JPS62232927A - Method and device for dry etching - Google Patents

Abstract

PURPOSE:To perform high-accuracy directional etching controllably to prevent damage to a surface of a processed substrate, by generating ions by optical excitation and then providing the ions with directionality by an electric field so that etching is performed. CONSTITUTION:D-c voltage is impressed on a sample board 13, and an electric field is impressed in the direction vertical to the surface of the substrate 12 at the vapor phase part near the surface of the processed substrate 12, and vacuum ultraviolet rays 26 are radiated close to the surface of the substrate 12. Radiation of the ultraviolet rays 26 causes ions, which are made by ionizing gaseous molecules by light in the vapor phase near the surface of the substrate 12. These ions are made incident to the surface of the substrate 12 by the electric field existing in the surface. Thus, anisotropic etching of P-addition polycrystal Si can be performed in a state of no trailing. Hence, controllable and high-accuracy directional etching is performed, preventing damages on the surface of the substrate 12.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to dry etching technology used in semiconductor device manufacturing processes, and in particular to anisotropic etching of LSI materials using light. The present invention relates to a dry etching method and a dry etching apparatus.

(Prior Art) Conventionally, dry etching techniques using charged particles, typified by reactive ion etching (RIE), have been mainly used in microfabrication methods in semiconductor device manufacturing processes. However, it is known that the incidence of these charged particles on a substrate to be processed has an adverse effect on device characteristics, and problems in processes using charged particles have become clear. That is, it has become clear that the incidence of charged particles damages the substrate to be processed.

Recently, photo-excited etching has been proposed as a method for etching without causing damage due to charged particles. In photo-excited etching, if only the etching species is supplied to the substrate, accurate microfabrication cannot be achieved because etching proceeds in the same direction depending on the material. Therefore, directional etching by photoexcitation has been proposed in which an etching species and a deposition species are simultaneously supplied and light is irradiated perpendicularly to the substrate to be processed (for example, USP 452,975). Although this pre-excited etching method achieves anisotropic etching without undercuts, the etching shape is not as shown in Figure 6 (
As shown in (a), the bottom of the etching may draw a ridge, which is a problem in a process that requires higher precision machining, as shown in (b) of the same figure. In FIG. 6, 61 is an etching stop layer, 62 is an object to be etched, and 63 is a mask.

On the other hand, a method has already been reported in which directional etching is performed by supplying a deposited species together with an etching species to a substrate to be processed housed in a container, and irradiating the substrate with light from a perpendicular direction (USP, 4529475 or 1985
Dry Process 5yIIIp,). this is,
As shown in FIG. 7(a), if there is no light irradiation, the thin film B4 will be deposited on the entire surface of the substrate to be processed and etching will not proceed, but if there is light irradiation 65 as shown in FIG. 7(b), On the light irradiated surface, the deposited film 64 is removed and etching progresses. Then, on the etched side where there is no light irradiation, a thin film 6
4 remains to prevent undercutting and thereby achieve directional etching.

Although this method performs directional etching without undercuts, the actual shape of the etching is as shown in FIG. 6(a), with a ridge drawn at the bottom of the etching. This is because the light intensity becomes weaker at the edge of the mask due to the diffraction effect, and becomes more pronounced as the wavelength of the light used becomes longer.

(Problems to be solved by the invention) As described above, in the conventional dry etching using optical excitation,
It has been difficult to perform highly accurate directional etching without causing damage to the substrate being processed.

The present invention has been made in consideration of the above circumstances, and its purpose is to enable highly controllable and highly accurate directional etching by using ions generated by optical excitation, and to An object of the present invention is to provide a dry etching method that can prevent damage to the surface of a processed substrate.

Another object of the present invention is to provide a dry etching apparatus for carrying out the above method.

[Structure of the Invention (Means for Solving Problems)] The gist of the present invention is to generate ions by optical excitation and to give directionality to the ions by an electric field for directional etching of materials for manufacturing semiconductor elements. The purpose is to perform etching.

