CN1155328A - Process for measuring depth of microstructure - Google Patents

Abstract

The proposal is for a process for measuring the depth of a microstructure on the transfer of the structure by means of a stamping process into a deformable layer, in which there is a geometrically simple reference grid structure in the microstructure to be transferred. This reference grid structure causes an interference of a measuring light beam. The colour distribution thus produced provides a measure of the structure depth obtained.

Description

Measure the method for depth of microstructure

The present invention relates to when structure being transferred on the yielding layer, measure the method for depth of microstructure by the punching press processing.

Recently, structure with Light Diffraction Effect is used for the false proof unit of those valuable documents (as cashier's check, credit card, identification card etc.) particularly or valuable product growingly, and this structure prints on the suitable yielding layer with a what is called " mother matrix " stamping die.This program is used for producing for example punching press paper tinsel, and false proof unit is transferred on the substrate from the punching press paper tinsel by the drop stamping operation.When forming this structure with Light Diffraction Effect, part is to operate less than the quite little press depth of the 1 μ m order of magnitude.Punching press can not be too shallow, otherwise required effect is obvious inadequately, yet again can not be dark excessively, and crossing deeply also can have adverse effect to obtainable effect.Therefore, pressed for a kind of method, can promptly measure the constructional depth that is reached at each production stage with simply and particularly do not destroy or change the measure of structure with Light Diffraction Effect.

Certainly adopt current known certain methods, for example to measure this form of degree of diffraction effect, the detection architecture degree of depth.Yet all these own perception methods are very uneconomical on process of measurement, carry out also very complicated.

Therefore, the objective of the invention is to propose a kind of like this method of measuring depth of microstructure, this method is simple especially, can widespread usage, and can implement with lower cost.

In order to reach this purpose, in such method that this instructions embodiment part is proposed, the present invention proposes to handle like this:

At least to become domain mode to provide a kind of geometric configuration simple benchmark strip structure, wherein the cross section of the line bar of strip structure specifically can be square, rectangle or triangle in the microstructure of need seal;

With a light beam irradiates benchmark strip structure that comprises a setted wavelength scope;

Measure the position that light intensity maximal value and light intensity minimum value in zeroth order diffraction spectrum, occur with transmission or reflection measurement pattern by the press depth decision that is reached, then according to the control value of relevant corresponding construction and illumination wavelength scope from the definite press depth that is reached in the position that records; Perhaps,

From comprehensive estimation, release the press depth that is reached according to control value to the zeroth order diffraction light color.

The ultimate principle of this method of the present invention is, in order to measure the press depth of microstructure, certain zone at least in microstructure forms a kind of benchmark architecture, this benchmark architecture is the simple strip structure of a kind of geometric configuration, preferably has square, rectangle or triangular-section.Then, measurement is in the transmission or the catoptrical spectral distribution of benchmark bar shaped structural area.In this case, the position that light intensity maximal value or minimum value occur can be as to the direct tolerance of press depth, depends on press depth because these maximal values and minimum value appear on which wavelength of spectrum.At this on the one hand, situation normally: along with reducing of constructional depth, minimum wavelength is with shorter and shorter.If correctly selected the cross section of reference stripe, the absolute value of minimum value frequency depends primarily on the refractive index of the substrate that needs the formation structure so.

Specifically, this method of the present invention be following in the face of being thought of as of studying of transmission mode and reflective-mode measurements basic.

Under the situation that transmission mode is measured, suppose that the transmission of the measured simple linear fringe with square-section can be with sufficiently high accuracy representing: $T\left(\mathrm{\λ}\right)={\cos }^2[\frac{\mathrm{\π}}{2}\·(a+c_1)\·\frac{n-1}{\mathrm{\λ}+c_2}]-----\left(I\right)$ Wherein:

T (λ) is for depending on the transmission of wavelength;

A is the resulting strip structure degree of depth (the line bar degree of depth), and corresponding with press depth, unit is nm;

λ is a wavelength, and unit is nm;

N is the substrate refractive index;

c ₁, c ₂Be empirical constant, unit is nm.

