JPH10189731A - Contact hole forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a contact hole having a smaller diameter than that of the hole formed by using normal ultraviolet ray I-line. SOLUTION: A non-conductive film and a patterned photoresist film 38 are formed on a semiconductor substrate, a polymer film 44 is uniformly deposited on the non-conductive film and the film 38, then the film 44 is etched to form polymer spacers 48A, 48B on the photoresist film. And, with the spacers 48A, 48B as masks, the non-conductive film is removed by etching up to the substrate to form a hole (e.g. a contact hole, a line pith, trench), and depositing and dry etching steps are executed under the same reaction conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a contact hole in an electronic structure, and more particularly, to a method for forming a contact hole on a sidewall of a photoresist film by using a polymer spacer.
The present invention relates to a method for forming a relatively thin contact hole, line pitch or trench in a non-conductive film of a semiconductor device.

[0002]

2. Description of the Related Art At present, a semiconductor device is built on a semiconductor substrate (for example, a silicon substrate), and a P-type doping region and an N-type doping region formed on the substrate are basic components of the device. A necessary circuit is formed by connecting these doping regions via a special structure. However, this circuit can be connected to the outside only after it is connected to the packaged chip through the conductive pad for general test. Therefore, in one semiconductor circuit, at least one conductive film pattern (for example, metal) must be deposited and patterned to form contacts or internal wiring between different regions of the chip. For example, in a typical semiconductor manufacturing process, a chip is first covered with an insulating film, a pattern is formed on the insulating film, a contact opening is formed by etching, and a conductive material is deposited inside the contact opening. Thus, a contact plug and an internal wiring node are formed.

Generally, a contact hole connected to silicon or silicide is formed in an insulating film, that is, a dielectric film using lithography and dry etching. Anisotropic etching is employed in the dry etching so that the formed contact hole can have a large aspect ratio and vertical side walls. Subsequently, a conductive material (for example, a metal) is buried in the contact hole to form a vertical contact made of the metal of the first layer. Of course, the contact hole can be formed by wet etching. The wet etching is performed by dipping the wafer in an appropriate etching solution or spraying the etching solution on the wafer.
However, since wet etching is isotropic etching, etching is performed simultaneously in the horizontal and vertical directions. Therefore, an undercut that is inconvenient for the process occurs at the lower end of the mask due to the horizontal etching. Conversely, since dry etching is anisotropic etching, the widths of the upper and lower portions of the formed contact hole are substantially the same. In addition, undercut does not occur in dry etching, and it is not necessary to allocate an extra horizontal area as a contact hole, so that waste can be suppressed. Therefore, most of current submicron devices employ dry etching. . Dry etching has other advantages, for example, because it reduces chemical hazards and reduces the number of manufacturing steps, making it easier to automate the manufacturing process and cluster tools. Currently, the most frequently used dry etching techniques include plasma etching and reactive ion etching.

[0004] Since the dry etching technology has greatly contributed to control of the device scale, V
Although widely used in LSI and ULSI manufacturing processes, dry etching also has some problems. One of the reasons is that dry etching cannot reduce the pattern formation size.
In current ULSI devices, semiconductor devices are:
Both horizontal and vertical dimensions are constantly being scaled down to meet the need for increased device integration density. Therefore, the manufacturing process technology for reducing the element size is also important accordingly. Therefore, feature dimensions that can be transferred onto a chip (Feature Si
ze), that is, the size of the contact hole, the minimum line width, or the line pitch is directly related to the integration density of the chip. For this reason, when advocating innovation in high-density chip design, it usually refers to lithography technology for reducing feature sizes.

[0005] Among the main lithography techniques (optical, electron beam, X-ray, ion beam), lithography using an ultraviolet light source is one of the most important. At present, the most widely used ultraviolet light sources for photolithography are arc lamp light sources and laser light sources.
The emitted light rays include, as main spectra, far ultraviolet rays (wavelengths in the range of 100 to 300 nm), medium ultraviolet rays (wavelengths in the range of 300 to 360 nm), and near ultraviolet rays (wavelengths in the range of 360 to 450 nm). For example, when adopting a mercury-xenon arc lamp light source,
Its wavelength is mainly deep ultraviolet (DUV), 365n
m (I-line), 405 nm (H-line), 4
There is 36 nm (G-line). Also, in order for the photoresist material to be used to be properly exposed, a photon energy amount of 2.5 eV or more is required in all cases. Therefore, the lithography technology must be used at a wavelength of 436 nm or a shorter wavelength. Can be used in
For example, when the feature size to be transferred to the chip surface is 2 μm or more, the photoresist film can be exposed by all the rays emitted by the mercury-xenon arc lamp, but the feature size to be transferred gradually becomes smaller. The wavelength must be corrected by lenses and filters, and other wavelengths in the spectrum must be removed. As an example, to expose a photoresist film in lithography technology, G-li
Ne can be used in a manufacturing process with a feature size of about 0.8 μm to be transferred, and I-line can be used in a manufacturing process with a feature size of about 0.4 to 0.8 μm. If you want to transfer shorter light rays (e.g., 248 nm light in DUV), the feature size is about 0.4
It can be used for manufacturing processes of μm or less.

