JP2003031549A - Apparatus for etching semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for etching a semiconductor wafer, capable of making an etching rate in side the surface of the wafer uniform and executing a predetermined etching treatment, without impairing the lapping shape. SOLUTION: The apparatus for etching the semiconductor wafer comprises an etching tank 6 for circulating an etching liquid, a carrier 7 for holding and rotating the wafer in the tank 6, an etching liquid supply port 8 installed at a lower part of the tank 6, a straightening unit 9, disposed adjacent to the port 8 for controlling supply of etching liquid flow toward the wafer held at the carrier 7, and an etching liquid recovery port 10 installed at an upper side from the carrier 7. In this case, the an inner wall surface of the port 8 side of the tank 6 is formed into a curved surface 6a along an outer peripheral edge of the wafer held at the carrier 7.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer etching apparatus, and more particularly, to a semiconductor wafer circulation etching apparatus. 2. Description of the Related Art Generally, in a semiconductor manufacturing process, for example, after slicing a silicon single crystal into a wafer, in order to prevent cracking or chipping of the silicon wafer, chamfering of an outer peripheral edge portion is performed. Done. further,
A process is performed in which a chamfered silicon wafer is subjected to a lapping process to flatten the surface of the silicon wafer and to make the thickness of the silicon wafer uniform. Further, in order to remove the processing distortion generated in the silicon wafer by the slicing process and the lapping process, and to secure the accuracy of the polishing process, an etching process by a chemical action is performed. Here, as the etching solution, a mixed solution of hydrofluoric acid, nitric acid, and acetic acid, or an alkaline aqueous solution such as an aqueous solution of sodium hydroxide is used, and the silicon wafer subjected to this etching treatment is polished in the next step. Processed. FIG. 3 is a sectional view showing a schematic configuration example of a circulation type etching apparatus conventionally used for etching a semiconductor wafer. Reference numeral 1 denotes an etching tank that stores an etching solution, and 2 denotes a carrier that holds a semiconductor wafer vertically in the tank 1 and rotates. The carrier 2 is rotated by a rotation mechanism (not shown). Reference numeral 3 denotes an etchant supply port provided below the semiconductor wafer held by the carrier 2 in the tank 1; 4 denotes an etchant recovery port provided above the carrier 2; An etchant circulation mechanism that connects and circulates between the supply port 3 and the recovery port 4. FIG. 4A is a cross-sectional view showing another schematic configuration example of a conventional circulating etching apparatus, and FIG.
FIG. 3A is a cross-sectional view along the line AA in FIG. FIG.
1A and 1B, reference numeral 1 denotes an etching tank containing an etching solution, and 2 denotes a carrier which holds a semiconductor wafer vertically in the tank 1 and rotates. The carrier 2 includes a driving shaft 2a and a driven shaft 2b. It is installed so that it can be rotated up and down in the vertical direction while being rotated by a rotating mechanism including 3a and 3b are a pair of etching solution supply ports provided below the semiconductor wafer held by the carrier 2 in the etching tank 1 and 4 are above the carrier 2 holding and mounting the semiconductor wafer. And an etching solution supply port 3a, 3b.
And an etching solution circulation mechanism for connecting the etching solution recovery port 4 and circulating the etching solution. In each of the above-described etching apparatuses, a carrier 2 which holds and rotates a semiconductor wafer vertically and is set in an etching tank 1 containing an etching solution is supplied by an etching solution circulating mechanism 5 to supply an etching solution 3 or an etching solution. 3a and 3b, and the etchant is recovered and circulated from the recovery port 4, thereby forming the carrier 2
In combination with the rotation of the wafer, uniform etching of the semiconductor wafer is performed. [0007] However, in the recent rapid improvement in the degree of integration of a semiconductor wafer, the above-mentioned means for etching a semiconductor wafer requires high parallelism and flatness of the active element forming surface of the semiconductor wafer for polishing. Not only is the process required, but also high etching accuracy is required for the back surface. Further, it is an essential condition to improve the flatness of the semiconductor wafer and to achieve both high glossiness (improved surface roughness). Conventionally, the composition of the etchant has been studied for the purpose of improving both the flatness and the surface roughness of the semiconductor wafer. However, the etching rate in the semiconductor wafer is not uniform. As a result, there is a problem that the wrapping shape cannot be maintained. That is,
In the process of etching a semiconductor wafer, the influence of the flow state of the etchant, and the intense reaction of the etchant with the semiconductor wafer generates heat, so that the temperature within the semiconductor wafer surface cannot be maintained and the etching rate becomes non-uniform. Invite you. FIG. 4 (c) is the same as FIG.
