RU2026411C1 - Method for applying coating of preset thickness shape to flat substrate movable at a constant rate - Google Patents

Abstract

FIELD: microelectronics. SUBSTANCE: process in which a stationary adjusting screen placed intermediate of the source of the particles to be deposited and the substrate ensures that every point of the latter stays in the coating site sufficiently long for a coating of preset thickness to be applied. The screen has its configuration adapted to every type of the preset coating shape. For this purpose pre-measured is the thickness distribution of the coating applied on the stationary substrate without a screen this distribution being specific to the particular source of particles to be deposited. The necessary mathematical equations are included. EFFECT: preset thickness distribution of coating at the substrate surface in the direction perpendicular to the movement of the latter provided that in the direction of the substrate movement the coating thickness is constant. 5 cl, 4 dwg

Description

 The invention relates to coating by a linearly propagating stream of particles, for example, evaporation in vacuum or ion sputtering, and can be applied in the technology of microelectronics, integrated optics and in the technology of optical coatings when it is necessary to obtain a given profile of the thickness of the coating on the surface of the substrate.

 Known inventions (patents NN 60-430, 59-40225, 59-40226, 53-39862, 53-33531, 63-60272 - Japan; 2476682 - France; 4315960 - USA, 219044 - GDR, ed. St. N 1093012 - USSR), in which, in order to obtain the desired profile of the thickness of the coating on the substrate, movable or stationary screens relative to the substrate are used.

The disadvantages of these inventions are:
the lack of a method for accurately determining the shape of the screen necessary to obtain a specific predetermined coating thickness profile;
the limitations of their use only for certain types of a given profile, mainly for coatings uniform in thickness;
the limitation of their use only for special cases of substrate motion, for example, only for rotational or only for translational motion;
the absence of taking into account the natural distribution of the flux density of the deposited particles in the space characteristic of this source of these particles, which leads to an increase in the error of the obtained profile with respect to the given one.

 Closest to the proposed invention is the coating method contained in patent N 33068870 (Germany), which takes into account the initial distribution of the thickness of the coating obtained without a screen.

The disadvantages of this method are:
the possibility of application only in the case of axially symmetric flows of deposited particles;
the possibility of application only for the case of rotation of the substrate around its own axis, coinciding with the axis of the flow.

 The aim of the invention is to expand the scope of the method for producing coatings of a given profile and increase its accuracy. It can be used for any kind of a given profile of the thickness of the coating in the direction perpendicular to the movement of the substrate, with a constant thickness in the direction of its movement; arbitrary distribution of the flux density of the deposited particles in space, i.e. for any sources of this stream; translational and rotational motion of the substrate, i.e. for a wide range of types of spraying equipment.

This is achieved by the fact that
1. The distribution (profile) of the thickness of the coating (Q ₀ ) obtained on a stationary substrate without a screen in a stationary mode is previously measured, i.e. at a constant flow in time. In this case, the substrate should cover the entire application zone, i.e. the area in the plane of the substrate, where the flow rate of the deposited particles is not equal to zero, and the application time t ₀ should be fixed. Measurements are made at points (X _i , Y _k ) of the substrate with a constant step (ΔX, ΔY) along both mutually perpendicular generalizations to the coordinates of the substrate, and the Y axis coincides with the direction of possible movement of the substrate. With the translational motion of the substrate, X, Y coincide with the Cartesian coordinates of the substrate X, Y with rotational motion X = r, Y = α, where α is the angle of rotation of the substrate;
r is the radius of rotation of the i-th point of the substrate.

3. Полученные зависимости q₀ (x_iy_к) для каждого значения X_i в общем случае аппроксимируются кусочно-линейным приближением, по которому вычисляются суммы вида
Δy

(x_iy_k) , где

(x_iy_к) - средняя скорость осаждения на k-ом промежутке,
n₀ - количество интервалов разбиения по оси Y.2. Based on the measured thickness Q ₀ (x _i y _k ) and time, the deposition rate of the coating is calculated
q _o (x _i y _k ) =

3. The obtained dependences q ₀ (x _i y _k ) for each value of X _i in the general case are approximated by a piecewise linear approximation by which sums of the form are calculated
Δy

(x _i y _k ), where

(x _i y _k ) is the average deposition rate on the kth gap,
n ₀ is the number of partitioning intervals along the Y axis.