That is, the present invention provides a dry etching method for directional etching the surface of a substrate to be processed, in which a gas is supplied to the surface of the substrate and an electric field is applied in a direction perpendicular to the surface of the substrate. In this method, the gas is ionized by irradiating the surface or the vicinity of the surface of the substrate to be processed, and the ionized particles are caused to enter the surface of the substrate to be processed by the electric field to etch the surface.

The present invention also provides a dry etching apparatus for carrying out the above method, which includes a container for accommodating a substrate to be processed, a means for introducing a gas into the container, and a light source that applies energy higher than the ionization potential of the gas. The apparatus is provided with means for irradiating the surface or near the surface of the substrate to be processed, and means for generating an electric field in a direction perpendicular to the surface of the substrate to be processed.

(Function) In the above method, ions are generated by exciting gas particles absorbed in the gas phase or on the surface of the substrate to be processed by light irradiation, and these ions are accelerated in the gas phase by an electric field or By drawing ions inward from the surface of the substrate to be treated, directional etching can be performed along the direction of the ions. In this case, by appropriately controlling the strength of the electric field, it is possible to eliminate damage to the substrate to be processed due to ion irradiation. Furthermore, in etching by this method, slow ions have no diffraction effect at the edge of the mask, and an etched shape as shown in FIG. 6(b) can be obtained. Furthermore, even in the etching of a substance in which the light intensity on the surface of the substrate to be processed affects the etching rate, the wavelength of the light that causes ionization of particles is generally short, so that the diffraction effect is small.

(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 according to a first 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 installed inside the container 11. The container 11 has a gas inlet 1
4.15, and one end of the discharge tube 1G is connected to the gas inlet 14. The discharge tube 16 is a microwave tail 71J! It is coupled to a waveguide 18 connected to 17. At the other end of the discharge tube 1B, F, C
, ff, respectively (e.g. NF3
and C)2) are introduced, and these gases are dissociated in the discharge tube 1G and then introduced into the container 11. Further, from the gas inlet 15, a deposition gas (for example, M
MA) is introduced. The gas in the container 11 is exhausted from the gas exhaust port 19.

On the other hand, a window 21 is provided in the upper part of the container 11, and light (second light) 23 from a light source 22 such as an Hg lamp is introduced into the container 11 through this window 21, and the substrate 12 to be processed is Illuminated perpendicular to the surface. Further, an ultraviolet light transmission window 24 is provided on the right side of the container 11, and ultraviolet light (first light) 2 is emitted from a vacuum ultraviolet light source 25 through this window 24.
G is introduced into the container 11 and irradiated horizontally near the surface of the substrate 12 to be processed.

Further, a DC power source 27 with the polarity shown is connected to the sample stage 13, thereby generating an electric field in the vertical direction on the surface of the substrate 12 to be processed.

Next, a dry etching method using the above apparatus will be explained. Here, NF3. C12 mixed gas, gas inlet 1
Methyl methacrylate (M
A case where P-doped polycrystalline silicon is anisotropically etched using MA) will be described.

NF3. C-2. Polycrystalline Si can be anisotropically etched by introducing MMA under certain conditions and irradiating the surface of the substrate 12 to be processed with ultraviolet light 23 from an Hg lamp or an excimer laser in a vertical direction. As shown in FIG. 6(a), the shape is such that the etched bottom part has a ridge.

Therefore, in this embodiment, a DC voltage is applied to the sample stage 13, an electric field is applied to the gas phase portion near the surface of the substrate 12 to be processed in a direction perpendicular to the substrate surface, and vacuum ultraviolet light 26 is applied to the substrate surface. irradiate. By irradiating the vacuum ultraviolet light 2B, gas molecules in the gas phase near the surface of the substrate 12 to be processed are ionized by the light to generate ions. These ions are incident on the surface of the substrate 12 to be processed due to the electric field present on the surface. At this time, the acceleration energy of the ion is 150 [e
Adjust the DC voltage so that it does not exceed V].

In this way, low-velocity ions can be made incident on the surface of the substrate 12 to be processed at the same time as the light irradiation, and the etched shape in this case becomes a shape without flaring as shown in FIG. 6(b). Furthermore, the etching speed is about twice as fast as when compared to etching using only light irradiation.

