JP2966127B2 - Method of forming resist pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the Invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern used in a semiconductor device manufacturing process.

[0003]

2. Description of the Related Art In recent years, LSI devices have been miniaturized, and lithography techniques capable of forming a fine pattern in a submicron region, which are difficult to realize with conventional optical lithography, include electron beams and deep ultraviolet light ( Lithography by an excimer laser or the like is drawing attention.

[0004] Therefore, as a resist material which can put such lithography technology into practical use, a highly sensitive resist material called a chemically amplified type having characteristics different from those of conventional resist materials has appeared and is expected.

[0005] This chemically amplified resist material uses a catalytic reaction of an acid to improve sensitivity and resolution. For example, a chemically amplified negative resist material comprises a resin, a crosslinking agent, and an acid generator. It is composed of When this resist material is exposed, an acid is generated from the acid generator. Thereafter, by performing a heat treatment (post-exposure bake treatment, hereinafter referred to as “PEB treatment”), the acid acts on the cross-linking agent while diffusing in the resist material to create active sites therein. Crosslinking with the resin proceeds through these active sites, and as a result, the crosslinked portion becomes hardly soluble in the developer, and a pattern is formed after development.

For such a chemically amplified resist material, reference is made to the literature “MPdeGrandpre, K. Graziano, SDThomps”.
on, H. Liu and L. Blum, 1988, SPIE, 923, p. 158-p. 171 ''
It has been known that a PEB treatment process peculiar to a chemically amplified resist material has a great effect on patterning characteristics, as reported in Jpn.

It is also considered that the degree of solvent removal from the resist material in the pre-bake process affects pattern precision and pattern shape.

[0008]

However, in the conventional resist process using a chemically amplified resist material, the heat treatment temperature in the pre-bake process and the PEB process is not optimized, and the accuracy of the resist pattern is not improved. And the shape was deteriorated.

Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a resist pattern capable of achieving an improvement in the dimensional accuracy of a pattern and an improvement in a pattern shape in a chemically amplified resist material. It is an object of the present invention to provide a forming method.

[Structure of the Invention]

[0011]

In order to achieve the above object, the present invention provides a coating step of forming a chemically amplified resist layer on a layer to be processed, and a step of forming a resist layer after the coating step on the layer to be processed. A pre-exposure bake step of heating at a heat treatment temperature T ₁ by a heat conductor in contact with the substrate including the layer and performing a bake treatment, and an exposure step of exposing a pattern to the resist layer after the pre-exposure bake step; the resist layer after the exposure step and the post-exposure heat treatment step of performing heating and post-exposure baked at the heat treatment temperature T ₃ by thermal conductor in contact with the substrate containing the treated layer, resist after the post-exposure heat treatment step And a heat treatment temperature T.
₁ and T ₃ are lower than the minimum heating temperature T _{2 at} which the evaporation amount of the solvent in the chemical amplification type resist layer becomes maximum,
It is set to be ₁ ≧ T ₂ and T ₁ ≧ T ₃ composed.

[0012]

In the method of forming a resist pattern according to the present invention described above, a resist material is applied as shown in FIG. 1 to a chemically amplified resist material coated and formed with a thickness of about 1 μm on a layer to be processed. a sample subjected to pre-exposure baking treatment at about 1 minute at the lowest heating temperature T ₂ less become example 85 ° C. of about the temperature at which evaporation amount of the solvent is maximized in, and the minimum heating temperature T ₂ above example 125 As for the gas components in the sample subjected to the same treatment at a temperature of about 1 ° C. for about 1 minute, an analysis result as shown in the gas chromatograph / mass spectroscopy of FIG. 2 was obtained. Note that FIG.
(A) shows the analysis result of the former sample, and (b) shows the analysis result of the latter sample.

In FIG. 2, FIG. 2 (a) and FIG. 2 (b)
Is a component of the common peak in the air, and FIG.
It has been found by mass spectroscopy that the component of the peak only appearing in the above is a solvent in the resist material.

From these facts, it becomes clear that the processing temperature in the pre-exposure bake processing is the main factor which determines the degree of solvent removal in the resist material.

In the patterning characteristics when the above-mentioned samples are subjected to exposure processing, post-exposure bake (PEB) processing, and development processing under the same conditions, the degree of solvent removal in the resist material depends on the pattern. It is confirmed that it has a remarkable effect on the patterning shape and patterning shape.

