JPS60182439A - Chromium mask material - Google Patents

Abstract

PURPOSE:To improve etching speed, stability of time necessary for processing, and uniformity by combining a layer made of chromium oxide with a layer made of a mixture of chromium oxide and nitride. CONSTITUTION:A 10-25nm thick layer (a) made substantially of chromium oxide contg. 40-60atom% oxygen, a layer (b) made substantially of a mixture of chromium oxide and chromium nitride contg. 8-18atom% oxygen and 7- 15atom% nitrogen, and a 20-30nm thick layer (c) made substantially of a mixture of chromium oxide and chromium nitride contg. 25-32atom% oxygen, and 19-28atom% nitrogen are formed on a support. The layer (a) has an effect of preventing diffusion of Na ions, and the nitrogen content may be lowered to <=10atom%. The layer (b) is controlled to a film thickness of 60-120nm so as to give an optical density of 2.6-3.2 with respect to light of 436nm wavelength.

Description

[Detailed description of the invention] ■ Background of the invention Technical field The present invention relates to a chrome mask material.

Prior art and its problems As LSIs become more highly integrated, they have higher resolution.

Photomasks with high precision and fewer defects are required.

The main material used for photomasks is chrome mask material, which is excellent in terms of durability, sharpness, and resolution. Conventionally, metal chrome is deposited on a support by vacuum evaporation or sputtering. A pattern is formed by etching the material with a chromium oxide layer on top of the layer.

In recent years, in order to improve pattern sharpness, line width reproducibility, and work standardization when etching chrome masks, the traditional dip-type etching method has been replaced by a spray-type etching method.

In spray etching, since the amount of liquid is small, if the etching speed of the upper layer is slow, a repelling phenomenon will occur before etching or chinking progresses, resulting in non-uniformity. On the other hand, if the etching speed is fast, the etching will proceed the moment the liquid is applied.
From the ninth stage onwards, a t+ferenchy wood-loving surface appears, resulting in uniform etching.

Conventional chrome mask materials have a slow etching speed of the chromium oxide layer on the surface, which can cause a loss of uniformity during spray etching due to changes over time.1 For example, when spray etching the entire surface, especially from the peripheral area, the line This results in uneven or scattered etching irregularities.

Furthermore, since the cutting speed is not sufficiently high for the metal chromium of the light-shielding layer, there is a drawback that when patterned, the cross-sectional shape of the pattern becomes overhang-like (eaves-like).

If there is a large overhang in the cross section of the pattern, it will lead to a decrease in sharpness during pattern transfer and an increase in defects such as chipping.

Furthermore, the chrome mask is made with strong acid (120%
℃ H2SO4 or 80℃ H2S04 H202 mixed solution) (several 10 times for 2 to 3 minutes/time), but with conventional chrome mask materials, metallic chromium is used as the light-shielding layer. It has poor chemical resistance, especially against strong acids often used in mask cleaning processes, and is difficult to use repeatedly when soiled.

Examples of these include, for example, Japanese Patent Publication No. 53-22426
No. 2, discloses a structure in which a thin film of metal such as chromium is deposited on a transparent substrate.

When the metal is chromium, it has poor acid resistance, so it cannot be used repeatedly, and because the etching rate of each layer is not controlled, the cross-sectional shape is no longer smooth, resulting in poor pattern sharpness and durability.

Further, JP-A-51-105271 discloses that a lower layer of chromium oxide, a middle layer of metallic chromium, and an upper layer of chromium oxide are provided on a glass support.

However, in this case, the etching rate cannot be controlled with chromium oxide alone in the upper layer, the etching uniformity deteriorates, and the cross section of the pattern becomes overhanging.
Sharpness and durability deteriorate.

Additionally, since the middle layer is made of metallic chromium, it has poor acid resistance and cannot be used repeatedly.

In the lower layer, Na
Ion diffusion prevention 1): is insufficient, and there is a drawback that Na ions diffuse into the chromium film or oxide film during storage, inducing pattern defects.

Furthermore, Japanese Patent Publication No. 48-3231 discloses the use of a chromium metal film as a lower layer and a chromium oxide film (for antireflection) as an upper layer on a glass or quartz substrate.

According to this, since there is no chromium oxide layer between the chromium metal film and the substrate, defects are induced due to Na ion diffusion. The chromium metal film has poor acid resistance and cannot be used repeatedly.

Furthermore, if the two layers are only a chromium oxide film, the etching rate cannot be controlled sufficiently, resulting in an overhang in the cross section and deterioration of etching uniformity.

JP-A No. 58-31338 discloses that a lower oxide and/or lower nitride is formed as an intermediate layer on a substrate,
It is disclosed that an upper layer of a higher oxide, a higher nitride, or a higher nitride is provided thereabove.

According to this, when the upper layer is made only of high-grade nitrides, the antireflection effect is insufficient and the etching rate is low, resulting in poor uniformity.