In the transmission measurement pattern,, can utilize following expression constructional depth a and detected minimum wavelength λ for measuring the computation structure degree of depth _MinBetween the direct equation of linear relationship: $a\left({\mathrm{\&lambda;}}_{\min }\right)={\mathrm{<figure-callout\; id="3"\; label="c"\; filenames="A9519453900101.png,A9519453900103.png"\; state="\{\{state\}\}">c</figure-callout>}}_3+\frac{{\mathrm{\&lambda;}}_{\min }}{(n-1)}-----\left(\mathrm{II}\right)$ Wherein:

λ _MinFor measured T (λ) is the wavelength at minimum value place, unit is nm;

N is the refractive index of substrate;

c ₃Be empirical constant.

If selected correct striped type, just can estimate constructional depth according to above equation (I) with (II) with the primary colors fast qualitative of the light that passes through substrate, also can the actual quantification measurement structure degree of depth.An instrument that so just can utilize suitable measurement spectrum color to distribute is easily promptly determined the degree of depth of resulting structure in transfer operation continuously, and also just basis is estimated roughly by the color of the light of substrate.This makes in forming the process of each corresponding microstructure fast reacts to the change of processing conditions (temperature, the setting rate during as stamping pressure, punching press, accept the thickness etc. of current each layer of punching press).

Though light intensity maximal value that occurs or the obvious corresponding relation between minimum value and the resulting constructional depth can be set up in the transmission measurement pattern usually, when carrying out reflection measurement, be difficult to set up, particularly using under the situation of white light.This is because light usually contains the component that some wavelength are significantly less than the desired structure degree of depth, this means the multiple interference of appearance.For example, in the spectrum that draws, have two minimum value or maximal value.Though still can be with the spectrum color that draws as the criterion that detects resulting constructional depth.

When measuring with reflected light, if adopt suitable striped, the relation that can obtain between catoptrical light intensity and the wavelength is as follows:

Wherein:

λ is a wavelength, and unit is nm;

A is a constructional depth, and unit is nm; And

The constants of c for need determining, unit be nm (under the situation of this striped that applicant is studied, c should be mutually-50nm).

Consider the complex situations of reflection measurement, hope can be dark according to the line of some standards, provides for the dark standardization chromatogram of these lines, estimates thereby can carry out quantitative look to the press depth that is reached.

With regard to the consideration of above theoretical property, be also pointed out that all these is based on that zeroth order is measured.

Mentioned that the benchmark strip structure wishes to have square, rectangle or triangular-section because situation is just the simplest like this, and what correction is application formula (I) to (III) do not need to carry out basically yet.This means that measurement expense is minimum, in addition, during measuring beam in using visible-range, can just carry out qualitative estimation without surveying instrument by range estimation.

Have found that, preferably use benchmark strip structure for this method of the present invention with following parameters:

Striped constant g:0.5 μ m≤g≤4 μ m

Line bar width/striped constant b/g:0.1≤b/g≤0.8

Constructional depth a:0.3 μ m≤a≤4 μ m

Released already and can estimate measuring beam in many ways.Preferably carry out the look estimation of measuring beam, because can provide reliable, accurate result like this with spectrometer.

If transmission measurement uses white light according to the present invention when measuring the color of the measuring beam that passes through the benchmark strip structure.

On the contrary, if need to measure reflection configuration, it is more favourable as measuring beam to be limited to the light of certain scope with wavelength so.In this case, if can exempt the light intensity maximum point and the smallest point that can on different frequency, occur with white light in a large number, so concerning the actual measurement constructional depth, a corresponding relation has clearly just been arranged between light intensity smallest point and constructional depth.

ED3518774C2 has disclosed and has a kind ofly formed the method that the high optimal layer in light efficiency rank makes diffraction characteristic the best of phase grating by generating one, this method relate to during generating phase grating, make basic monochrome measuring light at periodic phase grating place diffraction.Measure the light beam irradiates intensity of at least two diffraction orders, from the relation derivation processing parameter of light intensity and diffraction orders.These parameter indicatings should increase or reduce the light efficiency rank height of phase grating in order to make diffraction characteristic the best.

On the contrary, proposed by the invention is the method for measuring the microstructure press depth during punching operation.In the method, in order to measure the microstructure of going out, at least form a kind of benchmark architecture in certain zone of microstructure, after shining this benchmark architecture with the light velocity of setted wavelength scope, light intensity maximum point that occurs in zeroth order diffraction spectrum or smallest point just are used as the direct tolerance for the press depth that is reached, or by estimating the photochromic approximate evaluation of carrying out.

