JPH03105919A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable fine etching of a semiconductor substrate without giving heavy metallic contamination and damage to the semiconductor substrate and using a mask such as a resist film by exposing the surface of the semiconductor substrate in a decompression atmosphere to a reaction gas containing an oxidizing gas and hydrofluoric acid gas and heating the semiconductor substrate through light irradiation. CONSTITUTION:An Si substrate 12 is placed in a chamber brought to a decompression atmosphere and composed of fluoroplastics, and an O2/HF/N2 mixture gas is introduced. Nd-YAG laser beams or excimer laser beams are applied. Since a heavy-metallic contamination layer or a damage layer 13a on the surface of the Si substrate 12 is heated at approximately 1000 deg.C at that time, the layer 13a reacts with O2 in the O2/HF/N2 mixture gas, thus forming an SiO2 film 14a on the surface. The SiO2 film 14a formed reacts with HF in the O2/HF/N2 mixture gas, and is removed instantaneously. The reaction successively progresses by holding the state, and lastly the heavy metallic contamination layer or damage layers 13a/13b/13c are taken off. An etching rate at that time is determined by an oxidation reaction rate or an etching reaction rate.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology (Fig. 5) Problem to be solved by the invention (Fig. 5) Example of means and action for solving the problem ■ No. 1 First embodiment of the invention (Fig. 1) ■ Second embodiment of the first invention (Fig. 2) ■ Third embodiment of the first invention (
Fig. 3) Embodiment of the second invention (Fig. 4) Effects of the invention [Overview: Regarding the manufacturing method of semiconductor devices, more specifically, regarding the etching method of semiconductor substrates, there is no risk of heavy metal contamination or damage to the semiconductor substrates. The purpose of the present invention is to provide an etching method for a semiconductor substrate that allows localized and fine etching of the semiconductor substrate without using a mask such as a resist film. and heating the semiconductor substrate by irradiation with light and forming an oxide film on the surface of the semiconductor substrate in the optically illuminated part, and immediately etching the formed oxide film. Conceive.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, more specifically,
Concerning etching methods for semiconductor substrates. [Prior Art] Conventionally, as a fine etching method for semiconductor substrates, SF. By physically colliding gas particles with the surface of the semiconductor substrate, semiconductor atoms, etc. in the areas not covered by the resist film are scattered.
There is an etching method to remove it. Since this method performs physical etching, it has etching anisotropy.

Now, as shown in FIG. 5(a), when a groove is formed in the Si substrate 1 using the resist film 2 as a mask using this etching method, what is the shape of the groove 3 formed? The shape conforms to the two dimensions of the resist pattern without lateral etching.

This also makes it possible to form fine trenches.

Furthermore, etching of polysilicon may be required in the step of forming an insulated gate field effect transistor. FIG. 5(b) is a cross-sectional view of a main part of an insulated gate field effect transistor in the process of being formed.
5 is a St substrate, and 5 is a field oxide film. Further, 6 is a gate oxide film, 7 is a gate ti, and 9 is a SiO2 film, which form a gate portion 7a. Furthermore, 8a and 8b are S/
D 8N region, 10 is a polysilicon film on the gate portion 7a to be removed, and 1l is a resist film. As shown in FIG. 5(b), the source/drain (S) of an insulated gate field effect transistor is made of polysilicon.
/D) When forming the extraction electrodes 10a and 10b, the polysilicon If! connected through the top of the gate portion 7a! JIO
needs to be removed. In this case, the portion other than the top of the gate portion 7a is covered with the resist film 11 and the SF. Dry etching the polysilicon film using gas etc., each S/D
Extracting electrode 10a. 10b is separated and shaped. [Problems to be Solved by the Invention] However, when using this etching method, ionized SF. Gas particles collide with the walls of the chamber, scattering iron, chromium, A1, etc., which are the materials of the chamber, etc.
This may adhere to the semiconductor substrate and diffuse into the semiconductor substrate during subsequent heat treatment.

Moreover, as shown in FIG. 5(a), ionized SF
& Since the gas particles directly collide with the semiconductor substrate, the surface of the semiconductor substrate often suffers damage such as crystal defects.

For this reason, when a pn junction or a capacitor is formed near the etched surface of a semiconductor substrate, there is a problem in that leakage current increases and the performance of the semiconductor device is deteriorated.

