JPH01217911A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a transfer pattern from necking by performing a photolithography with two monochromatic ultraviolet lights for generating different wavelengths in films in a photoresist-coating film. CONSTITUTION:The surface of a polycrystalline silicon 2 deposited on a semiconductor wafer is covered with a photoresist-coating film 3 in which the thickness of the thinnest part is 1.33mum. The wafer 1 is prebaked and transfer-exposed with an element pattern 6 with monochromatic ultraviolet light A through a photomask 4. A monochromatic ultraviolet light B having 447.0nm of wavelength is irradiated onto the whole wafer by 1/2-1/10 exposure amount in a transfer exposure step, the wafer is then developed, and postbaked, thereby obtaining a photoresist pattern 7. When the two lights A, B are irradiated, the total photosensing amount on the regions of the film 3 becomes the sum of the exposure amounts of the transfer exposure and whole surface photosensing, the difference of the exposure amounts due to the difference of the thicknesses of the film 3 is compensated each other to be averaged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a process technology of photolithography.

[Conventional technology]

Conventionally, element patterns of semiconductor devices are formed through a photolithography process.

FIGS. 6(a) to 6(d) are process sequence diagrams of conventional photolithography processes. According to this, semiconductor wafer 1
After coating a photoresist film 3 (for example, positive type) on the upper polycrystalline silicon M2,
Refer to Figure (a)] Brie-baking is performed, and then Figure 6 (b)
), monochromatic ultraviolet light (
For example, transfer exposure of the element pattern 6 is carried out by irradiating with G-ray (G-ray) 5 having a wavelength of 435.8 nm, and then through development and a boss baking process, a photoresist pattern as shown in FIG. 6(C) is formed. 7.

[Problem to be solved by the invention]

However, in the conventional photolithography described above, the thickness of the photoresist coating film is uneven due to the unevenness of the surface of the semiconductor wafer, so the transfer exposure of the device pattern using monochromatic ultraviolet light is difficult. When photoresist is processed, the existence of this film thickness "unevenness" causes differences in the way ultraviolet light standing waves are generated within the photoresist, and this appears as a difference in exposure sensitivity.・
The resist pattern 7 is transferred in a shape having a narrow "waist" near the step blood. [See Figure 6(d)] In the conventional photolithography process, variations in exposure sensitivity due to minute differences in the thickness of the photoresist coating can be kept to a minimum. Generally, a film thickness at which the exposure sensitivity takes an extreme value is appropriately selected. However, even if such a method is adopted, for example, if the coating film thickness is uneven due to the unevenness of the wafer, the difference in film thickness is too large and it may be difficult to A steep gradient occurs in exposure sensitivity. Therefore,
As the transfer exposure progresses due to the difference in exposure sensitivity, the formed photoresist patterns come to have the above-mentioned differences in size and shape.

In view of the above circumstances, an object of the present invention is to provide a semiconductor device equipped with a photophosphorography process that can effectively minimize the difference in transfer exposure sensitivity caused by the "unevenness" in the thickness of a photoresist coating film. An object of the present invention is to provide a method for manufacturing a device.

[Means to solve the problem]

According to the present invention, a method for manufacturing a semiconductor device includes a device pattern transfer exposure step of irradiating a photoresist coating film on a semiconductor wafer with a first monochromatic ultraviolet light;
a photolithography process comprising a step of irradiating the entire surface of the photoresist coating film with a second monochromatic ultraviolet light that produces an in-film wavelength different from that of the first monochromatic ultraviolet light within one specific film thickness of the resist coating film; Consists of. At this time, it is most preferable that there is a "shift" of 1/8 wavelength between the in-film wavelength of the second monochromatic ultraviolet light and the in-film wavelength of the first monochromatic ultraviolet light.

