JP2000150484A - Plasma etching device and etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a process for an excellent heat-radiation characteristics by considering a form of an etching nozzle at the tip of an active seed gas supply pipe and adding an exhaust head and an air delivery nozzle around it. SOLUTION: An etching nozzle 24 is fixed air-tightly by an active seed gas supply pipe 23 and a connection part 22, comprising a structure wherein the etching nozzle 24 is replaced easily. An exhaust head 26 with suction function is provided around it, and a floating gas is effectively exhausted through an exhaust port 27. Related to the etching nozzle 24, a drawn port 24-1 at a drawn tip is provided with a beam shaping part 24-2. For the purpose of efficient etching, an active seed gas is confined in the gap between a semiconductor wafer 25 and the etching nozzle 24. Thus, a semiconductor wafer is etched evenly at high speed, in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus and, more particularly, to an apparatus and a method for uniformly thinning a crystal of a semiconductor wafer on which semiconductor elements and integrated circuits are formed from the back surface.

[0002]

2. Description of the Related Art A plurality of semiconductor elements and integrated circuits are formed on a surface of a semiconductor wafer by using a semiconductor wafer. In a final stage of a manufacturing process, there is a dicing step in which the semiconductor wafer is cut into chips and separated into pellets. Before this dicing step, the semiconductor wafer is polished or back-polished to increase the heat radiation effect of the chip or to reduce the consumption of cutting tools (such as cutters and saws) used in dicing and extend the life. There is a need for a process of reducing the thickness by cutting. Until now, when thinning the substrate crystal of a semiconductor wafer uniformly, a flat plate was pressed against the back surface of the semiconductor wafer via a polishing cloth by a polishing apparatus, and a polishing liquid was supplied to polish the wafer between the wafer and the polishing cloth. Generally, a method of polishing with a liquid interposed and a method of grinding with a grindstone in which hard material particles such as diamond particles are embedded and fixed by a grinding device are known. Also, a technique for uniformly thinning a substrate crystal by wet etching has been used.

[0003]

As semiconductor elements and integrated circuits become more sophisticated and highly integrated, the amount of heat generated increases and the temperature of the devices tends to increase. In order to effectively cool the heat and prevent the temperature from rising, it is necessary to reduce the thickness of the semiconductor substrate crystal as much as possible to enhance the heat radiation effect. However, in the conventional method of polishing or grinding, the semiconductor wafer is processed while applying a compressive stress or a shear stress to the substrate crystal. Also, during processing, processing waste, abrasive particles,
Foreign matter such as grinding particles or crystal particles is mixed in and causes damage. Furthermore, in machining, a damaged layer is formed to a certain depth on the processed surface of the wafer, and a post-process of wet etching using a chemical solution is added to remove this, making the process complicated and costly There are disadvantages. In addition, the above-mentioned foreign matter remains on the back surface of the chip, which reduces the contact area with the assembled heat dissipating member, resulting in a disadvantage that effective heat dissipation cannot be achieved. In this way, the process of reducing the thickness of the wafer by machining contaminates the entire wafer with polishing liquid, adhesive, etc., so a well-established advanced cleaning technology is indispensable, and the disadvantage of increasing the cost is is there. In the method of uniformly thinning the substrate crystal by wet etching, it is particularly important to protect the wafer surface, and the etching rate is low, so that the productivity is poor. Therefore, the present invention provides a method and an apparatus for uniformly thinning a substrate crystal by high-speed etching by plasma etching, which is dry etching, and simplifies the process by a processing method in which processing distortion does not remain in the substrate crystal; An object of the present invention is to supply a semiconductor element or an integrated circuit chip having excellent heat radiation characteristics at a high yield and at a low cost.

[0004]

