JP2014082240A - Drawing device, drawing method, evaluation method and article manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drawing device useful to evaluate a resist for a next generation drawing device.SOLUTION: A drawing device performs multiple drawing including first drawing with a first charged particle beam having a first energy, and second drawing with a second charged particle beam having second energy smaller than the first energy. The first energy and second energy are set so that the energy of a charged particle beam absorbed in a region on the back side of the resist in contact with a substrate is larger than that absorbed in a region on the front side of the resist, in a region of the resist irradiated with both first and second charged particle beams.

Description

  The present invention relates to a drawing apparatus, a drawing method, an evaluation method, and an article manufacturing method.

  With the miniaturization of semiconductor elements, the size of a pattern to be transferred has come to be less than several tens of nm, and an apparatus for drawing a pattern on a resist coated on a wafer using an electron beam has been put into practical use. 2. Description of the Related Art Conventionally, electron beam drawing apparatuses that have been used have been drawn with a high acceleration electron beam accelerated to 50 KV or more in order to reduce the Coulomb force between electrons and reduce the beam spot on the wafer. In recent years, drawing with a low acceleration electron beam of about 5 KV has been proposed in order to improve resist sensitivity and reduce the influence of backscattering from the wafer. Patent Document 1 proposes a method for manufacturing a semiconductor device in which development is performed in one development process after energy irradiation is performed at least twice on different pattern regions under different energy conditions. Patent Documents 2 and 3 propose methods for irradiating a resist with energy rays having different energy levels to form a pattern having excellent contrast and resolution. In Patent Document 3, irradiation is performed with a low-acceleration electron beam of 0.5 to 3 KV and a high-acceleration electron beam of 30 KV to generate an energy distribution in which large energy is deposited near the surface layer of the resist.

  On the other hand, simultaneously with the development of such a drawing apparatus, development of a high-resolution resist has been promoted. When a high acceleration electron beam is used, the resolution of the resist for the high acceleration electron beam can be evaluated because the high acceleration electron beam can be narrowed down. However, it is difficult for the low acceleration electron beam to narrow the beam finer than the high acceleration electron beam. For this reason, the resist could not be evaluated by using a narrowly focused low acceleration electron beam. In particular, even when trying to evaluate the resist evaluation and drawing performance for the next-generation low energy electron beam, there is no low-energy electron beam drawing apparatus with a finely-squeezed fine diameter, and direct evaluation cannot be performed. Therefore, instead of using a narrowly focused low acceleration electron beam, the resist was evaluated using a thinly focused high acceleration electron beam.

JP 2001-93977 A Japanese Patent Laid-Open No. 1-198018 JP-A-63-78523

  In order to accurately evaluate the resist for the low acceleration electron beam, not only the intensity distribution on the resist surface of the low acceleration electron beam incident on the resist but also the intensity distribution in the depth direction of the resist must be the same. This is because the resolution decreases when the amount of absorption at the bottom near the substrate is large. This is due to the following reason. As the resist is dissolved and removed from the surface of the resist, the difference in energy absorption amount near the surface causes a difference in time until the dissolved surface of the resist reaches near the bottom. Since the dissolution rate increases near the bottom, a pattern with a high energy absorption near the surface rapidly thins, leading to the collapse of the resist pattern. Therefore, it is necessary to evaluate the resist by correctly simulating the energy absorption distribution in the depth direction of the resist.

  In the evaluation of conventional resists for low acceleration electron beams using high acceleration electron beams, the energy absorption distribution in the depth direction of the resist was narrowed down even though the intensity distribution of the electron beams incident on the resist surface could be the same. It could not be the same as when using a low acceleration electron beam. For example, FIG. 9 shows a result obtained by Monte Carlo calculation of an energy absorption distribution imparted in a resist when a resist having a thickness of 30 nm is applied on a base layer. The calculation conditions are an acceleration voltage of 50 KV, the electron beam beam shape is a Gaussian distribution with a σ of 7.1 nm, a drawing line width of 16 nm, and a pitch of 32 nm. The solid line, dotted line, and broken line indicate the energy absorption distributions on the resist surface, middle part, and bottom, respectively, but it can be seen that the energy absorption distribution hardly changes in the resist depth direction.

