JPH1131677A - Method and device for etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an etching device through which local etching can be performed without damaging or contaminating an object to be etched. SOLUTION: Etching gas supplied to an active gas generating tube 13 is irradiated with ultraviolet rays produced by an ultraviolet(UV) light source 15 and is decomposed and activated. The activated etching gas is introduced into a chamber 2 under a reduced pressure, through an etching gas inlet tube 20. The activated etching gas is injected from an end of the etching gas inlet tube 20 to only the protruded region of the surface of an object 3 to be etched which is placed on a holding means 4 for object to be etched. Local etching is performed this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method and an etching apparatus, and more particularly to an etching method and an etching apparatus for locally etching the surface of an object to be etched to flatten the object to be etched.

[0002]

2. Description of the Related Art Heretofore, when flattening a substrate such as a silicon wafer or an aluminum disk, a flat plate is pressed from both sides of the substrate, rubbed while supplying water and an abrasive, and lapping and polishing for mechanical polishing. Methods are known. On the other hand, in recent years, instead of the mechanical processing method as described above, an etching method has been proposed in which local plasma etching is performed on the substrate surface to eliminate the surface irregularities and flatten or reduce the thickness of the substrate. (Japanese Patent No. 25656517, Japanese Patent Application Laid-Open No. 9-2748)
No. 2 gazette. )

As a technical requirement for improving the flatness of such a substrate, for example, in a semiconductor wafer, a high-density wiring and a multi-layer structure are progressing with an increase in the speed and the function of an LSI circuit operation. Therefore, as one of the solutions for increasing the density, the wiring width is reduced while suppressing the chip area from expanding to some extent.

In a lithography technique for optically forming a wiring pattern, the resolution (R) and the depth of focus (DOF) of an optical lens have a relationship expressed by the following equation. R∝λ / NA DOF∝λ / (NA) ² where λ is the exposure wavelength and NA is the aperture ratio of the optical lens. Due to such a relationship, when the exposure wavelength is reduced in order to perform finer processing, the depth of focus (DOF) also decreases, and the allowable minute unevenness of the substrate decreases.

As described above, in order to cope with miniaturization, it is indispensable to reduce the unevenness or thickness variation of the substrate and to planarize it. However, in the planarization by the conventional mechanical polishing, the flatness is limited. There is a problem that flattening of a semiconductor wafer for VLSI in the future cannot be coped with.

[0006]

On the other hand, the local etching by the plasma etching method described in the above-mentioned publication is a more effective method for flattening and smoothing the substrate than the mechanical polishing. However, the local etching method is based on the principle that etching is performed by reacting high-energy ions generated in plasma with atoms constituting the substrate surface. Contamination cannot be avoided.

[0007] The high-energy ions also etch the discharge tube wall material such as quartz surrounding the plasma generating portion. Therefore, a method of reducing the ion energy by reducing the power of the high frequency or microwave applied to the plasma to prevent substrate damage and material consumption can be considered, but the plasma becomes unstable, and the decrease in the ion energy decreases the etching rate. To do so, the above method is not feasible as a solution to the problem.

As described above, at this stage, it is inevitable to employ an inefficient method of removing a damage or a contaminated layer generated by etching the substrate by polishing again by a mechanical or chemical method. In view of the above problems, the present invention proposes an etching method and an etching apparatus capable of efficiently performing an etching process without damaging the surface of an object to be etched such as a substrate.

[0009]

According to the present invention, an etching gas is irradiated with ultraviolet rays in order to etch only a convex region on the surface of an object to be etched and only a surface region of a relatively thick portion of the portion to be etched. Decomposition and activation
The activated etching gas is jetted only to the protruding region on the surface of the object to be etched or only to a relatively thick surface region of the object to be etched, thereby etching the surface of the object to be etched.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of an etching apparatus according to the present invention will be described with reference to FIG. As shown in FIG. 1, an etching apparatus 1 includes an etching object holding means 4 for holding an etching object 3 such as a silicon wafer in a stainless steel chamber 2, and an X on which the etching object holding means 4 is mounted. -Y table 5 is arranged. A position control computer 9 is connected to the stepping motors 6 and 7 for moving the XY table 5 via an XY motor driver 8, and the position control computer 9 controls the XY table 5. Movement is controlled. Therefore, the etching object holding means 4 is a moving means for relatively moving the etching object 3 and an etching gas introduction pipe 20 described later. The chamber 2 is evacuated from the exhaust port 10 by a vacuum pump and decompressed, and the inside thereof is maintained at a reduced pressure of about 70 Pa (0.5 torr).