Thus, according to this embodiment, by using ions produced by light irradiation, it is possible to anisotropically etch the P-doped polycrystal S1 into a shape without trailing, and at the same time, the etching rate is lower than that achieved by conventional light excitation alone. can be approximately twice as fast. Moreover, by adjusting the voltage applied to the sample stage 13 to be lower than the voltage at which discharge occurs within the container 11, damage to the surface of the substrate 12 to be processed due to ion irradiation can be eliminated. Therefore, it will be extremely useful in future integrated circuit manufacturing technology.

Note that in the above embodiment, N is used as the gas for supplying active species.
F3. C, l? 2 and using MMA as the gas for generating the deposited species, but instead of NF3, CF, c2F8. C
3F8. SF8. Any gas containing F, such as F2, that generates etching species by electric discharge can be used. Similarly, C, e2 represents Niha, CCl2< ,
BCI! Any material including C, +7, such as 3° PCJ23, which generates etching species by discharge, can be used.

Furthermore, in the case of this system, since deposition occurs due to the reaction between the C, +7-based active species and MMA, only C12 may be used as the gas for supplying the active species. In addition, as a deposition gas,
Methacryl, acrylic organic gas, or other organic gas may be used instead of MMA. Further, as the deposition gas, an inorganic gas such as SiH4, SiCl2, or a mixed gas of these gases with oxygen and nitrogen may be used.
In this case, the deposition can be caused by discharging the gas that causes the deposition in a region separate from the etching chamber, exciting it in advance, and supplying it to the substrate to be processed.

Furthermore, the etching material is not limited to polycrystalline Si, but if an F-based material is used as the etching species, single crystal Si, S
It is possible to etch i02, S i3 N4, W, Mo, etc., and if C-based materials are used, AI is achieved.

Ga As, Ga A J! By selecting the gas, anisotropic etching of all kinds of semiconductors and metal insulators can be achieved.

The vacuum ultraviolet light 2B to be irradiated may be of any type as long as it can ionize the particles in the container 11. For example, Ar, K
A lamp using a rare gas discharge such as r, In the case of the example, in order to promote photoionization, Ar, Kr, Xe, He, etc. are mixed into the reactive gas, and the light energy is first absorbed by these inert gases, and the other gases are absorbed by the reaction with the excited species. ionize the particles of
By using so-called sensitizing action or catalytic action,
It is possible to improve the efficiency of ionization.

Further, since particles excited by the discharge are ionized by relatively low-energy light, if the particles are to be ionized, ordinary ultraviolet light may be used as the ionization light source.

Furthermore, in the above example, the ionizing light 2G is incident parallel to the surface of the substrate 12 to be processed to generate ions near the surface. The light may be incident perpendicularly to the surface. Here, the window 24 is used to allow the vacuum ultraviolet light 2B to enter, but 1
There are a limited number of window materials that allow light of [eV] or higher to pass through, and their light transmittance is also poor. Therefore, a method may be used in which the incident vacuum ultraviolet light is made to enter without using the window 24 by an actuated exhaust system.

In addition, in the above example, a method of performing directional etching using both etching and deposition reactions was described, but in this etching method that utilizes the directionality of ions, since the directionality of etching is originally good, the deposition gas It is not necessary to use In this case, although the etching speed is slow, the etched shape has no hemline as shown in FIG. 6(b), and it has been confirmed that good directional etching is achieved.

FIG. 2 is a block diagram showing the main parts of a second embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals. Since the gas introduction and exhaust systems are the same as those shown in FIG. 1, they are omitted here, and the outline of the apparatus configuration regarding the method of installing the substrate 12 to be processed and the method of light irradiation is shown.

The substrate 12 to be processed is placed on a sample stand 13 to which an electric field can be applied, and the sample stand 13 has a temperature adjustment mechanism 31 for adjusting the temperature of the substrate 12 to be processed. The light 2G for ionization is irradiated vertically onto the surface of the substrate 12 to be processed, but there is an optical mask 32 in the optical path from an ultraviolet light source (not shown), and the pattern of the mask 32 is irradiated on the surface of the substrate 12 to be processed. The image is formed on the surface.

