JPH0638410B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a semiconductor device including a step of selectively removing a semiconductor substrate and a deposited layer formed thereon by dry etching. It relates to a manufacturing method.

[Conventional technology]

Conventionally, as a method of manufacturing a semiconductor device of this type, for example, a photoresist is applied to a polycrystalline silicon film on an oxide film formed on a semiconductor substrate, and an exposure mask of a predetermined pattern and a projection exposure apparatus are used for exposure. A method is generally used in which after development, dry etching is performed using this photoresist pattern as a mask, and then the photoresist is removed by ashing to obtain a predetermined pattern.

In recent years, as high integration progresses, silicides of refractory metals such as M ₀ , W, Ta and Ti are often used as wiring materials for the purpose of lowering the resistance of wiring metals. Therefore, a semiconductor device having this structure will be described below.

FIG. 3 is a sectional view showing a structure of a deposited layer in a semiconductor device formed by a conventional manufacturing method. FIG. 3 is an intermediate process diagram for manufacturing a polycrystalline silicon gate MOS transistor. A silicon gate having a predetermined pattern having a two-layer structure in which a metal silicide film 4 is deposited on the polycrystalline silicon film 3. To obtain the electrode 9, first, the upper metal silicide film (for example, tantalum silicide) 4 is patterned by dry etching using the photoresist film 5 as a mask. This dry etching is performed at a high frequency (13.56 MH) in a low pressure (1 to 50 Pa) mixed gas of, for example, sulfur hexafluoride (SF ₆ ) and chlorine (C ₂ ).
z) Etching by radial fluoride (F radical) when plasma discharge is performed. Then, the supply of the etching gas and the high frequency power is stopped, and the inside of the hermetically sealed container is evacuated to a sufficiently low pressure (5 × 10 ^-1 Pa or less). ₂ F ₂ ) and nitrogen
Similarly, it is selectively removed by dry etching by plasma discharge using a mixed gas of (N ₂ ) and high frequency.

[Problems to be solved by the invention]

Thus, the above-described conventional method for manufacturing a semiconductor device is
Since the dry etching for the laminated film including the silicide film and the polycrystalline silicon film is performed in the same closed container using different reactive gases, the first etching step for the silicide film and the second etching step for the polycrystalline silicon film are performed. Gas exhaust treatment (usually within 5 minutes) or gas exhaust treatment after completion of the second etching step (usually within 5 minutes), the reactive gas or reaction on the inner wall surface of the container When the first etching step is performed again on a newly loaded wafer, the product remains attached and the etching characteristics are affected to change the etching characteristics, so that a predetermined shape cannot be obtained. Occurs. That is, as shown in FIG. 3, the undercut has a large shape, or the residue 8 is generated in the etching of the polycrystalline silicon film 3, so that the coverage of other films formed on the metal silicide 4 film is not affected. This has a bad influence and causes a problem that the conductor layers are short-circuited with each other.

In view of the above situation, an object of the present invention is to provide a method of manufacturing a semiconductor device capable of always performing dry etching on all wafers under the same conditions regardless of the order of loading into the reaction chamber.

[Means for solving problems]

According to the present invention, there is provided a method for manufacturing a semiconductor device including a plurality of dry etching steps of holding a semiconductor wafer in the same etching reaction chamber and selectively removing deposited layers laminated on the semiconductor wafer, The first dry etching step for the new semiconductor wafer is performed until the series of the plurality of dry etching operations for one semiconductor wafer are completed and the semiconductor wafer is taken out of the etching reaction chamber and the next semiconductor wafer is loaded. A dry treatment empty treatment process may be inserted into the etching reaction chamber in which plasma treatment is performed under the same conditions.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1 (a) and 1 (b) are sequential diagrams of a selective removal process of a deposited layer in a semiconductor device showing an embodiment of the present invention. According to this embodiment, first, as shown in FIG. 1A, a gate oxide film 2, a polycrystalline silicon film 3, and a metal silicide film 4 made of tantalum silicide are sequentially stacked on a silicon substrate 1. The photoresist film 5 having a predetermined pattern is formed thereon. Next, as shown in FIG. 1 (b), the silicon substrate 1 is set in the etching reaction chamber of the reactive ion etching apparatus, and sulfur hexafluoride (SF ₆ ) is added.
Gas containing chlorine (C ₂ ) mixed at a ratio of 3: 1 to 2: 1 is supplied into the etching reaction chamber (closed container). After making this mixed gas low pressure (1-30 Pa), high frequency
Plasma discharge at (13.56MHz), photoresist film 5
First etching is performed on the metal silicide film 4 using the as a mask. Since the purpose of this etching step is to etch only the upper metal silicide film 4 made of tantalum silicide, the end point of the etching can be confirmed by monitoring the emission spectrum. After the completion of this first etching step, the supply of the high frequency and the reactive gas is stopped, and the etching reaction chamber is sufficiently evacuated by a vacuum pump such as a rotary pump and a turbo molecular pump. This evacuation time depends on the volume of the etching reaction chamber, the evacuation capacity of the vacuum pump, and the first etching conditions (time, gas used, etc.), but the pressure in the etching reaction chamber is 5 × 10 ^{−1 in 1 to} 2 minutes. It will be below Pa. Then carbon chlorofluoride (CC
_{2 F 2)} and nitrogen (N _{2) 2:} 1~10: The mixed gas is a low pressure which is supplied to the etching reaction chamber (sealed container) in (1～30Pa) 1 ratio, a high frequency The lower polycrystalline silicon film 3 is patterned by plasma discharge at (13.56 MHz). That is, the second etching step is performed on the polycrystalline silicon film 3. After the completion of the second etching, as in the case of the completion of the first etching step immediately performed, the etching reaction chamber is sufficiently evacuated, and the wafer is kept under the atmospheric pressure with nitrogen (N ₂ ) gas and the like. Is taken out. Here, before carrying in the next wafer, the etching reaction chamber is subjected to an empty treatment under the same conditions (pressure, reactive gas, high frequency, etc.) as those of the first etching process described above. By this emptying process, the second wall attached to the inner wall of the etching reaction chamber
Of the reactive gas used in the first etching step, the reaction product with the object to be etched (polycrystalline silicon in this case), and the state of the remaining reactive gas in the reaction chamber of the reactive gas used in the first etching step. Replaced with the state of the wall. After such a replacement step is performed, the reaction chamber is sufficiently evacuated, and further, after being placed in an atmospheric state containing nitrogen (N ₂ ) gas and the like, the next wafer is loaded into the etching reaction chamber,
The first and second etching steps are performed again. By introducing such an empty processing step, all the wafers can be always subjected to the dry etching processing under the same conditions regardless of the loading order, so that the production yield can be remarkably improved.