If the upper layer is a mixture of higher oxide and higher nitride, the etching rate and antireflection effect will be insufficient unless the oxygen content is in the range of 25 to 32 atomic percent, making it impossible to provide a highly accurate photomask.

Further, when the middle layer is a mixture layer of lower oxide and lower nitride, the oxygen and nitrogen contents are 8 to 18, respectively.
If it is less than 7 to 15 at%, it will not be possible to provide a practical photomask material with good acid resistance, a film thickness of about 0.1 pLm, and an optical density of about 3.0. .

II. OBJECTS OF THE INVENTION The first object of the present invention is to provide a chromium mask material that has an extremely high etching rate and has improved stability and uniformity of etching processing time.

The second object is to provide a chrome mask material in which the overhang phenomenon of the upper layer is reduced in the cross-sectional shape of the pattern.

The third objective is to provide a chromium mask material that has a high optical density per unit film thickness and has excellent acid resistance.

A fourth object is to provide a chromium mask material that prevents pattern defects caused by deterioration of resist adhesion caused by diffusion of Na ions from a glass substrate or uneven etching rate.

Such objects are achieved by the invention described below.

That is, the first invention provides the following (a) on the support in order from the side closest to the support:
This is a chrome mask material characterized by having (b) and (C).

(a) Consists essentially of chromium oxide containing 40 to 60 atomic percent oxygen. (b) a layer with a thickness of 100 to 250 people, containing 8 to 18 atomic percent oxygen and 7 to 15 atomic percent nitrogen;
Layer (C) consisting essentially of a mixture of chromium oxide and chromium nitride containing 25 to 32 atomic % oxygen and 19 to 2 atomic % nitrogen;
A layer of chromium oxide containing 8 atomic % and chromium 00 to 300 chromium oxides and a layer of chromium 00 to 300, and the second invention, are formed by applying the following (a) and (b) on a support in order from the side closest to the support.
) and (C).

(a) J7 consisting essentially of chromium oxide containing 40 to 60 atom% of oxygen and 10 atom% or less of nitrogen is 100 to 2
50 layer (b) Contains 8 to 18 atomic percent oxygen and 7 to 15 atomic percent nitrogen
Layer (C) consisting essentially of a mixture of chromium butyride and chromium nitride containing 25 to 32 atomic % oxygen and 19 to 2 atomic % nitrogen;
A layer having a thickness of 2.0 to 300 layers consisting essentially of a mixture of chromium oxide and chromium nitride containing 8 at.

The support of the present invention is transparent to visible light, ultraviolet light, and far ultraviolet light, and is polished to a mirror surface without any kisses or pits. For example, the support is made of soda lime glass, alkali borosilicate glass, quartz glass, etc. Can be used.

The first layer formed as the bottom layer on the support contains 4 oxygen
It is a chromium oxide layer containing 0 to 60 atomic %, preferably 45 to 55 atomic %.

In this case, in addition to 40 to 60 atomic % of oxygen, nitrogen may be contained at 10 atomic % or less, particularly 5 to 10 atomic %.

If oxygen is less than 40 atomic %, the effect of preventing Na ion diffusion is insufficient and pattern defects are induced.

Note that since it is Cr2O3, 60 atomic % is not included.

Further, although the addition of nitrogen improves the light-shielding property, when it exceeds 10 atomic %, the oxygen content decreases and the effect of preventing Na ion diffusion decreases.

The film thickness is approximately 100 Å or more without pinholes, and may be increased to approximately 250 λ if necessary. Beyond this point, the effect remains unchanged and the film thickness only increases.

The second layer formed on the first layer is a light shielding layer, and is a mixed layer of chromium oxide and chromium nitride containing 8 to 18 at % of oxygen and 7 to 15 at % of nitrogen.

In this case, if the oxygen content is less than 8 atomic %, the acid resistance will be poor, and if it exceeds 18 atomic %, the optical density will be insufficient.

Further, if the nitrogen content is less than 7 atomic %, the acid resistance will be poor, and if it exceeds 15 atomic %, the optical density will be insufficient.

The second light-shielding layer is formed to have a thickness of 600 to 1200 and has an optical density of 2.6 to 3.2 for light having a wavelength of 436 nm.

Further, the third layer as an upper layer film formed on the second layer is a mixed layer of chromium oxide and chromium vacancy containing 25 to 32 at % of oxygen and 19 to 28 at % of nitrogen.

In this case, if the oxygen content is less than 25 atomic %, the reflectance is high and it is difficult to form a fine pattern.

Furthermore, if the oxygen content exceeds 32 atomic percent, the etching speed will be slow and uneven etching will occur during spray etching.
This results in an overhang phenomenon.

On the other hand, if the nitrogen content is less than 19 atom %, the etching speed If is slow, etching unevenness, and overhang phenomena occur.

