EP3624982A1 - Method for processing, in particular separating, a substrate by means of laser-induced deep reactive etching - Google Patents

Abstract

The invention relates to a method for processing a substrate by means of laser-induced deep reactive etching, wherein the laser radiation is moved along a processing line and individual pulses with a spatial laser pulse distance (d) are directed towards the substrate. An anisotropic material removal is then performed by means of etching at an etching rate (R) and an etching duration (t) under the condition 1 > d/(R*t) > 10-5.

Description

 METHOD OF MACHINING, ESPECIALLY FOR SEPARATING A SUBSTRATE BY MEANS OF LASER-INDUCED DEEP PADS

The invention relates to a method for processing, in particular for separating a particular planar substrate by means of laser-induced depth etching, wherein pulsed laser radiation is directed with a spatial laser pulse distance to the substrate and subsequently an anisotropic material removal by etching with an etch rate and an etching time is performed

The generic method for precision machining of glass by means of laser-induced deep etching has become known under the name LIDE (Laser Induced Deep Etching). The LIDE process enables the introduction of extremely precise holes (through glass via = TGV) and structures at high speed, thus creating the conditions for the increased use of glass as a material in microsystems technology.

In laser-induced depth etching (e.g., WO 2014/161534 A2 and WO 2016/04144 A1), a transparent material is conveyed over an elongated region along the beam axis, often across the entire thickness, by means of a laser pulse or pulse train

transparent material, e.g. in glass plates, modified so that the modification is anisotropically etched in a subsequent wet-chemical etching bath. If the laser pulses are emitted onto the material at a suitable spatial distance along a contour, the material is separated along the contour during the anisotropic removal of material.

The laser energy input serves to excite or trigger a reaction and a modification by conversion, the effect of which leads or is used only in the subsequent process step to the desired material separation. By the separation process due to the modification and optionally a subsequent anisotropic Materialabtrages done by an etching process, no sequential, but a two-dimensional erosion process is used for the separation process, which only makes very low demands on the process. In particular, can be about the

Period of action of the material removal quantitatively and qualitatively for all in the manner described pretreated and accordingly modified areas at the same time, so that the time required for the generation of the plurality of recesses or

Breakthroughs in the sum is substantially reduced.

Due to the principle-related concatenation of spaced locations of action of the individual pulses and their subsequent connection by the etching process, as a result, the separation surface is formed, the interface is not flat. Rather, a corrugation or a perforation, similar to a connected perforation.

This basically unwanted uneven parting surface can be defined by the

Set laser pulse distance, it is generally assumed that a small laser pulse distance leads to a lower expression of the waves or ridges.

Thus, in the method, the two fundamental objectives of a rapid processing progress by large laser pulse intervals on the one hand and a smooth as possible, a planar course approximated course of the cut surface on the other hand contrary.

The invention has for its object to provide a way to meet these two objectives in an optimal manner or to agree. This object is achieved by a method according to the features of claim 1. The further embodiment of the invention can be found in the dependent claims.

Thus, according to the invention, a method is provided in which the machining parameters are determined according to the following rule:

1> d / (R * t)> 1 0 ^"5 , preferably according to the condition:

1> d / (R * t)> 1 0 ^"3 , where d = laser pulse spacing, R = etching rate and t = etching time. The machined side surfaces of the cut by the LIDE process substrates or components thereby have a reduced roughness, the invention

surprising finding with respect to the dependence of the roughness on the pulse spacing and the etching time is based on that the pulse spacing for the smoothest possible surface is not chosen as small as possible, but must be determined according to the above rule.

In particular, the roughness of the surface as a function of the pulse spacing typically has a local minimum of approximately 1 μιη to 3 μιη. The position of this

Minimums depends on the substrate material, the etching chemistry used and other process parameters.

