JPS6225424A - Pattern forming method - Google Patents

Abstract

PURPOSE:To obtain a pattern of submicron order by composing a resist of lower and upper layers when forming a resist pattern on a substrate for an electronic device, first patterning the upper layer, then coating the exposed part with an organic silicone, and conducting dry etching of the lower layer with the silicone as a mask. CONSTITUTION:A lower layer resist film 14 and an upper layer resist film 15 made of polyimide are laminated on a substrate 13, and the film 15 is formed in the desired pattern by a wafer stepper. At this time a step formed on the substrate 13 is buried with the film 14 so that the film 15 becomes uniformly thick and the film 14 performs a role of absorbing ultraviolet rays, thereby forming an ultrafine pattern of approx. 0.6mum. Thereafter, an Si-added layer 16 is formed of (CH3)2 on the exposed surface of the pattern of the film 15, reactively ion etched with the layer 16 as a mask to form a pattern of submicron order.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Use" The present invention is a method for forming fine beams on substrates for semiconductors and various electronic devices. This relates to a method of forming an image using lff.

``Conventional Technology J'' Conventionally, a multilayer resist method has been developed as an effective method for forming extremely fine AI bars with high precision. It is possible to eliminate the negative influence on custom pattern formation caused by local fluctuations in resist film thickness due to steps existing on the substrate surface, and it is possible to reduce the resist film thickness of the top layer that forms an image by using a resist single layer. Although it has the advantage of being able to form fine patterns with high precision because it can be made thinner than conventional layered films, it has practical problems such as the complicated process and the need for special resist materials (which can lead to some major problems). Was.

These problems will be explained using cross-sectional views showing each process of the prior art shown in FIGS. 10-16.

JIQ to FIG. 13 show the steps of the three-layer resist method, and FIGS. 14 to 16 show the steps of the 2-layer V cyst method.

3. Shown in Figure 2 or Figure 13. In the case of the resist method, first, an organic polymer layer 2 is coated on a substrate 3, and after baking, an inorganic 9 film 184 made of Borin 11, SiO3, etc. is evaporated, and then deposited by snow coating or CVD.
After applying Kt using E or the like, a resist layer 1 is further applied thereon to form a three-layer structure as shown in FIG. Next, the upper resist layer 1 is coated with an eleventh resist layer using a known lithography technique.
As shown in the figure, an upper resist layer/Coon 11 is formed.

Then, as shown in FIG. 12, the inorganic layer 4 is etched using the upper resist layer 4.711k mask in Freon gas plasma to form an etching pattern 41.

Furthermore, the organic polymer/12 is dry-etched in oxygen gas plasma using the inorganic layer etching/notching bag 41 formed in the previous step as a mask, and patterns 31 and 41 are formed on the substrate 3 as shown in FIG. Form. In this case, C
The upper resist layer 4 is composed of elements such as , H, and O.
- 11 is not resistant to oxygen plasma, so it is etched and disappears in the previous process. In this way, the upper layer pattern 11
Since it is difficult to directly etch the underlying organic polymer layer 2 using the mask as a mask, the inorganic layer 4, which is resistant to oxygen plasma, must be used as a mask. As explained above, the 3rfIi resist method has a drawback in that it is impractical because the process is very complicated. In order to improve this drawback, two
A layered resist method was developed. The greatest advantage of this two-layer resist method, as shown in Figure 14, is the use of a resist material that is resistant to oxygen plasma for the upper layer resist IK used for pattern formation.If such a resist material can be developed, Lower organic polymer layer 2 without using inorganic layer 4
Using the upper resist pattern 11 shown in FIG. 15 as a mask, dry etching can be performed directly as shown in FIG. 16.

On the other hand, methods for applying oxygen plasma injection to resist materials made of organic substances have been carried out by copolymerization, grafting, or esterification reactions of compounds containing 81 in the main chain or side chain of the polymer used as the resist material. Several resist materials containing added Sl have been developed.

