JP3381119B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching apparatus such as a parallel plate type plasma etching apparatus, and more particularly, to a method for etching a multilayer film in multiple steps.
Plasma etching equipment and semiconductor device manufacturing method devised to improve in-plane uniformity of etching for each film
It is about the law . 2. Description of the Related Art In the manufacture of semiconductor devices, an etching process, particularly a plasma etching process or a reactive ion etching process, is widely used in connection with a photolithography method. For example, for forming a gate electrode,
Alternatively, a process of forming a pattern on a wafer surface by etching a thin film, for example, an oxide film, a metal film, or the like on a wafer for forming a wiring layer is almost inevitable in the manufacture of a semiconductor device. [0003] An outline of a parallel plate type plasma etching apparatus will be described below as an example. FIG. 3 is a schematic diagram showing a configuration of a conventional parallel plate type plasma etching apparatus.
As shown in FIG. 3, a conventional parallel plate type plasma etching apparatus (hereinafter simply referred to as an etching apparatus) 10 includes an etching chamber 14 that is sucked by a vacuum pump 12 and maintained at a predetermined pressure, and an etching chamber 14. And a load chamber 20 and an unload chamber 22 which are adjacent to both sides of the vacuum chamber and are vacuum-sucked by vacuum pumps 16 and 18, respectively. The etching chamber 14 is provided with a pair of an upper electrode 24 and a lower electrode 26, a wafer W to be etched is disposed on the lower electrode 26, and the electrodes 24, 2
During the period 6, the RF voltage is applied from the RF power supply 30 via the matching circuit 28. Further, a permanent magnet or electromagnet 32 may be arranged outside the etching chamber 14 above the upper electrode 24 to form a constant magnetic field in the etching chamber 14. The reaction gas is introduced into the etching chamber 14 from the cylinder while the flow rate is controlled by the flow rate controller 34, etches the wafer W while generating plasma in the etching chamber 14, and is sucked by the vacuum pump 12 and discharged to the outside. Is done. Note that a cassette for transporting wafers is arranged beside the load chamber 20 and the unload chamber 22. [0005] In order to form a connection hole, for example, an etching process is performed on a SiO ₂ film on a wafer.
A conventional operation method of the etching apparatus shown in FIG. 3 will be described. The etching apparatus is sequentially operated for each wafer according to the following steps (1) to (4). (1) a step of introducing a wafer to be etched from the load chamber 20 into the etching chamber 14 and then feeding a reaction gas into the etching chamber 14; (2) etching by sucking the reaction gas in the etching chamber 14 by the vacuum pump 12 Adjusting the pressure of the chamber 14 to a predetermined value, (3) applying an RF voltage between the electrodes 24 and 26 to etch the thin film on the wafer while generating plasma, and (4) setting the etching chamber 14 A step of sending the evacuated and etched wafer to the unload chamber 22; [0006] In recent etching processes, a multilayer film on a wafer is often etched in multiple steps using the same plasma etching apparatus. As shown in FIG. 4, the multilayer film is, for example, a TiON film and a W film sequentially laminated on an Al—Si wiring layer.
A multilayer film such as a film. On the other hand, in a conventional plasma etching apparatus, when it is intended to adjust etching conditions by changing certain conditions during operation, factors that can be changed are temperature, pressure, RF output, type of reaction gas and its flow rate, and the like. Factors related to the structure of the plasma etching apparatus,
For example, the structure of the lower electrode on which the wafer is mounted cannot be changed. For this reason, when etching a multilayer film on a wafer in multiple steps, problems often occur. For example, in the etching process of the multilayer film shown in FIG. 4, even if a satisfactory etching rate and in-plane uniformity of the etching can be secured in the etching of the W film, the lower TiON film performed in the next etching step. In the above-mentioned etching, even if the etching conditions are adjusted by changing the above-mentioned changeable factors, it is often impossible to ensure the in-plane uniformity at a satisfactory level. As a result, the in-plane uniformity of the etching deteriorates, and the amount of etching at the center of the wafer differs from the amount of etching at the periphery of the wafer. Product yield decreased. In addition, as the diameter of the wafer increases, it becomes increasingly difficult to ensure the in-plane non-uniformity of the etching. Therefore, the solution of this problem has become more important. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved plasma etching apparatus capable of ensuring in-plane uniformity of etching when a multilayer film on a wafer is etched in multiple steps. Means for Solving the Problems The present inventor pays attention to the flow of the reaction gas in the central portion and the peripheral portion of the wafer mounted on the lower electrode of the plasma etching apparatus, and as described below. An experiment was performed. The plasma etching apparatus used in the experiment is a parallel plate type plasma etching apparatus P-5000W made of Allied Materials, and its lower electrode has a structure as shown in FIG. In FIG. 5, A is a lower electrode, B is a wafer holder, C is a holder ring, and W is a wafer. Two hold down rings C ₁ and C ₂ having a height H from a certain reference plane (not a height from the wafer) of 25 mm and 19 mm were produced. Then placing a wafer having a multilayer film shown in FIG. 4 the lower electrode A, wearing the wafer presser B and the pressing ring C _1, it was subjected to etching test. Subsequently, etching was performed testing the same conditions by using the ring C ₂ retainer in place of the presser ring C _1. The etching condition of the W film is such that the RF output is 100 W and the reaction gas is SF ₆ / Ar / He 40 sccm / 20 sccm / 1.