  FIG. 2 shows an energy absorption distribution when a narrowly focused low acceleration electron beam that does not exist at the present time has a Gaussian distribution with an acceleration voltage of 5 KV and σ of 7.1 nm. The other conditions are the same as when a high acceleration electron beam with an acceleration voltage of 50 KV is used, and the surface energy absorption distribution is not different between 5 KV and 50 KV. However, when the acceleration voltage is 5 KV, there is a difference in the energy absorption amount depending on the depth direction of the resist, and it can be seen that the energy absorption amount at the bottom of the resist is the largest and the surface absorption amount is small. Furthermore, with a low energy electron beam, the probability and angle of forward scattering of electrons in the resist are large. Therefore, the electrons spread in the lateral direction, and the contrast at the bottom is lower than that near the surface. In this way, when drawing using a high acceleration electron beam, even if the surface energy distribution can be the same as the drawing using the low acceleration electron beam, the energy absorption distribution in the depth direction is larger than that drawn using the low acceleration electron beam. There is a difference. Therefore, resist evaluation using a high acceleration electron beam has not been an accurate evaluation of a resist for the next generation low acceleration electron beam.

  An object of the present invention is to provide a drawing apparatus useful for evaluating a resist for a next-generation drawing apparatus.

  One aspect of the present invention relates to a first drawing with a first charged particle beam having a first energy and a second charged particle beam having a second energy smaller than the first energy with respect to a resist on a substrate. A drawing apparatus for performing multiple drawing including a second drawing, wherein the first energy and the second energy are in the region of the resist irradiated with both the first charged particle beam and the second charged particle beam. The energy of the charged particle beam absorbed in the region on the back side of the resist in contact with the substrate is set to be larger than the energy of the charged particle beam absorbed in the region on the surface side of the resist. It is characterized by.

  According to the present invention, for example, a drawing apparatus useful for evaluating a resist for a next-generation drawing apparatus can be provided.

Electron beam irradiation area in Example 1 Diagram explaining energy absorption distribution of target low energy electron beam The figure explaining the principle of this invention The figure which shows the energy absorption distribution of the electron beam of acceleration voltage 50KV The figure which shows the energy absorption distribution of the electron beam of the acceleration voltage 5KV in Example 1. FIG. The figure which shows energy absorption distribution in Example 1 The figure which shows energy absorption distribution in Example 2 The figure which shows energy absorption distribution in Example 2 Diagram showing energy absorption distribution in the prior art Diagram showing drawing device

[Principle of the Invention]
In explaining the principle of the present invention, as shown in FIGS. 2 and 9, both the first charged particle beam (high acceleration electron beam) and the second charged particle beam (low acceleration electron beam) were irradiated. The reason why there is a difference in energy absorption distribution in the depth direction of the resist will be described. When the energy of the high acceleration electron beam and the low acceleration electron beam is the first energy and the second energy, respectively, the second energy is smaller than the first energy. The result obtained by calculating the distribution in the depth direction of the energy absorbed by the resist when the resist containing Cl having a thickness of 180 nm is irradiated with an electron beam with a uniform intensity distribution (irradiation amount: 10 μC / cm ² ) is obtained by Monte Carlo calculation. As shown in FIG. The horizontal axis represents the depth (z position) from the resist surface, and the vertical axis represents the energy density absorbed by the resist. Furthermore, the energy of the electron beam incident on the resist, expressed in terms of acceleration voltage, was taken as a variable. First, it can be seen that even with the same dose, the low acceleration electron beam absorbs more energy in the resist than the high acceleration electron beam. This is because as the energy of the electron beam is smaller, the energy (energy absorption rate) absorbed by the substance per unit length in the direction in which the electrons travel is increased.

In the case of an electron beam with an acceleration voltage of 50 KV, the density of absorbed energy is almost constant regardless of the depth. However, as the acceleration voltage decreases, the amount of absorption increases as the resist depth increases. In the high acceleration electron beam (50 KV), even if the electron advances by 80 nm, the energy of the electron beam is hardly attenuated and the energy absorbed per unit length is not changed, so that the amount of absorption is uniform. However, with a low-acceleration electron beam, the electrons travel through the resist and the electrons impart energy to the resist, and accordingly, the electron energy is reduced and the energy absorption rate per unit length absorbed by the substance is increased. In particular, when the acceleration voltage is less than 10 KV, for example, 5 KV, the absorption amount is about twice as long as 80 nm is advanced. Further, when the acceleration voltage is 1 KV, the absorption rate reaches a peak at a depth of 10 nm, and then the absorption rate decreases rapidly, and almost no electrons reach a position deeper than 40 nm. Therefore, when the resist thickness is in the range of several tens of nanometers, the energy absorption rate is divided into the following three regions depending on the acceleration voltage of the electron beam.
Region 1: In drawing with a high acceleration electron beam with an acceleration voltage of 10 KV or more, the energy absorption rate of the electron beam with respect to the resist depth is constant.
Region 2: In drawing with a low acceleration electron beam with an acceleration voltage of 3 to 8 KV, the energy of the electron beam absorbed in the region on the back side of the resist on the substrate is large.
Region 3: An electron beam with an acceleration voltage of 3 KV or less has a large energy of the electron beam absorbed on the resist surface side on the substrate.