“Problems to be Solved by the Invention” In general, when 81 is contained in the constituent elements of a polymer, it has a significant effect on the basic properties necessary for a resist, such as solubility in solvents, sensitivity, and beam resolution. It is known that Therefore, it has been extremely difficult to fully satisfy these basic characteristics and at the same time provide oxygen plasma resistance. There are only a few types of resists of this type that have been announced so far, such as negative type and positive type for ultraviolet rays, and negative type for electron beams, and these resists have poor overall performance as a resist material for the reasons mentioned above. However, the pattern quality obtained with the two-layer resist method is basically determined by the pattern quality of the upper resist layer and the oxygen plasma resistance, so it is difficult to fully satisfy the overall performance. At present, a two-layer resist method has not yet been put into practical use because no excellent Sl 2 -containing resist has been developed.

The present invention uses a resist containing 81 as the upper layer resist.
This was done to solve the drawbacks of the layered resist method.
The purpose is to provide an extremely versatile pattern forming method.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention uses a normal non-S1-containing resist as the upper layer resist to form a pattern, and then uses a photochemical reaction to form a pattern using a non-S1-containing resist. Afterwards, Sl is added to the resist surface to impart oxygen plasma resistance, and the resist is etched in an oxygen plasma atmosphere.

"Operation" The region to which Sl has been added and provided with oxygen plasma resistance can be selectively dry-etched as a mask.

Before explaining the present invention in detail, the basic principle of the present invention will be explained below.

The principle configuration for explaining the photochemical S1 addition reaction treatment of a resist film according to the present invention is shown in Figure @7.

Inside the container 5, a halogenated alkylsilane solution 6 such as Khhhυmethylchlorosilane, dimethylchlorosilane, dimethyldichlorosilane, trimethyliodide, etc. is filled 6''!A lower layer film 8 is applied onto the substrate 7, and the film is moved upward northward. !
- forming a pattern 9 using known linography techniques; immersing the sample in the alkylsilane solution 6; and capping the container 5 with transparent quartz glass lO; If you need it again,
Ultraviolet sharp cut filter J12 and quartz glass 10
KtlR above. Subsequently, the sample surface is irradiated with far ultraviolet light for a predetermined time through the quartz glass 10 using a far ultraviolet light source such as an Xθ-Hg lamp, and then the sample is taken out and dried. Thereafter, the surfaces of these samples were subjected to reactive ion etching in a parallel plate type sputter etching device in which aX gas was introduced, and various types of I
Measure the etch amount of the n-bar 4-79 and the lower layer 8, calculate the etch rate, and compare it with the etch rate of each layer above for the non-Si layer to investigate the presence or absence of Si conversion and the etch rate ratio. did. As a result, it was found that the addition reaction of 81 to jJ (Regis) strongly depends on the type of light source and the side of the film ttJM. Table 1 shows examples with and without the S1 addition reaction.

As a result, when irradiated with ultraviolet light that does not include light with a wavelength shorter than 350 nm, the Sl
No addition reaction was observed.

The wavelength is 250n by UV sharp cut filter.
When irradiated with far ultraviolet light that does not contain light below m, AZ-
UV resists such as +350J are converted into Si, but 2
Electron beam resist such as polymethyl methacrylate (hereinafter referred to as PMMA and Thf) or fluoroptyl methacrylate (hereinafter referred to as FBM), which does not exhibit photosensitivity to light of 50 nm or more, or a non-photosensitive board 117 such as polyimide is converted into Si. I did something. Furthermore, when irradiated with far ultraviolet light including UV light with a wavelength of 210 to 250 nm, non-photosensitive polyimide and polybutene sulfone (hereinafter referred to as PBS) usi
PMMA is not photosensitive to this wavelength band but is sensitive to this wavelength band.
, FBM, AZ-1350J, etc., the presence of Sl addition reaction was recognized.