Further, if the nitrogen content exceeds 28 atomic %, the reflectance becomes too high.

In such a case, the overhang phenomenon occurs critically at an etching speed of less than 80 people/sec.
With the above oxygen and nitrogen amounts, the etching rate exceeds 80 people/sec and no overhang occurs.

The third layer is formed to a thickness of 200 to 300 layers. This one
1 thickness is the pattern exposure wavelength (350 to 450 na)
In contrast, the reflected light is determined to be minimal.

Such a ROM mask material is formed by known methods such as reactive sputtering, ion plating, and cutting.

In this case, each layer may be formed continuously or intermittently.

As described above, the desired performance of the chromium mask material of the present invention cannot be achieved unless both the nitrogen and oxygen contents of each layer are controlled.

■ Specific effects of the invention The chrome mask material of the present invention cannot achieve the desired performance unless both the nitrogen and oxygen contents of each layer are controlled, but compared to conventional chrome mask materials, the etching rate is extremely high. Since the temperature is high (≧80 people/5ec), the dissolution reaction at the start of etching proceeds quickly, resulting in excellent uniformity.
There is little variation in the progress of etching within the plate.

FIG. 1 shows the relationship between the nitrogen and oxygen contents of the upper layer and the etching rate.

From Figure 11, the oxygen content in the upper layer is 25 to 32 at%,
When the nitrogen content is 19 to 28 at%, 80 people/se
It can be seen that an extremely high etching speed can be obtained from c.

As a result, the in-plane uniformity of the pattern lines [lJ] is excellent. Also, there is very little uneven etching.

In addition, the etching speed of the double layer 119 is high (≧80
person/5ee), so there is a light-shielding chromium layer (~30 people/5ee).
Since the etching speed is sufficiently higher than 5ec), no overhang phenomenon occurs in the cross section of the pattern.

In addition, the light-shielding chromium film contains 8 to 18 atomic percent and 7 to 15 atomic percent of oxygen and nitrogen, respectively, so it has excellent acid resistance and can be used for mask cleaning with concentrated sulfuric acid at 120°C for more than 2 hours. It is durable and has sufficient durability for repeated practical use (one time washing takes 2 to 3 minutes and it is washed several dozen times).

Figure 2 shows washing for 2 to 3 minutes with concentrated sulfuric acid at 120℃ for 30 minutes.
Areas that can withstand more than one cycle are indicated by hatches.

In addition, the optical density is 2.6/2, as shown in Figure 3.
It has a sufficient value of 100 Å or more.

In addition, the composition of the lower layer, which is the substrate adhesive layer, was changed to an oxygen content of 4.
By limiting it to 0 to 60 at%, Na from the substrate is
Since ion diffusion is efficiently suppressed, it is possible to prevent pattern defects caused by local deterioration of resist adhesion that occurs during storage or local increase in etching rate of the chromium film caused by heat treatment.

FIG. 4 shows the relationship between the number of pattern defects per 4 inches and the amount of oxygen.

(2) Specific Examples of the Invention Examples of the present invention will be shown below to further explain the present invention in detail.

EXAMPLE A substrate is placed in a planar magnetron spunter device, and the inside of the vacuum chamber is evacuated to l X I O'Torr.

Introducing the spunter gas and rotating the board at 15 rpm.
Rotate with .

At this time, A r = 54cc/min, N2 =
The flow rate is 30 cc/min, 02 = 16 cc/min.

Next, the waste pressure is set. (Total pressure=5×10-3To
rr) Furthermore, a negative voltage of about 450 V is applied to the black 1 target and the target to generate a glow discharge between the target and the substrate.

The applied voltage was adjusted so that the power was 1.5 KW, the shunter was opened, and the film was formed for 2 minutes.

Change the gas flow rate at the same time as closing the shutter.
At this time, A r = 81 cc/min, N2 =
1 'Occ/Iain, 02 = 9 cc/r
Bin.

Along with this, the gas pressure changes to 4XIO-3Torr.

The applied voltage was adjusted so that the power was 2 KW, the shunter was opened, and the film was formed for 4 minutes.

Next, the shutter is closed and the waste flow rate is changed at the same time. At this time, A r = 65 cc/min, N
2 = 30 cc/min, 02 = 5 cc/
It's a win.

Along with this, the gas pressure changes to 4.7×10 −3 Torr.

The applied voltage was adjusted so that the power was 0.7 KW, the shunter was opened, and the film was formed for 5 minutes.

Close the shunter and turn off the voltage.

Next, the vacuum chamber is returned to the atmosphere, and the film-formed substrate is taken out.

The composition of 19 films of the chromium mask material thus produced is shown in FIG.

When a chrome mask material having such a film composition was spray-etched over the entire surface, a uniform etching pattern fff was obtained with almost no unevenness.

