JP2007052220A - Resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resist pattern forming method by which deformation of a formed resist pattern is prevented. <P>SOLUTION: A resist layer is formed on a substrate using a positive resist material, the resist layer is patterned by sequentially carrying out prebaking, exposure and development, and the patterned resist layer is post-baked and then heat-treated at a starting temperature lower than the post-baking temperature in such a way that the temperature is raised to a final temperature of 140 to <160°C at a rate of temperature increase of at most 0.5°C/s while emitting ultraviolet light. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resist pattern forming method for preventing deformation of a pattern shape.

  In the resist pattern forming process, a so-called UV (ultraviolet) cure (UV) for the purpose of improving heat resistance and plasma resistance during etching of the resist pattern, preventing pattern shrinkage, promoting resist degassing before ion implantation, etc. Also known as curing.) Processing is known.

  The UV curing process is generally performed by causing the UV irradiation and the heating process to proceed in parallel on the developed resist pattern (substrate).

For example, when a color filter is manufactured using a positive photoresist material containing a large amount of dye of 10 wt% to 50 wt%, after the resist material is patterned, a heating and heating process is performed while performing an ultraviolet irradiation process. Performing, that is, a UV curing process is known (see Patent Document 1).
JP-A-11-014817

  The heat treatment in the UV curing process is generally performed by heating to raise the temperature in the processing chamber gradually. However, as disclosed in Patent Document 1 (see particularly the examples), the concentration is high. After patterning using a normal UV curable resist material that does not contain the dye, the resist pattern shape expands and contracts when a temperature rising heat treatment is performed at a temperature rising rate of 0.5 ° C./second or more. As a result, the pattern accuracy deteriorates, which may adversely affect the subsequent etching process or ion implantation process.

  The present invention has been made in view of the above-described problems of the prior art. That is, an object of the present invention is to provide a resist pattern forming method capable of effectively preventing expansion and contraction of a resist pattern due to a so-called UV curing process.

  In order to achieve these objects, the resist pattern forming method of the present invention includes the following steps.

  That is, a resist layer is formed on a substrate using a positive resist material. The resist layer is patterned by sequentially performing pre-bake processing, exposure processing, and development processing on the resist layer. Next, a post-baking process is performed on the patterned resist layer, that is, the resist pattern.

  Preset final temperature for heat treatment at 140 ° C. or more and less than 160 ° C. with a temperature increase rate of 0.5 ° C./second at the maximum while performing UV irradiation treatment with the starting temperature lower than the post-bake treatment temperature A heat treatment is performed to raise the temperature to the temperature.

  According to the method for forming a resist pattern of the present invention, a heat treatment for increasing the temperature to the final temperature is performed at a temperature rising rate of 0.5 ° C./second at the maximum while performing an ultraviolet irradiation process. By such a process, expansion / contraction (deformation) of the shape of the resist pattern due to the UV curing process can be effectively prevented. Therefore, the resist pattern shape accuracy can be made equal to the shape of the resist pattern before the curing process, that is, the desired shape, so that the subsequent etching process, ion implantation process, and the like can be performed accurately. As a result, the electrical characteristics of the semiconductor device manufactured by a simple process are improved. In addition, the product yield is expected to improve.

  Embodiments of the present invention will be described below with reference to the drawings. It should be understood that the following numerical conditions and the like are merely examples.

<Method for forming resist pattern>
First, a first method for forming a resist pattern will be described.

  A substrate such as a silicon substrate, a resin substrate, or a metal substrate to be a target for forming a resist pattern is prepared. The type of the substrate is not particularly limited, but in the case of applying the resist pattern forming method of the present invention in the semiconductor device manufacturing method, a conventionally known substrate such as a p-type silicon substrate (wafer) may be applied.

  Further, the resist pattern forming method of the present invention can be applied to the case where resist patterns are formed on various grounds. That is, the resist pattern forming method of the present invention forms not only a resist pattern directly on a substrate surface but also a resist pattern on a film structure such as an oxide film or a metal film formed on the substrate. It can also be applied to

  Next, a resist material is applied on the substrate (base) to form a resist layer. Although a resist material suitable for application to the resist pattern forming method of the present invention is not particularly limited, it is preferable to apply a resist material based on a so-called novolak resin.

  In general, the resist material may contain any suitable dye in an appropriate content. The resist material suitable for application to the resist pattern forming method of the present invention preferably contains no dye or contains a dye at a maximum of about 1% by weight. Is good.