On the other hand, Fig. 3 shows trimethylchlorosilane ((0(3)3
・5ict) An example of measuring the spectral absorption coefficient of a liquid is shown. Above 7
It can be seen that the run liquid has weak absorption with a peak around the wavelength of 320 nm and strong absorption of far ultraviolet light with a wavelength of 240 nm or less. Furthermore, the absorption characteristics of dimethylchlorosilane ((CH3)2・Sl・HCl'') and dimethyldichlorosilane ((CH3)2・Sl・CL2) mentioned above are almost the same as shown in Fig. 3.From this result, it can be concluded that these It is estimated that chloroalkylsilane is excited and activated by absorption of deep ultraviolet light as follows, hν (CH) ・Sl ・CL−(CH) ・Si” + C!
*hν Kyo (CH) ・Sl・HCt-(CH3)2Si ・H!
C1hν (CH3)2・Sl・CL2−(CH3)2・SL*C
4+C1*hν or (CH) ・8l-Ct-(CH) -8i**+
2C7'' Therefore, if we consider the results in Table 1 and Figure 9, the Si addition reaction of alkylsilane due to photochemical reaction is caused by the excitation reaction of the resist film constituent molecules and the excitation reaction of the alkylsilane simultaneously due to irradiation with far ultraviolet light. Therefore, as shown in Table 1, it is possible to selectively cause the 81 addition reaction by appropriately selecting the wavelength range of the light source and the resist material. found.

Next, the resist film subjected to the 81 addition process and the resist film not subjected to the addition process were subjected to reactive ion etching in oxygen gas, the etch number was measured, and the etch rate and etch rate ratio of each resist film were determined. The resist depth at which the reaction occurred was evaluated. Figure 9 shows pressure 3
．． This figure shows the relationship between the etch time and the etch depth of the S case, which was subjected to 11 active ion etching in an oxygen gas atmosphere of 5 pa under a constant high-frequency input of 65 mW/ctn. )2Si
When AZ −+350J resist film is irradiated with far ultraviolet light (wavelength 250u or more) for 10 minutes in HC1 solution, solid line a'
When irradiated for 5 minutes in the same solution and (CH3)
This is an example of irradiation for 10 minutes in a 3SICt solution, and the dotted line is (CH3) 2S 1) (reduced ultraviolet light (including wavelengths of 210 to 250 lm) for 10 minutes on a PMMA film in a ct solution)
This is the case when irradiation is performed. Furthermore, the dotted line C is for polyimide and AZ-+350J resists which have not been subjected to the S1 addition process, and the single-dot chain ID is for PMMA and PBS films which have not been subjected to the S1 addition process.

Note that the far ultraviolet light source used in this case was 500WXe −
With a Hg short arc lamp, the surface illuminance of far ultraviolet light with a wavelength of 350 nm or less is approximately 20 mW/cm2. From the results shown in Figure 9, it can be seen that (CH,)3Si 10
AZ-+350J
In resist, the depth of about 200 nm from the surface is 81
is added, and in PMMA similarly l 2
It can be seen that Si is formed to a depth of about Q nm. In addition, the active ion etch rate ratio of the Sl-formed Sareta resist film in Ni'22 gas is approximately 1/20° compared to the un-Si-formed AZ-1350J and BoIl-imide films. P
It was found that the oxygen plasma resistance of the resist film can be greatly improved by the addition treatment of Sl. In this experiment, an Xθ-Hg lamp light source with a parallel luminous flux of 1-1 was used as the light source, but since a scattered light source can sufficiently achieve the purpose, a low-pressure mercury lamp that emits strong far-ultraviolet light, a high-pressure mercury lamp,
Alternatively, by using a -2-wave excitation mercury lamp or the like, it is possible to generate a sufficient cSi addition reaction with extremely short irradiation treatment. In addition, in the wood η test, Si conversion reaction was confirmed for the three types of commercially available ultraviolet resists shown in Table 1. , and azide photosensitizer/vinylphenol 4? , Tweet for negative photoresist consisting of ff fat ηλ is similar to AZ-1350J (7) S
It is expected that an i-formation reaction will occur. The same applies to electron beam and X-ray resists, and other megcryl-based resists that are sensitive to deep ultraviolet light, and other Q resists such as polymethyl isopropyl ketone (PMIPK) and chloromethyl styrene (CMS). In principle, it is expected that the 81 conversion reaction will occur in beam resist as well.