[0006]

At present, in a VLSI manufacturing process, 16M and D having a larger capacity are used.
Most of the RAM adopts a manufacturing process of 0.4 μm or less (a manufacturing process of 0.25 μm), and the diameter of each contact hole is 0.3 μm or less. Since I-line can be used only for a manufacturing process of about 0.4 μm,
When fabricating DRAMs with higher M and capacity, DUV light with shorter wavelengths and more sensitive photoresist materials must be used.
However, the use of shorter wavelength DUV light, or the use of more sensitive photoresist materials, can significantly increase the cost of manufacturing semiconductor devices.

FIGS. 1 and 2 show the formation of a contact hole with vertical sidewalls in a dielectric film by a prior art lithography process, the minimum diameter of such a contact hole being the I-line wavelength. First, in FIG. 1, the semiconductor element 10 includes the semiconductor substrate 12, and the dielectric film 14 is deposited on the semiconductor substrate 12. The semiconductor substrate 12 can be a silicon substrate, and the dielectric film 14
Can be a silicon dioxide (SiO 2) film or a silicon nitride (Si ₃ N ₄ ) film.

Next, the photoresist film 1 is formed on the dielectric film 14.
After depositing 6, an opening 20 is formed by patterning. At this time, since the photolithography technique using the ultraviolet I-line light source is used for patterning the photoresist film 16, the feature size that can be transferred is 0.1 mm.
It is limited to 4 μm or more. In FIG. 2, when an opening 20 is formed in the photoresist film 16 by exposure, a contact hole 22 is formed in the dielectric film 14 by dry etching, and the diameter of the contact hole 22 becomes A. Since the dry etching (reactive ion etching) is anisotropic etching, the formed contact hole 22 has a vertical side wall. That is, the diameter of the upper portion and the lower portion of the contact hole 22 is about 0.4 μm, which is almost the same.

However, when it is desired to form a contact hole of 0.4 μm or less, it is necessary to use a more difficult lithography technique. Could not be achieved.

[0010] Therefore, the present invention provides an ordinary I-line
A main object of the present invention is to provide a method for forming a contact hole having a smaller diameter than a contact hole formed by using the method.

Another object of the present invention is to provide a method of forming finer holes in an electronic device without using a costly deep ultraviolet lithography technique and a deep ultraviolet photoresist.

Another object of the present invention is to provide a method of forming a finer hole in a semiconductor device by only making fine adjustments in a manufacturing process of a lithography technique using a conventional I-line light source. .

According to the present invention, the same reaction conditions (in-situ)
It is another object of the present invention to provide a method of forming a polymer spacer on a photoresist film to form a finer hole (for example, a contact hole or a line pitch) in a semiconductor device.

Another object of the present invention is to provide a method of etching a hole in a non-conductive film on a semiconductor substrate using a polymer spacer as a mask on a photoresist film and forming a finer contact hole or line pitch. Purpose.

The present invention provides a method for forming a polymer spacer with a reaction gas and forming a finer contact hole, the reaction gas being similar to a reaction gas used in a dry etching step. For another purpose.

The present invention provides a method for forming a thinner contact hole by forming a polymer spacer on a photoresist film and etching a contact hole on a dielectric film in the same reaction chamber. Its other purpose.

The present invention provides a method of forming a polymer spacer on a photoresist film using a mixture of reaction gases containing C ₄ F ₈ and CHF ₃ , and forming a finer contact hole. Its other purpose.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and achieve the above object, the present invention provides a method in which a finer hole is formed by a polymer spacer on a photoresist film in the same reaction chamber. Provide a way.