  The resist material can be applied to all resist materials that require a so-called UV curing process. Specifically, for example, a positive resist material is assumed.

  Next, under the conditions appropriate for the applied resist material, a conventionally known pre-bake treatment, exposure treatment and development treatment are sequentially performed to pattern the resist layer into any suitable pattern shape. Subsequently, post bake processing is performed. The step of performing the post-bake treatment is preferably performed within a temperature range of 110 ° C. to 120 ° C. according to any conventionally known suitable method.

  According to the resist pattern forming method of the present invention, a heat treatment step is further performed in which heat treatment and ultraviolet irradiation treatment are performed in parallel.

  This heat treatment is preferably performed in an air atmosphere with a starting temperature lower than the post-baking temperature.

  The heat treatment is preferably performed by starting from the start temperature and increasing the temperature from the start temperature to the final temperature at a maximum rate of 0.5 ° C./second. This final temperature may be an appropriate temperature for the resist material to be used. This final temperature is set to about 140 ° C. with some margin when the resist pattern shape deterioration is observed from about 160 ° C.

  The ultraviolet irradiation treatment performed in parallel is performed at least from the start of the heat treatment until the temperature reaches the final temperature.

This ultraviolet irradiation treatment can be performed with any suitable amount of light, but for example, it is preferable to use an ultraviolet lamp that generates ultraviolet light including light having a wavelength in the range of 200 nm to 600 nm. In addition, the ultraviolet irradiation process is preferably performed by setting the illuminance on the plate on which the wafer of the processing apparatus on which the process is performed as measured by an illuminometer to 500 mW / cm ² or approximately.

  According to such a resist pattern forming method, the temperature is raised to the final temperature at a temperature increase rate of 0.5 ° C./second at the maximum from the start temperature, that is, a so-called UV curing process is performed at a lower temperature increase rate. Therefore, the resist pattern can be formed with high accuracy without impairing the desired shape of the resist pattern.

  The step of performing the heat treatment already described is preferably a step of starting with a starting temperature of 100 ° C., which is lower than the normal post-baking temperature, and a final temperature of 140 ° C.

  As described above, when the start temperature is set to be equal to or lower than the post-bake temperature, the resist pattern shape deterioration due to heat can be more effectively suppressed.

  According to the second method for forming a resist pattern of the present invention, a so-called post-bake process, which has been conventionally performed, can be omitted.

  In this case, after the patterning step already described, the so-called post-bake treatment is not performed, and in the step of performing the heat treatment already described, the start temperature is set to 90 ° C. with respect to the substrate not subjected to the post-bake processing. The step of raising the temperature to the final temperature at a rate of temperature increase of 0.5 ° C./second at the maximum while performing the ultraviolet irradiation treatment.

  Although data is not shown, it is known that the deformation of a resist pattern based on a novolak resin starts at about 110 ° C. Therefore, if the patterning start temperature is 90 ° C., deformation of the resist pattern can be effectively prevented.

  According to the second forming method, the post-baking process can be omitted, and the number of processes is reduced. Therefore, it is possible to form the resist pattern with high accuracy and without impairing the expected shape of the resist pattern. As a result, a reduction in manufacturing cost is expected.

  The step of performing the heat treatment when the post-bake treatment is not performed may be a step of performing the final temperature at 140 ° C.

  In any of the resist pattern forming steps of the first and second methods already described, the ultraviolet irradiation process is preferably a process of gradually increasing the irradiation dose from the start of the temperature rise.

  Specifically, this ultraviolet treatment is preferably performed by gradually increasing the dose. Here, “stepwise” means that irradiation is performed by switching the lamp illuminance and the irradiation time into a set of several groups and switching in stages. Each of these steps is continuously performed without any interruption.

  In this stepwise ultraviolet treatment, for example, an ultraviolet lamp that is always lit may be used, and the illuminance may be adjusted by appropriately adjusting the diaphragm located under the ultraviolet lamp and the applied voltage. What is necessary is just to apply the lamp | ramp which emits the ultraviolet light of the wavelength of the range about 200 nm-about 600 nm, for example.

The stepwise ultraviolet irradiation treatment, a first step of irradiating 5 seconds from the start temperature increase as 1.5 mW / cm ² the lamp illuminance, a second step of irradiating 5 seconds lamp intensity as 200 mW / cm ^2, lamp It is preferable to include a third step of irradiating for 90 seconds with an illuminance of 500 mW / cm ² . In this way, a resist pattern can be formed with higher accuracy.

