JP2995762B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device having a step of etching silicon. INDUSTRIAL APPLICABILITY The present invention can be generally applied to the manufacture of a semiconductor device including an etching step of a material to be etched which has at least a silicon portion, and includes, for example, a so-called silicon trench etching step of forming a groove or a hole in a silicon material. It can be suitably applied to the manufacture of semiconductor devices.

[Summary of the Invention]

According to the present invention, in at least one step of a method for manufacturing a semiconductor device, by etching silicon using a mixed gas containing at least hydrogen bromide and nitrogen, a good etching shape can be obtained by means with a small number of contamination sources. It was made.

[Conventional technology and problems]

Various techniques for etching a silicon material are used in the field of semiconductor device manufacturing. For example, the so-called silicon trench etching technology for forming deep grooves and holes in single crystal silicon is used in the manufacture of various highly integrated semiconductor devices.For example, a trench transistor or a trench transistor in a high-megabit DRAM, or a high-speed bipolar transistor is used. It is used for trench isolation, etc., and is now becoming indispensable.

As a gas used for such a silicon trench etching, conventionally, a fluorine-based gas, a chlorine-based gas, and a mixed system thereof have been variously developed and put into practical use. Among them, SiCl ₄ / N ₂ gas is mainly used at present. Regarding this, the present applicant has made a basic proposal in Japanese Patent Application No. 61-217690 (Japanese Patent Application Laid-Open No. 63-73526). This technique is based on SiC generated by dissociation of SiCl _{4 in} plasma.
This is a skillful technique of achieving anisotropic processing by utilizing a reaction product of l _x and N ₂ for side wall protection. However, the remarkable progress of the technology has led to the finding that this technology has further problems to be solved. That is, in the above technique, since the etching gas itself contains Si, the deposition is large, and this tends to be a particle source causing contamination.

In high aspect ratio processing of fine holes and grooves with a small opening diameter, reaction products cannot enter the inside of the trench well,
It is easy to be defective in shape. This is especially true for batch etchers (batch etchers are generally
Even in systems where the production of reaction products that contribute to sidewall protection is small,
Which can provide sufficient protection).

And so on. As a countermeasure against this, the present applicant has disclosed in Japanese Patent Application No. 62-217456 (Japanese Patent Application Laid-Open No.
Although l ₂ / N ₂ gas has been developed and proposed, this is extremely effective for a single wafer type etcher that generates more reaction products, but for a batch type etcher with a low etching rate, the effect is It may not always be noticeable.

Therefore, there is a strong need for a technique capable of solving the above-mentioned problems irrespective of the etching apparatus and achieving etching with a small contamination source and a good shape.

JP-A-63-278339 describes a method using hydrogen iodide, hydrogen bromide, or CF ₂ Br ₂ as a gas for etching silicon or the like. Although the content of the technology disclosed in the publication is not always clear, it is described that when hydrogen bromide (HBr) is used, it is preferable to use a gas composed of HBr, SiF ₄ , O _2, and He ( Page 8, upper left column to upper right column of the publication). However, in this gas system, since SiF ₄ is used, as mentioned in the above-mentioned problem of the prior art,
Si becomes a particle source and causes contamination. Also O ₂
Is present, the surface of the silicon to be etched is oxidized, and the surface is easily roughened. Furthermore, the reaction product Si
O _x is in large quantities to produce I cooperation with and the SiF ₄ is contained in the gas, in addition to control of the shape is deteriorated, the conditions of tolerance and condition setting becomes stricter narrows like, practical The problem is big.

On the other hand, there is a document showing RIE technology using hydrogen bromide gas as a conventional technology for etching polysilicon (Mor.
itaka Nakamura et al. `` Variable Profile poly-Si Etchin
g with Low Temperature RIE and HBr gas '', 1988 DRY
PROCESS SYMPOSIUM, II-5, Proceedings 58-63). However, it is difficult to control the etched shape only by the technology described in this document, and it is considered that the shape changes greatly due to the temperature, as described in the same document, and undercuts may occur and the trench may be scrambled. It is difficult.

Further, as a prior art, Japanese Patent Application Laid-Open No. 64-46931 proposes a trench etching method using a gas containing bromine and water. This technique, which is cumbersome and uses bromine and water, has insufficient sidewall protection.