Therefore, when the g-line of a mercury lamp is used as the first monochromatic ultraviolet light, the second monochromatic ultraviolet light has a wavelength of 447.0 nm,
Desired effects can be achieved by selecting either 425.2 nm or 458.7 nm.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIGS. 1(a) to 1(e) are process order diagrams of photolithography showing an embodiment of the present invention. According to this embodiment, polycrystalline silicon 2 deposited on a semiconductor wafer 1.
A photoresist coating film 3 is first deposited on the surface of the photoresist film 3 so that the film thickness T at the thinnest part is 1.33 μm.
1(a)], the semiconductor wafer 1 is pre-baked, and then, as shown in FIG. 1(b), the device pattern 6 is transferred and exposed to monochromatic ultraviolet light A through a photomask 4. In this embodiment, the monochromatic ultraviolet light A is the g-line of a mercury lamp. Next, the wavelength (λ2
) Monochromatic ultraviolet light B of 447.0 nm is irradiated onto the entire surface of the wafer at an exposure dose of 1/2 to 1/10 of that of the transfer exposure process [see Figure 1(c)], and then development and A post-bake process is performed to obtain a photoresist pattern 7 [see FIG. 1(d)]. Here, a photoresist pattern 7 is obtained.
Assuming that the refractive index of resist coating [3] is 1.64, the film thickness at the thinnest part T: wavelength at 1.33 μm (λs
) The internal wavelength λl' of the g-line of 435.8 nm is 265
．． 7nm! In other words, there is a relationship of T = n - (n = 10 > is minimal, so the amount of light exposure is also minimal,
In other neighboring regions where the film is thicker than the thinnest film FJT, on the contrary, as the film thickness increases, the exposure sensitivity increases and the amount of exposure also increases.

On the other hand, the wavelength (λ2) at which the entire surface is irradiated is 447. Onm
The internal wavelength λ2' of the monochromatic ultraviolet light is 272.5 nm, and the relationship with the film thickness T at the thinnest part is T=(n--)λ2' +++++, (n = 10>. That is, Monochromatic ultraviolet light with a wavelength (λ2) of 447.On m, unlike g-line, generates a standing wave in a thick film thickness region in the vicinity of the thinnest film thickness T. Therefore, the exposure sensitivity is , T becomes minimum in the thick film thickness region in the vicinity of this region, and exhibits large exposure sensitivity and exposure amount in the regions of the thinnest films W and T and the thicker film region in the vicinity, respectively.

Figure 2 is a graph showing the relationship between the film thickness of the photoresist coating film and the exposure sensitivity of two monochromatic ultraviolet lights in the above example. It becomes minimum at 1.33 μm, and the wavelength (λ
2) It has been shown that the exposure sensitivity of monochromatic ultraviolet light of 447° Onm reaches a minimum at a position deviated from this minimum point by λ2'/8 in terms of the film wavelength. The size of this “shift 7” λ
2'/8 uses the relational expression between the film thickness T and the film internal wavelength λ/, the half-wave length of λ2'λt'/2, and λ2'/2. 4 x 1'/
2 and λ2'/2 are counted, and the difference between the two is converted into a wavelength. That is, using the above relational expression, λ1'/2. which falls within the distance corresponding to the film thickness T. The numbers of ^2'/2 are 10 and 9.75, respectively, and the difference between the two is calculated to be 0.25. Therefore, by converting this difference into wavelength, "shift"
We know that the size of is λ2'/8.

In this way, when two monochromatic ultraviolet lights A and B are irradiated, the total exposure amount in each area of the photoresist coating film 3 is the sum of the exposure amount in the transfer exposure and the exposure amount in the entire surface exposure, and the photoresist coating film 3 is - Differences in the amount of exposure due to differences in the thickness of the resist coating film are mutually compensated and averaged, so variations in the amount of exposure depending on the area are smoothed out extremely effectively.

FIGS. 3 and 4 are schematic diagrams showing the amount of exposure for each area and the total amount of exposure of the photoresist film by two monochromatic ultraviolet lights in the above example, respectively. This is a schematic representation of how the difference in exposure amount is mutually compensated for, averaged, and smoothed by irradiation with two monochromatic ultraviolet lights. As is clear from this schematic diagram, the decrease in the amount of exposure due to the g-line in the area of the thinnest film thickness T and its vicinity is
Compensated with a large amount of exposure due to monochromatic ultraviolet light of 77.0 nm, and the wavelength of 477.0 nm in other regions
The decrease in the amount of exposure due to the monochromatic ultraviolet light of m is compensated by the large amount of exposure due to the g-line. Therefore, the amount of exposure in the entire area of the photoresist coating M3 is always averaged and smoothed over the entire surface, regardless of the unevenness of the surface. Photoresist with extremely high dimensional accuracy as shown in
Pattern 7 is efficiently transferred.

FIGS. 5(a) to 5(d) are photolithography process steps showing another embodiment of the present invention.