As a result of the above, 2. In the resist structure, after forming the upper resist pattern, 81 was selectively added only to the upper resist pattern or only to the surface of the lower resist film not covered by the upper resist pattern by the above-mentioned Sl addition treatment method. By reactive ion etching in an oxygen gas atmosphere, p, S
Using the added resist film as a mask, it is possible to remove and process the non-Si 2 film to form a highly accurate pattern.

The method of the present invention was carried out based on the experimental contents described above, and examples will be described below.

"Example 1" Each of FIGS. 1 to 3 is a side view showing a process for explaining the method of the first embodiment of the present invention, in which 13 is a substrate, 14 is a lower layer film, and 15 is a Upper layer resist pattern, 16
17 is an additional layer of Sl, and 17 is a pattern formed by reactive ion etching.

To carry out the method of this embodiment, first, a polyimide film or PMMA film with a thickness of about 1 to 1.5 μm is coated on the substrate 13.
After applying the film to form the lower polymer film 14, a baking process is performed at a temperature of about 200°C for about 1 hour, and then a UV-sensitive resist (AZ
-+350J) to form an upper resist film, and
Bake treatment at 5°C for 5 minutes. After this, using a wafer stepper, the desired amount of J-715 is applied to the upper resist film.
In this case, by coating the lower resist film 14, the steps on the substrate 13 are buried, so that the thickness of the upper resist film can be made extremely uniform, and the thickness of the lower resist film 14 can be made extremely uniform. Since the film 14 serves as an ultraviolet light absorbing layer, it is possible to form fine patterns up to about 0.6/jm with good reproducibility. Thereafter, the sample is immersed in a dimethylchlorosilane [(CH3)251.HC4] solution, and 81 addition treatment is performed for about 10 minutes using a deep ultraviolet light source. In this case, if the lower resist film 14 is made of PMMA, a sharp cut filter 4 (UV-2s) is placed in the optical path to prevent irradiation with deep ultraviolet rays with a short wavelength of 250 nm or less in order to prevent the PMMA surface from becoming Si. insert. As a result, UV-sensitive resist (AZ
As shown in FIG. 2, organic silicon is added to the approximately 200 nm thick portion of the upper resist pattern 15 on the surface R5i of the upper resist pattern 15 consisting of the upper resist pattern 15 (-+350J) to form the S1 additional layer 16.

After that, the substrate 13 is transferred to a 11 active ion etching device, and etching is carried out at 10 to 3 times depending on the material of the lower resist film 14 and its size, referring to the etching conditions shown in Figure @9.
After etching for 0 minutes, a desired pattern 17 is obtained and the pattern processing is completed as shown in FIG.

If pattern processing is performed by the method described above, conventional resist materials can be used as they are instead of the Sl-containing resist as the upper layer resist and film, so high-resolution resists, negative resists, A resist material such as a positive resist can be freely selected as necessary.

Further, the above-described method has the advantage that basically any lithography method can be used. In other words, it can be applied to any phosphorography method such as deep ultraviolet, electron beam, X-ray, or ion beam, in addition to ultraviolet light, so it can be said to be an extremely versatile method for forming fine patterns. . Therefore, when the above-mentioned method is applied to pattern formation of various semiconductor elements, large-scale integrated circuits, or various electronic devices requiring submicron patterns,
This has extremely great advantages for the above reasons.

"Example 2" In order to implement the method of this example, first, a polyimide film with a thickness of 1 to 1.5 μm is coated on the substrate 13 as a lower resist film, and then it is coated at a temperature of about 200°C. After baking for about 1 hour, apply PMMA or chlorobutyl methacrylate (hereinafter referred to as FBM) resist as an upper layer resist to a thickness of about 0.3 to 0.5 μm.
Bake treatment is performed at 200°C. Thereafter, a desired pattern is formed on the upper resist film by electron beam phosphorography. In this case, instead of electron beam exposure,
It goes without saying that similar results can be obtained using radiation, ion beams, or far ultraviolet rays. Thereafter, the same Si addition process as in Example 1 is performed.

