JP4625153B2 - Plasma etching apparatus and etching method using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dry etching apparatus for processing at high speed, and more particularly to an apparatus for thinning a semiconductor wafer or an insulator wafer or precisely forming a through hole in a deep step or wafer.
[0002]
[Prior art]
A semiconductor wafer having a semiconductor element or an integrated circuit formed on the front surface is used by cutting the back surface uniformly and thinning it, then cutting it into chips and assembling it into a package. Chip thinning not only increases the heat dissipation effect of the chip, reduces the consumption of cutting tools (such as cutters and saws) used in dicing and extends the life, but also reduces the height of the package to achieve high-density mounting. It is necessary for the purpose. In addition, a technique for stacking chips for higher performance and higher density requires through-holes for conducting on the front and back of the wafer. The MMIC also uses through holes and conducting electrodes.
[0003]
Further, in MEMS (Micro-ElectroMechanical Systems), in order to form ultra-compact parts and devices, a technology for forming three-dimensional processing by forming deep steps and through holes in a semiconductor wafer or glass wafer is essential. Conventionally, in order to uniformly thin a substrate crystal of a semiconductor wafer, a polishing apparatus presses a flat plate against the back surface of the semiconductor wafer via a polishing cloth and supplies a polishing liquid between the wafer and the polishing cloth. In general, there are a method of polishing while interposing metal, a method of grinding with a grindstone in which hard material particles such as diamond particles are embedded and fixed by a grinding device, and a technique of finally finishing a substrate crystal by wet etching to remove processing distortion. It has been broken. A method of forming a through hole in a semiconductor wafer is based on a parallel plate or RIE (Reactive-Ion-Etch) using ICP (Inductive Coupled Plasma). In the case of a glass wafer, the sand blast method or wet etching is used.
[0004]
[Problems to be solved by the invention]
Conventional thinning of a wafer by polishing or grinding is performed while applying compressive stress or shear stress to a substrate crystal, so that there is a drawback that the semiconductor wafer is easily damaged as it becomes thinner. Wet etching has a drawback in that productivity is poor because the process is complicated and the etching rate is slow. For this reason, the present invention provides an apparatus for uniformly thinning a wafer at high speed and with high accuracy by a plasma etching method, which is dry etching, and forming a through hole, and a high-accuracy wafer processing method using the same. The purpose is to do.
[0005]
[Means for Solving the Problems]
In the present invention, in the dry etching apparatus having a mechanism for converting the etching gas and a mixed gas containing them into plasma and ejecting the generated active species gas or the mixed gas containing them as a gas flow for etching onto the sample surface, It is characterized in that a mechanism for adding an etching support material is provided.
[0006]
In the present invention, magnetic fine particles are used as the above-mentioned etching support substance, and this is added to the etching gas together with the carrier gas (Ar or H2 gas). The etching of the sample preferentially proceeds in the depth direction by jetting the magnetic fine particles and the active species gas contained in the etching gas flow. As a result, the perpendicularity of the processed cross-sectional shape is improved and the etching rate is increased. There is. Furthermore, in order to attract and accelerate the magnetic fine particles, the above effect is enhanced by applying an external magnetic field to the sample side.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram of the entire apparatus showing an embodiment of a plasma etching apparatus according to the present invention. A gas mixture of SF 6, hydrogen and Ar is injected into the plasma generation chamber 23 from the gas supply device 14 through the reaction gas supply pipe 3. Microwaves generated by the microwave oscillator 1 pass through the waveguide 2 and are absorbed in the plasma generation chamber, and the mixed gas is activated to form a plasma active region 6. The activated species gas is squeezed by the etching nozzle 4 through the activated species gas supply pipe 13 and is jetted onto the surface of the sample (Si semiconductor wafer) 5 at a high speed as an etching beam. The sample (Si semiconductor wafer) 5 is first inserted into the sample exchange chamber 11 and is then fixedly set to the sample holding mechanism 80 in the etching chamber 9 by the transport mechanism 15. The detailed structure near the etching nozzle 4 and the sample holding mechanism 80 is not shown in the drawing. These will be described separately with reference to FIG. Since the sample holding mechanism 80 is moved in the XY direction or the X-θ direction by the sample moving mechanism 7, the entire surface of the sample can be processed. The exhaust section is performed through valves 18 provided in the etching chamber 9, the exhaust head 16, the sample exchange chamber 11, and the transfer chamber 10, and each is exhausted. Exhaust gas emitted from the etching chamber 9 and the exhaust head 16 is exhausted through the exhaust / gas treatment device 17 after detoxification. Furthermore, the configuration of the present invention is characterized in that the active species gas supply pipe 13 has a mechanism for supplying magnetic fine particles, which are etching support substances, by mixing them. In this process, magnetic fine particles are supplied to the branch port of the active species gas supply tube 13 at a positive pressure by the etching assisting substance supply device 54 and the supply tube 55 and mixed with the active species gas.
[0008]