According to this embodiment, a photoresist coating film 3 is applied to the surface of a polycrystalline silicon film 2 deposited on a semiconductor wafer 1 so that the film thickness T at the thinnest part is <1j3 μm, the same as in the previous embodiment. is formed [see Figure 5(a)], and yellowtail is formed.
After baking, first the wavelength (λ2) 447.0 n
m monochromatic ultraviolet light B is irradiated over the entire surface with an exposure amount of 1/2 to 1/10 of the transfer exposure [see FIG. g
photoresist pattern 7
[See Figures 5 (c) and (d)] 0 Even if the process order of the transfer exposure using monochromatic ultraviolet light A and B and the entire surface exposure is reversed as in this example, as long as the various conditions are not changed. It is possible to obtain the same effects as in the previous embodiment.

The above is for transfer exposure and full surface exposure, respectively, for g-line and 4
Although we have explained the case where monochromatic ultraviolet light of 47.0 nm is used, there are also other cases where the wavelength within the film is transferred, such as a combination of g-line and 425.2 nm or g-line and 458.7 nm. The same effect can be achieved as long as it produces a shift of 1/8 wavelength from the film wavelength of the g-line of the exposure light.

Of course, the use of monochromatic ultraviolet light other than g-line as the transfer exposure light is not prohibited in any way, but it is also important that the 'shift' in the film wavelengths of the two monochromatic ultraviolet lights satisfies the optimum value of 1/8 wavelength. Almost the same effect can be achieved even if they are scattered around the surrounding area.

〔Effect of the invention〕

As explained in detail above, according to the present invention, photo
By performing photolithography using two monochromatic ultraviolet lights that produce different wavelengths within the resist coating, the difference in exposure due to unevenness in the photoresist coating can be mutually compensated for. Can it be averaged? )
Therefore, the constriction of the transfer pattern that conventionally occurs at the thinnest portion of the film is completely resolved, and a photoresist pattern with extremely high dimensional accuracy can be efficiently transferred. That is, it is possible to achieve a remarkable effect in forming a high-density pattern of a semiconductor S integrated circuit device.

[Brief explanation of the drawing]

Figures 1 (a) to (e) are process order diagrams of photo phosphorography showing one embodiment of the present invention, and Figure 2 shows the thickness of the photoresist coating film and two monochromatic ultraviolet rays in the above embodiment. Graphs showing the relationship with light exposure sensitivity, FIGS. 3 and 4 are schematic diagrams showing the sensitivity of each region of the photoresist film and the total sensitization amount by two monochromatic ultraviolet lights in the above example, respectively. FIGS. 5(a) to (d) are process order diagrams of photophosphorography showing another embodiment of the present invention, and FIGS. 6(a) to (d) are process orders of the conventional photophosphorography process. It is a diagram. DESCRIPTION OF SYMBOLS 1... Semiconductor wafer, 2... Polycrystalline silicon film, 3... Photo cyst coating 1i1.4... Photo mask, 6... Element butter, 7... Resist pattern, monochromatic ultraviolet light A... transfer exposure light, monochromatic ultraviolet light B... entire surface exposure light. Agent Patent Attorney Shintan Uchihara Tomoe Shi9cho A (1 share, λt: 4J5.5M) 謬 j
Figure 1 77 squares 5 “Storage °bu”” Figure 1 Figure 2! J5Jl! ! M 4 concave ivy 5 Fig. 6. Fig. 6. Fig. 6.

Claims (3)

[Claims] (1) A device pattern transfer exposure step of irradiating a first monochromatic ultraviolet light onto a photoresist coating film on a semiconductor wafer; A method for manufacturing a semiconductor device, comprising a photolithography step comprising a step of irradiating the entire surface of the photoresist coating film with a second monochromatic ultraviolet light that produces an internal wavelength different from light. (2) The semiconductor according to claim (1), wherein the in-film wavelength of the second monochromatic ultraviolet light is set to a phase difference of 1/8 wavelength from the in-film wavelength of the first monochromatic ultraviolet light. Method of manufacturing the device. (3) The first and second monochromatic ultraviolet lights are the g-line of a mercury lamp and wavelengths of 447.0 nm and 425.2 nm, respectively.
2. The method of manufacturing a semiconductor device according to claim 1, wherein either one of m and 458.7 nm is selectively used.