In the present invention, ions and radicals are generated in a plasma chamber by a high-frequency alternating-current electromagnetic field by flowing a reaction gas, and a radical active species gas is guided by a supply pipe to perform a gas phase chemical reaction. It is based on a method of etching a substrate crystal of a semiconductor wafer. In the present invention, it is possible to improve the etching characteristics of a local etching region by using a shape of an etching nozzle at the tip of an active species gas supply pipe and a structure in which an exhaust head and an air supply nozzle are added to the periphery thereof, thereby enabling efficient processing. Features. When the surface area of the semiconductor wafer is larger than the diameter of the etching nozzle, etching is performed over the entire surface of the wafer by relatively sweeping either one of them. Since the radical active species gas does not leave any processing strain in the semiconductor crystal, a wet etching process using a chemical solution is not required thereafter, and the process can be simplified. The reaction gas is selected according to the type of the semiconductor wafer. For example, for Si, halogen compound gas SF6, NF3, C
F4, C2F6, CCl4, CBrF3 or the like or a mixed gas containing the same is mainly used for GaAs, and chlorine or bromine-based Cl2, HCl, SiCl4, Br2, HBr, BCl
A gas such as 3, CCl4, CBrF3, or a mixed gas containing the same is used as a reaction gas. The plasma etching apparatus of the present invention is provided with a wafer transfer mechanism and a sample exchange chamber in order to perform processing efficiently in addition to the etching section described above. An exclusion device for treating exhaust gas is also provided.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIGS. 1 and 2 show an embodiment of a plasma etching apparatus according to the present invention. FIG. 1 is a schematic diagram of the configuration of the entire apparatus.
A mixed gas of SF6 and hydrogen gas is injected into the plasma generation chamber from the gas supply device 14 through the reaction gas supply pipe 3. The microwave generated by the microwave oscillator 1 passes through the waveguide 2 and is absorbed in the plasma generation chamber, and the mixed gas is activated to form the plasma active region 6. Since the active species gas is narrowed down by the etching nozzle 4 through the active species gas supply pipe 13 and supplied as a high-density local beam to the surface of the semiconductor wafer 5, the etching rate is greatly increased in this configuration. There is. Semiconductor wafer 5
Is first inserted into the sample exchange chamber 11, from which it is fixedly set on the movable table 8 of the etching chamber 9 by the transport mechanism 15. The moving table 8 can be moved in the XY direction or the X-θ direction by the sample moving mechanism 7. The semiconductor wafer 5 can be etched to a uniform thickness over the entire surface by the local beam generated by the active species gas from the etching nozzle 4 and the moving mechanism of the moving table 8. The exhaust unit includes an etching chamber 9, an exhaust head 16, and a sample exchange chamber 11.
The pipes are respectively connected to the transfer chamber 10 via a gate valve 18, and each is exhausted. Exhaust gas discharged from the etching chamber 9 and the exhaust head 16 passes through a gas processing device 17 and
Exhausted after harm. FIG. 2 is a detailed view around the etching nozzle 24. The etching nozzle 24 is fixed in a highly airtight manner by the active species gas supply pipe 23 and the connecting portion 22, and has a configuration in which the etching nozzle 24 can be easily replaced. In addition, an exhaust head 26 having a suction action is provided around this.
Is provided, and the floating gas is effectively exhausted through the exhaust port 27. The etching nozzle 24 has a structure in which a beam shaping section 24-2 is provided at a narrowed aperture 24-1 at the narrowed tip. This is a configuration for the purpose of performing etching efficiently, and is designed to have a configuration in which an active species gas is confined in a gap between the semiconductor wafer 25 and the etching nozzle 24. The shape of the shaping section is optimized in consideration of factors such as the flow rate of the active species gas, the presence or absence of an exhaust head, the degree of vacuum, and the gap of the space. Also,
The cross-sectional shape of the tip of the etching nozzle that emits gas may be circular, but for the purpose of reducing the overall thickness at a high speed, an elliptical, rectangular, or band-like shape is better for reducing the processing time. . For the purpose of uniformly thinning the back surface of the semiconductor wafer at a high speed, for example, a width of about 1 mm and a length of about 6
Sweeping with a local beam in a band shape from a nozzle having an elongated band-like cross-sectional shape of 0 mm has an effect of greatly shortening the sweep time as compared with a round beam. In the structure of the plasma etching apparatus having a configuration in which a large number of such etching nozzles 24 are provided, the sweep can be performed in only one direction, so that the sample can be processed continuously by a flow operation, thereby further improving the productivity. There are features.

Embodiment 2 Another embodiment of the etching nozzle according to the present invention will be described with reference to FIG. The present etching nozzle is fixed in a highly airtight manner by an active species gas supply pipe and a joint. In the etching nozzle of this embodiment, as can be seen from the side cross-sectional shape, the aperture 34-1 for narrowing the etching gas is not located at the tip of the etching nozzle, but is located inside. Further, the beam shaping unit 34-2 for shaping the released gas is characterized by having an angle (FIG. 7A). In addition, a feature is that a beam shape can be finely adjusted by adding an adjusting component 34-3 to the shaping area (FIG. 2B). Such an etching nozzle is often made of an integral part, but may be made by assembling a large number of parts.

