the substrate to be processed, the substrate to be processed is not damaged by charged particles. Furthermore, since active species of halogen elements other than F, such as carbon, are used, etching can be easily controlled.

In addition, when grooves are formed by reactive ion etching, etc.
Contamination may occur on the side walls of the groove, and when attempting to remove this contamination, conventional methods using liquid do not allow the liquid to enter the inside of the groove when the groove opening becomes narrow. Some parts may not be processed. On the other hand, in the present invention, since gaseous active species are used, the active species can easily enter the inside of extremely fine grooves, and the inside of the grooves can be sufficiently cleaned. Furthermore, an oxide film can be formed on the surface of 81 by mixing 02 with active species including Cλ and supplying the mixture to heated Si. By oxidizing the wafer and transferring it to the next process, it is also possible to prevent contamination during the transfer process.

[Example of invention in action]

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

FIG. 1 is a schematic diagram showing a surface treatment apparatus according to an embodiment of the present invention. In the figure, reference numeral 11 denotes a vacuum container, and inside this container 11 is installed a sample stage 13 on which a substrate 12 to be processed, such as a semiconductor urchin, is placed. Furthermore, one ends of discharge tubes 14a and 14b for introducing gas and its active species into the container 11 are connected to the side wall of the container 11, respectively.

The discharge tubes 14a and 14b are provided with a microwave power source 15a.

It is coupled to waveguides 16a and 16b connected to waveguide 15b. A CF4+02a mixture gas is introduced into the other end of the discharge tube 14a as a fluorine-containing gas. CQ2 gas is introduced into the other end of the discharge tube 14b as a gas containing a halogen element other than fluorine. And container 1
The gas inside 1 is exhausted through gas exhaust ports 17a and 17b.

Next, regarding the 3i surface treatment method using the above device,
This will be explained with reference to FIG.

First, as the substrate 12 to be processed, a 5iQ2 mask 22 is formed on a Si substrate 21, as shown in FIG.
A groove 23 was formed using IE. This substrate 12 to be processed has contaminants such as C on the sidewalls and bottoms of the grooves 23 on the surface due to RIE, and also has disordered crystallinity on the surface.

Also, once exposed to the atmosphere, the surface will naturally oxidize.
24 is formed.

The sample stage 1 of the apparatus shown in FIG.
First, CF4 +02 gas is introduced from the discharge tube 14a, F radicals, which are active species of fluorine gas, are generated by discharge, and these F radicals are introduced into the container 11. Then, the F radicals etch the natural oxide film 24 formed on the surface of the substrate 21 81 of the substrate 12 to be processed, as shown in FIG. 2(b). At this time, the treatment time may be extremely short as long as the natural oxidation 1!24 can be removed. Note that after the natural oxide film 24 is removed, the introduction of the above gas is stopped.

Next, Cλ2 gas is introduced into the discharge tube 14b, and C2 radicals, which are active species of chlorine gas generated by the discharge, are introduced into the container 11. Then, due to this Cρ radical, S
The surface of the i-substrate 21 is etched to a single point. This etching allows the surface of the 81 substrate 21 to be cleaned.

Next, Off+02 gas is introduced into the discharge tube 14b and active species generated by the discharge are sent in to form a thin protective oxide film 25 on the surface of the S+ substrate 21 as shown in FIG. 2(C). This makes it possible to stabilize the cleaned surface of the Sin plate 21.

Thus, according to the method of this embodiment, since the natural oxidation 11114 on the surface of the 3i substrate 21 is first removed by F radicals, the surface of the 3i substrate 21 can be etched by the subsequent introduction of CC radicals. That is, since the surface of the Si substrate 21 can be etched with active species of a halogen element other than F, the etching rate can be better controlled and an appropriate surface treatment can be easily performed. In addition, since it is a dry process, it is possible to perform sufficient surface treatment even within minute grooves.

Furthermore, since the region for generating active species is provided separately from the inside of the container 11, the substrate to be processed is not irradiated with charged particles, and damage caused by charged particles can be prevented.

FIG. 3 is a schematic configuration diagram showing a surface treatment apparatus used in another embodiment method of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

This device differs from the device shown in FIG. 1 above in that it has a single discharge section for generating active species. That is, one end of one discharge tube 14 is connected to the container 11, and this discharge tube 14 is coupled to a waveguide 16 connected to a microwave power source 15. CF4 gas, 02 gas, and CQ2 gas are supplied to the other end of the discharge tube 14 via bulbs 19a, 19b, and 19c, respectively.

If such an apparatus is used, the surface treatment of the substrate 12 to be treated can be performed as shown in FIGS. 2(a) to 2(C) by opening and closing the valves in the order of treatment. That is, first, the valves 19a and 19b are opened and the F radicals generated by the discharge of CF4+02 gas naturally oxidize p! 24
is removed, the valves 19a and 19b are closed, and the valve 19c is opened, and the CJ generated by the discharge of the C/12 gas is removed.
Etching the surface of the SIM board 21 with 2 radicals,
Then, by opening valve 19b, protective oxide B125 can be formed on the cleaned surface of 3i substrate 21.

In this way, according to the method of this embodiment, after the natural oxide film 24 on the surface of the Si substrate 21 is removed by F radicals, the CQ
The surface of the Sil plate 21 can be etched by the radicals. Therefore, the same effects as in the previous embodiment can be obtained.

Note that the present invention is not limited to the methods of each embodiment described above. For example, the gas used to remove the natural oxide film is not limited to CF4+02 gas, but may be any gas containing fluorine.

In addition, the gas that actually etches the Si surface is as follows:
It is not limited to Ca2, but also CC2q.

CHCff3. Any gas containing chlorine such as CH2C (12, CCj21-h, etc.) or gas containing a halogen element other than fluorine may be used. In addition, the means for generating active species is not limited to electric discharge, but may also be electron beam irradiation.

Possible methods include light irradiation or heat. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a surface treatment apparatus used in a method according to an embodiment of the present invention, FIGS. FIG. 3 is a schematic configuration diagram showing a surface treatment apparatus used in another example method. 11... Vacuum container, 12... Substrate to be processed, 13...
・Sample stand, 14.14a, 14b...discharge tube, 15
゜15a, 1.5'o-w microwave power supply, 16.16
a. 16b... Waveguide, 17... Exhaust port, 19a, ~. 19c...Valve, 21...Si substrate, 22...
5iQ2 mask, 23... Groove, 24... Natural oxide film, 25... Protective oxide film. Figure 2 Figure 3

Claims (6)

[Claims] (1) In a surface treatment method in which the surface of a substrate to be treated is thinly etched and treated, the surface of the substrate to be treated is first etched by active species generated by exciting a gas containing fluorine, and then a halogen element other than fluorine is used. A surface treatment method characterized by etching the surface of a substrate to be treated with active species generated by exciting a gas containing. (2) The surface treatment method according to claim 1, wherein chlorine gas is used as the gas containing a halogen element other than fluorine. (3) The surface treatment method according to claim 1, wherein the substrate to be treated is Si, and a thin native oxide film is formed on the surface of the substrate. (4) The surface oxide film of the substrate to be processed is removed by the active species of the gas containing fluorine, and the surface of the substrate itself is etched by the active species of the gas containing a halogen element other than fluorine. A surface treatment method according to claim 3. (5) The surface treatment method according to claim 1, wherein electric discharge, electron beam irradiation, light irradiation, or heat is used as means for exciting the gas to generate active species. (6) The first aspect of the present invention is characterized in that the means for generating active species by exciting the gas generates the active species in a region separated from a region where the substrate to be processed is arranged. The surface treatment method according to item 1 or item 5.