According to the present invention, there is provided a method of forming a polymer spacer on the side wall of a photoresist film under the same reaction conditions to complete a hole, comprising the steps of: covering a semiconductor substrate with a non-conductive film; Depositing and forming a pattern of a photoresist film on the substrate to expose a predetermined area of a hole portion to be formed; depositing a polymer film to cover a predetermined area of the photoresist film and the hole portion; Forming a polymer spacer on the sidewall of the photoresist film by anisotropically etching the film, and forming a hole by etching the non-conductive film until the semiconductor substrate is exposed. .

The present invention is also a method of forming a hole in a non-conductive film, wherein a step of depositing a non-conductive film on a semiconductor substrate and a step of forming a patterned photoresist film on the non-conductive film. And uniformly depositing a polymer film on the non-conductive film and the photoresist film; etching the polymer film to form a polymer spacer on the photoresist film; Forming a hole by etching until the substrate is exposed.

The present invention is also a method for forming a contact hole in a single reaction chamber, comprising the steps of: preparing a silicon substrate; depositing a dielectric film on the silicon substrate; Depositing a resist film; patterning the photoresist film to form a first opening exposing the dielectric film to form a contact hole; and uniformly depositing a polymer film over the first opening and the photoresist film. Depositing the polymer film, anisotropically etching the polymer film, forming a polymer spacer in the first opening to cover the photoresist film, and performing anisotropic etching using the polymer spacer as a mask. A second opening is formed until the silicon substrate is exposed, and the second opening is made smaller than the first opening to form a thinner contour. Forming a Tohoru, in which and a step of removing the photoresist film from the dielectric film.

[0022]

The operation of the present invention will be briefly described. The present invention provides a finer hole (for example, a contact hole, a line pitch, a trench) in a semiconductor device.
Under the same reaction conditions, a polymer spacer formed on the photoresist film is used as a mask for dry etching holes.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described below with reference to the drawings. In FIG. 3A,
A semiconductor element 30 is built on a silicon substrate 32 and forms a dielectric film 34 (for example, an oxide film) on the silicon substrate 32. This dielectric film 34 can be formed by thermal oxidation, or can be formed by depositing another dielectric material, such as nitride or boron.
Phosphorus silicate glass (BPSG = boro-phosphor-si
licate glass). The dielectric film 34 may also be deposited with other dielectric materials, having a thickness of about 3000-3000.
The range is 12000 °.

In order to form holes (for example, contact holes, line pitches, trenches) in the dielectric film 34, a photoresist film 38 is deposited on the dielectric film 34.
The photoresist film 38 is an exposure material,
It can be used for photolithography with a line wavelength. Next, an opening 42 for a contact hole is formed by patterning the photoresist film 38. At this time, unlike the prior art, a polymer film 44 is deposited on the photoresist film 38 instead of forming a contact hole by directly dry-etching the dielectric film 34. The point that the present invention has novelty is that the polymer film 44 can be easily deposited on the photoresist film 38 in the same reaction chamber (not shown), and the next etching step can be performed as it is. It is in. The polymer film 44 has an advantage that it can be deposited under the same reaction conditions.

As a mixture of reaction gases for depositing the polymer film 44, a mixture gas of C ₄ F ₈ , CHF ₃ , CO and Ar can be used. Generally, the proportion of the gas mixture used to deposit the polymer film 44 is 20 sc
cm C ₄ F ₈ , 80 sccm CHF ₃ , 140
It may be sccm of CO and 100 sccm of Ar. 40 sccm N2 can also be selectively added to the reaction gas mixture. When the deposition process is performed inside the reactive ion etching reaction chamber, the upper electrode is maintained at 20 ° C. and the lower electrode is maintained at 0 ° C., while the side wall of the reaction chamber is maintained at 40 ° C. When the pressure in the reaction chamber is 400 Torr, deposition is performed for 1 minute at a high frequency power of 500 W. In this atmosphere, the deposition rate of the polymer is about 3000 ° / min.
Becomes

In the step of depositing the polymer film 44, it should be noted that the polymer film 44 uniformly covers the side walls 48 and the openings 42 of the photoresist film 38 and the exposed portions 52 on the dielectric film 34 are removed. It is covering. In this deposition step, the thickness of the polymer film 44 and the diameter of the contact hole where the quality is formed are directly determined. That is, if the polymer film 44 becomes thicker, the polymer spacer becomes thicker, so that a narrow contact hole can be formed. In addition to the ratio of the reaction gas mixture, the contact hole has a power of the reaction chamber and a reaction chamber. And controlled and determined by the flow rate of the helium cooling gas. Therefore, the method of depositing a polymer film according to the present invention is superior in the manufacturing process to the method of forming a contact hole of the prior art. By properly controlling the above manufacturing parameters, a thick polymer film can be formed to complete a contact hole with a small diameter, and conversely, a thin polymer film can be formed to form a contact hole with a large diameter. It can be completed.