Third Embodiment An etching nozzle according to another embodiment of the present invention and an example of a configuration around the etching nozzle will be described with reference to FIGS. The present etching nozzle will be described with reference to FIG. The present etching nozzle is fixed in a highly airtight manner by an active species gas supply pipe and a joint. In the embodiment of FIG. 4, the etching nozzle 44 has a narrow narrow band-shaped tip.
And a configuration in which an exhaust head 46 is provided in opposition thereto. The exhaust head 46 is evacuated by an exhaust pump. Therefore, most of the active species gas, the etching compound, and the like released onto the semiconductor wafer 45 are sucked and exhausted. With this structure, in the case of an etching gas that easily corrodes a metal such as a chlorine-based gas, the gas is suppressed from diffusing throughout the etching chamber. This has the effect of reducing the cost and lengthening the service life. Further, since the foreign matters such as the etching compound hardly remain on the wafer surface, the processing yield was improved. Since the floating gas does not stay on the semiconductor wafer for a long time, anisotropic etching can be performed using a mask. FIG.
In the embodiment, the air supply nozzle 57 and the exhaust head 5 are located in the vicinity of the etching nozzle 54 having a narrow band-shaped tip.
6 is basically provided. As shown, these arrangements preferably have an etching nozzle 54 in the middle. He, Ar, N2 and H2 from the air supply nozzle 57
Gas 58 is blown onto the wafer. By providing this, it becomes possible to collect the gas discharged from the etching nozzle 54 to the exhaust head more positively than the structure shown in FIG. The gas of the air supply nozzle 57 also has an important role of suppressing a temperature rise due to the etching of the semiconductor wafer 55 and cooling the wafer. FIG. 5 shows the basic configuration of the etching nozzle portion, and it goes without saying that the shape of each component and the angle at which these components are arranged can be changed experimentally to be optimal. FIG.
As shown in FIG. 5 and the embodiment of FIG. 5, the present invention is characterized by the structure of the local etching portion formed by making the shape of the etching nozzle into a band shape. The etching nozzle described here may or may not include the beam shaping unit.

Embodiment 4 An embodiment of a manufacturing method for shaving the back surface of a semiconductor wafer thinly into a pellet by using an etching apparatus according to the present invention will be described with reference to FIG. Semiconductor wafers are currently available in Si, Ga
Material crystals such as As and InP are mainly used.
A GaAs semiconductor wafer 65 (a) having a semiconductor device circuit 61 of a high-power amplifier in which a BT (heterostructure junction transistor) is integrated has a size of about 30 to improve heat radiation characteristics.
Since it is necessary to reduce the thickness to a micron, an example of a manufacturing method in which the back surface of the semiconductor wafer 65 is thinned and processed into the pellet 63 will be described here. The surface of the semiconductor wafer 65 is fixed to an adhesive tape 69, which is reinforced by a support plate 68 (b). The back surface of the semiconductor wafer 65 is etched using the plasma etching apparatus according to the present invention. (C) shows the etching nozzle 64 of the plasma etching apparatus, the beam shaping part 64-2 at the tip and the semiconductor wafer 65. The shape of the etching nozzle 64 is not limited to this example. The entire surface of the wafer is etched in the optimum feed mode by the wafer moving mechanism, and the back surface of the semiconductor wafer 65 is uniformly processed without distortion. A mixed gas of SiCl4 and hydrogen is used as an etching gas. Thereafter, an Au-based metal layer 66 is applied on the semiconductor wafer 65 to reinforce the pellet, and is cut at the separation line 62 (d). Extend and expand the adhesive tape 69,
The semiconductor wafer chips are separated into pellets (e). As can be seen from the above description, the method of thinning the back surface according to the present invention is a completely dry process, and has a feature that the steps of cleaning or attaching and removing the semiconductor wafer can be omitted, and the number of steps can be significantly reduced. This is an optimal processing method particularly for a process of processing a compound semiconductor which is fragile to an extremely thin thickness, and can greatly improve the yield as compared with the conventional method. Further, since the film thickness can be monitored even during the etching step, there is a feature that high-precision processing can be achieved. Since the back surface of the semiconductor wafer 65 is often contaminated with an organic substance such as a photoresist during the process, a step of first removing this with a gas mainly containing oxygen gas in the plasma etching apparatus according to the present invention is required. Can be added. In the above, the example of processing the back surface of the semiconductor wafer thinly has been described with GaAs.