With such a configuration, by forming an optical image patterned by the mask 32 on the surface of the substrate 12 to be processed and irradiating it, only the light irradiated area can be etched and the pattern can be transferred. FIG. 3 is a schematic diagram showing the correspondence between mask patterns and etching shapes. in this case,
The mask 32 can be placed close to the substrate 12 to be processed using a close exposure method, or it can be installed away from the substrate 12 to be processed.
A projection exposure method may be used in which the image is projected onto the surface of the substrate 12 to be processed using an optical system.

FIG. 4 is a schematic diagram for explaining two different mechanisms for pattern transfer.

FIG. 4(a) shows a method in which an electric field E1 shown in the figure is applied in the gas phase near the surface of the substrate 12 to be processed, and ions 35 generated at the light irradiation part in the gas phase are It is accelerated by the electric field E1 and made incident on the surface of the substrate 12 to be processed to perform directional etching and pattern transfer. Also,
FIG. 4(b) shows a method of generating an electric field E2 inside the substrate 12 to be processed near its surface. In this case, when the gas particles 36 are adsorbed all over the surface and the light 26 is irradiated partially on the surface, the adsorbed particles 36 are ionized in the light irradiation area and become etching species 37, which causes the inside of the substrate 12 to be processed to be etched. Etching species 37 due to the electric field E2 of
By drawing the material inside, the etching reaction is promoted and the pattern is transferred.

Adsorption of reactive species tends to occur at low temperatures, and in order to control the amount of adsorption, it is necessary to adjust the substrate temperature to a low temperature. For example, if Si is used as the substrate and the substrate temperature is -3
When the temperature is adjusted to 0['C] or less and F2 gas is used as the reactive gas, the F2 gas is adsorbed to the substrate surface, but etching progresses extremely slowly. Therefore, if we irradiate light with an energy higher than lo [eV] that ionizes F2 gas to cause ionization of F2-F2+ and then apply an electric field inside the substrate, etching will occur in the light irradiated area. .

Here, the electric field generated near the surface does not have to be a DC electric field. When a DC electric field is applied, only positive or negative charges are incident on the substrate surface, and there is a possibility that the substrate will be charged up.

This is particularly noticeable when etching insulators. In order to prevent this charge-up, there is a method of applying an alternating current electric field and making positively charged particles and negatively charged particles alternately inject onto the surface of the substrate to keep the amount of charge inside the substrate neutral. The effect disappears.

FIG. 5 is a block diagram showing a main part of a third embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

This is a method in which light of two wavelengths is incident perpendicularly onto the surface of the substrate 12 to be processed. In the figure, 51 is a mirror that transmits only the light 23 from the light source 22 and reflects the light 2B from the light source 25. By using this mirror, both lights 23 and 26 are directed perpendicularly to the surface of the substrate 12 to be processed. It can be made incident from any direction. Also, two lights 23.26
may be irradiated simultaneously or may be irradiated alternately using a pulsed light source. Even in the case of a CW light source, by making the mirror 51 movable, light can be made to enter alternately.

Furthermore, if synchrotron radiation (SOR) is used, the wavelength components in the synchrotron radiation are extremely wide from the soft X-ray region to the infrared region, and by using a filter that cuts unnecessary wavelength regions, It is also possible to mix the necessary wavelengths and simultaneously irradiate the substrate to be processed.

In summary, the present invention provides a container for accommodating a substrate to be processed, a means for introducing an etching gas or the like into the container, a means for generating ions by irradiating the gas with ultraviolet light, etc. The basic element is a means for generating an electric field, and the type of gas, type of light, irradiation direction, etc. can be changed as appropriate according to specifications.

[Effects of the Invention] As described in detail above, according to the present invention, materials used for manufacturing semiconductor devices can be directionally etched with high precision without causing the bottom part of the etching to become flabby. Further, etching can be performed without damaging the etching substrate and its underlying substrate. Therefore, it is an ultrafine element.

It is suitable for manufacturing processes of high-speed devices or VLSIs.

