JP2559731B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention provides a first layer, which is the same material as the material to be etched, and a second layer, which is the material to be etched, in an actual pattern region in which a semiconductor device is formed. In a method for manufacturing a semiconductor device, which is sequentially provided, and in which the second layer is removed by dry etching by glow discharge of a predetermined reaction gas,
A comparison area covering the actual pattern area on the first layer, and including a peripheral unused portion on the periphery of the wafer and a scribe line for cutting the wafer to cut a semiconductor chip in a later step. A first step of forming an exposed oxidation resistant film, and after the first step, oxidation is performed to form a region of the semiconductor chip not covered with the oxidation resistant film and the second layer in the comparison region. And a second step of forming an oxide film of a different material and using this as a stopper layer,
A third step of removing the oxidation resistant film after the second step, and a fourth step of forming a second layer on the actual pattern area and the comparison area after the third step. And, after the fourth step, a fifth step of forming a mask pattern that covers a desired portion of the actual pattern area and does not cover at least the surface of the comparison area, and dry etching after the fifth step. And a sixth step of detecting a time point when the stopper layer in the comparison area is exposed and setting this as an end point in the actual pattern area.

[Industrial applications]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for detecting an end point in dry etching thereof.

[Conventional technology]

 A conventional technique will be described with reference to FIG.

FIG. 6 shows an ordinary dry etching apparatus, in which a container 1 which also serves as a cathode is provided with an anode plate 2 on which a wafer 3 provided with a material to be etched is placed. For example, a chlorine-based gas serving as a reaction gas is supplied, and a glow discharge is generated by the high frequency power source 4 inside the container 1 to etch the material to be etched.

[Problems to be solved by the invention]

The above-mentioned conventional dry etching apparatus uses the high frequency power source 4
A glow discharge is generated in the reaction gas by means of which the material to be etched is etched by the radicals and ions of the reaction gas generated thereby.

Usually, in such a dry etching apparatus, as a method for detecting the end point, for example, a method of determining the end point by the operator's visual observation, measuring the time required for etching in advance, and determining the etching end time based on it Was used. However, it is difficult for the former to accurately determine the etching amount, and the deterioration of the work environment due to visual observation under ultraviolet light poses a problem, and for the latter, due to misalignment of the high frequency power supply and fluctuations in the flow rate of the reaction gas, etc. There is a problem that it is difficult to accurately determine the end point because the discharge state cannot be kept constant and the condition changes for each etching.

In addition, as shown in FIG.
When the polysilicon 9 is provided on the upper surface and only the polysilicon 9 is to be removed by etching, first, as shown in FIG. 6B, the masking portion 13 covered with the etching mask 11 is cut off later to form a chip. Is formed only in the actual pattern area, and the polysilicon 9 as the material to be etched is exposed in the other area (the peripheral portion of the wafer 3), and then dry etching is performed to remove the polysilicon 9 on the surface. There is a method of detecting the time when the silicon oxide 12 underneath is exposed and the spectral intensity of the reaction gas changes as the etching end point.

According to this method, it is possible to accurately determine the etching end point in the actual pattern area without being affected by the discharge state or the gas flow rate, but this is because the material to be etched is different from the material below it. It is applicable only when the material to be etched is made of the same material as that of the material to be etched, and the spectral intensity of the reaction gas does not change.

[Means for solving problems]

The present invention comprises a first layer, which is the same material as the material to be etched, and a second layer, which is the material to be etched, which are sequentially provided in an actual pattern region in which a semiconductor device is formed. In a method of manufacturing a semiconductor device, wherein the second layer is removed by dry etching by glow discharge,
A comparison area covering the actual pattern area on the first layer and including a peripheral unused portion on the periphery of the wafer and a scribe line for cutting the wafer to cut a semiconductor chip in a later step. A first step of selectively forming an exposed oxidation resistant film, and after the first step, oxidation is performed to form a region of the semiconductor chip not covered with the oxidation resistant film and the second layer in the comparison region. And a second step of forming an oxide film of a different material and using this as a stopper layer,
A third step of removing the oxidation resistant film after the second step, and a fourth step of forming a second layer on the actual pattern area and the comparison area after the third step. After the fourth step, a fifth step of forming a mask pattern that covers a desired portion of the actual pattern area and does not cover at least the surface of the comparison area, and dry etching after the fifth step. And a sixth step of detecting a time point when the stopper layer in the comparison area is exposed and setting it as an end point in the actual pattern area.