  In any of the resist pattern forming steps of the first and second methods already described, the step of forming the resist layer is preferably a step of forming the resist layer from a positive resist material.

  Examples of the resist pattern forming method of the present invention will be described below with reference to FIGS.

Example 1
An example of a resist pattern forming method will be described with reference to FIG.

FIG. 1 is a graph for explaining the heat treatment conditions. (A) shows ultraviolet (UV) irradiation conditions, and (B) shows the temperature rising process over time. In FIGS. 5A and 5B, the horizontal axis represents time (seconds) indicated on the same scale. (A) The vertical axis in the figure represents the amount of light (mW / cm ² ), the symbol “N” is the minimum illuminance, that is, the illuminance (lamp illuminance) 1.5 mW / cm ² , and the symbol “L” is the low illuminance, The illuminance is 200 mW / cm ² , and the symbol “H” is high illuminance, that is, the illuminance is 500 mW / cm ² . Moreover, the vertical axis | shaft in (B) figure has shown temperature (degreeC).

  In this example, a p-type silicon substrate is used, the pre-baking process, the exposure process, and the development process described above are sequentially performed to pattern a resist layer made of a novolac resin-based positive resist (containing no dye). This is an example in which the sample subjected to the post-bake treatment was subjected to a heat treatment with an ultraviolet irradiation treatment. Specific heat treatment conditions will be described below.

  As shown in FIGS. 1A and 1B, ultraviolet irradiation and heat treatment (temperature increase) were started at the same time with time t0 as the start time.

In this example, the amount of ultraviolet light (lamp illuminance) at the start time (t0) is 1.5 mW / cm ² , and the heat treatment start temperature is set to 100 ° C., which is lower than the post-bake treatment temperature already described.

  The temperature increase rate of the heat treatment (rising temperature per second) was set to 0.5 ° C./second, and the final temperature was set to 140 ° C. Therefore, the time required for the temperature to rise from 100 ° C. to 140 ° C. [tN (time for performing the irradiation process with illuminance N) + tH (time for performing the irradiation process with illuminance H)] is 80 seconds. When the final temperature was reached, the temperature increase was completed, and a process (temperature decrease process) for decreasing the temperature at a temperature decrease rate of 3.0 ° C./second was performed.

  This temperature lowering process is also intended to cool the stage of the apparatus provided for the next process. Therefore, the temperature drop rate can be arbitrarily set as long as the conditions necessary for the next process are taken into consideration and the accuracy of the resist pattern is not adversely affected.

In the ultraviolet irradiation process, ultraviolet irradiation is performed at an illuminance of 1.5 mW / cm ² for tN seconds from the start time t0, in this example, for 5 seconds, and subsequently, irradiation is performed with an illuminance of 500 mW / cm ² for tH seconds, in this example, 75 seconds. Went.

  The adjustment of the illuminance may be performed by applying any suitable aperture means to the always-on ultraviolet lamp or by appropriately changing the voltage applied to the ultraviolet lamp itself.

(Example 2)
FIG. 2 is a graph (2) for explaining the heat treatment conditions. As in FIG. 1, (A) shows the ultraviolet (UV) irradiation conditions, and (B) shows the temperature rise process over time. In the (A) and (B) diagrams, the horizontal axis represents time (seconds) shown on the same scale. (A) The vertical axis in the figure represents the amount of light (mW / cm ² ), the symbol “N” is the minimum illuminance, that is, the illuminance (lamp illuminance) 1.5 mW / cm ² , and the symbol “L” is the low illuminance, The illuminance is 200 mW / cm ² , and the symbol “H” is high illuminance, that is, the illuminance is 500 mW / cm ² . Moreover, the vertical axis | shaft in (B) figure has shown temperature (degreeC).

  In this example, a p-type silicon substrate is used, the pre-bake treatment, the exposure treatment, and the development treatment described above are sequentially performed to pattern a resist layer made of a novolac resin-based positive resist (containing no dye). This is an example in which heat treatment with ultraviolet irradiation treatment was performed on a sample in which post-baking treatment was not performed. Specific heat treatment conditions will be described below.

  As shown in FIGS. 2 (A) and 2 (B), ultraviolet irradiation and heat treatment (temperature increase) were started at the same time, starting at time t0.