(x_iy_k) и заданному профилю ( φ₃(x_i)) вычисляются отношения вида Δy

(x_iy_k)

(x_i) наименьшее из которых принимается за коэффициент (постоянный) С.4. By the values of Δy

(x _i y _k ) and a given profile (φ ₃ (x _i )), relations of the form Δy

(x _i y _k )

(x _i ) the smallest of which is taken as a coefficient (constant) C.

где
a_i =

b_i =

n_i - предел суммирования, определяемый из неравенств

6. По расчетным значениям Y_эi изготавливается плоский экран, который устанавливается в плоскости, параллельной плоскости подложки так, чтобы между экраном и подложкой оставался зазор, обеспечивающий отсутствие трения между ними.5. Based on the data obtained, the coordinates of the screen boundary are calculated (Y _ei = Y _e (x _i) , which provides the specified profile of the thickness of the coating when the substrate moves at a constant speed according to the formula
y _ei =

Where
a _i =

b _i =

n _i is the summation limit determined from the inequalities

6. Based on the calculated values of Y _ei , a flat screen is made, which is installed in a plane parallel to the plane of the substrate so that there is a gap between the screen and the substrate, ensuring no friction between them.

 In FIG. 1 shows a diagram of the application process using a correction screen.

 It contains a moving substrate 1, a correction screen 2, the boundary of the deposition zone 3, the flow of the deposited particles 4, the source of the deposited particles 5.

7. Coating is carried out at an arbitrary constant substrate speed and a source of deposited particles that is random in a stationary mode of operation. The speed of movement of the substrate is limited by the inequality U ≥ U _cr , where U _cr is the speed of the substrate at which a given coating thickness profile is achieved in one pass of the deposition zone.

 Each substrate must pass the application area an integer number of times.

.8. If for some X _i it turns out a _i = 0, then the corresponding values of Y _{ei are} determined by the formula
y _ei = y _ni +

.

а искомые значения Yэi по формуле
y_эi=

, что дает двойное сокращение измерений и вычислений. Экран при этом условии становится двойным, симметричным относительно оси Х (см. фиг.2 и пример расчета);
б) в случае аналитически выраженных зависимостей q₀(x_iy) от координаты Y, т.е. при
q₀(X_iY) = f_i(y), где f_i(y) - известная вычисленная функция или функция, полученная аппроксимацией измеренных значений, то искомые координаты границы экрана определяются из уравнений

f(y)dy = Cφ_з(x_i),
в) если при тех же условиях (n "δ ") функции f_i(y) имеют один и тот же вид для всех X_i, то y_э(x) определяется из уравнения

f(y)dy = Cφ_з(x),
г) наконец, если q₀(x_iy) = C_i = const, то значения Y_э(х) находятся по формуле
y_э(x_i) = C

.9. In some special cases, the calculation of the shape of the screens is simplified, namely:
a) if there is a symmetry of the flow of the deposited particles with respect to a straight line perpendicular to the direction of motion of the substrate and passing through the center of the deposition zone, it is advisable to combine the X axis with this straight line, and the index n _i is determined from the inequalities

and the desired values of Yei according to the formula
y _ei =

, which gives a double reduction in measurements and calculations. The screen under this condition becomes double, symmetrical about the X axis (see figure 2 and an example of calculation);
b) in the case of analytically expressed dependences q ₀ (x _i y) on the Y coordinate, i.e. at
q ₀ (X _i Y) = f _i (y), where f _i (y) is a known calculated function or a function obtained by approximating the measured values, then the desired coordinates of the screen boundary are determined from the equations

f (y) dy = Cφ _s (x _i ),
c) if under the same conditions (n "δ") the functions f _i (y) have the same form for all X _i , then y _e (x) is determined from the equation

f (y) dy = Cφ _s (x),
d) finally, if q ₀ (x _i y) = C _i = const, then the values of Y _e (x) are found by the formula
y _e (x _i ) = C

.