  Therefore, when drawing is performed using an electron beam with an acceleration voltage of 5 KV, in the resist having a thickness of several tens of nanometers, the energy absorption rate is higher in the region on the back side of the resist than in the region on the front side as shown in FIG. growing. In this way, when the acceleration voltage region is different, the electron beam has a different energy absorption distribution in the depth direction of the resist. Therefore, the present invention performs multiple drawing including the first drawing with the high acceleration electron beam in the region 1 and the second drawing with the low acceleration electron beam in the region 2, so that the energy absorption distribution in the depth direction has a fine diameter. A latent image of a resist having the same tendency as that of a low-energy electron beam is produced.

  The low-energy electron beam with a fine diameter has good sensitivity to the resist and has little backscattering. Accordingly, development of a drawing apparatus using a low-energy electron beam having a fine diameter and a resist suitable for the low-energy electron beam having a fine diameter are being developed. Using multiple writing of the present invention in which the energy absorption distribution in the depth direction has the same tendency as that of a low-energy electron beam having a fine diameter, a resist for a narrowly focused low-acceleration electron beam used in a next-generation drawing apparatus is evaluated. be able to.

  In the following examples, two types of electron beams having different energies were used for multiple drawing. However, multiple drawing may be performed using charged particle beams other than electron beams such as ion beams.

[Example 1]
A first embodiment of the present invention will be described with reference to FIG. FIG. 1A shows a pattern drawn by a high acceleration electron beam and a low acceleration electron beam on the surface of a resist coated on a wafer (substrate). Pattern 1 indicated by oblique lines is a pattern drawn by a first electron beam (high acceleration electron beam) having an acceleration voltage of 10 KV or higher. A pattern 2 indicated by a broken line is a pattern drawn by a second electron beam (low acceleration electron beam) whose acceleration voltage is greater than 3 KV and less than or equal to 8 KV. FIG. 1B is an SS cross-sectional view of FIG. In Example 1, a base layer 4 having a thickness of 150 nm was provided on the wafer 5 in order to avoid the influence of reflected electrons from the wafer 5, and a layer of resist 3 having a thickness of 30 nm was formed thereon.

  Example 1 is a simulation evaluation of five resist patterns having a drawing line width of 16 nm and a period of 32 nm using a low acceleration electron beam having an acceleration voltage of 5 KV and a Gaussian distribution shape of σ = 7.1 nm. FIG. 2 shows the energy absorption amount in the resist in this case as determined by Monte Carlo calculation. A solid line, a dotted line, and a wavy line are energy absorption distributions at the surface, middle portion, and bottom of the resist, respectively, and the energy absorption distribution increases as the resist depth increases. Since it is still not possible to narrow the electron beam with an acceleration voltage of 5 KV to σ = 7.1 nm at the present time, in Example 1, energy absorption similar to that in FIG. 2 is performed by multiple drawing with a low acceleration electron beam and a high acceleration electron beam. Simulate the distribution.

  First, five bar patterns 1 having a line width of 16 nm and a pitch of 32 nm shown in FIG. 1 are drawn with a first electron beam having an acceleration voltage of 50 KV and a diameter of 3.5 nm (σ) (first drawing). FIG. 4 shows the energy absorption distribution in the resist by the first electron beam having the acceleration voltage of 50 KV. Almost the same energy absorption distribution is obtained at the bottom and the surface. Next, pattern 2 is drawn with a second electron beam having an acceleration voltage of 5 KV (second drawing). The pattern 2 is set so as to include at least a part of each of the plurality of patterns 1.