[Embodiment 2] FIG. 2 is a sectional view showing a structure of a deposited layer in a semiconductor device formed according to another embodiment of the present invention. This embodiment shows a forming method in the case where a smooth shape is required for the edge of the upper layer portion like a contact hole opened in the insulating film. That is, according to this embodiment, the first wafer is loaded into the reaction chamber. Here, the silicon oxide film 6 filling the opening of the metal silicide film 4 is formed by the first dry etching using the photoresist film 7 formed thereon as a mask and the fluorocarbon 23 (CHF ₃ ) as a reactive gas. The contact hole is opened, and the edge is made smooth by the second dry etching using a mixed gas of Freon 32 (CH ₂ F ₂ ) and oxygen (O ₂ ) as a reactive gas. Then, before loading the next wafer, the first etching gas, Freon 23 (CHF
_The plasma blanking process according to ₃ ) is performed as in the previous embodiment, and the first and second dry etching processes for the next wafer are performed again. This will dry etch all deposited layers on a given wafer under the same conditions,
A contact hole having a predetermined pattern can always be formed on any wafer. In addition, in the above-mentioned embodiment, the etching of the conductor film or the insulating film formed on the silicon substrate is described, but it goes without saying that the etching of the silicon substrate can be similarly performed.

〔The invention's effect〕

As described in detail above, according to the present invention, when dry etching is performed twice or more continuously, a series of processes is completed, the wafer plate is taken out of the reaction chamber, and then the next wafer is put in the etching reaction chamber. Since the blank process is performed on the wafer by the same plasma as the first etching, the effect of the preceding dry etching can be prevented. That is, for example, even when dry etching having a strong anisotropy is continuously performed, the shape of a predetermined pattern can be stably obtained without causing a difference between wafers, so that it is possible to always provide a semiconductor element with less variation in characteristics. it can. Further, by having a high selection ratio with respect to the film below the film to be etched, patterning can be performed without etching residue without etching the film below. Further, by smoothing the shape of the contact hole or the like, it becomes possible to prevent disconnection due to poor step coverage, which has been a problem in the past. Furthermore, conventionally, even if continuous etching cannot be performed in the same etching apparatus and a different etching apparatus is required in order to avoid the influence of a reactive gas, according to the present invention, it is possible to perform the etching with one apparatus at a time. It is possible to reduce the number of equipment, improve productivity, and so on, so that a significant cost reduction can be expected.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are flow charts for selectively removing deposited layers in a semiconductor device showing an embodiment of the present invention, and FIG. 2 is a semiconductor device formed according to another embodiment of the present invention. FIG. 3 is a sectional view showing the structure of the deposited layer, and FIG. 3 is a sectional view showing the structure of the deposited layer in a semiconductor device formed by a conventional manufacturing method. 1 ... Silicon substrate, 2 ... Gate oxide film, 3 ... Polycrystalline silicon film, 4 ... Metal silicide film, 5, 7 ... Photoresist film, 6 ... Oxide film, 8 ... Polycrystalline silicon film Residue, 9 ... Silicon gate electrode.

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device, comprising: a plurality of dry etching steps of holding a semiconductor wafer in the same etching reaction chamber and selectively removing deposition layers laminated on the semiconductor wafer. The same dry etching process as that for the new semiconductor wafer is performed until a series of the plurality of dry etchings for one semiconductor wafer is completed and the semiconductor wafer is taken out from the etching reaction chamber and the next semiconductor wafer is loaded. A method of manufacturing a semiconductor device, characterized in that an empty treatment step of dry etching is inserted into the etching reaction chamber in which plasma treatment is performed under the conditions.