The source gas supply device 11 is, for example, 3
Gas cylinders 11a to 11c.
a, etching gas SF ₆ , gas cylinder 11 b, oxygen mixed with the etching gas, gas cylinder 11 c
Are filled with argon (Ar) mixed as a carrier gas. These gases are supplied from the upstream side of the active gas generating tube 13 made of quartz through the raw material gas supply pipe 12, and a wavelength 185 emitted from an ultraviolet light source (UV light source) 15 driven by an ultraviolet (UV) light source power supply 14.
UV light 16 of nm is applied to the gas stream 18.

The gas stream 18 irradiated with the ultraviolet rays 16 is decomposed and activated. Then, the activated etching gas becomes an active gas flow 19 and becomes an active gas generation pipe 13.
Etching gas introduction pipe 20 made of quartz integrally formed with
And is sprayed from the tip of the etching gas introduction pipe 20 toward a local etching region of the etching target 3. Here, by forming a nozzle at the tip of the etching gas introduction pipe 20, it is possible to accurately inject the etching gas particularly only to the convex region on the surface of the object to be etched.

Further, when etching the surface region of a relatively thick portion of the object to be etched, the nozzle is omitted and the spray is uniformly performed on a relatively wide region. In this case, etching is performed by exchanging the active gas generating tube according to the surface state of the object to be etched.

On the opposite side of the active gas generating tube 13 from the ultraviolet light source 15, an aluminum reflecting mirror 21 for reflecting the ultraviolet light 16 is disposed.
6 can be reflected to efficiently irradiate the gas flow 18 with the ultraviolet light 16.

Although SF ₆ is used as the etching gas, CF ₄ or another fluorocarbon gas may be used instead of SF ₆ . Further, instead of oxygen mixed with the etching gas, an oxygen compound such as CO, H ₂ O, N ₂ O, and NO ₂ can be used. Alternatively, argon (Ar) may be used as a carrier gas.

Here, the material of the active gas generation tube and the etching gas introduction tube is quartz, and the wavelength of the ultraviolet light source is 185.
Although a low-pressure mercury lamp emitting ultraviolet light of nm was used, when the active gas generating tube is a quartz tube, ultraviolet light having a wavelength of about 170 nm can be used. When irradiating a gas stream with ultraviolet light having a shorter wavelength, for example, ultraviolet light having a wavelength of 160 nm, a calcium fluoride tube is used as an active gas generating tube, or a quartz tube or a fluorine resin tube is provided with a calcium fluoride window attached. Use the activated gas generating tube.

Hereinafter, specific examples of the active gas generating tube and the window for irradiating the gas stream with ultraviolet rays will be described. As shown in FIG.
The active gas generation tube 13a is made of fluororesin or quartz,
An ultraviolet irradiation window 22 made of calcium fluoride (CaF) transparent to the ultraviolet light 16 is provided on a side surface in the middle of the tube. The raw material gas supply device 11 is provided upstream of the active gas generation pipe 13a.
Is connected to a source gas supply pipe 12a for supplying gas. The etching gas introduction pipe 20a formed integrally with the active gas generation pipe 13a penetrates the flange 2a at the top of the chamber and enters the chamber, and its tip is arranged to face the surface of the object to be etched.

As shown in FIG. 3, the active gas generating tube 13b is made of fluorine resin or quartz, and has an ultraviolet irradiation window 23 of CaF which is transparent to ultraviolet light at the upstream end of the tube. A raw material gas supply pipe 12 for supplying gas from a raw material gas supply device 11 to an upstream side surface of the active gas generation pipe 13b.
b is connected. Further, an etching gas introduction pipe 20b formed integrally with the active gas generation pipe 13b penetrates the flange 2a at the top of the chamber and enters the chamber, and its tip is arranged to face the surface of the object to be etched.

The active gas generating tube shown in FIG. 2 is easy to mount the reflection mirror 21, can effectively use the energy of ultraviolet rays, and has a region where the gas is activated by irradiating ultraviolet rays. Since it is short, it is suitable for irradiating ultraviolet rays having a short wavelength (high energy). On the other hand, since the active gas generating tube 13b shown in FIG. 3 penetrates the gas flow path and is efficiently irradiated with ultraviolet rays, the region to be activated is elongated, and the decomposition and activation of the etching gas are efficiently promoted. It is suitable for decomposing and activating etching gas when using ultraviolet light having a long target wavelength.

In the etching apparatus, when etching a convex portion or a relatively thick portion on the surface of a semiconductor wafer such as a silicon wafer, information on the convex portion distribution or the thickness distribution of the silicon wafer is taken into the computer, and the desired information is obtained. The etching position and the etching depth are calculated so as to obtain the flatness. Based on this calculation result, X-
The movement of the Y stage is controlled. For example, when SF ₆ is used as an etching gas, a gas decomposed into SF ₅ + F ^* is jetted onto the convex portion of the silicon wafer to generate neutral radicals F ^*.
Isotropic etching is performed to eliminate the projections and flatten.