Another advantage of the present invention is that the step of depositing a polymer film and the step of reactive ion etching can be performed in the same reaction chamber. This is because the reaction gas mixture used to form the polymer film is similar to the reaction gas mixture used in reactive ion etching when etching the dielectric film to form contact holes. For example, in the deposition and etching steps, the CHF ₃ , N ₂ , and Ar in the reaction gas mixture are common and differ slightly from using CF ₄ in the etching step and C ₄ F ₈ , CO in the deposition step. It is just that. And that the reaction gas mixtures are similar,
According to the present invention, it is possible to simplify the gas storage and gas transport equipment.

In FIG. 3B, after the polymer film 44 is formed on the dielectric film 34, a polymer spacer 48a is formed by dry etching. In this case,
Reactive ion etching can be used, and since the reactive ion etching is anisotropic etching, the top surface 46 of the polymer film 44 (see FIG. 3A) and the exposed surface on the dielectric film 34 are exposed. Only the polymer film 44 deposited on the portion 52 can be removed by etching, and the polymer spacer 48a can be left as it is. CF ₄ , CHF ₃ , N ₂ , Ar
Can be used. This polymer spacer 48a
In the step of forming, a low power soft ash process can be employed. Suitable reaction gas mixtures include 100 sccm CF ₄ , 25 sccm CHF
₃ , 10 sccm N ₂ , 300 sccm Ar,
200 W power, 300 W
The reaction chamber pressure of Torr can be used.

In FIG. 3C, a contact hole 60 having a smaller diameter can be formed. Actually, in this step, the conditions of the reaction chamber were changed to the atmosphere of the oxidation etching step (reaction chamber pressure of 200 Torr, high frequency power of 1200 W, CF ₄ of 25 sccm, CH of 25 sccm).
F ₃ , Ar is changed to 300 sccm, and a contact hole 60 having a smaller diameter is formed by etching using the polymer spacer 48b as a mask. For example,
Initially, the diameter of the opening 56 portion of the contact hole 60 is in the range of 0.4 to 0.5 μm (see the opening 56 in FIG. 3B).
(See the opening 66 in FIG. 3C). At this time, if the polymer spacer 48b is used as a mask, and especially the thickness of the lower end of the polymer spacer 48b is used as a mask, the opening diameter of the exposed portion 52 can be 0.2 to 0.2 mm.
It can be reduced to a range of 0.3 μm. Actually, the contact hole 60 formed by the oxidative dry etching has a slightly inclined side wall 68, so that the lower end area 6
4 has its diameter reduced to approximately 0.1-0.2 μm.

After forming the contact hole 60 (or line pitch or trench), a plasma ashing process containing oxygen is performed.
Then, the photoresist film 38 is removed by a conventional technique in which a wet ashing process is combined (not shown). In this way, preparations for depositing a conductive film on the semiconductor element 30 to form a contact plug or performing a subsequent process (both not shown) are completed.

Although the present invention has been disclosed above with reference to the preferred embodiments, it is not intended to limit the present invention, but, as will be understood by those skilled in the art, Since many changes in form and detail can be made, the scope of protection of the present invention is based on the matters described in the claims.

[0032]

According to the structure described above, the method of forming a contact hole according to the present invention can form a finer contact hole by using a polymer spacer formed on a photoresist film. The invention also has the following advantages. First, formation of a polymer film serving as a spacer can be performed in the same reaction chamber as the next dry etching step under the same reaction conditions. This saves time for transferring the wafer to a different reaction chamber and eliminates the possibility of the wafer being contaminated during the transfer process. Next, by forming a contact hole having a small diameter according to the present invention, the feature size can be reduced to 0.25 without using a costly deep ultraviolet light source and a deep ultraviolet photoresist material.
It is possible to provide a manufacturing process technology realizing μm or less. Therefore, since the reaction gas required for depositing the polymer spacer and the reaction gas used in the later dry etching are basically the same,
This has a very practical value in that the existing manufacturing process of the wafer processing plant only needs to be slightly adjusted.

[Brief description of the drawings]

FIG. 1 is a process sectional view of a semiconductor substrate according to a conventional technique.

FIG. 2 is a process cross-sectional view in which a contact hole having a side wall perpendicular to the semiconductor substrate of FIG. 1 is formed.