0 sccm, the etching conditions for the TiON film were an RF output of 250 W, and a reaction gas of Cl ₂ / Ar 5 sccm / 75 sc
cm. The obtained results are as shown in FIGS. FIG. 6 shows the results of an etching test of the W film for the holding rings C ₁ and C ₂ , and FIG. 7 shows the results of the holding rings C ₁ and C 2.
₂ shows the results of another TiON film etching test. In the figure, the horizontal axis indicates the pressure (Pa) of the etching chamber. FIGS. 6 and 7 show that in the etching of the W film,
The press ring C _{1 having} a height of 25 mm can obtain better in-plane uniformity than the press ring C ₂ having a height of 19 mm.
_2/5 have shown that it is possible to obtain a good in-plane uniformity than ferrules C _1. Therefore, the present inventor, from the above experiment, when the height of the holding ring changes,
The flow state of the reactant gas on the wafer surface, especially the flow state of the reactant gas at the peripheral portion of the wafer, changes, thereby increasing the etching rate in the peripheral portion, and conversely, decreasing the etching rate in the central portion. It has been found that the inner uniformity is improved. Therefore, the present inventor provided a ring-shaped member surrounding a wafer placed on an electrode, and when etching different types of films constituting a multilayer film in multiple steps, the height of the ring-shaped member was variably set. By doing
The present invention has been completed by focusing on improving the in-plane uniformity of the etching of each film. In order to achieve the above object, based on the above findings, a plasma etching apparatus according to the present invention places a wafer on an electrode disposed in an etching chamber and introduces a reactive gas into the etching chamber. In a plasma etching apparatus that generates plasma and performs etching processing on a wafer, the plasma etching apparatus is disposed so as to surround the wafer mounted on the electrode, and the height of the top portion can be freely changed with respect to the wafer surface. And a driving means for driving the ring-shaped member to move up and down so that the height of the top of the ring-shaped member changes with respect to the wafer surface. According to the present invention, an etching process is performed by placing a wafer on an electrode installed in an etching chamber, introducing a reaction gas into the etching chamber, and generating plasma by performing a plasma etching method, for example, RIE plasma. Etching equipment or ECR
It can be applied to a plasma etching apparatus. When the present invention is applied to a parallel plate type plasma etching apparatus, it is mounted on a lower electrode in a parallel plate type plasma etching apparatus having a pair of an upper electrode and a lower electrode in an etching chamber. A ring-shaped member arranged around the lower electrode so as to surround the wafer and capable of freely changing the height of the top with respect to the wafer surface; and the height of the top of the ring-shaped member with reference to the wafer surface. And driving means for driving the ring-shaped member to move up and down so as to change. [0013] The ring-shaped member used in the present invention refers to a ring-shaped raised member arranged around the wafer so as to surround the wafer placed on the electrode. It is attached so that the height of the top of the member can be raised and lowered with respect to the wafer. For manual operation for driving the elevation of the ring-shaped member so as to change the height of the top of the ring-shaped member, elevating means using a known fluid pressure mechanism such as a hydraulic device or a pneumatic device can be used. More books
In the invention, the wafer is placed on an electrode placed in the etching chamber.
And introduce a reaction gas into the etching chamber.
When plasma is generated and wafers are etched
In the method of manufacturing a semiconductor device, comprising:
Ring-shaped member arranged to surround a wafer to be processed
The height of the top can be changed freely with respect to the wafer surface
It is characterized by doing so. According to the present invention, when the ring member is driven up and down by the driving means, the top of the ring member is raised or lowered with respect to the wafer surface placed on the electrode. can do. When the height of the ring-shaped member changes, the flow state of the reactant gas on the wafer surface, particularly the flow state of the reactant gas on the peripheral portion of the wafer surface, changes, so that the etching rates of the central portion and the peripheral portion change. Therefore,
By changing the height of the ring-shaped member, it is possible to control the etching rates of the central portion and the peripheral portion, and to improve the in-plane uniformity of the etching. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a semiconductor device according to an embodiment of the present invention;
The method will be described. FIG. 1 is a schematic partial cross-sectional view showing an essential part of an embodiment of a parallel plate type plasma etching apparatus according to the present invention. The parallel plate type plasma etching apparatus of the present embodiment has, in addition to the configuration of the parallel plate type plasma etching apparatus 10 shown in FIG. 3, a wafer holder 50, a ring-shaped member 52, and a driving means thereof as shown in FIG. 5
4 is provided. The wafer holder 50 is an annular disk-shaped member placed on the periphery of the wafer W to hold down the wafer W placed on the lower electrode 26. The outer peripheral shape and the outer diameter are the outer peripheral shape of the lower electrode 26. And the outer diameter. The opening is an opening for exposing the etched surface of the wafer W, and has a shape such that the diameter increases outward. The wafer holder 50 is made of aluminum or ceramic. The ring-shaped member 52 is formed of a short cylindrical member, and its inner peripheral shape is the lower electrode 26 and the wafer holder 50.