Furthermore, since ions are involved in etching,
Compared to conventional photo-excited etching, the etching speed can be increased, and practical effects can also be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a dry etching apparatus according to a first embodiment of the present invention, FIG. 2 is a diagram showing a main part of a dry etching apparatus according to a second embodiment of the present invention, and FIG. 3 is a conceptual diagram of pattern transfer. FIG. 4 is a schematic diagram for explaining the etching mechanism, FIG. 5 is a configuration diagram of main parts showing the third embodiment of the present invention, and FIGS. 6 and 7 are respectively related to conventional problems. FIG. 3 is a cross-sectional view for explaining the points. 11... Vacuum container, 12... Substrate to be processed, 13...
・Sample stage, 14.15...Gas inlet, 16...Discharge tube, 17...Microwave power supply, 18...Waveguide,
19...Gas exhaust port, 21.24...Window, 22.2
5... Light source, 23... Second light, 26... First light, 27... DC power supply, 31... Cooling mechanism, 32...
··mask. Applicant's agent Patent attorney Takehiko Suzue Figure 3 (a) Figure 4 Figure 5 Figure 6

Claims (21)

[Claims] (1) Gas is supplied to the surface of the substrate to be processed, an electric field is applied in a direction perpendicular to the surface of the substrate, and light is irradiated on or near the surface of the substrate to be processed to ionize the gas. A dry etching method characterized in that the particles are made incident on the surface of the substrate to be processed by the electric field to etch the surface. (2) The dry etching method according to claim 1, wherein an etching gas containing at least a halogen element is used as the gas. (3) The dry etching according to claim 1, wherein a mixed gas of an etching gas containing at least a halogen element and an organic deposition gas such as acrylic or methacrylic is used as the gas. Method. (4) A patent characterized in that the gas is a mixed gas of an etching gas containing at least a halogen element and a silane-based inorganic deposition gas, or a mixed gas to which nitrogen or oxygen is added. A dry etching method according to claim 1. (5) The dry etching method according to claim 1, wherein the gas is dissociated in advance before the light irradiation. (6) The dry etching method according to claim 1, characterized in that the light is irradiated perpendicularly to the surface of the substrate to be processed or horizontally irradiated near the surface of the substrate. (7) The substrate to be processed is patterned with a mask using a resist.
Dry etching method described in section. (8) The dry etching method according to claim 1, wherein the light is selectively irradiated onto the surface of the substrate to be processed. (9) A patent characterized in that, as the light, a first light for ionizing the etching gas and a second light for exciting the deposition gas or the surface of the substrate to be processed are used. A dry etching method according to claim 1. (10) The dry etching method according to claim 1, wherein the substrate to be processed is cooled. (11) a container for accommodating a substrate to be processed, a means for introducing a gas into the container, and a means for irradiating the surface or near the surface of the substrate to be processed with light having an energy higher than the ionization potential of the gas; A dry etching apparatus comprising means for generating an electric field in a direction perpendicular to the surface of the substrate to be processed. (12) The dry etching apparatus according to claim 11, wherein the gas is an etching gas containing at least a halogen element. (13) The dry etching according to claim 11, wherein the gas is a mixed gas of an etching gas containing at least a halogen element and an organic deposition gas such as acrylic or methacrylic. Device. (14) A patent characterized in that the gas is a mixed gas of an etching gas containing at least a halogen element and a silane-based inorganic deposition gas, or a mixed gas to which oxygen and nitrogen are added. A dry etching apparatus according to claim 11. (15) The dry etching apparatus according to claim 11, wherein the gas is dissociated in advance in another container connected to the container in a vacuum. (16) The dry etching apparatus according to claim 11, wherein the electric field generated on the surface of the substrate to be processed is smaller than a threshold electric field at which discharge occurs within the container. (17) The light is irradiated perpendicularly to the surface of the substrate to be processed, or horizontally near the surface of the substrate to be processed, according to claim 11. Dry etching equipment. (18) The dry etching apparatus according to claim 11, further comprising means for perpendicularly irradiating the substrate to be processed with light in a wavelength range other than the light that causes ionization of the gas. (19) The dry etching apparatus according to claim 11, wherein the substrate to be processed has a mask pattern made of resist formed on its surface. (20) The dry etching apparatus according to claim 11, wherein the light is selectively irradiated onto the surface of the substrate to be processed. (21) The dry etching apparatus according to claim 11, further comprising a cooling mechanism for cooling the substrate to be processed.