In this example, the amount of ultraviolet light (lamp illuminance) at the start time (t0) is 1.5 mW / cm ² , and the heat treatment start temperature is lower than the conventional post-bake treatment temperature described above. C.

  The heating rate of the heat treatment was set to 0.5 ° C./second, and the final temperature was set to 140 ° C. Therefore, the time (tN + tH) required for the temperature rise from 90 ° C. to 140 ° C. is 100 seconds. The temperature increase was completed when the final temperature was reached, and a process (temperature decrease process) for decreasing the temperature at a temperature decrease rate of 3.0 ° C./second was performed as in Example 1.

Ultraviolet irradiation was performed at an illuminance of 1.5 mW / cm ² for tN seconds from the start time t0, in this example for 5 seconds, and subsequently for 500 seconds at an illuminance of 500 mW / cm ² for tH seconds, in this example, 95 seconds.

(Modification)
FIG. 3 is a graph (3) for explaining the heat treatment conditions. As in FIG. 1, (A) shows the ultraviolet (UV) irradiation conditions, and (B) shows the temperature rise process over time. In the (A) and (B) diagrams, the horizontal axis represents time (seconds) shown on the same scale. (A) The vertical axis in the figure represents the amount of light (mW / cm ² ), the symbol “N” is the minimum illuminance, that is, the illuminance (lamp illuminance) 1.5 mW / cm ² , and the symbol “L” is the low illuminance, The illuminance is 200 mW / cm ² , and the symbol “H” is high illuminance, that is, the illuminance is 500 mW / cm ² . Moreover, the vertical axis | shaft in (B) figure has shown temperature (degreeC).

  In this example, a p-type silicon substrate is used, the pre-bake process, the exposure process, and the development process described above are sequentially performed to pattern a resist layer made of a novolac resin-based positive resist, and then the post-bake process is not performed. This is an example in which heat treatment involving ultraviolet irradiation treatment was performed on the implemented sample. Specific heat treatment conditions will be described below.

  As shown in FIGS. 3A and 3B, ultraviolet irradiation and heat treatment (temperature increase) were started at the same time with time t0 as the start time.

In this example, the amount of ultraviolet light (lamp illuminance) at the start time (t0) is 1.5 mW / cm ² , and the heat treatment start temperature is lower than the conventional post-bake treatment temperature described above. The temperature was 90 ° C.

  The heating rate of the heat treatment was set to 0.5 ° C./second, and the final temperature was set to 140 ° C. Therefore, the time (tN + tL + tH) required for temperature increase from 90 ° C. to 140 ° C. is 100 seconds. The temperature increase was completed when the final temperature was reached, and a process (temperature decrease process) for decreasing the temperature at a temperature decrease rate of 3.0 ° C./second was performed as in Example 1.

Ultraviolet irradiation is performed at an illuminance of 1.5 mW / cm ² for tN seconds from the start time t0, in this example for 5 seconds, and subsequently for tL seconds, in this example for 5 seconds, with an illuminance of 200 mW / cm ^2. After this, the illuminance was 500 mW / cm ² for tH seconds, in this example 90 seconds.

  In this way, if the step of increasing the amount of light at the time of ultraviolet irradiation is divided into a plurality of steps, it is possible to more effectively prevent foaming and rupture due to gas generated from the resist, and improve the shape accuracy of the resist pattern. .

  In this example, the example of combining the above-described ultraviolet irradiation treatment in the heat treatment (temperature increase) step of the second embodiment has been described. However, the heat treatment (temperature increase) step of the first embodiment may be combined.

(result)
With reference to FIG. 4, the resist patterns obtained by the resist pattern forming methods of Examples 1 and 2 already described will be described.

  FIG. 4 is a photograph for explaining the shape (profile) of the resist pattern. This photographic diagram shows the step defined by the substrate and the resist layer. FIG. 6A is a contrast diagram showing a resist pattern profile after patterning and before the UV curing step. FIG. 6B is a contrast diagram showing a profile of a resist pattern subjected to a conventionally known UV curing process described later. FIG. 4C shows a resist pattern profile of Example 1. FIG. 4D shows a resist pattern profile of the second embodiment.

  First, a conventional UV curing process in which the profile shown in FIG.