Here, when medacrylate, which shows a positive type under deep ultraviolet light, is used for the upper resist film, irradiation with deep ultraviolet light in a chloromethylsilane solution causes simultaneous conversion to Si and a reduction in molecular weight due to main chain scission. As a result, particularly in the case of FBM that is easily soluble in organic solvents, the FBM component with a lower molecular weight is easily dissolved in the chloromethylsilane solution, and film sagging is likely to occur. In order to prevent this and to effectively perform only Si conversion, it is necessary to (CH3)3S1Ct and (CH3)2.
η used by diluting 51HCt with a higher alcohol such as freon or allyl alcohol, which is a solvent in FBM.
Alternatively, instead of immersing the sample in the above-mentioned silane solvent, the sample can be heated to 40 to 50°C to generate high-concentration silane vapor, and the sample is then irradiated with deep ultraviolet light. However, it is also possible to convert FBM to Si, except that the rate of Si conversion is somewhat slower than in the immersion method. This method is effective only when FBM is used to convert a resist film that is susceptible to or easily dissolved into halogenated alkylsilane into S1. A desired pattern is completed by reactive ion etching the lower resist (polyimide) film using the upper resist bar 4, which has been converted to Si in this manner, as a mask.

In this example, we used a thin FBM which has high sensitivity but poor plasma resistance, a resist banner or a high-screen resist film (thin IAPHM which can draw a 9! degree pattern but has poor plasma resistance).
A: The advantage of being able to transfer the resist balloon with high precision to an organic film such as a polyimide film, which has relatively good resistance to plasma etching, is extremely large. Note that the upper resist contains other methacrylates such as PGMA and P (GMA-MA), as well as polymethyl isopropyl ketone (hereinafter referred to as PMI).
It can be easily predicted from the molecular structure and ultraviolet absorption characteristics of the resist that similar results can be obtained using an electron beam resist such as PK (referred to as PK) or the like.

Even in this embodiment, the same effects as in the first embodiment described above can be obtained.

"Embodiment 3" Figures 4 to 6 show an 8g3 embodiment of the present invention. In order to actually roll up the forming method of this embodiment, first, as shown in Figure 4, ultraviolet rays are applied onto the substrate 13. Photosensitive resist (AZ-13
50J) or PMMA to a thickness of 1 to 1.5 tim.
VC @ cloth to form the bottom 73vjix)vx14' and the temperature of each finger and foot! Perform baking process.

After that, UV-sensitive resist k (AZ-1350J)
On top, either FBM, PHMA or polybutenesulfone (hereinafter referred to as PI35) is applied to a thickness of 0.
- Apply the coating to a thickness of about 3 to 0.5 ttm, and use electron beam II lithography or the like to form a pattern 15', as shown in FIG. If P■ Buddha is used for 14', PBS is used as the upper layer resist and pattern 15 is used in the same way.
′ is formed. Thereafter, the lower resist film 14 was formed by combining a UV-sensitive resist (AZ-1350J) and applying far-ultraviolet light from which short wavelengths of 250 nm or less were removed using the sharp-cut filter in a halogenated alkylsilane solution. Irradiate for about 10 minutes. As a result, contrary to the cases of Embodiments 1 and 2, the upper resist pad 15'
The upper part is not converted to silicate, and only the exposed lower resist film surface 16' is converted to silicate as shown in No. 5N. In addition, when PBS is used for the upper resist layer, PBS has a wave r
It is not sensitive to far ultraviolet light of c200n, 11 or higher,
By direct irradiation with light from an ordinary Xθ-11g lamp without a filter, only the surface of the lower resist film 14' made of PMMA can be converted to Si to form an additional Sl layer 16'. Therefore, the additional layer 16 on the surface of the Si lower layer regime h pattern 14'
If reactive ion etching is performed with oxygen scavenging using ' as a mask, the lower resist film 14' where there is no upper resist film will remain as a pattern, contrary to the case explained in Embodiments 1 and 2. As a result, a positive/negative inversion pin 17' shown in FIG. 6 can be obtained.