Therefore, in the method of forming a resist pattern according to the present invention, the heat treatment temperature T ₁ of the pre-exposure bake treatment is set to be equal to or higher than the above-mentioned minimum heat temperature T ₂ (T ₁ ≧ T ₂ ). Accordingly, the residual solvent in the resist material is removed by thoroughly evaporate before pattern exposure, and equal to the heating temperature T ₁ of the pre-exposure heat treatment temperature T ₃ of the post-exposure bake described above baked or low ( By setting T ₁ ≧ T ₃ ), evaporation of a new solvent from the resist material during the post-exposure bake processing is suppressed.

According to the present invention, in each of the baking processes before and after the exposure, the resist material is heated by a heat conductor in contact with the substrate including the layer to be processed, so that the temperature of the resist material is instantaneously increased. In addition, the solvent is uniformly raised so that the solvent in the resist material is efficiently removed in a short time.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a sectional view showing a resist pattern and a comparative pattern in one embodiment of the method for forming a resist pattern according to the present invention.

The resist pattern 2 shown in FIG.
On a silicon semiconductor substrate 1, for example, SAL601-E
An R7 (Shipley, trade name) chemically amplified resist material is applied in a thickness of about 1 μm, and the substrate 1 coated with the resist material is placed on a hot plate, and the resist shown in FIG. A prebake treatment is performed for 1 minute at a heating temperature of about 125 ° C., which is about the same as the minimum heating temperature at which the amount of the solvent evaporated in the layer is the maximum, and a line having a design dimension of 0.25 μm is formed by an electron beam having an acceleration energy of about 40 KeV. / Space pattern is drawn and exposed, the substrate 1 is placed on a hot plate again, and a PEB process is performed for 2 minutes at a heating temperature of 115 ° C. lower than the heating temperature of the pre-exposure baking process. 2 is a resist pattern obtained by performing a development process for a minute.

The resist pattern 3 shown in FIG.
This is a resist pattern obtained by forming under the same conditions as shown in FIG. 3A except that the pre-bake treatment is performed at a heating temperature of about 85 ° C.

As is apparent from FIGS. 3A and 3B, the heat treatment temperature in the pre-bake treatment is set to be equal to or higher than the lowest heat temperature at which the amount of solvent evaporation in the resist layer is maximized, and PEB By setting the heat treatment temperature in the treatment lower than the heat treatment temperature in the pre-exposure bake treatment, the design dimensions are accurately realized, and the side walls of the pattern can be formed vertically.

This means that, in the resist pattern 2 shown in FIG. 3A, the solvent in the resist material is sufficiently evaporated and removed in the pre-bake treatment, and the resist material is exposed in such a state. In the resist pattern shown in FIG. 3B, the solvent in the resist material is sufficiently evaporated because the heating temperature is low in the pre-baking process, while the PEB process is performed in a state where the evaporation of the solvent is suppressed. This is because the exposure and PEB treatment are performed in a state where the solvent cannot be removed and the solvent remains in the resist material.

Next, the result of forming a pattern in the same manner as described above by changing the thickness of the resist material will be described.

The resist pattern 4 shown in FIG.
This is a resist pattern formed under the same conditions as shown in FIG. 3A except that the thickness of the resist material is set to about 0.5 μm, and the resist pattern 5 shown in FIG.
Is a resist pattern formed under the same conditions as shown in FIG. 3B except that the film thickness of the resist material is about 0.5 μm.

As is apparent from FIGS. 3C and 3D, although the influence of the difference in the heat treatment temperature in the pre-bake treatment on the patterning characteristics is reduced, the heat treatment temperature in the pre-bake treatment is changed to the resist. When the temperature is set lower than the minimum heating temperature at which the evaporation amount of the solvent in the layer is maximized, the patterning characteristic also slightly deteriorates. This indicates that the effect of removing the solvent in the resist material due to the difference in the heating temperature in the pre-bake treatment becomes more pronounced as the resist film thickness increases.

FIG. 4 is a view showing another embodiment of the present invention. A resist pattern 6 shown in FIG. 4 (a) is obtained by forming an alloy layer 7 made of Al-Si-Cu used for wiring and the like on a substrate 1. Is deposited on the alloy layer 7 by applying the same chemically amplified resist material having a thickness of about 0.5 μm as described above under the same conditions as shown in FIG. FIG. 4 (b) is a resist pattern obtained by
4 except that the heat treatment temperature in the pre-bake treatment is performed at a temperature of about 85 ° C.
4A is a resist pattern formed under the same conditions as in FIG.

As is clear from FIGS. 4A and 4B, when the base on which the resist pattern is formed is the alloy layer 7, if the heat treatment temperature in the pre-bake treatment is low, As can be seen in FIG.
The pattern is missing at the lower portion of the resist pattern 8, and it is recognized that the difference in the heat treatment temperature in the pre-bake treatment significantly affects the pattern shape.