[Action]

According to the etching end point detection method of the present invention, a stopper layer having a predetermined area different in material from the material to be etched is provided in the comparison region on the first layer, and is made of the material to be etched later formed on the entire surface. The etching amount of the material to be etched is accurately controlled by detecting, for example, a change in the light intensity of a specific wavelength in the reaction container as the etching end point when the second layer is removed by etching and the comparative region is exposed. It is possible.

〔Example〕

Hereinafter, one embodiment of the dry etching method according to the present invention will be described in detail with reference to FIGS. In this embodiment, the present invention is applied to the patterning of polycrystalline silicon (polysilicon) 9 formed on single crystal silicon 10.

FIG. 1 shows a dry etching apparatus according to the present invention,
A wafer 3 in which an anode plate 2 is provided in a container 1 which also serves as a cathode, and a material to be etched is provided thereon.
Is placed, and a high-frequency power source 4 generates a glow discharge while supplying chlorine gas as a reaction gas from the supply tank 5 to etch the material to be etched. Further, the container 1 is provided with a detector 7, and the control unit 8 outputs an ON-OFF signal to the valve 6 and the high frequency power source 4 by the signal thereof.

Next, the dry etching method of this embodiment using the above dry etching apparatus will be described.

1. First, as shown in FIG. 2 (A), single crystal silicon 10
After forming an oxidation resistant film 14 made of, for example, silicon nitride (Si ₃ N ₄ ) in an actual pattern area that will be cut into chips in the future (not shown), a normal oxidation process is performed to remove unused areas around the wafer. A silicon oxide 12 serving as a stopper layer is formed on the portion 15, the scribe line 16, the monitor chip portion 17, and the like. The region where the silicon oxide 12 is formed will be referred to as a comparison region.

Next, after removing the oxidation resistant film 14 in the actual pattern region and exposing the single crystal silicon 10 thereunder, FIG. 2 (B)
As shown in, the polysilicon 9 is formed on the entire surface by, for example, a vapor phase growth method.

Next, as shown in FIG. 2C, an etching mask 11 is formed only at a desired portion of the actual pattern area, and this is used as a masking portion 13.

A sectional view of a region indicated by a in FIG. 2 is shown in FIG. As shown in the figure, the polysilicon 9 in the comparison region is provided on the silicon oxide 12, and these are exposed on the surface. Further, the polysilicon 9 in the actual pattern region is directly provided on the single crystal silicon 10, and the desired portion where the polysilicon 9 is not removed is the etching mask 11
Is covered by. Further, an etching window 11a is opened in a portion where the polysilicon 9 is removed.

2. The wafer 3 having the above-described structure is placed on the anode plate 2 in the dry etching apparatus shown in FIG. 1, and then a reaction gas is introduced into the container 1, and then a high frequency power source 4 is applied to glow. Electric discharge is generated and successive etching is performed. At the same time as the etching, the detector 7 including a photodiode, for example.
Thus, for example, when the reaction gas is chlorine gas, the emission spectrum intensity at 510 nm resulting from it is always monitored.

Next, etching progresses, and polysilicon 9 on the comparison region is etched.
Is almost completely removed, a sharp increase in spectrum intensity as shown in FIG. 3 is observed. This is because the polysilicon 9 on the comparative region, which occupies most of the polysilicon 9 exposed on the surface, is removed to expose the silicon oxide 12 underneath, and the reaction gas that does not contribute to etching increases. .

In this embodiment, the valve 6 and the high frequency power source 4 are turned off by the control unit 8 at an appropriate time (for example, a time point indicated by a in FIG. 3) when the emission spectrum intensity of the reaction gas in the container 1 thus rises. , The etching is stopped.

As described above, according to this embodiment, by forming the comparison area on the wafer, it is possible to accurately detect the etching end point even when the lower part of the material to be etched is the same material as the material to be etched. Is.