Other characteristics of the present invention, advantage and details can be found out from the following description in conjunction with the accompanying drawings, in the accompanying drawing:

Fig. 1 a-1c shows the example in the three kinds of striped cross sections that can use for the present invention;

Fig. 2 shows the measuring principle of transmission measurement;

Fig. 3 shows the measuring principle of reflection measurement;

Fig. 4 shows under measurement situation as shown in Figure 2 the reception curve for certain given constructional depth spectrometer; And

Fig. 5 a-5d shows under the reflection measurement situation reception curve for different constructional depth spectrometers respectively.

Fig. 1 a-1c shows several simple as far as possible strip structures, and these structures can be used as the benchmark architecture of method proposed by the invention.Wherein, structure is called rectangular configuration shown in Fig. 1 a, and structure is called square structure shown in Fig. 1 b, and structure is called triangular structure shown in the 1c.Structure shown in Fig. 1 a-1c and all the other microstructures are formed on the substrate simultaneously.Substrate 1 is through suitably punching press, and the surface has just formed the line crack 3 between line bar 2 and the line bar 2.

Difference between these structures shown in Fig. 1 a-1c not only is the geometric configuration difference, and is the use difference.Specifically, structure is used for transmission measurement shown in Fig. 1 a and the 1c, and structure is used for reflection measurement shown in Fig. 1 b.

For this reason, structure shown in Fig. 1 a and the 1c must be made up of suitable material transparent fully.On the contrary, under the structure situation that is used for reflection measurement shown in Fig. 1 b, must guarantee that parallel with the striped principal plane at least those surfaces 4 (being shown thick line among the figure) have reflectivity, for example have been coated with reflective metal layer.

Take the measure of suitable formation reflection also to can be used for reflection measurement if be appreciated that the structure of Fig. 1 a and 1c, and if Fig. 1 b structure takes suitable transmission measure also to can be used for transmission measurement.

Fig. 1 a and two kinds of structures shown in the 1b are identical with regard to the cross section of line bar 2 all is rectangle basically.Difference is: in the structure of Fig. 1 a, the width b of line bar 2 is significantly less than the width g-b in the line crack 3 between the line bar 2; And in the structure of Fig. 1 b, the width in line bar 2 and line crack 3 is basic equating.

These structures can be used for the present invention, and structure should satisfy following condition:

Striped constant g:0.5 μ m≤g≤4 μ m

Line bar width/striped constant b/g:0.1≤b/g≤0.8

The dark a:0.3 μ of line m≤a≤4 μ m

Fig. 2 illustrates the method for measuring the constructional depth on the transparent substrate 5.For this reason, have at least a zone to have suitable benchmark architecture on the substrate 5; In illustrated embodiment, be square structure, that is to say that the cross section is equivalent to shown in Fig. 1 b, but do not have reflectivity.

Light source 6 is projected white light on the benchmark architecture in a suitable manner, use receiver 8 (spectrometer) measurement to measure the benchmark architecture degree of depth then by the chromatogram distribution of the light 7 of substrate 5.

The light distribution T (λ) that falls the light on the receiver 8 depends on wavelength X, and trend as shown in Figure 4.Under the situation of carrying out transmission measurement, irradiation light intensity T (λ) pairing wavelength X when minimum value occurring _MinThe degree of depth that depends on benchmark architecture on the substrate 5.Therefore, this just means minimum value or the corresponding wavelength X of measuring light intensity _MinAlso just directly measured the degree of depth that benchmark architecture reached.So, just can convenient, promptly determine the corresponding constructional depth a that reaches as long as determine the wavelength of light intensity minimum value.

This is illustrated with reference to following example.

Under the acceptance angle situation of regular transmission and 0 °, carried out transmission measurement, the rectangular configuration of used benchmark architecture, striped constant g is 2 μ m, and the ratio b/g of line bar width and striped constant is 1: 2.The refraction index n of substrate is 1.466.