FIG. 2 shows details of the etching gas flow ejection mechanism portion and the sample holding mechanism portion of FIG. The cycle of mixing the magnetic fine particles (etching assisting substance) may be continuous or intermittent, and the controller 20 has a configuration that can be arbitrarily programmed. The magnetic fine particles are transported in the supply pipe 55 by the carrier gas (Ar or N2) and merge with the active species gas in the active species gas supply pipe. For example, iron oxide or ferrite can be used as the material of the magnetic fine particles. In addition, a permanent magnet plate 60 for attracting and accelerating the magnetic fine particles is disposed in the vicinity of the surface of the movable table 8. As described above, the magnetic fine particles added to the activated species gas cause more processing damage to the sample. As a result, the etching rate increases as compared with the case where no magnetic fine particles are added.
[0009]
The schematic cross-sectional views of FIGS. 3 to 5 show some embodiments in the case where magnetic fine particles are added to and mixed with the activated species gas flow. FIG. 3 shows an example in which an ejection nozzle 37 provided at the tip of the magnetic fine particle supply pipe 35 is disposed in the etching nozzle 4. FIG. 4 shows an example in which the ejection nozzle 47 provided at the tip of the magnetic fine particle supply pipe 45 is disposed close to the outer periphery of the tip of the etching nozzle 4. FIG. 5 shows an example in which a fine particle ejection nozzle 87 is disposed at the tip of the magnetic fine particle supply pipe 85 so as to contain the etching nozzle 4.
[0010]
A method of cutting the back surface of the Si semiconductor wafer and processing it into a thin crystal substrate with the apparatus configuration described above will be described below. This step is performed after a high-density integrated circuit is formed on the surface of the wafer. Thereafter, the wafer is assembled into a package as a chip. First, the front surface is protected with a resin tape, and the back surface is attached to the etching nozzle. For example, when a Si wafer having a thickness of 600 μm is cut to a thickness of 50 μm, etching is performed by mixing an etching support substance (magnetic fine particles) with an etching gas until the thickness reaches about 100 μm. This is because Si is scattered by the above-mentioned etching assisting material or processing strain is left on the Si surface, and when etching gas beam containing active species is sprayed on this, Si is scraped at high speed by a chemical and mechanical synergistic effect. Because. When the Si surface is processed by mixing the etching support material, the processing strain remains on the surface. Therefore, as the processing procedure in this case, the etching to make the final 50 μm stops the supply of the etching support material and performs the etching including the active species. Etching is performed in an amount of about 50 μm using only a gas beam. This is because the etching of the active species gas beam is chemical polishing by dry, so that Si is not damaged. According to this method, the back surface processing of the Si wafer can be performed in a short time, and thereafter, the chemical polishing step by wet is unnecessary, so that the back surface processing can be completed in the same apparatus, and the productivity is dramatically improved. There is a feature that this process can be improved and the cost can be reduced.
[0011]
In the above, an example in which the apparatus according to the present invention is used for back grinding / polishing of a Si semiconductor wafer has been described. However, since this apparatus can also be applied to selective etching using a pattern mask, it can also be applied to pattern etching and formation of through holes. it can. Especially in the processing of glass substrates, glass has a lower etch rate than Si, but due to the synergistic effect of adding an etching aid, it can be cut faster than conventional sandblasting and dry etching, and the taper of the through holes is improved. .
[0012]
【The invention's effect】
(1) By jetting an etching gas flow and an etching assisting substance (magnetic fine particles) onto the surface of the sample, the sample can be processed at a high speed and a nearly vertical cross-sectional shape can be formed.
(2) The apparatus of the present invention makes it possible to thin the back surface of a semiconductor wafer by a dry process, which eliminates the need for a semiconductor wafer cleaning, affixing / removing process, and greatly shortening the process.
[0013]
[Brief description of the drawings]
FIG. 1 is a schematic diagram of the overall configuration of a plasma etching apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged schematic view of the main part shown in FIG.
FIG. 3 is a partially enlarged schematic view showing another embodiment of the device of the present invention.
FIG. 4 is a partially enlarged schematic view showing another embodiment of the device of the present invention.
FIG. 5 is a partially enlarged schematic view showing another embodiment of the device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Microwave oscillator 2 ... Waveguide 3 ... Reaction gas supply pipe 4 ... Etching nozzle 5 ... Sample 6 ... Plasma active region 7 ... Sample moving mechanism 8 ... Moving stand 9 ... Etching chamber 10 ... Transfer chamber 11 ... Sample exchange chamber DESCRIPTION OF SYMBOLS 12 ... Coupling part 13 ... Active species gas supply pipe 14 ... Gas supply apparatus 15 ... Conveying mechanism 16 ... Exhaust head 17 ... Exhaust / gas processing apparatus 18 ... Valve 20 ... Control apparatus 23 ... Plasma generation chamber 54 ... Etching assistance substance supply apparatus 35, 45, 55, 85 ... supply pipes 37, 47, 87 ... fine particle ejection nozzle 60 ... magnet plate 80 ... sample holding mechanism

Claims (2)

In a plasma etching apparatus provided with a mechanism for introducing an etching mixed gas containing an etching gas into a plasma generation chamber and a mechanism for jetting an etching mixed gas flow containing an active species gas generated in the plasma generation chamber to the sample surface,
A mechanism for adding magnetic fine particles into the mixed gas stream for etching containing the active species gas;
A plasma etching apparatus having a sample holding mechanism whose main part is composed of a magnet. An etching method comprising etching the sample surface using the etching apparatus according to claim 1.

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