The present invention solves the above-mentioned problems and uses a gas system which is hard to generate a contamination source, can be etched with good shape controllability, has no risk of surface roughness, and is easy to handle in the manufacture of semiconductor devices. The purpose of the present invention is to provide a technique capable of achieving an excellent etching.

[Means for solving the problem]

The method for manufacturing a semiconductor device of the present invention uses a mixed gas containing at least hydrogen bromide and nitrogen, and does not include a gas serving as a particle source and a gas that causes surface roughness. At the time of etching the silicon portion, a side reaction product of the silicon and nitrogen is generated at the time of etching, and etching is performed so that the opening of the material to be etched has a desired taper, and the flow rate ratio of nitrogen to hydrogen bromide is reduced. The desired taper shape control is performed by controlling.
Further, another method for manufacturing a semiconductor device of the present invention uses a mixed gas containing at least hydrogen bromide and nitrogen, and not including a gas serving as a particle source and a gas that causes surface roughness. In etching the silicon portion of the material to be etched, a by-product of the above-mentioned silicon and nitrogen is generated at the time of the etching so that the opening of the material to be etched has a desired taper, and the material to be etched is provided on the support portion. Is placed, and the material to be etched is brought into close contact with the supporting portion by the contacting means, and a temperature measuring means is disposed at a contact portion of the contacting means with the material to be etched to perform temperature detection, and based on the result of the temperature detection, In this case, the desired taper shape is controlled by controlling the temperature of the taper.

In the present invention, the flow ratio between hydrogen bromide and nitrogen used as an etching gas can be appropriately determined according to desired etching. In the present invention, the gas serving as a particle source (the above-described SiCl ₄
Etc.) and gases that cause surface roughness (such as O ₂ described above)
Is not included. However, it is optional to mix other gases that do not impair the effects of the present invention. For example, Ar, He, X
Use of a mixed gas to which a rare gas such as e or Kr is added is one of preferred embodiments of the present invention.

Although the present invention has a step of etching the silicon portion of the material to be etched as an essential step, the material to be etched is optional, and it is sufficient that at least a part of the material has the silicon portion to be etched. It goes without saying that a silicon substrate or the like made entirely of a silicon material may be the material to be etched.

In the present invention, the silicon portion is a portion made of a silicon material such as single crystal silicon, polysilicon, or a silicon-based thin film, and is a concept including a silicon compound such as silicide or a material containing these as a main component.

INDUSTRIAL APPLICABILITY The present invention can be preferably applied to the manufacture of a semiconductor device having an etching step of poly-silicon or other silicon-based thin films, including so-called silicon trench etching for forming deep grooves and holes in single crystal silicon. it can.

Further, the material to be etched is placed on the support portion, and the material to be etched is brought into close contact with the support portion by the contacting means, and a temperature measuring means is disposed at a contact portion of the contacting means with the material to be etched to detect temperature. In the present invention, the temperature of the material to be etched itself can be monitored, so that the desired appropriate shape control can be achieved by always performing etching under the optimum temperature condition based on the temperature.

(Operation)

In the present invention, since the silicon portion is etched by a mixed gas containing hydrogen bromide and nitrogen, SiBr is reacted by silicon and bromine atoms contributing to the etching.
_{Although x} is generated, the reaction product SiBr _x can form a sidewall protective film more effectively than, for example, SiCl _x according to a conventional method, so that etching with a good shape can be achieved. Further, since a by-product of silicon and nitrogen is produced, such by-products such as the reaction products SiBr _x and N
Side reaction products of ₂ also contributes to sidewall protection. Therefore,
In the practice of the present invention, and the side wall protective film according SiBr _x, further set the optimum conditions for better use of sidewall protective film due to side reaction products with N _2, such that a good shape can be obtained I do.

Such control of the etching shape can be controlled by the flow ratio of HBr and N _2, and can be further controlled by adding a proper amount of a rare gas.

According to the present invention, a gas system used for etching does not contain a silicon-containing gas (such as SiCl ₄ ) that can generate particles serving as a contamination source, which is advantageous for pollution control. This also improves shape controllability.

Further, according to the present invention, for mixing with HBr is N _2, as in the case with the addition of O _2, the occurrence of surface roughness of the silicon part can be prevented. And when O _{2 is} added, black Si is likely to be generated in the silicon portion, so it is necessary to add a gas such as SiF ₄ for this removal, but in the present invention, there is no such danger. Good etching can be achieved only with the HBr / N ₂ gas system, which is simple.