Furthermore, as shown in FIGS. 5(a) and 5(b), the process of patterning the resist film is necessary and time-consuming;
Even after the resist film is removed, resist may remain, reducing the reliability of semiconductor devices.Also, as semiconductor devices become denser and patterns become finer, patterning of the resist film may occur. There are also other problems, such as that it may become difficult to carry out the process using the resist film as a mask.

Therefore, the present invention has been made in view of the problems of the conventional method, and it is possible to locally and finely remove semiconductor substrates without causing heavy metal contamination or damage to semiconductor substrates, and without using a mask such as a resist film. The purpose of this paper is to provide an etching method for semiconductor substrates that can be etched. [Means for Solving the Problems] First, the above problems include exposing the surface of a semiconductor substrate in a reduced pressure atmosphere to a reaction gas containing an oxidizing gas and a hydrofluoric acid gas, and heating the semiconductor substrate by light irradiation. This problem is solved by a method for manufacturing a semiconductor device, which is characterized in that an oxide film is formed on the surface of the semiconductor substrate in the light source part, and the formed oxide film is immediately etched. The problem is solved by the method for manufacturing a semiconductor device according to the first method of the invention, characterized in that the semiconductor substrate according to the method of the invention is auxiliary heated by a heating means in addition to heating by light. ．． [Function] According to the manufacturing method of the first invention, by heating the semiconductor substrate by irradiating light, an oxide film is formed on the surface of the semiconductor substrate with an oxidizing gas, and the oxide film is fluorinated. Unlike conventional etching, it is chemically etched using acid gas, which prevents damage caused by ion particle collisions. In addition, since light is irradiated and heated only on the necessary parts of the semiconductor substrate, and the semiconductor substrate and reaction gas are reacted, heavy metals contained in the chamber walls and jigs inside the chamber are removed in a reduced pressure atmosphere. It does not occur. Furthermore, since light is used as a means to heat the semiconductor substrate, the area of the irradiated area can be freely changed by narrowing down or expanding the light. Moreover, since heating only needs to be carried out locally, the temperature can be raised in a short time, and therefore the heat hardly spreads to areas other than the light irradiated area. Thereby, local and fine etching of the semiconductor substrate can be performed without using a resist film or the like.

In addition, as in the manufacturing method of the second invention, the semiconductor substrate is auxiliary heated by a heating means in addition to the heating by light, so that the semiconductor substrate is not heated by the light for causing the oxidation reaction in the manufacturing method of the first invention. The energy of can be small. For this reason,
There is no need to use a high-performance light generation device, and the first
The effects of the manufacturing method of the invention can be achieved.

〔Example〕

Hereinafter, the first and second inventions will be specifically explained with reference to illustrated embodiments.

■First embodiment of the first invention Figures 1(a) to (d) show the application of the semiconductor substrate etching method of the first invention to the case of removing a heavy metal contamination layer or damaged layer on the surface of a semiconductor substrate. FIG. 2 is a sectional view illustrating a first example.

Figure (a) shows the Si substrate l after anisotropic etching.
2, the surface of the St substrate 12 has a heavy metal contamination layer due to heavy metals from the chamber and damage JW 13a caused by collisions of reaction gas particles.

First, this Si substrate 12 is placed in a chamber made of fluororesin in a reduced pressure atmosphere, and an Ox/}IF/Nz mixed gas is introduced. Then, Nd-YAG laser light or excimer laser light with a power of several watts is irradiated. At this time,
Si substrate] Heavy metal N contamination layer or damaged layer 13a on the surface of 2
is heated to around 1000″C, so Oz/HF/N
z Reacts with 02 in the mixed gas, forming SiOg11!1 on the surface.
4a is demonstrated ((b) in the same figure). Furthermore, the formal precept S
The iOz film 14a reacts with 1{F in the OJHF/Nz mixed gas and is immediately removed.

? This reaction proceeds sequentially by maintaining the state of
At the end is a heavy metal contamination layer or damage N13a/13b/
13C is removed ((b), (c), (d) in the same figure)
). The etching rate at this time is determined by the oxidation reaction rate or the etching reaction rate. The oxidation reaction rate or etching reaction rate can be adjusted by adjusting the amount of Ox/IIF/N and N2 in the mixed gas.

As described above, according to the first embodiment of the first invention, while forming the SiO2 film 14a/14b on the surface of the Si substrate 12 by heating using light energy, the SiO2 film 14a/14b is Since the etching is performed after removing the films 14a/14b, heavy metal contamination from the chamber and damage to the Si substrate 12 due to collisions of reaction gas particles as in the conventional case do not occur.