Further, in the present embodiment, the etching end point was detected by monitoring the change of the light intensity of the reaction gas. However, in addition, the light intensity of the material to be etched (silicon in the above embodiment) was monitored to detect the etching end point. It is also possible to detect. In this case, an appropriate time point at which the light intensity of the material to be etched in the container 1 decreases may be detected as the etching end point.

Further, as another embodiment of the etching end point detecting method, the etching end point is detected by irradiating the comparison area with laser light from the outside, for example, by the optical fiber 18 and monitoring the change in the reflected light intensity as shown in FIG. Is also good. In this case, since the thickness of the polysilicon is gradually decreased during etching of the polysilicon, the laser light interferes, and the detected reflected light is wavy as shown in FIG. When the silicon 12 is exposed and the reduction of the film thickness is stopped, the interference of the laser light disappears, and the etching may be finished at an appropriate time (for example, the time indicated by a in FIG. 5).

In the above embodiments, the comparison area is formed by forming the unused portion on the entire area of the wafer 3. However, the present invention is a portion where the actual pattern area is not formed on the wafer 3 as long as the etching end point can be determined. It is not necessary to form a comparison region in the entire region, and a first layer made of the same material as the material to be etched and a second layer made of the material to be etched are sequentially formed,
The same effect can be obtained with any other material to be etched as long as it is provided on the wafer and is a method for manufacturing a semiconductor device in which only the second layer is removed by dry etching. Is self-evident.

〔The invention's effect〕

As described above in detail, according to the present invention, by providing a comparison area having a predetermined area in a portion other than the actual pattern area on the wafer, even if the lower portion of the material to be etched is the same material as the material to be etched. The etching end point can be accurately detected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a dry etching apparatus according to the present invention, and FIG. 2 is a wafer configuration according to an embodiment of the present invention.
FIG. 3 is a diagram showing a change in emission intensity of a reaction gas according to an example, FIG. 4 is a diagram showing an end point detecting method according to another example, and FIG. 5 is a reflected light intensity according to another example. Figure showing,
FIG. 6 is a diagram showing an ordinary dry etching apparatus, and FIG.
The figure is a diagram for explaining a conventional end point detection method. In the figure, 1 is a container, 2 is an anode plate, 3 is a wafer, 4 is a high frequency power source, 5 is a supply tank, 6 is a valve, 7 is a detector, and 8
Is a control unit, 9 is polysilicon, 10 is single crystal silicon, 11
Is an etching mask, 11a is an etching window, 12 is silicon oxide, 13 is a masking portion, 14 is an oxidation resistant film, 15 is a peripheral unused portion, 16 is a scribe line, 17 is a monitor chip portion, and 18 is an optical fiber.

 ─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-57-39535 (JP, A) JP-A-55-85674 (JP, A) JP-A-58-168231 (JP, A) JP-A 61- 97927 (JP, A) JP 61-34944 (JP, A)

Claims (1)

(57) [Claims] 1. A first layer, which is the same material as the material to be etched, and a second layer, which is the material to be etched, are sequentially provided in an actual pattern region in which a semiconductor device is formed. In the method of manufacturing a semiconductor device, wherein the second layer is removed by dry etching using glow discharge, the first layer is covered with the actual pattern region, and a peripheral unused portion at the periphery of the wafer and A first step of forming an oxidation resistant film in which a comparative region including a scribe line for cutting a semiconductor chip to cut out a semiconductor chip is selectively exposed in a later step, and an oxidation is performed after the first step. A second step in which an oxide film made of a material different from that of the second layer is formed in a region of the semiconductor chip not covered with the oxidation resistant film and the comparison region, and the oxide film is used as a stopper layer; after A third step of removing the oxidation resistant film, and a fourth step of forming a second layer on the actual pattern area and the comparison area after the third step, and Then, a fifth step of forming a mask pattern that covers desired portions of the actual pattern area and does not cover at least the surface of the comparison area, and after the fifth step, dry etching is performed to stop the comparison area. And a sixth step in which the time point when the layer is exposed is detected and this is used as the end point in the actual pattern area.