Furthermore, the products which can be used for protecting the side walls are SiBr _x as a reaction product and Si _{x Ny} which is a by-product as described above, and generate a large amount of products as when O _{2 is} added. There is no concern and the process can be simplified.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. However, needless to say, the present invention is not limited to the embodiments described below, but can take various forms.

Example 1 In this example, the present invention was applied to the manufacture of an SRAM which is a highly integrated semiconductor device. In particular, the present invention is embodied in a trench etching step of forming a trench in single crystal silicon.

As shown in FIG. 1, the material to be etched in this embodiment includes a substrate 1, an insulating film 2 formed thereon, and a polysilicon film 3. This is etched using the photoresist 4 as a mask to form a trench 11. In this embodiment, specifically, the substrate 1 is a single-crystal silicon substrate, and the trench 11 is formed therein. Insulating film 2
Was formed from silicon dioxide. Therefore, in this embodiment, the single-crystal silicon substrate 1, the SiO ₂ insulating film 2, and the polysilicon film 3 each form a silicon portion, and these are etched.

In this example, the etching conditions were as follows.

Etching gas: HBr / N ₂ = 20/10 SCCM mixed gas system Gas pressure: 1.0 Pa RF power: 300 W Etching temperature: 15 ° C. Etching equipment: plasma etching equipment Etching conditions such as HBr / N ₂ flow rate ratio are desired. Can be changed widely depending on the etching shape and the equipment used. The above conditions are set for forming a vertical trench. However, for example, when it is desired to achieve a tapered etching in which the vicinity of the opening is widened, the conditions may be set so as to achieve a desired tapered etching. . Generally, when a taper is desired, the N ₂ flow rate should be increased. This is because sediment increases.

The etching temperature is related to the controllability of the shape, but in the present embodiment, it was set to 15 ° C. in relation to the equipment used. In terms of preventing scouring (prevention of undercut), lower temperatures are better. This is because, in the case of anisotropic etching, suppressing the reactivity makes it easier to obtain a favorable etching shape.

According to the present embodiment, a vertically formed well-shaped trench 11 as shown in FIG. 1 was obtained.

In this example, it is assumed that the reaction proceeds by the following mechanism.

A reaction product of SiBr _x is generated from the silicon trench portion struck by the HBr plasma, but this is unstable, so that it reacts with the gas component N ₂ in the gas phase to become Si _x N _y . This adheres to the side wall and becomes a protective film. In FIG.
The protection film is schematically depicted and indicated by reference numeral 5. Such a protective film 5
The etching proceeds while being protected by the. As a result, anisotropy can be obtained and a good etching shape can be obtained.

Although the details of the mechanism are unknown, the reaction product SiBr _x
However, since it is more unstable than, for example, SiCl _x by the conventional method, it easily reacts with N ₂ and more efficiently protects the side wall protective film 5.
It seems to form Therefore, sufficient anisotropy can be realized even in a system having a small amount of reaction products such as a batch type RIE means.

In addition, since the etching gas itself does not include a material that can be a particle source such as Si and C, it can meet the demand for further fine processing.

In the present embodiment, the present invention is applied to the trench etching, but it is needless to say that the present invention is not limited to this and can be arbitrarily applied to the manufacturing processing of various semiconductor materials to which the present invention can be applied.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, good temperature control is performed during etching.

Although the present invention can be carried out under a wide range of conditions,
For precise shape control, control of the etching temperature is important.

In recent years, control of the temperature of a material to be processed during etching processing or other processing has received particular attention, and such a temperature control technique is becoming indispensable in next-generation process technology.

In general, as a temperature monitoring means, a method based on measurement of thermoelectromotive force using a thermocouple, a fluorescent fiber thermometer using a fluorescence decay phenomenon due to temperature, and the like are known. It must be in contact with the front (or back) surface of the wafer to be etched,
The fixing method is a major problem. That is, when the sensor is attached to the surface of the material to be etched by the etching device,
The portion is not etched, and the contact from the back surface of the material to be etched has a difficult surface in consideration of the processing of the stage, the chamber, and the like as the support portion.

The present embodiment overcomes the above-described difficulties. As shown in FIGS. 2A and 2B, the material to be etched 10 is placed on the support portion 6 and The etching material 10 is brought into close contact with the support portion 6 and
The semiconductor device is manufactured by arranging a temperature measuring means 8 at a portion where the temperature measuring device 8 is in contact with the material 10 to be etched.