Thereby, a normal pn junction can be formed in this portion, so that the performance and reliability of the semiconductor device can be improved.

? Second Embodiment of the First Invention FIGS. 2(a) to 2(d) illustrate a second embodiment in which grooves are formed in a semiconductor substrate by the semiconductor substrate etching method of the first invention. FIG.

First, the SI board 15 (CB) in the same figure was placed in a chamber made of fluororesin in a reduced pressure atmosphere, and the SI board 15 was placed in a chamber made of fluororesin in a reduced pressure atmosphere.
Introduce the mixed gas. Then, a portion 17a forming a groove
Nd-YAG laser light or excimer laser light with a power of around 10 watts is irradiated. At this time, the light source part has a small volume, so its heat capacity is small, and the temperature rises in a short time. As a result, this portion 17a is heated to about 1000° C., and a Sill film 16a is formed in this portion 17a by reacting with the amount of O in the Ot/IP/Ng mixed gas (FIG. 4(b)).

Then, this SiOYOWI. 16a immediately Ox/HF
Etched and removed by HF in /Nz mixed gas. By maintaining this state, the Si substrate 15 is successively etched, and the groove 17b becomes deeper (FIG. 4(C)). After a predetermined period of time has elapsed, a groove 17c of a predetermined depth is formed in the Si substrate 15 (FIG. 1(d)). Thereby, a groove with an aspect ratio of 1 or more can be easily created.

As described above, according to the second embodiment of the first invention, by narrowing down the laser beam and irradiating a predetermined area in a short period of time, it is possible to cause a reaction only in the illuminated area.
Local and fine grooves 17c can be formed.

In addition, while forming a Stow film 16a/16b on the surface of the Si substrate 15 by heating with light, the SiOdli
Since 11.6a/16b is removed, no heavy metal contamination layer or damaged layer is generated as in the conventional case. Therefore, when a capacitor is formed in the full length 17c, the leakage current can be reduced, so that a capacitor with good performance and high reliability can be formed with less leakage of stored charge.

■ Third embodiment of the first invention FIGS. 3(a) to (C) show that a polycrystalline semiconductor layer is patterned by the semiconductor substrate etching method of the first invention,
FIG. 7 is a cross-sectional view illustrating a third embodiment in which an extraction electrode of an insulated gate field effect transistor is formed.

In the same figure (a), the St substrate l on which the gate electrode 22 is formed is shown.
8 is a cross-sectional view showing a state immediately after a polysilicon film 24 for an extraction electrode is formed on top of the polysilicon film 24. In the same figure (a), 19
20a. is a field oxide film that divides the surface of the Si substrate l8 into device-shaped regions; 21 is a gate oxide film; 22 is a gate electrode on the gate oxide film 21; 20a. 20b is the gate electrode 22
31 Source/drain (S/D) 8N region formed on the substrate 18 using as a mask, 2 3 brush- }'t pole 1
1 is an SiOz film for eliminating 1, and 24 is a polysilicon film formed on the entire surface and serving as an S/D extraction electrode.

First, as shown in FIG. 5(b), the St substrate 18 shown in FIG.
After that, the Ox/IP/Ni mixed gas is introduced. After that, the portion of the gate electrode 22 where the polysilicon film 24 is to be removed is irradiated with several watts of Nd-YAG laser light or excimer laser light for a short period of time. Ru. Then, the temperature only rises in the Koshozai part, and the temperature in the 02/l{F/Nz mixed gas increases.
2 gas reacts with the polysilicon film 24 to form Sin. membrane 25
is expressed.

This SiO* film 25 is immediately etched and removed by HF in the 0*/IP/Nz mixed gas. This state is then maintained until the polysilicon film 24 on the gate electrode 22 is removed. As a result, the opening 26 is shaped, the polysilicon film 24 is separated, and source/drain lead electrodes 27a and 27b are formed (FIG. 3(C)).

As described above, according to the third embodiment of the first invention, the gate electrode 22 can be fixed by narrowing the laser beam and irradiating the predetermined portion in a short time without using a resist film as a mask.
Only the upper polysilicon film 24 can be removed locally and with minute dimensions on the order of submicrons.