According to above-mentioned refraction index at C ₃For under the condition of-285nm by the relational expression of determining constructional depth a below the formula II gained:

a＝(2.1428·λ _min－285)nm

With the corresponding wavelength of the constructional depth that is reached and photochromic as shown in following:

Constructional depth minimum intensity of light wavelength is photochromic

a[nm] λ _min[nm]

1,000 600 indigo plants

800 510 is pink

600 414 is orange

400 320 is pale yellow

Details listed above clearly illustrates that and can determine the constructional depth that reached by accurate spectral measurement, and color relation that also can be by changing measuring beam is determined with the light intensity of which kind of color of eye estimate is low.

The measurement mechanism of determining the reflective substrate constructional depth is shown in Fig. 3.Substrate 5 ' also the be pressed with benchmark architecture that the degree of depth is a.It should be noted that substrate 5 at least ' towards light source 6 ' and be arranged in the receiver 8 of light source 6 ' the same side ' that surface be reflecting surface, for example be the surface that scribbles metallic coating 9.

In principle, light source 6 ' with receiver 8 ' can be identical with receiver 8 with the respective sources 6 of transmission mode measurement mechanism.Yet, may wish more that under the situation of reflection measurement light or receiver 8 ' reception wavelength that light source 6 ' emission wavelength is limited to certain scope are limited to the light of certain given range because like this can obtain under some environment light source 6 ' reflected light project receiver 8 ' on the maximum point of smallest point of light intensity and the direct corresponding relation of given constructional depth.

Fig. 5 a-5d show substrate 5 ' the light of reflecting surface 9 reflection with respect to the light distribution I of wavelength _R, shown be to use the light distribution of white light under air-metal boundary reflection situation.In this case, light distribution meets foregoing formula (III) substantially, and wherein constant c is assumed to be-50nm.

Fig. 5 a-5d for the light distribution of different structure degree of depth a (seeing affix) is shown more respectively.As seen, the minimum value of light distribution and maximal value move towards the shorter direction of wavelength along with reducing of constructional depth a.In this case, selective receiver 8 ' handled wavelength dexterously, make and under some environment, can handle just given light intensity maximal value, thereby can obtain the wavelength of more clearly corresponding light intensity maximal value or minimum value and the corresponding relation of constructional depth a for every kind of situation.And, use for some, may wish without white light for example to carry out work, because can significantly reduce the number of light intensity maximal value and minimum value like this with the infrared illumination lamp with the long as far as possible light of wavelength.This is especially for the bigger occasion of the reflection benchmark architecture degree of depth.And when handling small depth, certainly the light with visible wavelength range carries out work.

Be appreciated that when using infrared light, have to light be estimated constructional depth with estimating with suitable instrument.When using white light, visible light, even reflection measurement also can be estimated roughly qualitatively according to the photochromic of generation.Yet in this case, appearance is color mixture.

Claims (7)

1. handling the method for measuring depth of microstructure when being transferred to structure on the yielding layer with punching press for one kind, it is characterized in that:

In the microstructure of need transfer printing, provide a kind of geometric configuration simple benchmark strip structure in the mode that becomes the zone at least;

With a light beam irradiates benchmark strip structure that comprises a setted wavelength scope;

Measure the position that light intensity maximal value and light intensity minimum value in zeroth order diffraction spectrum, occur that determines by the press depth that is reached with transmission or reflective-mode, then according to the press depth of determining from the position that records about the control value of corresponding benchmark architecture and illumination wavelength scope to be reached; Perhaps

From comprehensive estimation, release the press depth that is reached according to control value to the zeroth order diffraction light color.

2. the method as being proposed in claim 1 is characterized in that the cross section of benchmark strip structure is square, rectangle or triangle.

3. the method as being proposed in claim 1 or 2 is characterized in that the benchmark strip structure has following parameters: the striped constant g:0.5 μ m≤g≤4 μ m line bar width/striped constant b/g:0.1≤b/g≤dark a:0.3 μ of 0.8 line m≤a≤4 μ m

4. the method as being proposed in a claim of above claim is characterized in that carrying out with a spectrometer color estimation of measuring beam.

5. the method as being proposed in a claim of above claim is characterized in that measuring beam forms with visible light.

6. one kind as the method that proposed in claim 5 is characterized in that using white light when estimating the color of the measuring beam by the benchmark strip structure.

7. the method as being proposed in the claim of claim 1-4 is characterized in that using the limited light of wavelength coverage as measuring beam.

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