FIG. 5 is a diagram showing a measurement result of pattern accuracy in another embodiment of the present invention.

FIG. 5A shows a chemically amplified resist material of, for example, SNR248-1.0 (manufactured by Shipley Co., Ltd.) with a thickness of about 1.0 μm on a silicon semiconductor substrate. A pre-baking process is performed on the plate at a heating temperature of 120 ° C. which is about the same as the minimum heating temperature T _{2 at} which the amount of the solvent in the resist layer of the resist material becomes the maximum, and a KrF excimer having an NA = 0.42 is obtained. Exposing the pattern with a laser stepper, PEB for 1 minute at a heating temperature of about 120 ° C on a hot plate
FIG. 5B shows the results of measurement of the mask linearity of the resist pattern obtained by performing the processing and developing with an alkali developing solution for 2 minutes. FIG. 5B shows the results except that the heat treatment temperature in the pre-bake treatment was set to about 100 ° C. Figure 5
FIG. 9 is a measurement result of the mask linearity of a resist pattern obtained by forming under the same conditions as in FIG.

As is clear from FIGS. 5A and 5B, the pattern accuracy is higher when the heating temperature in the pre-baking process is set to the lowest heating temperature at which the evaporation amount of the solvent in the resist layer is maximized. It can be seen that is improved. This is because diethylene glycol dimethyl ether, which is a solvent of the above-described resist material, is sufficiently evaporated and removed at a heating temperature of 120 ° C. in the pre-bake treatment.

As described above, by setting and controlling the heating temperature in the pre-bake process and the PEB process as shown in the above-described embodiment, it is possible to clearly improve the pattern accuracy and the pattern shape.

In the above embodiment, the heating time in the pre-bake treatment varies depending on the characteristics of the solvent contained in the resist material, but is equal to or higher than the lowest heating temperature at which the amount of evaporation of the solvent in the resist layer is maximized. May be set to a time at which the solvent can be sufficiently evaporated, for example, at least 1 minute or more.

[0034]

As described above, according to the present invention, the heating temperature of the pre-exposure baking is set to be equal to or higher than the minimum heating temperature, and the heating temperature of the post-exposure baking is reduced by evaporation of the solvent in the resist layer. Since the heating temperature is set to be equal to or lower than the minimum heating temperature at which the amount becomes maximum, the solvent in the resist material is sufficiently evaporated and removed in the heating treatment before exposure, and the solvent in the resist material is evaporated in the heating treatment after exposure. Can be suppressed. Thus, it is possible to improve the pattern accuracy and the pattern shape.

In addition, since the heat treatment before and after the exposure is performed by heating from the heat conductor in contact with the substrate including the layer to be processed, the solvent in the resist material is evaporated and removed in a short time and efficiently. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an evaporation amount of a solvent contained in a chemically amplified resist material used in a method for forming a resist pattern according to one embodiment of the present invention and a prebake temperature.

FIG. 2 is a view showing characteristics relating to an evaporation temperature of a solvent contained in a chemically amplified resist material.

FIG. 3 is a diagram showing a resist pattern and a comparative pattern in one embodiment of a method for forming a resist pattern according to the present invention.

FIG. 4 is a view showing a resist pattern and a comparative pattern in one embodiment of a method for forming a resist pattern according to the present invention.

FIG. 5 is a diagram showing pattern accuracy according to the method for forming a resist pattern of the present invention.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2, 3, 4, 5, 6, 8 resist pattern 7 alloy layer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Ichiro Mori 1 Toshiba, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-4-342260 (JP, A) JP-A Heisei 3-15849 (JP, A) JP-A-3-38028 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (1)

(57) [Claims] 1. A coating process for applying and forming a chemically amplified resist layer on a layer to be processed, and a heat treatment temperature T ₁ by applying a heat conductor in contact with the substrate including the layer to be processed after the application of the resist layer. A pre-exposure baking process for heating and baking, an exposure process of exposing a pattern to the resist layer after the pre-exposure bake process, and contacting the resist layer after the exposure process with a substrate including a layer to be processed. has a post-exposure heat treatment step of performing heating and post-exposure baked at the heat treatment temperature T ₃ by thermal conductor, and a developing step of developing the resist layer after the post-exposure heat treatment step, heat treatment temperatures T ₁
And T ₃ are set so that T ₁ ≧ T ₂ and T ₁ ≧ T ₃ with respect to the minimum heating temperature T _{2 at} which the amount of evaporation of the solvent in the chemically amplified resist layer becomes the maximum. A method for forming a resist pattern.