■Embodiment of the second invention FIGS. 4(a) to 4(c) are cross-sectional views illustrating an embodiment of the semiconductor substrate etching method of the second invention in which grooves are formed in a semiconductor substrate. ．． The difference from the etching method shown in FIG. 2 is that the etching is performed with the St substrate heated in advance. First, as shown in FIG. 3(a), 31 substrates 2 are placed on a mounting table 31 having a built-in heater in a chamber with a reduced pressure atmosphere.
8! ! After placing the Si substrate 28 thereon, the Si substrate 28 is heated by a heater to a temperature of 600 to 700° C. that does not cause an oxidation reaction.

Next, after introducing the Ox/IP/Ng mixed gas, a laser beam is irradiated onto the part where the groove is to be formed. Then, the temperature rises locally due to the laser beam irradiation, and only this area becomes 100%
The temperature will be around 0'C. As a result, the Ox gas in the Ox/IIF/N* mixed gas reacts with the Si substrate 28, and the StO
Although the z film 29 is formed, this SiO, lI! 29 is immediately removed by HF in the Ox/IP/N* gas mixture.

These reactions are repeated one after another, and the groove 30a gradually becomes deeper (FIG. 3(b)). In this case, since the Si substrate 28 has been heated in advance, the temperature required for oxidation is immediately reached by irradiation with a low energy laser beam. For this reason,
There is no need to use a high-performance light generation device.

By maintaining this state for a predetermined period of time, this reaction progresses one after another, forming the groove 30b of a predetermined depth (FIG. 3(c)). As described above, the second invention can be carried out. According to the example, Si
Since the oxidation reaction can be promoted by heating the group #Ji2B, it can be easily ethoched using a low energy laser beam. Although the above is an explanation based on the embodiments of the present invention, the present invention is not limited to the above embodiments and can be modified in many ways. For example, in the above description, coherent light such as Nd-YAG laser light or excimer laser light has been used as the light used for heating. Of course, it goes without saying that coherent light is useful for local heating, but incoherent light may also be used when applied to not-so-fine areas.

〔Effect of the invention〕

As described above, according to the manufacturing method of the first invention, etching is performed by repeatedly forming and removing an oxide film using light energy, so that heavy metal contamination and damage to the semiconductor substrate and semiconductor film are not caused. , and it is possible to locally and finely etch a semiconductor substrate, a semiconductor film, etc.

Further, for this reason, the heavy metal contamination layer and the damaged layer can be removed without affecting other parts without covering the parts of the semiconductor substrate other than the part to be etched. Moreover, no new heavy metal contamination or damage occurs in the removed traces.

This makes it possible to simplify the process and improve the performance and reliability of the semiconductor device. Furthermore, according to the manufacturing method of the second invention, since the semiconductor substrate is heated by the heating means separately from the heating by light, the energy of the light for causing the oxidation reaction in the manufacturing method of the first invention is It can be small. As a result, there is no need for a high-performance light generating device, and the effects of the manufacturing method of the first invention can be achieved more easily.

[Brief explanation of drawings]

FIG. 1 is a sectional view explaining the first embodiment of the first invention, FIG. 2 is a sectional view explaining the second embodiment of the first invention, and FIG. 3 is a sectional view explaining the first embodiment of the first invention. FIG. 4 is a sectional view illustrating a third embodiment of the invention; FIG. 4 is a sectional view illustrating a second embodiment of the invention; FIG. 5 is a sectional view illustrating a conventional etching method. (Explanation of symbols) 1, 4, 12, 15, 18.
28...St group 4 anti, 2,l1...resist film, 3. 17a, 17b. 17c, 30a, 30
b-... Groove, 5.19... Field oxide film, 6.21... Gate oxide film, 7.22... Gate electrode, 7a... Gate portion, 8 a, 8 b. 20a, 20b--S/Df
iJl area, 9. 14a, 14b, 16a,
16b 2 3 2 5...S+02 film, 10a, 10b, 27a, 27b-S/D extraction electrode, 1
3a... Heavy metal contamination layer or damaged layer, 24... Polysilicon film, 26... Opening, 31... Mounting table with built-in heater.

Claims (2)

[Claims] (1) The surface of the semiconductor substrate in a reduced pressure atmosphere is exposed to a reactive gas containing oxidizing gas and hydrofluoric acid gas, and the semiconductor substrate is heated by light irradiation, thereby forming an oxide film on the surface of the semiconductor substrate in the light irradiated area. 1. A method of manufacturing a semiconductor device, comprising immediately etching the formed oxide film while forming the oxide film. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor substrate according to claim 1 is heated auxiliarily by a heating means in addition to heating by light.