 As an example, we consider the definition of the screen shape for the case of an axially symmetric flow distribution (particle flux created by a round magnetron), whose axis does not coincide with the axis of rotation of the substrate.

 Figure 2 shows a diagram of the process.

 It has a rotating substrate 1, correction screens 2; the boundary of the deposition zone 3, the flow of deposited particles 4, round (symmetric) magnetron 5.

Under these conditions, the flow is symmetrical and relatively straight line connecting the center of symmetry of the flow from the substrate rotation center, and shape of the zone of application in the form of a sector with a central angle ⁹⁰ is sufficient measurement of the film thickness (Q ₀₎ only by half of the application zone, ie. F . in a sector with an angle of 45 ^about (item 8a).

All these conditions are realized in the SCM-600 setup with a round magnetron and substrate rotation at a constant speed. In this installation, in order to obtain the initial flow distribution (q ₀ (r, α), an Al + Ti alloy film was deposited on a fixed substrate.

 The thickness measurements (in microns) for the width of the substrate are given in table. 1.

= Δα

и найдены отношения
Δα

для φ₃(r), вид которой приведен на фиг.3,б.r _max - r _min = 220 - 120 = 100 mm, where ΔY = Δ α = 5 ^o = 0.087266 rad;
ΔX = Δ r = 10 mm;
n ₀ = 9 (α _no = 45 ^о )
t ₀ = 540 s
In the table. 2 for each ri sums are calculated

= Δα

and found relationships
Δα

for φ ₃ (r), the form of which is shown in figure 3, b.

The table shows that the smallest values of these ratios correspond to r _i = 120 mm and amount to C = 2.061 × 10 ⁻³ s ⁻¹ .

Based on the data table. 1 and 2, the values of a _i , b _i , n _{i are} calculated and, using the formula in p.8a, the desired values of α _{ei are found} , which are given in table. 2. The shape of the screens is shown in figure 3, a. An experimental verification of the method was carried out respectively in the same SCM-600 setup and with the same magnetron target (Al + Ti). Two samples of films were produced on substrates measuring 90 x 60 mm ² installed at a distance from the center of rotation r _min = 125 mm, r _max = 215 mm.

In the table. Figure 3 shows in absolute and relative units the set and measured thicknesses of the films obtained by applying to a rotating substrate in the presence of a screen. In this table: φ _3max - maximum specified thickness, microns; Q _and - the measured thickness of the obtained film, microns; Q and _max - maximum measured thickness, microns; Δ is the absolute deviation of the obtained thickness from a given value (in relative units); δ is the relative deviation of the thickness of the obtained film from a given value,%.

= 2,41%.From the data table. Figure 3 shows that the maximum relative error in obtaining a given profile does not exceed 8% with an average error

= 2.41%.

 As a second example, we consider plasma deposition of a resistive film, which requires constant surface resistivity (ρ), and hence the thickness over the entire surface of the substrate, moving translationally at a constant speed.

= α , которое не зависит от времени.Let the distribution ρ _o (x _i y _k ) over the film sprayed onto a fixed substrate with a circular target have the form of a paraboloid of revolution with an axis coinciding with the axis of symmetry of the target. Then
1) for all X:
ρ _o (x _i y) = ay ² + b (x) (Fig. 4, a)
2) the coefficients “a” of the parabolas are independent of X, and the coefficients “b” are a function of x: b (x) = ax ² + b (o)
3) the coefficients "a" and "b" depend on time, but the solution depends only on

= α, which does not depend on time.