  In order to create an intensity distribution as shown in FIG. 2 by multiple drawing, it is necessary to select an acceleration voltage in the range of 3 to 8 KV as the second electron beam from FIG. 3 so that the absorption amount is high at the bottom of the resist. is there. In Example 1, the acceleration voltage of the second electron beam having a low acceleration voltage is 5 KV, the diameter is σ = 10.6 nm, and the pattern 2 shown in the drawing is drawn with uniform intensity using the second electron beam. The diameter of the second electron beam may be larger than σ = 10.6 nm, but the diameter of the second electron beam is larger than the diameter of the first electron beam having a high acceleration voltage. FIG. 5 shows an energy absorption distribution by the second drawing with the second electron beam having a low acceleration voltage of 5 KV. An energy absorption distribution with high absorption at the bottom of the resist is obtained. FIG. 6 shows the energy absorption distribution in the resist when multiple writing is performed with the current ratio of the first electron beam having a high acceleration voltage of 50 KV and the second electron beam having a low acceleration voltage of 5 KV being 9: 1. The energy absorption distribution in the resist of multiple drawing in FIG. 6 has a larger energy absorption amount at the bottom than at the surface, and a distribution similar to the target energy absorption distribution shown in FIG. 2 is obtained.

The peak intensity I ₁ and the valley intensity I ₂ of the first electron beam in FIG. 4 are the same at the bottom and the surface, and the exposure amounts of the uniform bottom and surface of the second drawing by the second electron beam are D _b and D, respectively. _{Let s} . Let I _1s and I _2s be the maximum and minimum values of energy absorbed from the first electron beam and the second electron beam in the region in contact with the resist surface, respectively. In addition, the maximum and minimum values of energy absorbed from the first electron beam and the second electron beam in the region in contact with the back surface of the resist are defined as I _1b and I _2b , respectively. _Then, the _{I 1s = I 1 + D s} , I 2s = I 2 + D s, I 1b = I 1 + D b, I 2b = I 2 + D b.

(I _1s −I _2s ) / (I _1s + I _2s ) in the region in contact with the resist surface when multiple writing is performed with the ratio of the current of the electron beam having a high acceleration voltage of 50 KV and the electron beam having a low acceleration voltage of 5 KV being 9: 1. ) value C _s of the contrast represented by are as follows.
_{C s = (I 1s -I 2s} ) / (I 1s + I 2s) = (I 1 -I 2) / (I 1 + I 2 + 2D s)
Similarly, the value _{C b} of the contrast represented by the area in contact with the back surface of the resist _{(I 1b -I 2b) / (} I 1b + I 2b) is as follows.
_{C b = (I 1b -I 2b} ) / (I 1b + I 2b) = (I 1 -I 2) / (I 1 + I 2 + 2D b)
Since D _b > D _s , C _b <C _s and the contrast is smaller at the bottom on the back side. As described above, the energy absorption distribution by the multiple drawing of the first electron beam having a high acceleration voltage and the second electron beam having a low acceleration voltage, which are pseudo-manufactured, is different from the distribution by the drawing of the low acceleration electron beam having a fine beam diameter. The trend of low is in good agreement. Therefore, it is understood that the resist for low acceleration electron beam can be evaluated by developing the resist on which multiple drawing has been performed and evaluating the developed resist. The evaluation can be performed based on the shape of the developed resist using, for example, an inspection apparatus such as a scanning electron microscope (SEM).

[Example 2]
Example 2 will be described. In the second embodiment, the first drawing with the first electron beam with the high acceleration voltage is the same as the first embodiment, but the second drawing with the second electron beam with the low acceleration voltage is not performed with a uniform intensity distribution. Draw with the aperture within the range that can be obtained at present. FIG. 7 shows the energy absorption distribution in the resist when drawing is performed with a line width of 16 nm and a pitch of 32 nm using a second electron beam with an acceleration voltage of 5 KV with a diameter of 10.6 nm (σ). Compared with the target absorption distribution shown in FIG. 2, the contrast is low due to the difference in the beam diameter of the electron beam. Therefore, in Example 2, the intensity ratio between the first drawing with the first electron beam with the acceleration voltage of 50 KV and the second drawing with the second electron beam with the acceleration voltage of 5 KV in FIG. Multiple drawing at 3: 1. Then, the energy absorption distribution in the resist shown in FIG. 8 is obtained. The energy absorption distribution in the resist of multiple drawing shown in FIG. 8 agrees well with the target absorption distribution shown in FIG. 2 although the contrast is low, and the resist for low acceleration electron beam can be evaluated. I understand.

[Embodiment related to charged particle beam drawing apparatus]
FIG. 10 is a configuration diagram of the drawing apparatus according to the present embodiment. The drawing apparatus 10 will be described using a drawing apparatus that uses an electron beam as a charged particle beam as an example, but other charged particle beams such as an ion beam may be used. The drawing apparatus 10 includes a vacuum chamber 15, an electron optical system 13 (charged particle optical system) and a stage 14 accommodated in the vacuum chamber 15, and performs drawing on the substrate 12 using an electron beam in a vacuum. Is. The stage 14 is configured to be movable to position the substrate 12 with respect to the electron optical system 13, and includes a substrate holding device 11 (also simply referred to as a holding device) for holding the substrate 12.