As shown in FIG. 2 (b), the adhesion means presses the material to be etched 10 into contact with the support portion 6, and in this example, the material to be etched is particularly pressed and adhered by its own weight. .

In the present embodiment, the material to be etched 10 is a silicon wafer, and the support 6 is a stage on which the silicon wafer is mounted, and also serves as a cooling means for cooling the material to be etched 10 to the temperature of this stage. The contacting means 7 is for bringing the material 10 to be etched into close contact with the support portion 6 so that the cooling is efficiently achieved. Therefore, "close contact" here does not require airtight contact,
It means that the contact is performed so that the temperature transition is performed well.
The contact means 7 of this embodiment is a clamp for pressing and supporting the silicon wafer on the stage by its own weight as described above. That is, in this embodiment, specifically, the temperature is measured at the contact portion between the wafer as the material to be etched 10 and the wafer of the wafer clamp as the contact means 7 for increasing the cooling efficiency between the wafer stage as the support portion 6. When the temperature sensor as the means 8 is embedded and the wafer is held by the wafer clamp, the temperature measuring means 8 is always brought into contact with the wafer as the material 10 to be etched.

That is, in this embodiment, in a type of etching apparatus in which a clamp as shown in FIG. 2 is used as a contact means 7 to fix and cool a wafer, a thermocouple, a fluorescent fiber thermometer, etc. The sensor section of the temperature measuring means 8 is embedded.

Since the clamp and the wafer come into contact with each other during the etching process, the sensor section, which is the temperature measuring means 8 installed at the bottom of the clamp, naturally comes into contact with the wafer as the material 10 to be etched. In this case, since the weight of the clamp is applied as it is, there is no problem in the adhesiveness and the fixability. Thus, it is possible to monitor the temperature of the material to be etched 10 itself on the wafer without affecting the process or the like.

According to this embodiment, a temperature monitor can be easily achieved with good reproducibility in a form that does not affect the process, and the temperature of the etching can be controlled based on the temperature monitor result.
Therefore, desired taper shape control can be performed by appropriate temperature control. The specific conditions for etching are as follows:
Performed in the same manner as in Example 1.

In the present embodiment, the above-mentioned temperature monitor is performed at the time of etching the material to be etched 10, but in addition to other CVD, other processing before etching, or other processing after etching, the above-mentioned temperature monitor is used in combination. May be performed.

〔The invention's effect〕

According to the method of manufacturing a semiconductor device of the present invention, when etching, a gaseous source which is hard to generate a contamination source in the etching step, can achieve etching with good shape controllability, and has no risk of surface roughness, and which is easy to handle is used. Etching can be achieved.

[Brief description of the drawings]

FIG. 1 is a structural sectional view of a semiconductor device for illustrating an etching method according to one embodiment of the present invention. Fig. 2 (a)
(B) is a process explanatory view showing an etching method of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Single-crystal silicon substrate, 2 ... Insulating film, 3 ... Polysilicon film, 6 ... Support part, 7 ... Adhesion means, 8 ... Temperature measuring means, 10 ... Material to be etched.

──────────────────────────────────────────────────の Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/3065

Claims (2)

(57) [Claims] A silicon portion of a material to be etched is etched by using a mixed gas containing at least hydrogen bromide and nitrogen and not including a gas serving as a particle source and a gas that causes surface roughness. At the time of etching, a by-product of the above-mentioned silicon and nitrogen is generated at the time of the etching, and the etching is performed so that the opening of the material to be etched becomes a desired taper, and the flow rate ratio of the nitrogen to the hydrogen bromide is controlled. A method for manufacturing a semiconductor device, comprising controlling a taper shape. 2. A silicon portion of a material to be etched is etched by using a mixed gas containing at least hydrogen bromide and nitrogen and not including a gas serving as a particle source and a gas causing surface roughness. At the time of etching, a by-product of the above-mentioned silicon and nitrogen is generated at the time of etching, etching is performed so that the opening of the above-mentioned material to be etched has a desired taper, and the material to be etched is placed on the support portion, and the material is covered by the adhesion means. The etching material is brought into close contact with the supporting portion, and a temperature measuring means is disposed at a contact portion of the contacting means with the material to be etched, temperature is detected, and the desired taper is controlled by controlling the temperature based on the temperature detection result. A method for manufacturing a semiconductor device, comprising: performing shape control.