Even in this example, it is possible to obtain the same effect as in the first embodiment described above.

"Effects of the Invention" As explained above, the present invention forms a pattern using an ordinary resist material that does not contain Si, and then adds 81 only to the necessary areas. Since this method performs dry etching on areas where there is no etching, it has the effect of allowing a variety of resist materials to be selected freely. , also, using a normal resist material.
In other words, the present invention has the effect that various lamination lithography techniques using ultraviolet rays, far ultraviolet rays, electron beams, X-rays, ion beams, etc. can be applied for pattern formation. It is possible to select various +1 graphing techniques as appropriate, and the number of steps is small due to the two-dimensional resist method (therefore, it is an extremely versatile fine pattern forming method.Therefore, the present invention is applicable to various semiconductor devices, as well as This method is extremely excellent as a pattern forming method for large-scale integrated circuits or various electronic devices requiring submicron balloons.

[Brief explanation of the drawing]

Figures 1 to 3 show the first embodiment of the present invention, in which Figure 1 is a cross-sectional view showing a state in which an upper resist balloon is formed, and Figure 2 is a cross-sectional view showing a state in which an upper resist balloon is formed. FIG. 3 is a sectional view showing the state after dry etching, FIGS. 4 to 6 show the third embodiment of the present invention, and FIG. 4 is the pattern forming state. Figure @5 is a cross-sectional view showing the state in which 81 is added on the lower resist film, Figure 8g6 is a cross-sectional view showing the state after dry etching, and Figure 7 is a photochemical diagram of the resist film according to the present invention. A principle diagram for explaining the S1 addition reaction process. Figure 8 is a spectral absorption characteristic diagram of the trimethylchlorosilane solution used in the Sl addition reaction. Figure 9 is the relationship between etch time and etch depth when reactive ion etching is performed. The diagrams @10 to 13 are for explaining the steps of the conventional three-layer resist method, and Figure 10 shows the state in which an organic polymer layer, an inorganic layer, and a resist layer are formed on a substrate. 11 is a sectional view showing a state in which a pattern is formed on a resist layer, and FIG. 12 is a sectional view showing a state in which an inorganic layer is etched. Figure 13 is a cross-sectional view showing the organic polymer layer etched. Figures 14 through 16 are for explaining the steps of the conventional two-layer resist method. FIG. 15 is a cross-sectional view showing a state in which a pattern has been formed on the upper l/cyst layer, and FIG. 116 is a cross-sectional view showing a state in which an organic polymer layer has been etched. −
Ru. 13...Board, 14.14'...Bottom 7
r9 resist film, 15.15'...upper resist pattern, 16°16'...S1 additional layer, 1
7.17'...Ecchi2/ Gulp Turn Questioner Nippon Telegraph and Telephone Corporation Representative Patent Attorney Masatake Shiga '1,,,-,/ Eng1. + Time raI (mint Figure 10 Figure 13-1 2, 11

Claims (1)

[Claims] In a structure having two resist layers made of an organic polymer on a substrate, the upper resist film is coated with ultraviolet rays, deep ultraviolet rays,
After forming a desired pattern using lithography technology using electron beams, X-rays, ion beams, etc., deep ultraviolet light is applied while the substrate is in contact with a halogenated alkylsilane liquid or a halogenated alkylsilane. By irradiating it, the organic silicon component in the halogenated alkylsilane component is photochemically reacted and added only to the upper resist pattern or only to the surface of the lower resist film that is not covered by the upper resist pattern. oxygen gas,
The resist film to which organic silicon is not added is selectively removed and processed by dry etching in an oxidizing gas plasma atmosphere such as carbon dioxide, using the area to which the organic silicon component is added as a mask. pattern formation method.