According to the invention, an anisotropic material removal in the etching bath is made possible at the locations which have been modified by the laser radiation. As a result, structures with large aspect ratios (thickness D of the substrate to kerf width b) can be produced with the condition

 12> D / b> 1.

 In this case, the removal of material by the wet-chemical etching, described by the product of etch rate R and etching time t, compared to the thickness D of the substrate is low.

Preferably applies

 D / (R * t)> 3.

 Particularly preferred

 D / (R * t)> 1 2.

 The substrate material used is preferably glass which is transparent to the wavelength used for the laser-induced deep etching. Particularly high aspect ratios and low roughness can be achieved with quartz glass.

The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and will be described below. This shows in each case in a schematic representation in

1 shows a representation of different laser pulse distances (d) and etch times (t); 2 shows an illustration of a surface profile of a sectional area at a laser pulse interval (d = 3 μm) and an etching time (t = 35 min);

Fig. 3 is an illustration of a surface profile of a cut surface in a

 Laser pulse distance (d = 10 μιη) and an etching time (t = 35 min);

Fig. 4 shows the ratio of the laser pulse distance (d) and the roughness R _a at different material abrasions.

Figure 1 shows schematically how different ripples or roughnesses of

Cut surfaces as a function of the laser pulse distance d and the etching time t (at a constant etching rate R) arise. As expected, the roughness decreases, the lower the

Pulse distance d and the greater the etching time t is selected.

This is illustrated in FIGS. 2 and 3 on the basis of surface profiles of the cut surfaces. For the same etching time t = 35 min and the same etching rate R, ie for the same product R ^* t and thus the same material removal by the wet-chemical etching, arise in two

Laser pulse intervals d = 3 μιη (Figure 2) and d = 10 μιη (Figure 3) very different

Surfaces.

FIG. 4 shows the dependence of the roughness R _a (roughness) on the laser pulse distance d (pitch) for different material removal (etch removal). At a laser pulse distance d of about 2 to 3 μιη a local minimum roughness R _a of about 0.05 to 0.08 μιη is achieved. This is only slightly influenced by material removal, the product of etch rate and etching time.

Claims

PATE NTAN SPRU 1 . Method for processing, in particular for separating a particular planar substrate by means of laser-induced depth etching, wherein the laser radiation is moved along a processing line and individual pulses with a spatial  Laser pulse distance (d) are directed onto the substrate and subsequently an anisotropic removal of material by etching with an etching rate (R) and an etching time (t) is performed, characterized in that the setting of the  Processing parameters according to the condition are: 1> d / (R * t)> 1 0 ^"5 2. The method according to claim 1, characterized in that the setting of the processing parameters according to the condition is carried out: 1> d / (R * t)> 1 0 ^"3 3. Process according to claims 1 or 2, characterized in that the Aspect ratio of a thickness (D) of the substrate to a kerf width (b) across the machining line is set according to the condition: 12> D / b> 1 4. The method according to at least one of the preceding claims, characterized in that the ratio between the initial thickness (D) of the substrate and the product of etching rate (R) and etching time (t) is greater than 3: D / (R * t)> 3 5. The method according to at least one of the preceding claims, characterized in that the ratio of initial thickness (D) of the substrate and the product of etching rate (R) and etching time (t) is greater than 5: D / (R * t)> 5 6. The method according to at least one of the preceding claims, characterized in that the ratio of initial thickness (D) of the substrate and the product of etching rate (R) and etching time (t) is greater than 8: D / (R * t)> 8 7. The method according to at least one of the preceding claims, characterized in that the ratio of initial thickness (D) of the substrate and the product of etching rate (R) and etching time (t) is greater than 10: D / (R * t)> 1 0 8. The method according to at least one of the preceding claims, characterized in that the ratio of initial thickness (D) of the substrate and the product of etching rate (R) and etching time (t) is greater than 12: D / (R * t)> 1 2 9. The method according to at least one of the preceding claims, characterized in that the substrate consists of glass, in particular quartz glass.