The ring-shaped member 52 conforms to the outer peripheral shape of the lower electrode 2.
6 and the wafer holder 50 are slidable. As the driving means 54, an appropriate number of known hydraulic cylinders 54 are provided on the ring-shaped member 52. The hydraulic cylinder 54 is fixed at an appropriate place, and the ring-shaped member 52 moves up and down when the piston rod 56 expands and contracts. Further, a control device 58 is provided for remotely controlling the operation of the hydraulic cylinder 54. In order to avoid a sudden change in the shape of the surface of the wafer holder 50 and the inner peripheral surface of the ring-shaped member 52 inside the ring-shaped member 52, a ring 60 having a triangular cross section as shown in FIG. May be provided separately. The inclined ring 60
The outer periphery thereof coincides with the inner periphery of the ring-shaped member 52, and has an annular surface that is inclined inward and downward from the top, and rests on the wafer retainer 50 and stands still. It slides against it. Further, the wafer holder 50 and the inclined ring 60 may be formed integrally. Further, as shown in FIG. 2 (b), a plurality of inclined plates are superimposed on each other, and an inclined ring 60 configured like an aperture of a camera is attached to the ring-shaped member 52, and the ring-shaped member 52 is tilted up and down. The inclination of the ring 60 may be made to follow. In the case of etching a multilayer film as shown in FIG. 4 using the parallel plate type plasma etching apparatus of the present embodiment, the height of the ring-shaped member 52 is increased to etch the W film. The height of the member 52
By etching the ON film, in-plane uniformity can be improved in etching both types of films as shown in FIGS. According to the structure of the present invention, a ring-shaped member whose height can be freely changed with respect to the wafer surface,
By providing a driving means for driving the elevation of the ring-shaped member so as to change the height thereof, it is possible to change the etching conditions of the conventional plasma etching apparatus (temperature, pressure, RF output, type of reaction gas, flow rate). In addition, a mechanism is provided for controlling the flow of the reaction gas on the wafer surface placed on the electrode. Therefore, when etching a multilayer film in multiple steps using the same apparatus, the flow of the reaction gas on the wafer surface is controlled by changing the height of the ring-shaped member according to the type of the film to be etched. In-plane uniformity of the etching can be improved. By using the plasma etching apparatus according to the present invention, even in the case of a large-diameter wafer, the in-plane uniformity can be improved and the production efficiency can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic partial cross-sectional view showing a configuration of a main part of an embodiment of a parallel plate type plasma etching apparatus according to the present invention. FIGS. 2A and 2B are schematic partial cross-sectional views each illustrating a triangular ring. FIG. 3 is a schematic diagram showing a configuration of a conventional parallel plate type plasma etching apparatus. FIG. 4 is a cross-sectional view illustrating a multilayer film. FIG. 5 is a schematic partial sectional view showing a configuration of a lower electrode of a conventional parallel plate type plasma etching apparatus. FIG. 6 is a graph showing a test result of etching of a W film. FIG. 7 is a graph showing a test result of etching of a TiON film. DESCRIPTION OF SYMBOLS 10 Conventional parallel plate type plasma etching apparatus 12, 16, 18 Vacuum pump 14 Etching chamber 20 Load chamber 22 Unload chamber 24 Upper electrode 26 Lower electrode 28 Matching circuit 30 RF power supply 32 Electromagnet 34 Flow controller 50 Wafer Holder 52 Ring member 54 Driving means 56 Piston rod 58 Control device 60 Inclined ring

Claims (1)

(57) [Claim 1] A multilayer film on a wafer surface by placing a wafer on an electrode disposed in an etching chamber, introducing a reaction gas into the etching chamber, and generating plasma. To etch
A method of manufacturing a semiconductor device, which performs a polishing process, wherein said method surrounds said electrode and a wafer mounted thereon.
The short cylindrical ring-shaped part arranged in this state is
While maintaining the state surrounding the wafer
The multi-layer film is constructed by slidably moving
The above-mentioned refilling with reference to the wafer surface according to the type of film to be formed.
While changing the height of the top of the ring-shaped member,
Is characterized in that a plurality of films constituting
A method for manufacturing a semiconductor device.