  In this UV curing process, a p-type silicon substrate is used, the pre-bake process, the exposure process and the development process described above are sequentially performed to pattern a resist layer made of a novolac resin-based positive resist, and then a post-bake process. The sample subjected to the above is subjected to a heat treatment accompanied by an ultraviolet irradiation treatment. Specific heat treatment conditions will be described below.

  UV irradiation and heat treatment (temperature increase) were started simultaneously.

In this example, the amount of ultraviolet light (lamp illuminance) at the start time is 1.5 mW / cm ² , and the heat treatment start temperature is 120 ° C., which is higher than the post-bake treatment temperature already described.

  The heating rate of the heat treatment is 1.0 ° C./second, and the final temperature is 160 ° C. Therefore, the time taken for the temperature to rise from 100 ° C. to 160 ° C. is 40 seconds. The temperature increase was completed when the final temperature was reached, and a process (temperature decrease process) for decreasing the temperature at a temperature decrease rate of 3.0 ° C./second was performed as in Example 1.

Ultraviolet irradiation was performed for 5 seconds at an illuminance of 1.5 mW / cm ² for 5 seconds from the start time, and then for 35 seconds at an illuminance of 500 mW / cm ² .

  Comparing (A) figure with (B) figure which performed the conventional UV curing process, in (B) figure, the shape of the resist pattern is severely deformed, and the angle between the side edge of the resist pattern and the substrate surface Is getting bigger.

  When FIG. (A) is compared with FIG. (C) after the processing of Example 1, in FIG. (C), although there is some deformation in the shape of the resist pattern, FIG. It can be seen that the degree of deformation of the resist pattern is remarkably suppressed as compared with.

  When FIG. (A) is compared with FIG. (D) where the processing of Example 2 is performed, in FIG. (D), there is almost no deformation of the resist pattern. (C) It can be seen that the degree of deformation of the resist pattern is more remarkably prevented as compared with FIG.

  Although not shown in the photographic view, the resist pattern deformation preventing effect equivalent to that of the second embodiment can be obtained by the modification already described.

  As described above, a resist material suitable for application to the present invention does not affect the effect of the invention even if it contains or does not contain a dye. It is preferable to select a resist material of about 1% by weight.

(A) A figure and (B) figure are graphs (1) for demonstrating heat processing conditions. (A) A figure and (B) figure are the graphs (2) for demonstrating heat processing conditions. (A) A figure and (B) figure are the graphs (3) for demonstrating heat processing conditions. FIGS. (A), (B), (C) and (D) are photographic diagrams for explaining the shape of a resist pattern.

Claims (6)

Forming a resist layer on a substrate using a positive resist material;
A process of patterning the resist layer by sequentially performing a pre-bake process, an exposure process and a development process;
A step of performing a post-bake treatment;
A heat treatment that raises the temperature to a final temperature of 140 ° C. or more and less than 160 ° C. with a temperature increase rate of 0.5 ° C./second at the maximum while performing an ultraviolet irradiation treatment with a starting temperature lower than the post-bake treatment temperature. And a step of performing a resist pattern forming method. The step of performing the post-bake treatment is a step of performing within a temperature range of 110 ° C. to 120 ° C.,
The method of forming a resist pattern according to claim 1, wherein the step of performing the heat treatment is a step of performing the start temperature at 100 ° C. Forming a resist layer on a substrate using a positive resist material;
A process of patterning the resist layer by sequentially performing a pre-bake process, an exposure process and a development process;
Heat treatment for raising the temperature to a final temperature of 140 ° C. or higher and lower than 160 ° C. at a temperature rising rate of 0.5 ° C./second at the maximum while performing an ultraviolet irradiation treatment on the substrate at a starting temperature of 90 ° C. And a step of performing a resist pattern forming method.   4. The method for forming a resist pattern according to claim 1, wherein the ultraviolet irradiation process is a process of gradually increasing an irradiation dose. The ultraviolet irradiation treatment includes a first stage in which the lamp illuminance is set to 1.5 mW / cm ² and irradiated for 5 seconds from the start of temperature rise, a second stage in which the lamp illuminance is set to 200 mW / cm ^{2 and} irradiated for 5 seconds, and the lamp illuminance is set to The method for forming a resist pattern according to claim 4, further comprising a third step of irradiating for 90 seconds at 500 mW / cm ² .   4. The resist according to claim 1 or 3, wherein the step of forming the resist layer is a step of forming a resist layer from a resist material that does not contain a dye or contains at most 1% by weight. Pattern formation method.