FIG. 4 is a schematic diagram when visualization is performed by a tracer injection suspension method in the etching apparatus illustrated in (a) and (b) and a state of stagnation and convection (arrow) of an etchant circulation flow is confirmed. In order to improve the influence of the flow state of the etchant and to make the etching rate uniform in the semiconductor wafer surface, the flow rate of the etchant should be maximized in the central portion of the semiconductor wafer and increased from the central portion toward the outer periphery. Attempts have also been made to control the flow rate of the etchant to be small (Japanese Patent No. 3020910). However, even such an improvement does not sufficiently eliminate the nonuniformity of the etching rate, and the establishment of a practical solution is awaited. The inventors of the present invention have made intensive studies in view of such circumstances, and as a result, in a circulation system for supplying an etching solution from below, a part of the etching solution supply flow on the lower side of the semiconductor wafer has been removed. By controlling the flow along the outer edge of the wafer, or by controlling the flow of the etchant as a curved shape along the outer edge of the semiconductor wafer holding the inner wall of the etching tank on the side of the etchant supply port to the carrier, It has been found that the convection of the etchant is suppressed and the etching rate in the semiconductor wafer surface is easily made uniform. The present invention has been made based on the above findings, and has as its object to provide a semiconductor wafer etching apparatus capable of uniformizing an etching rate in a semiconductor wafer surface and performing a required etching process without impairing a lapping shape. And According to a first aspect of the present invention, there is provided an etching tank for circulating an etching solution, a carrier for holding and rotating a semiconductor wafer in the tank, and a carrier installed below the tank. An etchant supply port, a rectifier disposed adjacent to the supply port for controlling supply of an etchant flow toward the semiconductor wafer held by the carrier, and an etchant recovery disposed above the carrier; An etching apparatus for a semiconductor wafer having a mouth, wherein an inner wall surface of the etching bath on an etching solution supply side has a curved surface along an outer peripheral edge of the semiconductor wafer held by the carrier. This is a semiconductor wafer etching apparatus. According to the first aspect of the present invention, the supply of the etching solution toward the substantially central portion of the semiconductor wafer, and the supply flow does not convect and stagnate in the etching solution tank, and
The operation to be smoothly collected to the collection port side automatically proceeds. In other words, the semiconductor wafer automatically and uniformly retains the heat generated by the etching reaction in the semiconductor wafer surface, in combination with the rotation of the retained carrier and the overall smooth flow of the etching solution in the etching tank. As a result, the etching rate becomes uniform and the lapping shape is maintained. An embodiment will be described below with reference to FIGS. 1 (a) and 1 (b) and FIGS. 2 (a) and 2 (b). FIG. 1A is a sectional view showing a schematic configuration of an etching apparatus according to an embodiment. 6 is an etching tank for circulating an etching solution, and 7 is a semiconductor wafer held vertically in the tank 6 and rotated. A career to do. Etching tank 6
Has a depth of about 500 mm, a substantially U-shaped vertical section, and a substantially rectangular cross section (about 300 × 500 mm). The carrier 7 is made of polytetrafluoroethylene resin and is about 1 mm. , And about 25 semiconductor wafers can be supported vertically.
Here, the rotating carrier 7 includes a driving roller 7a and a driven roller 7a connected to a rotation driving source (not shown).
By b, a configuration of rotating in a predetermined direction is adopted.
The cross-sectional shape of the etching solution tank 6 may be rectangular depending on the shape of the carrier 7, the number of semiconductor wafers supported by the carrier 7, and the like. Reference numeral 8 denotes an etching solution supply port provided below the semiconductor wafer held by the carrier 7 in the etching tank 6, and 9 denotes an etching solution supply port which is disposed adjacent to the etching solution supply port 8. Is a rectifier that controls supply to the semiconductor wafer held by the carrier 7. Further, reference numeral 10 denotes an etching liquid recovery port provided above the carrier 7. Here, the etching solution supply port 8 is
An opening of about × 500 mm is set below the semiconductor wafer held by the carrier 7 and within the range of the semiconductor wafer diameter. The rectifier 9 is generally cylindrical in shape to control the supply of the etchant flow toward the semiconductor wafer held by the carrier 7, and depends on the number of semiconductor wafers supported. A structure with a wide open side is selected. Although not shown, the etching liquid in the etching tank 6 is supplied and recovered by an etching liquid circulation mechanism that connects the etching liquid supply port 8 and the etching liquid recovery port 10. Further, the etching apparatus according to the embodiment includes:
The inner wall surface of the etching bath 6 on the side of the etching solution supply port 8 is
The semiconductor wafer is processed into a curved surface 6 a having a shape along the outer peripheral edge of the semiconductor wafer held by the carrier 7. That is, this etching apparatus not only adopts a configuration in which the etching solution supply port 8 is set in a region directly below the semiconductor wafer held by the carrier 7 and the flow of the etching solution is forced by the rectifier 9, It is characterized in that the bottom surface side of the inner wall is set to be substantially U-shaped to secure an etchant flow that does not generate stagnation, stagnation, convection and the like as a whole. FIG. 1B schematically shows the state of the flow of the etchant when the etchant is circulated by the etchant circulation mechanism in the etching apparatus. That is, when the liquid visualized by the tracer suspension method was circulated and the flow (arrow) state in the etching tank 6 was confirmed, not only the supply power to the carrier 7 region increased, but also the peripheral portion of the carrier 7 region. ,