Next, this chrome mask material was patterned using a known photolithography method, and when the cross-sectional shape of this pattern was observed, as shown in Table 1, it was found that the overhang was almost 1. .

Furthermore, this patterned mask was heated to 120°C. When immersed in concentrated sulfuric acid, no abnormality occurred in the pattern even after 2 hours [Table 1].

In addition, this chrome mask had performance equivalent to that of masks produced by conventional methods in other properties such as pattern sharpness and resolution.

Note that the lower layer N310 also gave almost the same results.

Comparative Example A substrate was placed in a planar magnetron sputtering device, and the inside of the vacuum chamber was heated to 1×10 −5 Torr.

While introducing sputtering gas, the substrate was heated at 15 rpm.
Rotate with m. At this time, Ar=70 cc/wi
The wave amount is n, 02 = 30 cc/min.

Next, set the gas pressure. (Total pressure = 5×10'T
(orr) Furthermore, a negative voltage of about 450 V is applied to the chromium target to generate glow discharge between the target and the substrate.

The applied voltage was adjusted so that the power was 1.3 KW, the shutter was opened, and the film was formed for 2 minutes.

The waste flow rate is changed at the same time as the shutter is closed.
At this time, A r = 100 cc/min.

Along with this, the gas pressure changes to lXl0-3 Torr.

The applied voltage was adjusted so that the power was 1.5 KW, the shutter was opened, and the film was formed for 3 minutes.

Change the gas flow rate at the same time as closing the shutter.
At this time, A r = 70 cc/min, 02=
It is assumed to be 30 cc/sin. Along with this, the gas pressure changes to 1,5 X l 0-3 Torr.

The applied voltage was adjusted so that the power was 1.3 KW, the shank was opened, and the film was formed for 6 minutes.

Close the shutter and turn off the voltage.

Next, the vacuum chamber is returned to the atmosphere, and the film-formed substrate is taken out.

The film composition of the chromium mask material thus produced is shown in FIG.

When the entire surface of a chrome mask material having such a film composition was spray-etched, unevenness occurred on almost the entire surface except for the center.

Next, this chrome mask material was patterned using a known photolithography method, and when the cross-sectional shape of this pattern was observed, as shown in Table 1, the overhang was approximately 0, and the length of LILm was was observed.

Further, when this patterned mask was immersed in concentrated sulfuric acid heated to 120°C, the pattern of 5 μm or less had disappeared after 10 minutes.

Table 1 (Lem) Almost no change in the present invention 0.01 No change after 2 hours Comparative example Except for the center 0.1 1 < 5 pm or less generated on almost the entire surface after 1 minute Pattern disappears as shown in Table 1 The results clearly demonstrate the effectiveness of the present invention.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the oxygen content in the upper layer film and the etching rate in the present invention. FIG. 2 is a graph showing the relationship between the oxygen content and nitrogen content in the light-shielding layer, which shows the good acid resistance of the material in the present invention. Figure i3 is a graph showing the relationship between the oxygen content in the light shielding layer and the optical density in the present invention. FIG. 4 is a graph showing the relationship between the oxygen content in the lower layer and the amount of pattern defects in the present invention. Figure 5 shows the depth of the film composition of the example of the present invention! This is a graph showing [1]. FIG. 6 is a graph showing the depth distribution of the film composition of the comparative example. Applicant Roku Konishi Photo Industry Co., Ltd. Agent Patent attorney Akira Ishii - Figure 1 Self-inflicted t Ryo Yu Z Figure 2 Oxygen atom Z Figure 3 West side Blasphemy t Atom 2 Figure 4 White discoloration t Bleach + Z It Yes Amount (10%)

Claims (2)

[Claims] (1) Place the following (a) on the support in order from the side closest to the support.
), (b) and (c). (a) A layer of 100 to 250 people substantially consisting of chromium moltenide containing 40 to 60 atom % of oxygen; (b) A layer of 8 to 18 atom % of oxygen and 7 to 15 atom of nitrogen;
Layer (C) consisting essentially of a mixture of chromium oxide and chromium nitride containing f% oxygen and 19-2 atomic% nitrogen.
A layer 200 to 300 thick consisting essentially of a mixture of chromium oxide and chromium nitride containing 8 at.% (2) Place the following (a) on the support in order from the side closest to the support.
), (b) and (C). (a) Thickness consisting essentially of chromium oxide containing 40 to 60 atom % of oxygen and io to 25 atom % of nitrogen
0 layer (b) Contains 8 to 18 at% of oxygen and 7 to 15 of nitrogen
Layer (C) consisting essentially of a mixture of chromium moltenide and chromium nitride containing 25 to 32 atomic % oxygen and 19 to 2 atomic % nitrogen.
A layer of 200 to 300 people thick consisting essentially of a mixture of chromium oxide and chromium nitride containing 8 at.%