  The electron optical system 13 includes an electron gun (also referred to as an electron source or a charged particle source) 13s, and the acceleration voltage is variable over the acceleration voltage range over the region 1-2. For example, the electron gun 13s is configured such that the potential of the anode electrode can be changed discretely or continuously. The electron optical system 13 includes one or more electrostatic lenses (not shown), and the power of the electrostatic lenses can be adjusted according to the acceleration voltage of the electron gun 13s.

  With such a configuration, for example, the drawing apparatus 10 includes a first electron beam (diameter 3.5 nm (σ)) with a high acceleration voltage 50 KV and a second electron beam (diameter 10.6 nm (σ)) with a low acceleration voltage 5 KV. The multiple drawing described in the first or second embodiment can be performed. Note that the values of the acceleration voltage and the beam diameter are not limited to those described above. Further, the configuration of the electron optical system 13 is not limited to the above-described configuration. For example, the configuration may separately include a first electron optical system for high acceleration voltage and a second electron optical system for low acceleration voltage. Good.

[Examples related to article manufacturing method]
The method for manufacturing an article according to an embodiment of the present invention is suitable for manufacturing an article such as a microdevice such as a semiconductor device or an element having a fine structure. The manufacturing method includes a step of forming a latent image pattern on the photosensitive agent on a substrate coated with a photosensitive agent (resist) using the above drawing device (step of drawing on the substrate), and a latent image pattern in the step. Developing the substrate on which the substrate is formed. Further, the manufacturing method may include other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, and the like). The method for manufacturing an article according to the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method. The article is not limited to the devices and elements as described above, and can be, for example, a substrate including a developed resist subjected to the above-described evaluation.

Claims (8)

Multiple drawing including a first drawing with a first charged particle beam having a first energy and a second drawing with a second charged particle beam having a second energy smaller than the first energy with respect to a resist on a substrate. A drawing device for performing
The first energy and the second energy are absorbed in a region on the back surface side of the resist in contact with the substrate in the region of the resist irradiated with both the first charged particle beam and the second charged particle beam. The charged particle beam energy is set to be larger than the charged particle beam energy absorbed in the region on the resist surface side,
A drawing apparatus characterized by that.   The first charged particle beam is an electron beam accelerated by an acceleration voltage of 10 KV or more, and the second charged particle beam is an electron beam accelerated by an acceleration voltage greater than 3 KV and less than 8 KV. The drawing apparatus according to claim 1.   The drawing apparatus according to claim 1, wherein the second drawing is performed in a region including at least a part of each of the plurality of regions in which the first drawing is performed.   4. The drawing apparatus according to claim 1, wherein a diameter of the second charged particle beam is larger than a diameter of the first charged particle beam. 5. The maximum value and the minimum value of the energy of the charged particle beam absorbed in the region on the front surface side are I _1s and I _2s , respectively, and the maximum value and the minimum value of the energy of the charged particle beam absorbed in the region on the back surface side The values are I _1b and I _2b respectively,
The contrast in the region on the front surface side expressed by (I _1s −I _2s ) / (I _1s + I _2s ) is that of the back surface expressed by (I _1b −I _2b ) / (I _1b + I _2b ) The drawing apparatus according to claim 1, wherein the drawing apparatus has a contrast larger than a contrast in a side region. A drawing method for performing multiple drawing on a resist on a substrate,
Performing a first drawing on the resist with a first charged particle beam having a first energy;
Performing a second drawing on the resist with a second charged particle beam having a second energy smaller than the first energy;
Including
The first energy and the second energy are absorbed in a region on the back surface side of the resist in contact with the substrate in the region of the resist irradiated with both the first charged particle beam and the second charged particle beam. The charged particle beam energy is set to be larger than the charged particle beam energy absorbed in the region on the resist surface side,
A drawing method characterized by that. An evaluation method for evaluating a resist,
A step of performing multiple drawing on the resist on the substrate using the drawing apparatus according to claim 1;
Developing the resist subjected to the multiple drawing;
Evaluating the developed resist; and
The evaluation method characterized by including. A step of performing multiple drawing on the resist on the substrate using the drawing apparatus according to claim 1;
Developing the resist subjected to the multiple drawing;
A method for producing an article comprising:

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