Smooth flow is provided without convection. The stagnation of the liquid flow due to the influence of the rotation of the carrier 6 and the like
No convection is observed, and the liquid replacement efficiency in the etching bath 6 is improved. As a result, the etching reaction heat is suppressed and the etching proceeds at a constant temperature, so that a uniform etching rate is secured. Further, in the configuration of the above etching apparatus, the circulation amount of the etching solution is set to 150 liter / min, and the distance (distance) between the center position of the etching solution supply port 8 and the position immediately below the semiconductor wafer held by the carrier 6 is set. Alternately, the amount of the etchant flowing between the semiconductor wafer surfaces was measured and is shown as a curve A in FIG. In addition, the curve B in FIG. 2B shows the result of measuring the amount of the etchant flowing between the semiconductor wafer surfaces while changing the discharge angle of the semiconductor wafer held by the carrier 6 from the etchant supply port 8. FIGS. 2 (a) and 2 (b) show, for comparison, FIGS. 2 (a) and 2 (b) each showing a case of the etching apparatus having the structure shown in FIGS. 4 (a) and 4 (b). These are indicated by a and b, respectively. As can be seen from the above comparative experiments, in the case of the etching apparatus according to the present invention, the etching solution supply port 8 is set below the semiconductor wafer held by the carrier 6 and within the diameter range of the semiconductor wafer. By doing so, it is possible to increase the amount of the etchant flowing between the semiconductor wafer surfaces even when the same amount of the etchant is supplied. In addition, by controlling the supply of the etchant flow by installing a rectifier and ensuring a smooth flow by making the shape 6a of the inner wall surface of the etching tank 6 curved, the efficiency of replacement of the etchant is increased, and the reaction heat by the etchant is also reduced. As a result, the occurrence of variation in the etching rate in the semiconductor wafer surface is also eliminated, and a stable etching process proceeds. Next, an example in which a silicon wafer is subjected to an etching process by the etching apparatus having the above-described configuration will be described. First, a silicon single crystal having a diameter of 200 mm and N type of 10 Ω · cm is sliced, and a plurality of silicon wafers wrapped using alumina abrasive grains are held by a rotary carrier 7 and set in an etching bath 6. Next, by driving the etchant circulation mechanism, a mixed acid etchant of hydrofluoric acid, nitric acid, and acetic acid was circulated to etch two sets of silicon wafers in the etching bath 6. The temperature of the etching solution is 20 to 40 ° C.
The circulation rate is 100 to 200 liters per minute. When the flatness and high glossiness (degree of improvement in surface roughness) of each of the silicon wafers subjected to the etching treatment were measured and evaluated, the in-plane of each silicon wafer was substantially uniform and uniform. It was confirmed that etching was performed at the etching rate. According to the present invention, the semiconductor wafer is automatically formed in the semiconductor wafer plane by the rotation of the carrier and the smooth flow of the etching solution in the etching bath. The heat generated by the etching reaction in the step is kept uniform. Therefore, since the etching at a uniform etching rate is performed and the lapping shape is maintained, the semiconductor wafer can be processed with high yield and high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is a longitudinal sectional view showing a schematic configuration of an etching apparatus according to an embodiment, and FIG. 1 (b) schematically shows a state of an etching liquid flow in the etching apparatus according to the embodiment. FIG. FIG. 2 (a) is a curve diagram showing the relationship between the position of an etchant supply port and the amount of etchant flowing between semiconductor wafer surfaces in an etching apparatus, and FIG. 2 (b) is an etchant supply port for a semiconductor wafer. FIG. 4 is a curve diagram showing the relationship between the angle of the semiconductor wafer and the amount of etchant flowing between the semiconductor wafer surfaces. FIG. 3 is a longitudinal section showing a schematic configuration of a conventional etching apparatus. FIG. 4A is a longitudinal sectional view showing a schematic configuration of another conventional etching apparatus, FIG. 4B is a sectional view along AA in FIG. 4A, and FIG. 4C is an etchant flow in an etching bath. Sectional drawing which shows the state of FIG. [Description of Signs] 6 Etching bath 6a Inner wall curved surface portion 7 of etching bath Carrier 8 Etching liquid supply port 9 Rectifier 10 Etching liquid recovery port

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Noriaki Wakisaka             6865-15 Higashiko, Seirocho, Kitakanbara-gun, Niigata Prefecture             No. Niigata Toshiba Ceramics Co., Ltd. (72) Inventor Hirotaka Yanagisawa             33, Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa             Toshiba Production Technology Center F term (reference) 4K057 WA04 WA10 WB06 WE02 WE07                       WE12 WM01 WM13 WM18 WN01                 5F043 AA02 BB01 EE01 EE08 EE09                       EE21 EE28 EE33 EE35 FF07

Claims (1)

Claims: 1. An etching tank for circulating an etchant, a carrier holding and rotating a semiconductor wafer in the tank, an etchant supply port installed in a lower part of the tank, and an etchant. Controlling the flow of the flow toward the semiconductor wafer held by the carrier, etching of the semiconductor wafer having a rectifier disposed adjacent to the supply port and an etchant recovery port disposed above the carrier; An apparatus for etching a semiconductor wafer, wherein an inner wall surface on an etching solution supply side of the etching bath forms a curved surface along an outer peripheral edge of the semiconductor wafer held by the carrier.