= f (y) , где ρ_o(x_iy_к) - удельное поверхностное сопротивление пленки, напыленной за единицу времени;
С_о - постоянная.In this case, the deposition rate for all x is expressed as
q _oi =

= f (y), where ρ _o (x _i y _k ) is the specific surface resistance of the film deposited per unit time;
C _o is a constant.

f(y)dy = C_o

= C

arctg

y

= Cφ_з(x)

f(y)dy = C_o

= C

arctg

y

= Cφ_з(x),
где Y₀ - координата границы зоны нанесения;
Х₀ - полуширина подложки (см. фиг.4б), и, следовательно;

arctg

y

=

arctg

y

,
откуда
y_э(x) = ±

tg(φ

), где
φ =

, при х₀ = 5 и y = 7; φ = 0,0593.According to the formula p.8v

f (y) dy = C _o

= C

arctg

y

= Cφ _s (x)

f (y) dy = C _o

= C

arctg

y

= Cφ _s (x),
where Y ₀ is the coordinate of the border of the application zone;
X ₀ is the half-width of the substrate (see fig.4b), and therefore;

arctg

y

=

arctg

y

,
where from
y _e (x) = ±

tg (φ

) where
φ =

, at x ₀ = 5 and y = 7; φ = 0.0593.

The measurement data ρ _o (x, y) are given in table. 4. The calculated values of the coefficients "a" and "b" and the average value of a are also given there.

tg(

) и искомые значения Y_э(х). Схема процесса и вид соответствующих экранов показаны на фиг.4,а,б, где все обозначения аналогичны обозначениям на фиг.1.In the table. 5 shows the calculated values

tg (

) and the desired values of Y _e (x). The process diagram and view of the respective screens are shown in Figs.

Compared with the known, the present invention has the following advantages:
is universal, i.e. allows you to get any profiles of the thickness of the coating in the direction perpendicular to the movement of the substrate;
can be applied to any sources of the flow of the deposited particles, provided that these particles propagate linearly both during translational and rotational motion of the substrate, i.e. for a wide range of equipment types.

Claims (2)

A METHOD FOR APPLYING A COVER OF A PROPOSED THICKNESS PROFILE ON A PLANE SUBSTRATE, MOVING WITH A CONSTANT SPEED, consisting in the fact that between the source of the deposited particles and the substrate parallel to the plane of its motion, a corrective screen is installed, having previously calculated the coordinates of its boundaries, and then applied, the purpose of expanding the scope of the method and increasing its accuracy, the calculation of the coordinates of the screen boundary Y _e (X _i ), where (X, Y) is a system of orthogonal generalized coordinates, the Y axis of which coincides with the direction the motion of the substrate, based on a pre-measured distribution of the coating thickness Q ₀ (X _i , Y _k ) deposited on a fixed substrate without a screen in the stationary mode of the source for a time t ₀ with a constant step of the measurement points ΔY = Y _{k + 1} -Y _k by which the deposition rate of the coating is calculated

and relationships of the kind

Where

- the average deposition rate of the coating on the interval [Y _{k - 1} , Y _k ];
n ₀ is the number of intervals between measurement points Q ₀ (X _i , Y _k ) along the Y axis;
φ ₃ (X _i ) is the value of a given coating thickness at X = X _i ,
and the smallest of these relations is taken as a constant coefficient C in the formula for calculating the desired coordinates of the screen boundary

Where

n _i is the summation limit determined from the inequality

moreover, if for some X _i
a _i = 0,
then the calculation of Y _e (X _i ) is performed according to the formula

2. The method according to p. 1, characterized in that in the case of symmetry of the flow of the deposited particles relative to a straight line perpendicular to the direction of motion of the substrate and passing through the center of the deposition zone, the X axis is combined with this straight line, index n _i is determined from the inequality

and the desired coordinates Y _e (X _i ) according to the formula

moreover, the screen becomes two-sided, symmetrical about the X axis. 3. The method according to claim 1, characterized in that in the case of analytically expressed dependencies q ₀ (X _i Y) = f _i (Y), where f _i (Y) is a known function, the coordinates of the screens are determined from the equations

4. The method according to claim 1, characterized in that in the case when the functions f _i (Y) have the same form for all X _i , the values of Y _e (X) are determined from the equation

5. The method according to claim 1, characterized in that when q ₀ (X _i Y) = C ₁ = const, the values of Y _e (X) are determined from the equation

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