As an example, SF _{6 is used} as an etching gas.
A mixed gas of oxygen and oxygen is used, and the oxygen gas is adjusted by a needle valve in the gas flow path so that the partial pressure thereof is 10% of the whole. These gases are passed through a quartz tube having an outer diameter of about 13 mm, which constitutes an active gas generating tube, and irradiated with ultraviolet rays from the outside to decompose and activate. High purity quartz (T-1630S, manufactured by Toshiba Ceramics Co., Ltd.) was used for this quartz tube because if its purity is low, it absorbs ultraviolet rays and deteriorates etching characteristics.

Although a 200 W low-pressure mercury lamp was used as the ultraviolet light source, the same effect can be obtained by using a center wavelength of 172 nm. Then, the silicon wafer as an object to be etched is placed on an object-to-be-etched holding means equipped with a heater and heated to increase the etching rate by about 800 mm.
It was kept at a temperature of ° C. Further, the downstream end of the etching gas introduction pipe was opposed to the surface of the silicon wafer, and the XY table was moved and scanned according to a predetermined program while keeping the interval at 0.5 mm.

When 25 25-inch 6-inch silicon wafers were processed under the above conditions, the TTV (Total Thickness
s Variation) was 1.28 μm on average, but 0.54 μm on average after the etching treatment, and a sufficiently low flatness as compared with mechanical polishing could be achieved. Also, when the surface roughness was measured with an atomic force microscope (AFM),
At 16 points on a silicon wafer, Ra <5 nm showed significantly better values than the plasma etching method.

[0024]

According to the etching method and the etching apparatus of the present invention, the etching gas is decomposed and activated by irradiating ultraviolet rays, and the decomposed and activated active gas is locally jetted to the object to be etched. Since the etching is performed by the etching, damage and contamination of the object to be etched can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an etching apparatus of the present invention.

FIG. 2 is a configuration diagram of an active gas generation tube of the etching apparatus of the present invention.

FIG. 3 is another configuration diagram of the active gas generation tube of the etching apparatus of the present invention.

[Explanation of symbols]

1. Etching apparatus 2. Chamber 3. Etching object 4. Etching object holding means 11. Raw material gas supply device 13. Active gas generation tube 15. Ultraviolet (UV) light source 20. Etching gas Introductory pipe

Claims (12)

[Claims] 1. An etching method for etching only a convex region on a surface of an object to be etched and flattening the surface of the object to be etched, wherein the etching gas is irradiated with ultraviolet rays to decompose and activate, and the decomposition and activation are performed. An etching method, wherein the etching gas is jetted only to the convex region on the surface of the object to be etched to etch only the convex region, thereby planarizing the surface of the object to be etched. 2. The etching method according to claim 1, wherein the ultraviolet light has a wavelength of 185 nm or less. 3. The etching method according to claim 1, wherein said etching gas is a fluorine compound gas. 4. The etching method according to claim 3, wherein said etching gas contains oxygen or an oxygen compound. 5. An etching method for etching only the surface region of a relatively thick portion of an object to be etched and flattening the surface of the object to be etched. The surface of the object to be etched by injecting the activated etching gas only to the surface area of the relatively thick part of the object to be etched to etch only the surface area of the relatively thick part of the object to be etched Etching method characterized by flattening. 6. The etching method according to claim 5, wherein the ultraviolet light has a wavelength of 185 nm or less. 7. The etching method according to claim 5, wherein said etching gas is a fluorine compound gas. 8. The etching method according to claim 7, wherein the etching gas contains oxygen or an oxygen compound. 9. An ultraviolet light source, means for irradiating ultraviolet light generated by the ultraviolet light source to decompose and activate an etching gas, a reduced-pressure chamber, and provided in the reduced-pressure chamber, An object-to-be-etched holding means for holding an object; and an etching gas for introducing a decomposed and activated etching gas into the depressurized chamber and injecting the etching gas only into a convex region on the surface of the object to be etched. An etching apparatus comprising an introduction unit. 10. The etching apparatus according to claim 9, wherein said object-to-be-etched holding means is moving means for relatively moving said object-to-be-etched and said etching gas introducing means. 11. An ultraviolet light source, means for irradiating ultraviolet light generated by the ultraviolet light source to decompose and activate an etching gas, a depressurized chamber, and provided in the depressurized chamber. An object-to-be-etched holding means for holding an object to be etched, and a decomposed and activated etching gas introduced into the depressurized chamber, and the etching gas is jetted only to a relatively thick surface region of the object to be etched. An etching apparatus comprising: an etching gas introduction unit. 12. The etching apparatus according to claim 11, wherein the object-to-be-etched holding means is a moving means for relatively moving the object-to-be-etched and the etching gas introducing means.