[0009]

(1) A uniform beam can be obtained by the configuration of the etching nozzle and the configuration of the exhaust head and the gas supply gas provided around the nozzle, and uniform and high-speed etching of the semiconductor wafer can be performed in a short time. I can do it. (2) The apparatus of the present invention enables the thin layer processing of the back surface of a semiconductor wafer to be performed by a dry process, thereby eliminating the need for a cleaning step of the semiconductor wafer or a step of attaching and removing the semiconductor wafer, thereby greatly reducing the number of steps. Was. (3) According to the present method, since the crystal has no processing distortion, it can be formed with a high yield to an extremely thin thickness, and it has been found that it is particularly effective for processing the back surface of a compound semiconductor which is easily broken.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an overall configuration of a plasma etching apparatus that is Embodiment 1 of the present invention.

FIG. 2 is a side view of an etching nozzle of the plasma etching apparatus according to the first embodiment of the present invention.

FIG. 3 is a side view of another etching nozzle which is Embodiment 2 of the present invention.

FIG. 4 is a perspective view of a main part of another etching nozzle which is Embodiment 3 of the present invention.

FIG. 5 is a perspective view of a main part of another etching nozzle that is Embodiment 3 of the present invention.

FIG. 6 is a side view of an element in a main step of a manufacturing method from thinning a back surface of a semiconductor wafer to dividing into a pellet by using a plasma etching apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microwave oscillator 2 ... Waveguide 3 ... Reactive gas supply pipe 4, 24, 34, 44, 54, 64 ... Etching nozzle 5, 25, 45, 55, 65 ... Semiconductor wafer 6 ... Plasma generation area 7 ... Sample Moving mechanism 8, 28 ... Moving table 9 ... Etching chamber 10 ... Transport chamber 11 ... Sample exchange chamber 12, 22, 32 ... Coupling part 13, 23, 33 ... Active species gas supply pipe 14 ... Gas supply device 15 ... Transport mechanism 16 , 26, 46, 56: Exhaust head 17: Exhaust device and gas processing device 18: Gate valve 19: Gas exhaust pipe 20: Control device 21, 61: Semiconductor element circuit 24-1, 34-1: Restriction port 24-2 , 34-2, 54-2, 64-2 ... Beam shaping unit 27, 47 ... Exhaust port 29 ... Wafer holding unit 34-3 ... Adjustment parts 41, 51 ... Active species gas 49, 59 ... Exhaust gas 57 ... Sending Gas nozzle 58 ... Gas supply gas 62 ... Separation line 63 ... Pellet 66 ... Metal layer 69 ... Adhesive tape

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K057 DA02 DA20 DB06 DB20 DD05 DE01 DE02 DE04 DE06 DE07 DE08 DE09 DE11 DE14 DM13 DM29 DM37 DM38 DN01 5F004 AA01 AA16 BA03 BB11 BB18 BB24 BB28 DA00 DA01 DA02 DA04 DA05 DA10 DA11 DA13 DA18 DA22 DA23 DA24 DA25 DA29 DB01 DB19 DB20 DB22

Claims (8)

[Claims] In a process of flattening or thinning the front and back surfaces of a sample by dry etching, an active species gas generated in a plasma chamber is guided by an active species gas supply pipe, and the beam is supplied from the tip of an etching nozzle to the sample. , And partially etch, while moving the sample,
An apparatus for performing desired processing over the entire surface of a sample, wherein the etching nozzle includes a beam shaping unit or a beam shaping unit and a beam adjusting component. 2. The plasma etching apparatus according to claim 1, wherein a cross-sectional shape of the tip of the etching nozzle is an ellipse, a square, or a band. 3. The plasma etching apparatus according to claim 1, wherein an exhaust head for sucking a gas is arranged to face a tip of said etching nozzle. 4. The processing of a sample is performed by using a configuration in which the exhaust head and an air supply nozzle for blowing a gas such as He, N2, Ar, or H2 are provided around the etching nozzle. The plasma etching apparatus according to any one of 1, 2, and 3. 5. A sample is processed by arranging a large number of said etching nozzles.
The plasma etching apparatus according to 2, 3, or 4. 6. In etching a semiconductor wafer,
7. A semiconductor wafer using the plasma etching apparatus according to claim 1, wherein an active species gas is generated in a plasma generation chamber by a halogen compound gas or a mixed gas containing a halogen compound gas as an etching gas. How to etch this. 7. The semiconductor wafer is a compound semiconductor such as GaAs. In processing the substrate crystal, Cl2, HCl, SiCl4, Br is used as an etching gas.
7. The etching method according to claim 6, wherein the etching mainly comprises HBr, BCl3, CCl4, CBrF3, or the like. 8. The semiconductor wafer is made of Si, and in the processing of the substrate crystal, SF is used as an etching gas.
6, NF3, CF4, C2F6, CCl4, CBrF3
7. The etching method according to claim 6, wherein the etching is mainly performed.