FIG. 3 is a process sectional view showing a contact hole forming method according to the present invention, in which (a) is a process sectional view in which a polymer film is uniformly deposited on a photoresist film and a dielectric film, and (b) is a process sectional view. FIG. 2 is a process sectional view in which a polymer spacer is formed, and FIG. 3C is a process sectional view in which a thin contact hole is formed using the polymer spacer as a mask.

[Explanation of symbols]

 Reference Signs List 30 semiconductor element 32 silicon substrate 34 dielectric film 38 photoresist film 42 opening (first opening) 44 polymer film 48 side wall 48a polymer spacer 48b polymer spacer 56 opening (second opening) 60 contact hole 64 contact hole 64 lower end area of contact hole 68 Side wall

Claims (20)

[Claims] A step of covering a semiconductor substrate with a non-conductive film; a step of depositing and forming a pattern of a photoresist film on the non-conductive film to expose a predetermined area of a hole portion to be formed; Depositing a polymer film to cover a predetermined area of the photoresist film and the hole portion; and anisotropically etching the polymer film to form a polymer spacer on a sidewall of the photoresist film. Forming the hole by etching the non-conductive film until the semiconductor substrate is exposed, forming a polymer spacer on the side wall of the photoresist film under the same reaction conditions. How to complete. 2. The method of claim 1, wherein the hole is selected from a group consisting of a contact hole, a line pitch, and a trench. 3. The method according to claim 1, wherein the polymer spacer is formed by reactive ion etching. 4. The method of claim 1, wherein said step further comprises the step of removing said photoresist film from said non-conductive film. 5. The reaction gas according to claim 1, wherein a reaction gas used for depositing the polymer film is substantially the same as a reaction gas used for etching the holes on the non-conductive film. How to complete the hall. 6. The method of claim 1, wherein the reactive gas used to deposit the polymer film is CHF ₃ . 7. The method according to claim 1, wherein the reaction gas used for depositing the polymer film includes CHF ₃ , C ₄ F ₈ , and CO. 8. The method of claim 1, wherein the polymer spacer is used as a mask to form a hole in the non-conductive film. 9. The method according to claim 1, wherein the step of depositing the polymer film is performed in the same reaction chamber as the step of forming the polymer film and the step of etching the hole. how to. 10. The method according to claim 1, wherein the hole in the non-conductive film is
2. The method according to claim 1, wherein the hole is formed by oxidative dry etching. 11. A step of depositing a non-conductive film on a semiconductor substrate, a step of forming a patterned photoresist film on the non-conductive film, and a step of polymerizing on the non-conductive film and the photoresist film. Uniformly depositing a material film; etching the polymer film to form a polymer spacer on the photoresist film; and etching the non-conductive film until the semiconductor substrate is exposed. Forming a hole in the non-conductive film. 12. The method for forming holes in a non-conductive film according to claim 11, wherein said non-conductive film is made of a dielectric material. 13. The method for forming holes in a non-conductive film according to claim 11, wherein said semiconductor substrate is a silicon substrate. 14. The polymer film and the non-conductive film described above,
2. The method according to claim 1, wherein the first electrode is formed by dry etching.
2. The method for forming a hole in a non-conductive film according to item 1. 15. The method for forming a hole in a non-conductive film according to claim 11, wherein the hole is a contact hole or a line pitch. 16. The method for forming holes in a non-conductive film according to claim 11, wherein said step further comprises a step of removing said photoresist film by plasma containing oxygen and wet cleaning. 17. The method according to claim 17, wherein the hole in the non-conductive film is
The diameter is set to 0.5 μm or less.
A method for forming a hole in the non-conductive film according to the above. Providing a silicon substrate, depositing a dielectric film on the silicon substrate, depositing a photoresist film on the dielectric film, patterning the photoresist film, Forming a contact hole by forming a first opening for exposing the dielectric film; uniformly depositing a polymer film on the first opening and the photoresist film; Anisotropically etching to form a polymer spacer in the first opening to cover the photoresist film; and using the polymer spacer as a mask until the silicon substrate is exposed by anisotropic etching. 2 opening is formed, and the second opening is made smaller than the above-mentioned first opening. A method for forming a contact hole in a single reaction chamber, comprising: forming; and removing the photoresist film from above the dielectric film. 19. The method of forming a contact hole in a single reaction chamber according to claim 18, wherein said second opening has a diameter smaller than half the diameter of said first opening. 20. The polymer film according to claim 18, wherein said polymer film is deposited by a reaction gas, and said reaction gas is similar to a reaction gas used in anisotropic etching.
A method of forming a contact hole in a single reaction chamber as described.